Abstract:
An improved vibration attenuator for reducing undesired vibrations generated by cutter bits being drawn across the faces of a rotating brake rotor. The attenuator has friction pads with engagement members that extend therefrom which are configured to cause force to be exerted on the sides of fasteners that affix the cutter bits to the cutter arms in a direction parallel to the surface being machined and perpendicular to the direction of rotation of the rotor.

Description:
This application is a continuation-in-part of U.S. patent application Ser. No. 09/378,133 filed Aug. 19, 1999, now U.S. Pat. No. 6,227,085. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates to a vibration attenuator for attenuating the vibration caused during the machining or resurfacing of a disc brake rotor by a pair of cutter bits. 
     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. Additionally the rotors may become warped which could also have an adverse effect on the vehicle&#39;s braking capability as well as the undesirable effect of transmitting a pulsing to the brake pedal. The grooves and/or warpage must be removed by resurfacing or machining the face of the rotor. 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 the accompanying vibrations of the rotor and bits can adversely affect the accuracy of the machining. The vibration may also have an adverse effect on the bits causing them to over heat and wear prematurely. 
     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 effective in damping the machining noises. 
     Another system of the prior art utilizes a resilient band adapted to be stretched and placed about the circumference of the rotor. One must purchase a set of such bands to accommodate each of 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 to thereby damp rotor vibration. However, the pads are not effective to attenuate cutter bit vibrations. 
     U.S. Pat. No. 4,531,434 describes a device wherein two friction pads are biased against the rotor surfaces while the rotation of the rotors then forces the pads against the cutter arms and bits. Pins projecting from the pads engage the cutter arms to automatically maintain the pads in radial position relative to the arms or bits as they are gradually drawn across the faces of the rotor. However, its use in many lathe configurations is compromised in that the cutter bits must be extended an inordinate distance from the cutter arms in order to provide direct access to the bits by the pads. Although the resulting direct contact of the bit enhances the attenuating effect, the extension of the bit substantially offsets such effect as significantly greater vibration is being generated. Additionally, the handle of the device described in the patent interferes with the lathe carriage of many lathe systems which forces the pads to be angled relative to the bits and therefore further diminishes their efficacy. Further, in certain brake rotor lathe configurations, the cutter bit is attached to the cutter arm by a fastener that interferes with the direct contact of the bits by the attenuator pads as the pads are driven towards the bits by the rotation of the rotor. While such attenuator mechanism is fairly effective in attenuating the vibration, further improvement is desirable. 
     SUMMARY OF THE INVENTION 
     The vibration dampener of the present invention improves over previously known devices in that it is configured in such a manner so as to cause the force exerted on a brake rotor lathe&#39;s cutter bits to be oriented in a direction substantially perpendicular to the direction of rotation of the workpiece. Moreover, the device of the present invention provides for a substantial amount of the force that is generated by the rotation of the rotor against the device to be redirected into such perpendicular direction. The device functions in cooperation with a brake rotor lathe that has its cutter bits held in place on their respective cutter arms by a fastener with a raised head and wherein the cutter arms have an upwardly extending angled surface adjacent the fastener. By simultaneously engaging the angled surface and the side of the raised fastener, the attenuator is able to transfer a substantial amount of the force exerted by the rotating rotor on the device to the fastener and onto the bit in the appropriate direction. 
     An attenuator constructed in accordance with the present invention generally includes two friction pads fitted to two arms that are arranged in an opposed relationship wherein a spring extending between the arms biases the arms and hence the two pads towards one another so as to grasp a workpiece being rotated therebetween. The two arms are joined at their proximal ends to define a handle. More particularly, each of the friction pads includes a protruding engagement nub that is configured for simultaneously contacting the side of raised head of a fastener serving to affix the cutter bit to the cutter arm as well as the angled portion of the cutter arm. The handle is configured to enable the engagement nub to engage the side of the fastener and the angled surface of the cutter arm at the appropriate angle. 
     These and other features and advantages of the present invention will become apparent from the following detailed description of a preferred embodiment which, taken in conjunction with the accompanying drawings, illustrates by way of example the principles of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of the attenuator device in position on a brake rotor lathe; 
     FIG. 2 is an enlarged perspective view of the device of the present invention; 
     FIG. 3 is an enlarged side view of the attenuator in position on the lathe; and 
     FIG. 4 is an enlarged cross-sectional view taken along lines IV—IV of FIG.  1 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The attenuator device of the present invention is pinched onto a brake rotor during its resurfacing to reduce the noise that would otherwise be generated, to enhance the effectiveness of the machining operation and to extend the service life of the cutter bits. 
     FIG. 1 generally shows the device  42  of the present invention in position on a brake rotor  44  during a machining operation. The brake rotor is being rotated by the lathe arbor  46  in direction  47  and cutter bits  48  affixed to ends of cutter arms  50  are gradually drawn across the face of the rotor by the lathe&#39;s carriage  52  in a radially outward direction. The two cutter bits are held against the two faces of the rotor such that both faces of the rotor are simultaneously machined in a single machining operation. 
