The present invention relates to manual roller shades.
Roller shades include a flexible shade fabric windingly received on a roller tube for raising and lowering the shade fabric by rotating the roller tube. In manual roller shades, the rotation of the roller tube is provided by an input wheel that receives an input chain for converting a pulling force applied to the input chain into rotation of the input wheel. Manual roller shades include clutches having gear assemblies for transmitting the rotation of the input wheel to the rotation of the roller tube.
Roller shade installations sometimes include a top treatment (e.g., fascia) for concealing the roller tube from view. It is typically necessary to notch the fascia and/or redirect the chain as it drops from the input wheel to provide for passage of the chain beyond the fascia.
Traditionally, manufacturers of motorized roller shades do not manufacture manual roller shades, and vice versa. As a result, manual roller shades and motorized shades utilize different mounting hardware for installing the roller shades. As a result, upgrading in order to replace a manual roller shade with a motorized roller shade is rendered difficult and time consuming because incompatible mounting hardware of the manual roller shade must be replaced with, or supplemented by, mounting hardware adapted for the motorized roller shade.
According to one aspect of the present invention, a clutch mechanism is provided for a manual roller shade having a roller tube adapted for winding receipt of a flexible shade fabric. The clutch mechanism comprises a rotatably supported sprocket adapted to receive a drive chain for rotation of the sprocket in response to application of an input force to the drive chain and an output member adapted for engagement with the roller tube. The clutch mechanism also comprises a gear train coupled between the sprocket and the output member for transmitting rotation of the sprocket to rotation of the output member. The gear train includes a sun gear, a plurality of planet gears rotatably mounted on a planet carrier and meshingly engaging the sun gear, and a ring gear meshingly engaging the planet gears. The sun gear and the ring gear rotate during actuation of the gear train while the planet carrier is held against rotation. The clutch mechanism is characterized by a sprocket ratio representing a ratio between the diameter of the sprocket and the diameter of the roller tube selected such that mechanical advantage of the gear train is offset to provide an effective gear ratio for the gear train of approximately 2:1.
According to one embodiment, the clutch mechanism includes a brake mechanism for preventing back-driving of the gear train by the output member. The brake mechanism includes a brake input engaged to the ring gear to rotate with the ring gear and at least one brake spring having a coiled body portion. The brake input includes a side opening and is adapted for receipt within an interior of the output member. The brake spring includes outwardly directed contact tangs at opposite ends of the coiled body portion adapted for receipt through the side opening of the brake input to locate the tang between an edge of the brake input and an inner surface of the output member.
According to another aspect of the invention, a chain guide system is provided for a manual roller shade having an input sprocket adapted to receive a drive chain for applying an input force to actuate the manual roller shade. The chain guide system comprises a plurality of rotatably supported chain guide wheels. The chain guide wheels are spaced from each other to receive the drive chain from the sprocket wheel and control where the drive chain drops from the manual roller shade.
According to one embodiment, the chain guide system includes three chain guide wheels arranged to receive the drive chain and control where the chain drops from the manual roller shade in any one of multiple angular orientations for the manual roller shade. The chain guide wheels include a rounded periphery defining a scalloped edge adapted to receive a drive chain having spaced beads.
According to another aspect of the invention, a roller shade mounting system is adapted for ease of upgrading a roller shade installation from a manual drive system to a motorized drive system. According to one embodiment, the system includes identical first and second brackets each adapted to receive any one of an idler end assembly, an input end of a manual roller shade, and a drive end of a motorized roller shade. The roller shade mounting system provides for upgrade of an installed manual roller shade simply by removing the manual drive system from the input end of the roller shade and by replacing the manual drive system with the motor of the motorized roller shade adapted for receipt by the bracket. Thus, all that is needed to accomplish the upgrade is the motor. The invention provides a completely shared system that includes brackets, roller tube, idler end assembly, fabric, hembar, fascia, top/back, pocket, flap, flap hanger, end-caps, etc. No modification is needed for any of these shared features.
