Matrix Switch

Abstract

A finger-pressure actuated matrix switch assembly includes a map overlay and generates a binary coded signal corresponding to the coordinates of the point of application of pressure to the map. The assembly comprises a housing with a slot for positioning a replaceable map card in operative position and a storage chamber for a plurality of such map cards. Each of the map cards is edge-notched with a unique code identifying that card, and switches supported on the housing are actuated by these notches when a map card is inserted into its operative position to generate a binary electrical signal corresponding to that code. The matrix or grid is formed by orthogonally related sets of printed conductors on stacked boards spaced apart by resilient strip separators formed directly on one of the boards. Logic circuitry for converting the coordinates of contacting conductors into binary digits is carried on a single pluggable board detachably connected to the matrix boards for quick replacement to facilitate maintenance and repair.

Description

BACKGROUND OF THE INVENTION

This invention relates to matrix switches and more particularly to an improved pressure-actuated matrix switch assembly for generating electrical signals identifying the coordinates of the point of pressure on the assembly. Such a switch is useful in police and other vehicles for giving a remote station the location of the vehicle.

The police department of a medium size city having a population of 300,000 or more may have as many as thirty police patrol cars on duty at one time. In order to maintain a current and accurate record of the location of all patrol cars, the officer in each patrol car periodically calls the dispatcher to report his location. Each of these messages is verbally acknowledged by the dispatcher who then manually enters the information on a status board. Operation in this mode crowds the available communication channels with routine messages and prevents the dispatcher from addressing more important tasks requiring his attention. One of the prior art techniques proposed for automatically accomplishing this function comprises a transmitter in each car periodically transmitting at a unique characteristic frequency and several fixed receiving antennas at different stations around the city which triangulate on received signals to fix the location of the vehicle. Such systems are complex and expensive.

An improved vehicle location system utilizing a finger-actuated matrix switch in the vehicle to generate a binary coded signal for transmission over the radio network to the dispatcher is described in copending application Ser. No. 287,631 of Kent Penwarden. A key element in such a locator system is the pressure-responsive matrix switch assembly which generates a binary signal corresponding to the position of a selected pressure point on a street map overlaying the switch. This invention is directed to an improved construction of such a matrix switch.

An object of this invention is the provision of a grid coordinate matrix switch capable of accommodating a plurality of replaceable map cards forming subdivisions of a larger map.

Another object is the provision of a matrix switch of this type with means for automatically generating a signal to identify a selected map card when inserted into the operating position.

A further object is the provision of a matrix switch having a multilayer printed circuit board assembly with a pluggable component board to facilitate maintenance.

A further object is the provision of a low-cost matrix switch with grid-forming conductors printed on stacked circuit boards and spaced by resilient separators formed directly on one of the boards by silk screen or printing techniques.

SUMMARY OF THE INVENTION

A binary output matrix switch is capable of receiving one of a plurality of map overlay cards for generating a coded location signal in response to finger pressure at a selected point on the map. Each card carries an identification code which is translated into part of the binary output signal when the card is inserted into operating position. Grid conductors are formed by printed circuit techniques and an easily removed pluggable component board facilitates maintenance and trouble shooting of the unit.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partially schematic and partially perspective view of a vehicle locator system with a matrix switch embodying this invention;

FIG. 2 is a side elevation, partially in section, of the switch embodying this invention;

FIG. 3 is a perspective view of the switch showing details of the multilayer construction;

FIG. 4 is an exploded view of the multilayer assembly comprising the switch; and

FIG. 5 is a greatly enlarged transverse section of part of the switch assembly taken on line 5-- 5 of FIG. 3.

DESCRIPTION OF PREFERRED EMBODIMENT

Referring now to the drawings, a position locating system embodying this invention is shown in FIG. 1 and comprises a matrix switch assembly 10 which produces a binary signal output on line 11 in response to finger pressure by the hand H of the operator against the working surface 12 shown, by way of example, as a portion of a city street map. The binary output signal on line 11 is processed by a multiplexer 14 to form a coded binary word representing the coordinates of the finger pressure point on surface 12. This binary signal is applied to transmitter 15 for transmission over antenna 16 preferably as a tone burst when used in conjunction with a police communication network of the type described in U.S. Pat. No. 3,678,391 of Warren Gough. The transmitted signal is received at the remote station by antenna 17 and is processed in receiver 18 and decoder 19 for presentation on a display unit 20. A translucent map 21 on the surface of unit 20 is identical to the map on matrix switch surface 12 and is illuminated at point 22 corresponding to the finger pressure point on surface 12 by appropriate lighting means in response to the output of a logic circuit in decoder 19.

A general system including a binary signal generating matrix switch for vehicle location is described in the aforementioned application of Kent Penwarden and transmitter 15 may comprise a vehicle mounted digital communications unit described in the foregoing patent of Warren Gough. The instant invention resides in the matrix switch assembly 10.

Switch assembly 10 comprises a generally rectangular housing 24 having a front section 25 and a rear section 26 releasably connected together and a multilayer unit 27 mounted on front section 25. Front section 25 has side members 25a and 25b and top and bottom members 25c and 25d, respectively, defining an unobstructed rectangular opening which is traversed by the working surface or map area 12. Top member 25c and the upper parts of side members 25a and 25b project forwardly to form a shield and carry indicator lights 29 and 30 on opposite sides for monitoring operation of the switch assembly. In addition to signal output terminal 32, a power input terminal 33 and a control switch 34 are connected to circuits within the housing and project below bottom member 25d.

The utility and practicability of a matrix switch assembly 10 that is to be mounted in an already crowded police patrol vehicle, preferably adjacent the dashboard, is dependent on the compactness of the unit as well as its capability of displaying a sufficient area of a map to be effective. In order to balance these two limits -- minimum overall space occupied and maximum map viewing area -- provision is made in housing 24 to accommodate a plurality of replaceable maps or map cards 35 comprising portions of a larger map. To this end, the rearwardly facing edge of top member 25c of front section 25 is formed with a transversely extending recess 36 and each of the side members 25a and 25b has an inwardly opening vertically extending shoulder 38 (see FIG. 5) aligned in the plane of recess 36. Recess 36 and shoulders 38 define a slot for reception of map card 35 which comprises a plane rectangular frame 41, see FIGS. 4 and 5, enclosing the map 12 and having an upwardly projecting identification tab 42 with a visible code number thereon. In order to store a plurality of map cards 35, the rear housing section 26 has a compartment 44 with an upper opening 45 through which cards are removed and inserted; the tabs 42 of stored cards are staggered and project above top member 25c of the front section so as to be visually as well as physically accessible to the operator. The outline of a map card 35 partially inserted in recess 36 is shown in broken lines in FIG. 1.

The structure of multilayer unit 27 is shown more clearly in FIGS. 3-5, inclusive, and comprises a component board 48, a lower matrix board 49, an upper matrix sheet 50, a resilient magnetized cover 51, an a semi-permanent preferably small scale map 52. Replaceable map card 35 with a large scale map 12 overlies map 52. The side edges of matrix board 49 and sheet 50, cover 51 and permanent map 52 overlie the side edges of component board 48 as shown in FIG. 5 and receive screws 54 which secure these parts to sides 25a and 25b of front housing section 25.

Component board 48 is a relatively rigid sheet of 1/16 inch epoxy laminate and mounts circuit components 55 such as gates, flip-flops and core memories which comprise the logic elements of the switch assembly. These components are mounted on one side of the board, the underside as shown in FIGS. 4 and 5, the upper or top side of the board having printed conductors as shown for making intercomponent and other electrical connections. Board 48 also has terminal sockets 57 and 58 along adjacent side edges, respectively, for providing a releasable connection with the conductors on lower matrix board 49 and sheet 50 as described below. Signal output and power terminals 32 and 33 as well as control switch 34 are physically mounted on component board 48 and are electrically connected to the assembly through this board.

