Patent Publication Number: US-2004052646-A1

Title: Method for adjusting flow rate exhausted into a vacuum generator and vacuum generator with adjustable flow rate

Description:
[0001] The present invention relates to a process for the adjustment of the flow rate drawn into a vacuum generator as well as a vacuum generator, in particular for the practice of the mentioned process.  
       [0002] Vacuum generators known until now comprise at least one nozzle and a mixture communicating respectively with a vacuum chamber, as well as a body serving for holding in position the nozzle and the mixer. The design in a single piece respectively of the nozzle and of the mixer permits obtaining for the nozzle-mixer pair a single characteristic of flow rate and of vacuum level. The modification of the characteristics of the generator in terms of flow rate requires modifying the nozzle and the mixer. As a result, there is the need to have a stock of nozzles and mixtures of various passage cross-sections. Moreover, the large number of pieces of the generator require relatively long assembly and adjustment times.  
       [0003] The object of the present invention is to provide a vacuum generator whose design permits easily and rapidly varying the drawn-in flow rate into the vacuum chamber of the generator, over a wide range, whilst reducing the number of pieces to be stored.  
       [0004] Another object of the present invention is to provide a vacuum generator whose design permits precise adjustment of the demand of the flow rate to be drawn into the vacuum chamber of the generator.  
       [0005] Another object of the present invention is to provide a process for adjusting the flow rate to be drawn into the vacuum chamber of a generator, this process being simple to practice whilst permitting precise adjustment of the flow rate over a wide range of flow rates.  
       [0006] To this end, the invention has for its object a process for the adjustment of the flow rate drawn into a vacuum generator, of the type comprising at least one nozzle and a compressed air mixer communicating with a vacuum chamber, characterized in that the nozzle and/or the mixer are formed by assembly along a joint plane of at least two elements, and in that the geometry of the compressed air nozzle and/or of the mixture is varied, if necessary, as a function of the choice of the flow rate to be drawn into the vacuum chamber, in the sense of an increase of the passage cross-section by insertion into said joint plane of at least one spacer.  
       [0007] Thanks to the possibility of inserting into the joint plane of the nozzle and/or the mixer at least one spacer, it is possible to modify easily, simply and rapidly the performance of the vacuum generator without increasing the number of pieces to be stored. It will be seen moreover that the nozzle of the generator can have a shape other than cylindrical, without impairing the performance of the generator.  
       [0008] The invention also has for its object a vacuum generator, this generator comprising at least one nozzle and a compressed air mixer communicating with a vacuum chamber, characterized in that the nozzle and/or the mixer are formed of at least two elements assembled on a joint plane to permit the insertion, if desired, into said joint plane, of at least one spacer, this spacer permitting a modification of the passage cross-section of the nozzle and/or the mixer as a function of the choice of the flow rate to be drawn into the vacuum chamber.  
       [0009] The modular and adjustable design of this vacuum generator, in which the insertion of a spacer can be carried out in an easy manner, permits obtaining a vacuum chamber in which the drawn-in flow rate can be adjusted precisely within a wide range of flow rates. 
     
    
    
     [0010] The invention will be better understood from a reading of the following description of embodiments, with reference to the accompanying drawings, in which:  
     [0011]FIG. 1 is a longitudinal cross-sectional view of a vacuum generator according to the invention, without the interposition of a spacer in the joint plane;  
     [0012]FIG. 2 is a longitudinal cross-sectional view of a vacuum generator according to the invention, with the interposition of several spacers into the joint plane;  
     [0013]FIG. 3 is a perspective view of a constituent element of the vacuum generator;  
     [0014]FIG. 4 is a top plan view of a spacer present in the form of a perforated plate and  
     [0015]FIG. 5 is a perspective view of a vacuum generator in the assembled condition of its constituent elements, a spacer having been inserted in the joint plane. 
    
