US1919542A - Brake - Google Patents

Description

July 25,1933. B, DICK 1,919,542

BRAKE Filed Dec. 2, 1927' v Inventor Patented July 25, 1933 a UNITED STATES PATENT OFFICE BURNS DICK, OF ST. LOUIS, MISSOURI, ASSIGN'OR TO WAGNER ELECTRIG CORPORATION,

OF ST. LOUIS, MISSOURI, CORPORATION OF BRAKE Application filed December 2, 1927. Serial No. 237,165.

My invention relates to an improvement in brakes and is herein shown as embodied in a vehicle brake of the internal shoe type. The object of my invention is to prevent, or at least postpone until after a long period of use, the tendency of brakes to squeak and chatter. In brakes of the internal shoe type herein described, and which embody brake shoes pivoted at one end and provided with a lining engaging a surrounding brake drum, the production of squeaks and chatters seems more likely to occur when the pressure between the brake lining and drum near the free end of the shoe exceeds the '1 pressure between the drum and the lining near the heel or pivoted end of the shoe.

Brakes of the type referred to are commonly initially so adjusted that there is a smaller clearance, in off position of the brake shoe, between thedrum and lining at the heel of the shoe than between the drum and the lining at, the toe of the shoe. This adjustment causes a heavier pressure to be applied at the heel of the lining than at the toe in application of the brake and prevents ways stop when the heel and toe clearances have become the same? but, apparently due to the flexibility of the drum and the brake shoe and supporting members and the frictional reaction between the drum'and toe of the shoe, excess pressure on the heel of the shoe may continue until the wear has gone to the poi'ntto where the off position clearance between the heel of the shoe and the drum is greater than the clearance at the toe of the shoe. The tendency to produce squeaks and chatters seems to begin when the clearances approach equality and to be emphasized when the heel clearance exceeds the toe clearance. One object of my invention is to provide means for preventing,

or at least substantially reducing squeaks and chatters in the type of brake above described.

The invention will be explained by reference to the accompanying drawing in which Figure 1 is an elevational View of a twoshoe internal brake of a type in which my invention can be usefully embodied; Figure 2 represents the face View of a shoe with a form of lining construction embodying my invention; and Figures 3 and 4 represent alternative forms of lining.

In Figure 1 the brake drum 1 cooperates with the brake linings carried by the pivotally mounted brake shoes 2.

{as above explained, the preferred initial ad uStment of the relation of the shoes to the drum is such as to have the clearance between the drum and lining at] the heel of the shoe less than the clearance between the drum and the lining at the toe portion in the off position of the shoe. One suitable initial adjustment is to have the first mentioned clearance five-thousandths of an inch and the latter ten-thousandths of an inch in a brake having the relative dimensions shown in Figure 1. Inaccordance with my invention I'prevent the operation of the brakes from changing relation of these clearances to a point where there is a tendency for the toe of the lining to snub or seize the brake drum and thus produce squeaks and chatters, by so constructing the lining as to give it susceptibility to more rapid wear at the toe than at the heel. This end may be accom lished in a number of ways. 11 Figure 2 have shown the lining made up of two sections, 3 and 4, section 3 on the toe portion of the shoe having more rapid wearing characteristics than the section 4 at the heelof the shoe, the wearing characteristics of the lining being of course determinable by methods or materials of manufacture. A similar result may be obtained by. the use of a liningof uniform characteristics throughout but reduced in a single piece of material if, by an suitable means, the heel portion of the lining be made harder or otherwise so constructed or treated as to have greater wear resisting characteristics than the'toe portion. I prefer that the frictional coeflicients of. the toe portions of linings used be the same as the remaining portion in order that total braking-effect may not be materially reduced in relation to shoe dimensions.

