WO1996003726A1

WO1996003726A1 - Pressure sensitive switch

Info

Publication number: WO1996003726A1
Application number: PCT/US1995/009367
Authority: WO
Inventors: Paul F. Newham
Original assignee: Bed-Check Corporation
Priority date: 1994-07-27
Filing date: 1995-07-25
Publication date: 1996-02-08
Also published as: GB2305761B; GB9701632D0; WO1996003727A1; CA2194699C; CA2194698A1; GB2305297B; AU3145395A; GB9701402D0; GB2305297A; CA2194699A1; CA2194698C; AU3271395A; GB2305761A

Abstract

A pressure sensitive switch has upper, middle and lower laminar elongated members, the middle member having an opening therethrough defining a cavity between the upper and lower members. A first array of substantially parallel, spaced-apart electrically conductive bands is fixed to a lower surface of the upper member and traverses the cavity. A second array of substantially parallel, spaced-apart electrically conductive bands is fixed to an upper surface of the lower member and traverses the cavity. Selected lower member bands are discretely connected to an electrical input lead and other lower member bands are discretely connected to an electrical output lead. An array of substantially parallel, spaced-apart dielectric bands narrower than the conductive bands is fixed to one of the lower and upper members and traverses the cavity between the arrays of conductive bands at alternate overlapping points thereof and partially separates the arrays of conductive bands from electrical contact therebetween at said alternate overlapping points. The upper and lower members are resiliently flexible to permit the overlapping points of the arrays of conductive bands to close into and open out of electrical contact therebetween upon exertion and removal, respectively, of a threshold external compressive force to the cavity.

Description

PRESSURE SENSITIVE SWITCH

This invention relates generally to equipment for monitoring the presence of a patient in a hospital bed and enclosures for supporting a docking module component of a bed monitoring system. The components of a bed monitoring system include a pressure sensitive switch or sensor mat located on the bed to sense the presence of the patient in the bed, a remote monitoring station such as a nurses station where indicia of the patient's presence are displayed and the docking module which contains the power and control systems necessary to interconnect the mat with the remote monitoring station to provide the desired monitoring functions. The monitoring station is essentially a central, permanent, fixed hardware network capable of simultaneously monitoring a great number of beds. The sensor mat is a relatively inexpensive, disposable and easily stored device of the type disclosed in earlier U.S. Patents Nos. 4,484,043 and 4,565,910. The sensor mat of the prior patents is excessively bulky and inadequately sensitive for many situations.

The docking module on the other hand, is a relatively expensive, non-disposable device. A limited number are kept available and are mounted on or proximate the particular bed to be monitored as the need arises.

While it is not economically desirable to provide a docking module for every bed in a hospital, it may become desirable from time to time to monitor any of the hospital beds. The present practice is to mechanically fasten the docking module to or proximate the bed to be monitored when that need arises, and when the need is ended to mechanically disconnect and retrieve the module from the bed. This mechanical process is time consuming and requires the attention of personnel specifically assigned to and trained for the task. In every application, subjective decisions must be made as to where to mount the docking module so as to make connection of the module between the mat and the remote station relatively easy and yet maintain the integrity of the system against intended or inadvertent tampering or disruption by a patient of visitor. Once located, proper connections of the sensor mat cable and remote monitoring station cables to the docking module must be made. Unfortunately, due in part to the inconsistencies in location of the module and wiring, the integrity of the connected circuits may be compromised. These tasks and decisions are further complicated by the wide variety of bed frame structures generally found within a hospital. Consequently, in the present practice, inconsistent arrangements of cables in hospital rooms often cause less than optimally convenient, comfortable and safe environments for the patient and visitors. Moreover, the confidence and comfort level of the staff in administering the monitoring system in a manner most effective for the patient is also diminished. In accordance with this invention, a pressure sensitive switch is provided having upper, middle and lower laminar elongated members. The middle member has one or more openings which define one or more cavities between the upper and lower members. A first array of substantially parallel, spaced- apart electrically conductive bands is fixed to a lower surface of the upper member and traverses the cavities. A second array of substantially parallel, spaced-apart electronically conductive bands is fixed to an upper surface of the lower member and traverses the cavities and the upper member bands. Selected lower member bands are discretely connected to an electrical input lead and the other lower member bands are discretely connected to an electrical output lead. An array of substantially parallel, spaced-apart dielectric bands is fixed to the lower member upper surface and traverses the cavities between the first and second arrays of conductive bands at their alternate overlapping points, separating the first and second arrays of conductive bands to prevent electrical contact with each other in the area of overlap with the dielectric bands where no pressure is applied by a sitting or reclining patient. The upper and lower members are so resiliently flexible as to permit the overlapping points of the arrays of conductive bands to close into or open out of electrical contact except in the area of overlap with the dielectric bands, upon exertion or removal, respectively, of a threshold external compressive force to or from the cavities.

