Patent Publication Number: US-6988508-B2

Title: Device and method for the pneumatic control, and regulation of hydraulic fluid flows

Description:
PRIOR ART 
   The invention is based on an apparatus for open- and closed-loop control of flows of pressure fluid, and on a method for open- and closed-loop control of flows of pressure fluid. 
   Pneumatic open- and closed-loop control circuits are used in many technical applications. As an example, European Patent Reference EP 0 812 743 B1 can be noted, which describes a pressure fluid-operated windshield wiper motor. 
   The windshield wiper motor of EP 0 812 743 B1 has a bidirectional work cylinder, in which two piston faces are subjected to pressure fluid counter to one another. A reversing slide, depending on the position of the drive mechanism, feeds the pressure fluid in the region of the outer end positions of the piston faces and switches it through for venting purposes in the vicinity of the inner end positions of the piston faces. The two pistons or piston faces are coupled via a mechanical connection and provided with a rack. The rack in turn engages a driven rotary member, so that the linear motion between the two outer end positions of the piston faces are converted via the driven rotary member into a rotary motion for wiper actuation. 
   For reversal, that is, to reverse the rotary motion as soon as one of the end positions is reached, a so-called reversing slide is used. This is a valve in which the valve slide, analogously to the bidirectional work cylinder, is also actuated bidirectionally. The reversing slide executes motions that are opposite the motion of the bidirectional work cylinder. 
   From U.S. Pat. No. 4,655,505, a pneumatically controlled seat for a vehicle is known that makes it possible to vary the pressure distribution of the seat for the driver. This apparatus includes many flexible air chambers, integrated with the vehicle seat, which communicate with an air pump and a pressure sensor by way of a corresponding number of connecting means. Each connecting means has one valve, which can be triggered via electronic control means that evaluate the signal of the pressure sensor. 
   The combined pneumatic and electrical circuit of this apparatus, because of the many valves, makes it possible to build up defined pressures in the individual air chambers of the seat and thus not only to make the seat more comfortable but also take longitudinal or lateral accelerations of the vehicle into account. 
   In particular, the apparatus of U.S. Pat. No. 4,655,505 makes it possible to vary the pressure in each individual air chamber continuously over time, so that an optimized pressure distribution can be established, and from an oscillating change in pressure conditions in the air chambers, the driver experiences a massage effect. 
   To achieve this variation in pressure conditions in the individual air chambers of the seat in U.S. Pat. No. 4,655,505, a complicated electronic monitoring and control unit with corresponding electronics and at least one pressure sensor and a central arithmetic unit are all needed. 
   ADVANTAGES OF THE INVENTION 
   The apparatus of the invention has the advantage over the prior art that electrical or electronic components can be dispensed with virtually entirely. 
   The pneumatic circuit according to the invention for regulating the flows of pressure fluid requires no electrically triggered valves, no pressure sensors, and no computer-controlled monitoring device. Only a compressor or the pump for furnishing the pressure fluid may optionally be embodied as an electrically driven pump. 
   Because of the purely pneumatically driven valve piston of the open- and closed-loop control apparatus of the invention, a slide element is moved in such a way that in alternation, one outlet conduit of the pneumatic apparatus is connected to the single inlet conduit, while the other outlet conduit is simultaneously connected to the venting conduit of the apparatus. 
   In this way, it is possible for a first chamber to be filled with the pressure fluid and simultaneously for a second chamber to be evacuated in alternation, without having to control the delivery of pressure fluid to the chambers via electromagnetic valves. 
   Advantageous provisions of the apparatus of the invention will become apparent from the characteristics recited in the dependent claims. 
   Because of the embodiment of connecting conduits in the movable slide element, it is possible in a simple and elegant way to establish the respective communication between the single inlet conduit, the respective first and second outlet conduit, and the venting conduit. The slide element thus acts like an adjustable shunt, which takes on the task of the respective association with one another of the total of four conduits in the apparatus. 
   With an adjustable throttle, which regulates the flow of pressure fluid into a work chamber disposed parallel to the respective outlet conduit, it is possible in a simple way to achieve a delay element for the circuit of the invention, for instance, so that the time constant of the alternating motion can be adjusted flexibly. Not until a previously defined pressure prevails in the work chamber is a sufficiently strong back driving force exerted on the valve piston and the slide element connected to it. The slide element is then moved automatically, so that the alternative association among the conduits is established. Thus it is possible solely by way of the size of the work chambers and the adjustment of the throttles to achieve the time lag within the pneumatic circuit without electronic components. 
   Advantageously, the work chambers of the apparatus of the invention that are associated with the two outlet conduits are part of the valve chamber in which the valve piston moves. The work chambers are closed off from the valve chamber, for instance via a diaphragm, each diaphragm being connected to the valve piston in the vicinity of one of its ends. These elastic diaphragms, which can advantageously comprise an elastomer, such as rubber or silicone, transmit the pressure prevailing in the work chamber to the valve piston in a simple way. Thus by the relative pressure difference between the work chambers, the valve piston can be set into an oscillating motion, which correspondingly drives the slide element that controls the pressure fluid. 
   In order for the open- and closed-loop control apparatus claimed to be capable of building up a desired pressure, the valve piston is not disposed freely movably in the valve chamber but instead is secured by a locking device. This locking device counteracts the force on the valve piston that is generated by the pressure difference in the work chambers. The locking device, which can be in the form of a detent spring, for instance, thus also makes it possible to adjust the internal time constant of the pneumatic open- and closed-loop control apparatus of the invention in a desired way. 
   In an advantageous version of the apparatus of the invention, the force that the locking device exerts on the valve piston can be adjusted manually, or optionally automatically, so that the time constant of the oscillating motion of the valve piston can be changed in a simple way, for instance by the driver himself. 
   An economical and lightweight embodiment of the apparatus of the invention is obtained if it is made entirely or in part of plastic. However, other materials are also possible for the open- and closed-loop control apparatus claimed, without sacrifices in its mode of operation. 
   One advantageous application of the open- and closed-loop control apparatus of the invention is achieved if a small compressor for the pressure fluid, such as a vane-cell compressor or a membrane pump, is connected to one inlet conduit, and the two outlet conduits each communicate with a flexible air chamber. In this version, the open- and closed-loop control apparatus of the invention assures that in alternation, one of the air chambers at a time is pumped up, while the other is at the same time vented, causing an alternating motion of the air chambers, in the event that the apparatus of the invention is subjected only to a constant flow of pressure fluid. 
   The time constant of this alternating motion is determined solely by the passive means in the apparatus of the invention and can be varied and adapted to given requirements in a simple and advantageous way by means of various throttles and locking elements. 
   If the apparatus of the invention, including a pump that pumps the pressure fluid and the air chambers on the outlet side, is built into the seat of a vehicle, then as a result an advantageous massage effect, for instance, for the vehicle passengers can be achieved without having to use a complicated electronic circuit of the kind that is usual in the apparatuses of the prior art. The claimed invention achieves this massage system with a purely pneumatic open- and closed-loop control circuit. 
   It is thus possible to achieve a corresponding vehicle seat with great comfort, using only passive, pneumatic means. The use of electronic switching and closed-loop control devices can advantageously be dispensed with. This markedly lessens the effort and expense for achieving such massage systems. 
   The method of the invention makes it possible in a simple and advantageous way to control flows of pressure fluid in open- and closed-loop fashion solely by pneumatic means. In particular, the claimed method makes it possible in a simple way to realize adjustable time constants and suitably-adapted delays for the alternating motions, solely by means of pneumatically regulating the flows of pressure fluid. 

   
     DRAWING 
     In the drawing, several exemplary embodiments of the apparatus of the invention are shown, which are to be explained in further detail in the ensuing description. 
     Shown are: 
       FIG. 1 , a schematic illustration of a first exemplary embodiment of a circuit of the pneumatic apparatus of the invention, for a first end position of the slide elements of the apparatus; 
       FIG. 2 , a schematic illustration of the first exemplary embodiment of a circuit of the pneumatic apparatus of the invention, for a second end position of the slide elements of the apparatus; 
       FIG. 3 , a schematic illustration of a second exemplary embodiment of a circuit of the pneumatic apparatus of the invention, for a first end position of the slide elements of the apparatus; 
       FIG. 4 , a section through part of an exemplary embodiment of the apparatus of the invention, in a first end position of the slide element; and 
       FIG. 5 , a plan view on one exemplary embodiment of a conduit plate and a slide element, disposed beneath it, of the apparatus of the invention. 
