GB2248309A

GB2248309A - Automatic winding camera

Info

Publication number: GB2248309A
Application number: GB9119469A
Authority: GB
Inventors: Akihiro Arai
Original assignee: Asahi Kogaku Kogyo Co Ltd
Current assignee: Pentax Corp
Priority date: 1990-09-18
Filing date: 1991-09-12
Publication date: 1992-04-01
Also published as: JPH04125620A; CN1059971A; JP2902466B2; GB9119469D0

Abstract

An automatic winding camera is disclosed in which the rotation of an electrically driven motor (11) is transmitted to a winding spool (16) through a reduction gear train (13, 14, 15) to wind a film (F) onto the winding spool (16), including an overload clutch mechanism (16c, 16d) which is provided in a power transmission line from the motor (11) to the winding spool (16) and which permits the winding spool (16) to rotate when a load above a predetermined value is exerted on the winding spool (16) in a direction opposite to the winding direction. <IMAGE>

Description

AUTOMATIC WINDING CAMERA The present invention relates to an automatic winding camera and more precisely, it relates to a protecting apparatus of a driving system of a winding spool in an automatic winding camera.

In a known automatic winding and rewinding camera, the rotation of an electrically driven motor is transmitted to a winding spool through a reduction gear train to wind the film. Upon rewinding, the winding spool is either reversed or is free to rotate, and the rotation of the motor is transmitted to a rewinding fork provided in a film patrone (film cartridge) to rewind the film wound on the winding spool into the patrone.

In such a known automatic winding (and rewinding) camera, there are no problems with normal use, but if the back cover is opened by mistake before the film is rewound, the user may accidentally attempt to forcibly remove the film wound on the winding spool. If this should happen, the winding spool is forced to rotate in a direction opposite to the winding direction. As a result, if worst comes to worst, the reduction gear train and/or the motor may be damaged or broken. This is because, on one hand, when the film is forcibly drawn, the winding spool is rotated at a speed considerably higher than the normal rewinding or winding speed, causing a heavier than usual load on the reduction gear train, and on the other hand, the motor is forced to rotate at high speed by the reduction gear train which is deemed to be an acceleration gear train for the motor.These problems can be solved if the strength or rigidity of the reduction gear train and the motor is designed, taking the expected high load into account. However, this solution makes the reduction gear train and the motor large and bulky, and accordingly, is not practicable to realize a compact and small camera.

An object of the present invention is to provide an automatic winding camera in which the reduction gear train and the driving motor can be prevented from being broken or damaged if the winding spool is forcibly rotated in a direction opposite to the film winding direction.

According to the present invention, there is provided an automatic winding camera in which the rotation of an electrically driven motor is transmitted to a winding spool through a reduction gear train to wind a film onto the winding spool, the automatic winding camera comprising an overload clutch mechanism which is provided in a power transmission line from the motor to the winding spool and which permits the winding spool to rotate when a load above a predetermined value is exerted on the winding spool in the direction opposite to the winding direction.

In theory, the overload clutch mechanism can be located anywhere in the power transmission line, but it is preferred that the clutch mechanism be located between the winding spool and central gear which is coaxial to the winding spool and driven by the motor through the reduction gear train. This configuration is particularly preferable in a compact camera in which there is a limited space for the provision of the additional camera element, i.e., the overload clutch mechanism.

In a preferred embodiment, to constitute the overload clutch mechanism, elastically deformable arms are integrally formed at their base end with a winding spool made of synthetic resin so as to elastically deform in radial directions at their free end. The free end of the elastic arms are provided with pawls. The abutting surfaces of the central gear, which lie in a substantially radial plane, engage with the pawls when rotated opposite the winding direction.

With the preferred embodiment of the present invention, if the winding spool is rotated in a direction opposite to the winding direction, for example when the film wound on the winding spool is attempted to be forcibly removed after the back cover is opened by mistake, the winding spool may rotate with respect to the power transmission system. Consequently, it is possible to prevent the reduction gear train and the motor, constituting the power transmission system, from being broken.

An example of the present invention will be described below in detail with reference to the accompanying drawings, in which; Figure 1 is an exploded perspective view of part of an automatic winding camera embodying the present invention; and, Fig. 2 is a plan view of a winding spool and a central gear in the part of the automatic winding camera shown in Fig. 1.

In the illustrated embodiment, an electrically driven motor 11 has an output shaft 12 to which a pinion 13 is integrally secured. The pinion 13 is in mesh with an idle gear 14 which is in turn in mesh with a central gear 15.

The motor 11 is electrically connected to a battery B through a switch S, so that electrical power is supplied to the motor 11.

A winding spool 16 is coaxial with the central gear 15 and has at one end thereof a substantially circular opening 16a in which a shaft portion 15a of the central gear 15 is fitted.

The shaft portion 15a of the central gear 15 is provided with abutting surfaces 15b (power transmission surfaces) which lie in a substantially radial plane and relief surfaces 15c connected to the abutting surfaces 15b.

The winding spool 16 is provided with arched grooves 16b which partially surround the substantially circular opening 16a to form elastically deformable arched arms 16c which define a part of the substantially circular opening 16a. The elastically deformable arms 16c are, at their base ends, integrally formed with the winding spool 16 and have at their free end pawls (power transmission pawls) 16d which project in a radially inward direction of the winding spool. The free ends of the arched arms 16c are elastically deformable in a radially outward direction. Under normal operating conditions the pawls 16d engage with the abutting surfaces 15b of the central gear 15. The winding spool 16 is provided on its outer periphery with projections 16e which can be fitted in perforations P of a film F.

The pinion 13, the idle gear 14 and the central gear 15 constitute a reduction gear train to reduce and transmit the number of revolutions of the motor 11 to the winding spool 16. If necessary, one or more additional idle gears can be provided between the pinion 13 and the central gear 15.

The automatic winding camera as described above operates as follows.

When the voltage of the battery B is applied to the motor 11 through the switch S (when the switch S is turned ON), as shown by a dotted line in Fig. 1, the pinion 13, the idle gear 14 and the central gear 15 rotate in the directions Al, A2 and Al, respectively. In the illustrated embodiment, the direction A2 is in the clockwise direction, and Al is in the counterclockwise direction. The abutting surfaces 15b of the central gear 15 and the pawls 16d of the winding spool 16 engaging therewith are shaped so that when the central gear 15 rotates in the direction Al (counterclockwise direction), the winding spool 16 is rotated in the same direction Al. Consequently, the winding spool 16 is rotated in the direction Al by the central gear 15, so that the film F within a film patrone PA inserted in a patrone chamber of the camera is wound onto the outer periphery of the winding spool 16 by the projections 16e which are fitted in some of the perforations P of the film F.

The winding operation is carried out upon loading the film and upon taking each picture.

If a user opens the back cover (not shown) of the camera while the film F is wound onto the winding spool 16, the switch S is turned OFF as shown by a solid line in Fig.

1 to short the terminals of the motor 11, so that the motor 11 is braked. Note that the central gear 15 is also braked by the rotational resistance of the reduction gear train.

Accordingly, if a user attempts to draw the film F forcing the winding spool 16 in the direction A2 opposite to the direction Al, the elastically deformable arm 16c of the winding spool 16 elastically deforms outwardly in the radial direction, so that the pawl 16d is disengaged from the abutting surface 15b of the central gear 15.

Consequently, the winding spool 16 rotates with respect to the central gear 15 which is braked, so that substantially no rotation of the central gear 15 takes place. Thus, the reduction gear train including the central gear 15 and the motor 11 can be protected from being broken.

Although in the embodiment of the present invention the clutch mechanism is comprised of three elastically deformable arms 16c (three pawls 16d) and three abutting surfaces 15b of the central gear 15 in the illustrated embodiment, it is possible to provide any number of elastically deformable arms (pawls) and abutting surfaces.

Furthermore, although the motor 11 is located outside the winding spool 16 in the illustrated embodiment, the present invention can also be applied to a type in which the motor is incorporated in the central hollow portion of the winding spool 11.

Claims

CLAIMS:

1. An automatic winding camera comprising: an electrically driven motor; a winding spool rotated by said motor through a reduction gear train to wind a film onto the winding spool; and, an overload clutch mechanism which is provided in a power transmission line from the motor to the winding spool and which permits the winding spool to rotate when a load above a predetermined value is exerted on the winding spool in a direction opposite to the winding direction.

2. An automatic winding camera according to claim 1, wherein said overload clutch mechanism is located between the winding spool and a central gear coaxial therewith, which is driven by the electrically driven motor through the reduction gear train.

3. An automatic winding camera according to claim 2, wherein said overload clutch mechanism is integral with the winding spool which is made of synthetic resin, and said overload clutch mechanism comprises at least one elastically deformable arm having a base end integrally formed with the winding spool and having a free end which is deformable in the radial direction of the winding spool, and a pawl which is provided on the free end of the or each elastically deformable arm; and at least one abutting surface which is provided on the central gear to lie in a substantially radial plane and which is disengageably engaged by the pawl of the elastically deformable arm.

4. An automatic winding camera according to claim 3, wherein the or each said elastically deformable arm is provided on one end face of the winding spool.

5. An automatic winding camera according to claim 3 or 4, wherein the or each said pawl projects from the free end of the elastically deformable arm in a respective substantially radial direction of the winding spool.

6. An automatic winding camera comprising: A film winding spool for winding a film; a movement transmission mechanism which includes a substantially circular opening formed in the film winding spool, at least one elastically deformable arm which is deformable at a free end thereof in a substantially radially outward direction of the spool and which defines a part of the circular opening, wherein the or each said arm comprises a pawl projecting inwardly and radially from the free end of the elastically deformable arm; and, a central gear which has a shaft portion which can be fitted in the circular opening and which is provided with a respective radial abutting surface which comes into contact with the or each corresponding pawl of the movement transmission mechanism to transmit the movement.

7. An automatic winding camera according to claim 6, further comprising an electrically driven motor for rotating the film winding spool.

8. An automatic winding camera according to claim 7, wherein said central gear is driven by the electrically driven motor in the film winding direction, so that the rotation of the central gear is transmitted to the winding spool by the engagement of the or each pawl of the elastically deformable arm with the corresponding radial abutting surface.

9. An automatic winding camera according to claim 8 wherein the or each said elastically deformable arm elastically deforms radially and outwardly of said film winding spool when an external force above a predetermined value is applied to the winding spool side in a direction opposite to the film winding direction to disengage the or each pawl from the corresponding radial abutting surface of the central gear.

10. An automatic winding camera according to any one of claims 7 to 9, wherein said electrically driven motor is braked unless it is rotated in the film winding direction.

11. An automatic winding camera according to any one of claims 7 to 10 further comprising a gear train provided between the electrically driven motor and the central gear.

12. A film winding spool arrangement comprising a spool, a drive means for rotating the spool in a winding direction, and at least one arm member normally engaging between the drive means and spool to transmit the drive thereto; wherein the or each arm member is elastically deformable at or adjacent a free end thereof to disengage said drive transmission in response to a load above a value applied to the spool in a direction opposite to said winding direction.

13. An automatic winding camera substantially as hereinbefore described with reference to the accompanying drawings.

14. A film winding spool arrangement substantially as hereinbefore described with reference to the accompanying drawings.