Patent Application
20070008156
The present invention relates a bed and an in-bed state detection method for monitoring the in-bed state of a person in the bed.
Recently, as a detection device for a bedded person in a bed, JP-A-7-88089, for example, discloses a device in which a pressure sensitive sensor for detecting whether a cared person as a bedded person is in bed or not and for detecting the change of the physical condition of the cared person is provided at a bed disposed in a hospital or various kinds of care facilities etc. This bed is arranged in a manner that many sensors each generating a small voltage due to the piezoelectric effect are disposed in the width direction of the bed on the upper surface of the bed on which the bedded person lies, and a row of the sensors thus disposed are arranged with a predetermined interval in the longitudinal direction of the bed. The voltages from these sensors are detected thereby to confirm whether a cared person is in bed or not and manage the change of the physical condition of the cared person.
JP-A-10-229973 discloses a biomedical monitor apparatus in which piezoelectric sensors each having a long tape shape are disposed on the upper surface of a bed in the width direction of the bed thereby determine a blood pressure value and an arteriosclerosis intensity of a bedded person by using a vibration detection means formed by these sensors.
However, like the first example, in the bed in which the sensors formed by the many piezoelectric elements are provided on the upper surface of the bed on which the bedded person lies, many expensive sensors are disposed in a lattice pattern, so that the cost of the bed is inevitably raised. Further, since the sensitivity of the sensor itself is relatively low, the sensors are required to be provided almost just on the upper surface of the bed on which the bedded person lies, whereby the comfortability of the bed is degraded.
Further, like the second example, also in the bed in which the piezoelectric sensors each having the long tape shape are disposed in the width direction, it is possible to detect whether a person is in bed or not, but it is impossible to monitor the positional shift of the person on the bed to prevent the person from falling etc. in advance. Further, also in the case of this bed, since the piezoelectric sensors are provided on the upper surface of the bed on which the bedded person lies, it is inevitable to degrade the comfortability of the bed.
As another bed, JP-A-2003-52765 discloses an electrically operated bed in which the panel portion of the bed is adjustable and which is provided with a side fence also serving as an assistant means for prevent a quilt or a patient from falling. The conventional electrically operated bed of this type will be explained with reference to
However, the conventional electrically operated bed of this type has a problem that when the back raising panel portion 2 is raised while a part of a human body is inserted between the outer frame pipe 4a and the inner frame pipe 4b, the part of the human body becomes hard to slide on the outer frame pipe 4a or the inner frame pipe 4b due to a posture or a physique and a friction characteristics etc. of the human body or the cloth surface, so that the part of the human body is caught inadvertently.
As another bed, JP-A-8-282358 discloses an apparatus provided with a pad which can detect the heartbeats and the movement of breathing of a human body by using a pressure sensitive sensor.
In the figure, 70 depicts a seat, 71 a vibration detecting means, 72 a surface cloth, 73 an urethane foam, 74 a seat spring and 75 a seat frame. Each of the plural vibration detecting means 71 is fixed on the seat spring 74 constituting the seat 70 which is away by a constant distance r or more from the contact surface of the seat 70 with a human body via the surface cloth 72 and the urethane foam 73. In this case, r is the distance at which the presence of the vibration detecting means 71 is not felt by a human body seated on the seat 70. This distance becomes longer as the hardness of the outer casing of the vibration detecting means 71 is higher and the urethane foam 73 becomes softer.
In this manner, each of the plural vibration detecting means is fixed at the portion away from the surface of the seat made of urethane by the constant distance or more and the outputs of the plural vibration detecting means are processed to determine whether a human body exists on the seat or not. Since the plural vibration detecting means are disposed away from the contact surface with the human body, influence on the seating feeling can be reduced even when the plural vibration detecting means are configured by rigid parts.
However, this invention relates to a seat for a car. In the case of the seat for a car, since the entire weight of the upper part of a body higher than the hips is concentrated on the narrow hips, the detection can be made even if the vibration detecting means is provided at the lower surface of the seat made of urethane. When this technical concept was applied to a bed as it is, it was found that there arose the following problem.
FIGS. 35(a) to 35(c) show various kinds of the experimental examples in each of which the plural vibration detecting means (piezoelectric sensors) are used for a bed.
The signals (heartbeats generated from the heart of a human body) obtained from the cord shaped piezoelectric sensors 126 were detected in a state where a person lay down on the urethane layer bed 125 having the cord shaped piezoelectric sensors 126 disposed at the lower portion thereof, whereby the detection values detected by the cord shaped piezoelectric sensors 126 were small values.
The applicant of this invention considered that the reason of this results was as follows. That is, when a person lay on the urethane layer bed, the protruding portions on the back side of the human body P, that is, a head portion P1, shoulder blade portions P2, hip portions P3 and heel portions P4 abutted against the bed pad with strong forces and so sank deeply. However, since other portions of the human body did not sink so much, only these four portions served as vibration sources and so the heartbeat vibration from these portions was transmitted downward. As a result, a sufficient signal could not be detected even from the cord shaped piezoelectric sensors 126.
When the amplitude was increased, other noises (vibrations of cars passing outside, vibrations of persons passing near the bed, etc.) were caught much and so it was proved that the apparatus might be practical for car seats but not practical for the bed of
However, since a person lay on the sensor cable with a diameter of several millimeters which was bent for many times and disposed on the bed, there was a practical problem that the comfortability of the bed is not good.
The first invention of this application has been made in view of the aforesaid circumstances and an object of the first invention is to provide a bed and an in-bed state detection method which can surely detect the positional shift of a bedded person thereby to be able to prevent the fall of the person in advance while suppressing the increase of the cost and the degradation of the comfortability of a bed.
Further, an object of the second invention of this application is to provide a bed which can prevent the undesirable caught at the time of elevating a bed.
Furthermore, an object of the third invention of this application is to provide a bed having a bed pad which can surely detect heartbeat vibration and is comfortable to sleep.
The aforesaid objects can be attained by the following configurations.
(1) Abed for detecting shift of a position of a bedded person on a bedding surface, comprising:
a first pressure sensitive sensor and a second pressure sensitive sensor each having a cable shape, disposed separately along side edges of the bedding surface at both end sides in a width direction of the bedding surface, respectively, each of which detects an acceleration component caused by a movement of a bedded person; and
determination means which compares output signals from the first pressure sensitive sensor and the second pressure sensitive sensor to determine a shift state of the bedded person toward a side potion of the bedding surface.
According to this bed, the first detection sensor and the second detection sensor each formed by the cable-shaped pressure sensitive sensor are disposed at positions along the side edges of the bedding surface at the both end sides of the bedding surface, then the determination means compares the output signals from the first detection sensor and the second detection sensor thereby to determine the positional shift of a bedded person on the bedding surface toward the side portion, thereby preventing the bedded person from falling from the bedding surface in advance in accordance with the determination result. Further, since the cable-shaped pressure sensitive sensors are merely disposed along the both end sides of the bedding surface, the cost-up can be suppressed as much as possible and also the degradation of the comfortability to sleep can be suppressed as much as possible as compared with a case where sensors are disposed in a lattice pattern.
(2) The bed according to (1) is characterized in that the first pressure sensitive sensor and the second pressure sensitive sensor are arranged in a manner that a wiring density on a head portion side of the bedded person is set to be higher than other region.
According to this bed, since the wiring density of the pressure sensitive sensors on the head portion side of a bedded person is set to be higher, the detection sensitivity of a head portion is particularly improved. Thus, even in a case when such a shift arises that a bedded person lays his/her head near the side end portion on the bedding surface, the head portion of the bedded person can be detected with a high sensitivity thereby to accurately and surely grasp the shift state of the bedded person.
(3) The bed according to (1) or (2) is characterized in that the first pressure sensitive sensor and the second pressure sensitive sensor are arranged in a manner that a wiring density on a leg portion side of the bedded person is set to be lower than other region.
According to this bed, since the wiring density of the pressure sensitive sensor on the leg portion side of the bedded person is set to be lower, the detection sensitivity on the leg portion side becomes low. Thus, even when a shift state does not occur such that a bedded person lies at the center portion on the bedding surface with the person's leg being opened, it is possible to eliminate such a problem of an erroneous determination that the position of the bedded person is shifted.
(4) The bed according to (2) or (3) is characterized in that the first pressure sensitive sensor and the second pressure sensitive sensor are wired in a wave shape on the bedding surface, and the wiring density is changed in accordance with an interval between adjacent waves of the wave shape.
According to this bed, since each of the pressure sensitive sensors is wired in the wave shape on the bedding surface, and the wiring density is changed in accordance with the interval between adjacent waves of the wave shape, the wiring density can be arbitrarily set with ease.
(5) The bed according to (1) to (4) is characterized in that projection pieces are disposed on an upper side or a lower side of the pressure sensitive sensor and are overlapped on the pressure sensitive sensor at plural portions thereof.
According to this bed, since the projection pieces are disposed on the upper side or the lower side of the pressure sensitive sensor so as to be overlapped on the pressure sensitive sensor at plural portions thereof, the weight or movement of a bedded person can be acted on the pressure sensitive sensors as a large force locally, so that a large signal can be outputted and the detection sensitivity of the positional shift of a bedded person can be enhanced.
(6) The bed according to (5) is characterized in that the pressure sensitive sensor is adhered to a sheet and the projection pieces are adhered to a sheet, and the pressure sensitive sheet to which the pressure sensitive sensor is adhered and the projection piece sheet to which the projection pieces are adhered are laminated to each other.
According to this bed, the sensitivity of the pressure sensitive sensor can be improved with a quite simple configuration by merely laminating to each other the pressure sensitive sheet at which the pressure sensitive sensor is provided and the projection piece sheet at which the projection pieces are provided.
(7) The bed according to (1) to (6) is characterized in that the determination means outputs a notification signal when it is determined that positional shift of the bedded person on the bedding surface arises, and notification means is further provided which notifies occurrence of shift in response to the notification signal outputted from the determination means.
According to this bed, since the notification means notifies in response to the notification signal outputted from the determination means, the positional shift of a bedded person can be notified to a third party such as a cared person, so that the shift can be corrected quickly.
(8) An in-bed detection method of a bed for detecting shift of a position of a bedded person on a bedding surface, characterized by comprising the steps of:
obtaining a ratio between intensities of output signals from a first pressure sensitive sensor and a second pressure sensitive sensor each having a cable shape, disposed separately along side edges of the bedding surface at both end sides in a width direction of the bedding surface, respectively, each of which detects an acceleration component caused by a movement of a bedded person; and
determining that positional shift of the bedded person on the bedding surface arises when the ratio is in a predetermined range set in advance.
According to this bed, a ratio between intensities of the output signals from the first pressure sensitive sensor and the second pressure sensitive sensor is obtained, and it is determined that positional shift of the bedded person on the bedding surface arises when the ratio is out of the predetermined range set in advance. Thus, the positional shift of a bedded person can be surely and accurately detected in spite of the simple configuration.
(9) In a bed which includes at least one of a back raising panel portion and a knee raising panel portion and driving means which performs elevational driving of at least one of the back raising panel portion and the knee raising panel portion, and which is capable of attaching a side fence, the bed comprising:
a pressure sensitive sensor which is disposed at an entire periphery or a part of a surface end portion of at least one of the back raising panel portion and the knee raising panel portion;
determination means which determines touch of a bedded person to the pressure sensitive sensor based on an output signal from the pressure sensitive sensor; and
control means which controls the driving means in accordance with a determination signal from the determination means.
According to this bed, when it is determined that a bedded person contacts with the pressure sensitive sensor during the elevational operation of the back raising panel portion or the knee raising panel portion, such a control can be performed that the elevational driving of the back raising panel portion or the knee raising panel portion is stopped or the driving direction is reversed. As a result, an inadvertent caught at the time of the elevational movement of a bed can be prevented.
(10) The bed according to (9) is arranged in that the pressure sensitive sensor is formed by a non-linear flexible member which displacement amount with respect to a load is non-linear and a piezoelectric sensor with flexibility which deforms according to a displacement of the non-linear flexible member.
According to this bed, when the pressing load of a bedded person against the pressure sensitive sensor is the predetermined value or more, the non-linear flexible member deforms abruptly. Thus, since the piezoelectric sensor also deforms abruptly due to such a displacement of the non-linear flexible member, the output signal having a magnitude sufficient for detecting the contact due to the movement of the bedded person can be obtained from the pressure sensitive sensor.
(11) The bed according to (10) is aranged in that the non-linear flexible member is configured by a thin type elastic material which is formed in a belt shape and has a convex portion.
According to this bed, since the non-linear flexible member described in (10) or
(11) and the piezoelectric sensor are disposed in the deformation means capable of deforming according to a load, the non-linear flexible member and the piezoelectric sensor are further likely deformed when a load is applied, so that the sensitivity of the pressure sensitive sensor can be further improved.
(12) The bed according to (10) or (11) is arranged in that the non-linear flexible member and the piezoelectric sensor are disposed in deformation means capable of deforming according to a load
According to this bed, the non-linear flexible member and the piezoelectric sensor are further likely deformed when a load is applied, so that the sensitivity of the pressure sensitive sensor can be further improved.
(13) The bed is arranged in that the deformation means described in (4), in particular, has a hollow portion so that at least one of the non-linear flexible member and the piezoelectric sensor can be deformed easily.
According to this bed, the practical configuration of the deformation means can be realized.
