CA1248314A - Apparatus for making blow molded articles - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

An apparatus for making hollow articles having a rotatable polygonal turntable, a parison forming station at one side face of the turntable, a blow molding station at another side face of the turntable and a stripping station at still another side face of the turntable. The apparatus has means for connecting at least one core rod on which the parison is formed to the turntable , such that at least one core rod is parallel to a side face core rod is of the turntable, and for rotation therewith.

Description

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BACKGROUN~ OF T11E INVENTION

2 This invention relates to an appa atus for forming 4 blow molded articles, such as containers, from thermoplastic material. More particularly, the present invention is 6 directed to an apparatus capable of providing blow molded 7 containers of various heights (lengths).

8 The height or length of a container producible 9 from a blow molding apparatus such as that described in U.S.P. 4,047,873 is limited since the projected area of each 11 core rod must coincide with the center line of the mold 12 clamp. The h-igh pressures involved in such apparatus 13 require a balanced design since unbalancing will lead to 14 flashing of the parison from the core rod.
Heretofore the formation of long containers 16 necessitated the use of large blow molding machines~ and in 17 the case of ultra long containers, a two piece construction 18 had to be employed (two equal halves adhered -together).

Tt is an object of the present invention to 21 produce longer containers in one piece from blow molding 22 apparatus without increase in the size of the turntable or 23 withou~t necessitating movement of the beams.
24 The aforesaid object, as well as other objects and advantages~of the present invention is provided by an 26 apparatus for making hollow articles.~ The apparatus has a 27 rotatable polygonal turntable, a parison forminy station at 28 one~side~face of the turntable, a blow molding station at 2~ ~ ~ `
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1 another side face of the turntable and a stripping station

3 at still another side face of the turntable. The apparatus has means for connecting to the turntable at least one core

4 rod on which the parison is formed to the turntable, such 6 that at least one core rod is parallel to a side face of the 7 turntable and for rotation therewith. Such means for 8 connecting the core rods to the turntable include an 9 extension arm fixed to the turntable and extending perpendicularly outwardly from a side face thereof and means 11 for mounting a core rod perpendicular to the arm.
12 BRIEF DESCRIPTION OF THE DR~WINGS
13 For the purpose of illustrating the invention, 14 there is shown in the drawings forms which are presently preferred; it being understood, however, that this invention 16 is not limited to the precise arrangement and 17 instrumentalities shown. ~ -18 Fig. 1 is a top plan view of a prior art injection 19 blow molding apparatus having three stations for producing a single layer container, taken along the mold split line.
21 Fig. 2 is a top plan view of an injection blow 22 molding apparatus according to the present invention having 23 three stations for producing a simple layer container, taken 2i ~ along the mold split line.
E`ig. 3 is an elevational view in cross-sec~ion of 26 a typlcal trigger bar - core rod - mold assembly such as 27 employed in the injection blow molding apparatus of Fig. 2.
28 Flg. 4 is a diagrammatic view of the type of 29 apparatus depicted in~ Fig. 1, but showing core rods on only 3~
one side face of the turntable. Also shown on Fig. 4 is the parison size produced by the apparatus of Fig. 3 as compared to the parison size produced by the apparatus of Fig. 2.
Fig. 5 is a diagrammatic view of the type of apparatus depticted in Fig. 1, but showing core rods 411 with parisons thereon on only one side face of the turntable.
DE AILED DESCRIPTION OF THE INVENTION
Referring to the drawings in detail, wherein like numerals indicate like elements there is shown in Fig. 1 a prior art injection molding apparatus 116 comprising an injection molding station I, a blow molding station II and a stripping station III. The structure and operation of typical blow molding machines is described in U.S. Patents 4,047,873 and 3,816,046.
In Fig. 1 there is shown a triangular shaped (equilateral triangle) rotatable indexing turntable 10 having side faces 20, 21 and 22. Each of said face 20, 21 and 22 have a series of core rods 11 ttypical) mounted perpendicularly thereto and rotatably indexed at the aforementioned stations. The core rod 11 indexing is performed in the well-known customary manner.
The core rod 11 are of a similar configuration to the core rod and mechanism for actuating the core rod to provide blow air as described in U,S. Patent 3,836,305.
Side face 20, 21 and 22 contain trigger bars (not : ~ :

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l ~ own) to activate core rod valves (not shown) to allow air 23 to flow through the core rods.
4 At the injection rnolding station I, having a center of pressure Pl r a plastic parison 12 is injection 6 molded in mold 13 onto each core rod 11 by injector 14 v a 7 manifold 27 in the customary manner. Such injection molded 8 plastic can-be any thermoplastic.
9 The turntable 10 having a maximum swing radius R

is then indexed counterclockwise in the direction of arrow A
11 into blow molding station II, having a center of pressure 12 P~, wherein each parison 12 is blow molded in mold 18 to 13 form containers 17. During such rotation, rods 11 with 14 parisons 12 thereon, pass by machine obstruction 26. In such blow molding, retractably extensible valve heads 15 16 (which are depicted in a seated or retracted position in 17 Fig. 1) on core rods 11 open to allow pressurized gas, e.g. r 18 air, to flow in order to blow-up each parison 12 to form 19 containers 17.
After blow molding in station II, the turntable 10 21 is indexed once again in a counterclockwise fashion to 22 stripper station III, wherein the containers 17 are stripped 23 from core rods Il by stripper 19.
24 In order to keep the injection moldiny apparatus 16 balanced, the apparatUs 16 iS designed such t-hat the 26 center of the support posts 23 for apparatus 16 is located 27 at the point of intersectlon of the center lines J and K
28 which respectively pass through the middle (longitudinal 29 center) oL~ the molds~13 ~nd lB (lines J and K are :~ : :
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~ :-r respectively parallel to side faces 20 and 2L). The center 2 of post 24 is at the intersection of lines K and L; the 4 center of post 25 is at the intersection of lines J and I,.
The centers of posts 23, 24 and 25 coincide with the 6 imaginary lines Ll, L2 and L3, passing through point C and 7 the three points of intersection of faces 20 and 21; faces 8 22 and 21; and faces 22 and 20, namely points 40, 41 and 42.
9 Point C is located at the intersection of the three imaginary lines, L4, L5 and L6, perpendicular to and passing ll through the cen-ter of side faces 20, 21 and 22. Center of 12 pressure Pl for station I is at the intersection of the 13 imaginary line J passing through the centers of posts 23 and 14 25 and the imaginary line L4 passing through the center of lS side face 20 and center C of turntable 10. Center of 16 pressure P2 for station II is at the intersection of the 17 imaginary line K passing through posts 23 and 24 and the 18 imaginary line L5 passing through the center of side face 21 l9 and center C of turntable 10. Posts 23, 24, 25 have support beams (not shown~.
21 It is not possible to employ core rods 11 longer 22 than that those presently depicted in Fig. 1, therefore it 23 is not possible to produce longer containers 17 with the 24 prior art apparatus 16 since the pressure would be unbalanced, i.e., the imaginary lines between the center o~
26 the posts 23, 24, 25 would not coincide with the 27 longitudinal center of the rods 11. Furthermore, if the 28 rods 11 are too long, they will not clear the posts 23, 24, 29 25 d~ring indexing.

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l ~ In Fig~ 2 an injectloll moldiny apparatus according 2 ¦ to the present invention is depicted comprising an injection 3 ¦ molding station I', a blow molding station II' and a

5 1 stripping station III'. Such stations operate much in the

6 1 manner as described hereinabove for stations I, II and III

7 ¦ in Fig. 1.

8 ¦ In Fig. 2, there is depicted a triangular shaped

9 ¦ (equilateral trianyle) rotatable indexing turntable 110 lO 1 having side faces 120, 121 and 122.
ll ¦ Projecting out from turntable 110 and 12 ¦ perpendicular to side face 121 is extension arm 129;
13 ¦ projecting out from turntable 110 and perpendicular to side 14 ¦ face 122 is extension arm 130; and projecting out from 15 ¦ turntable 110 and perpendicular to side face 120 is 16 ¦ extension arm 131. Each arm 129, 130 and 131 has a trigger 17 ¦ bar located in a recess therein (not shown in Fig. 2).
18 ¦ Extending perpendicularly from each arm 129, 130, 131, l9 ¦ respectively, and parallel to side faces 120, 121, 122, 20 ¦ respectively, are a series of core rods 111 (typical).
21 1 At th`e injection molding station II', having a 22 ¦ center of pressure P'l a plastic parison 112 is injection 23 ¦ molded in mold 113 onto each core rod 111 by injector 114 in 24 ¦ the customary manner.
25 ¦ ~ The turntable 110 having a maximum swing radius R' 26 ¦ is then indexed counterclockwise in -the direction o~ arrow 27 ¦ A' into blow molding station II', having a center of 28 ¦ pressure P'2, wherein each parison 112 is blow molded in 29 ¦ mold 118 to form containers 117. In such blow molding, 30 ~ -7-I
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~ retractably valve heads 115 (which are depicted in a seated 3 or retracted position in Fig. 2) on core rods 111 open to 4 allow pressuriæed gas, e.g., air, to flow in order to blow-up each parison 112 to form containers 117.

6 After blow molding in station II', the turntable 7 110 is indexed once again in a counterclockwise fashion to 8 stripper station III', wherein the containers 117 are 9 stripped from core rods 111 by stripper 119.

Using the same size turntable and the same beam ll configuration as described above for the prior art apparatus 12 16, the apparatus 116 of the present invention is able to 13 produce much longer bottles 117, than bottles 17 produced 14 from prior art apparatus 16.
In apparatus 116, the two core rods 111 on each of 16 arms 129, 130, 131 are disposed equal distances on either 17 side of the imaginary center lines B, D and M passing 18 through the centers of posts 123, 124, 125, i.e., the rods l9 lll are thus balanced (the central axis of each core rod lll is disposed an equal perpendicular distance from the 21 imaginary line M joining the centers of posts 124 and 125;
22 the imaginary line D joining the centers of posts 123 and 23 124 and the imaginary line B joining the centers of posts 24 123 and 1~25)~. The centers of posts 123, 124 and 125 coincide with the imaginary lines B and D passlng 26 respectively through the longitudinal centers of molds 113 27 and 118~(lines B and D~are parallel to face 120 and face 28 121, respectively). The centers of posts 123, 124 and 125 29 coincide wlth the imaginary lines, M4, M5 and M6, passing ~ ~ -8-~' ' .
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2 through poin-t C and -the three points of intersection of 3 faces 120 and 121; faces 122 and 121 and faces 120 and 122.
4 Point C is located a-t the intersec-tion of the three imaginary lines M1, M2 and M3, perpendicular and passing 6 through the center of faces 120, 121 and 122.
7 If one rod lll is employed on each arm, the center 8 of such rod 111 would be positioned on such imayinary lines 9 B, D and M joining such adjacent posts. Center of pressure P1' for station I' is at the intersection of the imaginary ll line B passiny through the centers of posts 123 and 125 and 12 the imaginary line passing throught the center of side face 13 120 and center C' of turntable 110. Center of pressure P2' 14 for station II' is at the intersection of the imaginary line D passing through posts 123 and 124 and the imaginary line 16 passing through the center of side face 121 and center C' of 17 turntable 110. Imaginary line M passes through the centers 18 of posts 124 and 125.
19 It is to be understood that while there is above described operations for forming a one-layered parison, 21 these operations could be repeated to form any desired 22 number of l~ayered parisons and resultantly multilayered 23 ~ hollow artlcles such as that produced in U.S.P. 4,047,873.
24 It is also understood that while the preferred embodiment has been described in terms of the operation of 26 four-core rods at each station in Fig. 1 and two core rods 27 at eaoh s~tation in Fig.2, clearly any number of such core 28 :rods oould be mounted for operation at each of the stations 29 depending on the size of the apparatus.
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In Fig. 3 there is depicted a trigger bar assembly 235 for actuating core rod valves such as those of the apparatus of Fig. 2 so as to allow air to ~low in the direction of arrows E, F, G and H through the core rod to blow-up the parison thereon to form a container 217. The trigger bar assembly is described in great detail in U.S.
Patent No. 3,836,305 to William Grazine.
A trigger bar assembly 235 is disposed in each arm 129, 130, 131 of indexing turntable 210. Core rod 211 is secured to turntable 210 by split collar 236. Split collar 236 is secured to face plate 237 by screws 238 that extend through the split collar 236 and are threaded into the face plate 237.
The face plate 237 is secured to turntable 210 by other screws, not shown, which is a conventional molding machine construction.
There is an opening 239 in the face plate 237 for holding the core rod 211.
Core rod 211 has a valve head 215 secured to the outer end thereof.
Extending lengthwise with core rod 211 is operating element 240. Operating element 240 is connected to valve head 215. A spring (not shown~ in the core rod 211 holds the valve head 215 closed, and when the operating element 240 has its inner end pushed in the direction of the valve head 215 with su~ficient force to overcome the sprlng, the valve head 215 opens. The spring is not shown in Fig. 3 :

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1 ¦ since this description is of conventional structure, well 3 ¦ understood in the molding machine art.
4 ¦ The face plate 237 has a groove 241, of l rectangular cross-section, extending for most of the length 6 ¦ of the face plate 237 and into which the operating element 7 1 240 of core rod 211 extends. This groove 241 is of a height 8 ¦ slightly less than the diameter of the opening 239 into 9 I which the core rod 211 extends. Shoulder 242 is formed at lO ¦ the upper and lower parts of the opening 239 as the result ll ¦ of the lesser height of the groove 241.
12 ¦ There is a corresponding groove 243 in the 13 ¦ indexing turntable 210 immediately behind the groove 241 and 14 ¦ these grooves 241 and 243 cooperate to form a chamber in 15 ¦ which a trigger bar 244 is located.
16 ¦ The trigger bar 244 extends for substantially the 17 ¦ entire length of the grooves 241 and 243 with enough~
18 ¦ clearance from the sides and the ends of the grooves 241 and l9 ¦ 243 to permit the trigger bar 244 to move freely ln the 20 ¦ grooves toward and from the inner ends of the core rod 211.
21 I The trigger bar 244 has a groove 245 extending for 22 ¦ the full length of the upper side of the trigger bar 244 and 23 ¦ there is a similar groove 246 in the bottom ace of the~
24 ¦ trigger~bar 244. ~
25 ¦ ~ Thin plates 247 are clamped between the face plate 26 ¦ 237 and the opposing face of the head 210. These thin 27 ¦ plates 247 contact with one another beyond both ends of the 28 ¦ trigger bar 244, but they are spaced to provide clearance 29 ~ ~ ~f~-¦the trigger bar Z44~alo~g the length of the grooves 24l j ~

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21 and 243. The thin plates 247 extend into the grooves 245 3 and 246 and provide abutments which limit the rnovement of 4 the trigger bar 244 towarda and from the core rod 211.
Fig. 3 shows the trigger bar 244 in its most 6 retracted position; that is furthest away from the core rod 7 211. The slots (grooves) 245 and 246 are wide enough to 8 permit the trigger bar 244 to move towards the core rod 211 9 with sufficient motion to move the operating elements 240 to a posltion to open the core rod valve head 215.
11 There is a piston 248 behind the trigger bar 244 12 and this piston 248 slides in a cylindrical guide 249 and is 13 provided with an O-ring 250 for preventing air from escaping 14 past the piston 248 from the chamber in which the trigger . bar 244 slides.
16 There is an upper ball 251 which projects partway 17 into the cylindrical guide 249.
18 A lower ball 252 moves up and down in another 19 cylindrical guide 253 which extends substantially at right angles to the cylindrical guide 249. A threaded bushlng 254 21 screws into the lower end of the cylindrical guide 253 to 22 prevent the lower ball 25I from dropping out of the gulde 23 253. This bushing 254 can also be used to control the 24 at-~rest position~of the lower balI 251.
The cylindrical guides 249 and 253 open into a 26 juncture chamber 255 in which there is a stud 72 extending : . ~
27 downward into the juncture chamber 255 in a posltion to 28 serve as a stop for preventing the upper ball 251 from 29 rolling out of its cylindrical guide 255.
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~ 33:~L4 2 A plunger 256 is operated by an actuator 257 which 3 moves the plunger 256 up and down in timed relation wi-th the 4 operation of the indexing head ~turntable) 210 and the mold opening and closing apparatus.

6 When the indexing head 210 is to be rotated to 7 bring a different se-t of core rods to the blowing station 8 II', the actuator 257 is at rest with the plunger 256 9 depressed.

When the core rods 211 move into the blowing ll station II', and the blowing mold halves 258 and 259 (halve 12 259 rests on stationary lower platen 260 and halve 258 is 13 moved by upper platen 261) close around the core rod 211, 14 the actuator 257 moves the plunger 256 upwardly into contact with the lower ball 252 and lifts the lower ball 252 16 upwardly far enough to displace the upper ball 251 to move 17 the trigger bar 244 into position to open the valve 215.
18 The center line of pressure through the mold halves 258 and l9 259 is represented by line CL.
At the end of the blowing operation in statlon 21 II', the actuator 257 returns the plunger 256 to its 22 I depressed, inactive position,~and the springs of the valve 23 ¦ 215 push the operating element 240, trigger bar 244, piston 24 1 243, and balls 251 and 252 back to their original positions ¦ as shown in Fig. 3.
26 I Air for the core rod 211 is supplied under 27 I pressure to the chamber formed by the grooves 241 and 243 28 1 and the distribution of the air leng-thwise through this 29 ¦ chamber is facilitated by having a manifold passage 26~2 30 ¦ ~extending lengthwise of the trigger bar 244 with spaced .
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k ~ t ,~ ~, 2 outlet passages 265, one of which is shown in Fig. 3.
3 The balls 251 and 252 are free to ro-tate and they 4 have some random rotation which causes differen-t locations on the surfaces of the balls 251 and 252 to contact with 6 each other a-t different times so that the cam action of the 7 balls 251 and 252 with respect to one another does not 8 result in friction wear at any particular point of contact 9 of the balls 251 and 252.

In Fig. 4, a turntable - core rod assembly such as ll shown in Fig. 1 is depicted, wherein core rods 311 having 12 parlsons 312 thereon on only one side face 320 of the 13 turntable 210 are shown. Depicted in dotted line fashion is 14 the longer parision 31I' which would be required to make a bottle such as depicted in Fig. 2. Point Q represents the 16 intersection of the center line across the core rods 312 and 17 the imaginary line running perpendicularly acxoss the center 18 of side face 320. Distances El and E2 are equal distances l9 and are each the distance from the center of point Q to the outside edge of the outermost parison 312. El and E2 are 21 equal distances and are respectively the dlstance from the 22 beginning of the parison 312 to the center of point Q and 23 the center of point Q to the end of parison 312. Distance X
24 represents the increased parison leng-th produced by the apparatus of Fig. 2. A bottle having the initial parison len~gth El + E2 + X cannot be used by the apparatus 27 depicted in Fig. 1, since such long parison length would 28 require a long core rod that could not pass by posts 23 and 29 2: ln g. 1. Furthermore, the longer required core rod 1~
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l would cause a pressure unbalance on the clamping mechanism 2 for the molds.

4 There is shown in Fiy. 5 a turntable-core rod assembly according to the present invention and as shown in 6 greater detail in F`ig~ 2. Core rods 411 having parisons 412 7 thereon project from arm 431 of turntable 410. Points S

8 represents the intersection of the centerline between the 9 core rods and the imaginary line running perpendicularly through the center of side face 420. Distances E13 and E23 ll are equal and represent the distance between the center of 12 point S and the outermost edge of top edge of the upper 13 parison and bottom edge of lower parison of each parison.
14 Distances El4 and E24 are equal and are each one-half the length of the parison 412 measured outwardly from the center 16 of point S. Distance E1 ~ E2 of Fig. 5 is equal to 17 ¦ distance E1 ~ E2 + X of Fig. 3.
l~ ¦ It will be appreciated that the instant l9 ¦ specification and claims are set forth by way of 20 ¦ illustration and not limitation, and that various 21 modifications and changes may be made without departing from 23 the spirit and scope of the present inv~ntion.

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Claims (6)

WHAT IS CLAIMED IS:

1. In an apparatus for making a hollow article, wherein the apparatus includes a rotatable polygonal turntable, a parison forming station at one side face of the turntable, a blow molding station at another side face of the turntable and a stripping station at still another side face of the turntable, the improvement comprising means for connecting to the turntable at least one core rod on which the parison is formed to the turntable, such that at least one core rod is parallel to a side face of the turntable and for rotation therewith.

2. An apparatus according to claim 1, wherein the means for connecting the core rod to the turntable comprises at least one extension arm fixed to the turntable and extending perpendicularly outwardly from a side face thereof and means thereof for mounting a core rod perpendicular to the arm.

3. An apparatus according to claim 2 wherein the turntable has at least three side faces, at least one extension arm extending outwardly from each side face and each arm has means for mounting for at least one core rod thereon.

4. An apparatus according to claim 3, wherein each side face has an extension arm extending outwardly therefrom, said arm perpendicular to said side face.

5. An apparatus according to claim 3, wherein two core rods are disposed on said arm.

6. An apparatus according to claim 5, wherein said turntable has the shape of an equilateral turntable and which further comprises a mold enclosing the core rods in the injection station, a mold enclosing the core rods in the blow molding station and three posts, wherein the center of one post is disposed on an imaginary line through the center of the mold in the injector station and the center of another post is disposed on an imaginary line through the center of the mold in the blowing station, the center of each post is disposed on a imaginary line through the point of intersection of each adjacent side face of the turntable and the point of intersection of the imaginary lines through the center and perpendicular to each side face, each of said core rods being disposed an equal perpendicular distance from an imaginary line joining each post.