CA2233065A1 - Method and apparatus for removing hollow plastic articles from an injection moulding machine - Google Patents
Method and apparatus for removing hollow plastic articles from an injection moulding machine Download PDFInfo
- Publication number
- CA2233065A1 CA2233065A1 CA 2233065 CA2233065A CA2233065A1 CA 2233065 A1 CA2233065 A1 CA 2233065A1 CA 2233065 CA2233065 CA 2233065 CA 2233065 A CA2233065 A CA 2233065A CA 2233065 A1 CA2233065 A1 CA 2233065A1
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- CA
- Canada
- Prior art keywords
- hollow plastic
- injection moulding
- plastic articles
- hot
- conveyor
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
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Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C45/00—Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor
- B29C45/17—Component parts, details or accessories; Auxiliary operations
- B29C45/40—Removing or ejecting moulded articles
- B29C45/42—Removing or ejecting moulded articles using means movable from outside the mould between mould parts, e.g. robots
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C45/00—Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor
- B29C45/17—Component parts, details or accessories; Auxiliary operations
- B29C45/40—Removing or ejecting moulded articles
- B29C45/42—Removing or ejecting moulded articles using means movable from outside the mould between mould parts, e.g. robots
- B29C45/4225—Take-off members or carriers for the moulded articles, e.g. grippers
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C45/00—Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor
- B29C45/17—Component parts, details or accessories; Auxiliary operations
- B29C45/1769—Handling of moulded articles or runners, e.g. sorting, stacking, grinding of runners
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
- B29K2105/00—Condition, form or state of moulded material or of the material to be shaped
- B29K2105/25—Solid
- B29K2105/253—Preform
Abstract
The injection moulding apparatus for producing hollow plastic articles comprises an injection moulding machine having interlockable male and female mould portions for forming a number of hot hollow plastic articles in an injection moulding cycle. A
conveyor, spaced apart from the injection moulding machine, features receptacles for holding the hot hollow plastic articles in an upright position in order to let hot air disposed in the interior of each hot hollow plastic article to rise unheeded. A transfer mechanism quickly removes the hot hollow plastic articles from the injection moulding machine when in the mould-open position and deposits the hot hollow plastic articles upright in the conveyor receptacles. The transfer mechanism preferably comprises a carrier plate and a plurality of retractable jaw clamps disposed thereon for removing the hot hollow plastic articles from the injection moulding machine when it is in the mould-open position. A robot aligns and juxtaposes the jaw clamps with the hot hollow plastic articles when the moulding machine is in the mould-open position, and deposits the hot hollow plastic articles gripped by the jaw clamps into the conveyor receptacles.
conveyor, spaced apart from the injection moulding machine, features receptacles for holding the hot hollow plastic articles in an upright position in order to let hot air disposed in the interior of each hot hollow plastic article to rise unheeded. A transfer mechanism quickly removes the hot hollow plastic articles from the injection moulding machine when in the mould-open position and deposits the hot hollow plastic articles upright in the conveyor receptacles. The transfer mechanism preferably comprises a carrier plate and a plurality of retractable jaw clamps disposed thereon for removing the hot hollow plastic articles from the injection moulding machine when it is in the mould-open position. A robot aligns and juxtaposes the jaw clamps with the hot hollow plastic articles when the moulding machine is in the mould-open position, and deposits the hot hollow plastic articles gripped by the jaw clamps into the conveyor receptacles.
Description
FIELD OF INVENTION
The invention generally relates to the art of injection moulding and more specifically to systems for removing hollow plastic articles from an injection moulding machine, especially preforms made from polyethylene terephthlate (PET) which are subsequently blow moulded into end-user containers.
BACKGROUND OF INVENTION
Each cycle of an injection moulding machine produces a plurality of preforms which must be removed from the machine in order to enable the next cycle to commence. The preforms which must be removed from the injection moulding machine are quite hot due to the fact that the inj ection moulding operation is earned out at high temperatures and the preforms are only superficially or partially cooled during the injection moulding cycle. This incomplete cooling causes the preform to exhibit a temperature gradient wherein the inner and outer skin temperatures of the preform are relatively cool in order to solidify the preform for short-term handling. However, as PET preforms typically have relatively thick walls, e.g., about 4 to 6 mm, a substantial amount of heat remains trapped or stored in the interior of the preform walls.
Accordingly, the preforms have to be carefully handled upon removal from the injection moulding machine as otherwise the escaping heat could lead to the deformation of the preform should it be unduly stressed, or to "sticking" problems that arise when insufficiently cooled preforms are brought into contact with one another. (Of course, it is always possible to lengthen the period of the injection moulding cycle to thereby allow the preforms more time to cool in the machine; however, that would be counteractive to the goal of achieving high throughput).
An example of a prior art system for preform removal and cooling is disclosed in U.S.
Patent No. RE33,237 to Delfer. This system employs a robot-controlled take-out plate assembly having a plurality of cooled tubes or single-ended cavities formed therein, with the number of such cavities corresponding to a multiple of at least two times the number of preforms produced per injection moulding cycle. The extra set o~r sets of cavities in the Delfer take-out plate 20460283.1 _ _.___~____ _ 20460283.1 - _ .__-____-____ ___._ assembly allows preforms to be held and cooled in the take-out plate for a corresponding number of additional injection moulding cycles, thereby permitting the preforms a greater of amount time to be cooled before being transported for further processing.
The structure of such apreform removal and handling system, detailed for instance in U.S.
S Patent No. 4,729,732 to Schad et. al., U. S. Patent No. 4,173,448 to Rees et. al., and U. S. Patent No. 5,447,42f to Gesner et al., comprises an air pressure means and a cooling means. The air pressure means provides a vacuum or pressurized air to each tube or cavity of the take-out assembly. The vacuum enables preforms to be removed by suction from the moulding machine and held in the take-out plate cavities during ~~ransfer to a receiving station. Conversely, the pressurized fluid assists in ejecting preforms stored within the take-out plate cavities. The cooling means circulates cooling fluid throughout the take-out plate in order to chill the preforms temporarily stored therein.
