GB2132781A

GB2132781A - A lamellar focal-plane shutter

Info

Publication number: GB2132781A
Application number: GB08330009A
Authority: GB
Inventors: Hans-Jorg Schonherr; Rolf Seifert; Berto Kirsch; Heinz Schulze
Original assignee: Pentacon Dresden VEB
Current assignee: Pentacon GmbH Foto und Feinwerktechnik
Priority date: 1982-12-17
Filing date: 1983-11-10
Publication date: 1984-07-11
Also published as: DE8328346U1; DE3335993A1; DE3335993C2; GB8330009D0; GB2132781B

Abstract

A lamellar focal-plane shutter for photographic cameras is provided with an opening group of blades and a closing group (7, 7'). The respective pair of supporting levers (5, 5', 6, 6') is connected, at the distal ends thereof, to a slit-forming main blade (7, 7') so as to form a link parallelogram. There is provided in the central travel path of at least one group a cam (19, 21) which impulsively influences the main blade thereof (7, 7') in one sense of rotation to maintain the blades parallel. If cams are provided in both paths the senses of rotation are opposite. <IMAGE>

Description

SPECIFICATION A lamellar focal-plane shutter The invention relates to a lamellarfocal-plane shut- ter for photographic cameras which is provided with an opening group and a closing group, whose respective pair of supporting levers is connected, at the free ends thereof, to a slit-forming main blade so as to form a link parallelogram.

During the rational production of known shutters of this kind, there arises the difficulty, particularly for short exposure times, of the parallel designing of the exposure slit by the opposite slit-forming edges of the main blades, for the main blades strive to incline their slit-forming edges in a wedge-shaped manner relative to each other during the exposure operation.

Apart from the high precision requirement, no measures have been taken so far for reducing this wedge-shaped slit formation. There are only known cams which press the opening groups and the closing groups respectively in their end positions perpendicularly to their movement planes (DE OS 2341750, DE OS 2342451, DE OS 2622940) and which also influence the main blades in the sense of rotation within their movement planes; however, this influencing does not occur until the main blades have left the camera aperture so that there does not take place any correction of the travel position of the main blades during the exposure operation.

The object of the invention is a technical measure for maintaining a parallel exposure slit during the exposure operation. According to the invention, this is brought about in that there is provided in the central travel path of at least either the opening group or the closing group a cam which impulsively influences the main blade in one sense of rotation. in this way, there is carried out during the exposure operation a correction of the travel position of the main blade. Expediently, there are arranged in the central travel path of the opening group a first cam, which impulsively rotates the main blade thereof in one direction, and in the central travel path of the closing group a second cam, which implusively rotates the main blade thereof in the opposite direction.According to a preferred construction, the first cam is arranged in the travel path of the one main blade end that is directed away from the supporting levers and the second cam is arranged in the travel path of the other main blade end that is directed towards the supporting levers. According to another advantageous design of the invention, the first cam is arranged in the travel path of the one main blade end that is directed away from the supporting levers and the second cam is arranged in the travel path of a supporting lever of the other main blade. Expediently, the second cam is provided on an auxiliary lever which is mounted so as to be concentric with the supporting lever and which is loaded by means of a spring in the opposite direction to the travel sense of the supporting lever and is retainable in the central travel path of the supporting lever by a stop.According to a special construction, the correction according to the invention of the position of the slit-forming blade of the closing group during the exposure operation is brought about in conjunction with a catching pawl provided for bounce-proofing, in that the catching pawl is loaded by means of the return spring in the opposite direction to the travel sense of a supporting lever of the closing group and comprises the cam which projects into the central travel path of said supporting lever. This arrangement has, above all, the advantage that the bounce-proofing for the opening group is already cancelled at the end of the exposure operation and does not functionally burden the following tensioning operation.Expediently, the catching pawl is arranged on a catching slide which is slidably mounted in a straight-line guide, the guide way (a) extending steeply with respect to the inlet way (b) of the catching pin of the opening group and almost parallel to the run way (c) of an actuating arm of the closing group which disengages the catching pawl from the catching pin.

