Protection cover device and protection-cover-equipped apparatus

Abstract: A protection cover device and a protection-cover-equipped apparatus each comprise a protection cover, a moving member, and an elastic member which is incorporated into an inside of the protection cover and causes the protection cover to move in association with a movement of the moving member.

Description: This invention relates to a protection-cover-equipped apparatus, which opens and closes a front of a photo-taking optical system or the like. Some of cameras have a barrier disposed on a front of a lens barrel and arranged as a protection cover to be openable and closable and to protect a lens from being soiled and damaged while the camera is not used for photographing. The conventional barrier (protection cover) opening-and-closing mechanism is arranged as shown in Figs. 11, 12 and 13. Referring to these figures, two barriers 101 and 102 are rotatably secured to a base plate (not shown) in such a way as to be rotatable respectively on centers of rotation 101a and 102a. The base plate is disposed on a front of the lens barrel. A light-passing hole 103a is provided in the base plate for forming an optical path. An opening-and-closing ring 104 is mounted on the base plate in such a way as to be rotatable around an optical axis. A driving spring (tension spring) 105 is hooked on a spring peg part 103b of the base plate and is arranged to urge the opening-and-closing ring 104 to rotate clockwise as viewed in Fig. 11. A rotation stopper 103c is arranged on the base plate to prevent a further clockwise rotation of the opening-and-closing ring 104 when the ring 104 is rotated to a position where the barriers 101 and 102 are opened by the opening-and-closing ring 104. The barriers 101 and 102 are provided with arm parts 101b and 102b, respectively. Between the opening-and-closing ring 104 and each of the arm parts 101b and 102b, there is hooked an absorption spring (tension spring) 106, which is arranged to urge the barriers 101 and 102 to move in the direction of closing them. Further, closing stoppers 104a are formed on the opening-and-closing ring 104. When the barriers 101 and 102 are opened, the arm parts 101b and 102b come to abut on the respective closing stoppers 104a, which then prevent the barriers 101 and 102 from closing. The barrier mechanism configured in the above manner operates as follows. With no power applied to any parts of the barrier mechanism, the opening-and-closing ring 104 is in a state of being completely rotated clockwise by the urging force of the driving spring 105, and the barriers 101 and 102 are in an open state, as shown in Fig. 11. When a power F (which may be a retracting force of the zoom lens barrel, a rotating force of a focusing motor, or the like) is received from the lens barrel as shown in Fig. 12, the opening-and-closing ring 104 rotates counterclockwise. Then, the closing stoppers 104a rotate also counterclockwise. In association with this rotation, the barriers 101 and 102 rotate in the closing direction to cover the light-passing hole 103a. For covering the light-passing hole 103a, the amount of rotation, i.e., an angle B, of the opening-and-closing ring 104 may be set at an amount sufficient to cause the barriers 101 and 102 to close the light-passing hole 103a by abutting on each other. However, with the degree of finishing precision of various parts, the play of their fitting engagement, etc., taken into consideration, the amount of rotation (the angle B) should be set at an ample amount including some amount of allowance. The absorbing spring 106 then effectively acts to prevent the ample rotation from exerting any irrational force on the mechanism. In other words, when the amount of rotation of the opening-and--closing ring 104 is too much, the arm parts 101b and 102b of the barriers 101 and 102, which are in contact with the closing stoppers 104a of the opening-and-closing ring 104 in the open state, come a little apart from the closing stoppers 104a in the closed state. Further, in a case where the barriers 101 and 102 happen to be prevented from rotating in the direction of closing by some impediment such as grains of sand or the like while they are in process of closing, as shown in Fig. 13, the absorbing spring 106 further elongates to permit the counterclockwise rotation of the opening-and-closing ring 104. The absorbing spring 106 thus permits an escaping movement of the opening-and-closing 104 for the barriers 101 and 102, so that the absorbing spring 106 effectively prevents a mechanical disorder from taking place under such a condition. While a tension spring is used as the absorbing spring 106 in the above-stated case, the use of the tension spring is replaced with use of a torsion spring by hooking it at the center of rotation of the barriers in some case, for example, as disclosed in Japanese Laid-Open Patent Application