This type of preform removal and handling system tends to be relatively expensive and difficult to maintain for a number of reasons. First, the air pressure means and the cooling means each require the provision of extraneous equipment, such as air pumps and heax exchangers, as well equipment that may be integrate into the take-out plate such as valves and the like. Second, the air pressure and cooling means require that intricate integrated channels, bores and manifolds be milled into the take-out plate in order to distribute the appropriate fluids to each of the preform holding cavities or tubes. This requirement tends to make the take-out plate, which is precisely crafted, difficult and expensive to manufacture. Third, as the cavities or tubes of the take-out plate are typically designed to encompass the bodies of the preforms, the plate tends to be relatively thick and heavy. The robotic positioning device thus requires relatively powerful motors in order to quickly position the take-out plate in a stable manner.
Finally, this type of system tends to require relatively frequent maintenance due to its complexity.
20460283.1 - 3~ -SUMMARY OF INVENTION
The invention presents an alternative prefonn removal and handling system and a take-out plate assembly which does not incorporate the complexities of the prior art thereby providing the advantages of low cost and reduced maintenance requirements.
S According to one aspect of the invention, injection moulding apparatus for producing hollow plastic articles is provided. The apparatus includes an injection moulding machine having interlockable male and female mould portions for forming a first number of hot hollow plastic articles in an inj ection moulding cycle, and means for reciprocating the mould portions between a mould-closed position and a mould-open position. A conveyor is spaced apart from the injection moulding machine, and features receptacles for holding the hot hollow plastic articles in an upright position in order to let hot air disposed in the interior of each hot hollow plastic article to rise unheeded, the number of such receptacles being at least equal to the first number of hollow plastic articles produced in the injection moulding cycle. A
transfer mechanism quickly removes the hot hollow plastic articles from the injection moulding machine 1 S when it is in the mould-open position and deposits the hot hollow plastic articles upright in the conveyor receptacles.
This apparatus is effective because it is passible to handle the hot hollow plastic articles, such as PET preforms, for a period of less than approximately 15 seconds before the heat trapped in the interior of the walls of the hollow plastic article manages to spread out to the inner and outer skins of the article and soften the skins to a point where the article can no longer be actively manipulated. However, within this time period, the transfer mechanism deposits the hot hollow plastic articles into the receptacles of the conveyor, where the articles are held for cooling and not actively manipulated or unduly stressed. The hot hollow plastic articles are held in an upright position when disposed on the conveyor in order to efficiently cool the hollow plastic article. If the hollow plastic articles were held in an upside down manner, the closed end of the article 20460283.1 would trap sufficient heat in the hollow interior of the article to cause the above mentioned deformation and/or sticking problems.
The transfer mechanism preferably comprises a substrate, and a retractable clamping means, connected to the substrate, for gripping the first number of hot hollow plastic articles from S the injection moulding machine when in the mould-open position and for releasing the gripped articles. The substrate may comprise a carrier plate having a plurality of bores therein, and the clamping means may comprise jaw clamps, co-axial with each bore, with each jaw clamp being slidably mounted on the carrier plate for movement in a direction substantially normal to the corresponding bore. A motive means, such as a robot, aligns and juxtaposes the clamping means with the hot hollow plastic articles disposed on one of the mould portions when the moulding machine is in the mould-open position. The motive means also aligns and juxtaposes hot hollow plastic articles held by the clamping means with the conveyor receptacles in order to deposit the former into the latter.
The transfer mechanism of the present invention provides a mechanically stable system for the removal and handling of hot plastic articles from the injection moulding machine. In contrast to some prior art systems, the transfer mechanism of the present invention does not incorporate complicated cooling and air pressure means. Moreover, the substrate of the transfer mechanism can be made relatively thin and light thereby enabling the use of more economically efficient motors to be employed in the motive means.
20460283.1 BRIEF DESCRIPTION OF DRAWINGS
For the purposes of description, but not of limitation, the invention will now be explained in greater detail with reference to the accompanying drawings, wherein:
Figures lA - 1 C are perspective view illustrations of an injection moulding apparatus in accordance with the preferred embodiment, each of which illustrates a prefers ed transfer mechanism of the apparatus in a different operative position;
Figures 2A, 2B and 2C are partial cross-sectional views of the injection moulding apparatus taken along line I-I in Figure 1;
Figure 2D is a partial cross-sectional view of the transfer mechanism taken along line II-II
in Figure 1 C;
Figure 2E is a partial cross-sectional view of a preferred conveyor employed in the injection moulding apparatus taken along line Il(I-III in Figure 1C;
Figure 3 is a fragmentary, perspective view of a portion of the transfer mechanism;
Figure 4 is a front view also showing hidden details of a similar portion of the transfer mechanism shown in figure 3;
Figure 5 is an exploded view of a portion of the transfer mechanism shown in figure 3;
and Figures 6A - 6C are schematic diagrams illustrating various preferred patterns for storing hot hollow plastic articles onto the conveyor.
20460283.1 DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
An inj ection moulding apparatus 10 for producing hollow plastic articles such as PET
preforms is shown in Figs. lA to 1C. The apparatus 10 includes an injection moulding machine 12 and a hopper 14 for receiving PET pellets which are heated to produce PET
resin that is injected into moulds provided by the injection moulding machine as is well known in this art.
The inj ection moulding machine 12 includes interlockable male and female mould portions 16A and 16B. Referring additionally to the partial cross-sectional views of Figs. 2A and 2B, the male mould portion 16A carries a plurality of elongate cores 18 designed to penetrate corresponding cavities 20 in the female mould portion 16B and thereby provide a plurality of moulds. The mould portions 16A and 16B reciprocate between a mould-closed position and a mould-open position for each injection moulding cycle of the machine 14. In the mould-closed position, a number of elongate hollow preforms ~ 8 are produced, the exact shape of each article corresponding to the intersticial shape between a given core%avity. In the mould-open position, a gap 22 is present between the male and female mould portions 16A and 16B and the recently moulded, hot, hollow preforms must be removed from the machine 12 in order to enable the next injection moulding cycle to commence.
The injection moulding apparatus 10 includes a conveyor 24 which is spaced apart from the injection moulding machine 12. The conveyor includes a web 25 and receptacles 26, discussed in greater detail below, for holding the hot hollow preforms in an upright position in order to efficiently cool the performs. The number of receptacles 26 is at least equal to the number of preforms produced in each injection moulding cycle, and preferably more, as discussed in greater detail below. The conveyor 24 holds the preforms for a predetermined time period, preferably a multiple of injection moulding cycles, in order to give the preforms sufficient time to cool and stabilize. As the conveyor 24 proceeds in a forward direction, preforms at the head of the conveyor simply fall out of the receptacles 26 as the web 25 curves at about point 27 to 20460283.1 ;I -begin its return path. At this point, the preforms can be collected or transferred by other conveyor means (not shown) for further processing, such as blow moulding, etc.
The inj ection moulding apparatus 10 includes a transfer mechanism 28 for quickly removing the hot hollow prefonms from the injection moulding machine 12 when it is in the mould-open position and for depositing these preforms upright in the conveyor receptacles 26, as shown for example in Figure 2E. The transfer mechanism 28 comprises a frame or substrate, such as a take-out or carrier plate 30, and a retractable clamping means such as split ring clamps 32, discussed in greater detail below, for gripping and holding all of the preforms produced in an injection moulding cycle. A motive means, such as a three-axis gantry robot 34, aligns and juxtaposes the clamping means 32 with the hot preforms disposed on the male moulding portion 16A when the injection moulding machine 12 is in the mould-open position. The motive means also aligns and juxtaposes hot preforms held by the clamping means 32 with the conveyor receptacles 26 in order to deposit the hot preforms into the receptacles. The movement of the carrier plate 30 as provided by the motive means is partially depicted in Figs. 1 A, 1 B and 1 C, and, in cross-sectional view, by Figs. 2C, 2D and 2E.
The clamping means, as described in greater detail below, exerts some pressure onto the recently moulded and still quite hot PET preforms which typically have a skin temperature of about 10 to 30 degrees Celsius, depending on the operating characteristics of the machine 12, and a much higher internal temperature, e.g. about 200 degrees Celsius.
Nevertheless, it: is possible to apply a small amount of pressure to the PET preforms and thus handle them for a short time period before the heat trapped in the interior of the preform walls manages to diffuse or radiate to the inner and outer skins of the preforms and soften the skins to a point where they are no longer "set" and the preform can no longer be gripped or otherwise actively manipulated. This time period will vary depending on the length of the injection moulding cycle, the skin temperature, the temperature of operation, and the cooling efficiency of the injection moulding machine. A typical time period within which tine preforms may be handled is approximately 5 20460283.1 _$_ to 10 seconds. Accordingly, within this time period, the transfer mechanism 28 deposits the preforms into the receptacles 26 of the conveyor 24, where the preforms are temporarily stored until they stabilize. The preforms are not actively manipulated or unduly stressed when stored on the conveyor 24. The hot hollow preforrns are held in an upright position when disposed on the conveyor in order to let hot air disposed in the interior of each preform to rise unheeded and hence allow the preform to cool sufficiently without the need for an extraneous cooling means.
The upright positioning is important because if the hollow PET preforms were held in an upside down manner, the closed end of the preform would trap sufficient heat in the hollow interior thereof to thereby cause the preform to possibly deform and/or stick to other preforms when eventually brought into contact with one another.
Referring additionally to Figs. 2C, 3, 4 and 5, the structures of the take-out or carrier plate 30 and the clamping means are shown in greater detail.
The carrier plate 30 comprises a plurality of bores 36 therein arranged in a pattern corresponding to the pattern of elongate cores 18 present on the male portion 16A of the injection moulding machine 12. Each bore 36 is sized larger in diameter than a predetermined portion 3 5 of a corresponding preform exposed in the gap 2.2 between the male and female mould portions when the injection moulding machine 12 is in the mould-open position. Thus, as shown in the cross-sectional view of Fig. 4C, preforms 38 disposed on the male mould portion 16A can freely penetrate corresponding carrier plate bores 36.
The plate 30 features one split ring or jaw clamp 32 for each carrier plate bore 32. Each clamp 32 is co-axially aligned with its corresponding bore 36 and is slidably mounted on the take out plate, as described in greater detail below, for movement in a direction 39 normal to the bore.
Each clamp 32 includes jaws 40A and 40B disposed on opposing sides of the bore. The jaws 40A and 40B feature an inner perimeter 42 designed to substantially exactly match the shape of 20460283.1 _g_ a pre-determined periphery 44 of the preform 38 when the jaws are closed, thereby enabling the clamp 32 to grip the hot preform 38 without damage.
Means are provided for reciprocating each clamp 32 between a gripping or closed position and an open position. In the preferred embodiment, such reciprocating means comprises a double acting piston 46, tie rods 48A and 48B, channel-shaped clamp rails 52A and 52B
which respectively connect to clamp jaws 40A and 40B, and articulating means SO
connecting the tie rods 48A and 48B to the piston 46.
The tie rods 48A and 48B are respectively disposed in channels 54A and 54B
milled into one of the faces of the carrier plate 30.
Elongate slots 56 in the carrier plate 30 enable tie rods 48A and 48B to be respectively fastened to the clamp rails 52A and 52B via fastening screws 58A and 58B. Each pair of clamp rails 52A and 52B respectively straddles a row or column of bores 36. Clamp jaws 40A and 40B
are respectively disposed within the channels 60 of the clamp rails 52A and 52B and are floatingly connected thereto. The floating connections are provided by bolts 62, which are threaded into jaws 40A and 40B and which pass through, but are not threaded to, eyelets 64 located in a central wall 66 of clamp rails 52A and 52B. Each clamp jaw 40A
and 40B also includes bores 70 for partially housing compression springs 72 mounted between the central wall 66 and the body of each clamp jaw. The floating connections enable a given pair of jaws 40A
and 40B to gently grasp the hot pre-forms 3 8.
The articulating means 52 comprises double-legged bell cranks 74 having legs 76A and 76B respectfully connected to the tie rods 48A and 48B. The cranks 74 are pivotably connected to links 78 that are attached to the double acting piston 46.
20460283.1 In operation, whenever the double acting piston 46 is actuated from one position or pole to the other, the articulating means force tie rods 48A and 48B to move in opposite directions relative to another. The clamp rails 52A and 52B, and hence jaws 40A and 40B, will move in correspondence with the tie rods 48 and 48B since these components are interconnected as described above. In this manner, piston 46 can be operated to reciprocate clamps 32 between the closed or gripping position and the open position.
Fig. 2E, illustraxes the structure of conveyor 24 and receptacles 26 in greater detail. The web 25 of the conveyor is formed from a plurality of substantially flat metal slats 80, each of which features a number of holes 82. The holes 82 are sized to accept an elongate body 84 of preform 38, but are smaller than a flange 86 present on the upper end of the preform. Thus, as shown in Fig. 2E, flange 86 of the preform rests against the top periphery of the slat when the preform is disposed on the conveyor.
The conveyor 24 preferably comprises a greater number of receptacles 26 than the number of preforms produced in an injection moulding cycle in order to efficiently make use of the space on the conveyor and allow the preforms a longer time period in which to cool before being displaced from the conveyor. For instance, Fig. 6A, shows the conveyor 24 being configured for a three-position diagonally offset a drop pattern 90. In the illustrated embodiment, the injection moulding machine 12 features a 6 x 2 (row, column) preform production pattern.
In this embodiment, the transfer mechanism 28 is programmed to deposit preforms produced in a first injection moulding cycle in receptacles labelled "A". The conveyor web is then incrementally advanced for a distance equal to the height of two rows in the pattern 90.
Preforms produced in the next injection moulding cycle are then deposited in receptacles labelled "B". The conveyor web is again advanced as before, so that preforms associated with the next injection moulding cycle are deposited in receptacles labelled "C". The next advance of the conveyor web restarts the drop cycle wherein the next batch of prefornns are deposited in receptacles "A"'.
20460283.1 Fig. 6B, illustrates an alternative, laterally oi~set drop pattern 92. In this embodiment, the transfer mechanism 28 is programmed to deposit three, or alternatively some other number, of consecutive batches of prefornls in laterally offset receptacle groups A, B, C
before the conveyor web is advanced for a distance equal to the length of the pattern.
Fig. 6C, illustrates another alternative, single position sequential drop pattern 94, wherein the conveyor web is advanced for a distance eclual to the length of the production pattern after each batch A, B, C of preforms is deposited onto the conveyor.
Still further alternative drop patterns can combine any of three illustrated embodiments shown in Figs. 6A to 6C.
It will be appreciated by persons skilled in the art that the present invention is not limited by what has been particularly shown and described herein as numerous modifications and variations may be made to the preferred embodiment without departing from the spirit and scope of the invention.
ao4so2ss.1
The invention generally relates to the art of injection moulding and more specifically to systems for removing hollow plastic articles from an injection moulding machine, especially preforms made from polyethylene terephthlate (PET) which are subsequently blow moulded into end-user containers.
BACKGROUND OF INVENTION
Each cycle of an injection moulding machine produces a plurality of preforms which must be removed from the machine in order to enable the next cycle to commence. The preforms which must be removed from the injection moulding machine are quite hot due to the fact that the inj ection moulding operation is earned out at high temperatures and the preforms are only superficially or partially cooled during the injection moulding cycle. This incomplete cooling causes the preform to exhibit a temperature gradient wherein the inner and outer skin temperatures of the preform are relatively cool in order to solidify the preform for short-term handling. However, as PET preforms typically have relatively thick walls, e.g., about 4 to 6 mm, a substantial amount of heat remains trapped or stored in the interior of the preform walls.
Accordingly, the preforms have to be carefully handled upon removal from the injection moulding machine as otherwise the escaping heat could lead to the deformation of the preform should it be unduly stressed, or to "sticking" problems that arise when insufficiently cooled preforms are brought into contact with one another. (Of course, it is always possible to lengthen the period of the injection moulding cycle to thereby allow the preforms more time to cool in the machine; however, that would be counteractive to the goal of achieving high throughput).
An example of a prior art system for preform removal and cooling is disclosed in U.S.
Patent No. RE33,237 to Delfer. This system employs a robot-controlled take-out plate assembly having a plurality of cooled tubes or single-ended cavities formed therein, with the number of such cavities corresponding to a multiple of at least two times the number of preforms produced per injection moulding cycle. The extra set o~r sets of cavities in the Delfer take-out plate 20460283.1 _ _.___~____ _ 20460283.1 - _ .__-____-____ ___._ assembly allows preforms to be held and cooled in the take-out plate for a corresponding number of additional injection moulding cycles, thereby permitting the preforms a greater of amount time to be cooled before being transported for further processing.
The structure of such apreform removal and handling system, detailed for instance in U.S.
