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
• • 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
  • B29C45/17—Component parts, details or accessories; Auxiliary operations
  • B29C45/72—Heating or cooling
  • B29C45/73—Heating or cooling of the mould
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B42—BOOKBINDING; ALBUMS; FILES; SPECIAL PRINTED MATTER
  • B42F—SHEETS TEMPORARILY ATTACHED TOGETHER; FILING APPLIANCES; FILE CARDS; INDEXING
  • B42F1/00—Sheets temporarily attached together without perforating; Means therefor
  • B42F1/02—Paper-clips or like fasteners
  • B42F1/10—Paper-clips or like fasteners non-metallic
• • 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
  • B29C45/17—Component parts, details or accessories; Auxiliary operations
  • B29C45/72—Heating or cooling
  • B29C45/73—Heating or cooling of the mould
  • B29C2045/7343—Heating or cooling of the mould heating or cooling different mould parts at different temperatures
• • 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
  • B29C45/17—Component parts, details or accessories; Auxiliary operations
  • B29C45/72—Heating or cooling
  • B29C45/73—Heating or cooling of the mould
  • B29C2045/735—Heating or cooling of the mould heating a mould part and cooling another mould part during moulding

Definitions

• the present invention refers to a resilient element, preferably a clip, and a method and a device for the production thereof.
• Clips in the shape of a piece of sheet metal strip which is folded back to form a tongue or the like are well-known.
• the tongue of the prior clip has resilient properties, and in the non-distended condition of the clip the tongue is in contact with an area of the section of the piece of sheet metal strip not folded back.
• clips of plastic could not be manufactured, among other things for the reason that the tongue of the finished clip will not be in contact with the section of the piece of plastic strip not folded back and accordingly cannot be fastened round, for example, a sheet of paper, a piece of fabric etc.
• the basis of the invention is the problem of providing a resilient element, preferably a clip, which is made of plastic and which has a tongue or the like which in the non-distended condition of the resilient element is in contact with an opposite leg or the like.
• a resilient element of this kind may be produced, according to the invention, by using a plastic forming technique which implies that a shrinkage of the plastic material is actively utilized for producing an element with resilient properties, preferably a clip.
• the resilient element according to the invention is cast in a mould having a mould cavity which surrounds a core which in turn has a transitional portion which is integrally connected with the mould.
• the characteristics of the method are that the mould is chilled in an area surrounding the mould cavity, that the mould cavity is filled with heated plastic material which heats the core to a higher temperature than the surrounding mould, and that the plastic material is caused to solidify in the mould.
• the cast product is taken out of the mould there is a gap between the tongue and the opposite leg, but after a short period the gap closes and the tongue will come into contact with the leg or a corresponding part.
• Figure 1 shows a sectional view of a mould for producing a resilient element in the form of a clip.
• Figure 2 shows a plan view from above of the bottom mould part shown in Figure 1
• Figure 3 is a perspective view of the finished clip.
• Figure 1 shows a mould consisting of two mould parts 1, 2. By conventional means, not shown, the mould parts are brought into tight engagement with each other along the parting line 3 shown. The mould parts each have a mould cavity 4, 5, these cavities together defining the form of the finished product.
• rods or pins 6 which are slidable in the bottom mould part 1, the cast product is ejected from the bottom mould part (after the top mould part 2 being first removed).
• An injection moulding machine not shown, of a conventional type is connected to a sprue 7 for the injection of a heated plastic material through a gate 8 into the mould cavities 4, 5.
• a cooling channel 9 extends around the mould cavities 4, 5.
• the cooling channel 9 has an inlet 10 and an outlet 11.
• Figure 2 shows a plan view of the bottom mould part.
• the gate 8 communicates with each mould cavity via the channel 12 shown.
• Each mould cavity 5 surrounds a core 13 which at a transitional portion 14 is made integral with the mould part 1.
• the minimum thickness D of the transitional portion 14 is determined by mechanical strength requirements.
• the cooling channel 9 extends around the two mould cavities in the way illustrated. It is important that cooling of the mould takes place in. the area around the bend 15, that is the portion which is to form a section having resilience in the finished product.
• Casting takes place in a way well-known in the plastic forming technique.
• a cooling medium is supplied to the inlet 10 and is carried off at the outlet 11.
• a conventional injection moulding machine is filled with plastic material in the form of a granulate or the like which is heated to pass into liquid condition.
• the injection machine is applied to the upper part of the gate 8 shown in Figure 1 and hot liquid plastic material is injected into the mould cavities 5.
• the hot plastic material heats the cores 13 at the same time as the cooling medium cools the bends 15.
• the mould parts are maintained closed against each other under a high pressure, until the plastic material has been brought from liquid into solid condition by the cooling, before the mould part 2 is removed and thereupon the pins 6 are caused to eject the two clips from the bottom mould part 1.
• the clips Immediately after the ejection the clips have a gap between the tongue 16 ( Figure 3) and the leg 17, said gap accordingly being determined by the distance D. After a short time, however, this gap closes and the tongue 16 will get into contact with the leg 17.
• the cooling medium which preferably consists of cooling water, may be passed through the channel 9.
• the supply of cooling water is interrupted after the ejection of the cast products and is not resumed until new hot plastic material is injected into the mould cavities.
• each mould part may have three or more mould cavities 5 placed with a suitable geometry whereby a great number of units of the product may be cast simultaneously.
• the cooling channel is then located so as to pass along the bends 15 of all units.
• a number of clips were made from polyethylene which is sold in Sweden by Shell under the quality designation SM 6100 mixed, in one case, with a blue pigment (Master batch), blue clips being then obtained, and, in another case, with a white pigment, white clips being then obtained.
• Each clip was 32 mm broad, the folded back portion (the shorter tongue) had a length of 54 mm, and the longer tongue had a length of 70 mm.
• a blue clip and a white clip were chosen and with these the following measurements of the contact pressure were made.
• Example 2 The same clips as in Example 1 were used. The clip was fixed in a horizontal position with its edge side turned upwards. A thin piece of paper was inserted in the clip and the dynamometer was slowly pulled and the following values were read:
• the contact pressure varies between 100 gp. and 250 gp. (gram pond). If these figures are converted into line pressure (pressure per unit of length along the width of the clip, 3 and 5 gp/mm., respectively, are obtained. With regard to a certain inaccuracy of the results the line pressure varies for the clips made according to the invention beyond the measured values mentioned. For the chosen measured clips the line pressure will probably amount to about 5 gp/mm.

Landscapes

• Engineering & Computer Science (AREA)
• Manufacturing & Machinery (AREA)
• Mechanical Engineering (AREA)
• Moulds For Moulding Plastics Or The Like (AREA)
• Springs (AREA)
• Casting Or Compression Moulding Of Plastics Or The Like (AREA)
• Supports Or Holders For Household Use (AREA)

Priority Applications (3)

Applications Claiming Priority (2)

Publications (1)

Family

ID=20343375

Family Applications (1)

Country Status (3)

Cited By (1)

Citations (2)

• 1981
  • 1981-03-19 SE SE8101760A patent/SE428447B/sv not_active IP Right Cessation
• 1982
  • 1982-03-19 WO PCT/SE1982/000079 patent/WO1982003204A1/en active Application Filing
  • 1982-11-16 DK DK510482A patent/DK147538C/da not_active IP Right Cessation
  • 1982-12-09 SE SE8207050A patent/SE438632B/sv not_active IP Right Cessation

Patent Citations (2)

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