In order to automatically inform the remote station of the identity of a particular map card 35 which has been inserted into operative position in the housing, a plurality of switches 60, preferably four in number, are mounted on component board 48 and have outwardly projecting fingers 60a-60d, inclusive. The lower end of each map frame 41 is formed with notches 62 and teeth 63 defining an identification code for the particular card and switch fingers 60a-60d are positioned to cooperate with these notches and teeth. Switches 60 generate a 4-bit coded signal depending on the number and position of fingers 60a-60d which are depressed by teeth 63 (or not depressed by notches 62) and this identification code is transmitted as part of the output signal from the switch assembly; the signal is decoded at the remote station to enable the operator there to use a corresponding map on display unit 20. The number of switches 60 may be varied to suit the number of codes required to identify the replaceable maps. When no map card 35 is in the operative position, i.e., when small scale map 52 is exposed for use, none of the switch fingers are depressed which constitutes the code for indicating use of this map.

Lower matrix board 49 preferably is made of 1/8 inch epoxy glass laminate or similar material and has a plurality of straight laterally spaced parallel conductors 64 formed preferably by printed circuit techniques on the upper surface 49a and extending substantially the full length of the board. The ends of conductors 64 are electrically connected to pins 65 which extend along the lower edge, as viewed, and through the board for removable insertion into and electrical connection with aligned terminal sockets 57 on the corresponding edge of component board 48. Upper matrix sheet 50 is composed of relatively thin (0.004 inch) epoxy glass or similar material and has a plurality of laterally spaced parallel conductors 67 formed on the underside 50a and extending substantially the full width of the sheet at right angles to conductors 64 on matrix board 49. Conductors 67 are connected at one end to terminal elements 68 along the left side edge, as viewed, of sheet 50; elements 68 extend through sheet 50 and make electrical contact with pins 69 along the corresponding edge of board 49 when these parts are secured together in a stacked position. Pins 69 extend through board 49 and releasably engage sockets 58 in component board 48.

Conductors 64 and 67 on board 49 and sheet 50, respectively, are spaced from each other by a plurality of separator strips 71 formed on board 49 and extending parallel to conductors 64. Preferably one separator strip is located midway between adjacent conductors 64 and is coextensive with those conductors. Strips 71 are composed of a resilient compressible material such as neoprene, synthetic rubber, film rubber, or any other elastomer, which is applied to board 49 by deposition through a silk screen or the like in the manner employed to form masks in printed circuit processes. Thus the height and width of each separator strip is precisely controlled and all the strips are deposited simultaneously and rapidly. For example, the height of each strip which defines the separation gap between board 49 and sheet 50 and thus the length of the switch stroke is approximately 0.002 to 0.004 inch. Sheet 50 is sufficiently stiff to maintain a normally plane shape in the absence of a compressive force to insure separation of matrix conductors 64 and 67 at their crossover points, and yet has the desired flexibility for compressing separators 71 and permitting contact between conductors 64 and 67 in response to such force.

Cover 51 is composed of a resilient magnetized material about 0.030 to 0.040 inch thick and is designed to protect sheet 50 from damage by impact of a sharp object. In addition, the magnetic character of sheet 51 makes it a convenient mechanism for retaining a metallic washer or cursor 73, see FIG. 3, on a map surface overlaying the cover to indicate to the operator the last location transmitted by application of finger pressure to the map. A commercially available material useful in forming cover 51 is sold under the trademark Plastiform by 3M Company.

Sheet 52 preferably is a small scale map of an area of interest such as a city or county whereas the replaceable map cards 35 carry large scale maps constituting portions of map 52. Such a map arrangement permits the vehicle operator to quickly expose a large area of a city at any time simply by removing the map card 35 in use and also permits him to pinpoint his location more precisely by use of a magnefied view of various parts of that city available through selection of an appropriate map card 35. The electrical and mechanical operation of the matrix switch assembly 10 is the same with either large or small scale maps, the dispatcher at the remote station being instantly informed by the code switches 60 as to the identity of any map selected for use by the operator in the vehicle.

