US3572917A

US3572917A - Pickup devices

Info

Publication number: US3572917A
Application number: US753255A
Authority: US
Inventors: Bernard Albert Bentley
Original assignee: Essoldomatic Ltd
Current assignee: Essoldomatic Ltd
Priority date: 1967-08-17
Filing date: 1968-09-16
Publication date: 1971-03-30
Anticipated expiration: 1988-03-30
Also published as: GB1194056A; IE32289B1; IE32289L

Abstract

An electrically conductive pickup for sensing electrically conductive areas on a moving flexible film comprising a fixed support curved in a plane normal to the surface of the film for effecting sliding contact therewith, and having at least two mutually insulated conductive surfaces spaced apart in the direction of the film width.

Description

United States Patent 1,950,518 3/1934 Read [72] Inventor Bernard Albert Bentley Camberley, England 1 1 753,255

FOREIGN PATENTS 157,122 4/1952 Australia...................... 325,845 1,099,843

9/1920 Germany... 2/1961 Germany......

827,551 2/1960 GreatBritain...........:::..

Primary Examiner-Louis R. Prince Assistant Examiner-Frederick Shoon Attorney-Holcombe, Wetherill & Brisebois [5 4] PICKUP DEVICES 5 Claims, 4 Drawing Figs.

ABSTRACT: An electrically conductive pickup for sensing 22 m5 21 52 b 3 0 G [51] Int. [50] FieldofSearch............................................

electrically conductive areas on a moving flexible film comprising a fixed support curved in a plane normal to the surface [56] References and of the film for effecting sliding contact therewit UNITED STATES AT T at least two mutually insulated conductive su 4/1916 apart in the direction ofthe film width.

h, and having rfaces spaced PATENTEU M3019?! SHEET 3 BF 3 The invention relates to electrically conductive pickup devices for sensing a moving flexible film.

The invention finds important application in the problem of designing kinematographic projection system which are required to initiate ancillary functions such as the lowering of a safety curtain and the dimming and switching of auditorium lights. it is important that such ancillary functions be performed in a definite sequence whether prior to, during or after the actual film presentation and prior to the introduction of noninflammable safety film such functions had to be performed by means preferably independent of the film itself, and in general because of the necessarily strict fire risk precautions for limiting the permissible temperature rise of the film by means which maintain generated heat at an acceptable low level. For example, a well-known system of this kind includes a signal pickup associated with an idle film sprocket of the kinematograph projector, the pickup sensing electrically conductive areas of the film formed by coatings, e.g., of aluminum foil, stuck to the film. Such systems have been found to be objectionable for various reasons. For example since the idle film sprocket is rotating, slip-rings or equivalent devices are required for providing continuity of the signal path from the pickup to an external control circuit. Secondly it is known that it is difiicult in practice, with a nondriven sprocket, to preserve continuous contact between the film and the surface of the sprocket, and hence also between the conductive surfaces of the pickup and the conductive areas of the film. This is because the inertia of the idle sprocket often causes it to lag slightly behind the film, this condition resulting in lack of register between the holes in the film and the teeth of the idle sprocket. Random fluttering and jumping of the film then results, which causes either poor contact, or complete lack of contact between the conductive pickup surfaces and the conductive areas of the film. This effect is aggravated by the transfer to the sprocket of lacquer used to form a protective layer over the film emulsion. Transfer of even relatively minute quantities of lacquer form an insulating layer producing faulty operation of the pickup.

Since however the ancillary functions are required to be performed in a fixed sequence controlled by a sequence switching system, a fault or bad contact in the pickup device will result in a space instead of a mark in the signal program, and hence in a faulty or out-of-phase sequence in the switching control system which cannot later be corrected.

The purpose of the present invention is to provide an electrically conductive pickup for sensing data on flexible film in the form of electrically conductive areas, e.g. strips, and especially a pickup which will remove the chief disadvantages of the known sprocket-type pickups used in film projectors.

Furthermore an object of the invention is to make it possible to derive from a flexible record carrier, bearing data in the form of conductive areas, a series of signals in a predetermined sequence without risk of interruption or scrambling of the sequence.

in accordance with one aspect of the present invention these objects are broadly achieved by an electrically conductive pickup device having electrically insulated conductive surfaces which are always fixed with reference to the moving film.

More particularly the invention consists in an electrically conductive pickup device for sensing recorded data in the form of conductive areas on a moving flexible film, said pickup device including a fixed support shaped to guide the film and having at least two mutually insulated conducting surfaces spaced apart preferably in the direction of the film width. The shape of the fixed support and the conducting surfaces are such that contact between such surfaces and the film is made over a sufficient length of arc and at such a radius of curvature in a plane normal to the film surface as to avoid damage to the film or the conducting areas thereof.

