JPS6226001B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an improvement of a bellows for a plate-making camera.

(Prior Art) As is well known, bellows for plate-making cameras are cylindrical,
There are various shapes such as a rectangular cylinder shape or a truncated cylinder shape, but as shown in FIGS. 4 and 5, the bellows 21 has an inner fold 22 that projects inward and an outer fold 23 that projects outward. are arranged in alternating rows, and are formed to be expandable and contractible in the direction in which the folds are arranged.

The bellows 21 for a plate-making camera is large, with a mouth size ranging from several tens of centimeters to several meters, and has considerable weight, and as illustrated in FIGS. 4 and 5, it is in a hanging state. They are usually held in an extended state (or horizontally), repeatedly expanded and contracted, and subjected to harsh usage conditions.

Therefore, if the elasticity and shape retention of the bellows is insufficient, the bellows will lose its original stretchable characteristics after a short period of use, resulting in permanent sagging and deformation. When this happens, not only does the aesthetic appearance deteriorate, but in severe cases it obstructs the path of incident light, making it functionally unusable.

An analysis of the factors that influence the durability of the bellows includes conditions such as the type of material sheet forming the bellows, the method of forming the folds formed on the circumferential side, and the heat treatment after forming. Among these, the type of material sheet is a particularly important factor, and it is customary to use material sheets that have so-called "stiffness" and high rigidity.

(Problem to be solved by the invention) However, although it is true that by selecting various conditions and adjusting means as described above, it is possible to achieve a considerable improvement effect, on the other hand, it may not be permanent to some extent. It was also true that it could not withstand general use.

In particular, when the bellows 21 is installed vertically as shown in FIGS. 4 and 5, the upper part (A part) of the bellows 21
There was a problem that the telescopic function of the product deteriorated significantly.

In other words, due to its own weight, etc., when the bellows 21 is stretched, the interval between the folds 22 and 23 deforms unevenly, and the interval between the folds becomes larger in the A part than in the lower part (B part). , the opening angle α of the bent surface with the crease 23 at the apex in the A part is significantly larger than the opening angle β in the B part. Under such conditions, most of the expansion of the bellows 21 will be borne by the section A, and the elasticity and recovery power of the bellows after stretching will be significantly reduced in this section, and the wall strength will also be weakened. If an unexpected external force acts on it, it will easily become dented and deformed.

The present invention was made in view of these problems, and provides a novel bellows structure for plate-making cameras in which the elasticity, shape retention, and recovery power of the bellows do not deteriorate with use and are extremely durable. The purpose is to

(Means for Solving the Problems) The bellows for a prepress camera of the present invention, which was taken to achieve the above-mentioned purpose, is characterized by an inner fold 2 protruding inward and an outer fold protruding outward. In a cylindrical plate-making camera bellows in which folds 2 and 3 are arranged in alternating rows and can be expanded and contracted in the direction in which the folds are arranged, a restraining piece 4 for regulating the extension interval of the folds 2 and 3 when the bellows is extended is arranged in parallel. A retracting crease 6 is provided in the middle of the restraining piece 4, and is provided at the top of the adjacent inner or outer folds 2 and 3, and is bent to the opposite side of the fold when the bellows is contracted. The point is that

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.

The bellows 1 for a plate-making camera shown in FIGS. 1 to 3 has a rectangular cylindrical outer shape with a wide top and a narrow bottom, and its side peripheral wall has an inner fold 2 that projects inward and an outer side that projects outward. The folds 3 are formed so as to be arranged alternately in the vertical direction, and are formed to be expandable and contractible in the direction in which the folds 2 and 3 are arranged, that is, in the vertical direction.

The black material forming the side wall may be of any type, such as a laminated sheet with a core paper interposed therein, a soft vinyl chloride sheet, or a copolymer sheet of polyethylene and vinyl acetate. However, it is desirable that the surface of the material constituting the inner surface of the bellows 1 be subjected to a surface matte treatment.

As for the means for forming the bellows by arranging folds on the side peripheral wall, any known technique can be used as desired.

It should be noted that the outer shape of the bellows is not limited to that shown in the drawings, and may of course be cylindrical, truncated conical, or the like.

A restraining piece 4 is installed at the top of the adjacent inner folds 2, 2, and a large number of restraining pieces 4 are attached to the bellows 1.
Reinforcement bands, .

The restraining piece 4 is made of the same sheet material as the bellows main body, and preferably has a matte surface treatment.

As shown in detail in FIG. 3, the restraint piece 4 is
The distance between the inner folds 2 is determined, and the vertical length thereof is preferably set so that the opening angle θ of the curved surface with the inner or outer folds 2 and 3 as vertices is an acute angle.

Adhesive pieces 5, 5 are integrally extended at both upper and lower ends of the restraining piece 4, and the adhering pieces 5, 5 are attached to a flat wall formed from the inner fold line 2 to the outer fold line 3. The restraining piece 4 connects the tops of the inner folds 2, 2 in a bridging manner.

A pull-in crease 6 is provided in the center of the restraint piece 4, which is bent in the same direction as the outer fold 3.
As shown in FIGS. 1 and 2, when the bellows 1 is contracted, the restraining piece 4 is bent toward the outer fold line 3 and retracted.

In the bellows 1 described above, since the restraining pieces 4 are installed at the tops of the inner folds 2, 2,
When the bellows 1 is gradually stretched and the pitch of the folds 2 and 3 in its upper part becomes larger, the bending surface with the folds 2 and 3 as vertices is formed according to the length of the restraining piece 4, as shown in FIG. 3. The opening angle is prevented from exceeding a certain value (right angle in the illustrated example). Therefore, loss of elasticity and recovery power of the bellows due to exceeding a certain critical opening angle can be prevented. Moreover, when the bellows 1 is extended, the opening and widening of the bending surface is sequentially prevented from the upper part thereof, so even if the bellows 1 is extended greatly, the opening angle is guaranteed to be less than a certain angle.

In addition, in the configuration of the above embodiment, the adhesive pieces 5, 5 extending from both ends of the restraining piece 4 are attached to the flat wall forming between the folds 2, 3 of the bellows 1. The effect of increasing the stiffness of the wall surface can also be obtained, and this can also be expected to enhance the elasticity and recovery force.

Note that each restraining piece 4 has a retracting crease 6 in the middle thereof so that it is drawn in to the outer fold 3 side when the bellows 1 is contracted. It is possible to reliably avoid functional troubles such as those caused by bending inward in a protruding manner and obstructing the path of incoming light rays.

Regarding the manner in which the restraining pieces 4 are arranged in a row, various other modifications of the above embodiment can be devised. As already mentioned, the part of the bellows 1 that is most easily deformed is its upper part, and therefore, the restraining piece 4 may be connected only to the upper part. Furthermore, the installation position and number of restraining pieces 4 can be changed as desired.

In addition, in the case of a rectangular cylindrical body like the example shown in the figure, it is considered that it is sufficient to provide it on the long side thereof. That is,
This is because the long side peripheral wall and the short side peripheral wall of the bellows 1 are integrated with each other, and the restraining effect of the long side sufficiently spreads to the short side.

Next, the construction structure of the restraining piece 4 can be further simplified from that of the above embodiment. That is, the adhesive piece 5 in the above embodiment is omitted,
It is constructed with only the essential restraining piece 4. In this case, it is also possible to interconnect and integrate the restraining pieces 4 made up of independent elements.

(Effects of the Invention) As explained above, in the bellows for plate-making camera of the present invention, since the restraining piece is installed at the top of the adjacent folds of the bellows main body, the bent surface forming the peripheral wall of the bellows main body is It is possible to reliably prevent the loss of elasticity and recovery power of the bellows caused by being expanded beyond the critical angle, and the durability can be dramatically improved.

In addition, since the restraining piece is provided with a retracting crease that bends on the opposite side of the inner or outer fold when the bellows is contracted, the restraining piece can be folded into a protruding shape inside the bellows. Therefore, it is possible to reliably avoid functional troubles caused by obstructing the path of the incident light beam.

[Brief explanation of the drawing]

FIG. 1 is a partially cutaway perspective view showing an example of the bellows according to the present invention, FIG. 2 is a half-sectional side view of the same bellows, and FIG.
4 is a perspective view showing an example of a conventional bellows for a plate-making camera, and FIG. 5 is a half-sectional side view of the conventional bellows. 1... Bellows for plate making camera, 2... Inner fold,
3...Outer fold line, 4...Restriction piece, 6...Retraction fold line.

Claims (1)

[Scope of Claims] 1. A cylindrical bellows for a plate-making camera, in which inner folds 2 protruding inward and outer folds 3 protruding outward are arranged alternately and are expandable and contractible in the direction in which the folds are arranged. A restraining piece 4 for regulating the extension interval of the folds 2 and 3 when the bellows is extended is installed at the top of the inner or outer folds 2 and 3 that protrude adjacently, and on the opposite side of the fold when the bellows is contracted. A bellows for a plate-making camera, characterized in that a retracting crease 6 bent toward the crease side is provided in the middle of the restraining piece 4.