Abstract:
A shop vac includes a handle, a canister, a vacuum tube, and a pick-up device. The canister holds an enclosure that generates a negative pressure by forcing compressed, high velocity air through a orifice plug and out a muffler to create a vacuum in the enclosure. The vacuum in the enclosure is transferred to the vacuum tube and the pick-up device to pick up liquid or debris on a shop floor. The enclosure inside the canister includes a flow control valve such as a ball in cage device to prevent fluid from entering the enclosure. An evacuation spout is located at the bottom of the canister for draining the vacuum when the canister becomes full.

Description:
BACKGROUND 
       [0001]    Commercial shop vacuums, which are used in many automotive and industrial applications, are heavy duty vacuums that can be used to pick up materials that would not be suitable for ordinary house hold vacuums. For example, these “shop vacs” can pick up liquids, even viscous liquids, which make them particularly suitable for automotive repair and service facilities where oil and other fluids can be spilled on the floor. These shop vacs need to be light weight and easily maneuverable to clean up spills quickly and avoid dangers that can result from open puddles of fluid. 
         [0002]    One such shop vac is disclosed in U.S. Pat. No. 6,826,799 to Smith, entitled COMPRESSED AIR VACUUM CLEANERS, the contents of which are incorporated herein by reference. Smith teaches a compressed air vacuum that attaches to an air hose and forces air down the handle. The air is then is forced through a venturi nozzle, which causes a negative pressure to occur. It has a baffle deflection piece that stops the liquid and debris from coming up into the venturi nozzle, thus allowing the debris and liquid material to be dropped back into the canister of the vacuum. The handle, venturi nozzle, and baffle are all one piece. The canister with the pick-up tube for sucking is a separate piece and then they snap together. The canister is removable from the handle piece for easy clean up. 
         [0003]    While the above-mentioned vacuum is satisfactory for picking up light debris, it has a difficult time picking up larger items and heavier fluids. Thus, an improved compressed gas actuated shop vac is needed for today&#39;s modern automotive and industrial applications. 
       SUMMARY OF THE INVENTION 
       [0004]    The present invention is a hand held shop vac that includes a handle, a canister, a vacuum tube, and a pick-up device. The canister holds an enclosure that generates a negative pressure by forcing compressed, high velocity air through a orifice plug and out a muffler to create a vacuum in the enclosure. The vacuum in the enclosure is transferred to the vacuum tube and the pick-up device to pick up liquid or debris on a shop floor. The enclosure inside the canister includes a flow control valve such as a ball in cage device to prevent fluid from entering the enclosure. An evacuation spout is located at the bottom of the canister for draining the vacuum when the canister becomes full. 
         [0005]    Lab testing demonstrates that the high speed air stream exiting the nozzle acts to entrain air by the action of the pressure differential caused by the stream of high velocity air as it moves from the supply nozzle tip across the gap between the nozzle and the orifice plug opening. The high speed air also acts to “seal” the narrow orifice plug; thus preventing the vacuum chamber pressure from equalizing with atmospheric pressure through the muffler. The two primary factors related to vacuum generation relate directly to the orifice plug diameter and the air velocity. There is a definite increase in vacuum as the orifice plug diameter is decreased for the same air velocity. It should be noted that noise levels increase as the orifice plug opening narrows and/or the air velocity increases. However, exhaust air muffling may act to decrease the effectiveness of the vacuum generation. 
         [0006]    The pick-up device of the present invention preferably comprises a pair of metal plates that contain two plastic wipers that form a gap there between where the vacuum is transmitted. The wipers extend beyond the plates and provide tapered channels that transmit the fluid or debris and resists clogging. A center support is located adjacent the vacuum tube juncture to prevent flexing of the wipers that can cause vacuum degradation. 
         [0007]    These and other features of the present invention will best be understood with reference to the figures described below along with the detailed description of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]      FIG. 1  an elevated, perspective view, partially cut-away, of a first preferred embodiment of the present invention; 
           [0009]      FIG. 2  is an enlarged, elevated view of the pick-up device of the embodiment of  FIG. 1 ; 
           [0010]      FIG. 2A  is a section view of the wipers and plates that make up the front of the pick-up device; 
           [0011]      FIG. 3  is a cross-sectional view of the pick-up device of  FIG. 2  taken along lines  3 - 3 ; 
           [0012]      FIG. 4  is a sectional top view of the pick-up device of  FIG. 2 ; 
           [0013]      FIG. 5  is an enlarged, cross-sectional view in perspective of the wipers forming the tapered channels taken along line  5 - 5  of  FIG. 1 ; and 
           [0014]      FIG. 6  is a cross-sectional view of the enclosure of the canister showing the orifice plug and fluid control valve. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0015]      FIG. 1  illustrates a first preferred improved shop vac of the present invention, generally denoted  10 . The shop vac  10  comprises a handle  12  that includes at a top end an air fitting  13  that includes a jack  14  adapted to couple to an air supply hose (not shown) that delivers air under pressure as is found in most automotive facilities. The handle  12  is connected to a polyethylene plastic canister  16  having a cylindrical wall and upper and lower plates. Canister  16  is formed with cast-in threaded inserts, and upper and lower metal plates at each end bolt to the plastic canister via threaded inserts  61  (see  FIG. 6 ). The connection between the canister  16  and the handle  12  at the upper plate is sealed using a vegetable fiber gasket to prevent loss of pressure at the juncture. At the opposite end of the canister  16  protruding through the bottom plate is a vacuum tube  18  that connects to a pick-up device  20 , which also involves a gasket to prevent air leakage through this juncture. The canister  16  also includes a drain pipe  22  that can be used to drain the contents of the shop vac  10 . When the canister  16  is to be drained, the knob  21  moves an occlusion to open the passageway  29  that allows fluid or debris to empty through the drain pipe  22 . 
         [0016]      FIG. 6  illustrates the interior of the shop vac  10  at the juncture with the handle  12 . The handle  12  has an outer threading  25  that is used to connect the handle to a nozzle  24 . Nozzle  24 , which is preferably an ABS plastic, has internal threads that engage the outer threads  25  on handle  12  to form an airtight coupling of the handle  12  and nozzle  24 . The coupling of the handle  12  and the nozzle  24  includes a sealant to ensure that the connection is airtight and can withstand the vibration of the system while permitting the components to be replaced or repaired if needed. The nozzle  24  has a cylindrical collar  26  on an upper portion and a conical portion  28  that encloses a funnel-like narrowing  30  of an airway leading from the handle  12 . The funnel-like narrowing  30  leads to a cylindrical conduit  40  having a reduced air passage  32  that undergoes a first elbow  34  and a second elbow  36 , each of approximately ninety degrees (90°), so that the airflow through the handle  12  is transitioned smoothly through a one hundred eighty degree change of direction within the nozzle  24 . To combat the torque forces that are generated by the exiting air flow at the outlet  42 , the nozzle  24  includes a reinforcing rib  38  that is disposed between the collar  26  and the outlet  42  to strengthen the nozzle, particularly at the juncture between the collar  26  and the conduit  40 . As air is released through the outlet  42  of the nozzle  24 , the resultant torque force would tend to be concentrated at the location where the rib  38  is located. The rib  38  therefore prevents cracking, warping, vibration, or other unwanted effects at the nozzle due to the force of the air at the outlet  42 . In a preferred embodiment, the outlet  42  is further modified to add an additional area to boost air velocity and control volume of air delivered to orifice. 
         [0017]    The outlet  42  of the nozzle  24  is opposed a orifice plug  44 . The orifice plug  44  has a threaded outer surface  48  that engages a threaded inner surface  50  of a support tube  52  mounted on the canister  16 . The support tube  52  can be locked on the canister  16  via a weld to a locking plate  51  at the upper surface  56  of the canister. Locking plate  51  is attached to the upper surface  56  of the canister  16  using four 10-32 screws. The orifice plug  44  has a cylindrical passage  54  axially aligned with the support tube  52 , which extends through the upper surface  56  of the canister  16 . A muffler  58  is threadedly engaged with the opposite end of the support tube  52  and extends out of the upper surface  56  of the canister  16 . The upper surface  56  of the canister can be secured to the body of the canister by rivets or fasteners  61 . 
         [0018]    The pressurized air supply is connected to the handle such that high pressure air enters the handle  12  and is forced into the nozzle  24  and through the funnel-like narrowing  30 . Here, the air accelerates due to the reduction of cross sectional area through the reduced air passage  32  and out outlet  42 . This accelerated high velocity air moves out the outlet  42  and through the adjacent orifice plug&#39;s passage  54 , which has a diameter of approximately 0.375-0.500 inches and is spaced from the outlet  42  at a gap “D” of between 0.25-0.5 inches. The air can be accelerated further by reducing the outlet area slightly using a narrowing at the exit. This passage of the high pressure air creates a low pressure region (the “venturi effect”) in the volume defined by compartment  60  defined by enclosure  62  secured to the upper surface  56  about the nozzle  24 , handle  12 , orifice plug  44 , and muffler  58 . For typical shop compressed air supplies, the pressure is approximately ninety (90) psi directed through nozzle  24 . The area of the outlet  42  is between 2-4 mm, although other dimensions are possible too due to the system supplying compressed air and its ability to supply the necessary volume given the opening size (which would tend to reduce the size of the outlet). The handle&#39;s internal passage has a cross sectional area of about 0.546 sq. in. based on an internal diameter of 0.834 inches. Using an average outlet diameter of 3 mm (˜0.011 in) yields a cross sectional area of approximately 0.0109 square inches, resulting in a reduction of approximately 50:1. The ratio of handle to reduced passage area is approximately 50:1, boosting the velocity of the air prior to passage through the orifice plug  44 . These conditions have been found to increase the vacuum in the enclosure  62  up to nine inches (9″) of Hg. 
         [0019]    The enclosure  62  has an opening  64  at the bottom that is connected to a positive ball-in-cage shut-off device  66  with a Viton® rubber or silicon seal  68  to withstand harsh chemicals. When a fluid level enters the cage  70  and reaches the ball  72 , the fluid lifts the ball  72  up until the vacuum in the enclosure  62  pulls the ball  72  against the seal  68  in the round opening  64 , and isolates tank portion  74  of the canister  16  from the enclosure&#39;s interior  60 . 
         [0020]      FIGS. 2 and 2A  illustrate the pick-up device  20 , which includes a neck  80  that connects to the vacuum tube  18  at flange  82 . The pick-up device  20  includes two metal plates  84   a,b  that are connected by a plurality of fasteners  87 . Holes and fasteners  87  allow for the pick-up device  20  to be assembled first and then connected to the vacuum tube  18 , and allows for quick replacement of any component of the pick-up device (plate, wiper, center support, etc.). Sandwiched between the two plates  84   a,b  are a pair of plastic flexible wipers  86  that protrude slightly below the plates  84   a,b  (see  FIG. 4 ). The flexible wipers  86  mate easily together using cooperating pins and pin holes that lock the wipers in the correct position for incorporation into the pick-up device. The wipers  86  have angular tips or projections  88  that cooperate to form a V-shaped opening  90  along the length of the pick-up device  20  while maintaining a smooth and even contact with the floor surface. Each wiper  86  is formed with intermittent, aligned, expanding tapered channels  92  that allow debris and liquid to enter the pick-up device through the channels  92  and into the vacuum tube  80 , and the tapering of the channels resists clogging at the ends of the channels  92 . Channel walls  96  on each wiper prevent the channels  92  from collapsing under the vacuum pressure and maintain open passages for the collection of the debris and fluids. In a preferred embodiment, the angular projections  88  have rounded sides  99  so that the vacuum&#39;s pick-up device can be tilted while maintaining a reliable contact with the floor surface. The angular projections  88  ensure a smooth and continuous contact with the floor surface so that a vacuum is applied to the channels  92 , such that the pick-up device can pick up liquid or debris. 
         [0021]    As shown in  FIG. 3 , a center support  102  is provided to prevent the middle portion of the wipers  86  from collapsing inward. That is, the vacuum pressure tends to warp or bend the wipers  86  inward toward the vacuum tube  18 , but the positioning of the center support  102  fortifies the position of the wipers and prevents unwanted flex. The center support  102  is disposed between the pick-up device&#39;s opening  104  to the vacuum tube  18  and forces the center of the wipers  86  away from the opening  104  to ensure no flexing at the center region. Also,  FIG. 4  illustrates (in shadow) an optional scraper  110  that can be fastened to the front surface of the pick-up device  20  to loosen debris or collect fluid or debris for vacuuming. In a preferred embodiment, the scraper plate is rigid and extends just below the protruding tips  88  of the wipers  86 . 
         [0022]    In operation, the adapter  13  is connected at jack  14  to a supply of high pressure air (not shown). The high pressure air is forced through the handle  12  and into the nozzle  24 , where it is routed toward the venturi nozzle  24 . The high pressure, high velocity air having been accelerated by the nozzle  24  enters the orifice plug and through the muffler  58 . The passage of the air out the outlet  42  and through the orifice plug  44  creates a low pressure condition in the compartment  60 . This continuous low pressure condition is communicated to the vacuum tube  18  and to the pick-up device  20 , where the vacuum is present between the wipers  86 . Fluid, dust, debris, and other materials are sucked through channels  92  in the wipers  86 , and through the pick-up device and the vacuum tube  18 . The debris, liquid, etc. collects in the canister  16  in a collection area  107  but cannot pass through the flow valve  70  due to the ball  72  protecting the entrance to the compartment  60 . When the canister is full, the air supply is disconnected and the drain pipe  22  is opened via knob  21  to allow the contents of the canister to flow through to a waste bin or the like. The knob can then be returned to the closed position and further vacuuming can commence. 
         [0023]    The foregoing descriptions and illustrations are intended to be exemplary and not limiting. That is, one of ordinary skill in the art would readily appreciate that modifications and substitutions are available without departing from the scope and spirit of the invention, and that the present invention is intended to include all such modifications and substitutions. Accordingly, the proper construction of the scope of the invention is the words of the appended claims, using their plain and ordinary meaning, in view of but not limited by the preceding descriptions and the illustrations included herewith.