Abstract:
Disclosed is a hoist trolley having a pair of jacking plates with apertures for attaching the plates to a compressor. Fixed to the opposing ends of the jack-plates are telescopic legs with extendable retractable wheels and a screw jack that is used to elevate the load, once the plates are attached, enabling the wheels to be extended. Once extended, the jack base plate is raised with the wheels supporting the load. Transporting the load is accomplished by providing a pair of rails cantilevered from a stand. Also provides are additional elements to enhance the range of applications for the compressor trolley including a pry bar incorporating a motive member whereby the bar can be used in the similar function of supporting some part of the load while moving to a workspace and a depending pivot arm having one element of a fastener, with the other incorporated into an opposing jacking plate. Furthermore, the spaced apart trolley rails can include integral rollers.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to hoists and, more specifically, to a hoist trolley having means for elevating a load and means for transporting the load. Means for elevating the load comprises a pair of jacking plates having apertures passing through it providing means for attaching the plates to the load. Fixed to the opposing ends of the jack-plates are telescopic legs with extendable retractable wheels. In addition, the jacking element is incorporated therein comprising a screw jack that is used to elevate the load, once the plates are attached, enabling the wheels to be extended. Once extended, the jack base plate is raised with the wheels supporting the load. Transporting the load is accomplished by providing a pair of rails cantilevered from a stand. 
     The present invention also provides for additional elements to enhance the range of applications for the compressor trolley. Depicted within the illustrations is a pry bar incorporating a motive member whereby the bar can be used in the similar function of supporting some part of the load while moving to a workspace. Another illustration depicts a depending pivot arm having one element of a fastening means, with the other incorporated into an opposing jacking plate. Furthermore, the spaced apart trolley rails can include rollers spaced therebetween. 
     In operation, the rails are placed on each side of the load, in the preferred embodiment the hoist trolley is used to move one or more compressors from a refrigeration rack for maintenance or replacement. In this scenario, mounted compressors have bolt flanges that are spaced higher than the bottom of the compressor, about a quarter of an inch, enabling the base of the rails, which have a substantially L-shape in cross section, to be inserted under the bolt flanges and fastened to some structural support, the point being to prevent the rails from splaying especially under load. Jacking plates are then bolted to the compressor with the wheels suspended over the rails. Once fastened the screw jacks are employed to raise the compressor enough so that the wheels when lowered engage the rails and support the compressor. 
     It should be noted that the physical space needed to deploy the hoist trolley is not much more than the actual space taken up by the compressor. In some instances, a control panel is situated directly above the compressor(s) making it impossible or difficult to employ the prior art devices, such as comealong (Ratchet lever hoist), chain fall (Chain Hoist) and gantry crane. With the present invention the load need be raised no more than a few inches to drop the wheels down and moved along the rails to a point where maintenance can be more easily performed. 
     If it is necessary to replace the compressor, a frame and chain fall are provided as an additional element of the present invention. The rail-stand legs serve as sleeves to mount the chain fall frame providing means for dropping the defunct compressor and raising its replacement onto the rails. Installing or reinstalling a compress involves reversing the aforementioned process. 
     2. Description of the Prior Art 
     There are other jacking devices designed for load bearing. Typical of these is U.S. Pat. No. 1,709,153 issued to Pownall on Apr. 16, 1929. 
     Another patent was issued to Flowers on Oct. 31, 1933 as U.S. Pat. No. 1,933,211. Yet another U.S. Pat. No. 3,794,196 was issued to Terho et al. on Feb. 26, 1974 and still yet another was issued on Aug. 16, 1977 to Wallace as U.S. Pat. No. 4,041,875. 
     Another patent was issued to Wallace on Oct. 14, 1980 as U.S. Pat. No. 4,227,464. Yet another U.S. Pat. No. 4,446,587 was issued to Jump on May 8, 1984. Another was issued to Engler et al. on Aug. 16, 1988 as U.S. Pat. No. 4,763,800 and still yet another was issued on Sep. 20, 1994 to Wilson as U.S. Pat. No. 5,384,172. 
     Another patent was issued to Hall on Nov. 21, 2000 as U.S. Pat. No. 6,149,120. Yet another U.S. Pat. No. 6,273,662 was issued to Fleckenstein on Aug. 14, 2001. Another was issued to Fabriks Aktiebolaget Forslund on Sep. 26, 1951 as U.K. Patent No. GB657,946 and still yet another was issued on Jul. 27, 1983 to Penny as U.K. Patent No. GB2112737. 
