Method and apparatus for forming a rim, in particular on a lamp reflector

Abstract: In a method of forming a rim on a lamp reflector, a forming roller is positioned on one side of the reflector rim to be formed and a support roller is positioned on the other side. The reflector is rotated about its center axis and the rollers are rotated with the same circumferential speed as the reflector rim. Then the rollers are moved such relative to each other and to the reflector that the rim is flanged between the rollers. The forming roller is moved such that the final tangent line of the circumferential face of this roller to the reflector rim is tilted about a pivot point which is positioned substantially on the bending line of the reflector rim. The invention also includes an apparatus for performing this method.

Description: The present invention relates to a method and apparatus for forming a rim according to the preamble of claims 1 and 5, respectively. In a prior art method of forming a rim, the forming roller is a truncate ball-shaped roller of which a rotation axis is inclined relative to the rotation axis of the supporting roller which is perpendicular to the center axis of the reflector. To form the reflector rim, the forming roller is moved perpendicularly outwardly with respect to the reflector while leaving a gap bove between rollers between which the reflector rim is made. The tangent line of the support roller to the reflector rim determines the shape thereof, while the outwardly moving forming roller determines the deformation process. The control of the forming roller is based on position. This manner of displacing or controlling the forming roller leads to a poor surface quality of the reflector rim, often necessitating a finishing operation on a forming lathe. Furthermore, this method is only suitable for rims up to circa 5 mm. A method and apparatus according to the preamble of claims 1 and 5 are disclosed in US-A-2,097,691. The invention has now the object to provide an improved method and apparatus for forming a rim. For this purpose, the method and apparatus according to the invention have the features of claims 1 and 5, respectively. These features result in a further material compression of the rim and are, for example, particularly suited for reflectors which should be chemically brightened or anodized. For reflectors of which the end rim has a larger material thickness, it is favourable when the support roller is moved a number of times in one direction along and in abutting relationship with the reflector rim and is moved back each time spaced from the reflector rim. Then it is possible that the support roller abuts to this reflector rim only with a short terminal circumferential face which is shorter than the width of this reflector rim. The invention will hereafter be elucidated with reference to the drawing schematically showing embodiments of the invention by way of example. Fig. 1 is a schematic sectional view of a chuck having a formed lamp reflector thereon of which the end rim should be flanged. Fig. 2 shows on a larger scale detail II of fig. 1 including schematically the means for flanging the reflector rim. Fig. 3-5 are sectional views corresponding to fig. 2 and illustrating alternative embodiments of the invention. The drawing and first of all Fig. 1 shows a chuck 1 serving as exchangeable chuck in a forming machine that is not further illustrated. A lamp reflector 2 having a circular transverse section is formed on the chuck 1 and a rim 3 at the open end of the reflector 2 should then be flanged outwardly in order to serve as mounting rim for the lamp reflector, for example. Fig. 2-5 show four different embodiments of forming the rim 3. The means for forming the rim 3 include in all embodiments a support roller 4 and a forming roller 5. The support roller 4 is rotatable about a rotation axis 6 perpendicularly intersecting the center of the chuck 1. The circumferential edge 7 of the support roller 4 which is facing the chuck, determines the bending line of the reflector rim 3. The forming roller 5 consists of a truncated cone-shaped roller which is not only rotatable about its rotation axis 8, but which is also tiltable according to arrow I by means of drive means not shown. The tilting axis of the forming roller 5 is tangent to an end edge 10 of the chuck 1 determining the bending or flanging line of the end edge 3 of the reflector 2 together with the circumferential edge 7 of the support roller 4. The tilting movement of the forming roller 5 may be guided by means of a guide having the shape of a circular segment which is concentrically about the tilting axis at the position of the end edge 10. A circumferential groove 11 in the chuck 1 enables the placement of the forming roller 5 inwardly of the end edge 10 of the chuck 1. The method of forming the reflector rim carried out by the apparatus of Fig. 2 is as follows. After forming the lamp reflector 2 about the chuck 1, the chuck 1 is rotated about the longitudinal centerline again while the support roller 4 is brought into the position of fig. 2 and the support roller 4 will rotate about the rotation axis 6 with such rotational speed that the circumferential speed thereof will substantially correspond to the surface speed of the reflector rim 3 to be formed. The starting position of the forming roller 5 is shown in ghost lines in fig.2 and in which position the rotation axis of the forming roller 5 is parallel to or inclined at a small angle to the longitudinal centerline of the chuck 1. The reflector rim 3 will generally be deformed slightly during the formation of the lamp reflector, as shown in fig. 2, but that is not important in the further process. The forming roller 5, like the forming roller 4, is rotatable about its rotation axis 8 with such speed that the circumferential speed is substantially equal to the surface speed of the rim 3 to be formed. By rotating the chuck 1 together with the lamp reflector 2 and by slowly tilting the forming roller 5 in accordance with arrow I, the rim 3 will gradually be flanged by deformation and will finally be rolled between the rollers 4 and 5 with the forming roller 5 in the end position indicated by bold lines. The control of the forming roller 5 may be an open loop control based on force, that is forming roller 5 is tilted and is forced with a predetermined force or rolling pressure against the rim 3. Fig. 3 shows a modification of the embodiment of fig. 2 with is particularly suited in situations in which material compression of the reflector rim 3 should be carried out, contrary to the embodiment of fig. 2 in which less material compression takes place, so that the embodiment is particularly suited for reflectors having facets and for spray painted surfaces. The embodiment of fig.3 is better suited for chemically brightened or anodized reflectors. The difference to the embodiment of fig. 2 is that the support roller 4 is provided on the end face adjacent the chuck 1 with a short support portion 12 having a circumferential end face 13 having a larger diameter than the remaining portion of the support roller 4. As a result, the support roller abuts the reflector rim only with a short circumferential end face 13 which is shorter than the width of the reflector rim 3 to be formed. In order to cover and roll the whole reflector rim 3 any way, the support roller 4 is displaceable outwardly in a direction according to arrow II parallel to the reflector rim 3, in this case in a direction to the rotation axis 6. During displacement of the support roller 4, the wall 3 is compressed and finished. Fig. 4 shows an embodiment of the invention which is similar to fig.3, but wherein the support roller 4 can be moved a number of times in outward direction along the end rim 3 abutting this rim 3, while this supporting roller 3 is moved back each time spaced from the rim 3 by a lateral movement according to arrow III. This embodiment is particularly suited for thicker materials of the lamp reflector 2. The embodiment of fig. 5 is intended for rims 3 which should not be flanged perpendicularly but at a different angle. In this case, the rim 3 is deformed beyond the perpendicular plane, but it is also possible of course to flange the rim 3 to a smaller angle. In this embodiment the circumferential end face 13 is conical at the same angle as through which the rim 3 should be flanged. The rotation axis 6 of the support roller 4 is still perpendicular to the center line of the chuck 1, but the displacement according to arrow II of the support roller 4 is parallel to that of the end position of the rim 3, or at the same angle as the tangent of the circumferential end face 13 to the rim, adjacent to the forming roller 5, respectively. In fig. 5 it is shown that the forming roller 5 is tilted through a larger angle as with fig. 2-4. The invention is not restricted to the embodiments shown in the drawing and described hereinbefore by way of example which may be varied in different manners within the scope of the invention, as defined by the appended claims. The invention may be employed for round objects other than a lamp reflector, of which objects an end rim should be flanged.

Claims: Method of forming a rim (3) at the open end of an object having a circular transverse section, in particular a lamp reflector (2), wherein a forming roller (5) is positioned on one side of the reflector rim (3) to be formed and a support roller (4) on the other side, whereafter the reflector (2) is rotated about its centerline and the rollers (4, 5) being rotated with the same circumferential speed as the reflector rim (3) and then the rollers (4,5) are moved relative to each other and to the reflector (2) in such way that the rim (3) is flanged, wherein the forming roller (5) is moved such that the final tangent line of the circumferential face of this roller (5) to the reflector rim (3) is tilted about a pivot point which is positioned substantially on the bending line of the reflector rim (3), characterized in that, after the tilting movement of the forming roller (5), the support roller (4) is moved at least once parallel to the reflector rim (3) in abutting relationship with the reflector rim (3). Method according to claim 1, wherein the support roller (4) is moved a number of times in one direction along and in abutting relationship with the reflector rim (3) and is moved back each time spaced from the reflector rim (3). Method according to claim 1 or 2, wherein the support roller abuts this reflector rim (3) only with a short circumferential end face(13) which is shorter than the width of the reflector rim (3). Method according to claim 1, 2 or 3, wherein the reflector rim (3) is flanged to the outer side of the reflector side and the forming roller (5) being tilted on the inner side of the reflector (2). Apparatus for forming a rim (3) at the open end of an object having a circular transverse section, in particular a lamp reflector (2), comprising a chuck (1) for supporting the formed reflector (2), and for rotating the reflector about its centerline, a rotatable support roller (4) having a supporting circumference to which the reflector rim (3) will abut after the formation of this rim, and a rotatable and movable forming roller (5) for flanging the reflector rim (3) against the support roller (4), wherein the forming roller (5) is tilted about a tilting axis extending substantially perpendicularly to the centerline of the chuck(1), characterized in that the support roller (4) is movably suspended and displaceable in a direction parallel to the reflector rim (3) to be formed. Apparatus according to claim 5, wherein the end face of the support roller adjacent the chuck comprises a short support portion (12) having a larger diameter than the remaining portion of the support roller (4). Apparatus according to claim 5 or 6, wherein the support portion (12) is conical and the support roller (4) is displaceable parallel to the longitudinal circumferential line adjacent the forming roller (5). Apparatus according to one of claims 5-7, wherein the tilting axis of the forming roller (5) is substantially tangent to an end edge (10) of the chuck (1). Apparatus according to one of claims 5-8, wherein the forming roller (5) has the shape of the truncated cone, and the truncated edge contacts the tilting axis. Apparatus according to one of claims 5-9, wherein the pivot axis is realised by means of a guide of the forming roller (5) with has the shape of a circular segment which is concentric about the pivot axis.

Inventors: MASSEE JOHAN, MASSEE, JOHAN, Massée, Johan
Applicants: MASSEE JOHAN, MASSEE, JOHAN
Application year: 1995
Main classification: B21D53
IPC codes: B21D53, B21D19