US3802517A

US3802517A - Screwdrivers and like tools

Info

Publication number: US3802517A
Application number: US00262445A
Authority: US
Inventors: Yarborough E Cooke
Original assignee: Individual
Current assignee: Individual
Priority date: 1971-06-22
Filing date: 1972-06-14
Publication date: 1974-04-09
Anticipated expiration: 1991-04-09
Also published as: GB1340005A

Abstract

A handtool, such as a screwdriver, has a helically threaded shaft rotated by axial movement of a nut engaged thereon and driven by a reciprocable piston actuated by fluid, e.g. air, under pressure, and said shaft is attached to, and axially movable in relation to, a rotatable body constituting a mount for a tool bit. A pin-and-helical channel connection between the shaft and said rotatable body ensure rotation of the latter during axial movement of the shaft in relation thereto, and the pitch of said helical channel is coarser than the pitch of the helical thread on said shaft engaged by said nut. Latch means are provided to obstruct relative axial movement of the shaft and said rotatable bit-supporting, body until the force to effect such movement exceeds a prearranged value. The shaft may be hollow, and serve as a passage for the fluid under pressure, which may be admitted to the casing through manually operable valve means. Valve means may be provided in the casing for switching supply of fluid under pressure from one to the other side of a nut-driving piston, at each end of a stroke, in order automatically to maintain reciprocatory movements of the piston as long as fluid under pressure is admitted.

Description

United States Patent 11 1 Cooke-Yarborough 111] 3,802,517 14 1 Apr. 9,1974

[ SCREWDRIVERS AND LIKE TOOLS 22 Filed: June 14, 1972 211 Appl. No.: 262,445

[30] Foreign Application Priority Data 9/1920 Germany 144/32 Primary Examinerl-lenry C. Sutherland Assistant Examiner-William F. Pate, III Attorney, Agent, or FirmYoung and Thompson 5 7 ABSTRACT A handtool, such as a screwdriver, has a helically threaded shaft rotated by axial movement of a nut engaged thereon and driven by a reciprocable piston actuated by fluid, e.g. air, under pressure, and said shaft is attached to, and axially movable in relation to, a rotatable body constituting a mount for a tool bit. A pinand-helical channel connection between the shaft and said rotatable body ensure rotation of the latter during axial movement of the shaft in relation thereto, and

the pitch of said helical channel is coarser than the pitch of the helical thread on said shaft engaged by said nut. Latch means are provided to obstruct relative axial movement of the shaft and said rotatable bitsupporting, body until the force to effect such movement exceeds a prearranged value. The shaft may be hollow, and serve as a passage for the fluid under pressure, which may be admitted to the casing through manually operable valve means. Valve means may be provided in the casing for switching supply of fluid under pressure from one to the other side of a nutdriving piston, at each end of a stroke, in order automatically to maintain reciprocatory movements of, the piston as long as fluid under pressure is admitted.

10 Claims, 6 Drawing Figures SCREWDRIVERS AND LIKE TOOLS This invention relates to screwdrivers and like tools driven by fluid pressure e.g. compressed air.

The object of the invention is to provide a tool of simpler construction that those heretofore known.

With this end in view the invention consists in a screwdriver or like tool comprising, in a casing, a rotatable spindle driven by a member reciprocable by fluid pressure admitted into the casing.

The invention will be clearly understood from the following description of forms (given, however, merely by way of example) which it may assume, and this description will be more readily followed by reference to the accompanying drawings wherein FIG. 1 represents a longitudinal axial section of a tool in accordance with the invention:

FIG. 2 represents a transverse section in the plane A-A of FIG. 1: r

FIG. 3 represents a view of the tip of the tool shown in FIG. 1 in a different operative position:

FIG. 4 represents a detail of the assembly shown in FIG. 3.

FIG. 5 represents a section similar to that shown in I FIG. 1 of another tool in accordance with the invention: and

FIG, 6 represents a like view of the upper part of the tool shown in FIG. 5, seen in the direction of the arrow In carrying the invention into effect in one convenient manner, as shown in the aforesaid drawings, a screwdriver comprises a hollow cylindrical body 1 closed at its upper end by a head 2. A spindle 3 mounted co-axially in the'body 1 is rotatable in bearings 4 in the head, and ball bearings 5 mounted in the .lower end of the body. The spindle is provided with a helical screw thread 6 along its length. The part of the spindle running in the ball-bearings 5 may be an enlargement, or an added extension, formed as a mounting for screw-driver bit 7.

