(12) Unlted States Patent
`(10) Patent N0.:
`US 6,293,329 B1
`
`Toti
`(45) Date of Patent:
`*Sep. 25, 2001
`
`U5006293329B1
`
`(54) COIL SPRING DRIVE SYSTEM AND
`WINDOW COVER
`
`(76)
`
`(*) Notice:
`
`Inventor: Andrew J TOti, 311 W. River Rd,
`MOdeStO’ CAGE) 95351
`This patent issued on a continued pros-
`ecution application filed under 37 CFR
`15301), and is subjeffi t0 the twenty year
`patent
`term prOVISIOHS 0f 35 USC.
`154(a)(2).
`
`............................. 185/39x
`
`2/1958 Etten .
`2,824,608
`7/1964 Graybill
`3,139,877 *
`8/1983 Godsoe.
`4,399,959
`* Z132: Elia
`....................................... 160/189
`2,2231%;(1)
`ng -
`7
`7
`11/1988 Graham.
`4,784,122
`19/133; 23%? '
`3,233,133
`7/1996 Kuhar:
`5’531’257
`.
`4/1997 Matsumoto et al.
`5:615:729
`9/1998 Lysyj
`................................. 160/84.04
`5,813,447 *
`FOREIGN PATENT DOCUMENTS
`
`Subject to any disclaimer the term of this
`.
`’.
`Patent 15 mended 0r adJuSted under 35
`U~S~C~ 154(b) by0 daYS-
`
`0796994A2
`883709 *
`1068583 *
`
`9/1997 (EP) .
`3/1943 (FR) .................................. 160/8404
`1/1984 (SU) ..................................... 160/313
`
`(21) Appl. No.2 08/989,148
`
`* cited by examiner
`
`(22)
`
`Filed:
`
`Dec. 11: 1997
`R l t d U S A l'
`t'
`D t
`eae
`.. pplcalon aa
`
`Primary Examiner—Blair M. Johnson
`(74) Attorney, Agent, or Firm—Philip A. Dalton
`(57)
`ABSTRACT
`.
`.
`.
`.
`.
`.
`.
`Continuation—in—part of application No. 08/963,775, filed on
`A c011 spring drive unit for Window covers is disclosed,
`Nov. 4, 1997.
`Int. Cl.7 ........................................................ E06B 9/30 Wthh comprises a C011 spring drive and the combination
`(51)
`.
`.
`whose elements are selected from (1) a band shift transmis-
`(52) US. Cl.
`............................... 160/168.1 R, 160/170 R,
`sion which provides varying ratio power transfer as the
`_
`185/39
`cover is opened and closed; (2) gear means comprising
`(58) Fleld of Search ......................... 160/170 R, 168.1 P,
`various gear sets which provide frictional holding force and
`160/84~02> 84~04> 84~05> 190> 191> 192>
`fixed power transfer ratios; and (3) a gear transmission
`189, 313, 315, 318; 185/39
`which provides fixed ratio power transfer as the cover is
`e erences
`1 e
`C't d
`opened or closed. The combination permits the coil spring
`R f
`drive torque to be tailored to the weight characteristics of the
`U.S. PATENT DOCUMENTS
`window cover such as a horizontal slat or pleated or box
`blind as the blind is opened and closed, and permits the
`length of the blind and the distance between the open and
`closed positions of the blind to be altered for a given
`rotational distance of the coil spring.
`
`(63)
`
`(56)
`
`13,251
`2,266,160
`2,276,716 *
`2,324,536
`2,390,826
`2,420,301
`
`7/1855 Bixler .
`12/1941 Burns .
`3/1942 Cardona ........................... 160/170 R
`7/1943 Pratt .
`12/1945 Cohn .
`5/1947 Cusumano .
