Abstract:
A system for inexpensively placing an active fall-protection system in a floor is described. The floor is tessellated with large octagonal tiles and smaller square tiles. Each large octagonal tile contains a sodium azide-loaded airbag that expands, upon detonation, to 18 cm tall. Each square tile contains an infrared proximity detector and a differentiation. Upon accelerating approach of a large enough infrared-emitting object (such as a falling human body) the square tile detonates the four adjacent octagonal tiles. In this manner, the airbag tiles are deployed over the area of the floor destined to be impacted. Since the detectors respond to accelerating, large infrared-emitting objects, the floor tiles will not deploy during normal activities.

Description:
This is a continuation of Ser. No. 09/363,539, filed on Jul. 29, 1999. 
    
    
     BACKGROUND OF THE INVENTION 
     This invention relates generally to medical devices and more particularly to systems for preventing injury of patients in hospitals and nursing homes. 
     Patient falls are a major public health problem. Each year, injuries due to falls in hospitals and nursing homes cost hundreds of millions of dollars. For a woman over 80 years of age who falls in the hospital and breaks her hip, the chances of returning to independent living are less than 50% and the mortality is 20%. 
     Examples of deployable impact systems are shown in the following U.S. patents: 
     U.S. Pat. No. 5,057,819 (Valenti) discloses a safety cushion that is positioned on the floor adjacent one side of a baby crib for cushioning the fall of a child. The cushion also includes an alarm for alerting an adult of the child&#39;s fall. 
     U.S. Pat. No. 5,150,767 (Miller) discloses a portable self-contained impact device that automatically inflates when a person (e.g., someone trying to escape a fire from an elevated position) impacts the device and can be reset for another evacuee. 
     U.S. Pat. No. 5,592,705 (West) discloses an impact cushioning device for bed occupants. The device comprises an air cushion that is stowed under the bed and is adapted to be immediately positioned under the falling occupant when the weight of the occupant is removed from the bed. 
     Thus, there remains a need for an automatic, rapidly-deploying impact prevention system that emanates from the flooring. 
     OBJECTS OF THE INVENTION 
     Accordingly, it is the object of this invention to provide a system for protecting people from injury from falls in hospitals. 
     It is further the object of this invention to provide a system that protect children from falls out of cribs or high beds (i.e. “bunk beds”). 
     It is further the object of this invention to provide a system that is cost-effective. 
     SUMMARY OF THE INVENTION 
     These and other objects of the instant invention are achieved by providing an apparatus for use as a floor to automatically prevent an individual from falling against the floor. The apparatus comprises a detonator device having an inflatable means stored therein and wherein the detonator device has a top surface that acts as part of the floor when the inflatable means is in a stowed condition in the detonator device. The apparatus further comprises a detector device that is in electrical communication with the detonator device and is immediately adjacent the detonator device. The detector device has a top surface that acts as part of the floor. The detector device comprises a detector for detecting an individual falling towards the detector and activates the inflatable means to drive the top surface of the detonator device towards the falling individual. 
     These and other objects of the instant invention are also provided by a method for automatically preventing an individual from falling against a floor. The method comprises the steps of: providing a detonator device, positioned in the floor, with an inflatable means as part of the floor and stored within the detonator device; monitoring the immediate vicinity above the detonator device to determine if an individual is falling towards the detonator device; and activating the inflatable means whenever the individual is falling towards the detonator device to prevent the individual from striking the floor. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     Other objects and many of the attendant advantages of this invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein: 
     FIG. 1 is a top plan view of the reactive floor tiling system; 
     FIG. 2 is an isometric view of a detector tile and a detonator tile of the present invention; 
     FIG. 3 is a top plan view of a detonator tile and four immediately-adjacent detector tiles, any one of which can activate the detonator tile; 
     FIG. 4 is an enlarged view of the detector tile of FIG. 3 showing the internals of the detector tile; 
     FIG. 5 is cross-sectional view of the detonator tile and adjacent detector tile taken along line 5—5 of FIG.  3  and includes a view (in phantom) of a detonated air bag; and 
     FIG. 6 is an electrical schematic of the electronics of the detector tile. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now in greater detail to the various figures of the drawing wherein like reference characters refer to like parts, a reactive floor tiling system (hereinafter, “system”) constructed in accordance with the present invention is shown generally at  20  in FIG.  1 . The system  20  forms a tessellation, with large and small tiles, of a floor to be protected (e.g., a hospital floor, examination room floor, or any floor portion where a person may be prone to falling). The pattern shown in FIG. 1 is exemplary only. 
