US2336201A - Relieving attachment for machine tools - Google Patents

Description

Dec. 7, 1943. E. A. WALKER RELIEVING ATTACHMENT FOR MACHINE TOOLS 2 Sheets-Sheet l Filed Aug. 20, 1942 jgz Dec'. 7, 1943. E. A. WALKER 2,336,201

RELIEVI NG ATTACHMENT FOR MACHINE TOOLS Filed Aug. 20, .1942 2 Sheets-Sheet 2 Patented Dec. 7, 1 943 RELIEVING ATTACHMENT FOR MACHINE TOOLS Ernest A. Walker, Worcester, Mass, assignor to John Bath & Company, Worcester, Mass, a corporation of Massachusetts Application August 20, 1942, Serial No. 455,491

3 Claims.

This invention relates to machine tools, such as lathes and grinding machines, which are adapted for use in the manufacture of taps or similar articles having relieved surfaces.

In such manufacture, it has been proposed to shift the work radially relative to the cutting tool or grinding wheel to produce the desired relieving effect. All such proposals have, however, involved the use of relatively moving bearing surfaces and the relative movements have been so slight, such as one or two thousandths of an inch, that effective lubrication of the coacting surfaces has proved impractical.

It is the general object of my invention to provide an improved supporting structure for a re-.

lieving attachment, so formed that relatively moving bearing surfaces are entirely avoided.

To the accomplishment of this general object, I provide a relieving attachment in which the moving structure, such as the tail stock, is mounted on a rigidly clamped. but slightly flexible supporting member. Slight oscillatory movements of the tail stock are made possible by flexing said supporting member.

My invention further relates to arrangements and combinations of parts which will be hereinafter described and more particularly pointed out in the appended claims.

A preferred form of the invention is shown in the drawings, in which Fig. 1 is a plan view of a tail stock embodying my improvements;

Fig. 2 is a sectional front elevation, taken along the line 2-2 in Fig. 1;

Fig. 3 is a side elevation, partly in section, and looking in the direction of the arrow 3 in Fig. 1;

Fig. 4 is a detail sectional rear elevation, taken along the line 4-4 in Fig. 3; r

Fig. 5 is a fragmentary rear elevation, looking in the direction of the arrow 5 in Fig. 3; and

Fig. 6 is a diagrammatic view illustrating the relieving action.

Referring to Figs. 1, 2 and 3, I have shown portions of a machine specially designed for grinding taps and comprising a transverse slide (Fig. 3) supporting a tail stock base II which is adjustable longitudinally of the slide l0 and which may be held in adjusted position by a clamping bolt 12.

The tail center I4 is mounted in a rectangular bar I slidable longitudinally in the tail stock IS. The bar I5 is movable axially in the tail stock to engage the work, shown herein as a tap T. The bar 15 may be moved by a pinion I1 operated by a handle It, all of these parts being of the usual construction.

The tail stock It is provided with a rigid depending portion 20 (Fig. 3) which is slotted to snugly receive the upper edge of an axiallyextended flat spring plate 2|, which plate is rigidly clamped to the tail stock portion 20 by clamping screws 22 (Fig. 5).

The lower edge portion of the spring plate 2| abuts shoulders 24 and 25 (Fig. 3) in the tail stock base II and is rigidly held in position by a clamping bar 26 and a plurality of clamping screws 21.

The tail stock I6 is thus firmly supported on the tail stock base H but is capable of making slight swinging or'oscillatory movements relative to the base II by flexing the spring plate 2|. Such slight oscillatory movements will swing the associated end of the tap T intermittently rearward to relieve the cutting teeth of the tap, as will be hereinafter described.

In order to produce these slight oscillatory movements, I provide a cam 30 (Fig. 3) mounted on a driving shaft 3| (Fig. 2) which is rotated in timed relation to the rotation of the tap T.

In the drawing, the cam 30 (Fig. 3) is shown as having four lobes and the tap is shown as having four lands, and the driving connections will be such that the tap T and the driving shaft 3| rotate at the same speed.

