US2974553A - Torque control means for impact wrenches - Google Patents

Description

G. DONOWICK TORQUE CONTROL MEANS FOR IMPACT WRENCHES March 14, 1961 March 14, 1961 v G. DoNowIcK 2,974,553

TOROUR CONTROL MEANS ROR IMPACT wRENcHEs Filed May 2l, 1957 March 14, 1961 G. DONOWICK TORQUE CONTROL MEANS FOR IMPACT WRENCHES 3 Sheets-Sheet 3 Filed May 21, 1957 INVENTOR GEORGE DONOWICK ATTORNEY United States Patent O F 2,974,553 TORQUE CONTROL MEANS FOR IMPACT wRENcHEs George Donowick, Utica, N.Y., assignor to Chicago Pneumatic Tool Company, New York, N.Y., a corporation of New Jersey Filed May 21, 1957, Ser. No. 660,697

17 Claims. (Cl. 8152.3)

This invention relates to automatic control mechanism for limiting the application of torque to a driven member and is of the type which responds to a predetermined deceleration of the driving member. The invention has specific application to impact wrenches for driving threaded fasteners such as nuts, bolts and screws.

In the art of impact wrenches, various controls have been used to stopy the driving motor, or an associated rotating shaft, automatically when theV driven bolt has been tightened to a predetermined degree. In some instances the control is designed .to operate in response to a predetermined deceleration of the motor. Such controls are based on the theory that the motor deceleration at the time of impact is an indication of the force of the rotational blow delivered to the bolt and, therefore, of the tightness thereof. In general, the theory is correct because the deceleration of the motor, or associated impact delivering member is proportional to -t-he resistance offered by the impact receiving member, other things being equal. However, it often hap-pens that the first blow in a series of impacts, which occurs when the bolt has relatively slight resistance to rotation and when the motor is rotating at a relatively high speed, will be accompanied by anA instantaneous torque of `extremely short duration but disproportionately high intensity. This is especially true if there is looseness in the connections between the tool head or anvil and the Wrench socket and between the wrench socket and bolt. In that case, a. substantial por tion of the force of ,the impact delivered by the hammer element of the impact clutch to the anvil element is dissipated in accelerating the anvil while the latter is moving to take up the lost motion and while very little tightening of the driven bolt occurs. In other words, the instantaneous resistance oifered by the anvil at times is due to its own inertia rather than the tightness of the driven bolt.

The general object of this invention is the provision of a control device for a driving member or motor which responds to a predetermined deceleration of prolonged duration of such driving member but is unresponsive to deceleration which occurs` during an interval of extremely short duration, such as occurs during the iirst blow of a series delivered by an impact wrench.

Another problem which increases the diliiculty of predetermining the degree of tightness of a threaded fastener by lmeans of an automatic control, arises from variations in the structure to which the fastener is applied. In some instances, the resistance to rotation of the bolt develops suddenly when the head becomes seated on a hard rigid structure. In other instances, when the struct-ure includes a resilient element, the resistance increases gradually.

Another object of this invention, therefore, is to attain greater uniformity in the tightness of threaded fasteners drivenvby an impact wrench under varying conditions, Without the necessity of changing the control adjustment to suit such conditions.

A further object is to introduce lost motion between the motor and the deceleration responsive control device,

2,974,553 Patented Mar. 14, 1961 ICC for the purpose of canceling out the eifects of the lost motion in the driven elements which otherwise might give a false indication of the tightness of the bolt and cause premature operation of the control.

A feature of the invention resides in a iiywheel driver adapted to operate a deceleration responsive control, the driver being driven by the motor shaft through a friction clutch and through a free-wheel clutch arranged to prevlral; the tliywheeldriver from over-running the motor S t.