Preferably, the upper member array is orthogonal to the lower member array and the bands of the upper and lower member arrays have centerlines substantially equally spaced. In this arrangement, the overlapping of the centerlines of the conductive arrays defines a matrix of squares. Preferably, the bands of dielectric have one edge along the diagonal of alternative ones of the squares and cover one half of the overlapping portion of the conductive bands. The conductive bands are of substantially equal width and narrower than the conductive bands and preferably one half the diagonal of the area of the overlapping conductive bands so that, even at those overlap points partially separated by dielectric, electrical contact is possible. Such a metricized arrangement has been found to provide most suitable complements of ease of manufacture and consistency of operation. Preferably, the laminar members are of heat stabilized polyester and the conductive bands are formed of a conductive ink, such as a blend of graphite/silver ink, screened onto the members.

In making the pressure sensitive switch, one array of substantially parallel, spaced-apart electrically conductive bands is applied to the surface of the upper flat flexible member. Another array of substantially parallel, spaced-apart electrically conductive bands is applied to the surface of the lower flat flexible member. This array includes a conductive input lead connected to selected ones of the conductive bands and a conductive output lead connected to the other conductive bands. An array of substantially parallel, spaced-apart dielectric bands are also applied to the surface of the lower member and to the lower member conductive bands. One or more openings are cut through the middle flat flexible member. The upper, middle and lower members are laminated together with the conductive arrays traversing the openings and each other and the dielectric array diagonally aligned with alternate overlapping points of the conductive arrays and separating the conductive arrays from making electrical contact in the area of dielectric overlap.

The thickness of the members and the spacing of the bands of the arrays is such that the upper and lower members resiliently flexibly permit the overlapping points of the arrays of conductive bands, except in the area of overlap by the dielectric, to close into or open out of electrical contact upon exertion or removal, respectively, of the threshold external compressive force to or from the openings. Preferably the conductive and dielectric ink, respectively, on the member, and lamination is accomplished by heat sealing or adhesive bonding of the polyester members together.

A docking module associated with each bed having a switch or sensor mat includes an enclosure for mounting a bed monitoring docking module on a bed frame structure. The enclosure has an elongated sleeve-like housing with an interior cross-section substantially complimentary to the outer cross- section of the docking module. The docking module is slidably insertable into and removable from a supported position within the sleeve-like housing through an open forward end of the housing. A connector housing mounted within a back end of the sleeve-like housing contains enclosure power, control and sensor connectors which are atable with respective externally accessible docking module and sensor mat connectors. The connector housing has an aperture through a wall thereof for mounting the enclosure sensor connector for interfacing with a mat sensor connector and a pair of apertures through a forward wall thereof for mounting power and control connectors in alignment for interfacing with the docking module connectors as the module is inserted into the sleeve-like housing. The forward wall of the connector housing is contoured to position the enclosure power and control connectors such that, during insertion and removal, the control interface is connected before the power interface and the power interface is disconnected before the control interface, respectively.

