Vibration attenuator for disc brake rotor machining

A vibration attenuator for use in the machining of irregularly worn disc brake rotors. A pair of pads are arranged to rest upon lathe cutter bits acting against the opposite faces of the rotor. The pads are biased inwardly so that the rotation of the rotor forcibly urges the pads against the cutter bits and against the adjacent rotor surfaces for damping vibrations of these structures. Pins on the pads engage the cutter bits so that the pads move with the cutter bits as the machining operation proceeds, thereby maintaining damping engagement throughout the operation.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a vibration attenuator for attenuating the 
vibration caused during machining or resurfacing of a disc brake rotor by 
a pair of cutter bits. 
2. Description of the Prior Art 
After a period of use the faces of disc brake rotors of automobiles, trucks 
and the like become worn unevenly. A characteristic pattern of 
circumferentially arranged ridges and valleys develops which interferes 
with optimum braking action. These must be removed by resurfacing or 
machining. Typically this is done by mounting the rotor on an arbor 
assembly for rotation by a brake rotor lathe. A pair of cutter bits are 
moved by the lathe carriage across the faces of the rotating rotor to cut 
enough of the material away to render the faces flat or planar. During 
this operation the cutter bits and rotor typically produce loud, 
screeching noises which are not only unpleasant for the lathe operator and 
others in the vicinity, but there are accompanying vibrations of the rotor 
and bits which adversely affect the accuracy of the machining. 
Various means have been advanced to attenuate or eliminate such vibrations. 
One system employs damping pads designed to bear against the opposite 
faces of the rotor in a position out of the way of the cutter bits. The 
pads are carried by a relatively complex mounting structure which is 
secured to the brake lathe. Precise adjustment of the position of the pads 
is required, and an elaborate linkage arrangement is provided to 
accomplish this. The arrangement is relatively complex and costly, 
requires subtle adjustments, and is only partially affective in damping 
the machining noises. 
Another system of the prior art utilizes a resilient band adapted to be 
stretched and placed upon the circumference of the rotor. One must 
purchase a set of such bands to accommodate the various sizes of rotor to 
be machined. The system is unsatisfactory for that reason, and also 
because the vibration attenuation is not always adequate. 
Yet another arrangement of the prior art employs a U-shape rod or handle 
which mounts a pair of friction resistant pads at its extremities. The 
pads are placed in position to bear against the opposite faces of the 
rotor thereby to damp rotor vibrations. However, the pads are not 
effective to attenuate cutter bit vibrations. 
SUMMARY OF THE INVENTION 
According to the present invention, a vibration attenuator is provided 
which comprises a pad assembly including a pair of pads adapted to rest in 
frictional engagement against the opposite faces of a disc brake rotor. 
The pads are operative to rest upon the cutter bits, and bias means urge 
the pads against the rotor faces whereby rotation of the rotor in a brake 
lathe forcibly urges the pads against the lathe cutter bits. The 
consequent close association of the pads with the cutter bits attenuates 
their vibration, as well as that of the rotor. The pads each carry an 
element which projects into engagement with the cutter bits. On movement 
of the cutter bits in a cutting direction, these pad elements are carried 
by the bits, in turn causing movement of the pads in common with the 
cutter bits. The pads are thus constantly forcibly urged in damping 
relation against the cutter bits, this close, damping relation being 
maintained as the cutter bits move across the faces of the rotor during 
the cutting or resurfacing operation. 
In a preferred embodiment of the vibration attenuator, the pads are 
pivotable through 180 degrees in order to present fresh wearing surfaces 
once the original wearing surfaces have been worn down. 
Other objects and features of the invention will become apparent from 
consideration of the following description taken in connection with the 
accompanying drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
The present vibration attenuator, generally designated by the numeral 10, 
is illustrated in FIG. 4 in association with a typical brake rotor lathe 
which includes a usual lathe arbor assembly 12 and a cutter mounting 
carriage 14. The construction and operation of the rotor lathe will not be 
described in detail inasmuch as such details are well-known to those 
skilled in the art. Moreover, the lathe illustrated is merely exemplary. 
The attenuator 10 need not be associated with the particular lathe 
illustrated, but is adapted for operation with any lathe capable of rotor 
machining operations. The disc brake rotor 16 to be machined is fixed 
within the arbor assembly 12 for rotation by the lathe. The lathe carriage 
14 mounts a pair of tool holders 20, only one of which is illustrated, 
which carry a pair of cutting bits 18. Movement of the carriage 14 moves 
the cutter bits 18 across the opposite faces of the rotor 16 to machine or 
resurface the opposite rotor faces and render them parallel and flat or 
planar. 