The roller shade mounting system provides for a method of replacing a manual roller shade with a motorized roller shade (i.e., upgrading) by installing the first and second brackets at spaced locations at an installation site, mounting the manual roller shade at the installation site such that the input end and idler end assembly of the manual roller shade are respectively received by the first and second bracket, removing the manual roller shade from the first and second brackets, and mounting the motorized roller shade at the installation site such that the drive end and the idler end assembly of the motorized roller shade are respectively received by the first and second brackets.
For the purpose of illustrating the invention, the drawings show a form of the invention that is presently preferred. However, it should be understood that this invention is not limited to the precise arrangements and instrumentalities shown in the drawings.
Referring to the drawings, where like numerals identify like elements, there is illustrated in
The clutch mechanism 12 is located adjacent a first end of the roller tube 14 on the left hand side of the view shown in
Referring to
The idler assembly 16 of roller shade 10 includes a bracket mount portion 34 defining a periphery adapted for receipt within the aperture 22 of the bracket 18. The bracket mount portion 34 of the idler assembly 16 includes notches 36 spaced about its periphery for receiving the tabs 24 of the bracket 18. The idler assembly 16 includes a retaining clip 38 having a pair of prong-like elements 40 each arranged for receipt in an opening formed in the bracket mount portion 34 of the idler assembly 16.
Referring to
The outer portion 48 of the tube-end fitting 44 includes an idler bearing sleeve 41 defining a generally rounded periphery to provide for sliding receipt of the outer portion 48 within the open second end of the roller tube 14. The outer portion 48 also includes an idler slide 43 received in an open end of the idler bearing sleeve 41. As described below, the idler slide 43 is adapted to provide sliding movement of the idler bearing sleeve 41 with respect to the idler slide 43 to facilitate insertion of the manual roller shade 10 into the brackets 18.
The idler end assembly 16 includes a compression spring 45 within an interior of the idler bearing sleeve 41 having opposite ends respectively contacting the bearing sleeve 41 and the idler slide 43 for urging the bearing sleeve 41 away from the idler slide 43. This construction provides for relative axial movement between the bearing sleeve 41 and the idler spring pin 35 of the inner portion 46 as the spring 45 is compressed. The resulting shortening in the overall length of the manual roller shade 10 provided by the compression of the spring 45 facilitates insertion of the roller shade 10 into the bracket 18 as well as removal of the roller shade 10 from the brackets 18. As shown, the receipt of the retaining clip 38 by the idler spring pin 35 positions the retaining clip 38 between the bracket 18 and the idler bearing sleeve 41. As should be understood, the retaining clip 38 functions to limit the compression of the spring 45, thereby preventing inadvertent separation between the manual roller shade 10 and the brackets 18.
As shown, the idler bearing sleeve 41 of the tube-end fitting 44 defines elongated formations 50 spaced about its periphery for engaging receipt by corresponding formations 52 defined on an inner surface of the roller tube 14. In the front perspective view shown in
Referring to
The manual roller shade 10 includes a elongated drive chain 58 having substantially spherical beads 60 spaced along the length of the drive chain 58. As shown in
Arranged in this manner, each of the opposite hanging portions of the drive chain 58 is graspable by a user such that a pulling force can be applied to the hanging portion for drivingly rotating the roller tube 14 to either wind or unwind the shade fabric depending on which direction the roller tube 14 is rotated. The clutch mechanism 12 is adapted for bi-directional operation such that the associated roller tube 14 can be rotated in opposite directions by the clutch mechanism 12, to respectively wind and unwind a shade fabric secured to the roller tube 14, depending on which of the hanging portions of the drive chain 58 is pulled.
Referring to the sectional view of
The back cover 26 includes a drive chain rail 74 extending substantially in semi-cylindrical fashion about an upper half of the support post 72. The drive chain 58 is received by the drive chain sprocket 66 in a space defined between the drive chain sprocket 66 and the drive chain rail 74. Arranged in this manner, the drive chain rail 74 contains the drive chain 58 within the defined space for maintained engagement between the drive chain 58 and the drive chain sprocket 66. As shown in the sectional view of
The input wheel 62 includes a cylinder 76 extending from a surface of the disk 64 opposite the drive chain sprocket 66. The clutch mechanism 12 includes a carrier mandrel 78 defining an interior receiving the input wheel cylinder 76. The interior of the carrier mandrel 78 and the input wheel cylinder 76 are dimensioned to provide for a sliding interfit such that the input wheel 62 is rotatable with respect to the carrier mandrel 78. The carrier mandrel 78 includes a peripheral flange 80 extending about an upper portion of the carrier mandrel 78. As shown in
The clutch mechanism 12 includes a set of three chain guide wheels 90a, 90b, 90c. The chain guide wheels 90a, 90b, 90c define central apertures 92 for rotatably mounting the guide wheels 90a, 90b, 90c on support posts 96 located on a plate portion 94 of the carrier mandrel 78. As described below in greater detail, the chain guide wheels 90a, 90b, 90c are adapted to receive the drive chain 58 in multiple rotational orientations of the clutch mechanism 12 and to control the manner in which lower end portions of the drive chain 58 are suspended from the clutch mechanism 12. As shown, the periphery of the chain guide wheels 90a, 90b, 90c are rounded and scalloped to facilitate a nested engagement between the guide wheels and the beads 60 of drive chain 58. The construction of the guide wheels desirably reduces noise and reduces the required input force that must be applied to the chain by reducing drag forces.
The clutch mechanism 12 includes a gear assembly 98 having a sun gear 100 disposed at an end of a sun gear shaft 102 and a set of three planet gears 104. The sun gear shaft 102 is received by a support sleeve 106 carried by the input wheel 62 within an interior of the input wheel cylinder 76. The input wheel 62 includes a plurality of reinforcing ribs 108 interconnecting the support sleeve 106 and the input wheel cylinder 76. The support sleeve 106 is centrally disposed within the input wheel cylinder 76 such that a central axis of the sun gear 100 is substantially aligned with the rotational axis of the drive chain sprocket 66.
As shown in
Each of the planet gears 104 of gear assembly 98 is rotatably mounted to the carrier mandrel 78 for rotation of the planet gear 104 about a central axis of the planet gear 104. As shown, each planet gear 104 includes a central aperture 110 receiving an axle pin 112. The carrier mandrel 78 defines openings 114 adapted for receiving the planet gears 104. The axle pins 112 at received at opposite ends of the axle pins 112 in axle notches 116 located on opposite sides of the openings 114 such that the planet gears 104 communicate with both the interior and exterior of the carrier mandrel 78.
As illustrated in
The gear assembly 98 of the clutch mechanism 12 also includes a ring gear 122 having a substantially cylindrical body and elongated teeth 124 defined on an inner surface of the body. The ring gear 122 is received onto the exterior of the carrier mandrel 78 such that the ring gear teeth 124 meshingly engage the teeth 118 of the planet gears 104 mounted in the openings 114 in the carrier mandrel 78. The ring gear 122 is coupled to the output cover 54 by a brake input 126 and brake springs 128, as described below, such that rotation of the ring gear 122 results in rotation of the output cover 54. Arranged in this manner, the gear assembly 98 provides a drive train for the clutch mechanism 12 that functions to convert pulling force applied to the drive chain 58 into rotation of the output cover 54, thereby rotating the roller tube 14. As described in greater detail below, the brake input 126 and brake springs 128 are adapted to prevent the output cover 54 from back-driving the gear assembly 98 of the clutch mechanism 12 through the application of pulling force to a shade fabric windingly supported by the roller tube 14, for example.
The brake input 126 includes a semi-cylindrical wall 130 defining a side opening 132 and peripheral teeth 134 spaced about the wall 130 at an end 136 of the brake input 126. The brake input end 136 is received by the ring gear 122 such that the brake input teeth 134 meshingly engage the ring gear teeth 124 for simultaneous rotation of the brake input 126 with the ring gear 122.
The brake input 126 includes longitudinal flanges 138 extending along the wall 130 along each of opposite sides of the opening 132. The wall 130 and flanges 138 of the brake input 126 are dimensioned such that the brake input 126 is receivable within an interior defined by the output cover 54. The output cover 54 has a substantially cylindrical wall 140 including a trough-like indentation 142. The indentation 142 is dimensioned such that the brake input flanges 138 extend adjacent inwardly projecting portions of the inner surface of the output cover 54 defined on opposite sides of the indentation 142. Clearance is provided, however, between the brake input flanges 138 and the output cover indentation 142 to accommodate the brake springs 128 as follows.
