Apparatus and method for installing blind fasteners

[57] ABSTRACT

An automatically sequencing, hydraulically powered preentry pull-up tool for upsetting blind fastener sleeves on the blind side of a structure, and a novel sequencing method employed by said tool to assure complete and uniform fastener upsetting. The tool includes a hand gun having a protruding threaded mandrel insertable into a blind fastener sleeve to be upset, the mandrel rotating in one direction to engage with the sleeve, axially retracting to pull up and upset the sleeve, and then rotating in the opposite direction to disengage from the sleeve, these three steps being hydraulically powered in the hand gun by hydraulic power from a remote source, and being electrically controlled. According to the method of the disclosure uniform upsetting is assured by effecting the automatic shifting from stage to stage of the operation by sensing back pressure in the hydraulic system.

Claims, 23 Drawing Figures

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APPARATUS AND METHOD FOR INSTALLING BLIND FASTENERS

BACKGROUND OF THE INVENTION

The present invention relates to blind fasteners, i.e., bolt type fasteners which are capable of being installed from one side only of a structure, and it relates more particularly to apparatus and methods for installing blind fasteners efficiently and rapidly, and with assurance that each of a series of blind . _nfasteners will be fully expanded on the blind side of the work- ^Upiece and will be uniformly pulled up in the axial direction.

Large numbers of blind fasteners are required in such highly stressed structures as modern aircraft structures, in regions thereof where access to one side of a structural joint in dif- , ficult. ³

Most of such blind fasteners which are employed in modem high-speed aircraft embody a sleeve portion which is inserted from the access side of the structure into a bore through the structure, the sleeve having a head at one end adapted to seat 20 on the access side of the structure, an internally threaded pullup portion adjacent the other end thereof which is engageable by a threaded mandrel insertable through the sleeve from the access side, and an intermediate deformable section adapted to buckle outwardly in response to pull-up movement of the 25 mandrel. In this way, the structure is axially clamped between the head part of the sleeve on the access side and the outwardly buckled deformable section of the sleeve which functions as a nut. While some blind fasteners include only such a sleeve, in most cases the sleeve is secured against radial in- 30 ward deformation under tension, and is provided with additional shear strength, by insertion of a core pin or bolt into the central passage of the sleeve after the sleeve has been installed in the structure as aforesaid.

A major problem in the installation of such blind fasteners is 35 that the proper amount of axial take-up and radial expansion of the sleeve on the blind side of the structure is critical in achieving the fully rated strength of the fastened joint, but at the same time the part of the fastener which is thus taken up and expanded is on the blind side of the structure and is inaccessible to visual inspection to assure that it has in fact been taken up and expanded to the correct extent. Conventional apparatus and methods for pulling up and expanding blind fastener sleeves rely substantially completely on a determination by the installing operator as to the extent of engagement of the pull-up mandrel with the internally threaded pull-up portion of the sleeve, and the amount of axial movement of the mandrel that is applied to expand the deformable section of the sleeve and provide axial clamp-up force. One type of hydraulically powered tool currently widely used for this purpose has a cycle of operation for installing each blind fastener sleeve that includes three separate manual controls which must be sequentially actuated in order to complete an installation. A first manual control button is depressed to cause the pull-up mandrel to rotate in a clockwise direction for engagement with the internally threaded pull-up portion of the sleeve on the blind side of the structure. The extent of threaded en40 gagement of the mandrel with the sleeve depends upon how long the appropriate button is depressed, and is accordingly 60 variable according to operator judgement. The extent of threaded engagement of the mandrel with the sleeve is made further uncertain with such equipment by pulsating hydraulic power from a reciprocating type hydraulic pump, with the result that torque is applied intermittently to the threaded 65 mandrel. Then, when the mandrel is thus threadedly engaged with the sleeve and the first button is released, a second button is manually depressed to produce pull-up force on the mandrel for buckling the deformable section of the sleeve, this pull-up force being released only upon release of the second actuating 70 button. The final step with such conventional equipment is to provide anticlockwise rotation of the mandrel to unscrew the mandrel from the sleeve either by depressing a third button or by flipping a reversing lever and depressing the first button again. 75

With conventional equipment of this type, the extent of threaded engagement of the mandrel in the sleeve is uncertain, and consequently the extent of axial take-up is not fully predictable and reliable. If the operator should happen to let up too soon on the first button so that the threaded engagement is inadequate withstand the stresses of the second stage, then the threads can be tom out in the second stage and the fastener left in only partially assembled condition. Also, it is not infrequent that such fasteners are damaged by the operator inadvertently depressing the wrong button. Additionally, expansion and pull-up may be left incomplete if the operator should release the second button too soon.

SUMMARY OF THE INVENTION

In view of these and other problems in the art, it is an object of the present invention to provide a novel hydraulically powered pre-entry pull-up tool for expanding blind fastener sleeves on the blind side of a structure and axially clamping the sleeves, wherein the extent of each of the critical operative steps is automatically determined by the tool rather than manually so as to assure uniform installation characteristics of a series of similar blind fastener sleeves.

Accordingly, it is a more particular object of the invention to provide a hydraulically powered pre-entry pull-up tool of the character described wherein the extent of threaded engagement of the pull-up mandrel of the tool into the internally threaded part of the blind fastener sleeve is determined by sensing a predetermined reaction torque on the mandrel. Similarly, it is a more particular object of the invention to provide a tool of the character described wherein the extent of axial pull-up of the mandrel, and hence the extent of the axial upsetting movement and pull-up force on the blind fastener sleeve, is determined by sensing a predetermined axial reaction force on the mandrel.

Another object of the invention is to provide a hydraulically powered apparatus of the character described for installing blind fastener sleeves wherein the aforesaid predetermined reaction torque and axial reaction force on the mandrel are determined in the apparatus by sensing back pressures in the hydraulic system.

A further object of the present invention is to provide apparatus of the character described for installing blind fastener sleeves which is hydraulically powered, with the hydraulic power means electrically controlled so as to be automatically sequencing between screw-in, take-up, and screw-out modes of operation.

A still further object of the invention is to provide apparatus of the character described for installing blind fastener sleeves wherein the operator simply manipulates a hand gun having a protruding threaded mandrel that is insertable into each blind fastener sleeve, and wherein the entire sequence of operation for installing each blind fastener sleeve, including screw-in, pull-up, and screw-out, is effected by actuating a single triggering device on the hand gun which causes automatic electrical control of a hydraulic power unit remote from the hand gun.

An additional object of the invention is to provide a novel method of installing blind fastener sleeves of the character described, wherein uniform upsetting and pull-up in a series of blind fastener sleeves is assured by effecting the automatic shifting from stage to stage of the operation in response to back pressure in the hydraulic system at the completion of each stage of operation.

