Abstract:
In order to provide a device for producing a pulsating fluid stream, which is of simple construction and is easily producible and which enables a pulsating fluid stream to be produced at a comparatively high frequency, there is proposed a device for producing a pulsating fluid stream which comprises a fluid inlet, a fluid outlet and a blocking element that is arranged between the fluid inlet and the fluid outlet and is rotatable about a rotational axis, wherein the blocking element comprises a blocking member which cyclically closes and opens a fluid passage from the fluid inlet to the fluid outlet.

Description:
The present dislcosure relates to the subject matter disclosed in German Patent Application No. 101 51 864.1 of Oct. 24, 2001, the entire specification of which is incorporated herein by reference. 
     FIELD AND BACKGROUND OF THE INVENTION 
     The present invention relates to a device for producing a pulsating fluid stream, wherein the fluid stream may be a stream of liquid and/or a gas. 
     SUMMARY AND OBJECTS OF THE INVENTION 
     Such a pulsating fluid stream can be produced by means of a valve which is arranged in a pipeline through which the fluid will flow, and which alternately closes and opens a passage through the valve. 
     The object of the present invention is to provide a device for producing a pulsating fluid stream which is of simple construction and is easily manufacturable and which enables the production of a fluid stream that pulsates at a comparatively high frequency. 
     In accordance with the invention, this object is achieved by a device for producing a pulsating fluid stream which comprises a fluid inlet, a fluid outlet and a blocking element that is arranged between the fluid inlet and the fluid outlet and is rotatable about a rotational axis, wherein the blocking element comprises a blocking member which cyclically closes and opens a fluid passage from the fluid inlet to the fluid outlet. 
     In the device in accordance with the invention, the pulsating frequency of the resultant pulsating fluid stream corresponds to twice the rotational frequency of the blocking element. The pulsating frequency of the fluid stream can thus be adjusted in a simple manner by suitable choice of the rotational frequency of the blocking element. 
     In a preferred embodiment of the invention, provision is made for the blocking element to be in the form of a rotatably mounted shaft. 
     Furthermore, provision is preferably made for the blocking element to comprise a substantially cylindrical blocking member. 
     In order to enable the passage of the fluid from the fluid inlet to the fluid outlet when the device is in an open position, the blocking member is provided with at least one recess. 
     This recess may be in the form of a through passage opening through the blocking member which opens-out into the outer surface of the blocking element at two mutually separate locations. 
     In this case, provision is preferably made for the through passage opening to intersect the rotational axis of the blocking element. 
     If the blocking element is rotationally symmetrical, then the passage opening is preferably aligned radially relative to the axis of symmetry of the blocking element. 
     However, a blocking member which comprises at least one recess in the form of a depression in the outer surface of the blocking element has proved to be more expedient than a blocking member having a radial passage boring. In comparison with a blocking member having a radial passage boring, a blocking member incorporating such a depression enables the device to attain substantially faster opening and closing times for the same rotational speed of the blocking element. 
     It is particularly expedient, if the blocking member comprises at least two recesses in the form of depressions which are preferably arranged at mutually opposite sides of the blocking element. 
     In a preferred embodiment of the invention, the cross-section of the depression is substantially in the form of a segment of a circle, said depression preferably having a substantially semi-circular cross-section. 
     Furthermore, provision is preferably made for the recess not to intersect the rotational axis of the blocking element. In this way, there will remain in the vicinity of the rotational axis of the blocking element a web portion which blocks the fluid passage in the closed position of the device. 
     The geometry of the blocking member will be particularly expedient and the blocking member particularly easy to manufacture, if the depression comprises a boundary surface which is substantially in the form of a surface section of a cylinder. Such a depression can be made in a particularly simple manner by milling out the blocking member from a cylindrical blank. 
     In order to impede the passage of fluid from the fluid inlet to the fluid outlet to as little an extent as possible in the open position of the device, it is advantageous for the depression to extend substantially perpendicularly relative to a radial direction of the blocking element. 
     Furthermore, the depression preferably extends substantially perpendicularly relative to the rotational axis of the blocking element. 
     Furthermore, it is of advantage, if the rotational axis of the blocking element is aligned transversely, preferably substantially perpendicularly, relative to the mean direction of flow of the fluid through the device. 
     If the fluid inlet and the fluid outlet extend along a common axis, then the rotational axis of the blocking element is preferably aligned substantially perpendicularly relative to this common axis of the fluid inlet and the fluid outlet. 
     In practice, it has proved expedient if the blocking element is rotated at a rotational speed that preferably lies within the range of approximately 100 rpm to approximately 10,000 rpm, and preferably within the range of approximately 300 rpm to approximately 3,000 rpm. 
     In order to produce a fluid stream which is pulsated at as constant a frequency as possible, it is expedient if the device comprises a rotary drive for the blocking element, said drive having an adjustable rotational speed. 
     The rotary drive for the blocking element can, in particular, be a pneumatic, hydraulic or electrical rotary drive. 
     Claim  13  is directed toward a filter device which comprises a device for producing a pulsating fluid stream in accordance with the invention which is used for the purposes of cleaning, and in particular for back-washing, a filter. 
     When back-washing filter cloths, the device in accordance with the invention applies pressure surges to the surface of the filter cloth thereby loosening the particles that have been deposited on the filter cloth. At the same time, due to the flow rate of the back-washing medium flowing through the device as a result of the pulsating fluid stream, a current-flow is obtained from the clean side of the filter to the dirty side thereof. The particles loosened by the pressure peaks are rinsed out of the filter in this way. 
     Claim  14  is directed toward a cleaning device which comprises a unit for producing a pulsating jet of cleaning agent which, for its part, comprises a device for producing a pulsating fluid stream in accordance with the invention. 
     Dirt particles can be removed more effectively from a work piece requiring cleaning by the use of a pulsating jet of cleaning agent as compared with the use of a non-pulsating jet of cleaning agent. 
     In particular, such a pulsating jet of cleaning agent can be employed for washing down a work piece requiring cleaning in a flood injection washing process (wherein the work-pieces requiring cleaning are dipped into a bath of cleaning agent and simultaneously subjected to a jet of cleaning agent) or when blasting a work piece with compressed air. 
     The device in accordance with the invention is particularly suitable for producing a pulsating fluid stream for use in a high pressure spray cleaning device in which a jet of pulsating cleaning agent having peak pressures of approximately 10 bar is produced. 
     In particular, cuttings can be removed from the cavities in a work piece by means of such a pulsating jet of cleaning agent. 
     Further features and advantages of the invention form the subject matter of the following description and the graphic illustration of an exemplary embodiment. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a filter device incorporating a pulse valve for back-washing a filter; 
         FIG. 2  a schematic longitudinal section through the pulse valve along a rotational axis of a blocking element of the pulse valve, in a closed position of the pulse valve; 
         FIG. 3  a schematic cross-section through the pulse valve of  FIG. 2  along the line  3 — 3  in  FIG. 2 ; 
         FIG. 4  a schematic longitudinal section through the pulse valve according to  FIG. 2 , but in an open position of the pulse valve; 
         FIG. 5  a schematic cross-section through the pulse valve of  FIG. 4  along the line  5 — 5  in  FIG. 4 ; and 
         FIG. 6  a high pressure spray cleaning device incorporating a pulse valve. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     Similar or functionally equivalent elements are designated in all of the Figures by the same reference symbols. 
     A filter device that is illustrated schematically in  FIG. 1  and bears the general reference  100  comprises a filter  102  having a filter housing  104  which comprises a filter inlet  106  and a filter outlet  108 , wherein a supply pipeline  110 , through which the dirty liquid requiring cleaning can be pumped under adjustable pressure into a lower chamber forming the dirty side  112  of the filter  102 , is connected to the filter inlet  106 . The dirty side  112  is separated from the filtrate side  114  by a filter medium which, here, is formed by a candle filter  116  that is in the form of a candle shaped filter screen and is hung on the edge of a boring in a separating plate  118 . 
     When the filter is in operation, the liquid flows through the candle filter  116  from the outer side to the inner side thereof and, after passage through the interior of the candle filter  116 , it emerges as filtrate at the filtrate side  114  of the filter  102 ; from there, the filtrate is discharged through the filter outlet  108  and is supplied to a consumer via the blockable discharge pipeline  120 . There is a build-up of filtered impurities on the outer surface of the candle filter  116  as the duration of the filtering process increases. 
     In order to loosen these deposits from the filter walls and remove them from the dirty side  112  of the filter  102 , a pulse valve  70  is arranged in an outlet pipeline  122  which merges into the dirty side  112  of the filter  102  and leads to a collecting chamber  124 , said pipeline being blockable by means of a stop valve  125 . 
     With the aid of the pulse valve  70 , liquid can be transferred in the form of a pulsating stream having a certain, adjustable frequency from the interior of the filter  102  into the collecting chamber  124  by cyclically opening and closing the outlet pipeline  122 . 
     Thereafter, a first separation of the heavy impurities from the liquid can take place in the collecting chamber  124  by sedimentation at increased pressure. As an alternative thereto, sedimentation could also be effected by the provision of a dwell phase during the back-washing phase so that pre-deposition of the heavy components would then take place by sedimentation at the dirty side  112  of the filter  102 . 
     The effect of the pulse valve  70  can be increased still further by admitting compressed air into the dirty side  112  of the filter  102 . To this end, a suitable compressed gas from an accumulator  126  can be supplied, in the open-state of the stop valve  130 , through a supply pipeline  128  to the filtrate side  114  of the filter  102 . Hereby, either the filtrate contained in the filtrate side  114  will be forced to stream through the filter walls in a direction opposed to the direction of filtering or the outer wall of the candle filter  116  will be cleaned exclusively by the compressed gas from the accumulator  126 . In the case of such a back-washing process using a compressed gas, the supply pipeline  110  and the discharge pipeline  120  are closed and the stop valve  125  is opened. 
     The construction of the pulse valve  70  is illustrated in  FIGS. 2 to 5 . 
