CA1102382A - Pressure operated electric switch and an alarm system using such switch - Google Patents
Pressure operated electric switch and an alarm system using such switchInfo
- Publication number
- CA1102382A CA1102382A CA285,028A CA285028A CA1102382A CA 1102382 A CA1102382 A CA 1102382A CA 285028 A CA285028 A CA 285028A CA 1102382 A CA1102382 A CA 1102382A
- Authority
- CA
- Canada
- Prior art keywords
- pressure plate
- contact means
- switch
- base
- housing
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B5/00—Measuring for diagnostic purposes; Identification of persons
- A61B5/103—Detecting, measuring or recording devices for testing the shape, pattern, colour, size or movement of the body or parts thereof, for diagnostic purposes
- A61B5/11—Measuring movement of the entire body or parts thereof, e.g. head or hand tremor, mobility of a limb
- A61B5/1113—Local tracking of patients, e.g. in a hospital or private home
- A61B5/1115—Monitoring leaving of a patient support, e.g. a bed or a wheelchair
-
- G—PHYSICS
- G08—SIGNALLING
- G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
- G08B21/00—Alarms responsive to a single specified undesired or abnormal condition and not otherwise provided for
- G08B21/18—Status alarms
- G08B21/22—Status alarms responsive to presence or absence of persons
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
- H01H3/00—Mechanisms for operating contacts
- H01H3/02—Operating parts, i.e. for operating driving mechanism by a mechanical force external to the switch
- H01H3/14—Operating parts, i.e. for operating driving mechanism by a mechanical force external to the switch adapted for operation by a part of the human body other than the hand, e.g. by foot
- H01H3/141—Cushion or mat switches
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B2562/00—Details of sensors; Constructional details of sensor housings or probes; Accessories for sensors
- A61B2562/02—Details of sensors specially adapted for in-vivo measurements
- A61B2562/0252—Load cells
Abstract
ABSTRACT
The present invention provides a pressure operated electrical switch and an alarm system using the switch. The switch is constructed such that a force is applied to a pressure plate in the switch and once the load is reduced below a predetermined value the pressure plate will move under spring influence to close/open a microswitch or electrical contact means. The invention has particular application as an alarm system for use in hospitals and nursing homes. The normal force applied to the pressure plate is the load on the leg of a hospital bed when occupied. If the bed occupant gets out of the bed the load on the pressure plate is reduced below the predetermined value and the consequent movement of the pressure plate opens/closes the switch means to actuate the alarm.
The present invention provides a pressure operated electrical switch and an alarm system using the switch. The switch is constructed such that a force is applied to a pressure plate in the switch and once the load is reduced below a predetermined value the pressure plate will move under spring influence to close/open a microswitch or electrical contact means. The invention has particular application as an alarm system for use in hospitals and nursing homes. The normal force applied to the pressure plate is the load on the leg of a hospital bed when occupied. If the bed occupant gets out of the bed the load on the pressure plate is reduced below the predetermined value and the consequent movement of the pressure plate opens/closes the switch means to actuate the alarm.
Description
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The present invention relates to a pressure-operated electric swi.tch and an alarm system using the switch, and in one application is concerned with a switch whose contacts are closed when a force acting on the s~itch is reduced ~elow a predetermined value.
According to the present invention there is provi.ded a pressure-operated electric switch comprising a housing having a base and an overlying lid, a pressure plate mounted in the housing for vertical movement relative to the base and lid, compression spring means extending upwardly from a supporting surface in the housing below the pressure plate and biassing the pressure plate upwards, an aperture in th.e lid exposing a portion of the upper surface of the pressure plate and allo~ing the applicatlon of an external force to the pressure plate in opposition to the spring means, and first and second contact means inside the housing, the first contact means being carried by the pressure plate and the second contact means being supported in the housing at a posltion engageable by the first contact means upon .
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vertical movemen-t of the pressure plate, the said firs-t and second contact means being brought into engagement when the external force on the pressure plate crosses a predetermined thres~lold value.
In the preferred embodiment the second contact means is arranged above the firs-t contac-t means, whereby the first and second contact means are brought into engagement when the e~ternal force falls below a predetermined value.
A particular application of the preferred embodiment of the switch is to give an alarm to a nurse or other person minding a patient likely to get out of bed. In this application, the switch is acted on by a leg of the bed. The switch is constructed such that when the bed is occupied by the patient, the pressure acting on the switch is suf~icient to maintain the switch contacts in the open position whereas when the bed becomes ; unoccupied the switch contacts move to the closed position to give an alarm. The alarm may be audible and/or visible, e.g.
it may comprise a bell and/or a light.
Other applications of the pressure-operated switch and alarm system would be in connection with prams, cots, playpens, ,~ wheel chairs, invalid chairs, animal cages and pens, stables, safes either inside or outside, jewellers displays, museum objects or motor cars~ Indeed, the switch and alarm can be used in almost any instance where it is required to give an alarm upon movement of a person or object, and this alarm may be given when the movement of the person or object causes either an increase or a decrease of the pressure acting on the switch.
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Par-ticular e~bodimen-ts of pressure-operated electric switches and alarm sys-tems incorporating switches, are hereinafter described with reEerenc~ to the accompanying drawings, in which:-Figure 1 is a schematic diagram of a switch and alarm circuit as installed in use so as to be operable by the leg of a bed;
Figure 2 is a circui-t diagram of the switch and alarm circuit of Figure l;
Figure 3a is a plan view of the base of the switch of Figure l;
Figure 3b i9 a plan view of the lid of the switch of Figure l;
Figure 3c is a plan view of a housing for the main pressure springs of the switch of Figure l; ~
Figure 3d is a plan view of the pressure plate of the switch . : ~ .
