CAMERA BELLOWS AND A METHOD FOR PRODUCING THE SAME

Abstract: A camera bellows comprising a substantially rectangular, tubular body having two ends, the walls of which are provided with folds for extensibility, said folds extending perpendicularly to the longitudinal direction of the body, and reinforcements for retaining the rectangular shape of the bellows, wherein alternating elastic and rigid folds are provided, said elastic folds enabling transverse displacements of one end of the body relative to the other whilst the rigid folds serve to retain a free optical path through the bellows during said displacements. The invention also relates to a method for producing the above described camera bellows, said tubular body being formed by folding a sheet comprising a lustreless non-reflective inner lining, a weather-resistant outer lining and reinforcement strips laminated therebetween on fold surfaces adjacent to the folds, wherein said elastic folds are obtained in that the fold-surfaces of such a fold are free of reinforcement strips and that said inner lining and outer lining are made of elastic materials.

Description: TITLE Camera bellows and a method for producing the same TECHNICAL FIELD The present invention relates to a camera bellows, more particularly to a folded camera bellows which allows transverse displacements of one end relative the other. The invention further relates to a method for producing such a bellows. BACKGROUND OF THE INVENTION Some cameras are provided with a folded bellows in order to displace the image plane/film magazine relative the objective lens so as to achieve different photographic effects. The bellows normally comprises a lustreless non- reflective inner lining and a protective, weather-resistant outer lining. Additionally, a plurality of parallel reinforcement strips are laminated between said inner and outer linings. The reinforcement strips stiffen the bellows-material and enables it to be folded in a desired, predetermined manner. By dividing the reinforcement strips into parallel groups in their longitudinal direction, it is possible to bend the folded material so as to assume the characteristic rectangular cross-section and form an extensible, tubular body. A camera bellows of this kind is primarily suitable for extension and compression. It may also be curved. However, it has very limited possibilities, especially for the transverse, shearing displacements used when performing a so-called shift operation, in which the image plane of the camera is displaced perpendicularly to the optical axis of the objective lens. Such a shift operation is carried out, for example, in order to-compensate for perspective errors in architectural photography. When a conventional bellows is exposed to shearing, the walls which are parallel to the shearing movement will experience torsional stress result¬ ing in a strong resistance against the movement. If forced to undergo larger shearing displacements, the bellows may be heavily deformed and permanently damaged. A solution to this problem is proposed in US 4 662 734, which describes a bellows in which the reinforcement strips are divided into two portions on each fold-surface on the walls of the bellows, so as to allow the wall sides to collapse outwardly and thus reduce resistance to a shearing displacement. However, this collapsing movement is diffi¬ cult to control and there is an apparent risk of the bellows-material collapsing into the optical path through the bellows if said bellows is not made larger than a normal bellows. Since compactness is essential especially in the fields of small-format and medium-format cameras, this solution suffers from a decided disadvantage. Another way to allow shearing displacements in a camera bellows is to design the bellows as a large "bag", con- nected at its ends to the objective lens and image plane respectively. This solution, called a wide-angle bellows, is however everything but compact and is used predominantly in large-format cameras. SUMMARY OF THE INVENTION It is therefore the object of the present invention to provide a folded camera bellows which in extended as well as compressed position allows transverse, shearing dis- placements of one end of the bellows relative the other, whilst retaining a free optical path through the bellows and compact outer dimens-tons of the bellows . A further object of the present invention is to provide a method for producing such a camera bellows in a time- effective and cost-effective manner which requires minimal deviation from existing methods for producing conventional camera bellows. The first object is achieved in accordance with the present invention by means of a camera bellows comprising a substantially rectangular, tubular body having two ends, the walls of which are provided with folds for extensibility extending perpendicularly to the longitudinal direction of the body and reinforcements for retaining the rectangular shape of the bellows, wherein alternating elastic and rigid folds are provided, said elastic folds enabling transverse displacements of one end of the body relative to the other whilst the rigid folds serve to retain a free optical path through the bellows during said displacements . In an advantageous embodiment of the invention, the elastic folds are provided exclusively along two opposite walls of the bellows, so as to enable said transverse displacements to occur only in a direction substantially parallel to the longitudinal extension of said elastic folds. Additionally, said elastic folds preferably constitute in-folds in the bellows. The further object of the invention is achieved by means of a method for producing the above-described camera bellows, said tubular body being formed by folding a sheet compris¬ ing a lustreless non-reflective inner lining, a weather- resistant outer lining and reinforcement strips laminated therebetween on fold surfaces adjacent to the folds, wherein said elastic folds are obtained in that the fold- surfaces of such a fold-are free of reinforcement strips and that said inner lining and outer lining are made of elastic materials . BRIEF DESCRIPTION OF THE DRAWINGS The present invention will now be described in more detail, by way of example only, and with reference to the attached drawings, in which: Fig. 1 illustrates a transversely displaced camera bellows according to a preferred embodiment of the present invention; Fig. 2 illustrates an enlarged, cut-out cross-section of a rigid portion of a bellows-sheet including an interstitial reinforcement strip. Fig. 3 illustrates an enlarged, cut-out cross-section of an elastic portion of a bellows-sheet according to the invention. Fig. 4 shows a laid-out bellows-sheet, with the inner lining removed so as to expose the arrangement of reinforcement strips according to a preferred embodiment of the invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT In fig. 1 a side elevation of a folded camera bellows is shown comprising a substantially rectangular, tubular body denoted by reference numeral 1. The tubular body 1 has two ends 2,3 normally connected to an objective lens (not shown) and an image plane/film magazine (not shown) of a camera. The walls of said tubular body 1 are provided with folds 5,6 in a known manner for ~ extensibility, extending perpen¬ dicularly to the longitudinal direction of the body 1. Furthermore, the tubular body 1 is reinforced with rein- forcement strips 13 (see fig. 2 and 4) for retaining the rectangular shape of the bellows during displacements of the same. The bellows, according to the preferred embodiment of the invention as seen in fig. 1, is provided with alternating elastic and rigid folds 5 and 6 respectively. Said elastic folds 5 hereby enable transverse displacements of one end 2 of the body 1 relative to the other end 3 in parallel planes whilst the rigid folds 6 serve to retain a free optical path through the bellows during said displacements. The arrows 20 and 21 indicate the directions of displace¬ ment in the shown example. Furthermore, in the embodiment shown in fig. 1, the elastic folds 5 are provided exclusively along two opposite walls of the bellows, so as to enable said transverse displace¬ ments to occur only in a direction substantially parallel to the longitudinal extension of said elastic folds. In a shearing movement causing said transverse displace¬ ments, the elastic folds 5 will be exposed to some exten¬ sion diagonally as indicated in the figure by means of thin diagonally curved lines. However, no tensions will arise which would resist the shearing movements as is the case in conventional bellows. Additionally, it has been found that particularly good results have been achieved when said elastic folds consti¬ tute in-folds in the bellows, which is the case in the shown example. The present invention also provides a method for producing the above described camera bellows, which will now be described with reference to figs. 2 to 4 : The tubular body 1 is formed by folding a sheet 10 compris¬ ing a lustreless non-reflective inner lining 12, a weather- resistant outer lining 13 and reinforcement strips 13 laminated therebetween on fold surfaces 16 adjacent to the folds 6. For the sake of clarity, the inner lining 12 has been removed in fig. 4 so as to expose the special arrange¬ ment of reinforcement strips 13 according to the shown preferred embodiment of the invention. The sheet is folded in a conventional manner along - in the figure - vertical fold-lines 18 and horizontal fold-lines 19. In this way, the fold-surfaces 16 are defined as the areas delimited by said fold-lines 18,19. According to the invention, said elastic folds 5 are obtained in that the fold-surfaces 16 of such a fold are free of reinforcement strips 13 and that said inner lining 12 and outer lining x4 are made of elastic materials such as leather, cloth or rubber. The adhesive used to laminate the bellows-sheet 10 should have similar elastic properties as the inner and outer linings 12,14. In fig. 2, an enlarged, cut-out cross-section of a rigid portion of a bellows-sheet 10 is shown including a rein¬ forcement strip 13 laminated between the inner lining 12 and the outer lining 14. Fig. 3 shows a similar enlarged, cut-out cross-section of an elastic portion of a bellows-sheet 10 according to the invention, where the inner lining 12 is directly laminated to the outer lining 14. The described method of production is very convenient in that it requires minimal^ deviation from existing methods for producing conventional camera bellows, which eliminates the need for large investment in new production machinery. The invention is not restricted to the embodiment described above or shown in the drawings, but may be varied within the scope of the appended claims. For example, the number of elastic folds 5 may be varied with respect to the degree of displacement needed. Furthermore, if transverse dis¬ placements are desired in a horizontal as well as a vertical direction, all walls of the tubular body 1 may be provided with elastic folds 5. Additionally, the elastic folds 5 may be made of a softer, more elastic material than the rest of the bellows-sheet in order to obtain a bellows which is particularly suitable for very large transverse displacements .

Claims: Claims 1. A camera bellows comprising a substantially rectangu¬ lar, tubular body (1) having two ends (2,3), the walls of which body are provided with folds (5,6) for extensibility, said folds extending perpendicularly to the longitudinal direction of the body, and reinforcements (13) for retain¬ ing the rectangular shape of the bellows, c h a r a c t e r i z e d by alternating elastic (5) and rigid (6) folds, said elastic folds (5) enabling transverse displacements of one end of the body relative the other, whilst the rigid folds (6) serve to retain a free optical path through the bellows during said displacements. 2. A camera bellows according to claim 1, c h a r a c ¬ t e r i z e d i n that said elastic folds (5) are provided exclusive]y along two opposite walls of the bellows, so as to enable said transverse displacements only in a direction substantially parallel to the longitudinal extension of said elastic folds. 3. A camera bellows according to claim 1, c h a r a c ¬ t e r i z e d i n that said elastic folds (5) are in¬ folds in the bellows. 4. Method for producing a camera bellows according to claim 1, said tubular body (1) being formed by folding a sheet (10) comprising a lustreless non-reflective inner lining (12), a weather-resistant outer lining (14) and reinforcement strips (13) laminated therebetween on fold- surfaces (16) adjacent to the folds (6), c h a r a c t e r i z e d i n that said elastic folds (5) are obtained in that the fold-surfaces (16) of such a fold (5) are free of reinforcement strips (13) and that said inner lining (12) and outer lining (14) are made of elastic materials .

Inventors: PAPPILA LARS, PAPPILA, LARS
Applicants: HASSELBLAD AB VICTOR, PAPPILA LARS, PAPPILA, LARS, VICTOR HASSELBLAD AB
Application year: 1996
Main classification: G03B17
IPC codes: G03B17