On-vehicle disk brake lathe

Turning – Process of turning

Reexamination Certificate

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Details

C082S047000, C082S112000

Reexamination Certificate

active

06363821

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to an on-vehicle disk brake lathe which can provide an indication of the depth of cut on the surfaces of the disk, determine the lateral runout of the disk, and monitor the thickness of the disk which will result when the disk is machined.
BACKGROUND OF THE INVENTION
There are a variety of measuring devices that are currently used in combination with bench lathes that allow monitoring of the surface being cut or, alternatively, measuring the position of the cutting tip. U.S. Pat. No. 5,765,457 provides an example of a bench lathe which provides a measuring system for determining the position of one or more cutting tips relative to a reference position that allows one to back out the depth of cut. The '457 patent also teaches that, when the positions of both cutting tips are measured relative to a reference plane, one can calculate the thickness of the disk and determine a priori whether the disk is sufficiently thick that it can be machined to bring it into specification.
While the teaching of the '457 patent offers a solution for machining of brake disks on a bench lathe, there is no teaching of the use of such a mechanism on an on-vehicle lathe. Furthermore, the system requires the use of two sensors and a complex algorithm to ascertain the position of the cutting tips, and from this information supplemental calculations are needed to determine the thickness of the disk.
Thus, there is a need for an on-vehicle brake lathe which employs rudimentary hardware to determine both depth of cut and whether a disk brake can be machined to bring it within the specifications of the manufacturer.
OBJECTS OF THE INVENTION
It is an object of the invention to provide an on-vehicle disk brake lathe that will determine the thickness of a resurfaced brake before the disk brake is resurfaced.
It is another object of the invention to determine the thickness of the disk brake using a single displacement gauge.
It is another object of the invention to provide a compact on-vehicle disk brake lathe which can be readily adjusted.
It is yet another object of the invention to provide a cutting tool assembly which can be retrofitted to an on-vehicle disk brake lathe for determining the depth of cut and disk thickness.
It is a further object of the invention to provide a method for determining the depth of cut of a tool bit for an on-vehicle disk brake lathe which employs a single displacement gauge.
It is still a further object of the invention to develop a method for resurfacing brake disks which allows an operator to qualify the brake disk for resurfacing before such is undertaken.
It is a further object of the invention to develop an automated brake disk machining system which reduces the likelihood of operator error.
SUMMARY OF THE INVENTION
The present invention relates to on-vehicle disk brake maintenance, and more particularly to an improved on-vehicle disk brake lathe of the type which is mounted to a wheel hub which, along with a brake disk, rotates about a hub axis; related methods for the machining to resurface disk brakes while they remain on the vehicle; and a system suitable for practicing the method of the present invention and automating the on-vehicle disk brake lathes of the present invention.
The on-vehicle disk brake lathe of the present invention relates to an improved cutting tool assembly for holding a first tool bit for resurfacing a first disk surface of the disk and a second tool bit for resurfacing a second disk surface of the disk. The cutting tool assembly can be either an integral part of an on-vehicle disk brake lathe or can be retrofitted to an existing on-vehicle disk brake lathe. In either case, the disk brake lathe has a lathe frame attachable to the wheel hub, a means for aligning a lathe axis with the hub axis, a drive mechanism for rotating the wheel hub and the brake disk about the lathe axis, and means for advancing the tool bits along a feed path which is normal to the lathe axis.
The improved cutting tool assembly for the on-vehicle disk brake lathe described above includes a first tool holder to which the first tool bit is mounted. The first tool holder is translatably engaged with respect to the lathe frame such that it traverses a first tool holder path which is parallel to the lathe axis. Means for moving the first tool holder along the first tool holder path are provided to allow adjusting the spatial separation between the first tool bit and the first disk surface.
A second tool holder is provided to which the second tool bit is mounted. The second tool holder is translatably engaged with respect to the lathe frame such that it traverses a second tool holder path which is parallel to the lathe axis, and means for moving the second tool holder along the second tool holder path so as to adjust the spatial separation between the second tool bit and the second disk surface are provided.
The means for moving the first tool holder and the second tool holder may be any of a variety of mechanical and electromechanical activating devices such as screw mechanisms, stepping motors, servos, rack-and-pinion mechanisms, and hydraulic or pneumatic actuators.
A displacement gauge is positioned relative to the first tool holder and the second tool holder so as to respond to changes in the spatial separation therebetween and to provide an output signal proportional to the separation. Gauges which are capable of providing such a response are further described in U.S. Pat. No. 5,970,427, assigned to the assignee of the present application.
Means for reporting the output signal of the displacement gauge are provided, which can typically be a display, printer, memory device or microprocessor. Frequently, these means are an integral part of commercially available gauges. When a microprocessor is employed, the signal provided to the microprocessor should be a digital signal, which can be either the inherent output of the displacement gauge or, alternatively, can be provided by an A/D converter.
It is further preferred that means for coordinating the motion of the tool holders be provided. Such means can be electronic or mechanical in nature, or can be a combination of electrical circuits and mechanical devices.
It is also preferred for the improved cutting tool assembly to have means for providing pair-wise displacement of the tool holders with respect to the brake disk. One preferred means for providing pair-wise movement of the tool holders, which is partly mechanical, is to employ a support plate which is translatably attached with respect to a platform and traverses a path that is parallel to the lathe axis, while the platform moves along the feed path normal to the lathe axis. The support plate in turn supports the tool holders, of which at least one is slidably engaged therewith such that its tool holder path is parallel to the path of the support plate.
When a support plate is employed, means for positioning the support plate relative to the disk are provided. In an elementary manner, this might be done by hand; however, mechanical means are preferred. A jack screw which is turned by a crank handle is an example of one such means which could be employed. Alternatively, a rack and pinion could be substituted for the jack screw, and the crank handle which is turned by the operator could be replaced with a servo mechanism.
When means for positioning the tool holders do not provide sufficient inherent structure to assure that the tool holders remain axially fixed with respect to the lathe frame as the tool bits traverse the disk surfaces, supplemental means for maintaining each of the tool holders in a fixed axial position relative to the frame are preferably provided to hold the tool holders in position while the tool bits are advanced across the disk brake surface being machined.
While the above described cutting head assembly and on-vehicle brake lathe is capable of determining the thickness of a machined disk brake, the displacement gauge must be calibrated to provide measurements of thickness. This can be do

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