of Figure l;
Figure 3e is an end elevational view of the pressure plate of Figure 3d;
Figure 4a is a cross-sectional view of a second embodiment of the pressure-operated switch;
Figure 4b is a plan view of the switch of Figure 4a;
Figure 4c is a side elevation of the switch of Figure 4a;
`~ Figure 4d is a plan view of the pressure plate of the switch of Figure 4a;
Figure 4e is an end elevation of the switch of Figure 4a;
Figure 4f is a plan view of the spring mounting block o~ the switch of Figure 4a Figure 5a is a cross-sectional view of a thi.rd embodiment of the pressure-operated switch;
Figure 5b is an underneath plan view of the switch.of E`igure 5a;
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Figure 6 is a modification o the bedside alarm circuitry shown in Figure 2;
Figure 7 is a portable bell arrangement which ma~ be used in conjunction with the pressure-operated switch;
Figure 8a is a plan view partly in section of a fourth embodiment of the pressure-operated switch;
Figure 8b is a plan view of the base of the switch of Figure 8a;
Figure 8c is a plan view of the spring mounting block of the switch of Figure 8a;
Figure 8d is a plan view of the pressure plate of the switch of Figure 8a;
Figure 9a is a plan view partly in section of a fifth embodiment of the pre.ssure-operated switch;
Figure 9b is a plan view of the base of the switch of Figure 9a;
Figure 9c is a plan view of the spring mounting of the switch ~ of Figure 9a;
: E'igure 9d is a plan view of the p:ressure plate of the switch of Figure 9a;
Figure lOa is a plan view of a modification of a spring mounting ~.
block;
Figure lOb is an underneath plan view of a modification of a :
pressure plate;
Figure 11 is a side elevational view of a switch.base showing the pressure-setting lines facilitating adjustment of the switch operating pressure, and Figure 12 is a side elevational view of an adaptation of a pressure-operated switch so that it may support a large : object.
: ~s shown in Figure 1, a pressure-operated electri.c switch 1 is positioned below the end of a bed leg 2 and is connected to an : - ~
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3~2 alarm circuit 3 by pairs of wires 4.
The alarm circuit 3 ineludes a light 5, a bell 6, a battery 7 for energising the bell eireuit, a switeh 8 in the light eireuit and a switch 9 in the bell circuit. The light circuit is energised from a mains supply soc~et outlet 10. Normally, the switches 8, 9 are in the closed position but may be opened to interrupt the alarm. A push button switch 11 for use with the main house call bell is provided mounted on the bedhead. The eircuit diagram of the alarm circuit is shown in figure 2.
The connections of the pairs of wires 4 to the switeh 1 are preferably made by plug-and-socket eonnectors 12, 13, fig 2.
Thus, a portable bell as shown in Figure 7 may be plugged into ; the switch~ or, when the alarm system is used in a house, the main house bell may be conneeted to the switeh.
The switeh 1 eomprises a hollow box--like base 14, Figure 3a, with a eentral eavity 16, and an overlying lid 15, Figure 3b, whieh together with the base forms a hollow housing. The lid 15 has an aperture 17 for reeeiving the lower end of the bed leg 2. The lid 15 has depending side walls whieh surround the base 14 and is supported on the base by a pair of coiled springs (not shown surrounding screw-threaded soeket bolts or studs 18 upstanding fxom the base and extending through holes 19 in the lid. The upper ends of the springs abut the underside of the lid and the ends of the studs 18 extending through the lid holes 19 reeeive wing nuts bearing on the lid surfaee through washersO
The eavity 16, reeeives a spring housing 20 having apertures 21 for aeeommodating a pair of main eoiled springs (not shown) 3~2 for taking the load exer~ed by the bed leg. The housing 20 may be in the form of a block having a metal plate on its underside for closing the ends of the apertures 21. The upper ends of the main springs support a metal pressure plate 22, Figure 3d, which is engaged on its upper surface by the bed leg 2 extending -through aperture 17. The upper surface of the plate 22 carries a pair of bridging switch contacts 23, 24 which are insulatingly mounted on the plate. When the pressure exerted on the plate 22 by the leg 2 falls below a predetermined value, the plate is raised by the main springs so that the contacts 23, 24 bridge corresponding pairs of strip-type contacts 25, 26 mounted on the underside of the lid, Figure 2. The contact pairs 25, 26 are connected, respectively, in the light and bell circuits by the plug-and-socket connectors 12, 13 and thus both the light and hell are energised to yive the alarm.
To impart additional stability to the pressure plate 22 it may be provided on its underside with studs 27 which ext~nd through the main coiled springs, Figure 3e.
The pressure required on the plate 22 to separate the contacts 23, 24 from the contacts 25, 26 respectively may be varied by adjusting the wing nuts on the socket bolts or studs 18 to vary the vertical spacing between the lid 15 and base 14. Also, the pressure required to separate the contacts may be increased by inserting a packing plate between the base of the spring housing 20 and the floor o the base-cavity 16.
In one construction of the switch 1, the base 14, cover 15 and spring housing 20 are of wood, but any other suitable material may be used.
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~2,3~2 Referring now to the switch construction shown in Figure 4a to 4f, the switch comprises a base 30 with a central cavity 31 receiving a spring mounting block 32 having a pair of aper-tures 33 accommodating the lower ends of main springs 34. The upper ends of the springs 34 abut a pressure pla-te 3S and urge the plate towards the inner surface of a lid 36 having a central aperture 37 for receiving the leg of a bed. The block 32 is seated in a metal tray 38, and studs 39, 40 respectively are provided on the plate 35 and the tray 38 for stabilising the springs 34 The lid 36 is supported on the base 30 by screw-threaded bolts 41 co-operating with screw-threaded socket 42 secured to the base, the upper ends of the bolts having reduced neck portions 43 co-operating with brackets 44 sunk into the top surface of the lid.
The end of each bolt 41 has a knob 45 so that the bolts may be rotated to adjust the distance of the base from the lid and thus the pressure required to operate the switch. A pointer 46 on the knob registers on a circular scale 47 (figure 4_) provided on the lid. ~ further adjustment of the operating pressure may be obtained by inserting one or more packing plates beneath the tray 38. To permit rotating the knobs by e.g., a screwdriver, ; they may be provided with a slot. The screw-threaded sockets 42 are secured to the base by ~rackets 49 sunk into the base, the brackets 49 being of square cross-section for preventing rotation on the base.