An example of an electrically conductive pickup device according to the invention suitable for use in sensing data cartied in kinematographic films will now be explained in more detail with reference to the accompanying diagrammatic drawings, wherein:

FIG. 1 is a simplified diagram on an exaggerated scale of a cross section of a film carrying recorded data in the form of electrically conductive surfaces;

HO. 2 is an elevation partly in axial section of a pickup device suitable for sensing the film shown in FlG. 1;

H6. 3 is an end elevation;

FIG. 4 is an undersideview, partly in axial section, of the body of the pickup device.

Referring now to MG. 1, the emulsion area of the film representing the optical record, for example the diapositive frames, is indicated at 1, whilst a sound. record carried adjacent one edge of the film, and which may be any of the known types of optical variable area or variable density or magnetic recordings, is shown at 2. On that side of the film remote from the emulsion surface there are applied a convenient number of very thin electrically conductive coatings 3, which may be deposited or applied in any suitable manner, for example stripes of metallic foil, e.g. of aluminum, bonded to the film by adhesive. Alternatively, known chemical conducting compounds, of which stannous salts are an example, may be deposited.

Such electrically conductive surfaces may, as shown in the example, extend substantially acrossthe entire width of the film, but since the purpose of the coating is to form a conducting bridge, such full width dimension for the coating is not essential to the invention as will be apparent from the following description.

The electrically conductive sensing device indicated in FIGS. 2, 3, and 4 comprises a body of metal 4, for example of hard chrome steel, having at one end a flange 5 and three stepped zones 6, 7 and 8 of decreasing radius of curvature. Where, as in the example shown, the body is a major part of a generally cylindrical body of revolution, it may be machine turned from stock, the other end thereof having an integral spigot or shaft 9. Upon the shaft 9 there are mounted three

metal segments

10, 11 and 12 with intervening insulating spacing members l3, l4 and 15, for example of the material known under the registered Trade Name Tufnol, to insulate the segments from each other and from the body 4 of the support. Each of the segments 10, ll, 12 and the intervening insulating spacers l3, l4, 15 are mounted upon the shaft 9 and held in position by a bonding medium for example the compound known under the Trade Name Araldite. insulated

fixing screws

16 and 17 indicated in H68. 3 and 4 are used to assemble the parts it) to H5 inclusive to the body of the pickup. The segments w, ll, 12 and the insulating spacers may initially be made in form of collars or bushes machined to size from stock and provided with a bore to give them an interference fit over the shaft 9. After fitting has been completed the entire assembly may then be machined along a plane parallel to the common axis to provide a plane surface whereby the body of the pickup may be mounted upon a base mounting plate 18 of insulating material which again may be of the same material as the spacers 133, M and 15, by means of

screws

19 and 20. The base mounting plate is itself mounted upon a metal fixing plate 211 by means of screws 22.

Electrical connections to the electrically conductive insulated surfaces of the pickup are provided by screws such as 23 passing through the base of the mounting plate and provided with terminal studs and nuts 25.

If desired a single electrical connection may be made in this manner to a common conductive surface formed by the stepped surfaces 6, 7 and 8 of the pickup, and individual conductive connections through separate terminals may be made to the segments 10, ii and 112, each of which presents a conductive surface individually insulated and insulated from the common conductive surface 65, 7, 8. The pickup device may be ins alled in the appropriate position in a projector by means of an angle bracket (not shown), and in operation any one of three different widths of film may be fitted in the respective grooves of the pickup device. For example, a standard film of the smallest width may be provided with Conductive coatings, for example aluminum foil, to make bridging contact between the conductive flange 8 of the smallest radius and a conductive surface 26 of the segment it).

It will be clear however that alternatively, or in addition, bridging contact may be similarly made between the surface of the collar 27 and the surface 26.

With the larger sizes of film, bridging contact will be made between the stepped annular surfaces 7 and 6 respectively and the correspondingly radiused parts of the conducting segments iii and iii, the largest width of film being accommodated between the end flanges and 3% of the body of the support.

Obviously alternative arrangements are possible with a different spacing and arrangement of the conducting segments or collars it), ii and i2, and appropriate lengths of the conducting aluminum stripes on the film, the object being, in general, to obtain a sequence of signals due to the bridging over of insulated contact surfaces by conducting areas applied to the surface of the film passing over the pickup device. Most conveniently the control apparatus for controlling the sequence of ancillary functions comprises a sequence switch or stepping switch receiving the pulses at the appropriate intervals from the pickup device at a given speed of the film. However, since the device is capable of delivering a sequence of pulses, a binary, or otherwise coded, counting circuit with appropriate known storage and release facilities may be actuated to control the sequence of ancillary functions.

in the example shown in the drawing the body of the pickup device has a strictly cylindrical curvature making contact with the film over a circular arc. However, such shape is not essential and other geometrical forms of the contacting surfaces of the pickup device may be employed provided that the area of mutual contact between the film and the pickup device is adequate to prevent snagging of the film and to promote smooth running and contact with the conducting surfaces of the pickup.