The cam 30 is engaged by a cam roll 33 (Figs. 2 and 3) mounted in a cam lever 34 pivoted at 35 (Fig. 3) to the tail stock IS. The cam lever 34 can swing vertically within rather close limits and has an upward projection 40 engaging a wedge 4| held in position by a clamping stud 42 extending through a slot 43 in the tail stock l6 and provided with a clamping nut 44.

The cam lever 34 and wedge 41 thus transmit oscillatory movements from th cam 39 to the tail stock 16, and as the front end of the tail stock is raised and lowered, the tail center l4 (being directly over the spring plate 2|) will be moved slightly rearward and forward.

The normal grinding position is the forward position, which is positively determined by engagement of bearing surfaces 50 (Figs. 3 and 4) with the upper surface 5| (Fig. 4) of a sliding wedge 52. The wedge 52 is seated on an inclined bearing surface 53 and may be moved along said inclined surface by adjusting screws 54 and 55, the adjustment being retained by lock nuts 56.

The ends of the wedge 52 are beveled, as well shown in Fig. 4, so that the forces applied by the clamping screws 54 and 55 will firmly seat the wedge on the inclined surface 53. By adjusting the wedge 52 lengthwise, this will determine whether the work is to be straight or tapered.

A rubber block 60 (Fig. 3) may be inserted between shoulders GI and 62 in the front upper portion of the tail stock I6 and coacting surfaces in the fixed drive shaft casing 65. The block 60 acts as a spring or cushion to normally seat the wedge M (Fig. 3) on the lever extension 40, and the bearing surfaces 50 on the wedge 52, thus returning the parts to normal grinding position.

In Fig. 6 I have shown diagrammatically the relative positions of the tap T and the grinding wheel W during the grinding and relieving of a tap. In the upper part of Fig. 6, the work is; in forward or normal grinding position, corresponding to the position of the parts shown in Fig. 4

and with the regular grinding of the tap teeth taking place.

In the lower part of Fig. 6, the tap T has been moved slightly rearward, so that the following ends of the tap teeth will be slightly relieved for clearance. A separate relieving movement must be produced for each and every tooth on each land of the tap, which with a four-flute tap as shown would be four times per revolution, corresponding to the four lobes of the cam 3E3.

It willbe understood that the relieving action is greatly exaggerated in Fig. 6, the actual movement commonly being not over one or two thousandths of an inch and frequently less. By withdrawing the wedge 2!, 10st motion between the cam 30 and cam roll 33 may be introduced and the point of beginning of the relieving action may be delayed.

The steel plate 2| is thus subject to extremely slight flexure and may be relatively thick and rigid, so as to firmly support the tail stock and to remain operative throughout a long period of use.

By the use of the construction above described, the tail stock is movably supported without the use of any relatively movable bearing surfaces whatever, so that the problem of lubricating bearing surfaces having exceedingly slight relative movements is entirely avoided.

Having thus described my invention and the advantages thereof, I do not wish to be limited to the details herein disclosed, otherwise than as set forth in the claims, but what I claim is:

'1. In, amachine tool, a work support, a base, a rigidly secured but slightly flexible connection between said work support and said base, means to oscillate said work support on said flexible connection and relative to said base to relieve the work, and stops engageable to determine the normal working position of said work support relative to said base, one of said stops comprising a 'slidable wedge and means to adjust said wedge to thereby vary the normal position of said work support.

2. In a machine tool, a tail stock having a relieving motion transversely of its axis, a fixed tail stock base, an elongated and relatively heavy but slightly resilient metal plate, means to rigidly secure said plate to said tail stock and to said base, said plate forming the entire support for said tail stock on said base, and means rotatably mounted in fixed bearings and effective to oscillate said tail stock on said plate and relative to said base to relieve the work.

3. In a machine tool, a tail stock having a relieving motion transversely of its axis, a fixed tail stock base, a slightly flexible supporting member rigidly secured to said tail stock and to said base, a constantly rotated cam, a roll engaged by said cam, a lever for said cam roll freely pivoted on said tail stock, an abutment on said movable tail stock engaged by said lever, and means to selectively determine the setting of said abutment, whereby said tail stock is oscillated on said flexible supporting means by said cam to relieve the work to an amount predetermined by the setting of saidabutment.

ERNEST A. WALKER.

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