In the accompanying drawings which illustrate one embodiment of the invention:

Fig. l is a fragmentary longitudinal section of the rear portion of an impact wrench shovn'ng the rotary air motor, the passageway supplying live air thereto and the automatic control for such passageway;`

Fig. 2 is a fragmentary longitudinal section similar to Fig. l but showing the automatic control in its operated position just prior to the closing of the live air passage Way;

Fig. 3 is an enlarged longitudinal section of certain parts of the automatic control in assembled relation;

Fig. 4 is a cross-section as indicated by the arrows 4 in Fig. 3, showing the driving key, rotor extension and the friction drive plate;

Fig. 5 is a cross-section as indicated by the arrows 5 in Fig. 3, showing the fly-wheel driver, yswheel, cam and ball bearings in the idle position;

Fig. 6 is a view similar to Fig. 5 but with the parts in the operated position, the ily-wheel having overrun ythe driver to displace the cam rearwardly or toward the ob server;

Fig. 7 is a view in elevation of the `front face of the cam;

Fig. 8 is a cross-section as indicated -by the arrows 8 in Fig. 3 but on a still further enlarged scale, and showing particularly the overrunning clutch between the rotor extension and the fly-wheel driver.

F-ig. 9 is a cross-section on the line 9 9 in Fig. l, but drawn to the scale of Figs. 3*7, with part of the housing broken away.

Referring to Fig. l, the impact wrench, which is of the pneumatic type, comprises a clutch housing 11, a motor housing 12, and a control housing 13, secured in lixed relation by any suitable means, such as the usual arrangement of bolts and anges (not shown). The control .housing extends rearwardly .to form a grip handle- 14 (broken away) by means of which the wrench may be manually held.

A reversible air motor 15 Within the motor housing includes a cylinder or cylinder liner 16, the ends of which abut against end plates 17. The rear end plate has an annular flange 18 iitting a recess in the control housing 13, and a peripheral portion fitting the motor housing 12. The ange 18 surrounds and supports a ball bearing 19.

Arbutting against the front face of the front end plate 17 is a ball bearing 21 supported within motor housing 12. Ball bearings l19 and 21 support respectively rear and front shaft extensions 22 and 2.3 integral with and projecting from a rotor 24. The rotor is of cylindrical shape and is arranged coaxial with its shaft extensions and with the clutch housing 11, but eccentric with the cylinder 16 to provide a cresent shaped chamber between the rotor and cylinder. The rotor has a plurality of radial slots 25 in which blades 26 are mounted for movement with their outer edges in scraping contact with the cylinder liner 16 to divide the cresent shaped chamber, as usual, into a series of pockets between the inlet and exhaust ends.

At its front end, the rotor shaft extension 23 has a splined portion 23a adapted to drive the hammer element of an impact clutch (not shown). The impact clutch may be of any well-known construction of the type which causes the rotor to stop or sharply decelerate upon the delivery of a rotational impact by the wrench to the driven bolt or the like. For an illustration of an impact clutch suited for the application of the present invention, reference is made to the co-pending application entitled Impact Clutch, tiled January 12, 1955, by Lester A. Amtsberg, Serial No. 481,391, now patent 2,881,884, granted April 14, 1959.

The passageway for supplying pressure fluid or live air to the motor includes a manual and an automatic control. The live air in such passageway is admitted to the grip handle 14 through the usual hose connection (not shown) and then passes the usual manually controlled throttle valve (not shown) into the handle passage 27. The live air then passes around an automatic valve 28 (the purpose of which will be described later) into a valve bushing 2.9, through a series of radial ports 31 in the bushing and thence into an air supply chamber 32 fori ed in the control housing 13. From the supply chamber 32, live air flows through a longitudinal passage 33 and a port leading to the interior of reverse valve bushing 34. From there the live air is directed, t-hrough an inlet recess 3S in the reverse valve 36, to one side or the other of the air motor 15. The live air turns the rotor in a wellknown manner and passes out of the exhaust side of the motor through a passageway which includes an exhaust recess 37 in the reverse valve and an exhaust port 33 in the motor housing 12. The direction of rotation of the motor is controlled by the usual lever 39 at the rear end of the reverse valve 36, the lever being manipulative to turn the reverse valve. to transpose the inlet and exhaust recesses 35 and 37 respectively.

The automatic control valve 28 is surrounded by a coiled compression spring 41, interposed between the head 42 of the valve and the end wall of the recess in the valve bushing 29, whereby the spring at all times urges the valve outward or toward the open position. When the manipulative throttle valve (not shown) is closed, the pressure of the spring 41 is unopposed and acts to seat the outer extremity of the automatic control valve 28 against a plug 43, as shown in Figs. 1 and 9. The plug is secured to the control housing 13, being retained by a snap ring 44, and being sealed by a rubber O ring 45. The automatic valve 28 has a stem 46 slidably tting the bushing 29 and terminating in an inward extension or projection 47 separated from the main stem by a shoulder 48. In the idle condition of the parts, the projection 47 acts as a stop for a double arm lever or trigger 49 pivoted on a pin 50 supported transversely in the control housing 13. The trigger is held in contact with the valve extension 47 by yieldable means such as compression spring 51. The inner end of the valve 28, including the stem 47 and shoulder 48 thereof, is exposed to atmospheric pressure at all times by way of any suitable vent, such as the port 51a in the housing 13. Upon depression of the manipulative throttle lever (not shown), the operator admits live air through the handle passage 27 to initiate rotation of the motor as previously described. The fluid pressure in passage 27 acts against the outer end of the automatic valve 2S and, being unbalanced over the area of the valve stem 46, overcomes the relatively light spring 41 and shifts the control valve inward until the valve shoulder 48 seats against the trigger 49 and occupies a position slightly above the one shown in Figs. l and 9. As long as the trigger remains in the Fig. 1 position it holds the control valve 2S open to permit the live air to drive the motor 15.

The apparatus for operating the trigger 49 to release it from the path of the automatic valve 28, thus permitting the latter to close, will now be described. The rear shaft extension 22 of the rotor 24 is provided with an axially extending bore 52 for the reception of a rotor extension 53. Referring to Figs. 1, 2, 3 and 4, the rotor extension is constrained for rotary movement in unison with the rotor 24 by means of a tight press tit therebetween and also by means of a key S4 mounted rin a radially extending counterbored hole 5S in the rear shaft extension 22 and extending into a `longitudinal groove 56 in the rotor extension `53. In accordance with this invention, the rotor extension serves as the driving element of an overrunning or free wheel clutch shown in Figs. 1, 2 and 3, and particularly in Fig. 8. The driven element of the overrunning clutch is the ily wheel driver 57 having at its front end a large bore 58, the rear end of which bore lies closely adjacent to the front end face of the rotor extension 53. Bore 58 serves as a raceway for a plurality of rollers 59 (three being shown) each roller being mounted in a longitudinal recess 61 in the rotor extension 53. The rollers are retained against axial` movement, being in loose abutting contact at their rear ends with the bottom of the large bore 58 and at their front ends with a plate 62. The latter, as seen in Fig. 4, is generally in the shape of a ilat ring but has three tongues 63 projecting inward into the rotor extension recesses 61. By means of these tongues, the plate 62 is constrained to rotate in unison with the rotor extension 53, and therefore with the rotor 24.. lt serves yas a friction drive plate for the fly-wheel driver 57 being held in contact with the end face of the driver 57 by resilient means, to be described later. The rollers 59 and recesses 61 are so designed that with the parts rotating in a clockwise direction (looking forward as in Fig. 8), the rotor assembly 24, 22, 53 may overrun the flywheel driver 57 which is driven thereby, but the ily-Wheel driver, generally speaking, cannot overrun the rotor assembly. Accordingly, each of the rollers 59 is maintained by yieldable means with its center in advance of, or clockwise of, the position of maximum depth of the recess 61, such position being indicated in Fig. 8 by the dot-dash line 64 extending radially and perpendicularly to the bottom wall of the recess 61. The yieldable means last mentioned comprises a helical compression spring 65 associated with each roller 59 and housed in a recess 66 in the rotor extension 53. Each spring is under compression between the bottom of the recess and the associated roller and urges the latter in a clockwise direction. .The dameter of the roller is slightly less than the depth of the recess 61 along the radial line 64 and is equal to the depth of the recess at the point where the roller normally comes to rest under the pressure of spring 65. Surrounding the fly-wheel driver 57 is a y-wheel 67 having substantial mass and movement of inertia. The fly-wheel is swivelly supported for limited rotary (but not axial) movement relative to the driver by means of a row of ball Ibearings 68 (Fig. 3). The ball bearings roll around a raceway 69 in the driver and roll Within a half raceway 71 in the flywheel. Adjacent the latter is a split ring 72 which cooperates with the balls, the raceway and the half raceway to retain the iiy-wheel on the y-wheel driver and prevent relative axial movement therebetween. Referring to Figs. 5 and 6, the y-wheel driver 57 has three arms 73 extending radially outward into driving engagement with three arms 74 extending radially inward from the ily-wheel 67.

