US2717672A - Impact wrench torque control - Google Patents

Description

Sept. 13, 1955 s. B. MAURER IMPACT WRENCH TORQUE CONTROL 5 Sheets-Sheet 1 Filed Jan. 26, 1951 INVENTOR HIE/v65? 6. W025? BY M ATTORNEY QM MN p 13, 1955 s. B. MAURER 2,717,672

IMPACT WRENCH TORQUE CONTROL Sept. 13, 1955 s, MAURER 2,717,672

IMPACT WRENCH TORQUE CONTROL Filed Jan. 26, 1951 v 5 Sheets-Sheet 3 EL 1 /M1 BY Q W M ATTORNEY Sept. 13, 1955 3, MAURER 2,717,672

IMPACT WRENCH TORQUE CONTROL Filed Jan. 26, 1951 5 Sheets-Sheet 4 T: :BE.

M5 M4 m2 a I and A /43 J X \\& 39 as 7/9) ATTORN EY p 13, 1955 s. B. MAURER IMPACT WRENCH TORQUE CONTROL 5 Sheets-Sheet 5 Filed Jan. 26, 1951 *1) -49 may) 1/04/97 250 W INVENTOR pig/Vail? Z9. WMPFA W M ATTORNEY Unite rates Patent 0 IMPACT WRENCH ronoun coNTRoL Spencer B. Maui-er,

Pneumatic Tool Company, poration of New Jersey Application January 26, 1951, Serial No. 207,935 25 Claims. (Ci. 192-.02)

New York, N. Y., a cor- This invention relates to impact wrenches and more that the proper degree of tightness be achieved and further, that the load on a plurality of fastening means is uniformly distributed so that no one bolt carries more than its share of the load; if the work pieces are understressed, looseness may occur, whereas, if the work pieces are overstressed, the danger of material failure is present, the most common failure being the breaking of bolts during runup. In using an impact wrench for tightening operations, and especially in mass production work, for example in tightening parts of internal combustion engines, such as cylinder head bolts, connecting rod bolts, etc., it is highly desirable to achieve the proper degree of tightness in the minimum time.

Normally an impact wrench delivers impact power by a series of successive and intermittent torque impulses transmitted through a spindle or tool head which is integral with an anvil element of the wrench clutch. Assuming the work piece or load to be a bolt or nut which is to be tightened, the ultimate torque obtainable is limited by either the strength of the work piece or the flexibility of the tool head transmitting the torque impulses. Provided the strength of the work piece is not exceeded, the ultimate torque obtainable with a given impact wrench or tool operating under given conditions, is constant and occurs when no further turning of the work piece is possible and the entire energy output (excluding frictional losses) of each torque impulse is absorbed in elastic deflection or distortion of the tool head, or torque transmitting member. The ultimate torque is approached as a limit which is generally reached only after lengthy operation of the tool since the increment of each succeeding torque impulse decreases as the output torque rises. By regulating the power input to the wrench, the maximum rotary speed of the wrench and hence, maximum torque, can be established. By applying the wrench for a sufficient period of time, the desired tightness of the work piece can be achieved by forces which never become excessive so as to damage the work. The ultimate torque method of regulation, by which name the foregoing method is usually identified, is not very practical for mass production work because it is too time consuming.

The object of this invention is to provide an impact wrench with automatic means whereby the desired degree of work tightness is achieved, while the work operating cycle is completed in minimum time, so as to render the tool well suited for mass production operations. A further object is to arrange such automatic means so that the tool can be conveniently and permanently adjusted for any value of torque within the tool capacity.

In accordance with the foregoing objects the invention contemplates the use of an impact wrench operating under Cleveland, Ohio, assignor to Chicago I "ice power conditions greater than that which would be required to attain a given degree of tightness if the wrench were employed in the conventional ultimate torque method. The tool motor is in operation, that is, continues rotation, during the entire tightening period. An energy accumulator having a spring means, is interposed between the motor and an impact clutch connected to the tool head. Each impact blow causes elements associated with the impact clutch to rebound, and the energy of such rebound is stored in the accumulator to be utilized for accelerating the movable members of the impact clutch. As the resistance of the Work piece increases, the energy of rebound increases, with the result that the accumulator spring is progressively compressed a greater amount with each impact blow. When a certain predetermined spring compression is realized, the drivingpower of the motor is terminated by action of the torque control of the invention.

Some of the objects of the invention are similar to those attained by applicants prior invention disclosed in patent application Serial No. 644,501, filed January 31, 1946, which resulted in Patent 2,543,979, dated March 6, 1951. While both inventions are in general based upon the idea of using the degree of rebound of elements associated with the impact mechanism of the wrench, this invention utilizes the degree of axial movement due to rebound, whereas, the prior invention utilizes the degree of angular movement due to rebound.

A complete understanding of the invention will be obtained from the following disclosure and the accompanying drawings wherein:

Fig. 1 is a longitudinal section view of an impact wrench including a torque control means illustrative of the invention;

Fig. 2 is a cross sectional view as seen from line 22 in Fig. 1;

Fig. 3 is a plan view Fig. 1;

Fig. 4 is a cross sectional view of the spindle as seen from line 4-4 in Fig. 3;

Fig. 5 is a perspective view of an idler gear cage used in the tool of Fig. 1;

Fig. 6 is a perspective view of one portion of the jaw arrangement on the driving element of a disconnect of a spindle as used in the tool of M clutch used in the tool of Fig. 1;

Fig. 7 is a sectional view of the tool of Fig. 1 showing the operative position of various elements just prior to torque cut-0E;

Fig. 8 is a plan view of a spring plate cam as used in the tool of Fig. 1;

Fig. 9 is a section view of the spring plate cam as seen from line 99 in Fig. 8;

Fig. 10 is a development of the cam surfaces of the spring plate cam of Fig. 8;

Fig. 11 is a section view of the impact clutch assembly as seen from line 1111 in Fig. 7;

Fig. 12 is a section view of the impact clutch assembly as'seen from line 1Z--12 in Fig. 7;

Fig. 13 is a perspective View of a spring used in the torque control arrangement;

Fig. 14 is a longitudinal section view of an impact wrench having a torque control means illustrating a moditied embodiment of the invention;

Fig. 15 is a cross sectional view as seen from line 1s 1s in Fig. 14;

Fig. 16 is a perspective view of a spindle used in the tool of Fig. 14;

Fig. 17 is a perspective view of an idler gear cage used in the tool of Fig. 14;

Fig. 18 is a section View as seen from line 18-18 in Fig. 14;

Fig. 19 is an end view of an adjusting screw arm as used in the tool of Fig. 14;

Fig. 20 is a longitudinal section of the adjusting screw arm of Fig. 19; j

Fig. 21 is a longitudinal sec tion of a fixed adjusting screw arm as used in the tool of Fig. 14; e

Fig. 22 is an end view of the fixed adjusting screw arm of Fig. 21;

Fig. 23 is a sectional view of the tool of Fig. 14, showing the relative position of the movable parts when the tool is in non-operative position and showing some of the elements broken away;, H v

Fig; 24 is a sectional view of the tool of Fig. 14, and is similar to Fig. 23, except showing the movable parts in operative position;

Fig. 25 is the same as Fig. 23 except showing the movable parts at instant of torque cut-off; V

Fig. 26 is a graph showing the general relationship between the impact torque delivered by the tool and the amount of accumulator spring deflection, in a tool such as shown in Fig. 1; and

Fig. 27 is a graph showing the general relationship between the impact torque delivered by the tool and the amount of accumulator spring deflection, in a tool such as shown in Fig. 14.

Referring to Fig. 1, the tool comprises a rear housing portion 20, a connecting portion 21, and afront housing portion 22, all portions being maintained in position by conventional means such as bolt means, not shown.

Therear housing portion 20 comprises a motor section 23 which encloses and supports an electric motor 24, and a handle section 25 which encloses aswitch means 26, and supports a trigger 27. ,Astator 28, forming partof the motor 24, is affixed to the housingportion 20 by conventionalmeans such as cap screws 29, while a rotor 30 is rotatably mounted within the stator 28 on a shaft 31, the rear end of the shaft being mounted on a ball bearingv 32, whichis positioned in the housing portion 26, while the forward end is mounted on a ball bearing 33, which is positioned in a bushing 34supportedivithin a bore located in the connecting portion 21. The front end of the shaft has formed thereon a small pinion gear 35, while adjacent the bearing 33, and on the motor side thereof a fan blade 36 is 'affixed to the shaft 31 to provide forced ventilation of the tool motor. A M A,

The switch means 26 is affixed to abracket 37 secured within the ha ndle section 25, the bracket having two lug portions 38 which are formed to support a switch lever actuating rod in vertically reciprocal position. A portion of the actuating rod is notched to loosely enclose the head of a switch lever 40; movement of the actuating rod 39 in downward direction is designed to close the contacts (not shown) of the switch. Atop the bracket 37 and surrounding the actuating rod 39, is a compression spring 41, one end of which abuts the bracket, the other end of which abuts a washer 42 aflixed to the actuating rod. The spring 41 serves to urge the actuating rod 39 in an upward direction whereby the switch contacts are in open position. Ifivotally mounted on the upper end of the actuating rod 39 for movement in a single plane, is an L -shaped link or lever 43, the lower end of whichhas a short hook-like projection 44. A spring 45 (Fig. 13) is arrangedto urgethe lever 43 in a direction away from the actuating rod 39.

The trigger 27 is arranged for rotation about a pin 46 which is positioned in the handlesection 25, and has a slot 47 which engages a stop pin 48 to limit rotary movement of the trigger about the pin 46. A coiled tension spring 49 is arranged to maintain the trigger in nonoperative position as shown. The trigger is arranged to engage the hook-like projection 44 ofthe lever 43, by means of a corner edge 50. It will be seen that when the trigger is pressed in, the lever 43 is forced downward, causing the actuating rod 39 to move the switch lever 40, to close the switch contacts thereby establishing a circuit through cables 51 to the motor.

