Anti-backup mechanism for preventing reverse rotation of film winder in camera

A camera comprises manually rotatable film winding means, and a uni-directional clutch coupled to the film winding means to permit film winding rotation of the film winding means and to prevent reverse rotation of the film winding means. The film winding means includes a rotatable winder wheel having a toothed periphery. The uni-directional clutch includes a rotatable idler wheel having a toothed periphery engaging the toothed periphery of the winding wheel and provided with less teeth than the toothed periphery of the winding wheel, and a coil spring coiled tightly about a shank of the idler wheel and having an end portion secured with respect to the shank. The coil spring tightens on the shank to prevent the idler wheel and the winding wheel from being engagingly rotated when reverse rotation of the film winding means is attempted and relaxes on the shank to permit the idler wheel and the winding wheel to be engagingly rotated when film winding rotation of the film winding means is initiated.

FIELD OF THE INVENTION 
The invention relates generally to the field of photography, and in 
particular to cameras. More specifically, the invention relates to an 
anti-backup mechanism or uni-directional clutch for preventing reverse 
rotation of a film winder in a one-time-use or other relatively simple 
camera. 
BACKGROUND OF THE INVENTION 
Film and cameras that are all in one, commonly referred to as single-use or 
one-time-use cameras, have recently become well known. Typically, the 
one-time-use camera is a simple point-and-shoot type comprising a main 
body part which supports a fixed-focus taking lens, a film metering 
mechanism including a rotatable metering sprocket and a pivotable metering 
lever, a manually rotatable film winder thumbwheel, a pivotable 
single-blade shutter, a manually depressible shutter release button, a 
rotatable frame counter for indicating the number of exposures remaining 
for picture-taking, a direct see-through viewfinder, and a conventional 35 
mm film cartridge. A pair of front and rear cover parts house the main 
body part between them to complete the camera assembly. The rear cover 
part connects to the main body part and/or to the front cover part to make 
the main body part light-tight. A decorative cardboard outer box contains 
the camera assembly and has respective openings for the taking lens, the 
shutter release button, the film advance thumbwheel, the viewfinder, and 
the frame counter. 
To operate the one-time-use camera, the photographer manually rotates the 
thumbwheel in engagement with the protruding end of a spool inside the 
cartridge, to rotate the spool in order to wind an exposed frame of a 
filmstrip into the cartridge. The winding movement of the filmstrip the 
equivalent of slightly more than one frame width rotates the metering 
sprocket in engagement with the filmstrip, to decrement the frame counter 
to its next lower-numbered setting, and to pivot the metering lever into 
engagement with the thumbwheel to prevent further winding rotation of the 
thumbwheel. Then, manually depressing the shutter release button to take a 
picture unlatches a spring-driven high energy lever which pivots the 
shutter blade to momentarily uncover the taking lens, and pivots the 
metering lever out of engagement with the thumbwheel to again permit 
manual rotation of the thumbwheel to wind an exposed frame of the 
filmstrip into the cartridge. When the maximum number of exposures 
available on the filmstrip are exposed and the filmstrip is completely 
rewound into the cartridge, the one-time-use camera is given to a 
photofinisher who tears the outer box off the camera unit, separates the 
rear cover part from the main body part, and removes the cartridge with 
the filmstrip from the main body part. Then, he removes the filmstrip from 
the cartridge to develop the negatives and make prints for the customer, 
and he forwards the used camera parts to the manufacturer for recycling, 
i.e. remanufacture. 
It is desirable to make operation of the one-time-use camera relatively 
quiet. In this connection, it is customary for an anti-backup pawl to be 
spring-pivoted into continuous engagement with a toothed periphery of the 
thumbwheel to prevent the thumbwheel from being manually rotated in a 
direction opposite to the direction of winding rotation. However, 
engagement of the pawl with the toothed periphery produces a periodic 
ratcheting sound when the thumbwheel is windingly rotated. This noise 
presents a problem. 
In traditional (re-usable) cameras, such as shown in prior art U.S. Pat. 
No. 1,133,128, issued Mar. 23, 1915, and No. 2,220,599, issued Nov. 5, 
1940, it is suggested that a helical coil spring be coaxially disposed 
about the shaft of a manually rotatable film winding knob or handle, to be 
used as a uni-direction clutch to permit winding rotation of the knob or 
handle and to prevent reverse rotation of the knob or handle. Generally 
speaking, the coil spring is quieter than the anti-backup pawl. However, 
the coil spring as disposed does not provide a relatively strong 
counter-rotation force as compared to the anti-backup pawl. 
SUMMARY OF THE INVENTION 
A camera comprising manually rotatable film winding means, and a 
uni-directional clutch coupled to the film winding means to permit film 
winding rotation of the film winding means and to prevent reverse rotation 
of the film winding means, is characterized in that: 
the film winding means includes a rotatable winder wheel having a toothed 
periphery; and 
the uni-directional clutch includes a rotatable idler wheel having a 
toothed periphery engaging the toothed periphery of the winding wheel and 
provided with less teeth than the toothed periphery of the winding wheel, 
and a coil spring coiled tightly about a shank of the idler wheel and 
having an end portion secured with respect to the shank, whereby the coil 
spring will tighten on the shank to prevent the idler wheel and the 
winding wheel from being engagingly rotated when reverse rotation of the 
film winding means is attempted and will relax on the shank to permit the 
idler wheel and the winding wheel to be engagingly rotated when film 
winding rotation of the film winding means is initiated. 
In this instance, the coil spring provides a relatively strong 
counter-rotation force as compared to the coil spring in prior art U.S. 
Pat. No. 1,133,128 and No. 2,220,599. Preferably the toothed periphery of 
the winder wheel is provided with at least three times as many teeth as 
the toothed periphery of the idler wheel to provide at least a 3:1 gear 
ratio.

DETAILED DESCRIPTION OF THE INVENTION 
The invention is disclosed as being embodied preferably in a one-time-use 
camera. Because the features of a one-time-use camera are generally, the 
description which follows is directed in particular only to those elements 
forming part of or cooperating directly with the disclosed embodiment. It 
is to be understood, however, that other elements may take various forms 
known to a person of ordinary skill in the art. 
Referring now to the drawings, FIG. 1 depicts a one-time-use or single-use 
camera 10 having a plastic main body part 12, and a pair of plastic front 
and rear cover parts 14 and 16 which connect to one another to house the 
main body part between them in order to complete the camera assembly. The 
main body part 12 is adapted to be nested in the front cover part 14, and 
the rear cover part 16 is intended to be fitted to the main body part 12 
to make the main body part light-tight. 
As shown in FIG. 1, the main body part 12 has integral cartridge-receiving 
and film roll chambers 17 and 18 for a conventional 35 mm film cartridge 
19 and a film supply spool 20. The chambers 17 and 18 are located at 
opposite sides of a backframe or film exposure opening 21, at which 
successive frames of a filmstrip 22 are exposed during picture-taking. The 
filmstrip 22 comes stored in a roll form on a cartridge spool 23 rotatably 
supported inside the film cartridge 19, and has a longitudinal series of 
edge perforations 24 included along a film leader 25 which protrudes from 
the film cartridge. However, the filmstrip 22 beginning with the film 
leader 25 is substantially pre-wound onto the supply spool 20 to permit 
successive exposed frames to be returned to the film cartridge 19 after 
each film exposure. 
