Abstract:
A control valve for an air cushion bed includes a first main body, a membrane plate, a second main body, a sensor, and a depressurization unit. The membrane plate is clamped between the first main body and the second main body. The second main body at one side of the membrane plate is connected with the sensor. The sensor is used to detect the inputted air pressure. When the air is over, the air can be depressurized by the depressurization unit. The control valve of the present invention is applied to input and control the air of the air cushion bed, having depressurization and air detection functions.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a control valve for an air cushion bed, and more particularly to a control valve having depressurization and air detection functions for an inflatable air cushion bed. 
     2. Description of the Prior Art 
     When a patient lies on the bed for a long period time, he/she may get bedsores caused by unrelieved pressure. An air cushion bed is used for patients so as to prevent a bedsore. This air cushion bed has air strips at the middle portion thereof for air inflation and air exhaust so as to lower the probability of bedsore. The relief of pressure is to avoid further sores. 
     As shown in  FIG. 1 , a conventional control valve  9  for an air cushion bed comprises an air intake pipe  91 , an air bag  92 , two push plates  93  and a three-way pipe  94 . When the air enters the air bag  92  to inflate the air bag  92 , the two push plates  93  will be moved to activate an inductive switch. Sometimes, the traditional air bag  92  cannot run exactly to influence the inductive result due to its material and configuration. Besides, the conventional control valve  9  has to cooperate with the three-way pipe  94 . It is necessary to improve the entire effect and to lower the cost. 
     Accordingly, the inventor of the present invention has devoted himself based on his many years of practical experiences to solve these problems. 
     SUMMARY OF THE INVENTION 
     The primary object of the present invention is to provide a control valve for an air cushion. The control valve has depressurization and air detection functions. 
     In order to achieve the aforesaid object, the control valve for an air cushion bed of the present invention comprises a first main body, a membrane plate, a second main body, a sensor, and a depressurization unit. 
     The first main body has a first room, a first air chamber, a second air chamber and a fourth air chamber which communicate with each other. The first main body comprises a first pipe and a second pipe. The first pipe communicates with the first air chamber. The second pipe communicates with the second air chamber. The first main body further has a separate third air chamber which is located close to the fourth air chamber. The third air chamber communicates with a third pipe. The first main body has a first annular recess at an inner edge thereof. 
     The membrane plate is located between the first main body and the second main body. The membrane plate comprises a main membrane portion and an extension portion. The main membrane portion has a circle shape corresponding to the first room. The extension portion has a through hole corresponding in position to the fourth air chamber. The extension portion further has a hole at an outer end thereof. The hole corresponds in position to the third air chamber. The membrane plate has an annular press portion around an outer wall thereof. The annular press portion is placed in the first annular recess of the first main body. 
     The second main body has a second annular recess at an inner edge thereof. The second annular recess corresponds to the first annular recess of the first main body, so that the membrane plate is sealed between the first main body and the second main body. The second main body has a second room corresponding to the first room of the first main body. The sensor is disposed in the second room. The second main body comprises a depressurization pipe. The depressurization unit is disposed in the depressurization pipe to adjust pressure. The depressurization pipe communicates with an air pipe to exhaust air. 
     The sensor can be a micro switch. The sensor has a trigger portion. The trigger portion faces the main membrane portion of the membrane plate. When the air enters the first room, the main membrane portion of the membrane plate will be deformed to touch the trigger portion of the sensor. The trigger portion is retracted by the applied force. The sensor detects entrance of air and sends an electronic signal. 
     The depressurization unit comprises a valve body, an elastic member, a central post, a fixing sleeve, and an adjustment bolt. The adjustment bolt can be turned to change the position of the valve body so as to adjust the pressure of depressurization. 
     The first pipe comprises a first auxiliary pipe which is perpendicular to the first pipe. The second pipe comprises a second auxiliary pipe which is perpendicular to the second pipe. When in practice, one of the first pipe and the first auxiliary pipe and one of the second pipe and the second auxiliary pipe are selected for pipe fitting, preventing the pipes from being bent. The air pipe communicates with a fifth air chamber of the second main body. The fifth air chamber communicates with the third air chamber through the hole of the membrane plate. The third air chamber communicates with the third pipe. When in practice, one of the air pipe and the third pipe is selected as an air output for depressurization. 
