GB2263246A - Screwthreading apparatus - Google Patents

Abstract

A screwthreading apparatus for fitment to a lathe comprises a main body part 10, a die holder 14, a die 16, a carrier shaft (52, Fig. 2B, not shown), and disconnectable clutch means 20, 24, 26, 30 for locating the die holder 14 non-rotatably with respect to the main body part 10. Rotating handle 11 disconnects the clutch and allows the die 16 to rotate with respect to the main body part 10. <IMAGE>

Description

Screwthreading apparatus The invention relates to a screwthreading apparatus for fitment to a conventional CNC, Capstan or Turret lathe for example.

Various screwthreading attachments for fitment to lathes are known. The object of the invention is to provide an apparatus of low initial cost and of particular simplicity.

According to the invention, there is provided a screwthreading apparatus for fitment to a lathe, the apparatus including a main body part; a die holder mounted in advance of said main body part; a carrier shaft extending rearwardly of said main body part and adapted to be received nonrotatably in the tailstock of the lathe; means allowing said main body part and said die holder to float axially relative to said carrier shaft; clutch means for locating the die holder nonrotatably with respect to said main body part; and manually operable means for disconnecting said clutch means.

The means for disconnecting the clutch means may be constituted by a cam plate non-rotatably connected to the carrier shaft, an element of said clutch means being disconnected by said cam plate when the main body part is rotated relative to said cam plate. The main body part may be provided with a manually operable handle by means of which the main body part can be held in a first position, in which the clutch means are engaged, to enable screwthreading to proceed, or moved to a second position, in which the clutch means are disconnected, to allow the die holder to rotate freely.

The means allowing the main body part and die holder to float axially relative to the carrier shaft may include a cylindrical sleeve element a forward portion of which is connected to the cam plate mounted in the main body part and a rearward portion of which is slidably mounted on the carrier shaft, there being means permitting said sleeve to slide axially on said carrier shaft but preventing its rotation thereon.

In order that the invention may be fully understood and readily carried into effect, the same will now be described, by way of example only, with reference to the accompanying drawings, of which:- Figure 1 is a perspective side view of a screwthreading attachment embodying the invention, and Figures 2a and 2b are exploded views thereof.

Referring now to Figure 1 of the drawings, the screwthreading attachment there illustrated has a main body part generally indicated 10, a morse taper sleeve 12 at one end by means of which the attachment can be located in a machine tool tailstock, and at its other end a die holder 14 located in advance of the main body part with a split die 16 'located within it by three grub screws 17. A manually operable handle 11 is fixedly connected to said main body part, as shown.

Referring now to Figures 2a and 2b, these illustrate the construction of the attachment. As shown, the die holder 14, which is of annular form, is mounted on a forwardly projecting barrel portion 18 of a clutch member 20 and is rotatably mounted in the main body part with said barrel portion projecting outwardly through the bore 19. A rearward part of said clutch member has the form of a cylindrical disc element 22 with a notch 24 for the reception of a detent pawl member 26 which is located in the main body part 10. The pawl member is mounted for radial movement within the main body part but is acted upon by a coil compression spring 28 which urges it radially inwards and into engagement with the notch 24.

The detent pawl member is somewhat wider than the disc element 22 and overlaps the rearward edge thereof to extend across the width of a cam plate 30 which is located alongside the clutch member 20.

A cover plate 32, secured to a rearward face of the main body part 10 by three screws 34, locates the cam plate adjacent the disc element 22 with a pair of crinkle washers 36 and a felt washer 38 located between them. As shown, the cam plate has a flat portion 40 which at one end terminates in an upstanding shoulder 42 but which at its other end runs out into the periphery of the cam plate, the arrangement being such that when said flat portion is located beneath the detent pawl member 26 the latter is fully engaged with the notch 24 in the cylindrical disc element 22 and the die holder is thus held non-rotatably relative to the main body part 10.

