GB2210694A - Apparatus for detecting tension or flexing stress - Google Patents

Abstract

Apparatus sensitive to tension or flexing stress comprises a belt (13) with a tension sensor (22) fitted along its length including a loop (19) connected to a movable member (20). The tension sensor (22) includes a microswitch, a delay circuit and an oscillator. In use the belt (13) is adjusted to fit snugly when the wearer is comfortably supporting his or her own abdomen with the abdominal muscles. Relaxation of the abdominal muscles results in a slight enlargement of the waist causing closure of the microswitch which, after a short delay determined by the delay circuit causes the oscillator to generate an audible output signal to warn the wearer that muscle relaxation has taken place. Other warning signals may be produced, and the belt may be a seat belt for sensing driver alertness. <IMAGE>

Description

APPARATUS FOR DETECTING TENSION OR FLEXING STRESS The present invention relates generally to apparatus for detecting tension or flexing stress, and particularly to such apparatus adapted for use in observing muscle relaxation.

The present invention will be described herein with reference to its application to apparatus for use in maintaining muscle tone, but may also be used for other purposes as will be described hereinbelow.

The primary application of the apparatus of the present invention is as a posture monitor or for fitness training. Alternative uses include medical detection of stress or relaxation which may be usable for detecting the state of a patient or a part of a patient's anatomy during treatment either with the patient conscious or unconscious. Other applications may include an alertness monitor for combination with a seatbelt, capable of producing an output signal if the wearer (particularly the driver) were to exert increased tension on the belt, perhaps indicating that he had fallen asleep or was suffering from some form of illness preventing him from maintaining his body in the usual erect condition by the body's own musculature.

Apparatus for detecting physical stress (and here the term is used in its physical sense, namely as a force creating strain) has a wide range of applications and the present invention seeks to address the problem inherent in the application of a stress sensor to various situations.

It is widely known that muscle tone is degraded upon continuous relaxation and can, in the worst case, lead to atrophy of the musculature from lack of exercise. This is nowhere more apparent than in the network of muscles around the abdomen which in many individuals are allowed to remain almost continuously relaxed against the forces exerted by enlarging internal organs so that corpulence, particularly in middle age, is a widespread problem. The present invention is based on the understanding that this can be overcome by drawing to the individual's attention the state of relaxation of the musculature, particularly that around the abdomen, in order to develop the practice and habit of muscle tension leading to an increase in the muscle tone.

According to the present invention, therefore, there is provided apparatus for detecting muscle relaxation for use in maintaining muscle tone or other purposes, comprising an elongate flexible element having fastening means for securing the ends thereof to form the element into a loop, and stress sensor means sensitive to the tension in the element and/or the flexure of a part thereof in a direction parallel to or transversely of the length of the element and operative to produce a physically perceptible output signal if the tension or flexing stress exceeds a predetermined threshold value.

If it is desired to maintain the sensor element below the predetermined threshold tension stress then the perceptible indication output is generated when the threshold is passed from below. Of course, there are circumstances in which it may be desired to maintain the sensing element above the sensing threshold, for example in an exercising instrument, and in such cases the perceptible indication output is generated when the threshold is passed from above. In this latter case, for example, the exercise apparatus may be adapted to provide an output for as long as the user maintains a predetermined force on the apparatus, stopping when the force falls below the required threshold.Isotonic or isometric exercises requiring the exertion of a predetermined force can then be indicated either visually or audibly by the output so that successful performance of the exercises can be monitored readily by the user and by supervisors.

The physically perceptible output signal may, for example, be an audible signal or a visual signal.

Alternatively, the physically perceptible output signal may be a physical vibration of an element detectable by tactile contact with an observer.

In other embodiments the physically perceptible output signal may be of a different form, and it may be appropriate for this to be in the form of an electric shock current applied via electrodes in contact with the user or, if appropriate, a separate observer.

The apparatus of the invention may also include stress sensor means having a switch device biased to the contact open position by resilient biasing means the force of which determines the said predetermined threshold value.

Preferably, likewise, the said threshold value of the flexing or tension stress is adjustable.

As will be appreciated from the above, in many of the applications to which the present invention may be put it is convenient for the sensor to be associated with a time delay circuit operable to cause a predetermined time delay between the achievement of the predetermined threshold value of the-tension or flexing stress and the generation of an output indication signal. This would allow occasional, short-term movements exceeding the threshold value without causing an indication so that normal activity can be pursued whilst the apparatus of the present invention is fitted.

In its application as a device for monitoring the stress exerted on the muscles of the abdomen wall, the flexible element may be a belt adapted to be fitted around the waist of a user and the sensor may be formed as a flexible unit fitted into the length of the belt.

Alternatively, of course, the sensor may be carried on a rigid element to which two ends of the belt are attached.

Indeed, the belt itself, may be the transducer of the sensor element in the sense that it may comprise or include a material the physical properties of which vary with extension. In this respect the structure of the belt may incorporate a piezo-electric element the compression stress on which is varied according to the tension applied to the belt, or the belt may be made from an elastic material the extension of which causes a change in a physical or electrical property such as the resistance.