     U.S. Pat. No. 1,709,153 
     Inventor: Henry D. Pownall 
     Issued: Apr. 16, 1929 
     In a fracture bed and the like, an adjustably supported sling including a band, a plurality of supporting links secured to each of opposite edges of the band, cross bars connecting opposite links, a rod connecting the cross bars, a yoke slidably supporting the rod, and means for adjusting the position of the yoke on the rod. 
     U.S. Pat. No. 1,933,211 
     Inventor: Henry Fort Flowers 
     Issued: Oct. 31, 1933 
     In a vehicle for transporting a plurality of containers, a source of power, a plurality of means actuated by said source for moving said containers, at least one of said actuated means being located between two of said containers, and devices for connecting a plurality of said actuated means to a selected one of said containers at points thereof spaced at right angles to the direction of sliding movement to be given the container and operating for sliding the container to and from its transport position on said vehicle when said source of power is energized, the device associated with said one actuating means being selectively engageable with either of the adjacent containers. 
     U.S. Pat. No. 3,794,196 
     Inventor: Matti Terho et al. 
     Issued: Feb. 26, 1974 
     A carrier for the loading and unloading of elongated freight containers includes a U-shaped body consisting of beams forming an inner space corresponding to the size of the container, and hydraulic means gripping and lifting the container. The U-shaped body has four wheels at its corners with hydraulic motors and steering means, an engine and a hydraulic pump driven by the engine and operatively connected with the hydraulic wheel motors, the steering means and the hydraulic gripping and lifting means. The operative connections of the pump include control means. 
     U.S. Pat. No. 4,041,875 
     Inventor: Bernard E. Wallace 
     Issued: Aug. 16, 1977 
     A load-handling gantry having a single, unitary, bridging beam, and leg, brace and mounting components supporting the beam with provision for adjustment of gantry span, height, and spread, while maintaining gantry mobility. The mounting components are adjustable to enable use of the gantry in a number of configurations including inboard, outboard, and combination leg bracing, and with freedom for use under cantilever conditions. In the preferred embodiment, a predetermined camber, or longitudinal splay angle, of the plane of each pair of legs is provided, to decrease movement between the gantry legs and the beam, in the direction lengthwise of the beam, when the gantry is under load, thereby stabilizing the gantry in that sense. The selected splay angle is maintained by apparatus which couples the leg bracing struts to the beam and to the legs. Any selected angle, under the various arrangements of leg bracing, may be had, and may be maintained, by such coupling apparatus, which provides alteration of the effective bracing strut length, without the necessity of actually substituting struts of different lengths. Lateral clearance between the beam, and the legs and bracing struts, is maintained in the various configurations, at a value such as to permit free movement of the leg and strut assemblies along the length of the beam, and also a measure of lateral flexibility of the gantry. All adjustments relative to the beam may be made through external frictional gripping apparatus, cooperable with a standard imperforate beam. 
     U.S. Pat. No. 4,227,464 
     Inventor: Bernard E. Wallace 
     Issued: Oct. 14, 1980 
     Leg structure for portable, height-adjustable gantries is disclosed having an upper, single vertical tubular post member telescopingly received within an open-ended sleeve formed by coupled aligned channel members of lower, break-apart sectional supporting framework. The channel members are supported and elevated by diagonal bracing members and struts giving a generally inverted-Y shaped configuration to the leg so that it can straddle objects and permitting the free, unobstructed downward passage of the post through the lower opening of the sleeve. A locking bolt passes through aligned holes in the post and channels to selectively hold their relative positions, with hand-operated winch means aiding the movement of the post. Post extension members are disclosed which can be added to the leg post while the gantry is assembled. The plate connection between the top of the post and a load-supporting I-beam is externally and internally braced by triangles and post weldment or casting insert elements, respectively. Alternative embodiments show plate and tubular spacer channel coupling arrangements, and solid post-to-frame and non-breakdown frame leg configurations. 
     U.S. Pat. No. 4,446,587 
     Inventor: Clarence E. Jump 
     Issued: May 8, 1984 
     A patient positioning device characterized by a horizontal support beam, a pair of motors coupled to the support beam, a first cable and hook assembly associated with a first motor, a second cable and hook assembly associated with a second motor, and a motor controller operative to selectively actuate the first motor, the second motor, or both motors simultaneously. Rigid, body contoured supports and/or flexible slings are coupled to one or both of the motors to selectively lift portions of a patient&#39;s body from a bed. 
     U.S. Pat. No. 4,763,800 
     Inventor: Edgar D. Engler 
     Issued: Aug. 16, 1988 
     A mobile lifting apparatus has a chassis with front driving wheels and steerable rear wheels. A vertical mast comprised of a pair of extendible hydraulic cylinders is spacedly mounted on the front of the chassis. One or more jam stay cylinders are mounted on the chassis rearwardly of the vertical mast. A pair of extendable booms are mounted on the vertical mast and jam stay cylinders. The load may be attached to the end of the booms. A hydraulic or other power supply extends and retracts the boom and drives the driving wheels. A counterweight is mounted on the rear of the chassis and the chassis may be extended to increase the capacity and stability of the lifting apparatus. 
     U.S. Pat. No. 5,348,172 
     Inventor: Frederick F. K. Wilson 
     Issued: Sep. 20, 1994 
     A mobile crane has a triangular wheel arrangement with a steerable front wheel and a frame for carrying an operator and a boom which is adjustable both as to vertical angle and azimuth. Shock absorbing stabilizing arm assemblies extend from either side of the frame, and an adjustable counterweight assembly is pivotally mounted at the rear of the frame, and can be adjusted to its optimum position, depending on the load, by the operator without his having to exert any lifting effort. The crane boom is likewise adjustable as to azimuth and elevation angle without the operator&#39;s having to move any heavy weight. 
     U.S. Pat. No. 6,149,120 
     Inventor: Donald M. Hall 
     Issued: Nov. 21, 2000 
     This invention pertains to a device having a first and second upright, a support rail connecting the first upright and the second upright, and a vertical spacer having a first edge, a second edge and a bearing surface. A portion of the first edge is disposed on the first upright and a portion of the first edge is disposed on the second upright. A guide rail having a top surface is disposed along the second edge of the vertical spacer. The guide rail extends over the bearing surface. The device further includes a sliding support member having a first roller, a second roller and a third roller. The first roller engages the top surface of the guide rail and is oriented for transmitting substantially only vertical forces from the sliding support member to the top surface. The second roller engages the support rail and is oriented for transmitting substantially only horizontal forces from the sliding support member to the support rail. The third roller is disposed beneath the top surface of the guide rail and the first roller, and engages the bearing surface of the vertical spacer. The third roller is oriented for transmitting substantially only horizontal forces from the sliding support member to the bearing surface section. 
     U.S. Pat. No. 6,273,662 
     Inventor: Mark A. Fleckenstein 
     Issued: Aug. 14, 2001 
     The invention is directed to a lifting device that can be used to lift, support and align articles such as cabinets, counter tops, shelving and the like during installation and removal. The lifting device includes a base, a hydraulic ram assembly, an adjustable L-shaped bracket assembly and an adjustable platform. The lifting device has a height adjustable range from thirteen inches to eight feet and is adapted to allow the load to be positioned directly over the lift or offset if an extended outward reach is needed. The adjustable platform is designed to allow the lifted article to be pivoted in multiple axes of rotation thereby allowing precision alignment of the cabinet with respect to the wall to which it is to be secured prior to installation. 
     U.K. Patent Number GB657,946 
     Inventor: Fabriks Artiebolaget Forslund &amp; Co. 
     Issued: Sep. 26, 1951 
     A hydraulic crane for motor vehicles has a cantilever arm for carrying a load and swinging both in a horizontal and a vertical direction, and a hydraulic device comprising a pressure cylinder and a piston for the movement of said arm in a vertical direction, characterized in that said arm is hinged to a bracket for up and down movement in a vertical plane, said bracket being firmly secured to said cylinder, and that said cylinder is supported to turn about its axis. As shown in FIG. 1, a tubular pedestal 1 secured to a plate 2 on the frame of a motor lorry receives an extension 3 of a hydraulic cylinder 4 rotatably mounted by means of a collar 5 on a collar 6 secured to the pedestal 1. The cylinder 4 carries a bracket 7 shaped to extend over the driver&#39;s cab and providing a pivot for a jib 8. The jib 8 is connected by a link 10 to a piston 9 working in the cylinder 4 and serving to luff the jib. The jib 8 comprises a pair of spaced vertical plates or is tubular or U-shaped in section to provide for the mounting of pulleys 14 and 15. A hoisting rope 13 passes from a load hook 12 over the pulleys 14, 15 and a pulley 16 on the cylinder 4 to an anchorage 17 on the jib. For sluing pressure liquid is admitted through conduits 20, 21 (FIG. 2) to a part-cylindrical housing 18 in which works a vane 19 secured to the projection 3 of the cylinder 4 and dividing the housing 18 into two chambers. 