(14) The bed is arranged in that the determination means in one of (1) to (5), in particular, determines whether or not a bedded person continues to touch the pressure sensitive sensor based on an output signal from the pressure sensitive sensor.
According to this bed, the piezoelectric type pressure sensitive sensor can realize the operation similar to that of a pressure sensitive sensor of a static load detection type, the usability can be improved.
(15) The bed is arranged in that the control means in one of (9) to (14) is arranged to validate the determination signal from the determination means when the driving means performs the elevational driving and to invalidate the determination signal from the determination means when the driving means does not perform the elevational driving.
According to this bed, even if a bedded person or a third party touches the pressure sensitive sensor during the stationary state of the back raising panel portion, for example, the back raising panel portion is prevented from being inadvertently driven elevationally. Since the determination signal as to the contact to the pressure sensitive sensor is made valid only when the back raising panel portion is driven elevationally, it is possible to provide the electrically driven bed which provides the sense of security and does not perform erroneous operation.
(16) The bed is arranged by comprising:
a low-repulsion urethane layer; and
a pressure sensitive sensor disposed on a lower surface of the low-repulsion urethane layer.
According to this bed, the heartbeat vibration etc. can be surely detected and a bed pad being comfortable to sleep can be obtained.
(17) The bed is arranged by comprising:
a low-repulsion urethane layer;
a cushion lawyer made of usual urethane disposed on a lower surface of the low-repulsion urethane layer; and
a pressure sensitive sensor disposed on a lower surface of the cushion lawyer.
According to this bed,
According to this bed, the heartbeat vibration etc. can be surely detected and a bed pad being comfortable to sleep can be obtained with a low cost.
(18) The bed according to (16) or (17) is arranged in that the pressure sensitive sensor is configured by a cord-shaped piezoelectric sensor with flexibility.
According to this bed, the heartbeat vibration etc. can be further surely detected.
(19) The bed according to one of (16) to (18) comprising:
a rigid plate having unevenness formed on a surface thereof; and
a bed pad which is disposed on the rigid plate and recited in one of claims 16 to 18.
According to this bed, the heartbeat vibration etc. can be further surely detected.
(20) The bed is arranged by comprising:
a bed frame;
a movable plate attached on the bed frame so as to be able to incline; and
a bed element which is disposed on the movable plate and described in (19).
According to this bed, the heartbeat vibration can be surely detected and a care bed being comfortable to sleep can be obtained.
FIGS. 8(a) to 8(c) are schematic plan views each showing the position of a bedded person on a bedding surface.
FIGS. 12(a) to 12(c) are schematic plan views each showing the position of a bedded person on the bedding surface.
FIGS. 35(a) to 35(c) show various kinds of experimental examples using a piezoelectric sensor for a bed.
In the drawings, a reference numeral 11 depicts a projection sheet, 13, 55, 61 each depicts a pressure sensitive sheet, 15a depicts a bedding surface, 17, 53 each depicts a projection sheet, 21 depicts a pressure sensitive sensor (first pressure sensitive sensor), 22 depicts a pressure sensitive sensor (second pressure sensitive sensor), 23 depicts a center electrode, 25 depicts a piezo element material, 27 depicts an outer electrode, 29 depicts a sheath, 31 depicts a first signal processing unit, 33 depicts a second signal processing unit, 35 depicts an amplifier circuit, 37 depicts a filter, 39 depicts a smoothing circuit, 41 depicts a determination means, 43 depicts a notification means, 51, 52 each depicts a sheet, 50 depicts a bed, A, B each depicts an output, H depicts a bedded person, 80 depicts an electrically driven bed, 82 depicts a bedded person, 83 depicts a back raising panel portion, 84 depicts a knee raising panel portion, 85 depicts an elevationally driving unit, 86, 86a, 92, 93, 94, 110, 112, 114 each depicts a pressure sensitive sensor, 87 depicts a determination means, 88 depicts a side fence, 89 depicts a deformation means, 90 depicts a non-linear flexible member, 91 depicts a piezoelectric sensor (cable shaped), 97 depicts a flange portion, 98 depicts a center electrode, 99 depicts an outer electrode, 100 depicts a composite piezoelectric layer, 101 depicts a cover layer, 102 depicts a piezoelectric sensor end portion, 103 depicts a wire-breakage detection resistor, 104 depicts a cable, 105 depicts a connector, 107 depicts the side surface of a mattress, 108 depicts a low-repulsion urethane foam, 109 depicts a usual urethane foam, 111 depicts a hollow portion, 113 depicts a piezoelectric sensor (sheet shaped), 120 depicts a bed pad, 121 depicts a low-repulsion urethane layer, 122 depicts a usual urethane layer, 123 depicts a cord-shaped piezoelectric sensor laying sheet, 124 depicts a cloth sheet, 125 depicts a bed, 126 depicts a cord-shaped piezoelectric sensor, 127 depicts an uneven plastic plate, 128 depicts a plastic plate, 129 depicts a recess, 130 a cover bag, 131 depicts a sheet, 132 depicts a fastener, 134 depicts a bed frame, 135 depicts a picture-frame shaped frame, 136 depicts a movable plate, 137 depicts a supporting plate, 138 depicts a motor, 145 depicts a detection unit for heartbeats and breathing etc., 146 depicts a cord-shaped pressure sensitive sensor (cord-shaped piezoelectric sensor), 147 depicts a filter circuit, 148 depicts an amplifier circuit, 149 depicts a counter circuit and 150 depicts a display unit.
Hereinafter, the preferred embodiments of a bed and an in-bed state detection method according to the invention will be explained with reference to drawings.
As shown in
In the projection sheet 11, a plurality of projection pieces 17 are formed in parallel from one another along the longitudinal direction of the bed 50 on the upper surface side of the projection sheet. The projection pieces 17 are not limited to the configuration of the plural lines each formed by a linear continuous line shown in the figure, but may be projections of a linear shape provided intermittently, projections of a curved shape or projections provided discretely. The pressure sensitive sheet 13 constituting the detection device is laminated on the upper surface of the projection sheet 11 in a manner that pressure sensitive sensors are disposed on the lower side of the pressure sensitive sheet. The upper surface of the mattress 15 laminated on the upper surface of the pressure sensitive sheet 13 serves as a bedding surface 15a.
As shown in
The pressure sensitive sensors 21, 22, each of which is a piezoelectric sensor of a long cable shape using piezo element material, have straight line portions 21a, 22a disposed linearly along the edge portions of the both end sides of the sheet 19 and wave shaped portions 21b, 22b disposed in a wave-shaped fashion along the straight line portions at the inner sides of the sheet 19 than the straight line portions 21a, 22a, respectively. In these pressure sensitive sensors 21, 22, as shown in
Thus, the pressure sensitive sheet 13 provided with the pressure sensitive sensors 21, 22 is pushed down via the mattress 15 as shown in
Next, the concrete configuration of the pressure sensitive sensors 21, 22 will be explained.
