Abstract:
A series hydraulic circuit for permitting motorized operation and independent control of a plurality of cutting decks of a mower. The circuit allows separate operation of one of the decks while enabling operation of one or more of the other decks associated with the mower to simultaneously occur.

Description:
FIELD OF THE INVENTION 
   This invention relates generally to an electro-hydraulic control valve and more specifically, to the use of such a control valve in a series hydraulic circuit to simultaneously and separately control the operation of multiple cutting decks of a mowing tractor. 
   BACKGROUND OF THE INVENTION 
   It is known to provide a hydraulic circuit to conduct the flow of hydraulic fluid so as to allow a motor of a vehicle, such as a mower, to be operated. Typically, these circuits are provided with a series of valves and switches to direct the flow of that liquid, whereby pressure associated with that flow to that motor permits its device, a blade as in the case of a mowing tractor, to move. 
   In providing these circuits, at least two designs have been used to accomplish the above. A first design has included providing a separate circuit for each of the motors, and thus the devices whose motion they control. A second design has included providing a single circuit and connecting each of the motors in series whereby flow to a particular motor can be accomplished through control of an associated valve manifold or collection of valves within the circuit. 
   With each of the above designs, disadvantages exist. In the case of providing a separate circuit for each of the separate motors, each circuit would require its own pump and control valve whereby the cost of doing so disfavors providing an economical product to the consumer. In the case of providing a circuit having each of the motors connected in series, efficiency, or the ratio of the work output to the work input across a system, is often decreased. This decreased efficiency results from drops in pressure across the valves which control the direction and function of flow and pressure through the circuit. These valves exist to regulate, as stated above, the pressure across the circuit when it is necessary to control the flow of hydraulic fluid to a first motor while preventing flow to one or more of a series of motors when it is desired to only operate one or a combination thereof. As fluid passes over these valves, the system experiences a drop in fluid pressure causing the system to be less efficient than it could otherwise be. Additionally, cost disadvantages also exist in this design due to the provision of these control valves. 
   Thus, it would be beneficial to provide a circuit which could allow for the control of multiple motors in a series circuit while doing so with low parasitic loss, or the pressure drop across the manifold, and a minimal number of valves within the manifold as a result of how fluid is directed to a particular motor. 
   SUMMARY OF THE INVENTION 
   Accordingly, there is provided a hydraulic circuit which allows for the direction of hydraulic flow to a combination of motors and which includes a minimum number of parts to control that flow while preventing its unintended redirection. 
   In directing flow among at least three motors, the circuit allows for the operation of a front or first motor by itself. Additionally, since it is designed to align the motors in series, the circuit permits the operation of the front motor alone, the front and a left or second motor, the front motor and a right or third motor, or alternatively, operation of all three motors and their attached devices simultaneously. 
   To allow fluid to be communicated to at least the front motor without that flow being permitted to enter the flow path of the left and right motors, the circuit provides a switchable connection for directing the exit flow of the front motor through the manifold, bypassing the left and right motor. In other words, the flow path along which fluid from the front motor is communicated through the manifold is substantially prevented from entering the hydraulic lines servicing either the left or right motors. Further, the flow supplying the second or third motor, when operating separately, is substantially prevented from entering the hydraulic lines servicing the other of the second and third motors. Finally, when each of the second and third motors are operating, the supply of fluid from the first motor is delivered, initially, to a second motor whose exit flow is delivered to a third motor whose exit flow is then directed to an outlet. 
   Accordingly, the circuit is enabled to accomplish the efficient flow and individual operation of three motors, or a combination thereof, in a cost effective manner due to unneeded flow controls. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a schematic of the hydraulic circuit according to the instant invention whereby only the front motor is operating. 
       FIG. 2  is a schematic of the circuit showing the operation of both the front and left motors. 
       FIG. 3  is a schematic of the circuit showing the operation of the front, left and right motors. 
       FIG. 4  is a schematic of a series hydraulic circuit of the prior art whereby only the front motor is operating. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Looking to  FIG. 1 , there is shown a hydraulic circuit  10  for controlling flow of hydraulic liquid to one or a combination of each of three motors  12 ,  14 ,  16  whereby each of these motors moves a device (not shown), such as a blade of the lawn and garden tractor, for its intended purpose. Each of the front, left and right motors  12 ,  14 ,  16 , respectively, are designated in the diagram of  FIG. 1 . The circuit  10  permits operation of the front motor alone or in combination with the right and/or left motor by controlling the flow and associated pressurization of the flow in each of the hydraulic lines which services their respective motor. 
   As shown in  FIGS. 1-3 , the circuit  10  permits the flow of hydraulic liquid in each of three patterns R 1 ; R 1 , R 2  and R 1 , R 2 , R 3 . As shown in  FIG. 1 , R 1  represents the flow of fluid which supplies the front motor  12  and which is then circulated through the circuit  10 . As is shown, a hydraulic pump  18  is provided as part of the vehicle engine (not shown). Upon activation of a pressurized control switch (not shown), the pump  18  will supply fluid to the front motor  12  and then through an inlet  20  whereby it is then further distributed through the circuit  10  along the path R 1 , as shown in  FIG. 1 , until it exits through an outlet  22 . 
   Looking to  FIG. 2 , the flow of the hydraulic fluid permitting operation of the front and left motors  12  and  14 , respectively, is shown and represented as R 1 , R 2 . Likewise, as in the case of  FIG. 1 , fluid is supplied by the pump  18  through both the front motor  12  and the inlet  20 . This flow is R 1 . However, when it is intended that the left motor  14  be made operational, an operator will lower the left mower deck (not shown) into its operating position via a control lever (not shown), which is located on the tractor operator&#39;s panel, to cause the flow R 1 , R 2 . 
   Upon the operator lowering the left mower deck into position, a first switching means in the form of a two position, three way solenoid operated directional control valve  24 , will become energized by an electric current, causing the valve to shift from a first or “closed” position shown in  FIG. 1  to a second or “open” position shown in  FIG. 2 . This change to the “open” position allows flow to be communicated between the ports  28  and  30  of the valve  24 . After flowing through the valve  24 , hydraulic fluid is passed onward, as a pilot signal, to shift an externally pilot operated two position, four way directional control valve  32  or first fluid transfer means (discussed below). 
   The directional control valve  32 , prior to the energizing of the solenoid valve  24 , is closed, as is shown in  FIG. 1 , and is opened as shown in  FIG. 2  by pressure from flow which has passed through the solenoid valve  24 , as has been previously stated. As shown in  FIG. 1 , the directional valve  32  has four ports  38 ,  40 ,  42  and  44  therein whereby fluid can be passed through the port  38  to the port  44  whereby the ports  40  and  42  are closed to the motor  14 . Referring to  FIG. 2 , it is seen that upon pressurization by fluid traveling along a line  46  as a result of energizing the solenoid valve  24 , the directional valve  32  and its ports  38  to  40  and  42  to  44  are opened so as to allow the main flow of fluid R 1  supplying the front motor  12  to flow vertically upward therethrough and along a path R 1 , R 2  through an exit port  48  which supplies and permits fluid to be passed through the left motor  14 . After passing through the motor  14 , the fluid re-enters the path R 1 , R 2  through the port  50  where it then continues towards the outlet  22 . Fluid which escapes the motor  14  and which does not flow along the path R 1 , R 2  is routed to a drain port  52  which is combined with the drain flow of the directional valve  32  and is then returned to the tank  36 . A similar directional flow can be conducted in a corresponding manner when it is desired that the right motor  16  be made operational. 
