The masts of a front-end loader are releasably attached to vertical plates of a loader mounting frame located at the opposite sides of a tractor by latch hooks pivotally mounted to the masts and engaged with latching elements carried by the vertical plates. An over center biasing arrangement acts on each latch hook and acts to bias the latch hook to a closed position, but moves over center when the latch is manually opened so as to bias the latch to its open position. The pins pivotally coupling the latches to the masts also serve to couple the piston rods of a pair of loader boom lift cylinders to the masts. Extension of the cylinders during detaching the masts from the vertical plates causes the opened latch hooks to be pivoted to the extent that the biasing elements move over center and reset the latches to their closed positions, which positions are conducive for automatically reattaching the mast to the vertical plates.

FIELD OF THE INVENTION  
       [0001]     The present invention relates to front-mounted loaders, and, more specifically, relates to a latching system for attaching such a loader to a tractor.  
       BACKGROUND OF THE INVENTION  
       [0002]     Most current known loader latching systems require an operator to remove or to install pins to disconnect or attach the loader to the tractor and/or have latching systems that are complex and unreliable. United Kingdom Patent Application GB 2,131,391 A, published 20 Jun. 1984 discloses a loader boom comprising a pair of arms having respective masts pivotally attached to their rear ends and having a hydraulic boom lift cylinder coupled between each mast and arm for effecting raising and lowering of the arms of a mounted loader. A latching system is provided for respectively attaching the pair of masts to a pair of loader support frame plates joined to opposite sides of the tractor frame. The latching system includes a bushing and spring-biased latch hook carried by each mast, and a bushing receptacle provided in the top of, and a latch block fixed to, each frame plate. Mounting of the loader to the tractor is effected by manipulating the masts such that their respective bushings enter an associated one of the support plate bushing receptacles and such that the spring-biased latch hooks engage a deflecting surface of an associated one of the latch blocks and are deflected to respective positions permitting the latch hooks to move over the latch blocks, with the latch hooks then moving to respective latched positions wherein the latch hooks are engaged with respective notches provided in the latch blocks.  
         [0003]     A drawback of the loader latching system disclosed in the published United Kingdom application is that, when disconnecting the loader from the tractor, an operator must manually move the latch hooks to respective unlatched positions and hold them in their unlatched positions while manipulating hydraulic controls for operating the boom lift cylinders to effect disconnection of the loader masts from the frame plates.  
       SUMMARY OF THE INVENTION  
       [0004]     According to the present invention, there is provided an improved latching system for securing a loader to a tractor.  
         [0005]     An object of the invention is to provide a latching system which is a simple robust system, including latch hooks which automatically latch the loader to the tractor during installation, and which automatically remain in open positions so as not to require the attention of the operator at a time when the operator is controlling operation of the boom lift cylinders in order to disconnect the loader from the tractor.  
         [0006]     A further object of the invention, is to provide a latching system, as set forth in the foregoing object, wherein the latch hooks are automatically reset to a closed position, during disconnecting the loader from the tractor, such closed position being that required for later attaching the loader to the tractor.  
         [0007]     These objects are accomplished by a latching system wherein an over center biasing arrangement is associated with each latch hook for resisting movement of the latch from its latched position, but permitting the latch hook to be manually moved to the extent that the biasing arrangement moves over center and biases the latch hook to an open position. Further, the latch hook is mounted in such relationship to the loader boom lift cylinder that, during the extension of the cylinder, when detaching the loader mast from the tractor, the cylinder rod acts to reset the latch hook to its closed position, which is required for attaching the loader to the tractor.  
         [0008]     These and other objects of the invention will become apparent from a reading of the ensuing description together with the appended drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]      FIG. 1  is a right front perspective view of a forward end portion of a tractor equipped with a loader mounting frame and on which is mounted a front-end loader equipped with a latching system constructed in accordance with the principles of the present invention.  
         [0010]      FIG. 2  is a right rear perspective view showing the loader of  FIG. 1  mounted on the loader mounting frame, but omitting the remainder of the tractor and the parking stand for the sake of clarity.  
         [0011]      FIG. 3  is a right front perspective view of the loader and tractor of  FIG. 1 , but showing the loader in a parked position.  