As shown in
In each of the pressure sensitive sensors 21, 22, resin material having heat resistance durable to the usable temperature of 120 C.° is used as the piezo element material 25. This piezo element material has characteristics of capable of being used in a temperature region (120 C.° or less) higher than 90 C.° which is the maximum usable temperature of the conventional typical high-molecular piezo element material (uniaxially oriented polyvinylidene fluoride) or piezo element material made from chloroprene and piezoelectric ceramic powder.
Further, the piezo element material 25 is formed by resin with flexibility and piezoelectric ceramics, the center electrode 23 is formed by coil-shaped metal, and a flexible electrode of a film shape is used as the outer electrode 27, whereby the sensor has flexibility similar to that of a normal vinyl cord.
Furthermore, each of the pressure sensitive sensors 21, 22 has a high sensitivity similar to that of high-molecular piezo element material and has a high sensitivity similar to that of high-molecular piezo element material in a low frequency range (10 Hz or less) for detecting the motion of a human body. This is because the dielectric constant (about 55) of the piezo element material 25 is larger than that (about 10) of high-molecular piezo element material, so that the degree of the reduction of the sensitivity is low in even in the low frequency region (10 Hz of less).
The piezo element material 25 is constituted by complex, of resin material and piezoelectric ceramics powder of 10 μm or less. The vibration detection characteristics and the flexibility of the piezo element material are realized by ceramics and resin, respectively.
In the piezo element material 25, since chlorinated polyethylene is used as the resin material, flexibility facilitating the forming as well as high heat resistance (120 C.°) are realized, and further simple manufacturing processes eliminating a bridging process can be realized.
Each of the pressure sensitive sensors 21, 22 thus obtained does not have piezoelectric efficiency so long as the piezo element material 25 is merely formed. Thus, it is necessary to perform a processing (polarization processing) for applying piezoelectric efficiency to the piezo element material 25 by applying a high DC voltage of several kV/mm to the piezo element material 25. This polarization processing is performed in a manner that after forming the center electrode 23 and the outer electrode 27 at the piezo element material 25, the high DC voltage is applied to the both electrodes 23, 27.
When a small defect such as a crack exists within the piezo element material 25, discharge likely occurs at the defect portion and so there likely arises the short-circuit between the both electrodes, so that a sufficient polarization voltage can not be applied. However, in the pressure sensitive sensors 21, 22, since a unique polarization process is established in which an auxiliary electrode capable of adhering to the piezo element material 25 of a constant length is used, a defect can be detected and avoided thereby to stabilize the polarization, whereby the sensor can be elongated so as to have a length of 10 m or more.
Further, in each of the pressure sensitive sensors 21, 22, since the coil-shaped metal center electrode is used as the center electrode 23 and the film-shaped electrode (three layer laminated film of aluminum, polyethylene terephthalate and aluminum) is used as the outer electrode 27, the adhesiveness between the piezo element material 25 and the respective electrodes 23, 27 is secured. Further, an external lead wire can be coupled easily and a flexible cable-shaped mount structure can be realized.
A copper-silver alloy coil is used as the center electrode 23, the three layer laminated film of aluminum, polyethylene terephthalate and aluminum is used as the outer electrode 27, polyethylene resin plus piezoelectric ceramic powder is used as the piezo element material 25 and thermoplastic plastics, whereby the dielectric constant becomes 55, an electric charge generation amount becomes 10 to 13 C (coulomb)/gf and the maximum usable temperature becomes 120 C.°.
Each of the pressure sensitive sensors 21, 22 is arranged so as to output a signal only at a moment where a force is applied thereto and not to output any signal any more so longs as there is no deviation even if the force is continued to be applied thereto. Similarly, each of the sensors has characteristics of detecting acceleration such that a signal is outputted only at a moment where the force is removed. Thus, in each of the pressure sensitive sensors 21, 22, even when it is disposed in a bent manner, the sensor outputs a signal on a moment where it is bent but does not output a signal after the completion of the disposition. Thereafter, each of the pressure sensitive sensors 21, 22 outputs a signal only when a force is applied to a portion thereof.
Therefore, even in a case where the cord-shaped piezoelectric sensors are disposed in a wave-shaped fashion at the lower portion of the bed, the sensors are placed in on states at the moment where they are bent but do not output signals after the completion of the disposition. Then, thereafter, each of the cord-shaped piezoelectric sensors outputs a signal only when a force is applied to a portion thereof.
Next, the construction and function of the bed will be explained more in detail.
One and the other of a pair of the pressure sensitive sensors 21, 22 provided at the pressure sensitive sheet 13 serve as a first pressure sensitive sensor 21 and a second pressure sensitive sensor 22, respectively.
The first pressure sensitive sensor 21 is coupled to a first signal processing unit 31 and the second pressure sensitive sensor 22 is coupled to a second signal processing unit 33. In the signal processing units 31, 33, output signals from the pressure sensitive sensors 21, 22 are applied to amplifier circuits 35, respectively.
Each of the first signal processing unit 31 and the second signal processing unit 33 is arranged in a manner that a filter 37 and a smoothing circuit 39 are provided at the rear stage of the amplifier circuit 35, and that the output signal from the corresponding one of the first pressure sensitive sensor 21 and the second pressure sensitive sensor 22 is amplified by the amplifier circuit 35, then a required frequency component is filtered by the filter 37 and the signal waveform is smoothed by the smoothing circuit 39.
Then, each of the first signal processing unit 31 and the second signal processing unit 33 is coupled to a determination means 41. Electric signals smoothed by the smoothing circuits 39 are inputted into the determination means 41.
The determination means 41 determines the shift of the position of a bedded person lying on the bedding surface 15a of the mattress 15 based on the electric signals supplied from the first signal processing unit 31 and the second signal processing unit 33.
Further, a notification means 43 is coupled to the determination means 41. The notification means 43 is constituted by a sound output means such as a speaker or a display means such as a display. The determination means 41 outputs a notification signal to the notification means 43 based on the determination result of the positional shift of a bedded person. Then, the notification means 43 outputs an alarm by means of sound or display or the combination thereof in response to the reception of the notification signal from the determination means 41 thereby to notify that the position of a bedded person on the bedding surface 15a is shifted.
Incidentally, each of the first pressure sensitive sensor 21 and the second pressure sensitive sensor 22 is coupled to a power source 47 via a resistance circuit 45 and is supplied with a driving voltage for detection via the resistance circuit 45 from the power source 47 in advance.
The determination means 41 determines the positional shift of a bedded person based on a ratio between the intensities (using the integration intensities etc. of the amplitudes or peaks of the signals) of the electric signals from the first signal processing unit 31 and the second signal processing unit 33. To be concrete, as shown in
Then, when the ratio of the intensities of the outputs A, B is in the range of the shift state away from the non-shift state, the determination means 41 determines that the position of a bedded person on the bedding surface 15a is shift and so outputs the notification signal to the notification means 43.
