CA1139512A - Method and apparatus for drawing mouth-neck portions of synthetic resin bottles - Google Patents
Method and apparatus for drawing mouth-neck portions of synthetic resin bottlesInfo
- Publication number
- CA1139512A CA1139512A CA000341007A CA341007A CA1139512A CA 1139512 A CA1139512 A CA 1139512A CA 000341007 A CA000341007 A CA 000341007A CA 341007 A CA341007 A CA 341007A CA 1139512 A CA1139512 A CA 1139512A
- Authority
- CA
- Canada
- Prior art keywords
- mouth
- neck portion
- parison
- synthetic resin
- screw thread
- 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.)
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Abstract
ABSTRACT OF THE DISCLOSURE
Disclosed is a method for drawing a mouth-neck portion of a synthetic resin bottle in the radial direction, this method comprising inserting an expanding operation zone of a drawing apparatus into the mouth-neck portion in the heated state and expanding respective drawing pieces of the expanding operation zone in the radial direction. The drawing apparatus for practising this drawing method comprises a cylindrical wall constructed by a great number of drawing pieces, a pressing rod inserted into this cylindrical wall to expand the drawing pieces in the radial direction and an elastic tubular member to be inflated in the radial direction by high pressure compressed air.
Disclosed is a method for drawing a mouth-neck portion of a synthetic resin bottle in the radial direction, this method comprising inserting an expanding operation zone of a drawing apparatus into the mouth-neck portion in the heated state and expanding respective drawing pieces of the expanding operation zone in the radial direction. The drawing apparatus for practising this drawing method comprises a cylindrical wall constructed by a great number of drawing pieces, a pressing rod inserted into this cylindrical wall to expand the drawing pieces in the radial direction and an elastic tubular member to be inflated in the radial direction by high pressure compressed air.
Description
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The present invention relates to a method and apparatus for drawing a mouth-neck portion of a bottle composed of a saturated polyester resin or a precursor intermediate product thereof.
Saturated polyester resins are excellent in the physical properties and durability. ~lowever, in order to manifest these excellent physical proper-ties and durability in saturated polyester resins, it is indispensable that these saturated polyester resins should be drawn.
Therefore, according to conventional techniques, bottles of saturated polyester resins are prepared by forming a parison, i.e. a primary intermediate molded article, having an effec*ive cylindrical shape by injection molding, blow-molding this parison into a bottle and drawing the so formed bottle.
According to the conventional techniques, the bottles, are subjected to drawing at the blow-molding step, and as is well known, at the blow-molding step, the mouth-neck portion of the bottle is held on a mold for blow-molding. Therefore, the mouth-neck portion of the bottle is not substantially subjected to the drawing operation.
Accordingly, the undrawn mouth-neck portion is inferior to the drawn barrel portion of the bottle in the physical properties and durability and the bottle is not completely satisfactory.
For example, when a high concentration is stored in this conventional bottle, no trouble is caused in the barrel portion but the mouth-neck portion is whitened and becomes mechanically brittle since the alochol permeates in the mouth-neck portion. Furthermore, a great number of fine cracks are formed in the mouth-neck portion and the sealing effect is drastically reduced.
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Summary of the Invention According to one aspect of the present invention there is provided a method of forming a complete synthetic resin bottle from a parison having an open mouth-neck portion at one end and a closed barrel portion at the other end, comprising the steps of: holding a parison composed of synthetic resin material in a holding member; heating a mouth- neck portion of the parison to a temperature high enough to permit reshaping of the heated syn-thetic resin material; inserting a cylindrically-segmented molding tool carrying a rod between the cylindrical segments thereof into said mouth-neck portion; pulling the rod between the cylindrical segments of themolding tool to expand the cylindrical segments of the molding tool, whereby the mouth-neck portion of the parison is radially expanded; and blow-molding the remaining portion of the parison to form a barrel portion of a complete bottle.
According to another aspect of the present invention there is provided apparatus for forming a complete synthetic resin bottle from a parison having an open mouth-neck portion at one end and a closed barrel portion at the other end, comprising; a holding member for holding a parison composed of synthetic resin material; means for heating a mouth-neck portion of the parison to a temperature high enough to permit reshaping of the heated synthetic resin material; a hollow cylindrically-segmented molding tool for insertion into said mouth-neck portion, the cylindrical segments of said molding tool taper-ing inwardly at the forward end of the tool that first enters said mouth-neck portion with the forwardmost ends of alternate segments lying in over-lapped position with respect to forwardmost ends of the adjacent alternate ; segments; a rod adapted to move axially through said tool between the cylindrical segments towards said forward end of said tool to force the forwardmost segment ends outwardly and move them from the overlapped position
The present invention relates to a method and apparatus for drawing a mouth-neck portion of a bottle composed of a saturated polyester resin or a precursor intermediate product thereof.
Saturated polyester resins are excellent in the physical properties and durability. ~lowever, in order to manifest these excellent physical proper-ties and durability in saturated polyester resins, it is indispensable that these saturated polyester resins should be drawn.
Therefore, according to conventional techniques, bottles of saturated polyester resins are prepared by forming a parison, i.e. a primary intermediate molded article, having an effec*ive cylindrical shape by injection molding, blow-molding this parison into a bottle and drawing the so formed bottle.
According to the conventional techniques, the bottles, are subjected to drawing at the blow-molding step, and as is well known, at the blow-molding step, the mouth-neck portion of the bottle is held on a mold for blow-molding. Therefore, the mouth-neck portion of the bottle is not substantially subjected to the drawing operation.
Accordingly, the undrawn mouth-neck portion is inferior to the drawn barrel portion of the bottle in the physical properties and durability and the bottle is not completely satisfactory.
For example, when a high concentration is stored in this conventional bottle, no trouble is caused in the barrel portion but the mouth-neck portion is whitened and becomes mechanically brittle since the alochol permeates in the mouth-neck portion. Furthermore, a great number of fine cracks are formed in the mouth-neck portion and the sealing effect is drastically reduced.
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Summary of the Invention According to one aspect of the present invention there is provided a method of forming a complete synthetic resin bottle from a parison having an open mouth-neck portion at one end and a closed barrel portion at the other end, comprising the steps of: holding a parison composed of synthetic resin material in a holding member; heating a mouth- neck portion of the parison to a temperature high enough to permit reshaping of the heated syn-thetic resin material; inserting a cylindrically-segmented molding tool carrying a rod between the cylindrical segments thereof into said mouth-neck portion; pulling the rod between the cylindrical segments of themolding tool to expand the cylindrical segments of the molding tool, whereby the mouth-neck portion of the parison is radially expanded; and blow-molding the remaining portion of the parison to form a barrel portion of a complete bottle.
According to another aspect of the present invention there is provided apparatus for forming a complete synthetic resin bottle from a parison having an open mouth-neck portion at one end and a closed barrel portion at the other end, comprising; a holding member for holding a parison composed of synthetic resin material; means for heating a mouth-neck portion of the parison to a temperature high enough to permit reshaping of the heated synthetic resin material; a hollow cylindrically-segmented molding tool for insertion into said mouth-neck portion, the cylindrical segments of said molding tool taper-ing inwardly at the forward end of the tool that first enters said mouth-neck portion with the forwardmost ends of alternate segments lying in over-lapped position with respect to forwardmost ends of the adjacent alternate ; segments; a rod adapted to move axially through said tool between the cylindrical segments towards said forward end of said tool to force the forwardmost segment ends outwardly and move them from the overlapped position
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to an aligned configuration wherein th.ey form a continuous walled cylinder, whereby the mouth-neck portion of the parison is radially expanded; and means for blow-molding the remaining portion of the parison to form the barrel portion of a complete bottle.
Brief Description of the Drawings . . .
In the accompanying drawings, which illustrate exemplary embodiments of the present invention:
Figures 1 to 3 are diagrams illustrating a first embodiment of the present invention~ in which Figure 1 is a sectional view showing the state in which the drawing apparatus is inserted in an intermediate molded article 1 -2a-.
~13~ 2 of a bottle;
Figure 2 is a sectional view showing the state of the mouth-neck port-ion of the bottle after the drawing operation and Figure 3 is a view showing the section taken along the line III-III in Figure 2;
Figures 4 to 7 are diagrams illustrating a second embodiment of the present invention, in which Figure 4 is a sectional view showing the state in which the drawing apparatus is inserted in an intermediate molded article of a bottle, Figure 5 is a view showing the section taken along the line V-V in Figure 4, Figure 6 is a sectional view illustrating the state where the mouth-neck portion of the bottle is being drawn by the drawing apparatus and Figure 7 is a view showing the section taken along the line VII-VII in Figure 6;
Figures 8 to 10 are diagrams illustrating a third embodiment of the present invention, in which Figure 8 is a sectional view illustrating the state in which the drawing apparatus is inserted into an intermediate molded article of a bottle, Figure 9 is a view showing the section taken along the line IX-IX in Figure 8 and Figure 10 is a sectional view showing the state where the intermediate molded article is being drawn by the drawing apparatus; and Figure 11 is a sectional view illustrating the state in which the mouth-neck portion of a bottle is being drawn by the drawing apparatus in a fourth embodiment of the present invention.
Detailed Description of the Preferred Embodiments The first embodiment of the present invention will now be described with reference to Figuresl to 3.
An intermediate molded article 1 is a bottomed tubular member formed by injection molding of a saturated polyester resin. A drawable synthetic resin such as a polypropylene resin or vinyl chloride resin may be used instead of the saturated polyester resin.
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~ ~ 3 ~t~ z A mouth-neck portion 2 on the top end of the intermediate molded art-icle 1 is to be formed into a mouth-neck portion of the resulting bottle. In the present invention, also this mouth-neck portion 2 is drawn in the radial direction by a drawing apparatus 3 as well as the barrel portion.
The drawing apparatus 3 will now~be described.
The drawing apparatus 3 comprises a cylinder including a base portion 3a and a tapered top end. A great number o~ cut grooves 4 extending in the axial direction are formed in the tapered top end of the cylinder and a drawing piece 5 is mounted between every two adjacent cut grooves 4. A guide piece 6 is projected from the top end of each drawing piece 5 inwardly in the radial direction of the cylinder, and these guide pieces 6 are assembled to form in the central portion a taper hole 7 having a diameter decreased toward the upper portion. A taper rod 8 having a diameter increased toward the top end is insert-ed into the taper hole 7 and the upper end of the taper rod 8 is connected to a pressing rod 9 so that the upper end of said rod 9 is projected beyond the base portion 3a and the rod 9 is pushed and shifted in the axial direction.
More specifically an expanding operation zone 10 which can expand in the radial direction is constructed by the respective drawing pieces 5 so that when the pressing rod 9 is pulled up, the taper hole 7 is expanded in the radial 20 ! direction by the taper rod 8 and the respective drawing pi ces 5 are expanded in the radial direction.
When the mouth-neck portion 2 of the intermediate molded article 1 is dra~n by the above-mentioned drawing apparatus 3, the lower portion of the intermediate molded article 1 formed in advance by injection molding is held by a holding member 11. The mouth-neck portion 2 is heated at a temperature high enough to effect drawing. This heating may be performed before the mouth-neck portion 2 is held by the holding member 11. Then, expanding operation zone 10 of the dra~ing apparatus 3 is inserted in the mouth-neck portion 2 as shown in Figure 1. At this point, the small-diameter portion of the taper rod 8 is located in the taper hole 7 and the expanding operationzone 10 is in the contracted state.
Then, the pressing rod 9 is pulled up. At this point, the respective drawing pieces 5 are outwardly expanded by the inclined face of the taper rod 8 as shown in Figures 2 and 3. Accordingly, the mouth-neck portion 2 of the intermediate molded article 1 is drawn in the radial direction. Since the respective drawing pieces 5 are pushed by the inclined face of the taper rod 8 and they are expanded synchronously in the radial direction, irregular deformation of the mouth-neck portion 2 is prevented and the mouth-neck portion 2 is uniformly drawn in a predetermined manner.
nhen the pressing rod 9 is then downwardly pushed to return thetaper rod 8 to the original position, the respective drawing pieces 5 are re-turned inwardly in the radial direction by their own elastic force and the drawing pieces 5 separate from the inner circumferential face of the mouth-neck portion 2. Then, the expanding operation zone 10 of the drawing apparatus
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to an aligned configuration wherein th.ey form a continuous walled cylinder, whereby the mouth-neck portion of the parison is radially expanded; and means for blow-molding the remaining portion of the parison to form the barrel portion of a complete bottle.
Brief Description of the Drawings . . .
In the accompanying drawings, which illustrate exemplary embodiments of the present invention:
Figures 1 to 3 are diagrams illustrating a first embodiment of the present invention~ in which Figure 1 is a sectional view showing the state in which the drawing apparatus is inserted in an intermediate molded article 1 -2a-.
~13~ 2 of a bottle;
Figure 2 is a sectional view showing the state of the mouth-neck port-ion of the bottle after the drawing operation and Figure 3 is a view showing the section taken along the line III-III in Figure 2;
Figures 4 to 7 are diagrams illustrating a second embodiment of the present invention, in which Figure 4 is a sectional view showing the state in which the drawing apparatus is inserted in an intermediate molded article of a bottle, Figure 5 is a view showing the section taken along the line V-V in Figure 4, Figure 6 is a sectional view illustrating the state where the mouth-neck portion of the bottle is being drawn by the drawing apparatus and Figure 7 is a view showing the section taken along the line VII-VII in Figure 6;
Figures 8 to 10 are diagrams illustrating a third embodiment of the present invention, in which Figure 8 is a sectional view illustrating the state in which the drawing apparatus is inserted into an intermediate molded article of a bottle, Figure 9 is a view showing the section taken along the line IX-IX in Figure 8 and Figure 10 is a sectional view showing the state where the intermediate molded article is being drawn by the drawing apparatus; and Figure 11 is a sectional view illustrating the state in which the mouth-neck portion of a bottle is being drawn by the drawing apparatus in a fourth embodiment of the present invention.
Detailed Description of the Preferred Embodiments The first embodiment of the present invention will now be described with reference to Figuresl to 3.
An intermediate molded article 1 is a bottomed tubular member formed by injection molding of a saturated polyester resin. A drawable synthetic resin such as a polypropylene resin or vinyl chloride resin may be used instead of the saturated polyester resin.
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~ ~ 3 ~t~ z A mouth-neck portion 2 on the top end of the intermediate molded art-icle 1 is to be formed into a mouth-neck portion of the resulting bottle. In the present invention, also this mouth-neck portion 2 is drawn in the radial direction by a drawing apparatus 3 as well as the barrel portion.
The drawing apparatus 3 will now~be described.
The drawing apparatus 3 comprises a cylinder including a base portion 3a and a tapered top end. A great number o~ cut grooves 4 extending in the axial direction are formed in the tapered top end of the cylinder and a drawing piece 5 is mounted between every two adjacent cut grooves 4. A guide piece 6 is projected from the top end of each drawing piece 5 inwardly in the radial direction of the cylinder, and these guide pieces 6 are assembled to form in the central portion a taper hole 7 having a diameter decreased toward the upper portion. A taper rod 8 having a diameter increased toward the top end is insert-ed into the taper hole 7 and the upper end of the taper rod 8 is connected to a pressing rod 9 so that the upper end of said rod 9 is projected beyond the base portion 3a and the rod 9 is pushed and shifted in the axial direction.
More specifically an expanding operation zone 10 which can expand in the radial direction is constructed by the respective drawing pieces 5 so that when the pressing rod 9 is pulled up, the taper hole 7 is expanded in the radial 20 ! direction by the taper rod 8 and the respective drawing pi ces 5 are expanded in the radial direction.
When the mouth-neck portion 2 of the intermediate molded article 1 is dra~n by the above-mentioned drawing apparatus 3, the lower portion of the intermediate molded article 1 formed in advance by injection molding is held by a holding member 11. The mouth-neck portion 2 is heated at a temperature high enough to effect drawing. This heating may be performed before the mouth-neck portion 2 is held by the holding member 11. Then, expanding operation zone 10 of the dra~ing apparatus 3 is inserted in the mouth-neck portion 2 as shown in Figure 1. At this point, the small-diameter portion of the taper rod 8 is located in the taper hole 7 and the expanding operationzone 10 is in the contracted state.
Then, the pressing rod 9 is pulled up. At this point, the respective drawing pieces 5 are outwardly expanded by the inclined face of the taper rod 8 as shown in Figures 2 and 3. Accordingly, the mouth-neck portion 2 of the intermediate molded article 1 is drawn in the radial direction. Since the respective drawing pieces 5 are pushed by the inclined face of the taper rod 8 and they are expanded synchronously in the radial direction, irregular deformation of the mouth-neck portion 2 is prevented and the mouth-neck portion 2 is uniformly drawn in a predetermined manner.
nhen the pressing rod 9 is then downwardly pushed to return thetaper rod 8 to the original position, the respective drawing pieces 5 are re-turned inwardly in the radial direction by their own elastic force and the drawing pieces 5 separate from the inner circumferential face of the mouth-neck portion 2. Then, the expanding operation zone 10 of the drawing apparatus
3 is withdrawn from the mouth-neck portion 2, and the barrel portion of the intermediate molded article 1 is drawn according to a customary blow-mold-ing method to form a bottle.
As will be apparent from the foregoing illustration, according to the present embodiment, even the mouth-neck portion of the bottle is drawn, and therefore, the mouth-neck portion is not inferior to the barrel portion at all in the physical properties and durability, with a result that an excellent bottle can be provided according to the present embodiment. Moreover, since the drawing apparatus is arranged 50 that the respective drawing pieces consti-tuting the expanding operation zone are synchronously expanded by the taper rod, the mouth-neck portion can be drawn uniformly and precisely in a pre~
determined manner. Accordingly, the~mouth-neck portion of the bottle can be drawn effectively by the drawing apparatus having t~e above-mentioned simple structure. In the present embodiment, the mouth-neck portion is drawn prior to drawing of the barrel portion. In the present invention, the mouth-neck portion of the intermediate molded article may be drawn after drawing of the barrel portion.
The second embodiment of the present invention will now be describ0d with reference to Figures 4 to 7.
In this embodiment, a drawing apparatus capable of drawing the mouth-neck portion in a shape much closer to the cylindrical form is used. In this drawing apparatus 12, an expanding operation zone 13 is formed to have a tapered configuration in which the diameter is gradually decreased toward the top end. A plurality of cut grooves 14 extending in the axial direction are formed on the expanding operation zone 13 and a drawing piece 15 is formed between every two adjacent cut grooves 14. Every other drawing piece lS is inwardly bent so that both the ends of every alternate drawing pieces 15 are overlapped. A pressing rod 16 having substantially the same diameter as the inner diameter of the cylindrical expanding operation zone 13 is inserted in the expanding operation zone 13 as means for expanding the respective drawing pieces 15 in the radial direction. The pressing rod 16 is arranged so that when the expanding operation zone 13 i5 in the contracted state, the top end of the pressing rod 16 is located on bases of the drawing pieces 15. When the pressing rod 16 is pressed, the respective drawing pieces 15 are expanded in the radial direction against their own elastic force~ and when the drawing pieces 15 are expanded to such an extent tha~ both the inner draw-ing piecas 15 and outer drawing pieces 15 are located on the same circumference the drawing operation of the mouth-neck portion 2 is completed.
When the mouth-neck portion 2 is drawn by using the drawing apparatus 12 of this second embodiment, the intermediate molded article 1 is held by a holding membe] 11, and the expanding operation zone 13 is inserted in the mouth-neck portion 2 as shown in Figure 4. At this point, the respective drawing pieces 15 of the drawing apparatus 12 are in the alternately overlapped state as shown in Figure 5.
When the pressing rod 16 is then pushed into the expanding operation zone 13 by operating the base of the rod L6, the respective drawing pieces 15 are gradually expanded in the radial direction against the elastic force thereof, and when both the inner drawing pieces 15 and outer drawing pieces 15 are located on the same circumference, as shown in Figure 7, drawing of the mouth-neck portion 2 is completed.
~hen the pressing rod 16 is then withdrawn and returned to the original position, the respective drawing pieces are inwardly returned in the radial direction by the elastic force thereof and separate from the inner peripheral wall of the mouth-neck portion 2. In this embodiment, since the inner draw-ing pieces have a larger elastic return force that the outer drawing pieces, there is restored the state where every two drawing pieces are overlapped.
Then, the expanding operation zone 13 is withdrawn from the mouth-neck portion 2 and the intermediate molded article 1 is subjected to blow-molding to form a bottle.
According to the above-mentioned second embodiment, in the initial stage of the drawing step using the drawing apparatus 12, only the outer draw-ing pieces 15 fall in contact with the inner circumferential wall of the mouth-neck portion 2, but at the point of termination of the drawing operation, all the drawing pieces 15 fall in contact with the inner circumferential wall of the mouth-neck portion 2. Accordingly, the mouth-neck portion 2 is drawn in the shape ~much closer to a true circle. Even if the mouth-neck portion is shaped in the form other than the cylindrical form, the mouth-neck portion 2 can be drawn precisely along the drawing pieces expanded in a predetermined shape. In this second embodiment, the effect attained in the first embodiment ~lL3~
can be similarly attained. ~le present second embodiment is preferably adoptedwhen it is necessary to mold the mouth-neck portion of the bottle more precisely.
The third embodiment will now be described with reference to Figures 8 to 10.
In this embodiment, a screw thread is formed on each drawing piece of the drawing apparatus used in the second embodiment, and the mouth-neck portion 2 is screwed while it is being drawn.
More specifically, a spiral screw thread 19 is projected from the outer face of the top end of each of inner and outer drawing pieces 18a and 18b of the drawnng apparatus 17 so that when -the drawing pieces 18a and 18b are expanded on the same circle by pushing of a pressing rod 20, whereby all the drawing pieces are connected and one spiral screw is formed. A two-split mold 21 is used for drawing the mouth-neck portion 2, and a spiral screw groove 23 corresponding to the spiral screw 19 is formed in the hole wall 22 defining the mouth-neck portion.
The method for drawing the mouth-neck portion 12 by using the drawing apparatus 17 and mold 21 will now be described. The intermediate molded article 1 is held by the holding member 11 and the mouth-neck portion 2 is heated at a temperature high enough to effect drawing. The mouth-neck portion 2 is 2Q placed in the~'hole wall 22 of the mold 21 as shown in Figure 8, and the expand-ing operation zone 24 of the drawing apparatus 17 is inserted in the mouth-neck portion 2. At this point, the insertion state of the enlarging operation zone 24 of the drawing apparatus 17 is controlled so that the spiral screw 19 defined by the drawing pieces 18a and 18b is located at a position correspond-ing to the screw groove 23 of the mold 21. In this state, the side ends of the inner and outer drawing pieces 18a and 18b are overlapped as shown in Figure 9.
When the pressing rod 20 is then pushed into the expanding operation ~,?
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zone 24, the respective drawing pieces 18a and 18b are gradually expanded in the radial direction, and if they are expanded beyond a certain degree, the inner drawing pieces 18a are intruded between every two adjacent outer drawing pieces 18b. At the point of termination of drawing, the respective drawing pieces 18a and 18b are located on the same circumference and a continuous spiral screw 19 is formed by the threaded portions of the drawing pieces 18a and 18b. The mouth-neck portion 2 is drawn by the expanding operation zone 23 and falls in contact with the cavity wall 22 of the mold 21. At this point the peripheral wall portion of the mouth-neck portion 2 is pressed into the 10 spiral screw groove 22 of the mold 21 by projection of the spiral screw 19 formed by the drawing pieces 18a and 18b. Accordingly, a screw thread 25 is formed on the periphery of the mouth-neck portion 2 while it is drawn in the radial direction.
When the pressing rod 20 is then withdrawn, the respective drawing pieces 18a and 18b are returned inwardly in the radial direction by the elastic force thereof, and the expanding operation zone 24 is pulled out from the mouth-neck portion 2. Then, the mold 21 is split and the intermediate molded article 1 is subjected to blow molding to form a bottle.
As will be apparent from the foregoing illustration, a spiral screw thread can be formed on the periphery of the mouth-neck portion simultaneously with drawing of the mouth-neck portion of the bottle. Furthermore, since a screw thread is formed between the expanding operation zone of the drawing device and the mold, the drawing precision can be further improved. More-over, since the mouth-neck portion is drawn, the mouth-neck portion of the bottle is not inferior to the barrel portion at all with respect to the physical porperties and durability.
The fourth embodiment will now be described with reference to Figure 11.
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-In the present embodiment, there is adopted a drawing apparatus in which high pressure compressed air is injected into an elastic tubular member to inflate the tubular member and the mouth-neck portion 2 of a bottle is drawn by this inflation of the tubular member. This drawing apparatus 26 comprises a rod portion 27 and a small-diameter rod portion 29 formed on the top end of the rod portion 27. An elastic tube member 28 is fitted in the small-diameter rod portion 29 and a seal member 30 is attached to the top end of the small-diameter rod portion 29, whereby a hole passage 31 is formed along the rod portion 27 and the small-diameter rod portion 29 to apply high-pressure compressed air to the inner circumferential wall of the elastic tubular member 28.
The method for drawing the mouth-neck portion of a bottle by using the drawing apparatus 26 will now be described.
An intermediate molded article formed by injection molding is sub-jected to blow molding, except a mouth-neck portion 32, to form a bottle 33. At the step of molding of the intermediate molded article, a screw -i thread 3~ for engagement with a cap is formed on the periphery of the mouth-neck portion 32, and a flange 35 is formed on the outer face of the lower part of the mouth-neck portion 33.
The mouth-neck portion 32 of the bottle 33 is heated at a temperature high enough to effect drawing for exmaple, about 100C., and the mouth-neck portion 32 is set in a mold 36 having a spiral screw groove or flange groove formed on the inner circumferential wall face 37. In this state, the diameter of the `mouth-neck portion 32 is smaller than the diameter of the mouth-neck portion of the final bottle. Accordingly, a certain clearance 38 correspond-ing to the drawing size is formed between the inner circumferential wall face 37 and the mouth-neck portion 32~ The expanding operation zone 26a of the drawing device 26 is inserted in the mouth~neck portion 32, and a closing mold f~
39 is placed on the top face of the mold 36 so as to prevent leakage of high pressure compressed air injected in the inner circumferential wall of the elastic tubular member 28.
~ fhen high pressure compressed air is then injected into the hole passage 31 from a compressor or the like, the pressure in the inner circumfer-ential wall of the elastic tubular member 28 is elevated and therefore, the inner circumferential wall is expanded in the radial direction, with a result that the mouth-neck portion 32 is drawn in the radial direction. Then, high pressure compressed air is discharged through the hole passage 31, whereby the elastic tubular member 2~ is contracted and withdrawal of the drawing apparatus becomes possible.
In the fourth embodiment, the barrel portion is biaxially drawn prior to drawing of the mouth-neck portion. Of coursc, the mouth-neck portion may be drawn prior to drawing of the barrel portion.
In the fourth embodiment~ since an apparatus for inflating an elastic tubular member by high pressure compressed air is used as the drawing apparatus, the inner wall of the mouth-neck portion is not damaged at all by the drawing operation and the drawing operation can be facilitated. Therefore, the mouth-neck portion can be drawn at a much elevated precision.
As will be apparent from the foregoing illustration, according to the present embodiment, even the mouth-neck portion of the bottle is drawn, and therefore, the mouth-neck portion is not inferior to the barrel portion at all in the physical properties and durability, with a result that an excellent bottle can be provided according to the present embodiment. Moreover, since the drawing apparatus is arranged 50 that the respective drawing pieces consti-tuting the expanding operation zone are synchronously expanded by the taper rod, the mouth-neck portion can be drawn uniformly and precisely in a pre~
determined manner. Accordingly, the~mouth-neck portion of the bottle can be drawn effectively by the drawing apparatus having t~e above-mentioned simple structure. In the present embodiment, the mouth-neck portion is drawn prior to drawing of the barrel portion. In the present invention, the mouth-neck portion of the intermediate molded article may be drawn after drawing of the barrel portion.
The second embodiment of the present invention will now be describ0d with reference to Figures 4 to 7.
In this embodiment, a drawing apparatus capable of drawing the mouth-neck portion in a shape much closer to the cylindrical form is used. In this drawing apparatus 12, an expanding operation zone 13 is formed to have a tapered configuration in which the diameter is gradually decreased toward the top end. A plurality of cut grooves 14 extending in the axial direction are formed on the expanding operation zone 13 and a drawing piece 15 is formed between every two adjacent cut grooves 14. Every other drawing piece lS is inwardly bent so that both the ends of every alternate drawing pieces 15 are overlapped. A pressing rod 16 having substantially the same diameter as the inner diameter of the cylindrical expanding operation zone 13 is inserted in the expanding operation zone 13 as means for expanding the respective drawing pieces 15 in the radial direction. The pressing rod 16 is arranged so that when the expanding operation zone 13 i5 in the contracted state, the top end of the pressing rod 16 is located on bases of the drawing pieces 15. When the pressing rod 16 is pressed, the respective drawing pieces 15 are expanded in the radial direction against their own elastic force~ and when the drawing pieces 15 are expanded to such an extent tha~ both the inner draw-ing piecas 15 and outer drawing pieces 15 are located on the same circumference the drawing operation of the mouth-neck portion 2 is completed.
When the mouth-neck portion 2 is drawn by using the drawing apparatus 12 of this second embodiment, the intermediate molded article 1 is held by a holding membe] 11, and the expanding operation zone 13 is inserted in the mouth-neck portion 2 as shown in Figure 4. At this point, the respective drawing pieces 15 of the drawing apparatus 12 are in the alternately overlapped state as shown in Figure 5.
When the pressing rod 16 is then pushed into the expanding operation zone 13 by operating the base of the rod L6, the respective drawing pieces 15 are gradually expanded in the radial direction against the elastic force thereof, and when both the inner drawing pieces 15 and outer drawing pieces 15 are located on the same circumference, as shown in Figure 7, drawing of the mouth-neck portion 2 is completed.
~hen the pressing rod 16 is then withdrawn and returned to the original position, the respective drawing pieces are inwardly returned in the radial direction by the elastic force thereof and separate from the inner peripheral wall of the mouth-neck portion 2. In this embodiment, since the inner draw-ing pieces have a larger elastic return force that the outer drawing pieces, there is restored the state where every two drawing pieces are overlapped.
Then, the expanding operation zone 13 is withdrawn from the mouth-neck portion 2 and the intermediate molded article 1 is subjected to blow-molding to form a bottle.
According to the above-mentioned second embodiment, in the initial stage of the drawing step using the drawing apparatus 12, only the outer draw-ing pieces 15 fall in contact with the inner circumferential wall of the mouth-neck portion 2, but at the point of termination of the drawing operation, all the drawing pieces 15 fall in contact with the inner circumferential wall of the mouth-neck portion 2. Accordingly, the mouth-neck portion 2 is drawn in the shape ~much closer to a true circle. Even if the mouth-neck portion is shaped in the form other than the cylindrical form, the mouth-neck portion 2 can be drawn precisely along the drawing pieces expanded in a predetermined shape. In this second embodiment, the effect attained in the first embodiment ~lL3~
can be similarly attained. ~le present second embodiment is preferably adoptedwhen it is necessary to mold the mouth-neck portion of the bottle more precisely.
The third embodiment will now be described with reference to Figures 8 to 10.
In this embodiment, a screw thread is formed on each drawing piece of the drawing apparatus used in the second embodiment, and the mouth-neck portion 2 is screwed while it is being drawn.
More specifically, a spiral screw thread 19 is projected from the outer face of the top end of each of inner and outer drawing pieces 18a and 18b of the drawnng apparatus 17 so that when -the drawing pieces 18a and 18b are expanded on the same circle by pushing of a pressing rod 20, whereby all the drawing pieces are connected and one spiral screw is formed. A two-split mold 21 is used for drawing the mouth-neck portion 2, and a spiral screw groove 23 corresponding to the spiral screw 19 is formed in the hole wall 22 defining the mouth-neck portion.
The method for drawing the mouth-neck portion 12 by using the drawing apparatus 17 and mold 21 will now be described. The intermediate molded article 1 is held by the holding member 11 and the mouth-neck portion 2 is heated at a temperature high enough to effect drawing. The mouth-neck portion 2 is 2Q placed in the~'hole wall 22 of the mold 21 as shown in Figure 8, and the expand-ing operation zone 24 of the drawing apparatus 17 is inserted in the mouth-neck portion 2. At this point, the insertion state of the enlarging operation zone 24 of the drawing apparatus 17 is controlled so that the spiral screw 19 defined by the drawing pieces 18a and 18b is located at a position correspond-ing to the screw groove 23 of the mold 21. In this state, the side ends of the inner and outer drawing pieces 18a and 18b are overlapped as shown in Figure 9.
When the pressing rod 20 is then pushed into the expanding operation ~,?
s~
zone 24, the respective drawing pieces 18a and 18b are gradually expanded in the radial direction, and if they are expanded beyond a certain degree, the inner drawing pieces 18a are intruded between every two adjacent outer drawing pieces 18b. At the point of termination of drawing, the respective drawing pieces 18a and 18b are located on the same circumference and a continuous spiral screw 19 is formed by the threaded portions of the drawing pieces 18a and 18b. The mouth-neck portion 2 is drawn by the expanding operation zone 23 and falls in contact with the cavity wall 22 of the mold 21. At this point the peripheral wall portion of the mouth-neck portion 2 is pressed into the 10 spiral screw groove 22 of the mold 21 by projection of the spiral screw 19 formed by the drawing pieces 18a and 18b. Accordingly, a screw thread 25 is formed on the periphery of the mouth-neck portion 2 while it is drawn in the radial direction.
When the pressing rod 20 is then withdrawn, the respective drawing pieces 18a and 18b are returned inwardly in the radial direction by the elastic force thereof, and the expanding operation zone 24 is pulled out from the mouth-neck portion 2. Then, the mold 21 is split and the intermediate molded article 1 is subjected to blow molding to form a bottle.
As will be apparent from the foregoing illustration, a spiral screw thread can be formed on the periphery of the mouth-neck portion simultaneously with drawing of the mouth-neck portion of the bottle. Furthermore, since a screw thread is formed between the expanding operation zone of the drawing device and the mold, the drawing precision can be further improved. More-over, since the mouth-neck portion is drawn, the mouth-neck portion of the bottle is not inferior to the barrel portion at all with respect to the physical porperties and durability.
The fourth embodiment will now be described with reference to Figure 11.
_g_ , ~
-In the present embodiment, there is adopted a drawing apparatus in which high pressure compressed air is injected into an elastic tubular member to inflate the tubular member and the mouth-neck portion 2 of a bottle is drawn by this inflation of the tubular member. This drawing apparatus 26 comprises a rod portion 27 and a small-diameter rod portion 29 formed on the top end of the rod portion 27. An elastic tube member 28 is fitted in the small-diameter rod portion 29 and a seal member 30 is attached to the top end of the small-diameter rod portion 29, whereby a hole passage 31 is formed along the rod portion 27 and the small-diameter rod portion 29 to apply high-pressure compressed air to the inner circumferential wall of the elastic tubular member 28.
The method for drawing the mouth-neck portion of a bottle by using the drawing apparatus 26 will now be described.
An intermediate molded article formed by injection molding is sub-jected to blow molding, except a mouth-neck portion 32, to form a bottle 33. At the step of molding of the intermediate molded article, a screw -i thread 3~ for engagement with a cap is formed on the periphery of the mouth-neck portion 32, and a flange 35 is formed on the outer face of the lower part of the mouth-neck portion 33.
The mouth-neck portion 32 of the bottle 33 is heated at a temperature high enough to effect drawing for exmaple, about 100C., and the mouth-neck portion 32 is set in a mold 36 having a spiral screw groove or flange groove formed on the inner circumferential wall face 37. In this state, the diameter of the `mouth-neck portion 32 is smaller than the diameter of the mouth-neck portion of the final bottle. Accordingly, a certain clearance 38 correspond-ing to the drawing size is formed between the inner circumferential wall face 37 and the mouth-neck portion 32~ The expanding operation zone 26a of the drawing device 26 is inserted in the mouth~neck portion 32, and a closing mold f~
39 is placed on the top face of the mold 36 so as to prevent leakage of high pressure compressed air injected in the inner circumferential wall of the elastic tubular member 28.
~ fhen high pressure compressed air is then injected into the hole passage 31 from a compressor or the like, the pressure in the inner circumfer-ential wall of the elastic tubular member 28 is elevated and therefore, the inner circumferential wall is expanded in the radial direction, with a result that the mouth-neck portion 32 is drawn in the radial direction. Then, high pressure compressed air is discharged through the hole passage 31, whereby the elastic tubular member 2~ is contracted and withdrawal of the drawing apparatus becomes possible.
In the fourth embodiment, the barrel portion is biaxially drawn prior to drawing of the mouth-neck portion. Of coursc, the mouth-neck portion may be drawn prior to drawing of the barrel portion.
In the fourth embodiment~ since an apparatus for inflating an elastic tubular member by high pressure compressed air is used as the drawing apparatus, the inner wall of the mouth-neck portion is not damaged at all by the drawing operation and the drawing operation can be facilitated. Therefore, the mouth-neck portion can be drawn at a much elevated precision.
Claims (6)
IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A method of forming a complete synthetic resin bottle from a parison having an open mouth-neck portion at one end and a closed barrel portion at the other end, comprising the steps of: holding a parison composed of synthetic resin material in a holding member; heating a mouth- neck portion of the parison to a temperature high enough to permit reshaping of the heated synthetic resin material; inserting a cylindrically-segmented molding tool carrying a rod between the cylindrical segments thereof into said mouth-neck portion; pulling the rod between the cylindrical segments of the molding tool to expand the cylindrical segments of the molding tool, whereby the mouth-neck portion of the parison is radially expanded; and blow-molding the remaining portion of the parison to form a barrel portion of a complete bottle.
2. A drawing method according to claim 1 wherein the molding tool comprises a series of axially extending slits formed in a cylindrical wall to define said cylindrical segments.
3. A drawing method according to claim 2 wherein a neck mold having a screw thread formed thereon is positioned around said mouth-neck portion and a screw thread is formed on the mouth-neck portion simultaneously with the radial expansion of the mouth-neck portion.
4. A drawing method according to claim 2 wherein a helical screw thread section is formed on the outer face of each cylindrical segment of the mold-ing tool and a mold for molding of the mouth-neck portion is arranged around the periphery of the mouth-neck portion, a helical groove corresponding to said helical screw thread being provided on the inner circumferential wall of the mold, a screw thread being formed in said mouth-neck portion simultan-eously with the radial expansion thereof.
5. Apparatus for forming a complete synthetic resin bottle from a parison having an open mouth-neck portion at one end and a closed barrel portion at the other end, comprising; a holding member for holding a parison composed of synthetic resin material; means for heating a mouth-neck portion of the parison to a temperature high enough to permit reshaping of the heated synthetic resin material; a hollow cylindrically-segmented molding tool for insertion into said mouth-neck portion, the cylindrical segments of said molding tool tapering inwardly at the forward end of the tool that first enters said mouth-neck portion with the forwardmost ends of alternate segments lying in overlapped position with respect to forwardmost ends of the adjacent alternate segments; a rod adapted to move axially through said tool between the cylindrical segments towards said forward end of said tool to force the forwardmost segment ends outwardly and move them from the overlapped position to an aligned configuration wherein they form a continuous walled cylinder, whereby the mouth-neck portion of the parison is radially expanded;
and means for blow-molding the remaining portion of the parison to form the barrel portion of a complete bottle.
and means for blow-molding the remaining portion of the parison to form the barrel portion of a complete bottle.
6. A drawing apparatus as set forth in claim 5 wherein a helical screw thread section is formed on the outer face of the forward end portion of each cylindrical segment such that when the segments are expanded, the screw thread sections of the respective segments form a continuous helical screw thread.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000341007A CA1139512A (en) | 1979-11-30 | 1979-11-30 | Method and apparatus for drawing mouth-neck portions of synthetic resin bottles |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000341007A CA1139512A (en) | 1979-11-30 | 1979-11-30 | Method and apparatus for drawing mouth-neck portions of synthetic resin bottles |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1139512A true CA1139512A (en) | 1983-01-18 |
Family
ID=4115728
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000341007A Expired CA1139512A (en) | 1979-11-30 | 1979-11-30 | Method and apparatus for drawing mouth-neck portions of synthetic resin bottles |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1139512A (en) |
-
1979
- 1979-11-30 CA CA000341007A patent/CA1139512A/en not_active Expired
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