US2646966A - Power-operated wrench - Google Patents

Description

July 28, 1953 G. A. LINUBERG 2,646,966

POWR OPERATED WRENCH Filed Deo. 11, 1951 3 Sheets-Sheet 1 `.J Figi l l :LO i d Vv 8l '52 2@ a2 a4 ze Q3 QLF" L7 a "f3 h. "n ...IU fia is A p 83 Si 8,2. i@ 8g 4 a 2O Q5 1V r3 BQ i2 INVENTOR July 28, 1953 A, LINDBERG y 2.646,966

POWER OPERATED WRENCH Filed Deo. 11, 1951 v 3 Sheets-Sheet 2 l if d, srl o Fig 6 `rllllllliljglll muli /llO ATTORNEYS July 28, 1953 G. A. LINDBERG 2,646,966

POWER OPERATED WRENCH Filed Dec. 11, 1951 3 sheets-sheet s Il//l/ 32 125 71 I ya@ l ma no i3 L'ZL INVENTOR QB GLENN A. Lmmasac BY WFM/mm2 #Mm/:Mem

ATTORNEYS Patented July 28, 1953 UNITED STATES PATENT OFFICE POWER-OPERATED WRENCH Glenn A. Lindberg, Cut Bank, Mont.

Application December 11, 1951, Serial No. 260,991

Claims. (Cl. Z55- 35) This invention relates to power operated Wrenches, and more particularly to a power operated wrench for coupling and uncoupling oil well sucker rods and tubing.

It is among the objects of the invention to provide an improved power operated wrench which is readily portable and can be suspended from a well derrick or other supporting structure adjacent a well sucker rod or tubing string while in use; which imparts a series of impacts to a'sucker rod or tubing section engaged thereby to loosen the screw-thread connection between adjacent rod or tubing sections; which can be used to couple or uncouple rod or tube sections by simply inverting the wrench from one operation to the other; which has means releasably holding the wrench in open position for application of the wrench to a rod or tubing section; which holds one tube or rod section stationary while applying rotational impacts to an adjacent section; and which is simple and durable in construction, economical to manufacture, and positive and effective in operation.

Other objects and advantages will become apparent from a consideration of the following description and the appended claims in conjunction with the accompanying drawings, wherein:

Figure 1 is a somewhat diagrammatic illustration of a well rig including a sucker rod and showing in side elevation a power operated wrench illustrative of the invention suspended from the well derrick and operatively engaged with the sucker rod;

Figure 2 is a top plan view of the wrench, a portion being broken away to better illustrate the construction thereof;

Figure 3 is a cross-sectional view on the line 3-3 of Figure 2;

Figure 4 is a fragmentary cross-sectional view on an enlarged scale on the line 4-4 of Figure 2;

Figure 5 is a fragmentary cross-sectional view on the line 5-5 of Figure 3;

Figure 6 is a wiring diagram for the wrench when operated by an electric motor;

Figure 7 is a side elevational view of a power operated wrench similar to that illustrated in Figures l, 2 and 3, but modied to operate on well tubing rather than sucker rod sections;

Figure 8 is a cross-sectional view on an enlarged scale on the line 8-8 of Figure 7;

Figure 9 is a fragmentary cross-sectional View on the line 9 9 of Figure 8; and

Figure l0 is a fragmentary cross-sectional view on the line Iii-I0 of Figure 8.

With continued reference to the drawings, the

well rig illustrated in Figure 1 comprises an oil well derrick I0 of well known construction having a cross brace II spaced above the well platform l2. A well tubing string I3 extends from the upper end of the casing I4 through the platform I2 and a sucker rod assembly I5 extends longitudinally of the tubing string i3 and out of the upper end of the tubing string. The lower end of the sucker rod is connected to an oil pump, not illustrated, in a manner well known to the art, and the upper end of the rod is connected to a rod-reciprocating member, such as a walking beam, also not illustrated, but well known to the art.

The sucker rod I5 comprises a plurality of sections joined together in end-to-end relationship. As is particularly illustrated in Figure 3, each section of the sucker rod has at each end thereof a tapered, screw-threaded portion IB, an annular bead Il at the inner end of the screw-threaded portion I6, a squared portion I8 at the side of the annular bead I 'I remote from the screwthreaded portion I6, an annular bead I9 at the end of the squared portion I8 remote from the annular bead I1, and the intermediate portion 20 of the rod extends from the annular bead I9 away from the squared portion I8 and is usually of circular cross-sectional shape. Two adjacent rod sections are coupled together in end-to-end relationship by having the screw-threaded portions I6 at their adjacent ends threaded into the respectively opposite ends of a coupling sleeve or collar 2| which is slightly inwardly tapered from each end and provided in each end with screw-threads engaging the screw-threads on the end portions of the rod sections. The sections of the well tubing I3 are provided with external screw-threads at each end and are secured together by having their adjacent ends threaded intl) the respectively opposite ends of internally screw-threaded coupling sleeves or collars 22, as is particularly illustrated in Figure '7.

In the case of both the sucker rod sections and the well tubing sections, two adjacent sections are threaded into the associated coupling collar by rotating the sections in respectively opposite directions or by holding one section stationary while rotating the other and are uncoupled in the same manner by reversely rotating the movable section.

As the construction of well rigs including the well tubing or flow pipe and the pump sucker rod is Well known to the art and constitute no part of the present invention, it is considered that a more detailed illustration and description 3 of the well rig is unnecessary for the purposes of the present disclosure.

The present invention is primarily concerned with a power operated wrench for coupling and uncoupling sucker rod or well tubing sections, and such a wrench has been shown in two slightly modified arrangements in the accompanying drawings.

The wrench illustrated in Figures 1 to 6, inclusive, comprises a flat, hollow housing 25 of somewhat elliptical shape having top and bottom walls 25 and 21 disposed in spaced apart and substantially parallel relationship to each other, and a side wall 28 having arcuately rounded end portions of substantially semicircular extent and straight side portions interconnecting theiends of the arcuately curved end portions. l

Bearings rings 30 and 3l are disposed against the inner side of the top wall 25 and bottom wall 21 of the housing, respectively, substantially concentric with the center of Vcurvature of one end of the side wall 28 of the housing anda main gear 32 is disposed between and journaled on these bearing rings for rotation in the housing. This gear 32 has a centrally located bore or aperture 33 provided with longitudinally extending splines or serrations, and has a notch 34 extending from the aperture 33 to the periphery of the gear. The notch 34 has substantially parallel side surfaces spaced 'apart a distance slightly greater than the thickness of the squared portions I8 of the sucker rod,"these side surfaces being outwardly inclined near the periphery of the gear, as is particularly illustrated in Figure 2, to facilitate passing of the squared portions of sucker rods into'the notch in the gear.

A jaw element 35 having longitudinally extending serrations or splines on its outer surface and of Igenerally cylindrical shape is' inserted into the bore 33 of the gear 32 and has a notch 36 therein of substantially the same size and shape as the size and shape of the cross-sectional area of the squared portion I8 of the sucker rod.

The insert jaw 35 has at its end adjacent the bottom wall 21 of the housing an outwardly'extending annular flange 38 which closely fits the inner edge of the bottom bearing ring 3l.

The top wall 26 of the housing is detachably secured to the side wall bysuitable means, such as the screws 39, extending vthrough apertures in the marginal portion of the top wall and threaded into tapped holes in the top edge of the side wall, so that the gear 32 can be'removed from the housing upon removal of the top wall 26. The insert 35 can be removed from the gear when the latter is removed from the housing, and different inserts may be placed in the gear to accommodate the wrench to varying sizes of the squared portions of sucker rods.

The top and bottom vwalls 26 and 21 of the housing are provided with notches 40 and 4! which are in alignment withe'ach'other and register with the notch 34` in the gear 32 when the gear is in a predetermined rotational posi tion relative to the housing, 'as illustrated in Figure 2, and the side wall 28 is provided with an opening 42 in alignment with the outer ends of the notches 40 and 4| in the top`an`d bottom walls of the housing.

Idler gears 43 and 44 are journaled in the housing between the gear 32 and the end of the housing remote from the opening 42, and these idler gears mesh with the main gear 32 at spaced apart locations around the main gear, the distance between the locationshatwh-ichthe idler gears mesh with the main gear being greater than the width of the outer end of the slot 34 in the main gear, so that at least one of the idler gears will always be in mesh with the peripheral teeth on the main gear 32.

A screw shaft 45 extends through apertures 4G and 41 in the top and bottom walls 216 and 21 of the housing, which apertures are substantially concentric with the center of curvature of the end of the side wall 28. of the housing remote from the main gear 32.

.In the arrangement illustrated, an electric motor 5B is secured at one end to the bottom wall 21 of the housing 25 and the motor housing has in its end wall 53 adjacent the bottom wall of the housing an opening 5l registering with the opening 41 in the bottom wall 21. The screw shaft 45 is connected at one end to the adjacent end of the shaft of the motor 50, or, if desired, may be made continuous with the motor shaft and journaled in the housing of the electric motor.

A stop collar 52 is provided on the screw shaft 45 one at the end thereof remote from the motor.

Outwardly of the stop collar 52 the screw shaft is provided with an arbor 54 of reduced diameter journaled in a bearing 55 supported in the outer end of a hood-shaped brace 55 which extends transversely of the thickness of the housing 25 and is joined at its other end to the housing of the motor 55 at the end of the motor housing adjacent the wrench-housing 25. v

A drive gear 51, having a screw-threaded bore extending coaxially therethrough, is threaded onto the screw shaft 45 and meshes with both of the idler gears 43 and 44. This gear 51 is movable longitudinally relative to the idler gears 43 and 44, and remains in mesh with these gears at all times. f

A U-shaped handle 69 is connected at one end to the side wall 28 of the housing 25 and is connected at its other end to the housing of the motor 55, and switches 6l Vand 62 are mounted in the handle 55 in tandem relationship to each other and connected to the motor 50 by conduits, as indicated at 63. A grip lever 64 is pivotally mounted at one end in the handle 60 at the end of the handle remote from switches 5l' and 62 and carries at its end adjacent the switches a projectionor dog 65 for successively operating the switches 'BI and 62 when the grip member is moved toward -the 'intermediate portion of the handle. A compression spring 65, disposedbe'- tween the intermediate portion of the handle 60 and-the grip member 64, resilicntly urges the grip member away from the intermediate portion ofthe handle and4 to'a non-operating position relative to the switches GI and 62, the switches being operatedloy manually moving the grip member toward the intermediate portion of the handle against the force of the spring 66.

Power is supplied to the motor through a suitable extension cord 61, and it is to be understood that while an electric -motor has been illustrated and hereinabove described for operating the wrench, a hydraulic or pneumatic motor of known con-struction may be substitutedA for the electric'frnotorgif' desired, withut'in any va'y'e'x-l ceeding the scope of the invention.

With the arrangement illustrated, when one of the switches El or 62 is closed to energize the m-otor 5D, the screw shaft 45 will be rotated, and the gear-51 will be threaded outwardly along the screw shaft until it strikes the'stop collar 52. This sudden -termination :ofI relativel movement between the gear and the screw shaft causes the inertia of the rotatable armature of the motor 50 to deliver an impact to the gear 51 and from this gear through the idler gears 43 and 44 to the main gear 32. As soon as the impact has been delivered to the main gear 32, the grip member 64 is released to open the motor controlling switch and discontinue the application of power from the motor to the wrench gears. The gear 51 is provided at its end adjacent the motor 50 with an annular groove |59 in a skirt portion of the gear and an annular collar |5| has at one end an inwardly directed annular flange |52 rotatably received in the groove |58 in gear 51 and at its other end an annular external groove |53.

A coiled tension spring |54 surrounds the motor shaft and has one end coil secured in the groove |53 of collar |5| and its other end coil secured in an annular external groove |55 inA a second collar |56 secured on motor shaft 45 at a location spaced along the shaft from collar l5 I.

