US1750611A - Internal brake - Google Patents

Description

March l1, 1930. L. BLACKMOR E 1,750,611

INTERNAL BRAKE Filed Nov. 340, 192'? Patented Mar. ll, 1930 .UNITED STATES PATENT oFFlcE LLOYD BLACHIORE, OF HIGHLAND PARK, MICHIGAN, ASSIGNOR TO GENERAL MOTORS CORPORATION, OF DETROIT, MICHIGAN, A CORPORATION OF DELAWARE INTERNAL :BRAKE vApplication :Bled November 80, 1927. Serial No. 236,786.

This invention relates yto brakes. The invention is an improvement in rigid shoe brakes particularly intended for use on vehicles but useful in many other relations, in

fact in any relation where a drum may be carried by a member, the rotation of which is to be checked.

The invention aims to provide means Ato `actuate such a brake .which shall be automatically adjustable to `accommodate for selfactuation in either direction of rotation of the rotatin member.

Anot er object is to provide a novel brake anchor which shall opeiate in conjunction with the cam to produce effective frictional en agement between the drum and the shoes.

s another object the invention provides a shoe construction which isdesigned to offset the disadvantages consequent upon unequal heat effects which are present in brake shoes of usual construction.

Other objects and advantages will be understood from an examination of the accompanying drawing and a reading of the follow1ng specification.

The drawing illustrates what is now regarded as a preferred embodiment of the invention, being, however, illustrative in character only, it being understood that changes a0 may be made in structural details.

Figure 1 of the drawing is a view in side elevation of the shoe brake, the drum being y shown in section.

Figure 2 is a view substantially on line 2-2 of Figure 1.

Referring by reference characters to the drawing, numeral 3 represents the drum. It will be understood that the drum is to be attached to the part, the rotation of which is to be checked or stop ed. ln vehicles such a drum be and prefe 'ably is carried by the wheels. Adjacent the drum and preferably closing the open end, as is usual in vehicle practice, is a backing plate 5. In the case of the front wheel backing plate 5 will be carried` by the wheel knuckle while in the case of the rear wheel the corresponding plate will be carried by the axle housing.

The backing plate serves to anchor the brake shoes. Secured to the backing plate,

. sired one `shoe may be of greater length than -the other. In the drawing, she 23 is shown for the purpose of a shoe anchor, is an anchor bracket 7, its point of attachment bein near the periphery of the backing plate an at a point such as to secure the desired position for the brake cam or other actuating means. The anchor bracket may be secured to the backin plate by suitable fastening means 9, of whic three are shown in the drawing. Pivoted on a '5 pivot pin 11 carried by the anchor bracket are two links 13 and 15. 'Laterally disposed on 60 the anchor bracket 7 are upstanding lugs or stops 17 and 19, the purpose of these stops to be later explained.

Within the enclosed space defined by the drum and backing plate are lthe brake shoes 21 and 23. These shoes are preferably of channel shape in cross section and extend longitudinally in the form of an arc of substantially the same radius as that of the drum. Their length is such that the two shoes when applied to the drum engage almost the entire inner periphery. By this means there is insured a maximum area of frictional engagement between the shoes and the drum. If deas extending for somewhatr morel than the ysemi-circumference, and shoe 2l is less than a semi-circumference. This arrangement may be adopted to secure greater self-actuation in one^direction of rotation of the drum than in the other. In the case of vehicles it will obviously be arranged so that the self-actuation is greater for forward driving, thereby permitting less pedal movement. In the drawing it will be assumed that clockwise rotation of the drum corresponds to forward driving. Shoe 23 being relatively long, when engaged with the drum, tends to rotateclockwise about its anchor under the 'iniiuence of drum engagement and this force supplements the force exerted mechanically by the cam or other operating means. Shoe 21 similarly becomes self actuating upon a reverse movement of the wheel and drum. Since shoe 21 is relatively shorter it permits the use of a relatively longer shoe 23 and thereby facilitates the brake operationfor forward driving. ,It will be understood that any other desired ratio between the two shoes may be adopted with the resulting change in self actuation.

With further reference to the channel shaped shoes, it will be seen that the web of the shoe carries brake lining represented on the drawing by numeral 25. It will also be observed that the radial 'de th of the channel flanges is reduced throng the major part of the channel member as indicated by numeral 27. The radial depth is increased toward each end of the shoes. Within the channel adjacent the anchor end is riveted a plate 31 bent over to form an eye to carry pivot pin 35. It will be understood that this construction is adopted at that end of each shoe adjacent the anchor pin.- Links 13 and 15 are'pivotally mounted on pins 35 so that in moving into drum contact the ends of the shoes move in arcs of short length about fixed pivot 11 as a center. The links 13 and 15 are of substantially L-shape, cross each other at the elbow of the L` and extend inwardly as shown at 13 and 15. These ends are held normally at their maximum movement of separation by a coil spring 37 between the said ends 13 and 15. Centering studs 39 may be used on each link to properly position the spring. The lugs or stops 17 and 19 limit the outward movement of the links under the action of spring 37 and therefore determine the released position of the shoes in the vicinity of the anchor.