     In general, the system  20  comprises large, octogonal-shaped detonator tiles  22  and small, square-shaped detector tiles  24  that are secured to any conventional flooring foundation  21 . As will be discussed in detail later, each detector tile  24  is surrounded by four immediately-adjacent detonator tiles  22 . When a particular detector tile  24  detects a falling person, the detector tile  24  activates its four immediately-adjacent detonator tiles  22  which immediately inflate air bags (also discussed later) that are stowed in each detonator tile  22  to “catch” the falling person. 
     Power to the system  20  can be from conventional wall outlet power (e.g., 50/60 Hz, 110 VAC). An AC/DC converter (not shown) is used to generate the input voltage, V in  (FIG.  6 ), to the system  20  which is provided via two conductors  26 A/ 26 B (FIG. 1) to one of the detector tiles  24 . As can be seen most clearly in FIG. 2, electrical power contacts  28 / 30  on both the detonator tiles  22  and the detector tiles  24  permit the “propagation” of power throughout the system  20  whenever adjacent detonator tiles  22  and detector tiles  24  are in physical contact. The detonator tiles  22  comprise the electrical power contacts  28 / 30  only on their corner faces  32 A- 32 D whereas the detector tiles  24  comprise the electrical power contacts  28 / 30  on each their four sides  34 A- 34 D. It should be understood that the electrical power.contacts  28 / 30  in each detonator tile  22  are internally wired together to support this “propagation” of electrical power. Similarly, the electrical power contacts  28 / 30  in each detector tile  24  are also internally wired (FIG. 4) to also support this “propagation” of electrical power. 
     Another electrical contact, namely a “trigger” contact  36  is located on the detonator tile corner faces  32 A- 32 D and on the detector tile sides  34 A- 34 D. The trigger contact  36  provides the means for energizing the air bag  38  (FIG.  5 ). In particular, when the detector tile  24  detects a falling person, the detector tile electronics (FIG. 6, to be discussed later) passes the air bag triggering signal through its trigger contact  36  and into the detonator tile trigger contact  36  which, in turn, is coupled to an air bag electrical contact  40  (FIG. 4) which inflates the air bag when energized. 
     As stated previously, when a particular detector tile  24  detects a falling person, the detector tile  24  activates its four immediately-adjacent detonator tiles  22  which immediately inflate air bags  38  that are located underneath each detonator tile  22  to “catch” the falling person. Thus, the trigger contacts  36  of each detector tile  24  are internally wired together so that upon detection of the falling person, the trigger contact  36  on all four sides  34 A - 34 D of the detector tile  22  are asserted to activate the four immediately-adjacent detonator tiles  22 . Because each detonator tile  22  comprises a single air bag contact  40 , each trigger contact  36  on the corner faces  32 A- 32 D are also wired together at a junction point  42 . One consequence of this internal wiring is that a single triggering signal from one detector tile  22  could “propagate” throughout the entire system  20  causing all of the detonator tiles  22  to fire. To prevent this from occurring, a diode D 1  (FIG. 4) is positioned between each trigger contact  36  and the junction point  42  that feeds the air bag contact  40 . 
     As shown most clearly in FIG. 5, each detonator tile  22  comprises a hollow housing  44  in which the compressed air bag  38  is stowed. The air bag  38  comprises a sodium azide-loaded, inflatable plastic bag that expands, upon detonation, to approximately 18 cm (e.g., 4-5 liters of N 2 ). Detonation of the air bag  38  occurs, as is known in the art, when the sodium azide is electrically-charged via the trigger contact  36  of the detonator tile and to the air bag contact  40 . The air bag  39  is constructed exactly the same as automobile air bags, except because of the lower velocities the air bag  38  is smaller, uses less explosive, and can expand more slowly. In addition, the air bag  38  is not designed to deflate; instead, after detonation, the entire detonator tile  22  is removed and replaced with a new detonator tile  22 . A cap  46  is fixedly secured to the top of the air bag  38 . The cap  46  is shaped to rest on top of the housing sidewalls of the detonator tile  22 . 
