SUMMARY OF THE INVENTION

This invention combines a weight activated seat cusn- ion switcn with an exectron c αeiav circuit. The αevice is a seif-contameα plastic covered seat cushion witn up to three wires protruαing from one eαge. It fits on any seat suited for numanε. The wires can be connected to any safety or convenience αevice which requires activation by sitting on or rising from the seat. FIELD OF THE INVENTION

A thin plastic sheet encloses a foam rubber and wire mesh sandwich type switch. Two layers of thin foam rubber line the outside of the cushion. Underneath lie two sec¬ tions of electrically conductive wire mesn separateα DV a reiativeiv thicx insulating layer or foam rubber. £acn layer of wire mesh holds several contact washers. These washers pass tnrougn matching holes in the central insu¬ lating foam rubber pad. Matcning contact can πιaκe electri¬ cal contact in between the holes when the insulating layer is compressed by weight. Normally the wasners don't touch, leaving an open circuit between tne oositive and negative lead wires. Sitting on the cushion compresses the central insulating foam pad thus allowing one or more of tne wasn¬ ers to make contact with tne opposing wasner. one lead wire oasses through a solid state adjustable delay timer circuit board before exiting the cusnion. This circuit board uses transistors, resistors ana relays to αe_iay the opening cr tne circuit between tne positive and negative lead wires after the circuit is closeα by a person

sitting on the cusnion. A cnarged capacitor oiscnarging at an adjustable rate activates an electronic gate wnicn cnarges a coil thus opening a relay on tne leaα wire cir¬ cuit. The primary object of this invention is to provide a novel composite switch activating seat cushion ideally suited for vehicle safety applications.

A secondary object is to provide an inexpensive yet rugged design to allow for weight to bounce up ana down on the device for prolonged periods of time without disturbing the functionality of the cushion.

Other objects of this invention will appear from the following description and appended claims, reference being nad to the accompanying drawings forming a part of this specification wherein like reference characters designate corresponding parts in the several views. DESCRIPTION OF THE DRAWINGS

Figure 1 is a top side cutaway view of the cushion showing all the major parts with the delay circuit adjacent to its mounting position;

Figure 2 is the same view as Figure 1 with the delay circuit properly mounted in the cushion;

Figure 3 is the same view as Figure Z where the cushion has not been inserted into its plastic wrapper; Figure 4 is a top down view of the delay circuit show¬ ing the solid state components;

Figure 5 is a schematic diagram of the delay circuit. Before explaining the disclosed embodiment of the pre¬ sent invention in detail, it is to be understood that the invention is not limited in its application to the details of the particular arrangement shown, since the invention is capable of other embodiments. Also, the terminology used nerein is for the purpose of description and not of limita¬ tion. DETAILED DESCRIPTION

Referring to Figure i, a resilient compressible aper- tured separator i separates two wire esn contact sheets 2 and 3 in which conductive contacts 4 are mounted on several

opposing locations on sheets A ana . t-ioles 5 aiiow oppos¬ ing contacts 4 to touch wnen separator i is compressed. in normal operation this would occur wnen a person sits on tne device. Contacts 4 are electrically connected to contact sheets 2 and 3. Delay circuit 7 normally fits into slot 10. Lead wires 8 and 9 and G are normally connected to whatever activating device this invention triggers (not shown; . Resilient layers 17 and 18 protect contact sheets 2 and 3. Plastic cover 6 provides a protective outer cover for the device of the invention.

During operation twelve voits of DC electric power is applied across lead wires 8 and 14 by the activating device this invention triggers (not shown). Lead wire G attacnes to ground. A typical application using the present inven- tion would be a venicle emergency brake system configured to apply the emergency brakes when the driver lifted his weight off the invention for more than a few seconds. Typically this total system adds a measure of safety to a delivery truck operation requiring numerous park and stop maneuvers while the vehicle is running.

While contact is sensed between contact sheets 2 and 3 by the delay circuit 7, a direct electric path between leads 8 and 9 is provided by delay circuit 7. When contact stops between contact sheets 2 and 3, delay circuit 7 electronically delays opening the electric path between lead 8 and 9 for an adjustable period of time, usually 3-7 seconds.

Contact points 15 and 16 and wires 13 and 14 provide an electric path from sheets 2 and 3 through the delay circuit 7 via input terminal 11.

Figure 2 shows delay circuit 7 in position in slot 10. Lead wires 8, 9 and G normally protrude tnrough plastic cover 6. Lead wire 14 electrically joins wire 8 before exiting .cover 6. Figure 3 shows the invention without the plastic cover 6. Wire 14 is shown while wire i3 is hidden beneath delay circuit 7 (.see Figure 2). Contacts 4 are oehind delay circuit 7 and αo not touch delay circuit 7. Layers 17 and

id are αoubie siαeα aαnesive material.

Referring next to Figure 5, the circuit or tne αelav circuit 7 is snown. All + symbols mean a twelve volt DC power source is present. Normally when power is on the seat switch 50 is closed and capacitor 52 is cnargeo through resistor 51. At the same time, reference point 53 serves as a comparator 55 input signal which comparator 55 compares against reference point 54, tne other input leg into comparator 55. Resistor 56 in series with zener 57 creates a reference voltage at point 54 which is lower than 53.

Positive output from comparator 55 is at point 58 which drops across resistors 59 and 60 thus biasing (activating; transistor 61 to the ON position. When transistor t>l is ON a current is allowed to flow from power source 62 through coil 64 to ground 63. When coil 64 receives current, it inductively holds contacts 65 closed. In this condition, reference point 66 maintains a twelve volt charge to any external device (not shown) . Diode 67 is in a conducting state during the above conditions.

When seat switch 50 opens, power is removed from resis¬ tor 51 and capacitor 52 discharges through variable resis¬ tor 68. When reference point 53 becomes lower than refer¬ ence point 54, the output of comparator 55 drops to zero. Transistor 61 then switches to the OFF position stopping current through coil 64 thus causing contact 65 to open in a delayed time after seat switch 50 was opened. The dis¬ charge time of capacitor 52 as controlled by the value of resistor 68 controls the time delay of contact 65 opening. Coil b4 and contact 65 form an electronic relay 69.

Figure 4 shows one pnysical embodiment of the compo¬ nents described in E'igure 5 mounted on solid circuit board 70.