Abstract:
The invention concerns a valve, particularly a solenoid valve, with an inlet connection and an outlet connection, having between them a shut-off device with a valve seat and a closure member. In such a valve, it is endeavoured to obtain a small output with a simple design. For this purpose, the closure member has a closing element and a tappet separate from the closing element, the closing element being held in a guiding arrangement.

Description:
FIELD OF THE INVENTION 
     The invention concerns a valve, particularly a solenoid valve, with an inlet connection and an outlet connection, having between them a shut-off device with a valve seat and a closure member. 
     BACKGROUND AND SUMMARY OF THE INVENTION 
     In the following, the invention is described on the basis of a valve, which is meant for a humidification system. Such a valve controls relatively small amounts of fluid, for example, one to five liters per minute. 
     The invention is based on the task of providing a valve for small output quantities, with a simple design. 
     In a valve as mentioned in the introduction, this task is solved in that the closure member has a closing element and a tappet separate from the closing element, the closing element being held in a guiding arrangement. 
     Thus, it is possible to select practically any desired element as closing element, that is, also a relatively small component, which is able to close a correspondingly small valve seat. Since it is no longer required to fix the closing element on the tappet, the material for the closing element can be selected relatively freely. A material may be chosen that is particularly well suited for the fluid to be dosed. As the closing element is separated from the tappet, the guiding arrangement is provided to ensure that the closing element always returns to its bearing on the valve seat. 
     In a preferred embodiment, it is provided that in an open position the closing element bears on an auxiliary valve seat, which is connected with a tank connection, the guiding arrangement being arranged between the valve seat and the auxiliary valve seat. When the valve is open, the passage between the outlet connection and the tank connection is blocked. The fluid to be controlled thus gets direct from the inlet connection to the outlet connection. When, however, the valve is closed, the outlet connection is connected with the tank connection, as the closing element has released the auxiliary valve seat. Thus, a dropping at the outlet of the valve is prevented, when the valve is closed. In this connection, the guiding arrangement is exactly in the right position, that is, it guides the closing element from the valve seat to the auxiliary valve seat and back. Additionally, it constitutes a flow resistance, which prevents a short-circuiting between the valve seat and the auxiliary valve seat, while the closing element is moving. 
     Preferably, the guiding arrangement has an opening, in which the closing element is arranged, the diameter of the opening being equal to a diameter defined by the closing element plus a predetermined amount of play. Thus, it is ensured that the closing element can move without, or at least with only little, friction in the guiding arrangement. In addition, the opening in the guiding arrangement is substantially closed during movement of the closing element, during which the closing element bears on neither the valve seat nor the auxiliary valve seat, so that no unimpeded flow can take place from the valve seat to the auxiliary valve seat. 
     Preferably, the guiding arrangement includes a guide element in the shape of a bowl, which opens in the direction of the valve seat. The guide element ensures that the fluid cannot either create a short-circuiting path between the valve seat and the auxiliary valve seat by simply flowing around the closing element and the guiding arrangement. On the contrary, the path between the valve seat and the auxiliary valve seat is extended because of the guide element. The fluid is redirected by the bowl-shaped embodiment, so that a substantial throttling resistance is generated during the opening or closing movement of the closing element. This throttling resistance is sufficient to prevent significant fluid losses. In this connection, it must be observed that the time in which the risk of short-circuiting exists, is relatively short. 
     Preferably, the valve seat is arranged at the top of a pipe element that extends in the direction of the guide element. Thus, the fluid leaving the valve seat is initially redirected, before it can continue its flow. In the open state of the valve, this redirecting causes no problems, as the flow passage is small and throttling resistances play no significant part. For the opening process, however, the throttling resistance is sufficiently increased. 
     It is particularly preferred that the guide element and the pipe element create a gap, which is uniformly wide in the radial direction. Thus, the fluid is specifically guided, without being whirled. At increasing radial distance from the valve seat, the gap provides an ever increasing flow cross section, so that the fluid can propagate. 
     Preferably, an expanding zone is fitted to the gap, which zone opens radially in relation to the valve seat. Such an embodiment reduces the flow resistance in the open state, however, during the opening movement permits only a small fluid quantity to migrate from the valve seat to the auxiliary valve seat. 
     Preferably, the guide element has, in the area of the expanding zone, a radially extending circumferential flange. This circumferential flange can be used for the safe fixing of the guiding arrangement in the valve housing. The circumferential flange provides surfaces, which are perpendicular to the force, with which the fluid flowing through the valve seat acts upon the guiding arrangement. 
