Chain Drive System For Use In A Theatre

Abstract

A system for suspending a vertical curtain (especially a theatrical curtain) and for driving the curtain to move horizontally (for example, between a position covering a stage and a position not covering a stage). The curtain is suspended directly from a drive chain, along at least a portion of the drive chain, by chain attachment structures. Also, a rotating switch that can be actuated by a switch attachment structure supported by the drive chain. Also, the use of a dedicated encoder sprocket which is separate from the guide sprockets.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to systems for moving curtains and more particularly to systems chain drive systems for moving theatre curtains.

2. Description of the Related Art

Drive chain systems, using roller drive chain driven by motor and a driven sprocket, are conventional. FIGS. 1 and 2 show a small length of roller drive chain 50, including: pins 51; bushings 53; rollers 54; and plates 56. A drive sprocket (not shown) engages with the rollers and rotates to drive chain 50 along its direction of elongation. Some conventional chains do not include roller, and may include different or fewer components. Still, the roller drive chain 50 is a very popular and advantageous design for many drive chain applications. FIG. 3 shows hollow pin roller drive chain 60, including hollow pins 62. Hollow pins 62 each define through hole 63.

Some conventional roller drive chains are called attachment chains because support and/or attachment structures are built into the chain. These support and or attachment structures allow other objects to be attached to and/or supported by the roller chain. A few examples, showing a little of the wide variety of attachment chains are shown in FIGS. 4 to 9 and include: first attachment roller drive chain assembly 70 (including attachment structure 71); second attachment roller drive chain assembly 72 (including attachment structure 73); third attachment roller drive chain assembly 74 (including attachment structure 75); fourth attachment roller drive chain assembly 76 (including attachment structure 77); and fifth attachment roller drive chain assembly 80. As shown in FIGS. 8 and 9, fifth chain 80 includes: pin 81; plates 82; roller 83; and U-shaped attachment structure 85. Some attachment structures are built in a unitary and integral manner with the plates of the drive chain (see FIG. 6). Some attachment structures include piece parts that are additional to the plates (see FIGS. 4, 5 and 7). Some attachment structures attach ancillary structures in the plane defined by the chain rollers (see FIG. 6). Some attachment structures attach ancillary structures offset from the plane defined by the rollers (see FIGS. 4, 7, 8 and 9). Some attachment structures utilize the through holes in a hollow pin chain to attach the attachment structures (see FIG. 4).

There are conventional systems that use a chain drive to move a theatre curtain. In at least many of these systems a line or loop is formed, with the line or loop including a section made of chain and a section formed as a non-chain-style cable. The chain and non-chain sections are attached end to end. The chain section is driven to move by a sprocket. The non-chain-style section is mechanically connected (see DEFINITIONS section) to a theatre curtain. The driven motion of the chain section will pull the non-chain-style section along its direction of elongation to thereby move the theatre curtain, or at least a portion of the theatre curtain.

The following published documents may also include helpful background information: (i) Brochure entitled” Hall Stage PLASA 2010 Product Launch Chaindrive for T60 & T70 Track systems” date as of September 2010 (“Hall Stage Brochure”); (ii) U.S. Pat. No. 4,301,915 (“Michalik”; (ii) U.S. Pat. No. 5,526,832 (Shigenatsu”); (iii) U.S. Pat. No. 2,640,601 (“Van Wie”); (iv) U.S. Pat. No. 1,480,918 (“Szirmay”); (v) U.S. Pat. No. 3,490,514 (“Duncan”); (vi) 2,043,981 (“Travis Bickel”); (vii) US patent application 2005/0077107 (“Ramsey”); internet website based brochure entitled “Triple E Ltd. Chaintrack” date as of 8 Sep. 2010 (“Triple E Website”).

