Electronically controlled C.D. ignition and interlocking shut-off system

• US 4,236,494 A
• Filed: 09/21/1978
• Issued: 12/02/1980
• Est. Priority Date: 09/21/1978
• Status: Expired due to Term

• Current Assignee: Toro Company (Toro)
• Original Assignee: Outboard Marine Corporation (Bombardier Incorporated)
• Inventors: Fairchild, Harold W.
• Primary Examiner(s): Cox, Ronald B.
• Application Number:
  US05/944,335
• Time in Patent Office: 803 Days
• Field of Search: 123/148 S, 123/148 C, 123/148 CC, 123/198 DC, 56/10.5
• US Class Current: 123/630
• CPC Class Codes: F02P 1/086 for generating sparks by discharging a capacitor into a coil circuit
• CPC Class Codes: F02P 11/025 Shortening the ignition when the engine is stopped to prevent damage to the coil F02P3/0556
• CPC Class Codes: F02P 11/04 Preventing unauthorised use of engines of vehicles B60R25/04; ignition locks H01H27/00

Abstract

Disclosed herein is a lawn mower comprising a grass bag and chute, and a grass discharge cover, and an internal combustion engine having operation regulated by an electronically controlled C.D. ignition and interlocking shut-off system. The system includes a charge capacitor, an ignition coil including a primary winding having a first terminal connected to the charge capacitor and having a second terminal, the ignition coil including a secondary winding which fires a spark plug to operate the engine when the charge capacitor discharges through the primary winding. The system also includes a thyristor having an anode connected to the second terminal of the primary winding, and having a cathode and a gate, the thyristor being rendered conductive when a trigger pulse is applied to the gate to allow discharge of the capacitor through the primary winding, and a trigger coil having a first end connected to the thyristor cathode and a second end, and being adapted for generating trigger pulses applied to the thyristor gate. The system also includes a plurality of interlocking switches normally closed during engine operation and connected in series relation between the trigger coil second end and the thyristor gate, each of the switch means being selectively movable to an open position to interrupt current flow and prevent application of a trigger pulse from the trigger coil to the gate. At least one of the switches moves to an open position to prevent engine operation when one of the grass bag and chute, or the grass discharge cover, is not installed in a proper position on the lawn mower.

Claims

1. A lawn mower comprising an electronically controlled C.D. ignition and interlocking shut-off system including a charge capacitor, an ignition coil including a primary winding, a thyristor including an anode connected to one end of said primary winding, and including a cathode, and a gate connected to ground, said thyristor being rendered conductive when a trigger pulse is applied to said gate to allow discharge of said capacitor through said primary winding, a trigger coil adapted to generate trigger pulses applied to said thyristor gate, and having a first end connected to said thyristor cathode and having a second end, and a plurality of interlocking switch means electrically connected in series relation between said second end of said trigger coil and ground, each of said switch means being selectively movable to an open position for interrupting current flow and preventing application of a trigger pulse to said gate, thereby selectively preventing discharge of said charge capacitor through said primary winding.

4. A lawn mower in accordance with claim 1 further comprising means connected in parallel with said charge capacitor to prevent excess voltage from being developed across said capacitor when one of said switch means moves to an open position.

5. A lawn mower in accordance with claim 4, wherein said excess voltage prevention means comprises a varistor.

2. A lawn mower comprising an electronically controlled C.D. ignition and interlocking shut-off system including a charge capacitor, an ignition coil including a primary winding, a thyristor connected in circuit with said charge capacitor and said primary winding, said thyristor having a gate connected to ground and being rendered conductive when a trigger pulse is applied to said gate to allow discharge of said capacitor through said primary winding, a trigger coil adapted to generate trigger pulses applied to said thyristor gate, and having a first end connected to said thyristor cathode and having a second end, and a plurality of interlocking switch means each selectively movable to an open position to interrupt current flow and prevent application of a trigger pulse to said gate, thereby selectively preventing discharge of said charge capacitor through said primary winding.

6. A lawn mower in accordance with claim 2 and further comprising means connected in parallel with said charge capacitor to prevent excess voltage from being developed across said capacitor when one of said switch means moves to an open position.

7. A lawn mower in accordance with claim 6, wherein said excess voltage prevention means comprises a varistor.

3. A lawn mower comprising a grass bag and chute, and a grass discharge cover, and an internal combustion engine having operation regulated by an electronically controlled C.D. ignition and interlocking shut-off system, said system including a charge capacitor, an ignition coil including a primary winding having a first terminal connected to said charge capacitor and having a second terminal, said ignition coil including a secondary winding which fires a spark plug to operate said engine when said charge capacitor discharges through said primary winding, a thyristor having an anode connected to said second terminal of said primary winding, and having a cathode, and a gate connected to ground, said thyristor being rendered conductive when a trigger pulse is applied to said gate to allow discharge of said capacitor through said primary winding, a trigger coil having a first end connected to said thyristor cathode and a second end, and being adapted for generating trigger pulses applied to said thyristor gate, and a plurality of interlocking switch means normally closed during engine operation and connected in series relation between said trigger coil second end and ground, each of said switch means being selectively movable to an open position to interrupt current flow and prevent application of a trigger pulse from said trigger coil to said gate, at least one of said switch means moving to an open position to prevent engine operation when one of said grass bag and chute, or said grass discharge cover, is not installed in a proper position on said lawn mower, said lawn mower further comprising means connected in parallel with said charge capacitor to prevent excess voltage from being developed across said capacitor when one of said switch means moves to an open position.