Note: Descriptions are shown in the official language in which they were submitted.
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PRESSURE SENSITIVE SWITCH
This inventicn 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 statian where indicia of the patient's
1G 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
4,555,910. 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
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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 ox 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 far 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 ar
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 l:y 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
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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 arid 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
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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
graphitefsilver 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
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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
5 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
far 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 matable 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
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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;
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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 I1-lI of Fig. 10;
Fi.g. 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 1D consists of a flat, elongated,
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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 equa3ly displaced as the
center lines of the conductive bands 19 of tine 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
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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 mora openings 77 are provided
through the middle member 71 to define a cavity (78)
between sheets 11 and 31. 'Phe 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
WO 95103725 ~ PC'fIUS95l09367
dielectric grid 51 or the lengths 21 and 47 of the
arrays 17 arid 37 of upper and lower member
conductive bands 19. 39 and 43. Similarly, the
width 81 of the openings 77 is substantially equal -
5 to the width 57 of the dielectric grid 51 and the
widths 23 and 49 of the arrays I7 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,
10 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
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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
banding 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 ZO 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
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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 50J50
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
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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
S 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 9O 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 nay therefore be a permanent
part of the hospital bed wiring harness (not shown)
and communication to the remote monitoring station
98 can be accomp7.ishad 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
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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
2S bolts 108 agplied to upwardly extending threaded
posts I09. The posts are positioned so that the
angle iron i07 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 lil and 112 adjustably .
connected in back-to-back relationship to the first
angle iron 107 by the use of wing nuts 1i3. As
shown, the horizontal portion of the upper angle
WO 9GI03726 ~ 6 C~ PCTlUS95l09367
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
5 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
10 107 can be connected t:o 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
15 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 I20,
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
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power connector aperture 128. As can best be seen
in Fig. 13, the control connector 96 is selected to i
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
IO resiliently biased plunger 130 preferably disposed
between upper and lower guiding and shielding
extensions i31. 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 plunder 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 ar sensor
mat 90.
Many variations of the specific structure
herein disclosed are possible depending upon the
PCTfUS951D9367
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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 adagted 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.