Extending in part through each of the three portions of the tool is a push rod 52, the rearward end of which abuts a lever 43' which is pivoted at its upper end, the lower end being arranged to contact the lever 43 as shown. Push rod 52 has a shoulder 53 positioned near the for- Ward end abutting an inner Wall of the front housing portion 22. Adjacent the shoulder 53 is a threaded portion 54 which adjustably maintains a push rod lever 55, the lever 55 being confined to vertical position by loose contact with side walls 90 arranged in the front housing portion, as best seen in Fig. 2. A coil spring 56 surrounds the push rod 52, one end of the spring abutting an end of the lever 55, the other end abutting a surface of the connecting portion 21, to urge the shoulder 53 in contact with the inner wall of the front housing portion 22. A notch 57 on the exterior end of the rod 52 is adapted to receive a screw driver (not shown) so that i the rod 52 may be rotated for positioning the lever 55,

as will be further explained hereinafter.

It can be seen that when the push rod 52 is forced a suflicient amountrearwardly, the lever 43 is caused to move the lever 43 so that the hook-like projection 44 of the lever 43 is releasedfrom engagement with the corner edge Si) of thetrigger 27, to allow spring 41 to move the rod 39 upwardly, whereupon, lever 4t is moved to cut off power to the motor. Thus; a means is provided to discontinuetool operation, by a force acting with sufficient magnitude against the push rod lever 55.

Surrounding the forward end of the shaft 31, but spaced therefrom, is an idler gear cage 53, which is maintained for rotary motion by a ball bearing means 59 mounted in the bushing 34. Twoidentical gears 69 are mounted in the idler gear cage 58, by bearing means 61 which are supported by pins 62 afiixerl to the idler gear cage. The gears are arranged to mesh with the shaft pinion gear 35 and a large gear ring 63, which is mounted partly within the front housing portion 22 and the connecting portion 21, andsurrounds the gears 69. It will be seen that the gears fitl, 63 and shaft pinion 35 form what is referred to as a planetary gear system for transmitting power from the driving shaft 31 to the driven cage 58 at a reduced rate of speed.

Projecting from the front wall of the idler gear cage 58 is a cylindrical portion 64 (Fig. 5) having formed atits front half, two opposite sectors of an annulus 65, the arcuate length of each sector being approximately 60. The cylindrical portion 64 surrounds one end of a spindle 66 which is supported at two points for rotational movement, namely, the cylindrical portion 64, and a rear clutch plate 67. The forwardend of the spindle supports a driving cam or front clutch plate 68 having jaws which are adapted to mesh with jaws of the rear clutch plate 67. The clutch plates 67 and 68 form a disconnect clutch the purpose of which is toprevent transmission of power, when disconnected, to an impact clutch (later mentioned) inthe manner as is well known in the art. The rear clutch plate 67 is keyed to the spindle 66 by means of a key 69, and is rotatably mounted in a bearing 70 which is supported by a bearing support71; The bearing support 71 has a narrow walled cylindrical portion 72 which is closely fitted to the rear inner surface of the front housing 22. A key 73, arranged in part within the front housing 22 and the connecting portion 2]., maintains the bearing support 71 and the gearring 63 against rotational movement, the housing 22 and theconnectin'g portion 21 being further arranged to prevent lateral movement of the support 71 and the ring 63, as seen in Fig; 1. The cylindrical portion 72 has a slot 74 to provide clearance for the lever 55.

Enclosed within the cylindrical portion 72, and slidably surrounding a portion of the spindle 66, is a spring plate cam 75 having a flange 76 which is abutted by an accumulato'r spring 77, theoth er end of the spring abutting a wall of the idler gear cage 58. The spring 77 serves to accumulate and release energy as will be described in more detail hereinafter. The cam plate 75 has on the rearward end a pair of opposite sectors of an annulus 78 (Fig. 9), which are arranged to extend into the spaces between the sectors 65 of the idler gear cage 58, so that the spring plate cam 75 and the cylindrical portion 64 of idler cage 58 are substantially interlocked against rotational displacement, but free to move axially relative to each other. Two V-shaped notch earns 79 are formed on the forward inner surface of the spring plate cam 75, to receive balls 80, which ride in V-shaped grooves 81 formed on the surface of the spindle 66. A developed view of notch cams 79 is seen in Fig. 10.

Within the spindle 66 is a bore 82 which slidingly receives a portion of a pin 83, and a coil spring 84, the spring 84 being adapted to urge the pin outwardly from the bore 82. At the rear exterior portion of the spindle 66 is affixed a locking ring 85 which abuts a shoulder on the cylindrical portion 64 of the idler gear cage 58, to prevent forward movement of the spindle.

The rear clutch plate 67 has a pair of jaw members 86 (Fig. 6) which are adapted to interlock with jaw members on the driving cam 68. The front clutch plate 68 is affixed to an impact clutch arrangement 87, which comprises a pair of dogs 91, pivoted for rocking motion on pins 92 mounted in a cage 93 revolvable around anvil jaws 94, the dogs being driven by the driving cam 68, and arranged to deliver a series of rotational impacts to the tool head 88 in a well known manner. For further description of this type of impact clutch, reference is made to that shown and described in the patent to Amtsberg, 2,285,639, dated June 9, 1942. In non-operative position the jaws of clutch plates 67 and 68 are disengaged as shown, by virtue of the spring 84 forcing pin 83 forwardly to bear against a tool head or anvil 88, which is adapted to detachably connect with a socket member 89.

Turning now to a consideration of the operation of the Figure l embodiment of the invention as described above, the operator first engages the work piece by means of the socket member 89, and then forces the tool against the work piece and simultaneously presses trigger 27 to start the motor, thus causing the driving cam 68 to engage, i. e., interlock, with the rear clutch jaw 67 and turn the spindle 88. Once the jaws of 67 and 68 are interlocked they remain so, forming in effect a solid drive for as long as the operator keeps pressing on the work. Rotary motion is transmitted to the tool head 88, by way of the energy accumulator arrangement, including the idler cage 58, spring plate cam 75, balls 88, spindle 66, rear clutch jaws 67, driving cam 68, and the impact clutch arrangement 87.

During the first part of the tool operating cycle, or what may be called the run-up period, the impact clutch dogs remain in engaged condition, while the spring plate cam 75, due to the resistance of spring 77, moves rearward only a slight amount from full forward position as shown in Fig. 1. This rearward movement of the spring plate cam 75 results from the fact that the helical conformation of grooves 81 and notches 79 resolves the driving force into two components, one in a rotary direction to drive the spindle 66, and the other in a longitudinal direction tending to move cam 75 rearwardly relative to the spindle. As soon as the work piece is seated, or when the resistance to rotation increases a given amount, the impact clutch dogs become disengaged and an impact blow is delivered to the work piece, all as clearly described in the patent of Amtsberg supra. During the impacting cycle the torque load on the spindle 66 is pulsating and attains instantaneous values far in excess of the previous steady torque. The rise and fall of torque is accompanied bya corresponding increase and decrease in the amount of rearward displacement of cam plate 75 since the longitudinal component of force is proportional to the rotary or torsional component that drives spindle 66.

As the resistance to the tool head 88 increases further, the force of the hammer blow increases and the hammer assembly not only comes to a complete stop but actually rebounds in response to the energy stored in the anvil or tool head 88. The force of rebound is transmitted back to the driving cam 68, and clutch plate 67 to the spinle 66 causing the latter to reverse its direction of rotation momentarily. At the instant that the spindle is stopped in its rotation, the cam plate 75 has already moved rearwardly, as previously described. However, the rebound or reverse rotation of spindle causes a further rearward displacement of cam plate 75 as the latter continues to be driven by the cage 58 in the forward direction. During the interval between successive impacts the spring 77 is permitted to expand to return cam plate 75 to its forward position.

Each succeeding impact blow generates a force of rebound, which is transmitted from the spindle 66, through balls 80, to the spring plate cam 75, and then to the spring 77 with the resulting further compression thereof. As the resistance of the work piece to rotation increases, the energy of rebound increases and the spring 77 is successively compressed a greater amount with each impact blow. During this period the cam flange 76 is repeatedly displaced rearward at the end of each blow, with increasing amplitude to correspond with the increase in spring compression and energy accumulation. The energy stored in the spring, part of which occurs during rebound, is returned to the spindle by way of the balls and groove 81 arrangement, and such energy serves to accelerate the spindle 66 and the impact clutch arrangement 87 to an amount greater than would be possible by virtue of the motor 24 acting alone.

Referring to Fig. 26 it is seen that the curve starts at the point 0 and rises in a straight line (Hookes law), since the spring is not precompressed. Spring compression occurs during two steps, (1) while the impact clutch arrangement 87 is accelerating and the spindle 66 runs continuously, this step ending at the instant the dogs 91 declutch, (2) during the acceleration of the impact clutch arrangement while the spindle is still going faster than the clutch arrangement due to the inertia of the latter. The second step terminates at the instant when the clutch arrangement and spindle are going at the same speed after which the spring unwinds or expands. The total spring deflection is directly proportional to the force of the blow delivered by the tool head. While a gradual slope is shown, the torque is not continuously applied but rather is intermittent or pulsating. After the point of disengagement of the clutch dogs is passed, it is seen that the curve rises to a point at which the spring 77 deflection is of such magnitude as to cause cam flange 76 to come into contact with the associated abutment element or lever 55, thus causing movement of the push rod 52, to stop operation of the motor 24 by opening the contacts of switch 26, as heretofore explained. Simple adjustment of the normal axial position of the abutment element or lever 55 as explained, allows the tool to be set for any point of torque cut-ofi? within the range of the tool, which is 90 lbs. ft. in the example shown. It is to be noted that the embodiment shown is operative in either direction of rotation, for running up nuts or bolts, and further, that the trigger 27 must be completely released before the cut-off mechanism can be reset for the next operating cycle.

Thus it is seen that the invention, as applied to the embodiment described above, namely, a combination of power means with an energy accumulator and an impact clutch of the Amtsberg type, provides an arrangement whereby the operating cycle of the tool is completed in a very short time, and is automatically terminated when the point of desired torque is reached.

The method of utilizing the degree of accumulator spring deflection in a longitudinal direction to terminate the operating cycle of an impact wrench, is applicable to tools which differ structurally from that described above.

Referring to Fig. 14, another form of impact wrench,

illustrative of an embodiment of the invention, comprises a rear housing portion 100, vand a front housing portion 101, the portions being held together by bolt means 103, or equivalent. The rear portion encloses an electric motor or pneumatic motor (not shown), and has a handle extension 104 housing a switch means, not shown, of the conventional type, which is operated by way of a trigger 105. The forward portion of the motor shaft is supported for rotation in bearing 106, and has formed on the end thereof a pinion gear 107 adapted to engage a pair of gears 103, which are rotatably mounted in bearings 109. The bearings 109 are mounted on pins 110 which are affixed to an idler gear cage 111, the idler gear cage being mounted for rotation in bearing means 112 at one end, and at the other end by a shaft projection 113 which slidably fits a bore 114 arranged in a spindle 115. The gears 108 are further arranged to engage an internally geared ring 116, which extends about the gears, said gear ring 116 being held in position by engagement with the front and rear housing portions as shown. The arrangement of gears 1 07, 108 and ring 116 forms a planetary gear system whereby rotary motion of the motor shaft is transmitted so that the idler gear cage 111 rotates at a reduced rate of speed.

A splined section 117 is formed on a portion of the shaft projection 113 and is adapted to provide for reciprocal support of a rear clutch member 118 which has a pair of clutch jaws 119 arranged in opposition on the forward face. Abutting the rear face is a washer member 120 which supports a compression spring 121 at one end, the other end of the spring 121 contacting a wall 122 of the gear cage 111. A trigger member 123 is pivotally mounted on a pin 124 (Figs. 14 and 15) affixed within the front housing portion 101, and is urged by a spring 125 to latch on the edge of the washer memher 120, and restrict movement of the rear clutch jaw 118 and washer 120 when urged in the direction of spring 121. In contact with a forwardly extending portion of the trigger 123 is a fixed adjusting screw arm 126 which is positioned on a push rod 127. Adjacent the screw arm 126 is an abutment element or adjusting screw arm 128 which is threadably mounted on the push rod 127 by thread means as shown. The push rod 127 is positioned for longitudinal movement and is supported at a forward end in a bore 129 located in the front housing portion 101, and at the rear end in a bushing 130 which bears against the inner surface of the front housing portion 101, a portion of the spring 125, and an idler cage bearing 131. The latter closely surrounds the periphery of the idler cage 111, and provides further support thereto. A spring 132 surrounds the push rod 1.27 and urges a shoulder 133 of the push rod against an inner surface of the front housing 101 adjacent the bore 129. A slot 134 formed in the front housing 101 is arranged to maintain the adjusting screw arms 126 and 128 in downwardly extended position as best seen in Fig. 15. On the projecting extremity of the push rod 127 is a slot 135 adapted for the reception of a screw driver (not shown) which is used for the longitudinal adjustment of screw arm 128.

It will be seen that movement of the push rod 127 in the rearward direction, causes the adjusting screw arm 126 to move trigger 1.23 so as to pivot about pin 124 and disengage the end of the trigger from contact with the washer 120, and thus provide clearance for movement of the washer 120 and rear clutch member 118 rearward in opposition to the spring 121 as described below.

The rear end of spindle 115 has a clutch arrangement including two oppositely arranged jaws 136 which are adapted to mesh with the jaws 119 of the rear clutch member 113. This clutch arrangement is the disconnect clutch which permits the motor to run without the impact clutch being driven. Surrounding the shaft projection 113 and compressively maintained between the clutch memher 118 and the clutch arrangement of the spindle 115, is a spring 151 which is of such strength as to maintain the clutch jaws 119 and 136 in disengagement during neutral or non-operative condition of the tool, as shown in Fig. 14. The members 118 and 120 are arranged to float until they reach position in which the spring forces acting thereon are in balance. In other Words, with a tool head 146 in projected or in non-operative position, as shown in Fig. 14, springs 121 and 151 balance after the parts .118 and 120 reach a position just in front of the hook. on trigger 123. When the tool head 146 is forced rearwardly, i. e., in operative position, Fig. 24, the resultant force on springs 121 and 151 moves parts 118 and 120 back until the edge of washer 120 abuts against the book of trigger 123, and further rearward movement of parts and 120 is prevented.

Within the bore 114 of spindle 115, is a spring 137 which abuts at one end the shaft projection 113 of idler cage 111, and at the other end the spindle 115, to urge the spindle in a forward direction. The spindle 115 has a he ix groove arrangement 138 which is comprised of four right hand teeth. The purpose of the helix groove arrangement 138 is for the rotatable support of a clutch hammer 139, which is cylindrical in form and which extends about the spindle 115. A portion 140 of the hammer 139, has four right hand teeth, adapted to mesh with the helix groove arrangement 133. A ring 141 is aifixed to the shaft projection 113 to limit maximum forward movement of the hammer 139.

Extending about the spindle 115 and surrounded by the hammer 139, is a compression spring 142, the forward end of which abuts the hammer 139, the other end of which abuts a thrust bearing 143 which is supported on the spindle 115 at the end having the clutch arrangement, as best seen in Fig. 14. The forward end of the hammer 139 has a pair of oppositely arranged clutch jaws 144 which are adapted to engage a pair of clutch jaws 145 arranged on the anvil or tool head 146, which is rotatably mounted in a bushing 147 maintained in the front housing portion 101. The forward end of the tool head 146 has a socket arrangement 148 which is adapted to lockingly engage the shank of a screw driving or nut running implement, not shown. A portion 149 of spindle 115 is rotatably supported in a bore 150 located in the tool head 146.