The cam plate 30 is formed integrally with a spindle portion 44 which extends rearwardly of the main body part to be received in a forward portion of a cylindrical sleeve element 46 in which it is secured by a grub screw 48. A rearward portion of said sleeve element is provided with a longitudinal slot 50 and is a sliding fit on a forwardly projecting portion of a carrier shaft, generally indicated 52, from which a cylindrical spigot portion 54 extends radially outwards to be slidably engaged in the slot 50. The slot 50 opens from the rear end of the sleeve, as shown.

A rearward portion of the carrier shaft is shown to be non-rotatably held in the morse taper sleeve 12 which can itself be received in the tailstock of a lathe as shown in Figure 1.

The clutch member 20, cam plate member 30 and carrier shaft 52 are all provided with an axial bore 56 through which a workpiece can extend as it is being threaded by the die 16.

In use of the attachment, when an appropriate die 16 has been selected and fitted in the die holder and with the drive pin located at the inner end of the slot 50 in the sleeve element 46, the attachment can be advanced towards a workpiece rotatably mounted in the work holding chuck of the machine. At this time the handle will be in the vertical position as it is shown in Figure 2a and as shown in chain-dotted lines in Figure 1.

Consequently, the detent pawl member 26 will be in engagement with the notch 24 of the cylindrical disc element 22 and the clutch member 20 and die holder and die carried thereby will be held against rotation.

As the die 16 comes in contact with the rotating workpiece, thread cutting will commence and the machine operator will hold the handle 11 in the vertical position to hold the main body part 10 against the rotation of the workpiece. As thread cutting proceeds, the main body part will move along the workpiece, this movement being permitted by sliding movement of the sleeve 46 on the carrier shaft.

When the required length of thread has been cut, the operator will operate the handle, as shown in Figure 1, to rotate the main body part 10 relative to the carrier shaft 52, sleeve 46 and cam plate 30 which are non-rotatably connected to the tailstock of the lathe. This will cause the pawl member 26 to ride up onto the periphery of the cam plate and out of engagement with the notch 24 in the cylindrical disc element 22. Consequently, said disc element, together with the die holder and die, are able to rotate freely with the rotating workpiece.

The die can very quickly and easily be removed from the screwthreaded workpiece by putting the lathe into reverse and moving the handle back into the vertical position so that the pawl member can re-engage the notch 24 in the cylindrical disc element and thus hold the die holder and die against rotation.

Thus there is provided a screwthreading apparatus of low initial cost which is particularly simple to operate.

Various modifications may be made. For example, the clutch mechanism could be differently constructed, but will preferably still be disengageable by rotation of the main body part.

It will be understood that a number of different die holders may be provided to be usable selectively, each die holder being capable of receiving a different range of die sizes.

Claims (5)

CLAIMS:

1. Screwthreading apparatus for fitment to a lathe, the apparatus including a main body part; a die holder mounted in advance of said main body part; a carrier shaft extending rearwardly of said main body part and adapted to be received nonrotatably in the tailstock of the lathe; means allowing said main body part and said die holder to float axially relative to said carrier shaft; clutch means for locating the die holder nonrotatably with respect to said main body part; and manually operable means for disconnecting said clutch means.

2. Screwthreading apparatus according to claim 1, in which the means for disconnecting the clutch means are constituted by a cam plate non-rotatably connected to the carrier shaft, an element of said clutch means being disconnected by said cam plate when the main body part is rotated relative to said cam plate.

3. Screwthreading apparatus according to either one of the preceding claims, in which the main body part is provided with a manually operable handle by means of which said main body part can be held in a first position, in which the clutch means are engaged, to enable screwthreading to proceed, or moved to a second position, in which the clutch means are disconnected, to allow the die holder to rotate freely.

4. Screwthreading apparatus according to any one of the preceding claims, in which the means allowing the main body part and die holder to float axially relative to the carrier shaft include a cylindrical sleeve element a forward portion of which is connected to the cam plate mounted in the main body part and a rearward portion of which is slidably mounted on the carrier shaft, there being means permitting said sleeve to slide axially on said carrier shaft but preventing its rotation thereon.

5. Screwthreading apparatus constructed, arranged and adapted to operate substantially as hereinbefore described with reference to and as illustrated by the accompanying drawings.