Abstract:
A neutral start interlock for a hydrostatic drive system that uses potentiometers to electronically monitor at least the position of the hydrostatic displacement control such that the engine will not start unless such control is in the neutral position.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     The present invention relates generally to hydrostatically driven agricultural windrowers, and more particularly to a neutral start interlock that utilizes potentiometers to electronically monitor the position of the hydrostatic displacement control on such systems.  
         [0002]     Hydrostatic drive systems are often configured with the pump attached directly to the engine without a clutch or other mechanisms to stop rotation of the pump while the engine is running. The vehicle is then subject to movement based on the pump displacement control which most commonly is moved selectively through forward-neutral-reverse positions by the operator. Currently, vehicles equipped with this type of drive system utilize a mechanical latch to trap the displacement control in neutral for starting. The latch also activates a switch or series of switches to complete the electrical starting circuit. Most of these systems include several moving parts and require complicated adjustment to maintain functionality.  
         [0003]     It would be a distinct advantage to have a neutral start interlock for such hydrostatic drive systems that requires no mechanical adjustment and does not require a mechanical latch to be effective.  
       SUMMARY OF THE INVENTION  
       [0004]     Accordingly, it is an object of the present invention is to provide a neutral start interlock for a hydrostatic drive system that does not require a mechanical latch to be effective.  
         [0005]     Another object of the present invention is to provide a neutral start interlock for a hydrostatic drive system that requires no mechanical adjustments.  
         [0006]     It is another object of the present invention to provide a neutral start interlock for a hydrostatic drive system that employs software to interpret output from several potentiometers to determine if the required components are in a neutral position.  
         [0007]     Yet another object of the present invention is to provide a neutral start interlock for a hydrostatic drive system that uses potentiometers to electronically monitor the position of the hydrostatic displacement control.  
         [0008]     It is yet another object of this invention to provide a neutral start interlock for a hydrostatic drive system that is durable in construction, inexpensive of manufacture, carefree of maintenance, facile in assemblage, and simple and effective in use.  
         [0009]     These and other objects are attained by providing a neutral start interlock for a hydrostatic drive system that uses potentiometers to electronically monitor at least the position of the hydrostatic displacement control such that the engine will not start unless such control is in the neutral position.  
     
    
     DESCRIPTION OF THE DRAWINGS  
       [0010]     The advantages of this invention will be apparent upon consideration of the following detailed disclosure of the invention, especially when taken in conjunction with the accompanying drawings wherein:  
         [0011]      FIG. 1  is a side plan view of a windrower, with header, of the type herein under discussion;  
         [0012]      FIG. 2  is a partial left side view of the hydrostatic control system of the windrower, with some components of neutral start interlock of the instant invention;  
         [0013]      FIG. 3  is an enlargement of the mechanisms for engaging the potentiometers of the instant invention;  
         [0014]      FIG. 4  is a partial side and end view of the pintle arm and the structure used to engage the pintle arm potentiometer;  
         [0015]      FIGS. 5 and 6  are similar side views of part of the forward-neutral-reverse shift control mechanism  110 ; and  
         [0016]      FIG. 7  is a schematic of the electrical control and feedback circuitry of the neutral start interlock of the instant invention. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0017]     Many of the fastening, connection, processes and other means and components utilized in this invention are widely known and used in the field of the invention described, and their exact nature or type is not necessary for an understanding and use of the invention by a person skilled in the art, and they will not therefore be discussed in significant detail. Also, any reference herein to the terms “left” or “right” are used as a matter of mere convenience, and are determined by standing at the rear of the machine facing in its normal direction of travel. Furthermore, the various components shown or described herein for any specific application of this invention can be varied or altered as anticipated by this invention and the practice of a specific application of any element may already by widely known or used in the art by persons skilled in the art and each will likewise not therefore be discussed in significant detail.  
         [0018]      FIG. 1  shows the two primary components of a self-propelled windrower  10 , i.e., tractor  12  and header  14 . Tractor  12  has a main frame  16 , with a longitudinal horizontal axis from front to back, that is supported by a pair of drive wheels  18  (only one shown) on the forward portion thereof and a pair of rear wheels  20  adjacent the rear end. An engine, located under cowling  24 , a transmission and other components, all well known in the art, are supported on the main frame  16  and provide the power necessary for the machine to operate. A cab  26 , also supported on the main frame, encloses the operator&#39;s platform to provide an environmentally controlled location from which the windrower may be comfortably operated.  
         [0019]     Header  14  may be of several designs, but typically comprises a cutting mechanism, either a sicklebar or rotary cutter, a feeder mechanism and conditioning rolls. The header is supported by a hydraulic lift and flotation structure  28  that may be activated to selectively raise or lower the header between transport and operational positions.  
         [0020]     The general mode of operation of a modem windrower is to have tandem hydrostatic pumps, one for each of two drive wheels, each pump having a depending pintle arm such that forward and reverse movement of the pintle arm relative to a neutral position causes the associated hydrostatic pump, and thus the associated drive wheel, to rotate. During the original assembly of the windrower and during normal maintenance and repair operations in the life of the machine, the pintle arms must be adjusted to neutral.  
         [0021]     Referring now to  FIG. 2 , the hydrostatic control system is shown to further include a conventional steering wheel  40  and console  42  inside the operator&#39;s cab  26 . The cab would, of course, include additional components (not shown) such as a seat, electrical and mechanical controls for operation of the windrower, an air conditioning unit, and the like. The steering wheel is attached to a stub shaft  44  that is connected to the upper end of front shaft  46  by a universal connector (not shown). The universal connector is well known in the art as a mechanism to transmit rotational movement between two shafts that are not necessarily in axial alignment. The lower end of front shaft  46  is connected to elongate bottom shaft  50  by another universal connector, or power-take-off shaft,  48 . A length adjustment assembly  80  is attached to the rear most end of bottom shaft  50 .  
         [0022]     Length adjustment assembly  80  is connected, by another universal connector  82 , to elongate threaded rod-like member  84  one end with right-hand threads and the other with left-hand threads—, such that any turn of steering wheel  40  results in a proportional turn of member  84 . Two tandem hydraulic pumps  86 ,  88  are located above member  84  and each has a pintle arm  90 ,  92 , respectively, depending therefrom. Each pintle arm has an internally threaded block threaded onto member  84 , such that rotation of the rod causes the pintle arm to move either forwardly or rearwardly, depending upon the direction of rotation of member  84 . Thus, rotation of member  84  results in one pintle arm rotating in a clockwise direction and the other rotating in a counter-clockwise direction, when viewed from the side, as in  FIG. 2 . This causes one pump to increase flow and the other to decrease flow, turning the windrower. Engine  94  supplies power to the hydraulic pumps.  
         [0023]     Within cab  26  is a forward-neutral-reverse lever  100 . This is continuously and selectively movable to allow a change in speed in either the forward or reverse directions. The neutral position has either an indent or other mechanism to allow easy recognition by the operator. Lever  100  is intended to selectively move member  84  forwardly or rearwardly to simultaneously move both pintle arms an equal amount, thus allowing an equal increase or decrease in flow from the hydraulic pumps. In this embodiment, lever  100  is electrically connected (shown graphically as line  106 ) to linear motor  104  which, as will be discussed further below, moves bottom shaft  50  and member  84  through the action of the forward-neutral-reverse shift control mechanism  110  forwardly or rearwardly under the control of the operator.  
         [0024]      FIGS. 3 and 4  show that the lower end of each pintle arm terminates in a yoke. In this embodiment, arm  92  terminates in yoke  112  that is pivotably attached to internally threaded block  114  via a pair of horizontally aligned pivot pins on either side of block  114 . Block  114  is, in turn, threaded onto member  84 . Thus, rotation of member  84  causes block  114  and yoke  112  to move, pivoting the pintle arm  92 .  
         [0025]     A first potentiometer  120  is affixed to a mounting bracket  122  attached to a structural member or substantial component, such as the engine  94 , to provide a steady fixed relationship between the potentiometer and the member  84 . A bolt  126  attaches a small horizontally and forwardly extending plate  128  to yoke  112 . Adjacent the forward end of plate  128  potentiometer arm  124  is rotatably attached. Thus, as pintle arm  92  moves because of engagement of lever  100  or rotation of member  84 , the potentiometer arm  124  rotates, changing the voltage value generated through potentiometer  120 .  
         [0026]     While a single potentiometer associated with a single pintle arm is shown, it is possible to use two potentiometers, one with each pintle arm. This would allow a more positive determination of the neutral status of both pintle arms, but is not as efficient and cost effective as a single arrangement, because it is not likely that, once initially adjusted, the two will significantly change their relationship.  
         [0027]     A second potentiometer  140  is affixed to a mounting bracket  142  attached, similarly to bracket  122 , to a structural member or substantial component, such as main frame member  144 . A substantially L-shaped arm  146 , having legs  148  and  150 , is pivotably affixed to bracket  142  at pivot point  152  and fixed in relation to each other. Bottom shaft  50  is connected to arm  148  by a pivotable connector  154  such that as arm  148  rotates about pivot point  152 , connector  154  maintains a grip on bottom shaft  50  and allows relative pivoting between shaft  50  and arm  148 .  
         [0028]     The linear motor  104  is pivotably attached to bracket  142  at pivot point  160  and is set up to extend and contract arm  162  as prompted by the operator through lever  100 . Arm  162  is pivotably affixed to the end of leg  150  of L-shaped arm  146 , so that extension of arm  162  by motor  104  pivots the L-shaped arm counterclockwise, and contraction of arm  162  pivots the L-shaped arm clockwise. Another arm,  166  is pivotably affixed at one end to the end of leg  150  of L-shaped arm  146 , and pivotably attached at the opposing end to potentiometer arm  170 . Thus, when lever  100  is moved by the operator, motor  104  extends or contracts arm  162  in response thereto, pivoting the L-shaped arm  146  and moving bottom shaft  50  forwardly or rearwardly. At the same time that arm  146  is rotated, arm  166  rotates potentiometer arm  170 , changing the voltage value through potentiometer  140 .  
         [0029]      FIG. 7  is a graphic representation of the neutral start system, and shows potentiometers  120  and  140 , mounted as shown in  FIG. 2 , ECU (electronic control unit)  180 , starter  182  and starter switch  184 . The ECU can take several forms, such as, for example, a programmable processor. The basic function of the neutral start interlock is accomplished broadly by linking potentiometer  120  to the pintle arms of the hydrostatic pumps and potentiometer  140  of the forward-neutral-reverse shift control mechanism  110  and establishing a neutral voltage for each. The neutral voltage values are fed to the memory of an ECU. When the engine starting procedure is initiated by a starter switch  184  for instance, the software in the ECU compares the stored values with the current values. The ECU software either accepts the values and allows the engine to be started by starter  182 , or it rejects the values and directs instructions to an in-cab display to put the potentiometers to reach neutral, such as, for example, “turn steering wheel to the right”, or the like. The terms “accepts” and “rejects” as used herein means that a comparison is made of the current voltage values are compared with stored values and if there is a difference, the starter circuit is disabled. Since there is always some tolerance in mechanical structures and mechanisms, the voltage value that permits the starter circuit to be energized is usually within at least a small range of values. Generally, however, the difference in voltage values is understood to be zero.  
         [0030]     It is also possible to measure only the voltage difference at either the pintle arms or the forward-neutral-reverse shift control. Obviously, monitoring only one of these two components is not as effective or complete as measuring both, and thus is not the preferred embodiment.  
         [0031]     It will be understood that changes in the details, materials, steps and arrangements of parts which have been described and illustrated to explain the nature of the invention will occur to and may be made by those skilled in the art upon a reading of this disclosure within the principles and scope of the invention. The foregoing description illustrates the preferred embodiment of the invention; however, concepts, as based upon the description, may be employed in other embodiments without departing from the scope of the inventions. Accordingly, the following claims are intended to protect the invention broadly as well as in the specific form shown.