     U.K. Patent Number GB2112737 
     Inventor: John Summers Penny 
     Issued: Jul. 27, 1983 
     A van type vehicle 1 comprises adjacent one side 3 at its rear end, a single jib crane 5, incorporating a substantially vertical column, a lower end 7 of which is attached to, and supported from, the vehicle floor 2, and an upper and 6 of which is attached to the vehicle roof 4, a rotatable element mounted on the column and a jib 25 carried by the rotatable element and rotatably supporting a rotary pulley 30 or sprocket for a flexible lifting/lowering element 32 associated with the crane 5, means 31 to displace the flexible lifting/lowering element 32 and/or pulley 30 or sprocket, and the jib 25 being swingable from an inboard, storage position within the vehicle 1 to on outboard, operative position. 
     While these jacking devices may be suitable for the purposes for which they were designed, they would not be as suitable for the purposes of the present invention, as hereinafter described. 
     SUMMARY OF THE PRESENT INVENTION 
     A primary object of the present invention is to provide a trolley hoist for raising and transporting a load. 
     Another object of the present invention is to provide a trolley hoist having a pair of spaced apart rails providing means for transporting a load. 
     Yet another object of the present invention is to provide a trolley hoist wherein said rails extend from a stand in cantilevered fashion. 
     Still yet another object of the present invention is to provide a trolley hoist wherein said rails have a substantially L-shape cross section. 
     Another object of the present invention is to provide a trolley hoist having a pair of jack-plates. 
     Yet another object of the present invention is to provide a trolley hoist wherein said jack-plates include a plate having a plurality of throughbores whereby said jack-plates can be fastened to a load. 
     Still yet another object of the present invention is to provide a trolley hoist wherein said jack-plates incorporate extendable retractable wheels located on opposing plate ends. 
     Another object of the present invention is to provide a trolley hoist wherein said jack-plates have a screw jack forming an integral part therewith. 
     Yet another object of the present invention is to provide a trolley hoist wherein said wheels are in communication with said screw jack. 
     Still yet another object of the present invention is to provide a trolley hoist having a pry bar including a motive member forming an integral part therewith for supporting some part of the load during relocation. 
     Another object of the present invention is to provide a trolley hoist having a pair of said pry bars with connecting members spaced approximately similar to the track spacing during a relocation task. 
     Yet another object of the present invention is to provide a trolley hoist optionally incorporating support arms extending between jacks plates as additional support members. 
     Still yet another object of the present invention is to provide a trolley hoist wherein said support arms are pivotally extending from a jacking plate with the other plate having at least one element of a securing means. 
     Another object of the present invention is to provide a trolley hoist wherein said spaded apart rails can have roller bearings positioned therebetween. 
     Additional objects of the present invention will appear as the description proceeds. 
     The present invention overcomes the shortcomings of the prior art by providing a hoist trolley having means for elevating a load and means for transporting the load. Means for elevating the load comprises a pair of jacking plates having apertures passing through it providing means for attaching the plates to the load. Fixed to the opposing ends of the jack-plates are telescopic legs with extendable retractable wheels. In addition, the jacking element is incorporated therein comprising a screw jack that is used to elevate the load, once the plates are attached, enabling the wheels to be extended. Once extended, the jack base plate is raised with the wheels supporting the load. Transporting the load is accomplished by providing a pair of rails cantilevered from a stand. 
     The present invention also provides for additional elements to enhance the range of applications for the compressor trolley. Depicted within the illustrations is a pry bar incorporating a motive member whereby the bar can be used in the similar function of supporting some part of the load while moving to a workspace. Another illustration depicts a depending pivot arm having one element of a fastening means, with the other incorporated into an opposing jacking plate. Furthermore, the spaced apart trolley rails can include rollers spaced therebetween. 
     The foregoing and other objects and advantages will appear from the description to follow. In the description reference is made to the accompanying drawings, which forms a part hereof, and in which is shown by way of illustration specific embodiments in which the invention may be practiced. These embodiments will be described in sufficient detail to enable those skilled in the art to practice the invention, and it is to be understood that other embodiments may be utilized and that structural changes may be made without departing from the scope of the invention. In the accompanying drawings, like reference characters designate the same or similar parts throughout the several views. 
     The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is best defined by the appended claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING FIGURES 
       In order that the invention may be more fully understood, it will now be described, by way of example, with reference to the accompanying drawing in which: 
         FIG. 1  is an illustrative view of the present invention in use; 
         FIG. 2  is an illustrative view of the present invention&#39;s order of operations; 
         FIG. 3  is an end view of the present invention&#39;s order of operations; 
         FIG. 4  is an isometric view of the present invention&#39;s jacking mechanism; 
         FIG. 5  is an isometric view of the present invention&#39;s first order of operation; 
         FIG. 6  is an isometric view of the present invention&#39;s second order of operation; 
         FIG. 7  is an isometric view of the present invention&#39;s third order of operation; 
         FIG. 8  is an isometric view of the present invention&#39;s fourth order of operation; 
         FIG. 9  is an isometric view of the present invention&#39;s fifth order of operation; 
         FIG. 10  is an isometric view of the present invention&#39;s sixth order of operation; 
         FIG. 11  is an isometric view of the present invention in use; 
         FIG. 12  is an illustrative view of the present invention&#39;s hoist system; 
         FIG. 13  is an isometric view of an additional element of the present invention; 
         FIG. 14  is a top view of an additional element of the present invention; 
         FIG. 15  is a side view of an additional element of the present invention; 
         FIG. 16  is a side view of an additional element of the present invention; 
         FIG. 17  is an isometric view of an additional element of the present invention; and 
         FIG. 18  is a detailed isometric view of an additional element of the present invention. 
     
    
    
     DESCRIPTION OF REFERENCED NUMERALS 
     
         
         
           
               10  hoist 
               12  load 
               14  load support 
               16  load anchors 
               18  load common holes 
               20  jacking apparatus 
               22  crank 
               24  crank receiver 
               26  jack post 
               28  worm gear jack 
               30  jack base 
               32  jack plate 
               34  jack plate apertures 
               36  jack plate sleeve 
               38  jack plate sleeve aperture 
               40  extendible leg 
               42  extendible leg caster 
               44  extendible leg aperture 
               46  locking pin 
               48  rails 
               50  rails adjustable support 
               52  support extendible leg 
               54  locking pin aperture 
               56  locking pin 
               58  overhead frame 
               60  chain fall 
               62  pry bar 
               64  shaft 
               66  handle 
               68  prying tip 
               70  wheels 
               72  rollers 
               74  jack 
               76  jack arm 
               78  bracket 
               80  bracket aperture 
               82  locking pin 
               84  adjustable leg bore 
           
         
       
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The following discussion describes in detail one embodiment of the invention (and several variations of that embodiment). This discussion should not be construed, however, as limiting the invention to those particular embodiments, practitioners skilled in the art will recognize numerous other embodiments as well. For definition of the complete scope of the invention, the reader is directed to appended claims. 
     Referring to  FIG. 1 , shown is an illustrative view of the compressor trolley of the present invention. The compressor trolley  10  is design to remove a load  12 , such as compressor  12 , from a confined space  14  to a position providing access to the compressor&#39;s exterior surfaces and in some instances to replace the defective compressor  12 . The compressor trolley comprises jacking plates  20  that are fastened to the compressor  12  so that it can be raised sufficiently to lower the extendable legs having casters thereon, which engage rails  48  having an end positioned support  50  allowing the compressor  12  to be moved from the compressor rack  14  to a more advantageous workplace. 
     Referring to  FIG. 2 , shown are the operative steps employed in utilizing the present invention. In the preferred embodiment of the present invention, load  12  is depicted as a compressor but the utility of the compressor trolley  10  can be used in other areas where a load  12  having only inches within a support frame need to be removed therefrom. In step one, the compressor trolley  10  uses one or more jacking plates  20  that are releasably attached to compressor  12  using fasteners positioned within apertures  18  of plate  32  and fastened to the compressor common holes  18 . In step two, rails  48  are positioned under the compressor and using rails support  50  having extendible legs  52  are adjusted parallel with the compressor&#39;s base. In step three, the compressor is raised by extending jack base  30  of worm gear jack  28  using crank handle  22  to an appropriate height. As illustrated in step four, once raised to the appropriate height extendible legs  40  having casters  42  are lowered into engagement with rails  48  and secured using locking pins  46 . In step five, using crank  22  jack base  30  is raised until the compressor is supported by the extendible legs having castors  42  in engagement with rails  48 . In step six, shown is the compressor moved to a position along rails  48  to a desired workable location for service or replacement of the unit. 
     Referring to  FIG. 3 , shown is another illustration of the order of operation in the attachment and raising of the compressor. In step one, the compressor mounting bolts are removed. Shown in step two, the jacking apparatus is secured to the compressor using the compressor common bolt holes. In step three, the compressor is raised to the appropriate height for positioning of the rails. Shown in step four the rails are positioned under the casters and leveled. Shown in step  5 , the casters of the extendible legs are lowered into engagement with the rails, where as shown in step six the base of the jack is raised until the compressor is supported on the casters. 
     Referring to  FIG. 4 , shown in the jacking apparatus of the present invention. The jacking apparatus  20  is comprised of worm gear jack  28  having extendible jacking base  30  and jack post  26  for attachment of crank  22  using crank receiver  24 . The worm gear jack  28  is fixed to jack plate  32  having jack plate apertures  34  whereby jacking plate  32  can be releasably fastened to a load. Positioned on each end of jacking plate  32  are jack plate sleeves  36  with bore  38  passing therethrough. Sleeve  36  forms housing for extendible legs  40  having a plurality of leg apertures  44 , which when aligned with sleeve aperture  38  provides for insertion of locking pin  46 . Extendible legs  40  incorporate caster wheels  42  so that when extended means is provided for transporting a load  12  to a desired location. 
     Referring to  FIG. 5 , shown is an isometric view of a compressor mounted to a rack. As aforementioned, the compressor trolley  10  is design to remove a load, such as compressor  12 , from a confined space, such as refrigeration rack  14 . For clarity purposes the illustration of the confined space is limited to  FIG. 1 . To allow free movement of the compressor, the user removes all mounting hardware  16  that secures the compressor  12  to refrigeration rack  14  and attaches the jacking apparatus  20  to the compressor common bolt holes  18 . 
     Referring to  FIG. 6 , shown is an isometric view of the compressor trolley system of operation shown as step one in  FIG. 2 . In step one, the compressor trolley  10  uses one or more jacking plates  20  that are releasably attached to compressor  12  using fasteners positioned within apertures  34  of plate  32  and fastened to the compressor common holes  18 . 
     Referring to  FIG. 7 , shown is an isometric view of the compressor trolley system of operation shown as step two in  FIG. 2 . In step two, rails  48  are positioned under the compressor and using rails support  50  having extendible legs  52  are adjusted parallel with the compressor&#39;s base. 
     Referring to  FIG. 8 , shown is an isometric view of the compressor trolley system of operation shown as step three in  FIG. 2 . In step three, the compressor is raised by extending jack base  30  of worm gear jack  28  using crank handle  22  to an appropriate height. 
     Referring to  FIG. 9 , shown is an isometric view of the compressor trolley system of operation shown as step four in  FIG. 2 . As illustrated in step four, once raised to the appropriate height extendible legs  40  having casters  42  are lowered into engagement with rails  48  and secured using locking pins  46 . 
     Referring to  FIG. 10 , shown is an isometric view of the compressor trolley system of operation shown as step five in  FIG. 2 . In step five, using crank  22  jack base  30  is raised until the compressor is supported by the extendible legs having castors  42  in engagement with rails  48 . 
     Referring to  FIG. 11 , shown is an isometric view of the compressor trolley system of operation shown as step six in  FIG. 2 . In step six, shown is the compressor moved to a position along rails  48  to a desired workable location for service or replacement of the unit. By moving the compressor to an open area along the trolley, the user is provided means to work more safely and efficiently. The present invention provides compressor trolley  10  with one or more jacking plates  20  that are releasably attached to compressor  12  using fasteners positioned within apertures  18  of plate  32  and fastened to the compressor common holes  18 . Rails  48  are positioned under the compressor and using extendible legs  52  of rails support  50  are adjusted parallel with the compressor&#39;s base. The compressor is raised by extending jack base  30  of worm gear jack  28  using crank handle  22  to an appropriate height whereupon extendible legs  40  having casters  42  are lowered into engagement with rails  48  and secured using locking pins  46 . Crank  22  is used to raise jack base  30  until the compressor is supported by extendible legs  40  having castors  42  in engagement with rails  48  so that compressor can be moved along rails  48  to a desired workable location for service or replacement of the unit. 
     Referring to  FIG. 12 , shown is an additional element of the compressor trolley comprising a gantry for lowering a compressor and raising a replacement compressor. The gantry  58  is comprised of four extendible retractable legs with top most supports extending therebetween. A beam supported by an A-frame runs between and co-parallel with the rails  48  having a chain fall  60  depending therefrom. The gantry  58  provides the user means to place or remove a compressor  12  to and from the rails  48  utilizing a second pair of stanchions fastened to the rails so that once the jacking plates  20  are removed the compressor can be lowered. Once the replacement compressor  12  is raised between the rails  48  the jacking plate apparatus  20  are reattached and the compressor is moved back into position. The complete trolley system allows for improved efficiency and safety of compressor installation and maintenance. 
     Referring to  FIG. 13 , shown is an isometric view of another additional element of the present invention comprising a rolling pry bar used to raise the compressor&#39;s rear portion. In some instances there is insufficient room for the rear jacking apparatus  20  to be fixed to the rear of the compressor  12 . Therefore, the present invention provides a wheeled pry bar  62 . In operation, the compressor mounting bolts are removed and the front jacking apparatus  20  is secured to the compressor using the compressor common bolt holes. The compressor is raised and the rails  48  are positioned under the casters and leveled. The extendible legs are lowered into engagement with the rails and the jack base is raised until the front end of the compressor is supported on the casters. Now placing the wheels of the pry bar into the rails, the pry bar tip is used to elevate the back end of the compressor so that it can be rolled out to a desired position. 
     Referring to  FIG. 14 , shown is a top view of the rolling pry bar. Providing an alternate means of raising the rear of a compressor, the rolling pry bar  62  comprises shaft  64  with handles  66  at one end and prying tip  68  at the other end with wheels  70  therebetween. 
     Referring to  FIG. 15 , shown is a side view of the pry bar additional element of the present invention. The present invention provides an alternate means for raising the back end of a compressor when there is insufficient room to utilize jacking apparatus  20 . As illustrated, the compressor mounting bolts are removed and the front jacking apparatus  20  is secured to the compressor using the compressor common bolt holes. The compressor is raised and the rails  48  are positioned under the casters and leveled. The extendible legs are lowered into engagement with the rails and the jack base is raised until the front end of the compressor is supported on the casters. Placing the wheels  70  of pry bar  62  into rails  48 , the pry bar tip  68  is used to elevate the back end of the compressor  12  so that it can be rolled out to a desired position using pry bar handles  66 . 
     Referring to  FIG. 16 , shown is another additional element of the present invention comprising a series of rollers  72  that are especially suited for the removal of a compressor in a sideways means to allow for the removal of the compressor without hindrance from existing structure local to the compressor queued for removal. 
     Referring to  FIG. 17 , shown is an isometric view of another additional element of the present invention in the form of an alternate jacking apparatus  74 . With each of the caster supports extended into the rails, the jack cylinder is retracted by rotating the crank. When the jack base is raised above the compressor mounting surface, the load is transferred to the casters. In turn, the compressor is free to travel the length of the rails. 
     Referring to  FIG. 18 , shown is an enlarged isometric view of an additional element of the jacking apparatus of the present invention. An alternate jacking apparatus is provided that extends under the back end of the compressor and uses a similar worm gear jack  74  to raise and lower the compressor support. Extending from jack  74  is arm  76  terminating in bracket  78  having bracket aperture  80 . Bracket  78  straddles the front extendible leg having throughbore  84  with locking pin  82  extending through aperture  80  and bore  84  providing a swivel/pivot joint to connect the adjustable caster  74 . 
     It will be understood that each of the elements described above, or two or more together may also find a useful application in other types of methods differing from the type described above. 
     While certain novel features of this invention have been shown and described and are pointed out in the annexed claims, it is not intended to be limited to the details above, since it will be understood that various omissions, modifications, substitutions and changes in the forms and details of the device illustrated and in its operation can be made by those skilled in the art without departing in any way from the spirit of the present invention. 
     Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention.