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Home | Alpha Telephone | Domain Names | Web Hosting | Get Traffic | xrEvidence | xrSoccer United States Patent
CAM BARREL FOR HOLDING AT LEAST ONE DISPLACEABLE LENS ELEMENT A cylindrical barrel body comprises at least two axially aligned annular members, one of which is formed with a cam face which is inclined to the generatrices of said barrel body. Said two annular members have mutually confronting end faces extending along said cam face.
Assistant Examiner: Shoemaker; F. D. What is claimed is: 1. In an optical system, a cam barrel for holding at least one displaceable lens element, cam follower means provided on at least said lens element, which cam barrel comprises a cylindrical barrel body comprising a plurality of axially aligned annular members, at least one of which is formed with a cam face which is inclined to the generatrices of said barrel body, said cam follower means being adapted to follow said cam face, said cam face having two ends, defined by abutment surfaces of said cam barrel, whereby said cam face has different inclinations to said generatrices, and said annular members having mutually confronting end faces extending along said cam face. 2. A cam barrel as set forth in claim 1, in which said barrel body consists of a plurality of said annular members, which are formed with a plurality of cam faces, which are axially spaced apart and inclined to the generatrices of said barrel body, and each of said annular members has at least one end face that confronts another one of said annular members and extends adjacent to and along one of said cam faces. 3. A cam barrel as set forth in claim 1, in which said annular members are provided with interengaging coupling elements for transmitting rotation from one of said annular members to the other. 4. A cam barrel as set forth in claim 1, in which said cam face is formed on the inside of said one annular member and said one annular member comprises a web, which extends axially from said cam face and is formed with one of said end faces, which bears on the other of said annular members. 5. In an optical system, a cam barrel for holding at least one displaceable lens element, cam follower means provided on at least said lens element, which cam barrel comprises a cylindrical barrel body comprising, a plurality of axially aligned annular members, at least one of which is formed with a cam face which is inclined to the generatrices of said barrel body, said cam follower means being adapted to follow said cam face, said cam face having two ends, defined by abutment surfaces of said cam barrel, and biasing means urging said cam follower means of said lens element against a part of said cam face. 6. An optical system, as set forth in claim 5, in which said biasing means is formed as a compression spring. This invention relates to a cam barrel for holding at least one displaceable element of a lens, which barrel has cam faces which are inclined to the generatrices of the cylindrical barrel body and have preferably different inclinations. So far, the manufacture of such cam barrels has involved certain difficulties. The cam faces were milled into the cylindrical barrel body so that the strength thereof was greatly reduced. This remark is particularly applicable to pancratic lenses. When a very large zoom ratio is desired, these cam faces must be very long so that they extend over a large angle around the cam barrel. A special disadvantage involved in the manufacture of the cam faces by conventional methods resides in that the cam faces must be milled into the body of the barrel by means of small end mills. This machining operation results in scores, which are transverse to the direction of movement of the displaceable members and hinder the sliding movement of these displaceable members in the curve. Besides, the milling of the curves is very time-consuming. It is known, on the other hand, to manufacture a barrel having at least two cams by non-cutting methods; one of said cam consists of a cam groove and has such a finite depth that it does not extend through the outside surface of the barrel; the other cam consists of a raised cam in the interior of the barrel. That concept too has also failed to remedy the fact that cam faces extending over a large angle result in a substantial reduction of the strength of the barrel. Besides, the raised cam which is only frictionally engageable by the lens element to be controlled required additional space, which is not always available. To facilitate the formation of cam grooves, it is also known to provide each mount in the form of part of a hollow member, which is provided with the sections of the outside surface for the subsequent coupling with the mating inner surface of the lens housing and which extends at least on one of the sections in cross-section over an angle not in excess of 180.degree. with respect to the optical axis of the lens so that the mounts may be combined in such a manner that the optical components of both mounts alternate, and the optical axes of the components coincide when the mounts have been assembled in the required sequence. This concept is not suitable, however, for a cam barrel having cam faces which are inclined to the generatrices of the cylindrical barrel body. The invention eliminates the above-described disadvantages in that the barrel is composed in known manner of individual annular members, the end faces of these annular members extend along the cam faces, and each annular member is preferably provided with a coupling element for interengaging with the adjacent annular member. Whereas it is known from the printed German application No. 1,287,329 to provide a lens mount which is composed of a plurality of annular members, that concept does not suggest the present invention. Because the cam barrel according to the invention is composed of individual annular members and the end faces of these annular members extend along the cam faces, each annular member is inherently stable even when the cam faces extend around the barrel over an angle of, e.g., almost 360.degree.. Besides, the individual annular members can be made by inexpensive non-cutting methods, e.g., by sintering. Another advantage over the known design resides in that the movement of the lens elements can be positively controlled and additional space is not required. A rotation of the cam barrel will be reliably transmitted to the several annular members merely because the cam faces are inclined. Besides, coupling elements may be provided, e.g., in the form of dovetail-shaped projections, which are received by mating recesses in the adjacent annular member. It is also within the scope of the invention to provide the several annular members with self-lubricating sliding surfaces, where friction may arise. Additional features and advantages of the invention will become apparent from the following description of an embodiment which is diagrammatically shown by way of example in the drawing, in which FIG. 1 is a developed view showing a cam barrel according to the invention; FIG. 2 is a sectional view taken on line II--II in FIG. 1; and FIG. 3 is a perspective view showing the cam followers. The cam barrel shown in FIG. 1 is designed in accordance with the Austrian Pat. No. 296,649. Each of its two cams 1, 2 consisting of internal grooves has a leg 3 or 4, which serves to control the adjustment of the lens during a change of the focal length, and a leg 5 or 6 for controlling the adjustment of the lens during a focussing in the near range. In the embodiment shown by way of example, the two legs 5 and 6 of the cam adjoin the respective legs 3, 4 at that end thereof which corresponds to the wide-angle position of the lens. Because the cam may extend around the cam barrel virtually over an angle of 360.degree., the legs 5, 6 might adjoin the respective legs 3, 4 at that end thereof which corresponds to the telephoto position, although the legs 5, 6 would have to be much longer in this case. It is apparent that the cam barrel consists of several annular members 7, 8, and 9, which are shown in a developed view in FIG. 1. The end faces of said annular members extend along the cam faces 1 or 2, respectively. Because the cam faces 1, 2 define internal grooves, the annular members 7 and 9 have webs 10, 11 (FIG. 2), which act as spacers between adjacent annular members 7, 8, 9. The webs 10, 11 of the annular members 7 and 9 bear on the annular member 8. Whereas the webs 10, 11 could be omitted so that adjacent annular members 7, 8, 9 would be spaced apart only by those end face portions thereof which have no cam faces, e.g., by the end face portions at the left-hand and right-hand ends of the annular members of the cam barrel in FIG. 1, or, alternatively, the annular members 7, 8, 9 might be inserted and fixed in a surrounding shell, it will be understood that the embodiment shown in FIG. 2 is highly superior to the other embodiments which are contemplated. A rotation of the cam barrel will be reliably transmitted to the annular members 7, 8, 9 because the cams 1, 2 have different inclinations so that the annular members interengage. To ensure the transmission in any case as well as a predetermined relative position of the cams 1, 2, the embodiment shown by way of example comprises annular members 7, 9 provided with coupling elements consisting of projections 12, 13, which extend into mating recesses 14, 15 of the adjacent annular member 8. In the embodiment shown by way of example, these coupling elements 12, 13 and 14, 15 are formed at those end face portions of the annular members 7, 8, 9 which have no cam faces. If the cam faces extend throughout the periphery of the end faces of the annular members, the coupling elements could be formed on the webs 10 and 11. In this case, e.g., the web 10 could consist at least in one section of a projection of the annular member 7 and in at least one other section of a projection of the annular member 8 so that the projections of the two annular members interengage like teeth. It will be understood that the annular members 7, 8, 9 can easily be made by sintering. It will be advantageous to provide the annular members 7, 8, 9 with self-lubricating sliding surfaces, especially when the annular members consist of plastic material reinforced with glass fibers. These are the cam faces 1 and 2 and those surfaces of the annular members 7, 8, 9 in which friction arises during a change of the focal length. For this purpose, these sliding surfaces may be impregnated with oil in annular members made of metal, or the sliding surfaces may contain lubricating admixtures, such as graphite or molybdenum sulfide. It is a special advantage of the cam barrel according to the invention that the lens elements controlled by cams 1 and 2 may be spring-biased, so that part of the cam faces may have virtually any desired tolerances. If the two lens elements are biased by a tension spring, which forces the cam follower means 17, 18 (FIG. 3) for adjusting said lens elements against the cam faces of the cylindrical member 8, only the dimensional accuracy of the cam faces of the cylindrical member 8, but not the dimensional accuracy of the cam faces of the cylindrical members 7 and 9, is critical at all. Because the cylindrical members should be made by sintering, it will be more desirable to provide the biasing means 16 only as a compression spring means acting on the lens elements so that the cam follower means 17, 18 for adjusting the lens elements are forced against the cam faces of the cylindrical members 7 and 9. In this case, the dimensional accuracy of the cylindrical member 8 is not critical, whereas each of the cylindrical members 7 and 9 must be provided only with one cam face having smaller tolerances. In view of the shrinkage, such member can be made more easily than a cylindrical member having two cam faces with small tolerances. For U.S. patent law, rules, and procedures see MPEP. Disclaimer. Information presented on this page while believed to be reliable, is provided "as is" with no warranties of its accuracy or timeliness. For legal advice seek help of a licensed professional. |