Turning – Portable lathe for brake drum – disc – or shoe
Reexamination Certificate
2002-08-19
2004-11-09
Wellington, A. L. (Department: 3722)
Turning
Portable lathe for brake drum, disc, or shoe
C082S903000
Reexamination Certificate
active
06813979
ABSTRACT:
FIELD AND BACKGROUND OF THE INVENTION
This patent proposes a device for turning brake disks that includes an automatic compensation unit that functions to automatically compensate for runout between a lathe applied directly to the vehicle, and the brake disk to be turned.
The device according to this innovation has the advantage of being able to use an automatic alignment tool so that the job of turning the brake disks can even be entrusted to personnel without specific preparation or expertise. It also saves time compared to traditional manual systems.
It consists, in other words, of a device that allows totally automatic detecting of runout of the brake disk to be turned and consequently, using a suitable calculator, transforms signals coming from the detector into controls for an electromagnetic actuator that acts on a triad of rotating adjustment devices controlling the distance between the two faces of the alignment device.
As is known, disk brakes used on motor vehicles are subject to substantial frictional forces from brake caliper shoes, and undergo wear with the passage of time and periodically require replacement of the shoes and, if necessary, turning of the surface of the disk when the surface is found to be grooved by the shoes beyond admissible maximum values.
It is also known that the surface of the disk, in addition to the formation of grooves caused by shoe friction, is also subject to other forces that cause lateral warping of the disk. These abnormalities must also be detected and corrected during turning procedures since they could jeopardize the safety of the vehicle by generating dangerous vibrations during braking.
One of the main components of a vehicle wheel braking system employing disk brakes are the brake disks or brake rotors which provide a solid rotating surface against which the stationary brake friction pads are clamped or compressed to generate a frictional force, slowing the rotational movement of the brake disks or brake rotors and the associated vehicle wheels. These brake disks or brake rotors are subjected to repeated and substantial frictional forces by the brake friction pads, and over time, become worn. Uneven application of braking force, debris, or uneven frictional surfaces on the brake friction pads can result in the formation of grooves, channels, or scratches in the surfaces of the brake disks or brake rotors. Repeated heating and cooling of the brake disk or brake rotor resulting in extreme temperature variations can additionally result in the lateral warping of the brake disk or brake rotor.
A worn or warped brake disk or brake rotor may be resurfaced by cutting or grinding to provide a uniform smooth brake friction pad contact surface if sufficient brake disk or brake rotor material remains to provide an adequate braking surface without compromising the structural integrity of the vehicle braking system. However, once a brake disk or brake rotor has been worn below a minimum safe thickness, it is unable to safely dissipate the heat generated by a brake application, and must be replaced.
To provide for a uniform surface, any abnormalities in the brake disk or brake rotor, such as a lateral warping must be detected and compensated for during the resurfacing procedures. An additional source of lateral warping defects in a brake rotor or brake disk is often over tightened attachment bolts or an uneven mounting surface onto which the brake disk or brake rotor is secured in the vehicle wheel assembly. If the brake disk or brake rotor is removed from the vehicle wheel assembly for a resurfacing operation, any abnormalities or defects resulting from the mounting of the brake disk or brake rotor to the vehicle wheel assembly may not be accurately identified or corrected during the resurfacing procedure. Accordingly, a variety of brake resurfacing machines or brake lathes have been developed to resurface brake disks and brake rotors while they remain mounted to the vehicle wheel assembly.
At the present time, to detect and correct warping of the disk surface, monitoring devices are used to determine disk runout and to correct disk deformations.
These devices are of various types although recently the sector has seen increasingly widespread use of lathes applied directly to the hub of the vehicle. These avoid the need to remove the brake disk and consequently speed up the entire repair process and also, in addition, perform repair with greater precision.
It is necessary for these devices that the lathe applied to the wheel be subsequently aligned with the axis of the wheel hub because the lathe is mounted on the axle using the wheel hub itself.
However, the wheel hub, either because of manufacturing defects or due to the presence of rust that forms at the points where the fastening screws are tightened or due to deformation caused by excessive tightening of the heel fastening screws, is never perfectly aligned with its own axle and this runout must be corrected in order to turn the brake disk.
Known equipment for turning brake disks generally include a support on which the lathe is mounted, a motor that drives the disk to be turned and an alignment and compensation device. This device may be manual or automatic depending on the model of the device.
If the alignment device is the manual type then the machine operator corrects for runout detected by optical or electronic devices by correcting suitable manual adjusters that align the lathe axis with that of the disk in order to perform correct turning.
This system has the problem that the operator who uses it must have a great deal of experience in correcting compensation parameters. As a consequence it is not suited for personnel without special expertise.
In the automatic version correction is no longer done manually but is done using special automatic detection and adjustment devices.
The main problem these devices present is the difficulty they have in correctly detecting runout between the hub and the relative disk.
Brake resurfacing machines or brake lathes configured to resurface brake disks and brake rotors mounted to a vehicle wheel assembly are commonly referred to as on-car brake lathes. By eliminating the need to remove the brake disk or brake rotor from the vehicle wheel assembly, the overall efficiency of the resurfacing procedure is improved, and the chances for operator induced error are reduced. However, the resurfacing of brake disks and brake rotors which remain mounted to the vehicle wheel assembly requires that the on-car brake lathe and the vehicle wheel assembly, including the brake disk or brake rotor, be aligned along a common axis, typically, the axis of the vehicle wheel assembly hub onto which the on-car brake lathe is secured.
Often, the hub surface to which the vehicle wheel assembly mounts, is not aligned within a required tolerance to the axis of rotation for the axle upon which the vehicle wheel assembly is secured. This deviation between the hub surface and the axis of rotation for the wheel assembly is referred to as lateral runout, and must be compensated for either manually or automatically before beginning the resurfacing procedures with the on-car brake lathe.
Manual runout compensation procedures are tedious and complex. First, an operator secures the on-car brake lathe to the vehicle wheel hub using a suitable adapter. Next, a motor in the on-car brake lathe is activated to rotate the adapter and brake disk or brake rotor. Any runout present in the system is measured by one or more measurement devices, which provide the operator with a suitable visual indication representative of the actual runout experienced by the on-car brake lathe as the adapter is rotated through one or more complete rotations. Using the visual indication, the operator manually adjusts one or more mechanical adjustment elements, such as screws or dials, altering the rotational axis of the on-car brake lathe to reduce the observed runout to within an acceptable tolerance for performing the resurfacing of the brake disk or brake rotor.
To reduce the observed runout to within the
Notaro $ Michalos PC
Onstruzioni Meccaniche Caorle S.p.A.
Walsh Brian D.
Wellington A. L.
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