If the main gear 32 is engaged with an object to be rotated, such as a well sucker rod, and this object is not substantially rotated by the first impact delivered to the main gear 32 incident to the impact of the gear 51 against the stop collar 52, upon release of the grip member l64 to open the motor controlling switch, spring |54, which is stretched when gear 51 moves lalong shaft 45 to stop collar 52, contracts and returns gear 51 along shaft 45 to the end of the screw-threaded portion of this 'shaft adjacent the motor 50. If the motor controlling switch is now reclosed, a second impact will be delivered to the gear 32 and the impacts may be repeated until the sucker rod joint is freed and the portion of the sucker rod engaged in the main gear 32 caused to rotate. As soon as the joint has been freed, the motor controlling switch may be maintained closed until the sucker rod joint has been completely unthreaded. Y

A bracket 18 is secured to or formed integrall with the bottom wall 21 of the housing, and projects laterally f-rom the housing intermediate the length o'f lone of the straight portions of the side Wall 28. A post 1| of noncircular and preferably square cross-sectional shape extends through the bracket and is secured to the bracket ,adjacent the mid-length location of the post, the post being formed integrally with the bracket, if desired.

The post 1| is disposed substantially perpendicular to the planes of the top and bottom walls of the housing 25, and a back-up wrench 12 is detachably secured at one end to the post 1| 'and is provided at its other end With spaced apart jaws which receive a squared portion I8 of the sucker rod adjacent the squared portion received in the main gear 32 of the french, so that, when an upper sucker rod section is being turned by the wrench to couple or uncouple it 'from the vadjacent lower section, the lower section is held against rotational movement by the back-up wrench 12.

In the arrangement illustrated, the back-up wrench 12 is provided at its end adjacent-the post 1| with an eye formation 13 having a square hole therein through which the post extends and is provided with a spring pressed ball detent -a'ssembly 14 which engages in a depression, as indicated at15, in the post to releasably secure the back-up wrench in operative position on the post 1|.

Lugs 16 'and 11 are provided on side wall 28 of the housing, and are aligned transversely of the 6 housing near the end of the latter to which the' handle is attached. A U-shaped lbail 18 is pivotally connected at its ends to lugs 16 andY 11 and a coil tension spring 19 is connected at one end to bail 18 -at the end of the bail remote from housing 25 and is connected at its other end to a hook which is adapted to engage a support. such as the crossbar of well derrick I9, to suspend the wrench in operative position adjacent the sucker rod of the well.

Handle sockets 8| and 82 are provided on the upper side of the top wall 26 of the housing one -at each side of the latter, and open to the opposite side of the housing adjacent the mid-length location thereof. Handles 83 and 84 are secured each at one end in the sockets 8| and 82, respectively, and project outwardly from the respectively opposite sides of the housing substantially perpendicular to the longitudinal center lino of the housing.

With this arrangement, the wrench can be used in its upright position, as illustrated in Figure 3, for uncoupling adjacent sucker rod sections and can be inverted in the bail 18 and used in its inverted position for coupling adjacent sucker rod sections as a sucker rod is being run in the well.

A dome-shaped cover 9| is secured to the top wall 26 of the housing in covering relationship to the opening 46 and the bearing 55 to protect the gears from dust and other foreign matter.

When the wrench is inverted, the back-up component 12 is, of course, moved from one end to the other end of the post 1|, so that it will provide the same function in the inverted as in the upright position of the wrench.

A small solenoid 85 is mounted on the top wall 26 of the housing 25 above themain gear 32 and has a movable armature 86 projecting through registering apertures in the top wall 26 of the housing andthe upper bearing ring 38 and provided with a rounded end 81. The gear 32 is provided with a rounded depression at a Ilocation therearound, such that when the rounded end of the armature 86 is in the rounded depression in the gear, the gear is releasably held in a rotational position in the housing, such that the notch 34 in the gear registers with the openings 39, 4U and 4| in the top, bottom and side walls of the housing. -A compression spring 88 surrounds the armature 86 between the bottom end of the solenoid coil 89 and an abutment washer 98 secured on the armature to resiliently urge the armature into engagement in the depression in the gear and the coil 89 of the solenoid is connected through the switches 6| and 62 with the energizing circuit for the motor 50 so that the armature of the solenoid is automatically moved out of engagement with the gear 32 whenever the motor is energized. A manually releasable latch may be substituted for the solenoid operated latch, as described above, without in any way exceeding the scope of the invention.

A wiring diagram for the motor and the solenoid 85 is illustrated in Figure 6, and includes a source of electrical energy, such as a battery or auto transformer 92 and relay switches 93 and 94 in addition to the manually operated switches 8| and 62, the solenoid 85 and the motor 50.

The motor 50 is connected at one side to one end of the battery 92 by a conductor 95, and is connected at its other side by a conductor 96 to one contact 91 of the relay switch 93 and to one-contact 98 of the relay switch 94. The

gemiste (other bontactt?! -fofetheerelay s witc'zl'ia 93:: isco'rilnectedlaby aV conductor -to the 'otherfendfof theI batter-y 92, and the -Other1contact--|0| |`of 'the relay switch 94 is connectedftofthefbattery v92 between the ends ofthe batteryby-aiconduc'- tor |02, so thatfwhen the'lrelayi-switch?93-f is closed, the Amotor is operated at -Ifull-sipeedand when the relay switch .gfiisclosedg themotor is operated at a slow speed.

The coils |03 and |04-o'f AtheI` relay switchesj93 and S4.are both connected, each' at-one-end,by aconductor to theV conductor-|00 andathe end of the. batteryremote from that to-which the motor is connected by the=conductor195. The

`other `end-of the coil |03 is connected by coni ductors |05 and |01 vto one'contactla of the manually operated switch 6I, the other contact |09 of which is connected by a conductor ||0 to the conductor 95, so that, when the switch 6| is closed, the coil |03 will be energized to close the relay switch 93. The other end of the coil |04 of the relay switch 94 is connected by a conductor to one contact ||2 of the manually operated switch 62 and the other contact ||3 of this switch is connected by a conductor ||4 to the conductor 95, so that when the switch 62 is closed, the coil |04 will be energized, closing the relay switch 94.

The solenoid 85 is connected between the conductors |05 and |01 in parallel with the relay Y switch coil |03, so that it will be energized whenever the relay switch 93 is closed.

With this arrangement, the motor can be operated at full speed or at low speed by selectively closing the manually operated switches 6| and 62.

In the modied form of the arrangement illustrated in Figures 7 to 10, inclusive, the construction of the wrench is the same as that described above, except that the main gear 32 and the back-up wrench 12 are modified to engage tube sections instead of the sucker rod sections illustrated and described in connection with the form of the wrench shown in Figures l to 6, inclusive.

In the modified arrangement, the main gear 32' is provided with a central aperture |20 and a notch |2| leading from this central aperture to the periphery of the gear, the central aperture having a semicylindrical shape at the inner end of the notch, and the notch having a width somewhat greater than the outside diameter of the tube sections to be received therein.

The gear 32 is provided in the central aperture thereof with angularly spaced apart, longitudinally extending notches and tube-engaging elements |22 of rectangular cross-sectional shape are seated one in each of these notches and secured to the gear. At one side of the notch |2| the gear is provided with a recess |24 and a dog |25 is pivotally mounted in the recess |24 and has a partly cylindrical surface |26 facing the opening in the gear and provided with a longitudinally extending groove receiving a tube-engaging element |21 of rectangular crosssectional shape. The dog includes a finger portion |28 extending from the tube-engaging element |21 into the notch |2| and provided near its distal end with a tapped hole receiving a set screw |29 which is adapted to bear against the outer surface of a tube section I9 received in the wrench to limit the pressure between the tube-engaging elements |22 and |21 and the tube.

A leaf spring |30 is disposed within the recess 24 and engaged between the gear and the dos 'Il it tdresinenuy urge the 'dog into v'engagement with a tubesection |-3- received in the gear, and aiballdetent |3| is mounted in the gear at foriejehd of the rec'essv |24 and engages the distalendf of the-fingerportion |20 of the dog to .in retractedposition' andthe wrench is then 'nivedintoengagement with a tube section adjacent a connecting sleeve or collar 22 on the tube "stringi" the tube section moves into the open'- "ing'irr the gear; it tripsthe dog |25, so that the dog moves away from the ball detent |3| and the set screw |29 approaches the outer surface of the tube section, thetube-engaging elements |22 and |21 being brought into rm engagement with the outer surface of the tube section. Now, as the gear 32 is rotated, the element |21 is moved slightly toward the tube section, forcing the element and the element 22 to bite into the outer surface of the tube 'section and provide a firm grip between the gear and the tube section, this biting action 4being limited by Contact of the set screw |29 with the outer surface of the tube section.

The back-up wrench 12 of this form of the invention has at its end remote from the post 1| a jaw formation |33 shaped to receive a tube section |3 therein, and engages a tube string adjacent the lower end of a connecting collar 22 when the gear 32 engages the tube string adjacent the upper end of such a collar.

The jaw formation |33 of the back-up wrench 12 has a partly cylindrical inner surface and an opening through which the tube section enters the jaw formation and is provided in its inner surface with grooves extending longitudinally of the inner surface at angularly spaced apart locations. Tube section-engaging elements |34 of square or rectangular cross-sectional shape are mounted one in each of these grooves and secured to the jaw formation |33 in a manner to present a sharp edge for engagement with the outer surface of the tube section I3.

A dog |35 is pivotally mounted on the jaw formation |33`at one end of the latter by a pivot pin |36 and carries a tube-engaging element |31 similar'to the elements |34. At its distal end the dog |35 carries a set screw |38 which is engageable with the outer surface of a tube section received in the jaw formation |33 to limit the pressure between the elements |34 and |31 and an associated tube section, and a leaf spring |40 is mounted on the jaw formation 33 adjacent the pivot pin |36 and engages the dog |35 to urge the latter toward a tube section I3 received in the jaw formation.

In this case, the dog |35 is releasably latched in retracted position by a ball detent |4| carried by the dog and engageable in a recess |42 provided in the portion of the jaw formation |33 to which the dog is pivoted, this latch being released by the pressure of the tube section against the inner end portion of the dog as a tube section is inserted into the jaw formation |33 of the backup wrench component. As the gear 32' tends to turn one of the sections of the tube spring, the back-up wrench 12' engaging the adjacent section holds such adjacent section against rotation, so that the coupling between the two adjacent sections can be threaded together or apart, depending on the position of the wrench.

Various modifications of the wrench, such as increasing or decreasing the weight and strength thereof, providing a reduction gear between the motor and the screw shaft and modifying the wiring circuit to provide only a slow speed ofperation, may be made, if desired, without in any way exceeding the scope of the invention.

The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are, therefore, intended to be embraced therein.

What is claimed is:

1. A power operated wrench comprising a housing, a rst gear rotatably mounted in said housing and having a radially disposed notch extending from the periphery to the center thereof for receiving an object to be turned by said wrench, said housing having an opening therein registering with the notch in said gear when said gear is in a predetermined rotational position relative to said housing, idler gears rotatably mounted in said housing and meshing with said rst gear at spaced apart locations therearound, a second gear disposed in said housing and meshing with said idler gears, said second gear having a screwthreaded bore extending coaxially therethrough and being longitudinally movable relative to said idler gears, a screw shaft journaled in said housing and threaded through the bore of said second gear, a stop on said screw shaft limiting movements of said second gear longitudinally thereof, and a motor mounted on said housing and drivingly connected to said screw Shaft, said second gear being movable along said screw shaft from said motor to said stop to deliver an impact through said idler gears to said first gear when it engages said stop, and spring means connected to said second gear moving the latter away from said stop after delivery of the impact.

2. A power operated wrench comprising a housing, a, flrst gear rotatably mounted in said housing and having a radially disposed notch extending from the periphery to the center thereof for receiving an object to be turned by said wrench, said housing having an opening therein registering with the notch in said gear when said gear is in a predetermined rotational position relative to said housing, idler gears rotatably mounted in said housing and meshing with first gear at spaced apart locations therearound, a second gear disposed in said housing and meshing with said idler gears, said second gear having a screw-threaded bore extending coaxially therethrough and being longitudinally movable relative to said idler gears, a screw shaft journaled in said housing and threaded through the bore of said second gear, a, stop on said screw shaft limiting movements of said second gear longitudinally thereof, a motor mounted on said housing and drivingly connected to said screw shaft, said second gear being movable along said screw shaft from said motor to said stop to deliver an impact through said idler gears to said first gear when it engages said stop and being movable from said stop after delivery of the impact, and means mounted on said housing and engaging sai-d first gear releasably latching the latter in a rotational position relative to said l0 housing such that the notch in said rst gear is in registry with the opening in said housing.

3. A power operated wrench comprising a housing, a main gear rotatably mounted in said housing and having a radially disposed notch extending from the periphery to the center thereof for receiving .an object to be turned by said wrench, said housing having an opening therein registering with the notch in said gear when said gear is in a predetermined rotational position relative to said housing, a motor mounted on said housing, means in said housing connecting said motor to said main gear and effective to deliver rotational impacts to said main gear upon operation of said motor, a post mounted on said housing and extending to respectively opposite sides of the latter, and a back-up wrench detachably mounted on said post-and engageable with an object at a location spaced from said first gear to hold the object engaged thereby stationary while the object engaged by said rst gear is rotated relative to the object engaged by said backup wrench, said back-up wrench being selectively mountable on said post adjacent either end of the latter.

4. A power operated wrench comprising a housing, a main gear rotatably mounted in said housing and having a radially disposed notch extending from the periphery to the center thereof for receiving an object to be turned by said wrench, said housing having an opening therein registering with the notch in said gear when said gear is in a predetermined rotational position relative to said housing, a motor mounted on said housing, means in said housing drivingly connecting said motor to said main gear and imparting rotational impacts to said main gear upon operation of said motor, said main gear having a cavity therein opening into said notch,

i at least one work engaging element mounted on said main gear and presenting a sharp edge directed inwardly of said notch within the inner end portion of said notch at a location spaced from said cavity, a dog pivotally mounted on said gear within said cavity and at one side of said notch and having a finger extending into the notch in said gear, a work piece-engaging element mounted in said dog and presenting a sharp edge at the side of said dog adjacent the notch in said gear, a spring connected between said dog and said gear resiliently urging said dog inwardly of said notch, and a set screw carried by said dog adjacent the distal end of the finger thereof for engaging a work piece extending through said notch and engaged by said work piece engaging elements to limit the pressure between said work piece-engaging elements and the work piece engaged thereby.

power operated wrench comprising a housing, a main gear rotatably mounted in said housing and having a radially disposed notch extending from the periphery to the center thereof for receiving an object to be turned by said wrench, said housing having an opening therein registering with the notch in said gear when said gear is in a predetermined rotational position relative to said housing, a motor mounted on said housing, means said housing drivingly connecting said motor to said main gear and imparting rotational impacts to said main gear upon operation of said motor, a post mounted on said housing and extending to respectively opposite sides of the latter, and a back-up wrench detachably mounted on said post and engageable with an object at a location spaced from said main gear to hold the object engaged thereby stationary whilethe object said post adjacent either end of thelatter and 5` having at its end remote from said post a rounded jaw formation adapted to receive a Work piece of circular cross-sectional shape and having at least one Work piece-engaging element mounted therein and presenting a sharp edge Within said jaw formation, a dog pivotally mounted on said. backup wrench at the outer end of one side of said jaw formation, a work piece-engaging element carried by said dog and presenting a sharp edge inwardly of said jaw formation, a spring connected between said jaw formation and said dog resiliently urging said dog in a direction to engage the work piece-engaging element carried thereby with a work piece received in said jaw formation, and a set screw carried by said dog and engageable with a work piece in said jaw formation to llimit the pressure betWeensaidwork' piece-engaging elements, and a work piece engaged thereby.

GLENN A. LINDBERG.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Datev 1,300,995 Moody Apr. 15, 1919 1,820,545 Smith Aug. 25, 1931 1,831,259 Peterson et a1 Nov. 10, 1931 2,000,221 Dawson May '7, 1935 2,425,793 Fosnot Aug. 19, 1947 2,514,914 Van Sittert Julyll, 1950 2,550,045 De Hetre Apr. 24, 1951 2,556,536 Harris June 12, 1951 2,566,561 Edelberg Sept. 4, 1951 2,566,999 Stone Sept. 4, 1951 2,573,212 Martois Oct. 30, 1951 2,624,550

Lundeen Jan. 6, 1953

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