Brakes – Vehicle
Reexamination Certificate
2001-10-23
2003-06-10
Lavinder, Jack (Department: 3683)
Brakes
Vehicle
C074S50150R
Reexamination Certificate
active
06575270
ABSTRACT:
The present invention relates to a handbrake setting unit for setting the handbrakes of road vehicles, such as cars. The invention relates principally, but not exclusively, to the setting of handbrakes on the production assembly line of such vehicles and it will therefore be convenient to describe the invention in relation to that application. However the invention is not restricted to such use and could have other applications, such as for resetting the handbrake if the handbrake cable is replaced, or disassembled or requires further adjustment.
It is a problem with the handbrake or bowden cable of many new vehicles, that they require slack adjustment of the handbrake cable relatively soon after the vehicle is placed on the road. Slack in the handbrake cable occurs principally due to bedding and seating of components of the handbrake upon initial use of thereof, while cable stretching also contributes to the slack generated.
The tensioning of a handbrake cable on a production line to operating tension is known as “handbrake setting” and it would be preferable if the handbrake setting procedure was such as to avoid the need for early handbrake adjustment. This is desirable, because the requirement for early adjustment of the handbrake is not only inconvenient, but because most vehicle manufacturers provide free of charge at least the first post sale scheduled service, the cost of resetting the handbrake is normally a cost which must be absorbed by the manufacturer. Due to the high volume of vehicles requiring resetting, some manufacturers are therefore exposed to a significant and wasteful expense.
It has been found that applying a load to the handbrake cable of an assembled handbrake in the production line has benefit in bedding and seating the components of the handbrake. It has therefore been known to apply a tensile load to the handbrake cable during setting and in one form, the load has been applied to the handbrake cable through the handbrake adjuster nut. The handbrake is positioned in the applied position and a torque driver, fitted with a socket is positioned onto the handbrake adjuster nut. The driver is activated to rotate in a clockwise direction which in turn revolves the socket and the adjuster nut. In this method, the nut sits on the handbrake and it can therefore not move down the adjuster thread. As the nut is turned, the handbrake adjuster rises through the nut and as a result, tension increases within the handbrake cable. Consequently, the torque required to rotate the adjuster nut increases as tension in the handbrake cable increases. The torque driver stops rotating when the torque required to rotate the adjuster nut rises to that of the predetermined torque driver setting. This torque driver method, uses the adjuster nut to apply and maintain the tensile load applied to the handbrake cable. In practice, the load generated by the torque driver can vary with variation in the interference between the nut and the adjuster thread and that can result in a substantial variation from the load required to be applied to the cable. In particular, the load can be below that which is required. This process has thus been found to be very inconsistent and therefore has not found wide use.
It is an object of the present invention to overcome or at least alleviate the disadvantages of the prior art. It is a further object of the invention to provide a method of setting a handbrake such as to significantly delay the need for hand-brake adjustment when use of the handbrake commences. It is still a further object of the invention to provide a method by which the components of a handbrake assembly can be caused to substantially fully bed and seat during installation or setting of the handbrake. It is another object of the invention to provide a device for setting a handbrake to achieve one or more of the above mentioned objects.
According to the present invention there is provided method of setting the handbrake cable of an automotive handbrake, said handbrake cable including a threaded member fixed at one end and a nut threaded onto said member and in the set condition of the handbrake said nut engaging against a seat to maintain tension in said handbrake cable, said method including gripping said threaded member and retracting said member to apply a tensile bedding load to said cable, which bedding load exceeds the required set load of the cable in the set condition, returning said threaded member from the retracted position to reduce the tensile load on said cable to said set load, rotating said nut down said threaded member to engage said seat and releasing said threaded member.
The method of the invention advantageously causes the handbrake components to bed and the cable to stretch during the cyclic load to a significantly greater and more consistent extent compared with the methods for setting handbrakes, so that the slack generated in the handbrake during early use of the vehicle is significantly reduced and the period by which an adjustment setting is required is, as a consequence, extended.
The invention is particularly more beneficial than the torque drive method described earlier, in that the invention applies and releases cyclically, a dedicated load prior to setting, and that cyclic load application causes the handbrake components to bed and the cable to stretch. In contrast, the torque driver method applies a single load once during setting and the bedding and stretching benefits are negligible or at least very limited. However, that basically is the only known system, and it has continued to be used by some manufacturers in the absence of an alternative solution.
For convenience, hereinafter, the load applied to the handbrake cable will be referred to as the “bedding load”. The bedding load is applied at least twice, although preferably it is applied and released, or “cycled”, a plurality of times and the number of applications will depend on the characteristics of the handbrake being set. It is preferable that at least four bedding load cycles be applied to the handbrake, although additional cycles, taking the total number to perhaps six or eight, could equally be applied. Generally, the limiting factor in relation to the number of applied cycles, is the time allowable for such a procedure in the production line. It is envisaged that a cycle time of approximately 10-15 seconds will typically be available, to apply the bedding load or cycled bedding loads of the invention.
Preferably the bedding load applied to the handbrake cable exceeds the operating tensile load that would normally be applied to the cable under ordinary operating conditions of the handbrake. Preferably the bedding load exceeds the ordinary operating load by a reasonable amount in order to realise the advantages of the invention and preferably the difference between the bedding and the ordinary operating loads is in the order of approximately 100%, although the load should not exceed the designed abuse load of the handbrake system. In theory, a sufficiently large bedding load could bed, seat, compress and stretch all the relevant components of the handbrake sufficiently to extend the first service interval of the handbrake to a period equal to subsequent service intervals.
The difference between the bedding load and the ordinary operating load may be subject to the number of cycles applied to the handbrake, such that with a greater number of cycles, the bedding load could be reduced. However it must be appreciated that a limitless number of light loads will not, for example, pre-stretch the handbrake cable beyond a certain length. The only way that can be done is to apply a greater load. Conversely, a higher bedding load may require a reduced number of cycles to achieve the same level of handbrake bedding.
The method of the invention can be carried out in any suitable manner, and in one embodiment, the method involves gripping the handbrake cable with gripping means at, or in the region of the cable adjuster thread, and retracting the gripping means to apply a tensile bedding load to the ca
Bartz C. T.
Finnegan Henderson Farabow Garrett & Dunner
Sarlyn Pty. Ltd.
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