US1921836A - Brake shoe manufacture - Google Patents

Description

Aug. 8, 1933. R B PGUE 1,921,836

BRAKE SHOE MANUFACTURE Filed Jan. 4, 1952 Invenor: 5- C@ s 5f. 2M

Patented Aug. 8, 1933 UNITED STATES BRAKE SHQE MANUFACTURE Robert B. Pogue, @ra-nge, N. J., assigner to The American Brake Shoe and Foundry Company, Viilmlngton, Del., a Qorporation of Delaware Application January 4, 1932. Serial No. 584,740

i1 claims. (C1. 18s-258) This invention relates to that class of composite brake shoes in which reenforces of some kind are embedded in the cast iron body during the casting operation.

Heretofore it has been the practice to embed a ductile metal reenforce, commonly called a steel back, in the back of the cast iron body of a shoe to hold the parts of the body together in case of fracture so that the shoe may continue in service. The backs comprise rods, bars or plates and the plates have been per orated, slotted or cut out in a variety of skeleton forms. lt `has been proposed also to make the backs of expanded -`etal and other mesh material. It has also been the practice to provide reenforces such as bundles of expanded metal which are placed in the mold and embedded in the cast iron body of the shoe to hold the parts of the body together in case of fracture so that the shoe may continue in service and for other purposes, and sometimes these bundles are arranged so that the expanded metal vextends to the back of the body. These recnforces have been used separately and they have been used together, and in many different forms. The reenforces have been lightly coated 'f ith refractory material by dipping them in oil and allowing them to drain and then dipping the reenforces in silica hour or other such refractory material. Suicient silica hour adheres to the oiled surface of the reenforce to form a light coating which has been sufficient under the general conditions of manufacture to protect the reenforce from burning and losing its natural physical characteristics during the casting operation. The reeniorce is arranged in the mold and the hot metal to form the body is then poured into the mold. If the reenforce is not protected, it may burn or carb-onine under the heat of the hot metal and partially unite with the cast iron, making the reenforce brittle so that it is liable to break when the shoe fractures and at the point of fracture. When the reenforce is protected, it does not become united in this way with the cast iron body but it is firmly held by the cast iron body in intimate contact therewith throughout its length and under this condition it will break at the fracture in the body before, and sometimes long before, the body is worn out. This is due to the fact that the area of the reenforce which is freed by the fracture from intimate contact with the cast iron of the body is concentrated at the fracture and does not extend any appreciable distance into the body away from the fracture. The shoe is arcuate in shape and is ordinarily suspended in substantially upright 5 position in service, and therefore the vibrations to which the shoe is subjected in service will affect only that part of the reenforce which is freed from intimate contact with the body at the fracture. The reenforce breaks because of fatigue of metal which causes crystallization, and this fatigue is the result of at least four major conditions,-compression, tension, bending and vibration of the reenforce. Compression, tension and bending resultvfrom brake application. Bending also results from impact of the shoe against the wheel when the brake rigging is caused to swing which mostly occurs in switching service but also occurs in train operation. Vibration occurs in the loose end of the shoe Whenever the car is in motion and this vibration varies in intensity according to track conditions and is transmitted to the reenforce.' lThe compression, tension, bending and vibration strainsare concentrated in the reenforce at the fracture of the body if the reenforce is rigidly held in the body at the fracture and under these conditions the reenforce will break relatively quickly. The reenforce Within the body of the shoe Will break more quickly than a reenforce in the back of the shoe and this is especially true if the reenforce Within the body is a bundle of expanded metal. The body of the shoe will break rst, then the reenforce Within the body of the shoe will break, and, finally, if the shoe is provided with a reenforce back, the reenforce back will break. If a part of the shoe then falls away, as frequently happens, the efficiency and service of the shoe will be reduced and the detached part may lodge in a frog or a switch and cause derailment of a train or bounceA off of the track and cause injury to person and damage to property. y

My invention has for its object to control these causes of breaking in the reenforce or reenforces and to distribute the effect thereof over a considerable area of the reenforce so that the shoe will have a chance to Wear out in service before any part becomes detached. I have found that if the reenforce or reenforces are not united with and are not in intimate contact with the body of the shoe, the effect of vibration and braking strains is relieved to the extent that breaking of the reenforce is delayed, and this delay is in direct proportion to the length of the reenforce over which the vibration and braking strains are distributed, and from this I have determined that it is not desirable to hold the reenforce or reenforces rigid in the body at any point. Inl accomplishing this result, I treat the reenforces in a novel manner preparatory to embedment in the body so that they will be free from intimate contact with the body throughout their length. I do not mean by this that the reenforce should be loose so that it may rattle in the body or so that it may have any relative movement in the body When the shoe is at rest. rIhe conformation of the reenforce and the body is such that, even when the reenforce is not in intimate contact With the body as it has been in previous manufacture, it will be anchored in place suiiiciently to prevent rattling or relative movement or such a degree of looseness as would be indicated thereby.

In the accompanying drawing I have illustrated the invention in a plain car shoe in which Fig. l is a side View of the shoepartly broken away and in section.

Fig. 2 is a plan View of a ductile metal reenforce back.

Fig. 3 is a longitudinal sectional view of an expanded metal reenforce.

Fig. 4 is a sectional View on the line 1 -4 of Fig, 1 showing a shoe with a ductile metal reenforce back and an expanded metal reenforce.

The shoe selected for illustration comprises a cast iron body 5, a ductile metal reenforce back 6, a ductile metal lug strap 7, and a plurality of layers of expanded metal arranged in a bundie 8 and forming a reenforce which is embedded in the body between the wearing face and the back and beneath the reenforce back 6. The body and the reenforce back and the reenforce 8 may be made in any desired form and of any suitable material and embedded in any type of brake shoe for which they are or may be adapted. The shoe illustrated is provided with end lugs 9 as an integral part of the body and the metal of the lugs is anchored over the ends of the reenforce back and through the slots 10 or other openings in the back with the main part of the body so that the reenforce back is securely held to the cast iron body of the shoe. The lug strap '7 is of well-known form and the body metal is run up in a known manner at the sides of the strap. The expanded metal reenforce isl wholly embedded in the body of this type of shoe but it may be exposed at the sides and at the wearing face of the body. The reenforce back may be omitted and sufficient additional layers of expanded metal may be provided in the bundle 8 to serve the purpose of a reenforce back, and the expanded metal may be exposed at the back of the shoe if desired.

According to my invention, the reenforces are not united with the cast iron body, nor are they so intimately in contact with the body as to make them rigidly and firmly held therein. I accomplish this by subjecting the reenfcrces to a preparatory treatment before placing them in the molds for the casting operation. This treatment may be accomplished by giving the reenforces a coating of oil and silica flour in or about the manner heretofore described but if this method is followed the coating must be considerably thicker to accomplish the objects of my invention. A preferred treatment, as disclosed inY my application Serial No. 584,741, filed concurrently herewith, consists in coating the reenforce with oil of high viscosity having low carbon content and lowV sulphur, such as black lubricating oil known to the trade as summer and winter black, then to give the reenforce a coating of refractory material, such as silica flour, by dippingl it in the flour or in any other suitable manner, and then to bake the coated reenforce in an oven such as a core oven. I have found it desirable to start with a temperature of about 350 F. and continue the baking step for about thirty minutes. By this method the reenforce is provided with a tough semi-enamel coating which adheres tightly to the reenforce and produces a highly satisfactory protection during the casting operation which insures that the reenforce will not become united with the cast iron body and will not be firmly and rigidly held in intimate Contact therewith in the completed shoe. I prefer to apply the coating according to either method throughout the area of the reenforce, and this may include, if desired, the lug strap. The purpose of the treatment of the reenforce is to prevent the cast iron of the body from uniting with the reenforce during the casting operation, or from having such intimate contact with the reenforce that the latter will be held rigidly and firmly in the body. The oil which forms the bond of the coating will burn out under the high heat of the molten metal durirrT the casting operation leaving the refractory material unbonded and in a disintegrated state and forming a cushion for the reenforce where it remains therea'oout but liable to sift out of the shoe through any available opening during movement of the shoe under the conditions of handling and service. It is the intention of the invention that the reenforce shall not be rigidly and irmly held in intimate contact with the body but that it shall be embedded in the body so that it will be free from intimate contact with the body but anchored therewith. I do not mean that the reenforce should be out of contact throughout its length with the body because there may be contact, and always will be in commercial manufacture, between the reenforce and the body but not that intimate Contact which has been characteristic of brake shoes heretofore made and which effects a firm and rigid embedment of the reenforce in the body. To comply with my invention and to secure to the fullest extent the beneficial advantages thereof, the reenforce must be free from, by which I mean out of intimate contact with, the body sur iciently to permit vibration and braking strains at a fracture in the body to be distributed remotely in the reenforce from the fracture in the body. This will prevent the compression, tension, bending and vibration strains Yfrom being concentrated upon the reenforc'e at the fracture and permit these strains to be distributed along the reenforce in both directions and away from the fracture. By thus distributing the strains over a considerable area of the reenforce, instead of concentrating them at the line of fracture, the fatigue of the metal is very materially retarded and so much retarded that the body of the shoe will wear down to the limit of wear before the'reenforce breaks. Any kind of reenforce will have openings or recesses or some configuration to insure anchorage of the body to the reenforce and prevent parts from falling away immediately in case of fracture and the purpose of this invention is to prevent the reenforce from breaking and allowing a part of the shoe to fall away before the shoe wears out in service. In the caseof a reenforce consisting of bundle of expanded metal, it may be that some strands of the expanded metal will break before they are reached in the wear of the shoe but generally speaking there will be sufficient expanded metal remaining to function in accordance with my invention and there will always be expanded metal at the back of the shoe or some other type of reenforce at the back of the shoe to function in accordance With my invention even though the expanded metal in the Wearing part of the shoe is broken before the limit of wear of the shoe is reached. So that a shoe provided with a reenforce at the back and with or without a reenforce in the wearing part of the body will remain in service under general conditions until the limit of Wear of the shoe has been reached. As I have said before, there must be an anchorage of the reenforce with the body, as there has been in practice heretofore, but this anchorage must not involve a union of the reenforce and the body or such an intimate Contact of the reenforce with the body as Will result in a concentration of strains upon the reenforce at a fracture in the body. The reenforce must be suiflciently free from the body, and preferably throughout its length, to permit strains upon the reenforce resulting from a fracture in the body to be distributed through the reenforce over a considerable area thereof away from the fracture to retard the fatiguing effects which vibration and other strains upon the reenforce would impose. In this way the brake shoe will be enabled to perform in the manner and for the period expected of it.