The main body part 12 supports various known camera elements which are 
attached to the main body part before it is nested in the front cover part 
14 and the front and rear cover parts 14 and 16 are connected to one 
another to house the main body part between them. These camera elements 
are a fixed-focus taking lens 26 which is sandwiched between a snap-on 
lens retainer 28 and a lens support plate 30, connected to the main body 
part at its front; a shutter-flash synchronization switch contact 32 
attached to the lens support plate 30; a pair of front and rear viewfinder 
lenses 34 (only the front viewfinder lens is clearly shown in FIG. 1) and 
an integral frame magnifier 35, connected to the main body part at its 
top; a shutter mechanism comprising a keeper plate 36 having an integral 
manually depressible shutter release button 37, a pivotable shutter blade 
40, a shutter return spring 42, a pivotable high-energy lever 44 for 
actuating the shutter blade to pivot the blade open in order to uncover 
the taking lens to make a film exposure, and a lever actuating spring 46; 
a film advancing and metering mechanism comprising a manually rotatable 
thumbwheel or peripherally toothed winder wheel 48 for engaging an exposed 
end 49 of the cartridge spool 23 to rotate the spool in order to wind an 
exposed frame of the filmstrip 22 into the film cartridge 19 after each 
film exposure, a rotatable film metering sprocket 50 having an annular 
array of peripheral teeth 51 for successively engaging the respective 
perforations 24 in the filmstrip, and a cooperating rotatable metering cam 
52, pivotable metering lever 54 and metering spring 56 which operate in a 
known manner with a rotatable frame counter 60 (made readable via the 
frame magnifier 37), the winder wheel 48, and the metering sprocket 50 to 
decrement the frame counter to its next lower-numbered setting and to lock 
the winder wheel (until the shutter release button 37 is depressed) after 
the winder wheel is rotated to wind an exposed frame into the film 
cartridge 19; a light baffle 80 which forms the backframe opening 21; and 
an electronic flash illumination assembly 82 comprising a circuit board 
84, a capacitor 86, a flash emission lens 88, and a flash battery 90. The 
battery is held in a battery-receiving chamber 91 in the main body part 
12. A pair of front and rear decorative labels 92 cover central portions 
of the front and rear cover parts 14 and 16 after the front and rear cover 
parts are connected to one another to house the main body part 12 between 
them. 
As shown in FIG. 1, a breakaway cartridge-cover door 94 and a breakaway 
battery-cover door 96 are provided on the rear cover part 16, opposite the 
cartridge-receiving chamber 17 and the battery-receiving chamber 91. The 
two cover doors 94 and 96 can be pivoted open along respective hinge 
grooves along the inside of the rear cover part 16 to remove the film 
cartridge 19 and the battery 90 from the chambers 17 and 91. 
The rear cover part 16 has three identical corner pins 100 intended to be 
easily received only slightly in respective corner pin-holes (not shown) 
in the front cover part 14 when the main body part 12 is nested in the 
front cover part and the front and rear cover parts are relatively 
arranged in an intermediate partially-separated assembly position. At the 
same time an identical pair of top and bottom center hooks 104 on the rear 
cover part 16 are locally forced into respective top and bottom center 
slots 106 (only the top one is shown in FIG. 1) in the front cover part 14 
to prevent the front and rear cover parts from becoming further separated. 
Since the three corner pins 100 in the rear cover part 16 cannot be 
inserted further into the three corner pin-holes in the front cover part 
14 without some force, and the top and bottom center hooks 104 in the rear 
cover part are engaged with the front cover part at its two center slots 
106, a center portion of the rear cover part will be slightly bowed or 
flexed inwardly toward the metering sprocket 50 and there is some 
separation between the rear cover part and the main body part 12. 
The cartridge-cover door 94 and the battery-cover door 96 each have an 
identical pair of end holes 108 adapted to mate with respective pairs of 
hooks 110 (only one pair is shown in FIG. 1) at opposite ends of the front 
cover part 16 to connect the front and rear cover parts 14 and 16 to one 
another when the main body part 12 is nested in the front cover part and 
the front and rear cover parts are relatively arranged in a final 
non-separated assembly position. At the same time the three corner pins 
100 in the rear cover part 16 are machine press-forced further into the 
three corner pin-holes in the front cover part 14 to discontinue the 
inward bowing of the center portion of the rear cover part, allowing the 
rear cover part to inherently straighten. Thus, the rear cover part 16 is 
fitted to the main body part 12 to make the main body part light-tight. 