     Preferably, the guiding arrangement is made of a plastic material, however, the present invention is not limited in this regard. Plastic materials are easily shaped and adapted to predetermined functions. Additionally, they are able to work together with the closing element at low friction, which is particularly advantageous, when the valve is used for controlling the water in a humidification system. 
     Preferably, the guiding arrangement is fixed in a housing by means of a retaining part. The retaining part can be adapted to the housing and the guiding arrangement can be adapted to the retaining part. This simplifies the design of the housing and the mounting. 
     Preferably, the valve has a nominal output in the range from 1 to 5 l/min. Such small outputs are preferably required in irrigation structures. 
     It is also preferred that the closing element is made as a ball with a diameter in the range from 1 to 4 mm however the invention is not limited in this regard. A ball has the advantage that it needs no definite orientation in the valve to bear sealingly on the valve seat and on the auxiliary valve seat. Due to the small size, it is not possible to fix the ball on the tappet. In the embodiment shown, however, this is not necessary. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the following, the invention is described on the basis of a preferred embodiment in connection with the drawings, showing: 
     FIG. 1 cross-sectional, front elevational view of a valve embodying the present invention. 
     FIG. 2 an enlarged partial view of the valve according to FIG.  1   
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     As shown in FIGS. 1 and 2, a valve  1  has a housing  2  with an inlet connection P and an outlet connection A. Between the inlet connection P and the outlet connection A, a shut-off device  3  is arranged, which has a valve seat  4  and a closure member  5 . The closure member  5  has a closing element  6  in the shape of a ball, the ball defining a diameter in the range from 1 to 4 mm, in the present case approximately 2 mm however, the present invention is not limited in this regard, as other diameters may also be used. In the closed position shown in FIG. 1, the closing element  6  is pressed against the valve seat  4  by means of a tappet  7 . Via an intermediary piece  8 , the tappet  7  is loaded by a pressure spring  9 , which is supported on an electromagnet  10  that is part of the drive of the tappet  7 . Further, the electromagnetic drive has an armature  11 , which is movable in a housing against the force of the spring  9 . Thus, the armature  11  divides the interior of the housing into a first and second chambers  13  and  14 , respectively. The chamber  14  not being visible, as the armature  11  bears on a bottom seal  15 . When the armature is lifted, the second chamber  14  is formed between the armature  11  and the bottom seal  15 . The electromagnet  10  can also be arranged elsewhere. For example, magnet coils may surround the housing  12 . In this case, the pressure spring  9  is supported on an and stop. 
     When the electromagnet  10  is acted upon with current, the armature  11  moves upwards toward the electromagnet, until its shoulder  16  comes to rest on a sealing ring  17 , which is arranged on the bottom side of the intermediary piece  8 . In this connection, the armature  11  first performs an idle stroke a. During this idle stroke a, the fluid, which fills the housing  12 , can flow through a gap  18 , which exists between the armature  11  and the intermediary piece  8 , from the first chamber  13  into the second chamber  14  to create a fluid cushion. In total, the armature  11  can travel a distance b, which is larger than the idle stroke a, before it comes to rest on the electromagnet  10 . The difference (b-a) is then an effective stroke. During this effective stroke, the sealing ring  17  bears on the shoulder  16  of the armature  11  and blocks the passage from the first chamber  13  to the second chamber  14 . This does not mean that the connection between the two chambers  13 ,  14  is completely blocked. Small leakages will remain through which fluid from the first chamber  13  can continue to flow into the second chamber  14 . However, this fluid flow is heavily throttled. 
     When the intermediary piece  8  has been lifted off from the tappet  7 , the pressure in the inlet connection P causes the closing element  6  to lift off from the valve seat  4 , as it is no longer supported against this pressure. Fluid can thus flow from the inlet connection P to the outlet connection A. 
     After a predetermined movement, which is shorter than the effective stroke b-a, the closing element comes to rest against an auxiliary valve seat  19 . In a manner not shown in detail, this auxiliary valve seat  19  is connected with a tank connection T. When the valve is closed, the fluid at the outlet connection A can flow off to the tank connection T, to prevent a continued dripping of fluid, when the valve is closed. 
