US3512590A - Automatic throttle torque-responsive power tool - Google Patents

Description

D. W. TIBBOTT AUTOMATIC THROTTLE TORQUE-RESPONSIVE POWER TOOL Filed June 12, 1968 q 65 so If 47 I 6 44 0 43 ,55 48 I Q J. f, 4 5a 3 Sheets-Sheet 2 FIG. 6

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United States Patent 3,512,590 AUTOMATIC THROTTLE TORQUE-RESPONSIVE POWER TOOL David W. Tibbott, Phillipsburg, N.J., assignor to Ingersollgland Company, New York, N.Y., a corporation of New ersey Filed June 12, 1968, Ser. No. 736,343 Int. Cl. B25b 23/14 US. Cl. 17312 14 Claims ABSTRACT OF THE DISCLOSURE A fluid-operated rotary power tool having a motor supply valve seat which is moved into engagement with the valve in response to a clutch reaching a predetermined torque load, thereby closing the valve and stopping the motor. The movable valve seat is normally latched against movement and the torque responsive clutch releases the latch upon reaching the predetermined torque.

BACKGROUND OF INVENTION This invention relates to the art of power-operated rotary tools such as power screwdrivers and power wrenches.

It is conventional in the power tool art to provide a power wrench or screwdriver with a torque-responsive clutch which automatically releases the tool spindle from its motor when the torque load rises to a selected magnitude. It is also conventional in the air of fluid-operated power tool art to interconnect the torque-responsive clutch to the supply valve for the motor by a means that causes the valve to shut when the clutch releases. Prior tools accomplishing the above result have used a telescoping connection between the clutch and the valve and this connection is allowed to collapse when the clutch opens resulting in allowing the valve to close and stop the motor.

SUMMARY OF INVENTION The principal object of this invention is to provide a new type of mechanism which accomplishes the above results and eliminates the telescoping connection between the clutch and the valve.

Other important objects of this invention are: to provide a novel supply valve for a power tool; to provide a simplified shut-off mechanism for an air-operated power tool; and to provide a valve having one movable element for opening the valve and another movable element for closing the valve.

In general, the foregoing objects are provided by a rotary tool having a supply valve which is opened by the operator to start the motor and a movable valve seat which is latched in a normally stationary position to stop it from following the valve as it moves -to its open position. Means is provided for the tool to measure the torque load on the tool and, in response to a predetermined torque load, to unlatch the movable valve seat whereby the valve seat moves into engagement with the valve to close the valve and to stop the motor. Thereafter, the operator allows the valve to return to its normally closed position. In returning to its normally closed position, the valve will carry the movable valve seat with it to its normally latched position.

BRIEF DESCRIPTION OF DRAWINGS The invention is described in connection with the accompanying drawings wherein:

FIG. 1 is a longitudinal section of an air-operated power screwdriver employing a torque-responsive shutoff mechanism following the principles of this invention;

FIG. 2 is a section taken on line 22 in FIG. 1;

Patented May 19, 1970 FIG. 3 is a fragmentary section taken on line 33 in FIG. 1;

FIG. 4 is a fragment of FIG. 1 illustrating the air supply valve of the tool motor in its open position;

FIG. 5 is a view similar to FIG. 4 illustrating the valve mechanism immediately following the rearward movement of the valve seat to its engaged position with the valve to shut off air flow to the tool motor;

FIG. 6 is a longitudinal section of an air-powered angle wrench using the mechanism of this invention and illustrating the valve in its normally seated and closed position;

FIG. 7 is a fragment of FIG. 6 illustrating the valve in its open position;

FIG. 8 is a view similar to FIG. 7 illustrating the valve mechanism following the rearward movement of the valve seat to its engagement with the valve to shut off air flow to the tool motor;

FIG. 9 is a fragmentary vertical section of a third embodiment showing a screwdriver valve mechanism having the latch mechanism carried on the valve seat sleeve;

FIG. 10 is a fragmentary vertical section of a fourth embodiment showing a screwdriver valve mechanism having a ball latch; and

FIG. 11 is a fragmentary vertical section of a fifth embodiment showing a screwdriver valve mechanism having a pilot-operated valve.

