METHOD AND ARRANGEMENT FOR MANUFACTURING A MARKING UNIT PROVIDED WITH A COATING

Abstract: A method and apparatus for manufacturing a three-dimensional marking device (10) having a substantially solid shell (14) of a first material and a coating (15) of an elastic film with substantially reflecting or retroreflecting characteristics, which shell consists of an attachment part (13) for attachment to an object and a top reflection part (14). The method comprises the steps of: bringing together a sheet of said first material and said film; bringing said combined sheet of said first material and said film in vicinity of a mould (16) having one or several cavities (17), substantially shaped as a part of said marking device (10); exposing at least parts of said combined sheet of said first material sheet and said film to heat; and bringing parts of said combined first material sheet and said film into said form (17) by generating a force directed into said form (17), so that said combined first material sheet and said film form a part having substantially the form of the mould and the coating uniformly covering the formed part.

Description: METHOD AND ARRANGEMENT FOR MANUFACTURING A MARKING UNIT PROVIDED WITH A COATING TECHNICAL FIELD OF THE INVENTION The present invention relates to a method and an apparatus for manufacturing a three-dimensional marking device having a substantially solid shell of a first material and a coating of an elastic film with substantially reflecting or retroreflecting characteristics, which shell consists of an attachment part for attachment to an object and a top reflection part. BACKGROUND AND RELATED ART Motion analysis is now a well-known method using a camera unit and computer aid to analyse, e.g. bio-mechanics of human, animals or motions of a robot arm etc. In a simple system markers are attached to the object to be analysed. In the past, the object provided with the markers was first filmed and then manually analysed and digitalised to determine the correct position of the markers. This was a time-consuming procedure. One problem related with the markers is that they must be fully visible to be registered by the camera, i.e. they must have some illumination. Generally, it is difficult and expensive to have self illuminating markers. Consequently, the marker is usually provided with a reflecting coating to reflect the light from spotlights or flashes arranged in the surroundings. The reflecting coating is affixed onto the surface of the marker by manually cutting and then gluing the same onto the marker. This is a time consuming and expensive operation. Moreover, the surface is not even and does not reflect the light completely. SUMMARY OF THE INVENTION The object of the present invention to overcome above problems by presenting a novel, efficient and fast apparatus and method for manufacturing markers or the like, having a smooth, reflective or the like surface. These objects are achieved by means of a method according to the preamble comprising the steps of: bringing together a sheet of said first material and said film, bringing said combined sheet of said first material and said film in vicinity of a mould having one or several cavities, substantially shaped as a part of said marking device, exposing at least parts of said combined sheet of said first material and said film to heat, and bringing parts of said combined first material sheet and said film into said form by generating a force directed into said form, so that said combined first material sheet and said film forms a part substantially having the form of the mould and the coating uniformly covers the formed part. The apparatus according to the preamble is characterised in that it comprises means for bringing together a sheet of said first material and said film, means for bringing the combined sheet of said first material and said film in vicinity of a mould having a form substantially shaped as a part of said marking device, means for heating said combined sheet of said first material and said film, and means for generating a force directed into said form for bringing at least parts of said combined sheet of said first material and said film into said form. BRIEF DESCRIPTION OF THE DRAWINGS In the following the invention will be described with reference to enclosed drawings, in which: Fig. 1 is an embodiment of a marker made according to the present invention, with some part removed. Fig. 2 is a schematic view of a part of a sheet of materials and a mould for making markers according to the invention, before a shaping step. Fig. 3 is a schematic view of part of a tray of materials and the mould according to fig. 2 at the shaping step DETAILED DESCRIPTION OF AN EMBODIMENT Fig. 1 shows a marker 10 according to the present invention. The marker is formed substantially spherically with a hollow inner space, having an upper fully semispherical part 11 and a lower essentially semispherical part 12, provided with an attachment surface 13. Theshell 14ofthemarker is made of a plastic material, covered with a reflecting or retroreflective material 15. The retroreflective material, for example made by 3M, is an elastic film, which on one surface is provided with glass beads embedded in a substrate. The light falling on the retroreflective surface, on its way in, will be first refracted by the surface then it will be reflected inside the glass beads, then the reflected light is again refracted in its way out by the surface. This feature makes such material useful as substantially entire light is reflected back towards the light source. The attachment surface 13 is used to attach the marker to an object to be surveyed. The manufacturing steps are illustrated in figs. 2 and 3. In a first step, sheets of shell 14 and coating 15 materials are brought together into a new sheet, manually or by means of an apparatus not shown. The sheet of materials is then brought into vicinity or in contact with a mould 16. The mould 16 is a plate provided with one or several cavities 17 in the shape of the upper or lower parts of the marker 10. In the bottom of each cavity, a hole connecting the cavity through a pipe 18 to a vacuum pump (not shown) is arranged. In this example only the mould for the upper part 12 of the marker is presented. When the sheet of materials is in a heating position, a heat generating means (shown by arrows) such as an UN -radiator, microwave transmitter, heating elements or the like, is used to heat the entire surface or spots of the sheet material from the side not facing the mould. When the material is heated sufficiently, so that it is substantially softened, the vacuum pump is operated to evacuate the air in the cavity 14 under the sheet materials. The vacuum state generated in the cavity sucks the material into the cavity, as shown in fig. 3. After cooling, the formed sheet of materials is removed and new sheet material may be delivered to the moulding site. The second part of the marker is manufactured in the same way. The finished parts, lower 11 and upper 12 parts, respectively are then brought together, affixed and each marker is removed from the sheet of materials at the area of attachment composing the marker as fig. 1. Although, we have described and shown a preferred embodiment, the invention is not limited to said embodiment, variations and modifications may be occurring within the scope of the attached claims. The form av the marker is not limited to the spherical or semispherical shape. LIST OF DESIGNATION SIGNS 10 Marker 11 Lower part 12 Upper part 13 Attachment surface 14 Shell 15 Coating 16 Mould 17 Cavity 18 Pipe