`
`5 Claims, 3 Drawing Sheets
`
`
`
`Norman Int. Exhibit 1008
`
`Norman Int. Exhibit 1008
`
`

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`US. Patent
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`Sep.25,2001
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`Sheet170f3
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`US 6,293,329 B1
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`Norman Int. Exhibit 1008
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`Norman Int. Exhibit 1008
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`US. Patent
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`Sep.25,2001
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`US. Patent
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`Sep.25,2001
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`US 6,293,329 B1
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`Norman Int. Exhibit 1008
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`Norman Int. Exhibit 1008
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`

`

`US 6,293,329 B1
`
`1
`COIL SPRING DRIVE SYSTEM AND
`WINDOW COVER
`
`This is a continuation-in-part of application Ser. No.
`08/963,775, titled COIL SPRING DRIVE SYSTEM FOR
`WINDOW COVER, filed Nov. 4, 1997, inventor Andrew J.
`Toti.
`
`1. BACKGROUND OF THE INVENTION
`
`a. Field of the Invention
`
`invention relates generally to coil spring
`The present
`drives or motors, which are useful in numerous applications
`and,
`in particular,
`to the application of such coil spring
`drives in window cover systems.
`b. Definitions and Applicability
`Typically, as used here, “cover” refers to expandable or
`extendible structures. These include slat structures such as
`so-called venetian or slat blinds and so-called mini-blinds.
`
`These structures also include pleated folding structures such
`as single and plural pleat structures and box, hollow and
`cellular structures. “Cover” also refers to flat, sheet-type
`covers such as roller blinds. In this document, “cover” and
`“blind” are frequently used interchangeably. As applied to
`such covers, “operate” refers to the process of closing and
`opening the covers,
`typically (for horizontal covers) to
`lowering and raising the cover.
`As used here, “horizontal” window cover refers to hori-
`zontally oriented covers such as horizontal slat blinds,
`horizontal folded pleat blinds and horizontal cellular blinds.
`The present invention is applicable generally to horizontal
`window cover systems and to flat window cover systems. It
`is understood that “window,” as used for example in “win-
`dow cover,” includes windows, doorways, openings in gen-
`eral and even non-opening areas or regions to which “win-
`dow” covers are applied for decoration, display, etc.
`c. Current State of the Relevant Field
`
`Typically a horizontal cover or blind is mounted above a
`window or space which is to be covered, and is operated
`using lift cords to extend the cover and lower it across the
`area, stopping at a selected position at which the blind
`partially or fully covers the area. For typical horizontal slat
`blinds, the lift cords are attached to a bottom rail and the
`individual slats are supported by the cross members or
`“rungs” of a separate cord ladder. When the blind is fully
`lowered, each slat is supported by a rung of the cord ladder
`and relatively little weight is supported by the lift cords.
`However, as the blind is raised, the slats are “collected” on
`the bottom rail, and the support of the slats is thus increas-
`ingly transferred from the cord ladder to the bottom rail and
`the weight supported by the rail and the lift cords increases.
`Typical pleated, cellular, box, etc., blinds are formed of
`resilient material having inherent spring-like characteristics.
`As the resilient blind is raised toward the fully open position,
`the blind material is increasingly compressed, and requires
`increasingly greater force to overcome the compression
`force and move the blind and hold the blind in position.
`Effectively, then, both the slat blind and the pleated blind
`require increasingly greater force to open the blind and to
`maintain the blind open than is required to close the blind
`and maintain the blind closed.
`
`So-called coil spring drives have operating characteristics
`which make it difficult to assist the opening and closing
`operation of blinds such as horizontal and flat blinds. As
`applied to downward-closing embodiments of such blinds,
`coil spring drives typically are mounted at the top of the
`
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`2
`blind, and are operatively connected or coupled to the shaft
`about which the blind lift cord is wound. As described
`
`above, as the blind is lowered, the slat weight supported by
`the lift cords decreases and the compression force of the
`pleats decreases. However, as the blind is lowered,
`the
`spring is wound and the energy stored in the spring
`increases, such that the increasing torque or force of the
`spring may then raise the blind in fast, uncontrolled fashion.