   

   DESCRIPTION OF THE EXEMPLARY EMBODIMENTS 
   The schematic circuit of the pneumatic apparatus  10  of the invention, shown in  FIG. 1 , shows a slide element  12 , which connects an inlet conduit  14  of the apparatus with a first outlet conduit  16  and connects a second outlet conduit  18  with a venting conduit  20 . The venting conduit  20  need not necessarily be connected to atmospheric pressure. On the contrary, a closed circulatory system for the apparatus is also conceivable. 
   An adjustable throttle  15  precedes the inlet conduit  14 . The outlet conduit  16  communicates with a container  24  via connecting means  22 . The connecting means  22  has among other elements a throttle  26 , with which the flow through the connecting means  22  can be adjusted in a desired way. Branching off from the outlet conduit  16  is a further connecting means  28 , which via a delay element  29 , which in the present exemplary embodiment is embodied by a throttle  30 , leads to a reservoir  34 , which acts as a first work chamber  32  and can be emptied via a check valve  35  and the connecting means  28 . The reservoir  32  is in turn coupled in terms of pressure to the slide element  12  via a device  37 . 
   The second outlet conduit  18  on the one hand communicates with a second container  42  via connecting means  38  and a throttle  40 , and on the other is coupled to a reservoir  50 , acting as a second work chamber  48 , via connecting means  44  and a throttle  46 . The lead line to the reservoir  50  also has a delay element  31  and a check valve  37  for venting purposes. Like the reservoir  34 , however, the reservoir  50  is coupled on the opposite side to the slide element  12  via a device  39 . 
   In its interior, the slide element  12  has continuous conduits  52 , which each provide the respective communications between the one inlet conduit  14  and the two outlet conduits  16  and  18  and the venting conduit  20 , as a function of the position of the slide element  12 . The mobility of the slide element  12  is regulated by a locking device  54 , which is shown schematically in  FIG. 1  in the form of an elastic spring  64 . 
   The mode of operation of the pneumatic open- and closed-loop control apparatus  10  of the invention will now be described in further detail in terms of the illustrations in  FIGS. 1 and 2 . 
   If the inlet conduit  14  of the apparatus  10  of the invention, as shown in  FIG. 1 , is subjected to a pressure fluid, such as air, then the pressure fluid passes through a conduit  56  and the throttle  26  to enter the container  24 , which is embodied for instance as an elastic air cushion  58 . The air cushion  58  will fill with the pressure fluid and accordingly be inflated. At this moment, the container  42  communicates with the venting conduit  20  via a conduit  60 , so that atmospheric pressure, for instance, prevails in it. 
   While the air cushion  58  is being inflated, some of the flow of pressure fluid is delivered to the work chamber  32 , via the connecting means  28  and a suitably adjusted throttle  30 . The precise adjustment of the throttle  30  determines the time required to fill the work chamber  32 . The work chamber  32  communicates with the  12 , for instance via an elastic diaphragm  62 . When the pressure in the work chamber  32  rises, and the diaphragm  62  expands, the force on the slide element  12  is increased. The slide element  12  is locked via the locking device  54 , which is indicated in  FIG. 1  in the form of two elastic springs  64 . If the force exerted on the slide element  12  by the pressure in the work chamber  32  exceeds the detent force of the slide element  12 , then the slide element is displaced and assumes a position as shown in FIG.  2 . 
   In this position in  FIG. 2 , the container  24  now communicates with the venting conduit  20  via a conduit  66  in the slide element  12 , so that the pressure built up in the container  24  can escape, and the air cushion  58  thus empties again. At the same time, the associated work chamber  32  also empties via the valve  35 , the connecting means  28 , and the conduit  66  in the slide element  12 . 
   In the position of the slide element  12  shown in  FIG. 2 , the container  42 , which may be a flexible air cushion  68 , now communicates with the single inlet conduit  14  via a conduit  70  and is filled by the pressure fluid present there. At the same time, some of this pressure fluid is delivered to the second work chamber  48  via the connecting means  44  and the throttle  46 . 
   The pressure in the second work chamber now rises in accordance with the adjustment of the throttle  46 , while the container  42  is pumped up, as has already been described analogously above for the first work chamber. Via the device  37 , which by way of example may also be a diaphragm  72 , a force is thus exerted on the slide element  12 . If this force is great enough to overcome the detent force of the slide element  12  resulting from the locking device  54 , or in other words if a high enough pressure has built up in the work chamber  48 , then the slide element  12  is thrust back again into its first position—shown in FIG.  1 —so that the associated air cushion  68  is again vented via the conduit  60  of the slide element  12 . 
   Thus one complete cycle of the open- and closed-loop control apparatus of the invention is now concluded, and the system on its own begins again to fill the container  58 , in the way already described above. 
   Because of the alternating inflation and venting of the air cushions involved, it is possible, with a system based on this invention located in the seat of a vehicle, to improve the seating comfort and to provide relief for the spinal column through the resultant massage effect. The oscillation period of this motion can be adjusted by way of adjusting the relative throttle sizes, the size of the volumes involved, and not least also via the flow of pressure fluid pumped. By directly adjusting the strength of the locking device, the user himself can for instance easily adapt the frequency of the motion individually. 
   For the pneumatic supply to the apparatus, a small compressor, such as a vane-cell compressor, or a diaphragm pump, can be used. Such a device is shown in FIG.  3 . The pump  78 , driven by a motor  76  that is preferably employed in the form of an electric motor, subjects the apparatus  10  of the invention, via the adjustable throttle  15  and the inlet conduit  14 , to the pressure fluid, which is preferably air but can certainly be some other mixture or gas. 
   To shorten the running time of the pump and thus lengthen its service life, this pump can, as shown in the exemplary embodiment of the apparatus of the invention in  FIG. 3 , monitor a volume  82  that precedes the inlet conduit  14 . To that end, the motor  76  that drives the pump  78  is controlled via a pressure sensor  84  in the lead line  86  and an associated switch. 
   The pump  78  and the associated motor  76  driving it can be disposed in the immediate vicinity of the pneumatic apparatus  10 , or it can be spatially separated from it via appropriate connecting means and thus optionally decoupled acoustically from the vehicle seat. 
     FIG. 4  shows a cross section through one exemplary embodiment of the pneumatic apparatus of the invention. 
   The pressure fluid passes through the inlet conduit  14  and a conduit plate  88  to reach the slide element  12 . The slide element  12  is solidly connected to a valve piston  90 . The valve piston  90  is in turn disposed in a valve chamber  92 . The slide element  12  can be displaced relative to the conduit plate  88  under it, that is, on the side of the conduit plate remote from the inlet conduit or the outlet conduits, so that selectively, various openings in the conduit plate  88  come into coincidence with the conduits  52  of the slide element  12 . 
   This is shown in  FIG. 5  in a plan view on the conduit plate  88 . The movable slide element  12  is shown under the conduit plate  88 . The pressure applied to the inlet conduit  14  communicates permanently with the valve chamber  92 . The work chamber  48  is in constant communication with the outlet conduit  18 , and the work chamber  33  is in constant communication with the outlet conduit  16 . 
   In the position of the slide element  12  shown in  FIG. 5 , the connecting conduit from the valve chamber  92  to the outlet conduit  18  would be uncovered, and the outlet conduit  16  would communicate with the venting conduit  20  of the apparatus via a conduit in the slide element  12 . 
   By means of such a position of the slide element  12 , the pressure in the work chamber  32  is vented and is increased in the work chamber  48 . This takes place as long as the pressure difference between the two work chambers  48  and  32  is great enough to overcome the adjustable detent force of the locking device  54 , which in the exemplary embodiment of  FIG. 4  is embodied by a prestressed detent spring in the form of a snap ball  94 . However, the locking device  54  can equally well be embodied by a leaf spring or other locking devices familiar to one skilled in the art. The contact pressure of the locking device can be varied via an adjusting mechanism  96 . 
   The differential pressure of the work chambers  48  and  32  brings about a resultant force on the flexible diaphragms  62  and  72 , so that the valve piston  90  connected to the diaphragms is moved counter to the force of the detent spring  94 , and the slide element  12  is displaced into the second end position of the apparatus  10 . 
   In this position, the outlet conduit  16  is now uncovered by the slide element  12  and made to communicate with the valve chamber  92 . The outlet conduit  18  is made to communicate with the venting conduit  20  via a corresponding conduit in the slide element  12 . This position of the valve piston  90  is maintained until the differential pressure of the two work chambers  32  and  48  again overcomes the detent force of the locking device  54 , and the valve piston  90  and thus also the slide element  12  have been switched back again. 
   The apparatus of the invention is not limited to use for alternating inflation and venting of air cushions in vehicle seats. 
   In principle, all intermittent or oscillating motions of pistons and other adjusting elements are conceivable as additional areas of use of the pneumatic open- and closed-loop control apparatus of the invention.