US717620A - Brake-shoe. - Google Patents

Description

PATENTED JAN. 6, 1903.

D. & H. RAWSTRON.

I BRAKE SHOE. APPLICATION FILED MAR. 31, 1902.

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DONALD RAW'STRON, OF HARVEY, AND HENRY RAWSTRON, OF CHICAGO, ILLINOIS, ASSIGNORS T0 JAMES FRANCIS HILL, OF CHICAGO, ILLINOIS.

SHOE.

SPECIFIGATI ON forming part of Letters Patent No- 717,620, dated January 6, 1903.

Application filed March 31, 1902.

To ctZZ whom it may concern.-

Be it known that we, DONALD RAWSTRON, of the town of Harvey, and HENRY RAW- sTRON, of 7127 Wentworth avenue, in the city of Chicago, State of Illinois, have invented certain new and useful Improvements in Brake-Shoes, of which the following is a specification.

Our brake-shoe is made of any standard shape in cross-section and is preferably made of soft cast iron or steel, in which are molded hard-metal inserts of special design, as hereina'fter described, for the double purpose of dressing the wheel tread and flange and preventing the too rapid wear of the brake-shoe, a pocket or pockets being also. formed in the shoe filled with a friction-creating material for the purpose of furnishing the necessary friction with but little wear on the wheel-tire.

It is well known to those acquainted with the art that the rolling motion of a wheel upon a rail causes a groove to be worn upon the tread of the wheel adjacent to the flange and that the wheel-flange as the wheel-tread becomes worn is left projecting.

It is one of the objectsof our invention to so construct a brake-shoe that it will wear the wheel-tread to the greatest extent where the wheel-tread is least worn by the rail and so that it will dress down the edge of the proper proportion to the tread of the wheel. We attain this object by molding in the shoe hard-metal inserts, preferably formed of the hardest white cast-iron obtainable. These inserts may be of any desired shape, though a sub-e stantially triangular form is that which we deem preferable. These hard-metal inserts are molded in the face of the shoe with their bases adjacent to the outer surface of the shoe, their'points or apexes being turned inward and approaching to the fiange-groove.. Thus these hard-metal inserts present inclined shearing edges across the face of the shoe. As well as presenting shearing edges, the operative sides of the triangular inserts are set back at an acute angle to the wearing-surface, so that a very eflicient tool edge is formed by the hard metal of the inserts at their points of junction with the soft metal of the shoe. Owing to the triangular shape Serial No. 100,792. (No model and described position of the hard-metal inserts it follows that the greatest wearing-surface of hard metal is in contact with the least-worn portion of the wheel, and at this point, therefore, the wearing action of the brake shoe will be the greatest, resulting in the truing down of the tread of the wheel. At the same time, as the brake-shoe possesses a comparatively large area of hard metal, its braking or frictional power is necessarily considerably decreased. We compensate for this by forming in the face of the shoe pockets of substantially the same shape (in plan view) as the hard-metalinserts, but oppositely set-that is, with their bases adjacent to the flangegroove and their apexes toward the outer side of theshoe. The walls of these pockets are inclined to give a dovetail section to the pockets, so that they will eifectively retain the filler, which we will now describe. While any filler may be used in these pockets which will increase the frictional action of the shoe and which will preferably absorb ground-off particles of metal, we prefer to use the composition set out in United States Patent No. 596,132. This patent describes and claims a composition consisting of comminuted iron, asphaltum, and Wahsatch rock, intermixed in substantially the proportion of eighteen parts of iron, one part of asphaltum, and one part of Wahsatch rock, by weight. The composition will be prepared and the pockets filled substantially in the manner set forth in that patent. Owing to the arrangement described the greatest surface of this frictional compound is applied to the mostworn part of the wheel, fully compensating for the loss of braking power due to the hardmetal inserts, while producing very little wear on this rail-worn portion of the wheel-tread. This composition absorbs the ground-01f particles from the wheel and brake-shoe and by retaining them adds greatly to the life of the shoe. The flange-groove of the shoe is also provided with hard-metal inserts and pockets of filler, the inserts having, preferably, pointed operative ends.