It will be understood that in the references'to off position clearances herein I have assumed relations of pivots, centers and actuatinv meansshown in Figure 1. Change of these positions would change 'actual clearance differences and as to any particular construction the adjusted actual clearances are preferably to be such thatin brake application the heel of the lining contacts with the drum-before the toe of the.

lining comes into contact. This relation is referred to 1n the clalms asa dliference 1nv effective clearance between the drum and cal conditions of pressure, drum surface and the like, rather than to the relative amount of wear actually occurring in the respective parts under use in a brake.

It will be clear that when brake linings are formed in accordance with my invention the susceptibility to more rapidwearing of the lining'at the toe than at the heel will prevent, or at least delay for a long time, such change in effective clearance as will result in lower pressures between the heel of the lining and the drum than between the toe of the lining and the drum and thus prevent the seizing action of the toe on the drum which results in squeaks and chatters. It will be understood that I do not bind or limit myself to any theory or b any statement herein of causes of squeaking in brakes. I have definitely ascertained that with the arrangement herein described, em-

ploying a lining substantially as shown in Figure 4, the object of my invention is accomplished and variations in the clearance adjustments and other features herein described as preferred may also produce satisfactory results. I therefore do not intend that the scope of my invention be limited except as defined by thev appended claims.

Having fully described my invention, what I claim as new and desire to secure by Letters Patent of the United States is:

1. In braking apparatus, a brake shoe pivoted at one end and having an arcuate surface, and a brake lining secured to said surface, the part of the lining nearest the pivoted end of the shoe having less susceptibilit to wear than the part furthest remove therefrom.

2. In braking apparatus, the combination with a brake drum, of a brake lining whose entire width is adapted to cooperate with the drum, said lining having greater susceptibility to wear at one end of its effective braking surface than at the other end.

' o. In braking apparatus, the combination with a brake drum, of a brake lining whose entire width is adapted to cooperate with the drum, said lining having substantially uniform frictional coeflicient throughout its braking surface but having greater susceptibility to wear on one part of said surface than on the other.

4. In braking apparatus, the combination with a brake drum, of a brake lining whose entire width is adapted to cooperate with the drum, said lining having less braking surface per unit of length at one part than at another.

5. In braking apparatus, the combination with a brake drum, of a brake lining whose entire width is adapted to cooperate with the drum, said lining being of uniformmaterial throughout but having one end of its braking surface narrower than the other end.

6. In braking apparatus, the combination with a brake drum, of a brake lining whose entire width is adapted to cooperate with the drum, said lining comprising two sections in end to end relation, one of which has a other.

7. A brake shoe for vehicle wheel brakes comprising a body having a brake lining supporting surface, and means for pressing said lining against a cooperating brake member with a force per unit of length of said brake lining varying substantially in accordance with the area of said brake lining per unit of len th.

8. In a vehicle eel brake having an annular brake drum, brake lining for engagement' with-the drum, said lining increasing in effective width from one end toward theother, and means for pressing said lining against said brake drum, said means exerting a force on said lining varying from end.

to end thereof substantlalilfy in proportion to the variation in the e ective wldth of said lining.

9. In a vehicle wheel brake having a brake drum, a brake shoe comprising an arcuate body member provided with a brake lining.

supporting surface and brake linin fixed to said surface for engagement wlth the brake drum, said lining increasing in efiecgreater susceptibility to wear vthan the tive width from one end thereof toward the other, and meansfor exerting a force on said lining varying from end to end thereof substantially in proportion to the variation in 5 the effective width of said lining.

10. In a vehicle wheel brake having a brake drum, a brake shoe body for disposition within the brake drum comprising a body having a surface substantially concentrio with one wall of the drum, and a brake lining secured to the body for engagement with the drum, said lining increasing in effective width from one end thereof toward the other, and means for pressing said lining against said drum by exerting a greater force on one end of said lining than on the other end of said lining.

11. In a vehicle wheel brake having a brake drum, a brake shoe comprising a body 2 member and a brake lining carried by the body member for engagement with the drum when the body is moved, said lining being greater in effective width at one end than at the other, and means for pressing said 5 lining against said drum by exerting a greater force on the wider end of said lining than on the narrower end of said lining.

