US2741340A

US2741340A - Abrasive brake shoe

Info

Publication number: US2741340A
Application number: US456273A
Authority: US
Inventors: George K Newell
Original assignee: Westinghouse Air Brake Co
Current assignee: Westinghouse Air Brake Co
Priority date: 1954-09-15
Filing date: 1954-09-15
Publication date: 1956-04-10
Anticipated expiration: 1973-04-10

Description

A ril 10, 1956 G. K. NEWELL. 2,741,340

ABRASIVE BRAKE SHOE Filed Sept. 15, 1954 INVENTOR, @801 eKN BY AT TORNEY United States Patent ABRASIVE BRAKE snon George K. Newell, Pitcairn, Pa., ass ignor to Westinghouse Air Brake Company, Wilmerding, Pa., a corporation of Pennsylvania Application September 15, 1954, Serial No. 456,273.

2 Claims. (Cl. 188-256) This invention relates to improvements in brake shoes and more particularly to the type adapted for use with wheels of railroad cars and the like.

In the railway brake art, considerable progress has been made in developing brake shoes of composition materials which not only provide longer shoe life but also cause a minimum of wear of the railway car wheel, both of which qualities are essential characteristics of good brake shoes. It has been found, however, that composition brake shoes of non-wheel-wearing material are unable to effect rapid and satisfactory burnishing of the tread surface of the wheel, which surface is normally somewhat pitted and scarred, especially in the case of new wheels, which in addition to normal pits and scars also have tool marks; and because of such imperfections on the tread surface, the brake shoes will wear at an excessive rate until said surface has been burnished.

It has heretofore been proposed to provide a brake shoe comprising segmental blocks of iron or steel separated by recesses in which are accommodated blocks of Carborundum, the thickness of these abrasive blocks being substantially equal to the thickness of the metallic blocks. A brake shoe of this type, however, is not only relatively expensive to manufacture but excessive wear of the wheel results because the abrasive is effective during substantially the full life of the brake shoe.

The principal object of this invention is therefore to provide an improved composition brake shoe embodying abrasive means adapted to burnish and condition the brake-shoe-engageable surface of a wheel during only a limited period of use following initial installation.

Another object is to provide an improved composition brake shoe which is especially adapted to burnish and condition new railway car wheels, it being common practice to install a new set of brake shoes when such wheels are installed.

According to the foregoing objects, the improved brake shoe comprises a relatively thin portion or layer which comprises abrasive material and is preferably formed integrally with the non-abrasive. composition material, such as during molding of the brake shoe. This portion or layer may define a part or all of the arcuate, wheelengaging surface of the improved brake shoe, when in a new or unused state, such that after initial installation such layer or portion will be progressively worn away during successive contacts with the wheel until, at some time shortly after the wheel has been properly conditioned or burnished, only pure composition brake material will remain, for thereafter engaging the wheel and thus preventing undesired wear of the wheel.

Other objects and advantages will become apparent from the following description of the invention and from the accompanying drawing, wherein Fig. 1 is a side elevational view, partly in section, of a four-segment type brake shoe embodying the invention; and Fig. 2 is a side elevational view, partly in section, of a two-segment type brake shoe showing another embodiment of the invention.

2,741,340 Patented Apr. 10, 1955 ice Description As shown in Fig. 1 of the drawing, the improved brake shoe may, for sake of illustration, comprise the usual metallic, generally convex-concave backing plate 1 to the concave surface of which is suitably secured, as by molding, a body Z comprising four segments each preferably formed integrally with a common backing portion that is adjacent to and co-extensive with the backing plate 1. These segments have, at the opposite sides thereof from the backing portion,

respective surfaces

3, 4, 5, 6, for engaging the tread of a wheel that is to be braked; the surfaces 3 and 6 being those provided on the outer segments, that is, those which are farthest from each other.

The backing plate 1 is provided with the usual U-shaped lug or eyelet 7, which is preferably formed integrally with said plate at the opposite side thereof from the body 2 and centrally disposed adjacent the convex surface of said plate; said eyelet being provided for accommodating the usual key (not shown) whereby the brake shoe is connected to the usual brake head (not shown).

According to the first embodiment of the invention, the body 2 is composed solely of composition brake material except for portions or layers, designated by the reference numerals '8, 9, in which are contained abrasive material, such as silicon carbide particles, of preselected density for conditioning and burnishing the wheel as it is worn off or expended by frictional contact with the rotating wheel during an application of brakes; said portions preferably being formed integrally with body 2, as by molding, at the time said body is molded to the backing plate 1, as hereinafter explained. The abrasive portions 8, 9 are adjacent to, and in part define, the wheel-engaging surfaces 3, 6, respectively; and said surfaces are preferably in arcuate alignment with the wheel-

engaging surfaces

4, 5, such that when the improved brake shoe is first installed for use, all of said

surfaces

3, 4, 5, 6, will engage the wheel during the initial application of brakes. 1

A multiple-segment type body, such as the body 2, has been found preferable in tests because the

surfaces

3, 4, 5, 6 are separated by cavities 1t), 11, 12 respectively, which cavities not only permit abrasive material to be thrown free of the Wheel after wear from the surfaces 3, 6 but also impart greater flexibility to the brake shoe and facilitate cooling of the brake shoe.

In use, the abrasive material of portions 8, 9, will burnish the wheel and in so doing will be worn olf or expended or become dislodged without affecting the braking force applied to the wheel through the medium of the brake shoe. During successive applications of brakes, the wheel will gradually become conditioned and the portions 8, 9 will become progressively reduced in thickness. The portions 8, 9 are therefore preferably no thicker than necessary to assure proper conditioning of a wheel, so that when the wheel has been properly conditioned, the abrasive material of said portions will have been completely expended, and only non-abrasive composition brake material will thereafter engage the wheel for preventing undesired wear thereof during the remaining life of the brake shoe. I have found that best results are obtained when the thickness of the abrasive portions 8, 9 is about /s" to A.

