Abstract:
An auxiliary axle system for a work vehicle is disclosed including a pair of spaced arms pivotally mounted to the vehicle, at least one tag axle and wheel and a cross member and a latch pin carried on one arm. An operating system for moving the auxiliary axle assembly between a raised stowed position and a ground engaging support position is provided with a modular latch mechanism for retaining the auxiliary axle assembly in the elevated position by containing the latch pin. The modular latch mechanism is carried on a base plate mounted as a unit through adjustable bolt slots behind an existing vehicle metal structure so that only a hook device extends beyond the plate.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    I. Field of the Invention  
           [0002]    The present invention relates generally to auxiliary axle systems for load-hauling vehicles and, more particularly, to a stowable tag axle system that includes a safety latch which positively latches the axle in the stowed position when the axle is retracted or disabled for repairs. The invention provides an improved latching system for securing the tag axle which has a compact and unitary construction which readily installs on a truck body, is easily positionally adjusted and in which the mechanism is shielded from clogging debris and corrosive materials in the case of a transit mixer application.  
           [0003]    II. Related Art  
           [0004]    Optionally deployable auxiliary axle systems are well known and often associated with a variety of types of load-hauling vehicles, particularly those accustomed to time-varying loading, such as dump trucks, refuse collection vehicles and transit concrete mixers. Such vehicles typically include a chassis or frame, a cab and a dedicated truck body mounted on the chassis behind the cab. Such vehicles also include a forward steering axle placed near the front of the cab and one or more sets of drive axles spaced behind the steering axle, the drive axles often being provided in a dual axle arrangement. The auxiliary axle systems furnish additional load carrying capacity by adding an axle for assisting the steering and drive axles in supporting the load and in adjusting the inter-axle distance or increasing the overall front-to-rear axle span distance for the vehicle. In this manner, not only does the tag axle system assist in balancing the load carried by, for example, a transit mixing cement truck, but generally it also enables the truck to carry a higher legal total payload than would otherwise be permitted because weight restrictions placed on vehicles traveling over highways are typically measured in terms of load per axle in combination with overall spacing between the vehicle axles.  
           [0005]    Examples of such auxiliary axle assemblies that can be selectively engaged with the ground are shown, for example, in U.S. Pat. Nos. 5,897,123 and 5,018,755. Thus, it is known to have tag axle systems generally consisting of a rear tubular cross member carrying spaced wheel assemblies and carried by a pair of spaced tag axle arms which, in turn, are pivotally mounted to the rear portion of a truck chassis according to a generally known arrangement. Linear reciprocating operating devices, typically hydraulic cylinders, or pneumatic devices are employed to pivot the tag axle system between a raised or stowed position and a lowered or ground-engaging position.  
           [0006]    To assure that the tag axle assembly will remain in the elevated or stowed position until it is intentionally lowered to the ground-engaging position, it is known to add some type of external latching mechanism such as that which is shown in FIG. 1 which illustrates a fragmentary side elevational view of a transit mixer with a tag axle assembly in its raised or stowed position. The view includes a portion of a vehicle frame  12 , dual axle drive wheels  14 , a mixing drum  16  partially supported by a rear mixing drum mount support frame  18  and a tag axle assembly which includes a pair of arms  20  pivotally mounted at one of their ends to the frame to the vehicle. A tag axle  22  carrying a tag wheel  24  is mounted to the opposite end of each arm  20 . A common torque tube is shown at  26  and a shaped cam plate at  28  which cooperates with a cam follower wheel  30 . Retraction air actuators are shown at  32  with associated arms  34 . A further cam link assembly is provided which includes a pair of cam link arms, one of which is shown at  40  mounted from a pivot  42  and a pair of deployment air springs, one of which is shown at  44  which is affixed to the support frame  18  of the mixing drum using suitable means and to the cam link arms  40 .  
           [0007]    When the retraction actuators  32  are inflated, the arms  34  pull on the pivot members  36  connected to the torque tube cross member  26  to cause the tag wheels  24  to elevate to a retracted or stowed position. Conversely, deflation of the air actuators  32  and inflation of the deployment air springs  44  produces a downward force on the cam link arm  40  which is transferred to the arm roller  30  and then through the cam plate  28  of the tag assembly thereby lowering the tag axle wheels  24 .  
           [0008]    As previously indicated, to retain the tag axle assembly in the elevated position, there is further provided an external latching mechanism which includes a hook  50  pivotally mounted at one end to the mixing drum mount  18  and situated so that it can engage a pin  52  attached to the arm  20  of the tag axle assembly at an appropriate location. The hook is further provided with a biasing spring  53  and a pneumatic hook actuator at  54 . Inflation of the actuator  54  overcomes the biasing of the spring  53  thereby releasing the pin  52  from the grasp of the hook  50 . Otherwise, the biasing spring provides sufficient force to retain the pin  52  in the hook  50 .  
           [0009]    While this and other similar external hook arrangements have been known to function adequately, they consist of a number of parts which must be separately positioned relative to each other and aligned with the tag axle pin and the parts are exposed to mixing drum contents, acid washes and other hazards associated with the mixing and dispensing and cleanup of transit-mixed concrete. Accordingly, the parts readily become clogged with debris inhibiting operation of the spring and the pivoting of the hook to the point where operation of the hook  50  is impaired, thereby impairing the positive latching of the stowed tag axle system. In addition, corrosion of the separately attached parts leads to frequent difficult removal and replacement.  
           [0010]    Accordingly, there remains a need for a compact and efficient safety latch system for tag axles which is easily removed and replaced as a unit and which does not have its integral operating parts exposed to the materials and cleaning agents associated with transit concrete mixing or other materials.  
           [0011]    Accordingly, it is a primary object of the present invention to provide a compact modular safety latch for tag axles which is easily removed and replaced as an independent unit.  
           [0012]    It is a further object of the present invention to provide a safety latch for tag axles associated with load hauling vehicles such as transit concrete mixers which has its moving parts shielded from contact with mixed cement, mixing materials and wash materials.  
           [0013]    Other objects and advantages associated with the present invention will become apparent to those skilled in the art upon further familiarization with the specification, drawings and claims contained in this application.  
         SUMMARY OF THE INVENTION  
         [0014]    The present invention provides a compact modular safety latch assembly for retaining an associated pivoting tag axle assembly in a stowed position when not in use and when the system must be retained in an elevated position with the vehicle shut off as for the performance of maintenance on the vehicle. The system employs a cylinder-operated, spring-biased pivoting hook arrangement assembled as a modular unit or a base plate for attachment to and behind the rear mixing drum mount support metal structure of a transit mixer or the like so that only the catch portion of the hook member protrudes through a slot in the support plate of the drum support structure. The modular safety latch system may be mounted through slotted openings in the plate of the vehicle which cooperate with slotted openings in the base or support plate directed in the opposite direction so that both vertical and horizontal adjustment is provided in the system for easy mounting and final alignment adjustment of the relative location of the latch hook so that the retention pin attached to the tag axle swing frame can be captured as desired. In this manner, the moving parts of the system are all located behind the metal support plate and are less likely to encounter clogging and corrosive materials in use.  
           [0015]    The detailed embodiment of the modular safety latch itself includes a base plate carrying a pair of shaped, spaced parallel flange members fixed to it and which, in turn, carry the latch hook pivotally journaled on a pivot pin spanning and mounted in the flanges. The latch hook is a member of dedicated shape having a top or forward curved hook section above the pivot and a lower or rearward tail section below the pivot and a fluid cylinder is provided which is bolted to the flanges in a manner such that extension of the rod associated with the cylinder overcomes spring biasing (below) pushes on the tail of the latch hook and pivots the latch hook away from and releases the latch pin (as the system is mounted on the vehicle). A counter-biasing tension spring extends between the latch hook and a member attached to the rear of the latch-operating cylinder to pivot and hold the latch against the cylinder rod and in a fully lowered or latched position when the operating rod is retracted or collapsed into the cylinder.  
           [0016]    In operation, the operating cylinder is a normally retracted or collapsed and assumes this position when the fluid (hydraulic or pneumatic) pressure is lost in the cylinder. In this position, the biasing spring pivots the latch fully downward, placing it in the pin-capture position so that a stowed tag axle system will remain engaged by the latch hook until positive pressure operates the cylinder to extend the rod and overcome the spring tension thereby pivoting and raising the latch hook to release the pin.  
           [0017]    In this manner, a relatively fool-proof latch system is provided in which the mechanism is substantially protected from the clogging and corrosion associated with past systems. In addition, the invention provides a modular unit which is readily installed, adjusted and replaced as necessary during the life of the vehicle. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0018]    In the drawings, wherein like numerals are utilized to designate like parts throughout the same:  
         [0019]    [0019]FIG. 1 is a fragmentary side view showing a tag axle assembly in the raised position and utilizing a latch in accordance with the prior art;  
         [0020]    [0020]FIG. 2 is a side view of a transit concrete mixing work vehicle having an auxiliary axle of a class suitable for use with the latch of the present invention shown in the deployed position;  
         [0021]    [0021]FIG. 3 depicts a side view of the auxiliary axle assembly depicted in FIG. 2;  
         [0022]    [0022]FIG. 4 is a top view of the auxiliary axle assembly of FIG. 3;  
         [0023]    [0023]FIG. 5 is a perspective view of a modular tag axle latching system assembly constructed in accordance with the invention; and  
         [0024]    [0024]FIG. 6 is a fragmentary perspective view from the outside showing the modular latch of the invention installed through the plate metal of a transit mixer rear drum support structure. 
     
    
     DETAILED DESCRIPTION  
       [0025]    In accordance with the detailed description of the present invention, the particular embodiment illustrated and described is meant to be illustrative of the invention rather than limiting in any manner and it is believed that other structures may occur to those skilled in the art which remain well within the confines of the inventive concept. Also, the modular latch system of the invention may be used with other types of load hauling or work vehicles using tag axles which operate in the same or a similar manner.  
         [0026]    [0026]FIG. 2 shows a transit concrete mixing truck  100  having a cab  102  and a drum  104  mounted behind the cab for receiving materials through a hopper  106 , internally mixing concrete and dispensing same through the rear of the drum  104 . The vehicle includes a chassis  108  on which the drum and the cab are mounted and which is provided with a steering axle  110  and a dual axle drive wheel arrangement  112 . The chassis further includes a pair of spaced parallel chassis members, one of which is shown at  114 , which extend along the length of work vehicle  100  and from which an auxiliary axle, generally  200 , is pivotally mounted, as shown in more detail in FIGS. 3 and 4.  
         [0027]    In FIGS. 3 and 4, the auxiliary axle assembly  200  includes an arm assembly, generally at  210 , a rear assembly, generally at  230 , and an actuator assembly, generally at  250 . The arm assembly  210  includes a pair of spaced rearward extending arms  212  and between which an auxiliary axle  213  is mounted at the rear-most end of arms  212 . A tie rod may be provided as at  214 . The arms  212  which are substantially parallel and the front-most end of arms  212  is pivotally mounted to chassis members  130  by the rear assembly  230 , as will be described. The arms  212  are joined by a common torque tube  216  and a lever arm shown at  218  is affixed to and extends upward from the tube  216  and supports a spaced pillow block mounting arrangement as at  220  are affixed thereto and secure a mounting pin or shaft as at  222 . A fender is shown at  224 .  
         [0028]    The rear assembly  230  further includes a pair of pivot block brackets  232  affixed as by welding to chassis elements  114 . A pair of pivot shafts or pins  234  are mounted in a pair of pivot blocks  236  and each arm  212  is pivotally mounted about pivot shaft  234 . Actuator assembly  250  includes a double-acting hydraulic cylinder actuator  252  which includes a rod  254  mounted in pivoted relation to the blocks  220  as by shaft or pin  222 . The blind end of cylinder  252  is also pivotally mounted as at  254  by a clevis arrangement including mounting blocks  256  mounted in a cylinder cross member  258 .  
         [0029]    It will be appreciated that collapse or retraction of the rod  254  will pivot the tag axle system  200  (arms  212 ) about the shafts  234  thereby raising the tag axle to the stowed position and, conversely, extension of the rod  254  in cylinder  252  will deploy the tag axle system as shown in FIG. 3.  
         [0030]    It should be noted that the location of a retention pin is indicated by  226 . This pin is normally mounted on the inside of either of the arms  212  and is used in conjunction with the modular latch arrangement of the invention to retain the tag wheels in the raised or stowed position as desired.  
         [0031]    The latch mechanism itself is shown in the greatly enlarged perspective view of FIG. 5. The modular latch system, generally  300 , includes a base or mounting plate  302  having a plurality of slotted mounting holes  304  and in an elongated central slot  306 . A pair of spaced parallel shaped mounting flange members  308  are affixed to the base plate  302  and are provided with openings  310  which, in turn, carry a common mounting shaft or pin  312  on which a latch member  314  is mounted to pivot or rotate. The latch member  314  includes a hook arrangement  316  preferably having a particular internal curvature  318  adapted to releasably grab a pin member  226  affixed to an arm  212  of a pivoting tag axle arrangement. Bushings are provided at the pivot joint of the latch at  320 . The shaped latch hook member  314  further includes a tail section  322  and a tension spring  324  attached thereto as by a bolt member  326  which threadably engages the tail portion  322  of the latch member  314  at one end and is affixed to a pin or rod member  328  at the other as by an end loop  330 . The tension spring  324  spans a linear operator, preferably a hydraulic cylinder  332  which is a single-acting cylinder having a blind end fluid inlet and outlet port at  334 . The cylinder  332  is mounted as by bolts, one of which is shown at  336  to the shaped members  308  with the rod end of the cylinder addressing the tail portion  322  of the shaped latch member  314  in a manner such that when the cylinder is fully collapsed, the system will reside in the position shown in FIG. 5 with the latch hook in the latched or “down” position capturing the pin member  226  in the curved hook  318 . Extension of the cylinder rod associated with the cylinder  332  pushes on the tail section  322  of the latch member  314  overcoming the tension of spring  324  thereby raising the hook assembly relative to the pin  226  to release the tag wheel assembly for deployment. The rod member  328  is affixed to the blind end of cylinder  332  as by welding at  338 .  
         [0032]    Once assembled, the latch system presents a unitary structure which, as shown better in FIG. 6, can simply be bolted over an opening  400  in steel plate  402  utilized to support the rear end of the cement mixing drum  404  in a manner in which only the hook end of the latch  314  protrudes through the slot  306 . The modular system mounts on four bolts as at  406  through generally horizontally slotted openings as at  408  in a manner which combines with the generally vertically slotted openings  304  in the plates  302  of the modular system to provide hook location adjustment in both vertical and horizontal directions so that adjustment of the exact location of the hook is quite simple. Note that replacement of the modular system also only involves the removal of the four bolts  406  and there is no need to replace individually located separate parts as in older systems. In addition, should hydraulic or pneumatic pressure be lost in the cylinder  332 , the biasing spring  334  will assure that the latch hook member  314  remains in the “down” position and the pin  226  remains captured. The shape of the internal cavity of the hook  318  is such that while the pin  226  is captured by the end lip  319 , movement of the pin into the hook or the hook away from the pin will allow engagement or disengagement as desired, being realized that the pin moves in a wider arc along with the pivoting of the tag axle system.  
         [0033]    This invention has been described herein in considerable detail in order to comply with the patent statutes and to provide those skilled in the art with the information needed to apply the novel principles and to construct and use embodiments of the example as required. However, it is to be understood that the invention can be carried out by specifically different devices and that various modifications can be accomplished without departing from the scope of the invention itself.  
         [0034]    What is claimed is: