Abstract:
A rubber injection molding apparatus and method for simultaneously molding a plurality of work parts ( 40 ) in separate molds ( 30 ) using a single, vertically oriented press machine ( 22 ). A clamping mechanism ( 52 ) is responsive to the vertical, reciprocating motion of the press ram ( 26 ) for converting the generally vertical motion of the press ram ( 26 ) into a horizontal clamping force to squeeze and hold the molds while rubber is injected into their cavities ( 38 ). The molds ( 30 ) each have two mold halves ( 32, 34 ) joining one another along a parting line interface ( 36 ) with the mold cavity ( 38 ) in between. The mold halves ( 32, 34 ) are received in universal carriers ( 62 ), which in turn are suspended between and slideable along spaced-apart first ( 58 ) and second ( 60 ) rails. A large number of mold cavities ( 38 ) can be filled simultaneously using a vertically oriented press machine ( 22 ). The plurality of molds ( 30 ) may contain different part configurations which are filled simultaneously in a single molting operation. Because the molds ( 30 ) are not fastened to platens as in prior art vertical press machines, changeover times are substantially decreased.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     None. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     A rubber injection molding apparatus and method for simultaneously molding a plurality of work parts in separate horizontally arrayed molds using a single, vertically oriented press machine. 
     2. Related Art 
     One of the most common methods of shaping rubber resin into a work part is a process called injection molding. Injection molding is accomplished by an injection molding machine which, typically, is a large industrial piece of capital equipment. According to the injection molding process, rubber resin is fed into a hopper, where colorants or other properties may be introduced. A barrel or other device receives the resins and elevates their temperature to an appropriate melting point. Once molten, the resin is injected into a mold cavity. 
     Because of the extreme pressures developed during the injection process, the mold halves must be held firmly against one another in a high tonnage press machine. Such press machines as used in the injection molding art are, more often than not, arranged in a horizontal motion configuration, whereby the press ram and/or the press bed move in a reciprocating, generally horizontal path toward and away from one another. Such a configuration orients the parting line interface of the mold cavity in a generally vertical orientation, so that as the mold halves open to remove a finished, molded work part from the mold cavity. The molded part can be swept out and allowed to fall into a collection bin below. 
     Many manufacturing facilities include press machines having vertically oriented reciprocating elements. In other words, a typical vertical press may be used for stamping, compression molding or other general fabrication applications and include a vertically oriented press ram supported for reciprocating movement in a generally vertical path toward and away from a press bed. Such press machines represent heavy, expensive pieces of fixed equipment which are generally inefficient for use in high-volume rubber injection molding applications. 
     Accordingly, there is a need to easily convert and enable a typical prior art vertical press for use in high-volume rubber injection molding applications. 
     Furthermore, there is a need in this field to reduce the amount of time required to change molds. Studies have shown that leading causes of slow mold changes include the millwright using either the wrong tools or the wrong fasteners. Even fast mold changes consume valuable production time when changing molds from one job to the next and whenever the process cannot be readily automated. Accordingly, the time lost during mold changes is a serious issue in the field of injection molding. 
     SUMMARY OF THE INVENTION 
     A rubber injection molding apparatus is provided for simultaneously molding a plurality of work parts in separate molds using a single press machine. The apparatus comprises a rubber injection press machine including a press bed and a vertically oriented press ram supported for reciprocating movement in a generally vertical path toward and away from the press bed. A plurality of separate and distinct injection molds are positioned between the press bed and the press ram. Each mold has two mold halves joining one another along a parting line interface with a mold cavity defined in between. A supply of molten rubber communicates with the press ram for injecting into the molds. A clamping mechanism is directly responsive to the vertical motion of the press ram for compressing the plurality of molds in a direction normal to their parting lines. Each of the plurality of separate and distinct injection molds is arranged horizontally relative to one another such that each parting line is disposed generally parallel to the movement of the press ram. According to this configuration, the generally vertical motion of the press ram is converted into a generally horizontal clamping force by the clamping mechanism and thereby simultaneously compresses all of the molds together. 