         [0012]      FIG. 4  is a lower, right front perspective view of the mast and loader support frame, with the mast being shown rocked forwardly to a position it would occupy just before becoming separated from the loader support frame, as shown, in  FIG. 3 .  
         [0013]      FIGS. 5-8  are right side views of the right-hand mast and loader support frame, with portions removed for clarity, showing a sequence of positions assumed by the loader latch system during detaching the loader from the tractor.  
         [0014]      FIGS. 9-11  are right side views of the mast and loader support frame, shown in  FIGS. 5-8 , but showing a sequence of positions, following that shown in  FIG. 8 , for reattaching the loader mast to the loader support frame. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0015]     Referring now to  FIGS. 1-3 , there is shown a front end of a mobile vehicle, here shown as being a tractor  10 , and a front-end loader  50  mounted on the tractor.  
         [0016]     The tractor  10  includes a main frame  12  supported for movement over the ground by a pair of rear wheels (not shown) and a pair of front wheels  14 , here shown as being drive wheels. The frame  12  includes a pair of fore-and-aft extending, parallel, transversely spaced, side members  16  (only the right side member being visible) joined at their forward ends by a cross member  18  to which is mounted a front ballast weight bracket  20 . A pair of loader support frames  22  are respectively provided at the opposite sides of the tractor  10 , with each including a vertical mounting plate  24  bolted to an associated side member  16  and joined to an inner end of a horizontal, outwardly projecting tubular member  26  having its outer end joined to an inner surface of a lower region of a vertical plate  28 . Projecting through and fixed to the vertical plate  28  so as to have opposite end sections exposed at opposite sides of the plate  28  are a bottom cylindrical bushing  30 , located at a height just above the tubular member  26 , and a top cylindrical bushing  32 , located at an upper region of the plate  28 , the bushings  30  and  32  serving in the connection of the loader  50  to the tractor  10  in a manner described below.  
         [0017]     A hood  34  extends forwardly from a control console  36  and covers an engine supported on a forward section of the frame  12 . A steering wheel  38  is provided at the control console  36  for being easily reached by a seated operator having his or her feet in engagement with a foot rest zone  40  of a floor pan or platform  42 . It is noted that a forward region of the foot rest zone  40  is inclined upward toward the front and terminates at a top surface  44  ( FIG. 3 ), which is at a height approximately half way between the bottom bushing  30  and the top bushing  32 , the significance of this position being explained below.  
         [0018]     The loader  50  includes a boom structure comprising a pair of parallel loader boom arms  52 , each having rear and front sections  54  and  56 , respectively, of approximately equal length, with the rear section  54  being joined to the front section  56  so as to define an included angle of approximately 135°. As viewed with the loader in a lowered position, as shown in  FIGS. 1 and 3 , the arm rear sections  54  are curved slightly downwardly from rear to front, while the arm front sections  56  extend downwardly to respective forward end regions that are joined together by a tubular cross member  58  ( FIG. 3 ). A working tool or implement, here shown as a loader bucket  60  is coupled to the forward end of the loader boom arms  52  by a horizontal cross rod  62  that is received in aligned bushings provided in the arms, and in aligned bushings provided in lower regions of a pair of transversely spaced brackets  64  ( FIG. 2 ) fixed to the back side of the bucket  60 . The bucket  60  is thus coupled to the boom arms  52  for pivoting about a horizontal transverse axis. Coupled, as by a pin  65 , to each of the boom arms  52  at an upper region of the junction between the front rear arm sections  54  and  56  is the barrel of a hydraulic bucket tilt cylinder  66  having a rod pivotally coupled, as by a pin  68 , to an upper region of an associated one of the brackets  64 . Extension and retraction of the bucket tilt cylinders  62  will result in the bucket  60  being tilted one way or the other about its pivotal connection with the loader boom arms  52 .  
         [0019]     Upper ends of a pair of loader masts  70  are respectively pivotally coupled, as at pins  72 , to rear ends of the loader boom arms  52 . Referring now also to FIG.  4 , it can be seen that the loader masts  70  are each constructed of a pair of parallel plates  74  joined together by a rib structure  76 . The bottom ends of the plates  74  are joined together by a web  78  containing a fore-and-aft extending centering or guide groove  80  in which is located a forward edge portion of the loader support frame plate  28 . A bushing receptacle  82  is provided in the bottoms of each of the plates  74  and received in the receptacle is the opposite end portions of the lower cylindrical bushing  30 . It is to be noted that the cylindrical bushing  30  could be replaced by any pivot-defining support which would cooperate with a complementary receptacle in the bottom of the mast  70  so as to allow the mast to pivot about the support when the loader  50  being attached to, or detached from, the tractor  10 , as is described in more detail below.  
         [0020]     Coupled between each of the boom arms  52  and the associated mast  70  is a boom lift cylinder  84  having a barrel coupled, as by a pin  86 , to a bracket provided at an underside of the junction between the rear and front sections  54  and  56 , respectively, of the boom arms. A rod  88  of the lift cylinder  84  has an end defined by an eye which is located between, and coupled to, the mast plates  74  by a pin  90  at a location approximately midway between opposite ends of, and at a forward region of, the mast  70 .  
         [0021]     Located between the pair of plates  74  of each loader mast  70  is a latch assembly  92  comprising a latch hook  94  and a coil torsion spring  96 . The latch hook  94  is mounted for pivoting about the pin  90  and includes a pair of parallel, transversely spaced, side members  98  located on opposite sides of the eye of the cylinder rod  88 . The side members  98  have respective rear ends joined together by a first rib defining a toe pad  100 , and by a second rib defining an abutment  102  having a function described below. Forward ends of the side members  98  extend beyond the pin  90  and terminate in bifurcated ends  104 . Referring now also to  FIGS. 5-11 , it can be seen that the underside of each side members  98  of the latch hook  94  forms a downwardly opening latch element receptacle  106  bounded at its rear by a hook nose  108  having a smoothly curved rear surface  110 .  
         [0022]     The coil torsion spring  96  includes a central coil section disposed about a transverse axis and joined to an inwardly bent inner end  112  and an outer end bent to form an eye  114 . The inner end  112  is received in a hole provided in, and thus is anchored to, the inner plate  74  of the mast  70  at a location in the vicinity of the bifurcated end  96  of the latch member  86 , while the eye  114  of the torsion spring  96  is received between the furcations of the inner latch side  98  and held in place by a cross pin  116  extending through a transverse bore provided in the bifurcated end  104 . The torsion spring  96  is wound such that a spring force exists trying to separate the inner end  112  and the eye  114 . When the loader  50  is mounted on the tractor  10 , as shown in  FIGS. 1 and 2 , the line of force acting between the inner end  112  and the eye  114  is forward of the axis of the pin  90  resulting in the spring  96  acting to bias the latch hook  94  to a closed position, as shown in  FIG. 5 . When the latch hook  94  is manually moved clockwise from its latched position to the open position shown in  FIG. 6 , the line of action of the spring  96  will go over center so as to be rearward of the axis of the pin  90 , the spring  96  then acting to hold the latch hook  94  in an open position wherein the abutment  102  engages the rod  88  of the boom lift cylinder  84 , as can best be seen in  FIG. 4 . While the coil torsion spring  96  is preferred because of being compact so as to easily fit into the space between the mast sides  74 , an other biasing element such as a coil tension spring or gas cylinder could be used provided it is arranged so as to go over center for biasing the latch hook  94  both closed and open. Furthermore, the biasing element does not have to be coupled directly to the latch hook  94 . For example, the biasing element could be connected for transferring force to the latch hook  94  by a lever, linkage, cable, etc.  
         [0023]     A parking stand  116  is provided for supporting the rear end of the loader on the ground when the loader is parked, as shown in  FIG. 3 . The parking stand  116  is constructed of a tube bent to form a pair of transversely spaced parallel arms  118  having respective fore-and-aft extending rear arm sections  120  having forward ends joined to front sections  122 , which extend downwardly from, and form an included angle of approximately 90° with, the front arm sections. Lower ends of the front sections  122  are joined to each other by a transverse arm section  124 . The rear arm sections  120  of the parking stand  116  are disposed approximately perpendicular to, and have rear ends fixed to inner surfaces of the inner plates  74  of the masts  70 , in the regions of the pivot pins  90  by mounting members  126 . As can be seen in FIG.  1 , the transverse arm section  124  is located beneath the front-end weight mounting bracket  20  when the loader  50  is mounted on the tractor  10 .  
         [0024]     The operation of the latching system is set forth below. Starting with the loader  50  mounted on the tractor  10 , as shown in  FIGS. 1 and 5 , each latch hook  94  will be in its latched position with the associated loader mounting bushing  32  being captured within the latching element receptacle  106 . Further, the parking stand  116  will be in an elevated, non-working position, wherein the transverse section  124  is located in a space under the front-end weight bracket  20 . If it is desired to disconnect the loader  50  from the tractor, the operator will cause the lift cylinders  84  to be contracted so as to cause the loader boom arms  52  to lower and place the bucket  60  on the ground. The seated operator will then use his or her feet to apply a force to the toe pad  100  of each latch hook  94  to effect clockwise rotation of the latch members  94  about the pins  90 , with it being noted that the toe pads  100  are just above the front top edge  44  of the foot rest  40  so as to be within easy reach of the operator's feet. Once the line of force of each of the coil torsion springs  96  moves over center, the torsion springs will act to bias the latch members  94  to their open positions, shown in  FIG. 6 , wherein the abutment members  102  are in engagement with the piston rods  88  of the lift cylinders  84 .  
         [0025]     With the latches  94  in their open positions, the parking stand  116  is lowered by extending the hydraulic lift cylinders  84  so as to cause the masts  70  to pivot forward about the loader mounting frame lower bushings  30 , with the bucket  60  being slid forwardly on the ground to permit this movement. As masts  70  are pivoted by the extending lift cylinders  84 , the transverse section  124  of the parking stand arms  118  will first come into contact with the ground and will, upon further extension of the lift cylinders  84 , elevate the masts  70  sufficiently to disengage the bushing receptacles  82  from the respective bushings  30 . At the same time, the rods  88  of the hydraulic lift cylinders  84  will, through their contact with the abutments  102  of the latches  94 , cause the latches  94  to pivot counterclockwise about the pins  90  a sufficient distance to once again move the lines of action of the torsion springs  96  over center so that the torsion springs  96  act to rotate the latches further counterclockwise to reset them to an attach position, as shown in  FIG. 8 , which is conducive for the reattachment of the loader  50  to the tractor  10 . The disconnection of the loader  50  from the tractor  10  is then completed by disconnecting the hydraulic lines (not shown) coupled between the tractor hydraulic system and the loader. The tractor  10  will then be free of the loader  50 , as shown in  FIG. 3 , and can then be backed away from the loader.  
         [0026]     If it is desired to once again attach the loader  50  to the tractor  10 , the tractor will be driven between the masts  70  and boom arms  52  to a position approximately like that shown in  FIG. 3 . The hydraulic system of the tractor  10  will then be connected to the loader  50  and the lift cylinders  84  will be contracted so as to lower the bottom ends of the masts  70  onto the bushings  30 , the guidance of the masts  70  into place being facilitated by the front edges of the vertical plates  28  of the loader mounting frames  22  and the grooves  80  in the bottoms of the masts  70 . Once the bushings  30  are received within the receptacles  82 , further contraction of the lift cylinders  84  will rotate the masts  70  counterclockwise about the bushings  30  so as to bring the lower portions of the smooth rear surfaces  110  of the latches  94  into engagement with the upper bushings  32 , as shown in  FIG. 9 . Still further contraction of the lift cylinders  84  results in the latches  94  moving up and over the upper bushings  32 , as shown in  FIG. 10 , with the torsion springs  96  then acting to move the latches  84  into their latched positions, as shown in  FIG. 11 .  
         [0027]     Thus, it will be appreciated that the over center action of the torsion springs  96  makes it possible, during detaching the loader  50  from the tractor, for the operator to concentrate on effecting operation of the lift cylinders  84  once the latches  94  are manually opened, and that thereafter the latches  94  are automatically reset to a latch position so as to be ready for reattachment of the loader  50  to the tractor  10 , and that during this reattachment the latches are automatically moved to their latched positions.  
         [0028]     Having described the preferred embodiment, it will become apparent that various modifications can be made without departing from the scope of the invention as defined in the accompanying claims.