GB2098528A

GB2098528A - A power tool

Info

Publication number: GB2098528A
Application number: GB8211767A
Authority: GB
Original assignee: Desoutter Ltd
Current assignee: Air Compressors and Tools Ltd
Priority date: 1982-04-23
Filing date: 1982-04-23
Publication date: 1982-11-24
Also published as: GB2098528B

Abstract

The tool, which is particularly useful for installing threaded inserts which when installed become captive nuts, comprising a casing having a reversible motor (19) and a tool holder (28) mounted therein. The tool holder is rotatable by the motor. Means are also provided for reversing the motor under a predetermined condition. This means may comprise a torque sensitive clutch (13) between the motor and the tool holder which reverses the motor when the torque applied by the tool exceeds a predetermined value. Alternatively the means may comprise compression sensitive means (Fig. 5) operable to reverse the motor when the axial force applied to the tool holder exceeds a predetermined value or may comprise strain gauges responsive to a torsional and/or axial force applied to the tool. <IMAGE>

Description

SPECIFICATION A power tool This invention relates to a power tool such as for installing one piece threaded inserts which when installed become captive nuts. The power tool does, however, have other applications e.g. in tapping holes and inserting studs.

The aforesaid inserts have a sleeve portion at one end and an internally threaded portion at the other end.

In one known type of insert the region of the threaded portion adjacent the sleeve portion is frusto-conical and the threaded portion is joined to the sleeve portion by a breakaway section. In order to install the insert, it is threaded onto a complementarily externally-threaded bit of a power operated tool and is placed into a prepared hole with the internally threaded portion innermost. The motor of the tool is then actuated to turn the bit in one direction so as to pull the threaded portion towards the free end of the sleeve portion. This causes the breakaway section to break and the internally-threaded portion is drawn into the sleeve portion to expand the sleeve portion and secure the insert in the hole. The motor of the tool is then reversed to withdraw the threaded bit from the insert.

Another known type of insert for use with thin sheets of material does not have the breakaway section nor the frusto-conical region, but as the tool pulls the internally threaded portion towards the free end of the sleeve portion, the wall of the sleeve portion collapses radially outwards, and it is drawn tightly into engagement with the inner surface of the sheet to secure the insert therein.

In its broadest aspect, the invention provides a povver tool, comprising a casing having a reversible motor and a tool holder mounted therein, the tool holder being rotatable by the motor, and means for automatically reversing the motor under a predetermined condition.

In the narrower aspect, the invention provides a power tool for installing one piece threaded inserts, comprising a casing having a reversible motor and a tool holder mounted therein, the tool holder being rotatable by the motor and the casing having an end piece adapted to engage the free end of the sleeve portion of an insert, an externally threaded bit threadably engageable with the threaded portion of an insert being mounted in the tool holder and extending outwardly from the end piece, and means for automatically reversing the motor when the insert has been secured in a hole.

Thus the threaded bit is automatically removed from the threaded insert when the latter is secured in a hole.

In one embodiment, the automatic reversing means includes a torque sensitive clutch between the motor and the tool holder and operable to reverse the motor when the torque applied by the tool exceeds a pre-determined value.

In a second embodiment, the automatic reversing means includes compression sensitive means operable to reverse the motor when the axial force applied to the tool holder exceeds a predetermined value.

In a third embodiment the automatic reversing means includes one or more strain gauges responsive to a torsional and/or an axial force applied to the tool.

Other preferred and/or optional features are set forth in Claims 4-9 and 12 and 13.

The invention will now be more particularly described, by way of example, with reference to the accompanying drawings, wherein: Figure 1 is a longitudinal section of one embodiment of a power operated tool according to the invention, at the beginning of an insert installing operation; Figure 2 is a section of part of the tool of Figure 1, where the insert is secured in a hole; Figure 3 shows the pneumatic circuit of the tool of Figures 1 and 2, when the tool is set for forward operation; Figure 4 shows the circuit of Figure 3, when the tool is set for reverse operation; and Figure 5 is a longitudinal section of the front end of another embodiment of a power operated tool according to the invention, at the beginning of an insert installing operation.

Referring to Figure 1, the power tool shown therein comprises a pistol grip 9, and a casing having a control valve portion 10, a motor portion 11, a reduction gear portion 12, a torque sensitive clutch portion 13, and a head portion 14.

The grip 9 has an air inlet 15, an air outlet 1 6 and an on/off valve 1 7 operable by depressing a button 18. When the button 1 8 is depressed air flows to an air motor 19 in the portion 11 via an open valve 20 (see also Figure 3) in the portion 10 to drive the motor in one direction. Air is exhausted from the motor 1 9 via a spool valve 21 which is held in a first position by a spring (see Figure 3). When the valve 20 is closed (see Figures 2 and 4) as hereinafter explained, the air flows to the motor via the spool valve 21, which is moved to a second position by the pressure of the air, in a sense to drive the motor in an opposite direction and air is exhausted from the motor 1 9 via the spool valve in its second position.

The drive from the motor 1 9 passes to a reduction gear box 22 in the portion 12 by way of a hollow shaft 23 and emerges by way of a hollow shaft 24 in the torque sensitive clutch portion 1 3.

The torque sensitive clutch comprises a tubular member 25 which is splined upon the shaft 24 by splines 26.

A first non-torque sensitive clutch member 27 is integral with a tool holder 28 and is provided with closely spaced dogs 29 around its periphery.

A second non-torque sensitive clutch member 30 is supported for free rotation by balls 31 on the tubular member 25 and is provided with closely spaced dogs 32 around its periphery, which dogs match the dogs 29 on the member 27. The clutch member 30 is also provided on its end remote from the member 27 with teeth 33 having ramped load taking surfaces which constitutes the driven member of a torque sensitive clutch. Driving ramped teeth 34 of the torque sensitive clutch are provided on a ring-like member 35 and balls 36 are interposed between associated ramped teeth 33 and 34. The ring-like member 35 is connected to the tubular member 25 for rotation therewith and longitudinal movement relative thereto against the action of a spring 38 by balls 37 which engage angularly aligned slots 39 and 40 formed in the member 25 and member 35 respectively.

The clutch member 35 has a transverse pin 41 which is free to move longitudinally in slots 42 provided in the wall of the tubular member 25. A sleeve 43 is disposed in the tubular member 25 and one end of the sleeve is urged into engagement with the pin 41 by a spring 44.

Hence, the clutch member 35 and sleeve 43 move together.when the clutch member 35 moves under the action of torque.

One end of the tubular member 25 is provided with an external screw thread upon which is mounted an abutment ring 45 having a bevel gear 46 thereon. Adjacent the abutment ring 45 is a further ring-like member 47 which is slidable longitudinally over the thread on the tubular member 25, and which is prevented from rotation by an inwardly directed tooth 48 which enters the slot 39. The ring-like member 47 is provided with a transverse bore (not shown) into which may be inserted a key having a bevel gear thereon which engages the bevel gear 46 on the abutment ring 45, whereby the abutment ring 45 may be rotated on the tubular member 25 to adjust the pressure provided by the spring 38.

Sandwiched between the spring 38 and the ring like member 35 is a thrust washer 49 which forms one side of a groove containing a washer 50 which supports a third non-torque sensitive clutch member 51 having dogs 52, which are capable of bridging between the peripheral dogs on the members 27 and 30 as shown in Figure 1. The third clutch member 51 is urged to the left by a light spring 53. When the member 35 moves apart from clutch member 30 under the action of the torque provided by the tool, when it has reached a predetermined value, as shown in Figure 2, the dogs on the third clutch member become disengaged from the dogs 29 and the drive to the tool holder is interrupted. Movement of the member 35 will close the valve 20 as hereinafter described. The dogs 52 will re-engage with the dogs 29 and the tool holder will be driven in an opposite direction of rotation.

The sleeve 43 has three angularly spaced radial passages having balls 54 therein. A latch collar 55 is seated against a shoulder in the tubular member 25 and surrounds the sleeve 43. The latch collar 55 has a frusto-conical inner surface and when the sleeve is in its extreme left position as shown in Figure 1, the collar 55 urges the balls 54 into engagement with one end of push rod 56 which extends into the sleeve 43. The other end of the push rod is secured to the valve 20. As shown in Figure 1, the valve 20 is open and the push rod is engaged by the balls 54 to prevent movement of the push rod to the left. When the member 35 moves apart from the member 30, the sleeve 43 moves with it allowing the balls 54 to move out of engagement with the push rod 56. The valve 20 closes under the action of air pressure thereagainst and the push rod 56 moves to the left as shown in Figure 2.Rotation of the motor is thus reversed. When the button 1 8 is released the on/off valve 17 shuts off air supply to the end of the valve 20 and the push rod moves to the right under the action of a spring 57. Hence, the valve 20 opens and the tool is reset to drive the motor in a forwards direction when the button 1 8 is again depressed.

An externally threaded bit 58 having a collar 59 is mounted in the tool holder 28. The bit 58 extends through a reduced diameter portion 60 of a removable casing end piece 61 and four thrust washers 62 are disposed between the collar 59 and a shoulder 63 defined at the inner end of the portion 60.

To secure an insert 64 in a hole, the insert is threaded onto the threaded bit 58 until the free end of the sleeve portion 66 of the insert abuts against the free end of the end piece 61. The insert is then placed in to the hole. The button 1 8 is depressed and the motor 1 9 rotates to draw the threaded portion 65 of the insert into the sleeve portion 66 thereof. When the torque provided by the tool exceeds said predetermined value which is arranged to be indicative of the insert being secured in the hole, the motor is reversed as aforesaid and the threaded bit 58 is automatically removed from the threaded insert.

Referring now to Figure 5, there is shown therein the front end of another embodiment of a power tool for installing one piece threaded inserts, the rear end of this embodiment being identical to the embodiment of Figure 1. A sleeve member 70 is splined upon a shaft 24' which is fixed against axial movement and which is connected to the output drive of the reduction gearbox 22. The splined portion 71 of the bore of the sleeve member 70 merges with a larger diameter bore portion 72 by way of a frustoconical bore portion 73. A blind transverse hole 74 in the shaft 24' adjacent its free end accommodates a plunger 75 which is spring biassed into abutment with the bore in the sleeve member 70 and which is held against angular movement in the hole 74 by a pin 76 projecting into a groove 77 in the plunger 75.

