AUSTRALIA PATENTS ACT 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT (Original) APPLICATION NO: LODGED: COMPLETE SPECIFICATION LODGED: ACCEPTED: PUBLISHED: RELATED ART: NAME OF APPLICANT: John Anthony Neville Bromberger ACTUAL INVENTOR(S): John Anthony Neville Bromberger ADDRESS FOR SERVICE: LORD AND COMPANY, Patent and Trade Mark Attorneys, of 4 Douro Place, West Perth, Western Australia, 6005, AUSTRALIA. INVENTION TITLE: MOTION SENSOR PAD DETAILS OF ASSOCIATED PROVISIONAL APPLICATION NO'S: Australian Provisional Patent Application Number 2004900604 filed on 10 February 2004 The following Statement is a full description of this invention including the best method of performing it known to me/us: TITLE MOTION SENSOR PAD FIELD OF THE INVENTION The present invention relates to a motion sensor pad, in particular a motion sensor pad 5 for use in a patient motion monitoring apparatus. BACKGROUND OF THE INVENTION In hospitals and other facilities that care for the elderly or generally indisposed, it is sometimes necessary to monitor a patient in order to ensure that the patient remains in a state of substantial immobility or confinement, for example in a bed or chair or the 10 like. Patients who are physically capable of leaving a bed or chair but who are nonetheless subject to dizziness or fainting upon standing up, may fall and injure themselves if they are to leave the bed or chair when there is no attendant present. Studies show that falls by such patients commonly occur in and around bed and chair locations. Physicians, nurses and other attending persons who care for the elderly and 15 the incapacitated or confused are aware of the trauma and the consequences relating to such falls. Typically, trauma will often involve the fracturing of bones including hips, ribs and skulls among others, which clearly may debilitate the patient even further. Hence, decreasing the risk of falls when patients attempt to transfer into and out of a bed or chair without appropriate assistance is a potentially important safety 20 concern. Consequently, it is desirable that in such circumstances, a signal or an alarm be given in the event that the patient leaves the bed or chair to alert an appropriate attendant to this fact. In this manner, an appropriate attendant may assist to ensure that the patient does not suffer unnecessary trauma or injury. The use of such alarms can assist in 2 monitoring the movement of a patient, without the need for physical or chemical restraining means. Bed or chair occupancy sensors and alarms are known. For example, typical modem weight activated alarm sensors include a weight resistant layer of a material such as 5 foam, inserted between a pair of electrically conductive layers such as aluminium foil sheets. Each electrically conductive layer has a wire attachment connected to an alarm means. The combined weight resistance layer, flanking conductive layers and electrical wire attachment construction is then placed into a protective cover. This combination of components forms a weight activated alarm sensor pad. The weight 10 resistance substance layer has integral gaps such that when weight is applied the weight resistant substance is caused to compress. Compression of the weight resistant layer allows the pair of electrically conductive layers to contact, thus completing an electrical circuit. The successfully completed electrical circuit either turns on or off the alarm means, depending on the particular configuration and application of the 15 apparatus. Unfortunately, there is evidence that such weight alarm sensor pads may be prone to failure and hence be ineffective in use. For example, movement of the patient on a bed or chair may result in a cable attachment from the sensor pad to the alarm to become disconnected, resulting in a false positive or negative alarm being issued. 20 Failure or alarm malfunction of a bed or chair occupancy alarm due to any reason, including reduced functional life of the sensor pad may result in increased patient injury and trauma, sometimes leading to increased patient morbidity and mortality. 3 SUMMARY OF THE INVENTION In accordance with a first aspect of the present invention there is provided a motion sensor pad for use in a patient motion monitoring apparatus, comprising at least two conductive sheets disposed within a cover, the conductive sheets being in operative communication with a signalling means by way of a cable attached thereto, wherein the cover is provided with an opening, the conductive sheets being arranged to be removed from the cover through the opening and replaced, such that positioning of a patient upon the motion sensor pad causes an electrical connection to be established between the conductive sheets to permit a signal to be transmitted to the signalling means. Preferably the opening has a sealing means to enable the opening to be closed. DESCRIPTION OF THE DRAWINGS Figure 1 is a perspective view of a first embodiment of a motion sensor pad of the present invention; Figure 2 is a perspective view of the motion sensor pad of Figure 1 in use with a patient motion monitoring apparatus; and Figure 3 is an exploded perspective view of a first embodiment of the sensor pad of Figure 1. 4 DESCRIPTION OF AN EMBODIMENT OF THE INVENTION Referring to the Figures, there is shown a motion sensor pad 12 for use with a motion monitoring apparatus 10 for the monitoring of movement of patients, particularly to and from a place of occupancy such as a bed or chair. The motion sensor pad 12 5 includes at least two conductive sheets 14 disposed within a cover 16. The conductive sheets 14 are in operative communication with a signalling means 18 by way of a cable 20. Positioning of a patient upon the motion sensor pad 12 causes an electrical connection to be established between the conductive sheets 14 to permit a signal to be transmitted to the signalling means 18 via the cable 20. 10 The conductive sheets 14 are provided as flat members constructed from any suitable material that is able to conduct electricity, such as but not limited to a foil of aluminium or the like. The conductive sheets 14 are provided as pairs comprising one positive and one negative, such that an electrical connection may be established upon contacting of each conductive sheet 14 in each pair. 15 Preferably, each conductive sheet 14 is provided as a substantially flexible sheet member, having a thickness comparable to that of a foil. Providing the conductive sheets 14 as a flexible sheet member assists to reduce the capacity of the conductive sheets 14 to crack or tear, particularly when the sensor pad 12 is in use. Flexibility of each conductive sheet 14 may be achieved by the provision of a plurality of 20 perforations over a surface thereof. Alternatively, the conductive sheet 14 may be fabricated by spraying or otherwise transferring a conductive material onto a substantially flexible material, such as paper, plastic or a suitable woven material. Each conductive sheet 14 has an electrical wire 22 in communication therewith. Preferably, the electrical wire 22 is provided as a substantially bare wire able to 5 conduct electricity. The electrical wire 22 is arranged upon a surface of each conductive sheet 14, as shown in Figure 3. The electrical wire 22 of each conductive sheet 14 is in communication with, or an operative extension of the cable 20. The electrical wire 22 of each respective conductive sheet 14 preferably has a 5 plurality of attachment points 24 to make electrical contact with the respective conductive sheet 14. In this manner, if one or more attachment points 24 fail to make sufficient electrical contact with the conductive sheet 14, one or more other attachment points 24 will compensate. The electrical wire 22 is attached upon respective conductive sheets 14 by any 10 suitable means, such as by a tape or adhesive. Such attachment means assists in the electrical contact between the electrical wire 22 and the conductive sheet 14. A further means of providing sufficient electrical contact between the electrical wire 22 and respective conductive sheet 14 is the provision of a plurality of apertures (not shown) in each conductive sheet 14. The electrical wire 22 is threaded consecutively 15 through any number of the apertures to achieve the necessary attachment points 24 between wire 22 and sheet 14. In each method of attachment of the wire 22 to conductive sheet 14, the configuration of the wire 22 upon the surface of the respective conductive sheet 14 may be varied as desired or necessary. In this manner, a configuration that is optimal for prolonging 20 the functional life of the conductive sheets 14 of the sensor pad 12 may be achieved. For example, different wire 22 configurations may be optimal for sensor pads 12 used on a floor, bed or chair. The electrical wire 22 may also be provided as having a plurality of conductive strands (not shown), each conductive strand having a plurality of attachment points 24 6 to respective conductive sheets 14. In this manner, if one or more conductive strands or attachment points 24 thereof are damaged through normal or inappropriate use of the sensor pad 12, further conductive strands and attachment points 24 will permit the appropriate electrical connection to be established between the conductive sheets 14. 5 Preferably, a multi core electrical wire is used for this purpose. The electrical wire 22 of each respective conductive sheet 14 is preferably provided with a suitable coating over a surface thereof. Provision of such a coating assists in reducing friction between points of contact between the electrical wire 24 and respective conductive sheet 14, thereby reducing damage to the conductive sheet by 10 frictional wearing. The or each electrical wire 22 of each conductive sheet 14 is in communication with the cable 20. Preferably, the cable 20 is an insulated extension of the electrical wire 22 of each conductive sheet 14. Typically, the cable 20 consists of a first cable portion 21, adjacent to and in direct communication with the conductive sheets 14, 15 and a second cable portion 23. The second cable portion 23 extends from the first cable portion 21 by means of a suitable connector 30 and towards the signalling means 18. The cable 20 permits communication of the conductive sheets 14 to the signalling means 18 upon establishment of the electrical connection therebetween. The conductive sheets 14 are each disposed within the cover 16. The cover 16 20 comprises a substantially pouch-like arrangement, having a plurality of fastening means 17 disposed about an outer edge thereof. The fastening means 17, preferably provided as flexible closed loop members, are provided to enable the sensor pad 12 to be secured onto the relevant structure, such as chair or bed. 7 The cover 16 is further provided with a substantially sealable opening 26 adjacent an outer edge thereof. The opening 26 is provided to enable the conductive sheets 14 to be removed and replaced upon becoming worn or otherwise not performing to optimal capacity. The opening 26 is provided with an appropriate sealing means, 5 such as Velcro to enable the opening 26 to be securely closed when the sensor pad 12 is in use. The cover 16 is further provided with a cable restraining means 28. The cable restraining means 28 is preferably disposed within an interior of the cover 16 and adjacent the opening 26. In the embodiment shown in Figures 1 and 2, the cable 10 restraining means 28 is provided as a closed loop member 32. The first portion 21 of the cable 20 is typically looped or knotted around the loop member 32 to secure the first portion 21 of the cable 20 thereon. In this manner, the cable restraining means 28 limits movement of the cable 20 relative to the conductive sheets 14 to prevent disengagement of the cable 20 therefrom. Hence, in instances where a force is 15 applied to the cable 20, such as by pulling of the cable 20 or movement of the patient upon the sensor pad 12, the force is substantially transferred to the cable restraining means 28 and the cover 16. This transfer of force assists in preventing disengagement of the cable 20 and therefore prevents unintentional breaking of electrical communication between the sensor pad 12 and the signalling means 18. 20 Preferably, the portion of cable 20 intermediate of the electrical wire 22 and the point of attachment to the cable restraining means 28 is loosely arranged such that this portion of cable is slack. In this manner, there is relatively less risk of tension of this portion of the cable 20 causing the cable 20 to pull on the electrical wire 22 and thus 8 the conductive sheets 14, which may minimise the potential for damage to the conductive sheets 14. In a first embodiment, the sensor pad 12 further includes a weight resistant layer 34, typically disposed between a pair of corresponding conductive sheets 14, as seen in 5 Figure 3. The weight resistant layer 34 is typically comprised from a material such as, but not limited to, foam. The layer 34 typically has a plurality of apertures 36 over a surface thereof, to enable the electrical connection to be made between corresponding conductive sheets 14. The foam of the weight resistant layer 34 is preferably of a consistency and density wherein the weight of a patient positioned 10 upon the sensor pad 12 causes compression of the layer 34 that is sufficient to enable contacting of the respective conductive sheets 14. Preferably, the weight resistant layer 34 is secured to each of the pair of conductive sheets 14 by any suitable method such as but not limited to sewing, adhesives or stapling. In this manner, there is typically limited movement between the relative 15 layers of conductive sheets 14 and weight resistant layer 34. This may assist in prevention or reduction of damage of the respective layers from, for example, frictional forces between the respective layers. In some instances however, it is recognised that the weight of a particular patient may not be sufficient to provide the necessary force to compress a weight resistant layer 34 20 to enable contacting of the respective conductive sheets 14. In this respect, there is provided a second embodiment of the present invention, wherein the sensor pad 12 does not include such a weight resistant layer disposed between a pair of corresponding conductive sheets 14. In this embodiment, the conductive sheets 14 are each disposed substantially within the same plane of alignment. The positive and 9 negative conductive sheets 14 of each respective pair are arranged such that they are spaced apart from each other. Typically, the conductive sheets 14 are thus arranged upon any suitable and preferably flexible sheet. In this manner, a plurality of conductive sheets 14 are provided upon a single article, facilitating ease of removal 5 and replacement of conductive sheets 14. In this second embodiment, the necessary electrical connection between corresponding conductive sheets 14 is not established by the weight of the patient positioned upon the sensor pad 12. Instead, the spanning of at least a portion of the patients body from a positive to a negative conductive sheet 14 is sufficient to 10 complete the electrical connection. Thus, it is the patient themselves that completes the electrical connection between respective conductive sheets 14. The contacting or connecting of respective conductive sheets 14 in use, enables the completion of the electrical circuit from the sensor pad 12 to the signalling means 18. Either the completion or breaking of the electrical circuit may be arranged to trigger 15 the activation of the signalling means 18, depending on the particular application and arrangement of the sensor pad 12 in any motion monitoring apparatus 10. In the instance of sensor pads 12 in use upon a bed or chair, it is the breaking of the electrical connection by the patient moving from upon the sensor pad 12 that causes activation of the signalling means 18. In the instance of a floor pad, the placement of 20 the patients' feet upon the sensor pad 12, thus completing the electrical connection, activates the signalling means 18. The signalling means 18 may comprise any suitable means for emitting a stimulus, such as an audio, visual or a combination thereof, that is able to appropriately signal that the patient has moved from a position upon the sensor pad 12. 10 Preferably, the signalling means 18 comprises at least a primary signalling means, wherein the signal is directed towards alerting an attendant or nurse to the fact that the patient has moved from upon the sensor pad 12. Typically, such a primary signalling means will be remote from the place of patient occupancy. For example, the primary 5 signalling means may be situated within or near a nurse workstation. The signalling means 18 also preferably includes a secondary signalling means, typically located proximal to the place of patient occupancy. The secondary signalling means is provided so that a signal may be directed towards the patients themselves in the event that they move out of occupancy of the bed or chair. The 10 secondary signalling means is particularly suited for patients who have been conditioned to respond in a particular manner in response to a particular stimulus. For example, it is known in the case of dementia patients, that such patients may be behaviourally conditioned to sit upon hearing a particular sound, for example, a bird noise. 15 The sensor pad 12 of the present invention may thus be used in conjunction with any number of signalling means 18 as necessary. The function of the sensor pad 12 may be varied in this respect by the provision of any number and type of connectors and adaptors for placing the sensor pad 12 into operative communication with any number of these signalling means 18. In this respect, the sensor pad 12 is adaptable for use in 20 any environment where it is desired to monitor patient occupancy movement. In use, the sensor pad 12 with at least a pair of corresponding conductive sheets 14 within the cover 16 is placed adjacent a place of patient occupancy. The sensor pad 12 is secured into position with the fastening means 17. 11 The first portion 21 of the cable 20 is engaged with the cable restraining means 28. Typically, engagement of the cable 20 with the cable restraining means 28 is achieved by tying the cable 20 through and to the closed loop member 32. Upon suitable securing of the cable 20, the opening 26 of the cover 16 is closed. The second portion 5 23 of the cable 20, is then attached to the first portion 21 to enable the sensor pad 12 to be in operative communication with the signalling means 18. The sensor pad 12 may be placed into operative communication with as many signalling means 18 as necessary for a particular application. Placement of the patient or a portion thereof atop the sensor pad 12 completes the 10 electrical connection between corresponding conductive sheets 14, thereby establishing an electrical connection to the signalling means 18. Establishment of or breaking of the electrical connection activates the signalling means 18, depending on the particular place of application of the sensor pad 12. Upon the conductive sheets 14 becoming worn or otherwise performing at less than 15 optimal ability, the conductive sheets 14 may be removed from the cover 16. The first and second portions 21, 23 of the cable 20 are first disconnected so that the signalling means 18 is no longer in operative communication with the sensor pad 12. The cover 16 is then opened via the opening 26 and the first portion 21 of the cable 20 disengaged from the cable restraining means 28. The conductive sheets 14 are then 20 removed from inside the cover 16 through the opening 26. Replacement conductive sheets 14 are then placed through the opening 26 and into the cover 16. The conductive sheets 14 are smoothed out to ensure that they are substantially flat. The first portion 21 of the cable 20 is then secured to the cable restraining means 28 and the opening 26 closed. The first portion 21 of the cable 20 12 is then connected to the second portion 23 to place the sensor pad 12 into operative communication with the signalling means 18. Modifications and variations as would be apparent to a skilled addressee are deemed to be within the scope of the present invention. 13