   When operability of the front and right motors  12 ,  16  is desired, a second switching means in the form of a solenoid valve  55  will become energized in a fashion similar to that occurring with the valve  24 . The flow R 1  will bypass the directional valve  32  in its first or “closed” position whereby the fluid flows and is passed through a second fluid transfer means or directional control valve  56  and then through the right motor  16 . As such, a flow pattern similar to that of R 1 , R 2  may be used to symbolize the supply and directional movement of fluid directed to the right motor  16 . Similarly, a drain  54  is provided to receive excess drainage from the right motor  16 . 
   When it is desired that each of the front, left and right motors  12 ,  14  and  16  be operated together so as to turn the devices they operate, each of the solenoid valves  24 ,  55  will be separately shifted whereby this change in position can be seen when looking at  FIGS. 1 and 3 . With this shifting, the respective directional control valves  32  and  56  will move to their second or open position so as to permit their ports to be opened and allow the flow of fluid therethrough. 
   Accordingly, the left and right motors  14  and  16  will be made operational as hydraulic fluid is then able to be delivered to them. As can be seen in  FIG. 3 , actuation of both solenoid valves  24  and  55  associated with the left and right motors  14  and  16 , respectively, establishes a flow path R 1 , R 2 , R 3 . The flow of hydraulic fluid exiting the left motor  14  may do so only in one direction which is directed towards the outlet  22 . Consequently, flow is permitted to be directed only in a first entry and exit direction with respect to supplying the right motor  16 ; therefore, instances in which the flow R 1  , R 2  (supplied to the right motor  16 ) could re-enter the supply lines of the left motor  14 , with a directional flow which is different than that which has been described above, are substantially prevented. 
   As also shown in  FIGS. 1-3 , flow patterns R 1 , R 2  and R 1 , R 2 , R 3  each include a relief such as the valve  60  therealong, which is provided to release excess fluid in the circuit when a sudden increase in pressure driving the flow thereof is experienced. Such an increase in pressure may occur, as in the case of a rotating mower blade, when an object impacts the blade causing it to suddenly slow or stop so as to affect the work done by its respective motor. For example, the fluid pressure along R 1 , R 2  may be higher at the port  48  than that at the port  50  when an object impacts the blade. Because the front motor  12  is operating upstream of the motor  14  in the series circuit and possesses inertia, or a tendency to move the fluid therein due to the rotation of its blade, obstructions affecting the left motor  14  will cause the inertia of the motor  12  to yield a sudden increase in pressure in R 1 , R 2 . As the flow R 1 , R 2  is directed through the circuit, this pressure will be released through the relief valve  60  if it increases in an amount greater than that of the relief valve setting so as to bypass the obstructed motor  14  and preventing damage to its components. This component protection system can also be seen in the R 1 , R 2 , R 3  flow path. Where an obstruction affects the right motor  16 , the fluid will resume traveling along the designated pattern R 1  , R 2 , R 3  towards the outlet  22 , bypassing the right motor  16 . 
   During operation, if it is desired to disengage the left motor  14 , the operator will raise the left mower deck so as to cut the electrical signal to its associated solenoid valve  24 . In turn, the solenoid valve  24  is shifted to its first or closed position creating a flow path from the port  29  to the port  30 , as shown in  FIG. 1 , so as to connect it to the tank  36  along a line  34 . This allows the directional control valve  32  to return to its first or closed position due to a spring force acting on it to connect the ports  38  to  44  and close the ports  40  and  42 . With the left motor  14  still possessing inertia due to the rotation of its blade, the inertia will try to move the trapped fluid from the port  48  to the port  50 . Ordinarily, the momentum of the blade must be dissipated in a set time and is accomplished by the spring loaded check valve  58 . Since the pressure is lower on the left side of the motor  14  than on the right side thereof, the valve  58  will allow flow to pass through, from right to left. The flow is then returned to the left motor  14  through the port  48 . This path is repeated until the motor  14  is brought to a stop. A similar system can be seen in the right motor circuit. 
   Looking to  FIG. 4 , there is shown a hydraulic circuit  62  of the prior art whereby each of the front, left and right motors  64 ,  66  and  68 , respectively, are connected in series. Although the goal of permitting the front motor  64  to be operated in combination with either of the left or right motors  66 ,  68  or both, can be accomplished with this circuit  62 , the routing of flow through the circuit  62  requires a number of valves which are not present in the instant invention. As can be seen, fluid transmitted through the inlet  70  by a pump  72  will service a front motor  64  and be communicated along the path R 4 . Upon entry into the path R 4 , the hydraulic fluid will pass through the ports of a first logic control valve  74  which acts to pass flow to the also open ports of a second logic control valve  76  and towards the outlet  78 . 
   In the case in which it is desired to operate the front and left motors  64  and  66 , flow will be directed to a logic control valve  80  and then along a path R 4 , R 5  after a solenoid valve  82  has been energized by the operator having switched the control for the left motor  66  located on the vehicle operator&#39;s panel. The shifting of the solenoid valve  82  allows a pilot signal from R 4 , in the form of pressure, to shift the logic valve  74  to its closed position while connecting the pilot line  83  from the logic valve  80  to the tank  85  allowing it to open a flow path for R 4  to the motor  66 . Along this path, the flow R 4 , R 5  will encounter a pilot check valve  84  used for braking the motor upon shut down as well as a check valve  86  used to regulate flow only in the downward direction. Thereafter, the flow will continue to exit the system along the path designated R 4 , R 5 . With the flow just described being similar in nature for that required to obtain operation of the right motor  68 , only the operation of and the flow designated R 4 , R 5  servicing the left motor  66  has been described. 
   As can be seen in  FIG. 4 , should operation of the right motor  68  be desired, it is possible for its associated flow to be diverted backward towards the check valve  86 . Consequently, due to the routing of the flow R 4 ,R 5 , the check valve  86  is required to prevent the redirection of that flow R 4 ,R 5  towards the left motor  66 . In providing this valve  86 , the flow R 4 ,R 5  crosses it and will experience a further drop in pressure as a result of its placement. This drop in pressure, as discussed previously, causes a reduction in the amount of work done by the system so as to also cause a related drop in the efficiency of the circuit overall. 
   Additionally, with respect to instances in which the blade or other device powered by the left motor  66  is operating, a loop beginning with the pilot check valve  84  is created to restrict the flow which exits across the motor  66  when the circuit is turned off so as to slow the motor  66  and subsequently the blade thereof. The left motor  66  is taken out of, or not serviced by, the flow path R 4 ,R 5  by cutting power to its associated solenoid valve  82  so as to shift the pilot signal and redirect the flow R 4  to cross the logic valve  74 , the entire process closing off the logic valve  80  and the flow R 4 ,R 5  used to feed the motor  66 . As described above, momentum of the motor  66  must be dissipated in order to stop motion of the blade. Once pressure is reduced on the inlet side of the motor  66  at the left side thereof, the pilot check valve  84  is allowed to close, restricting the flow from the motor  66  and returning it in a closed loop fashion, as discussed in relation to the motor  14 , to the motor  66  across the check valve  90  until the motor has been stopped. During operation, the system experiences undesirable pressure drop(s) as a result of directing the flow R 4 , R 5  through the valves  84  and  86  and causes an associated loss in efficiency across the circuit. 
   Thus, in contrast to the circuit  62  just described and shown in  FIG. 4 , there is provided a hydraulic circuit  10  which connects each of three motors  12 ,  14  and  16  in series while eliminating restrictive valves within the operating flow path to allow for increased efficiency across the circuit  10 . This increase in efficiency is permitted by eliminating valves such as the check valve  86 . This increase is accomplished since the flows R 1  and R 1 , R 2  are routed into and out of their associated fluid transfer means, thereby achieving isolation of the left and/or right motor(s) so as to block flow not associated with either of those motors from inadvertently re-entering it. 
   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.