US2849092A - Air cooled brake shoe - Google Patents

Description

1958 R. w. FOSTER 2,849,092

' AIR COOLED BRAKE SHOE Filed Sept. 9, 1954 Fg'yrl I 712/97? for I069"! M faster estates Patented Aug. 26, T1958 AIR COOLED BRAKE SHOE Robert W. Foster, Sullivan, Ind., assignor of eight percent to Robert W. Matthews, fourteen percent to Ralph Molden, four percent to John Helmbold, three and oneeiglrth percent to Jack Anderson, five percent to Alden Fields, two and one-half percent to Harold Funcannon, one and nine-sixteenths percent to Carl Engle, one and one-half percent to Henry Branstetter, one percent to livan Marts, and one and nine-sixteenths percent to Gilbert Snyder Application September 9, 1954, Serial No. 454,904 Claims. (Cl. 188-264) This invention resides in the field of brake shoes and the like and is an improved air-cooled brake shoe. More specifically, my brake shoe is provided with a new and novel means for removing or expelling the heat contained in the body of the brake shoe which is built up due to its frictional engagement with a Wheel.

A primary object of my invention is a brake shoe adapted for use with railroad cars and the like, although it is not limited in this respect, which has a new and improved means for removing or extracting the frictional heat accumulated in the body of the shoe.

Another object of my invention is a brake shoe of the above type with a plurality of passages or air channels disposed through the body of the shoe in such a manner that a positive pressure will exist at the inlet end of the passages and a negative pressure or slight vacuum will exist at the outlet end of the passages regardless of the direction of rotation of the wheel relative to the shoe.

Another object of my invention is a brake shoe of the above type in which a pressure differential always exists across the passages when it is in use.

Another object of my invention is a new and improved brake shoe with air passages through it constructed and adapted to remove the majority of the heat collected in the center core of the shoe.

Other objects will appear from time to time in the ensuing specification and drawings in which:

Figure 1 is a plan view of my new and improved brake shoe;

Figure 2 is a side view of the shoe shown in Figure 1;

Figure 3 is a sectional view taken along line 33 of Figure 2; and

Figure 4 is a sectional view similar to Figure 3 but showing a modified form of my invention.

In Figures 1 and 2 I have shown generally the outline and configuration of a conventional brake shoe having a brake shoe body indicated generally at which is arcuate in configuration and has a wheel engaging arcuate surface 12. The shoe has a pair of opposed projecting lugs 14 disposed on its upper surface 16 which are adapted to receive the ends of a conventional brake hangar and supporting mechanism, not shown. A suitable clamp bracket 18 is positioned in the center of the shoe for supporting the shoe next to the wheel.

The body of the brake shoe is cast around an arcuate top plate 20 which is enclosed by the body of the shoe. The hangar bracket 18 may project downwardly and interlock with this top plate in any suitable manner.

The body of the shoe has a pair of substantially flat longitudinal sides 22. A plurality of diagonally disposed channels 24 are formed in the body of the shoe and extend from one side to the other with openings 26 and 28 on the side surfaces. As shown in Figure 2, the channels are disposed approximately midway between the top and bottom surfaces although, of course, this could be varied slightly depending upon design conditions. The channels are approximately parallel to each other, and each one is provided with a reduced cross section portion or venturi 30 approximately at its midpoint.

In Figure 4 I have shown a modified form of the invention in which the channels through the body of the shoe are arranged in pairs in a crossed or intersecting manner. For example, the two channels 32 and 34 at the left end of Figure 4 intersect at 36. Each channel reduces down to a venturi, or reduced cross section, and as shown in Figure 4, this is the point of intersection. While I have only shown three pairs of channels in Figure 4, it should be understood, of course, that more or less can be used as desired.

The use, operation and function of my invention are as follows:

One of the major problems in brake shoes is properly cooling the shoes. Many methods and apparatus have been suggested which have taken the form of various types of air scoops, fluid circulating systems to carry away the excess heat or different types of face groovings or finned surfaces. Due to its frictional contact with a wheel, a brake shoe will accumulate a large quantity of heat. The shoe will get hot and the surface of the shoe along the central core has been known to crystallize and crack. This materially reduces the life of the shoe and it is very important that the shoe be kept as cool as possible at all times to extend its life.

I have shown what I consider a conventional brake shoe body and I provide diagonally disposed channels through the body of the shoe approximately midway between the top and bottom surfaces, although, of course, this can be varied. The channels have openings on each side. Air will circulate through these channels and will remove a substantial amount of the heat that is accumulated in the body of the shoe due to its frictional contact with a wheel. The diagonal disposition of the channels is important. A rapidly rotating wheel collects a close, rapidly moving film of air which hugs the wheel.

This air will flow over the body of the shoe and will cool the outside. In effect, this results in a stream of air flowing along each of the side surfaces of the shoe. Assume for the moment that this stream of air is flowing from right to left in Figure 3, the openings 23 for the channel will be the inlet openings while file openings 26 will be the outlets. The air moving along the side surface by the inlet openings 28 increases the pressure at these openings and tends to force the air through the channels. At the same time, the air flowing along the other surface past the outlet openings 26 has a tendency to reduce the pressure at these openings and creates a partial vacuum or suction. Thus a decided pressure differential will be created across the channels. This materially increases the quantity and velocity of the air flowing through the channels.

If the direction of the wheel is reversed and the air flows from left to right in Figure 3, the openings 26 become the inlet openings. A positive or increased pressure will be created at the inlet 26. At the same time the air flowing past the openings 23 will create a partial vacuum and will tend to suck the air out of the channels. Thus the same pressure differential exists across the channel except that it is reversed.

It can therefore be seen that the diagonal disposition as shown in Figure 3 operates or functions equally well regardless of the direction of air flow. It should be understood, of course, that all of the channels could be disposed at approximately to the disposition shown in 3 Figure 3 and the function and operation would be the same.

Each channel is provided With a reduced cross section or venturi approximately midway between the ends. At this reduced cross section the velocity of the air will be increased to its maximum degree. It is well known that the rate of heat transfer to a moving fluid is greatest where the velocity is greatest. Therefore, heat transfer will be greatest approximately at the center or mid-point of the channels. Note in Figure 3 that the heat extraction due to this increased rate of heat transfer will be greatest in the center longitudinal plane of the shoe. This in reality is the plane of maximum heat accumulation, and it is therefore very desirable that the heat from this center plane or core of the shoe be dissipated as rapidly as possible. By the provision of the venturis or reduced cross sections, located approximately in the center longitudinal plane, the heat will be drawn out of the center core or central portion of the body of the shoe and the most dangerous area will be effectively cooled.

In Figure 4 the channels are arranged in groups or pairs of two disposed at approximately right angles so as to. intersect. In this species, the air will be taken in through each set of inlets and will intersect at the reduced venturi portion 36 and will exhaust through the outlet ends of the paired channels. The intersecting air at the venturis in addition to increasing its velocity by the reduced cross section will also provide substantial turbulence due to. the intersection of the two. channels. It is Well known that turbulence also increases the rate of heat transfer. Thus, an arrangement. of this nature: under certain circumstances. will. have advantages which. are not present in the Figure 3 species. It should be noted that fewer channels can be used due to the increased spacing of the paired channels and that only a small number of reduced cross sectioned portions can beprovided. Nevertheless the increased turbulence and increased heat transfer due to the turbulence may be of advantage in certain types of brake shoes. On the other hand, the total number of channels in Figure 3 will handle a. larger volume of air and in certain types of brake shoes this may be more important.

It should be understood that while I have shown the channels or air passages in each species as totally confined within the body of the shoe and disposed approximately midway between the top and bottom surfaces, the channels could be formed on the wheel contacting surface. Channels of this nature would be in effect closed channels when they engaged the wheel, and the same type of pressure difierential due to the moving air that hugs the wheel would be created as was set forth hereinabove with reference to Figures 3 and 4. A combination of channels disposed totally within the body of the shoe such as in Figure 2 and a few surface channels formed on the contacting surface 12 could also be used, if found desirable. In the Figure 4 species it is not absolutely necessary that the channels intersect. For example, they could be disposed one above the other. At the same time the pair channels could be more closely spaced as their ends would not intersect but could be made to overlap.

While I have shown and described the preferred form and one modification of my invention, it should be understood that numerous modifications, changes, substitutions and alterations can be made without departing from the inventions fundamental theme. I therefore wish that my invention be unrestricted except as by the appended claims.

I claim:

1. In a brake shoe, a. generally arcuate body portion having longitudinally extendingv side surfaces and an end surface adapted to conform generally to the surface of a wheel, a plurality of lateral passages extending through the body of the shoe with openings in the side surfaces, and a venturi in each such passage, all of the venturi being generally aligned longitudinally.

2. The structure of claim- 1 in which all of the lateral passages extend diagonally through the body of the shoe.

3. The structure of claim 1 in which the passages are within the body of the shoe.

4. The structure of claim 1 further characterized in that the passages are all substantially parallel.

5. The structure of. claim 1 further characterized in that the passages are grouped in pairs which intersect each other.

References Cited in the file of this patent UNITED STATES PATENTS 674,679 Gilman et al May 21, 1901 1,122,583 Gallagher Dec. 29, 1914 1,160,971 Bullock Nov. 16, 1915 1,974,905 Walker Sept. 25, 1934 2,406,067 Eurit Aug. 20, 1946 2,729,312 Foster Jan. 3, 1956 2,748,903 Foster June 5, 1956

Images