Mounted upon the ily-wheel driver 57 for relative axial movement is a cam 75 (Fig. 7). The cam has a central bore 76 for a purpose to be described later. Extending outwardly from the bore, the cam has three radial arms 77, each connected at its outer end with a forwardly projecting arm 78. The arms 78 project into the spaces between the arms 74 on ily-wheel 67 as seen in Figs. 3, 5 and 6. The leading end (assuming clockwise rotation) of each cam arm 78 is provided with a longitudinal raccway 79 having rolling engagement with a ball 81 which in turn has rolling engagement with a longitudinal raceway 82 on the trai-ling end of the associated arm 73 of thc fly-wheel driver 57, thus providing, with a minimum of friction, the relative axial movement aforesaid between the cam 75 and the fly-wheel driver. At its trailing end, eacharm 78 of cam 75 is provided with a cam raceway 83, the axisof which is vinclined. with respect to that of the longitudinal recess 79. Each cani raceway 83 rolls upon a ball 84 which in turn rolls upon a cam raceway 85 formed on the fly-wheel 67. The two'cam raceways 83 and 85 are complementary and adapted to lie co-axially with each other and are so inclined that when the ywheel 67 runs ahead of, or faster than, the cam (in a clockwise direction), it causes the balls 84 to displace the cam 75 rearwardly. Conversely, whenthe cam is .returned to its normal position and moved axially forward (lby means to be described presently), the ball cam arrangement compels the cam 75 to rotate ahead of (or faster than) the ily-wheel 67 in a clockwise direction.

The camv is resiliently urged in a forward direction at all times. For this purpose, the central bore 76 of the cam is provided with a counterbore 87 (Fig. 3) for receiving a ball bearing 88. The inner raceway of the ball bearing is firmly secured to a thrust button 89 by means of the usual bolt and nut connection. The rear extremity of the button 89 is llat and engageable with the nose 91 (Figs. 1 and 2) at the lower end of a swinging lever 92, the upper end of which pivots upon a pin 93 aixed to the -control housing'13. The swinging lever is flat, and near its ends it extends in planes transverse to the axis of rotation of the motor and of the control mechanism. lntermediate its ends, the lever 92 has an inclined portion in which is provided an aperture 94 to receive and cen- ;tralize the nose end of a plunger 95. The plunger extends perpendicular to the inclined intermediate portion of the swinging lever 92 and presses forward against the Alever at all times. Such pressure is provided resiliently by :a helical compression spring 96 interposed between the head of the plunger and the closed end of a bushing 97 :surrounding the spring. The bushing has a screw threaded connection with the control housing 13 and is provided at its outer end with a socket 98 for the reception of an hexagonal key to turn the bushing and thus adjust its position toward and from the swinging lever. A spring pressed detent or ball 99 yieldingly locks the bushing in adjusted position. By turning the bushing 97 in a clockwise direction, the operator increases the resilient thrust which is exerted forward on the swinging lever 92, through nose 91, thrust button 89, ball bearing 88 and cam 75. The resilient thrust tends to maintain the cam 75 in its most forward position shown in Pigs. 1, 3 and 5 with the balls 84 at the rear end of the cam raceway 83 in the cam 7S and at the front end of the cam raceway 85 in the ily-wheel 67. When the parts are in that position, the other set of balls 81 lie at the rear end of the longitudinal raceway 79 in cam 75 and at the front end of the longitudinal raceway 82 in the fly-wheel driver 57. Also in the Fig. l position, the rear face of the innermost end of the swinging lever 92, in back of the nose 91, lies a short distance forwardly of and out of contact with the `double arm lever or trigger 49. 'Ihe forward thrust of compression spring '916 is also transmitted through cam 75, through the cam balls 84 and ywheel 67 to the ilywheel driver 57 to hold the latter in frictional contact with the drive plate 62.

From the foregoing description it is seen that the rotor extension 53 is connected to the ily-wheel driver 57 through a plurality of transmission means, one o which comprises the drive plate `62 acting frictionally to transmit torque from the roto-r extension to the flywheel driver; and the other comprises the over-running clutch rollers 59 which act to transmit torque back to the rotor extension. The last named transmission means appears to function tirst as a exible connection and later as a positive drive, as will be explained in the description of operation.

In operation, let it be assumed that the parts are in the idle position shown in Figs. l, 3 and 5, and that the operator desires to tighten a bolt, having right hand threads, to the required degree of tightnessas predetermined by adjustment of the threaded bushing 97. He

- hecks, or re-sets, the position of the reverse valve 36,

moves the entire machine until the wrench socket rests on the head of the blot (not shown), depresses the throttle lever (not shown) and simply holds the lever down with the machine in position. The action from that time on is automatic and independent of the skill of the operator. -Live air ows past the throttle valve, through handle passage 27, past the automatic control valve 28 `into air supply chamber 32, through passage 33 and bushing 34 into inlet recess 35 of reverse valve 36 and from there to the motor 15. The live air drives the motor 15 in a clockwise direction (looking forward) by acting against the slidable blades 26 in passing through the crescent shaped chamber in the motor. The exhaust air flows from Ithe motor, through exhaust recess 37 and past the reverse valve 36 to atmospheric exhaust port 38.

As the head of the bolt comes into contact with the work, there is a sudden increase in resistance to rotation which sets 11p-a torque reaction to the rotor shaft 29 causing the -rnotor l5 to slow down. Following such deceleration, the impact clutch is released to permit the motor to accelerate until it has run 360 ahead of the driven bolt. At the end of the acceleration period, the impact clutch is re-engaged with an impact to exert a torsional thrust to the driven bolt, accompanied by a sharp torque reaction to the motor. This action is repeated automatically to drive the bolt with a series of rotational impacts.

Generally speaking, each succeeding impact of a series occurs over a shorter period of time, with a shorter degree of turning movement of the driven bolt, with a greater force of blow and with a greater amount of deceleration of the motor, as the bolt is driven tighter and meets with increasing resistance. It should be understood, however, that an instantaneous deceleration of the motor which occurs only during an infinitesimal period oi time is not a reliable indication of the tightness of the driven bolt. The reason is that the `force of the blow is delivered in two stages, the irst of which is instantaneous and variable with factors unrelated to the tightness of the bolt, and the second stage of which is of finite duration and proportional to'the resistance or tightness of the driven element. ln the rst stage of the force of blow, -a substantial part of the energy of the rotating parts of the impact cluch is dissipated by accelerating the anvil of the impact clutch to take up lost motion in the driving connections including the wrench socket.

During the rst stage of the impact, the amount of force required to accelerate the 'anvil head and wrench socket is disproportionate to the degree off tightness of the driven bolt, as it depends chiefly on the speed of the motor just before impact. In `fact, the maximum instantaneous impact force probably occurs on `the rst blow bccause of the high motor speed, whereas on subsequent impacts the motor is limited to the speed that .it can attain after starting from rest and turning only 360 degrees, or perhaps a few additional degrees in the case of rebound.

In accordance with the present invention, the torque control device is arranged to be responsive to a predetermined amount of motor deceleration of finite duration,

but unresponsive to motor deceleration of the same or even higher value which occurs instantaneously or for an infinitesimal period of time. Referring to Figs. 1, 3 and 4, when the motor l5 starts from rest, either upon initial operation or" the tool or at the end of one impact in a series, the rear shaft extensi-on 22 on the rotor 24 operates through the key 54, rotor extension 53 and friction drive plate 62 to drive the llywheel driver along with the rotor. The speed of the ilywheel driver 57 at iirst may be somewhat less than that of the motor inasmuch as the free wheel clutch permits the motor to run taster. The ily wheel 67 at this time is driven along with the driverV 57 by means of interengaging shoulders provided on the outwardly extending arms 73 and in- Wardlyrextending arms 74 (Fig. 5) provided on the y.-

wheel driver and fly-wheel respectively. The cant'75 at this time partakes of such rotary movement due to the torsional resilient engagement between y-wheel 67 and the cam 75 including cam raceways 8S, balls 84 and cam raceways 83, and the spring 96 cooperating therewith to hold the flywheel and cam together.