I do not limit the invention to any particular kind of brake shoe or reenforce or to the particular methods of treating the reenforce herein described and I reserve the right to maireany changes therein within the scope of the following claims.

I claim:

l. A brake shoe comprising a body and a dry reenforce embedded therein, said reenforce being free in the body but anchored therewith and capable of limited relative movement therein.

2. A brake shoe comprising a body and a dry reenforce back embedded therein, said reenforce back being free in the body but anchored therewith and capable of limited relative movement therein.

3. A brake shoe comprising a body and a dry reenforce embedded in the wearing part thereof, said reenforce being free in the body but anchored therewith and capable of limited relative movement therein.

A brake shoe comprising a body and a dry reticulated metal reenforce embedded in the wearing part thereof, said reenforce being free in the body but anchored therewith and capable of limited relative movement therein.

5. A brake shoe comprising a body and a dry expanded metal reenforce embedded therein, said reenforce being free in the body but anchored therewith and capable of limited relative movement therewith.

6. A brake shoe comprising a body and a dry reenforce consisting of a bundle of expanded metal embedded in the wearing part thereof, said reenforce being free in the body but anchored therewith and capable of limited relative movement therein.

7. A brake shoe comprising a body and a dry reenforce embedded therein, said reenforce being free in the body to permit strains upon the reenforce when the body fractures to be distributed over the reenforce for a considerable distance from the line of fracture.

8. A brake shoe comprising a body and a dry reenforce embedded therein, said reenforce being free over its entire area in the body to permit strains upon the reenforce when the body fractures to be distributed over the reenforce for a considerable distance from the line of fracture.

9. A brake shoe comprising a body, a dry reenforce embedded in the back and a dry reenforce embedded in the wearing part of the body, said reenforces being free in the body to permit strains upon them when the body fractures to be distributed for a considerable distance over the reenforces from the line of fracture.

l0. The method of making a brake shoe which consists in applying to a reenforce a coating comprising a refractory material and a bond, subjecting the coated reenforce to a baking heat and then arranging the reenforce in a mold, and pouring molten metal into the mold to form the brake shoe with the reenforce embedded therein, the heat of the molten metal destroying the bond of the coating and leaving the refractory material in a disintegrated state about the reenforce.

1l. The method of making a brake shoe which consists in applying to a reenforce a coating comprising silica flour and a bonding oil of high viscosity, subjecting the coated reenforce to a baking heat and then arranging the reenforce in a mold, and pouring molten metal into the mold to form the brake shoe with the reenforce embedded therein, the heat of the molten metal destroying the bond of the coating and leaving the refractory material in a disintegrated state about the reenforce.

ROBERT B. POGUE.

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