Slide projection overlapping apparatus

Claim 1

A slide projection overlapping apparatus comprising: a plurality of slide projecting means; power supply means for providing currents to said slide projecting means for the generation of luminous energy outputs from said projecting means; switching means coupled to said supply means for opening or closing said supply means; means for generating a pulse signal for shifting the connections between said projecting means; switch control means for selectively controlling the operation of said switching means in response to pulse signal generating means; voltage control means coupled to said supply means for varying the levels of illumination of said projecting means, said voltage control means being responsive to the application of a voltage thereto from a power supply source to cause the voltages controlled by said voltage control means to linearly increase until predetermined voltage levels are reached, said voltage control means also being responsive to the cut-off voltage from a power supply source to cause the voltages controlled by said voltage control means to linearly decrease until predetermined voltage levels are reached, said voltage control means also including time delay means for delaying the commencement of decrease of voltage levels when said supply source voltage is cut off; and wherein said power supply means is an AC voltage source provided with rectifier means for rectifying the alternating current from said AC voltage source, and wherein said voltage control means further includes time constant circuit means comprising a capacitor and a first resistor connected through said switching means to an output terminal of said rectifier means, a second resistor arranged to be connected to said capacitor when said switching means cuts off said supply means, a second switching means coupled to said supply means for controlling the supply of alternating current from said AC voltage source and a trigger means for generating a pulse for triggering the trigger circuit of said second switching means in accordance with the output of said capacitor, thereby the phase angle of conduction of said second switching means is controlled in accordance with the output of the time constant circuit so that the voltage output of said voltage control means will linearly increase or decrease. 2. A slide projection overlapping apparatus as described in claim 1, wherein said second switching means is a triac.

Claim 4

An apparatus for projecting images from a pair of slide projectors onto a common screen area, comprising; an electric power source for supplying current to lamps of each of said slide projectors; a first pair of switching means for connecting and disconnecting said electric power source to a corresponding projector lamp; a D.C. power source; a pair of time constant circuits having a resistor and a capacitor; means for producing a projector change over signal; a change over mechanism which connects one of said pair of time constant circuits to said D.C. power source and disconnects the other circuit from said D.C. power source in correspondence with said change over signal; a discharge path having resistor means, which is connected in parallel to the capacitor of the other time constant circuit by said change over mechanism; a pair of trigger pulse generating means connected to each of said time constant circuits to produce a signal passing through said pair of switching means corresponding to said time constant circuits; a voltage source for adding a voltage to the capacitor of one of said time constant circuits for delaying the start of the dimming of the projector lamp a predetermined time corresponding to said circuit when said change over mechanism disconnects one of the pair of time constant circuits from said D.C. power source; whereby one of the projector lamps commences illumination in association with said change over signal and the other lamp illumination decrease after a predetermined time.

Claim 5

An apparatus for projecting images from a pair of slide projectors onto a common screen area, comprising; an electric power source for supplying current to lamps of each of said slide projectors; a first pair of switching means for connecting and disconnecting said electric power source to a corresponding projector lamp; a D.C. power source; a pair of time constant circuits having a resistor and a capacitor; means for producing a projector change over signal; a change over mechanism which connects one of said pair of time constant circuits to said D.C. power source and disconnects the other circuit from said D.C. power source in correspondence with said change over signal; a discharge path having resistor means, which is connected in parallel to the capacitor of the other time constant circuit by said change over mechanism; a pair of trigger pulse generating means connected to each of said time constant circuits to produce a signal passing through said pair of switching means corresponding to said time constant circuits; a voltage source for adding a voltage to the capacitor of one of said time constant circuits for delaying the start of the dimming of the projector lamp a predetermined time corresponding to said circuit when said change over mechanism disconnects one of the pair of time constant circuits from said D.C. power source; whereby one of the projector lamps commences illumination in association with said change over signal and the other lamp illumination decrease after a predetermined time.