The notification means 43, in response to the notification signal, outputs an alarm to a third party such as a care person by means of sound or display or the combination thereof thereby to notify that the position of a bedded person on the bedding surface 15a is shifted.
In the bed provided with the detection device for a bedded person configured in the aforesaid manner, an adjustment is made prior to the detection of the shift in order to correct a personal difference among bedded persons, whereby the detection accuracy can be improved largely. As a concrete adjustment process, firstly, as shown in
In a state after this adjustment, when a bedded person H on the bedding surface 15a moves on the bedding surface 15a as shown by
Further, in particular, in a shift state shown in
Furthermore, in this case, a tensile force, which is caused by the sinking of the mattress 15 due to the weight of a bedded person H, acts at the straight line portions 21a, 22a of the first and second pressure sensitive sensors 21, 22, whereby the detection signal is also generated. Thus, the detection sensitivity is further improved.
In this manner, according to the detection device and the detection method for a bedded person described above, the first pressure sensitive sensor 21 and the second pressure sensitive sensor 22 each configured by the cable-shaped piezoelectric sensor are disposed along the side edges of the bedding surface 15a at the both end sides of the bedding surface 15a, respectively, and the determination means 41 compares the output signals from the first pressure sensitive sensor 21 and the second pressure sensitive sensor 22 thereby to determine the positional shift to the side portion of a bedded person on the bedding surface 15a. Thus, the bedding state of a bedded person can be grasped from the determination result and so a bedded person can be prevented from falling etc. in advance from the bedding surface 15a.
Further, since the cable-shaped piezoelectric sensors are merely disposed at the both end sides of the bedding surface 15a, the increase of the cost can be suppressed utmostly as compared with a case where many sensors each configured by an expensive piezoelectric element are disposed in a lattice fashion with a space therebetween in the width direction and the longitudinal direction of the bed.
Further, since each of the pressure sensitive sensors 21, 22 itself is a sensor with a quite high sensitivity, a sufficient detection sensitivity can be obtained even when the pressure sensitive sheet 13 provided with the pressure sensitive sensors 21, 22 is disposed beneath the mattress 15, so that it is possible to eliminate such a problem that the pressure sensitive sensors 21, 22 badly influence on the comfortability of the bed. Furthermore, even in the case where the pressure sensitive sensors 21, 22 are disposed just under the bedding surface 15a, since the pressure sensitive sensors 21, 22 are not disposed at the center portion of the bedding surface 15a and the pressure sensitive sensors 21, 22 themselves have flexibility, the degradation of the comfortability of the bed can be suppressed utmostly.
Furthermore, the detection sensitivity of the pressure sensitive sensors 21, 22 can be improved quite easily by merely laminating the pressure sensitive sheet 13 provided with the pressure sensitive sensors 21, 22 and the projection sheet 11 provided with the projection pieces 17.
Incidentally, in the aforesaid embodiment, although the sensitivity is intended to be improved by laminating the projection sheet 11 provided with the projection pieces 17 on the pressure sensitive sheet 13 provided with the pressure sensitive sensors 21, 22, the structure for improving the sensitivity maybe configured in the aforesaid manner.
The configuration shown in
The heart beat of a bedded person may be detected by the pressure sensitive sensors 21, 22, and the health condition of the bedded person can be managed based on the detection result.
Next, the explanation will be made as to a modified example of the pressure sensitive sheet of bed according to the first embodiment
A pressure sensitive sheet 61 is arranged in a manner that the interval of the adjacent waves of the wave-shaped portion of each of the pressure sensitive sensors 21, 22 is made shorter thereby to increase the wiring density in a region Wa which is the head portion side of a bedded person laying on the bedding surface 15a. In contrast, the interval of the adjacent waves of the wave-shaped portion of each of the pressure sensitive sensors 21, 22 is made longer thereby to decrease the wiring density in a region Wc which is the leg portion side of a bedded person laying on the bedding surface 15a (the figure shows an example where the pressure sensitive sensors are made linear in a bedding direction thereby to minimize the wiring density.
In general, as shown in
In the detection device for a bedded person according to the embodiment, as shown in
Further, since the pressure sensitive sensors 21, 22 are arranged so as to be low in their density on the leg portion side, as shown in
Further, as shown in
The pressure sensitive sensors 21, 22 in the respective embodiments are particularly desired to be piezoelectric sensors configured by the aforesaid material. However, in the invention, the pressure sensitive sensors are not limited to such sensors but various kinds of pressure sensitive sensors such as an electric contact type cable-shaped sensor may be used which is arranged in a manner that, for example, a pair of electric contacts are buried within a cable and the contacts are made contact to each other due to the bending of the cable thereby to detect a pressure.
The second embodiment of the invention will be explained with reference to FIGS. 13 to 27.
The second embodiment of the invention is explained based on FIGS. 13 to 27.
As shown in
As shown in
In
The sensor shown in
The piezoelectric sensor 91 is configured in a manner that a center electrode 98 serving as an electrode for extracting a signal, an outer electrode 99, a composite piezoelectric layer 100 made of composite electric material formed by mixing sintered powder of piezoelectric ceramics into rubber elastic material, and a cover layer 101 are laminated concentrically, then formed in a cable shape and subjected to the polarizing processing. This piezoelectric sensor has the similar configuration as that shown in
Incidentally, in order to shield from the electric noises in the external environment, the piezo electric sensor 22 serving as the pressure sensitive sensor 86 is preferably arranged in a manner that the outer electrode 99 is wound around the circumferential periphery of the composite piezoelectric layer 100 so as to be partially overlapped thereon. Although vinyl chloride or polyethylene may be used as the cover layer 101, elastic material such as rubber having better flexibility and elasticity than the composite piezoelectric layer 100 may be used so that the piezoelectric sensor 91 likely deforms elastically when a bedded person 82 touches the sensor. As such rubber, for example, ethylene propylene rubber (EPDM), chloroprene rubber (CR), butyl rubber (IIR), silicon rubber (Si) or thermoplastic elastomer may be used.
Next, the operation and function of the aforesaid configuration will be explained.
As shown in
The aforesaid operation control is performed only when the back raising panel portion 83 and the knee raising panel portion 84 are during the elevational driving but not performed during the non-driving state of the back raising panel portion 83 and the knee raising panel portion 84 even if the pressure sensitive sensor 86 detects the movement of a bedded person 82.
Further, in a case where a part of the body of a bedded person 82 protrudes from the upper end of the back raising panel portion 83 due to any reason during the elevational operation of the back raising panel portion 83, if the part of the body touches the pressure sensitive sensor 86, the output signal from the pressure sensitive sensor 86 is transmitted to the determination means 87, so that the determination means 87 determines that the bedded person 82 touches the sensor. Then, the elevational driving of the back raising panel portion 83 and the knee raising panel portion 84 is immediately stopped. Thus, it is possible to prevent such a problem that a part of the body abuts against the raising frame 81a inadvertently and a part of the body is caught by the raising frame 81a inadvertently.