DESCRIPTION OF I HE PREFERRED EMBODIMENTS The power-operated screwdriver 1 shown in FIGS. 1 to 5 includes a casing 2 housing an air motor 3 having a drive shaft 4. The screwdriver 1 has an air hose fitting 5 threaded into the rear end of the casing 2 for coupling to an air hose (not shown) for feeding air to the tool. The front nose 6 of the screwdriver 1 carries a screw finder 7 and a screwdriving blade 8 adapted to engage the slot of a screw. The blade 8 i detachably mounted in a spindle 9 which is rotatably and slidably mounted in a journal bearing 10 integrally formed in the interior of the casing. The bearing 10 carries a rearwardly facing shoulder '11 which engages a portion of the spindle 9 to limit its forward movement. The motor drive shaft 4 is mounted in the bearing 12. All of the foregoing structure is conventional in the screwdriver art.

The spindle 9 is interconnected to the motor drive shaft 4 by a torque responsive clutch mechanism 14 which releases under a predetermined torque load. The clutch mechanism 14 includes a hollow clutch shaft 15 having its rear end slidably splined in a socket 16 formed in the motor drive shaft 14, thus allowing the clutch shaft 15 to slide rearwardly into the socket 16 for a limited distance while maintaining a continuous driving connection therebetween.

The front end of the clutch shaft 15 is attached to the spindle 9 by a connection which allows the clutch shaft 15 to rotate relative thereto while being unable to slide axially relative to the spindle 9. This connection is formed by the front end of the clutch shaft 15 being seated in a rearwardly-opening bore 17 provided in the spindle 9 with several balls 18 being located in mating annular grooves formed in the clutch shaft 15 and the interior wall of the bore 17.

The clutch shaft 15 is urged forwardly by a light spring 20 engaged between the bearing 12 mounting the drive shaft 4 and a washer 22 resting on a rearwardly facing shoulder formed on the clutch shaft 15. As a result, the light spring 20 biases the spindle 9 against the shoulder 11 of the bearing 10. The clutch shaft 15 and spindle 9 are moved rearwardly in the tool by an operator forcing the tool blade 8 downwardly against a screw. The depth of the socket 16 in the drive shaft 14 limits the rearward movement of the clutch shaft 15.

The clutch shaft 15 carries an integral clutch plate 24 which contains a series of holes spaced around its center. These holes house corresponding clutch balls 25 adapted to seat in mating ball seats or recesses provided in the rear face of the spindle 9. The balls 25 are pressed into their seats in the spindle 9 by a presser ring 26 which is urged forward by a clutch spring 27. The rear end of the clutch spring 27 seats against a collar 28 which is keyed on the clutch shaft 15 and is held in place by a nut 29 threaded on the clutch shaft 15. A detent ball 30 is located in the rear face of the collar for seating in any of a series of cavities in the front face of the nut 29 to latch the nut 29 in its adjusted position. The nut 29 includes 'gear teeth 31 on its periphery for engaging with a Jacobs chuck key (not shown) to aid in turning the nut 29 to adjust the load on the clutch spring 27. The load on the clutch spring 27 will determine the magnitude of torque load at which the torque clutch 14 will release.

The presser ring 26 engages a cross bar 32 which slides in a diametrical slot 33 formed in the clutch shaft 15 and abuts the forward end of a push-rod 34 which extends rearwardly from the cross bar 32 through the hollow clutch shaft 15 and the drive shaft 4 of the motor 3. As a result of the foregoing arrangement, the disengagement of the clutch under torque will move the presser ring 26 rearwardly on the clutch shaft resulting in moving the push-rod 34 rearward.

The air fitting extending from the rear end of the casing 2 opens into a valve chamber 36 housing a valve 37 resting on a stationary valve seat 38. The valve 37 is attached to the rear end of the push-rod 34 and closes the top end of a valve bore 39. The valve bore 39 is connected to a motor supply passage 40 extending to the tool motor 3. The valve 37 controls the flow of air from the valve chamber 36 to the motor 3 via the bore 39 and the motor supply passage 40.

When the screwdriver is initially pressed downwardly on a screw, the spindle 9, the clutch shaft 15, push-rod 34 and valve 37 move rearwardly in the tool to raise the valve 37 above the stationary valve seat 38, as shown in FIG. 4, and allow air to flow through the motor supply passage 40 to the motor 3. This air will drive the motor 3 and the screwdriver will drive the screw engaged by the blade 8.

As the screw is driven home, it will become tight and the torque load on the spindle 9 will rise until it reaches the predetermined torque load that will cause the clutch mechanism 14 to release and slip. The release of the clutch mechanism 14 is caused by the clutch balls 25 rolling out of their seats or pockets on the rear end of the spindle 9 and this unseating movement of the clutch balls 25 forces the push-rod 34 and valve 37 further rearwardly in the tool. This additional rearward movement releases a movable valve seat sleeve 42 which is slidably mounted in the valve bore 39. A spring 43 urges the sleeve 42 rearwardly in the valve bore 39 so that the release of the valve seat sleeve 42 allows it to move rearward into engagement with the valve 37. The engagement of the valve seat sleeve 42 with the valve 37 closes the flow of air from the valve chamber 36 to the motor 3.

The latch mechanism for the valve seat sleeve 42 includes a pivoted latch 44 having a tongue 45 adapted to engage an annular groove 46 provided in the periphery of the valve seat sleeve 42. The tongue 45 is beveled on its top. A light spring 47 urges the latch tongue 45 into the groove 46. The latch includes a release arm 48 projecting into the path of an enlarged abutment 49' on the push-rod 34 and located so that the additional rearward movement of the push-rod 34, in response to the release of the clutch mechanism 14, will engage the release arm 48 and rotate the latch 44 to release the latch tongue 45 from the annular groove 46 in the valve seat sleeve 42. As soon as e the va ve seat sleeve 42 is released, it is moved upward by the spring 43 to engage the valve 37, thereby stopping the flow of air from the valve chamber 36 to the motor 3, as shown in FIG. 5. As a result, the motor 3 is stopped. Thereafter, the operator lifts the screwdriver 1 from the screw, thus allowing the spindle 9 to move forward to seat on the bearing shoulder 11. This movement allows the push-rod 34 and valve 37 to move forward until the valve 37 is again seated on the stationary valve seat 38. The forward movement of the valve 37 carries the valve seat sleeve 42 forwardly with it and the latch tongue returns to a latched position in the annular groove 46. The screwdriver 1 is now in the condition as shown in FIG. 1. At this time the screwdriver is ready for another cycle.

SECOND EMBODIMENT The second embodiment is an angle wrench 54 illustrated in FIGS. 6 to 8. The angle wrench 54 includes a casing 55 having an air hose fitting 56 fixed to its rear end and a socket arbor 57 projecting from its front end at right angles to its length. The wrench 54 contains a motor 58 and a throttle button 59 adapted to be pressed to feed air to the motor 58. All of the foregoing structure is conventional in the power wrench art.

In describing the novel structure in the angle wrench 54, elements which are similar or identical to those found in the first embodiment will carry identical reference numbers.

The torque responsive clutch mechanism 14 used in the second embodiment 54 is identical to the clutch mechanism 14 of the first embodiment except that the clutch shaft 15 cannot move rearwardly for a short distance. In brief, the spindle 9 drives the socket arbor 57 and is engaged by clutch balls 25 housed in a clutch plate 24 mounted on the clutch shaft 15. At a predetermined torque, the clutch balls 25 rise out of seats on the spindle 9 to move the presser ring 26 rearward. The rearward movement of the presser ring 26 acts through a cross bar 32 to move a push-rod 34 rearward.

The throttle button 59' operates a pilot-operated throttle mechanism. The air hose fitting 56 opens into a passage 60 extending to the forward end of a cylindrical valve bore 61. The cylindrical bore 61 contains a slidable valve seat sleeve 42 and a slidable spool valve 63 adapted to seat on the valve seat sleeve 42 to stop air in the bore 61 from entering a motor supply passage 64. The spool valve 63 is urged against the valve seat sleeve 42 by a spring 65. The spool valve 63 contains a small longitudinal vent 66 extending between its opposite ends. The end portion of the bore, rearwardly from the spool, is termed a pilot chamber 67. The throttle button 59 is connected to the pilot chamber 67 so that depression of the throttle button 59 will exhaust air pressure from the pilot chamber 67. The exhausting of the pilot chamber 67 creates a differential in pressure across the spool valve 63 to cause the valve 63 to move rearwardly to its open position as shown in FIG. 7. The spool valve 63 will remain in the open position as long as the throttle button 59 is depressed. At this time the tool motor 58 will be running and the arbor 57 is normally driving a fastener.

In the event the operator wishes to stop the wrench 54 before the fastener is driven to a selected torque load, the throttle button 59 is allowed to return to its raised position, the vent 66 will allow the differential of pressures across the spool valve 63 to return to a balanced condition and the spring will return the spool valve 63 to its closed position, as shown in FIG. 6.

The valve seat sleeve 42 of the second embodiment 54 is slidable in the valve bore 61 in the same way that the valve seat sleeve 42 is slidable in the valve bore 39 in the first embodiment. In addition, the valve seat sleeve 42 is urged rearwardly by a spring 43 and held in its forward position by a latch 44 having a tongue 45 engaging in an annular groove 46 provided in the circumference of the valve seat sleeve 42.

This latch mechanism is identical to the latch mechanism of the first embodiment with the exception that the rear end of the push-rod 34 is adapated to engage the release arm 48 of the latch 44 when the clutch mechanism 14 begins releasing or slipping at the predetermined torque load. When the latch 44 is released by the push-rod 34 at predetermined torque, the valve seat sleeve 42 moves rearwardly into engagement with the spool valve 63 to seal 01f air from the motor passage 64, as shown in FIG. -8, thus stopping the tool motor 58 in the same manner as inthe first embodiment.

Thereafter, the operator releases the throttle button 59 to again seal the pilot chamber 67 whereby the dilferential of pressure across the spool valve 63 is returned to a balanced condition and the spring 65 forces the spool valve 63 to return to its forward closed position as shown in FIG. 6, while carrying the valve seat sleeve 42 forward with the spool valve 63. In order for the spring 65 to accomplish this result, it is stronger than the valve seat sleeve spring 43. The wrench 54 is now in condition for another cycle.

THIRD EMBODIMENT The movable valve seat 42 can be latched in its forward position by various other forms of latches than that shown in the drawings. One example of this is shown in FIG. 9 and contains a latch detent 69 pivoted in a longitudinal slot 70 in the side Wall of the valve seat sleeve 42 and adapted to engage an annular groove 71 formed in the wall of the bore 39 holding the latch detent. The lower end of the latch detent 69 carries a cam ramp 72 adapted to cooperate with a cam cone 73 fixed on the push-rod 34 to disengage the latch detent 69 when the push-rod 34 rises in response to the tool reaching the predetermined torque load. The tool shown in FIG. 9 is a screwdriver and may contain the same clutch mechanism 14 as that shown in FIG. 1.

FOURTH EMBODIMENT The fourth embodiment shown in FIG. contains a ball-type latch for the valve seat sleeve 42. The valve seat sleeve contains an annular groove 75 adapted to receive a latch ball 76 which is housed in a hole provided in a thin section 77 of the Wall surrounding the bore 39. A latch bar 78 is slidably mounted behind the thin section 77 and contains a ball recess 79 adapted to receive the latch ball 76 when the latch bar 78 is raised from the position shown in FIG. 10. A spring 80 engages the top of the latch bar 78 to urge it downwardly. The latch bar 78 contains an arm 81 projecting inward over the abutment 49 for engaging it. The latch bar 78 is lifted by the push-rod 34, during its additional rearward movement, when the tool reaches the predetermined torque load. The upward movement of the latch bar 78 moves the ball seat 79 adjacent to the ball 76 whereby the ball can move into the ball seat 79 and release the valve seat sleeve 42.

FIFTH EMBODIMENT The fifth embodiment shown in FIG. 11 illustrates the use of the invention in connection with a pilot-operated valve in a screwdriver. A valve seat sleeve 84 is slidably mounted in a bore 85 provided in the tool body and contains an internal flange 86 projecting inward in the upper portion of the sleeve 84. The flange 86 contains a central opening 87. In addition, the valve seat sleeve 84 contains several ports 88 extending through its sides and adapted to carry air flow to the motor passage 40.

A pilot-operated valve spool 90 is slidably mounted in the lower end of the valve seat sleeve 84 and is adapted to engage the flange 86 to seal the flow of air to the motor passage 40. The top of the spool valve 90 contains a resilient pad 91 to aid the sealing action of the valve 90. A spring 92 urges the spool valve 90 toward its closed position.

The spool valve 90 contains a small axial passage 93 which allows the air pressure acting on the top of the valve to flow into a pilot chamber 94 located under the valve 90, thereby balancing the pressure across the valve. Normally, the pressure in the pilot chamber 94 is closed by a small pilot valve 95 attached to the top of the push rod 34. A latch crank 96 is pivoted in the pilot chamber 94 and has a portion adapted to engage a recess in the side wall of the valve seat sleeve 84, thus preventing it from moving downwardly until unlatched.

The pilot valve 95 contains a diametrical opening 97 receiving one arm of the latch crank 96. The opening 97 is large enough to allow the pilot valve 95 to open during the initial movement of the push-rod 34 without releasing the latch crank 96. As soon as the pilot valve 95 opens, the pilot chamber 94 is vented and the resulting pressure differential acting on the spool valve 90 opens it. Thereafter, when the tool reaches its predetermined torque load, the push rod 34 moves upwardly an additional distance to release the latch crank 96 and allow the valve seat sleeve 84 to move downwardly, due to the differential of pressure across it. Thus, the valve seat sleeve 84 will seat On the spool valve 90 and stop the flow of air to the motor.

Both the spool valve 90 and the valve seat sleeve 84 will return to their upper positions when the pilot valve 95 is closed, as a result of the force provided by the spring 92.

Although five embodiments of the invention are illustrated and described in detail, it will be understood that the invention is not limited simply to these embodiments, but contemplates other embodiments and variations which utilize the concepts and teachings of this invention.

I claim:

1. A fluid-operated rotary power tool comprising a casing;

a fluid motor driving a spindle;

a valve controlling the flow of motive fluid to said motor and movable in one direction from a closed position to an open position to start said motor;

a torque sensing means connected to said spindle to measure a predetermined load on said spindle and to create a signal; and

a member movably mounted on said casing and operative to receive said signal and move in response to said signal, to engage said valve in its open position to shut off the flow of motive fluid to said motor.

2. A fluid-operated rotary tool comprising:

a housing including a fluid-operated rotary motor;

a valve controlling the flow of motive fluid to said motor and movable from a closed position to an open position wherein motive fluid flows to said motor;

a valve seat normally disengaged from said valve in its open position and movable to engage said valve in said open position to shut olf the flow of motive fluid to said motor; and

torque sensing means connected to said motor to measure the torque on said motor and being operative, in response to a predetermined torque load on said motor, to eifect the movement of said valve seat to its engagement position with said valve.

3. The rotary tool of claim 2 including:

a rod interconnecting said torque sensing means with said valve seat.

4. The rotary tool of claim 2 including:

latch means locking said valve seat in a position normally disengaged from said valve in its open position and operative to release said valve seat when said torque sensing means reaches said predetermined torque; and

means urging said valve seat toward its engaged position with said valve.

5. The rotary tool of claim 4 wherein: said torque sensing means is a torque-responsive clutch connected to a rod extending towards said valve seat and operative to move said rod toward said valve seat when said clutch reaches said predetermined torque.

6. The rotary tool of claim 5 wherein:

said latch means includes a movable element adapted to engage a latch surface provided on said valve seat.

7. The rotary tool of claim 4 wherein:

said valve is engaged by said push-rod and is moved to an open position by the operator pressing the tool against a workpiece.

8. The rotary tool of claim 4 wherein:

said valve is movable to its open position by the operation of a throttle member by an operator.

9. The rotary tool of claim 4 wherein:

said latch means includes a movable element mounted on said valve seat.

10. The rotary tool of claim 4 wherein:

said valve is a pilot-operated valve.

11. The rotary tool of claim 10 wherein:

said pilot-operated valve is movably mounted within said valve seat.

12. A fluid-operated rotary tool including:

a fluid-operated motor; and

valve means including a first portion movable from a first position, wherein it shuts off the flow of motive fluid to said motor, to a second position, wherein it allows motive fluid to flow to said motor, and a second portion movable from a third position to a fourth position, wherein it engages with said first portion when in said second position to shut off the flow of motive fluid to said motor.

13. The rotary tool of claim 12 including:

means operable by an operator for moving said first portion of said valve means to said second position; and

other means operative, in response to a predetermined torque load on the tool, to move said second portion of said valve means to said fourth position.

14. A fluid-operated rotary tool comprising:

a housing including a fluid-operated rotary motor;

a spindle movable rearwardly in said housing;

valve means controlling the flow of motive fluid to said motor and movable rearwardly in said housing over a distance including first and second successive increments of travel, said valve means being movable rearwardly over said first increment of travel from a closed to an open position and movable rearwardly over said second increment of travel from an open to a closed position;

means interconnecting said spindle to said valve means to transmit the rearward movement of the spindle to the valve means for moving said valve means over said first increment of travel thereby to open said valve means; and

torque sensing means connected to said motor to measure the torque on said motor and being operative, in response to the rise of the torque load to a predetermined torque load, to cause said valve means to move over said second increment of its travel, thereby to close said valve means.

References Cited UNITED STATES PATENTS 3,059,620 10/1962 Eckman 17312 X 3,082,742 3/1963 Vicmerding et a1. 81-52.4 3,162,250 12/1964 Sindelar 173-12 3,242,996 3/1966 Wright et a1 173--12 X 3,385,377 5/1968 Amtsberg et a1 173-12 ERNEST R. PURSER, Primary Examiner US. Cl. X.R.

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