     The advantage of the present invention is that the control valve has depressurization and air detection functions to improve the shortcomings of the conventional depressurization structure and to enhance the speed and accuracy of assembly. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an exploded view of a conventional control valve; 
         FIG. 2  is a perspective view of the present invention; and 
         FIG. 3  is an exploded view of the present invention; 
         FIG. 4  is another exploded view of the present invention; 
         FIG. 5  is a schematic view showing the air flow of the first main body of the present invention; 
         FIG. 6  is a schematic view showing operation of the membrane plate and the sensor of the present invention; and 
         FIG. 7  is a schematic view showing depressurization of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings. 
     As shown in  FIG. 2  through  FIG. 4 , the control valve for an air cushion bed according to a preferred embodiment of the present invention comprises a first main body  1 , a membrane plate  2 , a second main body  3 , a sensor  4 , and a depressurization unit  5 . 
     The first main body  1  has a first room  14 , a first air chamber  141 , a second air chamber  142  and a fourth air chamber  144  which communicate with each other. The first main body  1  comprises a first pipe  11  and a second pipe  12 . The first pipe communicates with the first air chamber  141 . The second pipe  12  communicates with the second air chamber  142 . The first main body  1  further has a separate third air chamber  143  which is located close to the fourth air chamber  144 . The third air chamber  143  communicates with a third pipe. The first main body  1  has a first annular recess  15  at an inner edge thereof. 
     The membrane plate  2  is located between the first main body  1  and the second main body  3 . The membrane plate  2  comprises a main membrane portion  21  and an extension portion  22 . The main membrane portion  21  has a circle shape corresponding to the first room  14 . The extension portion  22  has a through hole  221  corresponding in position to the fourth air chamber  144 . The extension portion  22  further has a hole  222  at an outer end thereof. The hole  222  corresponds in position to the third air chamber  143 . The membrane plate  2  has an annular press portion  23  around an outer wall thereof. The annular press portion  23  is placed in the first annular recess  15  of the first main body  1 . 
     The second main body  3  has a second annular recess  36  at an inner edge thereof. The second annular recess  36  corresponds to the first annular recess  15  of the first main body  1 , so that the membrane plate  2  is sealed between the first main body  1  and the second main body  3 . The second main body  3  has a second room  34  corresponding to the first room  14  of the first main body  1 . The sensor  4  is disposed in the second room  34 . The second main body  3  comprises a depressurization pipe  33 . The depressurization unit  5  is disposed in the depressurization pipe  33  to adjust pressure. The depressurization pipe  33  communicates with an air pipe  331  to exhaust air. 
     The sensor  4  can be a micro switch. The sensor  4  has a trigger portion  41 . The trigger portion  41  is exposed out of the second room  34  and faces the main membrane portion  21  of the membrane plate  2 . 
     The depressurization unit  5  comprises a valve body  51 , an elastic member  52 , a central post  53 , a fixing sleeve  54 , and an adjustment bolt  55 . The adjustment bolt  55  can be turned to change the position of the valve body  51  so as to adjust the pressure of depressurization. 
     The first pipe  11  comprises a first auxiliary pipe  111  which is perpendicular to the first pipe  11 . The second pipe  12  comprises a second auxiliary pipe  121  which is perpendicular to the second pipe  12 . When in practice, one of the first pipe  11  and the first auxiliary pipe  111  and one of the second pipe  12  and the second auxiliary pipe  121  are selected for pipe fitting, preventing the pipes from being bent. The unselected pipes are sealed. The air pipe  331  communicates with a fifth air chamber  332  of the second main body  3 . The fifth air chamber  332  communicates with the third air chamber  143  through the hole  222  of the membrane plate  2 . The third air chamber  143  communicates with the third pipe  13 . When in practice, one of the air pipe  331  and the third pipe  13  is selected as an air output for depressurization. The unselected pipe is sealed. 
     The sensor  4  and the depressurization unit  5  are coupled to the second main body  3 . The membrane plate  2  is connected between the first main body  1  and the second main body  3 . 
     When in practice, the first pipe  11  functions as an air input end, namely, the first pipe  11  is connected with an air pump (not shown in the drawings). The second pipe  12  functions as an air output end. When the air enters the first air chamber  141  through the first pipe  11  and flows into the first room  14  (as shown in  FIG. 5 ), the main membrane portion  21  of the membrane plate  2  will be deformed by the saturated air and pressure (as shown in  FIG. 6 ). The central of the deformed main membrane portion  21  will touch the trigger portion  41  of the sensor  4 . The trigger portion  41  is retracted by the applied force. The sensor  4  detects the air and sends an electronic signal. Thus, the present invention provides an automatic function to transmit information. After that, partial air flows into the fourth air chamber  144  from the first room  14 . The fourth air chamber  144  communicates with a depressurization air chamber  37  through the through hole  221 . The depressurization air chamber  37  communicates with the depressurization pipe  33 . The air will flow into the depressurization pipe  33 , as shown in  FIG. 7 . The depressurization unit  5  is in the depressurization pipe  33 . The depressurization unit  5  comprises the valve body  51  which is biased by the elastic member  52 . When the pressure of the air is less than the elastic force of the elastic member  52  applied to the valve body  51 , the valve body  51  will be closed. When the pressure of the air is great than the elastic force of the elastic member  52  applied to the valve body  51 , the valve body  51  will be pushed away to compress the elastic member  52 . The air will be exhausted from the air pipe  331  so as to depressurize. 
     The output air from the air pipe  33  will be sent to the air pump for reuse, not to the surrounding in order to prevent noise. 
     In the conventional air cushion bed, the air pipe is always bent for pipe fitting. The air pipe may be damaged or disengaged from the bed. On the contrary, the present invention has interconnected vertical and transverse pipes for air input and output pipes. As shown in  FIG. 2  and  FIG. 3 , the first pipe  11  comprises the first auxiliary pipe  111  which is perpendicular to and communicates with the first pipe  11 . The second pipe  12  comprises the second auxiliary pipe  121  which is perpendicular to and communicates with the second pipe  12 . The air pipe  331  communicates with the fifth air chamber  332  of the second main body  3 . The fifth air chamber  332  communicates with the third air chamber  143  through the hole  222  of the membrane plate  2 . The third air chamber  143  communicates with the third pipe  13 . For pipe fitting, they can be selected as desired for connection of the pipes. 
     The first pipe  11  functions as an air input end and the second pipe  12  functions as an air output end, alternatively, the first pipe  11  functions as an air output end and the second pipe  12  functions as an air input end. 
     The first pipe  11 , the second pipe  12  and the third pipe  13  of the present invention can be designed to have a dual-layer joint for stable connection of the pipes. This can prevent the ends of the pipes from breaking or being damaged. 
     The traditional air pump, the air cushion and the control valve need a three-way connector for air distribution and transfer. The control valve of the present invention has the function of the three-way connector, which is convenient and simple for pipe fitting and assembly. When in practice, the present invention can cooperate with the three-way connector. One of the pipes of the present invention is blocked, and the outer end of the other pipe is connected with the three-way connector to communicate with the air pump and the air cushion bed. In principle, the arrangement of the air pump, the control valve and the air cushion bed is as follows:
         1. The air pump, the control valve and the air cushion bed are connected with the three-way connector.   2. The air pump is connected to the control valve alone, and the air pump is connected to the air cushion bed alone.   3. The air pump is connected to the control valve alone, and then the control valve is connected to the air cushion bed alone.       

     Although particular embodiments of the present invention have been described in detail for purposes of illustration, various modifications and enhancements may be made without departing from the spirit and scope of the present invention. Accordingly, the present invention is not to be limited except as by the appended claims.