`Also,
`it may be difficult to keep the blind at a selected
`position. Furthermore, if the blind is heavy, and requires a
`strong spring to maintain the blind open,
`the blind is
`particularly susceptible to instability and uncontrolled rais-
`ing operation when partially or fully extended or closed.
`Conversely, when the blind is at or near the upper limit of
`its travel (i.e., is open), the slat weight supported by the lift
`cords and the pleat compression is at or near maximum,
`while the spring torque is at or near minimum. In this
`position, then, unless the spring is strong (perhaps causing
`uncontrolled operation), the spring torque may be insuffi-
`cient to keep the blind open.
`Frequently, prior art coil spring drives use latching
`mechanisms in an attempt to hold the blind or cover in
`position.
`
`2. SUMMARY OF THE INVENTION
`
`the present invention is embodied in a
`In one aspect,
`spring drive unit comprising a shaft; a coil spring mounted
`around a shaft and having a fixed end and a rotatable end;
`and a gear transmission of fixed drive ratio, operatively
`connected at one end to the rotatable spring end and opera-
`tively connected at the opposite end to the shaft. As a result
`of this arrangement, the transmission applies holding fric-
`tion to the shaft and applies the fixed drive ratio between the
`coil spring and the shaft, determining the ratio of the shaft
`rotational distance to the spring winding distance and
`thereby controlling the force applied to the shaft by the
`spring. In another related aspect, the spring drive unit further
`comprises a band transmission of continuously varying drive
`ratio, which is itself operatively connected at one end to the
`rotatable spring end and operatively connected at the oppo-
`site end to the shaft, for applying the continuously varying
`drive ratio between the coil spring and the shaft to continu-
`ously vary the force applied to the shaft by the spring and to
`continuously vary the ratio of the shaft rotational distance
`and the spring winding distance.
`In another aspect, the present invention is embodied in a
`spring drive unit comprising a shaft; a coil spring mounted
`around the shaft and having a fixed end and a rotatable end;
`and a band transmission of continuously varying drive ratio,
`operatively connected at one end to the rotatable spring end
`and operatively connected at the opposite end to the shaft.
`As a result of this arrangement,
`the band transmission
`applies said continuously varying drive ratio between the
`coil spring and the shaft to continuously vary the force
`applied to the shaft by the spring and to continuously vary
`the ratio of the shaft rotational distance and the spring
`winding distance. In another related aspect, the spring drive
`unit further comprises a gear transmission of given drive
`ratio, which itself is operatively connected at one end to the
`rotatable spring end and is operatively connected at the
`opposite end to the shaft, for applying the given drive ratio
`to the shaft to fixedly alter the force applied to the shaft by
`the spring and to fixedly alter the ratio of the shaft rotational
`distance to the spring winding distance, and for applying
`inherent holding friction to the shaft.
`In another aspect, the present invention is embodied in a
`window cover system comprising an extendible window
`
`Norman Int. Exhibit 1008
`
`Norman Int. Exhibit 1008
`
`

`

`US 6,293,329 B1
`
`3
`cover; lift means including lift cords attached to the cover
`for raising and lowering the extendible cover to selected
`positions; and a spring drive unit connected to the lift cords
`for assisting the raising and lowering of the cover. The
`spring drive unit comprises a shaft; a coil spring mounted
`around the shaft and having a fixed end and a rotatable end;
`and a gear transmission of given (fixed) drive ratio,
`the
`transmission connected at one end to the rotatable spring end
`and at the opposite end to the lift cords. As a result of this
`arrangement, the transmission applies holding friction to the
`lift cord-supported cover and applies the given drive ratio
`between the coil spring and the lift cords, determining the
`ratio of the cover travel distance to the spring winding
`distance and thereby controlling the force applied to the
`cover by the spring.
