GB1574700A

GB1574700A - Transmission couplings

Info

Publication number: GB1574700A
Application number: GB4237275A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1977-01-17
Filing date: 1977-01-17
Publication date: 1980-09-10

Description

(54) TRANSMISSION COUPLINGS (71) I DAVID GEORGE HALL of 214 Roils Head Road, Norton Tower, Halifax in the County of York, a British subject, do hereby declare the invention, for which I pray that a patent may be granted to me and the method by which it is to be performed, to be particularly described in and by the following statement: The invention relates to transmission couplings, and more particularly to couplings for the transmission of a rotational motion from a driving member to a driven member. Such a coupling may be used, for example, to transmit driving motion to a cutting tool in a portable power tool. Throughout this specification, reference will be made to "driving" and "driven" members, but it is to be understood that these expressions are not intended to impose any limitation on the function of the two coupling members. Thus, the coupling could be used to transmit motion from the driving to the driven member, or vice versa.

According to the invention, a coupling comprises a driving member and a driven member the latter being insertable into a bore of the former, there-being a peg fixed to the driving member and projecting into the bore of the driving member, which peg is arranged to engage with an abutment extending across a helical track formed on the driven member so that torque is transmitted from one member to the other when the peg engages with the abutment on rotation of the driven member relatively to the driving member.

Preferably, the peg is arranged to engage with the helical track to produce alignment of the longitudinal axes of the driving and driven members. The peg may also be arranged to engage with the helical track during rotation of the driven member relatively to the driving member to produce axial movement of the driven member relatively to the driving member so that the peg is moved towards, or away from the abutment to respectively facilitate the engagement of the peg with, or the disengagement of the peg from the abutment.

As will hereinafter appear, this provides a means for quick disengagement of the driven member from the driving member.

In a preferred construction, the driven member comprises a substantially cylindrical shank having a helical channel formed in it from one end thereof, and partly around a central core thereof, this channel providing the helical track, one of the ends of the channel being open at the one end of the shank, and the other end of the channel being closed by an end wall, which provides the abutment, formed by part of the shank, which wall is generally axial of the shank.

Preferably, the peg protrudes substantially radially into the bore in the driving member, and the driven member is a sliding fit within the bore. It is also preferred that the driving member is adapted to releaseably secure the shank of the driven member within its bore, and to this end, there may be a resiliently loaded plunger provided in the bore of the driving member, and engaging in a circumferential groove in the shank.

According to a preferred feature of the invention, the axial distance between the circumferential groove in the shank and the part of the helical track which is engaged by the peg in the driving position is equal to the distance between the peg and the spring loaded plunger in the driving member.

According to another preferred feature of the invention, the end wall of the channel is undercut, or has a lip extending over the extremity of the channel to resist disengagement of the shank from the peg by movement of the shank in the axial direction, when the peg is in engagement with the wall.

One embodiment of a transmission coupling will not be described by way of example only, with reference to the accompanying drawings, in which: Figure 1 is an end elevation of a driving member of a transmission coupling, Figure 2 is-a side elevation of the driving member as shown in Figure 1, Figure 3 is a perspective view of a driven member of a transmission coupling, Figure 4 is a side view of the driven member as seen in the direction of arrow A in Figure 3, Figure 5 is an underplan view of the driven member as shown in Figure 3, and Figure 6 is a plan view of the driven member as shown in Figure 3.

Portable power tools such as portable drills are usually provided with three-jaw self-centering chucks, which have to be operated by a chuck key to fit and release a cutting tool or the like.

This is time consuming, if a number of operations have to be carried out, which require frequent tool changes.

With a view to facilitating and reducing the time required for tool changes, a special coupling is provided, which comprises a driving member 10, and a driven member 20. The driving member 10 is adapted to replace the conventional chuck of a portable power tool.

The driven member 20 is a sliding fit within the driving member, and is adapted to hold a tool to be rotated. In use, the driven member is so coupled with the driving eember that when the driven shaft of the portable power tool is arrested, the driven member is free to be removed from the driving member and replaced by another similar driven member, as and when required, with a minimum of manipulation and without unscrewing.

The driving member (see Figures 1 and 2) is indicated generally at 10, and comprises a boss 12, one end of which is formed with a blind bore 14, and from the other end of which projects a screw-threaded stud 16. The stud 16 is adapted to be screwed into a portable power drill (not shown) in place of the usual chuck. Once connected in this way, to the portable power drill, the driving member 10 rotates in the direction of arrow B in Figure 1 when the drill is operated.

A driving peg 18 fitted in the boss 12 protrudes substantially radially into the bore 14, adjacent to the closed end thereof. At a position axially displaced from the driving peg 18, a radial hole 34 is formed in the boss 12 and a ball 33 which is located in the hole 34 is urged inwardly by a compression spring 35, loaded by a grub screw 36 screwed into a screw-threaded outer part of the hole 34. The inner end of the hole 34 is partly closed off by peening over so that only a part of the ball 33 is able to protrude into the bore 14, but the ball may be deflected completely into the hole 34 against the action of the spring 35.

The driven member 20 comprises a sub stantially cylindrical shank 22 which is a sliding fit within the bore 14 of the driving member. At the end 32, the shank 22 is formed with a bore 44 which extends longitudinally and co-axially into the shank 22. This bore 44 is adapted to receive the stock portions of tools (not shown) such as drill bits. A screw 46 engages in a screw-threaded radial hole 48, communicating with the bore 44, and projects into the bore 44. The screw 46 may be tight ened against the stock portion of a tool to hold the latter firmly in place within the bore 44. It will be appreciated that other arrange ments could be used for locking the tool in the shank, such as the provision of a Morse tapered bore in the shank to receive a correspondingly tapered portion of a tool.

The shank 22 also has a circumferential groove 28 formed in its outer surface, and a knurled outer surface 30 is formed on the shank 22 at its end 32.

At the end 26 of the shank 22 opposite to the knurled end, a helical channel 24 is formed on the shank, leaving a part cylindrical stub 38 which extends from and forms part of the end 26 of the shank 22. It is to be noted that the channel 24 does not form a complete convolution about the stub 38, and that it is open at one of its ends (the extremity of the end 26 of the shank 22) but closed at its other end by an end wall 40. This end wall 40 is substantially axial of the shank, but has a reentrant lip 42 extending back over the extremity of the channel 24. It is a significant feature of the design of the coupling, that the axial distance between the shoulder formed by the channel 24 at its closed end and the groove 28 is substantially equal to the axial distance between the driving peg 18 and the spring-loaded ball 33 in the driving member 10.

In order to use the coupling, the stud 16 is screwed firmly into the rotatable head of a portable power drill in place of the usual chuck, so that on operation of the drill, the driving member 10 is rotated.

A tool to be rotated is selected and its stock is inserted into the bore 44 of the shank 22. The screw 46 is then tightened onto the stock of the tool to lock the tool in the shank.

The shank 22 is then held by the knurled surface 30 and the end 26 of the shank is inserted into the bore 14 of the driving member 10 until the peg 18 engages with the end 26 of the shank or woth the helical face of the channel 24. The ball 33 retracts into the hole 34 to allow the shank 22 to pass. The shank is then given a sufficient manual rotation to bring the end wall 40 into engagement with the peg 18, and at the same time, the shank is pressed axially into the boss 12, and when the peg engage with the end wall 40, the groove 28 will be aligned with the ball 33, and the latter engages in the groove to retain the shank in the driving member 10. In this position, the tool held within the end 32 of the shank, projects from the driving member 10, and the shank could only be released by pulling it outwardly with a force sufficient to overcome the load of the spring 35.

The portable power drill operated with the tool pressed against the workpiece. As the drill rotates with the shank 22 pressed into the bore 14 of the driving member 10, if the wall 40 has not already firmly engaged with the peg 18, the peg 18 rotates and winds around the stub 38 in the helical channel 24, until it engages with the wall 40 and rotation is transmitted to the shank thereby rotating the tool.

While the driving member '10 rotates with the peg 18 engaging with the wall 40, the shank cannot be accidentally extracted therefrom, since the lip 48 is held over the peg 18 by the force exerted by the peg on the wall. When the drill os stopped however, the driving member 10 ceases to rotate and the peg no longer exerts a force on the wall 40. In fact, the inetria of the shank will probably tend to disengage the peg 18 from the end wall 40.

The shank 22 can then be removed from the bore 14 of the driving member by holding the knurled surface 30 and rotating the shank in a direction which causes the peg 18 first to move out of alignment with the lip 42 and which then causes the peg to press the shank out of the bore 14 due to the interaction between the peg and the helical face of the channel. As the shank is retracted from the driving member 10, the ball 33 yields to permit the shank to pass. The shank 22 can thus be rapidly uncoupled from the driving member, once the drill is stopped, and can then be replaced by a second similar shank holding a different tool, the second shank being coupled to the driving member a s previously described.

It will be noted that the driving member must rotate in the direction of arrow B in Figure 5 or the peg 18 would not wind in the helical channel 24 towards the wall 40 and the shank would not then be driven by the peg 18.

Many alternative uses and forms are envisaged for the transmission coupling, and some of these are discussed below.

Various forms of tools could be held in the shank such as drill bits of differing sizes, abrasive wheels, circular saw blades and the like, provided that such tools are equipped with the necessary stock to be held in the hole 44 of the shank. To accommodate tools having different tool heads of different sizes, shanks could be provided having a range of differing diameter holes 44. It is in fact envisaged that a kit may comprise a single driving member and a plurality of driven members, having different sizes of hole 44.

As an alternative to the tool heads being releasably held within the hole 44 of the shank 22, the tools can be permanently secured therein or indeed formed integrally with the shank.

A similar method of coupling could also be used directly for, the tools, so that a helical channel and a wall such as the wall 40 could be provided on the tool itself, which could then be coupled directly with a peg 18 in the driving member or with a similar peg provided in the hole 44 in the shank 22.

In this arrangement, the tool itself becomes the driven member.

Similar couplings to the one herein described could also be used in series with members having alternate helical channels and pegs such that each peg would engage and rotatably drive an end wall of a channel on an adjacent member.

The driving member and/or the driven member may be formed of metal or alternatively of a plastics material such as glass filled nylon.

Claims

WHAT I CLAIM IS:

1. A coupling comprising a driving member and a driven member, the latter being insertable into a bore of the former, there being a peg fixed to the driving member and projecting into the bore of the driving member, which peg is arranged to engage with an abutment extending across a helical track formed on the driven member so that torque is transmitted from one member to the other when the peg engages with the abutment on rotation of the driven member relatively to the driving member

2 A coupling as claimed in Claim 1, where- in the peg is arranged to engage with the helical track to produce alignment of the longitudinal axes of the driving and the driven members.

3. A coupling as claimed in Claim 2, in which the peg is arranged to engage with the helical track during rotation of the driven member relatively to the driving member to produce axial movement of the driven member relatively to the driving member.

4. A coupling as claimed in Claim 3, in which the driven member comprises a substantially cylindrical shank having a helical channel formed in it from one end thereof and partly around a central core thereof, this channel providing the helical track, one of the ends of the channel being open at the one end of the shank and the other end of the channel being closed by an end wall, which provides the abutment, formed by part of the shank, which wall is generally axial of the shank.

5. A coupling as claimed in Claim 4, in which the peg protrudes substantially radially into the bore in the driving member, and the driven member is a sliding fit within the bore.

6. A coupling as claimed in Claim 4 or Claim 5, in which the driving member is adapted to releasably secure the shank of the driven member within its bore.

7. A coupling as claimed in Claim 6, in which the shank is releasably secured the bore by means of a resilently loaded plunger engaging in a circumferential groove in the shank.

8. A coupling as claimed in Claim 7, in which the axial distance between the circumferential groove in the shank and the part of the helical track which is engaged by the peg in the driving position, is equal to the distance between the peg and the spring-loaded plunger in the driving member.

9. A coupling as claimed in any one of Claims 4 to 8, in which the end wall of the channel is undercut, or has a lip extending over the extremity of the channel to resist disengagement of the shank from the peg by movement of the shank in the axial direction, when the peg is in engagement with the wall.

10. A coupling as claimed in any one of Claims 1. to 9, in which the driven member is adapted to releasably grip a tool or other member which is to be rotated.

11. A coupling as claimed in Claim 10, in which the driven member has a longitudinally extending hole wherein the tool or other member can be received, and a grub screw engaging in a ccrew-threaded hole in the driven member, and projecting into the said hole.

12. A coupling as claimed in any one of Claims 4 to 11, in which a tool or other member to be rotated is formed integrally with the shank.

13. A coupling as claimed in any one of Claims 1 to 12, in which the driven member has a knurled outer circumferential surface to facilitate easy insertion and removal of the driven member in the bore of the driving member such that when the driving and driven members are coupled together, the knurled surface is outside the bore in the driving member.

14. A coupling as claimed in any one of Claims 1 to 13, in which the driving member comprises a boss bores at one end to receive the driven member and having a threaded stud extending from the opposite end.

15. A coupling as claimed in any one of withe preceding claims, in which the driving member and/or the driven member is formed of metal or a plastics material.

16. A coupling as claimed in Claim 15, in which the driving member and/or the driven member is formed of glass filled nylon.

17. A coupling substantially as herein described with reference to the accompanying drawings.

18. A coupling as claimed in Claim 17, and as illustrated in the accompanying drawings.