GB2464965A

GB2464965A - Presence Detector

Info

Publication number: GB2464965A
Application number: GB0819994A
Authority: GB
Inventors: Jeffrey Thompson
Original assignee: QUANTUM ADVANCED SYSTEMS Ltd; ST INDUSTRIES Ltd; ST IND Ltd
Current assignee: QUANTUM ADVANCED SYSTEMS Ltd; ST INDUSTRIES Ltd; ST IND Ltd
Priority date: 2008-10-31
Filing date: 2008-10-31
Publication date: 2010-05-05
Anticipated expiration: 2028-10-31
Also published as: GB2464965A8; GB0819994D0; GB2464965B; GB2464965B8

Abstract

A presence detector (10) for detecting the presence of a patient on a supporting surface under which the detector is located is provided. The detector comprises first and second longitudinally extending, conducting elements (12, 14) each having an arcuate, axial cross section. A convex surface of the second element (14) is located adjacent to, but spaced from, a concave surface of the first element (12). A longitudinally extending, concave biasing element (18) is also provided, a concave surface of the second element (14) being located adjacent to a concave surface of the biasing element (18). A sheath (26) having a rib (28) formed on one side thereof and having feet (34) connected to the opposing side thereof encapsulates the elements and means for connecting respective conducting elements to a controller is provided.

Description

PRESENCE DETECTOR

The present invention relates to a presence detector for detecting the presence of a user on a supporting surface under which the detector is located. In particular, the presence detector is suitable for use in a nursing home environment where it is desirable to monitor whether a patient remains in bed or whether they may have fallen out, such that assistance is required.

Conventional presence detectors are configured as a mat having a large surface area. Such mats are typically fitted underneath a mattress of a bed or underneath the cushion of a chair. Such a pressure mat typically comprises two layers of foil backed cardboard having a thin layer of foam, with holes formed therein, located between the two foil layers. The mat is generally encased in a plastic coating. The foam acts as a spacer to prevent normal contact between the two conducting foil layers. When pressure is applied to an upper surface of the mat the foam is compressed and the foil layers make contact with one another through the holes formed in the foam. An electrical circuit is completed and a signal is passed to a control device.

Such pressure mats have numerous disadvantages. In order to be effective, the mat must be positioned in an approximately planar orientation without folds or wrinkles, underneath a substantial part of the supporting surface (e.g. a mattress or a chair cushion). Such placement can be difficult and unwieldy for the carer as the potentially heavy, mattress must be moved out of the way and replaced carefully. Use of pressure mats is, therefore, undesirable.

Furthermore, the thin layer of foam becomes readily compressed over time and worn away such that it no longer functions correctly and spurious contact is made between the foil sheets so that false alarms are raised. As the mat typically covers a large surface area, it experiences shear loading from movement of the mattress or cushion under which the mat is located. Such shear loading, rapidly leads to deterioration of the mat, in particular, through degradation of the plastic coating material.

Furthermore, conventional mats are, at best, splash proof and can suffer in their performance when liquid based accidents occur. If the liquid is a conductor, contact will be made between the two conducting layers, indicating the presence of a patient thereupon even when the patient is no longer present.

It is, therefore, desirable to provide a presence detector having improved robustness characteristics together with enhanced ease of installation by the carer.

According to a first aspect the present invention provides a presence detector for detecting the presence of a patient on a supporting surface under which the detector is located, the detector comprising; a first, longitudinally extending, conducting element having an arcuate, axial cross section; a second, longitudinally extending, conducting element having an arcuate axial cross section, a convex surface of the second element being located adjacent to, but spaced from, a concave surface of the first element; a longitudinally extending, concave biasing element, a concave surface of the second element being located adjacent to a concave surface of the biasing element; a sheath, encapsulating the elements therewithin having a rib formed on one side thereof and having feet connected to the opposing side thereof; and means for connecting respective conducting elements to a controller.

By providing a longitudinally extending presence detector, encapsulated by a sheath, for use underneath a supporting surface, a robust device is achieved that is resistant to damage thereof and which is straight forward to install, even by a single person. Further, by providing the detector with a rib on one side of the sheath and feet on the other side of the sheath different actuating mechanisms are achieved such that a multi-functional detector is provided. The multi-functional aspect of the device permits a single device to be used in any configuration of bed with different patients and presence of the patient can be detected thereby.

The sheath may comprise a waterproof shield component which may enable the detector to achieve an IP rating of 65, or preferably an IP rating of 67.

The detector may comprise a controller in electrical communication with each respective conducting element. The detector may comprise an internal source of power, such as a battery, alternatively it may be mains powered.

According to a second aspect, the present invention provides a patient presence alert system comprising: a detector of the aforementioned type; and an alarm means configured to receive a signal indicative of a status of the presence of a patient from the controller.

According to a third aspect, the present invention provides a nurse call system comprising a patient presence alert system of the aforementioned type.

The present invention will now be described in more detail, by way of example only, with reference to the following drawings, in which: Figure 1 represents an isometric exploded view of a presence detector; Figure 2 represents an axial cross-section of the presence detector of Figure 1; Figure 3 represents a longitudinal cross-section of the presence detector of Figure 1; Figure 4 represents an isometric view of one side of the presence detector; Figure 5 represents an isometric view of the other side of the presence detector; Figure 6 represents a presence detector installed in a bed; Figure 7 represents a presence detector installed in a chair; and Figure 8 represents a circuit illustrating the operation of the presence detector.

Figure 1 illustrates a presence detector device 10 having a combined functionality of a pressure switch and a flex switch. The detector 10 comprises a first conducting element 12 and a second conducting element 14. Each element is provided by a strip of metal or other electrically conductive material (e.g. copper) and is configured so that it has a concave axial cross-section. The two conducting elements 12, 14 are spaced from one another by a series of insulating pads 16. In this embodiment, pads 16 are made from dense foam having little compressibility, however, other similarly incompressible materials (e.g. plastics material) could be used to achieve the same effect. As the pads 16 are substantially incompressible, over time the spacing between conducting elements 14, 14 will be retained.

First and second conducting elements 12, 14 are located substantially parallel to one another as shown in the axial cross-section view illustrated in Figure 2.

Extreme ends of the elements 12, 14 are separated from one another, either using a pad 16 as illustrated, or by using a bespoke plastic spacing member to secure the ends in place whilst preventing contact between the elements 12, 14. A biassing element 18 provided by a third metal strip, also having a concave axial cross-section, is disposed adjacent to conducting element 14. Concave surfaces of elements 14, 18 face one another to thereby define a cavity 20.

The second conducting element 14 is secured to biassing element 18 at either end thereof. The element 14 may be bonded to element 18 using adhesive, alternatively they may be welded or soldered to one another or they may be bound together using an adhesive tape.

Wires 22, 24 are connected to a surface of each respective conducting element 12, 14. In this embodiment the wires 22, 24 are soldered to each respective surface although other connection means may be used so long as electrical conduction between each wire 22, 24 and a respective element 12, 14 is retained.

Figure 2 shows that all of the elements 12, 14, 18 are encapsulated in a sheath 26. The sheath 26 comprises a flexible, waterproof, coating material such as a polymer or other plastics material. The sheath 26 comprises an externally located, longitudinal rib 28, extending the length of device 10 adjacent to conducting element 12. Whilst rib 28, as illustrated in Figure 3, extends the entire length of the device 10, it may, alternatively, be provided by a plurality of shorter ribs positioned in series along the length of the device 10.

The rib 28 is shown in more detail in Figure 4 which illustrates an isometric view of the device 10. The sheath 26 is sealed 30 at either end of the device 10 to prevent ingress of fluid into the interior of the device 10. The seal 30 is robust, having an P rating of65 or, preferably an IP rating of67. These ratings indicate that the device 10 is totally protected against dust' and that it is protected against low pressure jets of water from all directions' (1P65) and, preferably the device is protected against the effects of temporary emersion between 15cm and 1000 mm over a 30 minute test duration' (1P67). The seal 30 may be provided by RF welding the sheath 26, alternatively a sock may be used to cover the ends of the device 10 and this sock may be RF welded in place. The latter configuration enhances the seal 30, especially in the vicinity of wires 22, 24. Alternatively, the sheath 26 may be provided with an internal coating of adhesive prior to encapsulation of the elements 12, 14, 18, the sheath 26 is then heat shrunk onto the elements to form a robust shield there around.

The wires 22, 24 pass through the seal 30 at one end of the device 10 and are, in turn, encapsulated 32 to both insulate and protect the wires 22, 24.

Figure 5 illustrates the other side of device 10 and shows a number of feet 34 formed thereupon. These feet 34 are spaced from one another along the length of the device 10. In this embodiment, the feet are distributed evenly along the length, however, this is not essential and the feet 34 may be unevenly distributed. The location of feet 34 may correspond to the locations of foam spacer pads 16 located between conducting elements 12, 14. The number of feet 34 provided along the device 10 can vary but may be in the range of 4 to 20 for a device 10 configured to be installed in a bed, say having a length of 1000 mm. Preferably between 5 and 10 feet are provided on such a device 10.

In operation, the device 10 is inserted underneath a mattress on the bed base or underneath the cushion of a chair as illustrated in Figures 6 and 7. Figure 6 illustrates a bed 100 having a mattress 110 located on a bed base 120. The bed base, as illustrated, is a slatted bed base and the device 10, in this embodiment having a length of approximately 1000 mm, is placed lengthwise on the bed base 120 underneath a central portion of the mattress 110.

Alternatively, the device 10 could be placed in a diagonal orientation from one corner of the bed base 120 to an opposite corner of the bed base. In another embodiment, a shorter device 10', having a length of, say 400 mm, could be used and placed in a lateral orientation across the bed base 120 underneath a location where the patient's shoulders would be expected to be. Such an embodiment would be configured to detect when the patient sat up in bed or, otherwise, lifted their shoulders from an upper surface of the mattress 110. In a yet further embodiment, the same, shorter device 10' may be placed on top of the mattress 110, underneath a pillow and is used to detect when a patient lifts their head from the pillow.

Figure 7 illustrates use of the device 10' in a chair 130. The chair comprises a chair frame 140 and a seat cushion 150. As illustrated, the device 10' can be positioned laterally across the chair frame 140, underneath the seat cushion 150. Alternatively, the device 10' could be placed diagonally across the chair frame 140.

Operation of the device 10 is achieved in different modes. In a first mode, the device works as a pressure switch. The device 10 is positioned as illustrated in Figure 5 with rib 28 lowermost, namely, the device 10 is presented such that weight exerted thereon (e.g. by a patient on the mattress) urges the device 10 onto the rib 28. As the device 10 is compressed conducting element 12 is urged towards conducting element 14 and, if the weight is sufficient, contact is made. Use of the rib 28 focuses the distributed load represented by the patient into a focussed point load that can readily be detected by the device 10. A circuit, represented in Figure 8 wherein a controller 40 is connected to wires 22, 24, is completed when contact is made between the conducting elements 12, 14, such that presence of the patient is detected by the controller 40. In this first mode, the device 10 displays little sensitivity but is appropriate for detecting the presence of a heavier patient.

In a second mode, the device 10 serves as a flex switch, wherein the device 10 experiences some longitudinal bending i.e. a severe longitudinal change in curvature. When a bend or fold is experienced by device 10 conducting elements 12, 14 readily come into contact with one another such that the circuit of Figure 8 is completed and the presence of a patient is detected.

In order to achieve such severe changes in curvature, it is necessary for the conducting elements 12, 14 to be positioned over a solid, yet discontinuous, surface such that the device 10 may be urged between the solid sections when pressure is exerted thereon. A slatted bed represents such a surface. As pressure is exerted on the device 10, one or more portions of the device are urged between the slats in the bed and a longitudinal deformation is experienced thereby. Conducting elements 12, 14 are brought together and the circuit is completed so that the presence of the patient can be detected.

In practice, whilst the device 10 experiences deformation due to bending in the latter two embodiments, such that the device 10 acts as a flex switch, direct contact of elements 12, 14 without bending may also occur simultaneously, such that the actuation mechanism is a combination of a pressure switch and a flex switch. Different weight distribution of the patient along the length of device 10 leads to different actuation mechanisms being dominant at different locations, any of which mechanisms achieves the detection of a patient.

The device may be placed with the feet 34 lowermost, and therefore in contact with at least some of the slats of the bed base 120, or alternatively, the device 10 can be positioned with the rib 28 lowermost and, therefore, in contact with slats of the bed base 120. For the lighter patient, when increased sensitivity is required, the rib 28 should be positioned lowermost as any weight exerted on the device 10 will be focused into a point load by the rib in the regions of the slats of the bed. If the patient is heavier, it is desirable to reduce the sensitivity and so the device 10 can be positioned with the feet 34 lowermost. In so doing, the distributed load originating from the presence of a patient on the device 10, whilst still being focused, acts over a broader area represented by the cross section of the feet 34, when compared to that of the rib 28. Consequently, a less sensitive configuration is presented.

