Abstract: A simple operator presence override circuit is connected between available terminals on a PTO switch and a brake switch, and to the seat relay of the operator presence system. The override circuit permits continued operation of the engine under certain restricted conditions when the operator leaves the vehicle seat. A blocking diode connects one side of the seat relay to ground via the brake switch and one set of terminals on the PTO switch. With the PTO switch in the off condition and the vehicle braking system activated so the brake switch is closed, the seat relay remains activated to prevent operation of the ignition grounding circuit that otherwise would shut the engine down when the operator leaves his seat. Switching the PTO switch on or deactivating the braking system without an operator on the seat will automatically open the seat relay so that the engine is killed.

Abstract: The pull-in coil of a fuel shut-off solenoid on an engine is connected to a thermistor circuit for limiting the current to the pull-in coil. The pull-in coil is connected to ground through terminals of a control relay and through a thermistor. The activation coil of the control relay is also connected to the thermistor. When power is initially supplied to the pull-in coil, the resistance of the thermistor is low and current flow is sufficient to activate the fuel shut-off solenoid. The initial low resistance also assures that the voltage at the control relay activation coil remains near ground so the control relay initially remains deactivated. As the thermistor heats and resistance increases, pull-in coil current diminishes and voltage at the control relay increases until the control relay activates to interrupt power to the thermistor. The thermistor cools so that upon occurrence of the next pull-in solenoid activation pulse, the solenoid pull-in coil will immediately activate.

Abstract: The pull-in coil of a fuel shut-off solenoid on an engine is connected to a relay which in turn is connected to the engine starting circuit. The relay is connected through the oil pressure light switch which opens after a short period of time as the result of a change in oil pressure as the engine is being cranked. Solenoid overheating is avoided since the relay pull-in coil current is cut off as soon as the oil pressure rises.

Abstract: An interlock circuit for a vehicle such as a lawn and garden tractor with a switch-controlled PTO and obstacle sensor. The circuit provides engine shutdown and PTO disconnect if a sensor switch is tripped while the vehicle is in reverse. Engine recovery is allowed with the sensor switch tripped if the transmission is shifted out of reverse. If the tactile sensor fails to reset when the vehicle moves forward, the circuit prevents PTO reactivation. Once the sensor resets, the PTO can only be turned on by cycling the PTO switch.

Abstract: An interlock circuit is provided for a vehicle having a first PTO shaft and an optional second PTO shaft. When the optional PTO is installed, a standard seat switch utilized with the base interlock circuit is connected to an additional relay to put the interlock into a potential defeat mode as soon as the operator leaves the seat, provided the vehicle parking brake is engaged and a mechanical selector lever is in a position wherein the optional PTO only is selected. Other interlock functions remain unaffected whether or not the optional PTO is installed.

Abstract: An interlock circuit is provided wherein a foot switch connected through a diode to the alternator is depressed during rope-pull starting and provides power from the alternator to energize a relay and disable a magneto kill circuit to facilitate manual start. As the engine turns over and current flows from the alternator, the relay is bootstrapped to the energized position so that the engine remains running even after the foot switch is released. Normal interlock features, such as those which rely on operator presence or the transmission being in neutral, remain operational without additional switches and without need for a battery being present in the circuit.

Abstract: The ignition switch for a vehicle such as a lawn and garden tractor is connected directly to a printed circuit board which also includes interlock systems components. The circuit board with the switch and other components is wave soldered in an automated process to make good electrical connections for reduced voltage drops, thereby reducing the number of relays required. Wiring harnesses are also soldered directly to the board during the soldering step. In the preferred embodiment, the ignition switch is fixed to the board and supports the board from the console of the vehicle. However, if the switch or another component on the circuit board needs to be remotely located with respect to the remainder of the board, the switch or component is mounted on a break-away section of the board, and the wires connecting the board sections are soldered with the remainder of the components during the automated process.

Abstract: A clutch and brake control circuit includes first and second relays connected to an interlock circuit and to the brake and clutch coils on a vehicle. The relays are interconnected with the coils so that the clutch coil cannot be energized unless the brake coil circuit is complete. Preferably, the brake coil circuit includes a delay timer for assuring that the brake is energized for a preselected time period after the clutch coil is deenergized. The circuit is constructed such that if the clutch coil is reenergized during the time period, power to the brake coil is interrupted and the clutch coil turns on immediately without delay. Any time after the clutch coil is deenergized, a clutch switch connected to the interlock circuit and the relays must be actuated before the clutch will engage. The interlock circuit, which may include such elements as transmission, parking brake and seat switches, is fully integrated with the brake and clutch control.

Abstract: An improved seat suspension for reducing the jolt transferred from the seat of a vehicle to an operator when the vehicle "bottoms out". The improved seat suspension consists of a base unit connected to the vehicle, a support unit housing an attenuation unit for attaching the seat to the seat suspension, and a unit for operatively connecting the base and support units. The attenuation unit consists of at least one spring member which is contacted by a bumper attached to the connection unit just prior to the collision of the support unit with the base unit. By the bumper contacting the spring member, the effect of the collision on an operator occupying the seat is reduced.

Abstract: A tractor includes a PTO clutch and is provided with a safety interlock circuit including an ignition switch having separate output terminals respectively coupled to PTO and transmission switches that must be closed, by disengaging the clutch and shifting the transmission to neutral, before the tractor can be started. A start relay is coupled for being energized only when the PTO switch is closed and it then acts to complete a current path between the transmission switch and a starter solenoid. When de-energized, the start relay acts to complete an alternate current path to the solenoid, this path containing a lamp for indicating clutch engagement and which acts to drop the voltage below that required for starting.

Abstract: A silencer means particularly suited to two-cycle internal combustion engines includes an exhaust inlet pipe to receive exhaust from the exhaust ports of an engine, communicating with a diverging conical section which is followed by an exhaust chamber. An elliptically-shaped flat plate is located in the straight tubular section comprising the exhaust chamber. The plate is angled to produce a converging area at the end of the expansion chamber. An exhaust pipe or stinger is in communication with the interior of the expansion chamber in close proximity to the surface of the flat plate to receive engine exhaust gases and conduct the gases to the surrounding environment. Alternatively, the stinger can be so constructed that both ends of the stinger are closed, having a plurality of perforations in proximity to each end of the stinger to receive and exhaust gases to the surrounding environment from the exhaust chamber.