     FIG. 2 illustrates the attenuator  42  of the present invention. The device consists of a pair of friction pads  54  attached to a pair of arms  56  that are joined at their proximal ends to define a handle  58 . A tension spring  60  biases the arms and pads towards one another. Extending from the bottom of the pads are engagement nubs  63  each having a proximal edge  69  and a distal edge  71 . 
     FIG. 3 illustrates the interaction of the attenuator with the lathe components. The cutter bit  48  is attached to the cutter arm  50  by a fastener  64  that extends through the bit and is threaded into the arm. The fastener has a raised head  66  such as for example an Allen head. The cutter arm has an angled surface  67  proximally adjacent to the fastener which extends upwardly from the level of the fastener head. The engagement nub is shaped and dimensioned to simultaneously engage the angled surface as well as the fastener head wherein the proximal edge  69  of the nub engages a point along the angled surface while the distal edge  71  of the nub engages the side of the fastener head. The pad is shaped such that its proximal end  73  avoids contact with any portion of the cutter arm while its distal end  75  avoids contact with the top of the fastener head. The nub may be positioned anywhere along the length of the pad including a configuration wherein the distal edge of the nub is aligned with the distal end of the pad, a configuration wherein the proximal edge of the nub is aligned with proximal end of the pad or any intermediate position such as is shown in the illustrated embodiment. Alternatively, the length of the entire pad may conform to the length of the nub such that the proximal and distal ends of the pad are aligned with proximal and distal edges of the nub. The attenuator arms  56  are shaped to similarly allow the engagement nub to properly contact the angled surface of the cutter arm as well as the fastener head. Such shaping may take the form of an offset  65  in the handle to allow the proximal end of the handle to clear any lathe components that would otherwise cause the undesirable angling of the pads  54  and hence the engagement nubs  63  vis-a-vis the fastener head  66  and angled cutter arm surface  67 . 
     FIG. 4 is cross-sectional view taken through the rotor  44  and radially outwardly to illustrate the relationship of the pads  54 , and more specifically, the engagement nubs  63  with respect to the head  66  of fastener  64 . While the rotation of the rotor in direction  47  causes the pads to be driven against arms  50 , the gradual movement of the lathe carriage  52  in a radially outward direction causes the fastener heads  66  to be driven against the engagement nubs  63 . Additionally, the rotation of the rotor causes the proximal edge  69  of the nub  63  to be forced against the angled surface  67  of the cutter arm  50  wherein the angle of the surface causes such force to be redirected and come to bear against the side of the fastener heads via the distal edge  71  of the nub. Resistance by the pads being urged against the rotating rotor generates the resistive force that serves to attenuate the undesired vibration. 
     The pads  54  are each initially about ⅜″ each thick and are formed of brake lining material. The engagement nubs are an integral part of the pad extend downwardly approximately ⅜″. The arms  56  and handle  58  are formed of stainless steel wire and extend about 7 ½″ from the pads. The offset  65  in the handle is about ⅜″. An attenuator of the present invention with such dimensions is ideally suited for use with a brake rotor lathe sold under the trademark PRO-CUT. 
     The attenuator device  42  of the present invention is fabricated by cutting brake lining material to size to form the pads  54  with integral engagement nubs  63 . Slightly undersized holes are then drilled in the edges to receive the arms  56 . The components are forced together and are held in place by the resulting friction fit. The handle is then dipped in a rubber or other suitable resilient plastic material that provides an non-slip surface. The spring  60  is clipped into place to complete the assembly process. 
     In use, the attenuator device of the present invention is pinched onto the rotor being turned by the lathe. The friction generated by the pads  54  being forced against the rotor  44  surfaces by spring  60  causes the device to be forced in the direction of rotation ( 47 ) until the proximal edges  69  of the engagement nubs  63  make contact with the angled surfaces  67  of the cutter arms  50 . The angled nature of the surface causes the pad to be deflected such that the distal edge of the nub bears against the side of the raised fastener head  66 . The shape of the pads  54  and the shape of the handle  58  facilitate the simultaneous engagement of the fastener heads and the angled surfaces by the nubs. The force with which the nub is driven against the cutter arm by the rotation of the rotor is thereby redirected against the side of the fastener. The force by which the lathe carriage  52  is gradually drawn radially outwardly additionally comes to bear against the side of the raised fastener heads as the resistance of the pads against the rotor creates a resistive force oriented perpendicular to the direction of rotation of the workpiece. The total force applied to the side of the fastener head is transferred to the cutter bit and serves to attenuate the undesired vibrations. 
     While a particular form of the invention has been illustrated and described, it will also be apparent to those skilled in the art that various modifications can be made without departing from the spirit and scope of the invention. Accordingly, it is not intended that the invention be limited except by the appended claims.