BOOT ASSEMBLY FOR A CONSTANT VELOCITY JOINTThis invention relates to a boot assembly for a constant velocity joint.
Constant velocity (CV) joints are used in the drive system of motor vehicles to provide rotational drive between two linked shaft. In order to keep the CV joint clean and sealed, and to retain lubricant within the joint, a boot assembly is provided around the CV joint.
The boot assembly typically comprises a boot having a convoluted surface, and a band clamp at each end of the boot to secure and retain the boot in position. The boot is usually moulded from elastomeric or thermoplastic material. When tightening a standard band clamp, end portions of the band clamp will overlap one another to produce a gap between the boot and the band clamp adjacent the inner end portion of the band clamp. This can lead to imperfect sealing and risks leakage. In order to overcome this problem, special designs of band clamp have been produced, typically referred to as stepless band clamps1 which attempt to clamp the boot without leaving a gap. An example of a stepless band clamp is disclosed in GB-A-2160577. Whilst these stepless band clamps provide a solution to this problem they are complicated to design and expensive to produce.
The object of the present invention is to overcome this disadvantage.
A boot assembly for a constant velocity joint in accordance with the present invention comprises a band clamp of annular configuration and having an inner surface with a step therein defined by overlapping end portions of the band clamp; and a boot having an outer surface engageable by the inner surface of the band clamp, the outer surface having a lip thereon which corresponds with and engages the step in the band clamp.
The present invention is less complicated and easier to produce relative to the arrangements using a stepless band clamp, and is much cheaper. The present invention makes use of standard band clamps.
The present invention will now be described, by way of example, with reference to the accompanying drawings, in which:Figure 1 is a cross-sectional side view of aCV joint having a boot assembly in accordance with the present invention;Figure 2 is a perspective view of the boot of the boot assembly of Figure 1;Figure 3 is a cross-sectional view on the line III-III of Figure 1; andFigure 4 is a similar view to Figure 3, but of a prior known arrangement.
Figure 1 shows a CV joint 10 connecting two rotatable shafts 12, 14. The CV joint 10 is any known arrangement and will not be described in detail. TheCV joint 10 has an outer housing 16 which is fixedly connected to one of the shafts 12. A boot assembly 20 in accordance with the present invention is attached to the outer housing 16 and to the other shaft 14.
The boot assembly 20 helps to prevent dirt, etc.
entering the CV joint 10 and also helps to retain lubricant within the CV joint.
The boot assembly 20, which is shown in more detail in Figures 2 and 3, comprises a boot 22 and a pair of band clamps 24,26. One of the band clamps 24 secures the boot 22 to the outer housing 16 of the CV joint 10, and the other band clamp 26 secures the boot to the other shaft 14. The band clamps 24,26 are substantially the same in configuration, but of differing diameters. The band clamps 24,26 are annular in configuration and each has free ends 28,30 which overlap one another on tightening of the band clamp to define a step 32 in the inner surface 34 of the band clamp. The tightening arrangement for the band clamps 24,26 is not shown but can be any arrangement well known to those skilled in the art.
Using this type of band clamp to secure a standard boot 36 (see Figure 4), a gap 38 is formed adjacent the step 32. The gap 38 means that a portion of the boot is not subjected to pressure on tightening of the band clamp which can lead to imperfect sealing and risks leakage.
The boot 22 is moulded from elastomeric or thermoplastic material. The boot 22 comprises a convoluted portion 40 intermediate end portions 42,44 which are substantially annular. The end portion 42 having the larger diameter has an outer surface 46 which is formed with a lip 48 therein. The height of the lip 48 is substantially the same the height of the step 32 in the band clamp 24.
The boot 22 is secured in place by bringing the step 32 in the band clamp 24 into abutment with the lip 48 in the outer surface 46 and then tightening the band clamp. As can be seen from Figure 3, this arrangement is such that no gap is formed adjacent the step 32 in the band clamp 24. Consequently, pressure is applied, on tightening of the band clamp 24, to the outer surface 46 around the whole of its periphery, thereby providing improved sealing.
Although not shown, the end portion 44 of the boot 22 is preferably formed with a similar lip.