US3865476A

US3865476A - Cinematographic apparatus

Info

Publication number: US3865476A
Application number: US428104A
Authority: US
Inventors: Jean Thevenaz; Claude Kreienbuhl
Original assignee: Bolex International SA
Current assignee: Bolex International SA
Priority date: 1973-01-04
Filing date: 1973-12-26
Publication date: 1975-02-11
Anticipated expiration: 1992-02-11
Also published as: ATA408873A; AT348858B; IT1000999B; GB1442713A; JPS49103626A; HK9477A; DE2365166A1; CH561429A5; NL7314191A

Abstract

A cinematographic apparatus having an intermittent film driving mechanism coupled to the driving mechanism of a rotatable shutter, the intermittent film driving mechanism comprising a claw, of the sliding-claw type, movable into and out of operative engagement with a film perforation, and a claw drive means for driving the said claw in a forward or reverse direction and including a drive wheel to turn constantly in the same direction at a rotation ratio of 4 shutter movements to 3 turns of the drive wheel to rotate the claw in a plane that extends across the plane of a film, and claw control means to move the claw into and out of an operative position relative to the film during predetermined portion of the drive wheel three rotation cycle.

Description

United States Patent Thvenaz et al.

CINEMATOGRAPHXC APPARATUS Inventors: Jean Thvenaz, Grandson; Claude Kreienbiihl, Yverdon, both of Switzerland Boleii International SA, Saint-Croix,

Switzerland Dec. 26, 1973 Assignee:

Filed:

Appl. No.: 428,104

Foreign Application Priority Data Jan. 4, I973 Switzerland 186/73 US. Cl 352/191, 226/54, 226/62, 226/68/352/168, 352/173 Int. Cl. G03b 1/22 Field of Search 352/191, 192, 193, 173, 352/168; 226/54, 62, 67, 68

' References Cited UNITED STATES PATENTS Masterson 352/l92X [451 Feb. 11, 1975 2,702,491 2/l955 I Favre 352/192 X 3,545,852 12/1970 WinklerQ 352/173 Primary ExaminerMonroe H. Hayes [57] ABSTRACT A cinematographic apparatus having an intermittent film driving mechanism coupledto the driving mechanism of a rotatable shutter, the intermittent film driving mechanism comprising a claw, of the sliding-claw type, movable into and out of operative engagement with a film perforation, and a claw drive means for driving the said claw in a forward or reverse direction and including a drive wheel to turn constantly in the same direction at a rotation ratio of 4 shutter movements to 3 turns of the drive wheel to rotate the claw in a plane that extends across the plane of a film, and claw control means'to move the claw into and out of an operative position relative to the film during predetermined portion of the drive wheel three rotation cycle.

6 Claims, 4 Drawing Figures PATENTEB FEB] H975 SHEET 4 OF 4 CIN EMATOGRAPHIC APPARATUS BACKGROUND The present invention relates to a cinematographic apparatus having an intermittent driving mechanism for film connected with the shutter driving mechanism and more particularly to such apparatus in which there is provided a claw, of the sliding claw type, with an eccentric wheel turning constantly in the same direction which drives the claw forwards or in reverse and wherein the ratio of 4 shutter movements to 3 turns of the eccentric wheel being maintained by the connection between the driving mechanism of the eccentric wheel and the shutter.

Claw mechanisms are known which allow forward and reverse action in a cinematographic apparatus (projector or camera). Generally, these mechanisms have several cams controlling the claw; one cam in particular controls the movement upwards and downwards of the claw and another cam controls the penetration of the claw into the film perforation during forward action. Reverse action is sometimes brought about by the intervention of another cam working out of phase with the first or by reversing the driving mechanism.

Cams are mechanical parts which must be manufactured with precision, with the result, that the cost of an apparatus increases proportionally with the number of cams included in its claw driving mechanism.

Furthermore, putting the motor of a projector into reverse causes the film to cease moving for an instant which in turn may cause the frame which is in front of the film-gate to be damaged or at least to become distorted by the heat of the projection lamp. A ventilator would remedy this fault but being normally driven by the same motor as the projector it would cease to function simultaneously with the claw mechanism thus increasing the chance of film damage.

In order to avoid these drawbacks, it is standard to provide a film driving mechanism having a claw, of the sliding claw type, driven by an eccentric wheel. One side of such a claw is arranged generally perpendicular to the plane of the film when engaging a perforation of the film in order to draw it forward, the other side is inclined relative to film plane so that it can slide out of the perforation without disturbing the stability of the film as it is withdrawn.

However, such a claw configuration can not be used in reverse.

SUMMARY OF INVENTION The present invention provides a new and improved claw mechanism that avoids the above-mentioned drawbacks and technical problems by combining a claw, of the sliding claw type, with an eccentric wheel driven mechanism that enables forward and reverse action without reversing the direction of the motor.

In a preferred embodiment the claw comprises an elongated bar with two symmetrical claws at one end, the other end being connected to a pivoting lever having two extreme positions, which correspond with forward and reverse action of the apparatus respectively. The central part of the bar is attached to one end of a small link the other end of which is movably held to an eccentric wheel. In one of the first extreme positions, e.g. the one which correspondswith the forward running of the apparatus, the claw bar is in a position such that one of the claws causes the film to move, whereas in the other extreme position, the one which corresponds with the reverse movement, the claw which is symmetrically opposite comes into action with the film.

DRAWINGS The present invention will be better understood on referring to the embodiments of the invention and the accompanying drawings in which:

FIG. 1 is a general perspective view of one embodiment of a film driving mechanism according to the invention.

FIG. 2 shows diagrammatically the cycle of the film driving mechanism in FIG. 1.

FIG. 3 shows the control circuit of the electromagnet retaining the claw bar.

FIG. 4 is similar to FIG. 1 showing another embodiment of a film driving mechanism.

DETAILED DESCRIPTION With reference to FIG. 1, a film driving mechanism comprises an elongated bar 1 with two claws (2 and 3) at one extremity. Each claw 2 and 3 extends symmetrically from the claw bar 1 in opposite directions along the plane and direction of the film path. Each claw 2 and 3 extend at an angle slightly greater than to the claw bar 1 for purposes discribed below. The other end of claw bar 1 is coupled to a lever 4 which pivots on an axle 5. Lever 4 can rock freely to permit claw 2 or 3 to operatively engage film 15 as described below or the electromagnet assembly 8 can be energized to draw lever 4 into gap 9 or 10 and thereby move bar 1 away from its operating position relative to film 15. The centre part of the bar 1 is linked to the extremity of a small rod or link 6, the other end of which is coupled for movement to an eccentric wheel 7. The lever 4 pivots between two extreme positions which correspond respectively with two positions of the claw. These two positions are shown in FIG. 1, the first (forward) in continuous lines, the second (reverse) in dotted lines.

The axle 5 has a permanent magnet 11 at the opposite end from the lever 4, which is operatively arranged between the poles of an electromagnet 12, this electromagnet 12 being supplied with direct current. The polarity of the poles is inverted, by reversing the direction of the electric current, using for this purpose a conventional current directions control device, not shown, which causes the permanent magnet 11 and the lever 4 to rock.

When the film is moving forward in the apparatus the first claw 3 functions while the second claw 2 does not come in contact with the film. Each of these claws has one side practically perpendicular to the plane of the film 15 and one side at an angle to this plane generally as shown.

FIG. 2 is a diagram of the film driving mechanism described above, coupled to a two-bladed shutter. A fourbladed shutter turning at half the speed could also be used.

Each complete rotation of the claw is broken down into six successive phases numbered I to VI. The vertical columns depict: A the action of the eccentric wheel; B the claw when driving the film forward; C the claw when driving the film in reverse; D the electromagnet which holds back the claw bar, and E the shutter, respectively. In the columns B and C the direction of the movement of the claw bar (shown by the arrow) is indicated for each phase of operation as well as the initial and final positions of the claws when operating forwards or in reverse. In column E, which shows the action of the shutter, the shaded areas indicate the periods when the shutter is closed. It should be noted that the eccentric wheel and the shutter mechanism are coupled in such a way that three turns of the eccentric wheel correspond with four shutter movements.

In phase I, the eccentric wheel makes half a rotation, indicated by a semi-circle in the thick line. If the mechanism is driving the film forwards the corresponding claw is engaged in a perforation of the film and its side which is perpendicular to the film pulls on one side of the perforation in such a way that this phase corresponds with a movement of the film. During this phase in which the film is moved, one of the blades of the shutter closes the film-gate and the electromagnet does not hold back the claw bar.

If the mechanism is working in reverse the corresponding claw 2 is engaged in a perforation and its inclinedside comes up against the side of perforation so that during this phase the claw slides along the film without causing it to move.

In phase II, the electromagnet holds back the claw bar 1 whether the mechanism is working in forward or in reverse. This phase is divided into equal parts, during .the first the film-gate is open, during the second the other blade of the shutter closes the film-gate.

In phase I" the electromagnet holds back the claw bar at first and releases it at the end of the phase allowing the claws corresponding with forward or reverse movement of the film to engage in a perforation. The second blade of the shutter continues to closethe filmgate during the beginning of this phase, but the filmgate is open for the whole of the second part of this phase.