S Patent No. 4,729,732 to Schad et. al., U. S. Patent No. 4,173,448 to Rees et. al., and U. S. Patent No. 5,447,42f to Gesner et al., comprises an air pressure means and a cooling means. The air pressure means provides a vacuum or pressurized air to each tube or cavity of the take-out assembly. The vacuum enables preforms to be removed by suction from the moulding machine and held in the take-out plate cavities during ~~ransfer to a receiving station. Conversely, the pressurized fluid assists in ejecting preforms stored within the take-out plate cavities. The cooling means circulates cooling fluid throughout the take-out plate in order to chill the preforms temporarily stored therein.
This type of preform removal and handling system tends to be relatively expensive and difficult to maintain for a number of reasons. First, the air pressure means and the cooling means each require the provision of extraneous equipment, such as air pumps and heax exchangers, as well equipment that may be integrate into the take-out plate such as valves and the like. Second, the air pressure and cooling means require that intricate integrated channels, bores and manifolds be milled into the take-out plate in order to distribute the appropriate fluids to each of the preform holding cavities or tubes. This requirement tends to make the take-out plate, which is precisely crafted, difficult and expensive to manufacture. Third, as the cavities or tubes of the take-out plate are typically designed to encompass the bodies of the preforms, the plate tends to be relatively thick and heavy. The robotic positioning device thus requires relatively powerful motors in order to quickly position the take-out plate in a stable manner.
Finally, this type of system tends to require relatively frequent maintenance due to its complexity.
20460283.1 - 3~ -SUMMARY OF INVENTION
The invention presents an alternative prefonn removal and handling system and a take-out plate assembly which does not incorporate the complexities of the prior art thereby providing the advantages of low cost and reduced maintenance requirements.
S According to one aspect of the invention, injection moulding apparatus for producing hollow plastic articles is provided. The apparatus includes an injection moulding machine having interlockable male and female mould portions for forming a first number of hot hollow plastic articles in an inj ection moulding cycle, and means for reciprocating the mould portions between a mould-closed position and a mould-open position. A conveyor is spaced apart from the injection moulding machine, and features receptacles for holding the hot hollow plastic articles in an upright position in order to let hot air disposed in the interior of each hot hollow plastic article to rise unheeded, the number of such receptacles being at least equal to the first number of hollow plastic articles produced in the injection moulding cycle. A
transfer mechanism quickly removes the hot hollow plastic articles from the injection moulding machine 1 S when it is in the mould-open position and deposits the hot hollow plastic articles upright in the conveyor receptacles.
This apparatus is effective because it is passible to handle the hot hollow plastic articles, such as PET preforms, for a period of less than approximately 15 seconds before the heat trapped in the interior of the walls of the hollow plastic article manages to spread out to the inner and outer skins of the article and soften the skins to a point where the article can no longer be actively manipulated. However, within this time period, the transfer mechanism deposits the hot hollow plastic articles into the receptacles of the conveyor, where the articles are held for cooling and not actively manipulated or unduly stressed. The hot hollow plastic articles are held in an upright position when disposed on the conveyor in order to efficiently cool the hollow plastic article. If the hollow plastic articles were held in an upside down manner, the closed end of the article 20460283.1 would trap sufficient heat in the hollow interior of the article to cause the above mentioned deformation and/or sticking problems.
The transfer mechanism preferably comprises a substrate, and a retractable clamping means, connected to the substrate, for gripping the first number of hot hollow plastic articles from S the injection moulding machine when in the mould-open position and for releasing the gripped articles. The substrate may comprise a carrier plate having a plurality of bores therein, and the clamping means may comprise jaw clamps, co-axial with each bore, with each jaw clamp being slidably mounted on the carrier plate for movement in a direction substantially normal to the corresponding bore. A motive means, such as a robot, aligns and juxtaposes the clamping means with the hot hollow plastic articles disposed on one of the mould portions when the moulding machine is in the mould-open position. The motive means also aligns and juxtaposes hot hollow plastic articles held by the clamping means with the conveyor receptacles in order to deposit the former into the latter.
The transfer mechanism of the present invention provides a mechanically stable system for the removal and handling of hot plastic articles from the injection moulding machine. In contrast to some prior art systems, the transfer mechanism of the present invention does not incorporate complicated cooling and air pressure means. Moreover, the substrate of the transfer mechanism can be made relatively thin and light thereby enabling the use of more economically efficient motors to be employed in the motive means.
20460283.1 BRIEF DESCRIPTION OF DRAWINGS
For the purposes of description, but not of limitation, the invention will now be explained in greater detail with reference to the accompanying drawings, wherein:
Figures lA - 1 C are perspective view illustrations of an injection moulding apparatus in accordance with the preferred embodiment, each of which illustrates a prefers ed transfer mechanism of the apparatus in a different operative position;
Figures 2A, 2B and 2C are partial cross-sectional views of the injection moulding apparatus taken along line I-I in Figure 1;
Figure 2D is a partial cross-sectional view of the transfer mechanism taken along line II-II
in Figure 1 C;
Figure 2E is a partial cross-sectional view of a preferred conveyor employed in the injection moulding apparatus taken along line Il(I-III in Figure 1C;
Figure 3 is a fragmentary, perspective view of a portion of the transfer mechanism;
Figure 4 is a front view also showing hidden details of a similar portion of the transfer mechanism shown in figure 3;
Figure 5 is an exploded view of a portion of the transfer mechanism shown in figure 3;
and Figures 6A - 6C are schematic diagrams illustrating various preferred patterns for storing hot hollow plastic articles onto the conveyor.
20460283.1 DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
An inj ection moulding apparatus 10 for producing hollow plastic articles such as PET
preforms is shown in Figs. lA to 1C. The apparatus 10 includes an injection moulding machine 12 and a hopper 14 for receiving PET pellets which are heated to produce PET
resin that is injected into moulds provided by the injection moulding machine as is well known in this art.
The inj ection moulding machine 12 includes interlockable male and female mould portions 16A and 16B. Referring additionally to the partial cross-sectional views of Figs. 2A and 2B, the male mould portion 16A carries a plurality of elongate cores 18 designed to penetrate corresponding cavities 20 in the female mould portion 16B and thereby provide a plurality of moulds. The mould portions 16A and 16B reciprocate between a mould-closed position and a mould-open position for each injection moulding cycle of the machine 14. In the mould-closed position, a number of elongate hollow preforms ~ 8 are produced, the exact shape of each article corresponding to the intersticial shape between a given core%avity. In the mould-open position, a gap 22 is present between the male and female mould portions 16A and 16B and the recently moulded, hot, hollow preforms must be removed from the machine 12 in order to enable the next injection moulding cycle to commence.
The injection moulding apparatus 10 includes a conveyor 24 which is spaced apart from the injection moulding machine 12. The conveyor includes a web 25 and receptacles 26, discussed in greater detail below, for holding the hot hollow preforms in an upright position in order to efficiently cool the performs. The number of receptacles 26 is at least equal to the number of preforms produced in each injection moulding cycle, and preferably more, as discussed in greater detail below. The conveyor 24 holds the preforms for a predetermined time period, preferably a multiple of injection moulding cycles, in order to give the preforms sufficient time to cool and stabilize. As the conveyor 24 proceeds in a forward direction, preforms at the head of the conveyor simply fall out of the receptacles 26 as the web 25 curves at about point 27 to 20460283.1 ;I -begin its return path. At this point, the preforms can be collected or transferred by other conveyor means (not shown) for further processing, such as blow moulding, etc.
The inj ection moulding apparatus 10 includes a transfer mechanism 28 for quickly removing the hot hollow prefonms from the injection moulding machine 12 when it is in the mould-open position and for depositing these preforms upright in the conveyor receptacles 26, as shown for example in Figure 2E. The transfer mechanism 28 comprises a frame or substrate, such as a take-out or carrier plate 30, and a retractable clamping means such as split ring clamps 32, discussed in greater detail below, for gripping and holding all of the preforms produced in an injection moulding cycle. A motive means, such as a three-axis gantry robot 34, aligns and juxtaposes the clamping means 32 with the hot preforms disposed on the male moulding portion 16A when the injection moulding machine 12 is in the mould-open position. The motive means also aligns and juxtaposes hot preforms held by the clamping means 32 with the conveyor receptacles 26 in order to deposit the hot preforms into the receptacles. The movement of the carrier plate 30 as provided by the motive means is partially depicted in Figs. 1 A, 1 B and 1 C, and, in cross-sectional view, by Figs. 2C, 2D and 2E.
The clamping means, as described in greater detail below, exerts some pressure onto the recently moulded and still quite hot PET preforms which typically have a skin temperature of about 10 to 30 degrees Celsius, depending on the operating characteristics of the machine 12, and a much higher internal temperature, e.g. about 200 degrees Celsius.
Nevertheless, it: is possible to apply a small amount of pressure to the PET preforms and thus handle them for a short time period before the heat trapped in the interior of the preform walls manages to diffuse or radiate to the inner and outer skins of the preforms and soften the skins to a point where they are no longer "set" and the preform can no longer be gripped or otherwise actively manipulated. This time period will vary depending on the length of the injection moulding cycle, the skin temperature, the temperature of operation, and the cooling efficiency of the injection moulding machine. A typical time period within which tine preforms may be handled is approximately 5 20460283.1 _$_ to 10 seconds. Accordingly, within this time period, the transfer mechanism 28 deposits the preforms into the receptacles 26 of the conveyor 24, where the preforms are temporarily stored until they stabilize. The preforms are not actively manipulated or unduly stressed when stored on the conveyor 24. The hot hollow preforrns are held in an upright position when disposed on the conveyor in order to let hot air disposed in the interior of each preform to rise unheeded and hence allow the preform to cool sufficiently without the need for an extraneous cooling means.
The upright positioning is important because if the hollow PET preforms were held in an upside down manner, the closed end of the preform would trap sufficient heat in the hollow interior thereof to thereby cause the preform to possibly deform and/or stick to other preforms when eventually brought into contact with one another.
Referring additionally to Figs. 2C, 3, 4 and 5, the structures of the take-out or carrier plate 30 and the clamping means are shown in greater detail.
The carrier plate 30 comprises a plurality of bores 36 therein arranged in a pattern corresponding to the pattern of elongate cores 18 present on the male portion 16A of the injection moulding machine 12. Each bore 36 is sized larger in diameter than a predetermined portion 3 5 of a corresponding preform exposed in the gap 2.2 between the male and female mould portions when the injection moulding machine 12 is in the mould-open position. Thus, as shown in the cross-sectional view of Fig. 4C, preforms 38 disposed on the male mould portion 16A can freely penetrate corresponding carrier plate bores 36.
The plate 30 features one split ring or jaw clamp 32 for each carrier plate bore 32. Each clamp 32 is co-axially aligned with its corresponding bore 36 and is slidably mounted on the take out plate, as described in greater detail below, for movement in a direction 39 normal to the bore.
Each clamp 32 includes jaws 40A and 40B disposed on opposing sides of the bore. The jaws 40A and 40B feature an inner perimeter 42 designed to substantially exactly match the shape of 20460283.1 _g_ a pre-determined periphery 44 of the preform 38 when the jaws are closed, thereby enabling the clamp 32 to grip the hot preform 38 without damage.
Means are provided for reciprocating each clamp 32 between a gripping or closed position and an open position. In the preferred embodiment, such reciprocating means comprises a double acting piston 46, tie rods 48A and 48B, channel-shaped clamp rails 52A and 52B
which respectively connect to clamp jaws 40A and 40B, and articulating means SO
connecting the tie rods 48A and 48B to the piston 46.
The tie rods 48A and 48B are respectively disposed in channels 54A and 54B
milled into one of the faces of the carrier plate 30.
Elongate slots 56 in the carrier plate 30 enable tie rods 48A and 48B to be respectively fastened to the clamp rails 52A and 52B via fastening screws 58A and 58B. Each pair of clamp rails 52A and 52B respectively straddles a row or column of bores 36. Clamp jaws 40A and 40B
are respectively disposed within the channels 60 of the clamp rails 52A and 52B and are floatingly connected thereto. The floating connections are provided by bolts 62, which are threaded into jaws 40A and 40B and which pass through, but are not threaded to, eyelets 64 located in a central wall 66 of clamp rails 52A and 52B. Each clamp jaw 40A
and 40B also includes bores 70 for partially housing compression springs 72 mounted between the central wall 66 and the body of each clamp jaw. The floating connections enable a given pair of jaws 40A
and 40B to gently grasp the hot pre-forms 3 8.
The articulating means 52 comprises double-legged bell cranks 74 having legs 76A and 76B respectfully connected to the tie rods 48A and 48B. The cranks 74 are pivotably connected to links 78 that are attached to the double acting piston 46.
20460283.1 In operation, whenever the double acting piston 46 is actuated from one position or pole to the other, the articulating means force tie rods 48A and 48B to move in opposite directions relative to another. The clamp rails 52A and 52B, and hence jaws 40A and 40B, will move in correspondence with the tie rods 48 and 48B since these components are interconnected as described above. In this manner, piston 46 can be operated to reciprocate clamps 32 between the closed or gripping position and the open position.
Fig. 2E, illustraxes the structure of conveyor 24 and receptacles 26 in greater detail. The web 25 of the conveyor is formed from a plurality of substantially flat metal slats 80, each of which features a number of holes 82. The holes 82 are sized to accept an elongate body 84 of preform 38, but are smaller than a flange 86 present on the upper end of the preform. Thus, as shown in Fig. 2E, flange 86 of the preform rests against the top periphery of the slat when the preform is disposed on the conveyor.
The conveyor 24 preferably comprises a greater number of receptacles 26 than the number of preforms produced in an injection moulding cycle in order to efficiently make use of the space on the conveyor and allow the preforms a longer time period in which to cool before being displaced from the conveyor. For instance, Fig. 6A, shows the conveyor 24 being configured for a three-position diagonally offset a drop pattern 90. In the illustrated embodiment, the injection moulding machine 12 features a 6 x 2 (row, column) preform production pattern.
In this embodiment, the transfer mechanism 28 is programmed to deposit preforms produced in a first injection moulding cycle in receptacles labelled "A". The conveyor web is then incrementally advanced for a distance equal to the height of two rows in the pattern 90.
Preforms produced in the next injection moulding cycle are then deposited in receptacles labelled "B". The conveyor web is again advanced as before, so that preforms associated with the next injection moulding cycle are deposited in receptacles labelled "C". The next advance of the conveyor web restarts the drop cycle wherein the next batch of prefornns are deposited in receptacles "A"'.
20460283.1 Fig. 6B, illustrates an alternative, laterally oi~set drop pattern 92. In this embodiment, the transfer mechanism 28 is programmed to deposit three, or alternatively some other number, of consecutive batches of prefornls in laterally offset receptacle groups A, B, C
before the conveyor web is advanced for a distance equal to the length of the pattern.
Fig. 6C, illustrates another alternative, single position sequential drop pattern 94, wherein the conveyor web is advanced for a distance eclual to the length of the production pattern after each batch A, B, C of preforms is deposited onto the conveyor.
Still further alternative drop patterns can combine any of three illustrated embodiments shown in Figs. 6A to 6C.
It will be appreciated by persons skilled in the art that the present invention is not limited by what has been particularly shown and described herein as numerous modifications and variations may be made to the preferred embodiment without departing from the spirit and scope of the invention.
ao4so2ss.1
Claims (11)
1. Injection moulding apparatus for producing hollow plastic articles, comprising:
an injection moulding machine having interlockable male and female mould portions for forming a first number of hot hollow plastic articles in an injection moulding cycle, and means for reciprocating the mould portions between a mould-closed position and a mould- open position;
a conveyor, spaced apart from the injection moulding machine, and having receptacles for holding the hot hollow plastic articles in an upright position in order to let hot air disposed in the interior of each hot hollow plastic article to rise unheeded, the number of such receptacles being at least equal to the first number of hollow plastic articles produced in the injection moulding cycle; and a transfer mechanism for quickly removing the first number of hot hollow plastic articles from the injection moulding machine when in the mould-open position and depositing the hot hollow plastic articles upright in the conveyor receptacles.
an injection moulding machine having interlockable male and female mould portions for forming a first number of hot hollow plastic articles in an injection moulding cycle, and means for reciprocating the mould portions between a mould-closed position and a mould- open position;
a conveyor, spaced apart from the injection moulding machine, and having receptacles for holding the hot hollow plastic articles in an upright position in order to let hot air disposed in the interior of each hot hollow plastic article to rise unheeded, the number of such receptacles being at least equal to the first number of hollow plastic articles produced in the injection moulding cycle; and a transfer mechanism for quickly removing the first number of hot hollow plastic articles from the injection moulding machine when in the mould-open position and depositing the hot hollow plastic articles upright in the conveyor receptacles.
2. The apparatus according to claim 1 wherein the transfer mechanism deposits the hot hollow plastic articles into the conveyor receptacles in less than about 10 seconds.
3. The apparatus according to claim 1, wherein the transfer mechanism comprises:
a substrate;
retractable clamping means, connected to the substrate, for gripping the first number of hot hollow plastic articles from the injection moulding machine when in the mould-open position and for releasing the gripped articles ; and motive means for aligning and juxtaposing the clamping means with the first number of hot hollow plastic articles when disposed on one of the mould portions when the moulding machine is in the mould-open position, and for aligning and juxtaposing hot hollow plastic articles gripped by the clamping means with the conveyor receptacles.
a substrate;
retractable clamping means, connected to the substrate, for gripping the first number of hot hollow plastic articles from the injection moulding machine when in the mould-open position and for releasing the gripped articles ; and motive means for aligning and juxtaposing the clamping means with the first number of hot hollow plastic articles when disposed on one of the mould portions when the moulding machine is in the mould-open position, and for aligning and juxtaposing hot hollow plastic articles gripped by the clamping means with the conveyor receptacles.
4. The apparatus according to claim 3, wherein:
the substrate comprises a take-out plate having at least one pattern of bores therein corresponding to a pattern of hollow plastic articles produced by the injection moulding machine, each bore being sized larger in diameter than a portion of a corresponding hollow plastic article exposed in a gap between the male and female mould portions when the injection moulding machine is in the mould-open position; and the clamping means comprises a substantially co-axial jaw clamp for each carrier plate bore wherein each jaw clamp slidably mounted on the take-out plate for movement in a direction substantially normal to the corresponding bore, and means for reciprocating each jaw clamp between a plastic article gripping position and an open position.
the substrate comprises a take-out plate having at least one pattern of bores therein corresponding to a pattern of hollow plastic articles produced by the injection moulding machine, each bore being sized larger in diameter than a portion of a corresponding hollow plastic article exposed in a gap between the male and female mould portions when the injection moulding machine is in the mould-open position; and the clamping means comprises a substantially co-axial jaw clamp for each carrier plate bore wherein each jaw clamp slidably mounted on the take-out plate for movement in a direction substantially normal to the corresponding bore, and means for reciprocating each jaw clamp between a plastic article gripping position and an open position.
5. The apparatus according to claim 4, further comprising a pair of rails straddling a given bore and slidably mounted on the plate for movement in a direction substantially normal to the given bore, wherein each jaw of the corresponding jaw clamp is floatingly connected to one of the rails in order to minimize the stress of gripping a hot hollow plastic article.
6. The apparatus according to claim 1, wherein the hollow plastic article includes an elongate body and a projecting flange, and wherein the conveyor receptacle comprises a hole in a substantially flat web, the hole being sized to accept the elongate body of the hollow plastic article such that the flange thereof seats against the web.
7. The apparatus according to claim 1 wherein the transfer mechanism is operative to deposit the hot hollow plastic preforms onto the conveyor in a sequential drop pattern, the conveyor being so configured.
8. The apparatus according to claim 1 wherein the transfer mechanism is operative to deposit the hot hollow plastic preforms onto the conveyor in a latitudinally offset drop pattern, the conveyor being so configured.
9. The apparatus according to claim 1 whereon the transfer mechanism is operative to deposit the hot hollow plastic preforms onto the conveyor in a diagonally offset drop pattern, the conveyor being so configured.
10. Apparatus for the removal of hot hollow plastic articles from an injection moulding machine when it is in a mould-open position and the hot hollow plastic articles are at least partially exposed in a gap between reciprocating portions of the machine, the apparatus comprising:
a carrier plate having at least having at least one pattern of bores therein corresponding to an injection moulding machine plastic article production pattern, wherein each bore is sized larger in diameter than an exposed portion of the corresponding hollow plastic article;
a substantially co-axial jaw clamp for each carrier plate bore, wherein each jaw clamp is slidably mounted on the carrier plate for movement in a direction substantially normal to the corresponding bore;
means for reciprocating each jaw clamp between a clamping position and an open position; and motive means for aligning and juxtaposing the carrier plate with the portion of the moulding machine on which the hot hollow plastic articles are disposed in order to enable the jaw clamps to grasp the exposed portions of the hot hollow plastic articles.
a carrier plate having at least having at least one pattern of bores therein corresponding to an injection moulding machine plastic article production pattern, wherein each bore is sized larger in diameter than an exposed portion of the corresponding hollow plastic article;
a substantially co-axial jaw clamp for each carrier plate bore, wherein each jaw clamp is slidably mounted on the carrier plate for movement in a direction substantially normal to the corresponding bore;
means for reciprocating each jaw clamp between a clamping position and an open position; and motive means for aligning and juxtaposing the carrier plate with the portion of the moulding machine on which the hot hollow plastic articles are disposed in order to enable the jaw clamps to grasp the exposed portions of the hot hollow plastic articles.
11. The apparatus according to claim 10, wherein the jaw clamps are floatingly connected to the carrier plate in order to minimize the stress of gripping a hot hollow plastic article.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 2233065 CA2233065A1 (en) | 1998-03-24 | 1998-03-24 | Method and apparatus for removing hollow plastic articles from an injection moulding machine |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 2233065 CA2233065A1 (en) | 1998-03-24 | 1998-03-24 | Method and apparatus for removing hollow plastic articles from an injection moulding machine |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2233065A1 true CA2233065A1 (en) | 1999-09-24 |
Family
ID=29409507
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2233065 Abandoned CA2233065A1 (en) | 1998-03-24 | 1998-03-24 | Method and apparatus for removing hollow plastic articles from an injection moulding machine |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2233065A1 (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6652262B2 (en) * | 2001-07-24 | 2003-11-25 | Caco Pacific Corporation | Injection mold apparatus with improved take-off plate |
| CN108790080A (en) * | 2018-07-25 | 2018-11-13 | 苏州超群智能科技有限公司 | A kind of multimachine injection molding production line |
-
1998
- 1998-03-24 CA CA 2233065 patent/CA2233065A1/en not_active Abandoned
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6652262B2 (en) * | 2001-07-24 | 2003-11-25 | Caco Pacific Corporation | Injection mold apparatus with improved take-off plate |
| CN108790080A (en) * | 2018-07-25 | 2018-11-13 | 苏州超群智能科技有限公司 | A kind of multimachine injection molding production line |
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