Abstract:
An apparatus and method for performing high-speed interruption of a high-speed fluid stream of the type used for cutting and particularly suited to cutting operations in the food services industry. The water blocker includes a housing ( 110 ) having a motor cavity ( 112 ), a motor ( 140 ), and a projecting portion ( 162 ) that is adapted to receive a conduit ( 95 ) supplying the fluid stream. The motor is drivably connected to a wheel ( 180 ) having a plurality of blocker pins ( 190 ). The blocking pins are aligned to selectively intersect the high pressure fluid stream. A programmable computer ( 149 ) controls the motor.

Description:
FIELD OF THE INVENTION  
         [0001]    This invention relates generally to a product cutter utilizing a high pressure fluid stream and, more particularly, to methods and apparatus for selectively interrupting the flow of a stream of high pressure water used in cutting applications.  
         BACKGROUND OF THE INVENTION  
         [0002]    High-speed fluid jets have been used to cut food, paper, and other products for years. The advantages are numerous: there are no blades that present a safety concern and that need to be regularly sharpened or replaced, minimal dust or other airborne particulates are generated, and the cutting process can be quick, flexible, and clean. The cutting is accomplished with a thin, high velocity stream of water or other fluid. Pressurized water is ejected from a small orifice to create the stream or jet of liquid. When the jet impinges on the target product, a thin slice of material is removed, typically without any appreciable water being absorbed into the product.  
           [0003]    Specific manipulation and interruption of the high-speed water jet, frequently under precise computer control, accurately cuts shapes in the products. Many of the desired cutting operations require precise high-speed interruption of the water jet. Generally, the greater the detail of the desired cutting operation, the faster the interruption of the jet must be in order to attain such detail. The overall speed of a cutting operation is frequently limited by the rate at which the high-speed stream can be controllably interrupted. A higher rate of water stream interruption, therefore, may reduce the overall product processing time required.  
           [0004]    Various methods and apparatus have been taught to controllably interrupt a high-speed water jet. One such method of interruption is to use a linear actuator to insert an object between the high-speed water jet and the product. Typically, a pneumatic linear actuator forces a blocker pin into the path of the water jet to interrupt the flow of the cutting stream and a spring provides a retracting force for the plunger pin. Existing pneumatic blocker pin devices are capable of reaching closure times of 50-90 ms and thereby limit the speed at which products may be cut by the water jet.  
           [0005]    U.S. Pat. No. 4,693,153 (Wainwright et al.) discloses another water jet interruption technique. When interruption of the high-speed water jet is desired, a second high pressure fluid is directed at the object cutting jet so as to disperse the latter and impair its cutting properties. The device that controls the second fluid flow is similar to the plunger pin device. A solenoid device within the jet obstructer device controls the fluid flow from the jet obstructer device. An energized solenoid closes a plunger mechanism that is normally held in an open position by a spring. In the open position the mechanism provides high pressure fluid to interrupt the object-cutting water jet. Similar to the plunger pin device, this device also lacks the high-speed interruption capabilities necessary for cutting products as rapidly as may be desired.  
           [0006]    International Patent Application No. WO93/10950 discloses a valve for controlling a constantly running liquid cutting jet. A pneumatically powered rotary cylinder  2  is attached to one end of and elongate plate  1  to rotate the opposite end of the plate in and out of the path of flow of the liquid cutting jet. However, the opening and closing times for this rotary plate are only slightly better than that of existing plunger pin devices. Also, the cutting jet strikes one position on the plate resulting in frequent replacement of the plate.  
           [0007]    A pivoting pin interruption mechanism is taught in U.S. Pat. Nos. 5,931,178 and 5,927,320 to Pfarr et al., and owned by the assignee of the present application. Pfarr et al. discloses a water jet blocking device that utilizes a blocking pin having a first end attached to a rotary actuator and a second end that is disposed near a high-speed fluid jet. The actuator pivots the blocking pin about a center fulcrum, such that the second end of the blocking pin can be selectively moved to block the high-speed jet stream. The pivoting pin interruption mechanism overcomes many of the disadvantages of the prior art, permitting faster activation times and a durable apparatus. However, further improvements in activation time and durability remain desirable. Accordingly, the present invention provides significant advantages over previous devices or methods controllably block highspeed fluid jets.  
         SUMMARY OF THE INVENTION  
         [0008]    The present invention is directed to a water blocker for a high pressure water jet that provides very high-speed switching between the blocking mode and the unblocked mode. The invention is particularly suitable for water jet cutting applications in the food processing industry, although other applications are contemplated as well.  
           [0009]    In accordance with this invention, a method and apparatus for controlling the flow of a stream of high pressure fluid is disclosed. The apparatus includes a main housing adapted to receive a conduit providing a high-pressure fluid stream with an aperture aligned with the high pressure fluid stream. A motor attached to the housing is drivably attached to a blocker wheel assembly having a plurality of radially-projecting, spaced-apart blocking pins. The blocker wheel is disposed next to the housing such that rotation of the wheel will cause the blocking pins to move in an arc intersecting the high-speed fluid stream.  
           [0010]    In one embodiment of the present invention, the motor is controlled by a programmable computer.  
           [0011]    In an embodiment of the invention, the motor is disposed within a cavity in the housing assembly, thereby protecting the motor from the fluid stream. A source of pressurized cooling air is directed around the motor to provide convective cooling, and an air exit channel is provided in the housing for exhausting the high pressure cooling air.  
           [0012]    In an embodiment of the invention, a tubular cooling sleeve is disposed around the motor, wherein the cooling sleeve has a pair of outwardly projecting flanges that cooperate with the housing to form an annular channel around the motor through which the cooling air is directed.  
           [0013]    In an embodiment of the invention, the blocker wheel is drivably connected to the motor through a gear assembly that includes a master gear connected to the motor and a slave gear connected to the blocker wheel.  
           [0014]    In an embodiment of the invention, the blocker wheel includes at least 16 blocking pins. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]    The foregoing aspects and many of the attendant advantages of this invention will become more readily appreciated as the same become better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein:  
         [0016]    [0016]FIG. 1 is a side cross-sectional view of an embodiment of a water blocker according to the present invention.  
         [0017]    [0017]FIG. 2 is an exploded view of the water blocker shown in FIG. 1.  
         [0018]    [0018]FIG. 3 is sectional plan view of the water blocker shown in FIG. 1 through section  3 - 3 .  
         [0019]    [0019]FIG. 4 is a plan view of the blocker wheel shown in FIG. 1.  
         [0020]    [0020]FIG. 5 is a cross-sectional view of the blocker wheel for the water blocker shown in FIG. 1 through section  5 - 5 .  
         [0021]    [0021]FIG. 6 is a block diagram showing the water blocker of FIG. 1 connected to a programmable controller. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0022]    An embodiment of a water blocker, according to the present invention, is shown in cross-section in FIG. 1, and in an exploded view in FIG. 2. The water blocker  100  includes a main housing  110  having a generally cylindrical motor cavity  112  with an open top end  111  and a partially-closed bottom end  113 . A cover plate  130  is attached to the main housing  110 , over the motor cavity  112 . In the preferred embodiment, the cover plate  130  is removably attached to the main housing  110  with a plurality of screws  114 , and the cover plate  130  includes a groove  135  to accommodate a sealing device such as an O-ring  115 , such that the top end of the motor cavity  111  is substantially sealed when the cover plate  130  is installed. A center circular orifice  120  is provided at the bottom end  113  of the motor cavity  112 .  
         [0023]    A motor  140 , and preferably a stepper motor, is installed in the motor cavity  112 . The motor includes a downwardly disposed rotor output shaft  142 , that extends out of the motor cavity  112  through the circular orifice  120 . A tubular cooling sleeve  150  having a pair of radially projecting end flanges  152  is slidably disposed about, and in thermal contact with, the motor  140 . The flanges  152  have an outer diameter approximately equal to, or slightly less than, the inner diameter of the motor cavity  112 , thereby forming an annular channel between the cooling sleeve  150  and the inside wall of the motor cavity  112 . The cooling sleeve  150  is preferably made from a good thermal conductor, such as aluminum or brass.  
         [0024]    The main housing  110  includes an electrical service orifice  122  providing a channel into the motor cavity  112  generally above the motor  140 . Power is provided to the motor  140  through electrical wires  90  that enter the motor cavity  112  through the electrical service orifice  122 . An air inlet orifice  124  provides another channel into the motor cavity  112 . The air inlet orifice  124  is located adjacent the motor  140 , such that convective cooling air can be provided in the channel formed by the cooling sleeve  150 . An air outlet orifice  126  is located generally opposite the air inlet orifice  124 , and provides an outlet for the convective cooling air. In the preferred embodiment the inlet orifice  124  provides a passageway through the main housing  110  terminating with a threaded outlet portion  125  adapted to receive a screw-type fitting  97 . Although the disclosed embodiment depicts press-fit connections to the electrical service orifice  122  and the air inlet orifice  124 , and a screw-type fitting  97  for the air outlet orifice  126 , it will be readily apparent that any conventional type of fitting could be provided at these orifices without departing from the present invention.  
         [0025]    The main housing  110  includes a recessed portion  118  at its bottom end, generally below the motor cavity  112 . The main housing  110  is attached to a base plate  160 , disposed below the main housing  110  with a plurality of screws  116 . In the disclosed embodiment, a second O-ring  117  is provided in matching grooves  119 ,  169  in the main housing  110  and the base plate  160 , respectively, to provide a sealed interface between these components. The recessed portion  118  of the main housing  110  and the base plate  160  cooperatively form a gear cavity  164  that is sized to accommodate a master drive gear  170  attached to the rotor shaft  142 , and a slave or driven gear  172  that engages, and is driven by, the master drive gear  170 . The main housing  110  and the base plate  160  are preferable composed of a high density plastic, such as Delrin®.  
         [0026]    The base plate  160  includes a bearing recess  161  disposed directly beneath the rotor shaft  142 . A bearing  171  disposed in the bearing recess  161  engages the end of the rotor shaft  142 . A stepped bore  165  extends through the base plate  160  at a location below the center of the driven gear  172 . The driven gear  172  has a downwardly disposed drive shaft  174  that projects through the bore  165 . A bearing  173  is provided in the reduced diameter portion of the bore  165 , to slidably receive the drive shaft  174 . In the preferred embodiment, a radial lip seal  176  is also provided, beneath the bearing  173 .  
         [0027]    The base plate  160  fits generally beneath the main housing  110 , and includes a laterally projecting portion  162  that extends away from the main housing  110 . The projecting portion of the base plate  162  includes a threaded bore  163 , that is adapted to receive a high pressure fluid fitting located at the end of a conduit  95 . A small aperture  166  is provided in the bottom of the threaded bore  163 . The high pressure fluid conduit  95  directs a stream of fluid (not shown) that is directed approximately perpendicular to the base plate  160 , and towards the small aperture  166 . In the preferred embodiment, an annular disk-shaped carbide insert  167  is provided in the bottom of the threaded orifice  163  to protect the base plate  160  from wear due to the high-speed water stream.  
         [0028]    A blocker wheel  180  is attached to the driven gear drive shaft  174 . The blocker wheel  180  includes a mounting wheel  182  and a plurality of radially extending blocking pins  190 . In the disclosed embodiment the blocking pins  190  are generally rectangular, although any other appropriate shape is also contemplated by the present invention, including, for example, elongate, tapering pins and pins having a narrow proximal portion and a larger distal portion. As the blocker wheel  180  is rotatably driven by the driven gear  172 , the blocking pins  190  move along a circular path immediately below the base plate  160 , and with the blocking pins  190  very close to the bottom surface of the base plate  160 .  
         [0029]    As seen most clearly in FIG. 3, which shows a sectional plan view of the water blocker  100 , the blocking pins  190  are sized to pass directly beneath the small aperture  166 , intersecting and thereby blocking the stream of fluid from the high pressure fluid conduit  95 . The motor  140  selectively drives the master drive gear  170 , which in turn rotates the driven gear  172 , rotating the blocker wheel  180 . When the blocker wheel  180  is in the position shown in FIG. 3, the high-speed water jet which is directed towards the small orifice  166  is blocked. A very small rotation of the motor  140  will move the blocking pin  190  away from the small aperture  166 , thereby unblocking the high-speed water jet.  
         [0030]    A plan view of the blocker wheel  180  is shown in FIG. 4, and a side cross sectional view is shown in FIG. 5. In the disclosed embodiment, the mounting wheel  182  includes a cylindrical hub section  184  that is slidably inserted part way into the bore  165 , thereby helping to maintain the blocker wheel  180  in the correct position. A lower hub portion  183  is provided with a pair of aligned slots or holes  181 , that align with a transverse hole  177  in the slave gear drive shaft  174 . A pin  178  inserted through the holes  177 ,  181  attaches the blocker wheel  180  to the drive shaft  174 .  
         [0031]    The blocking pins  190  may be attached to the mounting wheel  182  in any conventional manner, including for example, by welding, riveting, threaded fasteners, bonding, and/or friction fitting. The material composition of the blocking pins  190  can be important in reducing maintenance time. The blocking pins  190  may be composed of titanium, carbide, or a memory alloy such as a nickel-titanium, all of which are highly resistant to erosion by the high pressure water jet. The blocking pins may alternatively be composed of a carbide core covered with a stainless steel or other alloy cover. Alternatively, a very hard substance, such as a natural or synthetic diamond, could be inlayed into the blocking pins  190  to serve as a wear surface. As used herein, the term blocking pin is intended to mean any member that can be inserted into the fluid stream to block the water jet, such as a rod, pad, tab, plate, and the like.  
         [0032]    Although the master drive gear  170  in the depicted embodiment is larger than the driven gear  172 , thereby requiring smaller rotor  142  rotations to produce a given blocker wheel  180  rotation, in some applications an opposite gearing may be desirable. Selection of appropriate gearing ratios is within the normal skills of the art. It is also contemplated that the blocker wheel  180  could alternatively be attached directly to the rotor shaft  142  of motor  140 , thereby obviating the need for the gears  170 ,  172 .  
         [0033]    In the preferred embodiment of the present invention, and best seen in the block diagram presented in FIG. 6, a programmable processing system  149 , such as a computer having a central processing unit, is used to control the motor  140 . The processing unit  149 , with predefined routines, controls an electric signal sent to the motor  140 , which moves the blocker wheel  180 , thereby controlling the blocking and unblocking of the high-speed water jet. Multiple water blockers can be used in conjunction with a computer controller for performing multiple tasks simultaneously. It is contemplated that either the water blocker  100  or the product being cut, or both, would be positionally controlled to produce the desired cutting function.  
         [0034]    It will be appreciated that the present invention allows the motor  140  to be operated in one direction, rather than in an oscillatory manner, which simplifies the motor construction and reduces the wear on the motor, improving system reliability.  
         [0035]    It will also be appreciated that the blocker wheel  180  includes a plurality of blocker pins  190  (16 pins are shown in the disclosed embodiment, although more or fewer blocker pins are contemplated by the present invention). The amount of wear to any one blocker pin is correspondingly reduced, requiring less frequent maintenance to the system. Moreover, the blocker wheel  180  is rotated only a short amount to switch between the blocking and the unblocking mode. For evenly-spaced blocking pins, the wheel must rotate only 180/n degrees on average to switch between blocking and unblocking mode, where “n” is the number of blocking pins on the blocking wheel  180 . The resulting operation of the motor  150  is therefore reduced, again improving system reliability, and permitting the blocking function to be very rapidly and controllably alternated.  
         [0036]    It will be appreciated that the preferred embodiment has been described herein to teach and illustrate the present invention and that many variations in the specific apparatus disclosed may be made and are contemplated by the present invention. The disclosed water blocker  100  is intended for uses requiring a very large number of rapid blocking/unblocking operations, and therefore producing a high demand on the motor  140 , which will result in significant heat generation by the motor  140 . The invention can also be used in lower-demand applications, however, wherein the demands on the motor are less severe. In such applications the convective air cooling system wherein cooling air is forced past the cooling sleeve  150  may not be required.  
         [0037]    Also, although the preferred embodiment utilizes a main housing that encloses the motor and received the high-speed water jet conduit, the water jet could alternatively be provided in alignment with the water jet blocker without being directly attached to the housing.  
         [0038]    While the preferred embodiment of the invention has been illustrated and described, it will be appreciated that various changes can be made therein without departing from the spirit and scope of the invention.