COMPRESSION MOLDING APPARATUS

Abstract: A compression molding apparatus comprising a rotary compression molding means (2), a material feed means (4) and an article carrying means (6). The rotary compression molding means includes a rotating supporting member (12) mounted rotatably about its central axis (8), a plurality of molding die means (14) mounted on said rotating supporting member (12) at circumferentially spaced intervals, each of said molding die means (14) having an upper die assembly (72) and a lower die assembly (74) cooperating with each other, at least one of the upper die assembly and lower die assembly being freely movable with respect to the other, a driving source (52) for rotating said rotating supporting mem­ her (12) in a predetermined direction and moving said mold­ ing die means (14) through a circular conveying passage including a material charging zone (A), a molding zone (B), a cooling zone (C) and an article discharging zone (D) located successively, and a die opening and closing means (54, 56, 58, 60, 62, 64, 66, 68, 70) for moving at least one of said upper and lower die assemblies in a predetermined manner with respect to the other according to the movement of the mold­ ing die means. The material feed means (4) feeds a plastic material to the molding die means in the material charging zone (A). The article carrying means (6) carries the molded article from the molding die means in the article discharging zone (D).

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a compression molding apparatus, and more specifically, it relates, although not exclusively, to a compression molding apparatus suitable for producing container closures or the like at high speeds with a high efficiency. 2. Description of the Prior Art As is well known to those skilled in the art, metallic container closures have recently tended to be superseded by plastic closures of various forms. Generally, the plastic closures are produced by injection or compression molding techniques. To obtain industrial and commercial success, it is important to mold the plastic closures in high quality and at high speeds and low costs sufficient to cope with the quality of the metallic closures and the speed and cost of metallic closure molding. However, conventional molding apparatuses cannot meet the above requirements, and have made it impossible to produce plastic container closures having sufficient marketability to cope with the metallic closures. EP-A-0 091 653 discloses a compression molding apparatus comprising the features of the precharacterizing part of claim 1. On the other hand, US-A-4 081 230 discloses an extrudate cutting device comprising an extruder fitted with an extrusion die plate having orifices therein, frame means, fastening means at one end of said frame means for attaching said frame means to said extruder, adaptor means at the other end of said frame means receiving a rotatable elongated cutting means, said elongated cutting means comprising at least one cylindrical roller rotatably mounted in said frame means such that the axis of said roller is located in the direct path of extrudates leaving said orifices of said extrusion die plate of said extruder. SUMMARY OF THE INVENTION It is a primary object of this invention to provide a compression molding apparatus which can produce plastic articles such as container closures or the like of high quality at sufficiently high speeds and low costs. Other objects of this invention along with its advantages will become apparent from the following description taken in conjunction with the accompanying drawings showing preferred embodiments of the compression molding apparatus of this invention. According to this invention, there is provided a compression molding apparatus comprising a rotary compression molding means including a rotating supporting member mounted rotatably about its central axis, a plurality of molding die means mounted on the rotating supporting member at circumferentially spaced intervals, each of the molding die means having an upper die assembly and a lower die assembly cooperating with each other, at least one of the upper die assembly and lower die assembly being freely movable with respect to the other, a driving source rotating the rotating supporting member in a predetermined direction and moving the molding die means through a circular conveying passage including a material charging zone, a molding zone, a cooling zone and an article discharging zone located successively, and a die opening-closing means for moving at least one of said upper and lower die assemblies in a predetermined manner with respect to the other according to the movement of said molding die means; a material feed means for feeding a plastic material to the molding die means in the material charging means; and an article carrying means for carrying the molded article from the molding die means in the article discharging zone, characterized in that the material feed means includes an extruding means for extruding a molten plastic material through an extrusion opening and cutting means for cutting the plastic material extruded through the extrusion opening and feeding it to the molding die means; the extruding means includes a die head having a flow passage extending from the inlet of an extruder to the extrusion opening existing on its surface and a conduit means for connecting the outlet of the extruder to the inlet of the die head; the cutting means includes a rotating shaft extending from behind the die head forwardly beyond the surface of the die head on which the extrusion opening exists, a rotating cutting blade mounted in the forward end portion of the rotating shaft and disposed on said surface of the die head, a driving source and a drivingly connecting means for drivingly connecting the driving source to the rotating shaft; and at least the die head in the extruding means and at least the rotating shaft and the rotating cutting blade in the cutting means are mounted on a slidable supporting frame, and the supporting frame is provided for free sliding between an operating position at which the die head and the rotating cutting blade are positioned in the material charging zone and a non-operating position at which they are retracted from the operating position. In preferred embodiments of this invention, various improvements are made in the material feed means, the molding die means in the rotary compression molding means, and the article carrying means. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a simplified top plan view showing one specific embodiment of the compression molding apparatus constructed in accordance with this invention; Figure 2 is a partial sectional view showing a rotary compression molding means in the compression molding apparatus shown in Figure 1; Figure 3 is a partial sectional view showing an upper die assembly in the compression molding means shown in Figure 2; Figure 4 is a partial perspective view showing a restricted member and its related structure in the upper die assembly shown in Figure 3; Figure 5 is a partial sectional view showing a lower die assembly in the rotating compression molding means in Figure 2; Figure 6 is a side elevation, partly in section, of a container closure molded by the compression molding apparatus shown in Figure 1; Figures 7-A, 7-B, 7-C and 7-D are cam diagrams showing the ascending and descending movements of an outside supporting member and an inside supporting member in the upper die assembly shown in Figure 3 and of an outside supporting member and an inside supporting member in the lower die assembly shown in Figure 5; Figures 8-A to 8-F are each a partial sectional view showing the action of a molding die means in the rotary compression molding means shown in Figure 2; Figure 9 is a simplified side elevation showing a material feed means in the compression molding apparatus shown in Figure 1; Figure 10 is a simplified front elevation of the material feed means shown in Figure 9; Figure 11 is a partial perspective view showing a die head in the material feed means shown in Figure 9; and Figure 12 is a partial perspective view showing a feed hampering means in the material feed means shown in Figure 9. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS Preferred embodiments of the compression molding apparatus constructed in accordance with this invention will be described in detail with reference to the accompanying drawings. General Structure With reference to Figure 1, the illustrated compression molding apparatus is provided with a rotary compression molding means shown generally at 2, a material feed means shown generally at 4 and an article carrying means shown generally at 6. The rotary compression molding means 2 has a rotating supporting member 12 adapted to be rotated at a predetermined speed in the direction of an arrow 10 about a substantially perpendicularly extending central axis 8 (the axis 8 extends substantially perpendicularly to the sheet surface in Figure 1). A plurality of (12 in the drawing) molding die means 14 are mounted on the rotating supporting member 12 at circumferentially equally spaced positions. As will be stated in detail hereinafter, each of the molding die means 14 is comprised of an upper die assembly and a lower die assembly, and is opened or closed as required while being moved through a circular conveying passage incident to the rotation of the rotating supporting member 12. In the illustrated embodiment, a plastic material is fed into the molding die means 14 in the open state from the material feed means 4 while it is located in a material charging zone shown by A. Then, while the molding die means 14 is passing through a molding zone shown by B, it is gradually closed, and consequently, the plastic material is compression-molded into an article of the desired shape. While the molding die means 14 is passing through a cooling zone shown by C, it is maintained closed and the compression-molded article is cooled. While the molding die means 14 moves from the downstream end of the cooling zone C toward an article discharging zone shown by D, it is gradually opened, and in the article discharging zone D, the article separated from the molding die means 14 is carried away from the compression molding means 2 by the article carrying means 6. The individual constituent elements of the compression molding apparatus generally described above will be described below in detail. Rotary compression molding means The rotary compression molding means 2 will be described with reference to Figure 2. The illustrated rotary compression molding means 2 has a substantially horizontal stationary lower base plate 16 supported at a predetermined position by a suitable supporting structure (not shown). A plurality of (only one of which is shown in Figure 2) supporting posts 18 are provided on the peripheral edge portion of the lower base plate 16 at circumferentially spaced positions. A substantially horizontal stationary upper base plate 20 is fixed to the upper ends of these supporting posts 18. A