An externally threaded bit 78 is attached to the front end of the sleeve member 70 by a cross pin 79 which is retained by an '0' ring 80. A plurality of disc springs 81 surround the bit 78 and are interposed axially between a thrust race 82 carried by the bit 78 and a bearing 83 carried by the tool casing.

At the beginning of an insert installing operation, the insert is threaded on the bit 78, the free end of the sleeve portion 66 of the insert abuts against the free end of a removable casing end piece 84 and the plunger 75 abuts the bore portio.172. The motor is energized and the bit rotates to draw the threaded portion 65 of the insert into the sleeve portion 66 thereof and as this takes place the compression force applied to the disc springs increases as the bit 78 and sleeve member 70 are pulled forwards. The plunger 75 is moved against the bias of its associated spring until an aperture 85 in the plunger is aligned with the bore of the shaft 24'. This is arranged to occur when the compression force applied to the disc springs exceeds a predetermined value indicative of the insert being secured in the hole.The push rod is moved to the left as shown in Figure 4 and rotation of the motor is reversed as in the first mentioned embodiment.

The above described tools could be modified e.g. for tapping holes or inserting threaded studs in holes.

For tapping holes the bit 58 or 78 could be replaced by an output shaft to which a chuck is attached. A tap could be held by the chuck and when tapping a blind hole the motor will reverse when the tap bottoms in the hole. When tapping a through hole, a collar may be fixed to the tap so that the motor reverses when the collar engages the surface in which the hole is formed.

For inserting threaded studs the bit 58 or 78 could be replaced by an output shaft to which a stud running box is attached. A stud could be threaded into the stud running box provided at its inner end of its threaded bore with a thrust race or loose pad so that the motor reverses when the stud bottoms and the required torque is reached in its associated hole. The threaded connection between the stud and stud running box releases more easily than the connection between the stud and its associated hole so as to remove the stud running box from threaded engagement with the stud.

In another embodiment the motor of the tool is an electric motor having an associated electric control unit for reversing the direction of rotation of the motor. One or more resistance strain gauges are mounted for example on the casing of the tool and are responsive to a torsional and/or an axial force applied to the tool. When this force exceeds a predetermined value, the control unit operates to reverse the direction of the motor.

Claims

1 . A power tool comprising a casing having a reversible motor and a tool holder mounted therein, the tool holder being rotatable by the motor, and means for automatically reversing the motor under a predetermined condition.

2. The power tool of claim 1 , wherein the automatic reversing means includes a torque sensitive clutch between the motor and the tool holder and operable to reverse the motor when the torque applied by the tool exceeds a predetermined value.

3. The power tool of claim 1, wherein the automatic reversing means includes compression sensitive means operable to reverse the motor when the axial force applied to the tool holder exceeds a predetermined value.

4. The power tool of any one of the preceding claims, wherein the automatic reversing means includes a direction changing mechanism having an elongate actuating member and a latch mechanism for holding the elongate actuating member in a first position, the latch mechanism being releasable under said predetermined condition to allow the actuating member to move to a second position and reverse the direction of the motor.

5. The power tool of claim 4, wherein the motor is an air motor and the actuating member is connected to a valve member which reverses the direction of rotation of the motor when the actuating member moves from its first to its second position.

6. The power tool of claim 5, wherein the elongate actuating member is movable to its second position by air pressure acting on the valve member when the latch mechanism releases the actuating member and wherein a spring is provided to return the actuating member to its first position when the air supply to the valve member is cut off.

7. The power tool of claim 2 and any one of claims 4-6 wherein the torque sensitive clutch comprises torque sensitive clutch parts which move apart axially when the torque exceeds said predetermined value to release said latch mechanism.

8. The power tool of claim 2 or claim 7, wherein the torque sensitive clutch momentarily disconnects the drive between the motor and the tool holder when the torque exceeds said predetermined value.

9. The power tool of claim 3 and any one of claims 4-6, wherein the compression sensitive means includes one or more springs which load the holder axially and wherein the tool holder moves axially against the spring loading to release the latch mechanism when the axial force applied to the tool holder exceeds said predetermined value.

10. The power tool of claim 1, wherein the motor is an electric motor having associated control means for reversing its direction of rotation, the control means including one or more strain gauges responsive to a torsional and/or an axial force applied to the tool.

11. A power tool for installing one piece threaded inserts and as claimed in any one of the preceding claims, wherein the casing has an end piece adapted to engage the free end of the sleeve portion of an insert and an externally threaded bit is threadedly engageable with the threaded portion of an insert, the bit being mounted in the tool holder and extending outwardly from the end piece.

12. The power of any one of the preceding claims, wherein the tool is a hand held tool.

13. The power tool of claim 12, wherein the tool has a piston grip.

14. A power tool substantially as hereinbefore described with reference to, and as shown in, Figures 1-4, or Figures 1-4 as modified by Figure 5, of the accompanying drawings.