Thus, a docking module enclosure may be connected to every hospital bed with cables to the enclosures permanently included in the bed wiring harness. Any bed to be monitored can then be immediately, securely and conveniently connected to the monitoring network by simply inserting a docking module into the docking enclosure of the bed to be monitored. Objects of the invention not understood from the above will become clear from a review of the drawings and the description of the preferred embodiment which follows.

Objects and advantages of the invention will become apparent upon reading the following detailed description and upon reference to the drawings in which:

Fig. 1 is a bottom plan view of a preferred embodiment of the upper member of the pressure sensitive switch with a conductive grid applied thereon;

Fig. 2 is a top plan view of a preferred embodiment of the lower member of the pressure sensitive switch with the input and output conductive grid applied thereon,- Fig. 3 is a bottom plan view of a preferred embodiment of the dielectric grid to be applied over the conductive grid and the member illustrated in Fig. 2; Fig. 4 is a reversible plan view of a preferred embodiment of the middle member of the pressure sensitive switch;

Fig. 5 is an exploded plan view of a preferred embodiment of the pressure sensitive switch illustrating the matrix arrangement of the conductive and dielectric grids;

Fig. 6 is a sectional view taken along the line 6-6 of Fig. 5;

Fig. 7 is a bottom plan view of a preferred embodiment of the pressure sensitive switch;

Fig. 8 is a perspective view of a bed monitoring docking module;

Fig. 9 is a block diagram of a bed monitoring system incorporating the docking module enclosure of the present invention;

Fig. 10 is a perspective view of a preferred embodiment of the sleeve-like housing of the docking module enclosure;

Fig. 11 is a sectional view taken along the line 11-11 of Fig. 10;

Fig. 12 is a perspective view of a preferred embodiment of the connector housing of the docking module enclosure; and

Fig. 13 is a perspective view of the connector housing of Fig. 5 with a preferred embodiment of the enclosure power, control and sensor connectors mounted therein.

Turning to Fig. 1, an upper member of a pressure sensitive switch is illustrated. The first or upper member 10 consists of a flat, elongated, substantially rectangular sheet 11 having lengthwise edges 13 considerably longer than its widthwise edges 15. An array 17 of conductive bands 19 extends substantially longitudinally on the bottom face of the sheet 11. Preferably, the conductive bands 19 are parallel, of equal width and aligned on equally spaced centers. The array 17 extends substantially across the interior portion of the bottom face of the sheet 11, the length 21 and width 23 of the array 17 leaving a relatively wide perimeter portion of the bottom surface without any conductive grid. Preferably, the array 17 of conductive bands 19 is applied by screen painting.

As shown in Fig. 2, the third or lower number 30 of the pressure sensitive switch also consists of a flat, elongated, substantially rectangular sheet 31, preferably of length 33 and width 35 substantially equal to the length 13 and the width 15 of the upper member 10. An array 37 of conductive bands is applied to the top surface of the lower member 30, the width of each of the bands of the array 37 preferably being of equal width with each other and to the conductive bands 19 of the upper member 10. As shown, the lower member array 37 is preferably arranged in a width-wise grid orthogonal to the upper member conductive array 17 on center lines preferably equally displaced as the center lines of the conductive bands 19 of the upper member 10. Preferably, alternate ones 39 of the lower member conductive array 37 are discreetly connected to an electrically conductive input lead 41 while the other bands 43 of the lower member conductive array 37 are discretely connected to an electrically conductive output lead 45. Also preferably, the length 47 and width 49 of the array 37 are substantially the same as the length 21 and width 23 of the upper member array 19.

Looking now to Fig. 3, a dielectric grid 51 to be applied over the array 37 of conductive bands 39 and 43 on the lower sheet 31 is illustrated. It will be clear that the dielectric grid 51 may be applied over upper array 17 instead of lower array 37 if desired. The dielectric grid 51 consists of a plurality of substantially parallel and equally spaced apart bands 53 of dielectric material arranged in a fashion such that each band 53 traverses all of the conductive bands 19, 39 and 43. For reasons which will hereinafter become apparent, the bands 53 are aligned in a 45° angular relationship with respect to the widthwise conductive bands 39 and 43. The length 55 and width 57 of the dielectric grid 51 is substantially equal to the length 47 and width 49 of the conductive array 37. The width of each dielectric band 53 is less than the width of the conductive bands 19, 39 and 43 and preferably one half the diagonal of the overlapping area of the conductive bands 19, 39 and 43.

