Abstract:
A tow vehicle such as a tow truck, adapted to obliquely approach and engage an object to be lifted. The vehicle has a boom mounted to a stable base and a swivel joint dividing the boom into a proximal section and a relatively pivotal distal section. Preferably, an orbiting electrical gearmotor fixed to the proximal section pivots the distal section by engaging a toothed rack formed as part of the distal section. Pivot is limited to a maximum of ninety degrees to the right and ninety degrees to the left by limit switches, where these directions signify deviation from longitudinal alignment of proximal and distal sections of the boom. The gearmotor is controlled by a mobile control station having manual selective pushbutton operators. The boom is hydraulically raised and lowered, and terminates in a cradle pivotally fixed thereto. The cradle has jaws which can close over the object being lifted. The tow vehicle optionally includes powered outriggers for stability.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to motorized tow vehicles of the type having an inclinable boom for lifting an object to be towed and a cradle for engaging the object.  
           [0003]    2. Description of the Prior Art  
           [0004]    Tow trucks are frequently employed to tow disabled vehicles from one location to another. In many cases, the disabled vehicle is a passenger automobile which may be initially parked in a location which prevents the tow vehicle from approaching directly from the front or rear of the disabled vehicle. It is frequently the case, for example, that a vehicle which is parallel parked against a curb between surrounding vehicles must be towed from its location.  
           [0005]    This presents the tow truck driver with a problem. Namely, the vehicle to be towed must be sufficiently near the boom of the tow truck to be solidly engaged therewith. If direct access to the front or rear of the vehicle is obstructed by other parked cars or other obstructions, ready engagement of the vehicle to be towed becomes difficult.  
           [0006]    The prior art has suggested modifications to tow trucks to cope with this problem. Booms of tow trucks have, for example, been provided with swiveling lifting cradles. Conventional practice with such tow trucks is to maneuver until the tow vehicle and the vehicle to be towed are perpendicularly oriented. The lifting cradle of the boom is turned on a swivel joint so that it can appropriately engage the axle of the subject vehicle. The tow truck drives away in a direction perpendicular to that of the formerly parked vehicle. This situation presents obvious hazards if the subject vehicle is parked on a frequently used street. Also, the street may possibly be too narrow to permit the tow truck to maneuver into and out of position to enable the “right angled pick-up” described above.  
           [0007]    Other modifications to tow vehicles have been proposed. U.S. Pat. No. 4,955,777, issued to Malcolm P. Ineson on Sep. 11, 1990, shows a tow tractor having a boom which incorporates two swivel points. However, Ineson&#39;s tractor lacks a swivel located towards the center of the boom, as seen in the present invention, as well as structure for engaging wheels of a motor vehicle.  
           [0008]    U.S. Pat. No. 3,871,535, issued to Joseph G. Fenske on Mar. 18, 1975, illustrates a tow vehicle having a pivoting boom. There is no swivel joint at the center of the boom, as seen in the present invention.  
           [0009]    U.S. Pat. No. 5,709,522, issued to John M. Cullum on Jan. 20, 1998, shows a tow truck having two different pivot points at the crossbar of a boom. The pivot points have axes in different planes, unlike the present invention. Cullum lacks the jointed boom as seen in the present invention.  
           [0010]    U.S. Pat. No. 4,838,754, issued to Homer J. Beliles et al. on Jun. 13, 1989, discusses maneuvering similar to that performed when lifting a motor vehicle at a right angle. The novel boom is not seen in Beliles et al.  
           [0011]    U.S. Pat. No. 4,761,111, issued to Andrew M. Brown on Aug. 2, 1988, shows a lifting device having two pivot points wherein the axes are in the same plane. However, unlike the present invention, the pivot points are located at the vehicle engaging cradle rather than being centrally located relative to the boom.  
           [0012]    U.S. Pat. No. 5,782,601, issued to Paul M. Wilson on Jul. 21, 1998, shows use of gears and a worm drive in a boom. There is no swivel joint at the center of the boom.  
           [0013]    U.S. Pat. No. 4,473,334, issued to Andrew M. Brown on Sep. 25, 1984, describes local and remote controls for tow truck hydraulic systems, but fails to show a swivel joint at the center of the boom.  
           [0014]    The prior art fails to suggest tow vehicle having a boom including a swivel joint having a vertical axis of rotation. A need remains for a tow truck which can lift one end of a motor vehicle while parked parallel to, but out of direct longitudinal alignment with, a wheeled vehicle to be towed.  
           [0015]    None of the above inventions and patents, taken either singly or in combination, is seen to describe the instant invention as claimed.  
