Electricity: motive power systems – Motor-reversing – Periodic- or intermittent-reversing
Reexamination Certificate
2000-08-15
2001-11-13
Ip, Paul (Department: 2837)
Electricity: motive power systems
Motor-reversing
Periodic- or intermittent-reversing
C318S139000, C180S273000, C192S094000, C307S010600
Reexamination Certificate
active
06316891
ABSTRACT:
BACKGROUND OF THE INVENTION
1) Field of the Invention
The present invention relates generally to lawn and garden tractors or similar vehicles, and more specifically to an interlock circuit for such a vehicle.
2) Related Art
Vehicles such as some lawn and garden tractors with PTO driven attachments include an interlock circuit with several functions including the prevention of PTO operation when the vehicle is placed in reverse. Under certain conditions, operation of the PTO while the vehicle is in reverse is necessary. Various override systems have been proposed for this purpose, but many are difficult or inconvenient to operate. For example, one type of available override system on a mower allows PTO operation when the vehicle is backing up, but only after the PTO is automatically disconnected during the shift into reverse. Another type requires the operator to continuously push a switch during reverse operation. A further type is shown in U.S. Pat. No. 5,994,857 of common ownership with the present application, wherein several relays and a PTO switch provided with a momentary on position establish a temporary mow in reverse function. Prior circuits such as the one shown in the 5,994,857 patent commonly utilized a single pole seat switch and required extra circuitry to assure proper operation of interlock functions which rely on PTO, brake and operator presence conditions on the vehicle for enabling PTO operation in reverse. Providing an interlock circuit without need for multiple relays and with an override feature that is simple, convenient, and reliable has been a source of difficulty.
BRIEF SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide an improved interlock circuit for a lawn and garden tractor or similar vehicle. It is a further object to provide such an improved circuit which overcomes the aforementioned problems.
It is a further object of the present invention to provide an improved interlock circuit with an override function which facilitates PTO operation when the vehicle is in reverse provided certain operating conditions exist on the vehicle. It is yet another object to provide such an interlock circuit which does not require a large number of relays.
It is yet another object to provide an improved interlock circuit with a switch and latch circuit for operating the PTO under certain conditions when the vehicle is in reverse. It is a further object to provide such a circuit which does not require the operator to continuously push or hold the switch. It is a further object to provide such a circuit which permits an operator to shift the vehicle into reverse without having to restart the PTO if the operator depresses the switch when placing the vehicle in reverse.
It is another object of the present invention to provide an improved interlock circuit for selectively enabling PTO operation in reverse utilizing a two pole operator presence switch to isolate interlock functions and simplify the circuitry.
An interlock system constructed in accordance with the teachings of the present invention includes a latching circuit with a two-pole seat switch and an operator push button switch connected to a latch relay to provide operator actuated mow in reverse feature. The system provides a latching function which is actuated by the operator each time the vehicle is put into reverse to facilitate mowing in reverse. If the vehicle is placed in reverse with the PTO engaged and without the push button switch being depressed, the engine will be disabled. Also, if the operator leaves the seat while the vehicle is mowing in reverse, the engine will be disabled. The circuit is relatively simple and inexpensive and, as shown, requires only a single relay thereby eliminating the cost and complexity of multi-relay circuits. In addition, the operator presence switch is a two pole switch isolating the PTO switch from the brake switch so the circuitry permitting PTO operation in reverse and wiring of indicators can be simplified.
These and other objects, features and advantages of the present invention will become apparent to one skilled in the art upon reading the following detailed description in view of the drawings.
REFERENCES:
patent: 3649896 (1972-03-01), Mason et al.
patent: 3838748 (1974-10-01), Gray et al.
patent: 4974711 (1990-12-01), Peterson et al.
patent: 5156232 (1992-10-01), Muroya et al.
patent: 5203440 (1993-04-01), Peterson et al.
patent: 5994857 (1999-11-01), Peterson et al.
patent: 6056074 (2000-05-01), Heal et al.
patent: 6189646 (2001-02-01), Brandt et al.
Deere & Company
Ip Paul
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