Each of the brake springs 128 is coiled to form a substantially cylindrical body 144 having opposite ends. Each of the brake springs 128 also includes outwardly deflected portions at each of the opposite ends of the body 144 forming a tang 146. As should be understood, application of transverse forces to the tangs 146 of the brake spring 128 will tend to expand or contract the diameter of the intermediately located coiled body 144 depending on the direction in which force is applied to the tang 146 (i.e., inwardly directed forces for contraction of the coiled body 144 and outwardly directed forces for expansion).
The springs 128 are dimensioned such that the spring body 144 is receivable within an interior of the brake input 126 with the tangs 146 extending outwardly into the side opening 132 in the wall 130 of the brake input 126. The above-described clearance between the brake input 126 and the output cover 54 provides for receipt of the spring tangs 146 between the brake input flanges 138 and the inner surface of the output cover 54 defined by the indentation 142.
The exterior of carrier mandrel 78 includes substantially cylindrical surface portions 148, 150, 152, 154, 156 that decrease in diameter between surface portion 148 and surface portion 156. As shown in
The brake input 126 includes a transverse end wall 162 located at an end of the brake input 126 opposite end 136 defining teeth 134. The output cover 54 also includes a transverse wall 164 adjacent an end of the output cover 54. The transverse walls 162, 164 of the brake input 126 and the output cover 54 respectively include central apertures 166, 168. As shown in
As a result of the above-described location of the brake spring tangs 146 between the brake input flanges 138 and the output cover indentation 142, the brake springs 128 function to enable relative rotation between the output cover 54 and the carrier mandrel 78 when the clutch mechanism 12 is actuated by a user. The brake springs 128 also function to prevent the output cover 54 from rotating on the carrier mandrel 78 when torque is, instead, first applied to the output cover 54 (e.g., from a pulling force applied to a shade fabric windingly supported by the roller tube 14). As described below, the operation of the brake springs 128 is bi-directional such that relative rotation of the output cover 54 is enabled or prevented, respectively, regardless of which rotational direction the brake input 126 is driven by the clutch mechanism or which rotational direction a back-driving torque is applied to the output cover 54.
Referring to the end view of
A clockwise rotation of the brake input 126 in
The brake input 126 and brake springs 128 function to prevent the output cover 54 from back-driving the clutch mechanism 12 as follows. Referring still to
The back-driving prevention feature provided by the brake springs 128 is also bi-directional. Still referring to
As described above, the clutch mechanism 12 includes a set of three drive chain guide wheels 90a, 90b, 90c for controlling the manner in which the drive chain 58 hangs from the clutch mechanism 12. Referring to
The construction of the manual roller shade 10 is adapted to provide multiple orientations for installing the roller shade 10 using the same brackets 18, thereby providing a universal mourning system. Referring first to
As shown, the guiding interaction between the drive chain 58 and the drive chain guide wheels 90a, 90b, 90c is limited in the first mounting configuration because the hanging portions 178, 180 of drive chain 58 hang straight from the sprocket 66 between the above-mentioned pairs of the guide wheels 90a, 90b, 90c. As should be understood, however, the hanging portions 178, 180 of the drive chain 58 might be brought into contact with one of the guide wheels 90a, 90b, 90c during actuation of the clutch mechanism 12 in the event a user grasps and pulls one of the hanging portions 178, 180 at an angle instead of in the substantially vertical orientation shown. For example, if a user grasps drive chain portion 178 and raises it to the left (from the point of view shown in
Referring first to
The bottom panel 182 includes a support flange 186 extending longitudinally along the bottom panel 182. As shown, the support flange 186 is returned along a terminal edge portion of the support flange 186 such that the cross-section of the support flange 186 is substantially in the shape of an inverted J (from the point of view of
Referring to
Referring to
Referring to
Although not shown, the construction of the manual roller shade 10 provides for a fourth mounting configuration in which the roller shade 10 is rotated an additional ninety degrees in the clockwise direction from that shown in
The chain guide system of the present invention, therefore, provides the ability to mount the roller shade optimally in one of multiple orientations without requiring additional or different hardware. This desirably simplifies installation and reduces the inventory that must be maintained, thereby reducing costs and limiting delays in installation. As shown, the chain guide wheels 90a, 90b, 90c are spaced from each other in a triangular configuration. The spacing between the guide wheels, however, is not critical but should be sufficient to provide desired separation between the opposite portions of the drive chain 58 that are dropped from the guide wheels in the various configurations described above. The spacing between the guide wheels 90a, 90b, 90c should also be selected to drop the chain 58 in a position specifically chosen so as to avoid obstacles or to improve performance as determined by other aspects of the shade assembly or the installation.