`the spring
`In an alternative spring drive embodiment,
`drive unit comprises a shaft; a coil spring mounted along the
`shaft and having a fixed end and a rotatable end; and a band
`shift transmission of varying drive ratio. The band shift
`transmission is connected at one end to the rotatable coil
`
`spring end and at the opposite end to the lift cords. As a
`result, the band shift transmission applies said varying drive
`ratio between the coil spring and the lift cord,
`thereby
`varying the ratio of the cover travel distance to the spring
`winding distance as the cover is raised and lowered, and
`controls the force applied to the cover by the spring.
`In another aspect, the spring drive unit further comprises
`gear means connecting the coil spring to the band shift
`transmission. The gear means comprises a set of bevel gears
`and a second set of gears, preferably direct gears. The bevel
`gears are connected at one end to the spring free end for
`rotation therewith and at the opposite end mesh with one end
`of the direct gears for rotation therewith. The direct gears are
`connected at the opposite end to one end of the band shift
`transmission for rotation therewith. The opposite end of the
`band shift transmission is connected to the lift cord pulleys
`for rotation therewith. As a result of this arrangement, the
`gear means applies holding friction to the lift cord-supported
`cover. Also, the gear means has a given (fixed) drive ratio
`which further contributes to the overall ratio of the cover
`
`travel distance to the spring winding distance and so controls
`the force applied to the cover by the spring.
`In yet another aspect, the gear means comprises a gear
`transmission of given drive ratio, which is connected
`between the band shift transmission and the direct gear set,
`with one end of the transmission connected to said opposite
`end of the direct gear set and the opposite end of the
`transmission connected to said one end of the band shift
`
`transmission. The gear transmission thereby applies addi-
`tional holding friction to the lift cord-supported cover and
`applies the given ratio between the coil spring and the lift
`cord, further changing the overall ratio of the cover travel
`distance to the spring winding distance and the force applied
`to the cover by the coil spring.
`Other embodiments of the present invention are described
`in the specification drawings and claims.
`3. BRIEF DESCRIPTION OF THE DRAWINGS
`
`The above and other aspects of the invention are
`described below in conjunction with the following drawings.
`FIG. 1 is a front elevation view of a horizontal slat blind
`
`window cover system, showing the cover in a lowered
`(closed) condition.
`FIG. 2 is a front elevation view of the window cover
`
`system of FIG. 1, showing the cover in a nearly fully-raised
`(nearly open) condition.
`
`4
`FIG. 3 is a front elevation view of a horizontal pleated
`blind window cover system, showing the cover in a lowered
`(closed) condition.
`FIG. 4 is a front elevation view of the window cover
`
`system of FIG. 3, showing the cover in a nearly fully-raised
`(nearly open) condition.
`FIG. 5 is a simplified top plan view of a coil spring drive
`unit in accordance with the present invention, a coil spring
`drive unit adapted for use in the window cover system of
`FIGS. 1—4
`
`FIG. 6 is an exploded view of the gear transmission of
`FIG. 5.
`
`FIG. 7 is a simplified top plan view of an alternative coil
`spring drive unit in accordance with the present invention,
`one which comprises a coil spring drive, a band shift
`transmission, and connecting gear units, in accordance with
`the present invention.
`FIG. 8 is a front elevation view of the band shift trans-
`mission of FIG. 7.
`
`FIG. 9 is a top plan view of yet another alternative coil
`spring drive unit in accordance with the present invention, a
`coil spring drive unit which comprises a coil spring drive, a
`band shift transmission, a gear transmission, and connecting
`gear units, all in accordance with the present invention.
`FIG. 10 is a simplified top plan view of the coil spring
`drive unit of FIG. 5, showing the binding of the spring coils
`on the shaft when the spring is relatively fully wound and the
`associated cover is extended at or near the closed condition.
