U.S. patent number 3,724,350 [Application Number 05/155,415] was granted by the patent office on 1973-04-03 for electromagnetic drive for photographic shutters.
This patent grant is currently assigned to Rollei-Werke Franke & Heidecke. Invention is credited to Bodo Mielke.
United States Patent |
3,724,350 |
Mielke |
April 3, 1973 |
**Please see images for:
( Certificate of Correction ) ** |
ELECTROMAGNETIC DRIVE FOR PHOTOGRAPHIC SHUTTERS
Abstract
An electromagnetic drive for the blades of a photographic
shutter, using at least one pot-shaped magnet in fixed position. A
cylindrical coil, when properly energized, moves into or out of the
pot-shaped magnet. The coil is connected directly to a movable
shutter blade in one embodiment, or to a blade operating member
(such as a rotatable ring) in another embodiment. To obtain faster
exposures, the moving parts engage a resilient stop when the
shutter reaches fully open position, and this resilient stop
absorbs some of the kinetic energy of the opening movement and
gives it back to the moving parts in a closing direction.
Inventors: |
Mielke; Bodo (3300
Braunschweig, DT) |
Assignee: |
Rollei-Werke Franke &
Heidecke (Braunschweig, DT)
|
Family
ID: |
25759341 |
Appl.
No.: |
05/155,415 |
Filed: |
June 22, 1971 |
Foreign Application Priority Data
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Jun 26, 1970 [DT] |
|
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P 20 31 565.5 |
Apr 22, 1971 [DT] |
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P 21 19 609.8 |
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Current U.S.
Class: |
396/467;
396/453 |
Current CPC
Class: |
G03B
9/07 (20130101); G03B 9/58 (20130101); G03B
9/08 (20130101) |
Current International
Class: |
G03B
9/02 (20060101); G03B 9/07 (20060101); G03B
9/00 (20060101); G03B 9/58 (20060101); G03B
9/08 (20060101); G03b 009/08 () |
Field of
Search: |
;95/1C,53R,53E,53EA,53EB,58,59,60,62,64R,64D |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Peters, Jr.; Joseph F.
Parent Case Text
This is a division of application, Ser. No. 88,849, filed Nov. 12,
1970.
Claims
What is claimed is:
1. Electromagnetic drive for a photographic shutter blade,
comprising a pot-shaped magnet having a pot-shaped outer body and a
central core in position to provide an annular gap between the
outer body and the core, the outer end portion of said gap being
narrower than the major portion of the axial length of said gap, an
electrical coil of generally cylindrical shape wound with uniformly
spaced turns and mounted for axial movement through said narrower
portion of said annular gap upon electric energization of said
coil, and means operated by such movement of said coil for moving a
shutter blade, said coil having an effective length sufficiently
greater than the axial length of the narrower portion of said
annular gap so that in all axial positions of said coil during its
working stroke necessary for moving a shutter blade from open to
closed position, the same number of turns of said coil will lie
within said narrower portion of said gap.
2. A drive as defined in claim 1, characterized by the fact that
there is more than one shutter blade and that each shutter blade is
individually provided with its own moving coil and pot-shaped
magnet.
3. A drive as defined in claim 2, characterized by the fact that
the associated shutter blade is mounted to swing on a pivot, and
that the axis of the moving coil and the axis of the pot-shaped
magnet are curved circularly and concentrically with said pivot,
and that the curved coil is rigidly connected to the shutter
blade.
4. A drive as defined in claim 2, characterized by the fact that
the associated shutter has an exposure aperture with two blades
mounted for rectilinear movement radially with respect to the
exposure aperture, and that each blade is rigidly connected to the
moving coil of its individual drive.
5. A drive as defined in claim 1, characterized by the fact that
said central core of said magnet is a permanent magnet.
6. A drive as defined in claim 1, characterized by the provision of
two such pot-shaped magnets mounted coaxially in tandem relation to
each other with a separate coil movable in each pot-shaped magnet,
the two coils being connected to each other for joint movement in
the same direction.
7. A drive as defined in claim 6, in which only one coil is
energized to produce joint movement of the two coils in one
direction to open an associated photographic shutter, and in which
only the other coil is energized to produce joint movement of the
two coils in the opposite direction to close the shutter.
8. A drive as defined in claim 6, in which both coils are energized
to produce joint movement of the two coils in one direction to open
an associated photographic shutter, and in which both coils are
also energized to produce joint movement of the two coils in the
opposite direction to close the shutter.
9. A drive as defined in claim 1, wherein the moving coil of the
drive is directly coupled to one or more shutter blades by means of
a pin and slot connection.
10. A drive as defined in claim 1, further comprising an elastic
buffer member engaged by a moving part at substantially the
completion of a shutter opening movement, to absorb kinetic energy
from such opening movement and return the absorbed energy to such
part in a reverse direction to assist a closing movement.
11. A construction as defined in claim 10, in which the part which
engages said elastic buffer member is a part of said drive fixed to
and rigid with the moving coil of said drive.
12. A construction as defined in claim 11, further comprising a
second elastic buffer member engaged by and absorbing kinetic
energy from a shutter member separate from but driven by the moving
coil of said drive.
13. A drive as defined in claim 1, in combination with a
photographic objective shutter of the type having a plurality of
swinging blades and a rotatable blade driving ring for swinging the
blades between their closed and open positions, characterized by
the fact that said drive is mounted with the axis of said coil
approximately tangential to said blade driving ring and is
operatively coupled thereto to turn said ring from axial movement
of said coil.
14. A construction as defined in claim 13, further comprising a
first elastic buffer member engaged by a part of the moving coil
structure at substantially the completion of a shutter opening
movement, to absorb kinetic energy from such opening movement and
return the absorbed energy to the coil structure in a reverse
direction to assist a closing movement, and a second elastic buffer
member engaged by and absorbing kinetic energy from a portion of
said blade driving ring, to return the absorbed energy to the blade
driving ring to assist a closing movement in a reverse direction.
Description
BACKGROUND OF THE INVENTION
Electromagnetic drives for shutters are known, broadly. The present
invention provides an improvement in this broad class of drives. It
has been found, according to the present invention, that better
results can be obtained if, instead of the conventional
electromagnetics, the drive comprises one or more magnets having
thin annular gaps, such magnets being herein described as
pot-shaped, in conjunction with a hollow cylindrical coil movable
axially through the narrow gap or slot of each magnet, when the
coil is electrically energized. The moving coil may be operatively
connected to the movable shutter blade, either through intermediate
operating mechanism (e.g., a blade ring for operating several
pivoted shutter blades) or directly to a shutter blade without any
intermediate mechanism.
The use of a pot-shaped electromagnet in stationary position with a
coil operatively connected to a shutter blade, enables the shutter
to have operating mechanism of relatively low mass, since the coil
itself can be very light although adequately strong to perform its
function. Moreover, the magnet may be so shaped that the force
produced upon energizing the coil is uniform throughout the entire
stroke of the coil.
An object of the invention is the provision of a generally improved
and more satisfactory shutter drive of the general character above
mentioned.
Another object is the provision of such a drive so designed that it
is relatively inexpensive and easy to manufacture and to install in
the shutter.
Still another object is the provision of a shutter drive so
designed that such a drive may be used to power two or more shutter
blades, or alternatively, an individual electromagnetic drive of
this character may be used for each individual shutter blade.
A further object is the provision of a shutter so designed that at
the end of the opening movement, the moving parts engage with one
or more resilient or elastic members which absorb the kinetic
energy of the opening movement and give such energy back to the
parts in a closing direction creating a "bounce" effect which
assists in speeding up the shutter operation.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic view of a fragment of an objective shutter
according to a first embodiment of the invention, with parts in
elevation and parts in vertical section;
FIG. 2 is a section taken approximately on the line II--II of FIG.
1;
FIG. 3 is a schematic front view of a fragment of a different type
of shutter, illustrating a second embodiment of the invention;
FIG. 4 is a schematic view, partly in elevation and partly in
section, of a third embodiment of the invention, illustrating the
coils of the electromagnet connected directly to the shutter
blades;
FIG. 5 is a similar view of a fourth embodiment of the invention,
illustrating an arrangement in which the coil of the electromagnet
is directly connected to a pivoted blade; and
FIG. 6 is a view similar in general to FIG. 1, illustrating the
additional feature of elastic members to assist in quick return of
the shutter parts from open position to closed position.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring first to FIGS. 1 and 2, there is shown only a fragment of
an objective shutter which, except for the electromagnetic drive
parts, may be of conventional construction. Thus it may include a
conventional base plate 101 and an aperture plate 103, these two
plates having aligned openings through them which define the
exposure aperture. The plates are axially spaced from each other as
usual, providing a space between them for receiving the
conventional pivoted shutter blades 105 commonly found in objective
shutters, there usually being about five such blades although the
number may vary. The blades are mounted in the usual conventional
way for swinging movement between open and closed positions, the
swinging of the blades being accomplished by rotary movement of the
usual blade ring 111, mounted for rotation about the optical axis
as a center. In some objective shutters, the blades are mounted on
pivot pins, and pins are fixed to the blade ring to engage in slots
in the blades to cause swinging movement of the blades when the
blade ring is rotated. In other shutters, the blades are mounted on
pivots fixed to the blade ring, and the slots in the blades engage
other pivots mounted on another part of the mechanism, for causing
swinging of the blades when the blade ring is rotated relative to
the other part on which the other pivots are mounted. For purposes
of the present invention, it is entirely immaterial which of these
arrangements is used for mounting the blades, or whether some other
known arrangement for mounting the blades is used, since the
invention (in this first embodiment thereof) relates only to the
manner in which the blade ring is driven and is independent of the
manner in which the blades themselves are mounted. Merely as a
convenient example, FIGS. 1 and 2 illustrate a typical construction
in this respect, the blades 105 being mounted on fixed pins 114 and
having slots 113 (FIG. 6) for engaging the pins on the blade ring
111.
The electromagnetic drive of the present invention, which serves to
drive the blade ring 111 in one direction to open the blades and in
the opposite direction to close the blades, includes at least one
and preferably two pot-shaped magnets mounted in stationary
position. When two magnets are used, as in the preferred
construction, they face each other as seen in FIG. 1. The first
magnet has a cup-shaped or pot-shaped body 1 of soft iron and an
inserted core 2 consisting of a permanent magnet. Between the parts
1 and 2 is an annular gap or slot 3 to accommodate the moving coil
4. At the mouth or other end (considered in an axial direction
relative to the pot-shaped magnet) of the annular gap 3, it is
narrowed down considerably as indicated at 5, leaving just enough
space for free axial passage of the annular or hollow cylindrical
core 4. This produces in the gap 5 a very intense magnetic field,
so that the coil 4, over its entire length, is drawn into or
extracted from the pot 1, as the case may be, with a constant or
uniform force throughout the entire length of the axial movement,
when the coil 4 is appropriately energized by the electric
current.
Thus the electromagnetic drive is particularly suitable for a case
in which constant force is desired over a certain distance. By
reversing the polarity of the winding of the coil 4 (that is,
reversing the direction of the direct current flowing through it)
the system can be used with same effect in both directions, to
produce the desired constant or uniform driving force in either
axial direction throughout the entire range of movement, since the
same number of turns of wire in the coil will be within the
narrowed portion 5 of the gap in any position of the coil, assuming
that the coil is sufficiently long in an axial direction so that it
fills the full axial length of the narrow gap 5 in both of the
extreme or limit positions of the coil.
In this first embodiment, illustrated in FIGS. 1 and 2, the pot
magnet coil system is arranged on the tandem principle. The first
magnet system having the parts, 1, 2, 3, 4, and 5 is duplicated by
a second magnet and coil system arranged coaxially with the first
and faced toward the first system, with a gap between the two
systems. They are reverse duplicates of each other and the second
system requires no further description except to say that the main
body or pot of the second system is indicated at 6, and the coil
thereof at 7. The adjacent ends of the two coils 4 and 7 are
interconnected with each other by a connecting ring 8, which has
fixed thereto an arm 8a terminating in a forked portion 9 which
embraces a pin 10 on the previously mentioned blade ring or shutter
drive ring 111.
If one or both of the coils 4 and 7 are electrically energized in
the proper direction to move leftward in FIG. 1, in the direction
of the arrow B, the fork 9 engaging the pin 10 will swing the blade
ring 111 clockwise and will open the shutter blades. When one or
both coils are energized by direct current in the opposite
direction, so as to move rightwardly in FIG. 1, in the direction of
the arrow A, then the fork 9 moves the pin 10 to the right, turning
the blade ring 111 counterclockwise and closing the shutter
blades.
With an arrangement like this, with two electromagnetic drives
arranged in tandem relation and faced oppositely, it is possible to
operate the mechanism in various ways. For example, the electrical
connections (which can easily be made within the skill of the art,
in the light of the present disclosure) may be such that for
closing the shutter, only the coil 4 is energized in a direction to
pull the coil into the magnet 1, in the direction of the arrow A,
and for opening the shutter, only the coil 7 is energized, in a
direction to pull this coil into its magnet 6, in the direction of
the arrow B. Although this is possible, it is usually preferred to
operate both magnets for operating the shutter in both directions,
thereby producing greater force for quicker operation. Thus for
closing the shutter, the coil 4 is preferably energized by current
in a direction to pull the coil rightwardly into its magnet 1,
while at the same time the coil 7 is energized in a direction to
push it rightwardly out of its magnet 6. Reversely, for opening the
shutter, both coils 4 and 7 are energized for movement in a
leftward direction.
Since the number of coil turns or windings in the narrow gap 5
remains constant no matter what the axial position of the coil may
be, it is entirely possible, when the coils are connected in
opposition to each other, to produce a state of equilibrium,
whatever their position may be. Thus the present drive is also
suitable for use as a diaphragm regulator for exposure control
devices, if permanently flowing currents are used in place of the
short duration or impulse currents which would normally be employed
if one desires only the quick opening and quick closing of a
shutter.
Referring now to FIG. 3, there is illustrated a second embodiment
of the invention in which approximately the same pot magnet drive
is applied to a shutter of a different type having two blades 14
and 15 pivoted for opposite movement on the respective pivots 16
and 16a. The tandem magnet assembly is essentially the same as
illustrated in FIG. 1, the main bodies of the magnets being shown
in FIG. 3 by the same numerals 1 and 6 used in FIG. 1. The coils of
these magnets are as before, and are connected by a connecting ring
8 as before. The extension 8b on this ring carries the pin 10'
which engages appropriate slots 12 and 13 in the respective shutter
blades 14 and 15. When the coils and their connecting ring 8 move
to the left, the action of the pin 10' on the slots 12 and 13
swings both blades to their open positions illustrated in dotted
lines, to open the exposure aperture of the shutter. When the coils
and connecting ring move back in a rightward direction, both
shutter blades are swung back to their closed positions illustrated
in full lines.
FIG. 4 shows the application of the electromagnetic drive to a
shutter which has rectilinear sliding blades rather than pivoted
blades. The exposure aperture shown at 121 is open when the sliding
blades 17 and 18 are pulled back away from each other as
illustrated in FIG. 4, and are closed when the blades move toward
each other into an overlapping relation.
In this embodiment of the invention, each blade has its own
individual electromagnetic drive. The respective coils 19 and 20
are directly connected to the respective blades 17 and 18, without
any intervening moving parts. These coils operate in the respective
pot magnets 21 and 22, the coils and magnets being of essentially
the same construction and operating in the same way as in the first
embodiment described in connection with FIGS. 1 and 2. This
embodiment of the invention illustrates the applicability of the
invention to shutters having blades which are not pivoted, and also
to shutters in which it is desired to have each blade with its own
independent electromagnetic drive unit, and it also illustrates the
possibility of a direct connection between the coil and the
blade.
Another embodiment, illustrated in FIG. 5, shows that a shutter
with pivoted blades can also make use of the present
electromagnetic drive invention for each individual blade
separately, and with a direct connection, without intervening
moving parts. In FIG. 5, there are several pivoted shutter blades
which collectively close and open the exposure aperture 123, but
only one blade 23 is illustrated, pivoted for swinging movement on
the pivot 26. Directly connected to this blade is the coil 24 of
annular construction in cross section, but with its axis curved or
bent arcuately, concentric with the shutter blade pivot 26.
The magnet 25 is formed exactly like the magnets previously
described, except that its axis also is bent concentrically with
the shutter blade pivot 26. When the coil 24 is electrically
energized in a direction to push it out of the magnet 25, the blade
23 swings counterclockwise to its open position illustrated in FIG.
5. When the coil 24 is electrically energized in the opposite
direction, to pull it into the magnet body 25, this swings the
blade 23 clockwise on its pivot 26, so that this blade, in
conjunction with other similar blades arranged at intervals around
the exposure aperture, will cover the exposure aperture to close
the shutter.
The shutter driving arrangement according to the present invention
enables higher acceleration to be produced in opening and closing
the shutter blades, as compared with prior electromagnetic
shutters, this being due partly to the constant driving force
generated through the full length of the opening stroke or closing
stroke (as the case may be), and partly to the fact that the moving
masses can be kept very small, because the moving coils are very
light in weight. Thus the system provides not only a very short
switching time or exposure time, amounting to about one-fifth of
the time involved in the customary electromagnetic shutter drives
of the prior art so far as known to applicant at present, but also
these short times are obtained at the cost of a much more moderate
expenditure of electrical power, believed to amount to about
one-tenth or less then one-tenth of the power required in prior art
electromagnetic shutter drives known to applicant.
The blade driving system of the present invention is usable not
only for driving shutter blades between two defined limit positions
(fully open and fully closed) but also for driving diaphragm blade
systems or combined shutter and diaphragm blade systems of variable
stroke, such as required, for example, in preselection diaphragms
which have to be fully opened for viewing purposes (as in the case
of a single lens mirror reflex camera) and have to be reclosed to a
certain preselected aperture, before the photograph is taken. In
such a system, if the shutter is prestressed or biased, e.g.,
mechanically, in such a way that when the electromagnetic drive is
in the non-energized state the blades assume the fully open
position, then it is possible, by suitably regulating the flow of
current through the coil, via an exposure regulating device or
manual device, to cause the electromagnetic drive to close or open
the diaphragm to a certain preselectable distance.
The rapid exposures possible with the present invention have
already been mentioned. Still faster exposures are possible if,
according to another feature of the invention, resilient or elastic
members are used, against which the moving parts of the shutter hit
when the shutter reaches or closely approaches the fully open
position, so that the elastic elements will produce a "bounce"
effect on the moving parts, first absorbing kinetic energy from the
moving parts and then returning such energy to these parts in the
opposite direction, to cause quicker closing.
Merely as an example, FIG. 6 illustrates this feature of the
invention as applied to a shutter of the type disclosed in FIGS. 1
and 2. It is to be understood, however, that this same feature of
the invention, to produce a resilient "bounce" effect at the end of
the opening movement and beginning of the closing movement, could
be applied to any of the other forms of shutters such as
illustrated, for example, in FIGS. 3-5.
Referring now to FIG. 6, the construction is the same as previously
described in connection with FIGS. 1 and 2, except for the addition
of the resilient or elastic members. The same reference numerals
are used as in FIG. 1, for corresponding parts. The difference is
that, just as the moving parts are about to reach the position in
which the shutter blades are fully open, a flange 161 on the
connecting ring 8 strikes against an elastic or resilient arm 151
which is permanently mounted on a fixed part of the mechanism by
screws or rivets 153. Initially, the upper end of this elastic arm
is in the position shown in broken lines. As the moving ring 18
reaches its extreme position in the shutter opening direction, it
displaces the resilient arm 151 slightly from the broken line
position to the full line position, so that this arm absorbs
kinetic energy, helps to slow down rapidly the fast movement of the
ring 8, and then gives back its absorbed kinetic energy to the
ring, starting the ring rapidly back in the opposite or
shutter-closing direction.
If desired, such an elastic member may be used only in conjunction
with the connecting ring 8 and the associated coils 4 and 7.
However, it is preferred to use a similar elastic member also in
conjunction with a projection on the blade ring 111. Such a
projection is illustrated at 181, and it engages the resilient or
elastic arm 171 permanently mounted in fixed position by means of
screws or rivets 173. The projection 181 engages the elastic arm
171 at substantially the same time that the flange 161 engages the
elastic arm 151. The combined effect of both of these elastic arms
is to absorb smoothly a great deal of the kinetic energy of the
fast moving parts at the end of the opening stroke, and to create a
substantial "bounce" effect with helps to speed the parts at the
beginning of their closing stroke. Exposure times of less than
1/500th of a second can be obtained by utilizing this feature of
the invention.
These buffers or elastic members must be dimensioned in such a way
that the maximum storage of kinetic energy and elastic effect
becomes operative when the shutter drive is moving at its maximum
speed. In the case of lower opening speeds (longer exposure time)
they merely act as stops which, owing to their intrinsic
resilience, prevent violent impact. Of course the spring force and
the driving force of the moving coils have to be adapted to the
inertia forces of the shutter blades and other moving parts of the
shutter mechanism. The use of this bounce feature makes it
possible, without any appreciable extra expenditure of electrical
energy, to obtain very short exposure times. This is particularly
important from the point of view of dimensions to be adopted and
space to be provided for the driving batteries of the
electromagnetic drive system. The electromagnetic drive itself,
according to the present invention, provides a very suitable drive
which can be operated with minimum use of electric power, thus
enabling small batteries to be used and enabling minimum dimensions
of the casing or housing. When the further feature of the elastic
"bounce" is added to the advantages also obtainable merely from the
use of the electromagnetic drive, it is seen that a particularly
advantageous construction is the result, with great economy of
electrical power even though high shutter speeds are attained.
The elastic members 151 and 171 may be constructed of various
materials. Satisfactory results have been attained by the use of
spring steel, or by using phosphor bronze.
* * * * *