US2410091A - Feedhead for rotary tools - Google Patents

Description

INVENTOR.

A ATTO/wn Oct. 29,1946. E. J. L`YNcH FEED HEAD FOR ROTARY TOOLS vFiled July`12, 1944 'By fowl/eb J.' LYNCH n j @N E A d .w E N. 1J am t IIL.; u NN ||||||1||||||||||||1 .l ul l H|||||||11|I n m w mA NA r Q IU- Patented Oct. 29, 946

1 UNITED STATES PATENT GFFICE 2,410,091 FEEDHEAD' Fon ROTARY 'rooLs Edward J. Lynch, Detroit, Mich.

Application July 12, 1944, Serial No. 544,592

Y (c1. 'x7- 33) Claims.

1 This invention relates to rotary tools and particularly to automatic feed heads for such tools. It has been found desirable to derive the feed of various small'tools, as drills and taps, fro-m the centrifugaleresponse of Weights to a rotary drive in unison with the tools. Such a feed is exemplied in the reissue patent to Broders, 21,341, granted February 6, 1940. Objects of the present invention are to simplify and reduce the cost of prior centrifugal tool control mechanisms, to provide a very simple and effective brake mechanism for expediting deceleration when the drive is cut olf, and to provide an improved control for an electric motor energizing the feed head.

' These and various other objects are attained by the construction hereinafter described and illus-- trated in the accompanying drawing, wherein:

Fig. 1 is an axial sectionalview of the improved feed head showing its reciprocating parts retracted.

Fig. 2 is a similar View showing said parts at their forward limit of feed.

Fig. 3 isa cross section on 3-3 of Fig. l showing the mo-unting of the centrifugal weights.

Fig. 4 is an enlarged axial sectional detail of a flexible Ycoupling used in the construction.

In these views, the reference character I designates an electric motor having a tubular shaft 2. Aligned with and normally spaced slightly from said shaft is an extension shaft 3 connected to and driven from the motor shaft by a coupling 4, fiexible to compensate for any slight relative angularity or inaccuracy of `alignment of the two shafts. This coupling is hereinafter described in greater detail. The shaft 3 has its outer end journaled in an outboard bearing 5 integrally formed on a cylindrical casing 6 substantially coaxial with the shaft 3 vand bolted as indicated at I to the motor. The shaft 3 has a tubular o-uter portion wherein is slidably inserted a tool holder 8 .projecting beyond said shaft and the bearing 5 to Vmounta rotary tool such as a drill or the illustrated tap 9. To detachably mount the tool on its holder, there may be employed an ordinary collet andchuck I0 or some equivalent provision.

Freely rotative and slidable on the .shaft 3, about midway between its tubular portion and inner end, is a collar I I rigidly carrying a plurality of outwardly radiating' rods I2. Freely slidable on said rods is a plurality of similar Weights I3,

equiangrularly spaced and elongated lengthwise of the shaft.- The ends of saidweights are beveled and curved to engage and conform to the inner faces of a` pair of reversely disposed bell-'shaped members I4 and I5, the former xed by pins I6 on the shaft 3 in proximity to the coupling 4, and the latter formed at its apex with a forwardly extending sleeve I1 and being slidably mounted by such sleeve on the shaft 3. A pin I8 transversely fixed in .the tool holder 8 rigidly connects the latter to the sleeve I'I, the shaft 3 having an elongated slot I9 in its tubular portion to permit a predetermined travel of the pin relative to said shaft. A permanent drive from said shaft to the tool holder is moreover established by said pin. A coiled spring 20 has an end portion slipped over the sleeve I'I and abutting the bell-shaped member I5, the other end of the spring abutting a brake shoe 2l of disk form fixed on the shaft 3 by a set screw 22 and adapted to frictionally engage the inner face of the bearing 5. It is important to understand that the spring 20 is not intended nor adapted to apply the described brake, the expansive effort of the spring being resisted in both directions by the shaft 3. The fixed relation of the shoe 2l to said shaft entails a control of the shoe taking effect through the shaft 3 or at least tending to slidingly shift said shaft. 'Ihe purpose of the spring 2G is to normally yieldably establish the sliding member I5 at its minimum limiting distance from the member I4 as per Fig. 1, this position being determined by engagement of the weights I3 with the collar II. Said spring permits the member I5 to Withdraw from the member I4 responsive and in proportion to outward actuation of the weights as will presently more fully appear.

A unique feature of the invention is its utilization of flexibility, of the coupling 4 to yieldingly apply the brake. As best appears in Fig. 4, said coupling comprises two collars 23, rfixed respectively on the shafts 2 and 3 by set screws 24, and an intermediate annulus 25 formed largely of rubber, into which are set pins 26 formed on said collars. The arrangement is such that the annulus 25 isvconstantly compressively stressed by the two collars, the expansive reaction of the rubber imposing a forward thrust on the shaft 3 such as to urge the brake shoe 2I against the bearing 5 under `a predetermined pressure. Relief of this pressure during the actual working or cutting strokes of the tool will presently be explained.

A limit switch 21 of ordinary construction is supported by a bracket 28 on the rear end of the motor at the extended axis of the motor, and a control rod 29 for the switch is slidingly extended through the motor shaft 2 and partiallyA through the shaftV 3, the forward end of said rod being threaded into the tool holder 8, and acting as a set screw to secure the pin I8 firmly in place.

In use of the described feed head, the motor circuit is normally broken at the switch 21 and is closed in starting an operation by manual actuation of a button 30 carried by the switch. The shafts 2 and 3 and tool holder and tool are now driven, and the bell-shaped members I4 and I5 are driven respectively by the pins I6 and I8 from the shaft 3. Frictional engagement of the weights I3 by said mem-bers rotatively drives them and they slide centrifugally outward on the rods I2. The weights thus exert a camming effect on the two bell-shaped members, inducing a forward sliding of the member I and a compression of the spring 20. The rotating tool holder 8 participates in this forward sliding due to the pin I8, the length of the slot I9 predeterminedly limiting the advance of the tool holder and tool.

.During an initial portion of such advance, clearance of the tool from the work is taken up, the remaining advance representing the actual working stroke of the tool. The tool, when it encounters the work (not shown), is retracted slightly, together with the tool holder a small fraction of an inch (less than a thirty-second suiiices) Due to the pin I8, the bell-shaped member I5 is'retracted with the tool holder, and the weights I3 being centrifugally held outward, transmit the retraction to the member I4 and through the latter to the shaft 3. Compressibility of the rubber member 25 of the coupling 4 permits the required Slight retraction of the shaft 3, the extent of retraction being controlled by the normal slight clearance between the shafts 2 and 3. The brake shoe being fixed on the shaft 3, is thus retracted to clear the bearing 5 and is so maintained while the tool is exercising its function. As the tool reaches the limit of its stroke, the rod 29 automatically opens the limit switch. The rubber member of the coupling 4 is thereupon immediately relieved of compressive stress applied by the work, and the brake takes effect to greatly expedite deceleration of the rotating parts and the return of reciprocable parts by the spring 20 to a normal retracted position, as per Fig. 1.

The function of the brake in the described mechanism is of decided importance, since feed heads of the improved character are required to constantly repeat their operation, and their eiiiciency depends on the number of repeated operations that may be performed in a given time. Quick deceleration is hence a vital factor in reducing the interval between successive operations, whereas the momentum imparted by the rotating masses and more particularly the weights I3 tends to unduly prolong rotation. The fact that the brake is applied during the interval between starting the motor and advancement of the tool to its point of contact with the work has been found no detriment, since said interval is much too short to permit of objectionable wear or heating of the brake, and the fraction of power consumed in overcoming the brake during such interval is of negligible importance.

Mounting of the weights I3 to slide on the rods I2 in moving in and out is found to minimize friction and also to overcome their tendency to cock in prior constructions. It is a highly desirable feature also that the weights freely float rotatively with relation to both bell-shaped members, thus avoiding a localizing of such wear as is imposed by the weights on said members.

It is to be noted that the yieldable coupling 4 Y not only provides for a release of the brake when the tool encounters the work, but also serves to absorb the shock of tool impact, permitting a more rapid advance of the tool to the work than would otherwise be feasible.

What I claim is:

1. In a feed head for rotary tools, the combination with a driven shaft and a tool holder slidable along and rotative with said shaft to feed a tool forwardly to a piece o f work, a weight and means mounting it on the shaft for centrifugal outward actuation, a member slidable forwardly along the shaft responsive to outward actuation of the weight, and a tool-feeding connection from said member to the tool holder, of a brake shoe fixed on the shaft, a non-rotative member forwardly of and opposed to the brake shoe, a spring compressed between the shoe and said slidable member, to yieldably resist forward movement of said member, and means yieldably exerting forward pressure on the shaft to frictionally apply the brake shoe to said Opposed member.

2. In a feed head for rotary tools, the combination with a driven shaft and a tool holder slidable along and rotative with said shaft to feed a tool forwardly to a piece of work, a weight and means mounting it on the shaft for centrifugal outward actuation, a member slidable forwardly along the shaft responsive to outward actuation of the weight, and a toolfeeding connection from said member to the tool holder, of a brake comprising a shoe fixed on said shaft, means reacting between the shoe and said sliding member to yieldably resist forward movement of said member, and means yieldably exerting forward pressure on the shaft to apply the brake.

3. In a feed head for rotary tools, the combination with a motor, a shaft driven by the motor, a tool holder driven by the shaft and slidable along the shaft for tool feed purposes, a casing carried by and laterally extending from the motor and receiving said shaft, an outboard bearing for the shaft carried by the casing, a weight and means within the casing mounting the weight on the shaft for centrifugal outward actuation, a member slidable along the shaft in the direction of tool feed responsive to outward actuation of the weight, and a tool-feeding connection from said member to the tool holder, of a brake shoe fixed on the shaft within said casing for applying a braking pressure to the outboard bearing, a spring compressed between said slidable member and the shoe, yieldably resisting tool-feeding movement of said member, and means yieldably exerting forward pressure on the shaft to apply the shoe; the shaft being adapted for a limited sliding travel relative to the motor and casing to give effect to the last mentioned means.

4. In a feed head for rotary tools, the combination with a driving shaftv and a driven shaft, of a flexible drive coupling interconnecting said shafts affording the driven shaft a limited travel toward the driving shaft and yieldably resisting such travel, a tool holder driven by the driven shaft and slidable along such shaft for tool feed purposes, a weight and means mounting such weight on the driven shaft for centrifugal outward actuation, a member slidable along said shaft in the direction of tool feed responsive to outward actuation of the weight, a spring resisting the specified sliding of said member, a tool feeding connection from the slidable member to the tool holder, and a brake comprising a brake shoe fixed on the driven shaft, said shoe being subjected to a thrust applied to the driven shaft by the flexible coupling to normally apply the brake.

5. In a feed head for rotary tools, the combination with a driven shaft, drive means for said shaft, and a tool holder rotative with and slidable along said shaft to feed a tool forwardly to a piece of Work, a weight and means mounting the weight on the shaft for centrifugal outward actuation, a member rearward of and engaging the weight and fixed onvthe shaft, a member forward of and engaging the weight and slidable on the shaft responsive to outward actuation of the weight, a tool feeding connection from said sliding member to the tool holder, of a brake comprising a stationary member and a brake shoe fixed on said shaft to engage the stationary member, the shaft having a longitudinal play relative to its drive means to afford the necessary travel of the brake shoe, means yieldably exerting pressure on the shaft to urge the brake shoe into restraining engagement with the stationary mem-ber, the tool holder, sliding member, weights, and fixed .member jointly forming a means or transmitting to the shaft a retraction imposed on the tool by its engagement with Work, whereby the brake is released upon such engagement.

EDWARD J. LYNCH.

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