When the rotor l is deceleratcd upon delivery of an impact to a bolt (not shown) the rotor extension 53 and flywheel driver 57 lare constrained to decelerate correspondingly. The fry-wheel 67, due to its momentum tends to continue rotating from the position shown in Fig. 5 toward that of Fig. 6. The momentum is effective to set up a force between the balls 84 and associated cam raceways 83 and 85 which is resolved into an axial and a rotational component, the former tending to displace the cam 75 rearward and the other tending `to displace the flywheel 67 rotationally to break contact between the engaging shoulders or arms 73, 743, as in Fig. 6. As long as the lforce of the blow, and hence the deceleration of the rotor are within the limits set by the adjusting bushing 97 the axial component of force resulting from the momentum of the ily-wheel 67 will be insufcient to overcome the spring 96 and, therefore, the fly-wheel will remain in contact with the driver, as in Fig. 5, Iand rotate in unison therewith. When the driven bolt has been tightened to its maximum predetermined degree and the motor and fly-wheel driver 57 come to rest abruptly upon delivery of the last blow of a series, the deceleration of the driver 57 is sutiicient to permit the momentum of the fly-wheel 67 to carry it in overrunning relation to the driver 57 from the position shown in Fig. 5 to that of Fig. 6. Thereupon the cam 75 is displaced rearwardly carrying with it the thrust button 89 which engages the nose 91 of the swinging lever 92 to move the latter against the double arm lever or trigger 49. As soon as the trigger is rocked to the Fig. 2 position, it releases the shoulder 48 of automatic control valve 28 to permit the latter to move inward. The valve then moves inward by the pressure of live air acting over the unbalancedvarea of the stem portion thereof, as shown in Fig. 2, and continues moving until the head 42 seats aga-inst lthe outer end of valve bushing 29 to cut ott the supply of air to the motor 15. The control valve 28 remains closed and the motor 15 remains at rest as long as the operator holds the throttle valve (not shown) open to supply live air to the handle passage 27. In order to condition the tool for starting a new cycle of operation, the operator closes the throttle valve, whereupon the pressure acting on control valve 28 is relieved to permit the light spring il to open the valve with the result that the trigger 49 moves back to the Fig. l position, seated against the reduced extension 47 on the valve. in order to prevent delays in restoration of the valve which might be caused by live air trapped in handle passage 27, the valve 28 is provided with a central opening lill, terminating in a radial port which permits the live air to by-pass the head 42 of the valve.

In the foregoing discussion, it is assumed for the sake of simplicity that when a rotational blow is delivered by the impact clutch, the ily-wheel driver 57 decelerates with the rotor shaft extension 53, without regard to any relative movement therebetween. This assumption is suggested by Fig. 8 which shows a free wheel or overrunning clutch larranged to cause the iiy-wheel driver S7 to stop rotating clockwise when the rotor extension 53 stops. In actual operation, however, it has been found that the free-wheel clutch produces results which are not attainable in its absence, that is with the fly-wheel driver integrally joined to the rotor extension. ln such a simplified construction (omitting the free-wheel clutch) the control device often operates prematurely by displacing the cam 75 `and releasing the trigger i9 in res-onse to the irst impulse of a series in which the instantaneous deceleration of the motor gives a false indication of the tightness of the bol-t because of the high motor speed, as previously explained. With the present invention, the control device is unresponsive to instantaneous impulses such as the first impact of a series even though the accompanying motor deceleration happens to be sharper in intensity than the final deceleration which is effective to operate the trigger. While the precise reason for the success or the present invention is not definitely known, it is belived that the iirst impulse in a series is dissipated by the action of the rollers 59 (Fig. 3) in permitting a slight `overrun of the ily-wheel driver 57 relative to the rotor extension 53 during the peak of the iirst impact, as the rollers roll clockwise over the bottom walls of the recesses 6l with an epi-cycloid motion and along the driven ybore 58 with a hypo-cycloid motion. Such lost motion between the rotor shaft extension and the iiywheel driver does not prevent the cam 75 from being displaced rearwardly in response to subsequent impacts of a series because such subsequent impacts are prolonged in duration beyond the extremely short interval in which the clutch sli-ps suic-ientl'y to permit the rollers 59 to become firmly wedged between the rotor extension 53 and ily-wheel driver 57, following which the full reactive force of the impact on the rotor is transmitted baci; without attenuation to the ily-wheel driver 57.

By turning the bushing 97, the operator may increase 0r decrease the pressure resisting axial displacement of cam 75, and thus increase or decrease the tightness of the driven bolt required for automatically stopping the motor.

When the operator desires to loosen a bolt, he manipulates lever 39 to turn the reverse valve 36. The wrench delivers impacts as before but in reverse direction and in the reverse chronological order, that is to say the motor delivers (and receives the reaction of) heavy blows at first followed by blows of lessening intensity, and still later followed by a continuous drive. The torque reaction of the impacts is transmitted back to the rotor extension 53 but not with full force to the ily-wheel driver 57, because the rollers 59 permit the driver 57 to continue rotating counter-clockwise when the rotor stops, and as the friction drive plate 62 slips. Accordingly, the control device of the invention will stop the motor automatically only when driven in one direction which, in the illustrative embodiment, is the clockwise direction.

if the opertaor desires to disable the automatic control, he presses a plunger 102 (Figs. l and 9) supported for sliding movement in a bore provided in a boss 103 integral with control housing 13. When so pressed, the plunger is interposed in the path of the inner end of automatic valve 23 and prevents the automatic valve from closing, thus causing operation of the impact wrench to continue indefinitely or until the operator intervenes by closing the throttle valve manually. There is a boss 103 on each side of the housing adjacent the double arm lever 49, and there are two plungers 102, one accessible from each side `of the housing 13, to facilitate manipulation by either a left handed or right handed operator. The outer end of the plunger is provided with a button 104 (Fig. 9) adapted to be depressed against the pressure of a spring 10S.

What is claimed is:

l. A power operated machine comprising a rotatable shaft subject to deceleration upon sudden increase in resistance to rotation, a liywheel driver, transmission means between the shaft and flywheel driver, and control means responsive to a predetermined deceleration of the shaft for automatically limiting the application of torque to the shaft, said control means including a flywheel arranged for forward rotation with the iiywheel driver and for continued forward rotation ahead of the flywheel driver upon sudden deceleration of the latter, characterized in that said transmission means includes a lost motion connection, whereby to delay operation of said control means and thus make the latter unresponsive to deceleration of extremely short duration.

2. A power operated machine according to claim 1,

in which the transmission means between the shaft and flywheel driver also includes a friction clutch.

3. A power operated machine accordingto claim 1, in which the control means includes a cam connected to the flywheel driver for relative axial movement, and cooperating helical surfaces on the camand flywheel tending to cause relative axial movement between the cam and flywheel upon rotation of the latter ahead of the ilywheel driver.

4. An inertial control mechanism comprising a rotatable shaft subject to deceleration upon sudden increase in resistance to rotation, a llywheel driver, transmission means between the shaft and flywheel driver, and control means responsive to a predetermined deceleration'of the shaft for automatically limiting the yapplication of torque to the shaft, said control means including a flywheel arranged for forward rotation with the flywheel driver and for continued forward rotation ahead of the iiywheel driver upon sudden deceleration of the latter, characterized in that said transmission means includes a friction clutch for transmitting torque from the shaft to the liywheel driver during acceleration thereof and an overrunning clutch for transmitting torque from the vflywheel driver back to the shaft during the deceleration thereof.

5. In an impact wrench, an inertial control mechanism comprising a rotatable shaft subject to sudden deceleration upon delivery of a rotational impact, a ywheel driver, transmission means` between the shaft and ilywheel driver, and control means responsive to a predetermined deceleration of the shaft accompanyingthe delivery of an impact for automatically limiting the application of torque to the shaft, said control means including a flywheel arranged for forward rotation with the flywheel driver prior to impact and for continued forward rotation ahead of the flywheel driver upon impact and sudden deceleration of the flywheel driver, characterized in that said transmission means includes a free wheel clutch between the shaft and ywheel driver, said free wheel clutch being arranged to decelerate the flywheel driver upon deceleration of the shaft.

