FI65568C - FOERFARANDE FOER TILLVERKNING AV FORMADE DELAR OCH FORMYTA LAEMPAD FOER FOERFARANDET - Google Patents

Description

r, ADVERTISEMENT tec * o

Ma lbj UTLÄCCNincsskrift oodoo C / ^ c \ Fa ton * ..1 iEjr'C.'UiC v .y il - ^ ¾¾) 11 Patent cecdolit (51) ICv.lk?/Into.3 B 29 C 17/04 ENGLISH I - FI N LAN D (21) fcttuttlhikwnu · - PatmtmMcnliig 78081 5 (22) Hik * fnl »p * lvt — Amdknlnpdaj 15.03.78 '* (23) AlkupUvi — Glltl (h« ttda | 15.03.78 (41) Tullut JulklMlul —Bllvlt offwitH | 9Q nQ 7p

National Board of Patents and Registration ...,, .li.il. y.uy./Q

_ „_. . ^, (44) NihtJvUulptnon et al. -

Patent and registration form in 1 Aiwekan utlafd och utl. * Krlft * n puMkurad 29.02.84 (32) (33) (31) Requested privilege Begird prtorket 28.03.77

Sweden-Sverige (SE) 7703500-4 (71) Aktiebolaget Bofors, S-690 20 Bofors, Sweden-Sverige (SE) (72) Qunnar Johansson, Tidaholm, Per Ohlsson, Tidaholm, Lennart Persson, Tidaholm, Sweden-Sverige (SE) ) (74) Berggren Oy Ab (54) Method for the manufacture of molded parts and suitable mold surface - Förfarande för tillverkning av formade delar och formyta lärripad förfarandet

The present invention relates to a method of manufacturing translucent, embossed sheets or shades having a pattern adapted to direct light and comprising prismatic protrusions and recesses therebetween, the pattern being formed from a flat sheet of a thermoplastic material such as acrylic plastic forced at a temperature of plastic, to conform to a patterned mold surface having protrusions corresponding to the recesses in the desired light directing pattern, and between them recesses corresponding to the protrusions of the same pattern.

In order to achieve a uniform scattering of light and to prevent the light source from dazzling the viewer, several methods have been tried in the past for lamp shades, including colored shades and shades with various embossments formed by injection molding. These embossments are generally formed of sharp-edged pyramids arranged in regular succession into regular patterns intersecting sharp-edged ridges. The protrusions of the embossing are usually located on the light-emitting side. The manufacturing method used, i.e. injection molding in closed molds, has resulted in products with flat back surfaces and embossed front surfaces. The pattern is thus formed of closed prisms, which means that the substance has had to be used in relatively large quantities. In addition, when designing the patterns, it has been necessary to take into account that the material must be provided with appropriate flow channels in the mold. The patterns have therefore often led to trade-offs between production engineering considerations and the desired refractive effects.

The present invention now provides a new and simpler method of making embossed plates or shades. These shades are suitable for directing light and, in addition, are considerably more economical in terms of raw material consumption because they have a substantially uniform thickness of material over the entire embossed surface.

According to the invention, only the protrusions at the sharp-edged joints between the planar surfaces of the patterned mold surface are forced to repeat in the finished product by pressing the sheet against the mold edges or sharp corners, while the sheet material is only partially forced into the recesses of the mold surface.

Thus, by using a mold surface consisting of a plurality of bars resembling racks, in which triangular teeth are arranged side by side, the lateral displacement between the adjacent bars corresponding to half of the tooth, a finished product is obtained.

Shades with bottom surfaces of the type described are similarly formed in a matrix on the bottom surface of which a pattern has been formed, while the side edges of the mold may be smooth or grooved. These grooved side edges can also be provided against sharp-edged mold surfaces which are only partially repeated and which similarly cause rounded ridges separated by sharp-edged recesses.

Because the inner corner edges of the matrix are only partially repeated, the finished product has rounded joints along all corner edges.

3

The invention will be described in more detail below with reference to the accompanying drawings, in which 65568 Figures 1 and 2 show a central part I-I and II-II of Figure 3, which in turn shows a plan view of a small part of a mold member according to the invention; Fig. 4 is a partial sectional view of how the molded sheet material conforms to the mold surface of Fig. 3, while Fig. 5 is an oblique sectional view of a small portion of this mold surface; Fig. 6 shows a molded sheet material from a light emitting surface, i.e. a surface facing the mold surface, while Fig. 7 shows an opposite surface.

A plurality of rack-like portions 1 and 2, shown in Figures 1 and 2, are joined to form the mold surface shown in Figure 3, with the teeth of adjacent portions displaced relative to each other. The different parts could be connected to each other, e.g. by using a double adhesive tape against a conventional carrier plate placed on the back side.

In the example shown, the angle between the sides of the tooth, denoted by reference a in Fig. 2, is made 90 °, because this gives a very good light directing effect. For the same reason, the width of the tooth is made equal to the distance between the teeth. Other dimensions and angles are of course possible. As the figures show, all the edges between the sides and sides of the teeth are very sharp. This causes sharp folds at points 4 where the sheet material 5 is folded over the edge (see Figure 4). The folds, on the other hand, are considerably more rounded at points 6, where the sheet material is forced into the recesses in the mold surface by means of the pressure behind the sheet.

Thus, in the finished product, the brushes running along the tips of the protrusions are rounded in all directions, while the bottoms of the recesses are formed by relatively sharp folds.

The invention is not limited to the parts described above, but can be modified within the scope of the claims.

Claims (4)

4 Claims 6 5 5 6 8 A method of making translucent, embossed sheets or shades having a pattern adapted to direct light and comprising prismatic protrusions and recesses therebetween, the pattern being formed from a flat sheet (5) of a thermoplastic material such as acrylic plastic which is forced at a temperature of the material is plastic, to conform to a patterned mold surface (3) having protrusions corresponding to the recesses in the desired light directing pattern and between them recesses (6) corresponding to the protrusions of the same pattern, characterized in that the pattern between the planar surfaces in the patterned mold surface of the sharp-edged joints, only the protrusions are forced to repeat in the finished product completely by pressing the plate against the edges or sharp corners of the mold, while the sheet material is forced into the recesses of the mold surface only partially, resulting in rounded joints (6). Mold surface for producing patterned sheets or shades by the method according to claim 1, characterized in that the mold surface pattern consists of a plurality of rods (1, 2) resembling racks and triangular teeth arranged side by side, the lateral displacement between adjacent rods corresponding to half a tooth. 1. The provisions of this Directive apply to the use of materials or parts of a material which, in the case of a single material, are of the same type as those which are soon to be used (5). the temperature of the material is plastic in the case of a single type of mold (3), the upper part of which is of the same type of material (3). The plan is for the production of the genome to be reproduced and the reproduction of the genome is preceded by the formation of the body or the skarpa,