Abstract:
A gas mask is provided for normal-pressure and overpressure operation with at least one breathing port, an expiration valve with a valve spring, an adjusting element affecting the prestress of the valve spring and a pushing element having a first switching position and a second switching position. The pushing element is designed to act on the adjusting element during a translatory motion from the first switching position into the second switching position. A change in the prestress of the valve spring can be brought about and a switchover from a “normal pressure” mode into an “overpressure” mode can thus be carried out.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of priority under 35 U.S.C. §119 of European Patent Application EP 10 154 805.5 filed Feb. 26, 2010 the entire contents of which are incorporated herein by reference. 
       FIELD OF THE INVENTION 
       [0002]    The present invention pertains to a gas mask for normal-pressure and overpressure operation. 
       BACKGROUND OF THE INVENTION 
       [0003]    Gas masks are used, for example, for fighting unintended fires that may cause damage and when handling hazardous substances and materials. Gas masks with the “normal pressure” and “overpressure” modes are known. 
         [0004]    The “normal pressure” mode is present, for example, when a breathing filter is connected to the gas mask. The pressure level in the interior of the gas mask corresponds now to the atmospheric ambient pressure. The “overpressure” mode is present, for example, when a demand oxygen system of a compressed air breathing apparatus is connected to the gas mask. The pressure level in the interior of the gas mask is now higher than that of the atmospheric ambient pressure. Toxic gases are thus effectively prevented from entering the mask. 
         [0005]    However, it is not necessary to generate an overpressure for each application. The air breathed in by the user of the mask directly is purified, for example, by a filter located at a breathing port in the “normal pressure” mode. The expiration valve is usually closed and opens only during the expiration phase of the mask user due to the expiration pressure developing in the mask. The pressure level within the mask corresponds to the level of the outside pressure in the “normal pressure” mode. 
         [0006]    The pressure level within the mask is shifted in the “overpressure” mode by a certain positive amount compared to the level of the outside atmospheric pressure, so that the internal pressure in the mask is above the respective atmospheric pressure during both inspiration and expiration. The expiration valve opens during the expiration phase here as well due to the expiration pressure generated in the mask. In addition, the expiration valve must close against the now existing pressure gradient. 
         [0007]    Thus, different pressures act on the expiration valve as a function of the mode of operation. The expiration valve must consequently be controlled corresponding to the respective mode of operation in case of a gas mask with the “normal pressure” and “overpressure” modes. 
         [0008]    IT 1 227 248 discloses a spring, which counteracts the opening of the outlet valve and which acts on a pin projecting towards the outside of the mask. The pin is arranged such that it is pressed to increase the pressure of the spring when the internal pressure of the mask is increased, for example, by connecting a compressed air breathing apparatus. 
         [0009]    A gas mask with two series-connected springs having different prestresses is known from EP 0 667 171 B1. The spring with the lower prestress is active when the mask is used in the filter operation, whereas the spring with the higher prestress is activated during use with a demand oxygen system, i.e., with overpressure in the mask. 
         [0010]    DE 10 2004 052 173 B3 shows a gas mask of the type mentioned, in which a prestress of a valve spring can be varied by means of an adjusting means, wherein said adjusting means is designed as an angle lever pivotable about an axis of rotation. 
       SUMMARY OF THE INVENTION 
       [0011]    The basic object of the present invention is to improve a gas mask with the “normal pressure” and “overpressure” modes such that a switchover between the modes is possible in a simple manner. This object is accomplished by a gas mask for normal-pressure operation and overpressure operation with the features according to the present invention. 
         [0012]    The object is accomplished by the gas mask according to the present invention having at least one breathing port, an expiration valve with a valve spring, an adjusting element affecting the prestress of the valve spring, and a pushing element with first and second switching positions. The pushing element is designed, furthermore, to act on the adjusting element during the translatory motion from the first switching position into the second switching position, so that a change in the prestress of the valve spring can be achieved and a switchover from the “normal pressure” mode to the “overpressure” mode can thus be carried out. 
         [0013]    A switchover from the “normal pressure” mode into the “overpressure” mode and vice versa can thus be carried out in a simple manner for the user. 
         [0014]    In a first advantageous embodiment of the gas mask according to the present invention, the adjusting element may be designed as a pivotable lever arm. The lever arm preferably has a transmission element, which is designed such that it is oblique to the plane of the pushing element in an upper position of the lever arm, wherein the pushing element can be moved over the slope of the transmission element and the transmission element is arranged at the lever arm such that the lever arm presses the valve spring during a motion of the pushing element. 
         [0015]    In another advantageous embodiment, the pushing element has on the sides at least one locking element each for locking the pushing element in the first switching position and in the second switching position. Thus, the respective mode can be set securely for the user on the gas mask, on the one hand, and the respective mode can be unambiguously identified, on the other hand. 
         [0016]    The pushing element is advantageously designed as an elastic double clasp with two locking elements each on the front surfaces, wherein a moving together of the two locking elements of one front surface brings about the moving apart of the locking elements of the other front surface. In the cooperation of this elastic double clasp with a cover with two front-side openings each, which surrounds the pushing element, the respective front-side locking elements pass through the respective opening of the cover in both the first switching position and the second switching position. The locking in the respective desired switching position takes place, by principle, automatically because of the spring action of the double clasp. Locking of the pushing element can thus be brought about in a simple manner in both the first switching position and the second switching position. 
         [0017]    For optimally guiding the pushing element from the first switching position into the second switching position and back, the locking elements have a grip area each. By means of the grip area, the pushing element can be released from the locking and displaced manually in a simple manner. 
         [0018]    By principle, opposite deflection of both locking elements is necessary for unlocking based on the redundant design of the locking elements in the double clasp. An accidental unlocking of the pushing element can thus be prevented from occurring in a simple manner in both the first switching position and the second switching position. 
         [0019]    In another embodiment, at least one locking element is designed as a visual indicator for recognizing a setting of the “normal pressure” and “overpressure” modes. The at least one locking element is preferably arranged at the mask body such that the position of the locking element is recognizable by the user of the mask by means of the mask visor. The particular set mode of the gas mask can thus be recognized by the user of the mask in a simple manner. 
         [0020]    As an alternative hereto, a signal transmitter for recognizing the first and second switching positions of the pushing element may be provided at the pushing element. Furthermore, a detection element may be provided, which is preferably designed as an induction proximity switch, a Reed switch or a Hall sensor. The detection element is preferably arranged in a mask body. The “normal pressure” and “overpressure” modes can be advantageously displayed optically in the mask visor. 
         [0021]    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 preferred embodiments of the invention are illustrated. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0022]    In the drawings: 
           [0023]      FIG. 1  is a schematic view of the gas mask in a first switching position of a pushing element; 
           [0024]      FIG. 2  is a schematic view of the pushing element in cooperation with an adjusting element in the first switching position shown in  FIG. 1 ; 
           [0025]      FIG. 3  is a schematic view of an embodiment of the pushing element; 
           [0026]      FIG. 4  is a schematic view of the gas mask in a second switching position of the pushing element; 
           [0027]      FIG. 5  is a schematic view of the pushing element in cooperation with the adjusting element in the second switching position shown in  FIG. 3 ; 
           [0028]      FIG. 6  is a schematic view of the gas mask in the embodiment with a signal transmitter in the first switching position; and 
           [0029]      FIG. 7  is a schematic view of the gas mask with a signal transmitter in a second switching position. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0030]    Referring to the drawings in particular,  FIG. 1  schematically shows a detail of the gas mask according to the present invention with a mask body  10  and a mask visor  12 . A breathing port  14  is provided on the mask body  10 . The breathing port  14  has an opening  15  for a connection of a demand oxygen system in the “overpressure” mode on its side in the design embodiment being shown. 
         [0031]    A filter is connected at a second port arranged laterally in the mask body in the design embodiment being shown. 
         [0032]    A pushing element  22  (shown in  FIG. 3 ) is surrounded by a cover  38 . The pushing element  22  may alternate by a translatory motion between a first switching position  24  and a second switching position  26 . An arrow  48  indicates the direction of motion between the first switching position  24  and the second switching position  26 . The pushing element  22  acts on an adjusting element  18  during the translatory motion. The adjusting element  18  is shown in  FIG. 2  and is designed as a pivotable lever arm  28 . Furthermore, a transmission element  30 , which is in an oblique position to the plane of the pushing element  22  in an upper position of the lever arm  28 , is formed at the pivotable lever arm  28 . Pushing element  22  acts on the slope of the transmission element  30  during a motion between the two switching positions  24  and  26 . The transmission element  30  is arranged at the lever arm  28  such that lever arm  28  presses a valve spring  20  during the motion of the pushing element  22 . 
         [0033]    In the embodiment shown in  FIG. 1 , the pushing element  22  is in the first switching position  24 . The valve spring  20  is in a relaxed state in the first switching position  24  and generates only a minimal prestress on the expiration valve  16 . The first switching position  24  corresponds to the “normal pressure” mode. 
         [0034]      FIG. 3  schematically shows a design of the pushing element  22 . The pushing element  22  is designed as an elastic double clasp  34 . The elastic double clasp  34  comprises two lateral webs, which are connected to one another via a connection web  36 . Connection web  36  is made elastic. The locking elements  32  are arranged at the respective ends of the lateral webs. Moving together of the two locking elements  32  on one side brings about the moving apart of the two locking elements  32  of the other side. 
         [0035]    Pushing element  22  is movably guided within cover  38 . Cover  38  has two side openings  40 . In the embodiment shown in  FIG. 1 , the side locking elements  32  pass through the openings  40  of the cover  38  and fix the pushing element  22  in the first switching position  24 . 