It will be seen that the arrangement of the helix teeth on the spindle 115 and on the hammer 1 9 causes the hammer to move in a longitudinal direction as it rotates relative the spindle. The degree of mesh of jaws 144 and 145 is such that the hciix teeth arrangement will permit release of the jaws as the hammer 139 moves rearwardly along the spindle 115. In other words, the hammer 139, while moving rearward, will travel a distance greater than the depth of engagement of jaws 144- and 14-5, while rotating through an angle of approximately Considering now the operation of the embodiment of the invention above, the operator engages the work piece (not shown) by way of a screw driving or nut running implement (not shown) affixed to the socket arrangement 148, and simultaneously forces the tool in the direction of the work piece while pressing the trigger 105 to begin operation of the tool motor. In effect the housing portions 100 and 101 will move forward with respect to the tool head 146 and spindle 115, thereby causing the jaws 119 of rear clutch member 113, by reason of contact with trigger 123 which is affixed to housing 101 asv described, to enga e or interlock with the jaws 136 of spindle 115 (Fig. 24).

As the motor operates, the rotating motor shaft, by means of pinion 107, turns the idler gear cage 1.11, causing clutch member 118 to rotate and turn spindle 115. Since the resistance to rotation is generally small during the early or run-up portion of the operating cycle, the ham rner 139, due to the resistance of spring 142, is rotated with spindle 115, thereby causing rotation of thetool head 146 by way of engaged jaws 144 and 145. As the resistance to rotation of the work piece increases, the spring 142 is compressed by movement of the hammer 139 rearward relative to spindle 115, and the amount of interlocking of jaws 144 and 145 is decreased. This rearward movement results from helical conformation of grooved portion 138 which imparts to the hammer 139 a rearward or declutching component of force as well as a torsional or driving component. As the torque reaction increases, the driving component of force transmitted to the hammer increases correspondingly while the declutching component increases in proportion, thereby causing further compression of spring 142.

When the work piece is almost seated or driven tight, the resistance to rotation sharply rises, with the result that the compression of spring 142 is of such extent that jaws 144 and 145 are disengaged or unlocked. Immediately upon release of the hammer 139 from the anvil 146, it starts rotating and accelerating, but due to the inertia of the hammer it takes time to catch up to the speed of the spindle 115. During the catch up period, the spindle continues to run ahead of the hammer causing further compression of the spring 142. After the hammer attains the speed of the spindle the spring 142 expands and the hammer is accelerated beyond the speed of the spindle under the combined influence of the continued drive of the spindle and the action of the spring on the helical grooves. During the latter part of the acceleration period, while the spring expands and while the stored energy in the spring is released to the hammer, the latter moves forward until the clutch jaws 144, 145 strike with full engagement thereby resulting in an impact blow to the work piece. After each such impact blow the hammer 139 rebounds an amount which is proportional to the force of impact, and the energy of rebound is temporarily stored in the spring 142. As the rotational resistance of the work piece increases, the forces of rebound proportionally increase, and the dis placement or rearward longitudinal travel of the hammer increases to the point where the edge thereof contacts the abutment element or screw arm 128. Movement of screw arm 128 causes the push rod 127 to move rearwardly, whereupon screw arm 126 trips the trigger member 123; the rear clutch member 118 being thus released is caused to move rearwardly by virtue of spring 151, so that jaws 119 and 136 disengage, thereby discontinuing the tool operating cycle (Fig. 25).

By proper adjustment of screw arm 128 relative to hammer 139, the point of impact torque cut-off can be regulated to any degree within the range of the tool. It will be seen that before a new cycle of tool operation may take place, the tool must be moved away from the work piece a sutficient amount so that pressure on spring 151 is relieved to permit spring 121 to shift the washer member 120 forward, thus allowing spring 125 to return the trigger 123, whereupon the parts of the tool may assume the condition as illustrated in Fig. 14. Discontinuation of the tool motor operation during movement from one work piece to the next, is optional, as the clutch jaws 136 remain at rest in the Fig. 14 condition, whether the motor is running or not. The embodiment illustrated in Fig. 14 is for operation in one direction (right hand) of rotation, it being necessary to employ a tool having a spiral tooth arrangement reversed to that shown on the spindle 115, if rotation in the opposite direction is desired. It is to be noted that the torque cut-oft arrangement of the tool of Fig. 1, could be applied to the impact clutch of Fig. 14, and vice versa. For example, the part 55 of the Fig. 1 torque control would be in the plane now occupied by part 128 but at the bottom part of the housing.

Referring to Fig. 27 the distance X represents the amount of longitudinal movement of hammer 139 to effect impact clutch jaw disengagement; distance Y the additional longitudinal movement of hammer 139 to accelerate same to spindle speed with little or no rebound; and the point A represents the point where the degree of rebound is suificient to prevent secondary impact. Other important points of the graph are indicated thereon. As pointed out heretofore, and as illustrated on the graph, the amount of spring compression is proportional to the hammer rebound, after the force of blow has passed beyond the condition represented by point A.

Since the spring deflection increases proportionately,

with an increase of the force of the blow, the rearward movement of the hammer increases correspondingly. Therefor, in the embodiment of the invention illustrated in Fig. 14, the transmission of power is automatically cut oif on attainment of a predetermined rearward movement of the hammer, as soon as the force of the blow has attained a corresponding predetermined amount. The amount of hammer movement and hence of torque necessary to trip the trigger can be regulated by turning the push rod 127 thereby moving screw arm 128. For purposes of illustration the position of screw arm 128 is shown different in Fig. 14 than in Figs. 23,24, 25.