Turning now to Fig. 4, a middle member 70 consists of a flat, elongated, substantially rectangular sheet 71, preferably of length 73 and width 75 identical to the lengths 13 and 33 and widths 15 and 35 of the upper and lower sheets 11 and 31. One or more openings 77 are provided through the middle member 71 to define a cavity (78) between sheets 11 and 31. The openings 77 are substantially rectangular and arranged in longitudinal alignment across the middle member 70. The total length 79 of the openings 77 is substantially equal to the lengths 55 of the dielectric grid 51 or the lengths 21 and 47 of the arrays 17 and 37 of upper and lower member conductive bands 19, 39 and 43. Similarly, the width 81 of the openings 77 is substantially equal to the width 57 of the dielectric grid 51 and the widths 23 and 49 of the arrays 17 and 37 of upper and lower member conductive bands 19, 39 and 43.

Looking at Figs. 5 and 6, the relative alignments of the upper member conductive bands 19, the dielectric bands 53 and the input and output conductive bands 39 and 43 when the upper, middle and lower members 10, 70 and 30 are laminarly arranged. In the segment shown, conductive bands 19, dielectric bands 53 and input and output bands 39 and 43 are traversing one of the openings 77 in the middle member 70. The upper conductive bands 19 and lower conductive bands 39 and 43 form a matrix of squares while the dielectric bands 53 intersect alternate squares in a diagonal direction. Thus alternate overlapping portions of the wider upper and lower conductive bands 19, 39 and 43 are partially separated from the possibility of electrical contact therebetween by the narrower dielectric bands 53, as can best be seen in Fig. 6. Consequently, in the preferred arrangement, only fifty percent of the matrix of overlapping points can come into full electrical contact and the remaining overlapping points can achieve electrical contact over a maximum of fifty percent of their overlapping area.

This uniform distribution of full and partial contact points in spaced apart relationship affords the control necessary to assure the appropriate applications of threshold pressure to the cavity portions of the switch will consistently cause completion of the switching circuit and also that removal of or lack of such an appropriate threshold pressure will reliably cause the circuit not to be complete. In making the pressure sensitive switch, the conductive grids are screen painted onto their respective members. The upper and lower members 10 and 30 are 5 mil heat stabilized polyester and the conductive bands 19, 39 and 43 are formed by use of a suitable conductive ink such as 50/50 graphite/silver blend. The input and output leads 41 and 45 of the lower member conductive bands 39 and 43 are screen painted simultaneously with the conductive bands 39 and 43. After the conductive ink has been screened onto the lower sheets 31 a dielectric ink is used to screen the dielectric array 51 over the lower member conductive array 37. A plurality of arrays 17 and 37 can be screened onto a single sheet which may then be cut into a number of sheets 11 and 31. The openings 77 are die cut into the middle member 70 which is formed of 10 mil sheet such as a 7 mil polyester film with a 1 1/2 mil adhesive on each side thereof if adhesive bonding is used to accomplish lamination. The upper, middle and lower members 10, 70 and 30 are then laminated together, as by heat sealing or adhesively bonding the middle member 70 between the upper and lower member 10 and 30. Fig. 7 illustrates the upper member 10 of Fig. 1 and the lower member 30 of Fig. 2 with the dielectric array 51 of Fig. 3 superimposed thereon laminated to the middle member 70 of Fig. 3 using a clear polyester for the upper, middle and lower members 10, 70 and 30. The polyester need not necessarily be clear. The input lead 41 and the output lead 45 are 12 extended externally of the switch to a plug 82 for connection of the switch to an appropriate electrical power and control unit.

While the arrangement illustrated is preferred, it is not necessary that the conductive arrays 17 and 37 be in orthogonal relationship to each other or that they be on equally spaced centers. Depending on the particular application involved, it is necessary only that a limited matrix of full and partial contact points be established so as to provide the consistency of operation desired for given threshold pressures. It has been found that, for operation at a desired threshold pressure of approximately 2 pounds per square inch, a switch approximately 3.5 inches wide by 29 inches long with 5 mil heat stabilized polyester upper and lower members 10 and 30 and a 10 mil polyester middle member 70 with three openings 77 each 2 inches by 8 inches and spaced 1/2 inch apart and inset 2 inches from the ends of the device and 3/4 inches from the sides of the device is a very workable structure. In this arrangement, upper and lower member conductive grid bands 19, 39 and 43 of 0.09 inches on 0.18 inch centers with 0.06 inch wide dielectric bands 53 on 0.26 inch centers using 50/50 graphic/silver blend conductive ink for the conductive bands 19, 39 and 43 is an optimum arrangement.

Turning to Fig. 8, a docking module 83 for use with a docking module enclosure 100 which consists of a case 84 containing power and control circuits (not shown) having an externally accessible power connector 85 and an externally accessible control connector 86. The docking module 83 may also include an audio speaker 87 so as to provide an audible indication at the bed site of the patient's presence in or absence from the bed. The power connector 85 and the control connector 86 are specially selected for compatibility with the docking module enclosure 100 and the power connector 85 is provided with a prong 88 extending perpendicularly to the rear face 89 of the docking module 83.

Looking at Fig. 9, a sensor mat 90 is disposed on the hospital bed mattress (not shown) and is electrically connected via a cord 91 to a sensor connector 92. The mat 90 is essentially a switching device with its on/off status determined by distortion of or pressure on the mat 90 resulting from the presence or absence of a patient on the mattress. The sensor connector 92 in present practice, is normally connected to its associated docking module after the docking module has been permanently fixed to or proximate the bed. In this invention the docking module enclosure 100 is permanently secured to the bed frame 93.

The enclosure 100 has external sensor connectors 94 and power and control connectors 95 and 96 which are matable with the mat sensor connector 92 and module power and control connectors 85 and 86, respectively. Power and control wiring 97 to the enclosure may therefore be a permanent part of the hospital bed wiring harness (not shown) and communication to the remote monitoring station 98 can be accomplished via the wiring 97 or by wireless communication.

Turning now to Figs. 10 and 11, the sleeve-like housing 99 of the docking module enclosure 100 has a substantially channel or C-shaped cross-section having an inner contour substantially complementary to the outer contour of the docking module case 84. Thus, the back face 89 of the docking module 84 is somewhat snugly inserted into an open front end 101 of the enclosure 100 and the module 83 supported by the lower flanges 102 of the C-shaped housing 99. The top 103 of the housing 99 is provided with an audio aperture 104 which is aligned with the audio speaker 87 of the module 83 when the module 83 is fully inserted into the sleeve-like housing 99. A protective lip 105 extends outwardly from the sleeve-like housing 99 and forward of the speaker aperture 104 to protect the speaker 87 from damage when it is aligned with the aperture 104. The front portion 101 of the sleeve-like housing 99 has a taper 106 to its sidewalls extending rearwardly from top to bottom so as to facilitate easy insertion and removal of the docking module 83 into and from the sleeve-like housing 99.