    
     [0016] According to the invention, the vacuum generator, indicated generally by reference  1 , comprises at least one nozzle  2  and a compressed air mixer  3  communicating respectively with a vacuum chamber  4 . In general, a supply chamber for compressed air for the nozzle  2  is positioned upstream of the nozzle whilst an exhaust chamber is provided downstream of the mixer  3 .  
     [0017] As shown in FIGS.  1  to  3 , the nozzle  2  and the mixer  3  are formed by at least two elements  7 A,  7 B assembleable along a joint plane  9  to permit the possible insertion into the joint plane  9  of at least one spacer  8 . This spacer  8  permits a modification of the passage cross-section of the nozzle  2  and/or of the mixer  3  as a function of the choice of the flow rate to be drawn into the vacuum chamber  4 . Generally, the spacer  8  has an internal profile similar to that of the nozzle  2  and/or of the mixer  3 . Preferably, the internal profile of the spacer  8  is defined to permit a simultaneous and corresponding variation of the cross-section of passage of the nozzle  2  and of the mixer  3  whilst maintaining a constant ratio between the passage cross-sections of the nozzle  2  and the mixer  3 . Thus, the ratio between the passage cross-sections of the nozzle  2  and the mixer  3  defines the level of vacuum. This level must preferably be maintained constant. Conversely, variation of the cross-sections of passage of the nozzle  2  and the mixer  3  permits increasing or reducing the flow rate to be drawn into the vacuum chamber  4 . As a result, during the design of a vacuum generator, the ratio of the cross-sections of the nozzle  2  and mixer  3  is selected to define a level of vacuum, and then the passage cross-section of the nozzle  2  and of the mixer  3  is changed correspondingly to obtain for this predetermined constant vacuum level an adjustment of the flow rate drawn into the vacuum chamber  4  as a function of the selected passage cross-sections.  
     [0018] Although the spacers  8  can have a large number of shapes, in the illustrated examples, these spacers  8  have the shape of profiled plates. In practice, these plates comprise perforations or transverse openings corresponding at least to the profile of the nozzle  2  and of the mixer  3 .  
     [0019] Preferably, each constituent element  7 A,  7 B of the generator is assembleable along a joint plane  9  formed each time of a monobloc assembly comprising at least one nozzle portion  2  and one mixer portion  3 . This design of each constituent element permits reducing the assembly and adjustment time. Thus, in the illustrated examples, both the spacers  8  and the end elements of the generator called basic constituent elements  7 A,  7 B of the generator fulfill the definition above.  
     [0020] So as further to simplify the design of the vacuum generator  1 , each constituent element  7 A,  7 B of the generator  1 , and assembleable along a joint plane  9 , comprises, upstream of the nozzle  2 , at least one portion of a compressed air supply chamber  5  for the nozzle  2  and, downstream of the mixer  3 , at least one portion of an exhaust chamber  6 . It is to be noted that, above, by constituent element is meant each element entering into the construction of the generator  1 .  
     [0021] In an embodiment like that shown in the figures, the vacuum generator  1  is constituted by two basic elements  7 A,  7 B assembleable along a joint plane  9  into which can be inserted at least one spacer  8 , each basic element  7 A,  7 B having the shape of a half-shell, as shown in FIG. 3. The half-shells in the assembled condition thus constitute a generator  1  which corresponds to the smallest cross-section of passage of the nozzle  2  and of the mixer  3  for a predetermined level of vacuum. To permit a variation of the flow rate to be drawn into the vacuum chamber, it suffices simply to introduce, into the joint plane  9  of the basic constituent elements, one or several spacers  8 .  
     [0022] It is to be noted that, in an equivalent manner, the constituent basic elements of the generator could be constituted by simple plates with smooth surfaces taking part in the production of the nozzle and/or mixer conduit provided in the spacer. The vacuum chamber constituted by simple stacking of elements, becomes very easy to produce and to assemble. Thus, each stacked element can be provided with guides and/or reference marks facilitating its positioning. Moreover, this design of the generator in the form of a stacked assembly permits obtaining a very adjustable generator.  
     [0023] Such a vacuum generator can be made from metallic pieces of pieces of synthetic material. In the case of insertion of a spacer into the joint plane  9  of the basic constituent elements of the generator, there can be provided the interposition of one or several spacers. The manufacturer can decide on a production of standard spacer plates such that the passage cross-section of the nozzle and/or of the mixture will vary as a function of the number of spacers inserted into said joint plane  9 . In another embodiment of the spacers, it can be decided to provide the spacers in the form of a custom cutout profile as a function of the desired thickness of the spacer.  
     [0024] The number of reference pieces to be stored can in certain cases be limited to two, one corresponding to the basic constituent element of the generator, the other to the spacer. This is possible only if the basic constituent elements of the generator assembleable along a joint plane, are two identical elements, the joint plane constituting a plane of symmetry of said elements.  
     [0025] The basic constituent elements of the generator comprise on their external surface the necessary inlets for the proper operation of the vacuum generator, such as a compressed air inlet opening into the supply chamber  5  for compressed air of the nozzle  2  and an air inlet opening into the vacuum chamber  4 . Similarly, this vacuum chamber could comprise an outlet communicating with the chamber  6  for evacuation of the vacuum chamber.  
     [0026] The holding in the assembled condition, of the assembly of constituent elements of the vacuum chamber, can be effected by any means such as the use of securement members of the screw type or the like, the use of adhesive means such as cement, etc.