Impact Wrench

Abstract

An electrically driven impact wrench is adapted to be used both for assemblying end disassemblying threaded fasteners. The hammer of this wrench is rigidly connected to a rotor of the electric motor enclosing a stator; an anvil is constantly springly urged towards the hammer, while a space between the impact jaws of the anvil and hammer is defined by locking means operatively connected to a spindle.

Description

The present invention relates to electrically driven impact wrenches to be used for tightening and loosening threaded fasteners.

Electrically driven impact wrenches are known (cf. U.S. Pat. No.2,792,732, Cl.81- 52 and U.S. Pat. No.2,753,965, Cl.192- 30.5).

In these prior art wrenches a drive comprises an electric motor and a reducing gear. The output shaft of the reducing gear functions as the driving shaft of an impact clutch. In the wrench according to U.S. Pat. No.2,792,732 mounted on the driving shaft and on a hammer are sleeves provided with arcuated surfaces between which there are disposed balls. The hammer is urged to an anvil by a spring, and is rotating and reciprocating during the operation of the wrench. The anvil is made integral with a spindle.

The impact wrench according to U.S. Pat. No.2,753,965 comprises an intermediate member which is mounted for reciprocation, and is constantly connected to the rotating hammer by means of pins. The spring acts upon said intermediate member which is reciprocated by means similar to those disclosed in U.S. Pat. No.2,792,732.

In prior art impact wrenches the moment of inertia of the hammer and anvil, force of the spring, shape of cam and arcuated surfaces, gear ratio of the reducing gear, power and rotational speed of the motor represent interrelated variables defining the characteristics of the wrench, such as single impact energy, frequency of blows, weight of the wrench, as well as the respective specific parameters thereof.

The experience of operation of these impact wrenches shows that, with the optimum ratio between the above-mentioned interrelated variables single impact energy is low (smaller than 1 kgf.m), maximum frequency of blows is as high as 35 blows per second, and the wrench is rather heavy. During the tightening of threaded fasteners using these wrenches elevated noise and vibrations occur due to the high frequency of blows; furthermore, since the single impact energy is low, a large number of blows are required (of the order of 100-200) to tighten a threaded fastener, which results in low efficiency of the operation due to high energy losses.

The impact wrenches of the above-described types are not employed for tightening critical threaded fasteners, where high accuracy of the tightening force is required, since the monitoring of the tightening by means of torque control devices (torsion bars, inertial means, etc.) is rather difficult due to the high frequency of blows and the necessity of imparting a large number of blows.

The situation becomes more complicated, if one takes into account the fact that the amount of single impact energy varies from one blow to another.

It should also be noted that in view of relatively low single impact energy such wrenches have a limited range of application and cannot be employed for tightening large-size bolts.

Attempt were made to increase the single impact energy of a wrench and to provide for the control of the tightening by an operator by utilizing the energy of a rotating part of the electric motor at the instant of blow and by effecting the tightening of a threaded fastener by imparting single blows (cf.U.S.S.R. Inventor's U.S. Pat. Certificate No.324,139, Cl.B 25 b 21/02).

In this impact wrench the housing accommodates a hammer rotated by an electric motor and rigidly connected to a rotor of the electric motor, said rotor enclosing a stator, an anvil mounted coaxially with the hammer and provided with end teeth, and a spindle rigidly connected to the anvil and provided with means adapted to receive a socket wrench.

Mounted between the hammer and anvil is an intermediate member which is provided with impact jaws disposed at one end thereof for co-operation with impact jaws of the hammer and with end teeth disposed at the other end thereof to co-operate with the end teeth of the anvil, said intermediate member being connected to the hammer by means of a torsional spring ensuring a contact between non-working surfaces of the impact jaws during the acceleration of the hammer.

In such impact wrenches the edge application of blow is eliminated due to co-operation between helical surfaces on the hammer end and the end faces of the impact jaws of the intermediate member, which results in a very complicated structure of the wrench and friction losses. In addition, it should be noted that at the instant of engagement of the end teeth of the intermediate member and the anvil, respectively, the impacting resulting in vibrations and rapid wear of the component parts of the wrench takes place.

It should also be noted that this embodiment of the wrench does not allow reversible operation.

It is an object of the present invention to provide an impact wrench which can be used for tightening and loosening threaded fasteners.

It is another object of the present invention to provide an impact wrench in which the tightening takes place under the control by an operator with high single impact energy, the energy losses for engagement between the impact jaws of the hammer and anvil being minimized.

Still another object of the invention is to provide an impact wrench having a reliable and durable structure.

With these and other objects in view in an impact wrench comprising a housing accommodating a hammer rotated by an electric motor, said hammer being rigidly connected to a rotor of the electric motor, said rotor enclosing a stator, an anvil mounted coaxially with the hammer and provided with impact jaws adapted to co-operate with impact jaws of the hammer, and a spindle connected to the anvil for rotation therewith at the instant of the co-operation between said impact jaws, said spindle being provided with means adapted to receive a socket wrench, according to the invention, the anvil and the spindle are interconnected in such a manner as to allow a relative axial movement therebetween, while the anvil is constantly springly urged towards the hammer, locking means being provided to define a space between the impact jaws of the anvil and the hammer respectively during the acceleration of the hammer, said locking means being operatively connected to the spindle and during the initial movement of the spindle towards the hammer upon pushing forward the wrench housing preventing the anvil from moving towards the hammer, and during further movement of the spindle towards the hammer, releasing the anvil for its movement towards the hammer for co-operation with the impact jaws, means being provided to deenergize the electric motor during the movement of the anvil towards the hammer.

Due to the fact that the anvil and the spindle are axially movable relative to each other, and the anvil is constantly springly urged towards the hammer, the space being provided therebetween by locking means, the engagement between the impact jaws of the hammer and anvil is effected under the action of a preliminary applied urging force acting upon the anvil, whereby the whole power of the electric motor is utilized at the instant of the co-operation between the impact jaws to tighten a threaded fastener.