In Figure 1 we show a plan View of the face of a shoe adapted for flanged wheels. In Fig. 2 we show a similar view of the shoe adapted for wheels without flanges; In'Fig. 3 we show a cross-section through the line a; y in Fig. 1; in Fig. 4, a cross-section through the line ya in Fig. 1. In Fig. 5 we showa diagrammatical longitudinal section of a shoe with a single insert applied to a wheel, and in Fig. 6 We show in elevation and plan several forms of inserts.

In Fig. 1, A are the hard-metal inserts in the face of the shoe, and B the hard-metal inserts in the flange-groove. The inserts are substantially triangular, as described, to form the shearing edges 0, one being operative when the wheel is revolving in one direction and the other when the wheel is moving in the opposite direction. The operative sides at are inclined at an acute angle to the wearing-surfaces to give the edge of theinsert the effective tool action desired. In order to retain the inserts in position, we form the lips or flanges b on each insert, so that when the soft cast-iron of the shoe is cast around them it will securely hold the inserts in position. In the flange-groove the inserts will be similarly held in position. They will not, however, usually be of triangular shape, but may be formed of any suitable shape, preferably having their operative sides of a suitable shearing shape. Their operative sides will also generally be set at an acute angle to their wearing-surfaces, similar to the sides of the larger inserts in the face of the shoe. A small insert D is preferably molded in the face of the brake-shoe at the end opposite to the hole E, through which passes the bolt used when securing the shoe to the brake-head. The operative sides of the insert D are shown curved, giving them a shearing action, though a diamond or other shape might also be used. The operative sides of this insert may also be set at an acute angle to the wearing-surface, as is the case with the inserts A and B. The pockets of filler in the face of the shoe and in the flange-groove are lettered F and G, respectively, and are shaped as already described. I

In a shoe, such as shown in Fig. 2, intended for fiangeless wheels the inserts are so arranged and shaped that the greatest wearing or cutting action is secured at each side of the brake-shoe, as the center of the brakeshoe is the portion which comes in contact with the most-worn part of the wheel-tread. The arrangement of the pockets of frictional compound is of course just opposite to that of the metal inserts, so that in this form of shoe the arrangement is substantially the same as in Fig. 1, with the greatest surface of hard metal opposed to the least-worn parts of the tread of the wheel and the greatest surface of frictional compound in contact with.

the most-Worn portions of the Wh66l-'iil'6f.d.

Several important features relating'to'our invention should be noted. place, the body of the brake-shoe must be of the soft cast iron or steel of such a quality that it will not chill or only chill to a very small extent when cast around the hardscribed.

In the first metal inserts. This insures the formation of clearly-defined cutting edges at the operative sides of the inserts. If a quality of iron were used for the body of the shoe such as would readily chill and harden, our purpose in using the inserts would be largely frustrated. In the second place, it is difficult to form an effective cutting edge if the operative sides of the inserts are at right angles to or form obtuse angles with the wearing-surfaces. As illustrated in Fig. 6, a dressing-tool should form a real cutting edge. Inserts as they have hitherto been used have formed merely glancing edges. It is also important to secure the best effect that the operative sides of the inserts should be set at a shearing angle across the face of the shoe, as they thus act most effectively and at the same time are not apt to gouge into soft spots on the rim of a Wheel. The third important feature is the arrangement of pockets containing a frictional filler in such a manner as to compensate for the loss of braking power due to the use of the hard-metal inserts. The fourth feature consists in the arrangement of the inserts and the pockets of filler so that the dressing action of the shoe is greatest on the less-worn parts of the wheel and the frictional eifect greatest on the most-worn parts of the wheel. In this connection the arrangement of the inserts and pockets so thata dressing efiect is produced on the flange edge, which ordinarily is not worn at all, adds considerably to the value of the shoe. Another point to be noted is the eifect on the shoe of the use of an absorptive filler in the pockets. It is well known that the accumulation of the ground-0E particles (resulting from the application of the shoe to the wheel) on any portion of the face of the brake-shoe and the final fusing of them together by the generated heat produces an uneven surface on the shoe-face, thereby wearing irregular channels and tearing the Wheel tread and flange and finally putting the wheel out of action. An absorptive filler takes up these particles, using up this otherwise waste material in creating friction, thus increasing the life of the shoe. The life of the wheel is also prolonged, owing to the wheel-face being kept free from the roughness just de- Another advantage resulting from the use of this filler is that it prevents the hard portions of the surface of the brakeshoe from glazing, thus establishing a superior frictional contact-surface and developing a greater degree of friction in consequence.

