BRIEF DESCRIPTION OF THE DRAWINGS
The invention is explained below in further detail with the aid of exemplary embodiments shown in the drawings, wherein:
FIG. 1 is an end view of a mold pair in accordance with an embodiment of the invention; and
FIG. 2 is a cross sectional view along section line I-I in FIG. 1.
DETAILED DESCRIPTION OF THE INVENTION
The invention is explained in the following with the aid of the drawings in which like reference numbers represent like elements.
FIG. 1 shows a partial view of a pair of molds halves in accordance with the invention, first mold half 100 and second mold half 200. Mold halves 100, 200 come together and meet at parting line 10 to form a mold for molding a plastic container. In this example, the mold halves 100, 200 form one of a plurality of molds on a wheel type blow molding machine. In the blow molding process, mold halves 100, 200 come together around a parison which is then inflated to form at least one plastic container within cavities in the mold halves. In this example, mold half 100 has one cavity 110 and second mold half 200 has one cavity 210. However, it is noted that the mold halves can each have more than one cavity.
Also shown in FIG. 1 is a second pair of mold halves 1000, 2000 having cavities 1100, 1200. After mold halves 100, 200 have closed around the parison, they move away from the source of the parison and mold halves 1000, 2000 close around a subsequent portion of the parison to form another container or containers. There can be a gap between adjacent mold pairs (in this example, between the mold pair 100, 200 and the mold pair 1000, 2000) which results in a portion of the parison not being inside either mold pair. This portion is called the “gap flash” and is designated by 50 in the figures. The figures also show compression flash 60, 600 which is waste material that exists inside the mold pairs. The container and the compression flash generally are cooled during the molding process by a cooling water loop within the mold halves. The gap flash, however, is not normally cooled by the cooling water and, therefore, can remain molten and sticky. If the gap flash is not properly cooled prior to the container being ejected from the mold, the container may be ejected unevenly and/or long strands of plastic can be formed that cause problems with subsequent molding.
FIGS. 1 and 2 show a plurality of cooling jets 120 formed in first mold half 100. Cooling jets 120 are in fluid communication with an air manifold 130 which is in turn in fluid communication with an air supply duct 140. In this example, an air supply fitting 160 is fitted into an air supply fitting receptacle 150 that is formed in the end of air supply duct 140. Supply air (indicated by arrow 300) is introduced into air supply fitting 160 and is ultimately exhausted out of cooling jets 120 as cooling air 400. Cooling air 400 is directed at gap flash 50 to cool and harden it.
Similarly, second mold half 200 can be provided with a plurality of cooling jets 220 formed in second mold half 200. Cooling jets 220 are in fluid communication with an air manifold 230 which is in turn in fluid communication with an air supply duct 240. In this example, an air supply fitting 260 is fitted into an air supply fitting receptacle 250 that is formed in the end of air supply duct 240. Supply air (indicated by arrow 300) is introduced into air supply fitting 260 and is ultimately exhausted out of cooling jets 220 as cooling air 400. Cooling air 400 is directed at gap flash 50 to cool and harden it.
By supplying the air to the gap flash 50 through a plurality of spaced apart cooling jets, gap flash 50 is cooled substantially uniformly across its length, as shown in FIG. 1. In this example, cooling jets 120, 220 are angled relative to parting line 10 of the mold pair. The cooling jets can all be angled to the same degree, or can be angled differently. In particular embodiments, cooling jets 120, 220 are angled at between 20 degrees and 70 degrees relative to parting line 10.
Cooling jets 120, 220, air manifolds 130, 230, and air supply ducts 140, 240 can be machined directly in the mold halves. In this example, plugs 170, 270 are fitted into the ends of air manifolds 130, 230, respectively, to seal them after machining. By placing air supply fittings 160, 260 on outside faces of the mold halves that are opposite the cavities, they do not interfere with any mold operations.
The timing of the cooling air can be controlled by using an air circuit that is parallel to the air used to blow the container. By doing this, no additional cams, valves or other timing devices are needed.
The invention has been described in detail with respect to preferred embodiments and it will now be apparent from the foregoing to those skilled in the art that changes and modifications may be made without departing from the invention in its broader aspects. The invention, therefore, is intended to cover all such changes and modifications that fall within the true spirit of the invention.
Patent Application
20070275116
