DESCRIPTION FIELD OF THE INVENTION

The invention relates to a wearable sensing device and a method of attaching an elastic band to the wearable sensing device.

BACKGROUND

Wearable sensor devices are known for monitoring physiological parameters such as heart rate, skin resistance, temperature, etcetera. Such devices can be worn on various body parts and limbs. Wearable sensor devices can for example be worn on the wrist. In other applications sensor devices may be worn on the upper arm.

Wearable sensor devices have a sensor which measures a physiological parameter. An example of such a sensor is a photoplethysmographic sensor, which measures a heart rate using light transmitted into a subject's skin. Light from underlying tissue is reflected to a photosensitive sensor. The amount of reflected light depends on blood pressure. While the blood pressure varies in time with the subject's heart rate, the amount of reflected light thus allows the heart rate to be established accurately.

The accurately established heart rate can be used for monitoring the heart directly, or for establishing parameters derived from the heart rate. An example is epileptic seizure detection, wherein a sudden heart rate change is indicative for the presence of a seizure. Such detection may be combined with other parameters such as limb motion, posture or position to obtain a more accurate detection or reduce false detection.

In a cases wherein sensor pressure is of importance, accurate

(re)positioning and fastening of the wearable sensor device is essential. At the same time wearing comfort should be maintained and health hazard from pinching or squeezing is to be kept low. As there is great variation in limb or arm diameter a great variation in band length is be required to accommodate a large variety of users.

Commonly elastic bands or straps are used to achieve this. Straps, however, require clasps and do not provide sufficient comfort, flexibility and pressure accuracy during the period the sensor device is worn. Elastic band is an alternative, however, the variety in limb diameter is too great to accommodate all possible subjects. Attaching elastic band to the wearable device however may cause inaccuracy in the pressure applied to the device, since normally the band is fastened by folding it over a bar of the device and since then the elasticity modulus is not uniform, which causes the band to be non-uniformly stretched over its length. Thus it is an object of the invention to provide for a wearable sensor device which can be easily adapted for every wearer to provide accurate pressure control and comfort, and having a uniform elasticity modulus over the entire length of the band.

SUMMARY

The object is achieved in a wearable sensing device, comprising a sensor carrier having a sensor at a lower side for touching the wearers skin, an elastic band having two ends, a fastener attached to each end of the band, two elongated fastening slots extending from a top side opposite to the lower side of the sensor carrier, wherein the elongated fastening slots are located at opposite locations near an edge of the sensor carrier. The elongated fastening slots are arranged for removably receiving the fasteners. The fasteners are removably insertable into the fastening slots. The lower side having the sensor is the side of the sensor device to be pressed against the subject's skin. The top side is the visible side of the sensor device and is exposed to the environment. The lower side may contact the skin of a limb, e.g. an arm of the subject wearing the device, allowing it to perform its measurements.

By using fasteners, the elastic band can be used in one single piece without any folds and/or double layers. This ensures the uniform elasticity modulus to be maintained over the entire length of the elastic band. Using fasteners which are introduced into the top side of the sensor carrier allows a controlled pressure to be exerted in the direction of the lower side, the side that is in contact with the subject's skin.

In an embodiment, each fastener has an oblong shaped body, having an elongated slot for receiving the elastic band's end.

This allows the elastic band's end to be pulled through the fastener, which in turn allows the elastic band to be connected to the sensor device indirectly through the fasteners.

In an embodiment, the fastener body has a rim and an edge. The rim ensures that the fastener remains on top of the top side of the sensor device, and prevents it from falling through the fastenings slots thereof. The edge is designed to cooperate with a corresponding edge inside each fastening slot, for creating a snap fit retention. For this purpose, the fastener is made of resilient material which allows the fastener to be compressed for releasing from the snap fit. Thus involuntary release of the fasteners from the fastenings slots is prevented, while at the same time the fasteners can be simply released from the fastenings slots when required by the user without undue effort. In an embodiment, each elongated fastening slot has a guide element and an edge for catching the edge of the fastener body.

In an embodiment, each fastener has retention means within its elongated slot for retaining the band's end.

In an embodiment, the retention means comprise a plurality of teeth extending from each of the walls in a direction to the wall opposite of the elongated slot. The retention means can also be hooks, which engage the elastic band when it is inserted into the elongated slot of the fastener. By giving the retention means a single directed action, it causes the elastic band to be secured in one direction, while it can slide further into the elongated slot of the fastener in the opposite direction. Thus fine tuning of the elastic band length can be achieved.

The object is further achieved in a method of attaching an elastic band to a wearable sensing device according to any of the preceding claims, the method comprising measuring a circumference of a limb or body part at which the device is to be worn, cutting the elastic band in a single piece having a length greater than measured circumference, sliding a fastener over each end of the single piece of elastic band, inserting one of the fasteners in a corresponding fastening slot of the device, adjusting the position of at least one of the fasteners relative to its corresponding end of the elastic band, and finally trimming the corresponding end of the elastic band using a cutting means.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 shows a wearable sensor device according to an embodiment of the invention.

Fig. 2 shows a wearable sensor device according to an embodiment of the invention.

Fig. 3 shows a wearable sensor device according to an embodiment of the invention.

Fig. 4 shows a diagram of a fastener of the wearable sensor device according to an embodiment of the invention.

Fig. 5 shows a diagram of a cross section of a fastener of the wearable sensor device according to an embodiment of the invention.

Fig. 6 shows a detail of a wearable sensor device according to an embodiment of the invention.

DETAILED DESCRIPTION OF EMBODIMENTS

Figure 1 shows an wearable sensor device 100 having a sensor carrier

101 with an elastic band 102 attached thereon. The sensor carrier 101 has a sensor 103 at the bottom surface 106. The bottom surface 106 is the surface of the sensor carrier 101 facing the subject's skin. The position of the fixation of the elastic band 102 insures that the sensor carrier 101 is pressed against the subject's skin. At the bottom surface 106 fastening slots 104a, 104b can be observed, wherein fasteners 105a, 105b can be introduced which attach end of the elastic band 102 to the sensor carrier 101.

The sensor carrier 101 can be fabricated from a plastic, metal or any material suitable for housing a sensor and its electronic circuitry including a battery required for operation of the sensor 103. The sensor carrier 101 may furthermore accommodate controls such as switches to operate the sensor 103. Moreover, the sensor carrier may comprise visual or acoustic alarms or displays.

The elastic band 102 can be made from textile fibers, which may be supplemented with elastomer fibers, or from elastic textile fibers alone.

In figure 2 a cross section of the subject's limb 201 is shown having a an wearable sensor device 100 attached to it. The sensor carrier 101 is shown positioned with its bottom surface 106 pressed against the subject's skin 202. The fasteners 105a, 105b are shown having ends of the elastic band 102 guided there through. The fasteners 105a, 105b are inserted in the fastening slots 104a, 104b on the upper, top side 204 of the sensor carrier 101. From fig. 2 it is clear that the elastic band 102 emanates from the fastener 105a and bends around the arm 201 starting at tipping point 203a. On the other side, the band 102 bends back at tipping point 203b into fastener 105b. It will be clear from fig. 2 that a pulling force S,S' in the elastic band 102 cause a pressure P to be exerted at the surface 106, and more specifically at the sensor 103 in contact with the subject's skin 202.

In figure 3 the sensor carrier 101 is shown having the band 102 attached to the fastener 105b inserted in fastening slot 104b (not shown) in the top surface 204 of the sensor carrier. In fig. 3 another end of the elastic band 102 is shown inserted through fastener 105a, which is shown taking out from fastening slot 104a. Within the fastening slot 104a, a retention edge 301 is shown for retention of the fastener 105a.

Figure 4 shows a fastener 105a/b having walls 401 arranged adjacent an elongated slot 404, for guiding through an end of the elastic band 102. At least one of the walls 401 is provided with a guide element 403 which guide element 403 has an edge 406, for cooperating with a corresponding retention edge 301 in the fastening slot 104a, 104b of the sensor carrier 101. In fig. 4 both walls 401 are provided with a guide element (403). The walls 401 are provided with teeth 405 at a side of each wall facing the other wall 401 opposite the slot 404, which provide for retention of the end of the elastic band 102 inserted through the elongated slot 404. The teeth extend through the elastic band surface and retain the elastic band by deforming the band and/or by friction, and/or by engaging fibers in the elastic band. As an alternative for teeth, hooks may also be used.

In figure 5 a cross section of the fastener 105a/b is shown with the elastic band 102 extending through the elongated slot 404 and being retained by the teeth 405, which are arranged opposite each other on respective walls 401.

Furthermore in fig. 5 the guide elements 403 are shown extending from the walls 401 having an edge 406 for retention in the fastening slots 104a, 104b.

In figure 6 the fastener 105a/b is shown having an end of the elastic band 102 extending through the fastener, showing that an unused part 601 of the elastic bands end can be trimmed off at trimming line 602 just clear from the guide element 403 to obtain an appropriate length. The total length of elastic band 102 can be determined by measuring a circumference of the subject's limb, or the determined tentatively by testing the sensor carrier pressure P against the subject's skin 202, or by testing the pulling force S,S' of the elastic band 102 as shown in figure 2. The trimming can also be performed when the fastener 105a, 105 b is inserted in the corresponding fastening slot 104a, 104b.

In the examples described above, the elastic band is attached to the sensor carrier via two fasteners 105a, 105b, by inserting the fasteners 105a, 105b into corresponding fastenings slots 104a, 104b . It can be considered to permanently attach one end of the elastic band to the top side 204 of the sensor carrier 101 , while the opposite end of the elastic band 102 is attached with a fastener 105a or 105b in a corresponding fastening slot 104a or 104b of the sensor carrier 101.

The oblong shape of the fastener in combination with the elongated fastening slot may also be constructed with mutually corresponding shaped forms, such as round, oval or square.

The embodiments above are given by way of example only. Deviations and modifications to these embodiments are possible without departing from the scope of protection provided by the claims set out below.

REFERENCE NUMERALS

100 wearable sensing device

101 sensor carrier

102 band

103 sensor

104a, 104b receiving slot

105a, 105b fastener

106 bottom surface

201 arm

202 skin

203a, 203b tipping point

204 top side of the sensor carrier

301 retention edge

401 wall

402 rim

403 guide

404 slot

405 teeth

406 edge

601 unused part

602 trimming line