         SUMMARY OF THE INVENTION  
         [0016]    The present invention solves the problem of lifting a motor vehicle which has been “parked in” or otherwise obstructed from ready access to one axle for engagement lifting by a tow truck. This is accomplished by providing a swivel joint having a vertical axis of rotation in the boom of the tow truck. Because the cradle is mounted to the boom at a similar joint, orientation of the cradle and the tow truck chassis can remain parallel even when the azimuth of one section of the boom swings through an arc about the vertical axis of the joint at the center of the boom.  
           [0017]    It is therefore possible for a tow truck incorporating the present invention to lift and tow a motor vehicle from a parallel parking situation from a location ahead or behind that vehicle, yet also to the side of the vehicle. Illustratively, a tow truck could station itself forwardly of the vehicle to be towed, and parallel to the subject vehicle in the manner of a “double parked” vehicle. Once one axle of the vehicle was secured and lifted, the tow truck could drive away starting from an orientation similar to that of passing traffic. Need for maneuvering into oncoming traffic or otherwise intruding into active driving lanes of a street is minimized or eliminated. This ability in some cases will enable a tow truck to successfully tow a vehicle in situations lacking sufficient maneuvering space for a conventional tow vehicle. Even in those situations in which a conventional vehicle could tow the subject disabled vehicle, a tow truck incorporating the novel improvements could save time, effort, and exposure to risk of hazards.  
           [0018]    Preferably, a tow vehicle modified according to the present invention incorporates a source of power to swivel the rear section of the boom relative to the front section so that the rear section is maneuvered proximate an axle of the subject disabled vehicle. In the preferred embodiment, this is accomplished by a hydraulic gear motor powered from the conventional hydraulic system which powers the lifting function of the boom. The rear section of the boom has a toothed rack which cooperates with the gearmotor. Controls may include pushbutton controls either mounted on the tow truck body or chassis, in the cab, or may alternatively be located on a mobile, hand held control station.  
           [0019]    Accordingly, it is one object of the invention to provide a tow vehicle which has an inclinable boom incorporating a swivel joint along the boom, and preferably towards the center of the boom.  
           [0020]    It is another object of the invention to enable a tow vehicle to lift and tow an immobilized vehicle from an orientation parallel yet offset from the immobilized vehicle.  
           [0021]    It is a further object of the invention to enable a tow vehicle to maneuver into proximity with an immobilized vehicle without unduly intruding into nearby traffic lanes when maneuvering into position to lift the subject vehicle and when driving away with the subject vehicle in tow.  
           [0022]    Still another object of the invention is to enable a tow vehicle to approach an immobilized vehicle in tight quarters.  
           [0023]    An additional object of the invention is to provide a source of power for swinging the rear section of the boom.  
           [0024]    It is again an object of the invention to utilize an otherwise conventional hydraulic power system of a tow vehicle.  
           [0025]    Yet another object of the invention is to provide a mobile, hand held control station to operate the power system of the boom.  
           [0026]    It is an object of the invention to provide improved elements and arrangements thereof in an apparatus for the purposes described which is inexpensive, dependable and fully effective in accomplishing its intended purposes.  
           [0027]    These and other objects of the present invention will become readily apparent upon further review of the following specification and drawings.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0028]    Various other objects, features, and attendant advantages of the present invention will become more fully appreciated as the same becomes better understood when considered in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the several views, and wherein:  
         [0029]    [0029]FIG. 1 is an environmental, bottom plan view of one embodiment of the invention.  
         [0030]    [0030]FIG. 2 is an environmental, bottom plan view of the prior art.  
         [0031]    [0031]FIG. 3 is a side elevational detail view of a vehicle shown at the upper left of FIG. 1, drawn to enlarged scale.  
         [0032]    [0032]FIG. 4 is a bottom plan detail view of the vehicle shown at the upper left of FIG. 1, drawn to enlarged scale.  
         [0033]    [0033]FIG. 5 is a top plan detail view of the vehicle shown at the upper left of FIG. 1, showing optional outriggers.  
         [0034]    [0034]FIG. 6 is a diagram of power and control components of the embodiment of FIG. 1.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0035]    [0035]FIG. 1 of the drawings shows one embodiment of the invention wherein a tow truck  100  has approached and is lifting a disabled motor vehicle  10  to be towed. In the situation depicted in FIG. 1, motor vehicle  10  is parked parallel to a curb (not shown) between adjacent vehicles  12 ,  14 . Tow truck  100  has approached vehicle  10  and has engaged vehicle  10  from an oblique angle. Tow truck  100  includes a conventional frame, body, or chassis to which are connected front wheels  102 ,  104 , an engine  106 , a drive train including transmission  108  and differential gear assembly  110 , a rear axle  112 , and driven wheels  114 ,  116 . These elements are conventional and will not be further described herein.  
         [0036]    [0036]FIG. 2 shows a prior art tow truck  20  addressing a situation similar to that depicted in FIG. 1. Tow truck  20  must approach vehicle  10  at a right angle thereto, wherein the angle is defined between the longitudinal axes of vehicle  10  and tow truck  20 . Although in many cases the prior art approach is operable, the present invention addresses problems arising from the orientation and proximity of tow truck  20  to vehicles  10 ,  12 ,  14 . Notably, if there is insufficient space to maneuver tow truck  20  into the orientation and proximity shown in FIG. 2, or if such maneuvering would subject tow truck  20  to hazardous exposure to passing traffic (not shown) or to other hazards, then it will occasionally not be feasible to tow vehicle  10  from its parked location between vehicles  12 ,  14 . By contrast, location and orientation of tow truck  100  in FIG. 1 are far less exposed to hazards and are less intrusive relative to the roadway than are location and orientation of tow truck  20  in FIG. 2.  
         [0037]    Referring primarily to FIG. 3, a boom  118  and a stable base  120  to which boom  118  is mounted and supported are fixed to the chassis of tow truck  100  either directly or indirectly in a manner assuring that boom  118  can lift, tow, and control vehicle  10 . Boom  118  engages wheels  16 ,  18  of vehicle  10  by an engagement element. The engagement element engages the object being lifted (in the depiction of FIG. 1, this being vehicle  10 ) sufficiently securely to maintain grasp and control thereof while lifting and towing the same. As seen in FIG. 4, the engagement element comprises a cradle  122  of conventional nature, having a bar  124  on which are mounted jaws  126 ,  128 . Jaws  126 ,  128  rotate about pins  127 ,  129  until they assume the orientation shown in FIG. 1, lodged against wheels  16 ,  18 . Each wheel  16  or  18  is thus pinned between bar  124  and one jaw  126  or  128 . Cradle  122  is pivotally joined at distal section  134  of boom  118  by a swivel joint  130  to assist in maneuvering to engage wheels  16 ,  18 .  
         [0038]    Boom  118  has novel features including proximal and distal sections  132 ,  134  pivotally joined by a swivel joint  142  and a gearmotor  136  for moving distal section  134  relative to proximal section  132 . Range of motion of distal section  134  is indicated by arrows  138 ,  140 . A second swivel joint  144  fixed to base  120  engages proximal section  132  of boom  118 , enabling boom  118  to incline relative to base  120 . Joint  144  may be, for example, a clevis joint wherein a cylindrical pin  146  secured in a clevis formed in proximal section  132  engages a stand  148  fixed to base  120 . A powered actuator raises and lowers boom  118  relative to base  120 . Preferably, the actuator is an extensible hydraulic cylinder assembly  150  having an enclosed cylinder (not separately shown) and a piston (not separately shown) slidably disposed within the cylinder, connected to a powered hydraulic system carried aboard tow truck  100 . Hydraulic systems having extensible actuators are well known and need not be set forth in extreme detail herein.  
         [0039]    Structure of swivel joint  142  is shown in FIGS. 3 and 4. A toothed rack  152  is fixed to distal section  134  of boom  118 . Gearmotor  136  is fixed to proximal section  132  such that teeth  154  of gearmotor  136  engage teeth  156  of rack  152 . Distal section  134  of boom  118  swivels about axis  164  of joint  142  when the motor (not separately shown) of gearmotor  136  rotates responsively to teeth  154  engaging and driving teeth  156  of rack  152 . Maximum deviation of longitudinal orientation of distal section  134  of boom  118  is controlled by limit switches  158 ,  160 . Switch  158  is mounted on a tab  162  fixed to proximal section  132  of boom  118 , and switch  160  is mounted on gearmotor  136 . Limit switches  158 ,  160  limit azimuthal rotation of distal section  134  to an arc spanning one hundred eighty degrees of rotation (see FIG. 1). Maximal deviation from the longitudinal alignment of proximal section  132  and distal section  134  is ninety degrees to the right of the longitudinal orientation shown in FIG. 1 and maximal deviation to the left of the same orientation is ninety degrees from longitudinal orientation.  
         [0040]    [0040]FIG. 4 also shows left and right outriggers  168 ,  170  which are optionally provided as part of tow truck  100 . Outriggers  168 ,  170  are anchored to the chassis or other structural part of tow truck  100  which is fixed to base  120 . Outriggers  168 ,  170  are disposed to project laterally from base  120  when deployed (as shown in FIG. 5) to stabilize tow truck  100  when boom  118  is fully extended and heavy loads are imposed thereon. The retracted condition of outriggers  168 ,  170  and longitudinal orientation of sections  132 ,  134  of boom  118  are shown in FIG. 4.  
         [0041]    [0041]FIG. 3 shows relative orientation of swivel joints  130  (represented by axis of rotation  166 ),  142 , and  144 . Swivel joint  144  has an axis of rotation which is parallel to and concentric with pin  146 . The axis of rotation represented by pin  146  is horizontally oriented when base  120  of tow truck  100  is horizontally oriented. Swivel joints  142 ,  130  have respective axes of rotation  164 ,  166  which are vertically oriented when sections  132 ,  134  of boom  118  is horizontally oriented, as it would be if lowered from the position depicted in FIG. 3.  
         [0042]    Referring now to FIG. 6, gearmotor  136  is controlled from a mobile, hand held control station  172  connected to the electrical and hydraulic systems of tow truck  100 . Control station  172  is operably connected to a control valve  174  by a control line  176 . Control line  176  will be understood to include plural electrical conductors (not separately shown) and, where applicable, plural fluid conduits (not separately shown) preferably all contained within a common jacket (not separately shown).  
         [0043]    Outriggers  168 ,  170  and boom  118  are operated by respective hydraulic actuators  178 ,  180  (see FIG. 4) and  150  (see FIG. 3). Actuators  150 ,  178 ,  180  are controlled from control valve  174 , which may be, for example, one or more spool valves (not separately shown) connected to the hydraulic power system of tow truck  100 . The hydraulic power system includes a hydraulic pump  182  driven by engine  106 . Pump  182  is connected to a supply fluid conduit  184  (see FIG. 1) arranged to conduct hydraulic fluid under pressure from pump  182  to valve  174 . Spent fluid is returned from actuators  150 ,  178 ,  180  of boom  118  and outriggers  168 ,  170  by a return conduit  186  (see FIG. 1).  
         [0044]    Gearmotor  136 , which is that motor causing distal section  134  of boom  118  to pivot relative to proximal section  132 , is electrically operated from the electrical system of tow truck  100 . The electrical system is generally conventional, having a battery  188  supplying a power circuit represented at  190 . Motor  136  is operably connected to power circuit  190  by control station  172  and electrical conductor  192 .  
         [0045]    Control station  172  is arranged to rotate or swivel distal section  134  of boom  118  in one direction relative to proximal section  132 , in an opposed direction relative thereto, and to cease rotation or swiveling such that a selected angular relationship of sections  132  and  134  is maintained. Control station  172  will be understood to incorporate pushbuttons or selector switches or both to accomplish the functions described herein. This is easily accomplished by applying power to motor  136  selectively in either of two available polarities and by disconnecting power from motor  136  when desired angular relationship is achieved. Limit switches  158 ,  160  will disconnect power, thereby overriding manual controls, at the extreme permissible limits of rotation of distal section  134  of boom  118 .  
         [0046]    Additional hydraulic system controls are provided on control station  172  to extend and retract left and right side outriggers  168  and  170 , and to raise and lower boom  118 . The control scheme may take any one of several forms. Fluid power circuits (not separately shown) may be routed through and directly controlled by control station  172 . Alternatively, pilot hydraulic circuits may be routed through and controlled by control station  172 . If pilot circuits are employed, then they will control corresponding elements such as spools (not separately shown) of control valve assembly  174 .  
         [0047]    In a further alternative, hydraulic circuits operating outriggers  168  and  170  and boom  118  may be operated indirectly by electrical control circuits operating solenoids (not separately shown) disposed within control valve assembly  174  to accomplish the desired control functions. In a similar manner, motor  136  may be controlled indirectly by a control circuit (not shown) incorporating suitable relays rather than by applying and disconnecting power directly connected to motor  136  through control station  172 .  
         [0048]    The invention is susceptible to variations and modifications which may be introduced thereto without departing from the inventive concept. For example, either or both of sections  132  and  134  of boom  118  may include telescoping extensions (not shown). Also, location of swivel joint  142  may be varied from the depicted location proximate the center of boom  118 .  
         [0049]    Further examples of variations and modifications are as follows. Gearmotor  136  may be hydraulically powered and controlled, if desired. Control station  172  may be fixed to tow truck  100  rather than being a mobile station. Control station  172  may incorporate radio frequency signals rather than being mechanically connected to tow truck  100 .  
         [0050]    The engagement element which grasps the object being lifted and towed could comprise, in place of cradle  122 , a bar (not shown) having eyes and chains having connectors capable of releasably engaging the eyes. Alternatively, the engagement element could be a flexible tether terminating in a hook. If desired, the engagement element could take still other forms.  
         [0051]    Tow truck  100  could employ front wheel drive, all wheel drive, and powered treads or tracks in place of having the drive train and wheels as depicted. While the instant invention has been presented in terms of tow truck  100 , the inventive concept may be adapted to other tow vehicles, including, for example, tractors, mobile cranes, railway and industrial material handling equipment, freight loading cranes, boats, and still others (none shown).  
         [0052]    It is to be understood that the present invention is not limited to the embodiments described above, but encompasses any and all embodiments within the scope of the following claims.