Adjacent the actuating end of theshoes is a spring 41, the hooked ends of which engage pins 43 transversely positioned in the channels of the shoes. This s ring is to release the shoes from the drum. tops 45 may be provided with eccentric openings for adjustable rotation on'pins 47 mounted as usual in the backing plate to variably determine the brake release position of the shoes in the vicinity of the cam or other operatin means.

An important feature o the invention re` lates to the cam mounting. Instead of providing a simple rotatable support for the cam shaft 51 in the backing plate the cam shaft passes through a somewhat elongated opening 53 in said plate whereby the shaft with the cam may move transversely in a generally circumferential arc, thus permitting the cam to accommodate itself to the self-actuation eect of the drum on the shoes. Such movement of the cam has been heretofore provided by movably mounting the cam on its shaft or by journaling the cam shaft in a link mounted for swinging. The provision for floating the cam herein shown and described is extremely simple and avoids the additional swinging link. Each of the side flanges of each shoe adjacent the cam may be provided with .extensions 55 and 57, oneV outside. and one radially inward of the cam shaft. The extensions on one side of each shoe may lie in the plane of the side wall, and on the other side of the -shoe the extension may be outthe cam is positioned by the shoes themselves,

having spaced bearings adjacent opposite `side walls of the shoes between the upper and lower projections'55 and 57. The cam is therefore free to fioat so that the manual elfort of brake application is equally divided between the shoes and whereby full ad vantage may be taken of the well understood self-actuation inuence.

When the brake is applied the cam moves the" adjacent ends of the shoes against the band and through the tendency of the band to carry'the shoe around with it a certain degree of rotary movement about the pivot 1]. results against the resistance of spring 37.

This movement, however, has a radial component so that the' end` of the shoe carrying pin 35 is given a radial thrust toward the drum. It therefore follows that in the a plication of the brake a thrust of the bra e shoe towardthe drum is given at both ends of the shoe, thus rendering the action very powerful while preventing any tendency to lock. in the vicinity of the cam as frequently occurs in the case where the shoe is positively anchored, and more particularly when the lining near the anchor has become worn.

The reduced radial dimensions of the channel walls through the major part ofthe same andbetween the ends is an im ortant "feature of the invention. One isadvanta e commonly occurring is inherent in the rigid shoe type of brakea tendency of the shoe to become distorted, to curl and to shorten its radius with the result that a part of the shoe fails to contact with the drum resulting in `unequal wear of the lining near the anchor action and to give longer life to the lining.

I claim: 1. In a brake, a drum, bra-ke means to fricshown is effective to produce a better brake tionallyengage the drum, actuating means therefor, a rock shaft carrying said actuating means, means on the adjacent ends of said brake means to support said rock shaft.

2. In a brake, a drum, brake means to frictionally engage the drum, actuating means therefor, a rock shaft carrying said actuating means, means on both sides of the adjacent ends of said brake means to support said shaft.

3. In a brake, a drum, brake means to frictionally engage the drum, actuating means therefor, a rockshaft carrying said actuating means, bifurcated extensions on both sides of each of the adjacent ends of said brake means, each of said bifurcated extensions straddling and supporting said rock shaft at spaced positions.

4. The invention defined by claim 4, the extension on one side of each of said ends being outwardly bent and overlapping the matingi extension on the same side of the other en 5. In a brake, a drum, a backingplate having a slot, shoes in said drum, anchor means to anchor said'shoes to said backing plate. actuating means, a rock shaft rotatable and bodily movable in said slot, means on the ends of said shoes to support said rock shaft.

6. In a brake, a drum, brake shoes within said drum, a fixed plate, an anchor bracket on said fixed plate, a pivot pin on said anchor bracket, angular links rotatable on said pin outwardly extended and pivoted to said shoes, said links also'inwardly extended, a yielding means between said inward extensions, and stops on said anchor bracket to engage said shoes under the infiuence of said spring when the brake is released.

7. In a brake, a drum, opposed shoes, actuating means therefor, yielding means between said shoes adjacent said actuating means to release said shoes, adjustable stop means for one or more shoes adjacent the actuating means, anchor means for said shoes, other releasing means for said shoes adjacent said anchor, and other stops adjacent said anchor to limit the release action of said last named spring.

8. In a brake, a drum, a fixed plate, a fixed anchor pin carried by the plate, crossed levers rotatably carried by the anchor pin, shoes in said drum, said levers at their outer ends pivoted to said shoes, spring means between the inner ends of said levers and stops to limit the movement of said levers under the influence of said spring to determine the released position of the shoes adjacent the anchor.

9. In a brake, a drum, a plurality of shoes to frictionally engage the drum, actuating means associated with one pair ofadjacent ends of said shoes, an anchor at the other pair of adjacent ends, said anchor comprising a pair of links rotatable upon a fixed pivot l0. Ina brake, a. xed plate, a drum, a plurality of shoes floating in said drum, means to expand adjacent ends of said shoes against the drum, a plurality of links pivoted to a common point on the fixed plate and to the othenadjacent ends of the shoes, said links positioned to give a radial component to the motion of the adjacent ends of the shoes whereby both ends of said shoes are thrust against the drum in the act of applying the brake, said links being inwardly extended beyond their pivotal connection with the fixed plate, yielding means to actuate said links and release the anchored ends of said shoes, andstops to be engaged by said links under the influence of said yielding means.

In testimony whereof I affix my signature.

LLOYD BLACKMORE.

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