According to the invention, the toothed periphery of the winder wheel 48 
engages a similar-pitch toothed periphery of a rotatable idler wheel 112 
as shown in FIG. 2. The winder wheel 48 has at least three times as many 
peripheral teeth 114 as compared to the number of peripheral teeth 116 on 
the idler wheel 112, to provide at least a 3:1 gear ratio. A helical coil 
spring 118 is coiled tightly about a shank 120 of the idler wheel 112, and 
it has an end portion 122 that is anchored to a fixed pin 124 to secure 
the end portion with respect to the shank. See FIGS. 2 and 3. Preferably, 
the coil spring 118 has a diameter that is slightly less than the diameter 
of the shank 120, to obtain a compression fit of the coil spring on the 
shank. 
When the winder wheel 48 is manually rotated in a film winding direction 
126 (in engagement with the exposed end 49 of the cartridge spool 23 to 
rotate the spool in order to wind an exposed frame of the filmstrip 22 
into the film cartridge 19), as indicated in FIG. 2, the idler wheel 112 
is oppositely rotated in an uncoiling direction of the coil spring 118. 
Thus, as shown in FIG. 3, the coils of the coil spring 118 briefly turn 
with the shank 120 to loosen or relax on the shank. 
Conversely, when reverse rotation (opposite to the film winding direction 
126) of the winder wheel 48 is initiated, the idler wheel 112 is 
oppositely rotated in a coiling direction of the coil spring 118. Thus, as 
shown in FIG. 4, the coils of the coil spring 118 turn with the shank 120 
to tighten or constrict on the shank to thereby brake the shank. The coil 
spring 118 then, owing to at least a 3:1 gear ratio between the winder 
wheel 48 and the idler wheel 112, provides a relatively strong 
counter-rotation or anti-backup force which prevents reverse rotation of 
the winder wheel. 
As viewed in FIG. 2, the winder wheel 48 is rotatable 360 degrees in the 
film winding direction 126. The toothed periphery of the idler wheel 112 
engages the toothed periphery of the winder wheel 48 at a location that is 
within the forth quadrant (271 degrees-359 degrees) of unwinding rotation 
of the winder wheel. 
The invention has been described with reference to a preferred embodiment. 
However, it will be appreciated that variations and modifications can be 
effected by a person of ordinary skill in the art without departing from 
the scope of the invention. 
TS LIST 
10 one-time-use camera 
12 main body part 
14 front cover part 
16 rear cover part 
17 cartridge-receiving chamber 
18 film roll chamber 
19 film cartridge 
20 film take-up spool 
21 backframe opening 
22 filmstrip 
23 cartridge spool 
24 edge perforations 
25 film leader 
26 taking lens 
28 lens retainer 
30 lens support plate 
32 shutter-flash synchronization switch contact 
34 front and rear viewfinder lenses 
35 frame magnifier 
36 keeper plate 
37 shutter release button 
40 shutter blade 
42 shutter return spring 
44 high-energy lever 
46 lever actuating spring 
48 winder wheel 
49 exposed end of spool 23 
50 film metering sprocket 
51 peripheral teeth 
52 metering cam 
54 metering lever 
56 metering spring 
60 frame counter 
80 light baffle 
82 electronic flash illumination assembly 
84 circuit board 
86 capacitor 
88 flash emission lens 
90 battery 
91 battery-receiving chamber 
92 front and rear labels 
94 cartridge-cover door 
96 battery-cover door 
100 three corner guide pins 
104 top and bottom center hooks 
106 top and bottom center slots 
108 two pairs of end holes 
110 two pairs of end hooks 
112 idler wheel 
114 peripheral teeth of winder wheel 
116 peripheral teeth of idler wheel 
118 coil spring 
120 shank 
122 spring end portion 
124 pin 
126 winding direction