Furthermore, the provision of locking means allows the engagement between the impact jaws without impacting, whereby rapid wear of component parts and vibrations are eliminated resulting in higher reliability and durability of the impact wrench.

The provision in the impact wrench of means deenergizing the electric motor during the movement of the anvil towards the hammer prevents the electric motor from operating under braking conditions.

It is advantageous that the operational connection between locking means and the spindle be effected by means of cams and disengaging means co-operating therebetween during the movement of the spindle towards the hammer, the cams being oriented with respect to the impact jaws of the hammer and being associated there with while said disengaging means being oriented with respect to the impact jaws of the anvil, the orientation of the cams consisting in that said cams associated with the hammer are arranged at any appropriate angle with respect to the hammer jaws, while said disengaging means connected to the spindle are arranged at the same angle with respect to the anvil jaws.

This permits to release the anvil for its movement towards the hammer at the instant when the impact jaws of the hammer and the anvil are disposed opposite each other, whereby the edge application of blow is eliminated.

It is advantageous that spring urging of the anvil towards the hammer be effected by means of a spring, one end of the spring abutting against a bearing surface provided on the spindle, while the other end abutting against a bearing surface provided on the anvil.

It is advantageous that means deenergizing the electric motor comprise a switch mounted in the housing and inserted in the electric motor supply circuit, and a resilient lever, one end of the lever being pivoted to the housing, the other end being engaged with a projection of the anvil, and the intermediate portion of the lever being adapted to actuate said switch.

It is advantageous that the bearing surface of the spindle comprise an annular flange disposed on the external peripheral surface of the spindle, while the bearing surface of the anvil comprise a shoulder made on the external peripheral surface of the anvil.

It is advantageous that said locking means comprise a sleeve with a shoulder disposed between the anvil and the spring urging the anvil, said sleeve enclosing the anvil and said shoulder abutting against the shoulder of the anvil, said sleeve being maintained in this position by said spring, levers urged towards the anvil by means of an annular spring, each lever having an enlarged portion at one end and a hook at the other end thereof, said levers being placed in longitudinal slots, some slots being made on the peripheral surface of the anvil to receive the enlarged portions of the levers which are retained in said slots by means of said sleeve, and the other slots being made in the annular flange of the spindle, and a bushing provided with an annular projection adapted to be engaged by the hooks of the levers, the spindle extending through this bushing, said bushing being mounted in the housing at the point where the spindle extends outside the housing, the spindle being provided with an axial bore, the hammer being provided with a shaft mounted within the bore of the spindle, said cams oriented with respect to the impact jaws of the hammer being fixed to the peripheral surface of said shaft, while said disengaging means comprising pushers mounted in radial passages of the spindle, said pushers co-operating with the cams fixed to the shaft and with the levers during the movement of the spindle towards the hammer to disengage the levers from the annular projection of the bushing and to release the anvil for its movement towards the hammer.

A compression spring may be mounted in the spindle bore between the bottom thereof and the shaft, said spring returning the spindle into its initial position, while the peripheral surface of the spindle may be provided with a retaining ring adapted to limit axial movement of the anvil along the spindle.

According to another embodiment of the locking means it is advantageous to provide the spindle with an axial bore enlarging towards the hammer due to the provision of two portions of different diameters, said spring being mounted in the enlarged portion of the bore, the bearing surface of the spindle comprising a shoulder between the two portions of the bore, while the bearing surface of the anvil being formed by pins mounted in radial passages made in the anvil and extending into the enlarged portion of the bore through longitudinal slots of the spindle, the length of these slots being equal to that of the anvil axial movement along the spindle.

In this embodiment it is advantageous that the locking means comprise a sleeve mounted in said enlarged portion of the bore and provided with an annular groove, the pins connecting the sleeve to the anvil abutting against this groove, and levers having some ends interconnected by a compression spring and provided with thrust surfaces co-operating with the end face of the sleeve and with cam surfaces made in the form of bevels on the outer sides of the levers, the stator of the electric motor being provided with an axle extending through the spindle bore and provided with longitudinal slots on the peripheral surface, said slots accommodating the other ends of said levers which are retained in these slots by means of a bushing mounted on the axle, said disengaging means comprising cams having inclined surfaces and disposed on the end face of the spindle, and the cams oriented with respect to the impact jaws of the hammer being also provided with inclined surfaces and disposed on a flange of a tubular member which is springly urged towards the anvil, said tubular member being mounted on the hammer and enclosing said axle, the tubular member being mounted for rotation with the hammer and for axial movement with respect thereto and being provided with an internal radial annular projection adapted to co-operate with said cam surfaces of the levers during the co-operation between said cams oriented with respect to the impact jaws of the anvil and the hammer, respectively, whereby said levers enter the axle slots to release the sleeve and the anvil for movement towards the hammer.

In the narrower portion of the bore between the bottom thereof and the axle there is preferably mounted a compression spring which causes the spindle to move away from the hammer after the co-operation between the impact jaws of the hammer and anvil, while the external peripheral surface of tubular member is provided with a retaining ring which limits axial movement of the tubular-member with respect to the hammer.

In accordance with the third embodiment of said locking means the spindle is preferably provided with an axial bore enlarging towards the hammer due to provision of three portions of different diameters, the intermediate portion of the spindle accommodating said spring, the bearing surface of the spindle comprising a shoulder disposed between the wider portion of the bore and the intermediate portion thereof, and the bearing surface of the anvil comprising pins mounted in radial passages of the anvil and extending into the intermediate portion of the bore through longitudinal slots made in the spindle.

In this embodiment it is advantageous that said locking means comprise a hollow member connected to the spindle by means of a torsional recoil spring, said hollow member being mounted in the wider portion of the bore in such a manner that one end of said member projects beyond the spindle, said hollow member having a splined portion on the internal peripheral surface thereof and V-shaped grooves on the external peripheral surface thereof, balls disposed in said V-shaped grooves and in radial passages of the spindle, and a sleeve rotatably mounted in the wider portion of the bore and provided with projections adapted to abut against said pins and with a splined portion adapted to co-operate with the splined portion of the hollow member and to rotate the sleeve, the anvil being released for its movement towards the hammer upon said rotation, the stator of the electric motor being provided with an axle mounted in the spindle bore, said disengaging means comprising cams fixed to the end face of the hollow member, while the cams oriented with respect to the impact jaws of the hammer being fixed to a liner rigidly secured in the hammer bore, said axle extending through said liner.

In the narrower portion of the bore, between the bottom thereof and the axle there is preferably mounted a compression spring adapted to move the spindle away from the hammer after the co-operation between the impact jaws of the hammer and anvil, while the external peripheral surface of the spindle is provided with a retaining ring which limits axial movement of the anvil along the spindle.

Thus, the impact wrench according to the invention permits to enlarge the range of application of impact wrenches, to perform accurate tightening of threaded fasteners, improves the efficiency of the operation, considerably improves technical and operational characteristics and specific parameters of the wrenches, and contributes to reduction of noise and vibrations.

The invention will be better understood from the following description of specific embodiments of an impact wrench given with reference to the accompanying drawings, in which:

FIG.1 shows a general view of the impact wrench according to the invention;

FIG.2 is a longitudinal sectional view taken along line II--II in FIG.1;

FIG.3 shows a longitudinal sectional view of the locking means;

FIG.4 is a sectional view taken along line IV--IV in FIG.3;

FIG.5 is a sectional view taken along line V--V in FIG.3;

FIG.6 is a sectional view taken along line VI--VI in FIG.4;

FIG.7 shows a longitudinal sectional view of another embodiment of the wrench locking means;

FIG.8 is a sectional view taken along line VIII--VIII in FIG.7;

FIG.9 is a sectional view taken along line IX--IX in FIG.7;

FIG.10 is a sectional view taken along line X--X in FIG.7;

FIG.11 is a sectional view taken along line XI--XI in FIG.10;

FIG.12 shows a longitudinal sectional view of still another embodiment of the wrench locking means.

FIG.13 is a sectional view taken along line XIII--XIII in FIG.12;

FIG.14 is a sectional view taken along line XIV--XIV in FIG.13;

FIG.15 is a sectional view taken along line XV--XV in FIG.12; and

FIG.16 is a sectional view taken along line XVI--XVI in FIG.12.

An impact wrench comprises a housing 1 (FIG.1) accommodating a hammer 2, an anvil 3 mounted coaxially with the hammer and a spindle 4.

The hammer 2 is provided with impact jaws 5 adapted to co-operate with impact jaws 6 of the anvil 3.

The anvil 3 is mounted on the spindle 4 which is of a polygonal, e.g. hexagonal shape in its cross section (FIG.2), whereby the spindle and the anvil will rotate together during the co-operation of the jaws 5 and 6 (FIG.1) and are made axially movable relative to each other.

The end of the spindle 4, which extends outside the housing 1 is provided with means 7 adapted to receive a socket wrench.

The hammer 2 is rotated by an electric motor, a stator 8 of the electric motor being secured to a fixed axle 9 which is fixed to the housing by means of a screw 10, while a rotor 11 encloses the stator 8 and is rigidly connected to the hammer 2.

The hammer 2 and the rotor 11 are secured by means of screws 12 to a cover 13, which is mounted on the axle 9 and rests on a bearing 14.

The hammer 2 is journaled in the housing 1 by means of a bearing 15, the hammer 2 being supported by this bearing over the external surface of the hammer.

The anvil 3 is constantly urged by a spring 16 towards the hammer 2, one end of the spring 16 abbuting against a bearing surface 17 of the spindle 4, and the other end abutting against a bearing surface 18 of the anvil 3.

A space between the impact jaws 5 and 6 during the acceleration of the hammer 2 is defined by a locking means 19 which is operatively connected to the spindle 4.

During the initial movement of the spindle 4 towards the hammer 2, upon pushing forward the wrench housing 1, the spring 16 is compressed, and a locking means 19 prevents the anvil 3 from moving towards the hammer 2, while during further movement of the spindle 4 said locking means releases the anvil for its movement towards the hammer 2 under the action of the spring 16 and for the co-operation of the impact jaws 5 and 6.

The operative connection between the locking means 19 and the spindle 4 comprises cams 20 and disengaging means 21 which co-operate therebetween during the movement of the spindle 4 towards the hammer 2, the cams 20 being oriented with respect to the impact jaws 5 of the hammer 2 and being associated therewith, while said disengaging means 21 being oriented with respect to the impact jaws 6 of the anvil 3 and being connected to the spindle 4. The orientation of the cams 20 and disengaging means 21 consists in that the cams 20 are arranged at any appropriate angle with respect to the impact jaws 5, while said disengaging means 21 are arranged at the same angle with respect to the impact jaws 6.

The wrench is provided with two handles, one of which indicated at 22 may be made removable, so that it can be screwed in and unscrewed from the housing 1 when operating in reastricted locations, while the other handle 23 is rigidly secured to the housing 1.

In order to deenergize the electric motor upon each movement of the anvil 3 towards the hammer 2, there is provided a means 24. This means comprises a switch 25 mounted in the housing 1 and a resilient lever 26 having one end pivoted to the housing 1 at 27. The other end of the lever 26 is adapted to engage a flange 28 of the anvil 3, while the intermediate portion of the lever is adapted to actuate the switch 25.