In the preferred embodiment of the invention, as shown in Fig. l of the drawing, in which only the wheel-engaging surfaces 3, 6 of the brake shoe contain abrasive material, the rate of expenditure of such abrasive material will be desirably retarded due to the long-wearing characteristics of the composition brake material of which the

Wheelengaging surfaces

4, 5 are composed. With the rate of expenditure of abrasive material thus limited to the rate at which the pure composition brake material is worn from the

surfaces

4, 5, the abrasive material of surfaces t 3, 6 will effect what might be compared to a light sanding of the wheel for preventing undue wear of the wheel during conditioning. In other words, by so engaging the wheel, the wear-resistant surfaces .4, act in the nature of a stop for retarding and controlling the rate of wear of the abrasive surfaces 3, 6 which latter surfaces :might otherwise, under action of a heavy braking .force, cause undue wear of the'wheei.

According to the second embodiment of the invention, as shown in Fig. 2 of the drawing, a body 13 may, for sake of illustration, comprisetwo segments which are separated by a cavity 14 and have portions'lS, 16 that comprise abrasive material and are in part defined by arcuate, wheel-

engaging surfaces

17, 18, respectively. All parts which are identical With those shown in Fig. 1 of the drawing are designated by like reference numerals. The structure, as thus shown in Fig. 2 of the drawing, is especially adapted for usewith new wheels where more rapid burnishing and conditioning is desired in order to remove the usual ridges and tool marks from such wheels. Brake shoes of this type could be conveniently installed when :a new wheel is installed, .it being the common practiee to-install a new set of brake shoes at such time.

It will be noted that the abrasive material of the portions 15, 16 will become expended at a more rapid rate and thus more rapidly grind the ridges and tool marks ofi thetread surface of the new wheel, than will occur. with the type of brake shoe shown in Fig. 1 of the drawing and heretofore described. These abrasive portions 15, .16 are therefore preferably only thick enough to accomplish the desired conditioning of a new wheel, so that by the time the wheel has become reconditioned, the abrasive be readily manufactured at practically no increase in cost over those presently made. For sake of illustration, a mixture of abrasive material and composition brake material, previously prepared into a batch, could be spread at the bottom of the mold, either in the outer segments only or in all "segments, according to whether the .first or second embodiment of the invention is to be practiced; and then composition brake material devoid of abrasive material would be used to fill the rest of the mold. During application of 'heat and pressure to the mold for .moldingthe backing plate 1 to the body 2 or '13, inthe usual 7 manner, the "abrasive portions 8, 9 or 15,16, as .thecase may he, will be formed andmolded integrally with the body? orf13, respectively.

Summary It will now be seen that the improved brake shoe, in

either of its embodiments will condition the wheel for a restricted period of use following initial installation. With the first embodiment, in which only a part of the entire wheel-engaging surface initially contains abrasive material, a relatively light abrasive action will be effected over a relatively long period, and then when the abrasive material is completely expended, composition brake material devoid of such abrasive material will work upon a' Having now described the invention, what I. claim new and desire to secure by Letters Patent, is:

'1. A brake shoe comprising a body having aplurality of segments joined to a common backing portion having a generally convex surface at the side thereof opposite to said segments, said segments having respective arcuate surfaces adapted for engagement with a rotatable member to be braked, the segments adjacent opposite arcuatctends of said body comprising abrasive material for a depth .of a fraction of an inch as measured from their respective arcuate surfaces toward said convex surface, and the remainder of said body being composed of a material other than said abrasive material.

2. A :brake shoe body comprising a backing portion having a generally convex surface and a plurality of segments joined to said backingportion at :the opposite side thereof from said convex surface, said segments having respective-surfaces which are adapted for engagement with a rotatable -member to be braked and are disposed in arcuate alignment with each other and opposite fto :sa'id backingportion, the outer segments farthest from .each other each comprising a portion containing abrasive material, .the latter portion being a fractionof the :total thickness of the respective segment as measured from the corresponding arcuate surface to said backing portion and the segments intermediate said outer segments and remaining part of said outer segments being composed solely .of composition brake material.

References Cited intthe file of this patent UNITED STATES BAZIIENTS 1,1674937 Sayre Jan. 11,1916 1,369,497 Thompson Feb. 22, 1921 1,547,190 Zabinski July 2 ,1925 2,261,191 Matthews May '21 I940 aifteen n.

Claims

1. A BRAKE SHOE COMPRISING A BODY HAVING A PLURALITY OF SEGMENTS JOINED TO A COMMON BACKING PORTION HAVING A GENERALLY CONVEX SURFACE AT THE SIDE THEREOF OPPOSITE TO SAID SEGMENTS, SAID SEGMENTS HAVING RESPECTIVE ARCUATE SURFACES ADAPTED FOR ENGAGEMENT WITH A ROTATABLE MEMBER TO BE BRAKED, THE SEGMENTS ADJACENT OPPOSITE ARCUATE ENDS OF SAID BODY COMPRISING ABRASIVE MATERIAL FOR A DEPTH OF A FRACTION OF AN INCH AS MEASURED FROM THEIR RESPECTIVE ARCUATE SURFACES TOWARD SAID CONVEX SURFACE, AND THE REMAINDER OF SAID BODY BEING COMPOSED OF A MATERIAL OTHER THAN SAID ABRASIVE MATERIAL.