substantially vertically extending, nearly cylindrical stationary hollow supporting post 22 is disposed centrally in the lower base plate 16. The hollow supporting post 22 has a flange 24 at its lower part, and by fixing the flange 24 to the surface of the lower base plate 16, the hollow supporting post 22 is fixedly secured to the lower base plate 16. That part of the hollow supporting post 22 which is below the flange 24 extends downwardly through an opening formed in the lower base plate 16. A stationary tube 26 of a relatively small diameter is provided concentrically within the hollow supporting post 22, and the lower end portion of the tube 26 is supported by a suitable supporting structure (not shown). A hollow rotating joint 32 known per se and comprised of a stationary portion 28 and a rotating portion 30 supported rotatably on the stationary portion 28 is mounted on the upper end of the hollow supporting post 22. A receptacle 38 having two chambers 34 and 36 is fixed to the hollow rotating joint 32. The tube 26 extends through the hollow rotating joint 32 and communicates with the chamber 24 of the receptable 38, and the lower end of the tube 26 is connected to a supply source 40 for supplying a cooling medium which may be ordinary water. The cooling medium supplied from the supply source 40 is sent to the chamber 34 of the receptacle 38 through the tube 26 and then to the molding die means 14 through a plurality of tubes 42 (only one of which is shown in Figure 2) of the molding die means 14 to be described in detail hereinbelow. Streams of the cooling medium which have been allowed to flow through the individual molding die means 14 are caused to flow into the chamber 36 of the receptacle 38 through a plurality of tubes (only one of which is shown in Figure 2) extending from the molding die means 14 to the chamber 36. Then, the cooling medium comes into the hollow supporting post 22, or more specifically, into an annular space existing outwardly of the tube 26 and flows downwardly, and is then discharged through a discharge pipe line (not shown) connected to the lower end portion of the hollow supporting post 22. The rotating supporting member 12 is rotatably mounted on the outside of the hollow supporting post 22 by means of a lower bearing 45 and an upper bearing 46. The main part of the rotating supporting member 12 has a regular dodecagonal outer shape (see Figure 1), and a mounting block 48 for the molding die means is fixed to each of the twelve substantially vertically extending, substantially flat surfaces of the supporting member 12. Each molding means 14 to be described in greater detail hereinbelow is mounted on the mounting block 48. An input gear 50 is fixed to the periphery of the lower end of the rotating supporting member 12, and drivingly connected to a driving source 52, which may be an electric motor, through a suitable power transmission mechanism (not shown). As a result, the rotating supporting member 12 and the twelve molding die means 14 mounted on it are rotated at a predetermined speed in a predetermined direction (the direction shown by arrow 10 in Figure 1) by the driving source 52. An annular supporting block 54 is fixed to the upper surface of the lower base plate 16, and a stationary annular cam block 56 is fixed to the upper surface of the annular supporting block 54. Three annular cams 58, 60 and 62 are formed in the annular cam block 56 (as will be described hereinafter, cam followers provided in the lower die assembly in the molding die means 14 are adapted to come into engagement with these cams 58, 60 and 62). To the under surface of the upper base plate 20 is fixed a stationary annular cam block 64, and three annular cams 66, 68 and 70 are formed in the annular cam block 64 (as will be described in detail hereinafter, cam followers formed in the upper die assembly of the molding die means are adapted to come into engagement with the cams 66, 68 and 70). Each of the molding die means 14 will be described below. In the illustrated embodiment, each molding die means 14 is comprised of an upper die assembly 72 shown by a two-dot chain line in Figure 2 and a lower die assembly 74 shown by a two-dot chain line in Figure 2. With reference to Figure 3, the illustrated upper die assembly 72 is provided with an outside supporting member 76 and an inside supporting member 78. The outside supporting member 76 is composed of a square pillar having a nearly square cross section, and mounted on the mounting block 48 for free sliding in a substatially vertical direction. More specifically, the mounting block 48 has at its upper end portion a mounting portion 80 which protrudes diametrically outwardly, and a mounting channel 82 which extends substantially vertically and has an open outside surface in the diametrical direction is formed in the mounting portion 80. The mounting channel 82 has a cross-sectional shape corresponding to the cross-sectional shape of the outside supporting member 76. By placing the outside supporting member 76 in the mounting channel 82, and thereafter, fixing a cover plate 84 to the outside surface of the mounting portion 80, the outside supporting member 76 is mounted for free sliding in a substantially vertical direction. The outside surface of the upper end portion of the outside supporting member 76 is fixed the lower end portion of a member 86. The member 86 extends substantially vertically and a substantially horizontally extending shaft 88 is fixed to the upper end of the member 86. A cam roller 90 forming a cam follower is rotatably mounted on the inside end portion of the shaft 88. The cam roller 90 engages the annular cam 66 formed in the stationary annular cam block 64. When the molding die means 14 is rotated in the direction of arrow 10 in Figure 1, the annular cam 66 and the cam roller 90 cooperatively elevate or lower the outside supporting member 76 in a required manner. A substantially vertically extending through-hole 92 having a circular cross section is formed centrally in the outside supporting member 76. The inside supporting member 78 is composed of a cylindrical pillar having a circular cross-sectional shape corresponding to the cross-sectional shape of the through-hole 92 and is mounted on the outside supporting member 76 for free sliding in a substantially vertical direction by inserting it into the through-hole 92. The revolving of the inside supporting member 78 within the through-hole 92 is hampered by a key 98 inserted in a key groove 94 formed on the peripheral surface of the inside supporting member 78 and in a key groove 96 formed in the inner circumferential surface of the outside supporting member 76. A bifurcated portion 100 is formed in the upper end portion of the inside supporting member 78, and a substantially horizontally extending shaft 102 is fixed to the bifurcated structure 100. Cam rollers 104 and 106 constituting cam followers are rotatably mounted on the shaft 102, and respectively engage the annular cams 68 and 70 formed on the stationary annular cam block 64. The annular cam 68 and the cam roller 104 cooperating with it and the annular cam 70 and the cam roller 106 cooperating with it elevate and lower the inside supporting member 78 in a required manner when the molding die means 14 is rotated in the direction of arrow 10 in Figure 1. Die members 108 and 110 are mounted on the lower end of the inside supporting member 78 (as will be described hereinbelow, these die members 108 and 110 define the top panel wall of a container closure and the inside surface of its skirt wall). Specifically, a downwardly open hole 112 is formed in the lower part of the inside supporting member 78. An internal thread is formed on the inner circumferential surface of a portion 114 having a relatively large diameter located in the lower part of the hole 112. The die member 108 is nearly cylindrical on the whole, and an external thread is formed on the peripheral surface of a portion 116 having a relatively small diameter located at its upper end. The die member 108 is fixed to the lower end of the inside supporting member 78 by threadably fitting the portion 116 located at its upper end into the portion 114 of the hole 112. Within the hole 112 is disposed a seal member 118 located immediately above the upper end of the die member 108, and that part of the hole 112 which is above the seal member 118 defines a cooling medium flowing space 120. A cooling medium is caused to flow into the cooling medium flowing space 120 from the tube 42 and then discharged from the space 120 through the tube 44. The upper half of the through-hole 122 has a relatively small diameter, while its lower half has a relatively large diameter. A downwardly directed shoulder portion 124 exists in the boundary area between them. The die member 110, on the other hand, has a main portion 126 and a cylindrical mounting portion 128 extending upwardly from the main portion 126. The cross-sectional shape of the mounting portion 128 of the die member 110 corresponds to the cross-sectional shape of the lower half of the hole 122 of the die member 108, and the die member 110 is mounted for free sliding in a substantially vertical direction by inserting its mounting portion 128 into the lower half of the hole 122 of the die member 108. Vertically extending elongate slots 130 are formed in the lower half of the die member 108 at a plurality of circumferentially spaced positions, and corresponding thereto, diametrically outwardly projecting pins 132 are fixed to the mounting portion 128 of the die member 110 at a plurality of circumferentially spaced positions. The diametrically outside parts of the pins 132 are located within the slot 130, and therefore, the ascending or descending movement of the die member 110 with respect to the die member 108 is restricted to a space between an upper limit position at which the pins 132 abut against the upper end of the slot 130 and a lower limit position (the position shown in Figure 3) at which the pins 132 abut against the lower end of the slot 130. Between the shoulder portion 124 in the hole 122 of the die member 108 and the mounting portion 128 of the die member 110 is disposed a spring means 134 for elastically biasing the die member 110 to the aforesaid lower limit position with respect to the die member 108. In the illustrated embodiment, there is also disposed a heat pipe 136 for cooling the die member 110 (and the die member 108) sufficiently effectively. The heat pipe 136 may be of any known form, and its heat absorbing lower end portion is inserted in, and fixed to, the die member 110. On the other hand, the heat releasing upper end portion of the heat pipe 136 is received in the cooling medium flowing space 120 for free ascending and or descending movement. Heat transmitted from a plastic material to be compression-molded to the die member 110 (and the die member 108) is absorbed by the heat absorbing end portion of the heat pipe 136, and released into the cooling medium flowing in the space 120 from its heat releasing end portion. As a result, the die member 