METHOD FOR DEPOSITING RETROREFLECTING ELEMENTS ONTO THE ROAD SURFACE WITH PREARRANGEMENT OF SAME AND DEVICE FOR REALIZING THE METHOD

Abstract: A carrier sheet (B) having retroreflective elements (A) adhered thereto in a suitable spaced arrangement is drawn from a storage roll and directed around the sharp edge of a wedge-shape body (C) to cause the retroreflective elements (A) to at that point become detached from the carrier sheet (B) which subsequently is wound onto a take-up spool (E). Said sharp edge is disposed in the vicinity of the road surface (S) and the retroreflective elements (A), once detached from the carrier sheet (B), drop onto said surface (S) or onto a marking thereon, either freshly applied or already in service. One of the surfaces in contact at the interface between carrier sheet (B) and retroreflective elements (A) thereon is adhesive, while the other one has release characteristics.

Description: The invention relates to a method for depositing retroreflecting marking elements on a surface. Many experiments have been carried out in the more evolved countries in an effort to improve night-driving safety, even under foggy and rainy conditions, by using special road markings designed to provide an efficacious guide for the motorist. It has not been possible to achieve this goal, however, using conventional materials. The difficulty has been due to the fact that whenever the retroreflecting elements, located on the marking strip, become covered with a film of water, they no longer function as originally intended. With conventional marking strips, inexpensive glass beads are haphazardly spread over the strip. On the other hand, in EU-A 0 102 585, there are described composite organic retroreflecting elements which are more effective and which are necessarily more costly. Therefore, these elements have to be applied as to obtain the maximum retroreflecting efficiency. These retroreflecting elements, which have a certain not neglectable height when deposited on the road or surface, have been up to now been deposited from an inclined-plane arrangement using vibration or other means as described for instance in GB-A-20 24 898. The obtained road-marking efficiency has been good and very much better than that obtained with conventional types of retroreflecting elements. The obtained efficiency is very good under rainy conditions, but is not the maximum obtainable, due to imperfect mechanical depositing and any consequent imperfect element positioning. The high cost of the elements does not permit obtaining an efficiency that is less than the maximum possible. In connection with road marking element which are flat and do not have a substantive height over the road marking surface as with the organic retroreflecting elements, it is known from the US-A-40 89 730, to preposition these marking elements on a conveyor sheet which is reeled from a reel from which said conveyer sheet is withdrawn at the time of depositing the marking elements. For detaching a marking element from the conveyor sheet, an actuating mechanism is engaged so that a length of the conveyor sheet is drawn over a blade disposed adjacant the surface on which the marking element is to be deposited. This known apparatus may only be used with flexible marking elements, but not with unflexible retroreflecting marking elements which are not deformable, and if such retroreflecting marking elements would be moved nearly perpendicular to the surface on which they are deposited, there is a severe danger that these marking elements may overturn so that again the maximum efficiency is not obtained. The object of the present invention is to provide a method for depositing retroreflecting marking elements such that the retroreflecting marking elements are positioned in such a way as to obtain maximum roadmarking efficiency even under rainy conditions. According to the present invention, there is provided a method for depositing retroreflecting marking elements on a surface, which is either a road surface or the surface of road-marking material applied to the road surface itself, wherein said retroreflecting elements are detachably prepositioned at preestablished lengthwise distances on a conveyor sheet which is reeled with the retroreflecting elements thereon on a reel from which said conveyor sheet is withdrawn at the time of depositing said retroreflecting elements, said retroreflecting elements being detached from the conveyor sheet by drawing it over a sharp angled blade disposed adjacent said surface, said method being characterized in that, when said retroreflecting elements are detached and fall on the surface, they have a speed in the direction of movement of said assembly to deposit the elements on the surface without overturning, and in that said assembly is moved at a speed commensurate with the speed of movement of the conveyor sheet to reproduce the said preestablished lengthwise distances of said elements on said surface. Further details of the invention are indicated in the subclaims. Detaching surfaces are those that have been appropriatly treated with silicon resins, fluorated resins, or the like; self-adhesive surface are those that have been treated with a short-chain organic polymers - preferably ramified - in either the melted or plasticized state. The advantage of the method according to the invention is that it permits the precise prepositioning of the retroreflecting elements on the conveyor sheet before reeling takes place, so that the angled blade which is located in the immediate vicinity of the road surface can detach the elements and faithfully reproduce the prepositioned configuration onto either an existing road-marking strip or the road surface itself. The drawing shows a shematic diagram of a preferred apparatus for carrying out the method. The reeled conveyor sheet, upon which the retroreflecting elements 'A' are positioned at preestablished distances, is indidcated as 'B'. Sheet 'B' passes over the sharp angle 'C' of the angled blade and here is where the elements 'A' are detached. The detached elements are indicated as 'D' when deposited on the road surface or existing road-marking strip, either one being indicated as 'S'. After passing over the return roller 'F', sheet 'B' winds onto the rewind reel 'E'. This rewind reel is actuated by known means not shown in the diagram and draws sheet 'B'. The assem bly is moved, in the direction shown by the arrow, at a speed commensurate with the speed of sheet "B", so as to obtain the desired distancing of the elements "D". The said movement is obtained by known means not shown in the diagram. The prepositioning of the elements "A" on sheet "B" is done before reeling takes place, and is not disturbed during the unreeling phase, due to a certain degree of adherence provided by either the contact surface of the elements "A" or the contact surface of sheet "B". If the surface of sheet "B" has the adherence capability, the surfaces of the elements "A" will be treated with the detaching polymer. If the surfaces of the elements "A" have the adherence capability, the surface of sheet "B" will be treated with the detaching polymer. If the elements "A" are treated with the detaching polymer, the surface "S" will obviously have to be prepared with an appropriate adhesive substance. As shown in the diagram, the best way to mechanically detach the elements "A" from the moving sheet "B" is by making sheet "B" pass over the sharp angle "C of a blade. When the elements "A" are detached as described above and fall onto the surface "S", their speed will be in the direction as shown by the arrow. This permits them to be correctly located onto this surface without overturning. The advantage of the use of the sharp angle is that an immediate impulse is provided contemporaneously over the entire width of sheet "B", thus avoiding the occurrance of transverse displacement during the depositing phase. In this manner, the desired optimal arrangement on the surface "S" is obtained, as result of the combination of the arrangement on the sheet "B" with the translation speed of the assembly in the direction shown by the arrow. Besides obtaining particularly faithful results, carrying out the method claimed requires only a modest investment.

Claims: Method for depositing retroreflecting marking elements onto a surface (S), which is either a road surface or the surface of road-marking material applied to the road surface itself, wherein said retroreflecting elements (A) are detachably prepositioned at preestablished lengthwise distances on a conveyor sheet (B), which is reeled with the retroreflecting elements (A) thereon on a reel from which said conveyor sheet (B) is withdrawn at the time of depositing said retroreflecting elements (A), said retroreflecting elements being detached from said conveyor sheet by drawing it over a sharp angled blade disposed adjacent said surface (S), characterized in that, when said retroreflecting elements (A) are detached and fall on the surface (S), they have a speed in the direction of movement of said assembly to deposit the elements on the surface (S) without overturning, and in that said assembly is moved at a speed commensurate with the speed of movement of the conveyor sheet (B) to reproduce the said preestablished lengthwise distances of said elements (A) onto said surface (S). Method according to claim 1, characterized in that the retroreflecting elements (A) are deposited on an already existing marking strip (S). Method according to claim 1 or 2, characterized in that the conveyor sheet (B) is covered with an adhesive or sticky substance, while the surfaces of the retroreflecting elements (A) are treated with a detaching polymer. Method according to claim 1 or 2, characterized in that the conveyor sheet (B) is covered with a detaching polymer while the surfaces of the retroreflecting elements (A) are covered with an adhesive substance.

Inventors: EIGENMANN, HELMUT, DR.
Applicants: MINNESOTA MINING AND MANUFACTURING COMPANY
Application year: 1986
Main classification: E01C23
IPC codes: E01F9, E01C23