Description of the Related Art Section Disclaimer: To the extent that specific publications are discussed above in this Description of the Related Art Section, these discussions should not be taken as an admission that the discussed publications (for example, published patents) are prior art for patent law purposes. For example, some or all of the discussed publications may not be sufficiently early in time, may not reflect subject matter developed early enough in time and/or may not be sufficiently enabling so as to amount to prior art for patent law purposes. To the extent that specific publications are discussed above in this Description of the Related Art Section, they are all hereby incorporated by reference into this document in their respective entirety(ies).

BRIEF SUMMARY OF THE INVENTION

The present invention is directed to a system for suspending a vertical curtain (especially a theatrical curtain) and for driving the curtain to move horizontally (for example, between a position covering a stage and a position not covering a stage). The curtain is suspended directly from a drive chain, along at least a portion of the drive chain, by chain attachment structures. The present invention is further directed to a rotating switch that can be actuated by a switch attachment structure supported by the drive chain. The present invention is further directed to the use of a dedicated encoder sprocket which is separate from the guide sprockets.

According to an aspect of the present invention, a system suspends a curtain and drives the curtain in a generally horizontal direction. The system includes a curtain; a drive chain loop; a plurality of chain attachment structures; and a plurality of sprocket assemblies. The drive chain loop is made at least substantially entirely of drive chain; the plurality of sprocket assemblies each include: a sprocket, and a support sub-assembly structured and/or located to support the sprocket in an at least generally horizontal position so that all of the sprockets of the plurality of sprocket assemblies have an at least generally coplanar orientation. The drive chain is in sprocket-and-chain engagement with each sprocket of the plurality of sprockets. The plurality of chain attachment structures are mechanically connected to the drive chain. The curtain is mechanically connected to each of the chain attachment structures of the plurality of chain attachment structures so that the curtain will move when the chain is driven to move.

According to a further aspect of the present invention, a system suspends a curtain and drives a curtain in a generally horizontal direction. The system includes: a curtain; a loop; a plurality of curtain support structures; a switch attachment structure; a switch assembly; and a plurality of loop supporting assemblies. The curtain, the loop and the plurality of curtain support structures are located, structured and/or connected so that the curtain is pended from the loop by the plurality of curtain support structures. The plurality of loop supporting assemblies each include a: a loop guide, and a support sub-assembly structured and/or located to support the loop guide in an at least generally horizontal position so that all of the loop guides of the plurality of loop guides have an at least generally coplanar orientation. The loop is engaged with and defined in its shape by each loop guide of the plurality of loop guides. The switch attachment structure is mechanically connected to the loop. The switch assembly comprises a switch movable between a first position and a second position. The switch assembly, the loop and the switch attachment structure are structured and/or located so that the switch attachment structure will: (i) move the switch by physical interference from the first position to the second position when the loop and switch attachment structure move past the switch assembly in a first direction; and (ii) move the switch by physical interference from the second position to the second position when the loop and switch attachment structure move past the switch assembly in a second direction which is opposite the first direction.

According to a further aspect of the present invention, a system suspends a curtain and drives a curtain in a generally horizontal direction. The system includes: a curtain; a drive chain loop; a plurality of chain attachment structures; a plurality of sprocket assemblies; an encoder sprocket; and an encoder. The drive chain loop is made at least substantially entirely of drive chain. The plurality of sprocket assemblies each comprise: a guide sprocket, and a support sub-assembly structured and/or located to support the sprocket in an at least generally horizontal position so that all of the sprockets of the plurality of sprocket assemblies have an at least generally coplanar orientation. The drive chain is in sprocket-and-chain engagement with each sprocket of the plurality of sprockets. The plurality of chain attachment structures are mechanically connected to the drive chain. The curtain is mechanically connected to each of the chain attachment structures of the plurality of chain attachment structures so that the curtain will move when the chain is driven to move. The encoder sprocket is not in chain-and-sprocket engagement with the drive chain. The encoder sprocket is structured, located and/or connected to rotate corresponding to motion of the drive chain. The encoder is operatively coupled to the encoder sprocket to quantitatively detect rotation of the encoder sprocket.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be more fully understood and appreciated by reading the following Detailed Description in conjunction with the accompanying drawings, in which:

FIG. 1 is a perspective view of a segment of a prior art roller chain;

FIG. 2 is an exploded view of the roller chain segment of FIG. 1;

FIG. 3 is an orthographic top view of another prior art roller chain segment;

FIG. 4 is a perspective view of a prior art attachment chain segment;

FIG. 5 is a perspective view of another prior art attachment chain segment;

FIG. 6 is a perspective view of another prior art attachment chain segment;

FIG. 7 is a perspective view of another prior art attachment chain segment;

FIG. 8 is an orthographic end view of another prior art attachment chain segment;

FIG. 9 is an orthographic side view of the attachment chain segment of FIG. 8;

FIG. 10 is an orthographic top view of a first embodiment of a drive chain system according to the present invention;

FIG. 11 is an orthographic side view of the first embodiment system;

FIG. 12A is an orthographic bottom view of a component of the first embodiment system;

FIG. 12B is another orthographic bottom view of a component of the first embodiment system;

FIG. 12C is another orthographic bottom view of a component of the first embodiment system;

FIG. 13 is an orthographic side view of a first variation on a portion of the first embodiment system;

FIG. 14 is an orthographic side view of a component of a second variation on the first embodiment system;

FIG. 15 is an orthographic bottom view of a component of the second variation on the first embodiment system;

FIG. 16 is an orthographic end view of a component of the second variation on the first embodiment system;

FIG. 17 is an orthographic end view of a portion of the second variation on the first embodiment system;

FIG. 18 is an orthographic bottom view of a first embodiment chain guide track suitable for use in the present invention;

FIG. 19 is a perspective (generally end) view of the first embodiment chain guide track;

FIG. 20 is an orthographic end view of a second embodiment of chain guide track suitable for use in the present invention;

FIG. 21 is an orthographic bottom view of the second embodiment track;

FIG. 22 is a plan view of a portion of a second embodiment of a drive chain system according to the present invention; and

FIG. 23 is a plan view of a portion of the second embodiment system.

DETAILED DESCRIPTION OF THE INVENTION

FIGS. 10 to 12 show an embodiment of a chain drive system 100 according to the present invention, including: chain 102; curtain attachment structures 104; theatre curtain 105; switch attachment structure 106; sprockets 108,110,114,116; encoder sprocket 112; rotary encoder 120; drive motor 122; and switch 124. Switch 124 includes: rotating member 126; first protrusion 128; and second protrusion 130. System 100 is mounted to building structure 101, which is the ceiling of a theatre (for example, rafter beams located at the ceiling of a theatre. Systems according to the present invention may be mounted to other types of building structures, such as vertical walls or posts and brackets extending upwards from the floor. Although the sprockets are shown without teeth for clarity of illustration purposes, it will be understood that the sprockets generally have radially extending teeth that engage with the chain. Chain 102 is preferably a roller drive chain, but other types of chains are also possible. Alternatively, chain 102 could include non-chain-style line portions (for example, cable, but there should be chain at least at any portions that must engage with one of the sprockets.

Motor 122 drives drive sprocket 110 rotate in direction R3 in order to move chain in the D1 and D2 directions (that is, is the direction of elongation of the chain). The motion of the chain moves curtain in the D1 and D2 directions. Curtain attachment structures 104 mechanically connect curtain 105 to the chain in a relatively direct manner. Curtain attachment structures 104 are shown in FIGS. 10 and 11 in a schematic manner. A couple of specific attachment structures will be discussed in more detail below.

Guide sprocket 114 rotates in the R1 direction, and engages with encoder sprocket 112 to cause the encoder sprocket to rotate in the R2 direction. Rotary encoder 120 detects the rotation of the encoder sprocket (or its spindle (no separate reference number)) so that the position of the curtain can be determined on an ongoing basis as system 100 is operated to move the curtain back and forth. Rotary encoder may be any type of encoder no known or developed in the future. Such an encoder sprocket can be run off any guide sprocket that the chain does not wrap around too completely. According to another embodiment, a guide sprocket and an encoder sprocket are both mounted to the same rotating shaft. For example, these two sprockets could be formed as a single unitary piece with two rows of teeth.

The operation of switch 124 will now be explained with reference to FIGS. 12A to 12C. FIG. 12A shows 124 in its first position. Switch 124 is biased to remain in this position unless actively urged out of this position. As shown in FIG. 12A, switch attachment structure 106 is moving toward the switch in direction D1 as the chain is driven to move in direction D1. As switch attachment structure moves further in direction D1, it hits first protrusion 128. As shown in FIG. 12B, this physical interference caused rotating member 126 to rotate in the R4 direction so that the switch moves to a second position. the switch is biased to maintain this second position unless it is actively urged away from it. the movement of the switch from the first position to the second position is used to effect electronic control of the motion of the curtain. In this example, it causes the motor to stop driving the chain and curtain, so that the curtain will stop with its end in vicinity of switch 124.

As shown in FIG. 12C, the curtain has been controlled to start moving in direction D2. In FIG. 12C, the D2 direction motion has caused switch attachment structure to strike second protrusion 130 so that rotating member 126 is rotating back towards the first position again. In this way, the switch will be ready to be tripped again when the curtain comes back at a later time.

In system 100, curtain 105 is directly mechanically connected to chain 102 by curtain attachment structures 104. Curtain attachment structures 104 are a form of chain attachment structures (see DEFINITIONS section at definition of “chain attachment structure”). A couple of variations on the generic chain attachment structure 104 will now be discussed in connection with FIGS. 13-17.

FIG. 13 shows a first variation on system 100. In this variation, chain 102 includes: standard plates 152; standard pins 150; standard rollers 156; and chain attachment structure 154,159. Chain attachment structure 154,159 includes: plate portion 154; and hook portion 159. Curtain 105 is mechanically connected (see DEFINITIONS section) to the hook portion 159, and is thereby directly mechanically connected to the chain by the chain attachment structure. More specifically, curtain 105 includes grommet 158 that defines aperture 160, and the linking geometry of the grommet and the hook portion, in conjunction with gravitational forces, mechanically connect the curtain to the hook portion. In this embodiment, plate portion 154 and hook portion 159 are both rigidly mechanically connected to chain 102, but the hook portion could be movably mechanically connected (for example, rotatably engaged with, slidably engaged with) to the chain.

A preferred embodiment of the present invention is shown in FIGS. 14 to 17. In this embodiment, the chain includes: chain attachment structure 180,190; standard inner plates 195; standard outer plates 197; standard rollers 196; and standard pins 198. The chain attachment structure includes: U-shaped bracket 180; and wire clip member 190. The wire clip member includes: U-shaped portion 192 and securement arms 194. U-shaped bracket 180 includes: bracket arms 184; base portion 186; and clip-receiving holes 182.

As shown in FIG. 17, U-shaped bracket 180 is rigidly mechanically connected to the rest of the chain by pin 198 and inner plate 195, so that the base portion of the U-shaped bracket serves as an outer plate. Alternatively, the bracket could be extraneous to the plate geometry of the drive chain. As further shown in FIG. 17, the two bracket arms of the U-shaped bracket hand down and are mechanically connected to wire clip 190. More specifically: (i) the wire clip is structured so that it can be compressed in the R6 direction (see FIG. 16) to a compressed position; (ii) when the wire clip is in its compressed position the entire clip (including securement arms) can fit in the interior space of the U-shaped bracket; (iii) when the clip is released, it is biased to expand in the R7 direction to its expanded position; (iv) as the clip expands, securement arms 194 of the clip engage clip-receiving holes 182 in the bracket arms of the U-shaped bracket; (v) when the clip is in its fully expanded position, a rotatable (about the central axis of the clip-receiving holes) mechanical connection is formed between wire clip 190 and bracket 180; (vi) in this way, a curtain (not shown, but hanging from the bottom of the wire clip) is directly mechanically connected to the chain attachment structure and chain; and (vi) this is connection between the wire clip and the bracket is a detachably attachable mechanical connection because clip can be compressed again, by a user, to release the wire clip and the curtain from the chain and bracket.

As best shown in FIG. 16, securement arms 194 of wire clip 190 extend in a generally perpendicular direction from the two arms of the generally U-shaped clip. The securement arms have a portion that extends downward in the D3 direction (see FIG. 17). This downward-extending portion is preferable because it forms a more secure engagement with the clip-receiving holes. While wire clip 190 is formed by cutting and bending from standard spring wire, clip 190 could have many other cross-sectional profiles.

While FIGS. 13 and 17 shown only a single chain attachment structure for connecting to a single location on a curtain, preferred embodiments of the present invention will have many attachment points for a single curtain. For example, there may be attachment points spaced four inches apart along the length of the chain. In this way, the weight of the curtain is relatively evenly distributed over a relatively long length of drive chain, and the curtain does not sag excessively. In the preferred variation of FIGS. 14 to 17, standard attachment roller chain hardware is used for pins 198; outer plates 197; inner plates 195; rollers 196; and even U-shaped brackets 180. The wire clips are custom made. In some embodiments of the present invention, all of the chain attachment structure may be made up of standard, off-the-shelf pieces. In other embodiments of the present invention, the chain attachment structures may be made up of entirely custom-made part(s). Spacing of curtain clips controls how close it follows the track around tight corners, which the chain system allows

Above-described system 100 did not include chain supports (commonly called tracks) for runs of chain extending between two adjacent chain-engaging sprockets. As those of skill in the art will appreciate, tracks are often used in chain drive systems, and it is especially preferred to include tracks in embodiments of the present invention because the tracks can support not only the weight of the chain (as they do in conventional drive chain systems), but also support the weight of the curtain that is mechanically connected to the chain. However, when using tracks in systems according to the present invention, design care should be taken so that there is not physical interference between the tracks and switch attachment structures (if any) and curtain attachment structures (if any).

FIGS. 18 and 19 show track sub-system 200 for use as a track sub-system to support the chain in systems according to the present invention. Sub-system 200 includes track frame 202 and plastic inserts 206. The track frame is preferably metal, such as aluminum (for strength and stiffness). The inserts are preferably plastic to reduce friction with the chain, noise and wear on the chain. In some preferred embodiments, the plastic inserts are attached to the frame by blind expansion rivets.

FIGS. 20 to 23 show a preferred drive chain system according to the present invention, the system including: motor and drive sprocket portion 302; and track sub-system 304. Track subsystem 306 includes: track frame 306; plastic inserts 308; and rivets 310. Rivets 310 secure the plastic inserts in the axial direction with respect to the frame.

DEFINITIONS

Any and all published documents mentioned herein shall be considered to be incorporated by reference, in their respective entireties, herein to the fullest extent of the patent law. The following definitions are provided for claim construction purposes:

Present invention: means at least some embodiments of the present invention; references to various feature(s) of the “present invention” throughout this document do not mean that all claimed embodiments or methods include the referenced feature(s).

Embodiment: a machine, manufacture, system, method, process and/or composition that may (not must) meet the embodiment of a present, past or future patent claim based on this patent document; for example, an “embodiment” might not be covered by any claims filed with this patent document, but described as an “embodiment” to show the scope of the invention and indicate that it might (or might not) covered in a later arising claim (for example, an amended claim, a continuation application claim, a divisional application claim, a reissue application claim, a re-examination proceeding claim, an interference count); also, an embodiment that is indeed covered by claims filed with this patent document might cease to be covered by claim amendments made during prosecution.

First, second, third, etc. (“ordinals”): Unless otherwise noted, ordinals only serve to distinguish or identify (e.g., various members of a group); the mere use of ordinals shall not be taken to necessarily imply order (for example, time order, space order).

Electrically Connected: means either directly electrically connected, or indirectly electrically connected, such that intervening elements are present; in an indirect electrical connection, the intervening elements may include inductors and/or transformers.

Mechanically connected: Includes both direct mechanical connections, and indirect mechanical connections made through intermediate components; includes rigid mechanical connections as well as mechanical connection that allows for relative motion between the mechanically connected components; includes, but is not limited, to welded connections, solder connections, connections by fasteners (for example, nails, bolts, screws, nuts, hook-and-loop fasteners, knots, rivets, quick-release connections, latches and/or magnetic connections), force fit connections, friction fit connections, connections secured by engagement caused by gravitational forces, pivoting or rotatable connections, and/or slidable mechanical connections.

chain attachment structure: a structure that is directly mechanically connected an intermediate portion (as opposed to an end) of a chain; in preferred embodiments, the chain attachment hardware is standard chain attachment hardware for standard roller chains having plates, pins, rollers and bushings, but “chain attachment structure,” as used herein, is a broader term that refers to hardware that mechanically connects to any kind of chain; the term “chain attachment structure” does not necessarily imply that any further structures are attached to chain through the chain attachment structure, but, according to the present invention chain attachment structures can be used to attach a curtain to a driven chain; “chain attachment structures” are not necessary rigidly mechanically connected to the chain.

To the extent that the definitions provided above are consistent with ordinary, plain, and accustomed meanings (as generally shown by documents such as dictionaries and/or technical lexicons), the above definitions shall be considered supplemental in nature. To the extent that the definitions provided above are inconsistent with ordinary, plain, and accustomed meanings (as generally shown by documents such as dictionaries and/or technical lexicons), the above definitions shall control.

Unless otherwise explicitly provided in the claim language, steps in method steps or process claims need only be performed in the same time order as the order the steps are recited in the claim only to the extent that impossibility or extreme feasibility problems dictate that the recited step order be used. This broad interpretation with respect to step order is to be used regardless of whether the alternative time ordering(s) of the claimed steps is particularly mentioned or discussed in this document—in other words, any step order discussed in the above specification shall be considered as required by a method claim only if the step order is explicitly set forth in the words of the method claim itself. Also, if some time ordering is explicitly set forth in a method claim, the time ordering claim language shall not be taken as an implicit limitation on whether claimed steps are immediately consecutive in time, or as an implicit limitation against intervening steps.

Claims

1. A system for suspending a curtain and for driving a curtain in a generally horizontal direction, the system comprising:

a curtain;

a drive chain loop;

a plurality of chain attachment structures; and

a plurality of sprocket assemblies;

wherein:

the drive chain loop is made at least substantially entirely of drive chain;

the plurality of sprocket assemblies each comprise: a sprocket, and a support sub-assembly structured and/or located to support the sprocket in an at least generally horizontal position so that all of the sprockets of the plurality of sprocket assemblies have an at least generally coplanar orientation;

the drive chain is in sprocket-and-chain engagement with each sprocket of the plurality of sprockets;

the plurality of chain attachment structures are mechanically connected to the drive chain; and

the curtain is mechanically connected to each of the chain attachment structures of the plurality of chain attachment structures so that the curtain will move when the chain is driven to move.

2. The system of claim 1 wherein the drive chain loop is made at least substantially entirely of standard roller chain.

3. The system of claim 1 wherein each chain attachment structure, of the plurality of chain attachment structures comprise:

a U-shaped bracket; and

a wire clip member.

4. The system of claim 3 wherein the U-shaped bracket member includes:

a base portion that is structured to act as a roller chain plate; and

a pair of arms, each arm defining at least one hole, with the pair of arms extending from the base portion in an at least generally perpendicular direction.

5. The system of claim 4 wherein:

the wire clip member includes: a generally U-shaped portion including a base portion and a pair of arms extending from the base portion, and a pair of securement arms respectively extending at an angle from each arm of the U-shaped portion;

the wire clip member is shaped so that the securement arms respectively engage with the holes defined in the generally U-shaped bracket member; and

the wire clip member is further structured so that its generally U-shaped portion is slightly compressed from its at-rest position when it is engaged with the U-shaped bracket member.

6. The system of claim 5 wherein the securement arms respectively extend at a generally acute angle from the pair of arms of the wire clip.

7. The system of claim 6 wherein the wire clip is made from cylindrical spring wire.

8. A system for suspending a curtain and for driving a curtain in a generally horizontal direction, the system comprising:

a curtain;

a loop;

a plurality of curtain support structures;

a switch attachment structure;

a switch assembly; and

a plurality of loop supporting assemblies;

wherein:

the curtain, the loop and the plurality of curtain support structures are located, structured and/or connected so that the curtain is pended from the loop by the plurality of curtain support structures;

the plurality of loop supporting assemblies each comprise: a loop guide, and a support sub-assembly structured and/or located to support the loop guide in an at least generally horizontal position so that all of the loop guides of the plurality of loop guides have an at least generally coplanar orientation;

the loop is engaged with and defined in its shape by each loop guide of the plurality of loop guides;

the switch attachment structure is mechanically connected to the loop;

the switch assembly comprises a switch movable between a first position and a second position; and

the switch assembly, the loop and the switch attachment structure are structured and/or located so that the switch attachment structure will: (i) move the switch by physical interference from the first position to the second position when the loop and switch attachment structure move past the switch assembly in a first direction; and (ii) move the switch by physical interference from the second position to the second position when the loop and switch attachment structure move past the switch assembly in a second direction which is opposite the first direction.

9. The system of claim 8 wherein the switch rotates between the first position and the second position about an axis of rotation that is at least generally vertical.

10. The system of claim 9 wherein:

the switch comprises a first protrusion and a second protrusion; and

the switch attachment structure hits the first protrusion to rotate the switch as it moves past the switch assembly in the first direction; and

the switch attachment structure hits the second protrusion to rotate the switch as it moves past the switch assembly in the second direction.

11. The system of claim 8 wherein:

the loop is made at least substantially entirely of drive chain;

the loop guides are sprockets; and

the loop is in chain-and-sprocket engagement with the loop guides.

12. The system of claim 11 wherein the chain is standard roller chain.

13. A system for suspending a curtain and for driving a curtain in a generally horizontal direction, the system comprising:

a curtain;

a drive chain loop;

a plurality of chain attachment structures;

a plurality of sprocket assemblies;

an encoder sprocket; and

an encoder

wherein:

the drive chain loop is made at least substantially entirely of drive chain;

the plurality of sprocket assemblies each comprise: a guide sprocket, and a support sub-assembly structured and/or located to support the sprocket in an at least generally horizontal position so that all of the sprockets of the plurality of sprocket assemblies have an at least generally coplanar orientation;

the drive chain is in sprocket-and-chain engagement with each sprocket of the plurality of sprockets;

the plurality of chain attachment structures are mechanically connected to the drive chain;

the curtain is mechanically connected to each of the chain attachment structures of the plurality of chain attachment structures so that the curtain will move when the chain is driven to move;

the encoder sprocket is not in chain-and-sprocket engagement with the drive chain;

the encoder sprocket is structured, located and/or connected to rotate corresponding to motion of the drive chain; and

the encoder is operatively coupled to the encoder sprocket to quantitatively detect rotation of the encoder sprocket.

14. The system of claim 13 wherein the encoder sprocket is engaged with one of the guide sprockets so that rotation of the guide sprocket will drive the encoder sprocket to rotate.