110 (and the die member 108) is sufficiently effectively cooled. It should be noted in this regard that it is extremely difficult, if not impossible, to cool the die member 110 sufficiently effectively by directly passing a cooling medium through it because of its slidability to the die member 108 and to the inside supporting member 78, its relatively small size, etc., but that the use of the heat pipe 136 in the illustrated embodiment can lead to an effective cooling of the die member 110. Die members 138 and 140 are mounted on the lower end of the outside supporting member 76 (these die members 138 and 140 define the outside surface of a pilferproof bottom portion existing in the lower end portion of the skirt wall of a container closure as will be described in detail hereinafter). More specifically, a downwardly projecting cylindrical projecting portion 142 is formed at the lower end of the outside supporting member 76. The inside diameter of the projecting portion 142 is slightly larger than the outside diameter of the die member 108 fixed to the lower end of the inside supporting member 78, and an internal thread is formed on the inner circumferential surface of the projecting portion 142. The die member 138 is nearly cylindrical on the whole, and an external thread is formed on the outer circumferential surface of a portion 144 having a relatively small diameter existing in its upper half. The die member 138 is fixed to the lower end of the outside supporting member 76 by threadably fitting the portion 144 into the projecting portion 142. As shown in Figure 3, the die member 138 is located outwardly of the die member 108 fixed to the lower end of the inside supporting member 78, and the inside diameter of the die member 138 is made substantially the same as the outside diameter of the die member 108. The outside diameter of the lower half portion of the die member 138 is substantially the same as the outside diameter of the projecting portion 142. The die member 140 is disposed outwardly of the die member 138 and mounted on the outside supporting member 76 so that it can freely slide over a predetermined range in the direction of the longitudinal axis of the outside supporting member 76, namely in a vertical direction. A circular flange 146 is formed in the lower end portion of the outside supporting member 76, and correspondingly to it, a circular flange 148 is formed at the upper end of the die member 140. A plurality of (for example three) vertically extending holes 150 (only one of which is shown in Figure 3) are formed in the circular flange 148 at circumferentially spaced positions. The die member 140 is mounted on the outside supporting member 76 by inserting the main axial portion of a linking pin 154 having an enlarged head portion 152 at its lower end and an external thread formed at its upper end portion into the hole 150, and threadably mounting the upper end portion of the linking pin 154 on the circular flange 146 of the outside supporting member 76. It will be readily appreciated by reference to Figure 3 that the die member 140 can freely slide vertically relative to the outside supporting member 76 and the die member 138 fixed to it between a lower limit position, i.e. a projecting position (the position shown in Figure 3), at which the under surface of the circular flange abuts against the enlarged head portion 152 of the linking ping 154 and an upper limit position, i.e. a retracted position, at which the diametrically inwardly projecting portion formed in the inner circumferential surface of its lower end abuts against the under surface of the die member 138. Spring means 156 (only one of which is shown in Figures 3) which may be compression coil springs are disposed at a plurality of (for example, three) circumferentially spaced positions between the circular flange 146 of the outside supporting member 76 and the circular flange 148 of the die member 140. These spring means 156 elastically bias the die member 140 to the aforesaid projecting position (the position shown in Figure 3). In relation to the die member 140, an ascending hampering means is also provided in the illustrated embodiment which selectively hampers the ascending of the die member 140 to the retracted position from its projecting position. The ascending hampering means includes a restricted member 158 in the form of a nearly annular plate disposed outwardly of the die member 140. The ascending of the restricted member 158 is hampered by a plurality of protrusions 160 formed at circumferentially spaced intervals on the peripheral surface of the die member 140, and its descending is hampered by a lock nut 162 threadably mounted on the peripheral surface of the lower end of the die member 140. Thus, the restricted member 158 cannot move vertically with respect to the die member 140 but can rotate about the die member 140. With reference to Figure 4 taken in conjunction with Figure 3, a diametrically outwardly extending projecting portion 164 is formed in the restricted member 158, and a vertically extending pin 166 is fixed to the projecting portion 164. On the other hand, a diametrically outwardly extending pin 168 is fixed to the circular flange 148 of the die member 140. As shown in Figure 3, a spring means 170 which may be a tortion coil spring is interposed between the die member 140 and the restricted member 158. The spring means 170 elastically biases the restricted member 158 counter-clockwise as viewed from above in Figure 3 with respect to the die member 140, and thus elastically holds the restricted member 158 at a first angular position at which the pin 166 abuts against the pin 168, namely at the angular position shown in Figures 3 and 4. As clearly shown in Figure 4, three circumferentially spaced recesses or escape portions 172 are formed on the upper surface of the restricted member 158. When the restricted member 158 is at the aforesaid first angular position, each of the three escape portions 172 is positioned in alignment with the enlarged head portion 152 of the linking pin 154. Hence, by accomodating the enlarged head portion 152 in the escape portion 172, the restricted member 158 can be raised together with the die member 140 with respect to the outside supporting member 76, and consequently, the die member 140 can ascend to the aforesaid retracted position. On the other hand, a cam follower means 174 is rotatably mounted on the lower end of the pin 166, and as shown in Figure 1, a stationary cam means 176 (the member constituting the stationary cam means 176 is fixed to the lower base plate 16 via a suitable supporting member) adapted to act on the cam follower means 174 is provided downstream of the cooling zone C as viewed in the rotating direction 10 of the rotary compression molding means 2. When the molding die means 14 rotates and comes downstream of the cooling zone C, the stationary cam means 176 acts on the cam follower means 174 whereby the restricted member 158 is rotated through about 30 degrees for example, in a clockwise direction as viewed from above in Figure 3 against the elastic biasing action of the spring means 170 and brought to a second angular position. As a result, the escape portions 172 formed on the upper surface of the restricted member 158 come into out of alignment with the enlarged head portion 152 of the linking pin 154, and that part of the upper surface of the restricted member 158 which is between the escape portions 172, namely an abutting portion 178, is located opposite to the enlarged head portion 152 of the linking pin 154. Accordingly, as can be easily seen by referring to Figures 3 and 4, the abutting portion 178 of the restricted member 158 abuts against the enlarged head portion 152 to hamper the rising of the restricted member 158, and therefore, the die member 140 is prevented from rising to the aforesaid retracted position from the aforesaid projecting position (the position shown in Figure 3). Now, with reference to Figure 5, the lower die assembly 74 will be described. The illustrated lower die assembly 74 is provided with an outside supporting member 180 and an inside supporting member 182. Also, with reference to Figure 2, the mounting block 48 for molding die means also has a diametrically outwardly protruding mounting portion 183 at its lower end portion corresponding to the diametrically outwardly protruding portion 80 formed at its upper end portion (the upper die assembly 72 is mounted on the mounting portion 80). A mounting channel 184 extending substantially vertically and having an open diametrically outside surface is formed in the mounting portion 183. The cross-sectional surface of the mounting channel 184 is substantially square. A cover plate 186 is fixed to the diametrically outside surface of the mounting portion 183 to cover at least partly the open diametrically outside surface of the mounting channel 184. Again, with reference to Figure 5, the outside supporting member 180 is composed of a square pillar having a cross-sectional shape corresponding to the cross-sectional shape of the mounting channel 184, and its upper end portion is slidably received in the mounting channel 184. The upper end portion of a member 188 is fixed to the outside surface of the outside supporting member 180. To the lower end portion of the member 188 extending downwardly in a substantially vertical fashion is fixed a substantially horizontally extending shaft 190, and a cam roller 192 constituting a cam follower is mounted rotatably on the outside end portion of the shaft 190. The cam roller 192 engages the annular cam 58 formed in the stationary cam block 56. When the molding die means 14 is rotated in the direction of arrow 10 in Figure 1, the annular cam 58 and the cam roller 192 cooperatively raise or lower the outside supporting member 180 in a required manner. An outside power transmission member 194 is also provided in the mounting channel 184. The outside power transmission member 194 is composed of a square pillar having a cross-sectional shape corresponding to the cross-sectional shape of the mounting channel 184, and is received slidably in the mounting channel 184. A spring means 196 is interposed between the outside supporting member 180 and the outside power transmission member 194. The spring means 196 which may be made up of a plurality of circumferentially spaced compression coil springs (two of which are shown in Figure 5) elastically biases the outside power transmission member 194 vertically upwardly. The outside power transmission member 194 has a downwardly extending part which extends downwardly beyond the spring means 196. A diametrically outwardly protruding annular protruding portion 198 is formed at the lower end of the downwardly extending part of the member 194, and a stop ring 200 is fixed to the inner circumferential surface of the upper end portion of the outside supporting member 180. By the abutting of the annular protruding portion 198 against the stop ring 200, the vertically upward movement of the outside power transmission member 194 is restricted. To the upper end of the outside power transmission member 194 is fixed a nearly cylindrical die member 202 (which, as will be described in detail hereinafter, defines the outside surface of the main part of the skirt wall of a container closure). A nearly cylindrical member 204 is fixed to the periphery of the die member 202, and a cooling medium flowing channel 206 extending helically is formed on the inner circumferential surface of the member 204. A cooling medium is caused to flow into the cooling medium flowing channel 206 from the tube 42, and after flowing through the channel 206, flow away, thereby to cool the die member 202. Substantially vertically extending through-holes 208 and 210 having a circular cross-sectional shape are formed centrally in the outside supporting member 180 and the outside power transmission member 194 respectively. The upper half of the inside supporting member 182 has a circular cross-sectional surface corresponding to the cross-sectional shape of the through-holes 208 and 210, and is received slidably in the through-holes 208 and 210. The revolution of the inside supporting member 182 in the through-holes 208 and 210 is hampered by a key 216 inserted both in a key groove 212 formed in the peripheral surface of the inside supporting member 182 and in a key groove 214 formed in the inner circumferential surface of the outside supporting member. A bifurcated structure 218 is formed in the lower end portion of the inside supporting member 182, and a substantially horizontally extending shaft 220 is fixed to the bifurcated structure 218. Cam rollers 222 and 224 constituting a cam follower are rotatably mounted on the shaft 220. The cam rollers 222 and 224 respectively engage the annular cams 60 and 62 formed in the stationary annular cam block 56. The annular cam 60 and the cam roller 222 cooperating with it and the annular cam 62 and the cam roller 224 cooperating with it raise or lower the inside supporting member 182 in a required manner when the molding die means 14 is rotated in the direction of arrow 10 in Figure 1. Two members having a circular cross-sectional shape corresponding to the cross-sectional shape of the through hole 210, namely a first inside power transmission member 226 and a second inside power transmission member 228, are slidable received in the through-hole 210 formed in the outside power transmission member 194. The first inside power transmission member 226 has formed therein a through-hole having an upper portion 230 of a relatively large diameter and a lower portion 232 of a relatively small diameter. The axial portion of a bolt 234 whose head is received in the upper portion 230 of the through-hole extends through the lower portion 232 of the through-hole, and the lower end portion of the bolt 234 is threadably mounted on the upper part of the inside supporting member 182. A spring means 236 for elastically biasing the first inside power transmission member 226 vertically upwardly is interposed between the upper end of the inside supporting member 182 and the lower end of the first inside power transmission member 22. The vertically upward movement of the first inside power transmission member 226 is restricted by the abutting of an upwardly directed shoulder portion existing in the boundary between the upper portion 230 and the lower portion 232 of the through-hole against the head portion of the bolt 234. As will be clarified by a description given hereinafter, the spring means 236 should elastically bias the first inside power transmission member 226 with a considerably large force, and therefore, is conveniently made up of a plurality of plate springs stacked as shown in the drawing. An internal thread is formed on the inner surface of the upper end portion of the upper portion 230 of the through-hole in the first inside power transmission member 226, and corresponding to it, a small-diameter portion 238 having an external thread formed on its peripheral surface exists at the lower end portion of the second inside power transmission member 228. By threadably fitting the small-diameter portion 238 into the upper portion 230 of the aforesaid through-hole, the lower end portion of the second inside power transmission member 228 is fixed to the upper end portion of the first inside power transmission member 226. A die member 240 located inwardly of the die member 202 fixed to the upper end of the outside power transmitting member 194 (the die member 240, as will be described hereinafter, defines the outside surface of the top panel wall of a container closure) is fixed to the upper end of the second inside power transmission member 228. A small-diameter portion 242 having an external thread formed on its peripheral surface exists in the upper end portion of the second inside power transmission member 228, and corresponding to it, a hole 244 having an internal thread formed on its inner circumferential surface is located in the lower end portion of the die member 240. The die member 240 is fixed to the second inside power transmission member 228 by threadable engagement between the lower end portion of the die member 240 and the upper end portion of the second inside power transmission member 228. Blind holes cooperatively defining a cooling medium flowing space 246 are formed respectively in the upper half of the second inside power transmitting member 228 and the lower half of the die member 240. A tube 248 is concentrically fixed within the cooling medium flowing space 246. A cooling medium is caused to flow into the tube 248 form the tube 42, rises within the tube 248 and flows into the cooling medium flowing space 246 through an opening 250 formed in the upper end portion of the tube 248, after which it flows away through the tube 44. As a result, the die member 240 is cooled by the cooling medium. As will become clear from a description given later on, a number of vertically extending grooves for defining a number of axially extending protrusions on the outside surface of the main portion of a skirt wall in a container closure are formed on the inner circumferential surface of the die member 202 fixed to the upper end of the outside power transmission member 194, and corresponding to these, a number of protrusions are formed on the peripheral surface of the die member 240 fixed to the upper end of the second inside power transmission member 228. By partial engagement between the grooves and the protrusions, the revolution of the die member 240 itself within the die member 202 is inhibited. The molding die means 14 comprised of the upper die assembly 72 and the lower die assembly 74 is closed and opened in a predetermined manner while being moved through the circular conveying passage incident to the rotation of the rotating supporting member 12, and compression-molds the material into a container closure 252 in an upside-down state (upside down with respect to the normally standing state shown in Figure 6) as shown in Figure 6. With reference to Figure 6, the container closure 252 has a circular top panel wall 254 and a cylindrical skirt wall extending downwardly from the peripheral edge of the top panel wall 254. An annular protrusion 258 is formed on the inner surface of the top panel wall 254. The skirt wall 256 has a main portion 260 having a relatively large thickness and a pilferproof bottom portion 262 having a relatively small thickness. An internal thread 264 is formed on the inner surface of the main portion 260 of the skirt wall 256, and an annular protrusion 266 having a substantially horizontal under surface is formed in the lower end portion of the outside surface of the main portion 260. A number of slip-preventing protrusions 268 extending axially in circumferentially spaced intervals are formed in that area of the outside surface of the main portion 260 which is above the annular protrusion 266. On the inner surface of the pilferproof bottom portion 262 are formed a plurality of flaps 270 projecting diametrically inwardly at circumferentially spaced positions. According to the illustrated embodiment of the compression molding apparatus constructed in accordance with this invention, the container closure 252 having the aforesaid structure is formed by compression molding. The closure 252 is further subjected to the following treatment after compression molding. A plurality of circumferentially extending slits 272 are formed at some circumferentially spaced intervals as shown by the two-dot chain line in Figure 6 in the boundary between the main portion 260 and the pilferproof bottom portion 262 of the skirt wall 256 to form a weakened line composed of bridging portions 274 remaining among the slits 272. A seal member 276 composed of a suitable plastic material different from the plastic material constituting the closure 252 itself is applied to the annular protrusion 258 in the inner surface of the top panel wall 254. The closure 252 described above is only one example, and details of the structure and operation of the closure 252 itself are omitted in the present specification (for details about the closure 252, reference may, as required, be made to the specifications of Japanese Laid-Open Patent Publications Nos. 74445/1981, 30949/1983 and 51116/1983, for example). The operation of the molding die means 14 will be described in summary. Figures 7-A, 7-B, 7-C and 7-D are cam diagrams respectively showing the ascending and descending movement of the outside supporting member 76 of the upper die assembly 72 by the cooperative action of the annular cam 66 and the cam roller 90, the ascending and descending movement of the inside supporting member 78 of the upper die assembly 72 by the cooperative action of the annular cam 68 and the cam roller 104 and the cooperative action of the annular cam 70 and the cam roller 106, the ascending and descending action of the outside supporting member 180 of the lower die assembly 74 by the cooperative action of the annular cam 58 and the cam roller 192, and the ascending and descending movement of the inside supporting member 182 of the lower die assembly 74 by the cooperative action of the annular cam 60 and the cam roller 222 and the cooperative action of the annular cam 62 and the cam roller 224. With reference to these cam diagrams, Figure 1 and Figures 8-A to 8-F, it is seen that when the molding die means 14 is positioned in the material charging zone A shown in Figure 1, the upper die assembly 72 and the lower die assembly 74 are separated from each other in the vertical direction as shown in Figure 8-A. In this state, a predetermined amount of a suitable plastic material 278 such as polyethylene or polypropylene in the molten state is fed into the molding die means 14, and more specifically, into the die member 240 of the lower die assembly 74, from the material feed means 4 (the material feed means 4 will be described in detail hereinafter). When the molding die means 14 then rotates in the direction of arrow in Figure 1 and enters the molding zone B, the outside supporting member 76 and the inside supporting member 78 are gradually