Many beds, however, do not comprise slats. Rather they are of the divan type which represent a continuous surface. When the device 10 is to be installed in a non-slatted bed and the presence of a lightweight patent is to be detected, the sensitivity of the device 10 must be enhanced. Consequently, the device 10 is positioned with its feet 34 lowermost as depicted in Figure 4. In this way, solid edges are provided by the feet 34 and a depth of the feet 34 enables the device 10 to be longitudinally deformed as in the previous example without requiring the need for slats in the bed. Consequently, a light-weight patient can be detected even in a non-slatted bed.

The versatility of device 10 represents a presence detector having variable sensitivity that is capable of detecting not only a heavier patient but also light-weight patients or, indeed, patients who are, perhaps, not lying directly above the device 10. If a patient is lying slightly to one side of the device 10, the load due to their weight is even more distributed. As the device 10 is sufficiently sensitive to be actuated even by such indirect loading it is generally only necessary to provide a single device 10 along the length of the bed in a central position. For a particularly light weight patient, especially one who roams to the edge of the bed frequently, it may be desirable to install two devices 10, laterally spaced from one another.

When the patient gets up from the bed (or chair) the biasing element 18 acts in combination with the second conducting element 14 to return the device 10 to a substantially planar (or non-flexed) configuration. In such a neutral position the conducting elements 12, 14 are no longer in contact with one another and therefore the circuit of Figure 8 is broken. The controller 40 can, therefore, detect that the patient is no longer present and an alarm may be raised.

In order to reduce the frequency of false alarms for example when a patient moves temporarily to the extreme edge of the bed, a delay mechanism can be incorporated into the controller 40 such that an alarm is only issued where the absence of the patient is detected for, say 4 seconds. This value of 4 seconds is arbitrary and can, of course, be readily changed by a carer of the patient.

As the device 10 can be installed in different ways, as described above, a very versatile and robust product is effected. In particular, the type of installation can be selected in dependence on an assessment of a number of factors including the weight and agility of the patient, the weight, thickness and size of the mattress/cushion and the type of bed or chair base.

The device can readily be installed by a single carer during any routine bed linen change and may be secured to the bed using hook and loop fastening strips or other temporary fixing means. By securing the device 10 to the bed or chair disruption/displacement of the device 10 is inhibited.

The controller 40 may directly cause an alarm to be issued such that the device 10 functions autonomously. Alternatively, the device 10 may be included within a nurse call system having a central controller located at a nurses' station. In the latter embodiment alarms may be issued as lights or sounds at the nurse station. The device 10 may be hard wired to such a central system or, alternatively, a wireless connection to the nurse call system or to a dedicated alarm system may be achieved via radio signals. A wireless device represents additional benefits in that a trip hazard represented by hard wires can be eliminated.

The device can be powered by battery or by connection to mains power.

Claims

CLAIMS1. A presence detector for detecting the presence of a patient on a supporting surface under which the detector is located, the detector comprising; a first, longitudinally extending, conducting element having an arcuate, axial cross section; a second, longitudinally extending, conducting element having an arcuate axial cross section, a convex surface of the second element being located adjacent to, but spaced from, a concave surface of the first element; a longitudinally extending, concave biasing element, a concave surface of the second element being located adjacent to a concave surface of the biasing element; a sheath, encapsulating the elements therewithin having a rib formed on one side thereof and having feet connected to the opposing side thereof; and means for connecting respective conducting elements to a controller.
2. A detector according to any preceding claim, wherein the sheath comprises a waterproof shield component.
3. A detector according to Claim 2, wherein the detector achieves an IP rating of at least 65.
4. A detector according to Claim 3, wherein the detector achieves an IP rating of at least 67.
5. A detector according to any preceding claim, comprising a controller in electrical communication with each respective conducting element.
6. A detector according to Claim 5, comprising an internal source of power.
7. A patient presence alert system comprising: a detector according to Claim 5 or Claim 6; and an alarm means configured to receive a signal indicative of a status of the presence of a patient from the controller.
8. A nurse call system comprising a patient presence alert system according to Claim 7.
9. A presence detector for detecting the presence of a patient on a supporting surface under which the detector is located substantially as described herein with reference to the accompanying drawings.