Other objects and advantages of the present invention will appear during the course of the following part of the specification, wherein the details of construction, mode of operation, and method steps of a presently preferred embodiment are described with reference to accompanying drawings, wherein:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an axial, vertical section, with portions shown in elevation, illustrating the hand gun forming a part of the present invention.

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FIG. 2 is a perspective view illustrating the mandrel portion of the hand gun separated from the rest of the gun.

FIG. 3 is a fragmentary, plan view taken on the line 3—3 in FIG. 1 illustrating the bottom of the handle of the hand gun, and in particular illustrating the hydraulic and electrical ⁵passages into the hand gun.

FIG. 4 is a cross-sectional view taken on the line 4—4 FIG.

showing structural details in the forward portion of the gun.

FIG. 5 is a vertical sectional view taken on the line 5—5 in FIG. 1, with a portion thereof in elevation, showing further details of the gun in the region of the handle and body portions thereof.

FIG. 6 is another vertical sectional view, partly in elevation, taken on the line 6—6 in FIG. 1, also showing details of the 15 handle and body portions of the gun.

FIG. 7 is an enlarged, fragmentary, vertical section taken on the line 7—7 in FIG. 1 showing details of the hydraulic motor in the gun.

FIG. 8 is also an enlarged, fragmentary, vertical section, taken on the line 8—8 in FIG. 1, illustrating a portion of the gun forward of the motor.

FIG. 9 is an exploded perspective view illustrating a portion of the body of the hand gun and illustrating the various parts 25 of the gun making up the hydraulic motor and the support and housing structure therefor.

FIG. 10 is a fragmentary, vertical, axial, section, partly in elevation, illustrating the forward part of the hand gun operatively engaged in a blind fastener sleeve at the completion of 30 the screw-in phase of operation of the gun.

FIG. 11 is a view similar to the FIG. 10, but illustrating a further portion of the tool in section, showing the pull-up phase of operation of the gun.

FIG. 12 is a view similar to FIGS. 10 and 11, but illustrating ³⁵the screw-out phase of operation of the tool.

FIG. 13 is an enlarged, fragmentary, vertical section showing a portion of the structure illustrated in FIG. 7, and illustrating the screw-in phase of operation of the hydraulic motor 49 in the hand gun.

FIG. 14 is a view similar to FIG. 13, but illustrating the screw-out phase of operation of the hydraulic motor in the hand gun.

FIG. 15 is a fragmentary, axial, vertical section, partly in 45 elevation, similar to FIG. 10, but showing the forward portion of the hand gun adjusted to accommodate a blind fastener sleeve which is shorter than the blind fastener sleeve shown in FIG. 10.

FIG. 16 is a side elevational view, partly in section, illustrat- ³θ ing the remote power unit which provides the hydraulic driving power to the hand gun, and is electrically controlled from the hand gun.

FIG. 17 is a horizontal section, partly in elevation, taken on 55 the line 17-17 in FIG. 16.

FIG. 18 is a front elevational view, partly in section, taken on the line 18—18 in FIG. 16.

FIG. 19 is a vertical section, partly in elevation, taken on the line 19-19 in FIG. 16. 60

FIG. 20 is a fragmentary side elevational view of the remote power unit that is shown in FIGS. 16 to 19, taken on the line 20—20 in FIG. 18.

FIG. 21 is a diagrammatic view showing both the bottom of the handle of the hand gun as illustrated in FIG. 3 and a portion of the front panel of the remote power unit as shown in FIG. 18, with the hydraulic and electrical lines from the remote power unit to the hand gun illustrated diagrammatically. ₇₀

FIG. 22 is a diagram of the hydraulic system of the apparatus, together with a pneumatic system employed to drive the hydraulic system.

FIG. 23 is a diagram of the electrical system of the apparatus. 75

DETAILED DESCRIPTION

Referring to the drawings, and at first particularly to FIGS. 1 through 9 thereof, these figures illustrate the structure of the hand gun portion of the apparatus, which is generally designated 10. The hand gun 10 includes a generally hollow body 12 having an integrally formed handle 14 depending therefrom.

An annular nose piece 16 is threadedly engaged with the I body 12 at the front end thereof by threaded coupling 18, the nosepiece 16 having a rearwardly opening cylindrical chamber 20 in its rearward portion, and tapering down to a forwardly projecting, externally threaded, tubular forward portion 22.

The body 12 defines a cylindrical chamber 24 therein, which is axially aligned with and somewhat larger than the nosepiece cylinder 20, immediately to the rear of nosepiece 16. A piston 26 is slidably mounted within the body cylinder 24, the piston 26 having an integral forwardly extending tubular axial shaft portion 28 which extends into the nosepiece cylinder 20. The piston 26 is forwardly biased so as to normally seat against the rearward annular edge of the nosepiece 16 as illustrated in FIG. 1 by means of a coil compression spring 30, the forward end of which is engaged against the piston, and the rearward end of which is seated in an annular recess 32 in body 12 immediately to the rear of cylinder 24.

A spindle 34 is both rotatably and slidably mounted in the gun 10, with a forward portion thereof extending coaxially into the tubular forward portion 22 of nosepiece 16, and a rearward portion thereof extending coaxially through the tubular piston shaft 28. The spindle 34 has an enlarged, hollow rear end portion which projects rearwardly from the piston 26 and serves as a drive coupler for application of rotary power to the spindle. A snap ring 38 is engaged in a groove 40 in the spindle immediately forward of the tubular piston shaft 28, whereby the piston 26 and its integral shaft 28 are axially secured on the spindle 34 between the rear spindle enlargement 36 and the snap ring 38. In this manner, the piston 26 and spindle 34 move as a single unit in the axial direction. Accordingly, the piston spring 30 biases the spindle 34 toward its forwardmost position as illustrated in FIG. 1.

It will be noted that the spindle 34 is held in axially centered position within the body 12 and nosepiece 16 by engagement of the spindle in a constricted portion 42 of nosepiece 16, and by engagement of the rearward portion of the spindle in the piston assembly which in turn is centered by engagement of the piston in the body cylinder 24.

An O-ring seal 44 is engaged between the body 12 and nosepiece 16 rearwardly of the threaded coupling 18 to prevent escape of hydraulic field to the outside of the hand gun 10. Another O-ring seal 46 is engaged between the constricted portion 42 of the nosepiece and the spindle 34 so as to prevent escape of pressurized hydraulic fluid forwardly into the threaded tubular portion of the nosepiece. Escape of pressurized hydraulic fluid rearwardly past the piston 26 is opposed by a third O-ring seal 48 engageable between the piston and the body cylinder 24 in the form of a conventional piston ring, and a fourth O-ring seal 50 engageable between the piston 26 and the spindle 34.

The pull-up mandrel 52 of the tool has an enlarged rearward connector portion 54 which is coupled to the forward end portion of spindle 34 by means of a collet 56 which is threadedly connected to the forward end portion of spindle 34 by means of a left-hand threaded coupling. The mandrel 52 has a rearwardly projecting flat key 58 which is engaged in a complementary key slot 60 in the front end of spindle 34, whereby the spindle 34 and mandrel 52 will move as a single unit both axially and rotationally in both directions of rotation. The collet 56 has a cylindrical outer surface which is both slidably and rotationally engaged in the cylindrical inner surface of the tubular forward portion 22 of the nosepiece 16, providing axially centering support for the forward end of the spindle 34 and for the mandrel 52. The mandrel 52 is provided at its for3,654,792 ward end portion with right-hand threads 62, this threaded portion being releasably threadedly engageable with complementary internal threads in a blind fastener sleeve as described hereinafter in detail.

A tubular anvil 64 is annularly disposed about the mandrel 5 52, anvil 64 having a rearwardly extending, internally threaded skirt portion 66 which is threadedly coupled over the externally threaded tubular forward portion 22 of the nosepiece 16. Mandrel 52 is freely rotatable and slidable relative to the anvil 64, and anvil 64 has a generally flat forward working face 68 which engages against the blind fastener sleeve head during the screw-in and pull-up phases of operation of the apparatus as will hereinafter be described in detail.

Also threadedly engaged over the externally threaded tubular forward portion 22 of nosepiece 16, immediately to the ¹³rear of the anvil skirt portion 66, is a locking ring or nut 70 which serves to lock the anvil axially relative to the nosepiece. In FIG. 1 the anvil 64 is at its rearwardmost position on the nosepiece 16, which leaves a maximum length of the mandrel ₂q 52 projecting forwardly from the working face 68 of the anvil, to accommodate a relatively long blind fastener sleeve. Forward adjustment of the anvil 64 on the nosepiece 16, secured by means of the locking ring or nut 70, will accommodate blind fastener sleeves of shorter lengths. ₂5

Rotary power is supplied to the spindle 34 by means of a reversible, gear-type hydraulic motor mounted on the rear end of the hand gun body 12, the motor being generally designated 72. Motor 72 includes a power gear 74 and an idler gear 76 meshed with the power gear 74, the gears 74 and 76 having 30 standard involute gear teeth. Respective integral shafts 78 and 80 extend from both ends of the gears 74 and 76. The shaft 78 for power gear 74 includes a forwardly extending portion 82 of square cross section which is engaged in a complementary square aperture 84 in the enlarged coupler portion 36 of the 35 spindle 34. The coupler portion 36 of the spindle has a cavity 86 extending axially forwardly of the square aperture portion 84 to allow substantial rearward sliding movement of the drive coupler 36 over the square shaft portion 82 during the pull-up phase of operation of the tool, and dampening of this relative 40 axial movement between the coupler 36 and the square shaft portion 82 due to a close-fitting relationship therebetween, and due to the presence of hydraulic fluid in the cylinder 24, is avoided by providing bleeder passage means 88 which extends radially outwardly from the cavity 86 to the outside of drive ⁴³coupler 36.

The motor gears 74 and 76 are rotatably mounted in respective parallel, communicating, arcuate cavities 90 and 92 which extend axially through a motor gear housing plate 94 of substantially the same axial thickness as the length of the gears 74 and 76. Inside and outside manifold plates 96 and 98, respectively, seat flush against the front and rear surfaces of the motor gear housing plate 94, the manifold plates 96 and 98 each being provided with a pair of bores that are coaxial with the respective gear cavities 90 and 92 in the housing plate 94, to provide journals for the respective gear shifts 78 and 80.

The inside manifold plate 96 is adapted to seat flush against a generally flat rearwardly facing surface 100 of body 12, while a generally flat motor cover plate 102 is adapted to seat 60 against the rear surface of outside manifold plate 98.

The entire assembly consisting of motor gear housing plate 94 and the gears 74 and 76 therein, the two manifold plates 96 and 98, and the motor cover plate 102, is secured to the gun body 12 by means of a plurality of screws 104 which extend 65 through aligned apertures in the plates 94,96,98 and 102, and threadedly engage in the rear of body 12 as best seen in FIG. 1. Sealing rings 106 are engaged between each pair of mating surfaces in this assembly radially outwardly of the hydraulic motor gears 74 and 76 and shafts 78 and 80, to prevent the 70 escape of hydraulic fluid through the interfaces.

The hydraulic fluid passage system of the hand gun 10 includes three inlet conduits which receive hydraulic fluid under pressure from the remote power unit and one hydraulic fluid drain conduit. Thus, referring in particular to FIGS. 1, 3, and 75

5, looking forwardly from the rear of the gun as in FIG. 5, at the right-hand side of the handle is a conduit 108 which is connected to the remote power unit by a flexible hose to receive hydraulic actuating fluid for the screw-in phase of mandrel operation. Similarly, fluid conduit 110 in the left-hand side of the gun handle looking forwardly as in FIG. 5 receives hydraulic actuating fluid from the remote power unit through a suitable flexible hose for the screw-out phase of mandrel operation. Centered between the sides of the handle, and located forwardly of the conduits 108 and 110, is a third conduit 112 which receives hydraulic actuating fluid from the remote power unit through a suitable flexible hose for the pull-up phase of mandrel operation. Finally, a drain conduit 114 is centered between the sides of the handle to the rear of the conduits 108 and 110, the conduit 114 being connected to the remote power unit through a fourth flexible hose to return hydraulic fluid from the gun back to the power unit.

The fluid conduits 108 and 110 extend upwardly through the handle 14 and then rearwardly, generally parallel to each other, through the body 12 of the gun, opening into respective upwardly extending grooves 116 and 118 in the rear surface 100 of body 12. The upper ends of grooves 116 and 118 communicate with respective ports 120 and 122 which extend in the axial direction through inside manifold plate 96 and open in horizontally spaced relationship to the gear cavities 90 and 92 proximate the constriction where the cavities 90 and 92 come together; i.e., the ports 120 and 122 communicate with the gear cavities 90 and 92 proximate the horizontal centerline therebetween. As best shown in FIG. 7, the ports 120 and 122 are spaced apart slightly more than the thickness of a single tooth of either of the gears 74 and 76, and by providing a close tolerance fit between the gears 74 and 76 there will always be substantially a one-tooth seal between the ports 120 ad 122. A close tolerance fit is also provided between the outer periphery of power gear 74 and its gear cavity 90, and between the periphery of the idler gear 76 and its gear cavity 92. In this manner, the gears 74 and 76 provide a labyrinth type seal in their respective cavities 90 and 92 and the pressure falls off in a steep gradient from the parts 120 and 122 peripherally outwardly about the cavities 90 and 92. With this arrangement, the gear motor is highly efficient, and it is unnecessary to provide conventional bleed passages diametrically through the gears.

When fluid under pressure is supplied to the fluid conduit 108 in the handle 14, it passes upwardly through conduit 108 into groove 116 in surface 100 of the body and thence through the respective port 120 into the region where the gear cavities 90 and 92 join. Then, the fluid flows to the left as viewed in FIGS. 7 and 13, in the direction of the arrows in FIG. 13, displacing the meshed gear teeth to the left the fluid then discharging out through port 122, groove 118 and thence out of the hand gun portion of the tool through the fluid conduit 110. Thus, fluid flowing in this direction will cause the power gear 74 to rotate clockwise as viewed in FIGS. 5, 7, 9, and 13. Correspondingly, the shaft 78 of gear 74 will be rotated clockwise, and the square portion 82 thereof will cause the spindle 34 and the mandrel 52 to rotate in a clockwise direction.

Conversely, when hydraulic fluid under pressure is introduced into the hand gun through fluid conduit 110, it passes upwardly through the handle and rearwardly through the body portion of conduit 110 into groove 118, from which it passes rearwardly through port 122, and as indicated by the flow arrows in FIG. 14, flows to the right in the region where the gear cavities 90 and 92 join, forcing the meshing gear teeth to the right as viewed in FIG. 14. The fluid then flows out through the port 120, groove 116 and fluid conduit 108. Thus, when fluid under pressure is introduced into the gun through fluid conduit 110, it causes the power gear 74 to rotate in an anticlockwise direction as viewed in FIGS. 5, 7, 9, and 14, thereby rotating the power gear shaft 78 and its square forward portion 82 anticlockwise, and correspondingly rotating the spindle 34 and mandrel 52 anticlockwise.

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A small amount of the hydraulic fluid which is thus introduced into the hand gun through the fluid conduits 108 and 110 will flow into the journals for the gear shafts 78 and 80 so as to lubricate the latter, from the gear cavities 90 and 92 adjacent the ends of the gears 74 and 76. 5

Such of the hydraulic fluid as may seep into the interfaces between rear body surface 100 and manifold plate 96 or between plates 96,94,98, and 102, from any source, as for example from the grooves 116 and 118, the ports 120 and 122, the gear shift journals, or the gear cavities 90 and 92, will be ¹⁽prevented from escaping to the outside of the hand gun by the sealing rings 106 as aforesaid, and will be collected by a series of axially aligned leakage ports 124, 126, and 128, respective plates 98,94, and 96, and fed to a further leakage port 130 in ₍the body 12 opening at rear surface 100 thereof, the final * leakage port 130 extending forwardly into communication with the annular recess 32 in the body 12, from which such drainage fluid is enabled to flow out of the hand gun through the drain conduit 114.

Hydraulic fluid under pressure introduced into the fluid ^2Cconduit 112 passes upwardly through the handle 14 and thence forwardly in the body 12 into the body cylinder 24 forwardly of piston ring 48, thereby building up fluid pressure forward of the piston in the chambers 24 and 20 and forcing 25 the piston 26 rearwardly against the forward biasing force of spring 30, thus moving spindle 34 and mandrel 52 axially rearwardly in the hand gun relative to the anvil 64 Hydraulic fluid which may seep rearwardly past the piston ring 48 is simply collected in the cylindrical chamber 24 and annular recess 32 30 to the rear of the piston, and drains out of the hand gun through the drain conduit 114 which communicates at its upper end with the cylindrical body chamber 24. Actually, hydraulic fluid previously accummulated in the cylinder 24 and recess 32 from bypassing the piston 26 and from leakage 35 out of the hydraulic motor 72, is pumped out of the hand gun through drain conduit 114 each time the piston 26 is driven rearwardly during a cycle of operation of the tool.

Upon release of pressure of the hydraulic fluid in the conduit 112, the spring 30 is enabled to return the piston 26, and 40 consequently the spindle 34 and mandrel 52, forwardly to the position shown in FIG. 1, with excess fluid from chamber 20 in the nosepiece 16 and from the cylindrical body chamber 24 forward of piston ring 48 simply flowing back out through the fluid conduit 112. 45

The hand gun 10 has a single finger-actuated switch button 132 thereon which projects forwardly from a trigger-shaped, concave finger guide 134 projecting forwardly from the upper front portion of the handle 14. The switch button 132 actuates a normally open electrical switch 136, the two contacts of ⁵θ which are electrically connected to a pair of wires 138 and 140 which, together with a ground wire 142, constitute the electrical elements of an electrical cable 144 that extends from the hand gun 10 to the remote power source. Depressing tithe switch button 132 to close switch 136 completes an elec- ³⁵trical circuit which causes the hand gun 10 to hydraulically drive the mandrel 52 through a complete cycle of operation.

Such a complete cycle of operation is illustrated in the sequence of FIGS 10,11, and 12 of the drawings which show gg the installation of a blind fastener sleeve generally designated 146 in a structure generally designated 148 comprising a pair of overlapping panels 150 and 152. The exposed side 154 of panel 150 shall be considered to be the access side of the structure 148, while the exposed side 156 of the panel 152 65 shall be considered to be the blind side of structure 148. The structure 148 has a bore 158 extending therethrough from the access side 154 to the blind side 156, the bore 158 having a counterbore 160 at the access end thereof to receive the head 162 of the blind fastener sleeve where, as shown, the blind 70 fastener sleeve has a tapered type head.

The blind fastener sleeve 146 includes, in addition to the head portion 162 thereof, a tubular body portion 164 which is generally coextensive with the panel bore 158, but preferably terminates just short of the blind side 156 of the structure, a 75 thin-walled, undercut, deformable section 166 which extends substantially beyond the blind side 156 of the panel, and terminating in an internally threaded pull-up portion 168 of the sleeve.

Installation of the blind fastener sleeve 146 in the structure 148 is accomplished by first inserting the fastener sleeve 146 into the bore 158 from the access side 154 thereof until the sleeve head 162 seats in the counterbore 160. The hand gun 10 is then moved into position so that its forwardly projecting mandrel 52 is generally axially aligned with the sleeve 146, and the mandrel 52 is then inserted through the sleeve 146 until the forward end of the mandrel comes into contact with the threads in the pull-up portion 168 of the sleeve where that portion of the sleeve joins with the deformable section 166 of the sleeve. Both as an aid to guiding the forward end of the mandrel into the internally threaded pull-up portion 168 of the sleeve, and to achieve the desired nut configuration of the deformable section 166 of the sleeve after pull-up, the deformable section 166 preferably includes a radially inwardly tapering guide portion 170.

When the mandrel 52 is thus positioned, the operator simply presses the finger switch button 132 and holds the button down until the cycling has been completed. The first response to actuation of the switch 136 in the gun will be provision by the remote power source of hydraulic fluid under pressure to the fluid conduit 108 in the handle of the gun, which will provide fluid pressure to the gear motor 72 through port 120, thereby causing the mandrel 52 to be rotated clockwise so that the threaded end portion 62 of mandrel 52 will automatically screw into the internally threaded pull-up portion 168 of the blind fastener sleeve 146. This screw-in first phase of operation of the hand gun will continue until the forward working face 68 of anvil 64 and the sleeve head 162 are brought tightly into engagement and the tubular column comprising the nosepiece 16 and anvil 64 of the hand gun and the fastener sleeve 146 oppose further threaded engagement of the front end portion of mandrel 52 into the pull-up portion 168 of the sleeve, at which time the hydraulic motor 72 will stall, and corresponding back pressure in the fluid conduit 108 will be sensed in the remote power unit to automatically switch to the second phase of operation of the apparatus.

The second phase is effected by introduction of hydraulic fluid under pressure into the hand gun through fluid conduit 112, which builds up fluid pressure forward of the piston 26, forcing the piston 26 and hence the mandrel 52 rearwardly from the first-phaSe stall position shown in FIG. 10 to cause the deformable section 166 of the blind fastener sleeve to buckle outwardly as shown in FIG. 11. This pull-up phase of the operation continues until the deformable section 166 of the sleeve is collapsed to the point where it applies sufficient force in opposition to further collapse to build up back pressure of the hydraulic fluid in conduit 112 to a predetermined pressure which is sensed in the remote power unit and employed to automatically effect the shift from the second phase of operation of the tool to the third phase of operation which is illustrated in FIG. 12.

According to the third phase of operation, hydraulic fluid under pressure is introduced into the hand gun through the fluid conduit 110, from which it is conducted to the hydraulic motor 72 through port 122 to cause anticlockwise rotation of the mandrel 52, whereby the threaded forward end portion 62 of the mandrel will screw out of the internally threaded pullup portion 168 of the blind fastener sleeve. The three-phase installation cycle is complete when the threaded forward end of the mandrel clears the threads of the pull-up portion 168 of the blind fastener sleeve as illustrated in FIG. 12, and at that point the finger switch button 132 can be released by the operator to turn off the tool, and the mandrel withdrawn from the fully installed blind fastener sleeve 146.

FIG. 15 is similar to FIG. 10, illustrating the mandrel 52 of the tool fully threadedly engaged with the internally threaded pull-up portion of a blind fastener sleeve at the termination of the first or screw-in phase of operation of the tool. However,

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FIG. 15 differs from FIG. 10 by showing a shortened blind fastener sleeve 146a engaged through a bore 158α in structure 148α composed of a pair of relatively thin panels 150α and 152α. Because of the shortened length of the fastener sleeve 146α, if the tool were adjusted as in FIG. 10, with the anvil 64 and locking ring 70 fully rearwardly positioned on the tubular forward portion 22 of the nosepiece, then the threaded front end portion 62 of mandrel 52 would screw too far through the internally threaded pull-up portion 168c of the fastener sleeve and there would be an insufficient axial length of threaded engagement therebetween when the forward face of the anvil 64 bottomed against the head of the fastener sleeve at the completion of the first phase to assure that the pull-up phase could be accomplished without damaging the fastener sleeve. In fact, with an even shorter fastener sleeve than the sleeve 146a illustrated in FIG. 15, the threaded forward end 62 of the mandrel 52 might screw completely on through the threaded pull-up portion of the fastener sleeve so that the hydraulic motor stall-out to complete the first phase of operation might never occur.

To accommodate such a shorter fastener sleeve 146a, all that is necessary is to screw the anvil 64 forwardly on the tubular forward portion 22 of the nosepiece a sufficient amount to assure full threaded engagement of the threaded forward end 62 of the mandrel in the internally threaded pull-up portion 168α of the fastener sleeve, and then to lock the anvil 64 in this position by tightening the locking ring 70 against the rearward end of the anvil. The operation of the tool through the three phases, screw-in, pull-up, and screw-out, will then be identical to the operation described in connection with FIGS. 10,11, and 12.

FIG. 22 diagrammatically illustrates the hydraulic system, which is generally designated 172. Also illustrated in FIG. 22 is a pneumatic power system, generally designated 174, which provides the driving power to the hydraulic system. While the hydraulic pump of the hydraulic system 172 can be powered by any conventional prime mover, as for example an electric motor, the pneumatic power system 174 is particularly desirable in that it does not produce the sparks of an electric motor, and hence the explosion hazard of an electric motor, and it utilizes readily available shop air which is capable of bringing the hydraulic pump up to operational speed with a minimum time lag.

Referring at first to the pneumatic power system 174, shop air is supplied thereto through air inlet conduit 176, the air being directed through a filter 178, a pressure regulator 180, and a lubricator 182 to a normally closed solenoid-operated air valve 184. The lubricator 182 suspends a small amount of oil in the air for lubrication of the air motor. A pressure gauge 186 is connected between regulator 180 and valve 184 for monitoring the air pressure that is supplied through valve 184 to the air motor. When the solenoid-operated air valve 184 is energized and thereby moved from the closed position that is illustrated to its open position, it permits air to flow therethrough and thence through a flow control valve 188, which adjustably meters the rate of air flow, to air motor 190, which is silenced by a suitable muffler 192. The air motor 190 drives the hydraulic pump 194 of the hydraulic system 172 through a suitable drive shaft connection 196.

The hydraulic pump 194 is energized in response to actuation of the hand gun switch button 132 to close the normally open electrical switch 136 located in the hand gun. Closure of switch 136 moves the normally closed solenoid-operated air valve 184 to its open position, thereby energizing the air motor 190 and consequently hydraulic pump 194.

The hydraulic pump 194 furnishes hydraulic fluid under pressure through a check valve 198 to fluid output conduit 200 which is connected to directional control valve 202. Valve 202 is a four-way, three-position, solenoid-operated valve having a normally closed centered position as illustrated in FIG. 22, and being movable to a first off-center position wherein the mandrel 52 of the hand gun 10 is caused to rotate clockwise for the screw-in operation, and alternatively to a second off-center position wherein the mandrel 52 of the hand gun is caused to move anticlockwise for the screw-out operation.

When the hand gun switch button 132 is initially depressed to close the normally open electrical switch 136 in the hand gun, this not only opens electrical switch 136 in the hand gun, this not only opens the solenoid-operated air valve 184 as aforesaid to cause energization of the hydraulic pump 194, but also energizes the solenoid-operated directional control valve 202 to shift the valve element thereof as diagrammatically illustrated in FIG. 22 to the right, which connects the pump output conduit 200 to hydraulic line 204, and also connects hydraulic line 206 to a line 208 which returns the hydraulic fluid to reservoir 210. The hydraulic system is a recirculating one, the reservoir 210 being the source of the hydraulic fluid for the hydraulic pump 194, which receives this fluid through input conduit 212.

Hydraulic line 204 is connected through a speed control valve 214 and flexible hose 216 to the fluid conduit 108 that leads to one side of the hydraulic motor 72 in hand gun 10. The fluid conduit 110 leading to the other side of the hydraulic motor 72 in the hand gun is connected through flexible hose 218 to the hydraulic line 206.

Thus, in the initial mode of operation of the apparatus when the gun switch 136 is closed by depressing the switch button 132, with the hydraulic pump 194 energized and the directional control valve 202 in its first off-center position, to the right as illustrated in FIG. 22, hydraulic fluid will pass from the pump 194 through conduit 200 and valve 202 into the hydraulic line 204, and thence through flexible hose 216 to the hand gun conduit 108 so as to drive the hydraulic motor 72 in the hand gun clockwise to screw the mandrel 52 into the pull-up portion of the blind fastener sleeve. After driving the hydraulic motor, the fluid then returns to the reservoir 210 through hand gun conduit 110, flexible hose 218, hydraulic line 206, directional control valve 202 and hydraulic return line 208.

A pressure switch 220 is operatively connected to the hydraulic line 204, and when the hydraulic motor 72 stalls at the completion of the screw-in mode, the back pressure increase in hydraulic line 204 corresponding to this stall condition of the hydraulic motor 72 causes actuation of pressure switch 220, which in turn causes release of the directional control valve 202 back to its center position as illustrated in FIG. 22, thus cutting of the connection between conduit 200 and line 204 and thereby stopping the flow of hydraulic fluid to the hydraulic motor 72. Simultaneously, such actuation of the pressure switch 220 energizes a piston operating valve 222 to shift it from its normal position as illustrated in FIG. 22 to the right to its actuated position wherein it provides hydraulic fluid under pressure from the pump 194 to the hand gun cylinder 24 so as to force the hand gun piston 26 and the mandrel 52 rearwardly in the pull-up mode of operation of the tool. With the piston operating valve 222 thus shifted to the right as illustrated in FIG. 22 to effect the second or pull-up mode of operation, hydraulic fluid pressure is conducted from the pump 194 through output conduit 200 and thence through hydraulic line 224 and valve 222 to a hydraulic line 226, flexible hose 228, and fluid conduit 112 in the hand gun, to the cylinder 24 in the hand gun. Drainage fluid from cylinder 24, and from hydraulic motor 72, returns to the reservoir 210 through hand gun drain conduit 114 and a further flexible hose 230.

An adjustable pressure switch 232 is operatively connected to the hydraulic line 226, and when the back pressure in line 226 reaches a predetermined value, as preset on the switch 232, the switch 232 is actuated so as to cause release of the piston operating valve 222 back to its normal position as illustrated in FIG. 22, wherein the line 226 is disconnected from the pressure line 224 and line 226 is connected through valve 222 to a drain line 234. The drain line 234 is connected to a hydraulic return line 208, whereby fluid pressure from hand gun cylinder 24 is relieved through hand gun conduit 112,

3,654,792 flexible hose 228, line 226, valve 222, and lines 234 and 208 back to the reservoir 210, thereby allowing the hand gun piston 26 to be returned to its initial, inoperative position.

Such closing of the adjustable pressure switch 232 in response to back pressure in the hydraulic line 226 marks the completion of the pull-up cycle of the tool, and also causes the directional control valve 202 to shift to the left from its center position as illustrated in FIG. 2 so as to provide fluid connection from the pump output conduit 200 to hydraulic line 206, and also to connect the hydraulic line 204 to the hydraulic return line 208. This causes the hydraulic motor 72 in the hand gun to be driven anticlockwise to produce the third mode of operation of the tool, which is the screw-out mode wherein the mandrel 52 screws out of the internally threaded portion of the blind fastener sleeve. In this mode hydraulic fluid under pressure flows from the pump 194 through output conduit 200 and through directional control valve 202 to hydraulic line 206, from which the fluid passes through flexible hose 218, and fluid conduit 110 in the hand gun to the hydraulic motor 72. Fluid discharge from the motor 72 passes through conduit 108 in the hand gun and thence through flexible hose 216, hydraulic line 204, valve 202 and hydraulic return line 208 back to the reservoir 210. This third mode of operation continues until the operator releases the hand gun switch button 132 to open the switch 136, which allows directional control valve 202 to return to its center position as illustrated in FIG. 22, and which also releases the solenoidoperated air valve 184 in the pneumatic power system 174, the air valve 184 thus being allowed to return to its normally closed position as illustrated in FIG. 22.

Over-pressurization of the system is prevented by a relief valve 233 connected to output conduit 200. Slight pressure is maintained in the system when it is inoperative by a back pressure valve 235 in return line 208.

Reference will now be made to FIG. 23 of the drawings, which diagrammatically illustrates the electrical system employed in the present invention for controlling the hydraulic and pneumatic systems 172 and 174, respectively. Line current is fed through a wall plug 236 to a pair of conductors 238 40 and 240, the conductor 238 being shown as a bus line for one side of the system. Line 240 has a fuse 242 therein, and leads to a selector switch generally designated 244 which has three positions, an “off’ position an “auto” position for automatic cycling of the apparatus through the screw-in, pull-up and unscrew modes of operation, and an “unscrew” position which causes the screw-in and pull-up modes to be bypassed, and allows the apparatus to operate only in the third or unscrew mode. The “off’ section 246 of the selector switch 244 is an open contact section. The “auto” section 248 of switch 244 is an open contact section. The “auto” section 248 of switch 244 has two sets 250 and 252 of normally open contacts which are closed by moving the selector switch 244 to the “auto” position. Similarly, the “unscrew” section 254 of selector switch 244 has two sets 256 and 260 of normally open contacts which are closed by moving the selector switch 244 to the “unscrew” position.

Assuming that the selector switch 244 is moved to the “auto” position for normal automatic operation of the apparatus, ₆₀this will connect line conductor 240 through switch contacts 250 to a conductor 262. An indicator light 264 connected between conductor 262 and the bus line 238 will become illuminated to indicate that the apparatus is turned on. The energized conductor 262 is connected through electrical connec- 65 tor 266 to one of the wires 138 leading to the normally open hand gun switch 136, the other hand gun wire 140 leading through connector 266 to a conductor 268 that is connected to one side of the solenoid-operated air valve 184, the other side of which is connected to the bus line 238. Solenoid- 70 operated air valve 184 is closed in its normal, unenergized condition, and since the hand gun switch 136 is normally open as illustrated in FIG. 23, the air valve 184 will remain closed until the hand gun switch 136 is closed by depressing the switch button 132. When the hand gun switch 136 is closed, it 75 then completes an electrical circuit from the energized conductor 262 through the hand gun switch 136 to conductor 268 so as to actuate the solenoid-operated air valve 184, thus opening the valve 184 and actuating the air motor 190 and consequently the hydraulic pump 194.

When the selector switch 244 was initially moved to the “auto” position, contacts 252 thereof were closed to provide electrical connection between conductor 268 and a second bus line 270. Thus, when the hand gun switch 136 is closed to commence operation of the tool, and the conductor 268 is thereby energized as aforesaid, the bus line 270 is likewise energized by the connection from conductor 268 through selector switch contacts 252. The directional control valve 202 has two solenoid coils 202α and 2026 diagrammatically illustrated in FIG. 23. Energization of solenoid coil 202α causes the directional control valve 202 to shift to the right from the central position as illustrated in FIG. 22 for the screw-in phase of operation of the tool, while energization of the solenoid coil 2026 causes the directional control valve 202 to shift to the left from the central position as illustrated in FIG. 22 for the unscrew or final phase of operation of the tool. Energization of the bus line 270 upon closure of the hand gun switch 136 as aforesaid provides electric current to the solenoid coil 202α, thereby initiating the screw-in phase of operation. One side of solenoid coil 202α is electrically connected to the bus line 238. The other side of coil 202α is connected to the other bus line 270 through normally closed pressure switch 220.

Thus, closure of the hand gun switch 136 causes simultaneous energization of the solenoid-operated air valve 184 and of solenoid coil 202α of directional control valve 202, thereby simultaneously turning on the hydraulic pump and directing the fluid flow therefrom to turn the hydraulic motor 72 clockwise for the screw-in phase of operation of the tool.

When the hydraulic motor 72 of the hand gun stalls at the end of the screw-in mode of operation, the increased pressure in the hydraulic line 204 causes the pressure switch 220 to momentarily open, thereby releasing the solenoid coil 202α and allowing the directional control valve 202 to shift back to the center position as illustrated in FIG. 22. The momentary opening of pressure switch 220 also completes an electrical connection from bus line 270 to the coil 272 of a relay generally designated 274 which has normally open contact 276 and normally closed contact 278. Energization of relay coil 272 opens the normally closed contact 278 which is in the circuit to solenoid coil 202α, so that when the pressure switch 220 again closes after its momentary opening, it will not again energize the solenoid coil 202α. Energization of relay coil 272 closes the relay contact 276, which electrically connects the relay coil 272 between the bus lines 270 and 238, thereby holding the relay 274 in its energized condition with contact 278 open and contact 276 closed. Closure of contact 276 also electrically connects the piston operating valve 222 between the bus lines 270 and 238, thereby actuating the valve 222 to provide hydraulic fluid under pressure to the hand gun cylinder 24 to effect the second or pull-up phase of operation of the tool.

This condition of the circuit remains in effect until pull-up is completed as sensed by the adjustable pressure switch 232 which, due to increase of back pressure in the hydraulic line 226, moves from its normally open position to a momentarily closed position wherein it electrically connects the coil 280 of a relay 282 between the bus lines 270 and 238. Relay 282 has three contacts, a normally closed contact 284, and normally open contacts 286 and 288. The momentary closure of adjustable pressure switch 232 to energize the relay coil 280 causes a relay holding circuit to be completed between bus lines 270 and 238 by closure of the normally open relay contact 288, so that when pressure switch 232 again opens upon a drop of pressure in hydraulic line 226, the relay 282 will remain actuated. Actuation of relay 282 opens relay contact 284 which is in the circuit providing current to relay coil 272 and piston operating solenoid valve 222, thereby releasing the relay 274 and the piston operating solenoid valve 222, cutting off the supply of hydraulic fluid pressure to the hand gun cylinder 24.

3,654,792

Actuation of relay 282 further closes its normally open contact 286 which serves to electrically connect the directional control valve solenoid 202b between bus lines 270 and 238 so as to shift the directional control valve 202 to the left from the center position as illustrated in FIG. 22, thereby actuating the hand gun hydraulic motor 72 in the anticlockwise direction for the final or unscrew mode of operation of the apparatus.

Accordingly, when relay 282 is actuated at the commencement of the third or unscrew mode of operation, it causes release of the remainder of the circuit except for the solenoidoperated air valve 184 which remains energized to keep the hydraulic pump 194 operative, and except for the solenoid 202b of the directional valve 202 and the holding circuit itself for the relay 282. Then, when the hand gun mandrel 52 has unscrewed free of the installed blind fastener sleeve, release of the trigger switch button 132 allowing the hand gun switch 136 to open disconnects the power source from conductor 268 and hence from the bus line 270, thereby releasing relay 282 and hence also releasing the solenoid coil 202b of directional control valve 202 so that valve 202 returns to the center position as illustrated in FIG. 22. This returns the circuit to its full reset position, ready for another cycle of operation upon closing of the hand gun switch 136. However, with the selector switch 244 left in the “auto” position, the indicator light 264 will remain illuminated to indicate that the apparatus is prepared for another cycle of operation.

The “unscrew” position of selector switch 244 permits the unscrew mode of operation of the apparatus to be employed pursuant to actuation of the hand gun switch 136 without cycling through the screw-in and pull-up modes. Such independent use of the unscrew mode of operation may be desirable in the event the mandrel 52 should inadvertently become stuck in a blind fastener sleeve and it should be desired to simply back the tool out of the sleeve. Moving the selector switch 244 to the “unscrew” position closes contacts 256 and 260 thereof. Contact 256 connects line conductor 240 to the conductor 262, which turns on the indicator light 264 and energizes the circuit to hand gun switch 136. Closure of contact 260 connects the conductor 268 from the hand gun to a conductor 290 which is connected to one side of the directional control valve solenoid coil 202b, the other side of which is connected to bus line 238. Accordingly, closure of the hand gun switch 136 simply completes a circuit to the solenoid coil 202b to cause the directional control valve 202 to shift to the left from the center position as illustrated in FIG. 22, thereby causing the hand gun hydraulic motor to turn anticlockwise for the unscrew mode, which mode continues until the hand gun switch 136 is released.

If the hand gun switch button 132 is released to open the hand gun switch 136 at any time during either the automatic operation of the apparatus with the selector switch 244 in the “auto” position or during the unscrew mode as determined by positioning the selector switch 244 in the “unscrew” position, the entire electrical system will be de-energized, with the exception of the indicator light 264 which will remain illuminated, and all functions will cease. If the selector switch 244 is in the “auto” position, when the hand gun switch button 132 is again depressed to close the switch 136, cycling of the apparatus will again commence from the beginning, the apparatus going through the screw-in, pull-up and unscrew modes in sequence. If the selector switch is on the “unscrew ” position, reclosing the hand gun switch 136 will simply cause resumption of the unscrew mode.

If, for example, the automatic operation of the apparatus should be interrupted by opening of the hand gun switch 136 during the screw-in mode, rotation of the mandrel 52 will simply stop. Then, when the switch 136 is again closed, the first or screw-in mode will assume, and will continue until the stall condition of the hydraulic motor switches the apparatus to the second or pull-up mode, and the cycling will continue through the pull-up and unscrew modes. As another example, if the hand gun switch 136 should be opened during the pullup mode, the complete de-energization of the system will release the pull-up force, but leave the mandrel 52 screwed into the blind fastener sleeve. Then, when the hand gun switch 136 is reclosed, the system will go through all three cycles, although the screw-in cycle will be quickly traversed since the hydraulic motor 72 will almost immediately stall due to the fact that the mandrel is already fully threadedly engaged with the blind fastener sleeve. This stall condition of the hydraulic motor 72 switches the apparatus to the pull-up mode which is then effective for complete pull-up as determined by back pressure in the hydraulic system acting upon the adjustable pressure switch 232, and then the system will automatically switch to the unscrew mode.

Similarly, if automatic operation is terminated by opening of the hand gun switch 136 during but before the completion of the unscrew mode, when the switch 136 is again closed, the apparatus will cycle through all three modes. During the screw-in mode, the mandrel will screw back into the blind fastener sleeve to the extent that it had already screwed out, at which time the hydraulic motor 72 will stall to switch to the pull-up mode. The pull-up mode will be quickly traversed since the blind fastener sleeve will already be fully upset, and then the apparatus will again automatically switch to the unscrew mode, which will be completed assuming the hand gun switch 136 is held long enough in the closed position.

FIGS. 16 through 21 illustrate a presently preferred remote power unit generally designated 292 for providing the hydraulic driving power to the hand gun 10 pursuant to electrical control from the hand gun. The power unit 292 is preferably constructed in the form of a movable cart having a housing 294 with front, rear, and right and left side walls 296,298,300 and 302, respectively. The housing 294 stands on a stationary rear rest member 304 and a pair of forward wheels 306, and a forwardly and upwardly projecting handle 308 permits convenient moving of the power unit 292 by simply tipping the housing forwardly on the wheels 306 to raise the rear rest member 304 above the floor.

FIG. 16 illustrates the air motor 190 coupled to the hydraulic pump 194 through the drive connection 196, and also illustrates a hydraulic fluid filter 310 in the rear of the housing and a hydraulic reservoir filler port 312 projecting from the front of the housing which are not illustrated in the hydraulic system diagram of FIG. 22. The hydraulic pump 194 is shown located within the reservoir 210, and the hydraulic pump output is fed through a pipe 314 to a manifold 316 which contains most of the hydraulic system lines or conduits diagrammatically illustrated in FIG. 22. The manifold 316 is laid out generally horizontally in overlying relationship above the reservoir 210. As best shown in FIGS. 16 and 17, supported on top of the manifold 316 are the check valve 198, the directional control valve 202, speed control valve 214, piston operating valve 222, and relief valve 233. Projecting rearwardly from the manifold 316 are the back pressure valve 235 and hydraulic filter 310.

As best illustrated in FIGS. 16 and 18, the adjustable pressure switch 232 is mounted on the front wall 296 of the power unit housing 294.

The air system is best shown in FIG. 19 looking from the rear inside the housing 294. Illustrated in FIG. 19 are air filter 178 and pressure regulator 180, which are shown as a combination unit, lubricator 182, the solenoid-operated air valve 184, air flow control valve 188, and air motor 190. The air inlet conduit 176 is provided with shop air through an air input hose 318 shown in FIG. 20.

Also shown in FIG. 20 on the left-hand wall 302 are the selector switch 244 and indicator light 264 forming part of the electrical circuit diagram in FIG. 23.

The connections of the flexible hoses and electrical cable from the hand gun at the front wall 296 of the power unit are best illustrated in FIGS. 17, 18, and 21. Suitable connectors for the hoses and electrical cable are mounted on a connector panel 320 on front wall 296. These connectors include an electrical connector 322 for the electrical cable 144 from the hand gun, and hose connectors 324,326,328, and 330, for the respective hoses 216, 218, 228, and 230, all of which are dia3,654,792 grammatically illustrated in FIG. 22. Also mounted on the connector panel 320 is a plugged connection 332 to v/hich a system pressure gauge may be connected for testing purposes. The electrical cable and hose connections to the hand gun are diagrammatically illustrated in FIG. 21, which illustrates the 5 connector panel 320 and the base of the handle of the hand gun 10 substantially as illustrated in FIG. 3, with dotted line electrical cable and hose connections therebetween.

While one automatic sequencing circuit arrangement has been illustrated in FIGS. 22 and 23 and described herein, it is to be understood that other circuit means may be employed to provide automatic sequencing of the hand gun between the screw-in, pull-up, and screw-out modes of operation thereof within the scope of the invention. Thus, for example, the circuit means may include as a part thereof a conventional “- ¹⁵sequence valve” which has built into it pressure responsive sequencing means which would serve as the equivalent of the pressure responsive sequencing means illustrated in FIGS. 22 and 23 and described in connection therewith. _q

While the instant invention has been shown and described ²herein in what is conceived to be the most practical and preferred embodiment, it is recognized that departures may be made therefrom within the scope of the invention, which is therefore not to be limited to the details disclosed herein. -,c