MXPA98003797A - Method and apparatus for the molding by compression of plastic items - Google Patents

Abstract

The present invention relates to an apparatus for compression molding a plastic article that includes a plurality of tool means segmented in opposite pairs with the tool means of each pair, which includes male and female mold means, a means for mounting the pairs of tool means in an endless path and means for moving both tool means to selectively close the mold means during movement in the path for compression molding of the mold loads the mold and open means the mold means for releasing the articles from between the mold means: the improvement comprises a means carried by each pair of tool means for closing the mold means in a closed position during the movement in the path, independent of the closing means and a means separated from the tool means for selectively opening the closure means to allow the opening of the mold means e and the release of the articles

Description

METHOD AND APPARATUS FOR MOLDING BY COMPRESSION OF PLASTIC ITEMS Field of the Invention The present invention is directed to a method and apparatus for compression molding of plastic articles such as caps, and more particularly to an improvement in the method and apparatus described in U.S. Patent No. 5,554,327.

Background and Objectives of the Invention U.S. Patent No. 5,554,327, assigned to the assignee herein, discloses a method and apparatus for compression molding of plastic articles such as plastic caps. A plurality of tools is mounted in a circumferential array in a turret or revolver tool holder, rotatable in a plurality of opposite co-actuation pairs. The tools of each pair have sections of mold female and male, opposite that together, when closed, form a mold of cavity for REF. 27509 the compression molding of the desired articles. The revolver tool holder is mounted on a machine structure that also carries cams for an operative coupling with the tools to move the tools of each pair towards each other or mutual during a portion of the movement of the tools around the revolving tool holder shaft for the compression molding of the articles between the pairs of tools, and to move the pairs of tools away from one another during another portion of the displacement or advancement of the tooling to release the molded articles between the tools. Fluid cylinders are associated with each pair of tools to provide a constant, limiting molding force for each pair of tools. U.S. Patent No. 5,603,964, also assigned to the assignee herein, discloses an apparatus for cutting and supplying extruded plastic chips to successive molds of the molding apparatus. Although the methods and apparatus described in the aforementioned patents address and overcome the problems, thus existing in the art, further improvements remain desirable. For example, it is desirable to hold the tools and the mold halves in the compressed and closed position as it is possible to improve the cooling efficiency and the definition of the parts and the quality during the molding process. However, it is also undesirable to employ the cams in the machine structure to keep the molds closed in a normal molding force during most of the operating cycle, because this would place undesirable forces on the structure of the machine and increase the wear of the cam. For this reason, it is a conventional practice to reduce the molding forces during the healing portion of the cycle, with the corresponding reduction in the cooling efficiency and quality of the parts. It is also desirable to improve the efficiency of the machine by increasing the density of the tooling within a machine, and thereby increasing the total productivity per unit of floor space occupied by the plant. However, using conventional technology, this would only aggravate the problem of the strength of the mold, which in turn would require a redesign of the structure, cams and supports of the machine.

Therefore, it is a general object of the present invention to provide a method and apparatus for the compression molding of plastic articles that allows the maintenance of full compression force on the mold elements during the forming and curing of the molded component while that reduces the wear, in the cams that close the elements of the mold, and while it reduces the forces of reaction of subjection of the mold applied to the structure of the machine. Another object of the present invention is to provide a method and apparatus of the described character which achieves an improved efficiency in terms of density and utilization of the tooling of the occupied floor space of the plant.

Brief Description of the Invention A method and apparatus for compression molding of plastic articles such as caps according to the present invention includes a plurality of tools mounted in opposing pairs with the tools of each pair including opposite mold and female and male sections. The pairs of tools are assembled for movement in an endless path. The pairs of tools and associated mold sections are closed during movement in the trajectory by compression molding a load in the mold cavity, formed between the mold sections of each pair, and opening the mold cavity to release an article formed between the sections of the mold. According to one aspect of the present invention, a mechanism is associated with each pair of tools to immobilize the tools and sections of the mold in the closed position during movement in the independent path of the mechanism for closing the tools and halves of the mold. In this way, the forces imparted to the mold halves and the tools to keep the molds closed, are isolated from the structure of the machine. The immobilization mechanism is not selectively immobilized to allow the opening of the mold halves and release the molded articles by compression between the mold halves. The pairs of opposing tools are mounted, in the preferred embodiment of the invention, in a sliding mechanism that interconnects the tools of each pair. The immobilization mechanism is placed to couple the sliding mechanism to prevent the movement of the tools of each pair away from each other. The sliding mechanism in the preferred embodiment of the invention includes a sliding shaft coupled to one of the tools of each pair, with the other tool of each pair being slidable on the shaft. The locking mechanism includes a stop in the shaft and an engager placed in the other tool of each pair for movement between a first position in engagement with the associated stop to keep the tools and associated mold sections in the closed position, and a second position without engagement with the stop to allow the opening of the tools and the associated mold sections. The engager in the preferred embodiment of the invention is pushed to the first or latching position by a spring placed between the latch and the tool in which the latch is mounted, and moves to the second or position without engaging by means of a latch. actuator of the hook extending from each hook for coupling with a cam placed in a fixed position in the structure of the machine adjacent to the path of movement or advance of the tools. The engaging and stopping are thus shaped with respect to each other that an increase in the molding force within a cavity of the compression mold increases the contact coupling force between the engager and the stop. According to another aspect of the present invention, each of the tool assemblies carries cores and fasteners in the mold cavity to form a plurality of mold cavities in each pair of tools. The mold cavities are equally spaced apart circumferentially from the mold path, both within each set of tools and between the tool sets. In this way, the production density is greatly increased when compared to the prior art in which each pair of tools forms only one individual cavity. The elements and cavities of the mold are preferably placed in assemblies in each pair of tools concentric with the axis of the revolver tool holder. Preferably, each tooling within each assembly is equally and circumferentially spaced from its adjacent tooling within the same assembly. The cavities of the mold can be aligned radially or staggered radially with the same number of cavities in each set, or they can be placed such that there is a greater number of cavities in the exterior arrangement than in the interior arrangement.

Brief Description of the Drawings The invention, together with the objectives, features and additional advantages thereof, will be better understood from the following description, the appended claims and the accompanying drawings in which: FIGURE 1 in a sectional view in a side elevation of a compression molding apparatus according to a currently preferred embodiment of the invention; FIGURE 2 is a top plan view of the molding apparatus illustrated in FIGURE 1; FIGURE A is a fragmentary view on an enlarged scale of a portion of FIGURE 2; FIGURE 3 is a fragmentary elevational view of a portion of the machine illustrated in FIGURE 1 on an enlarged scale; FIGURE 4 is a fragmentary elevational view of another portion of the machine illustrated in FIGURE 1 on an enlarged scale; FIGURE 5 is a fragmentary elevational view showing a synchronization of several cams in the cam section of the apparatus; FIGURES 6A-E are elevational, fragmentary views that illustrate the assemblies of the upper and lower tooling in sequential stages of operation: FIGURE 6F is a view similar to that of FIGURE a showing a modified embodiment of the invention; FIGURE 7 is an elevational view taken of the direction 7 in FIGURE 6E; FIGURE 8 is a fragmentary, plan view of the molding loading station in FIGURE 2; FIGURE 9 is an elevational view of the molding loading station in FIGURE 8 in conjunction with the tooling of the apparatus of FIGURE 3; FIGURE 10 is a fragmentary elevational view, similar to that of FIGURE 4 but showing a modified embodiment of the invention; FIGURE 11 is a fragmentary elevational view, similar to that of FIGURE 5 but showing a modification thereof according to the embodiment of FIGURE 10; FIGURE HA is a fragmentary view on an enlarged scale of a portion of FIGURE 11; FIGURE 12 is a fragmentary elevational view, similar to those of FIGURES 4 and 10 but showing another modified embodiment of the invention, FIGURES 13 and 14 are fragmentary views on an enlarged scale illustrating respective modifications to the embodiment of FIGURE 2; FIGURE 15 is an elevational view of a portion of FIGURE 9 showing the chip feeder disk in greater detail; FIGURE 16 is an elevational view taken substantially from the direction 16 in FIGURE 2; Y FIGURES 17 and 18 are fragmentary views on enlarged scales of the portions of the apparatus within circles 17 and 18 in FIGURE 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIGURES 1-9 illustrate a compression molding apparatus 10 according to a currently preferred embodiment of the invention comprising a revolver 12 tool holder mounted for rotation about an axis 14 on and with respect to a structure of the machine 16. The revolver tool holder 12 has three radially spaced, axially spaced plates 18, 20, 22 forming a mounting bracket for the compression mold tooling, as will be described. A circumferential, uniformly spaced arrangement of sliding shafts 24 extends parallel to the shafts 14 of the revolver tool holder 12 through the sliding supports 26, 28, 30 supported by the plates of the revolver tool holder 18, 20, 22 respectively. A mounting of the upper tooling 32 includes an upper actuator 34 attached to the sliding shaft 24 on the opposite axial sides of the upper revolver tool holder plate 18. A upper cam roller 36 is supported by the actuator 34 for the rolling engagement with a conforming cam, upper 38 supported by the structure of the machine 16 above the revolver tool holder 12. The actuator 34 also supports a roller 40 which cooperates with a lifting cam, upper 42 in the structure 16 for raising the actuator 34 and mounting the tooling 32 ascendingly to release the molded parts. A tool holder, upper 44 is supported by each actuator 34 and slidably mounted on the turret holder plate of center 20. Each of the tool holders 44 includes a set of mold cores 46 (four in the illustrated embodiment). ) slidable in the associated core sleeves 48 and having lower ends that form the male portions of the mold cavities by compression. A separating or separating shirt 47 (FIGURES 3 and 6-7), surrounds the lower end of each core 46, and is biased downwardly therefrom by a spring of the stripper 45 (FIGURE 6). The springs of the stripper 45 are enclosed within the jackets 48. A lower tooling assembly 50 includes a slider 52 having axially spaced supports 54 that slidably embrace the shaft 24 between the plates of the revolver tool holder 20, 22 below and in opposition to each mounting of the upper tooling 32. A cavity clamp 56 is mounted on each slider 52, and supports a plurality of cavity clips 58 (four in the illustrated embodiment) forming the sections of the female mold which opposes the cores 46 of the tool assembly, upper, associated 32 to form the complete cavities for the compression molding of the desired articles. Each cavity clamp 56 supports a lower cam roller 61 which is positioned for engagement with a lower, conformation cam 60 supported by the lower section of the machine structure 16. Each cavity clamp 56 also has a roller 62 that it is engaged by a lower cam 64 supported by the structure 16 to pull the cavity clamp 56 and the slider 52 downwards, and thereby removing the molded parts from the interior of the cavities of the mold. Each cavity fastener 58 is biased upwardly by a spring mechanism, such as coil springs 64a (FIGURES 1,3-4 and 6F) or a fluid cylinder 65b (eg, a nitrogen gas spring, FIGURES 6A -6E). A rotating, upper union is mounted to the upper structure and conducts the cooling water to the revolver tool holder and the tooling mounted thereon, and is well known in the art of rotary compression molding. To the extent heretofore described, the operation of the molding apparatus 10 is generally as described in the aforementioned US Patent No. 5,554,327. Since the revolver tool holder 12 and the tooling mounting pairs 32, 50 move in the direction 120 in a circular, endless path (FIGURE 2) around the axis of the revolver tool holder 14, the mold loads are deposited by a mechanism of load 66 (FIGURES 2 and 8-9) in the cavity clips 58 when the cavities are in the open condition illustrated in FIGURES 2 and 9. The continued rotation of the revolver tool holder leads the rollers 36, 61 to the coupling with the cams of lower and upper shaping 38, 60, which in turn are profiled to move the tooling assemblies 32, 50 towards themselves and thereby lead the cores 46 to the shaping coupling of the compression cavity with the fasteners of the cavity 58 and the mold charges deposited therein. The tooling assemblies are then held in this closed position when the revolver tool holder continues to rotate for compression molding and the curing of the charges deposited in the mold cavities in the articles of the desired profile. In the apparatus described in the referred patent, this is. performed by the continuous coupling of the rollers 36, 61 with the cams 38, 60. As the tools rotate about the axis of the revolver tool holder towards the end of the forming cycle, the profiles of the cams 38, 60 are themselves to release the pressure of the mold in the cavities, and the tooling assemblies 32, 50 move away from each other by means of the cams 42, 64 and the cams rollers 40, 62 supported by the lower and upper tooling assemblies, respectively. The molded articles are released and separated from the tooling of the mold, and the assemblies of the tools are spaced from each other before receiving the new mold loads. According to one aspect of the present invention, continuous force is applied to the compression molding elements during the cure cycle by a latching mechanism 70 in conjunction with the spring 64a or 65b supported by each pair of the tooling and a stop collar 72 positioned at the lower end of each sliding shaft 24. More specifically, each detent collar 72 comprises a sleeve 73 slidably positioned inside each sleeve holder 30 that surrounds and joins the lower end of each shaft 24. Each liner 73 has a projecting projection, radially 74 at its upper end with a radially oriented, flat face, and a lower end in engagement with a ring or collar 76 that connects the collar 72 to the shaft 24. As shown In FIGURE 18, the collar 76 is secured to the lower end of the shaft 24 by a screw 77, and secured to the lower end of the sleeve. arrest collar 73 by screws 79. A generally L-shaped hook 78 is mounted on a pivot pin 80 within a receptacle 82 at the lower end of each slider 52. A coil spring 84 is captured in compression between a receptacle on a leg of the engager 78 and on a face opposite the receptacle 82 on the slider 52. The second leg of the engager 78 extends downwardly from the pin 80 to the face 88 for the contact coupling, opposite to the axial face of the detent collar 72. It will be noted that the face 88 of the engager 78 is angled with respect to the longitudinal dimension of the leg of the associated engager to be in engaged engagement, opposite with the detent collar 72 in the engaged position of the engager illustrated in FIG. FIGURE 4. A driving rod of the hook 90 is attached to one end of each hook 70 by a pivot pin 92, and extends downwardly through a support 94 in the plate of the revolver tool holder 92. As best seen in FIGURE 17, the pin 92 extends through a slot 93 in the latch 78 to rotatably adjust the latch 78 around the latch pin. pivot 80. The lower end of the actuator bar 90 supports a cam roller 96 which is positioned for axial coupling with a cam 98 supported by the lower section of the machine structure 16. A pin 100 is attached to the middle part from the plate of the revolver tool holder 20 by a screw 102, and extends downwardly from the plate 20 in a receptacle 104 formed in a slider 52 to prevent rotation of the slider 52 around the shaft 24. An anti-rotation clamp 103 (FIGURES 1-4 ) is fixed to each actuator 34, and slidably hugs the shaft 24 of the adjacent adjacent tooling pair (see FIGURES 2 and 2A) to imply the rotation of each actuator 34 The axis of its associated shaft 24. The screws 102, the pins 100 and the clamps 103 in this way keep the tooling pairs in alignment. The clamps 103 also maintain the tangential alignment of the rollers 36 with the cam 38. In operation, when the mold cavities open in the condition of FIGURES 3 and 6A to receive the mold loads, the lower leg of the engager 78 it is biased by the spring 84 in the sliding, radial coupling with the outer periphery of the projection 74 in the stop collar 72. When the revolver tool holder 12 continues to rotate past the molding loading station 66 (FIGURE 2), the lower and upper rollers 36, 61 are coupled by the lower and upper cams 38, 60 as previously described to close the sections of the mold. When the mounting of the tooling, lower 50 and the hook 78 are moved upwardly by the cam 60, and when the upper tooling assembly 32 and the sliding shaft 24 are moved down the cam 38, the hook 8 slides along of the radial, opposite surface of the stop collar 72 until the end of the catch 78 clears the projection 74 of the stop collar 72. At this point, the hook 78 is urged by a spring 84 to the engaged position illustrated in FIGURE 3 The forces applied by the upper cam 38 can now be removed, and the opposing mold sections are retained in the compression molding coupling by the operation of the latch 78 against the detent collar 72. This retained condition is subsequently maintained during a larger portion of the rotation of the revolver toolholder and the tool sections (FIGURE 2) until the tool mounts again enter the section of the cams 110 within which all the cams 38, 42, 64, 98 are placed. Then compressive forces are applied again to the upper cam 38 to release the hook 78 for movement. At this point, the cam roller 96 is brought into engagement with the release cam of the engager 98 (FIGURES 1, 3 and 5), which moves the actuator rod 90 upwardly and rotates the engager 78 out of engagement with the arresting collar 72. With the hook in this manner held by the cam 98 and the actuator bar 90 out of the latching position, the rotational or sliding forces on the upper roller 36 and the lower roller 61, and the rollers 40, can be released, 62 are put into engagement with the cams 42, 64 to separate the halves of the mold. In this way, the pair of particular tools is ready for a next load and a molding cycle. FIGURE 5 illustrates the timing of the cams 38, 42, 60, 64 and 98 within the cam section 110. With the mold tooling passing through the cam section in the 120 direction, the mold loads 121 (FIGURE 6A) are loaded into the mold cavities during the portion of the path 122 (FIGURES 5 and 6A) in which the mold tooling assemblies are held apart by the cams 42, 64 in cooperation with the rollers 40, 62. After the mold cavities are loaded, the continued rotation of the revolver tool holder in the direction 120 causes the lower tooling assembly 50 to be lifted by the lower shaping cam 60 in the portion of the path 124 (FIGURES * 5 and 6B). As the. Lower tool assembly continues to move upwardly, engaging 78 is in sliding contact with the side of the detent collar 72 for the maximum, upward stroke of the lower tooling. The clips of the cavity 58 contact the separator jackets 47 and the force of the separator jackets up against the springs of the separator sleeve 45 to close the mold cavities. The upper tool assembly 32 is then lowered into the path portion 126 (FIGURES 5 and 6C), by operation of the cam 38 and the roller 36, by a fixed stroke determined by the cam 38. Towards the end of this In this case, the force of limitation of the mold is reached and the cavity clips 56 are pressed against the force limiting mechanism provided by either nitrogen gas cylinders 65b or coil springs 65a. At this time, the force of the molding results in a reaction force against the cavity and its cavity holder 56 through the nitrogen or spring cylinder, and is opposed by the lower forming cam 60. In addition, the actuation of the actuator superior to its extended position, end at the path portion 128 (FIGURE 5) causes the cavity holder 56 to move further downward relative to the lower actuator slider 52, further compressing the fluid or coil spring, which limits the force of the mold. In this relative position of the upper actuator shaft 24 and the slider engager 78, the latch 78 clears the detent collar 72, and the latch spring 84 causes the latch to move in place above the detent collar. When the tooling progresses from the upper training cam 38 to the path portion 130 (FIGURE 5), the upper tooling assembly is lifted by the upward force of the coil or nitrogen spring until the engager 78 contacts the the upper surface of the detent collar 72, which prevents any further separation of the lower and upper tooling assemblies. At this point, the assembly of the complete, lower tooling 32 and 50 is maintained in a downward position against the reaction force of the spacer springs 45, and opposed by the lower cam 60 against the roller 61. The tooling assemblies of this They are maintained in a compressed state for the remaining rotation of the revolver tool holder (FIGURE 2) during curing by the operation of the latching device, with the minimum force applied to the lower cam and the upper cam that is completely absent. In this way, the assembly of the tooling is self-immobilized, and the opposing forces of the lower and upper tooling assemblies are contained within the tooling assembly, which results in only the spring force of the separator exerting an external force against the tool. structure of the machine. This force is approximately 30% of the total mold force and is applied in a downward direction against the lower cam and resisted by the revolver tool holder assembly. As the rotation of the revolver tool holder continues along the portion of the path 131 within the cam section 110 after the healing cycle, the upper rollers 36 are sequentially engaged in engagement with a releasing section of the upper cam 38, which it slightly compresses the force of the coil or nitrogen mold limiting the springs to reduce the force applied to the engager 78. While the engagement force is reduced in this manner, the roller 96 on the bar of the engagement actuator 90 engages with the cam 98, which releases the latching mechanism and keeps the latching mechanism open when the lower cam 64 engages the rollers 62 at time 132 to lower the lower tooling assembly. The mounting of the lower tooling in this manner is lowered to the portion of the path 134 (FIGURES 5 and 6D), at which point the cam 98 can release the bar from the driver of the hitch 90. The upper tooling assembly can then be released at time 136, and move upwardly on cam 42 and roller 40 to separate the formed portions of cores 46 between the tooling assemblies (FIGURE 6E) before loading the new mold loads.

FIGURES 8, 9 and 15 schematically illustrate the molding loading station 66. A pellet wheel assembly of the mold 140 has a circumferential, angularly spaced, internal arrangement of series assemblies or load pellet transfer cups 142 and in FIG. a circumferential, angularly spaced, outer arrangement of the series assemblies or load pellet transfer cups 144. Series assembly arrangements 142, 144 are placed on the respective radial, adjacent, annular wheel sections 146, 148. The section 148 is supported circumferentially and slidably by the section 146. The sections 146, 148 are fixed to each other by the screws extending through the oval holes (not shown). FIGURE 9 is a schematic representation of the wheel 140 having two series assemblies 142, 144 in alignment with a pair of molding load nozzles 150, 152 in a nozzle block 158, and a diametrically opposite pair of series assemblies. 142, 144 covering mold cavities 59 in which the mold loads are being placed. The nozzles 150, 152 are connected to the specialized charge melting channels 154, 156 within the nozzle block 158. These channels are supplied independently with the extruded material from a source 160 at a percentage proportional to the angular velocity of the tool holder. revolver 12. For mold cavities aligned radially, as illustrated in FIGURE 2, the two cavities can be loaded simultaneously. The radially aligned, rear cavities in the four-cavity tooling of the illustrated type will receive their mold materials at an increment later after the previous cavities within the group of four cavities. This time difference is not significant within the total time cycle. Two series assemblies or pellet cups 142, 144 are simultaneously aligned with two cavities 59 within the lower tooling assembly 50. As the pellet wheel 140 continues to rotate, an adjacent pair of pellet cups moves in alignment with the pellets. two cavities remaining within the group, and the pellets are discharged into the cavities. Since the instantaneous velocity of the cups of the pellets 144 is greater than that of the pellet cups 142, the path of the respective pellets of each will have a different trajectory towards the underlying cavity. Furthermore, the cavity coinciding with the pellet cups 144 will be moving at an instantaneous speed somewhat less than the cavity associated with the cup 142. For this reason, the outer ring 148 can be mechanically and circumferentially adjusted with respect to the inner ring 146 to compensate for such speed differences. In accordance with one aspect of the present invention, the mold cavities are provided in arrays that move in an endless path, preferably in a circular path, in equally circumferentially spaced arrangements. In this way, in FIGURE 2 there is a circular, inner arrangement of the mold cavities 59 and a circular, exterior arrangement of the mold cavities 59, with two cavities of each arrangement placed in each pair of the tooling. That is, each pair of the tooling maintains two cavities of the interior arrangement and two cavities of the exterior arrangement, or a total of four cavities. It will be noted in particular that the cavities 59 of the inner arrangement and the cavities 59 of the outer arrangement are spaced equally and equally from each other both within each clamp of the cavity 56 and between the clamps of the adjacent cavity. Similarly, the serial mounts or load transfer cups 142 and 144 on the transfer wheel 140 (FIGURES 8-9 and 15) are provided in evenly spaced circumferential arrangements. In this way, the angular velocity of the wheel 140 is coordinated with the angular velocity of the revolver tool holder 12 so that each can rotate continuously and at a constant speed during the operation. As noted above, the outer ring 148 is circumferentially adjustable with respect to the inner ring 146 for the synchronized delivery of the mold loads from the outer and inner cups. In the alternative embodiment of FIGURE 13, the number of serial mounts or transfer cups of the mold 142 within the inner ring 146 can be reduced by half or the source 160 can be synchronized to supply the extruded material to each two mounts In-line series 142. However, the wheel 140 will still rotate at an angular, constant speed, and the outer ring 148, can be easily adjusted to accommodate the non-parallel arrangement of the mold cavities in FIGURE 13. The mechanism for the The delivery of the mold loads to the serial transfers of the disc and from the serial assemblies of the transfer of the disc to the cavities of the mold is the same as in the North American patent, referred to above No. 5, 603, 964. FIGURE 7 illustrates a T-slot connection between the pins of the core 46 and the actuator 34 of each upper tooling assembly 32. The two T-slots 34a, 34b in each actuator 34 locate the total of the four pins of the core 46 within each assembly group of the tooling, each slot being of sufficient width to accommodate the linear separation difference between the cores in the interior arrangement and those in the exterior arrangement. By this means, the full 44 tool holder assembly can be quickly removed from the machine for maintenance or repair. It will also be recognized that, although a group of four cavities is illustrated in the drawings for each pair of tooling assemblies, the principles of the present invention in their broader aspects are not necessarily so limited. Each pair of actuators could hold a much larger part, or a group of three cavities in which the number of cavities in the outer arrangement would be twice as much as in the interior arrangement. Since the delivery path for each of the nozzles 50, 52 (FIGURE 9) is independently controlled, the weight in grams of the pellets received by the cavities in the interior arrangement may differ from those received in the exterior arrangement. Consequently, parts of a different size and shape can be manufactured in exterior and interior arrangements. The implementation of the invention as illustrated in FIGS. 1-9 reduces the loading of the machine by approximately 90% when compared to the prior art because some tools are simultaneously under compression of the forming cams. Although the mold pressure is applied, total in all the tools during the curing cycle, only the forces applied by the springs of the separating sleeves are resisted by the lower forming cam. All other forces are contained within the tooling by the latching mechanism, and those are isolated from the structure of the machine. There is a considerable reduction in forces (in the order of about 70%) applied to the lower shaping cam during the healing cycle, and a 100% reduction in the forces applied to the upper shaping cam. Simply stated, the upper shaping cam is needed only during the closing and opening stages of the mold tooling (FIGURE 5). As the number of cavities in the machine increases, this characteristic of the invention becomes increasingly significant. FIGURES 10, 11 and HA illustrate a modified apparatus 10a according to an alternative embodiment of the invention, in which the need for extending the lower lifting cam fully around the apparatus is eliminated. Specifically, an annular tool support ring 140 is rigidly mounted by a series of support columns 142 attached below the ring 22 of the revolver tool holder 12. The support ring 140 supports an array of circumferentially spaced collars 144 that are aligned in an assembly with the lower ends of the various tooling shafts 24. The axial lengths of the collars 44 are selected to receive the ends of the shaft 24 and to be contiguous with the axially lower face of the rings 76 that con the stop collars 74 to the shafts. 24. The support ring 140 and the collars 144 in this way limit the downward movement of these drive shafts, various 24, and resist the reaction force of the mold spacer springs 45 (FIGURE 6) that push down on the lower actuator and the latching mechanism, which transfers the force to the actuator shaft 24 when the tooling is in the hooked mode. The embodiment of FIGURES 10, 11 and HA increases the efforts within the revolver tool holder, but eliminates the load stress on the revolver tool holder supports. In addition, the need for extending the lower cam fully around the travel path is eliminated, so that the lower cam 60a is completely placed within the cam section 110a, as are the other cams. As shown in FIGURE HA, the lower cam 60a incorporates an elevation 60b which is synchronized in association with the chamber 98 to lift the lower actuators 56 and reduce the forces in the latching mechanism when the latches are released by the cam 98. Clearly, by selecting the appropriate profiles in the upper lev 38 and the lower cam 60, the release of the hitch could be accomplished by the action of the upper cam as previously described, and this alternative description of the function is not proposed to limit Such a prior embodiment FIGURE 12 illustrates another modified apparatus 10b according to the present invention, in which the need for extending the lower lifting cam all the way around the apparatus again is eliminated.A stop plate 150 is mounted on each upper actuator 34 that covers the plate of the revolver tool holder 18, and a stop pad 152 is placed on the plate 18 aba of each stop plate 150. When the upper actuator 34 and the tool assembly 32 are moved down the cam roller 36 to the engaged position, the stop plate 150 and the stop pad 152 cooperate to limit such downward movement When the hitch is actuated, the forces of the springs of the separator 45 (FIGURE 6) are transferred to the plate of the tool holder upper revolver 18, the actuator 34, the stop plate 150 and the stop pad 152. In this way it is eliminated the need for the upper cam completely around the displacement pad, although an increased load is placed on the securing of the upper actuator 34 to the shaft 24. In each case alternative methods of removing the lower elimination cam 60 in the portion of In the course of the cycle, an appropriate ramp down on the cam 60 would be required to allow the mounting of the latching tool 32, 56 to be lowered at the respective stops 150, 152 or 144, 140 in a controlled manner. FIGURE 13 illustrates a modification of the preferred embodiment particularly as shown in FIGURE 2, whereby each lower and upper tool assembly supports the tooling for three preferably four mold cavities. More specifically, the lower and upper tooling assemblies support the mold cavity fasteners 58a, the mold cores 46, the core liners, etc. for three mold cavities. In this way, there are two concentric arrangements of the tooling of the mold, with the external arrangements that have twice as many cavities as the interior arrangement. FIGURE 14 shows a modification in which the mold cavities, multiple in each tooling assembly, are replaced by an individual cavity tooling 56b, 58b of larger diameter. The following description refers to an alternative means for providing a selectable restriction of the opposing movement of the tooling pairs 32 and 50k and is included to illustrate that the above-mentioned locking means can be achieved by an alternate means, and as such the The application is not limited to the preferred means illustrated in the figures. For example, in a first modified form of the invention, with reference to FIGURE 3, the slider 52 and the upper actuator 34 could be connected by a hydraulic cylinder, with the bar of the cylinder attached to the actuator 34 and the cylinder body is attached to the slider 52 in a relationship parallel to the axis of the revolver tool holder. The stroke of the cylinder is fixed and the hydraulic pressure is controlled such that the closed condition of the tooling is sufficient to ensure compression of the pellet and the formation of the article, and the molding force is limited, by the spring means in the actuator lower, whereby the hydraulic forces exerted by the cylinder marginally exceed the force required to compress the spring means in the lower actuator. A rotating union could be attached, for example, to the base of the machine, and mounted coaxially with the revolver tool holder of a static, hydraulic power unit mounted to the base of the machine. By driving the pressurized oil to a plurality of four-way, mechanically operated hydraulic valves, each associated with one of each an equal number of hydraulic cylinders and mounted to the revolver tool holder, it is possible to remotely actuate the valves by a static cam on the base of the machine selectively to drive the cylinders and mechanically drive the tooling pair to a closed position or to an open position. Using this method, the upper cam 36 and / or the lower cam 60 could be used to ensure that the relative axial position of the pairs of the mold assemblies relative to the revolver tool holder is in a controlled path during the closing and opening of the mold by 'the drive. of the cylinders. This method would provide an immobilization means to keep the opposite opposed tooling independent of the external cams, and as would function as an immobilization feature as described in the preferred form of the invention, and they could also provide the driving force to close the molds In another form of the invention, a hydraulic cylinder could be used without the need for an externally mounted hydraulic power supply. In this case, each cylinder as described above, would preferably have a bar from side to side such that the annular area of the piston would be equal to that of the opposite side of the cylinder. A mechanically operated, two-way valve, positioned as described in the first modified form of the invention, would be connected to each of the two holes of the cylinder, such that the valve in the open condition, when the piston moves, the Oil contained within the cylinder on one side of the piston can be transferred to the opposite side of the piston that passes through the open valve. As both sides of the piston are for each, one of the two holes of the cylinder, such that with the valve in the open condition, when the piston moves, the oil contained within the cylinder on one side of the piston can be transferred to the opposite end of the piston. piston passing through the open valve. Since both sides of the piston are preferably of equal area, the total volume of the oil inside the cylinder remains constant and no oil input is required. Conversely, if the valve is kept closed, then the oil can not be transferred from one side of the piston to the opposite side and the piston is effectively immobilized in position and the opposing tooling can not move axially relative to each other. By causing the mechanically activated valve to be activated to an open condition, the tooling would be controlled by the cams as mentioned in the preferred method such that the tooling can be opened and closed with little resistance. Conversely, when the tooling is transferred to the healing portion of the cycle that does not have cams, the valve is biased by the spring to its free state, and the valve will be closed causing the tooling to be immobilized in an axial relationship as in the time of valve closing. This would substantially repeat the condition as described in the preferred method, the effective immobilization of the opposing tooling in a fixed axial relationship to hold the opposite closed tooling independent of the external cams, and as would function as a closing feature as shown in FIG. describes in the preferred form of the invention. In another form of the invention, the movement of the actuator 34 attached to the shaft 24 relative to the slide 56 can be selectively limited by a shaft clamp driven by the fluid pressure. This clamp is rigidly attached to the slider and comprises a pair of semi-cylindrical clamp shoes. A hydraulic drive cylinder compresses the shoes to the shaft and provides a frictional grip on the shaft, relative to the slider. The drive means for the hydraulic cylinder would be according to the first modified form, described above of the invention. In this case, the cam that drives the hydraulic valve would provide selective retention of the shaft, to provide a locking means to prevent relative movement of the actuator 34 to the slider 56. Thus, it can be understood that this form of the invention provides an alternative means to that of the mechanical engagement means of the preferred form of the invention. A further form of the invention uses a spherical screw and a spherical nut, together with a mechanical clutch brake. The clutch brake which is the spring loaded to the condition of the brake and mechanically driven to the brake condition. In this case, the spherical screw is rigidly joined to an extension of the upper actuator bracket 34 by means of a keyed shaft bushing and axially secured to the spherical screw, and this bushing is secured to a clamp of the actuator 34 when securing the screws . In this way, the spherical screw is held in a fixed relation to the actuator 34, and is mounted parallel to the axis of the revolver tool holder. The slider 52 has a corresponding spherical nut holder mounted coaxially with the spherical screw within the slider for relative, rotational movement with the slider, but is restricted from axial movement relative to the slider. Further, a mechanical clutch brake is mounted to the spherical nut and the slider such that in its maintained condition of the spring, the brake is applied to provide the rotational limitation to the spherical screw with respect to the slider. The clutch brake is actuated by a remote cam in a manner similar to that operated by the engager release in the preferred form of the invention, and in this case it will operate to oppose the clutch spring and allow the spherical nut to rotate. It can be understood from this description that the spherical screw can move axially relative to the slider only during the period when the brake is uncoupled, whereby the spherical nut is free to rotate as it is driven by the advance or retraction of the spherical nut. spherical screw. However, during the period where the brake is engaged, the spherical nut can not rotate relative to the slider, and the axial movement of the spherical screw relative to the slider is inhibited. This form of the invention provides a further alternative to the engaging means described in the preferred form of the invention.

It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention.

Having described the invention as above, the content of the following claims is claimed as property.

Claims (37)

1. An apparatus for the compression molding of a plastic article, comprising: an array of first tool assemblies each having a male mold associated therewith, an array of second tool assemblies each including a cavity mold opposite to the male mold of a first assembly of tools, a means for mounting each of a first assembly of tools and a second associated tool assembly for movement towards and away from each other to close and open, a means for moving each one of a first assembly of tools, a second associated tool assembly and a mounting means in an endless path, along a loading station wherein a load of extruded material is successively supplied to each cavity mold, one first fixed cam positioned along a portion of the endless path beyond the loading station for the successive movement of each of the first assembly d tools towards the second associated tool assembly, and a second fixed cam positioned along the portion of the endless path for the successive movement of each of the second tool assembly towards the associated first tool assembly such that the movements of the first assembly of tools and the second assembly of associated tools close the mold, characterized in that the apparatus also includes a means supported by the first and second tool assemblies to interlock each first tool assembly and the second associated tool assembly in one position of the mold closed when these move in the endless path away from the first fixed cam until the first and second tool assemblies arrive in an open position of the mold to a loading station, in which the first assembly of tools is moved relatively far from the second tool set such that a load of material and Xtruido can be supplied to the mold of the cavity.

2. The apparatus according to claim 1, characterized in that each of the first tool assembly and the associated second tool assembly comprise a plurality of male molds and a plurality of associated cavity molds which open and close simultaneously.

3. The apparatus according to claim 2, characterized in that the plurality of male molds and the plurality of cavity molds are arranged in a radially spaced relation along the endless path.

4. The apparatus according to claim 2 or 3, characterized in that the plurality of male molds and the plurality of cavity molds are arranged in a radially and circumferentially spaced relationship along the endless path.

5. The apparatus according to any of the preceding claims, characterized in that the means for mounting each of the first and second tool assemblies for movement towards and away from one another includes a means of the shaft in which the first assembly of the mold and the Second mold assembly are mounted for sliding movement.

6. The apparatus according to claim 5, characterized in that the first tool assembly is supported by the shaft and each of the second tool assembly includes a slider on the shaft to support the second tool assembly.

7. The apparatus according to claim 6, characterized in that the means supported by the tool assemblies that interlock each of the first tool assembly and each of the associated second tool assembly comprises a latching means.

8. The apparatus according to claim 7, characterized in that the hooking means comprises a hook on each slider operable to immobilize the second tool assembly in relation to the first tool assembly.

9. The apparatus according to claim 8, characterized in that it includes a stop collar on the shaft, the hook that is placed to engage the stop collar.

10. The apparatus according to claim 9, characterized in that it includes a means operated by the cam for coupling and uncoupling the hook.

11. The apparatus according to claim 10, characterized in that the hook is positioned for movement between a first position in the coupling with the stop collar to maintain the mold means in a closed position and a second position without engaging with the collar of the mold. stopping to allow opening the mold media.

12. The apparatus according to claim 11, characterized in that the means for selectively opening the immobilization means comprises means for selectively moving the hooker between the first and second positions.

13. The apparatus according to claim 12, characterized in that the immobilization means comprises a spring means operatively coupled to the hook to bias the hook towards one of the first and second positions, and the means for selectively moving the hook comprises a means for moving selectively the hooker to another of the first and second positions during the movement of the tool assemblies in the endless path.

14. The apparatus according to claim 13, characterized in that the immobilization means comprises an actuator of the hook in engagement with the hook and wherein the means for selectively moving the hook comprises the middle of the cam for the arrangement adjacent to the path for the hook. coupling with the actuator of the hook during a portion of the movement of the tool assemblies along the endless path to move the hook from the first position to the second position.

15. The apparatus according to claim 14, characterized in that the hook is mounted on a pivot in a. second assembly of tools and has an engaging face for the coupling found opposite with a stop collar.

16. The apparatus according to claim 11, characterized in that it also comprises a means for preventing the rotation of the means of the tools with respect to the shaft.

17. The apparatus according to claim 16, characterized in that the means for preventing rotation comprises a means that operatively couples the tool means to the means for mounting the tool means.

18. The apparatus according to claim 16, characterized in that the means for preventing the rotation comprises a means that slidably couples the tool means to the tree of the adjacent pair or the tool means in the arrangement.

19. A method of compression molding a plastic article, characterized in that it comprises the steps of: (a) providing a plurality of tool means mounted in opposite pairs, with the tool means of each pair including male and female molding means , opposing, (b) mounting the pairs of tool means for movement in an endless path with respect to the structure of the machine, (c) closing the molding means of each pair during a portion of movement of the means of tools in the endless trajectory for the compression molding of a molding load between the pairs of the mold, (d) immobilizing the molding means of each pair after step (c) in such a way that the forces imparted to the media of tools for keeping the molding means closed are substantially isolated from the structure of the machine, and (e) after the compression molding of the article between the pairs of molds, (the) disengaging the molding means and (e2) opening the molding means to release the article.

20. The method according to claim 19, characterized in that the steps (c) and (e2) are carried out when assembling the pair of the tool means in step (b) for movement towards and away from each other, and placing the cams on the machine structure to selectively close the pairs of molds in step (c) and open the pairs of molds in step (e2) during the associated portions of the motion in the endless path.

21. The method according to claim 20, characterized in that the steps (d) and (the) are carried out by mounting a latching mechanism on each pair of tooling means and an engager actuator extending from the latch mechanism, and placing a cam on the structure of the latching machine. coupling with the actuator of the engager associated with each pair of tool means during a portion of the movement in the endless path.

22. An apparatus for the compression molding of a plastic article including a plurality of segmented tool means mounted in opposite pairs with the tool means of each pair including opposite male and female molding means, the means for mounting the pairs of tooling means for continuous motion in an endless path and means for moving both tooling means of each pair to selectively close the molding means during movement in the trajectory for compression molding of the molding loading means between the molding means and opening the molding means to release a molded article from between the molding means, characterized in that each of the tool means includes a plurality of molding means for forming a corresponding plurality of mold cavities when the means of tools are closed, the means of molding within each tooling medium and between the media of tools that are equally spaced from each other.

23. The apparatus according to claim 22, characterized in that the molding means are placed in concentric arrangements in the tool means.

24. The apparatus according to claim 23, characterized in that one of the arrangements contains more of the molding means than the other of the arrangements.

25. The apparatus according to claim 23, characterized in that the molding means are placed in a radial alignment in the tool means.

26. The apparatus according to claim 23, characterized in that it further comprises means for supplying the mold loads to the molding means when the molding means are opened comprising: a disc placed to rotate about an axis to direct a periphery of the disc between the molding means when the molding means are opened, the first and second arrangements circumferentially spaced from the transfer means of the molding charge at the periphery of the disc radially spaced from each other with respect to the shaft by * a distance for , directing the transfer means in an overlying position with respect to the concentric arrangements of the molding means, and means for continuously rotating the disc in synchronism with the displacement of the molding means and the tool means in the endless path.

27. The apparatus according to claim 26, characterized in that the transfer means in each array are uniformly and circumferentially spaced from one another.

28. The apparatus according to claim 27, characterized in that the periphery of the disk includes a first portion in which an interior of the arrangements of the transfer means is placed, and a second portion in which an exterior of the arrangements of the means of transfer is placed, the second portion b circumferentially adjustable with respect to the first portion for the synchronized transfer of the mold loads to the exterior arrangement with respect to the interior arrangement.

29. The apparatus according to claim 28, characterized in that the means for rotating the disk comprises means for rotating the disk at a fixed radius to the movement of the molding means in the endless path.

30. A method of compression molding a plastic article comprising the steps of: (a) providing a plurality of tool means mounted in opposing pairs, with the tool means of each pair including male and female molding means, opposed , (b) mounting the pairs of tooling means for a continuous movement in an endless path, (c) closing the molding means of each pair during a portion of the movement of the tool means in the endless path for molding by compression of a molding charge between the molding means, and (d) after compression molding the article between the pairs of the mold, opening the molding means to release the article, characterized in that step (a) comprises the step of providing a plurality of female and male molding means in the tooling means of each pair for the compression molding of a plurality of molding loading means in step (c), molding means that are equally spaced from one another in the direction of the trajectory.

31. The method according to claim 30, characterized in that the molding means are provided in concentric arrangements in the tool means.

32. The method according to claim 31, characterized in that one of the arrangements contains more of the molding means than the other of the arrangements.

33. The method according to claim 31, characterized in that the molding means are placed in a radial alignment in the tool means.

34. The method according to any of claims 30-33, characterized in that it comprises the additional step of: (e) engaging the molding means of each pair after step (c) in such a way that the forces imparted to the means of tools for keeping the molding means closed are substantially insulated from the structure of the machine.

35. The method according to claim 31, characterized in that it comprises the additional step, while the tool means are opened, of supplying the molding charges to the molding means when: (the) mounting a disk to rotate it around an axis adjacent to the path such that a periphery of the disk rotates between the tool means when the tool means are opened, (e2) providing at least two arrays concentrically spaced from the transfer means of the molding charge at the periphery of the disk, with the arrangements that are radially spaced from one another by a distance corresponding to the lateral spacing between the molding means in each of the tool means, and (e3) continuously rotating the disc synchronization with the tool means in the path.

36. The method according to claim 35, characterized in that it comprises the additional step of (e4) adjustably positioning the circumferential arrangements of the transfer means circumferentially with respect to one another for the synchronized delivery of the molding charges to the media molding

37. The method according to claim 36, characterized in that the step (e3) comprises the step of rotating the disk at a fixed radius to the movement of the molding means in the endless path. SUMMARY OF THE INVENTION A method and apparatus for the compression molding of plastic articles such as caps includes a plurality of tools mounted in opposing pairs (32, 50) with the tools of each pair 'including opposite, female and male mold sections (46, 58). The pairs of tools are assembled for movement in an endless path. The pairs of tools and the associated mold sections are closed during movement in the path for compression of a molding charge in the mold cavity formed between the mold sections of each pair and open to release an article formed between the sections of the mold. A latching mechanism (70) is associated with each pair of tools to hold the tools and mold sections in the closed position during movement in the independent path of the mechanism to close the tools and the mold halves. In this way, the forces imparted to the mold halves and the tools for • keep the closed mold are isolated from the structure of the machine. The latch mechanism is selectively unengaged to allow opening the mold halves and release the compression molded article between the mold halves.