Although the example described employs metal, for example hard chrome, for the body of the pickup, it is nevertheless possible to make the body of the pickup of a different metal from the conducting surfaces, or wholly or partly of a suitable insulating material, e.g. a ceramic, upon which conductive coatings equivalent to the surfaces 6, 7 and 8 may be deposited by plating or any other suitable process. A metal body is however preferred on account of ease of manufacture and ease of heat dissipation. Again the conducting pickup areas may be deposits of noble metal, e.g., rhodium or platinum upon an intermediate plating metal. The surfaces of the parts ll), 11 etc. are finished to reduce to a minimum friction and consequent heat generation as a result of contact with the film. To this end, the insulating spacers l3 and 14 are undercut with respect to their adjacent surfaces, so as to prevent contact with the film and thereby further reduce frictional losses.

lclaim:

1. An electrically conductive pickup for sensing electrically conductive areas on a moving flexible film comprising a fixed support shaped to guide the moving film, said support having at one side a first conductive surface making contact with a marginal strip of the film surface, and having at the other side of the support a plurality of conducting surfaces mutually insulated from each other and from the first conductive surface, said plurality of conductive surfaces being spaced apart in the direction of the film width, whereby conductive contact can be established by bridging said first conductive surface and one or more of said plurality of conductive surfaces by conductive strips of various dimensions in the width of the film, and wherein said support is of stepped formation to present arcuate flanges forming film contacting surfaces which are of decreasing radii of curvature in planes which lie normal to the film surface and parallel to the direction of motion of the film and which are of decreasin dimension in the direction of the film width, whereby films of different width may be supported and contacted by pairs of flanges contacting longitudinal marginal zones of said film at opposite edges thereof, intervening portions of said support being undercut to prevent contact with said film surface except at said conductive surfaces of the support.

2. An electrically conductive pickup for sensing electrically conductive areas on a moving flexible film comprising a fixed support shaped to guide the moving film, said support having at one side a first conductive surface making contact with a marginal strip of the film surface, and having at the other side of the support a plurality of conducting surfaces mutually insulated from each other and from the common conductive surfaces, said plurality of conductive surfaces being spaced apart in the direction of the film width, whereby conductive contact can be established by bridging said first conductive surface and one or more of said plurality of conductive surfaces by conductive strips of various dimensions in the width ofthe film, and wherein the first conductive surface at said one side of the support is stepped to decreasing radii of curvature towards the center of the film, and wherein the support is similarly stepped for each of said plurality of conductive surfaces at the other side of the support, whereby films of different width may be guided between said respective steps to make bridging contact between said first conducting surface and one of said plurality of conducting surfaces.

3. An electrically conductive pickup as claimed in claim 2, wherein the body of the support is of electrically conductive material and the plurality of conductive surfaces are formed by electrically conductive segments having segments of insulating material intervening to insulate them from each other and from said first conductive surface.

4. An electrically conductive pickup as claimed in claim 2, wherein the body of the support is of electrically conductive material and the plurality of conductive surfaces are formed by electrically conductive segments having segments of insulating material intervening to insulate them from each other and from said first conductive surface, and wherein the intervening insulation is formed by a mass of cast resin.

5. An electrically conductive pickup device as claimed in claim 2, wherein the body of the support is of electrically conductive material and the plurality of conductive surfaces are formed by electrically conductive segments having segments of insulating material intervening to insulate them from each other and from said first conductive surface, and wherein the intervening insulation is performed by machining from stock.

Claims

1. An electrically conductive pickup for sensing electrically conductive areas on a moving flexible film comprising a fixed support shaped to guide the moving film, said support having at one side a first conductive surface making contact with a marginal strip of the film surface, and having at the other side of the support a plurality of conducting surfaces mutually insulated from each other and from the first conductive surface, said plurality of conductive surfaces being spaced apart in the direction of the film width, whereby conductive contact can be established by bridging said first conductive surface and one or more of said plurality of conductive surfaces by conductive strips of various dimensions in the width of the film, and wherein said support is of stepped formation to present arcuate flanges forming film contacting surfaces which are of decreasing radii of curvature in planes which lie normal to the film surface and parallel to the direction of motion of the film and which are of decreasing dimension in the direction of the film width, whereby films of different width may be supported and contacted by pairs of flanges contacting longitudinal marginal zones of said film at opposite edges thereof, intervening portions of said support being undercut to prevent contact with said film surface except at said conductive surfaces of the support.

2. An electrically conductive pickup for sensing electrically conductive areas on a moving flexible film comprising a fixed support shaped to guide the moving film, said support having at one side a first conductive surface making contact with a marginal strip of the film surface, and having at the other side of the support a plurality of conducting surfaces mutually insulated from each other and from the common conductive surfaces, said plurality of conductive surfaces being spaced apart in the direction of the film width, whereby conductive contact can be established by bridging said first conductive surface and one or more of said plurality of conductive surfaces by conductive strips of various dimensions in the width of the film, and wherein the first conductive surface at said one side of the support is stepped to decreasing radii of curvature towards the center of the film, and wherein the support is similarly stepped for each of said plurality of conductive surfaces at the other side of the support, whereby films of different width may be guided between said respective steps to make bridging contact between said first conducting surface and one of said plurality of conducting surfaces.