Furthermore, in a case where a part of the body of a bedded person 82 protrudes from the lower end of the knee raising panel portion 84 due to any reason during the elevational operation of the knee raising panel portion 84, if the part of the body touches the pressure sensitive sensor 86, the output signal from the pressure sensitive sensor 86 is transmitted to the determination means 87, so that the determination means 87 determines that the bedded person 82 touches the sensor. Then, the elevational driving of the knee raising panel portion 84 is immediately stopped. Thus, it is possible to prevent such a problem that a part of the body abuts against the raising frame 81b inadvertently and a part of the body is caught by the raising frame 81b inadvertently.
In
The reason why the combination of the non-linear flexible member and the piezoelectric sensor with flexibility is used as the pressure sensitive sensor according to the embodiment is as follows.
(1) In the case where, as a pressure sensitive sensor of a type for detecting a load, a tape-shaped pressure sensitive sensor of an electrode contact type or a pressure sensitive sensor of a pressure-sensitive resistance change type which resistance value changes depending on a load, each of which being used normally, is disposed at the periphery of the mattress of the bed, when the back raising panel portion or the knee raising panel portion is elevationally driven, the pressure sensitive sensor causes an erroneous detection due to a stress generated by the bending thereof at the portion where the mattress bends.
(2) In order to solve the aforesaid problem, when the pressure sensitive sensor is divided and the divided pieces thereof are disposed separately so as to avoid the bent portion, even when a subject contacts with the pressure sensitive sensor, the mattress absorbs the pressing force due to the softness of the mattress, whereby there arises a case that the contact can not be detected. In particular, in the case of employing a bed using a mattress of low-repulsion urethane foam being excellent in body pressure distribution property for preventing bedsore, such non-detection likely occurs.
In contrast, the pressure sensitive sensor of the embodiment uses the piezoelectric sensor with flexibility and generates the output signal according to the acceleration of the deformation. The operation speed of the elevational driving of the back raising panel portion and the knee raising panel portion is made low in view of the safety. Thus, the acceleration of the deformation of the pressure sensitive sensor caused at the bent portion of the mattress as described above becomes also small, so that the output signal from the piezoelectric sensor generated by the elevational driving can be suppressed to a small value. As a result, it is possible to avoid the erroneous determination by suitably selecting a threshold value for determining the contact in the determination mean.
Further, since the non-linear flexible member is also used, even if the mattress is soft and the contact speed is slow, the non-linear flexible member deforms abruptly when a load of the predetermined value or more is applied thereto due to the contact with a subject. Thus, since the piezoelectric sensor also deforms abruptly due to such a displacement of the non-linear flexible member, the output signal having a magnitude sufficient for detecting the contact with a subject can be obtained from the pressure sensitive sensor.
As described above, the embodiment is arranged to control the pressure sensitive sensor disposed at the entire periphery or the part of the surface end portion of at least one of the back raising panel portion and the knee raising panel portion, the determination means for determining the touch of a bedded person to the pressure sensitive sensor based on the output signal from the pressure sensitive sensor, and the driving means for elevationally driving the back raising panel portion and the knee raising panel portion in accordance with the determination signal from the determination means. Thus, when it is determined that a bedded person contacts with the pressure sensitive sensor during the elevational operation of the back raising panel portion or the knee raising panel portion, such a control can be performed that the elevational driving of the back raising panel portion or the knee raising panel portion is stopped or the driving direction is reversed. As a result, an inadvertent caught at the time of the elevational movement of the bed can be prevented.
Furthermore, since the pressure sensitive sensor is configured by the non-linear flexible member which displacement amount with respect to a load is non-linear and the piezoelectric sensor with flexibility which deforms according to the displacement of the non-linear flexible member, the sensitivity relating to the contact of a bedded person to the pressure sensitive sensor can be enhanced. This is because when the pressing load of a bedded person against the pressure sensitive sensor is the predetermined value or more, the non-linear flexible member deforms abruptly. Thus, since the piezoelectric sensor also deforms abruptly due to such a displacement of the non-linear flexible member, the output signal having a magnitude sufficient for detecting the contact with a subject can be obtained from the pressure sensitive sensor.
Further, since the non-linear flexible member is configured by a thin type elastic material which is formed in a belt shape and has a convex portion, it is simple and highly practical.
Furthermore, since the non-linear flexible member and the piezoelectric sensor are disposed in the deformation means capable of deforming according to a load, both the non-linear flexible member and the piezoelectric sensor are further apt to deform when a load is applied thereto, so that the sensitivity of the pressure sensitive sensor can be further improved.
Furthermore, the control means is arranged to validate the determination signal from the determination means when the driving means performs the elevational driving and to invalidate the determination signal from the determination means when the driving means does not perform the elevational driving. Accordingly, even if a bedded person or a third party touches the pressure sensitive sensor during the stationary state of the back raising panel portion, for example, the back raising panel portion is prevented from being inadvertently driven elevationally. Since the determination signal from the determination means is made valid only when the back raising panel portion is driven elevationally, it is possible to provide the electrically driven bed which provides the sense of security and does not perform erroneous operation.
Incidentally, concerning the embodiment, although the description is made as to the electrically driven bed in which the back raising panel portion 83 and the knee raising panel portion 84 are driven elevationally, the pressure sensitive sensor having the same configuration as the pressure sensitive sensor 86, 86a may be applied to the electrically driven bed in which only the back raising panel portion 83 is driven elevationally.
The arrangement of the pressure sensitive sensor with this configuration will be explained based on
Further, it may be arranged in a manner that the pressure sensitive sensors formed by the piezoelectric sensors are disposed at the both sides of the mattress so that the pressure sensitive sensors detect the shift of the laying position of a bedded person on the mattress, and when the shift is determined to exist, the elevational driving is inhibited thereby to prevent the caught in advance. In this case, the shift is determined in a manner that, for example, each of the piezoelectric sensors detects a small movement of the body based on the heartbeats or breathing of a bedded person, and it is determined that the shift exists when a ratio of the output signals of the piezoelectric sensors based on the small movement of the body is a setting value or more. That is, the output signals of the piezoelectric sensors based on the small movement of the body are used in a manner that it is determined that the shift exists when an amplitude of the output signal of one of the piezoelectric sensors is a predetermined times or more as large as the amplitude of the output signal of the other of the piezoelectric sensors. When it is determined that the shift exists, an alarm may be issued so as to notify that a bedded person is not safety due to the shift and a message may be issued so as to urge the bedded person to return to the center of a bed. Alternatively, the existence of the shift may be notified to a care person by means of a nurse call system or a communication means. Further, when both this configuration and the configuration of the second embodiment are employed, the caught can be prevented more effectively.
