MAGNETIC VOICE-COIL SHUTTER DRIVE ACTUATION

SYSTEM

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims an invention which was disclosed in a

United States provisional patent application filed November 15, 2006,

Serial No. 60/859,224, entitled "Magnetic Voice-Coil Shutter Drive

Actuation System". Priority benefit of the said United States provisional

application is hereby claimed, and the aforementioned application is

hereby incorporated herein by reference.

BACKGROUND AND SUMMARY

[0002] Most commercially-available electromagnetic shutters are

driven by linear solenoids. While readily available and inexpensive, they

are very inefficient shutter actuators. Inherently non-linear, they provide

much-reduced force at the beginning of pull-in (just when the shutter

requires maximum force to achieve high acceleration and short

actuation time). They provide very short stroke, typically requiring

troublesome lever mechanisms to match the longer stroke required by

the shutter drive mechanism. Furthermore, the short stroke often

requires tight manufacturing tolerance and/or custom alignment of

solenoid to drive linkage. At smallest sizes, solenoids provide very poor

power efficiency for given output force/stroke.

[0003] Rotary solenoids are sometimes used for shutter drive. And,

while these sometimes contain non-linear helical ramps to smooth out

the force/distance curve, they still have disadvantages in cost, energy

efficiency, and size.

[0004] DC motor actuators have occasionally been used. While they

offer more linear force/torque output and better power efficiency, they

still have several disadvantages. Their size/shape configuration is not

well matched to the low-profile donut-shaped space envelope

requirements of an optical shutter. Size trade-offs (tiny motors) reduce

power efficiency. Power coupling drives are sometimes costly and/or

inefficient. Motor inertia slows the start/stop response. And motor

brushes add reliability and debris concerns for this short- stroke

start/stop application.

[0005] Some proprietary electromagnetic shutter drives (i.e., Kodak)

use magnets and coils to drive a shutter. However, these all include an

iron core electromagnet. These have the disadvantage of higher

inductance of the coil assembly. And most of these designs have

magnet/pole cogging (requiring higher drive current just to overcome

magnet/pole attraction before actuator motion takes place.)

[0006] Thus, there is a continuing need for new and improved shutter

actuation mechanisms and technology. I have, therefore, developed a

voice coil drive for optical shutters. The resultant voice coil shutter

drive system, driven by Lorentz forces between electromagnet coil and

permanent magnetic flux, allows a very energy efficient, cost efficient

linear actuation mechanism for an optical shutter mechanism. In

addition, it offers numerous other advantages over current technology:

[0007] First, a superior linear force curve (force is fairly constant for

given drive current regardless of actuator position), allowing a smooth,

fast and efficient shutter drive.

[0008] Second, its coreless magnetic design allows driving at low

currents (as it does not have to overcome magnetic cogging of typical

motor designs).

[0009] Third, it can have low inertia moving mass, allowing efficient

high-speed actuation.

[00010] Fourth, its simplicity and long-strong actuation allow simple,

cost efficient manufacturing of shutter assemblies. Tight tolerances and

custom fit-up are not required.

[00011] Fifth, my direct drive system offers good system reliability and

efficient power transfer.

[00012] Sixth, the size/shape and configuration of my system can be

well matched to fit within compact shutter space envelopes, even while

allowing substantial magnet flux (and thus high energy efficiency).

BRIEF DESCRIPTION OF THE DRAWINGS

[00013] FIG. 1 provides a schematic perspective view of a side drive

voice coil shutter assembly.

[00014] FIG. 2 provides a schematic perspective view of a voice coil

shutter assembly with a moving coil having a side pivot.

[00015] FIG. 3 provides a schematic perspective view from above of a

swing link voice coil shutter assembly.

[00016] FIG. 4 provides a schematic perspective view from below of a

swing link voice coil shutter assembly.

[00017] FIG. 5 provides a more detailed view of a swing link of the

swing link voice coil shutter assembly.

DESCRIPTION

[00018] The exemplary side drive voice coil shutter assembly of FIG. 1

provides important insights into the functioning of my invention. As will

be noted, it has two permanent magnets, magnet 1 and magnet 2,

arranged with magnetic flux conducting members so as to create

opposite poles above/below conducting coil 3 and producing magnetic

flux IA (magnet 1) and 2A (magnet 2) between their respective poles.

The coil 3 is slideably mounted (as illustrated by arrows 4) so as to be

able to move toward Magnet 1 and away from Magnet 2, or vice versa,

depending on the magnetic flux direction created by current flow in coil

3. Coil 3 is attached to a wishbone linkage 5 which is, in turn, attached

to actuators 6 (slidable in housing slots 7) for the blade drive ring of the

shutter. Thus, as coil 3 is driven toward or away from, e.g., magnet 1,

by the Lorentz forces created between permanent magnets 1, 2 and coil

3, it will drive actuators 6 and 7, thereby driving the shutters of the

blade drive ring of shutter housing 8 towards an open or closed position.

(An alternate arrangement is to have the coil and magnets interchanged

so that there are two coils and one magnet — this is a simpler

arrangement although it will typically operate at a lower speed).

[00019] The side pivoted moving coil voice coil shutter assembly of

FIG. 2 uses the same basic principles, but applies the Lorentz force

created between its permanent magnets and the magnetic field created

by current in a coil to shift the pivotally mounted coil from side-to-side.

In this embodiment, each permanent magnet assembly includes iron

magnet frames 11, 12 serving as magnetic flux conductors for,

respectively, magnetic flux HA, 12A created by rare earth magnets HB,

12B mounted to frames 11, 12. Coil 13 is laminated on a ring shaped

plate 13A, which is pivotally mounted (by pivot 14) to shutter housing 15

so as as to be capable of shifting towards one of the permanent magnet

assemblies and away from the other permanent magnet assembly (as

illustrated by arrows 16) depending, once again, on the direction of the

magnetic flux created by current through coil 13. As coil 13 shifts, it

drives shutter actuator 17 via an extension 13B of ring shaped plate

13A, thereby driving the shutters of the blade drive ring of shutter

housing 15 towards an open or closed position.

[00020] The swing link voice coil shutter assembly of FIGS. 3, 4 and 5,

has a coil 20 that is non-moving and peripherally mounted in/on its

shutter housing 21. A plurality of swing links 22 connected to and

serving as actuators for respective shutter blades 23 are mounted so as

to interact with coil 20. Each swing link 22 is comprised of a permanent

magnet 22A (preferably a rare earth magnet) with magnetic flux

conducing pole plates 22B bonded to its respective poles so as to create

a magnetic flux 22C between the ends of opposing pole plates 22B. In

this particular embodiment the pivot axis 22D of each swing link is

inside of the coil 20 and directly mounted to a shutter blade 23, with its

ends free to swing outward or inward (as indicated by arrows 24,

depending on the direction of current in coil 20. Thus, depending on the

current direction in coil 20, shutter blades 23 are driven towards an

open or closed position.

[00021] In addition to the previously described configurations, my

invention could be produced in several other alternate configurations

having their own unique advantages and/or applications. These would

include a moving coil, side-mounted, center pivot with direct drive to a

shutter blade drive ring. This is the simplest arrangement (a

configuration similar to a computer disk drive read head actuator). They

could also include a moving coil, side pivot (with eccentric swing) for

highest efficiency in tight ID/OD cross section. Likewise, a moving

magnet can be arranged in a manner comparable to either of the first

two layouts set forth above, or in "swing link" fashion as shown in FIGS.

3 and 4 (swinging the pole pieces around the magnets). There could be

a vertical moving arrangement with helical ramps, flexures, or pivot

linkage to transfer motion to lateral plane. Finally, in terms of this

recitation, there could be various other combinations of the

features/systems described above (all using the basic principles of this

invention as applied to a shutter drive). Moreover, various of the above-

disclosed and other features and functions, or alternatives thereof, may

be desirably combined into many other different systems or applications.

[00022] Thus, as will be appreciated from review of this disclosure,

numerous variations can be made and/or produced without exceeding

the scope of the inventive concept. There are, therefore, a variety of

presently unforeseen or unanticipated alternatives, modifications,

variations or improvements therein which may be subsequently made by

those skilled in the art which are also intended to be encompassed by

this application and the claims to follow.

WHAT IS CLAIMED IS: