US2887189A

US2887189A - Brake beam of welded construction

Info

Publication number: US2887189A
Application number: US598714A
Authority: US
Inventors: Alvin E Harder
Original assignee: AO Smith Corp
Current assignee: AO Smith Corp
Priority date: 1956-07-18
Filing date: 1956-07-18
Publication date: 1959-05-19
Anticipated expiration: 1976-05-19

Description

May 19, 1959 A. E. HARDER 2,887,189

BRAKE BEAM OF WELDED CONSTRUCTION Filed July 18, 1956 INVENTOR. A LVIN 1E. HARDER M FM l Qdfforngs q 2,887,189 BRAKE BEAM or WELDEDCONSTRUCTION Alvin E. Harder, Brookfield, Wis., assignor to A'. OISinith Corporation, Milwaukee, Wis., a corporation of New York t This invention relates to certain improvements in railway brake beamsof welded construction.

Generally, a brake beam includes a forwardly disposed tension member and a rearwardly disposed compression member which are spaced from each other centrally of their length and joined by a strut. The members are bent laterally to a predetermined camber to bring the respective ends together to form a truss structure with the ends being commonly secured together by welding. A brake head is mounted on the respective ends of the beam in alignment with the railway car wheels. Uponactuation of the beam toward the ear wheels, shoes carried by the respective brake heads engage the wheels to brake the car, 1 A w" 1 The braking operation imposes a'relatively large load on the beam. To withstand the stresses and strains imposed by the load relatively long welds are necessary at the beam ends for securing the tension and compression members together and relatively large weld areas are necessary to secure the strut to themembers. Thus, the cross-section of the tension and compression members must not only be adequate to withstand the unit stress to be imposed on the members, but also to provide adequate weld area at the beam ends and centrally at the strut location. To fulfill these requirements, a brake beam is generally provided with a tension member having a constant cross-sectional area. The resultant beam represents a relatively rigid or stifi structure. Asa result of this stiffness, the tension member not only carries a pure tensile load but also tends to bend away from the compression member at the inner extremity or apex of the end welds when the brake load is applied to the beam placing the tension member at the apex in further tension. This compounded tension sometimes promotes cracking in the tension member adjacent to the apex of the welds resulting in brake beam failure.

According to this invention, a brake beam of welded construction is provided with a tension member portions of which have a reduced moment of inertia about the vertical neutral axis of bending stress extending perpendicular to the plan views of the member. The portions of the tension member having a reduced moment of inertia are disposed between the strut of the beam and the respective apexes of the end welds and extend over a major portion of the respective distances. The reduction in the moment of inertia about the vertical neutral axis in the portions of the tension member between the strut and the apexes of the welds results in a more flexible member which is less able to deflect or bend away from the compression member adjacent to the apexes of the welds, thus substantially reducing the additive stresses due to bending at that location. Cracking of the tension member adjacent to the apex of the end welds is thereby virtually eliminated.

A reduction in the moment of inertia about the vertical neutral axis of bending stress of the tension member may be effected by deforming the member to place the material forming the member closer to the neutral axis or by United States Patent 2,887,189 Patented May 19, 1959..

the removal of material disposed at a distance' from the axis. The removal of material from portions of the ten. sion member will obviously result in an increase of unit stress in the member during service. This increasejin unit stress, however, is well within the yield strength of the material.

The drawing furnished herewith illustrates the best mode of carrying out the invention as presently contemplated and set. forth hereinafter.

In the drawings: i r Figure 1 is a to plan viewof a railway brake beam of welded construction showing the tension member as having reduced cross-sectional area over-portions of its length in accordance with the invention;

Fig. 2 is an enlarged partial toplplan view of the beam shown in Figure 1; Fig. 3 is a section taken on line 3--3 of Fig. 2 and shows in broken line the approximate location of the vertical neutral axis of bending stress of the tension member; and r Fig. 4 is a view similar to Fig. 2 showing an embodiment of the invention wherein the portion of the tension member having a reduced cross-sectional area is tapered. Referring to the drawing, the railway brake beam is generally of the type shown and described in the patent issued to Donald W. Sherman No. 2,755,892 and assigned to the same assignee of this invention and is comprised of a channel-section compression member 1 and a channel-section tension member 2 disposed forwardly of the compression member with the flanges "3 and 4 on the respective members being disposed in facing relation. The members 1 and 2am spaced from each other-centrally of their length and joined by a strut 5 which serves to house. the actuating mechanism, not shown, for moving the beam into and out of braking engagementwith the car wheels 6 partially shown with broken lines. The strut 5 may be secured to the members 1 and 2 by welds 7 and 8 as shown.

The members 1 and 2 are bent laterally about their center to a predetermined camber to bring the end portions of the respective members in flange abutting relation and form a truss structure. The end portions of the members 1 and 2 are bent to place their respective webs in substantially parallel relation and the depth of

flanges

3 and 4, respectively, are reduced over the distance corresponding to the parallel webs to form boxsection end portions 9 on the brake beam. Longitudinally extending welds 10 join the abutting portions of

flanges

3 and 4 to complete the brake beam truss structure.

A brake head 11 carrying a brake shoe 12 forwardly is secured by welding or other appropriate manner on the respective end portions 9 of the brake beam. The spac ing of the heads 11 on the brake beam corresponds to the spacing of the car wheels 6 with which the beam is associated. In service, the brake beam is actuated forwardly to place the shoes 12 of heads 11 into braking engagement with the car wheels 6 to brake the car.

To provide the strength and rigidity required of such a brake beam the members 1 and 2 must not only have a cross-sectional area capable of withstanding the unit stresses to be imposed on the members: in service, but also should have adequate weld area for securing the members together. These requirements have generally been met for a brake beam of given capacity with members 1 and 2 each having a predetermined constant crosssectional area extending between the apexes 13 of the end welds 10.

In some brake beams, however, having members 1 and 2 of constant cross-sectional area, cracks developed in the flanges of the tension member adjacent to the apex 13 of the end welds 10 indicating a critical stress area. It was reasoned that the tension member 2 adjacent to the apex 13 not only carried the pure tensile load, but was also subjected to bending forces which further increased the tensile loading with the greatest additive stress occurring on the flange edges adacent the apex.

According to the invention, the tension member 2 is provided with an elongated portion between the strut 5 and the apexes 13 of the respective end welds having a modified cross-section. The modified cross-section may be provided in the tension member by removal of material or by rearranging the material closer to the vertical neutral axis of bending stress of the member to reduce the moment of inertia in the elongated portions of the mern her with respect to the neutral axis. The elongated portions of modified cross-section will provide a more flexible member and thereby redistribute the stress load to relieve the critical stress condition in the tension member adjacent to the a'pexes 13 of end welds 10.

According to Figs. 1, 2 and 3 of the drawing, the tension member 2 of the brake beam is provided with a pair of elongated recesses 14 on the rearward edge of the member. Each of the recesses 14 is disposed substantially midway between the strut 5 and the apex 13 and extends over a major portion of the distance between the strut and the apex. Thus, the tension member 2 is provided with a reduced cross-sectional area over a'portion of its length making it a more flexible member. As a more flexible member, the tension member 2 is less able to deflect or bend away from the compression member 1 at the apex 13. Thus, the additive stresses due to bending adjacent to the apex 13 have been reduced to correct the stress condition which previously existed.

' In the case of a channel section tension member 2 as shown in Figs. 1 and 2, tests have shown that if elongated recesses 14 are provided to reduce the flange depth of the member and consequently the cross-sectional area, stresses are materialy reduced in the tension member adjacent to the apex H. A reduction of 8% in the cross-sectional area of the tension member 2 over a major portion of the distance between the strut 5 and apex 13 reduced the stresses in the tension member adjacent to the apex about 17% while the stress along the axis of thetension" member increased less than 5%, the latter being well within the yield strength of the material.

According to the embodiment shown in Fig. 3, an

elongated tapered recess 15 is provided along the rear ward edge of the tension member 2 to each side of the strut 5.

The invention provides an effective means for redistributing the stress loads to advantage in the tension member of a welded brake beam.

Various modes of carrying out the invention are contemplated as being within the scope of the following claim particularly pointing out and distinctly claiming the subect matter which is regarded as the invention.

I claim:

In a brake beam assembly of the class described, a channel shaped compression member, a channel shaped tension member, said members having substantially uniform width and being disposed at an acute angle facing each other withthe flanges of one member aligned with the corresponding flanges of the other and rigidly integrally secured thereto at one end of the structure by welds joining the adjacent edges of the flanges, said welds extending to the apex formed by the angular relative position of the members at the point of coming together of the edges of the corresponding flanges, and the flanges of said tension member being reduced in strength from a point adjacent said apex and extending away from the apex so that cracking of the weld at said apex is substantially prevented under load.

References Cited in the file of this patent UNITED STATES PATENTS 528,522 Barnes Nov. 6, 1894 750,732 Stucki e Jan. 26, 1904 2,170,121 Busch Aug. 22, 1939 2,755,892 Sherman July 24, 1956 FOREIGN PATENTS 883,619 France Mar. 29, 1943