A switch 29 for energization of the electric motor is mounted in the handle 23, the switches 25 and 29 being cut in the electric motor supply circuit (not shown in the drawings).

The locking means 19 of the wrench may be of different structures, and the following description will disclose three embodiments thereof, which in our opinion, are the best for accomplishment of the objectives of the invention.

EMBODIMENT I

The locking means 19 comprises a sleeve 30 (FIG.3) having a shoulder 31, levers 32 urged towards the anvil 3 by means of an annular spring 33, and a bushing 34, through which the spindle 4 extends, said bushing 34 being mounted in the housing 1 at the place where the spindle 4 extends outside the housing.

In this embodiment of the locking means 19 the bearing surface 17 of the spindle 4 comprises an annular flange 35 disposed on the external peripheral surface of the spindle, while the bearing surface 18 of the anvil 3 comprises a shoulder made on the external peripheral surface of the anvil. The sleeve 30 is mounted on the anvil 3 in such a manner as to be disposed between the anvil 3 and the spring 16, the shoulder 31 of the sleeve 30 abutting against the shoulder 36, and the spring 16 urges the shoulder 31 to the shoulder 36, thereby retaining the sleeve 30 urged to the anvil 3, the shoulder 31 of the sleeve 30 being bent down as shown in FIG.3, this bent end of the shoulder 31 functioning as the flange 28 against which the lever 26 abuts.

Each lever 32 is provided with an enlarged portion 37 at one end and with a hook 38 at the other end, the enlarged portion 37 and the hook 38 being turned relative to each other so that they are disposed in mutually perpendicular planes (FIG.4). The levers 32 are placed in longitudinal slots 39 and 40. The slots 39 are made on the peripheral surface of the anvil 3 and are shaped so as to accommodate the enlarged portions 37 of the levers 32. The levers 32 are retained in the slots 39 by means of the sleeve 30 (FIG.3). Slots 40 (FIG.4) are made in the annular flange 35 of the spindle 4.

The bushing 34 (FIG.3) is mounted in the housing 1 in the place where the spindle 4 extends outside the housing, and is provided with an annular projection 41, the hooks 38 of the levers 32 engaging this annular projection.

The spindle 4 is provided with an axial bore 42, while the hammer 2 (FIG.1) is rigidly secured by means of screws 43 with a shaft 44 extending through the bore 42 (FIG.3) of the spindle 4. Mounted on the peripheral surface of the shaft 44 by means of screws 45 are the cams 20, i.e., the cams which are oriented with respect to the impact jaws 5 of the hammer 2, while the diengaging means 21 (FIG.1) comprise pushers 46 (FIG.3) disposed in radial passages 47 of the spindle 4. During the movement of the spindle 4 towards the hammer 2 each pusher 46 engages by one end one of the cams 20 (FIG.5), while the other end of the pusher co-operates with the lever 32, thereby expanding the spring 33 (FIG.6) disposed in the annular groove of the anvil 3 to disengage the hooks 38 (FIG.3) from the annular projection 41 of the bushing 34 and to release the anvil 3 for its movement towards the hammer under the action of the spring 16.

A compression spring 48 is mounted in the bore 42 of the spindle 4 between the bottom thereof and the end face of the shaft 44, said spring being adapted to return the spindle into its initial position upon engagement of the impact jaws 5 and 6, the spring 48 abutting by one end against a shoulder 49 of the shaft 44, and the other end of the spring abutting against a ball support 50.

A retaining ring 51 is mounted on the peripheral surface of the spindle 4 which is adapted to limit axial movement of the anvil 3 during its retraction into the initial position after the blow, i.e., upon interaction between the impact jaws.

In this embodiment of the locking means 19 the wrench functions as follows.

Upon actuation of the switch 29 (FIG.1) the electric motor is energized. The rotor 11 begins to rotate together with the hammer 2.

When the electric motor is running at full speed, the operator pushes forward the handles 22 and 23 to move the housing 1 towards a nut (or a bolt) to be tightened, the spindle 4 moving with respect to the bushing 34 (FIG.3) to compress the spring 48. At the same time, the annular projection 35 of the spindle 4 compresses the spring 16, the other end of the spring abutting through the intermediary of the shoulder 31 of the sleeve 30 against the anvil 3, which is retained by means of the hooks 38 of the levers 32 engaging the annular projection 41 of the bushing 34.

The pushers 46 mounted in the radial passages 47 of the spindle 4 engage the cams 20 of the shaft 44.

The cams 20 displace the pushers 47 in the passages 47, the pushers urging the levers 32 loaded by the annular spring 33. The hooks 38 of the levers 32 disengage from the annular projection 41 of the bushing 34, and the anvil 3 moves towards the hammer 2 under the action of the spring 16.

The anvil can move only after the impact jaws 5 of the hammer 2 and the impact jaws 6 of the anvil 3 have been positioned opposite each other, which is achieved due to the fact that the cams 20 of the shaft 33 are oriented with respect to the impact jaws 5 of the hammer 2, and the pushers 46 are oriented with respect to the impact jaws 6 of the anvil 3.

The anvil 3, while moving along the hexagonal surface of the spindle 4 (FIG.2) towards the hammer 2 (FIG.1), engages by its impact jaws 6 the impact jaws 5 of the hammer 2, and a blow is imparted, during which time period, the kinetic energy accumulated in the rotating hammer 2 and the rotor 11 is transmitted through the anvil 3 and the spindle 4 into the threaded fastener being toghtened. At the same time, the anvil 3, which moving towards the hammer 2, releases the resilient lever 26 which actuates the switch 25 to deenergize the electric motor of the wrench.

To impart a next blow it is necessary to move the wrench away from the threaded fastener, the spring 48 returning the spindle 4 into its initial position.

During the movement of the spindle 4 under the action of the spring 48 away from the hammer 2 (FIG.3) the retaining ring 51 causes the anvil 3 to move away from the hammer 2, while the levers 32 engage the annular projection 41 of the bushing 34 by their hooks 38.

The anvil 3 presses against the resilient lever 26 through the sleeve 30 with the shoulder 31, the lever actuating the switch 25. The switch 25 closes the electric motor supply circuit, and the blow can be repeated.

EMBODIMENT II

The locking means 19 (FIG.1) comprise a sleeve 52 (FIG.7) and levers 53. In this embodiment of the locking means the spindle 4, which passes through a bushing 54 mounted in the place of the housing 1, where the spindle extends outside the housing, is provided with an axial bore which becomes wider towards the hammer 2 due to provision of two portions 55 and 56 of different diameters.

The stator 8 of the electric motor is provided with an axle 57 which is made as a prolongation of the axle 9 (FIG.1) and is adapted to journal the hammer 2 in the housing 1.

The axle 57 extends through the bore of the spindle 4, and is provided with longitudinal slots on the peripheral surface thereof.

The spring 16 urging the anvil 3 towards the hammer 2 is mounted in the enlarged portion 56 of the bore. The bearing surface 17 (FIG.1) of the spindle 4 in this embodiment comprises a shoulder 59 (FIG.7) disposed between the portion 56 and the reduced portion 55 of the bore. The bearing surface 18 (FIG.1) of the anvil 3 is made up by pins 60 (FIG.8) mounted in radial passages 61 of the anvil 3 (FIG.7) and extending into the portion 56 of the bore of the spindle 4 through longitudinal slots 62 of the spindle 4, the length of the slots being equal to that of the axial movement of the anvil 3 along the spindle 4.

In this embodiment the sleeve 52 is placed in the portion 56 of the bore, and is provided with an annular groove made on the peripheral surface thereof, the pins 60 resting against this groove to connect the sleeve 52 with the anvil 3.

The sleeve 52 is provided with a hole 64 (FIG.8) disposed in the zone of the annular groove 63 to pass the pins 60 during the assembly of the wrench.

Some ends of the levers 53 (FIG.7) are interconnected by means of a compression spring 65, and are provided with thrust surfaces which co-operate with the end face of the sleeve 52 and with cam surfaces 67 made in the form of bevels provided on the outer sides of the levers 53. The other ends of the levers 53 are placed in the slots 58 of the axle 57 and are retained therein by means of a bush 68 mounted on the axle 57.

The disengaging means 21 (FIG.1) comprise cams 21a, the cams 21a and the cams 20, which are oriented with respect to the impact jaws 5 of the hammer 2, having inclined surfaces 69 (as is shown in FIG.9), the cams 21a being arranged on the end face of the spindle 4 (FIG.7), facing the hammer 2, and the cams 20 being arranged on a flange 70 of a tubular member 72 urged towards the anvil 3 by means of a spring 71, said tubular member 72 being mounted on the hammer 2, the axle 57 extending through this tubular member.

The tubular member 72 is mounted in the bore of the hammer 2 with the aid of sperical keys 73 (FIGS. 10 and 11), and is capable of rotating rogether with the hammer 2 while being axially movable with respect thereto. A retaining ring 74 is mounted on the external peripheral surface of the tubular member 72 to limit its axial movement relative to the hammer.

The internal surface of the tubular member 72 (FIG.7) is provided with a radial annular projection 75 adapted to co-operate with the cam surfaces 67 of the levers 53 during the interaction of the cams 20 and 21a. This co-operation results in that the levers 53 come into the slots 58 of the axle 57 to release the sleeve 52 and the anvil 3 connected to the latter by means of the pins 60, whereby the anvil moves towards the hammer 2.

The compression spring 48 similar to the compression spring 48 of the locking means according to the first embodiment is mounted in the portion 55 of the bore of the spindle 4 between the bottom of the bore and the axle 57. This spring abuts against the ball support 50 which is similar to the ball support 50 according to the first embodiment.

The wrench having the above-described locking means functions as follows.

After the operator has pushed forward the handles 22 and 23 (FIG.1), upon energization of the electric motor, the housing 1 of the wrench is moved towards a threaded fastener to be tightened, and the spindle 4 compresses the spring 48 while moving along the bushing 54 towards the hammer 2. At the same time, the spring 16, which abuts by one end against the sleeve 52 (FIG.7) and by the other end against the shoulder 59, is also compressed, the sleeve 52 abutting against the thrust surfaces 66 of the levers 53.

During the movement of the spindle 4 the cams 20 and 21a contact each other with their inclined surfaces 60 (FIG.9) to move the tubular member 72 (FIG.7). The tubular member 72, while moving within the hammer 2 axially thereof and away from the anvil, compresses the spring 71 and presses upon the cam surfaces 67 of the levers 53, whereby the levers are urged into the longitudinal slots 58 of the axle 57, the levers 53 compressing the spring 65 and releasing the sleeve 52. The sleeve 52, while moving through the enlarged portion 56 of the bore under the action of the spring 16, co-operates by its annular groove 63 with the pins 60 to move the anvil 3 towards the hammer 2.

Since the cams 20 of the tubular member 72 are oriented with respect to the impact jaws 5 of the hammer 2, and the cams 21a of the spindle 4 are oriented with respect to the impact jaws 6 of the anvil 3, the anvil 3 can move towards the hammer 2 only after the impact jaws 5 of the hammer 2 and the impact jaws 6 of the anvil 3 have been positioned opposite each other.

During its movement towards the hammer 2 the anvil 3 engages by its impact jaws 6 the impact jaws 5 of the hammer 2, and a blow is imparted, whereby the kinetic energy of the rotating hammer 2 and the rotor 11 is transmitted through the anvil 3 and the spindle 4 into the threaded fastener.

When the housing 1 of the wrench is moved in the opposite direction, the springs 16, 48, 65 and 71 return the parts of the wrench into the initial position to repeat the blow.

At the instant of a blow the electric motor is deenergized in the same manner as described in the case of the first embodiment.

EMBODIMENT III

In this case the locking means 19 (FIG.1) comprise a hollow member 76 (FIG.12) which is connected to the spindle 4 by means of a torsional spring 77, balls 78 (FIGS. 13 and 14) and a sleeve 79 (FIGS. 12 and 15) provided with projections 80.

In this embodiment of the locking means 19 the spindle 4, which extends through the bushing 54 of the housing 1, which is similar to the bushing 54 of the second embodiment (FIG.7), is provided with an axial bore which becomes wider towards the hammer 2 due to provision of three portions 81, 82 and 83 of different diameters.

The spring 16 urging the anvil 3 towards the hammer 2 is mounted in the intermediate portion 82 of the bore. The bearing surface 17 (FIG.1) of the spindle 4 comprises a shoulder 84 (FIG.12) disposed between the intermediate portion 82 and the narrower portion 83 of the bore, while the bearing surface 18 (FIG.1) of the anvil 3 is formed by pins 85 (FIG.12) mounted in radial passages 86 (FIG.16) of the anvil 3 and extending into the intermediate portion 82 (FIG.12) of the bore through slots 87 made in the spindle 4.

The stator 8 of the electric motor is provided with an axle 88 which is made as prolongation of the axle 9 (FIG.1), is mounted in the bore of the spindle 4, and extends through a liner 89 (FIG.12) rigidly secured in the bore of the hammer 2 for rotation therewith.

The disengaging means 21 (FIG.1) comprise cams 21b (FIG.12) fixed to the end surface of the hollow member 76, facing the hammer 2, while the cams 20 oriented with respect to the impact jaws 5 of the hammer 2 are secured to the end face of the liner 89 which is rigidly fixed to the hammer.

The hollow member 76 of the locking means is mounted in the wider portion 81 of the bore in such a manner that one end thereof carrying the cams 21b extends beyond the spindle 4. The internal surface of the hollow member 76 is provided with a splined portion 90 (FIG.15), while the external peripheral surface thereof is provided with V-shaped grooves 91 (FIG.14).

The spindle 4 is provided with radial passages 92 (FIG.13), the balls 78 being mounted in the radial passages 92 of the spindle 4 and in the V-shaped grooves 91.

The sleeve 79 (FIG.12) is rotatably mounted in the intermediate portion 81 of the bore of the spindle 4 and is provided with a splined portion 93 (FIG.15) adapted to co-operate with the splined portion 90 of the hollow member 76, whereby the rotation of the sleeve 79 takes place, the projection 80 of the sleeve 79 being adapted to abut against the pins 85 (FIG.12) to prevent the anvil 3 from axially moving towards the hammer 2, the retaining ring 94 being mounted on the axle 88 to limit the movement of the sleeve 79.

The compression spring 48 which similar to the springs 48 used in the first and the second embodiments of the locking means 19, is mounted in the portion 83 of the bore between the bottom thereof and the axle, the spring abutting against the ball support 50 which is similar to the ball support 50 of the first and the second embodiments.

The hollow member 76 (FIG.12) is provided with an annular projection 95, the torsional spring 77 bearing agains this projection.

A washer 96 is placed between the spring 16 and the pins 85. A retaining ring 97 (FIG.12) is mounted on the external peripheral surface of the spindle 4 to limit axial movement of the anvil along the spindle.

The wrench incorporating this embodiment of the locking means functions as follows.

After the operator has pushed forward the handles 22 and 23 (FIG.1) upon energization of the electric motor the housing 1 of the wrench is moved towards a threaded fastener to be tightened, the spindle 4 compressing the spring 48 during its movement with respect to the bushing 54 (FIG.12). At the same time, the spring 16 is compressed to act upon the pins 85 through the intermediary of the washer 96 disposed between the pins 85 and the spring 16.

In this position the pins 85 bear against the projections 80 of the sleeve 79 mounted on the axle 88.

The cams 21b of the hollow member 76 disposed in the wider portion 81 of the bore and urged towards the spindle 4 by means of the torsional spring 77 engage the cams 20 of the liner 89 mounted in the hammer 2. The hollow member 76, while moving within the wider portion 81 of the bore along the helical path due to the provision of the V-shaped grooves 91 (FIGS. 14 and 13) co-operating with the balls 78 mounted in the radial passages 92 of the spindle 4, co-operates by its splined portion 90 with the splined portion 93 (FIG.15) of the sleeve 79 to rotate the latter.

The pins 85 (FIG.12) are disengaged from the end faces of the projections 80 of the sleeve 79, and the anvil 3 moves towards the hammer 2 under the action of the spring 16.

Since the cams 21b of the hollow member 76 are oriented with respect to the impact jaws 6 of the anvil, and the cams 20 of the liner 89 are oriented with respect to the impact jaws 5 of the hammer 2, the anvil 3 can move towards the hammer 2 only after the impact jaws 5 of the hammer 2 have been positioned opposite the impact jaws 6 of the anvil 3.

During the movement of the anvil 3 towards the hammer 2, the impact jaws 6 of the anvil 3 come into engagement with the impact jaws 5 of the hammer 2, and a blow is imparted, i.e., interaction between the impact jaws 5 and 6 takes place, whereby the kinetic energy accumulated in the rotating hammer 2 and the rotor 11 is transmitted into the threaded fastener being tightened through the anvil 3 and the spindle 4.

Upon moving the housing 1 of the wrench in the opposite direction, the springs 16, 48, 77 return the parts of the wrench into the initial position.

The electric motor is deenergized at the instant of a blow as described in the case of first embodiment.

In all the embodiments of the invention the wrench is reversed by changing the direction of rotation of the electric motor, all the parts of the wrench operating as described hereabove.

Claims

1. An impact wrench comprising a housing; a hammer accommodated in said housing; an electric motor adapted to rotate said hammer; a rotor of said electric motor enclosing a stator and being rigidly connected to said hammer; impact jaws on said hammer; an anvil mounted in said housing coaxially with said hammer; impact jaws fixed to the end face of said anvil facing said hammer, said impact jaws being adapted to co-operate with said impact jaws of the hammer; a spindle connected to said anvil for rotation therewith at the instant of the co-operation between said impact jaws; said connection between the spindle and the anvil allowing a relative axial movement therebetween; said anvil being constantly springly urged towards said hammer; said spindle being provided with means adapted to receive a socket wrench; locking means accommodated in said housing, operatively connected to said spindle and adapted to define a space between said impact jaws of the hammer and anvil, respectively, during acceleration of the hammer, said locking means preventing the anvil from moving towards the hammer during the initial movement of said spindle towards said hammer upon pushing forward said housing, while said locking means releasing the anvil for its movement towards the hammer and for co-operation between the impact jaws during further movement of the spindle towards the hammer; means deenergizing said electric motor during

2. A wrench according to claim 1, wherein the operative connection between said locking means and the spindle comprises cams and disengaging means co-operating therebetween during the movement of the spindle towards the hammer, said cams being oriented with respect to the impact jaws of the hammer and associated therewith, while said disengaging means being oriented with respect to the impact jaws of the anvil and connected to the spindle, the orientation of the cams and said disengaging means consisting in that the cams associated with the hammer are arranged at any appropriate angle with respect the impact jaws of the hammer, while said disengaging means are arranged at the same angle with respect to the

3. A wrench according to claim 1, wherein the anvil is springly urged towards the hammer by means of a spring, one end of the spring abutting against a bearing surface of the spindle, and the other end abutting

4. A wrench according to claim 1, wherein said means deenergizing the electric motor comprise a switch mounted in the housing and inserted in the electric motor supply circuit, and a resilient lever having one end pivoted to the housing and the other end engaging a projection of the anvil, while the intermediate portion of the lever is adapted to actuate

5. An impact wrench comprising a housing; a hammer accommodated in said housing; an electric motor adapted to rotate said hammer; a rotor of said electric motor enclosing a stator and being rigidly connected to said hammer; impact jaws on said hammer; an anvil mounted in said housing coaxially with said hammer; impact jaws fixed to the end face of said anvil and adapted to co-operate with said impact jaws of the hammer; a spindle connected to said anvil for rotation therewith at the instant of the co-operation between said impact jaws; said connection between the spindle and the anvil allowing a relative axial movement therebetween; an annular flange on the external peripheral surface of said spindle defining a bearing surface thereof; a shoulder on the external peripheral surface of the anvil defining a bearing surface thereof; a sleeve mounted on said anvil; a shoulder of said sleeve abutting against said shoulder of the anvil; a spring mounted on said sleeve and having one end abutting against said annular flange and the other end abutting against said shoulder of the anvil through the intermediary of said shoulder of the sleeve, thereby springly urging the anvil towards the hammer; levers springly urged towards said anvil, each lever being provided with an enlargement at one end and a hook at the other end; an annular spring adapted to urge said levers towards said anvil; longitudinal slots accommodating said levers; a part of said slots being made on the external peripheral surface of said anvil and being adapted to accommodate said enlarged ends of said levers retained therein by means of said sleeve, while the other part of said slots being made in said annular flange of the spindle; a bushing with a spindle passing there through, said bushing being mounted in said housing at the point where the spindle extends outside the housing; an annular projection on the external surface of said bushing adapted to be engaged by said hooks of said levers; an axial bore in said spindle; a shaft rigidly connected to the hammer and extending in said bore of the spindle; cams oriented with respect to said impact jaws of the hammer and fixed to the peripheral surface of said shaft; disengaging means oriented with respect to said impact jaws of the anvil comprising pushers; radial passages in said spindle accommodating said pushers; said orientation of said cams and said disengaging means consisting in that the cams fixed to said shaft are arranged at any appropriate angle with respect to said impact jaws of the hammer, while said disengaging means comprising pushers are arranged in said radial passages of the spindle at the same angle with respect to the impact jaws of the anvil; said pushers engaging by one end thereof said cams fixed to said shaft and by the other end engaging said levers during the movement of said spindle towards said hammer to disengage said hooks of these levers from said annular projection of the bushing and to release said anvil for its movement towards said hammer; said spindle being provided with means adapted to receive a socket wrench; means deenergizing said electric motor during the movement of said anvil

6. A wrench according to claim 5, wherein a compression spring is mounted in the spindle bore between the bottom thereof and the shaft, said spring being adapted to return the spindle into its initial position, while the external surface of the spindle is provided with a retaining ring to limit

7. An impact wrench comprising a housing; a hammer accommodated in said housing; an electric motor adapted to rotate said hammer; a rotor of said electric motor enclosing a stator and being rigidly connected to said hammer; impact jaws on said hammer; an anvil mounted in said housing coaxially with said hammer; impact jaws fixed to the end face of said anvil facing said hammer and adapted to co-operate with said impact jaws of the hammer; a spindle connected to said anvil for rotation therewith at the instant of the co-operation between said impact jaws; said connection between the spindle and the anvil allowing a relative axial movement therebetween; an axial bore in said spindle which becomes wider towards said hammer; said widening-up of the bore consisting in provision of two portions, one having a larger diameter and the other having a smaller diameter; a shoulder disposed between said two portions of the bore and defining a bearing surface of the spindle; radial passages in said anvil; pins mounted in said radial passages of the anvil projecting into said portion of the bore having a larger diameter and defining a bearing surface of said anvil; longitudinal slots in said spindle, said pins extending into said portion of the bore having a larger diameter through said slots, the length of the slots being equal to that of the axial movement of the anvil along said spindle; a spring mounted in said portion of the bore having a larger diameter and adapted to urge said anvil towards said hammer, one end of the spring abutting against said shoulder of the spindle, and the other end abutting against said pins of the anvil; a sleeve mounted in said portion of the bore having a larger diameter; an annular groove on the external peripheral surface of said sleeve, said pins connecting said sleeve to said anvil abutting against said groove; levers; a compression spring interconnecting some ends of said levers; thrust surfaces on said one ends of the levers adapted to co-operate with the end face of said sleeve; cam surfaces comprising the bevels provided on the outer sides of said levers; an axle extending in said bore of the spindle and rigidly connected to said stator of the electric motor; longitudinal slots on the peripheral surface of said axle accommodating the other ends of said levers; a bush mounted on said axle and adapted to retain said levers in said slots; disengaging means comprising cams oriented with respect to said impact jaws of the anvil and arranged on the end face of said spindle facing the hammer; a tubular member mounted in said hammer to rotate therewith, said tubular member being axially movable with respect to the hammer, said axle extending through said tubular member; a spring enclosing said tubular member and adapted to urge said tubular member towards said hammer; a flange of said tubular member; cams oriented with respect to said impact jaws of the hammer and fixed to said flange of said tubular member, said cams being adapted to co-operate with said cams oriented with respect to the impact jaws of the anvil; inclined surfaces on the said cams oriented with respect to said impact jaws of the anvil and the hammer, respectively; said orientation of the cams consisting in that the cams oriented with respect to the impact jaws of the hammer are fixed to said flange of the tubular member at any appropriate angle with respect to the impact jaws of the hammer, while the cams oriented with respect to the impact jaws of the anvil are fixed to the end face of the spindle at the same angle with respect to the impact jaws of the anvil; a radial annular projection on the internal surface of said tubular member adapted to co-operate with said cam surfaces of the levers during the movement of said spindle towards said hammer and during the co-operation between said cams oriented with respect to the impact jaws of the anvil and the hammer, respectively, whereby said levers are caused to come into said slots of said axle to release said sleeve and said anvil for the movement of the latter towards the hammer; said spindle being provided with means adapted to receive a socket wrench; means deenergizing said electric motor during the movement of said anvil towards

8. A wrench according to claim 7, wherein a compression spring is mounted in the portion of the bore having a smaller diameter between the bottom thereof and the axle, said spring causing the spindle to move away from the hammer after the co-operation between the impact jaws of the hammer and the anvil, while the external peripheral surface of the tubular member is provided with a retaining ring to limit axial movement of the tubular

9. An impact wrench comprising a housing; a hammer accommodated in said housing; an electric motor adapted to rotate said hammer; a rotor of said electric motor enclosing a stator and being rigidly connected to said hammer; impact jaws on said hammer; an anvil mounted in said housing coaxially with said hammer; impact jaws fixed to the end face of said anvil facing said hammer and adapted to co-operate with said impact jaws of the hammer; a spindle connected to said anvil for rotation therewith at the instant of the co-operation between said impact jaws; said connection between the spindle and the anvil allowing a relative axial movement therebetween, an axial bore of said spindle, which becomes wider towards said hammer due to provision of three portions of different diameters, one portion having a larger diameter, the other having an intermediate diameter and the third portion having a smaller diameter; a shoulder disposed between said intermediate and said smaller-diameter portions of the bore, said shoulder defining the bearing surface of said spindle; radial passages of said anvil; longitudinal slots of said spindle; pins mounted in said radial passages and extending into the intermediate portion of the bore through said longitudinal slots of the spindle, said pins forming a bearing surface of the anvil; a spring mounted in the intermediate portion of the bore and adapted to constantly urge said anvil towards the hammer, one end of the spring abutting against said shoulder of the spindle and the other end of the spring abutting against said pins of the anvil; a hollow member mounted in the portion of the bore having a larger diameter in such a manner that one end thereof extends beyond said spindle; a torsional rcoil spring urging said hollow member towards said spindle and connecting this hollow member to the spindle; a splined portion of the internal peripheral surface of said hollow member; V-shaped grooves provided on the external peripheral surface of said hollow member; radial passages of said spindle; balls disposed in said V-shaped grooves and in said radial passages of the spindle; a sleeve rotatably mounted in said portion of the bore of a larger diameter; projections of said sleeve adapted to bear against said pins; a splined portion of said sleeve adapted to co-operate with said splined portion of the hollow member and to rotate this sleeve, whereby said anvil is released to move towards the hammer; an axle mounted in said bore of the spindle and rigidly connected to said stator of the electric motor, disengaging means comprising cams oriented with respect to said impact jaws of the anvil and fixed to the end face of said end of the hollow member extending beyond the spindle; a bore of said hammer; a liner rigidly mounted within the bore of the hammer, said axle extending through said liner; cams oriented with respect to said impact jaws of the hammer, fixed to said liner mounted within the bore of the hammer and adapted to co-operate with said cams oriented with respect to the impact jaws of the anvil; said orientation of the cams consisting in that the cams oriented with respect to the impact jaws of the anvil are arranged at any appropriate angle to these jaws on the end face of the hollow member, while the cams oriented with respect to the impact jaws of the hammer are fixed to said liner at the same angle with respect to the latter; said spindle being provided with means adapted to receive a socket wrench; means deenergizing said electric motor during the

10. A wrench according to claim 9, wherein a compression spring is mounted in the portion of the bore having a smaller diameter between the bottom thereof and the axle, said spring causing the spindle to move away from the hammer after the co-operation between the impact jaws of the hammer and the anvil, respectively, while the external peripheral surface of the spindle is provided with a retaining ring, the anvil abutting said ring to limit the axial movement of the anvil along the spindle.