     As can be seen from  FIGS. 2 and 4 , the pulse valve  70  comprises a two-piece housing  71 A,  71 B, in which a shaft  72  serving as a blocking element is mounted by means of Permagleit bushings  73 A,  73 B such that it is rotatable about a rotational axis  132 . The shaft end  72 ′, which is illustrated at the right-hand side of  FIGS. 2 and 4 , lies freely in a drive coupling space  74  in the interior of the right-hand housing part  71 A and is connected there in rotary-coupled manner to the drive shaft of a rotary drive motor  76  flanged onto a housing flange  75 . 
     The rotary drive motor  76  may be a pneumatic or hydraulic rotary drive motor or an electric motor. 
     A respective packet  77 A,  77 B consisting of a plurality of polytetrafluorethylene thrust collars  78 A,  78 B adjoins the Permagleit bushings  73 A,  73 B at each end of the shaft, said packets being held in position through the intermediary of sealing rings  80 A,  80 B and by means of head plates  79 A,  79 B. 
     A ring  81  having a substantially cylindrical pulse valve inlet  82  and a substantially cylindrical pulse valve outlet  83  that is in alignment with the pulse valve inlet  82  is seated between the housing parts  71 A,  71 B, whereby the connectors of respective pipelines can be screwed into the pulse valve inlet  82  and the pulse valve outlet  83 . 
     The ring  81  is inserted between the housing parts  71 A,  71 B and is sealed by means of O-rings  85 , said parts being fixed together with the aid of not shown machine screws which are displaced relative to the pulse valve inlet  82  and the pulse valve outlet  83 . 
     A blocking member  134  of the shaft  72  rotates within the ring  81 , said member being of greater diameter than the adjacent portions of the shaft  72 . 
     The blocking member  134  has a cylindrical outer surface  136  which is coaxial with the rotational axis  132 . 
     Two diametrically opposite depressions  138  are formed in the outer surface  136  of the blocking element  134 , said depressions being bounded by a respective boundary surface  140  in the form of a surface section of a cylinder whose cylinder axis  142  extends perpendicularly relative to the rotational axis  132 , perpendicularly relative to the radial direction of the blocking member  134  and tangentially relative to the outer surface  136  of the blocking member  134 , and it merges into the outer surface  136  of the blocking member  134  along an edge  141  (see  FIG. 4 ). 
     The depressions  138  are formed in the blocking member  134  by milling out two segments in the form of cylindrical sections having mutually parallel axes  142  from the initially fully cylindrical blocking member  134 , whereby the cylinder radius is smaller than the radius of the blocking member  134  so that a web portion  144  remains between the depressions  134  [sic]. 
     In the closed position of the pulse valve  70  illustrated in  FIGS. 2 and 3 , the depressions  138  extend perpendicularly relative to the common axis  142  of the pulse valve inlet  82  and the pulse valve outlet  83  so that the passage from the pulse valve inlet  82  to the pulse valve outlet  83  is closed by the web portion  144  of the blocking member  134  remaining between the depressions  138 . 
     When the shaft  72  has rotated on from the closed position of the pulse valve  70  illustrated in  FIGS. 2 and 3  into the open position of the pulse valve  70  illustrated in  FIGS. 4 and 5 , the depressions  138  extend in parallel with the common axis  146  of the pulse valve inlet  82  and the pulse valve outlet  83 . In this position, the upper depression  138   a  and the lower depression  138   b  open-out into both the pulse valve inlet  82  and into the pulse valve outlet  83  so that, in this open position, a fluid can reach the pulse valve outlet  83  from the pulse valve inlet  82  via both the upper depression  138   a  and the lower depression  138   b.    
     In the angular positions of the shaft  72  which lie between the closed position of the pulse valve  70  illustrated in  FIGS. 2 and 3  and the open position of the pulse valve  70  illustrated in  FIGS. 4 and 5 , the passage between the pulse valve inlet  82  and the pulse valve outlet  83  is only partially opened or closed. 
     Thus, by rotating the shaft  72 , the pulse valve  70  is transferred cyclically from the closed state into the open state and then back again into the open state so that a pulsating fluid stream is produced through the pulse valve  70  by means of the pulse valve  70 . 
     Due to the intermittent opening of the pulse valve  70 , the discharge from the filter  102  is effected in batch-like manner. Due to the pressure peaks applied to the dirty side  112  of the filter  102  which are produced by the closing of the pulse valve  70 , the deposits on the filter wall of the candle filter  116  are loosened and then washed away through the outlet pipeline  122 . 
     A further type of application for the pulse valve  70  is illustrated in  FIG. 6 . 
       FIG. 6  shows a schematic illustration of a high pressure spray-cleaning device  150  which comprises a cleaning agent reservoir  152  from which a liquid cleaning agent is supplied through a supply pipeline  154  to a high pressure nozzle  158  via a high-pressure pump  156  and a pulse valve  70  of the type described hereinabove. 
     A pulsating jet of cleaning agent  160 , which is used to remove dirt particles from a work piece  162  requiring cleaning, is produced at the high pressure nozzle  158  by means of the pulse valve  70 . 
     Particularly effective removal of dirt particles from the work piece  162  is obtained as a result of the pulsation of the jet of cleaning agent  160 .