GB2105628A - A powered feed tool - Google Patents

Abstract

A tapping or screwing-up tool includes a tool holder (16) which is driven in rotation by a pneumatic motor (13) through a torque sensitive clutch (15). Tool holder (16), together with the pneumatic motor (13) and the torque sensitive clutch (15) is moved towards a workpiece by a piston (11) slidable in a cylinder defined by a part of a casing (10). A first valve (50) is operated by the torque sensitive clutch via a push rod (49) when the tool reaches a predetermined torque to shut-off the air supply to the motor or to reverse the motor. A second valve (66) in a connector (58) is operated by the torque sensitive clutch via the push rod (49) and a push rod (65) to connect the cylinder to exhaust so that the tool holder is retracted by a spring (59) when the tool reaches the predetermined torque. <IMAGE>

Description

SPECIFICATION A power feed tool The invention relates to a power feed tool and particularly a pneumatic power feed tool for tightening fasteners e.g. screws, nuts or bolts.

Automatic feed screwdrivers are known which have an air motor for rotating a tool holder and a piston and cylinder arangement for extending and retracting the tool. These known screwdrivers have a torque sensitive clutch between the tool holder and the motor which acts when the screw is tightened down to the set torque to disconnect the air supply to the motor. However, in these known screwdrivers, the tool remains in an extended position until someone comes along to retract it. This is not very satisfactory and is highly inefficient at least in certain applications.

The invention provides a power feed tool comprising a housing, a pneumatic motor, a torque sensitve clutch and a tool holder within the housing, the tool holder being drivable by the motor through the torque sensitive clutch, pneumatically operated feed means for moving the tool holder towards a workpiece, first valve means for controlling the air supply to the motor and operable by the torque sensitive clutch when the tool reaches a predetermined torque, and second valve means operable by the torque sensitive clutch for automatically retracting the tool holder when the tool reaches the predetermined torque.

Preferably, the first valve means is for shutting off the supply of air to the motor when the tool reaches the predetermined torque, but it may be for reversing the direction of rotation of the motor, the latter being particularly useful in tapping tools or the like.

Preferably, the pneumatically operated feed means is a pneumatic piston and cylinder unit. The piston and cylinder unit is, advantageously, arranged co-axialiy with the motor, torque sensitive clutch and tool holder, but it would be possible to arrange it alongside the housing containing the motor, torque sensitive clutch and tool holder.

Preferably, the first valve means comprises a valve member movable between first and second positions, and a push rod having an associated latch mechanism, the push rod being movable by spring means to move the valve member to its second position when air is not supplied to the valve means and being held in its second position by the latch mechanism when air is supplied to the valve means and until the tool reaches the predetermined torque, the latch mechanism being releasable by the torque sensitive clutch when the tool reaches the predetermined torque so that air supplied to the valve means moves the valve member, and with it the push rod, to said first position against said spring means. In the case where the valve means is used to cut off the air supply to the motor, the valve member engages a seat when in its first position.

Preferably, the second valve means comprises a further valve member movable by a further push rod in response to movement of the first mentioned push rod. In the case where the feed means is a piston and cylinder unit, the second valve means is carried by a piston rod fixed to the piston and is connected by a flexible pipe to a control unit which is fixed with respect to the cylinder and which controls the air supply to the cylinder.

Conveniently, the tool holder and output member of the torque sensitive clutch are biassed apart axially by spring means and have complementary teeth interengagable against the bias of the spring means by rearward pressure applied to the front end of the tool holder.

The invention will now be more particularly described with reference to the accompanying drawings in which: Fig. 1 is a longitudinal section of one embodiment of a power operated tool according to the present invention and Fig. 2 is a longitudinal section of the front end of the tool of Fig. 1 on an enlarged scale.

Referring to the drawing, the power tool shown therein comprises a casing 10 which at its rear or left hand end as viewed in the drawing defines a cylinder having a piston 11 therein. The rear or left hand end of a housing 12 is mounted in the front or right hand end of the casing 10 for slidable movement relative thereto. The housing 12 has therein a pneumatic motor 13, a reduction gear box 14, a torque sensitive clutch 1 5 and a tool holder 1 6. A hollow piston rod 1 7 is secured to the piston 11. The front end of the piston rod 1 7 is rigidly connected to the rear end of the housing 12 by a transverse pin 1 8 so that movement of the piston extends and retracts the housing 1 2 relative to the casing 10.The rear end of the piston rod 1 7 projects from the rear end of the casing 10 and is provided with a cross head 1 8 housing valve which will be described later.

The drive from the reduction gear box emerges by way of a hollow shaft 20 in the torque sensitive clutch 15.

The torque sensitive clutch 1 5 comprises a tubular member 21 which is splined upon the shaft 20 by splines 22.

A first non-torque sensitive clutch member 23 is provided with closely spaced dogs 24 around its periphery. A second non-torque sensitive clutch member 25 is supported for free rotation by balls 26 on the tubular member 21 and is provided with closely spaced dogs 27 around its periphery, which dogs match the dogs 24 on the member 23. The clutch member 25 is also provided on its end remote from the member 23 with teeth 28 having ramped load taking surfaces which constitutes the driven member of the torque sensitive clutch. Driving ramped teeth (not shown) of the torque sensitive clutch are provided on a ring-like member 29 and balls 30 are interposed between associated ramped teeth.The ring-like member 29 is connected to the tubular member 21 for rotation therewith and longitudinal movement relative thereto against the action of a spring 32 by balls 31 which engage angularly aligned slots 33 and 33' formed in the member 21 and member 29 respectively.

The clutch member 29 has a transvarse pin 34 which is free to move longitudinally in slots provided in the wall of the tubular member 21. A sleeve 36 is disposed in the tubular member 21 and one end of the sleeve is urged into engagement with the pin 34 by a spring 37.

Hence, the clutch member 29 and sleeve 36 move together when the clutch member 29 moves under the action or torque.

One end of the tubular member 21 is provided with an external screw thread upon which is mounted an abutment ring 38 having a bevel gear thereon. Adjacent the abutment ring 38 is a further ring-like member 39 which is slidable longitudinally over the thread on the tubular member 21, and which is prevented from rotation by an inwardly directed tooth 40 which enters the slot 33. The ring-like member 39 is provided with a transverse bore 41 into which may be inserted a key when a cover 35 is slid fcrwards having a bevel gear thereon which engages the bevel gear on the abutment ring 38 whereby the abutment ring 38 may be rotated on the tubular member 21 to adjust the pressure provided by the spring 32.

Sandwiched between the spring 32 and the ring-like member 29 is a thrust washer 42 which fcrms one side of a groove containing a washer 43 which supports a third non-torque sensitive clutch member 44 having dogs 45. which are capable of bridging between the peripheral dogs on the members 23 and 25 as shown. The third clutch member 44 is urged to the right by a light spring 46. When the member 29 moves apart from clutch member 25 under the action of the torque provided by the tool. when it has reached a predetermined value, the dogs 45 on the third clutch member become disengaged from the dogs 24 and the drive to the clutch member 23 is interrupted.

The sleeve 36 has three angularly spaced radial passages having balls 47 therein. A latch collar 48 is seated against a shoulder in the tubular member 21 and surrounds the sleeve 36. The latch collar 48 has a frusto-conical inner surface and when the sleeve is in its extreme right position as shown the collar 48 urges the balls 47 into engagement with one end of a three part push rod 49 which extends into the sleeve 36. The other end of the push rod acts on a ball valve 50. As shown the valve 50 is open and the push rod is engaged by the balls 47 to prevent movement of the push rod to the right and hence closure of the valve 50 against seat 51. When the member 29 moves apart from the member 25, the sleeve 36 moves with it allowing the balls 47 to move out of engagement with the push rod 49.The valve 50 closes against seat 51 under the action of air pressure thereagainst (as described later) and moves the push rod 49 to the right. When the air pressure acting on the valve 50 is released as later described the push rod moves to the left under the action of a spring 52. Hence. the valve 50 opens and the tool is reset to drive the motor when air is again supplied to the motor via valve 50.

The tool holder 16 is journalled for rotation in the front end of the housing 12 and is axially biassed away from the clutch member 23 by a light spring 53 and so that a flange 54 at its rear end abuts against a shoulder 55. The tool holder 1 6 and clutch member 23 have complementary axially extending dog teeth 56 and 57 which engage with one another when axial pressure is applied to the front end of the tool holder e.g.

when pressure is exerted on a screw by a screwdriver bit in the tool holder. The tool holder will not rotate until the dog teeth 56 and 57 engaged.

Air under pressure is supplied by a control unit 58 to the left hand side of the piston 11 to move the piston to the right against a return spring 59.

This movement extends the housing 12 relative to the casing 10.

The hollow piston rod 1 7 has a plurality of apertures 60 which communicate with an elongate annular groove 61 in the control unit 58 once the piston rod 1 7 is moved slightly away from its fully retracted position.

Air under pressure is supplied by the control unit 58 to the groove 61 via a port 62 and this air passes into the piston rod 1 7 and to the air motor 1 3 via the ball valve 50. However, when the piston rod 1 7 is in its fully retracted position the apertures 60 are sealed against communication with the groove 61 by an annular sealing element 63. Thus, air will not be supplied to the motor until the piston rod 1 7 is partly extended.

The ball valve 50 engages a plunger 64 provided at the front end of a further push rod 65.

The rear end of the push rod 65 engages a spool valve 66 in a chamber 67 in the cross head 18.

The inside of the piston rod communicates with the left hand end of the chamber 67 via pages 68, 69 & 70 in the cross head 18 and an outlet port 71 in the cross head communicates with the chamber 67 via a passage 72. When the push rod 49 holds the valve 50 open, the spool valve 66 closes the passage 72. However, when the valve 50 closes the push rod 65 and spool valve 66 move to the right under the influence of air pressure on the left hand end of spool valve 66 and the passage 72 is opened so that air is supplied to the outlet port 71.

Air under pressure is supplied to the control unit 58 from an external source by way of a pipe (not shown). The control unit includes a spool valve (not shown). The spool valve is moved in one direction by a start button 73 or by a remote start signal provided by a valve operated by the arrival of a work piece in a desired position or by a master controller governing several tools and as a result air is supplied to the left hand side of piston 11 and to port 62. The spool valve in the control unit 58 is moved in an opposite direction by a stop button (not shown) or by a remote stop signal from the outlet port 71 to connect the left hand side of the piston 11 and port 62 to exhaust.

In operation, the tool is started by the start button 73 or by the remote start signal. Air under pressure is supplied to the left hand side of the piston 11 which moves to the right to move the tool holder towards a workpiece. As soon as the apertures 60 communicate with groove 61 air under pressure is supplied to the motor 13 via valve 50 and the clutch member 23 begins to rotate. When a screwdriver bit in the tool holder 1 6 engages a screw, the tool holder 1 6 moves axially towards the clutch member 23 and the dog teeth 56 8 57 engage one another. The tool holder then rotates and is simultaneously fed forwards, as the screw is inserted into the work piece by the piston 11.When the torque provided by the tool reaches a predetermined value, the torque sensitive clutch 1 5 moves the sleeve 36 to the left and the push rod 49 is unlatched. The valve 50 closes against seat 51 under the action of air pressure supplied from the control unit via the hollow piston rod 1 7 and the motor 13 stops.

The push rod 65 and spool valve 66 move to the right to supply air to the outlet port 71 in the cross head and this air signal is fed to the control unit 58 by a flexible pipe (not shown). As a result the control unit 58 connects the left hand side of the piston 11 and port 62 to exhaust. The piston is returned to its initial position by return spring 59 and the air pressure acting on valve 50 is released.

Hence, the valve 50 opens and the tool is reset as previously described.

Normally, the tool will be in a vertical position during operation but there is no reason why it should not be used in any other position.

The tool can be mounted alone or with a number of similar tools in a jig or similar support means a manner well known.

Claims (11)

1. A power feed tool comprising a housing, a pneumatic motor, a torque sensitive clutch and a tool holder within the housing, the tool holder being drivable by the motor through the torque sensitive clutch, pneumatically operated feed means for moving the tool holder towards a workpiece, first valve means for controlling the air supply to the motor and operable by the torque sensitive clutch when the tool reaches a predetermined torque, and second valve means operable by the torque sensitive clutch for automatically retracting the tool holder when the tool reaches the predetermined torque.

2. The power tool of claim 1, wherein the first valve means is for shutting off the supply of air to the motor when the tool reaches the predetermined torque.

3. The power tool of claim 1, wherein the first valve means is for reversing the direction of rotation of the motor when the tool reaches the predetermined torque.

4. The power tool of anyone of claims 1-3, wherein the pneumatically operated feed means is a pneumatic piston and cylinder unit.

5. The power tool of claim 4, wherein the piston and cylinder unit is arranged co-axially with the motor, torque sensitive clutch and tool holder.

6. The power tool of any one of the preceding claims, wherein the first valve means comprises a valve member movable between first and second positions, and a push rod having an associated latch mechanism, the push rod being movable by spring means to move the valve member to its second position when air is not supplied to the valve means and being held in its second position by the latch mechanism when air is supplied to the valve means and until the tool reaches the predetermined torque, the latch mechanism being releasable by the torque sensitive clutch when the tool reaches the predetermined torque so that air supplied to the valve means moves the valve member, and with it the push rod, to said first position against said spring means.

7. The power tool of claim 6, when dependent on claim 2, wherein the valve member engages a seat when in its first position.

8. The power tool of claim 6 or claim 7, wherein the second valve means comprises a further valve member movable by a further push rod in response to movement of the first mentioned push rod.

9. The power tool of claim 8 when dependent on claim 4, wherein the second valve means is carried by a piston rod fixed to the piston and is connected by a pipe to a control unit which is fixed with respect to the cylinder and which controls the air supply to the cylinder.

10. The power tool of anyone of the preceding claims wherein the tool holder and output member of the torque sensitive clutch are biassed apart axially by spring means and have complementary teeth interengagable against the bias of the spring means by rearward pressure applied to the front end of the tool holder.

11. A power feed tool substantially as hereinbefore described with reference to and as shown in the accompanying drawings.