The use of matrix switch assembly 10 in police communications networks as well as in other systems requires an extremely fast maintenance and repair capability if and when the assembly requires such attention. In order to accommodate this requirement, substantially all of the parts susceptible to failure are carried on component board 48, i.e., signal output terminal 32, power terminal 33, control switch 34, code switches 60 and all components 55. Terminal sockets 57 and 58 on board 48 permit rapid electrical connection with and disconnection from pins 65 and 69, respectively, the remainder of the multilayer unit 27 being securely held to the front housing section by screws 54. In order to repair a defective switch assembly, rear housing section 26 is removed from front section 25, the component board is unplugged, a new component board inserted in its place, and the rear housing section is replaced. The entire operation is accomplished in a few minutes.

The dimensional tolerances of map cards frame 41 and shoulders 38 in the side members 25a and 25b of the front housing section 25 are sufficiently close to permit ready insertion and removal of a map card without substantial play between the map card and the stationary multilayer unit 27. In order to hold map card 35 stationary when inserted into the operative position, a forwardly extending cam-type projection 75 is formed on each tab 42 of map card 35, see, FIG. 4, and is positioned to extend into and engage a transverse groove 76, see FIG. 2, in top member 25c of front housing section 25 along the inner face of re-cess 36. Projection 75 snaps into slot 76 when the map card is bottomed in its operative position and the latter is held firmly in that position until intentionally removed by the operator.

Claims

What is claimed is:

1. A matrix switch assembly comprising

a housing having an unobstructed opening and a stacked multilayer compression switch supported on said housing and traversing said opening, said unit comprising

a first electrically nonconductive sheet having a first set of laterally spaced parallel conductors on one side,

a second electrically nonconductive sheet having a second set of laterally spaced parallel conductors on a side facing said one side of said first sheet and extending transversely of the direction of said first set of con-ductors,

one of said sheets having a plurality of resilient separators formed thereon for spacing said first and second sets of conductors, each of said separators comprising an elongated strip disposed between adjacent conductors on said one sheet, and

means for generating an output signal in response to an electrical contact between a conductor of the first set and a conductor of the second set.

2. The assembly according to claim 1 in which said strips are parallel to and coextensive with the conductors of said one member.

3. The assembly according to claim 1 in which said conductors have a printed circuit construction.

4. The assembly according to claim 2 in which said strips are permanently bonded to said one member.

5. A matrix switch assembly, comprising

a housing having an opening therein,

a compression switch unit mounted on and within said housing and having a surface traversing said opening, said switch comprising a first set of spaced parallel conductors in a first plane and a second set of spaced parallel conductors in a second plane spaced from the first plane, the conductors in the first set overlying and extending transversely of the conductors in the second set and defining therewith crossover points at which electrical contact is made between conductors of the two sets in response to a compressive force applied transversely of said planes,

said housing having slot means in a plane parallel to and adjacent to said surface, and

card means removably insertable into said slot means to an operative position overlying said surface, said card means being capable of transmitting to said surface of the switch unit said compressive force when applied thereto.

6. The switch assembly according to claim 5 in which a portion of said card means is formed with an identification code, and switch means mounted on said unit and actuated by said portion of the card when the latter is in the operative position for producing an electrical signal corresponding to said identification code.

7. The switch assembly according to claim 6 in which said housing has a compartment adapted to receive and store a plurality of said card means.

8. The switch assembly according to claim 7 in which each of said card means is formed with a different identification code for generating a corresponding electrical signal whereby automatically to distinguish the card means from each other when inserted into said operative position.

9. The switch assembly according to claim 8 in which said housing has a transverse groove in a portion thereof defining said slot, each of said card means comprising a frame and a flexible sheet mounted in said frame, said frame having a projection engageable in said groove when the frame is in the operative position in said slot.