Camera mechanism

A camera mechanism in which a shutter plate operating member is slidably mounted for movement between a cocked position and rest position and biased by biasing means into said rest position, and in which actuator means is provided for effecting said sliding movement of said shutter plate operating member, said actuator means being adapted to be connected to a film wind-on device of a camera, wherein said actuator means comprises a cam mounted for rotation in said mechanism and an abutment surface on said shutter plate operating member for cooperating with said cam, so that, in use, rotation of the cam causes said shutter plate operating member to move from its rest position to its cocked position against the urging of said biasing means, said cam being provided with force-varying means whereby greater force is needed to rotate the cam over an initial part of the cocking stroke of the shutter plate operating member than is needed for a final part of said cocking stroke.

FIELD OF THE INVENTION 
The present invention relates to camera mechanisms and to cameras including 
such mechanisms. 
OBJECT OF THE INVENTION 
It is an object of the present invention to provide an improved camera 
mechanism, and in particular a camera mechanism which has an improved 
"feel" or tactile sensation for the user so that the user can determine 
more clearly the state (wound on or not wound on) of the camera. Such a 
mechanism would be particularly useful in inexpensive mass produced 
cameras, including disposable cameras. The users of such cameras generally 
take photographs infrequently, perhaps only during annual vacations and on 
certain special occasions. The users do not wish to read instructions on 
each infrequent occasion on which they take photographs. Accordingly, it 
is very important that the state of the camera and the operation of the 
camera be apparent from the camera itself without reference to any written 
instruction. 
SUMMARY OF THE INVENTION 
The present invention provides a camera mechanism in which a shutter plate 
operating member is slidably mounted for movement between a cocked 
position and a rest position and biassed by biassing means into said rest 
position, and in which actuator means is provided for effecting said 
sliding movement of said shutter plate operating member, said actuator 
means being adapted to be connected to a film wind-on device of a camera, 
wherein said actuator means comprises a cam mounted for rotation in said 
mechanism and an abutment surface on said shutter plate operating member 
for cooperating with said cam, so that, in use, rotation of the cam causes 
said shutter plate operating member to move from its rest position to its 
cocked position against the urging of said biassing means, said cam being 
provided with force-varying means whereby greater force is needed to 
rotate the cam over an initial part of the cocking stroke of the shutter 
plate operating member than is needed for a final part of said cocking 
stroke. 
The present invention also provides a camera having a camera mechanism as 
defined hereinbefore. 
The effect of varying the force needed to rotate the cam, in the manner 
defined, is to provide a camera incorporating the mechanism with improved 
"feel" when the film wind-on device of the camera is used to wind on the 
film and cock the camera. More particularly, in the case of a camera which 
has not been cocked, the user may apply pressure to the wind-on mechanism 
and will then encounter a relatively strong spring resistance. This spring 
resistance indicates to the user that the camera has not been cocked. If 
the user does not wish to immediately take a photograph the user may 
choose to leave the camera in the uncocked state, and can do so by simply 
suspending further pressure on the wind-on mechanism, safe in the 
knowledge that the previously applied pressure has not resulted in the 
camera becoming cocked. Alternatively, if the user does wish to take a 
photograph immediately, the user may choose to cock the camera and this is 
done by continuing or increasing the pressure so as to overcome the strong 
spring resistance, and as the pressure is continued or increased the 
spring resistance gradually decreases and ceases altogether indicating to 
the user that the camera is now cocked. Preferably the force-varying means 
comprises a second cam coaxially mounted for rotation with the first cam, 
said second cam having a helical cam profile which progressively decreases 
its radius of curvature in the direction of rotation of the cam during a 
cocking stroke. A pressure applicator is provided to bear upon the second 
cam and is, e.g. spring-biassed to apply pressure to the second cam. At an 
initial part of the cocking stroke the profile of the second cam will have 
a relatively large radius and thus rotation of the cams will be more 
impeded by the pressure applicator than will be the case at a later part 
of the cocking stroke when the profile of the second cam will have a 
relatively small radius. 
Ratchet and pawl means may be provided to ensure that the actuator means 
can rotate in one direction only. 
A stop member may be provided on the pressure applicator to prevent 
over-rotation of the actuator means by co-acting with a step in the cam 
profile of the second cam. 
The pressure applicator may be provided with an extension so that upon 
firing of the camera, when the shutter plate operating member returns from 
its cocked position to its rest position under the action of its biassing 
means, the extension is contacted by the shutter plate operating member 
and the stop member is moved out of engagement with the step in the cam 
profile of the second cam.