Although we prefer to use an absorptive filler such as described, yet other frictioncreating fillings might be employed with a considerable degree of advantage. Also for some purposes the hard sections instead of being formed by inserts might be formed by using a chilling-iron and casting the shoe with hard chilled sections. Though the dressing efiect of such a shoe would be reduced,

IIO

yet the advantages of prolonged life without loss of braking power would still be retained.

What we claim as our inventionisl. A cast-metal brake-shoe having a hardmetal insert molded in its face, said insert being so shaped that the metal of the body of the shoe retains it in place, and also having an operative side formed at an acute angle to its wearing-surface so as to present an efficieut cutting edge to act on a wheel, substantially as described.

2. A cast-metal brake-shoe having'a hardmetal insert molded in its face, said insert being so shaped that the metal of the body of the shoe retains it in place, and having an operative side set diagonally across the shoe and also formed at an acute angle to its wearing-surface so as to present an efficient cutting edge to act on a wheel, substantially as described.

3. A cast-metal brake-shoe having a substantially triangular faced hard-metal insert molded in its face with its base at or near the outer side of the shoe, the said insert having lugs or projections formed thereon to retain lugs or projections formed thereon to retain it in place and also having its operative sides formed at an acute angle to its wearing-surface so as to present an eflicient cutting edge to act on a wheel, substantially as described.

5. A cast-metal brake-shoe having hard sections formed therein in the process of molding, and provided with pockets filled with a frictional absorptive compound whereby the loss of braking power-due to the hard-metal sections is compensated for by the pockets of fric tional compound and ground-0E particles of metal from the shoe and wheel are absorbed, substantially as described.

6. A cast-metal brake-shoe having hard sections formed therein in the process of molding, and provided with pockets filled with a fric tional filler, the hard sections and pockets beingso arranged and proportioned that the greatest surface of hard metal is located at that part of the shoe which contacts with the least-worn part of a wheel and the greatest surface of frictional filler at that part of the shoe in contact with the most-worn part of a wheel, substantially as described.

7. A cast-metal brake-shoe having hardmetal inserts secured therein in theprocess of molding forming transverse cutting edges on the shoe at their lines of contact with the softer metal, and provided with pockets filled with a frictional filler whereby the loss of braking power due to'the hard-metal inserts is compensated for by the pockets of frictional filler, substantially as described.

S. A cast-metal brake-shoe having a substantially triangular faced hard section formed therein with its base at or near the outer side and provided with a similarly-shaped but oppositely set pocket filled with a frictional filler, substantially as described.

9. A cast-metal brake-shoe having a substantially triangular faced hard-metal insert secured therein in the process of molding, with its broad portion at or near the outer side and provided with a similar triangular-faced but oppositely-set pocket filled with a frictional filler, substantially as described;

10. A cast-metal brake-shoe having a substantially triangular faced hard-metal insert molded in its face with its base at or near theouter side of the shoe, the said insert having lugs or projections formed thereonto retain it in place, and also havingits operative side formed at an acute angle to its wearing-surface so as to present an efficient cut.- ting edge to act on a wheel, in combination with a substantially triangular faced pocket of frictional filler set oppositely to the insert, substantially as described.

11. A cast-metal brake-shoe having a plurality of substantially triangularfaced hardmetal inserts secured therein in the process of molding, and provided with a plurality of alternated triangular-faced pockets filled with a frictional filler, the inserts being set with their bases adjacent to the outer side of the shoe and the pockets of filler with their bases adjacent to the inner side of the shoe, substantially as described. 7

1 2, A cast-metal brake-shoe shaped to fit a flanged wheel having hard-metal inserts secured therein in the process of molding both in the bottom of the flange-groove and in the face of the shoe, the inserts in the. face of the shoe being so shaped and arranged as to give a larger proportion of hard metal at that part of the shoe which contacts with the least worn part of a wheel, in combination with pockets of frictional filler located both in the bottom of the fiange groove and in the face of the shoe, the pockets of filler in the face being so shaped and arranged as to give the greatest surface of frictional filler at that part of the shoe which contacts with the leastworn part of the tread of a wheel, substantially as described.

Toronto, March 14, 1902.

DONALD RAWSTRON. HENRY RAWSTRON.

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