Adjustment knobs 22 on the carriage 14 are rotatable to vary the depth of 
cut of the bits 18, as will be apparent to those skilled in the art. 
As previously indicated, machining of the rotor 16 by the cutter bits 18 
often produces very loud, harsh vibrations which are accompanied by 
vibration or chatter of the bits 18 such that accurate machining of the 
rotor faces is adversely affected. 
As best seen in FIGS. 1-3, the attenuator 10 comprises, generally, a pad 
assembly 24 which includes a pair of pads 26 made of suitable friction 
resistant material, such as the type of material used in automobile clutch 
linings. 
The pads are generally rectangular, measuring 13/4" by 11/4" by 3/8" thick. 
The pad assembly 24 also includes a U-shaped rod or handle 28 having a 
radius of approximately 2" at the bend area, the total length of the rod 
being approximately 18", with a 1/8" thick diameter. 
The handle 28 is dipped in a resilient liquid material, such as rubber or a 
suitable resilient plastic material, to provide a coating, indicated 
generally at 30 in FIGS. 5 and 6. The purpose of the coating 30 will be 
described subsequently. 
The extremities of the legs of the U-shaped handle 28 are press fitted 
within complemental openings drilled or otherwise formed in the pads 26. 
In addition, a pair of elements or pins 32 are press fitted within 
complemental openings provided in the underside of the pads 26, the pins 
32 thereby projecting downwardly for a purpose which will be described. 
The pins 32 preferably extend in their seating openings into contact with 
the legs of the handle 28. With this arrangement the pins 32 can be driven 
against the handle legs with a hammer to slightly indent the material of 
the handle legs and thereby constrain the pads against pivotal movement 
relative to the handle legs. However, as will be seen, the pads can be 
forcibly pivoted to reposition them to present fresh wearing faces. 
As seen in FIGS. 4-8, the handle 28 is normally positioned to rest upon the 
top of the carriage 14 with the pads 26 in frictional engagement with the 
opposite faces of the rotor 16, and in superjacent relation to the cutter 
bits 18. A bias means in the form of a tension spring 34 is disposed 
between the opposite legs of the handle 28. Loops (not shown) of the 
spring 34 are disposed about the handle legs and bear upon the coating 30. 
The coating presents a frictional constraint against inadvertent movement 
of the spring 34 along the length of the handle legs, preventing 
displacement of the spring 34 from the position in which it has been 
placed to develop an optimum spring force. The spring 34 can be 
deliberately moved by relieving the pull on the handle leg and moving it 
along the length of the handle leg, as desired. Springs of various spring 
rates can be selected, as required to provide optimum vibration damping 
for the particular type and size of rotor 16 and cutter bits. 
In FIG. 4 the rotation of the rotor 16 is seen to be clockwise, forcibly 
urging the pads 26 downwardly against the upper surfaces of the cutter 
bits 18. In addition, as the carriage 14 moves the cutter bits 18 radially 
outwardly in a cutting direction, the pads 26 are carried along with the 
cutter bits 18. This is accomplished by location of the pad pins 32 on 
that side of the cutte bits facing in the cutting direction. 
With the foregoing arrangement the pads 26 are always in biased contact 
with the cutter bits 18 and the adjacent faces of the rotor 16 during the 
cutting operation. This is in contrast to attenuators of the prior art 
which do not include any arrangement similar to the pins 32, whereby such 
prior art attenuators at best only damp vibrations of the rotor and have 
no corresponding affect on the cutter bits as such. 
As seen in FIGS. 9 and 10, once the inner faces of the pads 26 are worn 
down to the point where the legs of the handle 28 are in danger of being 
exposed, the pads 26 are pivoted 180 degrees to the positions illustrated 
in FIG. 10 to bring the unworn pad faces into operative position. 
From the foregoing it will be apparent that the present attenuator 10 is, 
unlike attenuators of the prior art, operative to maintain a close and 
continuing engagement with the cutter bits 18 to damp unwanted rotor and 
cutter vibrations at the exact source of such vibrations. This has been 
found to result in much quieter and more accurate machining of disc brake 
rotors. 
Various modifications and changes may be made with regard to the foregoing 
detailed description without departing from the spirit of the invention.