     When installing the detonator tile  22  into the system  20 , the tile  20  is dropped into place in between surrounding detector tiles  24 , thereby making a snug fit such that the electrical power contacts  28 / 30 , as well as the trigger contacts  36 , form a good electrical connection with the immediately adjacent detector electrical power  28 / 30  and trigger  36  contacts. Cut-outs  48  in the bottom surface of the housing  44  provide for alignment with securement flanges  50  of the detector tiles  24 , discussed next. 
     The detector tiles  24  are removably secured to the flooring foundation  21  via fasteners (e.g., screws  52 ) that secure the securement flanges  50  against the foundation  21 . Once the four immediately-adjacent detector tiles  24  are so installed, the detonator tile  22  can be snugly fit between them with the cut-outs  48  fitting over the securement flanges  50  (FIG. 5) and the electrical power contacts  28 / 30  and the trigger contacts  36  making good electrical contact. 
     FIG. 4 depicts the internal wiring of the detector tile  24 . In particular, all four of the positive power contacts  28  are electrically connected through jumper wires  28 A- 28 D. The negative power contacts  30  are electrically connected through jumper wires  30 A- 30 D. The trigger contacts  36  of the detector tile  24  are electrically connected to each other through jumper wires  36 A- 36 D. 
     The detonator files  22  (in their compressed air bag  38  state) and the detector tiles  24  are approximately 12 mm in thickness. 
     Operation of the detector tile  24  electronics is discussed next, as depicted in FIG.  6 . 
     The detector tile  24  basically comprises a passive infrared motion detector (PIR), a capacitor C AB , a charged-capacitor indicator (LED), and threshold circuit  54  which includes a silicon-controlled rectifier (SCR). In operation, the capacitor C AB  charges continuously, compensating for any leakage. When the capacitor C AB  is fully charged, the LED is illuminated. This allows maintenance personnel to visually scan the room for broken or defective detector tiles  24 . When the PIR detects motion of a human at a sufficient velocity, as determined by the threshold circuit  54  (to be discussed later), the threshold circuit  54  triggers the SCR, which discharges the capacitor C AB  into the four immediately-adjacent detonator tiles through the trigger contacts  36  and the air bag contact  40 . These air bags  38  expand to their full height, cushioning the fall and preventing injury. 
     The PIR is a standard, commercially available monolithic component. One exemplary type of PIR is a pyroelectric infrared sensor manufactured by NICERA (Nippon Ceramic Corporation of 372-4 kumoyama, Tottori-shi, Japan), such as the SSAC10-11 or SEA02-4 that have spectral responses in the 7-14 μm range. The human body radiates infrared radiation according to its temperature. It is also known in the art that the peak emission wavelength for a black body is given by λ m T=0.0029, where λ m  is the wavelength in meters, and T is the temperature in Kelvin. For a human body at, e.g., 37° C., this yields a peak emission at 9.35 μm, which directly falls within the spectral response of the PIR of 7-14 μm. As a result, the top surface  25  of the detector tile  24  comprises a material (e.g., epoxy or acrylic) that is transparent to the infrared range of 7-14 μm. 
     In particular, the human body emits infrared radiation, to a first approximation, according to the black-body equation:          I   λ     =         2      π                   c   2        h       λ   5            1            ch     λ                 kt         -   1                                
     where: 
     k=Boltzman&#39;s constant; 
     c=speed of light; 
     h=Planck&#39;s constant; 
     λ=wavelength of emitted radiation; and 
     I=intensity of the radiation. 
     Over the range of sensitivity of a typical infrared PIR detector (SSAC10-11, Nicera Corporation 372-4 kumoyama, Tottori-shi, Japan), 7-14 μm, a human body at 310 Kelvin, 1.2 m 2  surface area, emits:        P   =       ∫     7                 nm       14                 nm                2      π                   c   2        h       λ   5            1            ch     λ                 kt         -   1                          λ                                
     This gives an output P on the order of a few watts in the range of interest. Considering the angle subtended by the PIR (area 1.75 mm 2 ), the received energy is given by:        E   =     P        0.0175     4      π                   d   2                                  
     where d=distance from PIR to body in centimeters. 
     The PIR sensors have the property of relatively linear output, in the case of the SSAC 10-11, 2400 voltstwatt. So, the output voltage of the PIR is given by:        V   =     3.34     d   2                              
     Thus, a human body at 1 meter will, therefore, give a voltage on the order of 0.1 millivolts in this particular sensor. 
     The threshold circuit  54  operates based on this PIR sensor output. In particular, the output voltage of the PIR is checked against an absolute threshold detector comprising a comparator U 1  and a velocity threshold detector that comprises a differentiator circuit  56  and another comparator U 3 . The outputs of these two thresholds are then fed to an AND gate (e.g., a differential op amp U 4 ) whose output drives the SCR. Thus, if the output of both the absolute threshold detector and the velocity threshold detector are exceeded, the AND gate is asserted and triggers the SCR in order to fire the immediately-adjacent detonator tiles  22 . 
     The absolute threshold detector comprises an operational amplifier (e.g., one operational amplifier available on a Fairchild USA LM-324 quad op-amp IC) configured as a comparator with the PIR output coupled to the positive terminal of the op amp U 1  and the negative terminal of U 1  coupled to an adjustable voltage reference VR 1 . VR 1  is the PIR voltage output that corresponds to a human body detected at approximately 1 meter and, as discussed above, which is approximately 0.1 millivolts. If the PIR output equals or exceeds 0.1 mV, the comparator U 1  goes hardover to +V cc ; otherwise, the output of the comparator U 1  remains hardover at −V cc . Therefore, the absolute threshold detector is used to distinguish between a large object (e.g., the torso or buttocks of a human) detected by the PIR and a small object (e.g., the foot of a human corresponding to someone walking over the detector tile) detected by the PIR. 
     Simultaneously, the threshold circuit  54  also checks to see how fast the emission detected by the PIR is changing, i.e., if the large object is “falling.” In particular, the differentiator circuit  56  (e.g., with R 1 =500 kΩ and C 1 =0.1 μF wherein R 1 ·C 1 =0.05 sec, and an operational amplifier U 3  such as the quad op amp IC LM-324) takes the time derivative of the PIR output and is used to increase the sensitivity to high velocity. The circuit  56  then feeds the differentiator output to the comparator U 3  which compares the differentiator output against an adjustable voltage reference VR 2  which is a voltage value that corresponds to the gravitational acceleration constant, g(980 cm/sec 2 ), since a freely-falling object has a constantly increasing velocity close to g. If the differentiator output equals or exceeds VR 2 , the comparator U 3  will go hardover to the opposite power supply rail, V cc . 
     The output of comparator U 1  and comparator U 3  are fed into an AND gate which controls the activation of the SCR. Only when both outputs of comparators U 1  and U 3  are asserted (i.e., a human body is detected and it is falling) does the AND gate trigger the SCR. As shown in FIG. 6, one exemplary manner of implementing an AND gate is using a differential operational amplifier (U 4 , such as quad op amp IC LM-324) using 10 kΩ resistors. Thus, small objects falling may trigger the velocity threshold detector but will fail to trigger the absolute threshold detector, even if the small object is warm. Similarly, a human simply getting down to the floor to look for something will not trigger the detonator tile  22  because the velocity threshold detector does not detect sufficient velocity. 
     The cost of the detonator tiles  22  may be up to $50.00 each, thus costing about $5000.00 for a typical patient room in a hospital. However, over the life of the floor, this compares favorably to the cost of each extra hospital day ($1000.00) to care for a person injured by a fall. The savings are even greater when considering the prevention of a broken hip (˜$15,000.00). In addition, patients at riskforfalls are often restrained (tied) into beds or chairs. The floor of the present invention allows patients more freedom and safety. 
     Without further elaboration, the foregoing will so fully illustrate my invention that others may, by applying current or future knowledge, readily adopt the same for use under various conditions of service.