This film moves in reverse during phase IV. The claw corresponding with reverse movement penetrates into a perforation at the end of the preceding phase and its perpendicular edge pulls on the side of the perforation and makes the film move backwards. However, if the mechanism is running forwards the reverse claw presents its inclined edge to the side of the perforation and when the said claw is caused to move by the eccentric wheel it slides out of the perforation and over the surface of the film without causing it to move or disturbing its stability in front of the film-gate. During the whole of this phase the electromagnet does not influence the working of the claw and the film-gate is closed by the aforementioned second blade.

During phase V the electromagnet holds back the claw which therefore does not cause the film to move and the film-gate, which is open during the first half of this phase, is closed during the second half by the said second blade.

In phase V] the electromagnet continues to hold back the claw bar during the part of the phase when the filmgate is closed by the second blade of the shutter and releases the claw bar during the second part of the phase whenthe film-gate is open. During this phase the claw bar is held back at first, irrespective of whether the mechanism is running forwards or in reverse, and penetrates at the end of the phase into a perforation in order to recommence the cycle.

It should be noted that the closing of the film-gate always coincides with the phases during which the film is moved either forward or in reverse, without either reversing the direction of rotation of the eccentric wheel of modifying the working of the shutter mechanism. Furthermore, understanding that when projecting onto a small screen, shutter frequencies lower than 72 per second cause flickering, the two-bladed shutter must turn at a minimum rate of 36 turns per second. In this case the eccentric wheel will make 54 turns per second which corresponds with a film speed of 18 frames per second. It will be noted that the electromagnet 8 makes it possible to withdraw the claw from its working position thus interrupting the movement of the film for a predetermined length of time without modifying the rotation of the eccentric wheel. It is therefore, a simple matter to project a single frame or to vary the speed of filming or projecting with a basic constant speed of the eccentric wheel. E. g. when the eccentric wheel turns 54 times per second, the film can move at 54 frames per second, if the electromagnet 8 does not withdraw the claw.

In the embodiment of this invention described above there is a small magnet 31A on one of the shutter blades 31B which acts upon a reed 31C. This reed transmits a signal in the form of a rectangular impulse having the frequency of the frequency with which the said shutter blade 31B passes before the reed 31C at the input 31 of an electronic circuit controlling the electromagnet. This circuit is shown schematically in FIG. 3. The impulse from the reed 31C is transmitted to a bistable device 32 which divides each impulse received by two. The impulse leaving the bistable device 32 goes either directly orvia a second bistable device 33 which divides each impulse received by two, to a monostable device 34. The output impulse from the monostable device 34 and the input impulse from the reed to the terminal 31 which is reversed by a current reverser 35 go to the input of a NAND gate 36 from which the current flows via an amplifier 38 to the electromagnet 37.

Two inputs to the first monostable device control the projection of one frame and switching off respectively. In the example described, the two-bladed shutter makes 36 turns per second and the reed transmits impulses at a frequency of 36 per second. The bistable device 32 transmits at 18 per second and the bistable device 33 at 9 per second. The front of each impulse transmitted by a switch 41 reaches the monostable device 34 which has a constant time factor equal to two impulses transmitted by the reed. The NAND gate 36 allows the impulses from the reed to pass through during the impulses from the monostable device. The impulse is amplified by an amplifier 38 whose output terminal is connected to the electromagnet 37. The operation of the circuit is such so as to control the electromagnet as described above in connection with FIG. 2.

A variation of the present invention is shown in FIG. 4. A bar 51 ending in two claws is connected at the end opposite to the two claws to a lever 54 which pivots on an axle 55. A spring 56 which tends to withdraw the claw from the film perforation and an electromagnet 57 which attracts the claw bar 51 in the opposite direction to the spring 56 both act upon the claw bar. As before an eccentric wheel 58 turning constantly in the same direction drives the claw mechanism either forwards or in reverse by means of a link 59.

During the phases when the film is moving, the electromagnet is supplied with current and the plungercore 60 is drawn inside the magnetic coil drawing after it the slide 61. The lever 54 rocks on its axle 55 and pushes the claw into a perforation in the film. When the claw is withdrawn, the electromagnet is not supplied with current and only the spring 56 acts upon the lever 54. This form has the advantage that when the apparatus stops running the claw is withdrawn from the film.

Other and further modifications can be made to the invention as herein disclosed without departing from the spirit and scope thereof.

What we claim is:

1. Intermittent film driving mechanism for a motion picture apparatus coupled to a shutter device for creating open and closed phases for film therein, said mechanism comprising a claw device of the sliding claw type, an eccentric cam means for driving said claw device and being rotatable at a constant rate in the same direction and a control means for preventing the claw device from operatively engaging the film perforations, said claw device comprising two symmetric oppositely facing claws, rigidly fixed together, which engage the film perforations respectively during forward and backward transportation of said film, the ratio of closed phases and complete revolutions of the eccentric cam means is 4 to 3 and in which the control means comprises an electromagnet for preventing said claws from engaging the film at least during said open phases.

2. intermittent film driving mechanism as set forth in claim 1 wherein the claw device comprises a claw bar supporting on one end thereof the two symmetric claws and the other end of which is coupled to film direction control means to selectively move said claw bar between a first position in which only the first mentioned claw can operatively engage the film and a second position in which only the other claw can operatively engage the film.

3. intermittent film driving mechanism according to claim 2 wherein means are provided to sense a predetermined rotational position of the shutter and operate said claw control means in response thereto.

4. Intermittent film driving device mechanism according to claim 3 wherein the shutter device comprises a two bladed rotational shutter one of said blades at least comprising a magnet which cooperates with a reed pick-up device to transmit a control impulse to the electromagnet.

5. Cinematographic apparatus having an intermittent film driving mechanism according to claim 4 wherein the reed device operatively transmits impulses recurring at a frequency related to the shutter speed to the input of an electronic circuit operable to control the electromagnet, said circuit having two bistable devices to transform the impulses transmitted by the reed device into impulses having frequencies of respectively half and a quarter of that transmitted by the reed device, a monostable device in which the time corresponds with two impulses transmitted by the reed-device and a NAND gate coupled to allow impulses from the reed device to pass through during the impulses transmitted by said monostable device.

6. A cinematographic apparatus having an intermittent film driving mechanism coupled to the driving mechanism of a rotatable shutter, the intermittent film driving mechanism comprising a claw, of the slidingclaw type, movable into and out of operative engagement with a film perforation, and a claw drive means for driving the said claw in a forward or reverse direction and including a drive wheel to turn constantly in the same direction at a rotation ratio of four shutter movements to three turns of the drive wheel to rotate the claw in a plane that extends across the plane of a film, and claw control means to move the claw into and out of an operative position relative to the film during perdetermined portion of the drive wheel three rotation cycle, said claw comprises a claw bar with a pair of oppositely facing claws near one end thereof, one claw to engage the film during forward movement thereof and the other to engage the film during reverse movement thereof, and wherein means are provided to sense a predetermined rotational position of the shutter and operate said claw control means in response thereto, and wherein the claw means comprises an electromagnet to move the claw bar toward and away from the film and said last mentioned means comprise a magnet arranged on at least one of the blades of the shutter and cooperating with a reed pick-up device to transmit a control impulse to the electromagnet, and wherein the reed device transmits impulses recurring at a given frequency to the input of an electronic circuit which controls the electromagnet, said circuit having two bistable devices to transform the impulses transmitted by the reed device into impulses having frequencies of respectively half and a quarter of that transmitted by the reed device, a monostable device in which the time corresponds with two impulses transmitted by the reed device and a NAND gate which allows impulses from the reed device to pass through during the impulses transmitted by said monostable.

Claims

5. Cinematographic apparatus having an intermittent film driving mechanism according to claim 4 wherein the reed device operatively transmits impulses recurring at a frequency related to the shutter speed to the input of an electronic circuit operable to control the electromagnet, said circuit having two bistable devices to transform the impulses transmitted by the reed device into impulses having frequencies of respectively half and a quarter of that transmitted by the reed device, a monostable device in which the time corresponds with two impulses transmitted by the reed device and a NAND gate coupled to allow impulses from the reed device to pass through during the impulses transmitted by said monostable device.

6. A cinematographic apparatus having an intermittent film driving mechanism coupled to the driving mechanism of a rotatable shutter, the intermittent film driving mechanism comprising a claw, of the sliding-claw type, movable into and out of operative engagement with a film perforation, and a claw drive means for driving the said claw in a forward or reverse direction and including a drive wheel to turn constantly in the same direction at a rotation ratio of four shutter movements to three turns of the drive wheel to rotate the claw in a plane that extends across the plane of a film, and claw control means to move the claw into and out of an operative position relative to the film during perdetermined portion of the drive wheel three rotation cycle, said claw comprises a claw bar with a pair of oppositely facing claws near one end thereof, one claw to engage the film during forward movement thereof and the other to engage the film during reverse movement thereof, and wherein means are provided to sense a predetermined rotational position of the shutter and operate said claw control means in response thereto, and wherein the claw means comprises an electromagnet to move the claw bar toward and away from the film and said last mentioned means comprise a magnet arranged on at least one of the blades of the shutter and cooperating with a reed pick-up device to transmit a control impulse to the electromagnet, and wherein the reed device transmits impulses recurring at a given frequency to the input of an electronic circuit which controls the electromagnet, said circuit having two bistable devices to transform the impulses transmitted by the reed device into impulses having frequencies of respectively half and a quarter of that transmitted by the reed device, a monostable device in which the time corresponds with two impulses transmitted by the reed device and a NAND gate which allows impulses from the reed device to pass through during the impulses transmitted by said monostable.