Chain block

Information

  • Patent Grant
  • 6224039
  • Patent Number
    6,224,039
  • Date Filed
    Tuesday, October 19, 1999
    24 years ago
  • Date Issued
    Tuesday, May 1, 2001
    23 years ago
Abstract
A chain block which can ensure free rotation of a hand wheel when the hand wheel is rotated in a hoisting direction in the state in which an overload protection mechanism is in operation and also can ensure the lowering of a load when the hand wheel is rotated in a lowering direction. The chain block includes an one-way mechanism that permits the hand wheel to freely rotate in the hoisting direction with respect to the first hub of the hand wheel and restricts the hand wheel freely rotating in the lowering direction. The one-way mechanism is composed of a spring and a pin received in a recess and a receiving portion formed in the inner periphery of the boss of the hand wheel and forming therein a slanted surface for guiding the pin received in the receiving portion to the inner periphery of the boss when the hand wheel is rotated in the hoisting direction and a retaining surface for retaining the pin in the inside of the receiving portion when the hand wheel is rotated in the lowering direction.
Description




BACKGROUND OF THE INVENTION




1. Field of the Invention




The present invention relates to a chain block and, more particularly, to a hand operated chain block wherein a load sheave is rotated to wind up and down a load chain passing over the load sheave by the operation of a hand chain passing over a hand wheel.




2. Description of the Prior Art




In general, hand operated chain blocks of this type comprise a load sheave supported between two opposed side plates via bearings; a hand wheel disposed at the outside of one side plate to drive the load sheave through a drive shaft and a reduction gear mechanism; and a transmission mechanism having a mechanical brake which is interposed between the hand wheel and the load sheave to apply a given brake and are so structured that a load suspended from a hook of the load chain passing over the load sheave can be hoisted up and lowered down by the operation of a hand chain passing over the hand wheel.




Of these known chain blocks, some are provided with an overload protection mechanism that permits the hand wheel to freely rotate in the hoisting direction when a load in excess of a rated load of the chain block is applied to the load sheave, for preventing the hoist of the load more than the rated load.




The overload protection mechanism comprises, for example, a hub member threadedly mounted on the drive shaft and supporting thereon the hand wheel in a freely rotatable manner; a load setting mechanism, arranged at an axially outside end portion of the hub member, for setting a rated load; and two lining plates interposed in a freely rotatable manner between the hub member and the hand wheel and between the hand wheel and the load setting mechanism, respectively. The overload protection mechanism is so structured that when the hand wheel is rotated in the hoisting direction in the state in which a load more than a rated load as is preset by the load setting mechanism pressing the lining plates is being applied, slippage of the hand wheel can be caused between the two lining plates placed at both sides of the hand wheel to permit free rotation of the hand wheel with respect to the hub member.




On the other hand, for example when the overload protection mechanism is put into action in the hoist of the load by the application of a load more than the rated load, the hand wheel is held slipped between the two lining plates placed at both sides thereof, and as such cannot permit the lowering of the load. For permitting the lowering of the load in such a situation, the hub member is provided, in an outer periphery thereof, with a recessed portion in which a pin and a biasing spring for biasing the pin radially outwardly are housed and also a boss of the hand wheel is provided, in an inner periphery thereof, with a receiving portion that can permit the pin to be retained therein only when the hand wheel is rotated in the lowering direction, whereby an one-way mechanism that permits free rotation of the hand wheel with respect to the hub member only in the hoisting direction and restricts the free rotation of the hand wheel in the lowering direction is formed so that the lowering of the load can be permitted even when a load more than the rated load is applied.




With this arrangement, when the hand wheel is rotated in the lowering direction in the state in which it is being slipped between the two lining plates placed at the both sides of the hand wheel by the action of the overload protection mechanism, the pin is smoothly received in the receiving portion but is sometimes caught in the receiving portion even when the hand wheel is rotated in the hoisting direction, depending on the form of the receiving portion. As a result of this, despite the load being more than the rated load, the load is sometimes hoisted in an unstable state, or the pin and the receiving portion are sometimes damaged. Also, there is presented a disadvantage that the hand wheel, when rotated, may rattle to cause damage to the hub member and the hand wheel. In the hand operated chain block of this type, in particular, even a little pulling of the hand chain may cause the hand wheel to rotate a couple of turns, and as such will give increased opportunities of the pin and the receiving portion to confront each other, thus significantly expanding the influence of the disadvantages above. Further, when it comes to a small-sized chain block having the hand wheel of a small diameter, even the little pulling of the hand chain will give further increased opportunities of the pin and the receiving portion to confront each other, thus further significantly expanding the influence.




SUMMARY OF THE INVENTION




To solve the problems mentioned above, the present invention has been made. It is the object of the present invention is to provide a chain block that can ensure free rotation of a hand wheel when the hand wheel is rotated in a hoisting direction in the state in which an overload protection mechanism is in operation and also can ensure the lowering of a load when the hand wheel is rotated in a lowering direction.




The present invention provides a novel chain block comprising a load sheave with which a load chain is engageable; a hand wheel with which a hand chain is engageable; a transmission mechanism including a mechanical brake interposed between the hand wheel and the load sheave; an overload protection mechanism that supports the hand wheel and permits the hand wheel to freely rotate in a hoisting direction when a load more than a rated load is applied to the load sheave; and a drive shaft, passed through the load sheave, the transmission mechanism and the overload protection mechanism, to transmit drive applied from the hand wheel to the load sheave, wherein the overload protection mechanism includes a hub member threadedly engaged with the drive shaft and supporting thereon the hand wheel in a freely rotatable manner; and an one-way mechanism that permits the hand wheel to freely rotate in a hoisting direction with respect to the hub member and restricts the hand wheel freely rotating in a lowering direction; wherein the one-way mechanism includes a recess formed in an outer periphery of the hub member; an engaging member provided in the recess and normally biased radially outwardly; and a concave receiving portion, opening in an inner periphery of a boss of the hand wheel, to receive the engaging member therein; and wherein the receiving portion includes a slanted surface extended obliquely to guide the engaging member received in the receiving portion to the inner periphery of the boss of the hand wheel when the hand wheel is rotated in the hoisting direction; and a retaining surface, extended substantially along a radial direction of the inner periphery of the boss, to permit the engaging member received in the receiving portion to be retained in an inside of the receiving portion when the hand wheel is rotated in a lowering direction.




With this arrangement, when a load more than a rated load applied to the load sheave is tried to be hoisted by rotating the hand wheel in the hoisting direction, the hand wheel is permitted to freely rotate with respect to the hub member threadedly engaged with the drive shaft. Thus, the hoist of any load more than the rated load of the chain block is prevented. During the free rotation of the hand wheel with respect to the hub member, every time the engaging member of the one-way mechanism faces the receiving portions formed in the inner periphery of the boss of the hand wheel, the engaging member which is normally biased radially outwardly or toward the inner periphery of the boss of the hand wheel is received in the receiving portions, while on the other hand, the as-received engaging member is smoothly guided again to the inner periphery of the boss of the hand wheel along the slanted surface formed in each of the receiving portions.




This can produce the results that a possible problem that the engaging member may be caught in the receiving portion so that a load more than a rated load may be hoisted in an unstable state or a possible damage of the engaging member and the receiving portion can be minimized. Also, the rattling of the hand wheel that may be caused when rotated can be minimized and a possible damage to the hub member and the hand wheel can be minimized.




On the other hand, for example, when the overload protection mechanism is put into action in the hoist of a load by the application of load more than a rated load, the hand wheel can be restricted freely rotating in the lowering direction with respect to the hub member by the engaging member of the one-way mechanism being received in the receiving portion. This can permit the lowering of even a load more than the rated load. At that time, the engaging member received in the receiving portion is well retained by the retaining surface formed in the receiving portion.




This arrangement that enables the engaging member received in the receiving portion to be well retained by the retaining surface formed in the receiving portion when the hand wheel is rotated in the lowering direction can provide the result that the free rotation of the hand wheel with respect to the hub member can reliably be restricted and thereby the lowering of even a load more than a rated load can be ensured.




According to this invention, it is preferable that the slanted surface formed in the receiving portion is extended along a tangential direction to the inner periphery of the hand wheel and also is smoothed out at a boundary between the inner periphery of the boss of the hand wheel and the slanted surface.




With this arrangement, when the hand wheel is rotated in the hoisting direction in the situation in which the hand wheel is put in the state of being freely rotatable with respect to the hub member by application of a load more than a rated load to the load sheave, every time the engaging member received in the receiving portion faces the receiving portion, the engaging member is smoothly guided again to the inner periphery of the boss of the hand wheel along the tangential direction to the inner periphery of the hand wheel and along the slanted surface smoothed out at the boundary between the slanted surface and the inner periphery of the boss of the hand wheel. On the other hand, when the hand wheel is rotated in the lowering direction, the engaging member is smoothly received into the receiving portion along the tangential direction to the inner periphery of the hand wheel and along the slanted surface smoothed out at the boundary between the slanted surface and the inner periphery of the boss of the hand wheel.




In this arrangement, since the slanted surface of the receiving portion is so formed as to extend along the tangential direction to the inner periphery of the hand wheel and is smoothed out at the boundary between the slanted surface and the inner periphery of the boss of the hand wheel, when the hand wheel is rotated in the hoisting direction in the situation in which the hand wheel is put in the state of being freely rotatable with respect to the hub member by application of a load more than a rated load to the load sheave, the engaging member received in the receiving portion can be guided smoothly to the inner periphery of the boss of the hand wheel just the way it is, without causing the engaging member received in the receiving portions to rattle. Also, when the hand wheel is rotated in the lowering direction, the engaging member can be received into the receiving portion smoothly without causing the engaging member to rattle.




Thus, for example in a hand operated chain block in which even a little pulling of the hand chain in the hoisting direction causes the hand wheel to rotate with respect to the hub member a couple of turns during which the engaging member confronts the receiving portions several times, when the hand wheel is rotated in the hoisting direction in the situation in which the hand wheel is put in the state of being freely rotatable with respect to the hub member by application of a load more than a rated load to the load sheave, smooth free rotation of the hand wheel with respect to the hub member can be ensured, while also, when the hand wheel is rotated in the lowering direction, the engaging member can smoothly be received in the receiving portion to ensure the smooth lowering of load.




According to this invention, it is preferable that there are provided receiving portions which are opened in the inner periphery of the hand wheel at positions opposed to each other and of which slanted surfaces are formed to be substantially parallel to each other.




With this arrangement, when the hand wheel is rotated in the hoisting direction in the situation in which the hand wheel is put in the state of being freely rotatable with respect to the hub member by application of a load more than a rated load to the load sheave, the engaging member is received in each of the receiving portions provided at the opposed positions every time the hand wheel is rotated one turn. Even when the engaging member is received in any of the receiving portions, since the slanted surfaces in the receiving portions are so formed as to be substantially parallel to each other, the engaging member received is guided to the inner periphery of the boss of the hand wheel along the slanted surface under the same condition. On the other hand, when the hand wheel is rotated in the lowering direction, the engaging member is received in any of the receiving portions provided at the opposed positions during one-turn of the hand wheel.




This can provide the result that in the chain block in which even a little pulling of the hand chain causes the hand wheel to rotate a couple of turns, so as to give several opportunities of the engaging member to confront the receiving portions, since the receiving portions are provided at the opposed positions and also the slanted surfaces are so formed as to be substantially parallel with each other, even when the engaging member is given many opportunities to confront the receiving portions, the engaging member is received cliclically in the receiving portions as the hand wheel rotates and is guided to the inner periphery of the boss of the hand wheel along the slanted surfaces under the same condition. Thus, regular operations can be ensured. On the other hand, when the hand wheel is rotated in the lowering direction, since the engaging member is received in any of the receiving portions during one-turn of the hand wheel, the engaging member is brought into engagement in the receiving potion to permit the lowering of load until the hand wheel rotates one turn.




Thus, for example, in a small-sized chain block having the hand wheel having a small diameter in which even a little pulling of the hand chain causes the engaging member to confront the receiving portions many times, good operation of the engaging member and the receiving portions can be ensured and, thus, improved durability and reliability of the one-way mechanism can be provided.











BRIEF DESCRIPTION OF THE DRAWINGS




The present invention will now be described with reference to the accompanying drawings wherein:





FIG. 1

illustrates in longitudinal section a small-sized hand operated chain block as one embodied form of a chain block of the present invention;





FIG. 2

is a side view of a hand wheel of the chain block shown in

FIG. 1

;





FIG. 3

is a front view of the hand wheel shown in

FIG. 2

;





FIG. 4

is a side view of a first hub of the chain block shown in

FIG. 1

;





FIG. 5

is a front view of the first hub shown in

FIG. 2

;





FIG. 6

illustrates in longitudinal section a principal part of one embodied form of a chain block which is not equipped with an overload protection mechanism;





FIG. 7

illustrates in side elevation a principal part of an one-way mechanism; and





FIG. 8

illustrates in side elevation a principal part of the one-way mechanism.











DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS




Referring now to the accompanying drawing figures, an example of the preferred embodiment of the invention is described below.




Referring to

FIG. 1

, there is shown a longitudinal section of a small-sized hand operated chain block of one embodiment of the present invention. In the chain block, a load sheave


3


over which a load chain


61


passes in engaging relation is rotatably supported between opposed left and right side plates


1


,


2


via two bearings


4


,


5


.




A drive shaft


6


is inserted in a shaft hole of the load sheave


3


in freely rotatable relation, and a transmission mechanism


10


having a mechanical brake


9


and an overload protection mechanism


8


are supported by the drive shaft


6


at the outside of the right side plate


2


in an inserted state. A hand wheel


7


over which a hand chain


62


passes in an engaging relation is supported in the overload protection mechanism


8


. As will be mentioned later, the drive shaft


6


is substantially the same as a drive shaft used in a chain block which is not equipped with the overload protection mechanism


8


.




The transmission mechanism


10


includes a second hub


11


connected to the drive shaft


6


in a non-rotatable relation (in a threaded connection in FIG.


1


); a third lining plate


17


, an anti-reverse gear


12


; and a fourth lining plate


18


.




The second hub


11


is formed in one piece having a flange portion and a cylindrical portion extending axially therefrom. The anti-reverse gear


12


, the third lining plate


17


and the fourth lining plate


18


are rotatably supported on the cylindrical portion of the second hub


11


in such a manner that the third lining plate


17


is interposed between the anti-reverse gear


12


and a first hub


13


of the overload protection mechanism


8


mentioned later and the fourth lining plate


18


is interposed between the flange portion of the second hub


11


and the anti-reverse gear


12


.




A pawl shaft


14


is provided on the right side plate


2


and an anti-reverse pawl


15


engageable with the anti-reverse gear


12


is swingably pivoted on the pawl shaft


14


. Further, a pawl spring


16


for biasing the anti-reverse pawl


15


toward the anti-reverse gear


12


is provided between the anti-reverse pawl


15


and the right side plate


2


. The mechanical brake


9


of the transmission mechanism


10


is composed of the second hub


11


, the anti-reverse gear


12


, the anti-reverse pawl


15


, the third lining plate


17


and the fourth lining plate




The hand wheel


7


has on the outer periphery side thereof a plurality of pockets


20


for receiving therein chain links of a hand chain


62


and also has on the base side thereof a boss


22


in which a receiving hole


58


for receiving therein the first hub


13


of the overload protection mechanism


8


mentioned later is formed, as shown in

FIGS. 2 and 3

. Formed at both sides of the boss


22


are a second recess


56


and a third recess


57


formed in the recessed form for receiving therein a first lining plate


23


and a second lining plate


24


mentioned later, respectively. The second recess


56


and the third recess


57


are formed in circular, in side configuration, of slightly larger in diameter than the outer diameters of the first lining plate


23


and the second lining plate


24


and formed with a depth substantially equal to a thickness of the first lining plate


23


and the second lining plate


24


.




The overload protection mechanism


8


includes the first hub


13


of a hub member threadedly engaged with the drive shaft


6


, the load setting mechanism


21


for setting a rated load, the first lining plate


23


acting as a brake disc, the second lining plate


24


acting as the brake disc and one-way mechanism


25


that permits free rotation of the hand wheel


7


in the hoisting direction with respect to the first hub


13


and restricts the free rotation of same in the lowering direction, as shown in FIG.


1


.




The first hub


13


is formed in one piece having a flange portion


19


, a large-diameter cylindrical portion


30


extending axially outwardly from the flange portion


19


and a small-diameter cylindrical portion


31


extending axially outwardly from the large-diameter cylindrical portion


30


and being smaller in diameter than the large-diameter cylindrical portion


30


, as shown in

FIGS. 4 and 5

. The small-diameter cylindrical portion


31


has on an end surface thereof a first recess


32


opening in the form of a recessed portion. The first recess


32


is formed in circular, in side configuration, of not less in diameter than a set nut


34


mentioned later and formed with such a depth as to receive at least a part of the set nut


34


. The small-diameter cylindrical portion


31


is externally threaded.




The hand wheel


7


, the first lining plate


23


and the second lining plate


24


are rotatably supported on the large-diameter cylindrical portion


30


of the first hub


13


in such a manner that the first lining plate


23


is interposed between the boss


22


of the hand wheel


7


and a lining keep member


26


of the load setting mechanism


21


mentioned later and the second lining plate


24


is interposed between the flange portion


19


of the first hub


13


and the boss


22


of the hand wheel


7


. As a result of this, the first lining plate


23


and the second lining plate


24


are fitted in the second recess


56


and the third recess


57


formed at the both sides of the boss


22


of the hand wheel


7


, respectively.




The load setting mechanism


21


is composed of the lining keep member


26


, a belleville spring


27


serving as a biasing means, a locking member


28


and a tightening nut


29


. With contacting with the first lining plate


23


, the lining keep member


26


is rotatably supported on the large-diameter cylindrical portion


30


of the first hub


13


, as aforesaid. For biasing the lining keep member


26


toward the first lining plate


23


, the belleville spring


27


is supported on the small-diameter cylindrical portion


31


of the first hub


13


, with contacting with the lining keep member


26


. For adjusting the biasing force of the belleville spring


27


, the tightening nut


29


is threadedly engaged with the small-diameter cylindrical portion


31


of the first hub


13


, with pressing the belleville spring


27


through the locking member


28


.




Thus, when the tightening nut


29


is screwed forward along the small-diameter cylindrical portion


31


of the first hub


13


, the first lining plate


23


, the hand wheel


7


and the second lining plate


24


existing between the tightening nut


29


and the flange portion


19


of the first hub


13


are pressed through the lining keep member


26


by the belleville spring


27


so strongly that even when a heavy load is hoisted, the hand wheel


7


can be prevented from slipping over the first lining plate


23


and the second lining plate


24


, thus permitting the setting of an increased rated load. On the other hand, as the tightening nut


29


is screwed backward along the small-diameter cylindrical portion


31


of the first hub


13


, the pressing force of the belleville spring


27


to the first lining plate


23


, the hand wheel


7


and the second lining plate


24


between the tightening nut


29


and the flange portion


19


of the first hub


13


decreases, so that when a heavy load is hoisted, the hand wheel


7


can be slipped over the first lining plate


23


and the second lining plate


24


, thus permitting the setting of an decreased rated load.




The set nut


34


used as a restricting member is threadedly engaged with an end portion of the drive shaft


6


on which the overload protection mechanism


8


is mounted, with spaced at a predetermined interval from the first hub


13


threadedly mounted on the drive shaft


6


. In the first recess


32


opening in the end surface of the small-diameter cylindrical portion


31


of the first hub


13


, the set nut


34


is fixed to the end portion of the drive shaft


6


by a set pin


59


so that it cannot be moved in the axial direction. The axial movement range of the first hub


13


is restricted by the set nut


34


, with a washer


33


interposed between the set nut


34


and a bottom of the first recess


32


.




On the other hand, the drive shaft


6


is supported by the bearing


35


at the other axial end portion thereof, and the reduction gear mechanism


36


having a plurality of reduction gears is provided between the bearing


35


and the load sheave


3


and at the outside of the left side plate


1


. The reduction gear mechanism


36


is composed of the first gear


37


integrally formed on the axial end portion of the drive shaft


6


, the second gear


38


and the third gear


39


supported on a pair of intermediate shafts and engageable with the first gear


37


(which are not shown and only one of the second gear


38


and the third gear


39


is shown in

FIG. 1

) and the fourth gear


40


connected with an extended portion of the load sheave


3


and engageable with the third gear


39


. The drive from the drive shaft


6


is transmitted from the first gear


37


to the second gear


38


engaged with the first gear and then transmitted to the fourth gear


40


from the intermediate shaft supporting the second gear


38


thereon through the third gear


39


supported on the same intermediate shaft. Thus, the drive from the drive shaft


6


is transmitted to the load sheave


3


at a predetermined reduction ratio.




A gear cover


41


for covering the reduction gear mechanism


36


and a wheel cover


42


, opening at one side thereof, for covering the hand wheel


7


are detachably mounted on the left side plate


1


at the outside thereof and the right side plate


2


at the outside thereof, respectively, with three stay bolts connecting between the left side plate


1


and the right side plate


2


(only two stay bolts


43


,


44


are shown in FIG.


1


). Provided between the right side plate


2


and the hand wheel


7


is a brake cover


45


for covering a circumferential portion of the anti-reverse gear


12


. Further, a chain split


46


is provided between the left side plate


1


and the right side plate


2


at lower portions thereof, and a chain guide


47


for guiding the load chain


61


is provided between the left side plate


1


and the right side plate


2


at upper portions of the load sheave


3


. Provided above the chain guide


47


is an upper hook


48


for suspending the chain block.




According to the illustrated chain block thus structured, the set nut


34


can be fixed in the first recess


32


opening at the small-diameter cylindrical portion


31


of the first hub


13


to share the use of substantially the same drive shaft


6


as the one used in a chain block having the same specification as the illustrated chain block but the overload protection mechanism


8


, such as, for example, the chain block whose principal part is shown in FIG.


6


. This can permit the component sharing between the chain block with the overload protection mechanism


8


and the chain block having the same specification but having no overload protection mechanism, for simplifying the manufacturing operation or process and reducing costs. Especially, even a small-sized chain block whose drive shaft


6


is intended to have a reduced length for size reduction of the entire chain block can share the use of the drive shaft


6


substantially the same as that of the chain block having the same specification but having no overload protection mechanism


8


, so that the effect is particularly significant.




It is noted that the chain block shown in

FIG. 6

has the same specification as the chain block of the embodied form of the invention, except the provision of the overload protection mechanism, and the same members are indicated by the same reference numerals in FIG.


6


. Though not shown in

FIG. 6

, one end portion of the drive shaft


6


is extended through the shaft hole of the load sheave


3


, and the second hub


11


of the transmission mechanism


10


having the mechanical brake


9


is coupled with the drive shaft


6


in such a manner as to be non-rotatable relative thereto. Immediately at the axial outside of the second hub


11


, the boss


22


A of the hand wheel


7


A is threadedly engaged with the drive shaft, instead of the first hub


13


of the overload protection mechanism


8


. Also, the set nut


34


is threadedly engaged with the axial end portion of the drive shaft


6


, with spaced at a predetermined interval from the boss


22


A of the hand wheel


7


A threadedly engaged with the drive shaft


6


. The set nut


34


is fixed to the end portion of the drive shaft


6


by the set pin


59


so that it cannot be moved in the axial direction. The axial movement of the hand wheel


7


A is restricted by the set nut


34


, with a check washer


60


splined to the drive shaft


6


between the set nut


34


and the boss


22


A of the hand wheel


7


A.




According to the chain block of this embodied form of the invention, the first lining plate


23


and the second lining plate


24


of the overload protection mechanism


8


are received in the second recess


56


and the third recess


57


formed in the boss


22


of the hand wheel


7


, respectively, so that the overload protection mechanism


8


can be reduced in size in the axial direction thereof by an amount corresponding to the thickness of the first and second lining plates


23


,


24


. Thus, combination of the arrangement of the set nut


34


being fixed in the first recess


32


opening at the small-diameter cylindrical portion


31


of the first hub


13


with the arrangement of the first and second lining plates


23


,


24


being received in the second and third recesses


56


,


57


can produce the advantageous effect that even a small-sized chain block having a considerably shortened drive shaft


6


can share the use of the drive shaft


6


substantially the same as that of the chain block having the same specification but having no overload protection mechanism


8


.




For provision of the overload protection mechanism


8


combined with the hand wheel


7


, it is necessary that the hand wheel


7


be rotatably supported on the first hub


13


. Accordingly, the hand wheel separate from the hand wheel


7


A of the chain block with no overload protection mechanism


8


must be prepared. The specific arrangement that the first recess


32


, the second recess


56


and the third recess


57


are formed in only the part of the first hub


13


and the hand wheel


7


enables the sharing of the drive shaft


6


substantially the same as that of the chain block having the same specification but having no overload protection mechanism


8


. Thus, the component sharing of the chain block, e.g. a small-sized one mentioned above, is intended by the manufacturing of minimum component counts and thereby significant simplification of the manufacturing operation or process of such a small-sized chain block and cost reduction are intended.




Further, since the first lining plate


23


and the second lining plate


24


are received in the second recess


56


and the third recess


57


formed in the boss


22


of the hand wheel


7


, the first lining plate


23


and the second lining plate


24


are prevented from being out of position with respect to the boss


22


of the hand wheel


7


. Therefore, a reliable braking of the hand wheel


7


can be achieved by the first and second lining plates


23


,


24


to provide improved reliability of the overload protection mechanism


8


.




According to the chain block of embodied form of the invention, in particular, since the first lining plate


23


and the second lining plate


24


placed at the opposite sides of the hand wheel


7


are received in the second recess


56


and the third recess


57


formed in the boss


22


of the hand wheel


7


at the both sides thereof, respectively, the overload protection mechanism


8


can be reduced in size in the axial direction thereof by an amount corresponding to the thickness of the first and second lining plates


23


,


24


. This can produce the result that even a small-sized chain block having a shortened drive shaft


6


can share the use of the drive shaft


6


substantially the same as that of the chain block having the same specification but having no overload protection mechanism


8


. Also, since the hand wheel


7


can reliably be braked by both of the first lining plate


23


and the second lining plate


24


, improved reliability of the overload protection mechanism


8


is yielded.




Next, the usage of the thus-constructed chain block thus constructed of the embodied form of the invention will be described.




First, description will be given on the hoist of or the lowering of a load which is less than a rated load preset by the load setting mechanism


21


. The load is suspended from a lower hook (not shown) provided at the end of the load chain


61


. When the hand chain


62


is operated to rotate the hand wheel


7


in the hoisting direction for the hoist of the load, the first hub


13


of the overload protection mechanism


8


which is in the state of rotatable with the hand wheel


7


is screwed forward along the drive shaft


6


to press the third lining plate


17


of the transmission mechanism


10


, and thereby the drive shaft


6


is driven in the normal rotation direction through the second hub


11


of the transmission mechanism


10


coupled with the drive shaft


6


in such a manner as to be non-rotatable relative thereto. When the drive shaft


6


is driven, the drive is transmitted to the load sheave


3


through the reduction gear mechanism


36


and thereby the load sheave


3


is rotated in the direction for the load to be hoisted up. As a result of this, the load suspended from the lower hook provided at the end of the load chain


61


running over the load sheave


3


is hoisted up. The suspended load is kept in its hoisted position by the operation of the mechanical brake


9


or by the engagement of the anti-reverse pawl


15


with the anti-reverse gear


12


.




When the hand chain


62


is operated to rotate the hand wheel


7


in the lowering direction for the lowering of the load, the first hub


13


of the overload protection mechanism


8


which is in the state of rotatable with the hand wheel


7


is screwed backward along the drive shaft


6


. Then, the engagement between the flange portion


19


of the first hub


13


and the third lining plate


17


of the transmission mechanism


10


is disengaged to release the mechanical brake


9


, and as such can allow the drive shaft


6


to freely rotate. As a result of this, the drive shaft


6


is rotated in the reverse rotation direction under the weight of load, so that the load is lowered down. On the other hand, the reverse rotation of the drive shaft


6


causes the first hub


13


of the overload protection mechanism


8


threadedly engaged with the drive shaft


6


to be screwed forward again along the drive shaft


6


, to press the third lining plate


17


of the transmission mechanism


10


. As a result of this, the mechanical brake


9


acts again to prevent the rotation of the drive shaft


6


in the reverse rotation direction. Thus, when the load is lowered down, the mechanical brake


9


is made active and inactive alternately so that the load sheave


3


can be allowed to rotate in the lowering direction little by little. The suspended load is lowered down in this manner.




When a load more than a rated load as preset by the load setting mechanism


21


is tried to be hoisted by the operation of the hand chain


62


to rotate the hand wheel


7


in the hoisting direction, slippage of the hand wheel


7


between the first lining plate


23


and the second lining plate


24


is caused by the action of the overload protection mechanism


8


to permit free rotation of the hand wheel


7


with respect to the first hub


13


. Thus, the hoist of any load more than the rated load of the chain block is prevented.




On the other hand, for example when the overload protection mechanism


8


is put into action in the hoist of a load more than the rated load, the hand wheel


7


is held slipped between the first lining plate


23


and the second lining plate


24


, and as such cannot permit the lowering of the load. In this situation, the hand wheel


7


can be restricted by the one-way mechanism


25


freely rotating in the lowering direction with respect to the first hub


13


to permit the lowering of even the load more than the rated load.




Referring now to

FIGS. 7 and 8

, there are shown sectional views of a principal part of the one-way mechanism


25


for illustration thereof. In the following, the description on the one-way mechanism


25


will be given with reference to

FIGS. 2

,


7


and


8


.




In

FIG. 2

, the one-way mechanism


25


is composed of a recess


49


formed in the outer periphery of the large-diameter cylindrical portion


30


of the first hub


13


, a pin


50


of an engaging member provided in the recess


49


, a spring


51


of an biasing means for biasing the pin


50


radially outwardly, and concave receiving portions


52


opening in the inner periphery of the receiving hole


58


in the boss


22


of the hand wheel


7


to receive the pin


50


therein.




The recess


49


is formed in rectangle in side configuration, opening from the outer periphery of the large-diameter cylindrical portion


30


into the radial inside of the same. The spring


51


is inserted in the recess


49


and the column-like pin


50


is disposed at a free end of the spring


51


, such that the pin


50


is biased radially outwardly of the large-diameter cylindrical portion


30


by the biasing force of the spring


51


. On the other hand, two receiving portions


52


are formed in the inner periphery of the boss


22


of the hand wheel


7


at positions that are opposed to each other or shifted from each other at 180°.




The receiving portions


52


are each composed, as shown in

FIGS. 7

,


8


, of a slanted surface


53


, extended obliquely, for guiding the pin


50


received in the receiving portion


52


to the inner periphery of the boss


22


when the hand wheel


7


is rotated in the hoisting direction; a retaining surface


55


, extended substantially along the radial direction of the inner periphery of the boss


22


, for permitting the pin


50


received in the receiving portion


52


to be retained in the inside of the receiving portion


52


when the hand wheel


7


is rotated in the lowering direction; and a flat surface


54


, extending continuously to the slanted surface


53


and the retaining surface


55


, for holding the pin


50


received in the receiving portion


52


.




Each slanted surface


53


is extended along a tangential direction to the inner periphery of the boss


22


of the hand wheel


7


and also is smoothed out at the boundary between the inner periphery of the boss


22


of the hand wheel


7


and the slanted surface


53


. The slanted surfaces


53


of the receiving portions


52


that are located in opposition to each other are formed to be parallel with each other.




According to the one-way mechanism


25


thus constructed, when the hand wheel


7


is rotated in the hoisting direction for the hoist of a load more than a rated load, the hand wheel


7


is freely rotated with respect to the first hub


13


. During this, every time the pin


50


of the one-way mechanism


25


faces the receiving portions


52


formed in the inner periphery of the boss


22


of the hand wheel


7


, the pin


50


which is normally biased radially outwardly or toward the inner periphery of the boss


22


of the hand wheel


7


is received in the receiving portions


52


, while on the other hand, the as-received pin


50


is smoothly guided again to the inner periphery of the boss


22


of the hand wheel


7


along the slanted surface


53


formed in each of the receiving portions


52


(this state is shown in FIG.


7


). Since the pin


50


is smoothly guided again to the inner periphery of the boss


22


of the hand wheel


7


through the slanted surfaces


53


which are each extended along a tangential direction to the inner periphery of the boss


22


of the hand wheel


7


and smoothed out at the boundary between the inner periphery of the boss


22


of the hand wheel


7


and the slanted surface


53


, the pin


50


received in the receiving portions


52


can be guided smoothly to the inner periphery of the boss


22


of the hand wheel


7


just the way it is, without causing the pin


50


received in the receiving portions


52


to rattle.




As a result of this, a possible problem that the pin


50


may be caught in the receiving portion


52


so that a load more than a rated load may be hoisted in an unstable state or a possible damage of the pin


50


and the receiving portion


52


can be minimized. Also, the rattling of the hand wheel


7


that may be caused when rotated can be minimized and a possible damage to the first hub


13


and the hand wheel


7


can be minimized.




On the other hand, for example, even when the overload protection mechanism


8


is put into action in the hoist of a load by the application of load more than a rated load, such that the hand wheel


7


is held slipped between the first lining plate


23


and the second lining plate


24


, the hand wheel


7


can be restricted freely rotating in the lowering direction with respect to the first hub


13


by the pin


50


of the one-way mechanism


25


being received in the receiving portion


52


. This can permit the lowering of even a load more than the rated load. At that time, the pin


50


received in the receiving portion


52


is well retained by the retaining surfaces


55


formed in the receiving portion


52


(this state is shown in FIG.


8


). Thus, the free rotation of the hand wheel


7


with respect to the first hub


13


can be reliably restricted and thereby the lowering of even a load more than a rated load can be ensured.




When the hand wheel


7


is in the state in which it freely rotates in the hoisting direction with respect to the first hub


13


, every time the hand wheel


7


rotates one turn, the pin


50


is received in the receiving portions


52


provided at the opposed positions. Since the receiving portions


52


have the slanted surfaces


53


which are so formed as to be substantially parallel with each other, the pin


50


, even when received in any of the receiving portions


52


, is guided into the inner periphery of the boss


22


of the hand wheel


7


along the slanted surfaces


53


under the same condition. For example, in the hand operated chain block of the embodied form of the invention in which even a little pulling of the hand chain


62


causes the hand wheel


7


to rotate a couple of turns with respect to the first hub


13


, so as to give several opportunities of the pin


50


to confront the receiving portions


52


, since the receiving portions


52


are provided at the opposed positions and also the slanted surfaces


53


are so formed as to be substantially parallel with each other, even when the pin


50


is given many opportunities to confront the receiving portions


52


, the pin


50


is received cliclically in the receiving portions


52


as the hand wheel


7


rotates and is guided to the inner periphery of the boss


22


of the hand wheel


7


along the slanted surface


53


under the same condition. Thus, regular operations can be ensured, and as such can produce improved durability and reliability of the one-way mechanism


25


.




On the other hand, when the hand wheel


7


is rotated in the lowering direction, the pin


50


is received in either of the receiving portions


52


provided in the opposed positions during one-turn of the hand wheel


7


. Thus, the pin


50


is surely brought into engagement in the receiving potions


52


until the hand wheel


7


rotates one turn, thus enabling the immediate lowering of load.




Thus, even in a hand operated chain block, like the chain block of the embodied form of the invention, in which even a little pulling of the hand chain


62


in the hoisting direction causes the hand wheel


7


to rotate with respect to the first hub


13


a couple of turns during which the pin


50


confronts the receiving portions


52


several times, when the hand wheel


7


is rotated in the hoisting direction, smooth free rotation of the hand wheel


7


with respect to the first hub


13


can be ensured, while also, when the hand wheel


7


is rotated in the lowering direction, the pin


50


can smoothly be received in the receiving portions


52


to ensure the smooth lowering of load.




Especially, in a small-sized chain block having the hand wheel


7


having a small diameter, like that of the embodied form of the invention, in which even a little pulling of the hand chain


62


causes the pin


50


to confront the receiving portions


52


several times, good operation of the pin


50


and the receiving portions


52


can be ensured by the inventive arrangement above and, thus, further improved durability and reliability of the one-way mechanism


25


can be provided.




While the two receiving portions


52


in the one-way mechanism


25


of the embodied form of the invention are formed in the inner periphery of the receiving hole


58


of the boss


22


of the hand wheel


7


at the opposed positions, the receiving portions may alternatively be formed at different positions from the opposed positions. Further, one or three or more receiving portions may alternatively be formed. It should be noted, however, that too many receiving portions


52


would cause an increased rattling of the hand wheel


7


with respect to the first hub


13


, while on the other hand, only one receiving portion


52


could not provide the immediate lowering of load as mentioned above. In view of this, it is most preferable for the small-sized chain block like that of embodied form of the invention that two receiving portions be formed at opposed positions, in terms of improvement in operability, durability and reliability of the chain block.




While in the embodied form of the invention the second recess


56


and the third recess


57


are formed in the boss


22


of the hand wheel


7


at the both sides thereof, the recess may alternatively be formed in the boss at either side thereof. Further, instead of the pin


50


, a ball may be used in the one-way mechanism


25


.




While the illustrative embodiments of the present invention is provided in the above description, such is for illustrative purpose only and it is not to be construed restrictively. Modification and variation of the present invention that will be obvious to those skilled in the art is to be covered in the following claims.



Claims
  • 1. A chain block comprising:a load sheave with which a load chain is engageable; a hand wheel with which a hand chain is engageable; a transmission mechanism including a mechanical brake interposed between said hand wheel and said load sheave; an overload protection mechanism that supports said hand wheel and permits said hand wheel to freely rotate in a hoisting direction when a load more than a rated load is applied to said load sheave; and a drive shaft, passed through said load sheave, said transmission mechanism and said overload protection mechanism, to transmit drive applied from said hand wheel to said load sheave, wherein said overload protection mechanism includes a hub member threadedly engaged with said drive shaft and supporting thereon said hand wheel in a freely rotatable manner; and a one-way mechanism that permits said hand wheel to freely rotate in a hoisting direction with respect to said hub member and restricts said hand wheel freely rotating in a lowering direction; wherein said one-way mechanism includes a recess formed in an outer periphery of said hub member; an engaging member provided in said recess and normally biased radially outwardly; and a concave receiving portion, opening in an inner periphery of a boss of said hand wheel, to receive said engaging member therein; wherein said receiving portion includes a slanted surface extended obliquely to guide said engaging member received in said receiving portion to said inner periphery of said boss of said hand wheel when said hand wheel is rotated in said hoisting direction; and a retaining surface, extended substantially along a radial direction of said inner periphery of said boss, to permit said engaging member received in said receiving portion to be retained in an inside of said receiving portion when said hand wheel is rotated in a lowering direction; and wherein said slanted surface formed in said receiving portion is extended along a tangential direction to said inner periphery of said hand wheel and also is smoothed out at a boundary between said inner periphery of said boss of said hand wheel and said slanted surface.
  • 2. A chain block according to claim 1, wherein there are provided two receiving portions which are opened in said inner periphery of said hand wheel at positions opposed to each other and of which slanted surfaces are formed to be substantially parallel to each other.
Priority Claims (1)
Number Date Country Kind
10-301896 Oct 1998 JP
US Referenced Citations (3)
Number Name Date Kind
5305989 Nishi et al. Apr 1994
5351937 Nishi et al. Oct 1994
5472171 Nishi et al. Dec 1995
Foreign Referenced Citations (5)
Number Date Country
39-8908 Apr 1964 JP
55-14197 Jul 1978 JP
7-12912 Feb 1995 JP
7-8557 Mar 1995 JP
7-157290 Jun 1995 JP