No. HEI 7-159856. However, in the case of the barrier mechanism of the type employing the tension spring as the absorbing spring, the absorbing spring cannot be disposed within an action area including a barrier moving part in the direction of a photo-taking optical axis. The use of the tension spring thus imposes a limitation on the structural arrangement of the barrier mechanism to necessitate use of a wide space for it. Further, since the tension spring requires a space for its coil diameter in the direction of the optical axis, this causes an increase in the direction of thickness of the barrier mechanism. Meanwhile, the barrier mechanism of another type using a torsion spring as the absorbing spring requires a thickness space, as a coil part, for its number of turns on the reverse side of the barrier mechanism. The coil part also causes an increase in the direction of thickness of the barrier mechanism. Besides, in order to make the spring force of the torsion spring efficiently act on each of the barriers, its coil part must be disposed in the center of rotation of the barrier. These requirements impose limitations on the design and the structural arrangement of the barrier mechanism. Furthermore, US-A-4 161 365 discloses a neghold assembly which is used in photographic printers. The neghold assembly includes a transport base, a top insert holder, top and bottom aperture insert plates and a handle. The top insert holder and the top aperture insert plate are connected to the handle and pivot about an axis which is located near and parallel to the back edge of transport plate. DE-A-32 20 265 discloses a protection-cover-equipped apparatus. According to DE-A-32 20 265, the movement of a main barrier is achieved by an abutting engagement between a pin and a radial protrusion of a moving member whereby an engagement between the pin and the protrusion is achieved by the force of a spring. It is conceivable to reduce the necessary space by arranging the tension spring or the torsion spring to have a smaller coil diameter or a less number of turns. Such arrangement, however, tends to cause the spring to be used beyond the limit of elasticity within a normal range of action and thus hardly enables the spring to adequately fulfill its function. In accordance with one aspect of this invention, there is provided a protection-cover-equipped apparatus, having the features defined in claim 1. In another aspect of this invention there is provided an optical apparatus as defined in claim 9. The above and other aspects and features of this invention will become apparent from the following detailed description of embodiments thereof taken in conjunction with the accompanying drawings. Figs. 1(a) and 1(b) are a front view and an enlarged partial view, respectively, showing the opening action of a barrier mechanism according to a first embodiment of this invention. Figs. 2(a) and 2(b) are a front view and an enlarged partial view, respectively, showing the closing action of the barrier mechanism according to the first embodiment. Figs. 3(a) and 3(b) are a front view and an enlarged partial view, respectively, showing a forcible opening action of the barrier mechanism according to the first embodiment. Fig. 4 is a sectional side view showing a main part of the barrier mechanism according to the first embodiment. Fig. 5 is a front view of an absorbing spring used for the barrier mechanism according to the first embodiment. Fig. 6 is a rear perspective view of a main barrier used for the barrier mechanism according to the first embodiment. Fig. 7 is a front view showing the closing action of a barrier mechanism according to a second embodiment of this invention. Fig. 8 is a front view showing the opening action of the barrier mechanism according to the second embodiment. Figs. 9(a) and 9(b) are a front view and an enlarged partial view, respectively, showing a forcible opening action of the barrier mechanism according to the second embodiment. Fig. 10 is a front view of an absorbing spring used for the barrier mechanism according to the second embodiment. Fig. 11 is a front view showing the opening action of a conventional barrier mechanism. Fig. 12 is a front view showing the closing action of the conventional barrier mechanism. Fig. 13 is a front view showing a forcible opening action of the conventional barrier mechanism. Preferred embodiments of this invention are described in detail below with reference to the drawings. Figs. 1(a) and 1(b) to Fig. 6 show a barrier mechanism of a camera according to a first embodiment of this invention. Figs. 1(a), 2(a) and 3(a) are front views showing respectively opening, closing and forcible opening actions of the barrier mechanism. Figs. 1(b), 2(b) and 3(b) are enlarged views respectively showing essential parts of Figs. 1(a), 2(a) and 3(a). Fig. 4 is a sectional view taken on a line IV-IV shown in Fig. 3(b). A main barrier 1 and a