     According to a second aspect of the invention, a method is provided for simultaneously molding a plurality of work parts in separate molds using a single press machine. The method comprises the steps of providing a rubber injection press machine having a movable press ram and a press bed, reciprocating the press ram in a generally vertically path toward and away from the press bed, providing a plurality of separate and distinct injection molds each having two mold halves joining one another along a parting line interface with a mold cavity in between, positioning the molds between the press bed and the press ram in a horizontally extending array such that each of the parting lines are disposed generally parallel to the movement of the press ram, supplying molten rubber to the press ram, compressing the plurality of molds together in response to the reciprocating motion of the press ram, and the compressing step further including converting the generally vertical motion of the press ram into a generally horizontal clamping force and thereby simultaneously compressing all of the molds together. 
     The subject invention overcomes the shortcomings and disadvantages of prior art systems by enabling a vertical type press machine to be converted for use in a rubber injection molding application. The plurality of molds are arranged in a horizontally extending array in the path of the press ram, and are compressed together in the horizontal direction through the clamping mechanism or other appropriate technique to achieve the necessary resistance force to the rubber injection process. Advantages include the ability to inject molten rubber simultaneously into a large number of cavities. The plurality of molds filled simultaneously do not necessarily need to be identical to one another. Further perfecting features of the invention enable rapid mold exchanges and largely unattended automation in the molding process. Due to the increased ability for high product through-put, as well as the ability to convert existing capital equipment to new uses, the subject invention represents a unique and highly desirable advance in the field of rubber injection. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other features and advantages of the present invention will become more readily appreciated when considered in connection with the following detailed description and appended drawings, wherein: 
         FIG. 1  is a perspective view of a vertically oriented press machine including a plurality of molds arrayed in both the press zone as well as in an adjacent loading/unloading zone; 
         FIG. 2  is a fragmentary perspective view depicting a pair of mating mold halves separated from their respective carriers; 
         FIG. 3  is a fragmentary perspective view of a mold cavity formed in one mold half according to the invention; 
         FIG. 4  is a fragmentary perspective view illustrating the clamping mechanism of the subject invention in relation to an array of molds; 
         FIG. 5  is a cross-sectional view taken generally along lines  5 - 5  in  FIG. 2 , the section line extending through a gate leading to the mold cavity between the two mold halves; 
         FIG. 6  is a simplified cross-sectional view showing the press ram lifted away from the press bed with the plurality of molds positioned therein; 
         FIG. 7  is a view as in  FIG. 6  but showing the press ram in a fully compressed position against the press bed with the molds ready for an injection of molten rubber; 
         FIG. 8  is an exploded perspective view depicting a molded work part in relation to its associated mold cavity; 
         FIG. 9  is a simplified cross-sectional view through a mold cavity as in  FIG. 5 , but showing molten rubber injected through the gate and filling the mold cavity; and 
         FIG. 10  is a view as in  FIG. 9  and demonstrating the step of removing the molded part from the mold cavity with the assistance of a sweeping device. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to the Figures, wherein like numerals indicate like or corresponding parts throughout the several views, a rubber injection molding apparatus of the type for simultaneously molding a plurality of work parts in separate molds using a single press machine is generally shown at  20 . A rubber injection press machine, generally indicated at  22 , includes a press bed  24  and a vertically oriented press ram  26  supported for reciprocating movement in a generally vertical path toward and away from the press bed  24 . The press ram  26  may be equipped with heaters, a runner system  28  and nozzles, as suggested in  FIGS. 6 and 7 , so as to distribute molten rubber to and among the plurality of molds at the appropriate time in the molding cycle. 
     A plurality of separate and distinct injection molds, generally indicated at  30 , are positioned in the press zone, i.e., between the press bed  24  and the press ram  26  or, said another way, within the reciprocating path of the press ram  26 . Each mold  30  includes two mold halves  32 ,  34  adjoining one another along a parting line interface  36 . A mold cavity  38  is defined as an open space between each of the mold halves  32 ,  34 . In one embodiment, mold cavities  38  for molding parts that are primarily planar but have a large projected area can be made. Such parts will have small cross sections as taken in a horizontal plane, thereby giving very low projected areas in that perspective and requiring far lower tonnage clamping forces. 
       FIGS. 2 ,  3 ,  5  and  8 - 10  are particularly illustrative as to the molds  30  in one exemplary embodiment of a work part  40  made in the shape of a head gasket or valve cover gasket for an internal combustion engine. Here, each mold half  32 ,  34  is shown having a generally trapezoidal shape defined by tapering lateral edges  42  and generally horizontal, planar top edges  44 . A gate  46  is formed between each of the mold halves  32 ,  34  through the top edges  44 . The gate  46  leads to the mold cavity  38 , as best shown in  FIGS. 3-5  and  9 . Preferably, the gate  46  is of the well-known edge gate configuration style. However, other gate configuration styles may be used and/or preferred depending upon the application. The gate  46  may be offset toward, or proximate to, one of the lateral edges  42  as shown in  FIG. 2 . This may be preferred so that the next adjacent mold  30  in the press machine  22  can be rotated 180° and thereby alternate the gates  46  in an advantageously spaced orientation so that the runners  28  and nozzles in the press ram  26  are conveniently dispersed. 
     In  FIG. 3 , a pair of locator pins  48  are shown extending from the mold half  32  for mating in a complementary socket  50  in the opposing mold half  34 . The locator pins  48  and mating sockets  50  may be tapered to facilitate registration. Although two such locator pins  48  and sockets  50  are depicted in the drawings, those of skill will appreciate that fewer or more such features may be implemented as the case may be. Furthermore, it is not necessary that these locating features be tapered or otherwise resemble those features depicted in the drawings, but rather may take various forms to accomplish the same purpose of helping to properly align the two mold halves  32 ,  34  and maintain their aligned condition during the injection molding process. 
     The press machine  22  includes a clamping mechanism, as generally indicated at  52  in  FIGS. 1 ,  4 ,  6  and  7 . The clamping mechanism  52  is directly responsive to the vertical motion of the press ram  26  for compressing the plurality of molds  30  in a direction normal, or perpendicular, to each of the parting lines  36 . The clamping mechanism  52  may be designed in various ways, but in the drawings is depicted as a pair of movable wedges  54  directly connected to and movable with the press ram  26 . A pair of co-acting stationary wedges  56  are directly connected to or otherwise integrated in the press bed  24 . The movable  54  and stationary  56  wedges interact with one another in response to the reciprocating movement of the press ram  26 , thereby causing compression upon the molds  30  in a force vector normal to their parting lines  36 . 
     As illustrated, each of the injection molds  30  are horizontally arranged relative to one another within the press zone such that all of the parting lines  36  are disposed generally parallel to the movement of the press ram  26 . Thus, the generally vertical motion of the press ram  26  is converted into a generally horizontal clamping force by the clamping mechanism  52 , which acts to simultaneously compress all of the molds  30  together. In comparison to a prior art arrangement in which a vertically oriented press is equipped for rubber injection molding, the subject invention allows a greater number of mold cavities  38  to be filled simultaneously in the press machine  22 . Furthermore, it is not necessary that every mold cavity  38  be identical to those in other molds  30 . Therefore, different specification numbers may run simultaneously in the same batch. 
     Returning again to  FIGS. 1 and 2 , the press machine  22  is shown including first  58  and second  60  rails extending parallel to the direction of the clamping force on either side of the press zone. The rails  58 ,  60  may extend laterally from the press bed  24  to provide a loading and unloading zone so that batches of mold  30  can be moved through the press machine  22  more efficiently. The rails  58 ,  60  may support the molds  30  directly, or more preferably, support carriers  62  which in turn support the respective mold halves  32 ,  34 . The carriers  62  are designed to directly connect to and slide along the first  58  and second  60  rails while supporting a single mold half  32  or  34  in a universal manner. In other words, without changing or moving the carrier  62 , either mold half  32  or  34  can be placed in the carrier  62  in a forward or rearward facing orientation. Said another way, the offset gate  62  can be positioned either proximate the first rail  58  or proximate the second rail  60 . This universal, reversible coupling is accomplished by forming the tapered lateral edges  42  of each mold half  32 ,  34  with a universal registration interface. In the illustrative embodiment depicted, that registration interface may take advantage of the tapered lateral edges  42  on the mold halves  32 ,  34 . As shown, these lateral edges  42  may be formed with a bead for mating in a complementary groove  64  in each of the carriers  62 . Of course, other registration interface designs may be substituted with equal effect for the bead and groove  64  configuration depicted in the drawings. Furthermore, it is contemplated in an alternate embodiment that a single carrier  62  may support one or more entire mold assemblies  30 , i.e., a plurality of mold halves  32 ,  34 . 
     The method for simultaneously molding a plurality of work parts  40  in separate molds  30  using a single press machine  22  according to the subject invention may be appreciated by reference in particular to  FIGS. 6-10 . These steps include providing a rubber injection press machine  22  having a movable press ram  26  and a stationary or otherwise opposing press bed  24 . Those of the skill in the art will appreciate that the so-called “stationary” press bed  24  may in fact move relative to the foundation of the press machine  22 . Nevertheless, for illustrative and convenience purposes, the press bed  24  is described as stationary. In effect, it is only necessary that there is provided relative movement between the press bed  24  and the press ram  26  to permit the molds  30  to be shuttled into and out of a position for injection molding to occur. 
     The method further includes reciprocating the press ram  26  in a generally vertical path toward and away from the press bed  24 . A plurality of separate and distinct injection molds  30  each having two mold halves  32 ,  34  joining one another along a parting line interface  36 , are provided. A mold cavity  38  is formed in the space between opposing mold halves  32 ,  34 . 
     The method also includes the steps of positioning the molds  30  in the vertical path between the press bed  24  and press ram  26  in a horizontally extending arrangement so that each of the parting lines  36  are disposed generally parallel to the movement of the press ram  26 . Molten rubber is supplied to the press ram  26  using a conventional injection molding apparatus (not shown) and distributed through runners  28  or other flow passages formed in the press ram  26 . 
     The method also includes compressing the plurality of molds  30  together in response to the reciprocating motion of the press ram. The compressing step further includes converting the generally vertical motion of the press ram  26  into a generally horizontal clamping force and thereby simultaneously compressing all of the molds  30  together. Furthermore, the compressing step includes co-acting at least one movable wedge  54  connected to the press ram  26  with one stationary wedge  56  connected to the press bed  24 . Again, it will be appreciated that the terms “movable” and “stationary” are used as words of illustration and not of limitation. Therefore, the stationary wedges  56  are considered stationary in relative terms in view of the movable wedges  54 . 
     In one embodiment of the invention, the step of positioning the molds  30  in the vertical path of the press ram  26  includes the step of suspending the mold halves  32 ,  34  from at least one, but preferably two rails  58 ,  60  extending parallel to the direction of the compressing force. This step of positioning the molds in the pressing zone further includes supporting each mold half  32 ,  34  in a carrier  62 . The carrier  62  is, itself, supported directly upon the spaced rails  58 ,  60 . 
       FIGS. 9 and 10  depict, respectively, the steps of a mold cavity  38  being filled with molten rubber and then the resulting work part  40  being removed once it has sufficiently solidified. A method of the subject invention further includes the step of removing the molded work part  40  from the mold cavity  38  with the assistance of gravity. In other words, once the work part  40  is removed from the cavity  38 , it is allowed to fall under the influence of the earth&#39;s gravitational pull into a collection receptacle, onto a conveyor or other handling device (not shown). A rotary brush  66  or other sweeping or scraping device may be used to assist removal of the work part  40  from the cavity  38 . Accordingly, the method of this invention may further include the step of inserting a sweeper  66  between the opposing mold halves  32 ,  34 . 
     The subject invention accomplishes numerous objections and overcomes all of the shortcomings found in prior art systems of this type. For example, this approach gains the de-molding advantages of a horizontal press while using a vertical press machine. The number of mold parting lines  36  can be increased, resulting in more molded parts  40  yield per heat. This invention allows lower tonnage machines to be used, which reduces the capital costs through the use of simple locking wedges  54 ,  56  for clamping instead of hydraulics. The subject design does not require any fasteners to accomplish mold changes. This fact alone reduces mold change times in that delays resulting from wrong tool and/or fasteners are avoided. In addition, this approach is more versatile than prior art approaches in that more than one job can be run simultaneously provided they share the same compound and cure time. The design facilitates automation in that very simple x-y robots can be used to perform mold changes. 
     The foregoing invention has been described in accordance with the relevant legal standards, thus the description is exemplary rather than limiting in nature. Variations and modifications to the disclosed embodiment may become apparent to those skilled in the art and fall within the scope of the invention. Accordingly the scope of legal protection afforded this invention can only be determined by studying the following claims.