Title:
Machine for producing screw threads
United States Patent 2403075


Abstract:
This invention relates to machines for producing screwthreads of the kind having an element for supporting rotatably the work upon which the screwthread is to be produced, a driving member for transmitting power to the machine, means for imparting rotary movement from said driving member to...



Inventors:
Arthur, Green
Application Number:
US54028544A
Publication Date:
07/02/1946
Filing Date:
06/14/1944
Assignee:
Arthur, Green
Primary Class:
Other Classes:
74/89.2
International Classes:
B24B19/02
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Description:

This invention relates to machines for producing screwthreads of the kind having an element for supporting rotatably the work upon which the screwthread is to be produced, a driving member for transmitting power to the machine, means for imparting rotary movement from said driving member to said work, an element adapted to support a tool for forming the screwthread, said two elements being relatively reciprocable in a direction substantially along the axis of the thread to be formed, means for imparting reciprocating movement from said driving member to one of said two elements, and means interconnecting said two movements so that the pitch of the thread to be formed may thereby be controlled.

With machines of the above kind, in the case of an ordinary parallel thread, the two elements would be reciprocated relatively in a direction which was parallel to the axis of the thread to be formed, but in the case of a taper thread they would be reciprocated relatively in a direction which was only substantially parallel to the axis of the thread to be formed, i. e. in a direction substantially along such axis, there being a slight angle of inclination between the axis of the thread to be formed and the direction of relative reciprocation of the two elements.

Furthermore, in such machines, the reciprocating movement is sometimes imparted to the tool supporting element, or sometimes to the work element, or sometimes both elements are displaced so as to produce a relative reciprocation.

In such machines it is a common practice to drive the rotating work and the reciprocating element from the same driving shaft, the drive being transmitted by gearing to the work rotating member and by gear, which may take the form of a leading screw and nut, to produce the re- 4 ciprocating movement.

The mechanism forming the subject of this invention is not necessarily a complete machine for producing screwthreads, but may be an attachment adapted to be fitted to an existing ma- 4 chine having the necessary facilities for fitting and having a thread-producing tool.

The primary object of the present invention is to provide a new or improved form of mechanism for producing the movement of the recip- 5' rocating element.

Another object of the invention is to provide such mechanism which can conveniently be fitted as an attachment to an existing machine.

Other objects of the invention will become ap- 5, parent from the following description and accompanying drawings, whereinFigure 1 is a side elevation of one form of a machine for producing screwthreads and constructed in accordance with the present invention.

Figure 2 is an enlarged side view of part of the construction shown in Figure 1.

Figure 3 is a cross sectional view of a part of the construction.

Figure 4 is an end elevation in the direction 4-4 of Figure 1.

Figure 5 is a sectional view on the line 5-5 of Figure 2.

Figures 6 and 7 are plan and side views of an alternative construction.

In the construction illustrated in Figures 1-5 of the drawings, the rectilinear motion is transmitted directly to the reciprocating element and this carries the work on which the screwthread is to be cut, and the apparatus comprises a stationary main support 1b which at one side carries the thread producing tool indicated diagrammatically at I1. This tool may be of any known form and may for instance comprise a rotary wheel having one or more annular ribs for cutting the thread or the tool may consist of a simple screw-cutting tool, for example, a bar or shank with a cutting point shaped for forming the thread groove.

Mounted upon the upper surface of the support 10 so that it can reciprocate thereover in the direction indicated in Figure 1 by the arrows is 5 the reciprocating element 12 conveniently in the form of a table of known construction and carried from the support in any known manner.

One end of the reciprocating element carries a tailstock indicated diagrammatically at 13 for 0 supporting one end of the work 14 and the opposite end of the reciprocating element carries mechanism indicated generally at 15 for imparting rotation to the work and reciprocatory movement to the said element.

5 In the construction illustrated this mechanism comprises a gear casing 16 one end of which carries a driving shaft 17 extending transversely of the direction of reciprocation of the element 12 and which is either operated manually by pro0 viding it with a handle 18 or alternatively may be driven by a power unit not shown.

The end of the shaft opposite to the handle gears through worm gearing with an intermediate shaft 19 provided between its ends with a 5 worm 20 engaging a worm-wheel 21 carried by a rotary shaft 22 again extending transversely of the direction of reciprocation of the element 12, one end of which shaft extends through the casing 16 and carries the said rotary disc indicated at 23. Instead of using the worm gear 20, 21 bevel gears may be employed. For rotating the work the intermediate shaft gears through reduction gearing 53 with a headstock 24 which supports the other end of the work and rotates it through the medium of a lathe dog 25.

The rotary disc 23 is mounted removably upon the end of the shaft 22 by providing its hub 26 with coned clutch faces 27 which engage frictionally with corresponding coned faces 28, 29 provided respectively on the shaft 22 and on a removable locking member 30 which can be screwed on to the end of the shaft. The coned clutch faces permit infinite adjustment of the position of the disc 23 upon the shaft 22 and thus, "the position of the disc 23 at which the drive is imparted thereto by the shaft 22 can be set accurately in relation to the workpiece to enable corresponding accuracy in the commencement of the threading operation on the workpiece. The locking member 30 enables the rotary disc to be removed for the purpose described hereafter and also by slacking the member 30, the element 14 can be reciprocated rapidly manually when the driving shaft 17 is at rest. This arrangement allows the return movement to be effected at a greater speed than the forward movement.

Other forms of quick return construction may be used if desired.

The periphery of the disc 23 is engaged by flexible metal bands 32, 33 one end of each band being secured to the periphery of the disc as indicated at 34 in Figure 2, the length of the bands being such that at the opposite ends they have portions 31 and 35 which extend parallel to the direction of movement of the reciprocating element with the two end portions extending in opposite directions and being secured to brackets 36 mounted upon the support 10 in fixed relationship thereto.

With such an arrangement when drive is imparted to the shaft 17 the work 14 is rotated and at the same time rotary movement is imparted to the disc 23 so that one or the other of the two bands 32, 33 is wound thereon and owing to the fact that the shaft 22 carrying the disc is mounted in bearings 37 in the casing 16, the reciprocatory movement is imparted to the casing and hence to the element 12 and the work 14 in one or the other of the arrow directions indicated in Figure 1, rectilinear movement in one direction being imparted when the disc rotates in one direction and movement being imparted in the other direction when the disc rotates oppositely.

- The movement of the reciprocating element in the direction it takes while the thread is being cut is effected by winding the band 33 on to the disc. The other band 32 is a tensioning band, and has its end 31 secured by one of the brackets 36 to a bracket 53 having a downwardly extending flange 40. The bracket 53 is provided with a bolt 39 which extends through a slot 38 in an element 42 formed separately from the support but secured rigidly thereto. Extending through the flange 40 is an adjusting screw 41 so that after the bolt 39 has been loosened, the brackets 53 can be adjusted endwise by turning the screw 41 to adjust the tension on the band 32.

To enable the length of the reciprocating stroke of the element 14 to be changed for a given number of rotations of the work the gear wheels 53 may be readily removable from their shafts and replaceable by gear wheels of a different diameter so that the velocity ratio of this gearing is altered.

Further a reverse drive may be introduced into Sthe gearing.

As another method of enabling the length of the reciprocating stroke of the element 14 to be changed for a given number of rotations of the work, so as to alter the pitch of the thread, a 0 larger or smaller disc 23 may be substituted for the one previously in use, and to ensure that the end portions 31 and 35 of the bands may, with different disc diameters, still be parallel to the direction of reciprocation of the element 14, the element 42 may be mounted on the support so that it is bodily adjustable up and down towards the axis of the shaft 22. Alternatively, instead of making the element 42 adjustable on the support in this way, the element 42 may be fixed Son the support and distance blocks may be inserted one between the upper surface of the bracket 53 and the end 31 of one band, and the other between the element 42 and the end portion 35 of the other band.

A further alternative method of providing for Schanges in the pitch of the screwthread to be cut which avoids the necessity for the above adjustments can be obtained with the modified construction illustrated in Figures 6-7 of the drawings.

3 In this latter construction the rotary disc 23 is mounted upon an axis which is parallel to the direction of movement of the reciprocating element 12 and the flexible bands have the end portions 35 connected to a transverse slide 43 extending at right angles to the direction of reciprocation which transverse slide acts in the manner of a wedge between the reciprocating element and an inclined abutment 44 mounted upon the stationary support 10.

Conveniently, the transverse slide is provided with an inclined surface member 45 which is angularly adjustable in relation to the slide by providing the member 45 with an arcuate slot 46 through which extends an adjusting bolt 47 and 4this surface part is provided, at the end opposite to the slot, with a groove 48 into which extends the adjacent part of the abutment 44 while the latter is angularly adjustable in relation to the support 10 by fastening it thereto through the medium of an adjusting screw 49.

For supporting the transverse slide in relation to the element 12 it is provided with a dove-tail or "T" section rib 50 at the side opposite to the abutment which engages in a groove 51 of similar section shaped in the adjacent end of the reciprocating element, the rib and groove extending at right angles to the direction of reciprocation.

With such an arrangement when drive is imparted to the shaft 17 so that the work 14 and disc 23 are rotated in the manner already described the slide 43 is moved transversely to the axis of the work so that the inclined surface part 45 thereon moves along the inclined surface 44 of the abutment thus causing the slide to be displaced in the direction of movement of the axis of the work and the required reciprocatory movement to be transmitted to the element 12 and hence to the work 14.

The amount of movement transmitted for a given number of rotations of the work can readily be varied by altering the angle of inclination of the surface part 45 and the inclined abutment 44 as by slackening the screws 47, 49. As a result the machine can readily be adjusted to suit threads of different pitch.

In the construction shown in Figures 6 and 7 the endwise displacement of the reciprocating element is produced by the inclined abutment 44 engaged by the inclined side 45 and the slide.

The action is that of a wedge and it is immaterial whether the inclined surface is on the slide or on the abutment or on the end of the reciprocating element. Further the inclined surface may engage or be engaged by a similarly inclined surface or by a roller or other abutment. It is obviously desirable that the angle of inclination of the inclined surface shall be capable of adjustment.

A machine constructed in accordance with the present invention possesses the great advantage that by imparting the necessary movement to the reciprocating element from the rotary disc through the medium of one or more flexible bands in the manner described, lost or irregular motion between the relatively moving members is reduced to a minimum as compared with an arrangement in which the movement is transmitted by means of a lead screw or rack and pinion gearing so that the machine possesses a high degree of accuracy.

Although I have described a construction in which the reciprocating element carries the work and the thread producing tool is stationary it should be understood that it is within the scope of my inventidn that the thread producing tool could be mounted upon a reciprocating element so that it reciprocates therewith and the work merely rotates.

What I claim then is: 1. A machine for producing screwthreads comprising an element for supporting rotatably the work upon which the screwthread is to be produced, means for rotating said work, an element adapted to support a tool for forming the screwthread, said work supporting element being 4 mounted on said tool supporting element for reciprocatory movement relative thereto in a direction substantially along the axis of the thread to be formed, a shaft mounted rotatably on said work supporting element disposed trans- 4 verse to the direction of reciprocation of said work supporting element, means for imparting rotary movement to said shaft, a disc mounted detachably on said shaft, a pair of flexible bands arranged side by side and engaging the periphery of the disc, one end of each of said bands being secured to the disc, means securing the other ends of said bands adjustably to the tool supporting element, said adjustable means permitting of adjustment of said band ends relative 5 to the tool supporting element in a direction parallel to the direction of reciprocation of said work supporting element and in a direction at right angles thereto and within the plane of the disc, said two band ends which are secured to 6' the tool supporting element extending in opposite directions with respect to each other and substantially parallel to the direction of reciprocation of said work supporting element, and said rotary disc on rotation in either direction being 6i adapted to wind up and unwind respectively relative to the disc one or the other of the said two bands.

2. A machine for producing screwthreads comprising an element for supporting rotatably the 7( work upon which the screwthread is to be produced, an element adapted to support a tool for forming the screwthread, said work supporting element being mounted on said tool supporting element for reciprocatory movement relative thereto in a direction substantially along the axis of the thread to be formed, a gear casing mounted on one end of said work supporting element, an intermediate shaft mounted rotatably in said gear casing extending substantially parallel to the direction of reciprocation of said work supporting element, means for imparting rotary movement to said intermediate shaft, variable step up gearing driven from said intermediate shaft, means for imparting rotation from said step up gearing to said work, a rotary shaft mounted rotatably in said gear casing transverse to the direction of reciprocation of said work supporting element and driven from said intermediate shaft, one end of said shaft extending outside said casing; a disc mounted upon said shaft end and driven thereby, a pair of flexible bands arranged side by side and engaging the periphery of the disc, one end of each of said bands being secured to the disc and the other end to the tool supporting element with the said other ends extending in opposite directions with respect to each other and substantially parallel to the direction of reciprocation of said work supporting element, and said rotary disc on rotation in either direction being adapted to wind up and unwind respectively relative to the disc one or the other of the said two bands.

3. A machine for producing screwthreads comprising an element for supporting rotatably the work upon which the screwthread is to be produced, an element adapted to support a tool for forming the screwthread, said work-supporting element being mounted on said tool-supporting element for reciprocatory movement relative thereto in a direction substantially along the axis of the thread to be formed, a gear casing 10 mounted on one end of said work-supporting element, an intermediate shaft mounted rotatably in said gear casing extending substantially parallel to the direction of reciprocation of said worksupporting element, means for imparting rotary 15 movement to said intermediate shaft, step-up gearing driven from said intermediate shaft, means for imparting rotation from said step-up gearing to said work, a rotary shaft mounted rotatably in said gear casing transverse to the 0 direction of reciprocation of said work-supporting element and driven from said intermediate shaft, one end of said rotary shaft extending outside said casing, a disc mounted on said shaft end, an infinitely adjustable, double cone clutch 5 connecting said shaft end in driving relationship to said disc in a manner permitting infinite adjustment of the position of said disc on said shaft end and providing a firm drive from the shaft end to the disc at all positions of adjustment, a 0 pair of flexible bands arranged side by side and engaging the periphery of the disc, one end of each of said bands being secured to the disc and the other end to the tool-supporting element, with the said other ends extending in opposite 5 directions with respect to each other and substantially parallel to the direction of reciprocation of said work-supporting element and said rotary disc, on rotation in either direction, being adapted to wind up and unwind respectively rel0 ative to the disc one or other of the said two bands.

ARTHUR GREEN.