Optical: systems and elements – Lens – With support
Patent
1992-10-26
1994-05-03
Ben, Loha
Optical: systems and elements
Lens
With support
359823, 359827, 354295, G02B 702
Patent
active
053092872
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a screw-thread arrangement, and to a conversion arrangement for mounting optical units on cameras, particularly though not exclusively on film or television cameras.
Accordingly, the present invention provides a screw-thread arrangement for enabling two coaxial members to be rotated relative to one another to move the members axially one relative to another, the arrangement comprising:
a screw-thread formed on a radial surface of a first of the members and radially spaced from a second of the members; a plurality of follower positioned between the co-axial members and supported on the second of the members;
and means biasing the followers into engagement with the screwthread to cause the followers to follow the screw-thread on relative rotation of the members to move the members axially relative to one another.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention is further described hereinafter by way of example, with reference to the accompanying drawings in which:
FIG. 1 is a longitudinal section through a conversion arrangement for an optical unit for use with a camera, the arrangement incorporating a screw-thread arrangement according to one embodiment of the present invention, with certain parts omitted for clarity;
FIG. 2 is an enlarged sectional view of a first portion of the arrangement of FIG. 1;
FIG. 3 is an enlarged sectional view of a second portion of the arrangement of FIG. 1; and
FIG. 4 is a view in the direction of arrow A of FIG. 3 with certain parts omitted for clarity.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring now to the drawing, this shows a section through a conversion arrangement 10 which is intended for use with various types of optical unit. The conversion arrangement enables the optical unit to be mounted on to a camera such as a film or television camera. The conversion arrangement is fitted within the camera body, which is to the left as seen in the drawing, whilst the optical unit is contained within the conversion arrangement, facing to the right.
The conversion arrangement 10 comprises a mounting means or member A, a carrier or optical unit support B, a focusing gear C, and an iris drive gear D.
The mounting member A is dimensioned so as to fit on the front of a camera body and has a mounting adaptor 12 of suitable form and a mounting body 14. The adaptor 12 engages with the mounting arrangement on the camera to secure the conversion arrangement 10 in position. The mounting body also has an annular recess 18 which opens axially away from the camera body to receive a radially inwardly extending flange 20 of a focusing ring 22 of the focusing gear. The flange 20 is formed at the camera body end of the focusing ring 22 and is retained in the recess 18 by the action of a thrust ring 24 and retaining ring 26, this being described further below.
The optical unit is contained in the support B and is secured by a locking ring 34. The optical unit support B is coaxially mounted within the mounting member A so as to be axially slidable relative thereto but is prevented from rotating relative to the mounting member A. The optical unit support B is located in the mounting body 14 by a support bearing 36 at the rear, left hand end of the conversion arrangement 10 as seen in the drawing, and by a support ring 38 at the front of the arrangement 10. Both rings 34, 38 are adjustable, the ring 38 being adjustable by means of three equi-angularly spaced screws (not shown) and the ring 36 being adjustable by means of a clamp ring 40. The latter has a radially outer screw-thread which engages a screw-thread formed on a radially inner surface of the mounting body 14, enabling the clamp ring 40 to be screwed axially of the mounting body. The support bearing 36 has a radially outer frusto-conical bearing surface which bears on a correspondingly shaped radially inner surface of the mounting body 14.
The focusing ring 22, during manufacture of the arrangement 10, is provided with a cylindrical internal bore 42. An internal
REFERENCES:
patent: 4506952 (1985-03-01), Grollimund
patent: 4707083 (1987-11-01), Iizuka et al.
patent: 4898453 (1990-02-01), Hohenecker
patent: 4989950 (1991-02-01), Nakauchi
N. P. Chironis "Mechanism, linkages and mechanical control" 1965, McGraw-Hill, New York US, pp. 188-189.
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