Patent Application
20100193303
The present invention relates to brakes used on, for example, commercial truck or trailer axles, and includes a brake support known as a brake spider which transfers braking torque from a brake drum to an axle. An associated anchor pin assembly is also disclosed.
A brake spider is a support commonly used for a brake having dual webbed brake shoes, typically utilized at the wheel end of a heavy duty truck or trailer axle (such heavy duty axles and brakes are used on trucks and other heavy duty vehicles, collectively referred to as “commercial vehicles”). The brake spider is affixed to the vehicle axle, typically by welding or bolting. As shown in
Previously, brake spiders typically have been steel components, primarily steel forgings. Stamped steel and cast iron have also been used. This is a result of the need for a strong, rigid component that can withstand repeated application of braking forces, a high temperature environment, and a very high number of fatigue cycles. In addition, steel has been used because a large fraction of brake spiders are welded directly to their axles to ensure a strong, permanent fixture, and steel is best suited to welding in an industrial production environment. In contrast, ductile cast iron castings have not been widely used in this welded-on version of the application, as ductile cast iron is well known to be unsuitable for welding in production environments. This is due to the fact that a significant portion of ductile cast iron's extraordinarily high carbon content will tend to precipitate out of the liquid metal solution in and near the weld pool, resulting in undesirable metallurgy local to the weld joint which weakens the joint. On occasion, ductile cast iron has been used for welded-on brake spiders, however, this is usually only possible with undesirable compromise or complication, e.g., by making the ductile cast iron spider extraordinarily large and heavy (to provide sufficient material to absorb the expected brake loads) or by using a composite structures of ductile cast iron and steel components, such as the brake spider disclosed in U.S. Pat. No. 5,301,776. In the U.S. Pat. No. 5,301,776 disclosure, a steel core which can be welded to an axle is incorporated into a spider by casting ductile cast iron around the steel core.
Other alternative brake spider forms have included thick steel sheets which have been formed by stamping, rather than forging, such as the brake spider on U.S. Pat. No. 4,445,597. This brake spider must be formed from very heavy gauge steel plate in order to withstand braking forces, and as shown in
Regardless of their materials, the prior art brake spiders have been undesirably heavy, either as thick, solid steel forgings, heavy ductile iron castings, or thick steel sheets. These spiders have all also suffered from the problem of being relatively expensive to form, whether due to the costs associated with forging (forging dies and process equipment), ductile iron casting (molding equipment and material processing for casting, as well as additional costs associated with imbedding steel inserts into the castings) or stamping thick steel plates (special thick-plate stamping dies and high-powered stamping machines). As high fuel prices continue to drive vehicle operating costs higher, there is a strong demand for use of lighter weight components to decrease overall vehicle weight. However, merely shaving weight off of existing brake spider designs is not a viable approach, as removing material typically reduces strength and stiffness of these critical brake components. Accordingly, a completely new approach to brake spider design is needed to provide both significantly lighter spider weight, while still providing a spider which is sufficiently strong to survive high braking loads and has sufficient fatigue life to be able to survive a high number of duty cycles in commercial vehicle service.
In view of the foregoing, it is an objective of the present invention to provide an improved brake spider and anchor pin assembly in which weight, cost, manufacture, axle installation and maintenance is improved over prior brake spider designs.
In addressing these and other objectives, the present invention provides a solution to the problems of the prior art by forming a brake spider from light weight, relatively inexpensive stampings which are joined together, for example, by relatively inexpensive conventional welding techniques, to form a strong built-up brake spider component.
In a preferred embodiment, two steel stampings are formed with flanges and stamped strengthening ribs, and are welded together to result in a hollow, reinforced structure which has the strength to withstand high brake force loads and large numbers of brake cycles, with a fraction of the material cost and weight. Further, additional ribs and/or fillet plates may be included, for example, within the hollow portion of the built-up brake spider, in order to further strengthen the spider.
The thin stampings for such a weldment may be easily and relatively inexpensively formed by, for example, stamping thin steel plate stock in low-power steel stamping presses, and then welding about the periphery of the joint line between the two stamped halves of the spider to provided a hollow, light weight, strong and rigid brake spider. Alternative jointing approaches will be readily apparent to those of ordinary skill in the art, such as by including flanges about the periphery of the stamped halves of the brake spider, using fasteners such as bolts, adhesives, rivets, pinning, brazing, and/or connection by some form of mechanical lock. The flanges may meet to abut one another essentially exactly edge-to-edge, or alternatively may overlap one another, as long sufficient mating surfaces for joining the flanges together are provided (for example, by welding). In another embodiment, one or more of the thin stampings may have extensions formed as part of their jointing flanges. Such extensions may be used for mounting other brake components, such as dust shields.
In a preferred embodiment, prior to joining the two thin stampings, one or more inserts may be placed between and captured by the stampings. The insert(s) would protrude from holes in at least one of the stampings to serve as anchor pin locators and/or brake actuator rod bushings. The inserts preferably would have raised regions, such as an external ring or a plurality of radial tabs which both limit the depth of insertion of the insert(s) through the stampings as the brake spider stampings are being assembled, and after the brake spider weldment is formed, also serve to support the surfaces of the stampings, effectively further strengthening the brake spider weldment and providing additional lateral crush resistance.
The use of one or more captured inserts to support the highly localized loads at the locations of the anchor pins and the brake actuator rod pass-through permits the spider stampings to be formed without being made particularly thick and heavy in the immediate vicinity of the anchor pins and brake actuator rod pass-through. The insert(s) may be retained within the brake spider halves solely by virtue of being captured therebetween, or may be secured by being pressed into at least one of the spider halves in an interference fit or by welding about the periphery of the insert/spider plate interface.
The reinforcing insert(s) for the one or more anchor pins and/or the brake actuator rod pass-through may be formed as bushing through which an anchor pin or brake actuator rod passes, or the inserts may be provided with bearing bushings, such as replaceable bushings, on their inner surfaces which serve as the contact surfaces for the anchor pin(s) and/or actuator rod. This arrangement permits the insert to be reliably located and secured against drifting out of the brake spider, in a manner which has low cost and simplifies production. Further, the insert(s) for the anchor pins may be tubular elements which receive an anchor pin which passes through the brake spider, or the insert itself may include the anchor pin, i.e., the anchor pin extends axially outward from the outer face of the brake spider. In this latter embodiment, the anchor pin insert is preferably secured to at least one of the brake spider halves, such as by welding.
It may be possible to eliminate inserts entirely, relying entirely on the edges of the holes in the steel plates to provide sufficient bearing surfaces for anchor pins and/or actuator rods that pass through the spider. In one embodiment, anchor pins located directly into their corresponding holes in the brake spider plates are provided. In one embodiment, snap rings or similar retaining devices located about the outer circumference of the anchor pins, and located such that when positioned between opposing halves of the brake spider, the snap rings abut the inner surfaces of each spider half, precluding axial movement of the anchor pin. As a preferred alternative to the use of snap rings, the anchor pins may be formed with a trunion shape, i.e., with an outer circumference which is larger than the receiving holes in the spider halves in the region between the plates, and a smaller outer circumference in the region outside the steel halves. The width of the larger diameter portion of the anchor pin would be sufficient to permit the shoulders of the large diameter portion to contact the inner surfaces of the facing brake spider plate halves, preferably full 360 degree contact about the shoulders. Such an trunion-shaped anchor pin would eliminate the need for additional components such as snap rings, lowering cost and simplifying brake spider manufacture. The anchor pins optionally may be locally supported by reinforcing rings or plates at the pin pass-through hole in the brake spider. For example, a simple ring-shaped plate welded to the surface of the brake spider would reinforce the thin spider plate at low cost, potentially avoiding any need to increase the thickness of the spider plate to withstand directly-applied anchor pin loads during operational service.
The present invention's use of steel as compared to ductile cast iron permits the use of inexpensive and rapid conventional welding processes to join brake spider weldment directly to the axle, as is common on trailer axle ends. Alternatively, the weldment may be directly fastened to the axle, for example to a bolting flange on the axle using fasteners which pass through the weldment, as is common on drive and steer axle ends. The use of relatively thin steel stampings also permits the addition of a flange to the brake spider weldment for bolting on accessories such as a dust shield at virtually no cost.
The present invention thus provides a brake spider with a hollow, closed-box cross-section which minimizes total spider weight while maintaining high strength and stiffness, and does so at low cost using simple, readily available manufacturing processes.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.
a and 1b are oblique views of outboard and inboard sides, respectively, of a built-up brake spider in accordance with an embodiment of the present invention.
a and 2b are oblique views of front and back sides of the stamping forming the outboard side of the built-up brake spider shown in
a and 3b are oblique views of front and back sides of the stamping forming the inboard side of the built-up brake spider shown in
a and 8b are oblique views of outboard and inboard sides, respectively, of a built-up brake spider in accordance with another embodiment of the present invention.
c is an oblique view of a built-up brake spider having mutually-complementary flange portions in accordance with another embodiment of the present invention.
a-9b are oblique and cross-section views of brake spiders in accordance with embodiments of the present invention having anchor pins with snap rings and a trunion shape, respectively.
a and 1b show outboard and inboard, respectively, oblique views of a built-up brake spider 1 in accordance with an embodiment of the present invention, in which an outer shell plate 10 and an inner shell plate 20 are joined by welding along a seam 30 formed at mutually-contacting edge surfaces. In this embodiment, the shell plates have been formed by stamping of steel, however, other forming techniques, such as forging and hydroforming, made be used to form the shells, and the shells made be formed from materials other than plain steel, such as aluminum or dual-phase steel. This embodiment also illustrates joining of the shell plates along mutually-contacting edges, however the invention is not limited solely to such edge configurations, but includes any arrangements which permit the joining of adjacent portions of the shells, including abutting and/or overlapping surfaces and edges, and use of any joining technique, such as welding, brazing, adhesives, crimping, and/or mechanical fasteners such as rivets, screws and bolts. In addition, the invention is not limited to joining by methods such as welding only at the mutually-contacting surfaces of the shell plates, but may include any method of joining which permits the formation of a built-up brake spider, such as the combination of shell plates with edges which meet but are not joined (for example, interlocking or flanged edges which are not welded to one another) and the use of fasteners in other regions of the shell plates which hold the shell plates together so as to keep the shell plate edges in contact with one another.
At an anchor pin end 40 of the built-up brake spider 1, a deep recess area of the inboard shell plate 20 is covered by a flat portion of the outboard shell plate 10 to form a box area in which anchor pin apertures 50 are located. Similarly, at an opposite brake actuator rod end 60 of the built-up brake spider, holes 70 are provided to accommodate a brake actuator rod (not illustrated for clarity). In addition to the deeply drawn portions of the outboard and inboard shell plates, the shell plates in this embodiment are provided with reinforcing ribs such as embossed areas 80 which strengthen the shell plates. At the center of the shell plates, a large aperture 90 is provided through which an axle end (not illustrated) passes when the brake spider 1 is located on the axle. In this embodiment, no bolting holes are provided about aperture 90 because this spider is intended to be welded to an axle end, as opposed to being secured to the axle end with fasteners.
a and 2b provide oblique views of both the outer and inner surfaces of the outboard shell plate 10 of
The anchor pin insert 330 may be a solid component with an anchor pin projection extending outward from the face of the outboard side of the brake spider, or may have a tube shape to accommodate an anchor pin passing through the brake spider (not illustrated) or to receive a bushing insert (also not illustrated) in which an anchor pin may pass. The anchor pin insert may be secured by welding, such as by weld bead 339 shown in
a and 8b show outboard and inboard, respectively, oblique views of a built-up brake spider 600 in accordance with an embodiment of the present invention, in which an outer shell plate 610 and an inner shell plate 620 are joined by welding along a seam 630 formed at mutually-contacting edge surfaces (in this embodiment, overlapping flanges, as shown at the top of
a-9b are oblique views of a further embodiment of the present invention, in which the outer shell plate 910 and inner shell plate 920 are formed in one piece, with a connecting section 915 connecting the shell plates to one another. Advantageously, brake spider shell plates formed in this manner may be produced in a single forming operation, such as a single stamping operation, to lower manufacturing costs, and then the shell plates may be separated for later positioning to be joined, or may be bent about connecting section 915 to bring the shell plates' corresponding mating surfaces adjacent to one another to form the basic shape of the built-up brake spider.
The foregoing disclosure has been set forth merely to illustrate the invention and is not intended to be limiting. For example, one or more stamped shell elements may itself be built-up from a plurality of components, such as two or more partial stampings, or partial stampings joined with additional components such as reinforcing fillets and/or forged or cast pieces with complicated contours which cannot be cost-effectively stamped. Because other such modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, the invention should be construed to include everything within the scope of the appended claims and equivalents thereof.