It will be appreciated that while the illustrative embodiments of the invention set forth above show an electric motor as a power source, it is possible to arrange the torque control for operation in a pneumatically powered impact tool. For example, in the Fig. 1 embodiment the push rod 52 could be moved to close a spring loaded throttle valve.

While the invention has been described in conjunction with specific embodiments thereof, it is possible that structural changes and modifications may be made without departing from the true spirit of the invention, as described herein and as defined in the appended claims.

What is claimed is:

1. An impact tool comprising in combination drive means, an energy accumulator including a compression spring, an impact means adapted in conjunction with said energy accumulator to transform constant rotary output of said drive means into successive and intermittent impact blows, clutch means interposed between said drive means and said impact means, and automatic means adapted to cut off operation'of said impact means upon attainment of a predetermined amount of energy accumulation in said energy accumulater.

2. An impact tool according to claim 1 wherein said automatic means is adjustable to vary the point of torque cut-off to any value within tool range.

3. An impact tool comprising in combination drive means, an energy accumulator including a compression spring, an impact means adapted in conjunction with said energy accumulator to transform constant rotary output of said drive means into successive and intermittent impact blows, clutch means interposed between said drive means and said impact means, and adjustable automatic means adapted to cut oif operation of said impact means upon attainment of a predetermined degree of spring compression.

4. An impact tool comprising in combination a front housing portion, a connecting portion, a rear housing portion having a handle section, said portions joined together by holding means, motor means positioned in said rear housing portion, a switch means including a trigger member arranged in said handle section, an energy accumulator including a spring means positioned within said front housing portion, an impact clutch mechanism arranged within said front housing portion and adapted in conjunction with said energy accumulator to transform constant rotary output of said motor means into successive and intermittent impact blows to drive a tool head, and means adapted to automatically cut ofi operation of said motor upon attainment of a predetermined amount of spring compression.

5. An impact tool according to claim 4 in which the slidably supporting a spring plate cam against which said spring means abuts, said plate cam having groove means on the inner surface for engagement with ball means which are maintained in V-shaped grooves arranged on the periphery of said spindle.

7. An impact tool according to claim 6 in which a clutch jaw member is afiixed to said spindle and is adapted to interlock with a clutch jaw member affixed to said impact clutch mechanism.

8. An impact tool having in combination a drive means including a motor, an energy accumulator including a compression spring, and an impact means which is adapted in conjunction with said energy accumulator to transform constant rotary output of said drive means into successive and intermittent impact blows, an automatic means adapted to cut off operation of said drive means when the impact blows attain a certain predetermined value, said automatic means including a lever arrangement which is caused to be moved when said spring is compressed a given amount, to thereby shift a lever of a switch means connected to the motor to terminate operation of the motor.

9. An impact tool having an automatic means according to claim 8 in which said lever arrangement comprises a push rod having a push rod lever adjustably mounted thereon, said push rod being arranged to bear against a link member which is pivotally connected at one end to a switch actuating rod, said link member having a hook-like projection at the other end which operatively engages a corner edge of a trigger which is adapted to be manipulated to cause said actuating rod to be moved by way of said link member and operate said switch means, the push rod being further arranged upon movement thereof to cause disengagement of said hook-like projection of the link member and the corner edge of the trigger, whereupon the switch actuating rod is caused by a spring means to be moved so that said switch means is made inoperative.

10. An impact tool having a push rod according to claim 9, in which a shoulder is arranged near one end of said push rod, said shoulder being urged against an inner surface of a front housing of the tool portion by means of a compression spring, said push rod further having slot means on the end thereof for the longitudinal adjustment of said push rod lever.

11. An impact tool comprising in combination a front housing portion, a rear housing portion having a handle section, said portions joined together by holding means, motor means positioned in the rear housing portion, a switch means including a trigger member arranged in said handle section, an energy accumulator including an accumulator spring means and a hammer member positioned within said front housing portion, a first clutch means to connect said motor means to said energy accumulator, a second clutch means to connect said energy accumulator to a tool head, and automatic means to disconnect said first clutch means when a predetermined amount of energy is accumulated in said energy accumulator.

12. An impact tool according to claim 11 in which the energy accumulator is driven by the motor means through a planetary gear system.

13. An impact tool according to claim 12 in which, the planetary gear system includes a cage member having a shaft projection including a splined portion, said splined portion slidingly supporting a rear clutch jaw forming part of the first clutch means, a trigger member positionable to restrict rearward movement of said rear clutch jaw, and push rod means movable to release engagement of said trigger member with said rear clutch jaw so that the latter may move rearwardly on said splined portion and disconnect the motor means from the energy accumulator.

14. An impact tool according to claim 13 in which a spindle clutch means forming a part of the first clutch means is integral with a spindle, said spindle having a helix tooth arrangement for the rotatable support of the hammer member by way of a matching helix tooth arrangement on the hammer member, a thrust bearing arranged adjacent the spindle clutch means, said accumulator spring abutting at one end the hammer member and the thrust bearing at the other end.