Tb maintain even pressure adjustment between the two kno~s 45, the base is provided e~ternally with horizontal indicator lines 46a, b and c (figure 4c) for registering with the lower edge of the lid; also, the lines are indicative of the pressure setting.
Thus line 46a indicates low pressure, line 46b medium pressure and line 46c high pressure~
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The pressure plate 35, Figure 4d, insulatingly carries on each of its upper and lower surfaces 48, 49, two bridging contacts 50, 51. Figure 4d shows the two bridging contacts on the upper surface 48 and a similar pair of contacts, not shown, are provided on -the lower surface 49. The contacts 50, Sl on the upper surface serve to bridge corresponding pairs of fixed contacts (not shown) provided on the under surface of the lid when the pressure plate 35 is biassed by the springs 34 against the lid as shown in Figure 4a. Two further pairs of contacts 52, 53, Figure 4f, are provided on the upper surface of the block 32 and these are bridged by the bridging contacts on the underside of the pressure plate when sufficient force is applied to the plate to move it downwardly against the spring pressure. The two pairs of contacts carried by the lid are connected by wires to respective ones of the upper two plugs 54, 55 of four plugs 54 ~ 57, flush-mounted in one end of the lid 36, figure 4e, and ; the two pairs of contacts 52, 53 carried by the block 32 are similarly connected by wires to the lower plugs 56, 57.
The left-hand plugs 54l 56 serve for connection to the alarm bell circuit and the right hand plugs 55, 57 serve for connection to the light circuit described previously with reference to Figure 2. Thus, by inserting sockets into the lower or the upper plugs, a choice may be made as to whether the alarm is to be given and the light energised either when the force acting on the pressure plate is increased or when it is decreased.
. , In the embodiment of the pressure-operated switch shown in ; Figures Sa and 5b, the switch base 60 has a central aperture 65, in which an annular bracket 61 is secured rotatably supporting 3~:
a screw-threaded bol-t 62, by co-operating with a reduced neck portion 63 of the boltO A screw-threaded socket 69 in threaded engagemen-t with the bolt 62 r is slidably guided in the base aperture 65 and is attached to the underside of a metal tray 66, receiving a spring mounting block 67. The pair of springs 68 are stabilized by studs 6~ on the tray 66 and studs 70 on a pressure plate 71. A lid 72 is attached to the base 60 by bolts 73, co-operating with sockets 74. Pairs of bridging contacts, not shown, are provided on the upper and lower surfaces of the pressure plate similar to those of Figures 4d, and pairs of contacts, not shown, are provided on the underside of the lid 72 and on the spring mounting block 67, similar to those described with reference to Figures 4a and 4f. Also, the end of the cover 72 has four sockets arranyed similarly to those shown in Figure 4e. In this embodiment the switch operating pressure is adjusted by rotation of the single bolt 6-2 by means of a knob 75, this action causing raising or lowering of the tray 660relative to the lid 72. The knob 75 has a pointer 77 registering with a scale 76. ;
The bedside control panel circuitry shown in Figure 6, is similar to that shown in Figure 2 but includes sockets 80, 81 to enable connection to be made with the pressure-operated switch by means of flexible cables having plug at each end, one end being inserted into the switch and the other end being plugged into the control panel.
Figure 7 shows a portable bell 91 in a case having a carrying handle 92, the bell having a battery 90 controlled by a switch 94 and being provided with a flexible cable 95 having a plug 93 for connection to the pressure-operated switch.
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Figures8a to 8d show a simplified pressure-operated switch and alarm system for mounting on a pram. A switch base 100 is mounted beneath an aperture provided in the pram seat and a pressure plate 101 urged upwardly by springs (not shown) mounted in holes 102 in a spring mounting block 103 is retained by a rectangular frame 104 fitted into the pram sea-t and overlying the aperture. The underside of the frame carries a pair of ; contacts 105 which are bridged by a contact 106 on the pressure plate 101 when a downwardly acting force acting on the pressure-plate is removed.Thus,should a baby or small child fall out of or be removed from the pram, the alarm circuit is closed. Studs, not shown, on the underside of the pressure plate enter the springs in the apertures 102~ A bell and battery unit 108 may be mounted either inside the pram beneath the seat or mounted ~-outside the pram beneath the pram body and protected by a cover.
The alarm circuit may include a key-operated switch 107 to immobilize the alarm and a further switch (not shown) may be included in the alarm circuit and operated by the pram brake.
Figures 9a to 9d show another embodiment of a pressure-operated switch in which a spring mounting block 110 has a cut-away portion to provide a space 111 for receiving a bell and battery (not shown) connected in the alarm circuit. The pressure plate 112 has a bridging contact 113 on its upper surface and another, similar, contact (not shown) on its lower surfaceO A pair of contacts 11~ are carried by the block 110 and bridged upon a downward force acting on the pressure plate~ and a pair of contacts 115 on the underside of a rectangular frame 116 overlying the aperture of a base 117 are bridged when the pressure plate rises under the action of the springs, not shown, located in holes 118 in the block 110. An opening 119 is provided in 3~3~
-the base for a mounting bolt.
Fic3ures lOa and l~b show modifications of the spring housing block and pressure plate, respectively. Figure 11 is a side elevational view oE a base of a pressure-operated switch similar -to the base of the switch of F:igures ~a to 4f but having four pressure-setting indicator lines 120a, b, c and d, the line 120a corresponding to the lowest pressure and the line 120d to the highest pressure. The lines may be provided on each of the four sides of the base.
Figure 12 shows a method by which the pressure-operated switch may be adapted to support a large object such as a 26" television set. In this adaptation, a pedestal member 131 is inserted through the aperture provided in the top of the switch 130 to rest on the pressure plate (not shown) and a large platform 132 ;~
is positioned on the member 131. The object to be supported is then placed on the platform~ Thus, removal of the object closes the alarm circuit.