DESCRIPTION OF PREFERRED EMBODIMENT 
Referring to the drawings there is shown a shutter housing comprising a 
front wall 1 and a rear wall 2. The housing includes a printed circuit 
board 3 as well as various components of the camera operating mechanism as 
will be described in more detail hereinafter. The mechanism includes a 
shutter plate operating member 4. In operation it slides from a rest 
position (on the left in FIG. 1, on the right in FIG. 2) to a cocked 
position (on the right in FIG. 1, on the left in FIG. 2) during its 
cocking stroke, as indicated by arrow A. In so doing a pawl 5 mounted upon 
a resilient arm 6 deflects and passes beneath a pawl 7 of a pivotably 
mounted shutter plate 8 (which plate is prevented from counter-clockwise 
movement by a stop 9). Once this has happened, a projection 10 (shown only 
in FIG. 2) of the shutter plate operating member 4 is engaged by a trigger 
device (not shown). The shutter plate operating member 4 is biassed to the 
rest position by a spring 11 secured to finger 12. 
When the trigger device is actuated the spring 11 draws the shutter plate 
operating member 4 to the rest position and pawls 5 and 7 co-act 
momentarily to cause the shutter plate 8 to pivot and so to open and close 
a shutter aperture (not shown) of the camera. 
The shutter plate operating member 4 is provided with a rearward projection 
13 and an extension 4a, both of which are located outside the shutter 
housing 1,2. 
Mounted for rotation together about an axis perpendicular to the direction 
of sliding movement of shutter plate operating member 4 are a first cam 14 
and a second cam 15. In use, rotation of these elements is effected by a 
film wind-on lever or knob (not shown). 
Cam 15 is provided with a helical cam profile 16 which progressively 
decreases its radius of curvature with angular orientation. A 
spring-biassed (by means of a spring, not shown) pressure applicator 17 is 
mounted for pivotal movement about a pivot 18 and bears upon cam profile 
16. The applicator 17 includes a stop member 19 adapted to co-act with a 
step 20 provided in cam profile 16 and further includes an arm 21. A pawl 
24 mounted on the camera housing is provided to cooperate with a ratchet 
25 mounted on the cam assembly 14, 15 to ensure that the assembly can 
rotate in on direction only. 
From an initial condition in which the shutter plate operating member 4 is 
in the rest position, as the film winder is rotated a step 22 in cam 14 
co-acts with rearward projection 13 of shutter plate operating member 4 
and pushes it in the direction indicated by arrow A to the cocked 
position. As cam 15 correspondingly rotates, the pressure exerted upon the 
cam profile 15 by applicator 16 progressively decreases to improve the 
"feel" of the mechanism. 
A rotation continues, the shutter plate operating member 4 eventually 
reaches its cocked position. At this point, cam 14 can no longer urge 
shutter operating member 4 any further in the direction indicated by arrow 
A because of a step 23 provided in cam 14. Moreover at this point stop 
member 19 of pressure applicator 17 co-acts with step 20 of cam profile 16 
to prevent further rotation of assembly 14, 15 and hence of the film 
winder. 
When the shutter button or trigger of the camera (not shown) is pressed, 
rearward projection 10 of shutter plate operating member 4 is released, 
shutter plate operating member 4 moves in the opposite direction to arrow 
A, towards the rest position, shutter plate 8 is momentarily actuated and 
the shutter plate operating member 4 continues to move towards the rest 
position. In the rest position extension 4a of shutter plate operating 
member 4 has struck arm 21 of pressure applicator 17 and has disengaged 
stop member 19 of applicator 17 from step 20 of cam profile 16 thereby 
once more to allow rotation of assembly 14, 15. 
The present invention may be performed otherwise than as has been 
particularly described; all modifications, changes and variations which 
would be apparent to one skilled in the art are within the scope of the 
invention.