6. In an impact wrench, an intertial control mechanism according to claim 5, in which the free wheel clutch is arranged to slip to permitv a slight overrun of the flywheel driver relative to the shaft in the forward direction upon deceleration of the shaft, whereby to attenuate the reactive force of impacts of extremely short duration, in the transmission of such force to the fly-wheel driver. f

7. In an impact wrench, an inertial control mechanism according to claim 5, in which the free wheel clutch includes rollers mounted in longitudinal recesses in the shaft and engageable with a bore in the ywheel driver.

8. In an impact wrench, an inertial control mechanism according to claim 7, in which the free wheel clutch includes springs urging the rollers in a forward direction `relative to the shaft.

9. An inertial control mechanism comprising a shaft adapted to rotate forward and subjected to sudden deceleration, a ywheel driver connected to the shaft to receive decelerative impulses therefrom, a cam connected to the flywheel driver and movable axially relatively thereto, a flywheel mounted on the flywheel driver for relative rotative movement only, said shaft, ywheel driver, ywheel and cam being arranged to rotate forward together prior to sudden deceleration of the shaft, said flywheel being arranged to overrun the cam and flywheel driver upon sudden deceleration of the latter, and cooperating helical surfaces between the ywheel and cam arranged to displace the cam axially upon such overrun of the ilywheel.

.10. An inertial control mechanism according to claim 10 9, in which the helical surfaces comprise raceways receiving balls therebetween.

11. An inertial control mechanism according to claim 9, in which the cam is connected to the flywheel driver by one or more balls each rolling in longitudinal racevWays provided inthe llywheel driver and cam, said raceways being arranged to restrain the cam against rotation forwardly ahead of the ywheel driver.

12. An inertial control mechanism according to claim 9, which includes resilient means holding the cam against relative displacement, said resilient means being yieldable upon predetermined deceleration of the ywheel driver and overrun of the flywheel to permit the ywheel driver to rotate ahead of the cam, said resilient means acting to restore the cam to its original position by causing the cam to rotate forward faster than the flywheel.

13. An inertial control mechanism according to claim 12, in whichthe resilient means comprises a thrust button swivelly supported by the c-am and a swingable lever having a nose portion engaging the thrust button.

14. An inertial control mechanism according to claim 13,V in which the resilient means includes a plunger extending transverse to the swingable lever, a spring for actuating the plunger, a bushing for supporting the spring and means for adjusting the bushing toward and from the swingable lever.

15. In Aa pneumatic wrench, a passageway for supplying live air to operate the wrench, an automaticvalve controlling said passagewayand movable between open and closed positions to admit or cut olf the supply of live air, said Valve being biased toward closed position, a trigger holding the valve in open position, automatic control means responsive to a predetermined torque delivered by the Wrench for releasing the trigger to permit the valve to close, and a plunger selectively movable into and out of the path of the valve by manipulative means, said plunger being arranged to lock the automatic valve in open position independently of the trigger, thereby providing a selective automatic or manual control. l

16. A power transmission comprising a shaft, an inertia element arranged in surrounding relation to vsaid shaft, a friction clutch for transmitting torque from the shaft to the inertia element in the forward direction of rotation, and an overrunning clutch for transmitting torque from the inertia element to the said shaft in the forward direction, said overrunning clutch being arranged to engage upon relative motion between the inertia element and the shaft in one direction only.

17. A power transmission comprising a shaft, an inertia element arranged in surrounding relation to said shaft, a friction clutch for transmitting torque from the shaft to the inertia element in the forward direction of References Cited in the iile of this patent UNITED STATES PATENTS 2,427,239 Taylor Sept. 9, 1947 2,531,054 Kelley Nov. 21, 1950 2,543,979 Maurer Mar. 6, 1951 2,733,621 Newman Feb. 7, 1956 2,768,546v VAmtsberg Oct. 30, 1956 2,784,625 Maurer Mar. 12, 1957 2,821,276

Reynolds Ian. 28, 1958

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