12. In a vehicle wheel brake having a brake drum, a brake shoe comprising a body 2 member and a brake lining carried by the body member for engagement with the drum when the body is moved, said lining being greater in surface area per unit of length at the heel than at the toe portion thereof, 5 and means for pressing said lining against said drum by exerting a greater force on the heel of said .lining than on the toe portion thereof.

13. A brake shoe for internally expanding vehicle wheel brakes comprising a rigid arcuate body, means for pivotally mounting the body at one end thereof, a brake lining supported upon the body and extending substantially throughout the length thereof, said brake lining being substantially greater in surface area per unit of length at that portion of the body nearer the pivotally mounted end than at the free end.

14. In a vehicle wheel brake having a brake drum, a brake lining for engagement with the drum, said lining increasing in effective width from one end toward the other in a degree determinable by circumferential length of the lining, and means for pressing said lining against said drum with a force substantially proportional at all points along the length of said lining to the efiective width of said lining at said points.

' 15. A brake lining having agreater susceptibility to wear on onepart ofits efiective braking surface than on another, and means for forcing parts .of said lining against a brake member inversely proportional to the susceptibility to wear of said parts.

16. A brake lining having substantiallyc uniform frictional coefficient throughout its braking surface but having greater susceptibility to wear on one part of said surface than on another, and means for exerting different degrees of force on difierent parts ofsaid lining.

17. A brake lining having less braking surface per unit of length at one part than at another, and means for applying force to said lining, said force varying per unit of length substantially in accordance with the corresponding braking surface provided by said lining.

18. A brake shoe lining of uniform material throughout but having the toe portion of its braking surface narrower than the heel portion, and means for applying greater force to sa id.heel portion than said toe portion.

19. A brake member providing a braking surface having a dimension of length and a dimension of width,means for pressing the braking surface against a cooperating brake member with a force varying in amount along one of said dimensions, the other dimension of. said braking surface varying in effective extent substantially proportionally to the variation in said force to maintain a substantially equal unit pressure over the entire braking surface.

20. A brake member providing a braking surface having length and width, means for pressing the braking surface against a cooperating brake member with a force varying in amount along the length of said surface, said surface varying in efi'ective portions of said shoe and a frictional working surface of minimum area at the free portions of said shoe.

23. In a brake apparatus, a rotatable member, and means normally bearing against said'rotatable member with difierent force amplitudes at spaced locations during actuation of said apparatus and including a brake lining element 'having a frictional working surface of maximum area at the.location of maximum force amplitude and a frictional workin at the location 0 plitude.

the minimum force amsurface of minimum area 24. In a brake apparatus, a rotatable member, and means normally bearing against said rotatable member with different force amplitudes at spaced locations during actuation of said apparatus andincluding a brake lining element havin a fixed base portion and a protrudin frictional working surface of varying widt ,the maximum width of said surface being located at the region of maximum force and the minimum width of said surface being located at the region of minimum force.

25. In a brake apparatus, a rotatable member, and means normally bearing against said rotatable member with different force amplitudes at spaced locations during actuation of said apparatus and including a brake lining element having a frictional said apparatus and including a brake lining -27. In brake apparatus, a brake drum, a

brake shoe, means normally urging successive portions of said brake shoe toward said drum with different force amplitudes at spaced locations during operation of said apparatus, and a brake lining on said brake shoe, the area of successive portions .of the frictional surface of said linin being substantially proportional to the Iorce amplitudes at the corresponding portions of said brake shoe.

28. In brake apparatus,a brake drum, a self energizing brake band normally urged toward said drum with different force amplitudes at spaced locations during operation of said apparatus, and a brake lining on said band, the area of successive portions of the frictional surface 'of said lining being substantially proportional to the force amplitudes at the corresponding portions of said brake band. a

' BURNS DICK.

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