Variable projector speed control

Claim 2

In a motion picture projector having a film with successive image frames therealong, a drive system for intermittently advancing said film at varying speeds by the step distance between successive frames including a drive pawl to produce a step advance of the film for each reciprocation thereof, pulsing means, means controlled by said pulsing means for producing successive reciprocations of said pawl, and adjustable means for varying the time interval between said successive pulses.

Claim 3

The projector set forth in claim 1 wherein said drive means includes a rotatable cam for reciprocating said drive pawl, a drive motor for said cam, and an integrating clutch actuated by said pulsing means and connected between said motor and cam for producing a reciprocation of said drive pawl for each of said pulses.

Claim 4

The projector set forth in claim 2 wherein said cam is adapted to produce one reciprocation of said drive pawl for each revolution of the cam, and said integrating clutch is of a one-revolution type including a solenoid controlled by said pulsing means for controlling the clutch.

Claim 5

The projector set forth in claim 3 wherein said clutch includes a coupling spring with a single catch element and a cooperating latch for holding the clutch disengaged, and wherein said solenoid is actuated by each pulse of said pulsing means for an interval less than the time duration of one revolution of said cam to produce one step advance of said film for each pulse.

Claim 6

The projector set forth in claim 4 wherein said pulsing means is a monostable multivibrator operating in conjunction with a variable-resistance unijunction transistor, including an RC timing circuit having a rheostat for varying the time interval between successive pulses over a range from approximately 24 pulses per second to a lower limit of one pulse for each half second.

Claim 7

The projector set forth in claim 5 including a start switch for supplying continuous current to said solenoid to produce a step advance of said film at the rate of drive of said cam by said motor, an on-off switch for said pulsing means, and means rendered operative as said rheostat of said timing circuit is moved from minimum setting for closing said on-off switch to start said pulsing means and for concurrently cutting off said continuous current supply to said solenoid whereby to cause said solenoid to be controlled solely by said pulsing means.

Claim 8

In a motion picture projector having a film with successive image frames and sprocket holes: the combination of a drive means engageable with said film including a rotating drive shaft and a single revolution integrating clutch for advancing the film by one frame per revolution of said shaft, said clutch including a latch pawl and a single cooperating catch element for holding the clutch disengaged and for engaging the clutch for one revolution of the shaft responsive to a momentary release of the pawl for a time interval less than that of one revolution, a solenoid for releasing said pawl, means for supplying a voltage to said solenoid to cause said film to be advanced at a steady rate of one frame for each revolution of said shaft, a drive amplifier between said voltage supply means and said solenoid having a clamp circuit energizable to cut off the amplifier, a pulse generator for alternatively activating said solenoid to step said film ahead at a rate of one frame for each pulse of said generator, and an on-off switch for said generator for activating said generator and concurrently clamping said amplifier when the switch Is in on position and for stopping said generator and reabling said amplifier when the switch is in off position.

Claim 9

In a motion picture projector having a film with successive image frames and sprocket holes: the combination of a drive means engageable with said film including a rotating drive shaft and a single revolution integrating clutch for advancing the film by one frame per revolution of said shaft, said clutch including a latch pawl and a single cooperating catch element for holding the clutch disengaged and for engaging the clutch for one revolution of the shaft responsive to a momentary release of the pawl for a time interval less than that of one revolution, a solenoid for releasing said pawl, means for supplying a voltage to said solenoid to cause said film to be advanced at a steady rate of one frame for each revolution of said shaft, a drive amplifier between said voltage supply means and said solenoid having a clamp circuit energizable to cut off the amplifier, a pulse generator for alternatively activating said solenoid to step said film ahead at a rate of one frame for each pulse of said generator, and an on-off switch for said generator for activating said generator and concurrently clamping said amplifier when the switch Is in on position and for stopping said generator and reabling said amplifier when the switch is in off position.

Claim 10

The combination set forth in claim 7 wherein said generator includes a variable time circuit having a rheostat movable from a minimum setting to lower progressively the rate of said pulse generator, and means for turning said generator switch on and off as said rheostat is moved out of and back into said minimum setting.

Claim 11

The combination set forth in claim 8 wherein said generator is adapted to provide a pulse rate approximately equal to the rate of rotation of said shaft when said rheostat is at minimum setting.

Claim 12

The combination set forth in claim 7 including a flip-flop circuit having first and second outputs for supplying DC voltages at the first and second outputs respectively when the circuit is toggled and reset, said first output being connected to said amplifier to supply said DC voltage to said solenoid when the flip-flop circuit is in a toggled condition, an electronic switch having a control connection to said second output of said flip-flop circuit for cutting off the voltage supply for said generator and clamp circuit when the flip-flop circuit is in a reset condition, and means for toggling said flip-flop circuit for providing a steady activation of said solenoid to cause said film to be advanced at the rate of rotation of said shaft when said generator switch is in off position and for closing said electronic switch to cause said film to be advanced at the rate of pulsing of said generator when said generator switch is in on position.

Claim 13

The combination set forth in claim 10 including means for picking up a signal from said film at a predetermined frame for resetting said flip-flop circuit to cut off the steady current to said solenoid and to shift said electronic switch to open condition to stop the drive of said film when said predetermined frame is reached.

Claim 14

The combination set forth in claim 11 wherein said toggling means comprises a manual start switch connected to a set input terminal of said flip-flop circuit.