Abstract:
A pressure relief valve for flowing media has a closing element ( 6 ), whose closing force can be set with both the setting of the closing force and the brief release of the closing element ( 6 ) performed with a single setting element. Teeth ( 22, 23 ) are provided, by which the threaded sleeve ( 3 ) can be actuated such that it can perform a rotary movement and a lifting movement can be performed between the handwheel ( 2 ) and the threaded sleeve ( 3 ). The teeth are provided between a pin ( 21 ) of the handwheel ( 2 ) for setting the closing force and a threaded sleeve ( 3 ). The closing element ( 6 ) is connected to the handwheel ( 2 ) such that the closing element ( 6 ) follows the lifting movement of the handwheel ( 2 ).

Description:
FIELD OF THE INVENTION 
     The present invention pertains to a pressure relief valve with a closing element having a closing force that can be set and with a threaded sleeve that can be actuated by means of a handwheel for generating a variable closing force of the closing element as well as a valve shaft, which extends within the threaded sleeve toward the handwheel and is connected to the closing element. 
     BACKGROUND OF THE INVENTION 
     A pressure relief valve of this type has become known from DE 38 01 444 A1. The prior-art valve is used in the breathing gas line of an anesthesia apparatus or respirator to make possible the manual as well as the spontaneous respiration by the corresponding switching of a changeover switch. Thus, the valve is opened in the “manual respiration” mode by a possible overpressure in the breathing gas line against a preset closing force in order to release excess gas. The closing force is set by means of a handwheel and a valve spindle, and, depending on the position of the handwheel, a valve spring is compressed more or less strongly in order to thereby vary the opening pressure. In the “spontaneous respiration” mode, the closing element is released, by contrast, by the changeover switch, so that the closing force does not act any longer and the breathing gas can flow off without an appreciable expiration resistance. If the changeover switch is again shifted in the “manual respiration” direction, the original closing force again becomes established without corrections having to be made on the handwheel of the valve. 
     If complete pressure relief of the breathing gas line must be briefly performed during the manual respiration, this can be performed only if the changeover switch is shifted in the “spontaneous respiration” direction. However, it may now happen, especially when other settings also have to be performed on the anesthesia apparatus or respirator, that the operator forgets to shift the changeover switch to the “manual respiration” position. Delays may thus arise for the user in terms of the continuation of the manual respiration. 
     SUMMARY OF THE INVENTION 
     The basic object of the present invention is to improve a pressure relief valve of this type such that both the setting of the closing force and the brief release of the closing element can be performed with a single setting element without changing the set closing force in the process. 
     According to the invention, a pressure relief valve for flowing media is provided with a closing element having a closing force that can be set. A threaded sleeve is provided that can be actuated by a handwheel to generate a variable closing force of the closing element. A valve shaft extends within the threaded sleeve toward the handwheel and is connected to the closing element. The connecting element transmits the rotary movement of the handwheel to the threaded sleeve and makes possible a lifting movement. The connecting element is provided between the handwheel and the threaded sleeve. The connection of the valve shaft to the handwheel is designed such that the valve shaft follows the lifting movement of the handwheel. 
     The advantage of the present invention is essentially that the handwheel is connected to a threaded sleeve, which is used to set the closing force of the closing element, such that the rotary movement of the handwheel is transmitted to the threaded sleeve, on the one hand, and the handwheel can be actuated in relation to the threaded sleeve in such a way that it can perform a lifting movement, on the other hand. The handwheel is rigidly connected to the valve shaft accommodating the closing element, so that the closing element is also lifted off from the valve seat during the release of the handwheel. 
     The handwheel advantageously has a cylindrical pin, which is provided with external teeth and is directly connected to the valve shaft. The threaded sleeve, which is engaged by the pin, has, by contrast, internal teeth of a shape corresponding to the external teeth. Due to the meshing of the teeth, the rotary movement of the handwheel is transmitted to the threaded sleeve, on the one hand, while a relative movement is possible in the axial direction of the handwheel in relation to the threaded sleeve, on the other hand. 
     The threaded sleeve advantageously has three helically extending grooves located next to one another. The threaded sleeve is accommodated in a stationary cylinder, which has projections engaging the grooves. During its rotation, the threaded sleeve is displaced in the cylinder in the upward or downward direction. The threaded sleeve is in turn connected via a compression spring to the closing element, so that the closing force of the closing element is changed during the upward and downward movement of the threaded sleeve. 
     The grooves of the threaded sleeve advantageously have a different pitch in one section in order to make it possible to change the closing force of the closing element progressively. It may happen in the case of a linear adjustment of the closing force that a maximum closing force of, e.g., 70 mbar cannot be set with an acceptable scale in case of a preset angle of rotation of less than 360°. It should be taken into consideration in the case of such pressure relief valves that an accurate settability must be ensured in the range of up to about 40 mbar, whereas a coarse setting is sufficient at higher pressure values. Such a requirement can be met only if the closing force changes linearly up to about 40 mbar or 50 mbar and a progressive characteristic is selected at stronger closing forces. This characteristic can be set by selecting the pitch of the external thread on the threaded sleeve. 
     One exemplary embodiment of the present invention is shown in the figure and will be explained in greater detail below. The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawings and descriptive matter in which the preferred embodiment of the invention is illustrated. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a longitudinal sectional view of a pressure relief valve according to the present invention; 
         FIG. 2  is an exploded view of some components of the pressure relief valve according to  FIG. 1 ; 
         FIG. 3  is a perspective view of the cylinder; 
         FIG. 4  is a top view of the cylinder in direction of view A according to  FIG. 3 ; 
         FIG. 5  is a side view of the pressure relief valve with the partially cut-away handwheel; and 
         FIG. 6  is a side view according to  FIG. 5 , but for a position of the handwheel close to its end position for spontaneous respiration. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to the drawings in particular,  FIG. 1  shows the longitudinal section of a pressure relief valve  1  with a handwheel  2 , a threaded sleeve  3 , which is connected to the handwheel  2  in such a way that it can perform a lifting movement and a rotary movement, and grooves  4  located on the outside, as well as a valve shaft  5  rigidly connected to the handwheel for a valve disk  6  as a closing element guided therein in such a way that it can perform a lifting movement. The valve disk  6  has a guide bar  7  protruding into the valve shaft  5  with a bead  8 , wherein the bead  8  is fixed in the valve shaft  5  by means of a retaining ring  9 . A compression spring  11  is located between the valve disk  6  and a contact surface  10  at the threaded sleeve  3 , but only the turn of the compression spring  11  in the area of the contact surface  10  is shown for the sake of greater clarity. The threaded sleeve  3  is accommodated in a cylinder  12 , which has projections  13  distributed over the circumference on its inner side, the projections  13  engaging the grooves  4 . Only one of the projections  13  is shown in  FIG. 1  for the sake of greater clarity. 
     The pressure relief valve  1  has on its outer side a protective sleeve  14 , which is in turn connected to the handwheel  2  via a first snap-in connection  15  and to a support ring  17  via a second snap-in connection  16 , wherein the support ring  17  is axially displaceable on the outer side of the cylinder  12  and is supported against the cylinder  12  via a spring  18 . The threaded sleeve  14  is in contact on the underside with a guide ring  19 , which is fastened to the cylinder  2  via locking cams  20  (FIG.  2 ). 
       FIG. 2  illustrates in an exploded view the handwheel  2 , the protective sleeve  14  with the first snap-in connection  15 , the threaded sleeve  3  and the cylinder  12 . Identical components are designated with the same reference numbers as in FIG.  1 . The threaded sleeve  3  is illustrated in the perspective view for the sake of greater clarity. 
     The handwheel  2  has on its underside a pin  21  with external teeth  22 , which pin engages the threaded sleeve  3  with internal teeth  23  having a shape corresponding thereto. A rotary movement of the handwheel  2  is transmitted by means of the teeth  22 ,  23  to the threaded sleeve, and an axial displacement of the handwheel  2  in relation to the threaded sleeve  3  is also possible. The protective sleeve  14  has a scale  24  on its outside for various pressure values as well as an end position  25  for spontaneous respiration. 
     The grooves  4  on the threaded sleeve  3  comprise three individual grooves  41 ,  42 ,  43 , which are arranged offset by 120°, extend helically on the outside of the threaded sleeve  3  and have end sections  26  with an increased pitch. On its top side pointing toward the handwheel  2 , the cylinder  12  has a carrier  27 , which is located beneath the handwheel  2 . 