15. An impact tool according to claim 14 wherein the second clutch means connecting the energy accumulator to the tool head is arranged to disengage when the hammer member is caused to move longitudinally away from the tool head as it rotates on the helix tooth arrangement of the spindle, said longitudinal movement causing the push rod means to be moved after the hammer member has travelled longitudinally a predetermined distance.

16. An impact tool comprising in combination a tool head, an impact means for imparting impact blows to the tool head, a driving means for the impact means, a clutch adapted in operative position to couple the impact means with the driving means, torque control means arranged to disengage the clutch and thereby prevent further operation of the impact means when an impact blow of predetermined magnitude is delivered to the tool head, and means for maintaining the impact means inoperative until the operator first releases then reapplies longitudinal pressure to the tool head so that the impact means is coupled to the driving means.

17. An impact wrench comprising a motor having a rotor, a hammer assembly rotatably connected with the rotor, an elongated tool head having at one end an anvil arranged to receive a succession of torsional impulses delivered by the hammer assembly and at the other end being adapted to drive a wrench socket, means having a variable axial movement with respect to said hammer assembly in response to the force of the individual torsional impulses, and means operative upon a predetermined axial movement of the variably movable means to discontinue operation of the motor.

18. An impact wrench comprising a rotatable anvil, a rotatable hammer arranged to deliver a series of rotational impacts to said anvil and to rebound longitudinally therefrom subsequently to such delivery, driving means for the hammer, means for connecting the anvil to a driven element having gradually increased resistance to rotation whereby to cause a step-by-step increase in the peak torque of the impacts and consequently in the distance of rebound of the hammer from the anvil, a trigger arrangement interposed in the path of movement of the hammer and positioned to be operated thereby upon longitudinal movement of the hammer a predetermined distance, and automatic means responsive to the operation of the trigger arrangement for disabling the means for driving the hammer.

19. An impact tool comprising in combination a drive means, an energy accumulator driven thereby, an impact means driven by the accumulator and adapted in conjunction with said energy accumulator to transform output of said drive means into successive and intermittent impact blows of variable intensity, and mechanical means adapted to terminate operation of said impact means upon attainment of a predetermined amount of energy accumulation in said energy accumulator corresponding to an impact blow of predetermined intensity.

20. An impact tool comprising in combination a drive means, an energy accumulator driven thereby, an impact means driven by said accumulator adapted in conjunci3 tion with said energy accumulator to transform output of said drive means into successive and intermittent impact blows of variable intensity, and mechanical means movable in response to a predetermined amount of energy accumulation in said energy accumulator to terminate operation of said impact means.

21. A tool for production of impact blows comprising in combination a drive means, an energy accumulator which is driven thereby and is arranged for variable movement in response to reaction forces of the impact blows, an impact means adapted in conjunction with said energy accumulator to transform output of said drive means into successive and intermittent impact blows, and mechanical means responsive to a predetermined movement of said energy accumulator to terminate operation of said impact means.

22. An impact tool including a tool head, comprising in combination a drive means, an energy accumulator having a compression spring means, an impact means adapted in conjunction with said energy accumulator to transform output of said drive means into successive and intermittent impact blows of variable intensity to the tool head, displaceable means movable successively in varying amounts corresponding to the amount of spring compression and mechanical means adapted to automatically cut off operation of said drive means upon attainment of a predetermined amount of spring compression said out off means comprising an abutment element positioned adjustably in the path of the displaceable means to be contacted thereby.

23. An impact wrench comprising a rotatable anvil, a rotatable hammer arranged to deliver a series of rotational impacts to said anvil and to rebound longitudinally therefrom subsequent to such delivery, driving means for the hammer, means for connecting the anvil to a driven element having gradually increased resistance to rotation whereby to cause a step-by-step increase in the peak torque of the impacts and consequently in the distance of rebound of the hammer from the anvil, and means for automatically disabling the driving means upon a predetermined longitudinal rebound of the hammer.

24. An impact wrench comprising a rotatable hammer, rotatable means for driving the hammer, a tool head having at one end an anvil arranged to receive a succession of torsional impulses of variable intensity delivered by the hammer and at the other end being adapted to drive a wrench socket, displaceable means associated with the hammer and having a variable axial movement with respect to the anvil in response to the force of the individual torsional impulses, and automatic means operative upon a predetermined axial movement of the displaceable means to terminate rotation of the means for driving the hammer, said terminating means comprising an abutment element interposed in the path of the displaceable means and capable of adjustment toward and from the anvil.

25. An impact wrench according to claim 24 in which the abutment element is adjusted by means of a screw threaded connection to predetermine the extent of axial movement of the displaceable means required for the actuation of said element.

References Cited in the file of this patent UNITED STATES PATENTS 1,130,463 Barrett Mar. 2, 1915 1,314,678 Long Sept. 2, 1919 1,881,728 Levedahl Oct. 11, 1932 2,144,769 Melmer I an. 24, 1939 2,160,622 Olson May 30, 1939 2,219,865 Fitch Oct. 29, 1940 2,261,204 Amtsberg Nov. 4, 1941 2,285,638 Amtsberg June 9, 1942 2,285,639 Amtsberg June 9, 1942 2,372,723 Symons Nov. 24, 1942 2,533,703 Wilhide Dec. 12, 1950 2,539,678 Thomas Jan. 30, 1951 2,543,979 Maurer Mar. 6, 1951

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