TECHNICAL FIELD

The invention relates to a vibration damper for a control cable.

BACKGROUND

Particularly where a control cable is used for changing gear, the fastening to the gearbox of the casing for the cable's wire needs to be damped. Without such damping, vibration and noise from the gearbox is transmitted to the gear lever. The only heavy vehicles in which wire control is at present commonly used are buses. A damping unit with four rubber pads in an inner and an outer sheetmetal console is known for buses. Disadvantages of such a unit are that it has many constituent parts, which makes it heavy and take a long time to fit, and that it occupies space and is expensive.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a vibration damper of the kind indicated in the introduction which eliminates the advantages indicated above of the state of the art.

This is achieved by the features indicated in the attached claims.

According to one version of the invention, the vibration damper comprises an inner sleeve adapted to being connected firmly to an outside of a casing for the cable, an outer sleeve adapted to being connected firmly to a vibration-prone vehicle component coaxially with the inner sleeve, and an annular intermediate space between the inner sleeve and the outer sleeve, which intermediate space is filled with a vibration- damping material. Such a vibration damper with only one damping body which coaxially or annularly surrounds the casing represents a considerably simplification compared with the state of the art.

Stop means are preferably provided to limit axial relative movement between the inner sleeve and the outer sleeve. The stop means prevent the casing from moving too far on the occasion of rapid gearchanges or so-called panic gearchanges, e.g. when the driver has to engage a lower gear quickly on an uphill run, an operation which involves significantly greater forces than in a normal gearchange. Using such stop means also makes it possible to use a more flexible material with gentler damping characteristics.

The inner sleeve and the outer sleeve may be connected firmly to the vibration- damping material in order to constitute a unit in the form of a conventional bushing. Such bushings are known for various other purposes and are stocked by bushing suppliers.

Other features and advantages of the invention are indicated by the following detailed description and the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded side view of a gearchange cable and a vibration damper according to the invention which is provided for said cable;

FIG. 2 depicts on a larger scale the gearchange cable with the vibration damper according to FIG. 1 fitted to a gearbox; and

FIG. 3 is a sectional view along the line 3-3 in FIG. 2. DETAILED DESCRIPTION OF AN EMBODIMENT

The schematic diagrams in the drawings depict a vibration damper 10 adapted to being placed on a casing 42 of a gearchange cable 40. The cable 40 is a gearchange cable of pull and push type, which means that the wire 44 in the casing 42 has to be able to transmit both pulling and pushing forces to a gearchange mechanism for a gearbox 50 of a motor vehicle such as a heavy truck.

As particularly indicated in FIG. 1, the end of the cable sleeve 42 which is to be connected to the vibration damper 10 is firmly connected to an endpiece 12. The endpiece 12, as also other undepicted end parts of the cable 40, are supplied in this preassembled state by the cable supplier.

The vibration damper 10 comprises a damping element 20 in the form of a bushing comprising a hollow cylindrical rubber damping body 26 (FIG. 3) vulcanised to a pair of concentric steel sleeves 22, 24, i.e. an inner sleeve 22 and an outer sleeve 24.

The outer sleeve of the damping element 20 is adapted to being pressed into and held firmly by pressure fit in an aperture 32 (FIG. 3) in a retainer 30 for the damping element 20. The retainer 30 is itself adapted to being connected firmly to the gearbox 50 by fastening elements 52 which extend through holes 36 in connection flanges 34 of the retainer 30.

As may in particular be seen in FIG. 3, the endpiece 12 of the cable casing 40 is fastened to the vibration damper 10 by the fact that a stem 14 of the endpiece 12 is pushed in through one end of the inner sleeve 22 of the damping element until the inner sleeve engages with a stop 16 of the endpiece 12. The endpiece 12 is fixed axially at the opposite end of the inner sleeve 22 by a nut 38 which engages with threads 18 on the stem 14.

To limit axial movement of the cable casing 40 and the endpiece 12, there are stop means 28, 28 each on their respective side of and at a distance d from the damping element 20. As indicated above, violent or panicky operation of a gear lever (not depicted) which is connected to the wire 44 will also affect to a greater or lesser extent the cable casing 42. If the cable casing 42 tends to move further than the distance d, the respective stop means 28 will then engage with the outer sleeve 24 of the damping element 20 and prevent further movement until the elasticity of the damping body 26 brings the cable casing 40 back to the central position depicted in FIG. 3. This arrangement makes it possible to use a softer or more flexible rubber/damping material with great vibration-damping capacity without risk of the damping material 26 being damaged, e.g. on the occasion of a panic gearchange. As may be seen from the drawings, the stop means may take the form of separate washers 28. The washers 28 are kept at the distance d from the outer sleeve 24 by the fact that the inner sleeve 22 protrudes for a corresponding distance d from each side of the damping element 20.