lowered, and simultaneously the outside supporting member 180 and the inside supporting member 182 of the lower die assembly 74 are gradually raised, as the molding die means 14 rotates. Before the molding die member 14 reaches the position shown by B-1 in Figure 1, the lower end of the die member 140 of the upper die assembly 72 abuts against the upper end of the die member 202 of the lower die assembly 74, and because of this, the die member 140 of the upper die assembly 72 is elevated relative to the outside supporting member 76 and the die member 138 fixed to it against the elastic biasing action of the spring means 156 (Figure 3) and brought to the aforesaid retracted position (see Figure 8-B) from the aforesaid projecting position (see Figure 8-A). While the molding die means 14 rotates from the position shown by B-1 in Figure 1 to the position shown by B-2, the outside supporting member 180 of the lower die assembly 74, and therefore the die member 202, are lowered as the outside supporting member 76 of the upper die assembly 72, and therefore the die members 138 and 140, are lowered. As a result, at the position B-2, the die members 138, 140 and 202 assume the positions shown in Figure 8-B. On the other hand, while the molding die means 14 rotates from the position B-1 to the position B-2, the inside supporting member 182 of the lower die assembly 74 and therefore the die member 240 are held at their uppermost positions without further rising. But the inside supporting member 78 of the upper die assembly 72 is kept descending and the lower end of the die member 110 abuts against the plastic material 278. Accordingly, the die member 110 is raised to the raised position shown in Figure 8-B (at this raised position, the lower surface of the main portion 126 of the die member 110 abuts against the lower surface of the die member 108) relative to the inside supporting member 78 and the die member 108 against the elastic biasing action of the spring member 134 (Figure 3). Furthermore, as shown in Figure 8-B, the plastic material 278 is slightly compressed and deformed between the die member 110 and the die member 240. While the molding die means 14 rotates from the position B-2 to the downstream end of the molding zone B (and therefore the upstream end of the cooling zone C), the inside supporting member 78 of the upper die assembly 72, and therefore the die members 108 and 110, are lowered slightly. As a result, the plastic material 278 is compressed and deformed into the closure 252, as can be understood from a comparison of Figure 8-B with Figure 8-C. It will be appreciated in this regard by comparison of Figure 8-B with Figure 9-C and also by referring to Figures 7-A and 7-C that since in the aforesaid compression molding, the outside supporting member 76 of the upper die assembly 72, and therefore the die members 138 and 140, are elevated by a predetermined amount and the outside supporting member 180 of the lower die assembly 74, and therefore the die member 202, are also elevated by a predetermined amount, the flowing of the plastic material 278 for skirt wall formation between the peripheral surface of the die member 110 and the inner circumferential surfaces of the die members 202, 140 and 138 is promoted, and the closure 252 is accurately molded as predetermined. The following fact should further be noted with regard to the compression molding operation. It is extremely difficult, if not impossible, to adjust the amount of the plastic material 278 to be fed to the molding die means 14 in the material charging zone A quite precisely to the required one, and generally, there is some variation in the amount of the plastic material 278 to be fed to the molding die means 14. According to the molding die means 14 in the compression molding apparatus 2 constructed in accordance with this invention, the variations in the amount of the plastic material 278 can be corrected by changing the thickenss t (Figure 6) of the top panel wall 254 of the closure 252 without changing the effective height h (Figure 6) from the inner surface of the top panel wall 254 to the lower end of the skirt wall 256. Specifically, in the illustrated molding die means 14, the positions shown in Figure 8-C of the die members 110 and 108 at the inside supporting member 78 of the upper die assembly 72, and the positions shown in Figure 8-C of the die members 140 and 138 at the outside supporting member 76 of the upper die assembly 72 (and therefore, the position shown in Figure 8-C of the die member 202 of the lower die assembly 74) are mechanically defined at fixed positions by the cooperative action of the annular cam 68 and the cam roller 104, the cooperative action of the annular cam 70 and the cam roller 106 and the cooperative action of the annular cam 66 and the cam roller 90. In contrast, in the lower die assembly 74, the position of the inside supporting member 182 in Figure 8-C is mechanically defined at a fixed position by the cooperative action of the annular cam 60 and the cam roller 222 and the cooperative action of the annular cam 62 and the cam roller 224, but the spring means 236 is interposed between the inside supporting member 182 and the die member 240. The spring means 236 elastically biases the die member 240 upwardly with a force large enough to compression-mold the plastic material 278, but the action of a force greater than the elastic biasing force of the spring means 236 on the die member 240 causes the die member 240 to descend against the elastic biasing action of the spring means 236. If, therefore, the amount of the plastic material 278 fed is, for example, slightly larger than a predetermined amount, the die member 240 is lowered slightly from the predetermined position, and the thickness t of the top panel wall 254 becomes larger by an amount corresponding to the lowering of the die member 240 and thus sets off the excess of the amount of the fed plastic material 278. If, on the other hand, the amount of the fed plastic material 278 is slightly smaller than the predetermined amount, the die member 240 slightly rises from the predetermined position. As a result, the thickness t of the top panel wall 254 becomes smaller by an amount corresponding to the rising of the die member 240, and thus sets off the shortage of the amount of the plastic material 278. Generally, the effective height h of the closure 252 is important to the sealing property, etc. of the closure 252, but the thickness t itself of the top panel wall 254 does not adversely affect the sealing property, etc. of the closure 252. Accordingly, the illustrated molding die means 14 can permit molding of the container closure 252 having the required sealing property, etc. irrespective of some variations in the amount of the plastic material 278 fed. While the molding die means 14 continues to rotate in the direction of arrow 10 in Figure 1 and is passing through the cooling zone C, the die members 110, 108, 140 and 138 of the upper die assembly 72 and the die members 202 and 204 of the lower die assembly 74 are held at the positions shown in Figure 8-C. During this time, the molded closure 252 is fully cooled. When the molding die means 14 has left the cooling zone C and further continues to rotate, the outside supporting member 76 and the inside supporting member 78 of the upper die assembly 72 are gradually raised, and the outside supporting member 180 and the inside supporting member 182 of the lower die assembly are gradually lowered. At this time, in the upper die assembly 72, the die member 110 descends to its lowest position shown in Figure 8-D relative to the inside supporting member 78 and the die member 108, and the die member 140 descends to its projecting position shown in Figure 8-D relative to the outside supporting member 76 and the die member 138. As a result, the die members 110 and 140 assume the state shown in Figure 8-D. In this state, the die members 108 and 138 are out of engagement with the closure 252. When the state shown in Figure 8-D is assumed, the stationary cam means 176 acts on the cam follower means 174 to bring the restricted member 158 to the second angular position against the elastic biasing action of the spring 170 as described hereinabove with reference to Figures 3 and 4. Consequently, when the die member 110 is later moved away from the closure 252, the die member 140 is prevented from rising relative to the outside supporting member 76 and the die member 138 and returning to its retracted position from its projecting position. Thereafter, the rising of the outside supporting member 76 of the upper die assembly 72, and therefore the die members 140 and 138, is interrupted, but the inside supporting member 78 of the upper die assembly 72 and therefore the die members 110 and 108 continue to rotate, and the outside supporting member 180 of the lower die assembly 74 and therefore the die members 202, and the inside supporting member 182 and therefore the die member 240 continue to descend. As a result, the die members 110, 202 and 240 are moved away from the closure 252 as shown in Figure 8-E. Then, the rising of the outside supporting member 76 of the upper die assembly 72 and therefore the die members 140 and 138 is resumed, and as shown in Figure 8-F, the die member 140 is also moved away from the closure 252, and the closure 252 is dropped onto the article carrying means 6 (which will be described in detail hereinafter) in the article discharging zone D. While the molding die means 14 further rotates toward the material charging zone A, the outside supporting member 76 and the inside supporting member 78 of the upper die assembly 72 are further raised, and the outside supporting member 180 and the inside supporting member 182 of the lower die assembly 74 are further lowered. As a result, the die members 108, 110, 138 and 140 of the upper die assembly 72 and the die members 202 and 240 of the lower die assembly 74 are returned to the state shown in Figure 8-A. Material Feed Means The material feed means 4 will now be described in detail. With reference to Figure 1, the illustrated material feed means 4 is provided with an extruding means 280 comprised of an extruder 282, a conduit means 284 and a die head 285. The extruder 282 which may be of a known type heat-melts a suitable plastic material such as polyethylene or polypropylene and discharges the molten material from its exit. One end of the conduit means 284 is connected to the exit of the extruder 282, and its other end is connected to the inlet of the die head 286. The molten plastic material discharged from the exit of the extruder 282 is fed to the die head 286 through the conduit means 284. As will be described in more detail hereinafter, an extrusion opening which may be circular is formed in the front surface (the upper surface in Figure 1) of the die head 286, and the molten plastic material fed to the die head 286 is extruded through the extrusion opening. As will be described in detail hereinafter, a cutting means is provided in relation to the extrusion opening of the die head 286. The plastic material extruded from the extrusion opening is cut by the cutting means and fed to the molding die means 14 in the material charging zone A. In the illustrated material feed means 4, the die head 286 (and at least a part of the cutting means provided in relation to it) are mounted on a supporting frame 292 mounted for free sliding between an operating position shown by a solid line in Figure 1 and a non-operating position shown by a two-dot chain line in Figure 1. When the plastic material is actually fed to the molding die means 14 in the material charging zone A, the supporting frame 292 is held at the operating position, and therefore, the die head 286 and its related structure are positioned in a required relation to the molding die means 14 in the material feed zone A. When it is desired to inspect the molding die means 14 for maintenance in the material charging means A, the supporting frame 292 is held at the non-operating position and the die head 286 and its related structure are moved away from the material charging zone A. As a result, the molding die means 14 can be inspected fully, easily and safely without hampering by the die head 286 and its related structure. To permit the aforesaid movement of the die head 286 relative to the extruder 282 which is stationary, the conduit means 284 connecting the extruder 282 to the die head 286 includes at least two articulated joints (three articulated joints 294, 296 and 298 in the illustrated embodiment). Specifically, the illustrated conduit means 284 includes a first, a second and a third conduit 300, 302 and 304. The first conduit 300 and the second conduit 302 are connected through the articulated joint 294, the second conduit 302 and the third conduit 304, through the articulated joint 296; and the third conduit 304 and the inlet of the die head 286, through the articulated joint 298. The articulated joint 294 permits pivoting of the second conduit 302 about an axis 306 extending substantially vertically (perpendicular to the sheet surface in Figure 1) relative to the first conduit 300. The articulated joint 296 permits relative pivoting of the second conduit 302 and the third conduit 304 about an axis 308 extending substantially vertically. The articulated joint 298 permits pivoting of the third conduit 304 about a substantially vertically extending axis 310 relative to the inlet of the die head 286. Consequently, the die head 286 is permitted to move as shown above relative to the extruder 282. Now, with reference to Figures 9 and 10, a stationary base station 312 is disposed at a predetermined position. The stationary base station 312 includes a pair of side wall structures 314 spaced from each other in the left-right direction in Figure 10 and a horizontal base plate 316 fixed between the side wall structures 314. Inwardly extending guide walls 317 are formed respectively in the upper ends of the pair of side wall structures 314. The supporting frame 292 is mounted between these guide walls 317 so that it can slide freely in the left-right direction in Figure 9 and in a direction perpendicular to the sheet surface in Figure 10. In more detail, guided walls 318 having an L-shaped cross section are formed respectively in both side surfaces of the supporting frame 292 which is in the form of an elongate plate as a whole, and the guided walls 318 are secured respectively to the lower surfaces of the guide walls 317 of the pair of side wall structures 314 via roller bearing members 320. As a result, the supporting frame 292 is mounted slidably. As shown in Figure 9, a fluid pressure cylinder mechanism 322 for sliding the supporting frame 292 is disposed between the supporting frame 292 and the stationary base station 312. The fluid pressure cylinder mechanism 322 is comprised of an air cylinder mechanism extending in the left-right direction in Figure 9. A cylinder 324 constituting the air cylinder mechanism is fixed to the lower surface of the supporting frame 292 by a pair of securing brackets 326, and a piston 328 also constituting the air cylinder mechanism has a free end fixed to the rear end of the stationary base station 312. Consequently, when the fluid pressure cylinder mechanism 322 is in the extended state, the supporting frame 292 is held at the operating position shown in Figure 9 (the operating position shown by a solid line in Figure 1). When the fluid pressure cylinder mechanism 322 is in the contracted state, the supporting frame 292 is moved a predetermined distance to the left in Figure 9 and held at the non-operating position shown by a two-dot chain line in Figure 1. If desired, the supporting frame 292 may be slided manually without using moving means such as the fluid pressure cylinder mechanism 322. With further reference to Figures 9 and 10, a supporting bracket 338 is fixed to the front end portion (the right end portion in Figure 9) of the supporting frame 292. The supporting bracket 338 has a horizontal portion 340 projecting forwardly (to the right in Figure 9), and the die head 286 is fixed to the horizontal portion 340 (the die head 286 itself will be described more in detail hereinafter). Furthermore, feed hampering means shown generally at 342 (to be described in more detail hereinafter) located below the horizontal portion 340 is mounted on the supporting bracket 338. Most of the constituent elements of a cutting means shown generally at 348 (to be described in more detail hereinafter) are mounted on the supporting frame 292. Accordingly, the die head 286, the feed hampering means 342 and most of the constituent elements of the cutting means 348 are moved between an operating position shown by a solid line in Figures 1 and 9 and a non-operating position shown by a two-dot chain line in Figure 1 incident to the movement of the supporting frame 292. The die head 286 will be described in detail with reference to Figure 11. The illustrated die head 286 is comprised of a nearly parallelpipedal die block 350 and a cooling plate 351 and a die plate 352 fixed successively to the front surface of the die block 350. A relatively large cut portion 354 is formed on one side portion of each of the die block 350 and the cooling plate 351, and corresponding to the cut portion 354, a through-hole 356 is formed in the die plate 352. A rotating shaft 358 of the cutting means 348 extends through the cut portion 354 and the through-hole 356, and a rotating cutting blade 360 is secured to the forward end of the rotating shaft 358 which projects forwardly beyond the die plate 352 (the rotating shaft 358 and the rotating cutting blade 360 of the cutting means 348 will be described further hereinafter). An extrusion opening 362 is further formed in the die plate 352. An extrusion flow passage 364 extending from the aforesaid inlet to the extrusion opening 362 is formed in the die block 350 and the cooling plate 351. Thus, the molten plastic material 278 fed to the inlet of the die head 286 from the extruder 282 through the conduit means 284 flows through the extrusion flow passage 364 and is extruded through the extrusion opening 362. The plastic material 278 extruded from the extrusion opening 362 is cut by a cutting edge 368 of the rotating cutting blade 360 rotating in the direction of an arrow 366 and dropped onto the molding die means 14 located in the material charging zone A (Figure 1), and more specifically onto the die member 240 of the lower die assembly 74 of the molding die means 14 (see Figure 8-A also). A circulating passage (not shown) through which to circulate a cooling medium such as water is formed in the cooling 351, and via the cooling plate 351 and the die plate 352, the rotating cutting blade 360 is cooled by the cooling medium circulating through the circulating passage. Experiences of the present inventors tell that when the amount of the plastic material 278 to be cut is relatively large and the rotating speed of the rotating cutting blade 260 is relatively low, the plastic material 278 which has been cut by the cutting edge 368 of the rotating cutting blade 360 and has descended along the surface of the die plate 352 to the lower edge of the die plate 352 incident to the rotation of the rotating cutting blade 360 tends to advance to the under surface of the die plate 352 and adheres to it without leaving the die plate 352 well and dropping downwardly. In order to circumvent this tendency, a gas stream jetting means is provided in the illustrated die head 286. The feed hampering means 342 will be described in detail with reference to Figure 12 in conjunction with Figures 9 and 10. The illustrated feed hampering means 342 comprises a receiving member 376 in the form of an elongated rectangular tray and a positioning means 378 comprised of a pneumatic pressure cylinder mechanism. A receiving stand 380 is fixed to the supporting bracket 338 (see Figures 9 and 10) secured to the supporting frame 292 through a suitable linking member (not shown). The receiving member 376 is movably placed on the receiving stand 380. Mainly with reference to Figure 12, a substantially horizontally projecting linking piece 382 is fixed to one side surface of the receiving member 376, and the upper end of a substantially vertically extending pin 384 is fixed to the linking piece 382. A supporting member 386 is also fixed to the supporting bracket 338 (Figures 9 and 10), and a substantially vertically extending pin-receiving hole is formed in the front end portion of the supporting member 386. The pin 384 is rotatably inserted in the pin-receiving hole of the supporting member 386. A linking piece 390 is fixed to the lower end of the pin 384 which projects downwardly from the pin receiving hole, and a linking piece 392 is pivotably connected to the linking piece 390. To the linking piece 392 is fixed the forward end of a piston rod 394 in the pneumatic cylinder mechanism constituting the positioning means 378. On the other hand, a supporting member 396 is also fixed to the supporting bracket 338 (Figures 9 and 10). The base end of a cylinder 398 in the pneumatic pressure cylinder mechanism constituting the positioning means 378 is pivotably linked to the supporting member 396 by means of a substantially vertically extending linking pin 400. Thus, when the pneumatic pressure cylinder mechanism constituting the positioning means 378 is contracted, the receiving member 376 is pivoted about the pin 384. When the pneumatic pressure cylinder mechanism is contracted to pivot the receiving member 376 in the direction shown by an arrow 402 and hold it at its non-operating position shown by a solid line in Figure 12, one side surface of the receiving member 376 abuts against a first stop piece 404 mounted on the receiving stand 380 whereby further pivoting of the receiving member 376 in the direction shown by the arrow 402 is hampered. When the pneumatic cylinder mechanism is contracted to pivot the receiving member 376 in the direction shown by an arrow 406 and hold it at its operating position shown by a two-dot chain line in Figure 12, the other side surface of the receiving member 376 abuts against a second stop piece 408 mounted on the receiving stand 380 whereby further pivoting of the receiving member 376 in the direction shown by the arrow 406 is hampered. As stated above mainly with reference to Figure 11, the plastic material 278 extruded from the extrusion opening 362 of the die head 286 and cut by the rotating cutting blade 360 leaves the rotating cutting blade 360 and is dropped toward the die member 240 of the lower die assembly 74 of the molding die means 14. When the receiving member 376 is held at the aforesaid operating position, the front end portion of the receiving member 376 is located within a path of dropping of the plastic material 278. Hence, the plastic material 278 drops onto the receiving member 376, and the supplying of the plastic material 278 to the die member 240 of the lower die assembly 74 is hampered. On the other hand, when the receiving member 376 is held at its non-operating position, it is located away from the path of dropping of the plastic material 278, and therefore, the plastic material 278 drops onto the molding die member 240. A gas stream jetting means 410 is provided at the front end of the receiving member 376. The gas jetting means 410 includes a block 412 fixed to the front end of the receiving member 376. The block 412 has formed therein a flow passage 414 extending laterally from one end of the block 412 over a required length, and a plurality of laterally spaced gas jetting holes 416 extending rearwardly from the flow passage 414 and opening to the rear surface of the block 412 (instead of the plurality of gas jetting holes 416, one or more elongate slits may be formed). The flow passage 414 is connected to a gas supply source (not shown) through a line (not shown) including a control valve. When the receiving member 376 is positioned at the operating position, the control valve is opened to supply a gas which may be compressed air to the flow passage 414 from the gas supply source. The gas is then jetted out from the gas jetting holes 416. The gas streams jetted from the gas jetting holes act on the plastic material 278 which has dropped onto the front end portion of the receiving member 376 and forces it toward the rear end portion of the receiving member 376. With reference to Figure 12 as well as Figures 9 and 10, a passage means 418 composed of a duct is provided in the illustrated embodiment in relation to the receiving member 376. As shown in Figure 10, the passage means 418 is detachably mounted on the supporting frame 292 by detachably linking securing bracket 421 fixed to the inside surface of the upper end portion of the passage means 418 to a securing bracket 419 fixed to the under surface of the supporting frame 292, and can therefore be moved incident to the movement of the supporting frame 292. The inlet formed at the upper end of the passage means 418 is positioned correspondingly to the rear end of the receiving member 376. The lower end of the passage means 418 is caused to communicate with a stationary resin reservoir tank 420. The plastic material 278 forced to the rear end portion of the receiving member 376 by the aforesaid gas streams is fed to the inlet of the passage means 418 from the receiving member 376, passed through the passage means 418, and enters the resin reservoir tank 420. In the resin reservoir tank 420, the plastic material 278 is cooled and hardened by water placed in it. In order for the molten plastic material 278 to move well through the passage means 418 without adhering to its inner wall, it is preferable to supply water to the inlet of the passage means 418 by a suitable means (not shown) thereby forming a water stream flowing from the inlet toward the outlet, and to carry the plastic material 278 on the water stream through the passage means 418. The following fact should be noted with regard to the feed hampering means 342. When a predetermined period of time elapses from the starting of the operation of the extruder 282, the action of the extruder 282 is not stable, and the amount and temperature of the plastic material 278 extruded from the extrusion opening 362 do not reach required values. It will be readily understood that if the plastic material 278 is fed to the molding die means 14 at this time and molded, the resulting molded product becomes poor in quality and adverse effects are likely to be exerted on the molding die means 14. In the illustrated embodiment, however, before the action of the extruder 282 is sufficiently stabilized, the receiving member 376 is held at its operating position to check the supplying of the plastic material 278 to the molding die means 14. Consequently, the production of poor molded products can be prevented and adverse effects on the molding die means 14 can be accurately avoided. Furthermore, when the action of the extruder 282 is stable but it is desired to stop the feeding of the plastic material 278 to the molding die means 14 by some reason, for example owing to some trouble that has occurred in the rotary compression molding means 2, the feeding of the plastic material 278 to the molding die means 14 can be hampered by holding the receiving member 376 at its operating position without the need to stop the operation of the extruder (once the operation of the extruder 282 is stopped, a waiting time is required upon resumption of its operation until the action of the extruder 282 becomes stable). Now, with reference again to Figures 9 and 10, bearing blocks 422 and 424 spaced from each other in the front-rear direction (the left-right direction in Figure 10) are fixed to the supporting frame 292. The rotating shaft 358 of the cutting means 348 is mounted by means of these bearing blocks 422 and 424 such that it can rotate freely and move freely in the front-rear direction over some distance. As can be easily understood by referring to Figure 11, to cut the plastic material 278 extruded from the extrusion opening 362 formed in the die plate 352 of the die head 286 sufficiently well by the rotating cutting blade 360, it is important that the cutting edge 368 of the rotating cutting blade 360 should be in sufficiently good contact with the surface of the die plate 352. To meet this requirement accurately, a unique method of mounting the rotating cutting blade 360 to the forward end portion of the rotating shaft 358 is employed in the illustrated cutting means 348. As stated hereinabove with reference to Figure 11, the rotating shaft 358 of the cutting means 348 extends through the cut portion 354 formed in the die block 350 of the die head 286. The extrusion flow passage 364 is formed in the die block 350, and the molten plastic material 278 flows through the extrusion flow passage 364. Hence, the die block 350 attains a considerably high temperature, and owing to this, the rotating shaft 358, particularly its front portion, tends to attain a considerably high temperature. Such considerably high temperatures adversely affect the shaft supporting structure of the rotating shaft 358. At the same time, the heat is transmitted from the rotating shaft to the cutting blade 360, and the cutting blade 360 may be exposed to unacceptably high temperatures. To solve this problem, a cooling means is annexed to the rotating shaft 358 of the cutting means 348 in the illustrated embodiment. With reference to Figure 9, the rotating shaft 358 of the cutting means 348 is drivingly connected to the driving source 52 (which functions both as a driving source for the rotary compression molding means 2 and a driving source for the cutting means 348 in the material feed means 4) through a drivingly connecting means including a power transmission system described below. Downwardly extending supporting walls 464 and 466 spaced from each other in the front-rear direction (the left-right direction in Figure 9) are provided on the under surface of the supporting frame 292, and a power transmission shaft 468 is rotatably mounted across the supporting walls 464 and 466. A timing pulley 470 is fixed to the front end portion (the right end portion in Figure 9) of the power transmission shaft 468. As a result, the rotating shaft 358 is drivingly connected to the power transmission shaft 468. A first rotating angular position adjusting mechanism shown generally at 478 and a second rotating angular position adjusting mechanism shown generally at 480 are mounted on the upper surface of the horizontal base plate 316 in the stationary base station 312 (the first and second rotating angular position adjusting mechanisms 478 and 480 will be described in detail hereinafter). A non-uniform speed rotating mechanism shown generally at 482 (which will be described in detail hereinafter) is mounted on the under surface of the horizontal base plate 316. A timing pulley 486 is fixed to the output shaft 484 of the first angular position adjusting mechanism 478, and a timing pulley 488 is attached to the rear end portion (the left end portion in Figure 9) of the power transmission shaft 468. The timing pulley 488 is mounted on the power transmission shaft 468 so as to rotate as a unit with the power transmission shaft 468. The power transmission shaft 468, however, is adapted to move relative to the timing pulley 488 in the front-rear direction (the left-right direction in Figure 9). A supporting bracket 490 is fixed to the upper surface of a housing including the first rotating angular position adjusting mechanism 378, and the timing pulley 488 is connected to the supporting bracket 490 so that it is freely rotatable but cannot move in the front-rear direction. As a result, the movement of the timing pulley 488 in the front-rear direction is hampered. Thus, when the supporting frame 292 is moved in the front-rear direction (the left-right direction in Figure 9) by the fluid pressure cylinder mechanims 322, the power transmission shaft 468 and the timing pulley 470 fixed to its front end portion are moved in the front-rear direction, but the timing pulley 488 mounted on the rear end portion of the power transmission shaft 468 is not moved in the front-rear direction but held at the position shown in the drawing. An endless timing belt 492 is wrapped about the timing pulley 488 and the timing pulley 486, and consequently, the power transmission shaft 468 is drivingly connected to the output shaft 484 of the first rotating angular position adjusting mechanism 478. A timing pulley 496 is fixed to the input shaft 494 of the first rotating angular position adjusting mechanism 478, and a timing pulley 500 is fixed to the output shaft 498 of the non-uniform speed rotating mechanism 482. An endless timing belt 502 extending through an opening 473 formed in the horizontal base plate 316 is wrapped about the timing pulleys 496 and 500. As a result, the input shaft 494 of the first rotating angular position adjusting mechanism 478 is drivingly connected to the output shaft 498 of the non-uniform speed rotating mechanism 482. A timing pulley 506 is fixed to the input shaft 504 of the non-uniform speed rotating mechanism 482, and a timing pulley 510 is fixed to the output shaft 508 of the second rotating angular position adjusting mechanism 480. An endless timing belt 514 extending through an opening 512 formed in the horizontal base plate 316 is wrapped about the timing pulleys 506 and 510. As a result, the input shaft 504 of the non-uniform speed rotating mechanism 482 is drivingly connected to the output shaft 508 of the second rotating angular position adjusting mechanism 480. The input shaft 516 of the second rotating angular position adjusting mechanism 480 is drivingly connected to the driving source 52 through a suitable driving system (not shown). Thus, the rotation of the driving source 52 is transmitted to the rotating shaft 358 through the second rotating angular position adjusting mechanism 480, the non-uniform speed rotating mechanism 482, the first rotating angular position adjusting mechanism 478 and the power transmission shaft 468 to rotate the rotating shaft 358 and the cutting blade 360 mounted on it. As shown in Figure 9, the non-uniform speed rotating mechanism 482 has a housing 475 fixed to the under surface of the horizontal base plate 316. The output shaft 498 is rotatably mounted on the housing 475 by means of a bearing 477, and the input shaft 504 is also rotatably mounted on the housing 475 by means of a bearing 479. An elliptical gear 481 is fixed to the output shaft 498, and an elliptical gear 483, to the input shaft 504. The elliptical gears 481 and 483 which mesh with each other convert the uniform speed rotation transmitted to the input shaft 504 into non-uniform speed rotation and transmit it to the output shaft 498. The following fact should be noted with regard to the non-uniform speed rotating mechanism 482 described above. It is necessary that the rotating cutting blade 360 should cut the plastic material 278 extruded from the extrusion opening 362 (see Figure 11) of the extruding means 280 in synchronism with the rotation of the molding die means 14 (see Figure 1) in the rotary compression molding means 2. Hence, the time required for the rotating cutting blade 360 to rotate through one turn is determined univocally by the rotating speed of the molding die means 14 in the rotating compression molding means 2. Experiences of the present inventors show, on the other hand, that to cut the plastic material 278 extruded from the extrusion opening 362 in a required manner, it is important to adjust the angular velocity ω₂ of the rotating cutting blade 360 at the time of crossing the extrusion opening 362 to a predetermined value, usually a sufficiently large value. If the angular velocity ω₂ of the rotating cutting blade at the time of crossing the extrusion opening 362 is set at a relatively large value (usually, at max ω₂) and is gradually decreased immediately after cutting the plastic material 278 across the extrusion opening 362, the following advantage can be obtained. When the angular velocity ω₂ of the rotating cutting blade is decreased immediately after cutting the plastic material 278, the cut plastic material 278 tends to keep moving by inertia at an angular velocity corresponding to the angular velocity (usualy max ω₂) of the rotating cutting blade 360, whereas the movement of the rotating cutting blade 360 gradually decreases and thereby the separation of the cut plastic material from the rotating cutting blade 360 is accelerated. If desired, two or more pairs of elliptical gears may be used in order to increase the rate of change in the velocity of the rotating cutting blade 360. In the illustrated embodiment, the rotation of the molding die means 14 in the rotary compression molding means 2 and the cutting of the plastic material 278 by the cutting blade 360 are kept in synchronism in the required manner by properly adjusting the rotating angular position of the output shaft 508 relative to the input shaft 516 by the second rotating angular position adjusting mechanism 480. Furthermore, the angular velocity ω₂ of the rotating cutting blade 360 at the time of crossing the extrusion opening 362 is preset at a suitable value between min ω₂ and max ω₂ by properly adjusting the rotating angular position of the output shaft 484 relative to the input shaft 494 by the first rotating angular position adjusting mechanism 478. Desirably, in view, for example,of the ease of the adjusting operation, the first and second rotating angular position adjusting mechanisms 478 and 480 are desirably of such a type that the rotating angular position of the output shaft relative to the input shaft can be adjusted without stopping the rotation of the input shaft and the output shaft.

Claims: A compression molding apparatus comprising a rotary compression molding means (2) including a rotating supporting member (12) mounted rotatably about its central axis (8), a plurality of molding die means (14) mounted on the rotating supporting member (12) at circumferentially spaced intervals, each of the molding die means having an upper die assembly (72) and a lower die assembly (74) cooperating with each other, at least one of the upper die assembly and lower die assembly being freely movable with respect to the other, a driving source (52) rotating the rotating supporting member in a predetermined direction and moving the molding die means through a circular conveying passage including a material charging zone (A), a molding zone (B), a cooling zone (C) and an article discharging zone (D) located successively, and a die opening-closing means (56, 58, 60, 62, 64, 66, 68, 70) moving at least one of said upper and lower die assemblies in a predetermined manner with respect to the other according to the movement of the molding die means; a material feed means (4) feeding a plastic material to the molding die means in the material charging means; and an article carrying means (6) carrying the molded article from the molding die means in the article discharging zone (D), characterized in that the material feed means (4) includes an extruding means (280) for extruding a molten plastic material through an extrusion opening and cutting means (348) for cutting the plastic material extruded through the extrusion opening and feeding it to the molding die means (14); the extruding means (280) includes a die head (286) having a flow passage extending from the inlet of an extruder (282) to the extrusion opening existing on its surface and a conduit means (284) for connecting the outlet of the extruder (282) to the inlet of the die head (286); the cutting means (348) includes a rotating shaft (358) extending from behind the die head forwardly beyond the surface of the die head (286) on which the extrusion opening exists, a rotating cutting blade (360) mounted in the forward end portion of the rotating shaft (358) and disposed on said surface of the die head (286), a driving source (52) and a drivingly connecting means (468) for drivingly connecting the driving source (52) to the rotating shaft (358); and at least the die head (286) in the extruding means (280) and at least the rotating shaft (358) and the rotating cutting blade (360) in the cutting means (348) are mounted on a slidable supporting frame (292), and the supporting frame (292) is provided for free sliding between an operating position at which the die head (286) and the rotating cutting blade (360) are positioned in the material charging zone (A) and a non-operating position at which they are retracted from the operating position. The apparatus of claim 1, which further comprises a fluid pressure cylinder mechanism (322) for sliding the supporting frame (292). The apparatus of claim 1 wherein the extruder (282) in the extruding means (280) is held stationary at a predetermined position, and the conduit means (284) in the extruding means (280) includes at least two articulated joints (294, 296, 298). The apparatus of claim 3 wherein the conduit means (284) includes a first and a second rigid conduit members (302, 304), the upstream end of the first conduit member (302) is connected to the outlet of the extruder (282) through an articulated joint (294), the downstream end of the first conduit member (302) is connected to the upstream end of the second conduit member (304) through another articulated joint (296), and the downstream end of the second conduit member (304) is connected to the inlet of the die head (286) through still another articulated joint (298). The apparatus of claim 1, wherein the plastic material extruded from the extrusion opening of the die head (286) is cut by the rotating blade (360) and dropped; and the supporting frame (292) has further mounted thereon a receiving member (376) which is freely movable between an operating position located in a path of dropping of the plastic material and a non-operating position spaced away from the path of dropping, and a positioning means (378) for selectively holding the receiving member (376) at the operating position and the non-operating position. The apparatus of claim 1 wherein said cutting means (348) for cutting the plastic material extruded through the extrusion opening serves also to drop it toward the molding die means (14), and the material feed means (4) includes also a feed hampering means (342) for selectively hampering the feeding of the plastic material to the molding die means (14); and the feed hampering means (342) includes a receiving member (376) mounted for free movement between an operating position located in a path of dropping of the plastic material toward the molding die means (14) and a non-operating position spaced from the dropping path, and a positioning means (378) for selectively holding the receiving member (376) at the operating position and the non-operating position. The apparatus of claim 6 wherein the feed hampering means (342) further includes a resin reservoir tank (420), and when the receiving member (376) is held at the operating position, the plastic material dropped onto the receiving member (376) is sent to the resin reservoir tank (420) from there. The apparatus of claim 7 wherein the resin reservoir tank (420) holds water therein. The apparatus of claim 8 wherein a passage means (418) is disposed between the receiving member (376) and the resin reservoir tank (420) so that the plastic material dropped onto the receiving member (376) is sent to the resin reservoir tank (420) through the passage means (418). The apparatus of claim 9 wherein a gas stream jetting means (410) for jetting gas streams which force the plastic material dropped onto the receiving member (376) to one end portion of the receiving member (376) and carry it to the inlet of the passage means (418) is annexed to the receiving member (376). The apparatus of claim 9 wherein a water stream is formed in the passage means (418) flowing from its inlet to its outlet, and the plastic material is carried on the water stream.

Inventors: KUBO, TATEO, OSHIMA, NORITSUGU, SAKAGUCHI, KENICHI, TAKEDA, HIROSHI
Applicants: TOYO SEIKAN KAISHA LIMITED
Application year: 1985
Main classification: B29C43
IPC codes: B29C43, B29C37, B29B9, B29C31, B29C69, B29B11, B29C47, B29L31