A brace bush

Abstract: A bush (10) intended for vehicle wheel suspension braces or struts and particularly for use in pneumatic suspension systems for trucks comprises an outer metal sleeve (11), a metal central part (12), and a rubber shock absorbing layer (13) disposed between the sleeve and the central part and vulcanised to surrounding metal surfaces, wherein the central part (12) has a thicker midway section (15) formed rotationally symmetrical about a longitudinal axis and embraced generally by the outer sleeve (11), and two wing-like side sections (14) that project out in the direction of said long axis. The bush is characterised in that the central part (12) is divided into two halves (12a,b) along a plane that extends parallel with said long axis, such that said midway section (15) comprises two cupped halves which are placed together with full mutual contact therebetween, and such that each of said wing-like side sections (14) also comprises two halves; and in that the two halves (12a,b) of the central part are held fixed together with fastener devices that extend through openings or slots (17) in each side section (14). The two halves (14a,b) of the side sections are also suitably cup-shaped and provided with abutment surfaces that afford mutual contact between the side sections (14).

Description: The present invention relates to a bush for vehicle wheel suspension braces, particularly for bracing rods included in truck pneumatic suspension systems. The bush has a metal outer sleeve, a metal central part and a rubber shock absorbing layer disposed between said sleeve and said central part and firmly vulcanised to surrounding metal surfaces, wherein the central part has a thicker midway section formed rotationally symmetrical around a long axis and substantially embraced by the outer sleeve, and two wing-like side sections that project out in the direction of said long axis. The bracing rods are intended to fixate a wheel axle but, at the same time, allow it to move. The bushes used with such bracing rods thus function essentially as a ball bearing but with the difference that the bush has a rubber layer disposed between the moveable parts with the intention of obtaining a construction that requires no maintenance. In the case of known bushes, the central part is comprised of solid forged steel so as to achieve requisite mechanical strength properties with regard to the material used, for instance the requisite yield point. One drawback with this approach is that this part of the bush becomes unnecessarily heavy and also expensive to manufacture. Another drawback is that after being forged, it is necessary to work the central part of the bush mechanically so that it will into the bush with a predetermined tolerance. It is also necessary to provide said part with holes or channels, e.g. by drilling, for receiving fasteners by means of which the bush can be fixed in place. Wheel suspension braces of the aforesaid kind that include a metal central part are described in W089/04773 (Saab-Scania) and in EP-A-0351689 (Jörn GmbH). These publications do not describe how the central part of the bush is produced or constructed, but merely describe its shape. As before mentioned, however, only solid central parts, often forged, are commercially available. With this exception, the aforesaid publications describe in detail the construction of these known devices and the manner in which they are assembled. In these contexts, reference can be made to these two prior publications for a greater understanding of the general function and construction of the braces and the bushes themselves. The object of the present invention is to provide a simple and neat solution to the problem of heavy, complicated bushes that are expensive to produce, more particularly with respect to the central part of such bushes. This object is achieved with an inventive bush that has the characteristic features set forth in the accompanying Claims. The inventive bush thus includes a central part which is divided into two halves along a plane that extends parallel with the longitudinal axis of the bush, such that the midway section of the central part consists of two cup-shaped halves which lie in full mutual abutment with each other, and such that each of the wing-like side sections also comprises two halves. The two halves of the central part of the bush are held fixed together by fastener elements that extend through openings or slots in each side section and which are used in fitting and securing the bush. The shell of the central or midway section will suitably have a thickness of 1-7 mm. The two side section halves may also be cupped and provided with abutment surfaces that provide mutual contact between the side sections, although they may alternatively be solid so that no interspace is formed between the sections when the bush is assembled. In one embodiment of the invention, which is sometimes preferred from the aspect of manufacture, those parts of the central-part halves that are in mutual contact may have planar contact surfaces. Alternatively, these contact surfaces may be inclined if so desired, such as to prevent said halves from being displaced (pushed) relative to one another. The contact surfaces may also include grooves or be given some other geometry that can further facilitate precise positioning of said halves in relation to each other when fitting the bush. Each half of the central-part and its side sections may be forged as an integral unit, as in the case of earlier known conventional bushes, although an important advantage afforded by the invention is that the central part can be made of sheet metal, in which case each half of said central-part and its side sections can be formed as an integral unit by being pressed from metal sheet, wherewith the openings or slots required in the side sections may conveniently be formed by the press tool at the same time. When the side sections are in the form of shell-like structures, support blocks, preferably sintered or die-cast metal blocks, may be disposed between the side-section halves so as to avoid collapsing of said halves when subjected to shear forces. Despite the inventive bush having a central part which is divided into two halves, the bush as a whole will have the necessary mechanical strength properties, similar to a bush made of solid material. The two halves of the central part are namely fixed together with the fastener devices, e.g. screws or bolts, that are used when anchoring the bush to the brace, and at least the central or midway section of the central part is constructed so that said two halves will be in contact with each other, wherewith the loads acting on said part will be distributed to both halves thereof. In certain cases the bush will be subjected to loads that act in the screw direction, this being the normal case, although the bush may also be subjected to heavy loads that act in a direction transversely to the screws. The bush is then prevented from sliding on the underlying surface by friction. In these cases, the dimensions of the screws are increased in relation to this normal loading condition, in order to obtain sufficiently high friction. The sheet metal alternative with support blocks in the form of sintered metal is suitable in this respect. The sintered parts can be readily formed to fit in grooves, slots or like openings on accommodating surfaces. The invention will now be described in more detail with reference to the accompanying drawings, in which Figure 1 illustrates an assembled bush; Figure 2 illustrates a preferred embodiment of one half of a central part obliquely from one side; and Figure 3 is a similar view illustrating another preferred embodiment of one half of a central bush-part. Figure 1 illustrates a preferred embodiment of an inventive bush 10. The bush 10 comprises an outer metal sleeve 11 which has a springing function in the illustrated case and which embraces a central part 12 that comprises two halves 12a,b. Disposed between the outer sleeve 11 and the central part 12 is a rubber layer 13 which is vulcanised firmly to the inner metal surface of the outer sleeve 11 and also to the central part 12. The side sections 14 of the illustrated central part are divided into two parallel halves 14a,b that extend parallel to the longitudinal axis of the bush and that are in full contact with one another along the entire parting surface. Figure 2 illustrates an embodiment of one half 12a,b of the central part, which half may be forged and the side sections 14 may be solid. The midway section 15 of the illustrated half has a generally hemispherical shape, although it may have other rotational-symmetrical shapes around said long axis that are non-spherical without deviating from the inventive concept. In the illustrated case, each half 12a,b has flat contact surfaces 16, although said surfaces may be inclined or have some other shape and may be provided with grooves or the like but nevertheless constructed for intimate contact with each other without departing from the inventive concept. The wall of the shell-like midway section 15 may have a thickness of 1-5 mm. Each side section 14 includes a hole 17 for receiving fastener means, such as screws for instance. Figure 3 illustrates another preferred embodiment which can be conveniently pressed from sheet metal. The Figure 3 embodiment includes the same components as the Figure 2 embodiment, with the exception that the side section 14 is not solid but is, instead, formed as an integral part of a sheet metal shell having the same wall thickness as the midway section 15. Each side section 14 includes a groove or recess 17 for receiving fastener devices such as screws, for instance. Although not shown, it may be desirable in the case of this embodiment to provide supporting blocks of sintered metal or the like in the space formed between the cup-shaped halves of the side sections.

