ACCUMULATOR HEAD FOR PRODUCING A STORAGE DRUM WITH A VIEW STRIPE

Abstract: An accumulation head for a blow molding machine which produces a parison of a first melt material having a stripe of a second extruded plastic material formed by directing a second extruded plastic material into the stream of a first plastic material as the material in the accumulator is extruded to form the parison.

Description: This invention relates generally to blow moulding machines and more particularly to an extrusion head of the accumulator type for forming a parison tube having a transparent view stripe in the body of the tube. Coloured plastic containers are generally opaque and therefore the level of contents within the container cannot be directly ascertained when viewed from the outside. One solution is to form the container from clear plastic material and provide a sleeve cover or film of coloured material having a thin vertical transparent strip so that the container has what appears to be a clear vertical view stripe in its side. This approach has a disadvantage that the container must have a separately applied coloured sleeve or wrapping, which adds to the cost and complicates the production process. The accumulator head utilised in this invention is a modification of a conventional accumulator head. Such an accumulator head having a diverter sleeve to eliminate weld line formation is fully described in our US-A-4 609 340 which provides the basis for the prior art portion of claim 1. The principal object of this invention, as defined in claim 1 is to provide an improved accumulator head which is capable of forming a tube with an integral view stripe in a single operation. In the preferred and later illustrated construction, the second inlet is provided through an annular die ring positioned around said die mandrel and having directed guide portions extending toward said mandrel and positioned in said flow stream of said first plastic material, an inlet passage for the second plastic material extending through one of said guide portions to open to the inside of said die ring on the underside of said one of said guide portions for directing said second extruded plastic material into the stream of first plastic material which has been radially split as said annular piston pushes said first plastic material past said die ring and around said one die portion. The injection of the second plastic material through the second inlet orifice is timed to coincide with the discharge of melt from the accumulation chamber. The result is an improved accumulator head which enables the production of a high quality moulded container such as a storage drum having a portion of its wall composed of a different plastic material such as a transparent plastic stripe allowing visual observation of the level of contents within the container. Further objects, features and advantages of the invention will become apparent from a consideration of the following description and the appended claims, when taken in connection with the accompanying drawing. Brief Description of the Drawings Figure 1 is a top view of the accumulator head of the present invention; Figure 2 is a vertical sectional view of the accumulator head of this invention as seen from substantially the line 2-2 in Figure 1 showing the accumulator piston in its discharge position; Figure 2A is an enlarged fragmentary sectional view of the second inlet orifice area in the accumulator shown in Figure 2; Figure 3 is an enlarged fragmentary sectional view of the accumulator head showing the second inlet orifice area as seen from substantially the line 3-3 in Figure 2; Figure 4 is a fragmentary enlarged sectional view of the second inlet orifice area of the accumulator head as seen from the line 4-4 in Figure 2A; and Figure 5 is a perspective view of a storage drum formed using the accumulator head of the present invention showing the vertical view stripe. DETAILED DESCRIPTION OF THE INVENTION With reference to the drawing, the accumulator head of this invention, indicated generally at 10, is shown in Figures 1 and 2 connected to a first extruder 12 by a first inlet body member 14. The extruder 12 provides a continuous flow of first molten thermoplastic material 16, preferably an opaque material, to the accumulator head 10 through an inlet passage 18 in body member 14. The accumulator head 10 includes a die mandrel 20 that has an air conduit 22 extending axially therethrough to a conventional blow pin (not shown). Mandrel 20 is connected at its upper end to an adjustment cylinder 24 capable of moving the mandrel 20 for up and down directions. A die body 26 is supported in spaced relation around die mandrel 20 so as to define therewith in series an annular inlet orifice 28, an annular accumulation chamber 30 and annular outlet orifice 32. Annular piston 34 is slidably mounted on the mandrel 20 for up and down movement. When the annular piston 34 is moved downwardly from its retracted position toward its discharge position, it is operable to force molten plastic downwardly through the outlet orifice 32 so as to form a downwardly extending parison. A hydraulic cylinder 36 has a piston rod 38 connected to the piston 34 for moving the piston 34 downwardly. Operation of the accumulator head thus described is as described in U.S.-A-4,609,340. Located around the lower end of die mandrel 20 is a ring shaped die ring 40 having four equally spaced guide portions 42, 44, 46, and 48. These guide portions are diamond shaped in vertical cross section as shown in Figure 3 to smoothly split the flow of melt as the melt is pushed by piston 34 past guide portions 42, 44, 46, and 48. A second conventional extruder 50 is connected to die ring 40 by a second inlet body member 52. The second extruder 50 provides an intermittent flow of a second extruded thermoplastic melt material 54, preferably a transparent material, to extrusion head 10 through a second inlet passage 56 in second inlet body member 52 and a passage 58 in die ring 40. Passage 58 extends through die ring 40 and through the underside of guide portion 48. Passage 58 opens to the inside of the die ring 40 and the underside of guide portion 48 as shown in Figures 3 and 4. The injection of the second melt material 54 via second extruder 50 is timed to coincide with the passage of first plastic melt 16 by mandrel 20 and out annular outlet orifice 32 to form a tubular parison having a vertical strip of second melt material 54 which then is blown to form the storage drum 60 having an integral view stripe 62 as shown in Figure 5. While the invention has been described particularly with respect to forming a container with a view stripe, it is to be understood that the invention can be practiced without the second melt material 54 being transparent. From the above description it is seen that this invention provides an improved accumulator head 10 which is operable to form a parison extruded by the head 10 having a portion of the body of the parison formed from a second molten plastic material such that a container having a transparent view stripe can be produced in a single operation.

Claims: An accumulator head for a blow moulding machine for extruding a tube of plastic material wherein said head includes a mandrel (20), a die body (26) enclosing said mandrel to define therewith an annular outlet orifice (32), a first inlet orifice (28), an annular accumulation chamber (30) in communication with and located between said inlet (28) and outlet (32) orifices, and an annular piston (34) movable in said accumulation chamber (30) so as to discharge accumulated first plastic material (16) therein through said outlet orifice (32), characterised in that means (48) are provided operatively associated with the mandrel (20) and the die body (26) located between the accumulation chamber (30) and the outlet orifice (32) to form a radially extending split in the stream of said first plastic material (16) as said first plastic material is discharged from the accumulation chamber (30) to said outlet orifice (31), and in that a second inlet orifice (58) is located between said accumulation chamber (30) and said outlet orifice (32) for injection of a second plastic material (54) into said split in the flow stream of said first plastic material (16) as said first plastic material exits (16) to said outlet orifice (32) whereby the total extruded plastic flowing out of the annular outlet orifice (32) forms a tube (60) having a strip (62) of said second plastic material in said tube extending longitudinally thereof. An accumulator head according to claim 1, wherein said second inlet (58) is provided through an annular die ring (40) positioned around said die mandrel (20) and having directed guide portions (48) extending toward said mandrel (20) and positioned in said flow stream of said first plastic material (16), an inlet passage (58) for the second plastic material extending through one of said guide portions (48) to open to the inside of said die ring (40) on the underside of said one of said guide portions (48) for directing said second extruded plastic material (48) into the stream of first plastic material (16) which has been radially split as said annular piston (34) pushes said first plastic material (16) past said die ring (40) and around said one die portion (48). An accumulator head according to claim 2, wherein each guide portion (48) has a generally elongated diamond shaped cross section oriented coaxially with said stream so as to create minimal turbulence in said stream.

Inventors: SHAPLER, THOMAS ARTHUR
Applicants: HOOVER UNIVERSAL, INC (A MICHIGAN CORPORATION)
Application year: 1988
Main classification: B29C47
IPC codes: B29C47, B29C49