Abstract:
A valve and trigger cyclically connect a vacuum and a blower to a filter. The valve box has three openings, the first connectable to the vacuum, the second connectable to the blower and the third connectable to the filter. A gate inside the box, biased by the blower and the vacuum toward closing the first opening, is held against the bias by a trigger outside the box to close the second opening. The external trigger intervally operates to release the interior gate to close the first opening and open the second opening. The blower operates only if the trigger is operating. The gate is released once for approximately 1/12 of a cycle interval during each trigger operating interval. A plurality of valves can be combined in a system with one trigger for cyclically sequentially connecting a plurality of filters to the vacuum and the blower.

Description:
This application is a continuation of application Ser. No. 10/016,353, filed Dec. 10, 2001 now U.S. Pat. No. 6,830,599. 

   BACKGROUND OF THE INVENTION 
   This invention relates generally to vacuum type cleaning machines and more particularly concerns back-flow valves and valve triggers facilitating cyclical washing of the cleaning machine filters. 
   Back flow valves typically employ gates which are directly mechanically or electrically driven. Consequently, the speed of movement of the gate is governed throughout its range of motion. The result is a response time that is detrimental to the smooth operation of the machine, the filtering action being blocked for unnecessarily long intervals because of the slow response of the back-flow valve. Furthermore, these mechanical and electronic systems are extremely complex and expensive and available only on the most expensive cleaning machines. For lower priced equipment, down time for filter replacement or cleaning is required. 
   In one valve system disclosed in U.S. Pat. No. 4,618,352 to Nelson, cams within the system air ducts rotate in direct physical contact with their valve gates, holding the gates in horizontal planes until notches in the cams allow them to rotate into diagonal planes. This system has serious power and efficiency problems. First of all, the cams are disposed on a common shaft. The common shaft arrangement of the cams requires side-by-side alignment of the system ducts transverse to the common shaft. This adds to duct length and imposes location requirements which increase system losses and structural complexity. Second, the notches are angularly displaced on the cams to synchronize the operation of the gates. Since the gates are in direct contact with the cams, the notches must be relatively wide in order for the gates to open for a sufficient interval. This imposes limitations on the blower to vacuum time ratios which greatly reduce the efficiency of the system. Third, in the horizontal condition the gates completely seal the openings to the blower ducts. However, in the diagonal condition only the free ends of the gates engage the vacuum ducts, so that there is no seal and air loss occurs. Fourth, since the cam notches receive the gates, the cam diameters must be greater than the ducts the gates close. Consequently, for the gates and cams to maintain physical contact, the ducts must be slotted to receive the cams. Therefore, special housings are required to prevent further air losses in the system. Fifth, the cams are constantly driven so that the back-flow cycle occurs throughout the cleaning process, reducing the normal operating efficiency of the system. Sixth, because there is no seal during the vacuum process, the speed of operation of the gate is left essentially to an initial push by the blower and the force of gravity rather than taking advantage of the vacuum to help slam the gate home. Seventh, the blower and the vacuum share a common shaft, so the blower is operating unnecessarily throughout the vacuum process. The composite result of these individual problems is that the system is ineffective for cleaning at any appreciable distance from the machine. 
   It is, therefore, an object of this invention to provide a back-flow valve and valve trigger which facilitate cyclical washing of the cleaning machine filters. Another object of this invention is to provide a back-flow valve and valve trigger which have a rapid response time so as to limit the duration of the back flow interval. A further object of this invention is to provide a back-flow valve and valve trigger using a gate which is air-flow biased by both a blower and a vacuum source toward a back-flow condition. Yet another object of this invention is to provide a back-flow valve and valve trigger using a gate which is not mechanically controlled during its transition from normal operation to back-flow operation. It is also an object of this invention to provide a back-flow valve and valve trigger using a gate which is not electrically controlled during its transition from normal operation to a back-flow operation. Still another object of this invention is to provide a back-flow valve and valve trigger using a gate which is not governed during its transition from normal operation to back-flow operation. Another object of this invention is to provide a back-flow valve and valve trigger which do not unnecessarily increase the length of the internal duct system. Another object of this invention is to provide a back-flow valve and valve trigger which eliminate openings and gaps which would cause pressure losses in the system. Still another object of this invention is to provide a back-flow valve and valve trigger in which an external valve trigger controls an internal valve gate. Still another object of this invention is to provide a back-flow valve and valve trigger which provide a relatively short back-flow interval during each filter cycle. Another object of this invention is to provide a back-flow valve and valve trigger which require only intermittent use of the back-flow system during the normal vacuuming process. An additional object of this invention is to provide a back-flow valve and valve trigger which are relatively simple and inexpensive. And it is an object of this invention to provide a back-flow valve and valve trigger which require operation of the blower only during the back-flow process. 
   SUMMARY OF THE INVENTION 
   A valve and a valve trigger are provided which cyclically connect a vacuum and a blower to a filter. The valve has a box with three openings. The first opening is connectable to the vacuum. The second opening is connectable to the blower. The third opening is connectable to the filter. A gate within the box is adapted to be biased by the blower and the vacuum to close the first opening. The gate is held against the bias by the external trigger to close the second opening. The external trigger is intermittently operated and is adapted to intervally release the internal gate to the bias to close the first opening and open the second opening. The preferred gate is a flapper hinged for angular motion between the first and second openings. The preferred trigger is a rotating cam with a follower fixed to the flapper. The cam operation is controlled by a timer. As the cam perimeter remains engaged with the follower, the flapper is held against the bias to close the second opening. An irregularity in the perimeter of the cam intermittently disengages the cam from the follower and releases the flapper to the bias of the air flow, allowing the flapper to slam against and close the first opening and open the second opening. The blower is energized in response to the timer so that it operates only when the cam is rotating. 
   A plurality of valves can be combined with a single trigger in a system for cyclically connecting a plurality of filters to the vacuum and the blower. In the preferred system, a plurality of cam followers are equally angularly displaced along the perimeter of a circular cam. The cam irregularity is shaped to release each gate for approximately 1/12 rotation of the cam and intervally releases the gates to the bias to sequentially close their first openings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other objects and advantages of the invention will become apparent upon reading the following detailed description and upon reference to the drawings in which: 
       FIG. 1  is a mechanical schematic drawing of a three filter cleaning machine employing three back-flow valves and a single valve trigger; 
       FIG. 2  is a perspective assembly view of the back-flow valves and valve trigger of  FIG. 1 ; 
       FIG. 3  is a perspective view of the assembled back-flow valve and valve trigger of  FIG. 1 ; 
       FIG. 4  is a perspective assembly view of a preferred embodiment of the valves of  FIG. 1 ; 
       FIG. 5  is a top perspective view of the assembled valve of  FIG. 4 ; 
       FIG. 6  is a bottom perspective view of the assembled valve of  FIG. 4 ; and 
       FIG. 7  is an electrical schematic drawing of the machine of  FIG. 1 . 
   

   While the invention will be described in connection with a preferred embodiment, it will be understood that it is not intended to limit the invention to that embodiment. On the contrary, it is intended to cover all alternatives, modifications and equivalents as may be included within the spirit and scope of the invention as defined by the appended claims. 
   DETAILED DESCRIPTION 
   Turning first to  FIG. 1 , a three-filter cleaning machine employing three back-flow valves and a single valve trigger is illustrated. During normal operation, a vacuum source S connected through valve V 1 , V 2  or V 3  pulls air contaminated with undesirable particles into three filters F 1 , F 2  and F 3  which remove the undesirable particles. While most of the accumulated particles are discharged into a filter pan, some of the particles amass on and clog the filter walls, diminishing the efficiency of the system. For back-flow operation, a blower B is connected to push air through the valves V 1 , V 2  and V 3  to their respective filters F 1 , F 2  and F 3  to dislodge the clogging particles from the filter walls. Each of the valves V 1 , V 2  and V 3  has a gate G 1 , G 2  and G 3 , respectively, which seals off flow from the blower B into the valves V 1 , V 2  or V 3  and permits the vacuum source S to draw contaminated air into the filters F 1 , F 2  and F 3  during the normal vacuuming process. The gates G 1  and G 2  and G 3  are mechanically held in place against the bias created by the blower B and the vacuum source S during the normal vacuuming process by a trigger T. The trigger T cyclically sequentially releases the gates G 1 , G 2  and G 3  to the bias of the blower B and the vacuum source S to cause them to seal off the suction of the vacuum source S and allow air pushed by the blower B to blast into the filters F 1 , F 2  and F 3 . The trigger T is external to the valves V 1 , V 2  and V 3 . In switching to the back-flow process, the trigger T completely disengages mechanical connection to the gates G 1 , G 2  and G 3  so that the bias afforded by the blower B and vacuum source S causes the gates G 1 , G 2  and G 3  to rapidly slam from the vacuum to the back-flow condition. 
   Looking now at  FIGS. 2 and 3 , the valve deck  10  is illustrated in greater detail. Valves V 1 , V 2  and V 3  are mounted on a base  11 . For the three-filter machine illustrated, the base  11  has three passages  12 ,  13  and  14  which are equidistantly spaced from a center point  15  on axes  16 ,  17  and  18  and are equally angularly displaced from each other. The filters F 1 , F 2  and F 3  are mounted below the plate  11  and aligned with the passages  12 ,  13  and  14 , respectively, as best seen in  FIG. 1 . The valves V 1 , V 2  and V 3  are secured to the top face of the base  11  by mounting plates  21  which receive bolts  22  extending upwardly from the base  11 . 
   The valves V 1 , V 2  and V 3  are illustrated in greater detail in  FIGS. 4–6 . The mounting plates  21  have openings  23  which align with the passages  12 ,  13  and  14  through the base  11 . A hub  24  at the center of each opening  23  allows the filter F 1 , F 2  or F 3  to be engaged beneath its respective opening  23 . Each of the valves V 1 , V 2  and V 3  has sidewalls  25 ,  26 ,  27  and  28  and a cover  29  which, in cooperation with the mounting plate  21 , defines the valve box. Two of the walls  25  and  28  have ports  31  and  32 . Adapters  33  and  34 , respectively, are secured at the ports  31  and  32  to facilitate connection of system ducts, seen in  FIG. 1 , to the valve box. As shown, the ports  31  and  32  are in adjacent orthogonal sidewalls  25  and  28 . A clapper  35 , such as an approximately square sheet of metal stock, has circular disks  36  and  37  of compressible material attached to its opposite faces. The adapters  33  and  34  have circumferences within the valve boxes to provide a suitable sealing surface and the disks  36  and  37  are sized and textured to cooperate with the adapters  33  and  34  to seal the passages  31  and  32 . One edge of the clapper  35  abuts and is fixed to a shaft  38  which extends above and below the upper and lower edges of the clapper  35 . A brass bushing  42  is fitted into an aperture  41  in the corner of the cover  29  at the junction point of the sidewalls  25  and  28 . Another brass bushing  44  is fitted into another aperture  43  in the mounting plate  21  which is vertically aligned with the aperture  41  in the cover  29 . The upper and lower ends of the flapper shaft  38  are journaled for rotation in the bushings  42  and  44  so that the flapper  35  can rotate between a first position in which one of the disks  36  seals one of the ports  31  and a second position in which the other of the disks  37  seals the other of the ports  32 . The upper end  45  of the shaft  38  further extends through its bushing  42  upwardly beyond the top of the cover  29  for engagement with one end of a follower arm  46 . The arm  46  is secured proximate one of its ends to the top end of the shaft  45 . A threaded screw  47  through a split in the arm  46  tightens the aperture  48  into which the end  45  of the shaft is inserted. The arm  46  extends radially outwardly from the shaft  38  to a cam follower  51  which is journaled for rotation using a washer  52  on a post  53  extending upwardly from the arm  46 . The seams of the valve box are sealed with a suitable duct sealant to insure the pneumatic integrity of the valves V 1 , V 2  and V 3 . 
   Returning to  FIGS. 2 and 3 , a motor  54  is mounted beneath a motor mounting plate  55  with the shaft  56  of the motor  54  extending upwardly through the mounting plate  56 . The bottom face of the motor mounting plate  56  is fastened to the top faces of the valve covers  29  with the axis  57  of the motor shaft  56  in vertical alignment through the center point  15  of the symmetrical arrangement of valves V 1 , V 2  and V 3 . A circular cam  58  is concentrically mounted on the top of the motor shaft  56  by the cam hub  59 . The diameter of the cam  58  is such that its circumference engages the cam followers  51  to hold the flapper disks  36  against the valve ports  31 . This can be assured by adjustment of the angular position of the follower arms  46  in the gate shafts  38 . An irregularity  61  in the circumference of the cam  58  completely disengages the cam  58  from mechanical contact with the follower  51  so that, when the follower  51  is released, its corresponding flapper  35  is free to rotate on its shaft  38  until the other disk  37  on the flapper  35  seals the other port  32  of its respective valve V 1 , V 2  or V 3 . Looking at  FIGS. 1 ,  2  and  3 , a manifold  62  has outlets  63  connected by ducts  64  to their respective inlet ports  33  in the valves V 1 , V 2  and V 3 . The blower B is connected by a duct  65  to the inlet of the manifold  62 . Similarly, the vacuum source S is connected to the ports  32  of the valves V 1 , V 2  and V 3  by ducts  66 . 
   Looking at  FIGS. 1 and 7 , the operation of the machine can be understood. The cam drive motor  54  is controlled through a switch  67  and time delay circuit  68  which are part of the trigger T. The cam  58  is normally engaged with the cam followers  51  so as to hold the flappers  35  with their disks  36  sealing the blower inlet ports  31  into the valves V 1 , V 2  and V 3 . In this position, the suction of the vacuum source S and the pressure from the blower B, the former drawing against the vacuum side disks  37  and the latter pushing against the blower side disks  36 , biases the flappers  35  to rotate from the blower inlet ports  31  toward the vacuum outlet ports  32 . However, the flappers  35  are held against the bias by the mechanical engagement of the cam  58  with the followers  51 . As the cam motor  54  rotates the cam  58 , the irregularity  61  in the cam circumference sequentially releases the cam followers  51  completely from mechanical engagement so that the gates G 1 , G 2  and G 3  are free to rotate in response to the bias to open the blower inlet ports  31  and slam the vacuum outlet ports  32  closed. Thus, air is no longer drawn by the vacuum source S into the filter F 1 , F 2  or F 3  associated with the released gate G 1 , G 2  or G 3  in the forward flow direction  71  but air is blown into the filter F 1 , F 2  or F 3  in reverse-flow direction  72  to dislodge particles collected on the filter walls during the vacuuming process. The contour of the irregularity  61  of the cam  58  is selected so as to release each cam follower  51  from mechanical engagement for approximately 1/12 of a rotation of the cam  58 . Because of the rapid response of the mechanically released gates G 1 , G 2  and G 3 , each filter F 1 , F 2  and F 3  experiences back flow for only 1/12 of a cam rotation and the entire system is experiencing back flow for only ¼ of a cam rotation. Thus, even during the back flow process, the normal vacuum process continues at 100% effectiveness for ¾ of the cam rotation. Furthermore, the timer rheostat  68 A can be adjusted by the machine operator to cause its switch  68 A to operate at any desired interval, preferably in a range of from 1.5 to 30 minutes. When the switch  67  is closed, a first relay  81  is energized, closing its normally open contacts  81 A to energize the vacuum source S. The timer  68  is energized simultaneously through normally closed contacts  84 A. As long as the timer  68  is energized, it will cause its switch  68 B to operate at the intervals set by the timer rheostat  68 A. Assuming, for example, a selected interval of twenty minutes, the timer switch  6 B will close twenty minutes after the switch  67  is turned “ON” and every twenty minutes thereafter. This will energize a second relay  83  which closes two of its normally open contacts  83 A and  83 B to engage the blower B and the cam motor  54 , respectively, and third normally open contacts  83 C in the circuit of a third relay  84 . The third relay  84  controls the normally closed contacts  84 A which control the timer  68 . The energized cam motor  54  causes the cam  58  to rotate. A post  85 A fixed to and rotating with the cam  58  activates a proximity switch  85  in the circuit of the third relay  84 . The proximity switch is normally open. If the blower B and cam motor  54  are energized, the second relay contacts  83 C are closed. When the proximity switch  85  closes, the third relay  84  opens the contacts  84 A to de-energize the timer  68 , opening the timer switch  68 B and de-energizing the second relay  83  to shut off the blower B and cam motor  54  and reset the system which will repeat itself when the selected time interval of twenty minutes has elapsed. The proximity switch  85  is operated after one revolution of the cam  58 . Therefore, each of the filters F 1 , F 2  and F 3  will receive one blast of blower air every twenty minutes and the blower B and cam motor  54  are energized for only one rotation of the cam  58  every twenty minutes. If, for example, the cam motor  64  drives the cam  58  at one (1) rpm, the back-flow process is in operation for only 1/20 of the vacuuming process and each filter will sequentially receive one five second blast of blower air during the one minute back-flow interval. In this manner, the back-flow process can be used to eliminate down time to replace or clean filters without any significant reduction in the power and efficiency of the vacuum process, even while back-flow is occurring. While the invention has been described in relation to a three-valve system, any number of valves and filters can be used applying the principles of the invention. 
   Thus, it is apparent that there has been provided, in accordance with the invention, a back flow valve and valve trigger for a cleaning machine that fully satisfies the objects, aims and advantages set forth above. While the invention has been described in conjunction with a specific embodiment thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art and in light of the foregoing description. Accordingly, it is intended to embrace all such alternatives, modifications and variations as fall within the spirit of the appended claims.