sub-barrier 2, which serve as a lens protection cover, are disposed on a front of a base plate 3. In the base plate 3, there is formed a light-passing hole 3a, adjacent to which a photo-taking optical system is disposed. The main barrier 1 and the sub-barrier 2 are mounted on the basis plate 3 in such a way as to be rotatable respectively on centers of rotation 1a and 2a. The main barrier 1 and the sub-barrier 2 engage with each other at gear parts 1b and 2b. When the main barrier 1 is rotating, its rotating force is transmitted to the sub-barrier 2. An opening-and-closing lever 4 which is rotatable on the almost same center of rotation as the main barrier 1 is mounted on the reverse side of the base plate 3. A driving spring (tension spring) 5 is arranged to urge the opening-and-closing lever 4 to move clockwise as viewed Fig. 1(a). A stopper 3b is formed on the base plate 3 to prevent the opening-and-closing lever 4 from rotating to an excessive extent beyond a predetermined position. The opening-and-closing lever 4 is provided with a driving shaft 4a, which extends toward the front. The driving shaft 4a extends through a slot 3c formed in the base plate 3 and is fitted into an absorbing slot 1c formed in the main barrier 1. As shown in Fig. 6, a counter-boring part 1d is formed on the reverse side of the main barrier 1. An absorbing spring 6, which is a linear-shaped spring as shown in Fig. 5, is accommodated in the counter-boring part 1d. Referring to Fig. 5, the absorbing spring 6 is composed of a fixed part 6a which is inserted into and secured to a groove part 1e formed in the main barrier 1, a deforming part 6c which continues from the fixed part 6a and is arranged to be elastically deformed mainly within the counter-boring part 1d, and an acting part 6b which continues from the deforming part 6c. The absorbing spring 6 is arranged to be in a linear shape before deforming as indicated with a full line in Fig. 5, and is arranged to be deformed as indicated with a broken line so as to generate an urging force in the direction of an arrow f at the acting part 6b in a normal state of being attached to the main barrier 1 as shown in Figs. 1(a) and 2(a). The urging force f of the absorbing spring 6 acts to keep the driving shaft 4a of the opening-and-closing lever 4 abutting on one end face of the absorbing slot 1c of the main barrier 1, as shown in Fig. 1(b). The action of the absorbing spring 6 not only allows the main barrier 1 and the opening-and-closing lever 4 to rotate together but also causes the sub-barrier 2 to rotate. In order to enable the absorbing spring 6 to sufficiently exert its elastic force without exceeding its limit of elasticity, the deforming part 6c must be arranged to have a sufficient length. Therefore, the area on the reverse side of the main barrier 1 where the counter-boring part 1d is formed is arranged to be as wide as possible. In addition to the use of the wide area, the length of the deforming part 6c is increased by forming it in a curved shape by curving it along the shape of the counter-boring part 1d. This arrangement enables the absorbing spring 6 to adequately fulfil its function although it is a torsion spring and has no coiled part. It is an advantage of the absorbing spring 6 that, compared with a case where a tension spring or a torsion spring having a coiled part is employed as an absorbing spring, it permits the barrier mechanism to be arranged to have a less thickness. Operation of the barrier mechanism which is configured as described above is next described as follows. Under such a condition that no power is applied to any part of the barrier mechanism, the opening-and-closing lever 4 is in a state of having been fully rotated clockwise by the urging force of the driving spring 5, and the main barrier 1 and the sub-barrier 2 are in an open state as shown in Figs. 1(a) and 1(b). Referring to Figs. 2(a) and 2(b), when the opening-and-closing lever 4 is rotated counterclockwise by receiving a power F (which may be a retracting force of the zoom lens barrel, a rotating force of a focusing motor or the like) from the lens barrel, the driving shaft 4a rotates also counterclockwise. Then, the main barrier 1 rotates counterclockwise integrally with the driving shaft 4a, and the sub-barrier 2 rotates clockwise, thereby covering the light-passing hole 3a. The amount of rotation of the opening-and-closing lever 4, i.e., an angle A, to be made in this instance may be set at an amount sufficient to cause the main barrier 1 and the sub-barrier 2 to close the light-passing hole 3a by abutting on each other. However, with the degree of finishing precision of various parts, the play of their fitting engagement, etc., taken into consideration, the amount of rotation (the angle A) should be set at an ample amount including some amount of allowance. The deforming part 6c of the absorbing spring 6 is then deformed to prevent the ample rotation of the opening-closing lever 4 from exerting any irrational force on the barrier mechanism. In other words, the end face part of the absorbing slot 1c and the driving shaft 4a, which are arranged to abut on each other when the barrier mechanism is in an open state, come to stay a little apart from each other when the barrier mechanism is in its closed state. In a case where the main barrier 1 and the sub-barrier 2 happen to be prevented from rotating in the direction of closing by some impediment such as grains of sand or the like while they are in process of closing, as shown in Figs. 3(a) and 3(b), the deforming part 6c of the absorbing spring 6 is further deformed to permit the counterclockwise rotation of the opening-and-closing ring 4. In other words, a gap X which is brought about by the closing action between the end face of the absorbing slot 1c and the driving shaft 4a increases. The absorbing spring 6 thus permits an escaping movement of the opening-and-closing lever 4 with respect to the main barrier 1 and the sub-barrier 2, so that the absorbing spring 6 effectively prevents a mechanical disorder from taking place under such a condition. When the impediment is removed, the acting part 6b of the absorbing spring 6 pushes the driving shaft 4a toward the end face of the absorbing slot 1c. The main barrier 1 and the sub-barrier 2 are thus closed as shown in Figs. 2(a) and 2(b). Fig. 7 to Figs. 9(a) and 9(b) show a barrier mechanism of a camera according to a second embodiment of this invention. The second embodiment differs from the first embodiment in that the urging direction of a driving spring 15 and that of an absorbing spring 16 of the second embodiment are arranged to be reverse to those of the corresponding springs of the first embodiment. Since the absorbing spring 16 is arranged to have its urging direction reverse to that of the absorbing spring 6 of the first embodiment, the absorbing spring 16 is in a shape as shown with a full line in Fig. 10 when it is not deformed. In the state of being in use, the absorbing spring 16 is in a shape as shown with a broken line in fig. 10 and generates an urging force f'. With no power applied to the barrier mechanism, a main barrier 11 and a sub-barrier 12 are kept in a closed state by the tensile force of the driving spring 15 as shown in Fig. 7. An opening-and-closing lever 14 is restrained from rotating by the closing of the barriers 11 and 12. Therefore, no inconvenience takes place without the action of the absorbing spring 16 under this condition. When the main barrier 11 and the sub-barrier 12 are opened by a force F as shown in Fig. 8, the opening motion of the main barrier 11 is restricted as the main barrier 11 comes to abut on an abutting part 13a formed on a base plate 13. The restriction imposed on the opening extent of the main barrier 11 by the abutting part 13a is arranged to permit the opening-and-closing lever 14 to rotate to a greater amount than the amount of rotation of the main barrier 11. Therefore, when the barrier mechanism is in an open state, a driving shaft 14a of the opening-and-closing lever 14 no longer abuts on an end face of an absorbing slot 11c provided in the main barrier 11. However, since the urging force of the absorbing spring 16 is acting in the direction of opening, the barriers 11 and 12 never come to close under that condition. In a case where the main barrier 11 and the sub-barrier 12 happen to be prevented from rotating in the direction of opening by some impediment such as grains of sand or the like while they are in process of opening, as shown in Figs. 9(a) and 9(b), the absorbing spring 16 is deformed more than in the state of Fig. 8 to increase a gap Y between the end face of the absorbing slot 11c and the driving shaft 14a. The absorbing spring 16 thus permits an escaping movement: of the opening-and-closing lever 14 with respect to the main barrier 11 and the sub-barrier 12, so that any mechanical disorder can be prevented from taking place under such a condition. The individual components shown in schematic or block form in the drawings are all well-known in the camera arts and their specific construction and operation are not critical to the operation or best mode for carrying out the invention. While the present invention has been described with respect to what is presently considered to be the preferred embodiments, it is to be understood that the invention is not limited to the disclosed embodiments. To the contrary, the invention is intended to cover various modifications and equivalent arrangements included within the scope of the appended claims. For example, protection covers to which this invention is applicable are not only the type arranged to open and close a front of a photo-taking optical system in the manner described in the foregoing but also to protection covers arranged to have different structures and shapes or for different purposes. This invention is carried out by combining as necessary the technological elements described in the foregoing. Further, this invention is applicable to cameras of varied kinds, such as a single-lens reflex camera, a lens-shutter type camera, a video camera, etc., optical apparatuses other than cameras, devices adapted for cameras, optical apparatuses and other apparatuses, and component elements forming these apparatuses and devices. As described in the foregoing, each of the embodiments is arranged to permit the barrier member to enter a closing action range in the direction of an optical axis by placing an elastic member in a counter-boring space or the like provided in the barrier member on its side opposed to the photo-taking lens. Compared with the conventional barrier device which restrains its elastic member from entering the closing action range of its barrier member, the arrangement of each of the embodiments not only allows a greater amount of design latitude but also permits reduction in size of the barrier device by obviating the necessity of having a space for the elastic member outside of the barrier member. According to each of the embodiments described above, the elastic member can be arranged to have only a thickness which corresponds to the diameter of a linear material in the direction of the optical axis of the photo-taking lens by forming the elastic member with the linear material. This arrangement effectively permits a reduction in thickness of not only the elastic member but also that of the whole barrier device in the direction of the optical axis. Further, according to each of the embodiments described above, the length of the elastic member can be increased to enable the elastic member to increase its limit of elasticity by arranging the elastic member to have a curved portion within a plane orthogonally intersecting the optical axis. That arrangement gives a large amount of elastic deformation tolerance sufficient for absorbing an escaping movement of the driving member which takes place with respect to the barrier member.

Claims: A protection-cover-equipped apparatus, comprising: a protection cover (1, 2; 11, 12) rotatably mounted on a front of a base plate (3) which has a light-passing hole (3a), and consisting of a main barrier (1; 11) and a sub-barrier (2; 12) coupled together so as to be movable towards to and away from each other, and wherein said barriers (1; 11; 2; 12) covers said light-passing hole (3a) when said main barrier and said sub-barrier (2; 12) are in a closed position; a moving member (4, 4a; 14, 14a) for moving said main barrier (1; 11) and said sub-barrier (2; 12) into an opened position or said closed position; and an elastic member (6; 16) urging said main barrier into engagement with said moving member for causing said main barrier to move in association with said moving member, characterized in that said main barrier (1; 11) has a recessed part (1d), and said elastic member (6; 16) is incorporated inside of said recessed part (1d), wherein said elastic member (6; 16) is in engagement with said moving member (4, 4a; 14, 14a) and said recessed part so as to deform and to exert a moving force on said main barrier when said moving member moves. An apparatus according to claim 1, wherein said elastic member is formed with a linear material (6, 16) which extends along said recessed part of said main barrier. An apparatus according to claim 1, wherein said elastic member is formed with a linear material (6, 16) which is deformed along said recessed part of said main barrier. An apparatus according to claim 1, wherein said apparatus includes a photo-taking optical system and said protection cover (1, 2, 11, 12) is disposed to open and close a front of (said) photo-taking optical system. An apparatus according to claim 4, wherein said elastic member is incorporated into a side of said main barrier opposed to said photo-taking optical system. An apparatus according to claim 1 to 6, wherein said elastic member is arranged to urge said main barrier (1, 2, 11, 12) to move in a closing direction. An apparatus according to claim 1 to 7, wherein said elastic member is arranged to urge said main barrier (1, 2, 11, 12) to move in an opening direction. An apparatus according to claim 1 to 8, wherein the urging force of an absorbing spring (6) acts to keep a driving shaft (4a; 14a) as part of said moving member (4, 4a; 19, 14a) abutting on one end face of an absorbing slot (1c) of said main barrier (1; 11). An optical apparatus including the protection-cover-equipment apparatus according to any one of claims 1 to 9. An optical apparatus according to claim 10, wherein the optical apparatus is a camera.

Inventors: ICHINO KAZUSHIGE, YOSHII HIROSHI, ICHINO, KAZUSHIGE, YOSHII, HIROSHI
Applicants: CANON KK, CANON KABUSHIKI KAISHA
Application year: 1997
Main classification: G03B17
IPC codes: G03B11, G03B17