Incidentally, although it is possible to detect a small movement of the body based on the heartbeats or breathing of a bedded person by using the mattress formed by usual urethane foam, the small movement of the body based on the heartbeats or breathing of a bedded person can be detected with better sensitivity by using the low-repulsion urethane foam. This will be explained based on
The remarkable difference of the physical property value between the usual urethane foam and the low-repulsion urethane foam is that the rebound resilience value of the former is about 35% but that of the latter is about 5%. In other words, the usual urethane foam has a larger repulsion property. This will be described based on the experimental verification results performed by the applicant etc. of the invention. In the case of the usual urethane foam 109, as shown in
In contrast, in the case of the low-repulsion urethane foam 108, as shown in
Due to such a difference of the characteristics, in the case of the usual urethane foam 109, since the body partially contacts with the mattress, the small movement of the body based on heartbeats or breathing is hardly transmitted to the mattress. As a result, since the small movement of the body is hardly transmitted to the piezoelectric sensor, the displacement of the piezoelectric sensor due to the small movement of the body is small. In contrast, in the case of the low-repulsion urethane foam 108, since the whole body contacts with the mattress uniformly, the small movement of the body based on heartbeats or breathing is likely transmitted to the mattress. As a result, since the small movement of the body is likely transmitted to the piezoelectric sensor, the displacement of the piezoelectric sensor due to the small movement of the body is made larger. When the low-repulsion urethane foam is used in this manner, the small movement of the body based on heartbeats or breathing can be detected with better sensitivity as compared with the case of using the usual urethane foam.
Next, an modified example of the second embodiment will be explained. This example shows another configuration of the pressure sensitive sensor.
Incidentally, although the aforesaid embodiments are arranged in a manner that the pressure sensitive sensor 86 is disposed on the major surface of the back raising panel portion 83 and the knee raising panel portion 84, another configuration may be employed. For example, as shown in
Further, as shown in
Furthermore, the pressure sensitive sensor may be disposed so as to extend over the major surface and the rear surface of the back raising panel portion 83 and the knee raising panel portion 84. In this case, a subject is prevented from being inadvertently caught between the side fence 88 and all the surfaces including the major surface, the side surface and the rear surface of the back raising panel portion 83 and the knee raising panel portion 84.
In the case where the back raising panel portion 83 and the knee raising panel portion 84 are provided with a mattress, as shown in
Hereinafter, as a bed according to the third embodiment of the invention, a bed etc. capable of detecting heartbeats will be explained in detail with reference to drawings.
Firstly, the cord-shaped piezoelectric sensor used in this embodiment will be explained briefly.
The cord-shaped piezoelectric sensor is a cable-shaped sensor using piezo element material practically developed by the applicant of the invention. The configuration of the piezoelectric sensor is shown in
In
(1) That is, at a time point t0 where no load was applied to the cord-shaped piezoelectric sensor 126, the sensor output was 2 (V).
(2) When a bending load was applied to the cord-shaped piezoelectric sensor 126 in a constant direction at a time point t1, the sensor output increased to 4 (V) instantaneously after the application of the load, then immediately reversed to 0 (V) and then returned to 2 (V) again.
(3) Thereafter, the sensor output was kept to 2 (V) even when the bent state was maintained.
(4) When the cord-shaped piezoelectric sensor 126 was restored to the original state at a time point t3, the sensor output reduced to 0.8 (V) instantaneously after the restoring, then immediately reversed to 2.2 (V) and then returned to 2 (V) again.
In this manner, since this cord-shaped piezoelectric sensor generates the output in response to the acceleration, this sensor outputs a signal only at the moment where a force applied thereto, and does not generates the output any more even if the force is continuously applied thereafter so long as the sensor does not deform, that is, there is no acceleration. Similarly, the sensor has characteristics that it also generates the output only at the moment where a force having been applied thereto is removed. Thus, even if this cord-shaped piezoelectric sensor is disposed at the lower portion of the bed in a wave-shaped manner, although the sensor is placed in an on state at the moment where it is bent but does not generate any output after completion of the displacement. Thereafter, the cord-shaped piezoelectric sensor generates the output only when a force is applied to a part thereof.
In
According to this configuration, the vibration of heartbeats could be surely detected despite that the cord-shaped piezoelectric sensor 126 was disposed away from a person laying on the bed.
This reason is considered that since the low-repulsion urethane layer 121 is used as the bed, the portions of the back side of a person such as a neck, s shoulder, a back, a waist, a hip, thighs, calves, heels of legs etc. from a head side sink uniformly, sot that the vibration of heartbeats is transmitted from the whole surface of the urethane layer to the cord-shaped piezoelectric sensor as shown in the figure.
In the figure, 120 depicts a bed pad according to the invention, which is configured by the low-repulsion urethane layer 121 and a usual urethane layer 122 thereunder. The thickness of the low-repulsion urethane layer 121 is ½ or less as large as the entire thickness of the bed pad 120.
123 depicts a cord-shaped piezoelectric sensor laying sheet, which is configured by a cloth sheet 124 like a sheet and the cord-shaped piezoelectric sensor 126 which is disposed thereon in a wave-shaped manner.
127 depicts an uneven plastic plate which unevenness is formed by providing many recesses 129 on the surface of a plastic plate 128. The function and effects of the unevenness will be described later.
130 depicts a cover bag which is formed in a manner that a large sheet 131 is folded in two and three sides thereof are made so as to be opened and closed freely by a fastener 132. The fastener 132 is opened, then the bed pad 120, the cord-shaped piezoelectric sensor laying sheet 123 and the uneven plastic plate 127 are laminated in this order and housed within the cover bag 130 in the laminated state, and then the fastener 132 is closed, whereby a cushion portion of the bed is completed.
134 depicts a bed frame in which supporting plates 136, 137 are attached within a picture-frame shaped frame 135. The supporting plate (movable plate) 136 is arranged to incline by the operation of a motor 138 as shown by the figure. The cover bag 130 is placed on the supporting plates 136, 137 thereby to complete the bed.
The explanation will be made as to “the low-repulsion urethane” and “the usual urethane” constituting the bed pad 120.
The “low-repulsion urethane” is formed in a manner that the composition of urethane foam, that is, the kind of polyisocyanate, the number of functional group and the hydroxyl value of polyol are selected and constituted so as to cause the glassy transition at a temperature (usually a room temperature) where the urethane foam is used, thereby providing the low-repulsion property by the glassy transition phenomenon.
In contrast, the “usual urethane” is constituted so as not to cause the glassy transition at a temperature (a room temperature) where the urethane foam is used, thereby providing the high-repulsion property
The physical property values of the low-repulsion urethane and the usual urethane are as follows.
The usual urethane foam is classified into three kinds according to the hardness, that is, a soft type, a medium type and a hard type.
1) The urethane foam of the soft type has a density of 20±2 kg/m3, a hardness of 6±1.5, a tear strength of 0.2 kg/cm or more, a tensile strength of 0.6 kg/cm2 or more, an elongation percentage of 150% or more, an impact resilience of 35% or more and a residual strain of 6% or less.
2) The urethane foam of the medium type has a density of 20±2 kg/m3, a hardness of 11±1.5, a tear strength of 0.2 kg/cm or more, a tensile strength of 0.7 kg/cm2 or more, an elongation percentage of 120% or more, an impact resilience of 35% or more and a residual strain of 6% or less.
3) The urethane foam of the hard type has a density of 21±2 kg/m3, a hardness of 15±2.0, a tear strength of 0.2 kg/cm or more, a tensile strength of 0.7 kg/cm2 or more, an elongation percentage of 120% or more, an impact resilience of 35% or more and a residual strain of 6% or less.
The low-repulsion urethane foam has a density of 65±10 kg/m3, a hardness of 5.5±2.0, a tear strength of 0.2 kg/cm or more, a tensile strength of 0.5 kg/cm2 or more, an elongation percentage of 150% or more, an impact resilience of 5% or less and a residual strain of 3% or less.
The aforesaid densities and the hardnesses were measured by JIS-K6401, the tear strengths, the tensile strengths and the elongation percentage were measured by JIS-K6301, and the impact resiliences and the residual strains were measured by JIS-K6401.
Although the bed pad may be configured only by the low-repulsion urethane layer, the bed pad 120 is configured by the two-layer structure of the low-repulsion urethane layer 121 and the usual urethane layer 122 as shown in
In this case, it was proved to be preferable to use such a bed pad which was arranged in a manner that a half or less of the predetermined thickness was formed by the low-repulsion urethane layer, and an urethane layer of usual cushion material with the remaining thickness was adhered under the low-repulsion urethane layer.
In the case where the cord-shaped piezoelectric sensor 126 is provided on a flat plate 143 as shown in
In contrast, in the case where the cord-shaped piezoelectric sensor 126 is provided on the uneven plastic plate 127 provided with the recesses 129 as shown in
Thus, it is preferable to provide the uneven plastic plate 127 under the cord-shaped piezoelectric sensor 126. Incidentally, the bed pad may be configured as a bed pad of a sandwiched type in which the cushion lawyer made of usual urethane is disposed on the upper and lower surfaces of the low-repulsion urethane layer, and the piezoelectric sensor may be disposed on the lower surface of the bed pad of a sandwiched type.
The heartbeats and breathing of a person on the bed pad can be detected through the known signal processing based on the output signal of the cord-shaped piezoelectric sensor according to the embodiment.
In
As shown in
The band width of the filter circuit 147 is set in a range of about 0.7 to 2 Hz in the case of counting the number of heartbeats, set in a range of about 0.1 to 0.5 Hz in the case of counting the number of breathings and set in a range of about 1 to 10 Hz in the case of counting the number of the body movement such as turning-over. When the body is moved in the case of counting the number of heartbeats, since the level of the output signal caused by the body movement is larger than that caused by the heartbeats, the output signal is distorted and so an erroneous operation may be caused. Thus, an upper limit and a lower limit are provided in the case of counting the number of heartbeats, and the number of times corresponding to the heartbeats where the output signal exceeds the predetermined threshold value is counted in the case where the output signal exists within the range between the upper and lower limits. The similar procedure is performed in the case of counting each of the number of breathings and the number of the body movement.
In the aforesaid example, although each of the number of heartbeats and the number of breathings is counted by counting the number of times where the output signal increases to the predetermined threshold value or more, another known method may be employed. For example, a method may be employed in which the output signal of the pressure sensitive sensor 146 is converted into a digital data through the A/D conversion by a microcomputer, and an autocorrelation coefficient is calculated from the time-series data of the digital data thereby to calculate the number of heartbeats and the number of breathings.
Further, although the cord-shaped pressure sensitive sensor is used as the cord-shaped pressure sensitive sensor, another sensor capable of detecting vibration such as an electrostatic capacitance sensor of a coaxial shape, a pressure sensitive resistance type sensor of a cable shape may be used instead thereof. Further, a belt-shaped or sheet-shaped pressure sensitive sensor as well as a cable-shaped one may be used so long as it is possible to be disposed on the lower surface of the bed pad and capable of detecting the vibration due to heartbeats or breathings of a human body.
According to the bed and the in-bed state detection method of the invention, the first detection means and the second detection means each formed by the cable-shaped pressure sensitive sensor are disposed along the laying direction at the both end sides of the bedding surface, then the determination means compares the output signals from the first detection means and the second detection means thereby to determine the positional shift of a bedded person on the bedding surface toward the side portion, thereby preventing the bedded person from falling from the bedding surface in advance in accordance with the determination result.
Further, since the cable-shaped pressure sensitive sensors are merely disposed at the both end sides of the bedding surface, the cost-up can be suppressed as much as possible and also the degradation of the comfortability to sleep can be suppressed as much as possible as compared with a case where sensors each formed by an expensive piezoelectric elements are disposed on the bedding surface in a lattice pattern.
The invention is arranged to control the pressure sensitive sensor disposed at the entire periphery or the part of the surface end portion of at least one of the back raising panel portion and the knee raising panel portion, the determination means for determining the touch of a bedded person to the pressure sensitive sensor based on the output signal from the pressure sensitive sensor, and the driving means for elevationally driving the back raising panel portion and the knee raising panel portion in accordance with the determination signal from the determination means. Thus, when it is determined that a bedded person contacts with the pressure sensitive sensor during the elevational operation of the back raising panel portion or the knee raising panel portion, such control can be performed that the elevational driving of the back raising panel portion or the knee raising panel portion is stopped or the driving direction is reversed. As a result, an inadvertent caught at the time of the elevational movement of the bed can be prevented.
Further, the bed pad is configured by the low-repulsion urethane layer and the piezoelectric sensor disposed on the lower surface of the low-repulsion urethane layer or configured by the low-repulsion urethane layer, the cushion lawyer made of usual urethane disposed on the lower surface thereof and the piezoelectric sensor disposed on the lower surface of the cushion layer, so that such a bed pad can be provided which can surely detect heartbeat vibration and is good in the comfortability of the bed.
Furthermore, when a rigid plate having unevenness formed on the surface thereof is added, the heartbeat vibration can be detected more surely. When the bed is formed by using such the bed pad, the bed comfortable to sleep can be obtained.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2003-177087 | Jun 2003 | JP | national |
| 2003-178103 | Jun 2003 | JP | national |
| 2003-193430 | Jul 2003 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP04/08931 | 6/18/2004 | WO | 12/15/2005 |
