The present invention relates to diaphragms and, more particularly, to flexible diaphragms used in brake actuators operated by fluid pressure.
Diaphragms used in brake actuators operated by fluid pressure, such as actuators in air braking systems of trucks and trains, are made from a layer of fabric, e.g., nylon, sandwiched between two layers of flexible material, generally rubber or synthetic rubber, to form an integral structure. The diaphragm generally is supported at its periphery within a housing of the actuator. Upon introduction of fluid pressure, such as compressed air, on one side of the diaphragm, the diaphragm moves a push plate or piston to actuate a braking mechanism. The diaphragm is returned to its normal position when the compressed air is released by a spring exerting an opposite force on the push plate or piston.
Diaphragms of this type generally are cup shaped with a bottom wall or base merging into a conical annular wall. The conical annular wall terminates at an annular lip or flange which is clamped between upper and lower portions of the housing.
In normal operation, a diaphragm of this type is inverted by the force of the compressed air, and returned to its normally biased position, many thousands of times. Such repeated motion places extreme stress on the diaphragm, often causing wear or rupture. In order to increase the life of diaphragms of this type, various spacing structures at the zone of merger between the diaphragm""s bottom wall and annular sidewall have been proposed. See, e.g., U.S. Pat. Nos. 3,135,173; 3,435,734; 3,872,777; and 3,911,796. Although these structures may increase the life of the diaphragm, they also increase the cost, and the quantity of materials needed, for manufacture.
The present invention provides a fabric reinforced, resilient brake diaphragm for use in fluid pressure operated braking systems. The diaphragm has a durability equal to, or exceeding, that of present brake diaphragms but requires substantially less materials to manufacture and, therefore, is substantially less costly to manufacture.
A brake diaphragm in accordance with the present invention has an annular outer flange for engaging the housing of a braking system and a bottom planar wall having an interior surface for engaging a piston of the braking system. The bottom planar wall has a thickness of between approximately 0.06 inches and approximately 0.10 inches. The diaphragm also has an annular sidewall, connecting the outer flange and the bottom planar wall, and a plurality of spaced planar tabs disposed on the interior surface of the bottom planar wall. Each of these tabs extends radially, from the intersection of the annular sidewall and bottom planar wall, toward the center of the interior surface of the bottom planar wall.
The thickness of the annular sidewall preferably also is between approximately 0.06 inches and approximately 0.10 inches, and the height of each of the planar tabs above the interior surface of the bottom planar wall preferably is approximately 0.05 inches. The spaced planar tabs preferably are evenly spaced on the interior surface along the intersection of the annular sidewall and bottom planar wall. In a particularly preferred embodiment, the bottom planar wall has a thickness of approximately 0.08 inches, the annular sidewall has a thickness of approximately 0.08 inches, the height of each of the planar tabs above the interior surface of the bottom planar wall is approximately 0.05 inches, and the planar tabs are evenly spaced on the interior surface along the intersection of the annular sidewall and bottom planar wall. These tabs are rectangularly shaped, moreover, and four in number.
Notwithstanding the thinness of the walls of a brake diaphragm having a structure in accordance with the present invention, and the substantial savings in materials and costs, diaphragms having such a structure meet or exceed all of the SAE (Society of Automotive Engineers) standards for diaphragms of this type.