US3696892A

US3696892A - Brake head-centering device for railway brake apparatus

Info

Publication number: US3696892A
Application number: US113280A
Authority: US
Inventors: Thomas H Engle
Original assignee: General Signal Corp
Current assignee: SPX Technologies Inc
Priority date: 1971-02-08
Filing date: 1971-02-08
Publication date: 1972-10-10
Anticipated expiration: 1989-10-10
Also published as: CA946757A; ZA72817B

Abstract

The disclosure concerns brake apparatus for railway cars and locomotives in which the brake head is journaled on a pivoting hanger and is centered by a biasing spring. The hanger is moved by an elongated actuating member having a substantially fixed orientation with respect to the horizontal, and a four-bar parallelogram linkage orients the seat of the biasing spring relative to the actuating member so as to maintain alignment of the head with respect to the braking surface of the wheel during pivotal movement of the hanger.

Description

7 United States Patent Engle 1451 Oct. 10, 1972 541 BRAKE HEAD-CENTERING DEVICE 2,480,073 8/1949 Barrows ..188/212 x FOR RAILWAY BRAKE APPARATUS 2,588,645 3/1952 Miers 1 88/212 Inventor:

[72] Thomas H. Engle, Cape Vincent,

Assignee: General Signal Corporation Filed: Feb. 8, 1971 Appl. No.2 113,280

US. Cl ..l88/2l2, 188/52 Int. Cl ..F 16d 65/06 Field of Search ..l88/52, 209, 212, 213, 231

[56] References Cited UNITED STATES PATENTS 12/1918 Cremean ..l88/2l2 X '2/1939 Baselt ..l88/2l2 X Primary Examiner-Duane A. Reger AttorneyDodge & Ostmann ABSTRACT 4 Claim, 4 Drawing Figures minim SHEET 2 4 FIG-2 THOMAS ENGLE ATTORNEYS PATENTEDBBT 10 m2 3.696 892 SHEET 3 BF 4 INVENTOR THOMAS H. ENGLE BY i ATTORNEYS PATENTEnuctiomn 3.696.892

SHEET 8 0F 4 FIG-4 INVENTOR THOMAS H. ENGLE BY Q EWV ATTORNEYS BRAKE IIEAD-CENTERING DEVICE FOR RAILWAY BRAKE APPARATUS BACKGROUND AND SUMMARY OF THE INVENTION In the most common type of railway brake, the brake shoe for each wheel is attached to a head journaled on a pivot carried by a hanger which itself depends from a pivot supported by the truck frame. The head is equipped with a centering device which is intended to keep it aligned with the braking surface of the wheel when the brakes are released and thereby prevent dragging of the shoe. Several kinds of centering devices have been proposed. One type consists of a leaf spring which reacts between the head and a cam surface on the hanger, and which biases the head toward a prescribed position relative to the hanger in which the shoe is supposed to be aligned with the mating rotary braking surface. The simplicity of this approach makes it appealing; however, it is not satisfactory in cases where the brake-actuator includes a slack adjuster and a small running clearance between the shoe and the wheel is to be maintained. The reason for this is that the slack adjuster progressively changes the release position of the hanger as the shoes wear during service. Since the centering device orients the head with respect to the hanger, it follows that the orientation of the head relative to the wheel will change. With small shoe clearances, this change can cause the shoe to rub on the wheel under release conditions.

A better approach to the head-centering problem is to use a friction clutch or yielding latch which retards tilting movement of the head relatively to the hanger, but allows the head to pivot as required to align the shoe with the wheel under the action of the braking force developed during a brake application. While,

. from the theoretical standpoint, this solution is capable of maintaining a satisfactory degree of shoe alignment, experience indicates that, as the parts wear during service, the clutch or latch tends toslip and become unreliable.

ln installations employing a direct acting actuator, i.e., an actuator, such as the one disclosed in U.S. Pat. No. 3,512,615, granted May 19, 1970, which is attached to the hanger at the head pivot, the centering problem can be solved easily by using the' leaf spring mentioned earlier and allowing it to seat on a cam surface carried by the actuator. Since the orientation of the actuator with respect to the horizontal changes vary little under service conditions, the leaf spring always biases the head to the same orientation with respect to the wheel regardless of the angular position of the hanger. Thus, proper shoe-wheel alignment is achieved in a relatively simple and reliable manner. Unfortunately, this solution is not available in the more common case where space considerations require that the actuator be located below the horizontal plane containing the head pivot, and the hanger, in effect, becomes a force-multiplying link.

The object of this invention is to provide a simple and reliable brake head-centering device which performs the centering function as well as the device last mentioned and can be applied to installations wherein the actuator is attached to the hanger at a point offset from the head pivot. According to the invention, the brake head is equipped with a biasing spring which orients it with respect to a seat journaled on a pivot carried. by the hanger, and the brake apparatus incorporates a four-bar parallelogram linkage which maintains a prescribed orientation of that seat relative to the hanger actuator. The orientation of the actuator with respect to the horizontal varies only slightly during pivotal movement of the hanger, and therefore proper correlation of the orientation of the seat relative to the actuator produces the desired result of maintaining alignment of the brake shoe with respect to the wheel. And, since the parallelogram linkage is inherently simple and, in contrast to the friction clutches and latches of the prior art, affords positive control over relative motion between the head and the hanger, centering action is afforded in an economical and reliable manner.

BRIEF DESCRIPTION OF THE DRAWINGS The preferred embodiment of the invention is described herein with reference to the accompanying drawings in which:

FIG. 1 is a side elevation view of a tread brake installation for a four-wheel truck.

FIG. 2 is an enlarged view of the brake unit for one of the wheels shown in FIG. 1.

FIG. 3 is a sectional view, on slightly reduced scale, taken on line 3-3 of FIG. 2.

FIG. 4 is a sectional view, on slightly enlarged scale, taken on line 44 of FIG. 3.

DESCRIPTION OF PREFERRED EMBODIMENT The brake apparatus shown in FIG. 1 includes two of the improved braking units 11 equipped with flanged shoes 12 arranged to coact with the treads of the

wheels

13 and 14, respectively, on one side of a fourwheel truck. The units are supported by the truck frame 15 and are actuated by a common hydraulic brake cylinder 16 which is hung between them in a position inboard of the equalizer bar 17. Cylinder 16 comprises relatively movable cylinder and rod elements 18 and 19, respectively, which are pivotally connected to the lower ends of hangers 21, and also includes a lock mechanism 22 which enables the apparatus to serve as a hand brake. Preferably, mechanism 22 is constructed in accordance with the teachings in application Ser. No. 882,655, filed Dec. 5, 1969. The wheels at the opposite side of the car are provided with an identical brake apparatus, and the hydraulic lines 23 for the two cylinders and lock mechanisms are joined to the cars hydraulic circuit by a tee and bleed fitting 24 attached to the car body. It is preferred that this circuit be constructed in accordance with the teachings in U.S. Pat. Nos. 3,508,794, granted Apr. 28, 1970, and 3,513,656, granted May 26, 1970.

As shown in FIGS. 2-4, the hanger 21 of each brake unit 11 is a one-piece casting including spaced side members 21a and 21b and an intermediate, joining web 210. The hanger depends from a pivot bolt 25 which is journaled in a bracket 26 attached to a pad 27 cast integrally with the truck frame 15. At their lower ends, the side members of hanger 21 are bridged by a second pivot bolt 28 on which is journaled the fitting 29 carried by the rod element 19 of brake cylinder 16, and which, therefore serves as the pivotal connection for the brake cylinder. Intermediate the two

pivots

25 and 28, members 21a and 21b are bridged by a third bolt 31 which serves as the pivot for a brake head 32 to which shoe 12 is attached.'Bolt 31 also serves as a pivot for a cam member 33 which is positioned between the integral ears or legs 32a and 32b of head 32. The cam is formed with a flat seating surface 34 which is engaged by the intermediate portion of a leaf spring 35 whose opposite ends are held captive by a pair of transverse pins 36 extending through head 32. The spring 35 tends to assume the illustrated null position in which it lies flat against surface 34, and consequently it biases the head about pivot31 to a prescribed angular position with respect to cam member 33. The spring is stiff enough to hold the head in this position under service conditions whenever the brakes are released, but not so stiff as to preclude the head motion required during a brake application to accommodate conditions such'as out-of-round wheels and vertical movement of pivot 25 relatively to the axle.

As shown most clearly in FIG. 4, cam member 33 is joined to rod fitting 29 by an articulated link 37 whose opposite ends are journaled on

pins

38 and 39 carried by these members. It also will be observed in this Figure, that the axes of

pivots

28, 31, 38 and 39 are located at the corners of a four-bar parallelogram A-B- C-D made up of portions of hanger 21, fitting 29, cam member 33 and link 37. This four-bar linkage inherently maintains parallelism between bars B and D during pivotal movement of hanger 21, and therefore fixes the orientation of cam surface 34 relative to the axis of cylinder 16. Since the cylinder is a long member and its axis remains substantially horizontal throughout service, and spring 35 fixes the orientation of head 32 relative to surface 34 when the brakes are released, it follows that the angular position of the head in space under release conditions will remain fixed. Thus, if the inclination of surface 34 with respect to the vertical is selected initially to provide concentricity between shoe 12 and the tread of wheel 13, this alignment will be maintained during service regardless of the fact that the angular position of hanger 21 under release conditions changes as slack is taken up. Of course, since pivot 25 does move vertically with respect to the axle, and pivot 31 moves in an are about pivot 25, and not on a true radius of wheel 13, as the hanger pivots, it is evident that perfect alignment cannot be maintained. However, as those skilled in the art will realize, the degree of alignment which is afforded is satisfactory.

Although the brake head-centering scheme of this invention can be employed in various types of brake rigging, the one which has been illustrated is particularly desirable because it facilitates maintenance. Servicing of the components requires only removal of the pivot bolts 28'at the ends of cylinder 16, and, unless shop repair or replacement of the cylinder itself is needed, the hydraulic lines 23 need not be opened.

While the invention has been described in connection with tread brakes for a four-wheel truck, it should be obvious that it is equally useful in other applications. For example, in the case of tread brakes for a six-wheel truck, the center and one outside wheel on each side are handled as shown in FIG. 1, and the remaining wheel on each side is equipped with another brake unit 1 1 which is provided witha separate hydraulic cylinder pivotally connected to the truck frame. In the case of disc brake uni on t e other hand, the c l' der 16 is arranged parallel wit the axle, and the 11 are hung adjacent the brake plates attached to the hubs of the two wheels on the axle. Here, of course, the brake shoe 12 takes the form of the separate brake blocks normally used in disc brakes, and head 21 is designed to accept this type of braking element.

I claim:

1. Brake apparatus for a wheel of a vehicle comprisa. a hanger (21) depending from a pivot (25) sup ported by a portion (15) of the vehicle;

b. a brake head (32) carrying a shoe (12) arranged to coact with a braking surface of the wheel and journaled on a pivot (31) supported by the hanger;

c. spring means (35) reacting between the head (32) and a movable seat (33) carried by the hanger and biasing the head toward a prescribed orientation relative to the seat; and a four-bar parallelogram linkage (A, B, C,'D) connected to the. seat (33) and serving, during pivotal movement of the hanger (21 to change the orientation of the seat relative to the hanger as needed to maintain alignment of the shoe with respect to said braking surface. Brake apparatus as defined in claim 1 which a. includes an elongated actuating member (16) having a substantially fixed orientation relative to the horizontal and connected with the hanger (21) for moving the latter about its pivot (25); and b. the parallelogram linkage (A, B, C, D) is connected to maintain a prescribed orientation of the seat (33) relative to the actuating member. Brake apparatus as defined in claim 2, in which a. the actuating member (16) is connected to the hanger (21) by a pivot (28) located at a greater moment arm with respect to the hanger pivot (25) than the head pivot (31); the seat (33) is journaled on the head pivot (31);

and c. the four bar parallelogramlinkage (A, B, C, D) includes portions of the seat (33), the hanger (21) and the actuating member (16, 29), a link (37) pivotally connected to the seat (33) and the actuating member (16, 29), and the head pivot (31), the actuating member pivot (28) and the pivots (38, 39) ofsaid link (37). Brake apparatus as defined in claim 2, including a. an additional hanger (21), brake head (32), spring means (35), seat (33) and four-bar parallelogram linkage (A, B, C, D) as described previously and associated with a second wheel (14) of the vehicle; and b. in which said actuating member is a horizontal brake cylinder (16) located between the two wheels (13, 14) and pivotally connected at its opposite ends to the two hangers (21).

Claims

1. Brake apparatus for a wheel of a vehicle comprising a. a hanger (21) depending from a pivot (25) supported by a portion (15) of the vehicle; b. a brake head (32) carrying a shoe (12) arranged to coact with a braking surface of the wheel and journaled on a pivot (31) supported by the hanger; c. spring means (35) reacting between the head (32) and a movable seat (33) carried by the hanger and biasing the head toward a prescribed orientation relative to the seat; and d. a four-bar parallelogram linkage (A, B, C, D) connected to thE seat (33) and serving, during pivotal movement of the hanger (21), to change the orientation of the seat relative to the hanger as needed to maintain alignment of the shoe with respect to said braking surface.

2. Brake apparatus as defined in claim 1 which a. includes an elongated actuating member (16) having a substantially fixed orientation relative to the horizontal and connected with the hanger (21) for moving the latter about its pivot (25); and b. the parallelogram linkage (A, B, C, D) is connected to maintain a prescribed orientation of the seat (33) relative to the actuating member.

3. Brake apparatus as defined in claim 2, in which a. the actuating member (16) is connected to the hanger (21) by a pivot (28) located at a greater moment arm with respect to the hanger pivot (25) than the head pivot (31); b. the seat (33) is journaled on the head pivot (31); and c. the four-bar parallelogram linkage (A, B, C, D) includes portions of the seat (33), the hanger (21) and the actuating member (16, 29), a link (37) pivotally connected to the seat (33) and the actuating member (16, 29), and the head pivot (31), the actuating member pivot (28) and the pivots (38, 39) of said link (37).

4. Brake apparatus as defined in claim 2, including a. an additional hanger (21), brake head (32), spring means (35), seat (33) and four-bar parallelogram linkage (A, B, C, D) as described previously and associated with a second wheel (14) of the vehicle; and b. in which said actuating member is a horizontal brake cylinder (16) located between the two wheels (13, 14) and pivotally connected at its opposite ends to the two hangers (21).