         [0036]    The locking elements  32  have, furthermore, a grip area  42 . Pushing element  22  can be released with the grip areas  42  from the locking by a motion of the locking elements  32  in the first switching position  24  and displaced manually in the direction of the second switching position  26 . Pushing element  22  can be moved under the cover  38  into the second switching position  26 . The locking elements  32  protrude through the openings  40  of the cover  38  in the second switching position and thus fix the pushing element  22  in the second switching position  26  (shown in  FIG. 4 ). 
         [0037]    The pushing element  22  is moved over the slope of the transmission element  30  during the displacement of the pushing element  22  from the first switching position  24  into the second switching position  26 , while the transmission element is rigidly coupled with the lever arm  28  and presses same onto the valve spring  20 . The opening pressure of the expiration valve  16  is increased due to the compression of the valve spring  20  and the greater prestress acting on the expiration valve  16 , which is associated therewith. The prestress of the valve spring  20  and hence the opening pressure of the expiration valve  16  can be affected by varying the slope of the transmission element  30  and the ratio of the length of the transmission element  30  to the length of lever arm  28 . 
         [0038]      FIG. 4  shows the pushing element  22  in the second switching position  26 . Valve spring  20  has the maximum prestress in switching position  26 . Lever arm  28  is located in the vicinity of the expiration valve  16  (shown in  FIG. 5 ). This second switching position  26  corresponds to the “overpressure” mode. 
         [0039]    The side locking elements  32  are designed in the first switching position  24  shown in  FIG. 1  such that they can be recognized by the user of the mask through the mask visor  12 . The locking elements  32  thus have a dual function in the first switching position  24 . On the one hand, they lock the pushing element  22  and are used, on the other hand, as visual indicators  44  for recognition of the first switching position  24  and hence the “normal pressure” mode by the mask user. 
         [0040]    The locking elements  32  of the first switching position  24  or the visual indicators  44  are outside the visual field of the mask user in the second switching position  26 . The mask user can thus advantageously recognize the setting of the gas mask according to the present invention in the “normal pressure” mode and in the “overpressure” mode in a simple manner. 
         [0041]    As an alternative hereto, the schematic views in  FIGS. 6 and 7  show an embodiment with a signal transmitter  46  provided at the pushing element  22 . Furthermore, a detection element  50  is provided, which is preferably arranged in the mask body  10 . 
         [0042]      FIG. 6  shows the pushing element  22  in the first switching position  24  with a relaxed valve spring  20 . Valve spring  20  has a minimal prestress, as a result of which a low opening pressure is necessary for opening the expiration valve  16 . Detection element  50  detects the position of the pushing element  22  by means of a signal of the signal transmitter  46  in this “normal pressure” mode. The detection element  50  is connected with a display element, which is arranged in the mask body  10  and which optically signals the “normal pressure” mode. The display element may be designed as an LED. The display may optically display the mode in the mask visor. 
         [0043]      FIG. 7  shows the pushing element  22  in the second switching position  26 . Valve spring  20  has a maximum prestress, as a result of which the opening pressure of the expiration valve  16  is increased. The position of the pushing element  22  is recognized by the detection element  50 , which in turn detects a signal of the signal transmitter  46  arranged at the pushing element  22 . The second switching position  26  of the pushing element  22  and hence the setting of the “overpressure” mode on the gas mask can thus be recognized by the detection element  50 . A display element in the mask body  10  (not shown), which display element is connected to the detection element  50 , signals the “overpressure” mode. 
         [0044]    Detection element  50  may be designed as an induction proximity switch or as a magnetic switch embodied as a Reed switch or Hall sensor. 
         [0045]    While the present invention was described with reference to the preferred exemplary embodiments, various changes and modifications are obvious to the person skilled in the art. All these changes and modifications should fall within the scope of protection of the claims given. 
         [0046]    While specific embodiments of the invention have been 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. 
       APPENDIX 
     List of Reference Numbers 
       [0047]      10  Mask body 
         [0048]      12  Mask visor 
         [0049]      14  Breathing port 
         [0050]      15  Opening 
         [0051]      16  Expiration valve 
         [0052]      18  Adjusting element 
         [0053]      20  Valve spring 
         [0054]      22  Pushing element 
         [0055]      24  First switching position 
         [0056]      26  Second switching position 
         [0057]      28  Lever arm 
         [0058]      30  Transmission element 
         [0059]      32  Locking element 
         [0060]      34  Double clasp 
         [0061]      36  Connection web 
         [0062]      38  Cover 
         [0063]      40  Openings 
         [0064]      42  Grip area 
         [0065]      44  Visual indicator 
         [0066]      46  Signal transmitter 
         [0067]      48  Pushing direction 
         [0068]      50  Detection element