In the preferred embodiment, however, the tension is detected by a resilient biased microswitch which closes when a predetermined tension is applied to the belt.

Alternatively, however, flexure may be detected in a plane parallel to the length of the belt by a rigid belt insert having strain gauges or piezo-electric transducers connected to or associated therewith.

The output signal from the transducer may be transmitted not to a loud speaker, in the case of an audible output, but to a connector socket for an optional ear piece output.

The present invention also comprehends a posture monitoring indicator device comprising a flexible elongate belt adapted to fit around the waist of a wearer, tension sensitive indicator means connected to or fitted into the length of the belt and including a sensor for detecting the tension applied to the belt and for producing an output audio signal when the tension in the belt exceeds a predetermined threshold value.

Two embodiments of the present invention will now be more particularly described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a perspective view of a flexible belt formed as an abdomen muscle tone monitoring device in accordance with the principles of the present invention; Figure 2 is a circuit diagram of the electrical components of the apparatus of Figure 1; and Figure 3 is a perspective view of an alternative embodiment of the invention.

Referring now to Figures 1 and 2 of the drawings, the apparatus shown comprises a flexible elongate belt generally indicated 11 separated into two parts by a detector unit 12, the two parts being identified with the reference numerals 13 and 14. The part 14 carries a buckle 15 and the part 13 has a free end 16 having a plurality of openings 17 for inter-engagement with the tongue 18 of the buckle 15 in a conventional manner whereby to adjust the length of the belt and thereby the diameter of the waist around which the belt is fitted.

The detector unit 12 is securely attached to the other end of the belt section 13 whilst the belt section 14 carries a loop 19 linked to a movable member 20 of the detector unit 12 by a pivot coupling 21 which allows the two parts 13, 14 of the belt to turn with respect to one another both in the plane of the tangent to the belt and in a plane perpendicular to this tangent at the coupling point.

The movable member 20 is guided within a casing 22 of the detector so that it can perform only rectilinear movements against the biasing of a spring (not illustrated) as the tension in the belt 13 is increased.

The movable member 20 is connected so that, upon movement, it closes the contacts of a microswitch 23 (see Figure 2) to energise an audible warning after a given delay.

Referring now to Figure 2, the circuit of the detector device 12 comprises the aforementioned microswitch 23 connected between the positive pole of a power supply generally indicated 24 and a negative line 25 by two series connected resistors 26, 27 the latter of which is shunted by a capacitor 28 connected between a node 29 between the two resistors 26, 27 and the return line 25 which is grounded.

The node 29 is connected to one input of a NAND gate 30 the output of which is connected to both inputs of a second NAND gate 31 and fed back via a high value resistor 32 to the second input of the NAND gate 30 which is also connected, via a capacitor 33 to the output of the NAND gate 31. The values of the resistor and capacitor 32, 33 are selected such that the circuit comprising these passive components and the two NAND gates 30, 31 constitutes an astable circuit having a frequency in the region of 6 Hertz. The output from the NAND gate 31 is fed to one input of a further NAND gate 34 connected with a fourth NAND gate 35 in a similar astable circuit configuration with feedback capacitor 36 and resistor 37. The values of this second astable circuit are chosen such that it oscillates at a frequency in the region of 10 KHz.The output from the astable circuit constituted by the two NAND gates 34, 35 is supplied, via a socket 38, to a crystal speaker 39. The socket 38 may receive a plug 40 of an earphone circuit comprising a transistor 41 the connector of which is connected via a resistor 42 and a switch 43. to an earpiece 44 and the emitter of which is grounded. When the plug 40 is inserted into the socket 38 the speaker 39 is isolated and the signal generated upon closure of the microswitch 23 by the two astable circuits is applied to the earpiece 44.

In use of the device described a wearer fits the belt around his or her waist adjusting the buckle 15 until a comfortable position is reached with the abdomen muscles held firmly. If, whilst wearing the belt, the abdomen muscles should inadvertently relax applying an increased tension sufficient to cause displacement of the movable member 20 against the spring (not shown) the microswitch 23 will close energising the two astable circuits after the capacitor 28 has charged to cause a predetermined delay which allows the occasional brief relaxation of the abdomen muscles or movement of the body sufficient to cause an increase in the tension, for example bending or stretching to pick up something from the floor.After the capacitor 28 has charged the two astable circuits are energised and the speaker 39 will emit a sufficiently loud signal to alert the wearer to the fact that the abdomen muscles have been inadvertently relaxed. Upon tensing the muscles back to a normal holding position pulling in the abdomen the spring will pull back the movable member 20 allowing the microswitch contact 23 to open de-energising the oscillators and silencing the acoustic indicator. If the wearer should require to have a private indication of the relaxation of his or her abdomen the plug 40 is inserted into the socket 38 and the earpiece worn.

Other alerting indications may be provided instead of the audible indication described in relation to the specific embodiment of Figure 1. For example, instead of having oscillators a capacitive charging circuit may be provided with a trigger which discharges through electrodes worn close to the skin thereby giving a brief electric shock periodically when the microswitch contacts are closed. A physical vibrator may, likewise, be placed in the position of the acoustic indicator so that, again, a private indication of the relaxation state is achieved.

Apart from alerting the wearer, the device may be used to alert supervisory personnel to the relaxation state of muscles. This may be useful for physiological or other medical treatments, and as outlined in the preamble the idea may also be applied, in reverse as it were, to provide an indication that a predetermined muscle tension is being exerted. In this case the spring which resists the motion of a movable member 20 may be made very much stronger and the detector 12 may be formed as a much more robust element, perhaps with a handle at each end by means of which a deliberate tension may be applied.

Embodiments of the present invention adapted as a posture-improving belt, such as that illustrated in Figure 1 have the beneficial advantage of improving the musculature around the abdomen thereby improving the support to the spine in that region and it is believed this will offer relief to backache sufferers as well as improve the digestive system as beneficial by-products of the posture improvement.

In effect, the wearer is subject to bio-feedback in that he forms part of a loop which conditions his behaviour almost subconsciously to cause the correct posture to be adopted even when not wearing the belt. It has been found in practice that by wearing the belt for two or three days each week sufficient reminder is generated to maintain the conditioning and keep the improved posture without conscious thought.

In Figure 3 there is shown a practical configuration illustrating how the microswitch is mounted. In this embodiment the casing 45 is held to one end of the belt 46 by a rigid bar 47 spanning two lugs 48 of the casing 45 whilst the other end of the belt 46 is held on a similar fixing bar 44 spanning two rigid arms 50 of a sliding carriage 51. The arms 50 slide in slots in the casing 45 which ensure smooth rectilinear motion and avoids the possibility of failure of the microswitch to close due to misalignment of the tension forces at each end of the belt. Each of the arms 50 of the carriage 51 has a respective notch 53 defined at the free end of the arm 50 by a finger 54 which traps a coil spring 55 between itself and an upstanding projection 56 of the casing 45. The springs 55 urge the carriage 51 to withdraw into the casing 45, which is closed by a cover 48 bearing an acoustic indicator (not illustrated) joined to the printed circuit board 52 by wires 49 shown in broken outline.

The printed circuit board 52 is mounted on the casing 45 and itself carries the microswitch 57 with its sensor element facing towards a cross bar 58 carried between the two arms 50 of the carriage 51 and positioned so as to depress the microswitch actuating button when brought into contact therewith by extension of the springs 55.

Claims (15)

1. Apparatus for detecting muscle relaxation for use in maintaining muscle tone or other purposes, comprising an elongate flexible element having fastening means for securing the ends thereof to form the element into a loop, and stress sensor means sensitive to the tension in the element and/or the flexure of a part thereof in a direction parallel to or transversely of the length of the element and operative to produce a physically perceptible output signal if the tension or flexing stress exceeds a predetermined threshold value.

2. Apparatus as claimed in Claim 1, in which the physically perceptible output signal is an audio signal.

3. Apparatus as claimed in Claim 1, in which the physically perceptible output signal is a physical vibration of a element detectable by tactile contact with an observer.

4. Apparatus as claimed in any preceding Claim, in which the stress sensor means include a switch device biased to the contact open position by resilient biasing means, the force of which determines the said predetermined threshold value.

5. Apparatus as claimed in any preceding Claim, in which the said threshold value of the flexing or tension stress is adjustable.

6. Apparatus as claimed in any preceding Claim, in which the sensor is associated with a time delay circuit operable to cause a predetermined time delay between the achievement of the predetermined threshold value of the tension or flexing stress and the generation of an output indication signal.

7. Apparatus as claimed in any of Claims 4 to 6, in which the flexible element is a belt adapted to be fitted around the waist of a user.

8. Apparatus as claimed in Claim 7, in which the sensor is formed as a flexible unit fitted into the length of the belt.

9. Apparatus as claimed in Claim 7, in which the belt itself is the transducer of the sensor element.

10. Apparatus as claimed in Claim 9, in which the belt is made from a resiliently elastic material the extension of which causes a change in a physical or electrical property thereof.

11. Apparatus as claimed in Claim 9, in which the structure of the belt incorporates a piezo-electric element the compression stress on which is varied by a variation in the tension applied to the belt.

12. Apparatus as claimed in any preceding Claim, in which the tension is detected by a resiliently biased microswitch.

13. Apparatus as claimed in any of Claims 1 to 11, in which flexure is detected in a plane parallel to the length of the belt by a rigid belt insert having strain gauges or piezo-electric transducers connected to or associated therewith.

14. Apparatus as claimed in any preceding Claim, further including a connector socket for an ear mounted acoustic transducer.

15. Apparatus substantially as hereinbefore described with reference to, and as shown in, the accompanying drawings.