Plastic and nonmetallic article shaping or treating: processes – Direct application of fluid pressure differential to... – Including application of internal fluid pressure to hollow...
Reexamination Certificate
2001-10-22
2004-05-04
Davis, Robert B. (Department: 1722)
Plastic and nonmetallic article shaping or treating: processes
Direct application of fluid pressure differential to...
Including application of internal fluid pressure to hollow...
C264S538000, C425S526000, C425S529000, C425S533000, C425S534000, C425S540000
Reexamination Certificate
active
06730260
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention broadly relates to a parts transfer system for an integrated injection molding and blow molding system.
The key concept to this invention is that two groups of parisons in a single set of parisons arrive at the blow-molding unit in nearly the same condition. This is achieved by staggering the indexing of the table in order to enable different sections of the table to remain at different stations around the table for differing time intervals and/or by moving related sets of parisons from station to station in rapid succession to one another. With the staggered indexing of the table each set of parisons remains on the table for periods of time that are sufficiently similar to ensure that each set of parisons reaches the blow mold clamp in a similar condition. The movement of related sets of parisons within minimal separation intervals also enables related sets of parisons to arrive at a blow-molding unit in similar condition.
2. Summary of the Prior Art
U.S. Pat. No. 4,793,960 to Schad et al (incorporated herein by reference) describes a system for transferring parisons carried on pallets through conditioning stations before entering a finishing or blow molding station. In this system, all parisons from an injection cycle are transferred simultaneously to a plurality of pallets that are then fed sequentially to the blow molding station. With this system, each pallet carrying parisons remains in the transfer path for a different period of time thus requiring different temperature conditioning for each set of parisons on a pallet.
U.S. Pat. No. 5,753,279 to Takada et al (incorporated herein by reference) describes an injection stretch blow molding apparatus in which the array pitch of the preforms is changed so that the preforms can be blown in a blow mold. The patent does not disclose means for ensuring minimal temperature differential between parisons reaching the blow molding machine.
U.S. Pat. No. 5,744,176 to Takada et al (incorporated herein by reference) describes a parison transfer system where each parison travels through a heating section and a standby section before entering the blow molding section. The transfer system operates synchronously.
U.S. Pat. No. 5,902,612 to Ogihara (incorporated herein by reference) describes an injection stretch blow molding apparatus which includes an injection unit which forms a set of parisons during an injection cycle which is a multiple of the number of parisons that can be blown in a blow molding machine during each cycle. The transfer of parts from the injection molding machine to the blow molding machine is synchronous.
U.S. Pat. No. 4,310,282 to Spurr et al (incorporated herein by reference) describes a parison transfer system that has storage means for storing parisons while they are awaiting transfer to a blow molding station. The patent does not provide means for asynchronously transferring parisons so as to ensure their arrival at a blowing station in substantially the same condition.
U.S. Pat. No. 4,824,359 to Poehlsen (incorporated herein by reference) describes a parison transfer system that operates synchronously to transfer parisons from an injection molding station to a blow molding station.
U.S. Pat. No. 6,139,789 to Neter et al (incorporated herein by reference) describes a system for thermally conditioning each batch or set of parisons in a like manner by holding each batch in a separate conditioning unit. The patent does not suggest transporting the sets of parisons through transfer stations in a like manner.
U.S. Pat. No. 6,146,134 to Kresak et al (incorporated herein by reference) describes a transfer system for transferring parisons from an injection molding station to a blow molding station that includes adjustable temperature conditioning stations in the transfer path. The transfer table moves synchronously.
U.S. Pat. Nos. 5,501,589 and 5,578,262 to Marcus (each incorporated herein by reference) describe a transfer apparatus that uses an axially and laterally indexed platen to transfer the parisons. The system provides a multiple number of blow stations corresponding to the number of injection cavities in the injection-molding unit.
U.S. Pat. No. 5,509,796 to Settembrini (incorporated herein by reference) describes a preform transfer system where the preforms are blown into bottles. The preforms that have been held the longest on the transfer path are blown first. By blowing the bottles in reverse order to their travel time on the transfer system, the effects of variations in the characteristics of the preforms can be minimized.
U.S. Pat. No. 5,443,360 to Lamb et al (incorporated herein by reference) describes a synchronous transfer system for transferring a sub-multiple of the injection molded parisons to a blow molding machine during each molding cycle.
None of the prior art references address the problem of temperature deviation in separate sets of parisons arriving at the blow molding station. In some cases, the problem would not occur because there is a one-to-one correspondence between the injection molding unit and the blow-molding unit. In these cases, each parison is treated equally. In other cases, the temperature change in the parisons remains within an acceptable window during the transfer process and would not create a problem. In still other cases, the problem may not have been recognized and a certain amount of waste product was expected and accepted.
There are a number of problems and deficiencies with the known prior art devices. When transferring parts from an injection molding machine directly to a blow molding machine it is essential that the parts arrive at the blow molding machine in a uniform or similar condition. With injection molding machines that inject more than one group of parts at a time, the parts are sometimes delivered to the blow-molding machine with different temperature profiles. If these profiles are significantly different, the blown parts may have significantly different configurations. As the object is to create consistent parts, this is obviously unacceptable machine performance. In practice, it has been found that, for many parts, the temperature decay during transfer is acceptable and the parts still arrive at the blow-molding machine in sufficiently similar condition that the subsequently blown parts will be consistent with one another. However, this is not the case with all parts. In particular, parisons that require longer cycle times or are formed of particular materials, such as polypropylene that has a lower tolerance for temperature change, need to arrive at the blow molding station with little temperature variation. The present invention enables uniform blown parts to be generated for all types of parisons. The invention is achieved by enabling the parts transfer device to operate in a synchronous or asynchronous mode dependent on the character of the parison being created by the injection-molding machine.
SUMMARY OF THE INVENTION
The general aspect of the present invention is to provide an improved method and apparatus for transferring parts from an injection molding machine to a blow molding machine.
Another aspect of the present invention is to transfer parts from an injection molding machine to a blow molding machine where each part arrives at the blow molding machine in a substantially similar condition.
The foregoing aspects are achieved by providing a novel transfer system and method for transferring groups of parisons from an injection molding unit to a blow molding unit where the injection molding unit generates a plurality of groups of parisons simultaneously. The transfer mechanism transfers the parisons from the injection-molding unit to the blow-molding unit in such a way that each parison in each group of parisons is treated in a like manner. Each set of parisons is dropped from an arm of a robot attached to the injection-molding unit onto a transfer pallet on the transfer mechanism and transported to the blow-molding machine. The blow-molding machine is operated to recei
Mason Stephen J.
Vardin Christian Nicholas
Davis Robert B.
Husky Injection Molding Systems Ltd.
Katten Muchin Zavis & Rosenman
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