       FIG. 3  shows a perspective view of the cylinder  12  with the projections  13  located on the inside, the carrier  27  and the locking cams  20  for the guide ring  19  corresponding to FIG.  1 . 
       FIG. 4  shows a top view of the cylinder  12  in direction of view A according to  FIG. 3  with three projections  13 , which are offset by 120° in relation to one another and engage the grooves  41 ,  42 ,  43  of the threaded sleeve  3 , FIG.  2 . The cooperation between the grooves  41 ,  42 ,  43  and the projections  13  causes the threaded sleeve  3  to be axially displaced within the cylinder  12  upward or downward during its rotation. 
       FIG. 5  shows a side view of the pressure relief valve  1  with a partially cut-away handwheel  2 . The carrier  27  of the cylinder  12  extends here on an annular sliding surface  28 , which ends in an oblique plane  29 . The sliding surface  28  has notches  30 , which correspond to settings of the scale  24  and send a tactile feedback for settings, which equal an integer multiple of 10 mbar, via an elastic locking member  31 , which is located at the carrier  27 . 
     The scale  24  comprises a range of 5 mbar to 70 mbar, wherein the setting takes place in equidistant sections between integer multiples of 10 mbar up to about 50 mbar, whereas the end sections  26  of the grooves  41 ,  42 ,  43 ,  FIG. 2 , are used with a progressive adjustment of the compression spring  11  ( FIG. 1 ) between 50 mbar and 70 mbar. The progressive adjustment of the closing force in the area between 50 mbar and 70 mbar is necessary to still be able to set the maximum of 70 mbar with sufficient accuracy at a maximum angle of rotation of less than 360°. A compromise must be found here between the most accurate possible setting of the opening pressure up to about 50 mbar with a sufficiently large setting angle and a maximum opening pressure of 70 mbar, which can be set with greater tolerance, within a maximum adjustment angle of less than 360° for the handwheel. 
       FIG. 6  illustrates a side view of the pressure relief valve  1 , in which the handwheel  2  is cut up in the area of the oblique plane  29  compared with FIG.  5 . The oblique plane  29  becomes active when the handwheel  2  is rotated below a setting of 5 mbar of the scale  24  in the direction of the end position  25  for spontaneous respiration. The handwheel  2  is now raised by ΔH together with the protective sleeve  14  by the carrier  27  and the locking member  31 , and the locking member  31  snaps into the recess  32  in the end position  25  and blocks the handwheel  2  in the end position  25 . 
     The pressure relief valve  1  according to the present invention operates as follows: 
     Depending on the rotary movement of the handwheel  2  ( FIG. 1 ) the threaded sleeve  3  is moved upward or downward, and the pretension of the compression spring  11  which is in contact with the valve disk  6  changes in the process. The valve disk  6  now lies on a valve seat of a breathing gas line, where the valve seat is not shown specifically and the breathing gas line is not shown. Depending on the pretension of the compression spring  11 , different pressure values will be obtained corresponding to the scale  24 , at which pressure values the valve disk  6  is lifted off from the valve seat, i.e., at which the pressure relief valve  1  opens and excess breathing gas can escape. Regardless of the angular position of the handwheel  2  within the scale  24 , the pressure relief valve  1  can be opened at any time without the setting performed previously having to be changed. The handwheel  2  is pulled for this purpose upward along the arrow  33 , while the valve shaft  5  firmly connected to the handwheel  2 , and the guide bar  7  with the valve disk  6 , follow the movement of the of the handwheel  2 . As can be determined from  FIG. 2 , the pin  21  with the external teeth  22  slides within the internal teeth  23  of the threaded sleeve  3  during the pulling movement of the handwheel  2 . The spring  18  ( FIG. 1 ) is compressed during the pulling movement of the handwheel  2 , and it exerts a restoring force on the handwheel  2  via the support ring  17  and the protective sleeve  14 . 
     As can be determined from  FIG. 6 , the open position of the pressure relief valve  1  is also reached when the handwheel  2  is rotated from the scale  24  in the direction of the end position  25 . The locking member  31  now slides along the oblique plane  29  up to the recess  32 , as a result of which the handwheel is raised by ΔH together with the protective sleeve  14 . 
     While a specific embodiment of the invention has been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles.