Optical seat switch

• US 4,683,373 A
• Filed: 10/23/1986
• Issued: 07/28/1987
• Est. Priority Date: 09/05/1985
• Status: Expired due to Fees

• Current Assignee: Caterpillar Incorporated
• Original Assignee: Caterpillar Incorporated
• Inventors: Tupman, David J.
• Primary Examiner(s): LaRoche, Eugene R.
• Assistant Examiner(s): MIS, DAVID C
• Application Number:
  US06/921,892
• Time in Patent Office: 278 Days
• Field of Search: 250/221, 340/556, 180/272
• US Class Current: 250/221
• CPC Class Codes: B60Q 9/00 Arrangement or adaptation of signal devices not provided for in one of main groups B60Q1/00 - B60Q7/00 , e.g. haptic signalling
• CPC Class Codes: B60R 16/023 for transmission of signals between vehicle parts or subsystems
• CPC Class Codes: G07B 13/02 Details; Accessories
• CPC Class Codes: H03K 17/941 using an optical detector H03K17/968 takes precedence

Abstract

Seat switches for detecting the presence and absence of an occupant in the seat of a vehicle are commonly used on industrial and commercial vehicles. It is desirable that the control signal produced by such seat switches be responsive only to the presence and absence of the vehicle occupant, and be relatively simple, rugged, and inexpensive. The instant invention includes an emitting device for directing a source of coded radiant energy across a vehicle seat, and a detecting device for receiving radiant energy, including a portion of the coded radiant energy in response to the seat being vacant. The detecting device produces an electrical signal in response to the received radiant energy. An electrical circuit produces a control signal only in response to the detecting device receiving the coded radiant energy.

Claims

1. Apparatus for producing a control signal in response to the presence and absence of an occupant in the seat of a vehicle, comprising:

emitting means for directing a source of coded radiant energy across said vehicle seat;

detecting means for receiving radiant energy, including a portion of said coded radiant energy in response to said seat being vacant, and producing an electrical signal in response to said received radiant energy;

discriminating means for distinguishing said electrical signal produced in response to said detecting means receiving said coded radiant energy, from electrical signals produced in response to said detecting means receiving spurious uncoded radiant energy; and

circuit means for producing said control signal only in response to said detecting means receiving said coded radiant energy.

2. Apparatus, as set forth in claim 1, wherein one of said emitting and detecting means is located behind and above the level of said seat, and the other of said emitting and detecting means is located in front of and below the level of said seat.

3. Apparatus, as set forth in claim 1, wherein said emitting means includes pulse generator means for substantially continuously producing a series of current pulses having a predetermined frequency and duty cycle, and an infrared light emitting diode connected to said pulse generator means and adapted to produce radiant energy having a wavelength substantially within the infrared spectrum, in response to receiving each of said current pulses.

4. Apparatus, as set forth in claim 3, wherein said detecting means includes a phototransistor adapted to produce a current signal in response to receiving radiant energy, and current to voltage converter means for receiving said current signal from said phototransistor and responsively producing a voltage signal, said current to voltage converter means being connected to said phototransistor.

5. Apparatus, as set forth in claim 4, wherein said discriminating means includes first voltage comparator means for receiving said voltage signal, comparing said voltage signal with a first predetermined voltage reference signal, and producing a comparison signal in response to said voltage signal having a magnitude exceeding the magnitude of said first predetermined voltage reference signal, and pulse to level converter means for receiving said comparison signal and producing a voltage level signal in response to said received comparison signal.

6. Apparatus, as set forth in claim 5, wherein said circuit means includes second voltage comparator means for receiving said voltage level signal, comparing said voltage level signal with a second predetermined voltage reference signal, and producing a control signal in response to said voltage level signal having a magnitude exceeding the magnitude of said second predetermined voltage reference signal.

7. Apparatus for sensing the presence and absence of an occupant in the seat of a vehicle, and producing a control signal in response to the presence and absence of such occupant, comprising:

pulse generator means for substantially continuously producing a series of current pulses having a predetermined frequency and duty cycle;

a light emitting diode adapted to receive said current pulses, produce radiant energy in response to receiving each of said current pulses, and direct said produced radiant energy across said vehicle seat;

a phototransistor adapted to receive radiant energy and produce a current signal in response to said received radiant energy;

current to voltage converter means for receiving said current signal and responsively producing a voltage signal;

first voltage comparator means for receiving said voltage signal, comparing said voltage signal with a first predetermined voltage reference signal, and producing a comparison signal in response to said voltage signal having a magnitude exceeding the magnitude of said first predetermined voltage reference signal;

pulse to level converter means for receiving said comparison signal and producing a voltage level signal in response to said comparison signal; and

second voltage comparator means for receiving said voltage level signal, comparing said voltage level signal with a second predetermined voltage reference signal, and producing a control signal in response to said voltage level signal having a magnitude exceeding the magnitude of said second predetermined voltage reference signal.

8. A method for sensing the presence and absence of an occupant in the seat of a vehicle, and producing a control signal in response to the presence and absence of such occupant, comprising the steps of:

directing a source of coded radiant energy across said vehicle seat;

receiving radiant energy including a portion of said coded radiant energy in response to said seat being vacant;

producing an electrical signal in response to receiving said radiant energy;

distinguishing said electrical signal produced in response to receiving said coded radiant energy, from electrical signals produced in response to receiving spurious uncoded radiant energy; and

producing a control signal only in response to receiving said coded radiant energy.