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US 4,306,798 AGranted
Electromagnetically driven slit exposure shutter
AssigneeCanon Kabushiki Kaisha
InventorsTakashi Uchiyama, Ryoichi Suzuki, Nobuaki Date, Yoji Sugiura
Life of this patent
Estimating the term…
Abstract
A slit exposure shutter having the front and rear screens thereof respectively arranged to be driven by a source of an electromagnetic driving force is provided with a minimum slit width insuring means which prevents uneven exposure resulting from difference in travelling speed between the front and rear shutter screens during a high speed shutter operation and particularly prevents a total absence of the slit, the shutter is also provided with a nullifying means which nullifies the insuring means when the shutter screens are on their return travels.
Claims13
An electromagnetically driven slit exposure shutter for a camera, comprising:
- a front shutter screen which is arranged to travel when it is driven by an electromagnetic drive source;
- a rear shutter screen which travels when it is driven by another electromagnetic drive source and is arranged to form a slit for effecting an exposure between it and said front shutter screen;
- a closing-travel preventing device which is arranged to keep the width of said slit formed between said front and rear shutter screens at a value larger than a predetermined value;
- means for nullifying said closing-travel preventing device to prevent the formation of said slit when said front and rear shutter screens are on their return travels;
- said closing-travel preventing device including a displacement member which travels together with said front or rear shutter screen and also including restricting means, which, for an exposure effecting travel operation of the shutter, controls said displacement member to have the displacement member moved to a position in which the width of said slit is kept above said predetermined value and, for the return travels of said front and rear shutter screens, controls said displacement member to have it moved to another position in which said front and rear shutter screens are not allowed to form any slit between them.
2 more elements
An electromagnetically driven slit exposure shutter for a camera, comprising:
- a front shutter screen which is arranged to travel when it is driven by an electromagnetic drive source;
- a rear shutter screen which travels when it is driven by another electromagnetic drive source and is arranged to form a slit for effecting an exposure between it and said front shutter screen;
- a closing-travel preventing device which is arranged to keep the width of said slit formed between said front and rear shutter screens at a value larger than a predetermined value;
- means for nullifying said closing-travel preventing device to prevent the formation of said slit when said front and rear shutter screens are on their return travels;
- electromagnetic coils for driving said front and rear shutter screens;
- power supply circuits for supplying driving currents to said electromagnetic coils in the normal and reverse directions, said power supply circuits including constant current circuits to cause said electromagnetic coils to drive said front and rear shutter screens with a constant driving force respectively;
- means for supplying said front screen driving electromagnetic coil with a greater driving current than said rear screen driving electromagnetic coil during the return travels of said front and rear shutter screens.
4 more elements
An electromagnetically driven slit exposure shutter for a camera, comprising:
- a front shutter screen which is arranged to travel when it is driven by an electromagnetic drive source;
- a rear shutter screen which travels when it is driven by another electromagnetic drive source and is arranged to form a slit for effecting an exposure between it and said front shutter screen;
- a closing-travel preventing device which is arranged to keep the width of said slit formed between said front and rear shutter screens at a value larger than a predetermined value;
- means for nullifying said closing-travel preventing device to prevent the formation of said slit when said front and rear shutter screens are on their return travels;
- electromagnetic coils for driving said front and rear shutter screens;
- power supply circuits for supplying driving currents to said electromagnetic coils to the normal and reverse directions, said power supply circuits including constant current circuits to cause said electromagnetic coils to drive said front and rear shutter screens with a constant driving force respectively;
- means for delaying somewhat the starting time of the power supply to said rear screen driving electromagnetic coil to make it somewhat later than the starting time of the power supply to said front screen driving electromagnetic coil at the time of the return travels of said front and rear shutter screens.
4 more elements
An electromagnetically driven slit exposure shutter comprising:
- a front shutter screen driven by an electromagnetic driving source;
- a rear shutter screen driven by an electromagnetic driving source and forming a slit for exposure between the front shutter screen and the rear shutter screen;
- a displacement member which runs along a constant path with one of the front and rear shutter screens;
- an engagement member which runs along a constant path with the other of the front and rear shutter screens;
- and
- electromagnetic means for shifting the displacement member to a position enabling engagement with the engagement member at an initial stage of the running for exposure and for maintaining the width of the slit greater than a predetermined value during the shutter travel.
3 more elements
Dependencies are inferred from the claim text.