`
`the coil springs illustrated in the above
`Please note,
`drawing figures are simplified, with enlarged spacing
`between the coils, to better illustrate the shaft and other
`components. For example, the individual coils of the spring
`shown in FIGS. 5 and 10 are packed together, and in fact the
`increased packing of the wound spring is at least partially
`responsible for the binding illustrated in FIG. 10.
`4. DETAILED DESCRIPTION OF THE
`
`PREFERRED EMBODIMENT(S)
`
`As used here, the term “operatively connected” includes
`both direct connections of one component to another without
`intervening components and connections via intervening
`components including gears, transmissions, etc.
`FIGS. 1 and 2 depict an exemplary horizontal slat
`(venetian) blind cover system 10 in closed (fully lowered)
`and nearly fully open positions, respectively. Typically, the
`blind cover system 10 comprises an elongated support
`member or housing 11 within which is mounted a coil spring
`drive unit such as unit 15, FIG. 5. The associated blind 12
`comprises horizontal slats 13 and a bottom rail 14 which can
`be the same as the slats but, preferably, is sufficiently heavy,
`or is weighted, to impart stability to the blind.
`FIGS. 3 and 4 depict a second exemplary, horizontal
`pleated blind cover system 20 in closed and nearly fully
`opened positions, respectively. Typically, the blind cover
`system 20 comprises elongated support member or housing
`11 within which the coil spring drive unit 15 or other suitable
`spring drive unit
`is mounted. The associated blind 22
`typically comprises light weight fabric or other material
`which is resilient and maintains the shape of the horizontal
`pleats 23. The blind also includes a bottom rail 24 which is
`sufficiently heavy, or weighted, to provide stability to the
`blind 22.
`
`Referring also to FIG. 5, the illustrated spring drive unit
`15 includes a shaft 30 comprising middle shaft or section 31
`and left and right end shafts or sections 32 and 33. Adjacent
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`Norman Int. Exhibit 1008
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`Norman Int. Exhibit 1008
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`

`

`US 6,293,329 B1
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`5
`ends 34, 36 of the middle and left shafts and adjacent ends
`35, 37 of the middle and right shafts have reduced radius or
`size and are joined by collars 38 and 39. The separate shaft
`sections facilitate removal of the shaft 30 and installation
`and replacement of the drive components mounted on the
`shaft. The shaft 30 is rotatably journaled within transverse
`frame members 41, 42, 43, 44 and 46. Cord pulleys 18 are
`mounted on the shaft 30 adjacent supports 41 and 46,
`respectively. Spaced blind lift cords 16 are attached to
`bottom rail 14 (blind 10, FIG. 1), or to bottom rail 24 (blind
`20, FIG. 3) and are wound about the pulleys 18 for raising
`and lowering the attached bottom slat or rail and thus the
`blind 10 or 20.
`
`Regarding slat blind 10, FIGS. 1 and 2, and as is typical
`of such blinds, spaced cord ladders 17 are suspended from
`the support 11 and the cross members 21 of the ladders are
`routed along and/or attached the underside of the individual
`slats 13 so that when the ladders are fully extended
`(lowered) and the blind 12 is thus fully lowered, as depicted
`in FIG. 1, the weight of each slat is supported by the ladders,
`with little weight on the lift cords. In contrast, as the blind
`12 is raised from the lowermost position, for example to the
`partially raised/lowered position depicted in FIG. 2, the slats
`are sequentially “collected” on the bottom rail 14, starting
`with the bottommost slats, so that an increasing weight is
`supported on the bottom rail and by the lift cords 16. Thus,
`and perhaps counter-intuitively, the weight supported by the
`lift cords is a maximum when the blind is fully open (raised),
`and a minimum when the blind is fully closed (lowered).
`As discussed previously, the force requirements of hori-
`zontal pleated blinds such as blind 20, FIGS. 3 and 4 are
`somewhat similar to the slat blind 10 in that the compression
`of the pleats 23 increasingly opposes movement of the blind
`as it is raised, thus increasing the force required to open the
`blind and to maintain the blind in position. Conversely, the
`decreasing compression of the material as the blind is
`lowered toward the closed position decreases the force
`requirement.
