US2037304A

US2037304A - Feed collet

Info

Publication number: US2037304A
Application number: US752761A
Authority: US
Inventors: Baxendale Samuel
Original assignee: Individual
Current assignee: Individual
Priority date: 1934-11-12
Filing date: 1934-11-12
Publication date: 1936-04-14
Anticipated expiration: 1953-04-14

Description

S. BAXENDALE FEED COLLET April 14; 1936.

Filed Nov. 12, 1934 INVENTOR SAMUEL BAXENDALE ATTORNEYS Patented Apr. 14, 1936 UNITED STATES PATENT OFFICE 3 Claims.

The invention relates to feed mechanisms such as used in connection with automatic machines for the feeding of a bar of. stock, and it is the primary object of the invention to lessen the waste of material. It is a further object to obtain a construction which is free from certain defects in constructions heretofore used, and to this end the invention consists in the construction as hereinafter set forth.

In the drawing:

Fig. 1 is a central longitudinal section through the revolving spindle of an automatic machine showing my improved feed collet applied thereto;

Fig. 2 is a similar view of the end portion of the collet showing it engaged with the rear end of a stock bar;

Fig. 3 is a cross section on line 33, Fig. 1;

Fig. 4 is an end elevation of the feed collet;

Fig. 5 is a side elevation-of the feed collet;

Fig. 6 is a similar view showing a slightly modified construction.

In the present state of the art feed collets have been used in connection with automatic machines these consisting essentially of a longitudinally slotted tubular member having the bars intermediate the slots bowed inward to form resilient gripping jaws for frictionally engaging the stock bar. With such constructions the collet will be eifective for feeding the stock bar until its rear end passes to the forward end of the bowed bars, after which no further longitudinal feed is possible, inasmuch as the gripping points are necessarily spaced some distance in rear of the forward end of. the collet. This leaves a portion of the stock bar which can not be used and must be scrapped. In a modified construction also heretofore used the gripping point is advanced towards the front end of the collet by giving an abrupt inward turn to the bars at the forward end and by also slitting one side of the tube through the forward end. The objection to such construction is that the abrupt inward bend of the bars concentrates stress at the bend with the result that collets are frequently broken. Furthermore, even with such construction, the stock bar can not be fed to the forward end of the feed col-' let as the point of bearing is still somewhat in rear of this end.

With my improved construction the gripping bearing of the collet on the stock is normally at the center of the bowed bars, but when the rear end of. the stock bar passes beyond this point it will be gripped by the forward end of the collet, which will advance it to a point immediately adjacent to the chuck of the automatic machine.

By such a constrution a saving is effected which in the aggregate amounts to considerable value.

As specifically shown, A are the jaws of the chuck or collet for the automatic machine which are operated in the usual manner by a lorigitu- .5 dinally movable sleeve B extending through the tubular revolving spindle C which latter has a conical head D at its forward end for radially contracting said jaws. E is the feed collet which is longitudinally reciprocated within the sleeve B 1-0 by an inner sleeve F. As the mechanism for actuating the sleeves B and F forms no part of the present invention, it is not necessary to further describe the same. 7

My improved feed collet E is formed of a tube 15- Which at its rear end has a threaded portion G for engagement with the sleeve F, this portion being of an internal diameter in excess of the diameter of the stock bar to be fed. At the forward end H the internal diameter is smaller 20 so as to be slightly less than the diameter of the stock bar, and to permit of the passage of said bar one side of this portion is slitted at I. Intermediate the portions G and H the tube is longitudinally slotted to form a series of bars J that are bowed inward so that the normal point of bearing against the stock bar is substantially at the center of the length of the collet and some distance in rear of the forward end thereof. The radial thickness of the bar J is less than that of the portion H and their forward ends are provided with fillets merging into this portion so as to avoid a localization of stresses at such point. The collet is preferably formed of steel suitably heat treated to impart thereto the desired hardness and resiliency. With the construction as just described, the stock bar such as L is first manually advanced through the collet E to engage its forward end with the jaws A of the chuck. The reciprocation of the collet E will then move the same rearward during the machining operation on the portion held by the jaws A and upon the cutting off of the finished work and release of the jaws the stock will be advanced by the forward movement of the collet E. During this operation the point of gripping will be located at the center of the bars J and this continues until the rear end of the stock bar is advanced beyond such center. When this occurs the point of gripping bearing will be transferred to the portion H which being of such greater thickness will be tensioned by a very slight expansion due to the larger diameter of the stock. This will permit the feeding to continue until the rear end of the stock bar reaches the front end of the portion H which is immediately adjacent the jaws A. Thus no portion of the bar is wasted excepting that which is engaged by the jaws A and is in rear of the finished work.

In the modified construction shown in Fig. 6 the outer surface H of the portion H is eccentric to the inner surface thereof to vary the thickness of the wall, with the slot I passing through the thinnest portion. This will permit a more uniform radial expansion of the inner diameter of this portion and also a better gripping of the rear end portion of the stock bar.

What I claim as my invention is:

1. A feed collet comprising a tubular member of an internal diameter greater than the external diameter of the stock bar to be fed therethrough, the extreme forward end of said tubular member having a radially inwardly extending portion of a diameter slightly less than the external diameter of the stock bar, the intermediate portion of said tube being longitudinally slotted to divide the same into spaced bars with one of the slots extending through the forward end and said spaced bars being bowed inwardly to resiliently grip the stock whereby the stock bar when engaged with said bowed portions will expand the slotted forward end portion free from gripping engagement with said stock bar, and whereby said forward end portion will grip the stock bar when the rear end of the latter passes out of engagement with said bowed portions to continue the feeding to the extreme rear end of said stock bar.

2. A feed collet comprising a tubular member having an internal diameter greater than the external diameter of the stock bar to be fed therethrough, the extreme forward end of said tubular member having a radially inwardly extending portion of an internal diameter slightly less than the external diameter of said stock bar, said inwardly extending portion having a rounded fillet between the same and the portion of larger internal diameter, the intermediate portion of said tubular member being longitudinally slotted to divide the same into spaced bars, one of the slots extending through said forward end and said spaced bars being bowed inward to form a gripping bearing for engaging the stock bar, said tubular member being formed of resilient material whereby the engagement of the stock bar with said bowed portions will expand said forward end portion to free the same from the stock bar and whereby said forward end portion will grip and continue to feed said stock bar when the rear end thereof disengages from said bowed portion.

3. A feed collet comprising a tubular member of internal diameter greater than the external diameter of the stock bar to be fed therethrough, the forward end portion of said tubular member extending radially inward so that the internal diameter thereof is slightly less than the external diameter of the stock bar and the outer surface of said end portion being eccentric to the inner surface thereof to form a progressively changing radial thickness, the central portion of said tubular member being longitudinally slotted to divide the same into spaced bars, one of the slots extending through the end portion on the thin side thereof and said bars being bowed inward for gripping engagement with the stock bar whereby the engagement of said stock bar with said inwardly bowed portions will expand the outer end to free the stock bar and whereby said outer end portion with its varying thickness of wall will resiliently clamp the stock bar when the rear end thereof passes out of engagement with said bowed portion.

SAMUEL BAXENDALE,