Description: This invention relates to bed guards.

Bed guards are used extensively in hospitals, especially in geriatric and paediatric wards, to prevent patients from falling out of their beds. A bed guard usually comprises a moveable rail that, when raised, is located adjacent, and above the level of, the mattress, thereby presenting a barrier to inhibit or prevent the patient from rolling, or falling, out of the bed. However, patients do occasionally need to leave their bends, for example, to go to the toilet during the night, and when the bed guard has been raised, this can present difficulties because the bed guard can usually only be lowered from the bedside, that is to say, not from within the bed by the patient. As such, many patients, when trying to get out of bed, end up attempting to climb over the bed guard rail, which can lead to accidents, especially, as is the case where a patient is hospitalised for whatever reason, the patient has restricted mobility, or is weak or frail.

In order to ameliorate the problem of patients trying to climb over their bed guards, sensors are often placed in the bed or on the guard rail to warn hospital staff when patents attempt to do this. Existing sensors of this type broadly fall into two categories, namely: "pressure off" sensors that are located below the mattress and which trigger an alarm when a patient's weight is not detected on the bed; and "pressure on" sensors that are fitted to the guard rail that trigger an alarm when weight is placed on the guard rail. Another known type of "pressure on" sensor comprises a support member that is slide underneath the mattress, and which has an up stand to which the sensor can be affixed. This avoids having to fit the sensor to the bed guard rail itself, but due to the differences in the designs of hospital beds, a different type of support member is needed for each different type of bed. This greatly increases the inventory of a hospital ward, which is expensive and time consuming. Both types of system (i.e. pressure-on and pressure-off) are susceptible to false alarms, i.e. when a patient rolls over in bed but is not attempting to get out of the bed; or when an arm or leg rests on the rail when reaching for items on a bedside table, respectively. Eventually, false alarms become a nuisance, especially where alarms are triggered whilst other patients on the ward are trying to sleep, which can lead to the alarms being disabled by hospital staff or patients, which entirely defeats their purpose.

A solution is needed to one or more of the above problems, and the present invention aim to do this and/or to provide an alternative type of system for warning when patients are attempting to leave their beds.

Various aspects of the invention are set forth in the appendent claims.

According to the invention, there is provided an alarm system for a bed comprising:

a support member comprising: a base portion slideable, in use, between a bed base and a mattress, and an up stand portion extending at substantially right angles to the base portion for supporting, in use, a sensor, the sensor comprising: a main body portion manufactured from a resiliently deformable material; a cover for the main body portion comprising a pocket into which, in use, the up stand is slidingly receivable to detachably connect the sensor to the support member; and a pressure-on contact detector located inside the cover and interposed, in use, between the main body portion and the up stand.

In known sensors, the pressure-on contact detector is placed on the outside of the main body portion such that contact with the exterior of the sensor triggers the alarm. This can lead to higher rates of false alarms because the sensor is triggered when a person brushes against the side of the bed, or when a bed occupant rests his/her arm on the sensor. The invention, by contrast, places the pressure-on contact detector between the main body portion and the up stand, as opposed to on the outside of the sensor. This has two main effects: First, because the pressure-on contact detector is protected externally by the resiliently deformable main body portion, a person brushing past the bedside needs to impart a higher force to trigger the sensor, which reduces the number of false alarms. Second, because of the location of the pressure-on contact detector relative to where the pocket joins the cover, a pivoting or camming effect can be created which results in a downward force applied to the top of the sensor being resolved into a horizontal component that triggers the alarm. However, due to the reduction in the applied force to the pressure-on contact detector as a result of the resolution of forces, a higher downward force applied to the sensor is required to trigger the alarm, thereby reducing the number of false alarms caused by, say, an arm simply resting on the bed guard.

The overall result obtained by the invention is suitably a de-sensitisation of the pressure-on detector (thereby reducing false alarms) whilst at the same time, providing an arrangement that nevertheless triggers the alarm when bed exiting events occur, such as the weight of a patient's legs on the sensor.

One possible aspect or advantage of the invention, therefore, is that it may be able to distinguish between a movement of the patient's leg horizontal to the cushion in which the detector is placed, which will not cause an alarm, and a perpendicular movement of the patient's leg against the cushion which will cause an alarm to activate. This functionality is believed to be unique and not found in other, known systems.

The support member comprises a base portion that is slideable, in use, between a bed base and a mattress, and an up stand portion extending at substantially right angles to the base portion. The base and up stand portions are suitably integrally formed, for example, being manufactured from a bent sheet of plastics, such as acrylic or ABS, which are readily cleanable and/or sterilisable: an advantage in a hospital environment.

In known alarm systems, the support member needs to be adapted to fit different types and/or makes of bed, for example to accommodate the levers, bars, legs etc. of the bed, and so the base portion and/or up stand portions of known bed guards comprise cut outs, slots and apertures to accommodate the various projections of a bed. In the present invention, however, the support member is adapted to fit a wider range of beds and this may be accomplished by making the base portion relatively narrow, so that it can easily fit between various projections of the bed, and the up stand portion correctly dimensioned to fit into the sensor's pocket. Such a configuration can render the up stand portion too flexible at its ends because such a structure essentially forms a set of relatively unsupported wings that extend outwardly from either side of the base portion. Such a configuration is clearly contraindicated because it can lead to the sensor flexing under loading, rather than triggering an alarm.

In certain embodiments of the invention, the pocket additionally comprises a stiffener, which can comprise a relatively thin sheet of web of plastics. The pocket suitably comprises a retainer or internal partition that holds the stiffener, where provided, in a desired location. Suitably, the desired location is on the opposite side of the up stand member to the main body portion, when the sensor is affixed to the support member. By locating the stiffener thus, the overall stiffness and/or rigidity of the sensor-support member arrangement is increased above and beyond what would be expected by summing the rigidity/stiffness of the up stand and the stiffener. The reason for this is the interaction between the cover, the stiffener and the up stand portion of the support member, which when installed, together form a laminated structure in which the stiffener enables the pocket to be taut against the opposite side of the up stand portion to the main body portion. The overall result is an unexpected increase in stiffness, and in certain circumstances, a stiffness that is equivalent to the situation in which the up stand portion is as wide as the base portion of the support member. Thus, certain embodiments of the invention provide a support member that is more universally useable with a wider range of beds, but whose structural integrity and/or stiffness is not compromised.

The sensor comprises a main body portion that is manufactured from a resiliently deformable material, which may be a foam material. Suitably, the main body portion has a generally D-shaped cross section, having a flat side that faces towards the up stand member, in use, and a curved side that faces outwardly, in use, away from the bed. Such a configuration suitably provides a more ergonomic and less obtrusive sensor arrangement.

The cover is suitably manufactured from a web of flexible, cleanable material, such as PVC sheet. The cover may comprise stitched and/or glued seams, but in any event, it is preferably for the seams to be sealed to inhibit or prevent the ingress into the interior of the cover, of contamination and/or cleaning fluids. The cover suitably comprises a closure means, such as a zip, or a strip of hook- and-loop fastener, to enable the main body portion and/or the pressure-on contact detector to be removed and/or replaced periodically, for example, for cleaning and/or maintenance purposes. Suitably, where a closure means is provided, it is located inside, and at or towards, an upper part of the pocket. Such a configuration aids the shedding of contaminants and/or cleaning fluids away from the closure means, thereby improving the cleanliness of the sensor.

The pocket is suitably connected to the cover, or is integrally formed therewith, via a join line running along an upper edge, in use, of the sensor, and down its oppose side ends. This creates a downwardly-open pocket that enables the sensor to be slid onto the up stand portion from above.

The pressure-on contact detector suitably comprises a pair of opposed, electrically conductive sheets that when brought into contact with one another, form an electrical connection thereby acting as a switch means. A resiliently-deformable spacer means is suitably interposed between the electrically-conductive sheets to form a "normally open" switch, that when pressure is applied to the pressure-on contact detector, closes the switch.

The pressure-on contact detector is suitably connectable, in use, to an alarm controller, which has a circuit adapted to emit an alarm upon a trigger from the pressure-on contact detector. Suitably, the pressure-on contact detector is operatively connected to the circuit via a fly lead and a plug and socket arrangement. Suitably, the plug and socket arrangement comprises an J11 or and RJ45 connector, which suitably enables the pressure-on contact detector to be connected to hard-wired hospital alarm systems. Known sensors that employ fly leads are prone to breakage due to the tension applied to the fly lead breaking soldered connections of the fly lead's conductors to the detector. This is problematic in the case of pressure-on sensors as the disconnection of one of the fly lead's conductors will not result in an error signal (the switch is normally open), but the pressure-on detector will be rendered inoperative. To reduce the likelihood of damage to the pressure-on detector caused by snagging the fly lead, embodiments of the invention comprise two countermeasures: First, the fly lead can comprise a coiled portion which absorbs shock in the fly lead by stretching before tension is applied to the conductors' termination. Second, a supplementary connection is provided between the sheath of the fly lead and the terminations to the pressure-on contact detector such that tension applied to the fly lead is borne via mechanical means, rather than by the terminations themselves.

An embodiment of the invention shall now be described, by way of example only, with reference to the accompanying drawings in which:

Figure 1 is a schematic cross-section of an embodiment of an alarm system in accordance with the invention;

Figures 2 and 3 show how lateral and vertical loads, respectively, applied to the alarm system of Figure 1 are resolved;

Figure 4 is a perspective view of an embodiment of the invention in a disassembled state;

Figure 5 is a perspective view of the embodiment of Figure 4 assembled;

Figure 6 is a perspective view of a known fly lead termination for a pressure-on detector; and

Figure 7 is a perspective view of a fly lead termination for a pressure-on detector in accordance with the invention.

Referring to Figures 1 to 3 of the drawings, an alarm system 10 in accordance with the invention comprises a main body portion 12 formed by a D-section foam bar retained within a correspondingly-shaped internal cavity 14 of a cover 16. The cover 16 is manufactured from a sheet of PVC, which wraps around the main body portion 12 and which is stitched 18 along its upper edge. A zip fastener 20 is provided on the flat side 22 of the cover 16 to enable the foam bar 12 to be removed and/or replaced at intervals.

A planar pressure-on contact detector 24 whose outer dimensions substantially correspond to those of the flat side of the foam insert 12 is interposed between the flat side 22 of the cover and the flat side of the foam inset 12, as shown. A fly lead 26 extending from the pressure-on contact detector 24 extends through an open portion of the zip fastener 20 and to the exterior of the alarm system 10 for connection to a control circuit (not shown). The cover 16 additionally comprises a pocket 30, which is formed by a further elongate strip of PVC 32 which is stitched to the cover 16 along the same stitch line 18 as mentioned previously. The elongate strip 30 has a return 34 along its lower edge that forms an internal flap of the pocket 30, which retains a stiffener 36 formed from a thin sheet of plastics.

The lateral ends (not shown in Figures 1 to 3) of the elongate strip 30 forming the pocket 30 are stitched to the cover 16 as can be seen in Figures 4 and 5, along an additional stitch line 40 to form a downwardly open pocket 30 that receives, in use, the up stand 50 portion of a support member 52 manufactured from a single sheet of bent acrylic or ABS. The support member 52 further comprises an integrally formed base portion 54, which extends perpendicularly from the lower edge 56 of the up stand portion 50, and the base portion 54 can be slid underneath a mattress 58 in use, to connect the alarm system 10 to a bed (not shown).

Referring now to Figure 2, the alarm system 10 comprises a pressure-on contact detector 24 that comprises a pair of spaced-apart, electrically-conductive webs forming a normally open switch, that, when the webs are pressed together so that they touch, close the switch to generate a signal. By placing the pressure-on contact detector 24 between the up stand 50 and the foam bar 12, when a lateral force 60 is applied to the system 10, the foam bar 12 must first compress a little before sufficient force is transferred to the pressure-on contact detector 24 to bring its electrically-conductive webs into contact with one another to close the circuit and thus generate a signal. This arrangement advantageously reduces the number of false alarms caused by people brushing past the bedside and touching the system 10 gently. In known systems of this type, the detector is placed on the exterior of the foam bar to increase its sensitivity, but this just leads to too many false alarms.

Referring to Figure 3 of the drawings, when a vertical load 64 is applied to the system 10, the foam bar 12 is retained in the cover 16 which is retained to the up stand 50 along its upper edge, i.e. by the stitch line 18. This creates a lever effect, which pivots the foam bar 12 about a point substantially corresponding to the stitch line 18, and thus, the vertical force 64 is resolved into a lateral force 66 which is applied to the pressure-on contact detector 24. Given that the vertical force 64 is resolved into a much smaller lateral force 66 at the detector 24, a higher vertical force is needed to trigger an alarm event. Thus, the invention overcomes the problem of false alarms that blights known sensors that have their contact detectors located externally of the foam bar.

It should be added in passing that the location of the pressure-on contact detector 24 internally of the foam bar 12 and between the foam bar 12 and the up stand 50, as in the invention, is counterintuitive. Specifically, accepted wisdom in the art dictates the location of the detector in the region indicated by arrow 68 in Figure 3 as this position enables a single detector to be used to detect both lateral and vertical forces. However, the invention places the detector 24 in an altogether different, and counter-intuitive location, but nevertheless achieves the objective of the sensor, i.e. to indicate a "climbing out of bed" event whilst simultaneously reducing the number of nuisance or false alarms.

In Figure 4 of the drawings, it can be seen that the support member 52 and the sensor 10 are separable elements, which facilitates storage, transportation, installation, maintenance and cleaning. The support member 52 comprises, as previously described, a relatively narrow base portion 54 that slides underneath the edge of a mattress of a bed to which it is to be installed. The up stand portion 50 of the support member 50 is considerably wider than the base portion 54, and generally has a pair of unsupported, wing portions 70 extending laterally sideward from the base 50. The up stand portion 50 is slidingly, and snugly receivable in the opening 72 of the pocket 30, as indicated by arrow 74, to form the system 10 shown in Figure 5.

One would expect the unsupported wing portions 70 of the system 10 to be relatively floppy, as indicated by arrows 76, but this is not, in fact the case due to the provision of the stiffener 36 described previously. As can be seen from Figure 5, the additional stitch line 40 serves to tension the elongate strip 32 forming the pocket 30 thereby clamping and tensioning the stiffener therewithin. Thus, the stiffener frictionally engages the up stand portion 50 as well as the interior wall of the elongate strip 32 and the flat wall 22 of the cover 16 thereby stiffening the arrangement considerably, and much more than might be expected to result from the stiffness of the up stand 50 and the stiffener 36 either alone or in combination. The result is that the base portion 54 of the support member 50 can be made relatively small, so that the system 10 can be applied to a wider range of beds than can known bed guards.

Also shown in Figures 4 and 5 is a cut-out 80 or aperture, which may be added in certain applications, for example to accommodate cabling etc., although this is not always necessary. Further, it will be noted from the drawings that the fly lead 26 comprises a coiled portion 82, which reduces tension applied to its terminations, as shall be described below.

In Figure 6, a known fly lead termination 86 (shown peeled apart) comprises a glue pad 88 to which the sheath 90 of the fly lead 26 is glued during assembly. The fly lead 26 has conductors 92 that are soldered to contacts 94 of the termination 86. When tension is applied to the fly lead 26, the glue pad 88 can fail resulting failure of the contacts 94.

In the invention, as shown in Figure 7, the termination 96 has been modified to include a tang 98 that mechanically crimps to the fly lead's sheath 90, thereby forming a mechanical connection of the fly lead 26 to the contact detector 24. Thus, tension applied to the fly lead 26 is first absorbed by the coil portion 82 and then by the mechanical connection 98, which configuration is an improvement on contact detectors of the type used in the invention.

The invention is not, of course, restricted to use in hospitals, but also to people in their own homes being cared for by formal or informal carers. The invention can be linked to a pager carried by a carer, which could be linked and provide an effective range of between 50 and 2000m. The invention has been found to work equally well with standard and hospital-type beds.

The invention is not restricted to the details of the foregoing embodiments, which are merely exemplary of the invention. For example, any shapes, materials or dimensions mentioned (whether explicitly or impliedly) are exemplary and are not necessarily restrictive of the invention whose scope is set forth in the appendent claims.