Claims: A bush (10) intended for vehicle wheel suspension braces or struts and particularly for use in pneumatic suspension systems for trucks, wherein the bush comprises an outer metal sleeve (11), a metal central part (12), and a rubber shock absorbing layer (13) disposed between the sleeve and the central part and vulcanised to surrounding metal surfaces, and wherein the central part (12) has a thicker midway section (15) formed rotationally symmetrical about a longitudinal axis and embraced generally by the outer sleeve (11), and wherein said bush also includes two wing-like side sections (14) that project out in the direction of said longitudinal axis, characterised in that the central part (12) is divided into two halves (12a,b) along a plane that extends parallel with said longitudinal axis, such that said midway section (15) comprises two cupped halves which are placed together with full mutual contact therebetween, and such that each of said wing-like side sections (14) also comprises two halves; and in that the two halves (12a,b) of the central part are held fixed together with fastener devices that extend through openings or slots (17) in each side section (14). A bush according to Claim 1, characterised in that the two halves (14a,b) of the side sections are also cup-shaped and provided with abutment surfaces that afford mutual contact between respective halves of the side sections (14). A bush according to Claim 1 or 2, characterised in that those portions of the halves (12a,b) of said central part that are in mutual contact have planar contact surfaces (16). A bush according to Claim 1 or 2, characterised in that those portions of the halves (12a,b) of said central part that are in mutual contact have oblique contact surfaces or other non-planar contact surfaces (16). A bush according to any one of Claims 1-4, characterised in that each central-part half (12a,b) and its side sections (14a,b) are forged as an integral structure. A bush according to any one of Claims 1-4, characterised in that each central-part half (12a,b) and its side sections (14a,b) are pressed as an integral structure from sheet metal. A bush according to any one of Claims 2-6, characterised by support blocks disposed between respective halves (14a,b) of said side sections, said blocks preferably being comprised of sintered or die-cast metal. A bush according to any one of Claims 1-7, characterised in that said midway section (15) has a wall thickness of between 1 and 7 mm.

Inventors: LANDHOLM STEFAN, SVENSSON NICOLAS, LANDHOLM, STEFAN, SVENSSON, NICOLAS
Applicants: TRELLEBORG AB, TRELLEBORG AKTIEBOLAG
Application year: 2000
Main classification: F16F1
IPC codes: F16F1, B60G7