Walk behind self-propelled crawler snowplow

Information

  • Patent Grant
  • 6550161
  • Patent Number
    6,550,161
  • Date Filed
    Friday, April 19, 2002
    22 years ago
  • Date Issued
    Tuesday, April 22, 2003
    21 years ago
Abstract
A walk behind self-propelled crawler has a travel ready lever mounted to one of the left and right handlebars and adapted to be gripped by a human operator to place the electric motors in an operative condition, and a clutch control pushbutton switch disposed on the control board at a position close to the other handlebar, the clutch control pushbutton switch being adapted to be manually operated to actuate the electromagnetic clutch.
Description




FIELD OF THE INVENTION




The present invention relates to a walk behind self-propelled crawler snowplow having driving wheels mounted on a vehicle body for driving the snowplow, an auger for removing snow, and left and right handlebars extending from a rear end of the vehicle body in a rearward direction of the snowplow.




BACKGROUND OF THE INVENTION




Walk behind self-propelled crawler snowplows are known from Japanese Patent Laid-open Publications Nos. (SHO) 63-223207, (HEI) 02-38606 and (HEI) 03-107009. The known snowplows have left and right operation handlebars extending from a rear end of a vehicle body, and a snow-removing mechanism including an auger and a blower that are mounted on a front portion of the vehicle body. During snow-removing operation, the auger and the blower are driven while the handlebars are properly manipulated to keeping a desired traveling posture of the snowplow. In general, the snowplows have various operation control levers that are manipulated to control travel conditions of the vehicle body and drive conditions of the auger and blower. A typical example of the conventional operation control levers will be described in greater detail with reference to

FIGS. 20A and 20B

.




As shown in

FIGS. 20A and 20B

, left and right operation handlebars


100


L and


100


R extending from a rear portion of the vehicle body (not shown) each have a grip


101


L,


101


R. A travel control lever


102


is pivotally mounted via a bracket


102




a


to the left handlebar


100


L in the proximity of the grip


101


L. An auger control lever


103


is pivotally mounted via a bracket


103




a


to the right handlebar


101


R in the proximity of the grip


101


R.




In operation of the snowplow, the travel control lever


102


is manually operated to swing in a direction indicated by the arrow shown in FIG.


20


A. By thus swinging the travel control lever


102


, a power transmission belt associated with a travel clutch (neither shown) for actuating the same is stretched or tensioned to thereby place the travel clutch in the engaged condition or state. The travel clutch enables power to be transmitted to driving wheels (not shown).




The auger control lever


103


is manually operated to swing in a direction indicated by the arrow shown in FIG.


20


B. With this angular movement of the auger control lever


103


, a power transmission belt associated with an auger clutch (neither shown) for actuating the same is stretched or tensioned to thereby place the auger clutch in the engaged state. The auger clutch enables power to be transmitted to an auger (not shown).




To keep the travel control lever


102


in its operating position, it is necessary for the human operator to continue gripping of the travel control lever


102


using its left hand. However, due to a great force required to tension the power transmission belt to actuate the travel clutch, continued gripping of the travel control lever


102


means that a great force F (

FIG. 20B

) must be continuously applied to the travel control lever


102


so as to keep the lever in its operating position. With this requirement, the left hand of the human operator is subjected to undue load when the snow-removing operation continues for a long time. A similar problem occurs when the auger control lever is operated with the right hand of the operator so as to keep the engaged state of the auger clutch.





FIG. 21

shows another example of the conventional operation control levers, which is disclosed in Japanese Patent Laid-open Publication No. (HEI) 02-38606. As shown in this figure, a travel control lever


102


mounted to the left handlebar


100


L and an auger control lever


103


mounted to the right handlebar


100


R are connected together by a connecting mechanism


105


. The connecting mechanism


105


is arranged such that when the auger control lever


103


is operated to swing toward an operating position while the travel control lever


102


is held in its operating position, a locking cam (not shown) of the connecting mechanism


105


engages the auger control lever


103


to thereby lock the lever


103


in the operating position.




So long as the operator continues gripping of the travel control lever


102


to maintain a force F exerted on the lever


102


, the auger control lever


103


is held in its operating position even when the operator releases the lever


103


. The right hand of the operator is thus freed from the auger lever handling work and is able to undertake manipulation of other levers and switches. This may increase the working efficiency of the snowplow.




The connecting mechanism


105


, which is provided to lock the auger control lever


103


in its operating position while allowing the operator to release the same lever, gives rise to a problem that the snowplow is rendered complicated in construction and costly to manufacture. Additionally, due to the structural complexity, the snowplow requires much labor for maintenance.




SUMMARY OF THE INVENTION




It is accordingly an object of the present invention to provide a walk behind self-propelled crawler snowplow, which can be maneuvered with reduced labor, is relatively simple in construction and can be manufactured less costly.




According to the present invention, there is provided a walk behind self-propelled snowplow comprising: a vehicle body; at least one driving wheel mounted on the vehicle body for propelling the snowplow; a first power transmitting mechanism; an electric motor that drives the driving wheel via the first power transmission mechanism; a snow-removing auger mounted on the vehicle body; a second power transmission mechanism; a power source that drives the auger via the second power transmission mechanism; an electromagnetic clutch incorporated in the second power transmission mechanism for the connection and disconnection of the power source and the auger; left and right handlebars extending from a rear end of the vehicle body in a rearward direction of the snowplow; a control board disposed between the left and right handlebars; a travel ready lever mounted to one of the left and right handlebars and adapted to be gripped by a human operator to place the electric motor in an operative condition; and a clutch control pushbutton switch disposed on the control board at a position close to the other handlebar, the clutch control pushbutton switch being adapted to be manually operated to actuate the electromagnetic clutch.




Use of the travel ready lever and the clutch control pushbutton switch in combination enables the operator to maneuver the snowplow with reduced labor, makes the snowplow relatively simple in construction.




In one preferred form of the invention, the first power transmission mechanism includes an electromagnetic brake, and the travel ready lever comprises a brake control lever operatively connected to the electromagnetic brake in such a manner that when the brake control lever and the one handlebar are gripped together by the human operator, the electromagnetic brake is released to thereby allow power from the electric motor to be transmitted to the driving wheel.




The snowplow may further include a brake control switch operatively connected to the electromagnetic brake. The brake control switch is adapted to be actuated by the brake control lever to disengage the electromagnetic brake when the brake control lever and the one handlebar are gripped together by the human operator. Preferably, the clutch control pushbutton switch is connected to a power supply via the brake control switch.




It is preferable that the clutch control pushbutton switch and the travel ready lever are operationally linked with each other. The snowplow may further include a travel ready switch adapted to be actuated by the travel ready lever to place the electric motor in the operative condition, the clutch control pushbutton switch being electrically connected with the ravel ready switch. In another preferred form of the invention, the electromagnetic clutch and the travel ready lever are operatively connected together via the travel ready switch and the clutch control pushbutton switch in such a manner that the electromagnetic clutch is engaged and disengaged when the clutch control pushbutton switch is actuated while the travel ready lever is being gripped together with the one handlebar, the electromagnetic clutch is forcibly disengaged when griping of the travel ready lever is released after the clutch control pushbutton switch is actuated to engage the electromagnetic clutch, and the electromagnetic clutch is engaged and disengaged when clutch control pushbutton switch is actuated while the travel ready lever is released.




In a further preferred form of the invention, the snowplow further include a travel ready switch adapted to be actuated by the travel ready lever to place the electric motor in the operative condition, and a U-shaped bracket attached to the one handlebar so as to define therebetween a hollow space. The travel ready switch has a switch body received in the hollow space of the U-shaped bracket and attached to the bracket, an actuator retractably mounted on the switch body and projecting outward from an open end of the U-shaped bracket. The travel ready lever has a pusher part normally held in abutment with the open end of the bracket and closing the open end of the bracket while forcing the actuator of the travel ready switch in a retracted position. The pusher part is displaced away from the open end of the bracket to thereby allow the actuator of the travel ready switch to project outward from the open end of the bracket when the travel ready lever is gripped. The pusher part of the travel ready lever may be integral with a body of the travel ready lever. Alternatively, the travel ready lever may be composed of a lever body and a pusher member pivotally connected with the lever body, the pusher member forming the pusher part. The lever body has an engagement portion normally spaced from the pusher member, the engagement member being engaged with the pusher member to pivot relative to the lever body in a direction away from the open end of the bracket as the lever body approaches the one lever. The open end of the bracket forms a stopper engageable with a part of the travel ready lever to limit a range of pivotal movement of the travel ready lever.











BRIEF DESCRIPTION OF THE DRAWINGS




Certain preferred embodiments of the present invention will hereinafter be described in detail, by way of example only, with reference to the accompanying drawings, in which:





FIG. 1

is a left side view of a walk behind self-propelled crawler snowplow according to an embodiment of the present invention;





FIG. 2

is a plan view of the crawler snowplow;





FIG. 3

is a diagrammatical view showing the operational relationship between an operation control part and drive mechanisms of the crawler snowplow;





FIG. 4

is a diagrammatical view showing an arrangement for controlling the operation of crawler driving motors and an auger clutch;





FIG. 5

is a time chart illustrative of the operation of the arrangement shown in

FIG. 4

;





FIG. 6

is a view similar to

FIG. 3

, showing a particular example of connection between the operation control part and the drive mechanisms of the crawler snowplow;





FIG. 7

is a diagrammatical view showing an arrangement for controlling the operation of electromagnetic brakes associated with the crawler driving motors and an electromagnetic clutch associated with an auger drive mechanism;





FIG. 8

is a perspective view showing the general arrangement of the operation control part of the crawler snowplow;





FIG. 9

is a plan view of a control board of the operation control part;





FIG. 10

is a side view showing a left operation handlebar and a travel ready lever mounted to the handlebar;





FIG. 11

is an exploded perspective view of a switch mechanism having a switch adapted to be actuated by the travel ready lever;





FIGS. 12A through 12C

are side views illustrative of the operation of the switch mechanism;





FIG. 13

is a partial cross-sectional view taken along line XIII—XIII of

FIG. 8

, showing a clutch control push button switch of the operation control part;





FIG. 14

is a circuit diagram showing the connection between the clutch control pushbutton switch and a switch associated with the travel ready lever;





FIG. 15

is a time chart showing the operation of the crawler snowplow;





FIG. 16

is a flowchart showing a control procedure for controlling the operation of the crawler snowplow;





FIG. 17

is a flowchart showing a blanched part of the control procedure;





FIG. 18

is a side view showing a switch mechanism according to a modification of the present invention;





FIG. 19

is a side view showing a switch mechanism according to a further modification of the present invention;





FIGS. 20A and 20B

are perspective views showing the operation of a lever arrangement of a conventional snowplow; and





FIG. 21

is a view similar to

FIG. 20

, showing another example of the conventional lever arrangement.











DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS




The following description is merely exemplary in nature and is in no way intended to limit the invention or its application or use.




Referring to the drawings and

FIG. 1

in particular, there is shown a walk behind self-propelled crawler snowplow


10


according to an embodiment of the present invention. The snowplow


10


generally comprises a propelling frame


12


carrying thereon left and right crawler belts (only the left crawler belt


11


L being shown), a vehicle frame


15


carrying thereon a snowplow mechanism


13


and an engine (prime motor)


14


for driving the snowplow mechanism


13


, a frame lift mechanism


16


operable to lift a front end portion of the vehicle frame


15


up and down relative to the propelling frame


12


, and a pair of left and right operation handlebars


17


L and


17


R extending from a rear portion of the propelling frame


12


obliquely upward in a rearward direction of the snowplow


10


. The propelling frame


12


and the vehicle frame


15


jointly form a vehicle body


19


.




The operation handlebars


17


L,


17


R are adapted to be gripped by a human operator (not shown) walking behind the snowplow


10


in order to maneuver the snowplow


10


. A control board


51


, a control unit


52


and batteries


53


are arranged in a vertical space defined between the handlebars


17


L,


17


R and they are mounted to the handlebars


17


L,


17


R in the order named when viewed from the top to the bottom of FIG.


1


.




The operation handlebars


17


L,


17


R each have a grip


18


at the distal end (free end) thereof. The left handlebar


17


L has a travel ready lever


41


disposed in the proximity of a grip


18


for easy manipulation by the human operator. The control board


51


has a pushbutton


47


(

FIG. 2

) disposed near the right handlebar


17


R. The left and right handlebars


17


L,


17


R further have turn control levers


55


L,


55


R disposed in the proximity of the respective grips


18


,


18


.




The crawler snowplow


10


is arranged such that power from an output shaft (crankshaft)


35


of the engine


14


can be transmitted via a driving pulley


36


and a power transmission belt


37


to the snowplow mechanism


13


. To this end, an electromagnetic clutch


45


is mounted on the output shaft


35


. The driving pulley


36


is freely rotatably mounted on the output shaft


35


of the engine


14


and is connected with the output shaft


35


when the electromagnetic clutch


45


is actuated or placed in the engaged state.




The snowplow mechanism


13


has an auger


31


, a blower


32


and a discharge duct or shooter


33


that are mounted to a front portion of the vehicle frame


15


. The auger


31


and the blower


32


are rotatably mounted on a rotating shaft


39


. The rotating shaft


39


has a driven pulley


38


connected in driven relation to the driving pulley


36


via the power transmission belt


37


.




In operation, the power from the engine output shaft


35


is transmitted via the electromagnetic clutch


45


to the driving pulley


36


, and rotation of the driving pulley


36


is transmitted via the power transmission belt


37


to the driven pulley


38


. With this rotation of the driven pulley


35


, the rotating shaft


39


concurrently rotates the auger


31


and the blower


32


. The auger


31


cuts snow away from a road, for example, and feeds the snow into the blower


32


. The blower


32


blows out the snow through the discharge duct


33


to a distant place.




In

FIG. 1

reference numeral


56




a


denotes an auger case, numeral


51




b


denotes a blower case, numeral


56




c


denotes a scraper formed integrally with a lower edge of the auger case


56




a


, numeral


56




d


(

FIG. 2

) denotes a charging generator for charging the batteries


53


, numeral


56




e


denotes a lamp, numeral


56




f


denotes a cover for protecting the generator


56




d


and the electromagnetic clutch


45


, and numeral


56




g


denotes a stabilizer for urging each crawler belt


11


L,


11


R downward against the ground surface.




As shown in

FIG. 2

, the left and right crawler belts


11


L,


11


R are driven by left and right electric motors


21


L,


21


R, respectively. The crawler belts


11


L,


11


R are each trained around a driving wheel


23


L,


23


R and an idler wheel


24


L,


24


R. The driving wheel


23


L,


23


R is disposed on a rear side of the crawler belt


11


L,


11


R, and the idler wheel


24


L,


24


R is disposed on a front side of the crawler belt


11


L,


11


R. The crawler snowplow


10


of the foregoing construction is self-propelled by the crawler belts


11


L,


11


R driven by the electric motors


21


L,


21


R and is also maneuvered by the human operator walking behind the snowplow


10


while handling the handlebars


17


L,


17


R.




In order to drive the charging generator


56




d


, a generator driving pulley


61


is mounted to the engine output shaft


35


, and a generator driven pulley


62


is mounted to a shaft of the generator


56




d


. The driving and driven pulleys


61


,


62


are connected by a V-belt


63


, so that rotation of the engine output shaft


35


is transmitted to the charging generator


56




d.






The control board


51


has a lift control lever


51




a


for controlling operation of the frame lift mechanism


16


(FIG.


1


), a shooter control lever


51




b


for changing the direction of the shooter


33


, a forward/reverse speed control lever


51




c


for adjusting the forward/reverse speed of the crawler snowplow


10


, and a throttle lever


51




d


for controlling rotational speed of the engine


14


. The forward/reverse speed control lever


51




c


has a function to reverse the direction of rotation of the electric motors


21


L,


21


R so as to change or shift the direction of travel of the crawler snowplow between the forward direction and the reverse direction.




As better shown in

FIG. 3

, power from each electric motor


21


L,


21


R is transmitted via a speed reducer


22


L,


22


R to the corresponding driving wheel


23


L,


23


R to thereby drive the associated crawler belt


11


L,


11


R. The speed reducer


22


L,


22


R forms a power transmission mechanism and is equipped with an electromagnetic brake


25


L,


25


R.




The travel ready lever


41


is pivotally connected by a pin


42


to a bracket (not designated) attached to the left handlebar


17


L. This lever


41


is manually operated to place the crawler snowplow


10


in a condition ready for traveling and snow-removing operation. A travel ready switch


40


is disposed close to the travel ready lever


41


for activation and de-activation by the lever


41


. The switch


40


is electrically connected with the control unit


52


so that the position of the travel ready lever


41


can be represented by the ON-OFF state of the travel ready switch


40


.




The travel ready lever


41


is normally disposed in an inclined inoperating position P


1


shown in FIG.


3


. When gripped with the left hand of the operator, the travel ready lever


41


is placed in a recumbent operating position where the lever


41


lies flat on the grip


18


. When released from the operator's left hand, the travel ready lever


41


automatically returns to the original in operating position P


1


by the force of a return spring (not shown in FIG.


3


). The stroke of pivotal movement of the travel ready lever


41


is set to be sufficiently large so that the foregoing travel ready condition of the snowplow


10


does not occur unless the travel ready lever


41


is pressed deeper to assume the operating position where the lever


41


lies flat on the grip


18


of the left handlebar


17


L. This arrangement increases the operational reliability of the travel ready lever


41


.




When the travel ready lever


41


reaches the recumbent operating position, the travel ready switch


40


is turned on and an electric signal indicative of the arrival of the lever


41


at the operating position is supplied from the switch


40


to the control unit


52


. Upon receipt of the electric signal, the control unit


52


places the crawler snowplow


10


in the aforesaid condition ready for traveling and snow-removing operation. The structure and operation of the travel ready lever


41


will be described in detail with reference to

FIGS. 10

to


12


.




The travel ready lever


41


is disposed generally above the travel ready switch


40


so that the switch


40


is protected against unintentional access tending to turn on or off the switch


40


.




While the engine


14


is operating, power from the engine


14


can be transmitted via a power transmission mechanism


34


to the snowplow mechanism


13


. The power transmission mechanism


34


includes the driving pulley


36


mounted on the output shaft


35


of the engine


14


via the electromagnetic clutch


45


, the driven pulley


38


mounted to the rotating shaft


39


, the power transmission belt


37


connecting the driving and driven pulleys


36


and


38


, a worm gear speed-reducing mechanism


39




a


interconnecting the rotating shaft


39


and an auger shaft


39




b


. The rotating shaft


39


is connected to the blower


32


, and the auger shaft


39




b


forms a part of the auger


31


.




The pushbutton


47


that is provided on the control board


51


at a position close to the right handlebar


17


R for activation and deactivation of the electromagnetic clutch


45


forms a part of a clutch control switch


46


. Thus, the clutch control switch


46


comprises a pushbutton switch. The clutch control pushbutton switch


46


is mounted on a rear end portion


51




f


of the control board


51


and located close to the right handlebar


17


R.




The pushbutton


47


of the pushbutton switch


46


is normally disposed in an in operating position shown in FIG.


3


. When depressed by the operator using a finger of the right hand, the pushbutton


47


is temporarily locked in a depressed operating position. When the operator pushes the pushbutton


47


again, the pushbutton


47


is released and automatically returns to the original inoperating position by the force of a return spring (not shown in FIG.


3


). The clutch control pushbutton switch


46


may have a built-in lamp, such as a backup lamp, which facilitates visual observation of the clutch control pushbutton switch


46


in the dark or during snowfall.




When the operator pushes the pushbutton


47


down to the operating position by using its right hand finger, the clutch control pushbutton switch (hereinafter referred to, for brevity, as “clutch switch”)


46


is turned on and sends an electric signal to the control unit


52


, which in turn generates a command signal to engage the electromagnetic clutch


45


. The electromagnetic clutch


45


is thus activated, and rotation of the engine output shaft


35


is transmitted via the electromagnetic clutch


45


to the snowplow mechanism


13


, thereby rotating the auger


31


and the blower


32


.




The pushbutton


47


is surrounded by a guard


48


that is attached to the rear end portion


51




f


of the control board


51


so as to protect or guard the pushbutton


47


against unintentional access tending to turn on or off the clutch switch


46


.




The left and right turn control levers


55


L,


55


R are connected with potentiometers


65


L,


65


R (FIG.


4


). When each of the turn control levers


55


L,


55


R and the grip


18


of the associated handlebar


17


L,


17


R are gripped together, the potentiometer


65


L,


65


R changes its voltage value whereupon a regenerative braking force is applied to the corresponding electric motor


21


L,


21


R under the control of the control unit


52


. By the effect of the regenerative braking force, the rotational speed (number of revolutions per unit time) of the electric motor


21


L,


21


R is slowed down to thereby turn the vehicle body


19


(

FIG. 1

) in a leftward or a rightward direction.




The forward/reverse speed control lever


51




c


is also connected to a potentiometer


66


(FIG.


4


). This lever


51




c


is normally disposed in the upright neutral position shown in

FIG. 3

, where the control units


52


generates a command signal to stop traveling of the crawler snowplow


10


. When the control lever


51




c


is tilted down in a forward direction of the crawler snowplow


10


, the control unit


52


generates a command signal to move the crawler snowplow in the forward direction at a speed corresponding to the amount of angular displacement of the lever


55




c


from the neutral position. Similarly, when the control lever


51




c


is tilted down in the rearward direction of the crawler snowplow


10


, the control unit


52


generates a command signal to move the crawler snowplow


10


backward at a speed corresponding to the amount of angular displacement of the lever


51




c


from the neutral position. The potentiometer


66


is designed to vary the voltage value in proportion to the amount of angular displacement of the control lever


51




c


from the neutral position.




Operation of the crawler snowplow


10


will be described with reference to FIG.


4


. The travel ready lever


41


is normally disposed in the inclined inoperating position P


1


. When gripped with the operator's left hand together with the left grip


18


, the travel ready lever


41


is angularly moved from the inoperating position P


1


to the recumbent operating position where the lever


41


lies flat on the left grip


18


. When the travel ready lever


41


reaches the recumbent operating position, the travel ready switch


40


is turned on or activated whereupon an electric signal indicative of the arrival of the travel ready lever


41


at the operating position is supplied to the control unit


52


. The control unit


52


operates to place the crawler snowplow


10


in a condition ready for travel and snow-removing operation, allowing the electric motors


21


L,


21


R and auger


31


to rotate. In this instance, since the travel ready lever


41


has a large swing stroke, it is possible to keep the travel ready switch


40


in the off state until the travel ready lever


41


arrives at its operating position. With this arrangement, unintentional activation or deactivation of the travel ready switch


40


does not occur, and the reliability in operation of the travel ready lever


41


increases. When the travel ready lever


41


is released, rotation of the auger


31


and running of the crawler snowplow


10


are stopped.




While gripping the travel ready lever


41


with its left hand, the operator depresses the pushbutton


47


using a finger of the right hand until the pushbutton


47


assumes the operating position P


3


. With this depression of the pushbutton


47


, the clutch switch


46


is turned on whereupon an electric signal pulse is supplied from the switch


46


to the control unit


52


, which in turn generates a command signal to actuate or engage the electromagnetic clutch


45


. When the pushbutton


47


is depressed again, the clutch switch


46


is turned off and a signal pulse is supplied from the switch


36


to the control unit


52


. The control unit


52


in turn generates a command signal to disengage the electromagnetic clutch


45


.




While keeping a grip on the travel ready lever


41


, the operator further grips the left and right turn control levers


55


L,


55


R to thereby vary the voltage values of the potentiometers


65


L,


65


R. variations of the voltage value are read in the control unit


52


, which in turns operates to apply regenerative braking forces to the electric motors


21


L,


21


R to thereby change the rotating speeds of the electric motors


21


L,


21


R. By properly adjusting the amount of angular displacement of the speed control levers


55


L,


55


R (corresponding to the magnitude of regenerative braking forces on the electric motors


21


L,


21


R), it is possible to turn the crawler snowplow


10


in a desired direction with a desired radius of curvature.




The control unit


52


may have a diagnostic function to detect and isolate a malfunction or a failure in the crawler snowplow on the basis of signals supplied from the travel ready switch


40


and the clutch switch


45


. This will increase the maintainability of the crawler snowplow.





FIG. 5

is a time chart illustrative of operation of the crawler snowplow


10


. In (a) of

FIG. 5

, the vertical axis represents the position of the travel ready lever


41


corresponding to the state of the travel ready switch


40


, and the horizontal axis represents the time. Similarly in (b) of

FIG. 5

, the vertical axis represents the position of the forward/reverse speed control lever


51




c


, and the horizontal axis represents the time. In (c) of

FIG. 5

, the vertical axis represents the rotational condition of the electric motors


21


L,


21


R, and the horizontal axis represents the time. Similarly in (d) of

FIG. 5

, the vertical axis represents the position of the pushbutton


47


which corresponds to the state of the clutch switch


46


, and the horizontal axis represents the time. In (e) of

FIG. 5

, the vertical axis represents the state of the electromagnetic clutch


45


, and the horizontal axis represents the time.




It appears clear from (a) and (b) of

FIG. 5

that the forward/reverse speed control lever


51




c


can be set in the forward (F), neutral (N) or reverse (R) position regardless of whether the travel ready lever


41


is disposed in the operating (ON) position or in the inoperating (OFF) position. As evidenced from (a), (b) and (c) of

FIG. 5

, the electric motors


21


L,


21


R are allowed to undertake repeated rotation in the forward (F) and reverse (R) directions so long as the travel ready lever


41


is disposed in the operating (ON) position. When the travel ready lever


41


is in the inoperating (OFF) position, the motors


21


L,


21


R are stopped regardless of the position of the forward/reverse speed control lever


51




c.






As shown in (a) and (d) of

FIG. 5

, the clutch control pushbutton switch


46


is able to create a pulse signal regardless of whether the travel ready lever


41


is in the operating (ON) position or in the inoperating (OFF) position. As evidenced from (a), (d) and (e) of

FIG. 5

, whenever the travel ready lever


41


is in the operating (ON) position, the electromagnetic clutch


45


repeats on-off operation in response to a signal pulse generated from the clutch control pushbutton switch


46


. When the travel ready lever


41


is disposed in the inoperating (OFF) position, the electromagnetic clutch


45


is held in the disengaged (OFF) state.




As thus for explained, both the electric motor


21


L,


21


R and the auger


31


(

FIG. 1

) that is drivable when the electromagnetic clutch


45


is in the engaged (ON) state are placed in a rotatable condition when the travel ready lever


41


is disposed in the operating (ON) position. When the travel ready lever


41


is brought to the inoperating (OFF) position, rotation of the electric motors


21


L,


21


R and auger


31


is stopped. Thus, the travel ready lever


41


serves as a lever that places the crawler snowplow


10


in a condition ready to undertake traveling and snow-removing operation and also as a deadman lever that stops traveling and snow-removing operation automatically when the travel ready lever


41


is released in case of emergency.




As thus for explained, the crawler driving wheels


23


L,


23


R are independently driven by electric motors


21


L,


21


R, and the power transmission mechanism associated with the auger


31


includes an electromagnetic clutch


45


. The electric motors


21


L,


21


R and the electromagnetic clutch


45


are electrically actuated by using on-off operation of electric switches


40


,


46


(


47


). The switches


40


,


46


(


47


) are actuatable by a force which is considerably smaller than that required to actuate the mechanical clutches incorporated in the conventional snowplows. The snowplow according to the present invention can be maneuvered with small muscular effort.




Furthermore, since the travel ready lever


41


is mounted to only one handlebar


17


L, the operator is allowed to undertake the operations using the right hand thereof. This will increase the maneuverability of the snowplow. Additionally, the clutch control pushbutton switch


46


is disposed on the control board


51


at a position close to the right handlebar


17


R. By thus arranging the clutch control pushbutton switch


46


, the operator is allowed to undertake other operations using the right hand thereof. This may lead to a highly efficient snow-removing operation.





FIGS. 6 and 7

diagrammatically show a particular example of the arrangement, which places the crawler snowplow


10


in a condition, ready for traveling and snow-removing operation. In

FIGS. 6 and 7

, the same reference characters designate these parts which are like or corresponding to those of the foregoing embodiment shown in

FIGS. 1-5

. The arrangement shown in

FIGS. 6 and 7

differs from the arrangement of

FIGS. 3 and 4

only in that the travel ready lever


41


is operatively connected via the travel ready switch


40


to the electromagnetic brakes


25


L,


25


R incorporated in the power transmission mechanism (


22


L,


22


R). Thus, the travel ready lever


41


and the travel ready switch


40


are referred to as a brake control lever and a brake control switch, respectively.




When gripped by the left hand of the human operator, the brake control lever


41


pivots from the original inoperating position P


1


to an operating position in which the lever


41


lies flat on the left grip


18


. With this pivotal movement of the brake control lever


41


, the brake control switch


40


is turned on whereupon the electromagnetic brakes


25


L,


25


R are disengaged. This will allow the crawler belts


11


L,


11


R to be driven by power transmitted from the electric motors


21


L,


21


R via the power transmission mechanisms


22


L,


22


R to the driving wheels


23


L,


23


R.




As shown in

FIG. 7

, the brake control switch


40


is connected between the battery


53


and the electromagnetic brakes


25


L,


25


R. The brake control switch


40


and the brake control lever


41


are arranged such that when the brake control lever


41


is disposed in the original inoperating position P


1


, a base portion


41




a


of the brake control lever


41


presses or forces an actuator (not designated) of the brake switch


40


to thereby keep the OFF state of the brake control switch


40


.




When the brake control lever


41


is caused to swing in the direction of the arrow until the recumbent operating position of the brake control lever


41


is reached, the base portion


41




a


of the brake control lever


41


is disengaged from the actuator of brake control switch


40


whereupon the brake control switch


40


is turned on. The brake control switch


40


comprises a switch having a normally open contact. The electromagnetic brakes


25


L,


25


R engage when released from electric actuation. Electric actuation disengages the electric brakes


25


L,


25


R.




The clutch switch


46


is disposed between and connected in series with the brake control switch


40


and the electromagnetic clutch


45


. The clutch switch


46


is tuned off when the pushbutton


47


is in the original inoperating position P


2


indicated by the solid line shown in FIG.


7


. When the pushbutton


47


is depressed to assume the phantom-lined operating position P


3


, the clutch switch


46


is turned on. Thus, the clutch switch


46


is a switch having a normally open contact. Electric actuation engages the electromagnetic clutch


45


. The electromagnetic clutch


45


disengages when electric actuation is released.




Though not shown, these switches


40


,


46


are electrically connected to the control unit


52


(

FIG. 1

) so that the initial state of the switch contact is checked for detection of a failure of each switch


40


,


46


. This arrangement increases the reliability in operation of the switches


40


,


46


.




In operation, the brake control lever


41


is gripped together with the grip


18


of the left handlebar


17


L. This operation causes the brake control lever


41


to swing from the original in operating position P


1


to the recumbent operating position. When the brake control lever


41


reaches the operating position, the brake control switch


40


is turned on to thereby electrically actuate the electromagnetic brakes


25


L,


25


R. Upon actuation, the electromagnetic brakes


25


L,


25


R disengage so that power from the electric motors


21


L,


21


R can be transmitted via the power transmission mechanisms


22


L,


22


R to the crawler driving wheels


23


L,


23


R, thus propelling the crawler snowplow


10


.




While keeping this condition, the pushbutton


47


is depressed with the operator's right hand until the pushbutton


47


assumes the phantom-lined operating position P


3


. When the pushbutton


47


reaches the operating position, the clutch switch


47


is turned on to thereby electrically actuate the electromagnetic clutch


45


. Electric actuation engages the electromagnetic clutch


45


whereupon the auger


31


and the blower


32


are rotated by rotational power from the engine


14


(FIG.


6


).




The push button


47


of the clutch switch


46


is temporarily locked in the operating position to thereby keep the engaged state of the electromagnetic clutch


45


even when the pressure on the pushbutton


47


is released. The operator is therefore allowed to use its right hand for the purpose of operating other levers. This will increase the efficiency of the snow-removing operation by the snowplow


10


.




Furthermore, since the electromagnetic clutch


45


remains in its engaged position even after removal of a manual pressure on the pushbutton


47


, it is no longer necessary to provide such a connecting mechanism which is used in the conventional snowplow to mechanically join two levers mounted on the left and right handlebars. Due to the absence of the connecting mechanism, the actuators (brake control lever


41


and the clutch control pushbutton switch


46


) used for actuating the electromagnetic brakes


25


L,


25


R and the electromagnetic clutch


45


, that is the brake control lever


41


and the clutch switch


46


are simple in construction and easy to maintain and do not increase the manufacturing cost of the snowplow


10


.




Thereafter, the pushbutton


47


of the clutch switch


46


is pushed again while the brake control lever


41


is kept gripped in the operating position P


3


. The pushbutton


47


is thus allowed to automatically return to the inoperating position P


2


. With this backward movement of the pushbutton


47


, the clutch switch


46


is turned off, thereby disengaging the electromagnetic clutch


45


. Transmission of rotational power from the engine


14


to the snow-removing mechanism


13


is terminated with the result that rotation of the auger


31


and blower


32


is stopped.




When gripping of the brake control lever


41


is released while the pushbutton


47


is held in the operating position, the brake control lever


41


automatically returns to the original inoperating position P


1


. With this return movement of the brake control lever


41


, the brake control switch


40


is turned off and, hence, the electromagnetic brakes


25


L,


25


R return to the engaged state. By the effect of braking forces applied from the electromagnetic brakes


25


L,


25


R, the electric motors


21


L,


21


R are locked against rotation and, hence, traveling operation of the crawler snowplow


10


is terminated.




In this instance, since the brake control switch


40


is disposed in series circuit between the battery


53


and the clutch switch


76


, the supply of electric power from the battery


53


to the electromagnetic clutch


45


is interrupted when the brake control switch


40


is turned off. Thus, the electromagnetic clutch


45


is forcibly returned to the disengaged state and rotation of the auger


31


and blower


32


is stopped even though the pushbutton


47


of the clutch switch


46


is held in its operating position P


3


. It will be appreciated that merely by releasing brake control lever


41


, running of the crawler snowplow


10


and rotation of the auger


31


and blower


32


are stopped concurrently.





FIG. 8

is a detailed view of an operation control part


50


of the crawler snowplow


10


(FIG.


1


). The operation control part


50


includes the control board


51


disposed between the left and right handlebars


17


L,


17


R, the travel ready lever


41


mounted to the left handlebar


17


L in the proximity of the grip


18


, and the left and right turn control levers


55


L,


55


R mounted to the left and right handlebars


17


L,


17


R in the proximity of the grips


18


.




The control board


51


is composed of a control box


51


A extending between the left and right handlebars


17


L,


17


R and a control panel


51


B covering an upper opening of the control box


51


A. The control panel


51


B is provided with the lift control lever


51




a


, the shooter control lever


51




b


, the forward/reverse speed control lever


51




c


and the throttle lever


51




d


that are all described previously. The control box


51


A is provided with the pushbutton


47


forming an integral part of the clutch switch (auger switch)


46


(FIG.


4


), a main switch (key switch)


51




g


, a choke knob


51




h


that may be used when the engine


14


(

FIG. 1

) is started, a light button


51




i


for turning on and off the lamp


56




e


(FIG.


1


), and a failure lamp


51




j


adapted to be turned on when a failure occurs.

FIG. 9

is a plan view of the control panel


51


. As shown in this figure, the control panel


51


B has an upwardly projecting cover portion


49




a


for covering a base portion of the travel ready lever


41


, an elongated guide groove


49




b


for guiding movement of the forward/reverse speed control lever


51




c


, generally circular openings


49




c


and


49




d


used for mounting the lift control lever


51




a


and the shooter control lever


51




b


, respectively, and an elongated guide groove


5




d


for the throttle lever


51




d


. Reference character


49




f


denotes fastener holes used for attaching the control panel


51


B to the control box


51


A by means of screws.




The guide groove


49




b


is cranked and extends in the longitudinal direction (front-to-rear direction) of the crawler snowplow. The guide groove


49




b


has a forward first guide region A


1


used for propelling the snowplow in the forward direction, an intermediate second guide region A


2


used for moving the snowplow back and forth, and a rearward third guide region A


3


used for propelling the snowplow in the backward direction.





FIG. 10

shows a switch mechanism


80


generally comprises the travel ready lever


41


mounted to the left handlebar


17


L via a bracket


84


, and the travel ready switch


40


adapted to be actuated by the travel ready lever


41


. The bracket


84


has a U-shaped cross section, and the switch


40


is disposed in an internal space of the U-shaped bracket


84


and has an actuator


85




b


projecting outward from an upper end


84




c


of the bracket


84


. The travel ready lever


41


has a pusher member


89


designed to push the actuator


85




b


while closing the open upper end


84




c


of the U-shaped bracket


84


. This arrangement is able to isolate the switch


40


from rain or snow and thus increases the service life of the switch


40


and the reliability of the switch mechanism


80


as a whole.




As best shown in

FIG. 11

, the bracket


84


has a U-shaped cross section and is attached by welding to the left handlebar


17


L with its bottom wall facing upward (the bottom wall being hereinafter referred to as “top wall”). The bracket


84


thus attached has an internal space in which the travel ready switch


40


is accommodated. The bracket


84


has two holes


84




a


,


84




a


used for mounting the switch


40


to the bracket


84


, and a pair of laterally spaced support lugs


84




b


used for pivotally supporting the travel ready lever


41


. The support lugs


84




b


are formed as a part of the sidewalls of the bracket


84


. One end


84




c


of the U-shaped bracket


84


, which is located close to the support lugs


84




b


, is open. The open end


84




c


serves as a stopper that limits the range of pivotal movement of the travel ready lever


41


. Use of the bracket


84


having a stopper function reduces the number of structural components of the switch mechanism


80


and contributes to the cost reduction of the switch mechanism


80


.




The travel ready switch


40


has a switch body


85




a


, the actuator


85




b


retractably mounted on the switch body


85




a


, and a wire harness


85




c


drawn from the switch body


85




a


. The switch body


85




a


is attached to the bracket


84


by a plurality of screws


86


and nuts


86




a


(only one being shown).




The travel ready lever


41


is composed of a lever body


87


adapted to be gripped by the human operator, the pusher member


89


pivotally mounted by the pin


42


to the support lugs


84




b


of the bracket


84


together with the lever body


87


, a torsion spring


91


acting between the pusher member


89


and the left handlebar


17


L, and a tension spring


92


acting between the lever body


87


and the left handlebar


17


L. The pin


42


is locked in position by a stop ring


88




a.






The lever body


87


has a U-shaped cross section and also has a transverse hole extending through a base portion (proximal end portion) of the lever body


87


for the passage therethrough of the pin


42


, a spring support lug


87




b


to which one end of the tension spring


92


is connected, and an recessed engagement portion


87




c


for engagement with the pusher member


89


to activate the switch


40


. The opposite end of the tension spring


92


is connected to a spring support lug


92




a


formed on the left handlebar


17


L.




The pusher member


89


has a U-shaped cross section including a flat bottom wall


89




b


and a pair of sidewalls (not designated) having holes formed therein for the passage therethrough of the pin


42


. The sidewalls receive therebetween the base portion of the lever body


87


. The flat bottom wall


89




b


depresses the actuator


85




b


of the switch


40


and closes the open end


84




b


of the bracket


84


, as will be explained later on. The torsion spring


91


has a coiled portion


91




a


loosely fitted around the pin


42


. One end of the torsion spring


91


engages the flat bottom wall


89




b


of the pusher member


89


, and the other end of the torsion spring


91


engages a portion of the left handlebar


17


L.




Operation of the switch mechanism


80


will be described with reference to

FIGS. 12A through 12C

. The switch mechanism


80


is initially disposed in the position shown in FIG.


15


A. As shown in

FIG. 15A

, the flat bottom wall


89




b


(

FIG. 11

) of the pusher member


89


is held in abutment with the open end


84




c


of the U-shaped bracket


84


so that the open end


84




c


is closed and the actuator


85




b


of the switch


40


is in its retracted position as it is depressed by the pusher member


89


. The switch


40


is in the OFF state when the actuator


85




b


is in its retracted position. The engagement portion


87




c


(

FIG. 11

) of the lever body


87


is disengaged from the pusher member


89


. As previously described with reference to

FIGS. 1-5

, the travel ready lever


41


is a lever adapted to be manually operated to place the electric motors


21


L,


21


R (

FIG. 1

) in an operative condition.




When the travel ready lever


41


is gripped by the human operator, the lever body


87


is caused to swing toward the handlebar


17


L against the force of the tension spring


92


, as shown in FIG.


15


B. In the course of pivotal movement of the lever body


87


, the engagement portion


87




c


of the lever body


87


does not engage the flat bottom wall


89




b


of the pusher member


89


until the lever body


87


reaches a predetermined position located near the operating position of the travel ready lever


41


where the lever body


87


lies flat on the grip


18


of the left handlebar


17


L, as shown in FIG.


15


C. Accordingly, the pusher member


89


is held in its original position by the fore of the torsion spring


91


(FIG.


11


), So that the open end


84




c


of the bracket


84


is kept closed and the actuator


85




b


of the switch


40


is held in its retracted position. The switch


40


is in the OFF state.




Further gripping of the travel ready lever


41


cause the lever body


87


to approach the operating position (

FIG. 15C

) of the travel ready lever


41


. As the lever body


87


approaches the operating position of the travel ready lever


41


, the engagement portion


87




c


first comes in contact with a lower edge of the flat bottom wall


89




b


of the pusher member


89


, and subsequently forces the flat bottom wall


89




b


upward to thereby turn the pusher member


89


clockwise about the pin


42


(

FIG. 15A

) against the force of the torsion spring


91


(FIG.


11


). Thus, the flat bottom wall


89




b


of the pusher member


89


is displaced away from the open end


84




c


of the bracket


84


, allowing the actuator


55




b


of the switch


40


to move from the retracted position to the projecting position shown in FIG.


15


C. With this projecting movement of the actuator


85




b


, the switch


40


is turned on and, hence, the electric motors


21


L,


21


R (

FIG. 1

) are placed in an operative condition by, for example, releasing or disengaging the electromagnetic brakes


25


L,


25


R associated with the electric motors


21


L,


21


R.




The travel ready lever


41


, which is composed of the lever body


87


and the pusher member


89


pivotally connected together with a space initially defined between the engagement portion


87




c


of the lever body


87


and the flat bottom wall


89




b


of the pusher member


894




c


, forms a lost motion mechanism that provides a delay between the movement of a driver (lever body


87


) and the movement of a follower (pusher member


89


). By properly setting the spacing between the engagement portion


87




c


and the flat bottom wall


89




b


, the on-off timing of the switch


40


can be adjusted. The switch mechanism


80


of this construction has a higher degree of design freedom.




The clutch switch (auger switch)


46


shown in

FIG. 13

comprises an automatic reset pushbutton switch that keeps the ON state only when the pushbutton


47




a


is depressed; when the pushbutton


47




a


is released, the switch


46


automatically returns to the OFF state. The auger switch


46


includes a case


47




b


having a built-in lamp


47




c


. Light emitted from the lamp


47




c


passes through a transparent plate


47




d


provided at the top of the pushbutton


47




a


, so that the switch


46


can readily be visually recognized even in the dark or during snowfall.




The case


47




b


of the switch


46


also has a guard


48


extending around the pushbutton


47




a


. The guard


48


projects outward from the front surface of the pushbutton


47




a


so as to protect the switch


46


against unintentional access tending to turn on or off the switch


46


.





FIG. 14

is a circuit diagram of a control circuit in which the auger switch


46


of

FIG. 13

is used in combination with the travel ready lever


41


. As shown in

FIG. 14

, the control unit


52


, the electromagnetic clutch


45


, the failure lamp


51




i


, an auger lamp


51




k


, and the left and right electric motors


21


L,


21


R are connected via the main switch


51




g


to the battery


53


. A contact set


46




a


of the auger switch


46


and a contact set


85




d


of the travel ready switch


40


are connected to the control unit


52


.




The contact set


46




a


of the auger switch


46


is a normally open contact, and only when the pushbutton


47




a


(

FIG. 13

) is depressed, the contact


46




a


is closed, thereby activating or setting the auger switch


46


in the ON state. Upon activation of the auger switch


46


, an ON signal is supplied from the switch


46


to the control unit


52


. The contact set


85




d


of the travel ready switch


40


is also a normally open contact, and only when the travel ready lever


41


is in the operating position as it is gripped together with the left grip


18


, the contact


85




d


is closed, thereby activating or setting the travel ready switch


40


in the ON state. Upon activation of the travel ready switch


40


, an ON signal is supplied from the switch


40


to the control unit


52


.




The control unit


52


judges by the presence of the ON signal from the travel ready switch


40


that the crawler snowplow


10


is in a condition ready for traveling. Based on this judgment, the control unit


52


turns on internal switches


52




a


,


52




b


to thereby place the electric motors


21


L,


21


R in an operative condition.




The control unit


52


also activates the electromagnetic clutch


45


and turns on the auger lamp


51




k


on condition that both the ON signal from the travel ready switch


40


and the ON signal from the auger switch


46


have been received.




The control unit


52


further performs a diagnostic function so as to detect a failure in the switches


40


,


46


. The control unit


52


checks the initial state of the switch contact


46




a


,


85




d


of each switch and when a failure is detected, the control unit


52


turns on the failure lamp


51




j


. Checking is achieved on the bases of the presence of chattering of the switch contacts


46




a


,


85




d


, or the level of voltage appearing across the switch contacts


46




a


,


85




d


. By thus checking the initial state of the switch contacts, the reliability in operation of the switches


40


,


46


is improved.





FIG. 15

is a time chart illustrative of operation of the control unit


52


. (a) of

FIG. 14

shows the on-off operation of the travel ready switch


40


. (b) of

FIG. 4

shows the travel ready condition of the crawler snowplow. As evidenced from (a) and (b) of

FIG. 14

, the crawler snowplow is set in the travel ready condition when the travel ready switch


40


is in the ON state. When the when the travel ready switch


40


shifts from the ON state to the OFF state, the travel ready condition of the crawler snowplow is reset.




(c) of

FIG. 15

shows the operation of the forward/reverse speed control lever


51




c


. As shown in this figure, the forward/reverse speed control lever


51




c


is movable between the forward (F), neutral (N) and reverse (R) positions. (d) of

FIG. 15

shows the operation of the electric motors


21


L,


21


R. As evidenced from (b) and (d) of

FIG. 15

, the electric motors


21


L,


21


R are allowed to rotate only when the crawler snowplow is set in the travel ready condition. As seen from (c) and (d) of

FIG. 15

, when the forward/reverse speed control lever


51




c


is in the forward (F) position, the electric motors


21


L,


21


R rotate in the forward (F) direction, thereby propelling the snowplow in the forward direction. When the forward/reverse speed control lever


51




c


is disposed in the neutral (N) position, the electric motors


21


L,


21


R is stopped (S). Similarly, when the forward/reverse speed control lever


51




c


is in the reverse (R) position, the electric motors


21


L,


21


R rotate in the reverse (R) direction, thereby propelling the crawler snowplow in the reverse or backward direction.




(e) of

FIG. 15

shows the on-off operation of the auger switch


46


, and (f) of

FIG. 15

shows the operation of the electromagnetic clutch


45


. As evidence from (a), (b), (e) and (f) of

FIG. 15

, the electromagnetic clutch


45


operates in three different modes. The first operation mode occurs when a first ON signal pulse S


1


(tending to activate or engage the electromagnetic clutch


24


) and a subsequent second ON signal pulse S


2


(tending to deactivate or disengage the electromagnetic clutch


45


) are supplied repeatedly while the crawler snowplow is set in the travel ready condition. In the first operation mode, the electromagnetic clutch


45


repeats on-off operation.




The second operation mode of the electromagnetic clutch


45


occurs when the travel ready condition of the crawler snowplow is reset after the first ON signal pulse S


1


has been received and before the second ON signal pulse S


2


is received. In the second operation mode, the electromagnetic clutch


45


is deactivated or disengaged when the travel ready condition of the crawler snowplow is reset.




The third operation mode of the electromagnetic clutch


45


occurs when an ON signal pulse S


3


from the auger switch


46


is received when the travel ready switch


40


is in the OFF state (namely, the travel ready condition of the crawler snowplow has been reset). In the third operation mode, the electromagnetic clutch


45


is activated or engaged.




As seen from (e) of

FIG. 15

, the control unit


52


recognizes the receipt of the first ON signal pulse S


1


when the pulse duration (i.e., ON time of the signal pulse S


1


) reaches a preset first reference time T


1


. Similarly, the receipt of the second ON signal pulse S


2


is recognized by the control unit


52


when the pulse duration of the signal pulse S


2


reaches a preset second reference time T


2


. The control unit


52


recognizes the receipt of the ON signal pulse S


3


when the pulse duration (i.e., ON time of the signal pulse S


3


) reaches a preset third reference time T


3


. By thus checking the receipt of the signal pulses S


1


-S


3


by comparison with the corresponding preset reference times, the on-off operation of the electromagnetic clutch


45


is performed with high reliability. The first, second and third reference-times T


1


, T


2


, and T


3


may be equal to one another.




When the travel ready switch


40


is in the ON state as shown in (a) of

FIG. 15

, a first condition is satisfied in which the signal produced from the travel ready switch


40


upon actuation by the travel ready lever


41


forms a travel permission signal that permits rotation of the driving wheels


23


L,


23


R by the electric motors


21


L,


21


R. Similarly, when the travel ready switch


40


is in the OFF state as shown in (a) of

FIG. 15

, a second condition is satisfied in which the signal produced from the travel ready switch


40


upon actuation by the travel ready lever


41


forms a stop signal that stops rotation of the driving wheels


23


L,


23


R by the electric motors


21


L,


21


R.




In (e) of

FIG. 15

, the first ON signal pulse S


1


from the auger switch


46


meets a third condition in which at least one clutch-on signal from the auger switch


46


has been received. Similarly, in (e) of

FIG. 15

, the signal S


3


from the auger switch


46


meets a fourth condition in which the clutch-on signal from the auger switch


46


is recognized as a continuous signal.




When the first and third conditions are satisfied, it is possible to activate or engage the electromagnetic clutch


45


. Similarly, when the second and fourth conditions are satisfied, it becomes possible to activate or engage the electromagnetic clutch


45


.




The control unit


52


may be composed of a microcomputer in which instance the control procedure is carried out in a manner as shown in the flowcharts shown in

FIGS. 16 and 17

. As shown in

FIG. 16

, step


01


(ST


01


) initializes all values. For example, flag AU is set to 0 (AU=0), and the timer is reset. Then, step


02


(ST


02


) reads data, such as switch signals from the auger switch


46


and the travel ready switch


40


. Step


03


(ST


03


) judges whether or not the travel ready switch


40


is in the ON state. If “YES”, this means that the travel ready switch


40


is in the ON state as the travel ready lever


41


is being gripped, and the control procedure advances to step


04


(ST


04


). If “NO”, this means that the travel ready switch


40


is in the OFF state as the travel ready lever


41


has been released, and the control procedure branches to step


17


(ST


17


) shown in FIG.


17


.




Step


04


(ST


04


) passes judgment that the travel is ready and, and based on this judgment, this step ST


04


places the electric motors


21


L,


21


R in an operative condition. The operative condition means that the electric motors


21


L,


21


R will start rotation when instructed from the control unit


52


in response to manipulation of the forward/reverse speed control lever


51




c


(FIG.


3


). Then, step


05


(ST


05


) judges whether or not the auger switch


46


is in the ON state. If “YES”, this means that the auger switch


46


is in the ON state, and the control procedure advances to step


06


(ST


06


). If “NO”, this means that the auger switch


46


is in the OFF state, and the control procedure returns to step


02


(ST


02


).




At step


06


(ST


06


), a judgment is made to determine as to whether the internal timer of the control unit


52


is operating. If the judgment result is “YES”, the control procedure goes on to step


08


(ST


08


). Alternately, if the judgment result at ST


06


is “NO”, the control procedure branches to step


07


(ST


07


) where the timer is started after resetting. Step


08


(ST


08


) judges whether or not AU=0. If “YES”, this means that the ON signal from the auger switch


46


is a first ON signal pulse S


1


, and the control procedure advances to step


09


(ST


09


). Alternately, if the judgment result at ST


05


is “NO”, this means that the ON signal from the auger switch


46


is regarded as a second ON signal pulse S


2


, and the control procedure branches to step


13


(ST


13


).




At step


09


(ST


09


), a judgment is made to determine whether or not the count Tc of the timer (i.e., the time period passed after the timer is started) reaches a preset first reference time T


1


. If the judgment result is “YES”, this means that the first ON signal pulse S


1


is normal, and the control procedure advances to step


10


(ST


10


) where the flag is set to 1 (AU=1). Alternately, if the judgment result at ST


09


is “NO”, this means that the first ON signal pulse S


1


is not normal, and the control procedure returns to step


02


(ST


02


). Step


10


(ST


10


) is followed by a step


11


(ST


11


) where the electromagnetic clutch


45


is activated or engaged. Then, step


12


(ST


12


) turns on the auger lamp


51




k


, and the control procedure returns to step


02


(ST


02


).




At step


13


(ST


13


), a judgment is made to determine whether or not the count Tc of the timer (i.e., the time period passed after the timer is started) reaches a preset second reference time T


2


. If the judgment result is “YES”, this means that the second ON signal pulse is normal, and the control procedure advances to step


14


(ST


14


) where the flag is set to 0 (AU=0). Alternately, if the judgment result at ST


13


is “NO”, this means that the second ON signal pulse S


2


is not normal, and the control procedure returns to step


02


(ST


02


). Step


14


(ST


14


) is followed by a step


15


(ST


15


) where the electromagnetic clutch


45


is deactivated or disengaged. Then, step


16


(ST


16


) turns off the auger lamp


51




k


, and the control procedure returns to step


02


(ST


02


).




Referring next to

FIG. 17

, step


17


(ST


17


) passes judgment that the travel ready condition of the crawler snowplow is released and, based on this judgment, ST


17


places the electric motors


21


L,


21


R in an inoperative condition. The inoperative condition means that the electric motors


21


L,


21


R are held immovable (or locked against rotation) even when the forward/reverse speed control lever


51




c


(

FIG. 3

) is operated. Then, step


18


(ST


18


) judges whether or not the auger switch


46


is in the ON state. If “YES”, the control procedure advances to step


19


(ST


19


). If “NO”, the control procedure branches to step


25


(ST


02


).




At step


19


(ST


06


), a judgment is made to determine whether the internal timer of the control unit


52


is operating. If the judgment result is “YES”, the control procedure goes on to step


21


(ST


21


). Alternately, if the judgment result at ST


06


is “NO”, the control procedure branches to step


20


(ST


20


) where the timer is started after resetting. Step


21


(ST


21


) judges whether or not the count Tc of the timer (i.e., the time period passed after the timer is started) reaches a preset third reference time T


3


. If the judgment result is “YES”, this means that the third ON signal pulse S


3


is normal, and the control procedure advances to step


22


(ST


22


) where the flag is set to 1 (Au=1). Alternately, if the judgment result at ST


21


is “NO”, this means that the third ON signal pulse S


3


is not normal, and the control procedure branches to step


25


(ST


25


).




Step


22


(ST


22


) is followed by a step


23


(ST


23


) where the electromagnetic clutch


45


is activated or engaged. Then, step


24


(ST


24


) turns on the auger lamp


51




k


, and the control procedure returns to step


02


(ST


02


) shown in FIG.


16


. At step


25


shown in

FIG. 17

, the flag is set to 0 (AU=0) of FIG.


17


. Then, step


26


(ST


26


) deactivates or disengages the electromagnetic clutch


45


, and at step


27


(ST


27


) the auger lamp


51




k


is turned off. The control procedure then returns to step


02


(ST


02


) shown in FIG.


16


.




ST


06


, ST


07


, ST


09


and ST


13


shown in FIG.


16


and ST


19


, ST


20


and ST


21


shown in

FIG. 17

are not compulsory because these steps are incorporated for the purpose of improving the reliability of auger switch


46


.





FIG. 18

shows a modified form of the switch mechanism shown in FIG.


10


. The modified switch mechanism


81


differs from the assembly


80


of

FIG. 10

in that a travel ready lever


93


is composed of a lever body


95


of a U-shaped cross section, and a pusher member


94


having an engagement portion


94




a


received in a base portion of the lever body


95


. The engagement portion


94




a


is normally spaced or disengaged from the lever body


95


. During a forward stroke of its pivotal movement (in the direction toward the handlebar


17


L), a portion


95




a


(inside surface of the top wall) of the lever body


95


comes in contact with the engagement portion


94




a


and subsequently forces the engagement portion downward to thereby turn the pusher member


94


clockwise about the pin


42


. Since the pusher member


94


is substantially received in the base portion of the lever body


95


, the travel ready lever


93


of the modified switch assembly


81


is more compact than the lever


41


of the switch assembly


80


shown in FIG.


10


.





FIG. 19

shows another modified form of the switch assembly. The modified switch assembly


82


differs from the assembly


80


shown of

FIG. 10

in that a travel ready lever


96


has a one-piece structure and includes pusher part


96




a


formed as an integral part of the base portion of the lever


96


. The pusher part


96




a


is disposed on a side opposite to a body of the lever


96


with respect to the pivot pin


42


. The pusher part


96




a


has a flat surface extending at an angle to the longitudinal axis of the lever


96


. Reference character


92




b


denotes a support lug formed on the handlebar so as to anchor one end of the tension spring


92


. When the lever


96


is in the original inoperating position shown in

FIG. 19

, the pusher part


96




a


is held in abutment with the open end


84




c


of the bracket


84


by the force of the tension spring


92


so that the bracket open end


84




c


is closed and the actuator


85




b


of the switch


40


is held in its retracted position. When gripped by the human operator, the lever


96


pivots clockwise about the pin


42


against the force of the tension spring


92


. During that time, the pusher part


96




a


is gradually displaced rightward away from the open end


84




c


of the bracket


84


, allowing the actuator


85




b


of the switch


40


to gradually project outward from the bracket open end


84




c


. When the lever


96


reaches its operating position where the lever


96


lies flat on the grip


18


, the actuator


85




b


arrives at its projecting position and, hence, the switch


40


is turned on. The on-off timing of the switch


40


can be adjusted by properly setting the angle of inclination of the pusher part


96




a


relative to the longitudinal axis of the lever


96


. Since the pusher part


96




a


is formed as an integral part of the lever


96


, the switch mechanism


82


has a smaller number of parts than the switch mechanisms


80


,


81


shown in

FIGS. 10 and 18

. This may reduce the manufacturing cost of the switch mechanism


82


.




Obviously, various minor changes and modifications of the present invention are possible in the light of the above teaching. It is therefore to be understood that within the scope of the appended claims, the present invention may be practiced otherwise than as specifically described.




The present disclosure relates to the subject matter of Japanese Patent Applications Nos. 2001-123282, 2001-280148, 2001-285690 and 2001-333248, filed Apr. 20, 2001, Sep. 14, 2001, Sep. 19, 2001 and Oct. 30, 2001, respectively, the disclosures of which are expressly incorporated herein by reference in their entirety.



Claims
  • 1. A walk behind self-propelled snowplow comprising:a vehicle body; at least one driving wheel mounted on the vehicle body for propelling the snowplow; a first power transmitting mechanism; an electric motor that drives the driving wheel via the first power transmission mechanism; a snow-removing auger mounted on the vehicle body; a second power transmission mechanism; a power source that drives the auger via the second power transmission mechanism; an electromagnetic clutch incorporated in the second power transmission mechanism for the connection and disconnection of the power source and the auger; left and right handlebars extending from a rear end of the vehicle body in a rearward direction of the snowplow; a control board disposed between the left and right handlebars; a travel ready lever mounted to one of the left and right handlebars and adapted to be gripped by a human operator to place the electric motor in an operative condition; and a clutch control pushbutton switch disposed on the control board at a position close to the other handlebar, the clutch control pushbutton switch being adapted to be manually operated to actuate the electromagnetic clutch.
  • 2. The walk behind self-propelled snowplow according to claim 1, wherein the first power transmission mechanism includes an electromagnetic brake, and the travel ready lever comprises a brake control lever operatively connected to the electromagnetic brake in such a manner that when the brake control lever and the one handlebar are gripped together by the human operator, the electromagnetic brake is released to thereby allow power from the electric motor to be transmitted to the driving wheel.
  • 3. The walk behind self-propelled snowplow according to claim 2, further including a brake control switch operatively connected to the electromagnetic brake and adapted to be actuated by the brake control lever to disengage the electromagnetic brake when the brake control lever and the one handlebar are gripped together by the human operator.
  • 4. The walk behind self-propelled snowplow according to claim 3, further including a power supply for supplying electric power to the electromagnetic clutch and the electromagnetic brake, wherein the clutch control pushbutton switch is connected to the power supply via the brake control switch.
  • 5. The walk behind self-propelled snowplow according to claim 1, wherein the clutch control pushbutton switch and the travel ready lever are operationally linked with each other.
  • 6. The walk behind self-propelled snowplow according to claim 5, further including a travel ready switch adapted to be actuated by the travel ready lever to place the electric motor in the operative condition, wherein the clutch control pushbutton switch is electrically connected with the ravel ready switch.
  • 7. The walk behind self-propelled snowplow according to claim 6, wherein the electromagnetic clutch and the travel ready lever are operatively connected together via the travel ready switch and the clutch control pushbutton switch in such a manner that the electromagnetic clutch is engaged and disengaged when the clutch control pushbutton switch is actuated while the travel ready lever is being gripped together with the one handlebar, the electromagnetic clutch is forcibly disengaged when griping of the travel ready lever is released after the clutch control pushbutton switch is actuated to engage the electromagnetic clutch, and the electromagnetic clutch is engaged and disengaged when clutch control pushbutton switch is actuated while the travel ready lever is released.
  • 8. The walk behind self-propelled snowplow according to claim 1, further including a travel ready switch adapted to be actuated by the travel ready lever to place the electric motor in the operative condition, and a U-shaped bracket attached to the one handlebar so as to define therebetween a hollow space, wherein the travel ready switch has a switch body received in the hollow space of the U-shaped bracket and attached to the bracket, an actuator retractably mounted on the switch body and projecting outward from an open end of the U-shaped bracket, and the travel ready lever has a pusher part normally held in abutment with the open end of the bracket and closing the open end of the bracket while forcing the actuator of the travel ready switch in a retracted position, the pusher part being displaced away from the open end of the bracket to thereby allow the actuator of the travel ready switch to project outward from the open end of the bracket when the travel ready lever is gripped.
  • 9. The walk behind self-propelled snowplow according to claim 8, wherein the pusher part of the travel ready lever is integral with a body of the travel ready lever.
  • 10. The walk behind self-propelled snowplow according to claim 8, wherein the travel ready lever is composed of a lever body and a pusher member pivotally connected with the lever body, the pusher member forming the pusher part, the lever body having an engagement portion normally spaced from the pusher member, the engagement member being engaged with the pusher member to pivot relative to the lever body in a direction away from the open end of the bracket as the lever body approaches the one lever.
  • 11. The walk behind self-propelled snowplow according to claim 8, wherein the open end of the bracket forms a stopper engageable with a part of the travel ready lever to limit a range of pivotal movement of the travel ready lever.
Priority Claims (4)
Number Date Country Kind
2001-123282 Apr 2001 JP
2001-280148 Sep 2001 JP
2001-285690 Sep 2001 JP
2001-333248 Oct 2001 JP
Foreign Referenced Citations (6)
Number Date Country
63223207 Sep 1988 JP
01163304 Jun 1989 JP
01038681 Nov 1989 JP
02038606 Feb 1990 JP
03107009 May 1991 JP
09114535 May 1997 JP