Abstract:
An implement draft tongue is moved through a range of working positions to a transport position extending transverse to the working direction of the implement by an extensible and retractable hydraulic actuator. A control for the hydraulic cylinder includes an interrupter valve that is actuated, in response to a preselected extension of the hydraulic cylinder so as to prevent the cylinder from extending beyond a position for moving the draft tongue to one extreme of its operating range, when an actuating device for the interrupt valve is enabled. When the actuating device for the interrupt valve is disabled, the hydraulic actuator may be extended fully to place the draft tongue in its transport position.

Description:
FIELD OF THE INVENTION 
     The invention concerns a control arrangement for a draft tongue of a towed implement, and more particularly relates to a powered arrangement for moving the draft tongue between first, working positions and a second position, wherein the draft tongue extends transverse to the direction of operation of the implement. 
     BACKGROUND OF THE INVENTION 
     U.S. Pat. No. 3,919,831 discloses a towed mowing implement with a draft tongue that can be repositioned between operating positions and a transport position by means of a hydraulic cylinder, where the tongue extends transverse to the direction of operation of the mowing implement in the transport position. In the transport position, the mowing implement can be towed on a trailer behind an agricultural tractor or the like. The repositioning movement of the hydraulic cylinder is transmitted by a scissors-like linkage, where the hydraulic cylinder is retracted in the transport position. The effect of the hydraulic motor is controlled jointly by two hydraulic cylinders so that with the full stroke of the hydraulic cylinder once the tongue reaches its transport position and the other time it does not. 
     U.S. Pat. No. 4,558,560 also discloses a control arrangement, that includes a hydraulic cylinder, for the pivoting of a draft tongue of a mowing implement into a transport position. The hydraulic cylinder operates upon the end of the tongue and is limited in its stroke during the operation by mechanical stops of a plate between the tongue and a frame of the mowing implement. In order to be able to completely retract the pressurized fluid motor and thereby to pivot the tongue into a transport position, the plate with the stops is pivoted into a further position. 
     The problem underlying the invention is seen in the fact that the cost of known devices for limiting the stroke of the hydraulic cylinder to avoid a stroke leading to the transport position is too great. 
     SUMMARY OF THE INVENTION 
     According to the present invention, there is provided an improved control for selectively limiting the stroke of an extensible and retractable hydraulic actuator, used for swinging the draft tongue of a towed implement horizontally, so that during ordinary operation of the implement, the tongue can only be swung through a working range, but which may be placed a state for permitting full extension of the actuator when it is desired that the tongue be placed in a transport position. 
     An object of the invention is to provide a control arrangement for an implement draft tongue, as discussed above, which is of a simple, inexpensive design. 
     A more specific object of the invention is to provide a control arrangement, as defined in the above object, which embodies an interrupt valve that is selectively operable to prevent full extension of the hydraulic actuator. 
     Yet another object of the invention is to provide a control arrangement, as defined in the immediately preceding object, wherein the interrupt valve includes an actuating device that, in an enabled condition, is operated in response to the piston rod reaching a pre-selected state of extension so as to prevent further extension. In the disclosed embodiment, this is accomplished by mounting a switching device to the piston rod, mounting the interrupt valve with its actuating device to the cylinder of the hydraulic actuator, with the actuating device being movable between a an enabled position wherein it is in the path of movement of the switching device so as to be contacted and operated thereby, and a disabled position, wherein it is moved from the path of movement of the switching device. 
     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 
     FIG. 1 is a schematic top plan view of a train consisting of a towing vehicle and a towed implement. 
     FIG. 2 is a diagram of the hydraulic circuit for controlling an extensible and retractable hydraulic actuator for swinging the draft tongue of the implement. 
     FIG. 3 is a perspective view of the hydraulic actuator shown in its retracted condition. 
     FIG. 4 is a view, like that of FIG. 3, but showing the hydraulic actuator in a partially extended condition in the region of the transition between a range of operating positions and a transport position. 
     FIG. 5 is a view, like that of FIG. 3, but showing the hydraulic actuator in a fully extended condition corresponding to the transport position. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to FIG. 1, there is shown a towed implement  10  and a towing vehicle  12 . The implement  10  is configured as a mowing implement, but may, however, be a ground breaking implement, a harvesting implement, a plant processing implement, or any other towed implement. 
     The implement  10  includes a frame  14  and wheels  16  that support it on the ground and carry a front attached crop mowing and windrowing arrangement  18 . A bearing  20  is provided at a center location between opposite ends of the frame  14  and couples a rear end of a draft tongue  22  for swinging transversely thereabout, the forward end of the draft tongue  22  being coupled over a bearing  24  and draft coupler  26  to a draft hitch arrangement  28  of the towing vehicle  12 . The relative position of the draft tongue  22  to the frame  14  is controlled by an extensible and retractable hydraulic actuator  30 , whose actuation is performed by a control arrangement  32 , shown in FIG.  2 . 
     The control arrangement  32  includes a fluid reservoir  34 , a pump  36 , a pressure relief valve  38 , a direction control valve  40 , an interrupter valve  54 , an actuating device  42 , a switching device  44  and a deactivating element  46 . The control arrangement  32  is located partially on the implement  10  and partially on the towing vehicle  12 , where the deactivating element  46  leads to the towing vehicle in the vicinity of the operator. 
     The hydraulic actuator  30  is configured as a double-acting hydraulic cylinder and includes a piston rod  48  and a cylinder housing  50  in which the piston rod  48  with its piston, not described in any further detail, is guided in a straight-line motion. 
     The reservoir  34  is filled with hydraulic fluid that can be drawn by the pupmp  36  over a line, not described in any further detail. The pump  36  is configured for an open system and conducts pressurized hydraulic fluid through the relief valve  38  to the direction control valve  40 . A configuration as a closed system would require a few changes but could also be employed. The relief valve  38  operates to return pressurized fluid to the reservoir  34 , when the system pressure exceeds a certain threshold, for example, if the valve  40  is open and the actuator  30  has reached one or the other of its end positions. 
     The direction control valve  40  is configured as a four-way, three-position valve, that is here shown as controlled manually, but may be controlled electrically or hydraulically. In a retracting position “a”, pressurized fluid is conducted by the pump  36  to the piston rod end of the cylinder housing  50 , and from the head end of the cylinder housing  50  into the reservoir  34 . In a neutral position “b”, a flow of pressurized fluid is prevented in every direction and the pressurized fluid conducted by the pump  36  is returned to the reservoir  34 . In an extension position “c”, pressurized fluid is conducted from the pump  36  to the head housing  50  and out of the piston rod end of the cylinder housing  50  into the reservoir  34 . Obviously other embodiments of the valve  40  are possible, for example, even valves separated from each other, whose operation attains the same results as the valve  40 . 
     The interrupter valve  54  is configured as a two-way, two-position valve and can be brought into a switch position “d” with a pressurized fluid opening  70  and a switch position “e” with a check valve  72 . A spring  52  is provided on the interrupter valve  54  that always forces the interrupter valve  54  into its position “d” with free pressurized fluid flow. 
     The actuating device  42  is configured as a lever which can also be configured differently with other embodiments, for example, with cams, tilting arms or the like. The actuating device  42  is located in the path of movement of the switching device  44  and can be repositioned by this during the repositioning of the piston rod  48 . When the actuating device  42  is grasped by the switching device  44 , the interrupter valve  54  moves out of its position “d” into its position “e” and interrupts the pressurized fluid flow out of the hydraulic actuator  30 . 
     The deactivating element  46  is formed in this embodiment by a tension device  56  configured as a rope that acts upon the actuating device  42 . When the deactivating element  46  is actuated, the actuating device  42  moves out of the path of movement of switching device  44 , which has the result that the interrupter valve  54  remains in its position “d” Until a repositioning by the spring  52  occurs, and the piston rod  48  can be fully extended. The tensioning device  56  extends from an operator&#39;s cab of the towing vehicle  12  to the actuating device  42 . However, a lever could be provided to which the tensioning device  56  is attached and the tensioning device  56  could also be configured as a push-pull cable control. The arrow shown in the actuating device  42  represents its repositioning capability and should not be confused with an actual embodiment. 
     Referring now to FIGS. 3-5, there is shown the details of the hydraulic actuator  30  and part of the control arrangement  32  including the interrupter valve  54 , the actuating device  42 , the switching device  44  and the deactivating element  46 . 
     The interrupter valve  54  is mounted on the cylinder housing  50 , in particular, between its ends at a location that corresponds to the transition region from the range of operating positions to the transport position. The actuating device  42  is configured as a lever pivoted from the interrupter valve  54  with a contact arm  60  and an actuating arm  62 . The switching device  44  is configured as an elongate rail having a first end fastened to the free end of the piston rod  48  and which extends in parallel, radially spaced relationship to the cylinder housing  50 , and is guided on the cylinder housing  50  by means of a screw  64  received in a slot  66  extending lengthwise in the rail. Provided on the end of switching device  44  that is remote from the piston rod  48  is a stop or abutment  68  in the form of a plate that can be brought into alignment with the contact arm  60  of the actuating device  42 . In the retracted condition of the hydraulic actuator  30 , the switching device  44  extends generally over the entire length of the cylinder housing  50 . 
     The deactivating element  46 , configured as a simple, flexible tensioning element  56 , is connected to the actuating arm  62 . If tension is applied to the element  56 , then the actuating device  42  pivots into its position shown in FIG. 5, in which it cannot be contacted by the stop or abutment  68 . 
     On the basis of the above description, the operation is as follows. 
     When the direction control valve  40  is in its position “a”, the piston rod  48  is retracted, as is shown in FIG.  3 . The hydraulic actuator  30  remains in this position as long as the valve  40  is in its position “a” or “b”. 
     In order to extend the hydraulic actuator  30 , the valve  40  is brought into its position “c”. If the deactivating element  42  is not actuated, the switching device  44 , in particular, its stop  68  comes into contact with the contact arm  60  due to the extending movement of the piston rod  48  after a certain path has been covered, and moves the arm  60  so as to reposition the interrupter valve  54  into its position “e”, in which the flow of pressurized fluid is interrupted. This position marks the one end of the operating region, as indicated in FIG.  1 . 
     If the hydraulic actuator  30  is to be fully extended, the deactivating element  42  is actuated by a pull on the tension element  56 , which acts to pull on the actuating arm  62 , before the contact arm  60  comes into contact with the stop  68  so that the contact arm  60  is no longer loaded by the stop  68  and the interrupter valve  54  is no longer brought into its position “e” preventing the return of fluid from the rod end of the actuator  30 . The interrupter valve  54  remains in its position “d”, the valve  40  in its position “c” and so the piston rod  48  of the hydraulic actuator  30  is extended until it is fully extended whereupon pressure builds and opens the relief valve  38 . Other solutions are also conceivable with which the interrupter valve  54  can be brought into its position “d” even during the contact of the arm  60  on the stop  68 , and the actuator  30  then extends further. 
     While in this embodiment, the interrupter valve  54  or the actuating device  42  are provided at the cylinder housing  50  and the switching device  44  is provided at the piston rod  48 , this obviously can also be reversed. Furthermore, the actuating device  42  could be provided at the frame  14  or the like; it is essential that the actuating device  42  can be brought into connection with the adjustment path of the hydraulic actuator  30 . 
     Furthermore, the actuating device could be configured in such a way that it can be loaded in one direction, that is when the piston rod  48  is retracted, but by reason of a free-wheeling arrangement or the like it cannot bring about a switching movement. 
     It will be appreciated that the invention can be easily retrofit to existing machines since it merely requires that the switching device  44  and interrupter valve  54  with the actuating device  42  be mounted on the cylinder of the hydraulic actuator normally provided for swinging the implement draft tongue. 
     Further, it will be appreciated that the interrupter valve  54  could be controlled electrically through the use of a solenoid selectively energized by completing an electrical circuit, for example, through the use switches, light barriers, reed switches or the like that are actuated when the circuit is on and the hydraulic actuator  30  reaches a pre-selected state of extension. The deactivating element can also be controlled remotely without wiring if desired. 
     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.