A piston 8 longitudinally slidable in the body 1 is internally screw threaded to form a nut engaging on the spindle 3. Pneumatic seals are provided between the piston and the body 1 and also between the piston and spindle 3. The piston is restrained from rotation in relation to the body 1. This may be effected by a projection of the piston slidably engaging a key-way in the wall of the body, or, as illutrated in FIG. 2, by forming the body 1 internally of non-circular cross-section (e.g. elliptical, as shown), and the piston of like peripheral shape. By virtue of such restraint, axial movement of the piston 8 in the body 1 causes the spindle 3 to rotate about its axis in one or other sense according to the direction of movement of the piston.

Means are provided to reciprocate the piston in the cylinder body by fluid pressure, eg by compressed air. For this purpose there are provided in the head 2 one fluid duct 9 communicating with the space in the body 1 above the piston 8 and another fluid duct 10 commu nicating with small chamber surrounding the upper end of the spindle 3, and thence by way of an axial duct 11 through the spindle, and an outlet 12 at the lower end of the spindle, leading to the space in the body 1 beneath the piston 8. The outer ends of the

ducts

9 and 10 are connected to lines fitted with manually operable valve means, such that by one operation of the valve means, one can be connected to a cource of fluid pressure (e.g. compressed-air) while the other is open to atmosphere, and by another operation of the valve means these connections can be reversed.

In a convenient form of valve arrangement which may be employed, as illustrated, a handgrip comprises a tubular sleeve 29 slidable on the body 1, attached by a collar 30 and screw holding lug 31 to the lower end of a spool valve 32'slidable in a bore in the head 2. When the hand grip is in its upper position the spool valve admits air to the underside of the piston, while in its lower position it admits air to the upper side of the piston.

When a predetermined pressure, and thus torque, is reached a relief valve 33 rises to admit air to a chamber 34 lifting an upper piston 35 to raise the valve 32 by way of an arm 36 and thus reverse the pressure.

The tool described above represents a simple form of tool in accordance with the invention. Commencing from the setting shown in FIG. 1 the screwdriver 7 may be engaged with the slot in the head of a screw to be tightened, and the valves operated to introduce fluid pressure by way of duct 9 to the space above the piston 8, whereby the piston is driven to the lower end of the body 1, and by its movement turns the spindle 3 and the screw-driver 7 to drive home the screw. With the screwdriver disengaged from the screw the valve means may be reversed, and fluid pressure now applied by way of

ducts

10, 11 & 12 to beneath the piston 8, lifts the piston to the position shown in FIG. 1. It will be apparent that by displacing the piston to its lowermost position by fluid pressure, and then applying it to a screw head, the raising of the piston by reversed fluid pressure will effect an unscrewing operation.

As illustrated, the spindle is so mounted as to allow a degree of end float or axial play. The lower end of the body 1 may be fitted with a conical tip'13, (housing the bearings 5), having an axial bore 14 to accommodate the screwdriver 7, inside it. The bore 14 may be of suitable diameter to serve as a guide to locate the bit 7 over a screwhead, and when fluid pressure is applied to force down the piston 8, it first moves the spindle 3 downwards by the amount of end fl'oat allowed, thus moving the bit into engagement with the screwhead slot, whereafter the screw is driven as described above. When the fluid pressure is reversed, the spindle is lifted by the permitted end float to disengage the bit 7 from the screw, thus allowing the piston to be raised to its upper position without lifting the tool from the screw. This is convenient if more than one operation is necessary to complete a screwing-in operation. If, however, in this arrangement it is desired to use the tool for unscrewing, mechanical means (not shown) are provided to eliminate the end float or axial play of the spindle. If desired a mechanical stop may be provided in the body 1 to limit travel of the piston 8, and thus limit the number of turns imparted to a screw. The torque applied by the screwdriver may be controlled and adjusted by providing means to limit the fluid pressure introduced, e.g. a restrictor, or relief valve as described above; and similar arrangements may be made to limit the fluid pressure applied during a non-operative return strike of the piston, in order to economise on consumption of compressed air or other fluid.

The simple form of tool described above can in accordance with the invention be rendered more useful by additional features illustrated in the aforesaid drawings, but not yet described.

The mount for the bit 7, in this form of the invention, comprises a sleeve which is a slidable fit on a cylinder block 18 secured to the spindle 3 and in the wall of the sleeve is a helical slot 16 of substantially greater pitch than the thread 6 of the spindle. A peg 17, projecting radially from a cylindrical block 18 secured to the spindle, engages the slot 16. Thus axial movement of the spindle 3, block 18 and peg 17 applies a torque to the sleeve 15 by way of the slot 16, but the movement is restrained by a latch device comprising an outer sleeve 19 slidable on the inner sleeve 15 having a short slot 20 engaged by a pin 21 of the inner sleeve 15 towards which the outer sleeve 19 is urged by a coiled compression spring 22 seated on a flange 23 at the base of the inner sleeve 15. The peg 17 normally bears against the upper edge of the outer sleeve 19 adjacent to another longitudinal slot 24 in the outer sleeve 19.

When the piston 8 is forced down from the position shown in FIG. 1 by fluidpressure, it drives the spindle with the

sleeves

15 and 19 and the bit 7 as described above, until the resistance of the tightened screw reached a prearranged value Increased fluid pressure then moves the piston and spindle, as a unit, in an axial direction. As a result the peg l7 forces open the latch device and imparts a rotational movement to the bit by way of the sleeve 15. Owing to the coarser pitch of the slot 24, this operation applies an increased torque to the bit 7 for finally driving in the screw. In order to prevent the sleeve 15 and the spindle from rotating during the final operation there is provided in the casing a ring 25, keyed in the casing or of non-circular shape to prevent rotation, urged upwards by a coiled spring 26. The upper annular surface of this ring 25 is formed with radial slots 27 (FIG. 4) which are engaged by the peg 17 when moved downwards and the peg, block 18 and spindle are thus held against rotation during final tightening of the screw. A stop 28 is'provided to limit the upward movement of the ring 25.

In case of difficulty in providing adequate air-sealing between the piston 8 and the spindle 3 shown in FIG. 1, a modified form of tool in accordance with the invention may be adopted. In this form of the invention (FIGS. 5 & 6) the upper part of the body 1 is separated from the lower part by an internal partition 101, and the piston 8 reciprocable in this upper chamber has a comparatively long tubular extension 102 slidable in a gland 103 in the partition 101. The piston 8 and its chamber may be of circular cross-section, in which case the extension 102, below the partition is provided with a flange 104 having a notched edge engaging a key-rib 104a to prevent rotation. Alternatively the flange and lower chamber may be of non-circular cross-section, as previously described, for this purpose. At its lower end beneath the flange 104 the extension is provided with a nut 105 screw-threaded to engage on the spindle 3, in order to drive the spindle when forced downwards by the

piston assembly

8, 102. Preferably the nut 105 is separate from the extension 102, and adapted to engage therewith by ratchet teeth so that during each upward movement the nut 105 can rotate when driving the spindle in a sense reverse to that by which it is driven during a downward stroke of the nut, and in this case no end-float mounting of the spindle is necessary. The nut is held against the extension 102 by a compression spring 106. The piston is reciprocated in its chamber by fluid pressure, e.g. compressed air, and

it will be appreciated that the spindle 3 is driven by the nut in the same way as described above with reference to FIG. 1. The bit and associated driving and latch mechanisms are the same as described above with reference to FIG. 1, and function in the same way when the spindle 3 is driven.

While the fluid pressure to drive the

piston assembly

8, 102 may be controlled by manually operated, reversible trigger-valve or other valve means, there may be incorporated, as illustrated, means for automatic continuous reciprocation of the piston assembly as long as the fluid pressure is applied by way of an on-off finger valve.

A hollow valve tube 107 extends slidable through a bore in the piston 8 projecting downwards in the hollow extension 102 to a cylindrical foot 108 which is a slidable fit in the extension. Above the piston the valve tube 107 is held by a fixed collar 109 slidable in a bore of the tool head 2, and the tube extends upwards to a port 110 between bearing rings 111 slidable in the said bore. A spool 112 at the top of the tube 107 cooperates with a spring detent 113 (FIG. 6) to locate the tube 107 in one or other of the two positions between which it is longitudinally displaceable. At its lower end, adjcent to the foot 108 the tube is provided with a port 114, and the extension 102 is provided with a port just beneath the piston 8.

When the piston is in its uppermost position (FIG. 1) the piston 8 has lifted the collar 9 to displace the valve rod 107 to the upper position shown. Compressed air admitted by way of duct 9 acts upon the upper face of the piston 8 and forces it downwards. Approaching its lowermost position the piston strikes the foot 108 of the tube 107 and moves the tube downwards to its lower position where the port 1 10 registers with the air duct 9. Compressed air now flows by way of duct 110, tube 107,

ports

114 and 115 to the piston chamber beneath the piston and forces the piston upwards. At its uppermost position the piston again lifts the collar 109 and tube 107, and the cycle is repeated as long as the fluid pressure continues to be applied. Exhaust passages 116 in the tool head allow escape of air from the space of the piston chamber towards which the piston is driven. The valve arrangements controlled by a slidable tubular handgrip are the same as described above with reference to FIGS. 1-4 except that in this case when the sleeve 29 is in the lower position air is admitted to the upper side of the piston.

From the above description it will be seen that the invention provides a convenient screwdriver or like tool operable by fluid presusre, such as compressed air, but it should be understood that the invention is not limited solely to the details of the forms described above, which may be modified, in order to meet various conditions and requirements encountered, without departure from the scope of the invention, as defined in the appended claims.

What I claim is:

1. A handtool comprising, in a casing, a shaft having limited axial movement and being rotatable about its own axis, said shaft being formed with a helical groove, a nut in engagement with said helical groove and movable in an axial direction along said shaft to rotate said shaft, means for applying fluid pressure to said nut in order to move it axially along said shaft, a cylindrical body aligned with, and located at one end of, said shaft, and connected to said shaft by a pin of one engaging a helical channel of the other, whereby said body is rotated about its own axis by axial movement of said shaft, the said helical channel being of coarser pitch than said helical groove of the shaft, latch means preventing axial movement of said shaft in relation to said cylindrical body until the force applied to effect such axial movement exceeds a prearranged value, and means for releasably mounting a tool bit in said rotatable body for use.

2. A handtool according to claim 1 wherein said nut and casing are shaped to cooperate in order to prevent rotation of the nut, in the casing, about the casing axis.

3. A handtool according to claim 1 wherein said latch means comprise a slidable member against which the shaft bears, said member being spring-loaded to resist axial movement of the shaft in relation to said cylindrical body.

4. A handtool according to claim 1 wherein said latch means comprise a sleeve slidably associated with said cylindrical body and in contact with an extension from said shaft.

5. A handtool according to claim 1 wherein said latch means comprise a spring-loaded sleeve mounted on, and axially slidably in relation to, said cylindrical body, and means preventing'relative rotation of said sleeve and said cylindrical body until said sleeve is displaced axially in relation to said body by a prearranged distance, against the resistance of its load spring.

6. A handtool according to claim 1 wherein said means for applying fluid pressure to said nut comprise a piston associated with said nut and reciprocally movable in said casing.

7. A handtool according to claim 1 wherein said nut is driven by a piston slidable in said casing, and a passage through said casing admits fluid under pressure to drive the piston.

8. A handtool according to claim 1 wherein said nut is driven by a piston slidable in said casing and alternately available ducts admit fluid under pressure to the casing on opposite sides of the piston for moving the piston in opposite directions.

9. A handtool according to claim 1 wherein said shaft is hollow and serves as a passage to admit fluid under pressure into the casing for moving said nut.

10. A handtool according to claim 1 comprising a piston slidable in said casing for driving said nut, means for alternatively admitting fluid under pressure to opposite sides of the piston to move it in opposite directions, and valve means for automatically switching the supply of fluid under pressure from one to the other side of the piston when the piston reaches the end of a stroke in each direction.

Claims

5. A handtool according to claim 1 wherein said latch means comprise a spring-loaded sleeve mounted on, and axially slidably in relation to, said cylindrical body, and means preventing relative rotation of said sleeve and said cylindrical body until said sleeve is displaced axially in relation to said body by a prearranged distance, against the resistance of its load spring.

10. A handtool according to claim 1 comprising a piston slidable in said casing for driving said nut, means for alternately admitting fluid under pressure to opposite sides of the piston to move it in opposite directions, and valve means for automatically switching the supply of fluid under pressure from one to the other side of the piston when the piston reaches the end of a stroke in each direction.