Abstract:
Devices and methods for protecting against the theft of mobile equipment having at least one hydraulic cylinder (telescoping support member) that is extendable to a equipment immobilizing position, in which position the equipment is rendered immobile. A hollow strut which is dimensioned to receive the shaft of such a hydraulic cylinder and has sufficient length to maintain the hydraulic cylinder in its equipment immobilizing position, thereby maintaining the heavy equipment in its immobile state. The strut has two halves hinged to each other and is mountable about the shaft and lockable thereabout with an anti-theft locking mechanism. The anti-theft locking mechanism is concealed when the strut is maintaining the hydraulic cylinder in its equipment immobilizing position.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The field of the invention relates to locking devices and methods, more particularly the field of the invention relates to protecting against the theft of heavy construction equipment, mobile farm equipment and the like. 
     2. Brief Description of the Prior Art 
     A wide variety of mobile apparatus is used in the construction and farming industries. Such equipment is used in the moving and removing of earth, in the lifting and transporting of heavy materials, etc. The appararatus normally incorporates hydraulic cylinders which are power operated to move between positions of various extension, causing the tool equipment and the apparatus to perform its work functions. Hydraulic cylinders are also used to position temporary supports which improve the stability of the equipment during work operations. 
     It has been recognized that hydraulic cylinders can be immobilized by placing safety devices along the shaft of the cylinder. U.S. Pat. No. 3,135,555 to MeCaskey discloses a safety guard for the ram of an hydraulic hoist. In this patent there is disclosed the use of the safety guard to maintain the bed of a dump truck in a raised position. Similarly, U.S. Pat. No. 2,397,516 discloses a safety locking device that is adapted to lock a piston rod in a position to prevent accidental closure of bomb bay doors on workmen. U.S. Pat. No. 4,122,758 discloses a U-shaped support member to straddle the rod of a lift cylinder of a loader-type vehicle. Another such device for use with the brake assembly of railroad cars is disclosed in U.S. Pat. No. 3,430,735. Devices of this type serve their safety function quite well, but they do not serve the function of preventing theft, since they are readily removable. Moreover, many of the examples of use would not significantly affect the theft of the vehicle they are used on. 
     Theft of such mobile equipment is a problem of major proportions. Because of the equipment&#39;s inherent mobility, it is very susceptible to theft. When left unattended, the vehicle can easily be jump started and driven away. Even when attended, the vehicles are often not substantially protected against theft. Various pieces of equipment are often spread out over large areas. As a result, security is often inadequate to protect against unauthorized trespass. It is not unusual for a vehicle to be driven away (or onto a trailer) before the unauthorized trespass is detected. 
     SUMMARY OF THE INVENTION 
     In general terms, the invention relates to devices and methods for protecting against the theft of mobile equipment. Such equipment includes at least one hydraulic cylinder (telescoping support member) that is extendable to a position in which the equipment is rendered effectively immobile, such as in a weight-supporting or vehicle-turning position. A hollow strut is dimensioned to receive the shaft of such a hydraulic cylinder and has sufficient length to maintain the hydraulic cylinder in its equipment immobilizing position. The strut is mountable about the shaft and lockable thereabout with an anti-theft locking mechanism. In certain embodiments, the anti-theft locking mechanism is concealed when the strut is maintaining the hydraulic cylinder in its equipment immobilizing position. The objects and advantages of the present invention will become further apparent from the reading of the following specification. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side elevational view of a piece of mobile equipment being maintained in an immobile state by anti-theft device 10 in a longitudinally compressed state. 
     FIG. 2 is a fragmentary view of the hydraulic cylinder and support leg of the mobile equipment of FIG. 1, with anti-theft device 10 in an uncompressed state and in a position to be placed about the shaft of the cylinder. 
     FIG. 3 is a top plan, partially fragmented view of anti-theft device 10, sectioned along plane A--A of FIG. 4. 
     FIG. 4. is a fragmentary, side elevational view of anti-theft device 10 of FIG. 2. 
     FIGS. 5A and 5B display a fragmentary view of anti-theft device 10 of FIG. 2, with the device being in an unlocked condition (FIG. 5A) and in a locked condition (FIG. 5B). 
     FIG. 6 is a prospective view of anti-theft device 10 of FIG. 2, illustrating the hinged attachment of the two substantially half-tube members. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     For the purposes of promoting an understanding of the principles of the invention, reference will now be made to the embodiments illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, such alterations and further modifications in the illustrated device, and such further applications of the principles of the invention as illustrated therein being contemplated as would normally occur to one skilled in the art to which the invention relates. 
     Referring now to the drawings, FIG. 1 illustrates a piece of heavy mobile equipment 50 which is being maintained in an immobile state by anti-theft device 10. Mobile equipment 50 is a mobile earth shoveler, and includes an earth shovel 52 which is controllably operated by hydraulic cylinders 53 and 54. An operator can control the work function of earth shovel 52 from cabin 51. In cabin 51 an operator may also control the steering of the front wheels and the application of power to the rear wheels 55 and 56 of the mobile equipment 50. To improve stability during certain work functions, equipment 50 includes temporary support legs 57 and 58. Support legs 57 and 58 are moveable into weight supporting positions, whereby equipment 50 is stabilized and made immobile during work functions. In FIG. 1, temporary support leg 57 is in its retracted position, in which it is not in a weight supporting position. Support leg 58 is extended to a weight supporting position by extended hydraulic cylinder 59. Anti-theft device 10 is shown mounted to the shaft of hydraulic cylinder 59 in a longitudinally compressed state, thus maintaining support leg 58 in a load bearing condition to render equipment 50 immobile. 
     In FIG. 2, anti-theft device 10 is in an uncompressed state in a position to be placed about shaft 59A of hydraulic cylinder 59. Anti-theft device 10 includes a hollow strut of two substantially half tube members 11 and 12 whose bodies are made of cast aluminum. Half tube members 11 and 12 are hingeably attached to each other along one longitudinal joining line (see FIG. 6) and are latchably attached to each other along the opposite joining line. Half tube member 11 has a series of longitudinally spaced locking posts which extend tangentially from member 11. Half tube member 12 has a series of reciprocal longitudinally spaced bores, bores 31, 32, 33, 34, and 35, which are spaced and dimensioned to receive locking posts 21, 22, 23, 24, and 25. Handles 17 and 18 are attached to half tube members 11 and 12 respectively. Additionally, substantially half ring stainless steel plates 13, 14, 15, and 16 are attached to the end portions of half tube members 11 and 12. These half ring plates are removeable and may be replaced with other rings having a different inside diameter, so that the assembly could be used with other hydraulic cylinders having different shaft sizes. 
     In FIG. 3, it can be seen that half tube members 11 and 12 are hingeably attached to each other by longitudinal stainless steel pin 19. Anti-theft locking mechanism 45, of conventional plug lock design (circular tumbler design), is also visible in FIG. 3, and is key operated between locked and unlocked conditions. Alternatively, a combination lock or an in-line tumbler lock, etc. may be used in place of the circular tumbler design shown. Steel shield means include a plurality of longitudinally oriented stainless steel pins 41 archically spaced about anti-theft locking mechanism 45. In place of the stainless steel, hardened steel could be substituted. Steel pins 41 help to prevent a thief from obtaining access to anti-theft locking mechanism 45 by drilling through the aluminum casing. 
     In FIG. 4, it can been seen that stainless steel plate 14, which covers the anti-theft locking mechanism 45, is spring biased to an open position, whereby anti-theft locking mechanism 45 is exposed when anti-theft device 10 is not in a compressed, weight maintaining position. Steel plate 14 has three stainless steel shafts 42A, 42B, and 42C which are slideably positioned in holes such as hole 43 which contains spring 44. Retaining pins, such as pin 72B, are positioned in grooves, such as groove 71B, to limit the outward travel of the shafts 42A-C. 
     FIGS. 5A and 5B illustrate the manner in which anti-theft locking mechanism 45 selectively locks and unlocks the anti-theft device 10. Longitudinal rod 46 has a head 46X with a hexagonal recess into which a conventional hexagonal tool (such as an Allen wrench) may be inserted to rotate the rod with substantial torque. Access to end 46X of longitudinal rod 46 is controlled by anti-theft locking device 45. Rod 46 is positionable between: (1) a locked position (FIG. 5B) in which rod 46 intersects with longitudinally spaced bores 31, 32, 33, 34, and 35, thereby preventing removal of locking posts 21, 22, 23, 24 and 25 respectively, and (2) an unlocked condition (FIG. 5A) in which groved portions 46A, 46B, 46C, 46D, and 46E are rotated in the position wherein rod 46 does not interesect with bores 31, 32, 33, 34, and 35, whereby bores 31-35 can receive locking posts 21-25 respectively. In the same fashion that plate 14 has rods 42A-C, plates 13 15 and 16 have rods (not shown) extending into corresponding holes. However, these rods do not have the springs nor grooves associated with them. The set screw slot end of pin 72C is shown and is representative of the corresponding pins 72B and 72A (not shown). Set screws 72D-F and 74A-F are used to hold the rods from plates 13, 15 and 16. If desired, the plates may be modified to include rubber surfaces abutting the cylinder rod to minimize the chance of damage to the polished surface of the rod. 
     As an example of use, the support leg 58 of heavy mobile equipment 50 is extended to lift wheel 56 substantially above the ground. With the wheel 56 off of the gound, the propelling means of the mobile equipment is rendered inoperable. The extended shaft 59A of hydraulic cylinder 59 is placed in a weight supporting position bearing a portion of the weight of the equipment. Anti-theft device 10 in an uncompressed state, is mounted about shaft 59A and the anti-theft locking mechanism 45 is operated with a key (not shown) to latch mechanism 45 in a closed position. The hydraulic cylinder 59 is then released to compress against the anti-theft device 10. This not only conceals the anti-theft locking mechanism 45 beneath a load bearing surface of the strut, but also maintains the support leg 58 in a load bearing condition in view of the length of the anti-theft device 10. 
     While the invention is described in connection with the extension of a strut of mobile equipment, it is equally applicable to the extension of any other member of a piece of mobile equipment which would render the equipment immobile. This would include weight bearing implements of mobile equipment, for example, the blades of a road grader, the bucket of a backhoe, the front blade of a bulldozer, etc. Similarly, it would include other means of immobilization by preventing operation of steering cylinders on articulating machines or hydraulic assisted steering cylinders on power steering devices. Equipment which had its steering restricted to prevent driving straight ahead would would be effectively rendered immobile. 
     While there have been described above, the principles of this invention in connection with specific apparatus and techniques, it is to be clearly understood that this description is made only by way of an example and not as a limitation to the scope of the invention.