Patent Grant
6883617
This application relates to pneumatic tools and, in particular, to control mechanisms therefore. The application relates specifically to shutoff mechanisms for disconnecting a pneumatic motor from a supply of pressurized pneumatic fluid.
Pneumatically operated tools of varying types are known, including a wide variety of pneumatically-operated hand tools. Many such tools are designed for torque application to a workpiece and may include devices such as screw or nut driving tools, impact wrenches and the like. Such tools are typically provided with a trigger valve mechanism to manually control the flow of pressurized pneumatic fluid, typically air, to an air motor. Some pneumatic tools are also provided with automatic shutoff mechanisms, responsive to a particular event or condition, such as the application of a predetermined torque level. Such prior shutoff arrangements have typically been rather complex, bulky, expensive, relative slow acting and/or difficult to adjust.
There is disclosed herein an improved technique for automatic shutoff of a pneumatic tool.
The technique includes use of a valve member biased to a normal open position and a trip apparatus responsive to application of a predetermined torque by the tool for moving the valve member into the pressurized airflow path a distance sufficient that the airflow itself will then drive the valve member to a closed position, shutting off airflow to the motor.
In a mechanical embodiment of the shutoff mechanism, the trip assembly includes an inertia member coaxial with the motor rotor shaft and a helical coupling between the inertia member and the rotor shaft such that they rotate together at constant velocity, but that upon rapid deceleration of the rotor shaft the inertia member moves rotatably and axially relative to the rotor shaft to a position spaced from the valve member a distance inversely proportional to the torque applied by the tool, the trip assembly moving the inertia member into engagement with the valve member upon application of the predetermined torque.
Where the pneumatic tool is an impact tool, in one mechanical embodiment of the shutoff mechanism the inertia member is biased to a home position spaced a maximum distance from the valve member and, in response to each impact, moves toward the valve member a distance proportional to the torque applied and then back to the home position.
In another embodiment, the trip assembly includes a clutch mechanism responsive to movement of the inertia member from its home position for preventing its return to the home position until the valve has been tripped, and preventing premature tripping upon transition from free run down of a fastener to initial torque resistance.
In another embodiment, the shutoff mechanism is electromechanically operated, the valve member being a solenoid actuated in response to a torque sensing device.
There is also a disclosed method for automatically shutting off a pneumatic torque-applying tool when a predetermined torque is reached by disposing a valve member adjacent to the pressured airflow path upstream of the motor and, when the predetermined torque is reached, moving the valve member from its open position to a trip position disposed in the airflow path and spaced from the open position a distance such that the valve member is exposed to a pressured air load which drives it to the closed position.
For the purpose of facilitating an understanding of the subject matter sought to be protected, there are illustrated in the accompanying drawings embodiments thereof, from an inspection of which, when considered in connection with the following description, the subject matter sought to be protected, its construction and operation, and many of its advantages should be readily understood and appreciated.
Referring to
Referring now also to
The shutoff mechanism 30 also includes a valve seat 40 (
The shutoff mechanism 30 also includes an end plate 50 which has a front face 51 (see
Referring in particular to
The shutoff mechanism 30 also includes a shaft extension 70 having a coupling end 71 with flats formed thereon and mateably receivable in the stub shaft 23 of the motor rotor 17 for rotation therein. Just rearwardly of coupling end 71 is a radially outwardly projecting annular flange 73 which is disposed in the central bore 36 of the valve plate 31 and is encircled by a lip seal 74. Formed in the outer surface of the shaft extension 70 rearwardly of the flange 73 are a plurality of circumferentially spaced helical grooves 75, which may be three in number, in each of which is seated a corresponding ball 76. The shaft extension 70 is coaxially encircled by an annular actuation member in the form of an inertia ring 80, which has plural helical grooves 81 formed in the inner surface thereof, respectively cooperating with the grooves 75 in the shaft extension 70 for forming helical tracks for the balls 76 and confining the balls therein. Provided on the rear face of the inertia ring 80 is an annular thrust bearing 82, which is engaged with an annular end flange 83 of a cylindrical thrust washer 84. The rear end of the cylindrical thrust washer 84 is counterbored to define an annular shoulder 85, against which is seated one end of a helical compression adjustment spring 86, the other end of which is seated against the flange 66 of the adjustment screw 65 (see FIG. 2).
The cylindrical thrust washer 84 extends through the center of an annular valve member in the nature of a disc valve 87, which seats in the counterbore 37a of the valve plate 31. The disc valve 87 has a annular counterbore 88 formed in the rear face thereof, in which is seated one end of a helical compression reset spring 89, the rear end of which is seated against the flange 63 of the plug insert 60 (see FIG. 2). It will be appreciated that the disc valve 87 is resiliently retained by the reset spring 89 in a normal open position seated in the valve plate counterbore 37a. This spring force also retains the plug insert 60 seated in the end plate counterbore 57. Also, the thrust washer 84 and the inertia ring 80 are biased forwardly to a normal rest or home position, shown in the drawings, by the adjustment spring 86 with a force which can be varied by the adjustment screw 65.
In operation of the air motor 15 in a forward or fastener-tightening direction, when the trigger valve assembly 14 is actuated, pressurized airflow will pass upwardly through the handle portion 13 of the housing, through the open trigger valve assembly 14, and then rearwardly through the inlet port 34 of the valve plate 31 to the rear face thereof, and then upwardly through the channel formed by the Y-shaped grooves 35 and 45, as indicated by the arrows in
As is well known, when a fastener is being run in, there will initially be negligible torque and the motor rotor 17, shaft extension 70 and inertia ring 80 will all rotate together. As torque builds up, the impact mechanism 21 will begin imparting impulses or impacts to the work piece. With each such impact, the rotor 17 and shaft extension 70 will momentarily stop. However, the inertia ring 80, which is not fixed to the shaft extension 70, will try to continue rotating. The continued rotation of the inertia ring 80 relative to the shaft extension 70 will cause the inertia ring 80 to move axially rearwardly by operation of the helical ball-and-groove coupling to the shaft extension 70, thereby driving the thrust washer 84 axially rearwardly against the urging of the adjustment spring 86. The extent of the axial movement will be proportional to the amount of torque applied. Immediately after the rotor 17 and the shaft extension 70 resume rotation, the thrust washer 84 and inertia ring 80 will be returned forwardly to their home positions under the urging of the adjustment spring 86.
Typically, each successive impact will exert a slightly higher torque than the preceding one. Thus, with each impact of the impact mechanism 21, the inertia ring 80 will move axially a slightly greater distance rearwardly, returning each time to its home position between impacts. Eventually, when a predetermined torque level is reached, corresponding with the adjustment setting of the adjustment screw 65, the inertia ring 80 will move rearwardly a sufficient distance that the end flange 84 of the thrust washer 84 will engage the front face of the disc valve 87, unseating it and pushing it rearwardly from its normal open position a slight distance into the pressurized airflow. This will expose the front face of the disc valve 87 to the pressurized airflow, the pressure of which will then slam the disc valve 87 rearwardly the rest of the way to a closed position, sealed against the O-rings 44 of the valve seat 40, thereby shutting off airflow through the arcuate apertures 48 in the valve seat 40, blocking airflow to the air motor 15 and shutting it off. It will be appreciated that the O-rings 44 could be located on the disc valve 87 instead of on the valve seat 40 (see FIG. 2). As soon as the operator releases the trigger valve assembly 14, the pressurized airflow from the source will be shut off, relieving the air pressure on the disc valve 87, and permitting it to return to its normal open position under the urging of the reset spring 89.
Thus, automatic shutoff of the tool 10 is accomplished at a predetermined torque level preventing over torquing of the work piece. It is significant that the disc valve 87 need be moved only a very small distance from its normal open position, typically in the range of from about 0.01 inch to about 0.02 inch, to permit the pressurized airflow to take over and drive the disc valve 87 to its closed position, thereby using the pressurized airflow to perform most of the work in overcoming the force exerted by the reset spring 89 and effecting a very rapid shutoff. The shutoff mechanism is easily adjusted to vary the shutoff torque, is very compact, with all parts located at the rear of the air motor, and is relatively inexpensive.
If the reversing valve assembly 25 is actuated to operate the air motor 15 in a reverse or fastener-loosening direction, the pressurized airflow path will be different, bypassing the shutoff mechanism 30, which is not needed, since there will be no torque limit to be concerned with. Thus, in this case, the airflow will be directed so that, at the front face 32 of the valve plate 31, it will not enter the inlet port 34, but will rather enter the reverse groove 39, which channels it directly to a reverse-direction inlet port in the motor rear end plate 19 without going past the disc valve 87.
Referring now also to
The shutoff mechanism 90 includes an inertia ring 100 which coaxially encircles the shaft extension 91 and has plural helical grooves 101 formed on the inner surface thereof for cooperation with the grooves 92 in the shaft extension 91 to form helical tracks for the balls 93. Mounted at the rear end of the inertia ring 100 is a thrust bearing 102 which engages the forward end of a thrust washer 103, which has at its rearward end a reduced-diameter cylindrical portion which is axially slotted to define a plurality of equiangularly spaced fingers 104, the inner surfaces of which are counterbored to define a part-annular shoulder 105.
The forward end of the adjustment spring 86 seats against the shoulder 105 on the fingers 104 of the inertia ring 100. The shutoff mechanism 90 also includes a disc valve 106, which is similar to the disc valve 87 described above and again seats in a normal open position in the counterbore 37a of the valve plate 41. However, the disc valve 106 is provided with a counterbore 107 and with a plurality of equiangularly spaced arcuate apertures 108 therethrough, shaped and dimensioned for respectively receiving therethrough the fingers 104 of the inertia ring 100. The disc valve 106 is retained in its open position by the reset spring 89 in the same manner as was described above with respect to the disc valve 87.
Disposed coaxially within the inertia ring 100 is a cylindrical reset sleeve 110 which has a main body 111 disposed in use coaxially between the helically grooved portions of the shaft extensions 91 and the inertia ring 100, the main body 111 having plural circumferentially extending slots 112 therein for respectively receiving the balls 93 therethrough. The main body 111 is integral at its rearward end with a radially inwardly extending annular shoulder 113, which is in turn integral at its radially inner end with a rearwardly projecting, reduced-diameter end portion 114 which has a plurality of equiangularly spaced axial slots 115 formed therein defining fingers 116, the outer surfaces of which are grooved adjacent to their distal ends for receiving therein a washer 117 and a retaining ring 118. When assembled, the radial spokes 96 of the shaft extension 91 will respectively project radially outwardly through the slots 115 of the reset sleeve 110, but remain inside the fingers 104 of the inertia ring 100, as can best be seen in
The operation of the shutoff mechanism 90 is similar to that of the shutoff mechanism 30, described above. However, in this case, with each impact of the impact mechanism 21, when the inertia ring 100 moves axially rearwardly relative to the shaft extension 91, it will not return to its normal home position before the next impact. Rather, the reset sleeve 110 cooperates with the sloping helical grooves 92 in the shaft extension 91 to operate as a clutch to prevent return of the inertia ring 100 between impacts. More specifically, it can be seen that the reset spring 119 continuously urges the reset sleeve 100 and, thereby, the balls 93, forwardly, continuously tending to wedge the balls 93 between the radially converging helical grooves 92 and 101. Thus, in response to an impact, the inertia ring 100 is permitted to move rearwardly through the helical groove-and-ball coupling action described above, but is prevented from returning forwardly to its home position by its wedging action of the balls. Thus, there is a step-wise or additive movement of the inertia ring 100 rearwardly until, when the predetermined torque is reached, the thrust washer 103 engages and unseats the disc valve 106, which is slammed to its closed position by the pressurized airflow stream in the manner described above. As the disc valve 106 moves to its closed position, it engages the washer 117 on the reset sleeve fingers 116, pulling the reset sleeve 110 and, thereby, the balls 93, rearwardly, releasing the clutch wedging action and permitting the inertia ring 100 to return to its home position under the urging of the adjustment spring 86. The disc valve 106 will be reset after release of the trigger valve assembly 14, in the same manner as described above.
Referring now to
The shutoff mechanism 120 includes a trip assembly 129, which includes a shaft extension 70A which is substantially the same as the shaft extension 70, described above, except that its helical grooves 75A are disposed adjacent to its distal end rather than adjacent to the flange 73. An inertia ring 130 encircles the shaft extension 70A and has helical grooves 131 on its inner surface which cooperate with the grooves 75A on the shaft extension 70A to perform helical tracks for balls 76A, in the manner described above, except that the helices are curved in the opposite direction. The inertia ring 130 has a radially inwardly extending annular end flange 132 at its forward end and has formed axially in the front surface thereof an annular groove 133. Encircling the shaft extension 70A adjacent to the flange 73 is an annular thrust washer 134 which is channel-shaped in transverse section and is secured to the valve plate 31 as by screws 135 (one shown). The thrust washer 134 seats a thrust bearing 136. A helical reset spring 137 has one end thereof seated against the thrust washer 134 and the other end thereof seated in the groove 133 of the inertia ring 130 for resiliently urging the inertia ring 130 rearwardly. A suitable magnetic sensor 138 is seated in a radial cavity 139 in the valve plate 31 immediately above the inertia ring 130.
A disc valve 140 is seated in the counterbore 37a of the valve plate 31 so that it is spaced a slight distance rearwardly of the inertia ring 130 in its normal home position illustrated in the drawings. Formed in the rear face of the disc valve 140 is an annular spring groove 141 in which is seated one end of a helical reset spring 142, the rear end of which is seated in a counterbore 143 in the end plate 121 for resiliently urging the disc valve 140 to its normal open position. Disposed in the central bore of the end plate 121 is a solenoid 145, which has a forwardly extending plunger or shaft 146 which extends through a central opening in the disc valve 140 and is connected to a suitable retainer on the front side of the disc valve 140. A circuit board 147 is seated in the circuit board recess 123 of the end plate 121 and is electrically connected to the solenoid 145 and to the sensor 138 by suitable leads (not shown). It will be appreciated that the circuit board 147 may include a suitable display which is visible through the display window 126 in the end cap 125, and may also be provided with suitable input devices, such as a push buttons or the like, which may extend through suitable apertures (not shown) in the end cap 125.
In operation, the inertia ring 130 will move axially back and forth in response to impacts delivered by the impact mechanism 21, in much the same way as was described above in connection with the shutoff mechanism 30, except that in this case the inertia ring 130 will move forwardly when the rotor extension 70A stops and will return rearwardly to its home position. These movements will be sensed by the sensor 138, which will output an electrical signal having a value proportional to the axial extent of the movement, which signal will be compared by a microprocessor or other suitable circuitry on the circuit board 147, with a preset signal level corresponding to a predetermined torque value, which may be input by the user through the input means described above. When the predetermined torque level is reached, the circuit board 147 will output a signal to the solenoid 145, which will actuate to pull the disc valve 140 a slight distance rearwardly into the air stream, causing it to slam to a closed position in the manner described above.
Referring now to
While, in the illustrated embodiments, the pneumatic tool 10 is a hand tool, it will be appreciated that the automatic shutoff principles disclosed herein would be applicable to other types of pneumatic devices. Also, while the illustrated embodiments are utilized in a torque-applying tool, it will be appreciated that the automatic shutoff principles disclosed herein, particularly those in the electromagnetic embodiments of
From the foregoing, it can be seen that there has been provided an improved automatic shutoff mechanism for a pneumatic tool which is relatively simple, compact, inexpensive, fast-acting and easy to adjust.
The matter set forth in the foregoing description and accompanying drawings is offered by way of illustration only and not as a limitation. While particular embodiments have been shown and described, it will be apparent to those skilled in the art that changes and modifications may be made without departing from the broader aspects of applicants' contribution. The actual scope of the protection sought is intended to be defined in the following claims when viewed in their proper perspective based on the prior art.
This application claims the benefit of the filing date of U.S. Provisional Application No. 60/379,071, filed May 9, 2002, now abandoned.
| Number | Name | Date | Kind |
|---|---|---|---|
| 2727598 | Mitchell et al. | Dec 1955 | A |
| 2768546 | Amtsberg | Oct 1956 | A |
| 2973069 | Sturrock | Feb 1961 | A |
| 3315754 | Holdo et al. | Apr 1967 | A |
| 3368631 | MacNaughton | Feb 1968 | A |
| 3643749 | Pauley | Feb 1972 | A |
| 3703933 | Schoeps | Nov 1972 | A |
| 3920082 | Dudek | Nov 1975 | A |
| 3930764 | Curtiss | Jan 1976 | A |
| 4004859 | Borries | Jan 1977 | A |
| 4113080 | Thackston et al. | Sep 1978 | A |
| 4359107 | Smith | Nov 1982 | A |
| 4402138 | Glöckle et al. | Sep 1983 | A |
| 4899598 | Gumaste et al. | Feb 1990 | A |
| 4903783 | Rushanan et al. | Feb 1990 | A |
| 5155421 | Hansson | Oct 1992 | A |
| 5201373 | Bloechle | Apr 1993 | A |
| 5289885 | Sakoh | Mar 1994 | A |
| 5366132 | Simonelli | Nov 1994 | A |
| 5492185 | Schoeps et al. | Feb 1996 | A |
| 5544710 | Groshans et al. | Aug 1996 | A |
| 5573074 | Thames et al. | Nov 1996 | A |
| 5704435 | Meyer et al. | Jan 1998 | A |
| 5868208 | Peisert et al. | Feb 1999 | A |
| 5887335 | Garshells | Mar 1999 | A |
| 5984020 | Meyer et al. | Nov 1999 | A |
| 6158526 | Ghode et al. | Dec 2000 | A |
| Number | Date | Country |
|---|---|---|
| 0502748 | Jun 1996 | EP |
| Number | Date | Country | |
|---|---|---|---|
| 20030226674 A1 | Dec 2003 | US |
| Number | Date | Country | |
|---|---|---|---|
| 60379071 | May 2002 | US |