Claims: CLAIMS 1. A method for manufacturing a three-dimensional marking device (10) having a substantially solid shell (14) of a first material and a coating (15) of an elastic film with substantially reflecting or retroreflecting characteristics, which shell consists of an attachment part (13) for attachment to an object and a top reflection part (14), characterised in, that the method comprises the steps of: - bringing together a sheet of said first material and said film, - bringing said combined sheet of said first material and said film in vicinity of a mould (16) having one or several cavities (17), substantially shaped as a part of said marking device (10), exposing at least parts of said combined sheet of said first material and said film to heat, and - bringing parts of said combined first material sheet and said film into said form (17) by generating a force directed into said form ( 17), so that said combined first material sheet and said film forms a part substantially having the form of the mould and the coating uniformly covers the formed part. 2. A method according to claim 1, characterised in, affixing said attachment part (13) and the upper refection part (14) to build said body (10). 3. A method according to claim 1, characterised in, that said first material is plastic. 4. An apparatus for manufacturing a three-dimensional marking device (10) having a substantially solid shell (14) of a first material and a coating (15) of an elastic film having substantially reflecting or retroreflecting characteristics, which shell consists of an attachment part (13) for attachment to an object and a top reflection part (14), characterised in, that the apparatus comprises means for bringing together a sheet of said first material and said film, means for bringing said combined sheet of said first material and said film in vicinity of a mould (16) having a form (17) substantially shaped as a part of said marking device (10), means for heating said combined sheet of said first material and said film, and means for generating a force directed into said form (17) for bringing at least parts of said combined sheet of said first material and said film into said form (17). 5. An apparatus according to claim 6, characterised in, that said means for generating the force into said form ( 17) is a pump for generating a substantially vacuum state in said form (17).

Inventors: JOSEFSSON THORLEIF, TACKMAN JOERGEN, JOSEFSSON, THORLEIF, TACKMAN, JOERGEN
Applicants: JOSEFSSON THORLEIF, QUALISYS AB, TACKMAN JOERGEN, JOSEFSSON, THORLEIF, TACKMAN, JOERGEN
Application year: 1998
Main classification: B29C51
IPC codes: B29C51, G02B5