Abstract:
An apparatus and method are provided for forming a sheet of thermoformable stock material into a desired shape on a relatively-small and relatively-inexpensive “table top” version of a thermoforming and/or vacuum forming machine. Unlike conventional machines that utilize external electric or gas powered air compressors and/or separate electric vacuum pumps, the apparatus integrates a compressed fluid/suction generating device within the machine itself so that the need to connect the machine to an external source of compressed fluid or vacuum is eliminated.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The present invention relates to an apparatus and method for thermoforming and/or vacuum forming thermoplastic materials, and more particularly, the present invention relates to a forming station used to form packaging products and the like from sheets of thermoplastic material. 
         [0002]    Thermoforming and vacuum forming are known techniques used to produce packaging products for the pharmaceutical, neutraceutical, medical device, food, consumer goods, and other industries from a variety of thermoplastics and like materials. The packaging is produced in a variety of sizes and shapes, and examples of such packaging include, for instance, solid-dose pharmaceutical packaging, containers for liquid-dose packaging, food trays, and packages for batteries and other consumer articles. Typically, these types of packaging are created using vacuum forming, air-pressure forming, and mechanical molding techniques and/or a combination of these techniques. 
         [0003]    Conventional thermoforming and/or vacuum forming machines used to produce packaging materials are relatively expensive and have a relatively large foot print requiring a considerable amount of floor space. These machines utilize compressed air from electric or gas powered generators and vacuum generated by an electric vacuum pump or compressed air vacuum generator. Many machines also include a plug assist mechanism for producing packaging requiring deep drawing of the thermoplastic material. 
         [0004]    A thermoforming and/or vacuum forming machine used to make packaging products typically will include at least some or all of the following: a thermoforming material presentation station or area; a thermoforming material heating station or area; a forming station or area; a filling station or area; a lid stock presentation station or area; a lid stock printing station; a package sealing station; a material advance station; a trimming or cutting station; and a package discharge station. Some machines also include other stations, for example, a product verification station, a package perforation station, a package punch station, a barcode verification station, and an excess material take-up station. Of all the stations listed above, the package forming station is the most critical station of the machine. 
         [0005]    A problem with many thermoforming and vacuum forming machines is that the machines require the use of, and connection to, external sources of compressed air typically supplied by an electric or gas powered air compressor. This adds expense to the system and prevents use of the equipment in locations that do not have a sufficient external source of compressed air. These compressors create considerable noise when operated, and thus, add further cost in connection with the need to suppress noise for providing an acceptable work environment. 
         [0006]    In addition, most machines require a vacuum pump provided as an electric vacuum pump or an air powered vacuum generator. The need for the electric vacuum pump adds cost to the system, and the air powered vacuum generator requires compressed air and is also very loud adding cost to suppress the noise for an acceptable work environment. 
         [0007]    Further, many machines require use of a mechanical plug assist mechanism in the forming process. Although such mechanisms assist in creating deeper packages, they also require compressed air, vacuum, or both. This requires additional parts for the equipment thereby raising the cost and complexity of the machine and replacement tooling. 
         [0008]    Finally, various types of packaging materials tend to stick to the wall of the mold or form and make it difficult to eject the formed package from the mold. Mechanical devices such as ejector pins and the like are typically required to eliminate this problem. However, this adds more parts to the equipment and increases the cost of the machine and replacement tooling. 
         [0009]    By way of example, the following patents disclose thermoforming and vacuum forming machines, in general: U.S. Pat. No. 4,057,382 issued to Yamamori; U.S. Pat. No. 7,293,976 B2 issued to La Sorda; U.S. Pat. No. 6,257,866 B1 issued to Fritz et al.; U.S. Pat. No. 5,641,524 issued to Rush et al.; U.S. Pat. No. 5,314,324 issued to Wendt; U.S. Pat. No. 3,767,349 issued to Jezuit; U.S. Pat. No. 4,360,334 issued to Kiefer; U.S. Pat. No. 6,010,323 issued to Sekino; U.S. Pat. No. 5,225,213 issued to Brown et al.; U.S. Pat. No. 5,162,124 issued to Hausler et al.; U.S. Pat. No. 4,878,826 issued to Wendt; U.S. Pat. No. 5,176,609 issued to Wedler et al.; and U.S. Pat. No. 3,808,772 issued to Turtschan. 
         [0010]    Although the machines disclosed by the above referenced patents may be satisfactory for their intended purpose, there is a need for a forming station of a thermoforming and/or vacuum forming machine that does not require use of, or connection to, an external source of compressed air or vacuum. Preferably, the forming station should be inexpensive to manufacture and maintain and should be relatively quiet in operation. In addition, preferably the forming station should be provided in a relatively-compact, portable, and self-contained form and should be capable of providing a so-called “table top” version of a package forming machine. 
       BRIEF SUMMARY OF THE INVENTION 
       [0011]    The present invention is directed to an apparatus and method for forming a sheet of thermoformable stock material into a desired shape on a relatively-small and relatively-inexpensive “table top” version of a thermoforming and/or vacuum forming machine. Unlike conventional machines that utilize external electric or gas powered air compressors and/or separate electric vacuum pumps, the present invention integrates a compressed fluid/suction generating device within the machine itself so that the need to connect the machine to an external source of compressed fluid or vacuum is eliminated. 
         [0012]    According to a preferred embodiment, a compressed air/suction generating device includes a piston moveable within a sealed cylinder that defines chambers within opposite ends of the cylinder. The chambers include ports that communicate via valves with air ports in upper and lower forms, or molds, of the machine. Thus, movement of the piston within the cylinder is used to generate an air blast, a vacuum, or both. For example, as the piston moves toward one end of the cylinder, an air blast is delivered via the chamber having a reduced volume and a vacuum is simultaneously drawn via the opposite expanding chamber. This enables equalization of the push/pull on the thermoplastic sheet sealed between opposite upper and lower forms. Also, when the piston is moved in an opposite resetting direction, the generated air blast can be used to eject the molded thermoplastic sheet from the mold. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         [0013]    The present invention should become apparent from the following description when taken in conjunction with the accompanying drawing, in which: 
           [0014]      FIG. 1  is a cross-sectional view of a forming station having a self-contained compressed gas/vacuum generator according to the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0015]    The present invention is directed to an apparatus  10  and a method for forming product packaging or like material from a relatively-planar sheet  12  of stock material. The sheet material  12  is typically made of a thermoplastic or like material and is provided in individual elongate sheet form or in the form of a continuous, indefinite length, spiral roll. The apparatus  10  can comprise a “forming station” of a larger multi-station machine or can be provided and used as a stand-alone forming machine. 
         [0016]    According to one contemplated embodiment, the apparatus  10  has a relatively small footprint and provides a so-called “table top” version of a forming station requiring only a minimum of table top surface area or floor space. Such a table-top version is compact and portable and can be used and operated at any location, including non-industrial locations such as laboratories, testing facilities, product development workshops, small offices, hospitals, pharmacies, prisons, long-term care facilities, residential dwellings, and the like. Of course, the apparatus  10  can also form part of a typical, relatively-large, industrial-sized thermoforming and vacuum forming machine. Accordingly, the apparatus  10  can be owned and operated by individuals and small companies as well as large companies. 
         [0017]    In most cases, a package forming machine will include a thermoforming material presentation station (not shown) that stages the thermoplastic sheet material  12 , either in sheet or roll form, to a material heating station (also not shown). The heating station typically uses either contact or non-contact heating and heats the material  12  to a predetermined temperature required for proper forming/molding. According to the present invention, after the material  12  is heated it is moved into the forming station apparatus  10  illustrated in  FIG. 1 . 
         [0018]    The forming station  10  of the present invention includes at least an opposed pair of forms, or molds parts,  14  and  16 , that can be disposed in open and closed positions. In the open position, the forms  14  and  16  are spaced-apart from one another thereby permitting the sheet material  12  to be positioned between or advanced relative to the forms,  14  and  16 , and/or molded portions of the sheet material  12  to be discharged from the forms,  14  and  16 . In the closed position, the forms  14  and  16  can be brought into a fluid-tight engagement with the opposite faces of the sheet material  12  so that the sheet material  12  can be forced into engagement with at least one contoured mold cavity surface of at least one of the forms,  14  and  16 , such as by air blast, suction, or both. 
         [0019]    In the illustrated embodiment, the mold parts include an upper form  14  and a lower form  16 . However, this simply provides one possible arrangement and other molding arrangements can also be utilized, such as the use of more then two forms or using forms disposed laterally or at an angle to the horizontal or vertical. 
         [0020]    In  FIG. 1 , the upper form  14  is supported on a form mount  18  and has a port  20  in fluid communication with a void area  22  within the upper form  14 , and the lower form  16  is supported on a form mount  24  and has a port  26  in fluid communication with a void area  28  within a mold cavity of the lower form  16 . The forms,  14  and  16 , are further supported on framing or like machine structure (not shown) that holds these items in place, for instance, as shown in  FIG. 1 . 
         [0021]    By way of example, the upper form  14  can be mounted in a stationary condition, and the lower form  16  can be movable toward and away from the upper form  14  into the open and closed mold positions. The lower form  16  may be moved into place, for instance, via a manually operated or automatic mechanical, electro-mechanical, or hydraulic mechanism (not shown). Of course, various modifications can be made to this arrangement. For example, the upper form  14  can be movable relative to a stationary lower form  16 , or both forms,  14  and  16 , can be moveable relative to each other. 
         [0022]    An important aspect of the present invention is that the forming station apparatus  10  has a self-contained, integral, compressed fluid/vacuum generator  30 . By way of example, the fluid can be a gas, a liquid, a gel, or other type of flowable material. In a preferred embodiment as discussed below, the fluid is air; however, this aspect of the present invention can be readily altered. 
         [0023]    The generator  30  is integrally connected to the structure of apparatus  10 , such as to the mount  24  of the lower form  16  as shown in  FIG. 1 . However, the generator  30  could be connected to the upper form  14  or any other structural component, such as a framing component, of the forming station apparatus  10 . 
         [0024]    The preferred embodiment of the generator  30  includes a cylinder piston  32  contained within a hollow cylinder body  34  having opposite closed end walls,  36  and  38 . Preferably, the cylinder body  12  has a substantially circular cross-section; however, as an alternative, the hollow body can be provided with an oval, triangular, square, multi-sided or other shaped transverse cross-section and is not limited to a circular cross-section. 
         [0025]    The piston  32  includes a longitudinally-extending stem  40  extending through the end wall  38  in a sealed, fluid-tight manner and a transversely-extending sealing plug  42  that engages an inner surface of the sidewalls of the hollow cylinder body  34  in a fluid-tight manner thereby defining opposite hollow chambers,  44  and  46 , within the cylinder body  34  on opposite sides of the sealing plug  42 . Accordingly, a first chamber  44  within the cylinder body  30  is located adjacent the end wall  36  and a second chamber  46  is located adjacent the end wall  38 . These chambers,  44  and  46 , are sealed from one another by engagement of the sealing plug  42  of the piston  32  with the inner surfaces of the sidewalls of the cylinder body  34 . 
         [0026]    The piston  32  is movable back and forth in a longitudinal direction “A” within the hollow cylinder body  34 . This movement causes the volume and size of one of the chambers,  44  or  46 , to be reduced while simultaneously increasing the volume and size of the other chamber,  44  or  46 , by a substantially equal amount. Movement of the piston  32  can be provided via engagement of the stem  40  of the piston  32  with a mechanical, electromechanical, or hydraulic mechanism (not shown). This mechanism can be the same or a different mechanism used to move the forms,  14  and  16 , into the open and closed positions. 
         [0027]    A hose or like conduit  48  connects a port  50  of the first chamber  44  of the cylinder body  34  in fluid communication with the port  26  of the lower form  16  via a valve  52 , and a hose or like conduit  54  connects a port  56  of the second chamber  46  of the cylinder body  34  in fluid communication with the port  20  of the upper form  14  via a valve  58 . In the illustrated embodiment, the first chamber  44  is used for purposes of drawing a vacuum within the lower mold  16  and the second chamber  46  is used for purposes of providing an air blast within the upper mold  18 . Of course, these functions can be re-designed and reversed, as desired. 
         [0028]    In use, at least a portion of the stock sheet material  12  is heated and then positioned between the forms,  14  and  16 , and thereafter, the forms,  14  and  16 , are moved into the closed position in which the heated sheet material  12  is pinched in place between the forms,  14  and  16 . In this engaged position, the material  12  cannot move relative to the forms,  14  and  16 , and a fluid-tight seal is created between the material  12  and the forms,  14  and  16 . 
         [0029]    After the forms  14  and  16  of the forming station apparatus  10  are positioned in the closed position about the thermoplastic sheet material  12 , the cylinder piston  32  is moved away (in a downward direction as viewed in  FIG. 1 ) from its “home position”, which is the position illustrated in  FIG. 1 . As discussed above, the movable piston  32  divides the sealed cylinder body  34  and defines the opposite chambers,  44  and  46 , and the cylinder body  34  includes ports  50  and  56  that communicate via valves  52  and  58  with air ports  20  and  26  in the upper and lower forms,  14  and  16 . 
         [0030]    Accordingly, movement of the piston  32  within the cylinder body  34  results in the generation of an air blast, a vacuum, or both. For example, as the piston  32  moves away from the home position (in a downward direction as viewed in  FIG. 1 ) an air blast is delivered via the second chamber  46  due to a reduction of its volume and a vacuum is simultaneously drawn by the expansion of the first chamber  44 . Thus, the sheet material  12  is pushed by the air blast applied to the void space  22  in the upper form  14  and pulled by suction applied via the vacuum drawn in the void space  28  in the lower form  16  such that the sheet material is forced to conform to the inner mold surface of the lower form  16 . Thus, as viewed in  FIG. 1 , the sheet material  12  is pushed/pulled downwardly into engagement with the mold cavity surface of the lower form  16 . 
         [0031]    The generator  30  according to the present invention ensures equalization of the amount of push/pull on the material sealed between the opposite forms,  14  and  16 . For example, the air displaced by the reduction of the volume of chamber  46  is equal to the air displaced in the void area  28  in the lower form and the increase in volume of the chamber  44 . This ensures an appropriate amount of air blast needed to force the sheet material  12  into conformance with the mold surface, but also limits the air blast to prevent the forms,  14  and  16 , from being undesirably blown apart due to an over application of air blast. Thus, the generator  30  is self-limiting without the need of other control mechanisms to limit the air blast. In addition, the generator  30  is self-adjusting in that it can be used with different sized forms requiring different volumes of air displacement without requiring any adjustment. 
         [0032]    After the sheet material conforms to the mold cavity surface  60  of the lower form  16 , the forms  14  and  16  are separated to expose the molded piece. The piston  32  is moved back to its home position in an opposite resetting direction (in an upward direction as viewed on  FIG. 1 ) via a mechanical, electro-mechanical, or hydraulic mechanism. This movement can be precisely timed to start prior to, simultaneously with, or shortly after the opening of the forms,  14  and  16 . The air blast generated during this movement can be used to eject the molded thermoforming material from the lower mold  16 . 
         [0033]    The valve system of the present invention can be controlled to provide only an air-blast to one of the forms, only a vacuum to one of the forms, or a combination of both an air blast and vacuum simultaneously to opposite forms. For example, a shallow packaging product may be capable of being formed with only an air blast or suction; whereas, a relatively deep drawn packaging product may require the simultaneous application of an air blast and vacuum. Accordingly, the forming  4 station apparatus  10  provides flexibility in that it can readily form shallow packages as well as deep-drawn packages. 
         [0034]    Accordingly, the present invention provides a small, self-contained, relatively inexpressive, and robust forming station and method of providing compressed air and vacuum to the forming station for a thermoforming/vacuum forming packaging machine. The invention provides the above while providing an economical and safe method of manufacturing a relatively small, “table top” packaging machine. The generator  30  eliminates the need for loud, expensive and potentially dangerous air compressor and vacuum sources. The piston/cylinder generator also provides equalization between air blast and vacuum and is both self-limiting and self-adjusting. This enables improved molding of sheet material, and it also enables less complexity and expense with respect to the structural mechanism clamping the forms together. For example, since the air blast is self-limited to the vacuum being drawn, an over amount of compressed air will never occur thereby eliminating a safety hazard. Further, forms of different sizes and shapes requiring different amounts of air displacement can be used without any need to make adjustments to the generator  30 . 
         [0035]    While preferred apparatus and methods have been described in detail, various modifications, alterations, and changes may be made without departing from the spirit and scope of the apparatus and methods according to the present invention as defined in the appended claims.