`Referring again to FIG. 5, coil spring 47 is positioned
`between supports 42 and 43, and is positioned around
`middle shaft section 31 (that is, the shaft 31 is inside the
`spring coils), for independent rotation around the shaft 30. A
`first end of the coil spring 47 is attached by fastener 48 to
`support 42 so that the first end (illustratively, the left end)
`does not rotate. The opposite (right) end of the coil spring is
`attached by fastener 49 to gear sleeve 52 of transmission 50.
`As described in detail below, that sleeve is connected to
`transmission idler gear 51, so that the right end of the spring
`47 rotates with the idler gear 51 of the transmission 50 and
`vice versa. The transmission 50 is designed to offset the
`normal operating characteristics of the coil spring 47. The
`stored energy of the spring increases as the spring is wound
`when the blind 10 or 20 is lowered and thus the increasing
`torque of the spring increasingly opposes lowering the blind.
`In short, the spring torque increases as the blind is lowered,
`while the lift cord-supported slat weight or the pleat com-
`pression is decreasing. Conversely, when the blind is raised,
`under the impetus or assistance of the spring, the stored
`spring energy and associated spring torque decrease, while
`the supported slat weight or the pleat compression of the
`raising blind is increasing.
`Referring to FIGS. 5 and 6, in one illustrated exemplary
`embodiment,
`the transmission 50 comprises an array of
`gears 51, 53, 55 and 57, in which idler gears 51 and 53 are
`intermeshed and idler gear 55 and power gear 57 are
`intermeshed. Idler gear 51 and integral sleeve or collar 52
`are mounted on and free to rotate about shaft section 35.
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`Gears 53 and 55 are joined, forming a gear set. This gear set
`and integral collar 56 are mounted on shaft 54, which is
`mounted to and between supports 43 and 44. The gear set
`and the collar rotate around shaft 54 and/or shaft 54 itself is
`mounted for rotation. Power gear 57 and integral collar 58
`are mounted on and fastened to shaft section 35. Power gear
`57 meshes with gear 55 of the two-gear set, the other gear
`53 of which meshes with idler gear 51.
`As mentioned, shaft end section 35 is part of the inter-
`connected shafts (or shaft sections) 31, 32, 33. Thus, at one
`end of the transmission gear train, power gear 57 is joined
`to and rotates at the same rate as the shaft 30. At the opposite
`end of the transmission gear train, idler gear 51 rotates freely
`about the shaft 30 and is fastened to the free spring end by
`fastener 49, so that the idler gear 51 and coil spring 47 rotate
`at
`the same rate. As the result of this arrangement,
`the
`pulleys 18 and lift cords 16 rotate at one rate, the same rate
`as gear 57 and shaft 30, and the coil spring 47 rotates at
`another rate, the same rate as gear 51. The transmission gear
`ratio is selected so that the idler gear 51 and coil spring 47
`preferably rotate at a slower rate than the power gear 57 and
`the lift cord pulleys 18. For example in one application, the
`fixed drive ratio of transmission 50 is 1:3 to 1:8 so that gear
`57 and pulleys 18 rotate 3—8 revolutions for each revolution
`of the gear 51 and coil spring 47.
`The above transmission gear ratios and the different
`rotation rates diminish proportionately the wind up of the
`spring 47 and the rate at which the torque exerted by the
`spring 47 increases as it is wound and the blind is lowered.
`This permits the use of a powerful spring to hold a large,
`heavy blind in position at the uppermost position, where the
`supported weight (or the pleat compression force) is the
`greatest, and diminishes the inherent rate of increase of the
`torque exerted by the spring as the blind is moved toward the
`lowermost, closed condition where the supported weight
`(the pleat compression force) is a minimum. Also, and
`referring to FIG. 10, as the spring winds up, it buckles in
`serpentine fashion along the shaft 31, and contacts the shaft
`at a multiplicity of locations 40 (only one such location 40
`is shown), exerting pressure on the shaft and preventing the
`shaft from turning on its own, thereby providing braking
`action against shaft rotation. The braking helps keep the
`shaft and pull cord from moving when at rest but does not
`impede raising and lowering movement. Furthermore, the
`transmission 50 has inherent friction which acts as a brake
`
`and helps retain the blind at the selected positions between
`and including fully opened and fully closed.
`As a result of the above factors,
`the spring does not
`overpower the weight of the blind and does not uncontrol-
`lably raise the blind. The transmission gear ratio also
`increases the length of travel available to the blind for a
`given spring, permitting a longer blind for a given spring or
`a given spring travel. The combination of the coil spring,
`transmission fixed gear ratio, gear friction and the spring
`buckling braking action allows the spring drive unit 15 to
`hold the blind 10, 20 in position at even the “heaviest”
`(uppermost) blind positions, prevents the spring from over-
`powering the blind, especially when the spring is wound (at
`the lower blind positions), and allows the blind to be pulled
`downward to any selected position by gently pulling the
`blind to that position and, conversely, to be pushed upward
`to any selected position by gently pushing upward to that
`position. Little force is required to move the blind up and
`down, the blind stops accurately at any selected position
`between and including the fully opened and fully closed
`positions, and the blind remains at the selected positions.
`As an example of the improved operation resulting from
`the use of a spring drive 15, when a standard coil spring was
`
`Norman Int. Exhibit 1008
`
`Norman Int. Exhibit 1008
`
`

`

`US 6,293,329 B1
`
`7
`used in 3'><4' DUETTE hollow pleat blind, near the end of
`the 4' travel of the blind, the increasing spring torque became
`too great for stable operation and overpowered the weight of
`the blind, retracting the blind. The use of spring unit 15
`comprising the same standard coil spring as before and the
`gear transmission, in a 4'><6' DUETTE hollow ; pleat blind
`provided smooth stable operation in which the blind stayed
`in position, even in the 6' fully extended, fully closed
`position. The 6' travel effected sufficient buckling to provide
`braking action which assisted in keeping the blind at rest. In
`contrast, the 4' travel of the smaller 3'><4' blind did not cause
`enough buckling to noticeably effect buckling braking.
`FIG. 7 depicts an alternative spring coil drive unit 65
`which comprises a coil drive spring 47, fixed ratio gear sets
`or transmissions 67 and 70, and a continuously varying,
`varied ratio, cord or band shift transmission 80. Preferably
`transmissions 67 and 70 are direct drive but can be other
`
`the support or housing 11
`Illustratively,
`ratios as well.
`includes transverse supports including support 42, and trans-
`verse shafts 43, 44 and 46. The spring 47 is mounted along
`and freely rotatable around a longitudinal shaft 66, which is
`journal mounted to spaced transverse supports (only one, 42,
`of these two supports is shown). One end of coil spring 47
`is mounted to support 42 by fastener 76, and the opposite
`end of the spring is attached by fastener 77 to the collar 78
`of gear 68 of bevel gear set 67. Mating bevel gear 69 is
`mounted on transverse shaft 43, interconnected to gear 71 of
`preferably direct drive transmission 70. Adjacent gear 72 of
`the transmission 70 is mounted on transverse shaft 44 and
`
`meshes with gear 71.
`transmission 80
`Referring also to FIG. 8, band shift
`comprises output drum 81 (or spool) and storage drum 82 (or
`spool) about which a band 83 is wrapped. Preferably, the
`cord or band 83 is an elongated strip of thin cloth or thin
`steel having a flat rectangular cross-section. However, other
`suitable materials can be used, and other cross-section
`shapes can be used which provide controlled variation in the
`radii on the drums. Hereafter the term “band” will be used
`
`in accordance with the preferred embodiment of a thin, fiat
`rectangular, but with the understanding that “bands” of other
`suitable cross-section shape can be used as well. The band
`shift transmission (hereafter band transmission) provides a
`varying drive ratio which is used to increase or diminish the
`torque or force of the spring drive unit. The cord or band
`transmission applies the varying drive ratio between the
`spring drive and the lift cord pulleys. The ratio of the band
`transmission is determined by the radius of the band stored
`on each drum. The radii vary as the band winds and
`unwinds, varying the associated gear ratio. Thus, increasing
`(decreasing) the thickness of the band, increases the rate at
`which the radii increase and decrease, and increases the gear
`ratio provided by the transmission. By way of example but
`not limitation, a band thickness of 0.014 inches has given
`satisfactory results. The manner of mounting the band can be
`used to decrease or increase the ratio of the speed of the
`spring output drum relative to that of the lift cord pulleys as
`the blind is lowered.
`
`Referring further to FIG. 8, output drum 81 is mounted on
`the shaft 44 with gear 72 and take-up drum 82 is mounted
`on transverse shaft 46 along with cord pulley unit 73. This
`is a conventional pulley unit, about whose pulley(s) 74 are
`wound the spaced lift cords 16 which support the blind, such
`as blind 10, 20. Structurally, the pulley unit 73 differs from
`pulleys 18 in that pulleys 74 and 75 are mounted together on
`a transverse shaft near the right end of the blind, necessi-
`tating that one of the cords be routed to the left side of the
`blind. The pulleys 74 operate the same as pulleys 18.
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`40
`
`45
`
`50
`
`55
`
`60
`
`65
`
`8
`As shown in FIG. 7, the direct drive transmission 70 and
`the pulley unit 73 are mounted parallel to the band shift
`transmission 80, reducing the overall length of the spring
`drive unit 65. The ratio of the band shift transmission is
`
`determined by the radius of the band stored on each drum.
`The radii vary as the spring 47 winds and unwinds, con-
`tinuously varying the associated gear ratio. As mentioned,
`the band mounting can be used to decrease or increase the
`ratio of the winding or rotational velocity of the spring
`relative to that of the pulleys as the blind is lowered.
`Preferably, the band 83 is mounted so the band radius on
`output drum 82 increases (alternatively, decreases) relative
`to the band radius on storage drum 81 as the blind is lowered
`(raised) and the cord-supported weight decreases
`(increases),
`thus offsetting somewhat or decreasing the
`increasing power with which the spring opposes the blind
`during lowering operation, and offsetting or decreasing
`somewhat the decreasing lifting power of the spring during
`raising of the blind, and increasing the distance traveled by
`the blind relative to the spring drive and thereby increasing
`the maximum operational length of the blind (the distance
`between the fully raised and fully lowered positions.
`In short, the continuously varying ratio, band shift trans-
`mission 80 continuously alters (preferably decreases) the
`rate at which the spring winds up and the torque increases as
`the blind is extended lower and alters (preferably increases)
`the operating length of the blind.
`As mentioned, the operationally fixed ratios of bevel gear
`set 67 and gear set 70 can be direct drive,
`that is 1:1.
`Alternatively, the ratios can be smaller or greater than 1:1,
`to alter the overall ratio of the drive unit such as 65. The
`
`ratios also alter the maximum possible length of the blind
`and the distance between the open and closed positions of
`the blind for a given rotational distance traveled by the coil
`spring. For example, the ratio of at least one of these gear
`sets can be smaller than 1:1, as described for transmission
`50, FIG. 5, and with similar results. Where the ratios of both
`bevel gear set 67 and gear set 70 are approximately 1:1,
`stopping the blind at any of selected positions and keeping
`the blind at the selected positions are effected by both (1) the
`continuously varying ratio of the band unit 83 which
`decreases the change in power of the coil spring as it winds
`and unwinds, (2) the friction of the bevel gear set 67 and the
`gear transmission 70, and (3) the “buckling” b