1461160734-c8d611df-6825-4b07-8a53-cf1ad1a9edab

1. A lens-fitted photo film unit comprising:
a housing pre-loaded with unexposed photo film;
a flash device for emitting flash light; and
an attaching portion disposed on said housing, and adapted to securing of said flash device in a removable manner, said attaching portion being used for securing a dummy block in producing a type of said lens-fitted photo film unit lacking said flash device, wherein a peripheral contour of the flash device is approximately the same as a peripheral contour of the dummy block;
wherein said flash device includes:
a flash emitter having a flash discharge tube;
a flash circuit board for causing said flash discharge tube to illuminate in synchronism with an exposing operation;
a battery for supplying said flash circuit board with power; and
a tightly closed flash case for containing said flash emitter, said flash circuit board, and said battery.
2. A lens-fitted photo film unit as defined in claim 1, wherein said housing includes:
a main body pre-loaded with said unexposed photo film;
a front cover secured to a front of said main body;
a rear cover secured to a rear of said main body;
a recess, formed in said front cover to constitute said attaching portion, the recess being sized to accommodate a selected one of said flash device and said dummy block.
3. A lens-fitted photo film unit as defined in claim 2, wherein an outer surface of both said flash device and said dummy block lies in an extension of a surface of said front cover.
4. A lens-fitted photo film unit as defined in claim 3, wherein said recess and said flash device are L-shaped as viewed downwards.
5. A lens-fitted photo film unit as defined in claim 3, wherein said recess and said flash device are substantially box-shaped.
6. A system for selectively producing a lens-fitted photo film unit either with or without a flash capability, the system comprising:
a housing pre-loaded with unexposed photo film, the housing having a first type of attachment element disposed thereon;
a flash device capable of emitting flash light, the flash device having a second type of attachment element configured to allow the housing and flash device to be secured to one another;
a dummy block having a peripheral contour that is approximately the same as a peripheral contour of the flash device, the dummy block having the second type of attachment element;
wherein the lens-fitted photo film unit can be assembled so as to have flash capability by attaching the flash device to the housing without the dummy block, and the lens-fitted photo film unit can be assembled so as not to have flash capability by attaching the dummy block to the housing instead of the flash device;
wherein the first type of attachment element comprises electrical contacts that allow for control of the flash device.

The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.

1. A centrifugal concentrator for separating particulate material of higher specific gravity from particulate material of lower specific gravity comprising:
a) a hollow drum having an open end and interior surface;
b) means for rotatably supporting the drum on an axis;
c) drive means for rotating the drum about the axis; and
d) material supply means to deliver the particulate material into the end of the drum spaced from the open end;

wherein the interior surface of the drum comprises a migration zone, a retention zone above the migration zone for retaining said particulate material of higher specific gravity and a lip zone above the retention zone, and where the respective lengths of said migration, retention and lip zones and the relative degrees of inclination of the migration and lip zones are selected to provide a sufficient component of force on the particulate material to expel the lighter particulate material from the drum and to permit the heavier particulate material to be retained in the retention zone, and wherein the lip zone has a variable diameter provided by a flexible cylindrical member having an inner diameter which is selectively and uniformly decreased or increased by variation of the pressure applied to the member, wherein pressure is variably applied to the outer surface of said flexible cylindrical member by a flexible annular member whereby by decreasing the inner diameter of the lip zone the volume of material able to be retained in said retention zone is increased.
2. The concentrator of claim 1 wherein the rate of decrease of the diameter is controlled through control of a supply of pressurized fluid.
3. The concentrator of claim 2 wherein said pressurized fluid is compressed air.
4. A method of operating a centrifugal concentrator to maximize the recovery of target particles, wherein said centrifugal concentrator comprises a) a hollow drum having an open end and interior surface; b) means for rotatably supporting the drum on an axis; c) drive means for rotating the drum about the axis; and d) material supply means to deliver the particulate material into the end of the drum spaced from the open end; and wherein the interior surface of the drum comprises a migration zone, a retention zone above the migration zone for retaining said particulate material of higher specific gravity and a lip zone above the retention zone, and where the respective lengths of said migration, retention and lip zones and the relative degrees of inclination of the migration and lip zones are selected to provide a sufficient component of force on the particulate material to expel the lighter particulate material from the drum and to permit the heavier particulate material to be retained in the retention zone, and wherein the lip zone has a variable inner diameter whereby by decreasing the inner diameter of the lip zone the volume of material able to be retained in said retention zone is increased, said method comprising varying the diameter of the lip zone over time and controlling the rate of decrease of the diameter of the lip zone over the centrifuging cycle.
5. The method of claim 4 wherein said decrease in diameter of the lip zone is carried out in a series of discrete reductions.
6. The method of claim 4 wherein said decrease in diameter of the lip zone is carried out continuously.
7. The method of claim 4 wherein the rate of decrease in diameter of the lip zone is carried out uniformly.
8. The method of claim 4 wherein the rate of decrease in diameter of the lip zone is varied over the course of the concentration cycle.
9. The method of claim 4 wherein the rate of decrease in diameter of the lip zone is more rapid earlier in the concentrating cycle than later.
10. The method of claim 4 wherein the rate of decrease in diameter of the lip zone is more rapid later in the concentrating cycle than earlier.
11. A centrifugal concentrator for separating particulate material of higher specific gravity from particulate material of lower specific gravity comprising:
a) a hollow drum having an open end and interior surface;
b) means for rotatably supporting the drum on an axis;
c) drive means for rotating the drum about the axis; and
d) material supply means to deliver the particulate material into the end of the drum spaced from the open end;