According to another construction, the catching pawl is preferably provided on a catching lever which is rotatably mounted on a journal which is arranged close to the inlet way (b) of the catching pin of the opening group.

The invention will be explained with the aid of illustrated and described exemplified embodiments.

In the drawings: Figure 'shows an arrangement while the shutter is travelling, Figure 2 shows the arrangement after the central position has been reached, Figure 3 shows a lateral view thereof, scaled-up, Figure 4 shows another arrangement while the shutter is travelling, FigureS shows the other arrangement after the central position has been reached, Figure 6 shows a lateral view of the other arrangement, Figure 7shows a shutter when the opening group has travelled, Figure 8 shows the shutter while the closing group is travelling, Figure 9 shows the shutter in the end position, Figure 10 shows a lateral view thereof, scaled-up, and Figure ii shows another construction for bounceproofing.

Between the base plate 1 and the wafer 2, which is parallel thereto, the supporting levers 5 and 6 are rotatably mounted by means of the fixed pivots 3 and 4 (see Figure 1). The slit-forming main blade 7 of the closing group is articulatedly connected to the free ends of the supporting levers 5 and 6; the other blades of the closing group, which are not shown, are articulatedly fastened in known manner to the supporting levers 5 and 6 at a shorter distance from the pivots 3 and 4. On the pivot 4 there is arranged, also in a rotatable manner, the driving lever 8 which the driving spring 9 seeks to rotate in the clockwise sense. A known lock pawl not shown keeps the driving lever 8 in the locked position against the driving spring 9. The driving lever 8 projects with the driving pin 10 through the outer supporting lever 6.

On the driving pin 10 as well as the pivot 4 there have been loosely placed between the supporting lever 6 and the base plate 1 and the wafer 2 respectively the spacers 12, 13 and 14 respectively, which practically fill the space between the supporting lever 6 and the base plate 1 and the wafer 2 respectively.The supporting lever 6 is aligned in a plane parallel to the base plate 1 by these spacers 12, 13 and 14 respectively. Another spacer 16 is located between the inner supporting lever 5 and the base plate 1. The opening group with the slit-forming main blade 7', together with the supporting levers 5' and 6', is arranged homologously to the closing group in the same manner.

The guide plate 16 is arranged along the travel path of the ends of the main blades 7 and 7', which ends are directed away from the supporting levers 5, 6 and 5', 6' respectively, between the movement planes of the blades and parallel to the base plate 1; further guide plates 17 and 17' are respectively located between the closing group with the main blade 7 thereof and the wafer 2 as well as the opening group with the main blade 7' thereof and the base plate 1.

The main blade 7' of the opening group has, at the end that is directed away from the supporting levers 5' and 6', a narrow extension 18, in whose central zone of its travel path the guide plate 17' is provided with a small cam 19 (see also Figure 3). The main blade 7 of the closing group is provided with a narrow extension 20 at the end that is directed towards the supporting levers 5 and 6, the wafer 2 carrying a small cam 21 in the central zone of the travel path thereof.

The mode of operation is as follows: The releasing of the driving lever 8' causes the exposure operation to be initiated, in that the opening group with the slit-forming main blade 7' uncovers the exposure aperture 15. During this movement, the spacers 12', 13' and 14' respectively slide, together with the supporting lever 6', in the space between the supporting lever 6' and the base plate 1 and the wafer 2 respectively. During this process, the supporting lever 6' is moved, corresponding to the thickness of the spacers 12', 13' and 14' respectively, parallel to the base plate 1 and to the wafer 2 respectively, which results in a corresponding parallel guidance of the blades of the opening group.For short exposure times, there directly follows the driving lever 8 of the closing group with the slit-forming main blade 7 so that a narrow exposure slit comes about between the main blade 7' and the main blade 7. During the exposure operation, the main blades 7' and 7 give rise to the exaggeratedly shown wedge shape (see Figure 1) of the exposure slit, in that the end of the opening main blade 7', which end is directly away from the supporting levers 5' and 6', and the end of the opening main blade 7', which end is directed towards the supporting levers 5 and 6, and the end of the closing main blade 7, which end is directed towards the supporting levers 5 and 6, tend to run in advance. In the central zone of its travel, the extension 18 of the opening main blade 7' encounters the cam 19 and is forced to swerve.The impulsive delay, bound up therewith, of the main blade 7' end carrying the extension 18 corrects the position of this blade along the lines of a reduction of the wedge shape in the anti-clockwise sense. Also in the central zone of its travel, the extension 20 of the closing main blade 7 encounters the cam 21. As a result of the impulsive delay, bound up therewith, of the main blade 7 end carrying the extension 20, the position of this blade is corrected along the lines of a reduction of the wedge shape in the clockwise sense (see Figure 2). According to another arrangement according to the invention, which substantially has the same construction as that shown in Figures 1 and 2, a small cam 22 is provided in the central zone of the travel path of the supporting lever 5 for the closing group (see Figure 4).This cam 22 is arranged on an auxiliary lever 23 which is mounted so as to be concentric with the supporting lever 5. The return spring 24 seeks to place the auxiliary lever 23 against the stop 25 of the base plate 1, the small cam 21 being in the central zone of the travel path of the supporting lever 5.

The mode of operation corresponds, with respect to the opening main blade 7', to the arrangement shown in Figures 1 and 2. The correction of the closing main blade 7 is however brought about in that the supporting lever 5 encounters in the central zone of its travel the cam 21 and rotates the auxiliary lever 23 against its weak return spring 24. The impulsive delay of the supporting lever 5, which occurs during this process, results in a correcting relative movement of the main blade 7 in the clockwise sense, which counteracts the wedge shape (Figure 5).

A special construction of the invention, and one which takes bounce-proofing into consideration, (see Figures 7 to 10) again shows basically the same design as the arrangement according to Figures 1 and 2.

For catching the opening group in its end position, which uncovers the exposure aperture 15, there is arranged the catching pawl 22 in the travel path of the spacer 12' which has been placed on the driving pin 10' for the supporting lever 6'. The catching pawl 22 forms part of a catching slide 27 which, by means of slots 28 and 29, has been passed through the spacer 13', on the one hand, and through the pin 26, on the other hand. The catching slide 27 carries the cam 21 which, in the position of rest of the catching slide 27, lies in the central travel path of the supporting lever 5 for the closing group. The weak return spring 24 engaging in the cam 11 seeks to pull the catching slide 27 continuously into the position of rest thereof.

The mode of operation is as follows: The releasing of the driving lever 8' causes the exposure operation to be initiated, in that the opening group with the slit-forming main blade 7' uncovers the exposure aperture 15. During this movement, the spacers 12', 13' and 14' respectively slide, together with the supporting lever 6', in the space between the supporting lever 6' and the base plate 1 and the wafer 2 respectively. During this process, the supporting lever 6' is moved, due to the spacers 12', 13' and 14' respectively, parallel to the base plate 1 and the wafer 2 respectively, which results in a corresponding parallel guidance of the blades of the opening group.When the open position of the opening group, which uncovers the exposure aperture 15, is reached (see Figure 7), the spacer 13' has overcome the catching pawl 22 which, due to the return spring 24, is placed behind the spacer 13'. The opening group is prevented from rebounding by the catching pawl 22.

The closing group 7 is released, in accordance with the exposure time set, by the tripping of the driving lever 8 (see Figure 8). During the closing operation, the end of the slit-forming main blade 7, which end is directed towards the supporting levers 5 and 6, tend to run in advance, causing the exaggeratedly shown inclined position of the main blade 7 to come about. However, the supporting lever 5 of the main blade 7 encounters in the central zone of its travel path the cam 11 of the catching slide 27. Due to the impulsive delay, bound up therewith, of the supporting lever 5 of the main blade 7, the position of the latter is corrected along the lines of a resetting of the main blade 7 in the clockwise sense. At the same time, the catching slide 27 is moved against the return spring 24 (see Figure 9), causing the catching pawl 22 to release the spacer 13' of the opening group.Now the return of the blade groups to their tensioned positions can be effected without hindrance.

According to another construction, which again has the same basic design as that of Figures 1 to 3, the cam 21 a, which lies in the travel path of the supporting lever 5 for the closing group, is provided on a rotatably mounted catching lever 30 (see Figure 11) which, in turn, carriesthe catching pawl 22. The catching lever 30 is rotatably mounted on the journal 31. The return spring 24, which is unchanged, seeks to place the catching lever 30 with the arm.32 against the fixing stop 33. In this position of rest, the catching pawl 22 is in the locking position of the spacer 13' and the cam 1 lea lies in the central travel path of the supporting lever 5 of the closing group.

Because of its variability, the invention is not confined to the exemplified embodiments shown. It is however always essential that the slit-forming main blades should experience an impulsive correction of position during the exposure operation along the lines of a reduction of the wedge shape of the exposure slit, particularly in that one of the paired supporting levers 5,6 of the closing group overcomes a component carrying the catching pawl 22 for the opening group against the return spring 24 of this component.

Claims

1. A lamellarfocal-plane shutter for photographic cameras which is provided with an opening group and a closing group, whose respective pair of supporting levers is connected, at the free ends thereof, to a slit-forming main blade so as to form a link parallelogram, characterised in that there is provided in the central travel path of at least either the opening group or the closing group a cam (19, 21) which impulsively influences the main blade thereof (7, 7') in one sense of rotation.

2. A lamellarfocal-plane shutter as claimed in Claim 1, characterised in that there are provided in the central travel path of the opening group a first cam (19) which impulsively rotates the main blade (7') thereof in one direction and in the central travel path of the closing group a second cam (21) which impulsively rotates the main blade (7) thereof in the opposite direction.

3. Alamellarfocal-plane shutter as claimed in Claim 2, characterised in that the first cam (19) is arranged in the travel path of the end of one main blade (7'), which end is directed away from the supporting levers (5', 6'), and the second cam (21) is arranged in the travel path of the end of the other main blade (7), which end is directed towards the supporting levers (5, 6).

4. Alamellarfocal-plane shutter as claimed in Claim 2, characterised in that the first cam (19) is arranged in the travel path of the end of one main blade (7'), which end is directed away from the supporting levers (5', 6'), and the second cam (21) is arranged in the travel path of a supporting lever (5) of the outer main blade (7).

5. A lamellarfocal-plane shutter as claimed in Claim 4, characterised in that the second cam (21) is provided on an auxiliary lever (23) which is mounted so as to be concentric with the supporting lever (5) and which is loaded by means of a return spring (24) in the opposite direction to the travel sense of the supporting lever (5) and is retainable in the central travel path of the supporting lever (5) by a stop (25).

6. A lamellar focal-plane shutter as claimed in Claim 5, characterised in that a catching pawl (22) which is provided for bounce-proofing for the opening group, is loaded by means of the return spring (24) in the opposite direction to the travel sense of a supporting lever (5) of the closing group and comprises the cam (21,21 a) which projects into the central travel path of said supporting lever (5).

7. A lamellar focal-plane shutter as claimed in Claim 6, characterised in that the catching pawl (22) is arranged on a catching slide which is slidably mounted in a straightline guide (28, 29), the quide way (a) extending steeply with respect to the inlet way (b) of the catching pin (e.g. spacer 13') of the opening group and practically parallel to the run way (c) of a supporting lever (5) of the closing group, which lever disengages the catching pawl (22) from the catching pin.

8. A lamellar focal-plane shutter as claimed in Claim 6, characterised in that the catching pawl (22) is arranged on a catching lever (30) which is rotatably mounted on a journal (31) which is arranged close to the inlet way (b) of the catching pin (e.g. spacer 13') of the opening group.

9. A lamellar focal-plane shutter substantially as described by way of example and reference to Figures 1-3, Figures 4-6, Figures 7-10 or Figure 11 of the accompanying drawings.