Patent Publication Number: US-6216736-B1

Title: Three-way antimix valve for a pourable food product packaging machine

Description:
FIELD OF THE INVENTION 
     The present invention relates to a three-way antimix valve for a pourable food product packaging machine. 
     BACKGROUND OF THE INVENTION 
     Machines for packaging pourable food products, such as fruit juice, wine, tomato sauce, pasteurized or long-storage (UHT) milk, etc., are known in which packages are formed from a continuous tube of packaging material defined by a longitudinally sealed strip. 
     The packaging material has a multilayer structure comprising a layer of paper material covered on both sides with layers of heat-seal material, e.g. polyethylene. In the case of aseptic packages for long-storage products such as UHT milk, the packaging material comprises a layer of barrier material defined, for example, by an aluminium film, which is superimposed on a layer of heat-seal plastic material and is in turn covered with another layer of heat-seal plastic material which eventually defines the inner face of the package contacting the food product. 
     For producing aseptic packages, the strip of packaging material is unwound off a reel and fed through a sterilizing unit in which it is sterilized, for example, by immersion in a bath of liquid sterilizing agent such as a concentrated solution of hydrogen peroxide and water. 
     More specifically, the sterilizing unit comprises a bath filled, in use, with the sterilizing agent in which the strip is fed continuously; and an aseptic chamber in which the strip of packaging material issuing from the sterilizing bath is treated to remove any residual sterilizing agent, e.g. by means of drying rollers and jets of high-temperature sterile air. 
     Before leaving the aseptic chamber, the strip is folded into a cylinder and sealed longitudinally to form in known manner a continuous, vertical, longitudinally sealed tube. The tube of packaging material, in fact, forms an extension of the aseptic chamber and is filled continuously with the pourable product and then fed to a forming and (transverse) sealing unit for forming individual packages and by which the tube is gripped between pairs of jaws to seal the tube transversely and form aseptic pillow packs. 
     The pillow packs are separated by cutting the sealed portions between the packs, and are then fed to a final folding station where they are folded mechanically into the finished form. 
     On known machines of the type briefly described above, the tube of packaging material is filled continuously by a conduit forming part of a circuit for supplying the pourable food product for packaging (hereinafter referred to simply as the “product circuit”). The product circuit must be sterilized with aseptic air before the start of each processing cycle, and flushed with a liquid solution at the end of the work cycle; for which purpose, the product circuit must therefore be connected selectively to a flush solution supply circuit and a sterile-air supply circuit by means of a switching assembly for preventing mixing of the various fluids and any traces of the flush solution in the product due to imperfect sealing. For safety reasons and to ensure sterility of the product circuit, the product circuit is normally connected to the switching assembly by means of a service conduit fitted with a two-way, aseptic, e.g. steam-barrier, on-off valve. 
     Substantially two switching assembly design solutions are known. 
     A first consists simply in using a movable fitting connected permanently to the service conduit of the product circuit and having connecting means for selective connection to the flush solution and sterile-air supply circuits. Though straightforward and cheap, this solution has the drawback of switching manually from one work stage to the other, by physically disconnecting and reconnecting the movable fitting to the relative circuits. 
     A second known solution consists in using three three-way valves, each of which has a pair of gates connected to a respective pair of circuits, and a third gate connected to a drain conduit for draining off any leakage from the valve and so preventing undesired leakage caused by pressure on the seals of the other valves. 
     Though enabling automatic switching, this second solution is expensive and involves considerable load losses. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a three-way antimix valve designed to eliminate the aforementioned drawbacks typically associated with known switching assemblies. 
     According to the present invention, there is provided a three-way antimix valve for a pourable food product packaging machine, the valve comprising a casing having a lateral wall defining a cavity having an axis of symmetry and communicating with a bottom drain opening; and a rotary shutter rotating about said axis and housed in said cavity with a respective lateral surface cooperating in fluidtight manner with said lateral wall of said casing; said casing having a first gate and a second gate, both formed in said lateral wall and spaced angularly by a first angle, and a third gate formed in said lateral wall in an intermediate position with respect to said first and second gate and spaced angularly with respect to each by a second angle equal to half said first angle; said rotary shutter having a first and a second opening, both formed in said lateral surface and spaced angularly by an angle equal to said second angle, and an inner passage connecting said first and second opening; said lateral wall of said casing having two inner recesses formed respectively between said first gate and said third gate and between said second gate and said third gate; said rotary shutter comprising at least three recesses, of which a first recess is formed between said first and second opening, a second recess is formed on the opposite side of said second opening with respect to said first recess and spaced angularly with respect to the first recess by an angle equal to said second angle, and a third recess is located on the opposite side of said first opening with respect to said first recess and spaced with respect to the first recess by an angle equal to said second angle; said recesses of said casing and said recesses of said rotary shutter communicating with said bottom drain opening of said casing; said valve comprising actuating means for moving said rotary shutter between a first work position in which said first and second opening of said rotary shutter communicate respectively with said first gate and said third gate of said casing, an intermediate position in which said first and second opening of said rotary shutter communicate with respective said recesses of said casing, and said first, second and third gate of said casing communicate with respective recesses of said rotary shutter, and a second work position in which said first and second opening of said rotary shutter communicate respectively with said third gate and said second gate of said casing. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     A preferred, embodiment of the present invention will be described purely by way of example with reference to the accompanying drawings, in which: 
     FIG. 1 shows a view in perspective of a valve in accordance with the present invention; 
     FIG. 2 shows a cross section of the FIG. 1 valve; 
     FIG. 3 shows a section along line III—III in FIG.  2 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     A preferred embodiment of the three way antimix valve in accordance with this invention is indicated in FIGS. 1-3 by the reference numeral  1 . The valve  1  substantially comprises an outer casing  2  of axis A; and a rotary shutter  3  housed in casing  2  and rotating about axis A. Casing  2  substantially comprises a lateral wall  4  having a conical inner surface  5  tapering downwards and defining a cavity  6  communicating externally via a bottom drain opening  7 . Casing  2  also comprises a top cover  8  fitted to a top annular flange  9  of lateral wall  4 . 
     Lateral wall  4  (FIG. 2) comprises three substantially circular through openings or gates  10 ,  11 ,  12 , at which originate respective connecting conduits  13 ,  14 ,  15 . More specifically, gates  10  and  11  are diametrically opposite and coaxial with each other (i.e. the respective axes form a center angle α of 180°) and are connected by respective connecting conduits  13 ,  14  to a sterile-air supply circuit (not shown) and to a liquid flush solution supply circuit (not shown); whereas the third gate  12  is located in an intermediate position with respect to gates  10 ,  11 , so as to form with each a center angle β of 90°, and is connected by respective connecting conduit  15  to a service conduit forming part of a circuit for the pourable food product for packaging, and which is fitted with a further on-off valve (not shown). 
     Lateral wall  4  also comprises two recesses  17 ,  18 , which are defined by concave, cylindrical-bottomed grooves with generating lines parallel to axis A, extend respectively between gates  10  and  12  and gates  11  and  12  along respective generating lines of inner surface  5  of lateral wall  4 , and communicate with bottom drain opening  7 . 
     Shutter  3  comprises a conical lateral surface  20  cooperating in fluidtight manner with inner surface  5  of lateral wall  4  of casing  2  by virtue of a spring  21 , as described in detail later on. Shutter  3  comprises a first opening  22  and a second opening  23 , both formed in lateral surface  20 , spaced 90° with respect to each other, and connected to each other by an elbow passage  24  (FIG. 2) defining a 90° curve. Shutter  3  also comprises four recesses  25 ,  26 ,  27 ,  28  equally spaced angularly and extending along respective generating lines of lateral surface  20 . Like recesses  17 ,  18 , recesses  25 ,  26 ,  27 ,  28  have cylindrical bottom surfaces with generating lines parallel to axis A, and communicate with bottom drain opening  7  of casing  2 . More specifically, recess  25  is located between openings  22  and  23 ; recesses  26  and  27  are located on opposite sides of respective openings  22  and  23  with respect to recess  25 ; and recess  28  is diametrically opposite recess  25 . 
     Passage  24  (FIG. 3) conveniently slopes from a respective intermediate portion towards openings  22 ,  23 , so as to improve drainoff of the liquid inside the passage towards openings  22 ,  23 . 
     Shutter  3  is conveniently made of a good sealing polymer with a low coefficient of friction to improve under-load rotation of shutter  3  inside casing  2 ; for which purpose, PTFE-based composite materials may conveniently be used, such as Rulon® J manufactured by FURON COMPANY, Laguna Niguel, Calif. (U.S.A.). 
     Valve  1  also comprises a disk  35 , of axis A, for driving shutter  3 , and which rests on a top face  36  of shutter  3  and is angularly connected to shutter  3  by two face teeth  37  extending downwards from disk  35  and engaging respective seats  38  formed on face  36  of shutter  3 . Disk  35  has an axial control shaft  39  extending integrally upwards from the disk and fitted through cover  8 , inside a bush  40 . 
     Spring  21  (FIG. 3) is interposed between cover  8  and disk  35  to keep disk  35  and shutter  3  engaged, and also to increase the contact pressure between lateral surface  20  of shutter  3  and inner surface  5  of lateral wall  4  of casing  2 . Spring  21  comprises a central annular connecting portion  44  fitted to cover  8  and about shaft  39  by means of a number of screws  45 ; and a number of blade-type arms  46  projecting radially from portion  44  and cooperating elastically with a peripheral flange  48  of disk  35 , which flange has a shaped upper surface  49 . More specifically, surface  49  is undulated so as to variably flex arms  46  of spring  21  as shutter  3  rotates. Which flexure is conveniently maximum in the work positions of the valve, so as to increase the elastic reaction of spring  21  and, hence, the contact pressure between surface  20  of shutter  3  and surface  5  of casing  2 , and is less in the intermediate positions to assist rotation of shutter  3 . 
     Rotation of shutter  3  is controlled by a three-position pneumatic actuator  50  (FIG. 1) which acts on control shaft  39  via a crank  51 . More specifically, actuator  50  comprises a cylinder  52  hinged to a fixed structure (not shown) of the machine; and a rod  53  movable axially with respect to cylinder  52  and having a fork-shaped free end  54  hinged to one end of crank  51 . The opposite end of crank  51  is connected prismatically to shaft  39 . 
     Operation of valve  1  will now be described as of a first work position indicated by the letter a in FIG.  2  and wherein openings  22 ,  23  of shutter  3  are positioned facing respective gates  10 ,  12  of casing  2 ; gates  10 ,  12  are therefore connected to each other by passage  24  of shutter  3 ; and the product circuit is therefore connected to the sterile-air supply circuit. This position is used in the course of the machine operating cycle to effect so-called pre-sterilization of the product circuit. 
     When shutter  3  is rotated 90° anticlockwise in FIG. 2, valve  1  is set to a second work position indicated by the letter b and wherein passage  24  connects gates  11  and  12  to connect the product circuit to the flush solution supply circuit. This position is used to flush the product circuit at the end of the work cycle. 
     As can be seen, any possibility of the fluids mixing is prevented by recesses  25 ,  26 ,  27 ,  28  interposed between gates  10 ,  11 ,  12 . That is, to get from one gate to another, any leakage due to imperfect sealing of shutter surface  20  and surface  5  of casing  2  is first intercepted by one of said recesses and drained off through drain opening  7 . 
     Between the above two work positions, shutter  3  may also assume an intermediate drain position wherein, still with reference to FIG. 2, the shutter is rotated 45° anticlockwise with respect to the first work position, or 45° clockwise with respect to the second work position, so that openings  22 ,  23  of shutter  3  correspond with recesses  17 ,  18  of casing  2 , and any liquid inside passage  24  flows from passage  24  through recesses  17 ,  18  to drain opening  7  of casing  2 . Moreover, recesses  26 ,  25 ,  27  correspond respectively with and so connect gates  10 ,  11 ,  12  to drain opening  7  to drain the circuit branches connected to the gates. 
     Actuator  50  is controlled by a control unit (not shown) of the packaging machine by means of known solenoid valves (not shown), which control unit coordinates operation of valve  1  with the other functions of the machine. 
     The advantages of valve  1  according to the present invention will be clear from the foregoing description. 
     In particular, as compared with known solutions featuring manually operated movable fittings, valve  1  provides for automatic selective connection of gates  10 ,  11 ,  12 ; switching is therefore straightforward and extremely fast; and valve  1  also provides for a drain position by which to drain off the operating fluids, in particular the flush solution. 
     As compared with known valve assemblies performing the same functions, valve  1  is straightforward, inexpensive, and involves very little load loss of the air or flush solution. 
     Clearly, changes may be made to valve  1  as described herein without, however, departing from the scope of the accompanying claims. In particular, gates  10 ,  11 ,  12  may be arranged differently, e.g. 120° apart; shutter  3  may comprise only three recesses 120° apart and each interposed between a pair of gates; and recesses  17 ,  18  of casing  2  and recesses  25 ,  26 ,  27 ,  28  of shutter  3  may have a different profile.