A CHUCK ASSEMBLY

FIELD OF THE INVENTION

THIS INVENTION relates to a chuck assembly and in particular but not limited to a chuck assembly suitable for use in conjunction with a woodworking lathe.

BACKGROUND OF THE INVENTION

Woodworking lathes employ a head stock with a chuck adapted to engage a work piece. The chuck has jaws centred on an axis of rotation of the lathe and are adapted to travel radially in and out in order to secure or release the work piece. The work piece is therefore positioned coaxially in relation to the chuck for rotation of the work piece in the chuck so that the work piece may be turned with a tool to shape the work piece into a pre-determined configuration by an operator. The placement of the work piece in the chuck is a manual process whereby an operator progressively tightens the chuck around the work piece. This tightening process usually involves one or more tools placed in the chuck and used to apply force to the jaws until the operator is comfortable with the grip on the work piece.

Present chucks are available in two forms that use different tools and each has certain advantages and disadvantages. In one case a pair of levers are inserted radially into offset holes enabling rotation of a rotary jaw guide relative to the drive shaft. This has the advantage of a relatively high applied moment and a long stroke so that the operator may rapidly apply and release the chuck. However, it requires the use of two hands. Other chucks use a key fitted into a radially extending key way. The key is rotated around the key way axis and the

jaws open and close. This chuck has the advantage of single handed operation but lacks the advantages of the two handed example.

OUTLINE OF THE INVENTION The present invention embodies a chuck assembly rotatable about a chuck axis, the chuck assembly having a set of jaws and at least one radial rotatable key way having a radial axis of rotation, the key way being adapted to receive a tool used to open and close the chuck, whereby in a first action the set of jaws may be opened or closed by inserting a tool in the key way and manually moving the tool circumferentially about the chuck axis, and also by a second action by rotating the tool in a key way about the key way axis.

Generally speaking, the first action involves the utilisation of a pulling action transverse to the longitudinal axis of the chuck and the second action involves a rotary action about an axis extending generally transverse to the axis of the chuck. Preferably, the key way comprises an aperture in which the tool is engaged, that tool being used to both initiate the first action of the chuck and also at the end of that stroke to provide a fine adjustment and final closure of the chuck.

While the expression key way has been used it will be appreciated that any equivalent mode to engage the chuck for the described actions will be equally applicable.

Preferably, the key way is a central hole in a pinion gear used to rotate a jaw guide scroll. Typically, two, three or four pinions may be used running on a ring gear opposite the guide scroll, the ring gear and guide scroll may be formed integrally on opposite sides of a plate.

In a preferred embodiment there is provided a chuck assembly having a body rotatable with a drive about a central axis, the body having radial jaw

guides, jaws configured to travel radially in the jawguides, a plate having a spiral drive acting on the jaws simultaneously to drive the jaws along the jawguides as the plate rotates about the central axis, the body having a central collar so that it may be mounted on a drive spindle, the plate having a peripheral ring gear opposite the guide drive, the collar having a hollow pinion carrier rotatable on the collar, the ring gear projecting into the pinion carrier where it meshes with circumferential Iy spaced pinions, each pinion being rotatable about respective radial pinion axes, and each pinion having a tool key way so that a corresponding tool may be positioned in one of the pinions, to rotate the scroll plate relative to the pinion carrier or in concert with it.

Preferably, the assembly includes at least one locking means, typically a releasable locking pin being adapted to secure the pinion carrier to the collar to prevent relative movement between the pinion carrier and collar when the locking means is in a locking position and to allow relative movement between the pinion carrier and collar when the locking means is released. The locking means may comprise a radially or axially operable quick release means. In the case of an axially operable locking means a lever and cam may be used to actuate a radial pin.

BRIEF DESCRIPTION OF THE DRAWINGS In order that the present invention can be more readily understood and be put into practical effect, reference will now be made to the accompanying drawings which illustrate one preferred embodiment of the invention and wherein:

Figure 1 is an end view of a chuck assembly according to the present invention;

Figures 2 and 3 are radial sections through the chuck assembly of Figure 1 showing the jaws closed and open;

Figure 4 is an exploded sectional view of the chuck assembly; and Figure 5 is an end view of a further embodiment; Figure 6 is a section through A-A of Figure 5; and Figure 7 is a section through B-B of Figure 5 DETAILED DESCRIPTION OF THE DRAWINGS

Referring to the drawings there is illustrated a chuck assembly 10 having a body 11 and four jaws 12, 13, 14 and 15 which are configured to retract and close radially from the central axis at 16 by reason of the rotation of guide scroll plate 17 about central axis 16, central axis 16 being illustrated clearly in Figures 2 and 3. The scroll plate 17 has a guideway in the form of a spiral 18 which engages guide slots 19 in the underside of jaw travellers 20 which travel radially in jaw slots 21 in the body 11. The body 11 has a central collar 22 so that it may be mounted on a drive spindle. The scroll plate 17 has a peripheral ring gear 23 formed opposite the guide spiral. The collar 22 has a pinion carrier 24 rotatable on the collar 22. The ring gear 23 projects into the pinion carrier 24 where it meshes with circumferentially spaced pinions 25. Each pinion has a stub 26 which rotates in holes 27 the pinion carrier 24. The pinion carrier 24 is free to rotate subject to the freedom of the pinions. To this end the pinions have hexagonal profiled key ways 28 so that a corresponding tool may be positioned in one of the pinions. Subject to the movement applied to the pinion the ring gear may be rotated relative to the pinion carrier or with the pinion carrier.

Where the pinion is rotated about its central axis it will drive the scroll relative to the pinion carrier and the spiral guideway will open or close the chuck jaws. Where the tool is used to move the pinion and the pinion carrier about the chuck axis, the pinion is effectively held coupled to the ring gear and again the chuck opens or closes depending on direction. It will be appreciated that the

collar, body 11 remain stationary during this process consequently the adjustment of the chuck is effectively independent of the drive and is all single handed.

This means that when the chuck is closed to a position where the movement of the tool circumferentially with the pinion fixed would cause the chuck and body to rotate, the tool may then be used in the second action to finally tighten the chuck. Since the means to tighten the chuck is effectively independent of the drive application of initial torque to the chuck will not cause any inconvenient and potentially dangerous inadvertent release of the chuck. Referring to Figures 5 - 7 there is illustrated a further embodiment 30

(where appropriate like numerals illustrate like features) whereby locking pins 31 are used to secure the pinion carrier 32 to the collar 33. The collar 33 has circumferentially spaced holes 43, in this case twelve evenly spaced holes 43 are employed. The locking pins may be released for the coarse adjustment and then locked for the fine adjustment using the pinons 44. All other aspects are the same as in the previous embodiment.

Whilst the above has been given by way of illustrative example of the present invention many variations and modifications thereto will be apparent to those skilled in the art without departing from the broad ambit and scope of the invention as set out in the appended claims.