As shown in Fig. 10, to facilitate mounting of the docking module enclosure 100 to the bed frame, a bracket assembly is mounted on an outer surface of the sleeve-like housing 99. The bracket assembly consists of an elongated L-shaped bracket 107 which is fastened to the top 103 of the housing 99 by bolts 108 applied to upwardly extending threaded posts 109. The posts are positioned so that the angle iron 107 has one of its legs extending upwardly in alignment with a sidewall of the housing 99. The upwardly extending leg of the angle iron 107 is provided with slots 110 for connection of an adjustable clamp. The adjustable clamp consists of additional angle irons 111 and 112 adjustably connected in back-to-back relationship to the first angle iron 107 by the use of wing nuts 113. As shown, the horizontal portion of the upper angle iron 111 is shorter than the horizontal portion of the lower angle iron 112 and the lower angle iron 112 has an upwardly extending flange 114. By loosening of the wing nuts 113 to vary this geometry, the angle irons 111 and 112 can be manipulated to grip any of a wide variety of structural shapes presented by a given bed frame 93. Threaded posts 109 are provided on both sides of the sleeve-like housing 99 so that the bracket assembly 107 can be connected to either side of the housing 99. Also, the top of the housing 99 is provided with a pair of slots or apertures 115 and 116 for extension of power and control wiring 97 to and from the docking module enclosure 100. A U-shaped spring clip 117 may also be secured to the underside of the top 103 of the housing 99 by use of a screw or rivet (not shown) through an aperture 118 provided in the housing 99 to assure that the module 100 is securely held within the enclosure 83. Turning no to Figs. 12 and 13, a connector housing 119 for containing and supporting the power, control and sensor connectors 94, 95 and 97 of the docking module enclosure 100 consists of a substantially C-shaped member having a base 120, back and front faces 121 and 122 and back and front flanges 123 and 124. The flanges 123 and 124 are provided with threaded apertures 125 so that the connector housing 119 can be fastened in the rear portion of the sleeve-like housing 99 by screws 126 as shown in Fig. 10. The back face 121 is provided with a sensor connector aperture 127 and the front face 122 is provided with power and control connector apertures 128 and 129. The front face 121 of the connector housing 119 is contoured to place the control connector aperture 129 forward of the power connector aperture 128. As can best be seen in Fig. 13, the control connector 96 is selected to mate with the control connector 86 of the docking module and extends forwardly from the control connector aperture 129 so as to interface with the docking module control connector 86 as the docking module 83 is inserted into the docking module enclosure 100. The power connector 95 is mounted in the power connector aperture 128 and includes a resiliently biased plunger 130 preferably disposed between upper and lower guiding and shielding extensions 131. Compression and expansion of the resiliently biased plunger 130 is located for alignment with the prong 88 on the docking module 83 and the extensions 131 assure proper engagement between the plunger 130 and the prong 88 and also prevent inadvertent operation of the plunger 130. Given this physically staggered relationship of the power and control connectors 95 and 96, as the docking module 83 is inserted into the docking module enclosure 100, the interfacing of the control connectors 86 and 96 is securely completed before the interfacing of the power connectors 85 and 95 is completed and before the prong 88 and plunger 130 have completed the power switching. Conversely, upon removal of the docking module 83 from the docking module enclosure 100, the power switch is turned off and the power interface interrupted before interruption of the control interface. The sensor connector 94 is mounted in the sensor connector aperture 127 for connection with the connector 92 associated with the switch or sensor mat 90.

Many variations of the specific structure herein disclosed are possible depending upon the desired contour and contact configuration of the docking module itself. It is contemplated that any such docking module contour and contact configurations can be accommodated by a suitably configured docking module enclosure, so as long as the enclosure is contoured to support the docking module, is adapted for mounting to a wide variety of bed frame structures and provides power and control interfaces physically arranged to insure that power is not applied to the network prior to firm connection of the control circuit components.

Claims

CLAIMS :

1. A pressure sensitive switch comprising: first (11) , second (70) and third (31) elongate members laminated together with the second member being sandwiched between the first (11) and third (31) members, the second member (70) having an opening (77) therethrough defining a cavity (78) between the first (11) and third (31) members; a first conductor (19) fixed to the first member (11) ; and a second conductor (37) fixed to the third member (31) , such that application of compressive force on the second member (70) can cause electrical contact between the first (19) and second (37) conductors, characterized in that the first conductor comprises an array (17) of substantially parallel, spaced-apart electrically conductive bands (19) fixed to a surface of the first member (11) and traversing the cavity (78) ; the second conductor comprises an array (37) of substantially parallel, spaced-apart electrically conductive bands (39, 43) fixed to a surface of the third member (31) and traversing the cavity (78) and the first member bands (19) , certain third member bands (39) being discretely connected to an electrical input lead (41) and other third member bands (43) being discretely connected to an electrical output lead (45) ; and the first (11) and third (31) members being resiliently flexible to permit the overlapping points of the arrays (17, 37) of conductive bands (19, 39, 43) to close into and open out of electrical contact therebetween upon exertion and removal, respectively, of a threshold external compressive force to and from the cavity (78) .

2. A switch according to claim 1 characterized by an array (51) of substantially parallel, spaced-apart dielectric bands (53) fixed to the first (11) or third (31) member and traversing the cavity (78) between the arrays (17, 37) of conductive bands (19, 39, 43) at alternate overlapping points thereof and partially separating the arrays (17, 37) of conductive bands (19, 39, 43) from electrical contact therebetween at the alternate overlapping points.

3. A switch according to claim 1 or 2 characterized in that first member array (17) is orthogonal to the third array (37) .

4. A switch according to any one of the preceding claims characterized by the bands (19) of the first member array (17) having centerlines substantially equally spaced.

5. A switch according to any one of the preceding claims characterized in that the bands

(39, 43) of the third member array (37) have centerlines substantially equally spaced.

6. A switch according to claim 2 characterized in that the bands (19, 39, 43) of the first (17) and third (37) member arrays have centerlines substantially equally spaced whereby overlapping of the centerlines defines a matrix of squares and the bands (53) of dielectric have one edge diagonally overlapping alternate ones of these squares.

7. A switch according to claim 2 or 6 characterized by the dielectric bands (53) being narrower than the conductive bands (19, 39, 43) .

8. A switch according to any one of the preceding claims characterized in that it is operatively connected to a docking module (83) , this module having a case (84) with externally accessible power (85) and control (86) connectors and a switch

(90) having a sensor connector (92) , the module (83) being mounted in an elongate sleeve-like housing

(99) having an interior cross-section substantially complimentary to an outer cross-section of the docking module (83) , an open forward end (101) in the housing (99) being arranged for slidably inserting and removing the docking module (83) ; and a connector housing (119) being mounted within a back end of the sleeve-like housing (99) for containing enclosure power (95) , control (96) and sensor connectors (94) matable with their respective module and switch connectors (85, 86) .

9. A switch according to claim 8 characterized by a frame (111, 112) mounted to an outer surface of the sleeve-like housing (99) for fastening the module (83) to a frame (93) of a bed.

10. A method of making a pressure sensitive switch comprising: applying a first conductor (19) to a first member (11) ; cutting an opening (77) through a second flat flexible member (70) ; applying a second conductor (37) to a third member, such that application of compressive force to the second flat flexible member (70) can cause electrical contact between the first (19) and second (37) conductors, characterized in that an array (17) of substantially parallel, spaced-apart electrically conductive bands (19) are applied to the surface of the first member (11) , which is flat and flexible; an array (37) of substantially parallel, spaced-apart electrically conductive bands (43, 39) are applied to a surface of the third member (31) , which is flat and flexible, the array (37) including a conductive input lead (41) connected to certain third member bands (39) and a conductive output lead

(45) connected to other third member bands (43) ; an array (51) of substantially parallel, spaced-apart dielectric bands (53) are applied to the surface of the first (11) or third (31) member traversing the first or third member conductive bands; the first (11) , second (70) and third (31) members are laminated together with the conductive arrays (19, 39, 43) traversing the opening (77) and each other and the dielectric array (51) being diagonally aligned with alternate overlapping points of the conductive arrays and partially separating the conductive arrays from electrical contact therebetween at the alternative overlapping points; whereby the first (11) and third (31) members resiliently flexibly permit the overlapping points of the arrays (19, 39, 43) of conductive bands to close into and open out of electrical contact therebetween upon exertion and removal, respectively, of a threshold external compressive force to and from the opening (77) .