     The closing process of the valve occurs in the opposite order. When the electromagnet  10  is de-energized, the armature  11  moves, via the biasing of the pressure spring  9 , back to rest against the bottom seal  15 . During the effective stroke, the sealing ring  17  again bears on the shoulder  16  of the armature  11 , so that the connection between the first and second chambers  13 ,  14  is blocked, not taking into account small leakages. The return movement of the armature  11  into the starting position shown in FIG. 1 thus occurs with a heavy damping and an accordingly reduced speed, so that the load on the closing element  6  is kept small. Additionally, with armature  11  in a retracted position, the pressure in the second chamber  14  acts upon the tappet  7 , which cooperates with the sealing ring  17 . Thus, the tappet  7  is maintained in its bearing on the closing element  6 . Also during the closing movement, the tappet  7  can hit the closing element  6  with a high speed. For reasons of completeness, it should also be mentioned that the gap  18  also continues in the area of the narrow passage, which is formed between the shoulder  16  and the lower end of the armature  11 . 
     Shown schematically are several seals  20 ,  21 , with which the housing  12  is sealed in relation to the housing  2 . Further, particularly the seal  21  is able to adopt certain tolerances. 
     To ensure that the closing element  6  always reaches the valve seat  4  or the auxiliary valve seat  19 , a guiding arrangement  22  is provided, which is shown in detail in FIG.  2 . The guiding arrangement  22  has an opening  23 , whose diameter is slightly larger the diameter defined by the closing element  6 . The diameter of the opening  23  corresponds to the diameter of the closing element  6  plus a predetermined play. When the closing element  6  is lifted off from the valve seat  4 , the direct path from the valve seat  4  to the auxiliary valve seat  19  is blocked, as the closing element  6  almost fills the opening  23 . Accordingly, only a small part of the fluid can flow off through the tank connection T during the movement of the closing element  6 . 
     The guiding arrangement  22 , which is arranged in a retaining part  24  and thus retained in the housing  2 , has a guide element  25  in the shape of a bowl, which opens in the direction of the valve seat  4 . The valve seat  4  is arranged at the top of a pipe element  26 , which has a conical outside. Accordingly, a gap  27  is formed between the pipe element  26  and the guide element  25 , the gap  27  having, over a certain distance in the radial direction, a substantially constant thickness. At the radial end, the gap  27  has an expansion zone  28 . Above the expansion zone  28 , the guide element  25  has a flange  29 , with which the guiding arrangement  22  is retained in the retaining part  24 . For this purpose, the flange  29  has retaining surfaces  30 ,  31 , which are directed perpendicularly to the pressure direction, which is defined by the fluid available the inlet connection P. 
     The guiding device  22  with the guide element forms a deflector, which improves the opening behaviour of the closing element  6 . The guide element  25  forms a separation between a high pressure area, which is arranged between the pipe element  26  and the guide element  25  an a low pressure area on the other side of the guide element  25 . Thus, the low pressure practically acts upon the upper side of the closing element  6  and causes a pressure drop. Thus, forces occur on the closing element  6 , which reliably ensure that the closing element  6  can change its position from the valve seat  4  to the auxiliary valve seat  19 . This compensates for the fact that only small forces can act upon the closing element  6  in the opening direction due to the small opening of the valve seat  4 . 
     Both the guiding device  22  and the retaining part  24  are made of a plastic material, the material of the guiding device  22  having in particular been chosen so that it cooperates with the material of the closing element  6  with only little friction. The use of a retaining part  24  makes the working of the housing  2  and the mounting relatively easy. 
     The closing element  6  is preferably a commercially available steel ball with a diameter of about 2 mm, however, the present invention is not limited in this regard. The pressure drop over the valve is relatively small, meaning that the forces acting upon the ball will be accordingly small. Instead of a steel ball, also a ball made of another material can, of course, be used, for example plastic or ceramics. 
     The guiding device  22  has several tasks. It guides the closing element  6  on its way from the valve seat  4  to the auxiliary valve seat  19  and back. In addition, it causes a relatively high throttling of a fluid flow from the valve seat  4  to the auxiliary valve seat  19  in the period, during which the closing element  6  bears on neither of the valve seats  4 ,  9 . The fluid leaving the valve seat  4  is first led through the gap  27  between the pipe element  26  and the guide element  25 , that is, it is prevented from directly trespassing to the auxiliary valve seat  19 . 
     The movement of the tappet  7  when closing the valve is heavily damped. The reason for this is, firstly, that the tappet  7  always bears on the closing element  6  and, secondly, that the return movement of the armature  11  can only take place at a heavily damped speed.