Abstract:
A trolley is provided for supporting and portably moving an on-car brake lathe. The trolley includes wheels for mobility and a pneumatic cylinder for height adjustment. The pneumatic cylinder includes a piston rod, piston, and air valve. The piston has an equalizing port for dampened movement throughout the cylinder&#39;s stroke. The air valve allows static height adjustment of the lathe.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates generally to equipment for servicing vehicle brakes. More particularly, the present invention relates to an on-car brake lathe having an improved support trolley. 
     It is well-known that the brake rotors of a disc brake must be periodically resurfaced in order to maintain optimum braking capacity. Traditionally, brake rotors have been resurfaced using a bench-mounted lathe. This process requires removing the rotor from the vehicle, machining the surface of the rotor on the bench-mounted lathe, and reinstalling the rotor. As one skilled in the art will appreciate, such a process requires substantial time and labor. 
     Unlike a bench lathe, an on-car brake lathe does not require removal of the brake rotor from the vehicle. Instead, the lathe device is attached to the vehicle hub so as to machine the rotor in place. An example of an on-car lathe is described in U.S. patent application Ser. No. 09/611,535, assigned to the assignee of the present application, and incorporated here by reference. 
     A typical on-car lathe weighs 60-100 pounds and includes a motor and drive shaft for turning the rotor, as well as cutting tools for machining the rotor surface. In addition, the on-car lathe includes a mechanism for attaching the lathe to the hub and aligning the lathe with the hub. That is, the drive shaft of the lathe motor should rotate about the same axis as the hub so the cutting tools will machine the rotor surface perpendicular to the hub&#39;s axis of rotation. 
     In practice, the on-car brake lathe must be mounted on the hub of a vehicle that is elevated on a hydraulic lift in a garage. Therefore, to be functional, the operator must be able to maneuver the lathe around the garage between various obstacles, such as other vehicles. In addition, the operator must raise or lower the lathe and change the orientation of the lathe to facilitate convenient and accurate alignment with the hub. 
     Current lathe support systems for on-car brake lathes generally employ a three spoke base with wheels for movement. Either a counterbalance or mechanical support structure is provided to adjust the height to facilitate attachment of the lathe to the vehicle. 
     A counterbalance support system uses a spring or gas shock located in a vertical telescoping structure to counterbalance the weight of the lathe at a single height. Although a counterbalance system is adequate for a single height, considerable operator effort is required to position the lathe at a height other than the equilibrium. 
     A mechanical support system uses a screw, ratchet, or hydraulic piston to raise or lower the lathe. Although this type of support system allows the operator to adjust the static height of the lathe, the adjustment is cumbersome, slow, and rigid. 
     SUMMARY OF THE INVENTION 
     The present invention recognizes and addresses the needs discussed above and others of prior art constructions and methods. Accordingly, it is an object of the present invention to provide an improved support trolley for an on-car brake lathe. 
     It is an additional object of the present invention to provide a support trolley that allows the operator to smoothly raise or lower an on-car brake lathe. 
     It is also an object of the present invention to provide a support trolley in which the nominal support height can be easily adjusted by an operator. 
     Some of these objects are achieved by an apparatus comprising an on-car brake lathe device and a trolley supporting the on-car brake lathe device. The trolley has a cylinder assembly including a cylinder housing, a piston located within the cylinder housing and a piston rod attached to the piston. The on-car brake lathe device is connected to the trolley such that relative reciprocative movement between the piston and the cylinder housing causes raising and lowering of the on-car brake lathe device. The piston defines an equalizing port for gas communication between an upper chamber and a lower chamber of the cylinder housing. 
     In some exemplary embodiments, the cylinder includes valve means for introducing and releasing air from the cylinder housing. For example, the valve means may comprise a SCHRADER® style valve. 
     Often, the trolley may further include a base structure and a mounting structure to which the on-car brake lathe is connected. The cylinder assembly is located between the base structure and the mounting structure. In many cases, the cylinder will be inverted such that a distal end of the piston rod is attached to the base structure. The cylinder housing, in turn, is attached to the mounting structure in such embodiments. 
     In some cases, the mounting structure may comprise an offset member adapted so that the on-car brake lathe will be located directly above the cylinder assembly. In addition, it will often be desirable to configure the apparatus such that the on-car brake lathe device will be pivotally connected to the trolley. A locking mechanism may be provided to lock the on-car brake lathe device in a selected pivoted position. 
     Other objects of the present invention are achieved by a trolley for supporting and positioning a piece of equipment. The trolley comprises a base structure and a mounting structure to which the piece of equipment is connected. A cylinder assembly is connected between the base structure and the mounting structure. The cylinder assembly includes a cylinder housing, a piston located within the cylinder housing and a piston rod attached to the piston. The piston separates first and second gas chambers in the cylinder housing. In addition, the piston defines an equalizing port to permit gas communication between the first and second chambers. 
     Other objects, features and aspects of the present invention are provided by various combinations and subcombinations of the disclosed elements, as well as methods for practicing the same, which are discussed in greater detail below. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A full and enabling disclosure of the present invention, including the best mode thereof to one of ordinary skill in the art, is set forth more particularly in the remainder of the specification, including reference to the accompanying figures, in which: 
     FIG. 1 is a perspective view of an apparatus constructed in accordance with the present invention; 
     FIG. 2 is a cross-section of the pneumatic cylinder taken along line  2 — 2  of FIG. 1; 
     FIG. 3A is a view of the piston taken along line  3 A— 3 A of FIG. 2; and 
     FIG. 3B is a view of the piston taken along line  3 B— 3 B of FIG.  2 . 
     Repeat use of reference characters in the present specification and drawings is intended to represent the same or analogous features or elements of embodiments of the invention. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     It is to be understood by one of ordinary skill in the art that the present discussion is a description of exemplary embodiments only and is not intended to limit the broader aspects of the present invention even though broader aspects are embodied in the present invention. 
     FIG. 1 illustrates an embodiment of a brake lathe  10  installed on a trolley  12  of the present invention. Trolley  12  generally comprises a base  20 , an intermediate support structure  22 , and an upper mounting assembly  24 . Base  20  includes a plurality of legs  26  that extend radially outward from a common center. Caster wheels  28  are located at the distal end of each leg  26  to facilitate movement of the trolley from place to place. 
     As can be seen, mounting structure  24  includes an offset arm  30  having one end attached, as indicated at  32 , to the upper portion of support structure  22 . Offset arm  30  includes a main arm portion  34  into which a telescoping member  36  is received. Telescoping member  36  may be raised or lowered to a desired vertical position and secured via bolt  38  or other suitable securement means. 
     Telescoping member  36  defines a pivot support  37  to which a mounting arm  39  is connected. Brake lathe  10  is, in turn, located on mounting arm  39 . As one skilled in the art will appreciate, the coupling between mounting arm  39  and brake lathe  10  can utilize any one or combination of several known methods such as welding, bolting, clamping and the like. Because brake lathe  10  is located on mounting arm  39 , it can be easily rotated about an axis A 1 . A locking mechanism  40  is provided so that an operator can lock brake lathe  10  in the desired angular orientation. 
     Referring now also to FIG. 2, support structure  22  includes a cylinder assembly  44  having a cylinder housing  46  in which a piston  48  is located. The proximal end of a piston rod  50  is secured to piston  48 . The distal end of piston rod  50  is secured to base  20 , as indicated at  51  in FIG.  1 . As a result of this “inverted” arrangement, piston  48  will remain fixed as cylinder housing  46  undergoes reciprocative movement in the vertical direction. Preferably, cylinder assembly  44  will also be constructed such that cylinder housing  46  (and all supported components) can be rotated relative to piston  48  about axis A 2  (FIG.  1 ). 
     Cylinder housing  46  includes respective end caps  52  and  54  so as to define a closed volume. It can be seen that piston rod  50  extends through a hole defined in bottom end cap  54 . The interface between piston rod  50  and bottom end cap  54  includes an o-ring or other suitable seal to prevent gas communication between the interior of cylinder housing  46  and the outside environment. 
     As can be most easily seen in FIG. 1, a valve fitting  56  is preferably provided for changing the quantity of gas in the cylinder housing. Preferably, fitting  56  may be a valve similar to that used on most inflatable tires having a valve fitting that opens when depressed (commonly referred to as a SCHRADER®style valve). This allows the operator to add air to increase the pressure in the cylinder using an air hose which is readily available in most repair garages. Fitting  56  also allows the operator to easily bleed air to reduce pressure inside the cylinder housing. 
     FIGS. 2,  3 A and  3 B are useful in explaining the operation of support structure  22 . Preferably, the diameter D 2  of piston rod  50  may be relatively large compared to the diameter D 1  of the piston. As can be seen, piston  48  separates the cylinder volume into an upper chamber  56  and a lower chamber  58 . A small equalizing port  60  is defined in piston  48  to allow gas communication between chambers  56  and  58 . As a result, the gas pressure in the respective chambers will be equal. 
     Assume initially that the support structure  22  is at equilibrium. At equilibrium, the height of cylinder housing  46  is static, and the air pressure above piston  48  exactly equals the air pressure below piston  48 . Additionally, the net upward force produced by the air inside of cylinder housing  46  exactly equals the weight being supported by support structure  22  (i.e., the weight of the lathe, mounting structure and cylinder housing). 
     From this initial equilibrium, assume the operator pushes down so as to lower the lathe. The operator&#39;s action causes cylinder housing  46  to also move down relative to the fixed piston. As cylinder housing  46  moves down, the total volume that may be occupied by air inside of cylinder housing  46  is decreased. This is because a longer portion of piston rod  50  will now be located inside of cylinder housing  46 . As a result, the pressure exerted by the air inside of cylinder housing  46  will increase and a greater net force in the upward direction will be produced. 
     Thus, downward movement of cylinder housing  46  produces a net increase in the supporting force which serves to oppose further downward movement. This damping characteristic provides for smooth movement of mounting assembly  24  in response to vertical forces. If the operator stops pushing down on mounting assembly  24 , the forces and reactions will be reversed. Cylinder housing  46  then returns to the original equilibrium height. 
     If the operator desires to raise the equilibrium height of lathe  10 , air is simply introduced into cylinder housing  46  through fitting  56 . The charged air increases the pressure within cylinder housing  46 , thus increasing the net upward force. Cylinder housing  46  will then move in the upward direction so as to increase the internal volume that can be occupied by air. Eventually, cylinder housing  46  reaches a new, higher equilibrium height. The equilibrium height may be similarly lowered by bleeding air from cylinder housing  46 . 
     It can thus be seen that the present invention provides a brake lathe device having an improved support trolley in furtherance of the noted objects. The pneumatic cylinder not only statically supports the lathe at an adjustable height, but it also facilitates smooth raising and lowering of the lathe in order to match the height of the vehicle&#39;s hub. The air fitting on the cylinder permits the operator to change the air pressure in the cylinder to change the static height of the lathe. The piston&#39;s equalizing port permits the cylinder to mechanically assist the vertical movement of the lathe throughout the cylinder&#39;s entire stroke. 
     While preferred embodiments of the invention have been shown and described, modifications and variations may be made thereto by those of ordinary skill in the art without departing from the spirit and scope of the present invention, which is more particularly set forth in the appended claims. In addition, it should be understood that aspects of the various embodiments may be interchanged both in whole or in part. Furthermore, those of ordinary skill in the art will appreciate that the foregoing description is by way of example only, and is not intended to be limitative of the invention so further described in such appended claims.