The preferred embodiments of the present invention described above describes a pressure operated electrical switch which incorporates helical sprinys for taking the load exerted by the bed leg when the invention is in use in an alarm system in use in hospitals. The present invention also envisages as a further embodiment a design of switch housing which accommodates external to the housing a leaf spring centrally mounted on the base and adapted under the influence of a load i.e. the load exerted by the bed leg for vertical movement relative to said base. The leaf spring, acts not only as a spring but in the con-text of the present invention also acts as the pressure pla-te. A small strip , . ~ .
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of metal, which is operatively connected to -the leaf spring, acts as a level indicator and the said strip of metal co-operates with a micro-switch i.e. ~irsk and second contact means housed within the casing.
The second embodiment is particularly adapted to accommodate a castor wheel i.e. a wheel at the bottom of a bed leg, by having the leaf spring/pressure plate openly centrally mounted on the base and walled in on its two sides by the switch casing which houses the switch mechanism which responses to the movement of the level indicator attached to the leaf spring.
In this manner the castor wheel is positively located in a guideway formed by side walls formed by the casing an~ the leaf spring mounted within the guideway so formed acts not only as the spring means and pressure plate of the invention but also as a locating ramp for the castor wheel.
It will be readily appreciated that the alarm system of the present invention has particular application in hospitals and nursing homes. In such use it is desirable and technically feasible using known/conventional electrical and/or electronic components to integrate the alarm system of the present invention with existing nurse cally systems.
The present invention relates to a pressure-operated electric swi.tch and an alarm system using the switch, and in one application is concerned with a switch whose contacts are closed when a force acting on the s~itch is reduced ~elow a predetermined value.
According to the present invention there is provi.ded a pressure-operated electric switch comprising a housing having a base and an overlying lid, a pressure plate mounted in the housing for vertical movement relative to the base and lid, compression spring means extending upwardly from a supporting surface in the housing below the pressure plate and biassing the pressure plate upwards, an aperture in th.e lid exposing a portion of the upper surface of the pressure plate and allo~ing the applicatlon of an external force to the pressure plate in opposition to the spring means, and first and second contact means inside the housing, the first contact means being carried by the pressure plate and the second contact means being supported in the housing at a posltion engageable by the first contact means upon .
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vertical movemen-t of the pressure plate, the said firs-t and second contact means being brought into engagement when the external force on the pressure plate crosses a predetermined thres~lold value.
In the preferred embodiment the second contact means is arranged above the firs-t contac-t means, whereby the first and second contact means are brought into engagement when the e~ternal force falls below a predetermined value.
A particular application of the preferred embodiment of the switch is to give an alarm to a nurse or other person minding a patient likely to get out of bed. In this application, the switch is acted on by a leg of the bed. The switch is constructed such that when the bed is occupied by the patient, the pressure acting on the switch is suf~icient to maintain the switch contacts in the open position whereas when the bed becomes ; unoccupied the switch contacts move to the closed position to give an alarm. The alarm may be audible and/or visible, e.g.
it may comprise a bell and/or a light.
Other applications of the pressure-operated switch and alarm system would be in connection with prams, cots, playpens, ,~ wheel chairs, invalid chairs, animal cages and pens, stables, safes either inside or outside, jewellers displays, museum objects or motor cars~ Indeed, the switch and alarm can be used in almost any instance where it is required to give an alarm upon movement of a person or object, and this alarm may be given when the movement of the person or object causes either an increase or a decrease of the pressure acting on the switch.
23~9~Z
Par-ticular e~bodimen-ts of pressure-operated electric switches and alarm sys-tems incorporating switches, are hereinafter described with reEerenc~ to the accompanying drawings, in which:-Figure 1 is a schematic diagram of a switch and alarm circuit as installed in use so as to be operable by the leg of a bed;
Figure 2 is a circui-t diagram of the switch and alarm circuit of Figure l;
Figure 3a is a plan view of the base of the switch of Figure l;
Figure 3b i9 a plan view of the lid of the switch of Figure l;
Figure 3c is a plan view of a housing for the main pressure springs of the switch of Figure l; ~
Figure 3d is a plan view of the pressure plate of the switch . : ~ .
of Figure l;
Figure 3e is an end elevational view of the pressure plate of Figure 3d;
Figure 4a is a cross-sectional view of a second embodiment of the pressure-operated switch;
Figure 4b is a plan view of the switch of Figure 4a;
Figure 4c is a side elevation of the switch of Figure 4a;
`~ Figure 4d is a plan view of the pressure plate of the switch of Figure 4a;
Figure 4e is an end elevation of the switch of Figure 4a;
Figure 4f is a plan view of the spring mounting block o~ the switch of Figure 4a Figure 5a is a cross-sectional view of a thi.rd embodiment of the pressure-operated switch;
Figure 5b is an underneath plan view of the switch.of E`igure 5a;
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Figure 6 is a modification o the bedside alarm circuitry shown in Figure 2;
Figure 7 is a portable bell arrangement which ma~ be used in conjunction with the pressure-operated switch;
Figure 8a is a plan view partly in section of a fourth embodiment of the pressure-operated switch;
Figure 8b is a plan view of the base of the switch of Figure 8a;
Figure 8c is a plan view of the spring mounting block of the switch of Figure 8a;
Figure 8d is a plan view of the pressure plate of the switch of Figure 8a;
Figure 9a is a plan view partly in section of a fifth embodiment of the pre.ssure-operated switch;
Figure 9b is a plan view of the base of the switch of Figure 9a;
Figure 9c is a plan view of the spring mounting of the switch ~ of Figure 9a;
: E'igure 9d is a plan view of the p:ressure plate of the switch of Figure 9a;
Figure lOa is a plan view of a modification of a spring mounting ~.
block;
Figure lOb is an underneath plan view of a modification of a :
pressure plate;
Figure 11 is a side elevational view of a switch.base showing the pressure-setting lines facilitating adjustment of the switch operating pressure, and Figure 12 is a side elevational view of an adaptation of a pressure-operated switch so that it may support a large : object.
: ~s shown in Figure 1, a pressure-operated electri.c switch 1 is positioned below the end of a bed leg 2 and is connected to an : - ~
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3~2 alarm circuit 3 by pairs of wires 4.
The alarm circuit 3 ineludes a light 5, a bell 6, a battery 7 for energising the bell eireuit, a switeh 8 in the light eireuit and a switch 9 in the bell circuit. The light circuit is energised from a mains supply soc~et outlet 10. Normally, the switches 8, 9 are in the closed position but may be opened to interrupt the alarm. A push button switch 11 for use with the main house call bell is provided mounted on the bedhead. The eircuit diagram of the alarm circuit is shown in figure 2.
The connections of the pairs of wires 4 to the switeh 1 are preferably made by plug-and-socket eonnectors 12, 13, fig 2.
Thus, a portable bell as shown in Figure 7 may be plugged into ; the switch~ or, when the alarm system is used in a house, the main house bell may be conneeted to the switeh.
The switeh 1 eomprises a hollow box--like base 14, Figure 3a, with a eentral eavity 16, and an overlying lid 15, Figure 3b, whieh together with the base forms a hollow housing. The lid 15 has an aperture 17 for reeeiving the lower end of the bed leg 2. The lid 15 has depending side walls whieh surround the base 14 and is supported on the base by a pair of coiled springs (not shown surrounding screw-threaded soeket bolts or studs 18 upstanding fxom the base and extending through holes 19 in the lid. The upper ends of the springs abut the underside of the lid and the ends of the studs 18 extending through the lid holes 19 reeeive wing nuts bearing on the lid surfaee through washersO
The eavity 16, reeeives a spring housing 20 having apertures 21 for aeeommodating a pair of main eoiled springs (not shown) 3~2 for taking the load exer~ed by the bed leg. The housing 20 may be in the form of a block having a metal plate on its underside for closing the ends of the apertures 21. The upper ends of the main springs support a metal pressure plate 22, Figure 3d, which is engaged on its upper surface by the bed leg 2 extending -through aperture 17. The upper surface of the plate 22 carries a pair of bridging switch contacts 23, 24 which are insulatingly mounted on the plate. When the pressure exerted on the plate 22 by the leg 2 falls below a predetermined value, the plate is raised by the main springs so that the contacts 23, 24 bridge corresponding pairs of strip-type contacts 25, 26 mounted on the underside of the lid, Figure 2. The contact pairs 25, 26 are connected, respectively, in the light and bell circuits by the plug-and-socket connectors 12, 13 and thus both the light and hell are energised to yive the alarm.
To impart additional stability to the pressure plate 22 it may be provided on its underside with studs 27 which ext~nd through the main coiled springs, Figure 3e.
The pressure required on the plate 22 to separate the contacts 23, 24 from the contacts 25, 26 respectively may be varied by adjusting the wing nuts on the socket bolts or studs 18 to vary the vertical spacing between the lid 15 and base 14. Also, the pressure required to separate the contacts may be increased by inserting a packing plate between the base of the spring housing 20 and the floor o the base-cavity 16.
In one construction of the switch 1, the base 14, cover 15 and spring housing 20 are of wood, but any other suitable material may be used.
, . . .
~2,3~2 Referring now to the switch construction shown in Figure 4a to 4f, the switch comprises a base 30 with a central cavity 31 receiving a spring mounting block 32 having a pair of aper-tures 33 accommodating the lower ends of main springs 34. The upper ends of the springs 34 abut a pressure pla-te 3S and urge the plate towards the inner surface of a lid 36 having a central aperture 37 for receiving the leg of a bed. The block 32 is seated in a metal tray 38, and studs 39, 40 respectively are provided on the plate 35 and the tray 38 for stabilising the springs 34 The lid 36 is supported on the base 30 by screw-threaded bolts 41 co-operating with screw-threaded socket 42 secured to the base, the upper ends of the bolts having reduced neck portions 43 co-operating with brackets 44 sunk into the top surface of the lid.
The end of each bolt 41 has a knob 45 so that the bolts may be rotated to adjust the distance of the base from the lid and thus the pressure required to operate the switch. A pointer 46 on the knob registers on a circular scale 47 (figure 4_) provided on the lid. ~ further adjustment of the operating pressure may be obtained by inserting one or more packing plates beneath the tray 38. To permit rotating the knobs by e.g., a screwdriver, ; they may be provided with a slot. The screw-threaded sockets 42 are secured to the base by ~rackets 49 sunk into the base, the brackets 49 being of square cross-section for preventing rotation on the base.
Tb maintain even pressure adjustment between the two kno~s 45, the base is provided e~ternally with horizontal indicator lines 46a, b and c (figure 4c) for registering with the lower edge of the lid; also, the lines are indicative of the pressure setting.
Thus line 46a indicates low pressure, line 46b medium pressure and line 46c high pressure~
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.
3~Z
The pressure plate 35, Figure 4d, insulatingly carries on each of its upper and lower surfaces 48, 49, two bridging contacts 50, 51. Figure 4d shows the two bridging contacts on the upper surface 48 and a similar pair of contacts, not shown, are provided on -the lower surface 49. The contacts 50, Sl on the upper surface serve to bridge corresponding pairs of fixed contacts (not shown) provided on the under surface of the lid when the pressure plate 35 is biassed by the springs 34 against the lid as shown in Figure 4a. Two further pairs of contacts 52, 53, Figure 4f, are provided on the upper surface of the block 32 and these are bridged by the bridging contacts on the underside of the pressure plate when sufficient force is applied to the plate to move it downwardly against the spring pressure. The two pairs of contacts carried by the lid are connected by wires to respective ones of the upper two plugs 54, 55 of four plugs 54 ~ 57, flush-mounted in one end of the lid 36, figure 4e, and ; the two pairs of contacts 52, 53 carried by the block 32 are similarly connected by wires to the lower plugs 56, 57.
The left-hand plugs 54l 56 serve for connection to the alarm bell circuit and the right hand plugs 55, 57 serve for connection to the light circuit described previously with reference to Figure 2. Thus, by inserting sockets into the lower or the upper plugs, a choice may be made as to whether the alarm is to be given and the light energised either when the force acting on the pressure plate is increased or when it is decreased.
. , In the embodiment of the pressure-operated switch shown in ; Figures Sa and 5b, the switch base 60 has a central aperture 65, in which an annular bracket 61 is secured rotatably supporting 3~:
a screw-threaded bol-t 62, by co-operating with a reduced neck portion 63 of the boltO A screw-threaded socket 69 in threaded engagemen-t with the bolt 62 r is slidably guided in the base aperture 65 and is attached to the underside of a metal tray 66, receiving a spring mounting block 67. The pair of springs 68 are stabilized by studs 6~ on the tray 66 and studs 70 on a pressure plate 71. A lid 72 is attached to the base 60 by bolts 73, co-operating with sockets 74. Pairs of bridging contacts, not shown, are provided on the upper and lower surfaces of the pressure plate similar to those of Figures 4d, and pairs of contacts, not shown, are provided on the underside of the lid 72 and on the spring mounting block 67, similar to those described with reference to Figures 4a and 4f. Also, the end of the cover 72 has four sockets arranyed similarly to those shown in Figure 4e. In this embodiment the switch operating pressure is adjusted by rotation of the single bolt 6-2 by means of a knob 75, this action causing raising or lowering of the tray 660relative to the lid 72. The knob 75 has a pointer 77 registering with a scale 76. ;
The bedside control panel circuitry shown in Figure 6, is similar to that shown in Figure 2 but includes sockets 80, 81 to enable connection to be made with the pressure-operated switch by means of flexible cables having plug at each end, one end being inserted into the switch and the other end being plugged into the control panel.
Figure 7 shows a portable bell 91 in a case having a carrying handle 92, the bell having a battery 90 controlled by a switch 94 and being provided with a flexible cable 95 having a plug 93 for connection to the pressure-operated switch.
;238~
Figures8a to 8d show a simplified pressure-operated switch and alarm system for mounting on a pram. A switch base 100 is mounted beneath an aperture provided in the pram seat and a pressure plate 101 urged upwardly by springs (not shown) mounted in holes 102 in a spring mounting block 103 is retained by a rectangular frame 104 fitted into the pram sea-t and overlying the aperture. The underside of the frame carries a pair of ; contacts 105 which are bridged by a contact 106 on the pressure plate 101 when a downwardly acting force acting on the pressure-plate is removed.Thus,should a baby or small child fall out of or be removed from the pram, the alarm circuit is closed. Studs, not shown, on the underside of the pressure plate enter the springs in the apertures 102~ A bell and battery unit 108 may be mounted either inside the pram beneath the seat or mounted ~-outside the pram beneath the pram body and protected by a cover.
The alarm circuit may include a key-operated switch 107 to immobilize the alarm and a further switch (not shown) may be included in the alarm circuit and operated by the pram brake.
Figures 9a to 9d show another embodiment of a pressure-operated switch in which a spring mounting block 110 has a cut-away portion to provide a space 111 for receiving a bell and battery (not shown) connected in the alarm circuit. The pressure plate 112 has a bridging contact 113 on its upper surface and another, similar, contact (not shown) on its lower surfaceO A pair of contacts 11~ are carried by the block 110 and bridged upon a downward force acting on the pressure plate~ and a pair of contacts 115 on the underside of a rectangular frame 116 overlying the aperture of a base 117 are bridged when the pressure plate rises under the action of the springs, not shown, located in holes 118 in the block 110. An opening 119 is provided in 3~3~
-the base for a mounting bolt.
Fic3ures lOa and l~b show modifications of the spring housing block and pressure plate, respectively. Figure 11 is a side elevational view oE a base of a pressure-operated switch similar -to the base of the switch of F:igures ~a to 4f but having four pressure-setting indicator lines 120a, b, c and d, the line 120a corresponding to the lowest pressure and the line 120d to the highest pressure. The lines may be provided on each of the four sides of the base.
Figure 12 shows a method by which the pressure-operated switch may be adapted to support a large object such as a 26" television set. In this adaptation, a pedestal member 131 is inserted through the aperture provided in the top of the switch 130 to rest on the pressure plate (not shown) and a large platform 132 ;~
is positioned on the member 131. The object to be supported is then placed on the platform~ Thus, removal of the object closes the alarm circuit.
The preferred embodiments of the present invention described above describes a pressure operated electrical switch which incorporates helical sprinys for taking the load exerted by the bed leg when the invention is in use in an alarm system in use in hospitals. The present invention also envisages as a further embodiment a design of switch housing which accommodates external to the housing a leaf spring centrally mounted on the base and adapted under the influence of a load i.e. the load exerted by the bed leg for vertical movement relative to said base. The leaf spring, acts not only as a spring but in the con-text of the present invention also acts as the pressure pla-te. A small strip , . ~ .
~ ~fU ~ 3~
of metal, which is operatively connected to -the leaf spring, acts as a level indicator and the said strip of metal co-operates with a micro-switch i.e. ~irsk and second contact means housed within the casing.
The second embodiment is particularly adapted to accommodate a castor wheel i.e. a wheel at the bottom of a bed leg, by having the leaf spring/pressure plate openly centrally mounted on the base and walled in on its two sides by the switch casing which houses the switch mechanism which responses to the movement of the level indicator attached to the leaf spring.
In this manner the castor wheel is positively located in a guideway formed by side walls formed by the casing an~ the leaf spring mounted within the guideway so formed acts not only as the spring means and pressure plate of the invention but also as a locating ramp for the castor wheel.
It will be readily appreciated that the alarm system of the present invention has particular application in hospitals and nursing homes. In such use it is desirable and technically feasible using known/conventional electrical and/or electronic components to integrate the alarm system of the present invention with existing nurse cally systems.
Claims (17)
1. A pressure-operated electric switch for use in con-junction with a hospital bed and adapted for insertion under one leg of the bed to signal the absence of a patient therein, the electric switch comprising a portable housing having a base, a generally horizontal pressure plate mounted in the housing for vertical movement relative to the base, the pressure plate having an upper surface, spring means extending upwardly from a supporting surface in the housing below the pressure plate and biasing the pressure plate upwards, at least a portion of the upper surface of the pressure plate being exposed to allow the application of an external force to the pressure plate in opposition to the spring means, means for locating the lower end of a leg of a bed in overlying relationship to said pressure plate, first and second contact means mounted inside the housing and adapted for actuation by movement of the pressure plate whereby the first and second contact means are brought into engagement at a selected height of the pressure plate above the base, and means, to adjust the height of the pressure plate at which the contact means are brought into engagement.
2. A switch as claimed in claim 1 in which the pressure plate and the spring means are unitary and comprise a single leaf spring mounted on the base, the pressure plate comprising a generally horizontal raised portion of the leaf spring and the spring means comprising at least one downwardly inclined portion of the leaf spring which extends outwardly from one side of the raised portion.
3. A pressure-operated electric switch for use in con-junction with a hospital bed and adapted for insertion under one leg of the bed to signal the absence of a patient therein, the electric switch comprising a portable housing having a base, a generally horizontal pressure plate mounted in the housing for vertical movement relative to the base, the pressure plate having an upper surface, compression spring means extending upwardly from a supporting surface in the housing below the pressure plate and biasing the pressure plate upward, at least a portion of the upper surface of the pressure plate being exposed to allow the application of an external force to the pressure plate in opposition to the compression spring means, means for locating the lower end of a leg of a bed in overlying relationship to said pressure plate, first and second contact means mounted inside the housing, and adapted for actuation by movement of the pressure plate whereby the first and second contact means are brought into engagement at a selected height of the pressure plate above the base, and means to adjust the height of the pressure plate at which the contact means are brought into engagement.
4. A switch according to claim 1, wherein the first contact means is carried by the pressure plate and the second contact means is carried by the housing, the second contact means is arranged above the first contact means, whereby the first and second contact means are brought into engagement when the external force falls below a predetermined value.
5. A switch according to claim 3, wherein the first contact means is carried by the pressure plate and the second contact means is carried by the housing, the second contact means is arranged above the first contact means, whereby the first and second contact means are brought into engagement when the external force falls below a predetermined value.
6. A switch according to claim 1, wherein the adjusting means comprises means for adjusting the vertical position of the supporting surface of the spring means relative to the base.
7. A switch according to claim 3, wherein the adjusting means comprises means for adjusting the vertical position of the supporting surface of the spring means relative to the base.
8. A switch according to claims 6 or 7, wherein the supporting surface is a surface of a supporting element separate from the base, and the adjusting means comprises a screw-threaded member operatively associated with the base and supporting element in such manner that rotation of the member effects relative vertical movement between the base and supporting element.
9. A switch according to claims 4 or 5, further comprising cooperating third and fourth contact means inside the housing, the third contact means being carried by the pressure plate and the fourth contact means being arranged below the third contact means, the third and fourth contact means adapted for actuation by movement of the pressure plate whereby the third and fourth contact means are brought into engagement at a selected height of the pressure plate above the base and whereby the third and fourth contact means being brought into engagement when the external force increases above a second predetermined value.
10. A switch according to claim 3, wherein the pressure plate has an underside and the compression spring means com-prises a plurality of coil springs extending between the supporting surface and the underside of the pressure plate.
11. A switch according to claim 10, wherein the switch further comprises a plurality of studs on the underside of the pressure
11. A switch according to claim 10, wherein the switch further comprises a plurality of studs on the underside of the pressure
Claim 11 continued..
plate, each coil spring being located at its upper end by a respective stud which enters the said upper end.
plate, each coil spring being located at its upper end by a respective stud which enters the said upper end.
12. A switch according to claim 10, wherein the lower ends of the coil springs are accommodated in respective apertures in a spring housing block disposed on the supporting surface of the springs.
13. A switch according to claims 4 or 5, wherein the second contact means comprises a pair of spaced contacts and the first contact means comprises a bridging contact.
14. A switch according to claim 2, wherein said locating means comprises a pair or upstanding side walls of the housing defining therebetween a passageway for a wheel, the leaf spring extending along the length of the passageway with the downwardly inclined portion thereof forming a ramp for the wheel.
15. A switch according to claim 3, wherein said first and second contact means are embodied in a microswitch.
16. A switch according to claim 15, wherein the adjusting means comprises means for adjusting the height of the microswitch relative to the base.
17. An alarm system comprising the combination of a switch according to claims 1 or 3 and an external alarm circuit electri-cally connects to the first and second contact means in such a manner that engagement of the first and second contact means completes the circuit for raising the alarm.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| IE1867/76A IE43156B1 (en) | 1976-08-20 | 1976-08-20 | A load-operated electric switch and an alarm system using such switch |
| IE1867/76 | 1976-08-20 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1102382A true CA1102382A (en) | 1981-06-02 |
Family
ID=11031374
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA285,028A Expired CA1102382A (en) | 1976-08-20 | 1977-08-19 | Pressure operated electric switch and an alarm system using such switch |
Country Status (7)
| Country | Link |
|---|---|
| US (2) | US4381434A (en) |
| JP (1) | JPS5326974A (en) |
| CA (1) | CA1102382A (en) |
| DE (2) | DE7725830U1 (en) |
| FR (1) | FR2362482A1 (en) |
| GB (1) | GB1551191A (en) |
| IE (1) | IE43156B1 (en) |
Families Citing this family (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5585223A (en) * | 1978-12-22 | 1980-06-27 | Stanley Electric Co Ltd | Fixed quantity discharge method of fluid |
| US5019950A (en) * | 1990-05-25 | 1991-05-28 | Johnson Gerald L R | Timed bedside night-light |
| US5196827A (en) * | 1991-05-13 | 1993-03-23 | Allen William J | Alarm apparatus for handgun security |
| FR2693640B1 (en) * | 1992-07-16 | 1994-10-07 | Dominique Egalgi | Bed and seat type item. |
| US6400269B1 (en) | 1999-12-01 | 2002-06-04 | Anthony Savastano | Firearm alarm |
| CA2393880A1 (en) * | 2002-07-17 | 2004-01-17 | Tactex Controls Inc. | Bed occupant monitoring system |
| EP1740143B1 (en) * | 2004-04-30 | 2010-08-25 | Hill-Rom Services, Inc. | Patient support |
| US7868743B1 (en) * | 2007-03-23 | 2011-01-11 | Chester Brown | Alarm termination floor apparatus |
| US20090058644A1 (en) * | 2007-08-31 | 2009-03-05 | French John R | System and method for reducing inventory shrink |
Family Cites Families (26)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR491879A (en) * | 1916-05-29 | 1919-06-20 | Eleazar Brodsky | Underground circuit breaker |
| US1411167A (en) * | 1917-12-29 | 1922-03-28 | Robert J Cutshall | Burglar alarm |
| US1758546A (en) * | 1927-09-08 | 1930-05-13 | Wartmann Karl | Signal |
| GB420071A (en) * | 1934-04-12 | 1934-11-26 | Louis William Hirst | Improvements in or relating to automatic vehicle operated signalling and announcing devices |
| US2260715A (en) * | 1939-09-22 | 1941-10-28 | Ketchem Roy | Circuit closer |
| US2436898A (en) * | 1945-01-20 | 1948-03-02 | Jefferson Electric Co | Plunger switch |
| US2463980A (en) * | 1945-05-11 | 1949-03-08 | William A Lee | Tractor switch |
| US2458192A (en) * | 1947-03-11 | 1949-01-04 | William R Niles | Automatic signal device for automobiles |
| FR971535A (en) * | 1948-09-10 | 1951-01-18 | Push-in control, such as foot pedal, for safety installation and other applications | |
| US2707214A (en) * | 1952-09-10 | 1955-04-26 | Darwin Products Inc | Pedal switch mechanism |
| US2713645A (en) * | 1953-03-19 | 1955-07-19 | Charles W Lerch | Automatic control mechanism for elevators |
| CH321353A (en) * | 1954-02-23 | 1957-04-30 | Luethi Hans | Lane contact threshold |
| US2818477A (en) * | 1956-12-07 | 1957-12-31 | Paul J Gollhofer | Baby protective signal system for cribs |
| US3273038A (en) * | 1963-04-08 | 1966-09-13 | Mt Jefferson Lumber Co | Battery recharging method and apparatus for electrically powered vehicles |
| JPS4020191Y1 (en) * | 1964-05-27 | 1965-07-14 | ||
| AU422234B2 (en) * | 1968-05-27 | 1972-03-13 | Bruce Kenton Henry | Improvements in or relating to a switch actuator |
| US3656141A (en) * | 1970-01-23 | 1972-04-11 | Frank C Hill | Bird-scattering device |
| DE2148760C3 (en) * | 1971-09-30 | 1981-07-16 | Siemens AG, 1000 Berlin und 8000 München | Pedal switch device actuating electrical contacts |
| US3824536A (en) * | 1972-05-01 | 1974-07-16 | J Cherico | Wheel blocking alarm and indicating system |
| GB1383068A (en) * | 1972-11-13 | 1975-02-05 | Gradisar I A | Excessive load warning device |
| US3852736A (en) * | 1973-03-05 | 1974-12-03 | Beaumont W Hospital | Bed egress alarm circuit |
| US3845261A (en) * | 1973-05-24 | 1974-10-29 | Essex International Inc | Occupant sensor seat switch with deformable conductive spacer pads |
| DE7428286U (en) * | 1974-08-21 | 1974-11-21 | Kirsten F Elektrotechnische Spezialfabrik | Contact switches for motor vehicle seats made of foam |
| US3961201A (en) * | 1974-09-06 | 1976-06-01 | Rosenthal Morris H | Patient monitoring |
| US4263586A (en) * | 1976-08-20 | 1981-04-21 | Noel Nicholas | Pressure operated electric switch and alarm system using such switch |
| US4164637A (en) * | 1977-03-10 | 1979-08-14 | Olympus Optical Co., Ltd. | Dual tread plate foot switch |
-
1976
- 1976-08-20 IE IE1867/76A patent/IE43156B1/en unknown
-
1977
- 1977-08-19 JP JP10007477A patent/JPS5326974A/en active Pending
- 1977-08-19 GB GB34988/77A patent/GB1551191A/en not_active Expired
- 1977-08-19 DE DE7725830U patent/DE7725830U1/en not_active Expired
- 1977-08-19 FR FR7725477A patent/FR2362482A1/en active Granted
- 1977-08-19 DE DE2737562A patent/DE2737562C2/en not_active Expired
- 1977-08-19 CA CA285,028A patent/CA1102382A/en not_active Expired
-
1980
- 1980-12-18 US US06/217,605 patent/US4381434A/en not_active Expired - Fee Related
- 1980-12-18 US US06/217,607 patent/US4378476A/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| US4378476A (en) | 1983-03-29 |
| DE7725830U1 (en) | 1980-11-13 |
| GB1551191A (en) | 1979-08-22 |
| FR2362482A1 (en) | 1978-03-17 |
| IE43156B1 (en) | 1980-12-31 |
| US4381434A (en) | 1983-04-26 |
| FR2362482B1 (en) | 1982-06-04 |
| DE2737562C2 (en) | 1982-06-24 |
| JPS5326974A (en) | 1978-03-13 |
| IE43156L (en) | 1978-02-20 |
| DE2737562A1 (en) | 1978-02-23 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |