CA1160410A - Process for the production of canisters and canisters obtained therewith - Google Patents
Process for the production of canisters and canisters obtained therewithInfo
- Publication number
- CA1160410A CA1160410A CA000366469A CA366469A CA1160410A CA 1160410 A CA1160410 A CA 1160410A CA 000366469 A CA000366469 A CA 000366469A CA 366469 A CA366469 A CA 366469A CA 1160410 A CA1160410 A CA 1160410A
- Authority
- CA
- Canada
- Prior art keywords
- side walls
- blank
- molded
- injection
- diffusion
- 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.)
- Expired
Links
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
- B29C45/16—Making multilayered or multicoloured articles
-
- 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
- B29C2949/00—Indexing scheme relating to blow-moulding
- B29C2949/30—Preforms or parisons made of several components
- B29C2949/3032—Preforms or parisons made of several components having components being injected
Abstract
ABSTRACT
The invention relates to a process for the production of a plastic canister from thermoplastic material in the 5, 10, 20 and 30 liter range which has an upper wall, four side walls and a bottom and suitable corner sections. The bottom is fabricated in the hot state of the thermoplastic material by a squeezing-off operation. The upper wall and side walls are injection-molded, with the side walls being substantially longer than would correspond to the height of the finished canister.
The blank is at least in the lower region of the side walls raised to the squeezing-off temperature and placed in a divided blow-mold and there put under blowing pressure, and the bottom is squeezed off from the lower lengths of the side walls in known manner.
The invention relates to a process for the production of a plastic canister from thermoplastic material in the 5, 10, 20 and 30 liter range which has an upper wall, four side walls and a bottom and suitable corner sections. The bottom is fabricated in the hot state of the thermoplastic material by a squeezing-off operation. The upper wall and side walls are injection-molded, with the side walls being substantially longer than would correspond to the height of the finished canister.
The blank is at least in the lower region of the side walls raised to the squeezing-off temperature and placed in a divided blow-mold and there put under blowing pressure, and the bottom is squeezed off from the lower lengths of the side walls in known manner.
Description
116~
PROCESS FOR T~IE PRODUCTION OF CANISTERS AND CANISTERS OBTAINED
THEREWITH
The in~ention relates to the production of a plastic canister from thermoplastic material in the 5, 10, 20 and 30 liter range which has an upper wall, four side walls, a bottom and suitable corner sections and whose botton is fabricated in the hot state of the thermoplastic material by a squeezing-off operation.
Canisters of this type must meet many different conditions at the same time:
a) To begin with, according to the acceptance conditions, the wall thickness of the fabricated canisters must correspond to the wall thickness of the sample canister suhmltted toGovernmental bodies for inspection and acceptance according to Governmental standards that apply to large canisters, such as West German standard DIN 16904 or Dutch standard NEN 3365.
b) The canisters are, at very extreme temperature conditions and pressures and in drop tests, subjected to cond~tions which are intended to demonstrate that the canisters are able to withstand particular stresses. Viewed from the angle of the wall strength, a canister has its weakest point where the wall thickness is thinnest. The plastic canisters ~abricated thus far are produced by the extrusion-blowing process. This results in the fact that the wall is thinnest at the very points where they are subjected to the greatest stresses, namely in the corner sections.
c) The strength of the walls is low. Up to the present, there exist only extrusion-blowing or centrifugal-casting processes. In these processes, practically no pressure is applied to the ma-terial (a few atm. in the extrusion process).
For this reason, the material remains flabby. With the same '~
1 ~6041~) material, injection-molded under the customary injection pressures of a few hundred atm., a very substantially greater stiffness is obtained for the walls.
d) Such a canister must also survive the tests specified in the ~overnmental inspection standards in which the canister is dropped from a height to land upside down on the cap. In the case of the heavy 20 and 30 liter canisters, it is to this end necessary to frame the blown pouring spout with a supporting construction.
e) In order that the surface of the canister cannot develop localized static charges which might perhaps give rise to a spark during the pouring out of gasoline, the material must have a certain surface resistance low enough so that the surface charges can be equali~ed.
f) At the same time, however, the wall must also be diffusion-tight in view of the highly volatile liquid or gaseous hydrocarbons. Otherwise, an ignitable mixture may be formed after a certain time, for example, in the trunk of a car or in a storage room. It is very difficult to find thermo-plastic materials which are both extrudable and diffuslon-proof, possess a low surface resistance and, in addition, meet still various other conditions. For example, it is necessary to add to the plastic a speclal grade of carbon black obtainable only ;
from a special factory in Ireland. This creates a condition of very great dependence and also an inconstancy of deliveries in the case of strikes and the like.
It is the object of the invention to specify a process which makes it possible to overcome the aforementioned short-comings and to achieve further advantages.
According to one broad aspcct, the presen-t lnven-tion provides a method of producing plastic canis-ters from thermo-plastic material in the 5, 10, 20 and 30 liter range, each said ,": ' ~ _ . _ _ _ _ . . . . . ... .
t 160410 canister having an upper wall, four side walls, a bottom wall and suitable corners between said walls including the steps of:
a) injection molding the upper wall and side walls to form a blank, said blank having side walls substantially longer than the side walls of the finished canister;
b) heating said blank at least in the lower region of said side walls to the squeezing-off temperature of said thermoplastic material, placing said blank in a divided blow mold and applying blowing pressure;
c) squeezing off the lower region of said blank whereby said bottom is formed from the lower lengths of sald side walls.
With this procedure, the aforementioned disadvantages are overcome and a diffusion-tight canister can be produced because it is easier to find materials developed only for diffu-sion-tightness which need not at the same time also possess ~
surface-resistance properties. The same is true for a material with the required surface-resistance properties. A plastic canister fabricated in this manner has not only greater diffusion-tightness but also better resistance values. Polyethylene material used typically in canister technology may be used to achieve both the low resistance and diffusion tightness requlre-ments because the invention takes advantage of the good effects of injection molding in addition to blow molding on polyethylene material with respect to these properties. Since it is ~a substantially stiffer structure, it does not bulge so much in the sun, even in the partly filled state. It is also possible to structure the surface precisely, if, for example, the surface must be made nonskid. In the extrusion-blowing process it is, after all, only to a limited extent possible to obtain precise imprints in the negative mold~ It is now also much easier to produce the legible manufacturer's address, canister l 160~1P
weight, registration number, manufacturing date, etc., demanded by the registration authority.
Accordiny to a further aspect of the invention it is now made still easier to produce the compression seam because the diffusion layer which participates only very reluctantly or not at all in the tightness of the compression seam is now excluded from the process and merely the surface-resistance layer participates in the compression seam, which results in a good joint~
In accordance with the present invention, there is also provided a plastic canister in the 5, 10, 20 and 30 liter range comprising an injection-molded upper wall, four injection-molded side walls, and an injection-molded and blow-molded bottom having a blow-molded squeezed-off compression seam therein, formed from the lower portion of said injection-molded side walls.
The invention shall now be described with reference to a practical example. On the drawing, Fig. 1 shows a schematic presentation of a tool together with the result of the first fabrication step;
Fig. 2 shows a view similar to Fig. 1 after a further ~abrication step;
Fig. 3 shows a cross section through the lower region o~ a side wall of the blank;
Fig. 4 shows a view similar to Fig. 3 but in the squeezed state;
Fig. 5 shows a horizontal section through the side wall with the wall brace in place.
~ ccording to Fig. 1, a tool for the injection-molding process has a lateral part 11 which can be removed toward the rear, a bottom part 12 which can be removed in a downward direction and another lateral part (not shown) designed to ~ -- 5 ~
1 l~04ln complement the lateral part 11 and capable of being moved forward.
Moreover, a slide 13 is provided which is capable of motion in the two lateral parts and which can be pulled out of the injection mold upward toward the right. Through an injection channel of which one half 14 is shown schematically the injection-molding material can be injected.
A blank 16 of a first fabrication step is shown on the drawing in dot-dash outline. The blank has a forward side wall 17, a left side wall which is not visible, a forward side wall 18, an upper wall 19 and, because of a nipple 21, a slanting wall 22. Since the lateral part 11 has not yet been removed, only one half eachof the side wall 18, the upper wall 19 and the nipple 21 can be seen. Accordingly, only half the negative shape of the blank 16 is worked into the lateral part 11 .
Projecting upward, a core (not shown) is provided on the bottom part 12 which projects into the blank and determines its internal shape.
The material of the blank is a diffusion-proof material.
The wall material is comprised of diffusion-tight thermoplastic, adequate to prevent highly volatile liquid or gaseous hydrocarbons rom forming at the surface. The blank 16 is now transferred into another injection-mold similar to the one in Fig. 1. ~ere, however, the lateral parts are shaped in such a way that an adhesion-imparting layer 23 can now be injection-molded onto the blank 16. In Fig. 3, this adhesion-imparting layer is, for the sake of clarity, shown as a very thick layer. Both the side wall 17 consisting of the diffusion-tight material and the adhesion-imparting layer 23 terminate according to Fig. 3 in a transition poin-t 24.
This blank of a higher fabrication step is now once more placed in a mold similar to the one in Fig. 1, whose ~ ., . . , . . . . . ... . _ l 16041P
dimensions are such that it is now possible to injection-mold a surface-resistance layer 26 onto the adhesion-imparting layer 23. The material of layer 26 is comprised of thermo-plastic material having an electrical surface resistance low enough so that static surface charges are equalized and do not give rise to sparks at the surface of the canister.
The wall layers 17, 26 have a diffusion-tightness and an electrical surface resistance according to DIN 16904 or NEN 3365 which are respectively the West German and Dutch safety standards for large canisters.
Here, the design according to Fig. 2 of the tools is such that an injection-molded apron 27 projects in the downward direction. This apron need by no means point outward like a truncated cone as shown in Fig. 2, but may also project downward in a straight line. As shown ln Fig. 3, on its inner~
surface there is neither adhesion-imparting nor diffusion-tight material.
This blank is now heated and inserted in a blow~mold.
It is, however, also possible to heat this blank in the blow-mold, particularly in the region of the apron 27. In this blow-mold from which the apron 27 hangs down, the blank which until then has still been open at the bottom is squeezed off approx-.imately along the broken line 29.
The results in the compression seam 31 as shown in Fig. 4. The side wall 27 with its diffusion-tight material and the adhesion-imparting layer 23 end shortly before this seam.
How this squeezing technique is carried out is shown in standard works such as, for example, Kunstoffbucherei Volume 10 by W. Mink "Fundamentals of the hollow-body blowing technique", p. 47, Figs. 4, 5 and 6 or p. 59, Illustration 29, Figs. 3, 4 and 5.
_ During this final operation according to the invention it is, of course, necessary to inject supporting air in the usual manncr through the nipple.
If the canisters contain gasoline and if they are not completely filled with this gasoline, the latter develops at summer temperature a vapor pressure whlch inflates the canister like a balloon. T-lowever, the canisters are very frequently carried along in~standard harnesses, and it is then no longer posslble to pull~ the inflated canister out of the harness.~ ~
Hitherto, attempts have been made, for example, in US Patent 3 9~0 002 or 3 552 599, to counteract~this tendency by double conical wall portions. However, with this solutlon a portion of the holdlng~capaclty~ is l~ost~
due to the double conuses. Moreover,~since~these~double conuses are deep-drawn, they always~have~a smaller~;wall~
thickness than the rest of the~body and can,~therefore,~
not be mechanically stressed to the same extent and,~
above all, the diffuslon of the gasoline vapors lS greate-st at these points.
Yet, the invention makes it possible, almost without~
loss of volume, to reduce this tendency of the canlster~
to become inflated almost to zero. To this~end,;the blank 16 is, between the fabrication steps shown in Figs. 1 and 2, respectively, provided from the direction of its lower, open side with a wall brace 3]. This brace has a tension part 32 extending vertical]y from the one side wall 17 to the other side wall 17 which at lts two extremities ends in anchoring plates 33 which are disk-shaped (for example, circular or oval) and whose l 160410 outer surface is welded to the inner surface of the side wall 17 in a welding region 34. The reason why this is possible with the process according to the invention is that the blank 16 has already a finished shape and that particularly the side walls 17 are already in their final position.
With the conventional blowing process it would not be possible to introduce such a wall brace~31 since the tube from which the canister is blown has a diameter of only, for example, 10 cm while the distance between the side walls 17 has nothing to do with this 10 cm.
The subsequent insertion oE the wall brace 31 also presents the advantage that it can be omitted in canisters of which it is known for a certainty that they will always be filled only with-water or milk or wine or diesel oil or the like.
It is in this case always possible to start from the basic principle and to go to the expense of installing a wall brace only where it is really~necessary.
PROCESS FOR T~IE PRODUCTION OF CANISTERS AND CANISTERS OBTAINED
THEREWITH
The in~ention relates to the production of a plastic canister from thermoplastic material in the 5, 10, 20 and 30 liter range which has an upper wall, four side walls, a bottom and suitable corner sections and whose botton is fabricated in the hot state of the thermoplastic material by a squeezing-off operation.
Canisters of this type must meet many different conditions at the same time:
a) To begin with, according to the acceptance conditions, the wall thickness of the fabricated canisters must correspond to the wall thickness of the sample canister suhmltted toGovernmental bodies for inspection and acceptance according to Governmental standards that apply to large canisters, such as West German standard DIN 16904 or Dutch standard NEN 3365.
b) The canisters are, at very extreme temperature conditions and pressures and in drop tests, subjected to cond~tions which are intended to demonstrate that the canisters are able to withstand particular stresses. Viewed from the angle of the wall strength, a canister has its weakest point where the wall thickness is thinnest. The plastic canisters ~abricated thus far are produced by the extrusion-blowing process. This results in the fact that the wall is thinnest at the very points where they are subjected to the greatest stresses, namely in the corner sections.
c) The strength of the walls is low. Up to the present, there exist only extrusion-blowing or centrifugal-casting processes. In these processes, practically no pressure is applied to the ma-terial (a few atm. in the extrusion process).
For this reason, the material remains flabby. With the same '~
1 ~6041~) material, injection-molded under the customary injection pressures of a few hundred atm., a very substantially greater stiffness is obtained for the walls.
d) Such a canister must also survive the tests specified in the ~overnmental inspection standards in which the canister is dropped from a height to land upside down on the cap. In the case of the heavy 20 and 30 liter canisters, it is to this end necessary to frame the blown pouring spout with a supporting construction.
e) In order that the surface of the canister cannot develop localized static charges which might perhaps give rise to a spark during the pouring out of gasoline, the material must have a certain surface resistance low enough so that the surface charges can be equali~ed.
f) At the same time, however, the wall must also be diffusion-tight in view of the highly volatile liquid or gaseous hydrocarbons. Otherwise, an ignitable mixture may be formed after a certain time, for example, in the trunk of a car or in a storage room. It is very difficult to find thermo-plastic materials which are both extrudable and diffuslon-proof, possess a low surface resistance and, in addition, meet still various other conditions. For example, it is necessary to add to the plastic a speclal grade of carbon black obtainable only ;
from a special factory in Ireland. This creates a condition of very great dependence and also an inconstancy of deliveries in the case of strikes and the like.
It is the object of the invention to specify a process which makes it possible to overcome the aforementioned short-comings and to achieve further advantages.
According to one broad aspcct, the presen-t lnven-tion provides a method of producing plastic canis-ters from thermo-plastic material in the 5, 10, 20 and 30 liter range, each said ,": ' ~ _ . _ _ _ _ . . . . . ... .
t 160410 canister having an upper wall, four side walls, a bottom wall and suitable corners between said walls including the steps of:
a) injection molding the upper wall and side walls to form a blank, said blank having side walls substantially longer than the side walls of the finished canister;
b) heating said blank at least in the lower region of said side walls to the squeezing-off temperature of said thermoplastic material, placing said blank in a divided blow mold and applying blowing pressure;
c) squeezing off the lower region of said blank whereby said bottom is formed from the lower lengths of sald side walls.
With this procedure, the aforementioned disadvantages are overcome and a diffusion-tight canister can be produced because it is easier to find materials developed only for diffu-sion-tightness which need not at the same time also possess ~
surface-resistance properties. The same is true for a material with the required surface-resistance properties. A plastic canister fabricated in this manner has not only greater diffusion-tightness but also better resistance values. Polyethylene material used typically in canister technology may be used to achieve both the low resistance and diffusion tightness requlre-ments because the invention takes advantage of the good effects of injection molding in addition to blow molding on polyethylene material with respect to these properties. Since it is ~a substantially stiffer structure, it does not bulge so much in the sun, even in the partly filled state. It is also possible to structure the surface precisely, if, for example, the surface must be made nonskid. In the extrusion-blowing process it is, after all, only to a limited extent possible to obtain precise imprints in the negative mold~ It is now also much easier to produce the legible manufacturer's address, canister l 160~1P
weight, registration number, manufacturing date, etc., demanded by the registration authority.
Accordiny to a further aspect of the invention it is now made still easier to produce the compression seam because the diffusion layer which participates only very reluctantly or not at all in the tightness of the compression seam is now excluded from the process and merely the surface-resistance layer participates in the compression seam, which results in a good joint~
In accordance with the present invention, there is also provided a plastic canister in the 5, 10, 20 and 30 liter range comprising an injection-molded upper wall, four injection-molded side walls, and an injection-molded and blow-molded bottom having a blow-molded squeezed-off compression seam therein, formed from the lower portion of said injection-molded side walls.
The invention shall now be described with reference to a practical example. On the drawing, Fig. 1 shows a schematic presentation of a tool together with the result of the first fabrication step;
Fig. 2 shows a view similar to Fig. 1 after a further ~abrication step;
Fig. 3 shows a cross section through the lower region o~ a side wall of the blank;
Fig. 4 shows a view similar to Fig. 3 but in the squeezed state;
Fig. 5 shows a horizontal section through the side wall with the wall brace in place.
~ ccording to Fig. 1, a tool for the injection-molding process has a lateral part 11 which can be removed toward the rear, a bottom part 12 which can be removed in a downward direction and another lateral part (not shown) designed to ~ -- 5 ~
1 l~04ln complement the lateral part 11 and capable of being moved forward.
Moreover, a slide 13 is provided which is capable of motion in the two lateral parts and which can be pulled out of the injection mold upward toward the right. Through an injection channel of which one half 14 is shown schematically the injection-molding material can be injected.
A blank 16 of a first fabrication step is shown on the drawing in dot-dash outline. The blank has a forward side wall 17, a left side wall which is not visible, a forward side wall 18, an upper wall 19 and, because of a nipple 21, a slanting wall 22. Since the lateral part 11 has not yet been removed, only one half eachof the side wall 18, the upper wall 19 and the nipple 21 can be seen. Accordingly, only half the negative shape of the blank 16 is worked into the lateral part 11 .
Projecting upward, a core (not shown) is provided on the bottom part 12 which projects into the blank and determines its internal shape.
The material of the blank is a diffusion-proof material.
The wall material is comprised of diffusion-tight thermoplastic, adequate to prevent highly volatile liquid or gaseous hydrocarbons rom forming at the surface. The blank 16 is now transferred into another injection-mold similar to the one in Fig. 1. ~ere, however, the lateral parts are shaped in such a way that an adhesion-imparting layer 23 can now be injection-molded onto the blank 16. In Fig. 3, this adhesion-imparting layer is, for the sake of clarity, shown as a very thick layer. Both the side wall 17 consisting of the diffusion-tight material and the adhesion-imparting layer 23 terminate according to Fig. 3 in a transition poin-t 24.
This blank of a higher fabrication step is now once more placed in a mold similar to the one in Fig. 1, whose ~ ., . . , . . . . . ... . _ l 16041P
dimensions are such that it is now possible to injection-mold a surface-resistance layer 26 onto the adhesion-imparting layer 23. The material of layer 26 is comprised of thermo-plastic material having an electrical surface resistance low enough so that static surface charges are equalized and do not give rise to sparks at the surface of the canister.
The wall layers 17, 26 have a diffusion-tightness and an electrical surface resistance according to DIN 16904 or NEN 3365 which are respectively the West German and Dutch safety standards for large canisters.
Here, the design according to Fig. 2 of the tools is such that an injection-molded apron 27 projects in the downward direction. This apron need by no means point outward like a truncated cone as shown in Fig. 2, but may also project downward in a straight line. As shown ln Fig. 3, on its inner~
surface there is neither adhesion-imparting nor diffusion-tight material.
This blank is now heated and inserted in a blow~mold.
It is, however, also possible to heat this blank in the blow-mold, particularly in the region of the apron 27. In this blow-mold from which the apron 27 hangs down, the blank which until then has still been open at the bottom is squeezed off approx-.imately along the broken line 29.
The results in the compression seam 31 as shown in Fig. 4. The side wall 27 with its diffusion-tight material and the adhesion-imparting layer 23 end shortly before this seam.
How this squeezing technique is carried out is shown in standard works such as, for example, Kunstoffbucherei Volume 10 by W. Mink "Fundamentals of the hollow-body blowing technique", p. 47, Figs. 4, 5 and 6 or p. 59, Illustration 29, Figs. 3, 4 and 5.
_ During this final operation according to the invention it is, of course, necessary to inject supporting air in the usual manncr through the nipple.
If the canisters contain gasoline and if they are not completely filled with this gasoline, the latter develops at summer temperature a vapor pressure whlch inflates the canister like a balloon. T-lowever, the canisters are very frequently carried along in~standard harnesses, and it is then no longer posslble to pull~ the inflated canister out of the harness.~ ~
Hitherto, attempts have been made, for example, in US Patent 3 9~0 002 or 3 552 599, to counteract~this tendency by double conical wall portions. However, with this solutlon a portion of the holdlng~capaclty~ is l~ost~
due to the double conuses. Moreover,~since~these~double conuses are deep-drawn, they always~have~a smaller~;wall~
thickness than the rest of the~body and can,~therefore,~
not be mechanically stressed to the same extent and,~
above all, the diffuslon of the gasoline vapors lS greate-st at these points.
Yet, the invention makes it possible, almost without~
loss of volume, to reduce this tendency of the canlster~
to become inflated almost to zero. To this~end,;the blank 16 is, between the fabrication steps shown in Figs. 1 and 2, respectively, provided from the direction of its lower, open side with a wall brace 3]. This brace has a tension part 32 extending vertical]y from the one side wall 17 to the other side wall 17 which at lts two extremities ends in anchoring plates 33 which are disk-shaped (for example, circular or oval) and whose l 160410 outer surface is welded to the inner surface of the side wall 17 in a welding region 34. The reason why this is possible with the process according to the invention is that the blank 16 has already a finished shape and that particularly the side walls 17 are already in their final position.
With the conventional blowing process it would not be possible to introduce such a wall brace~31 since the tube from which the canister is blown has a diameter of only, for example, 10 cm while the distance between the side walls 17 has nothing to do with this 10 cm.
The subsequent insertion oE the wall brace 31 also presents the advantage that it can be omitted in canisters of which it is known for a certainty that they will always be filled only with-water or milk or wine or diesel oil or the like.
It is in this case always possible to start from the basic principle and to go to the expense of installing a wall brace only where it is really~necessary.
Claims (6)
OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A method of producing plastic canisters from thermo-plastic material in the 5, 10, 20 and 30 liter range, each said canister having an upper wall, four side walls, a bottom wall and suitable corners between said walls including the steps of:
a) injection molding the upper wall and side walls to form a blank, said blank having side walls substantially longer than the side walls of the finished canister;
b) heating said blank at least in the lower region of said side walls to the squeezing off temperature of said thermo-plastic material, placing said blank in a divided blow mold and applying blowing pressure;
c) squeezing off the lower region of said blank whereby said bottom is formed from the lower lengths of said side walls.
a) injection molding the upper wall and side walls to form a blank, said blank having side walls substantially longer than the side walls of the finished canister;
b) heating said blank at least in the lower region of said side walls to the squeezing off temperature of said thermo-plastic material, placing said blank in a divided blow mold and applying blowing pressure;
c) squeezing off the lower region of said blank whereby said bottom is formed from the lower lengths of said side walls.
2. A method as claimed in claim 1 wherein after said injection molding step (a) a wall brace is inserted through the open bottom of said blank and welded to the inner surfaces of a pair of opposing side walls, said wall brace having a length substantially equal to the distance between a said pair of opposing side walls and having at each of its extremities an anchoring plate weldable to said thermoplastic material.
3. A method as claimed in claims 1 or 2 wherein said blank is injection molded from three layers including an inner diffusion-blocking layer, an intermediate adhesion imparting layer situated on the outside of said diffusion blocking layer and an outer surface-resistance layer, said diffusion-blocking layer extending toward the bottom of said blank to a lesser extent than said surface-resistance layer and, in the squeezed off state situated outside the compression seam.
4. A plastic canister in the 5, 10, 20 and 30 liter range, comprising:
a) an injection-molded upper wall;
b) four injection-molded side walls;
c) injection-molded corner sections;
d) an injection-molded and blow-molded bottom, having a blow-molded squeezed-off compression seam therein, formed from the lower portion of said injection-molded side walls.
a) an injection-molded upper wall;
b) four injection-molded side walls;
c) injection-molded corner sections;
d) an injection-molded and blow-molded bottom, having a blow-molded squeezed-off compression seam therein, formed from the lower portion of said injection-molded side walls.
5. A plastic canister according to claim 4 having a wall brace inserted through the open bottom of said blank and welded to the inner surfaces of a pair of opposing side walls, said wall brace having a length substantially equal to the distance between a said pair of opposing side walls and having at each of its extremities an anchoring plate weldable to said thermoplastic material.
6. A plastic canister according to claim 5 wherein said blank is injection molded from three layers including an inner diffusion-blocking layer, an intermediate adhesion imparting layer situated on the outside of said diffusion blocking layer and an outer surface-resistance layer, said diffusion-blocking layer extending toward the bottom of said blank to a lesser extent than said surface-resistance layer and, in the squeezed-off state situated outside the compression seam.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE3008737A DE3008737C2 (en) | 1980-03-07 | 1980-03-07 | Method of making a fuel canister |
| DEP3008737.7 | 1980-03-07 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1160410A true CA1160410A (en) | 1984-01-17 |
Family
ID=6096515
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000366469A Expired CA1160410A (en) | 1980-03-07 | 1980-12-10 | Process for the production of canisters and canisters obtained therewith |
Country Status (2)
| Country | Link |
|---|---|
| CA (1) | CA1160410A (en) |
| DE (1) | DE3008737C2 (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3047091A1 (en) * | 1980-12-13 | 1982-07-22 | Wolfram Dr. 7140 Ludwigsburg Schiemann | Injection moulded plastic canister - where side extensions of open preform are remoulded and bent inwards to form base |
| US4569816A (en) * | 1985-01-03 | 1986-02-11 | Schiemann Dr Wolfram | Method of manufacturing a canister |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3878282A (en) * | 1971-08-10 | 1975-04-15 | Ilikon Corp | Process for molding multilayer articles |
-
1980
- 1980-03-07 DE DE3008737A patent/DE3008737C2/en not_active Expired
- 1980-12-10 CA CA000366469A patent/CA1160410A/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| DE3008737C2 (en) | 1986-12-18 |
| DE3008737A1 (en) | 1981-09-24 |
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