In addition, the mounting flexibility provided by the present invention desirably eliminates the need for notching of fascia or other top treatments to provide for chain drop. Such notching increases manufacturing/installation costs and is not aesthetically pleasing in appearance. Preferably, the components of the clutch mechanism 12 that are contacted by the drive chain 58, such as the sprocket 66 and the guide wheels 90a, 90b, 90c are made soft, low friction materials. Such construction desirably limits noise generated by the parts as the drive chain beads 60 move into and out of contact with these components and also limits drag on the drive chain 58.
Other prior manual shades incorporate deflectors, instead of notching, to provide for chain drop. This option, however, undesirably increases input force as discussed above by substantially increasing drag forces. Such manual shades also tend to be noisier and do not operate in a smooth, consistent, manner.
The manual roller shade 10 of the present invention is adapted to vary drop position of the drive chain 58 depending on the installation orientation (e.g., to avoid fascia). The present invention accomplishes this without added drag and without increased size. The present invention also provides the desired benefits in a relatively inexpensive manner while at the same time improving the performance of the clutch mechanism 12.
Referring to
Referring first to the idler end of the motorized shade 192, which is located on the right-hand side of the motorized shade 192 in the views shown in
Referring to the motorized end of the motorized roller shade 192, which is on the left-hand side of the motorized roller shade 192 in
Regarding the above-described brackets 18 that are identical in construction and adapted for mounting either the manual shade 10 or the motorized shade 192, several constraints were important in configuring the bracket. For a manual roller shade, the mounting system, and therefore the hardware, is traditionally designed with an entirely different set of constraints than that for a motorized shade. The constraints associated with a manual shade include use of a chain, the drop location for the chain, and the deflection of the drive chain. The constraints associated with a motorized shade include the use of buttons (e.g., for programming, setting limits, etc.), light-emitting diodes (LEDs) (e.g., for status and troubleshooting feedback), user access to the buttons and visibility of the LEDs, and the location of a printed circuit board (PCB) and wires. General constraints applicable to both manual shades and motorized shades include manufacture/assembly, shade fabric gaps, spring-pin installation style, identical bracketing, overall size, and systems for retaining the shade.
The size of the aperture 22 of bracket 18 must be sized to receive the idler end assembly 16 such that the tabs 24 about the aperture 22 of bracket 18 fit within the inner diameter (ID) of the bearing idler sleeve 41. This is necessary for providing the above-described compression feature for the idler end assembly 16. If the tabs 24 do not fit within the sleeve ID, the spring 45 will not compress sufficiently to allow for insertion of the opposite drive side of the roller shade into the opposite bracket 18.
Referring to
Optimized Force Reduction In a manual roller shade, the force that must be applied to the drive chain to raise or lower the shade fabric (i.e., the “input force” or the “Force In”) has three components. The three components of the input force include a shade force, an input drag, and a clutch drag. The shade force component of the input force represents a contribution of the weight of the shade fabric as converted through the clutch into a force at the input chain. The conversion of the shade weight through the clutch is dependent on roller tube diameter, diameter of the input wheel (i.e., the sprocket), and the gear train (i.e., the gear ratio). The input drag component of the input force represents the drag forces generated on the input wheel sprocket and the drive chain. As input force increases, the input drag increases. The clutch drag represents drag forces in the clutch anywhere other than the input wheel sprocket and chain and is a function of the gear ratio, the diameter of the input wheel sprocket, the fabric weight and the frictional characteristics of the clutch. As the fabric weight increases, the clutch drag increases.
Obviously, the most direct way to reduce input force is to reduce the fabric weight. Assuming fabric weight is a constant, however, other variables must be controlled to reduce input force. To reduce the shade force component, the gear ratio can be increased. However, other constraints typically limit the gear ratio that is utilized.
Input drag includes contributions from a number of interacting surfaces associated with the input wheel sprocket and the drive chain and is dependent on coefficients of friction and normal forces that are directly proportional to the input force. The drag of the chain is increased substantially when the chain is deflected around obstacles such as fascia or other top treatments. In the above-described manual roller shade 10 according to the invention, the use of rotating guide wheels 90a, 90b, 90c to deflect the chain substantially reduces chain drag compared to the use of fixed deflector surfaces for example. The drag from the input wheel sprocket is reduced by lowering coefficient of friction through material selection (e.g., by using low friction engineering polymers).
Clutch drag includes contributions from multiple sources most principally from brake drag, bearing drag in the clutch assembly, and bearing drag at the idler end. The effect of clutch drag can be reduced by increasing gear ratio. However, as discussed above, this is limited by other considerations. Brake drag can be minimized by material selection for friction reduction and geometry of the brake component parts (e.g., brake input and brake springs). Bearing drag at the idler end and in the clutch assembly is preferably reduced by including a ball bearing assembly. Bearing drag can also be reduced further by component geometry and material selection.
The manual shade 10 of the present invention optimizes reduction of force based on other practical constraints: Two main constraints include clutch size and chain travel. As shown in the figures, a portion of the clutch mechanism 12 is sized to fit within the interior of the roller tube 14. Thus, the clutch cannot be enlarged beyond this constraint. The second main constraint is the chain travel versus fabric travel. For a jointed chain (i.e., a drive chain having a joint piece not adapted to travel about the sprocket), the practical maximum chain travel is no more than twice the fabric travel (i.e., the “fabric drop”). This assumes that the chain extends from the roller shade approximately the same distance as the fabric drop. Although, the chain could be made longer than the fabric drop, this is not desirable.
The chain travel constraint can be used to optimize force reduction as follows. Work is equal to force applied multiplied by distance (i.e., W=F·d). In shade terms, work is represented by input force times the chain travel (i.e., WCHAIN=FCHAIN·dCHAIN) and also by fabric weight times fabric travel (i.e., WFABRIC=FFABRIC·dFABRIC). For a given shade, the above work terms are equal and fixed (i.e., WCHAIN=WFABRIC). Thus, using a maximum chain travel equal to twice the fabric travel (i.e., dCHAIN=2·dFABRIC) will provide minimum input force (i.e., FCHAIN=FFABRIC·dFABRIC/dCHAIN=½·FFABRIC). As should be understood from the above work relationships, the ratio of chain travel to fabric travel must equal the ratio of fabric weight to input force (i.e., dCHAIN/dFABRIC=FFABRIC/FCHAIN). This ratio, which represents the optimum gear ratio GR, therefore, ideally should be 2:1.
As should be understood, the desired gear ratio of 2:1 is for a jointed-chain (i.e., a chain that is not intended to the be driven in continuous fashion about the sprocket). For a drive chain adapted to be driven in continuous fashion, one could reduce the input force FCHAIN as far as desired simply by increasing the gear ratio.
Epicycle gear trains are well known in a variety of different types of products and are ideal for providing compact, robust and reliable gear reduction with relatively simple parts and low cost. They provide far greater strength at a given diameter as compared to other types of gear trains. Epicycle gear trains include planetary, solar, and star trains each having a sun gear, planetary gears and a ring gear. In a planetary epicycle gear train, the ring gear is stationary while the sun gear and a planetary carrier are rotated. In a solar epicycle gear train, the sun gear is fixed while the ring gear and planetary carrier are rotated. In a star epicycle gear train, the planet carrier is fixed while the sun gear and ring gear are rotated. The manual roller shade 10 of the present invention incorporates a star epicycle gear train.
The gear reduction that is provided in the different types of epicycle gear trains depends on which component is used as the input and which is used as the output. Planetary epicycle gear trains can easily and practically provide gear ratios between 3.1:1 to 12.1:1 with the smaller ratios being more difficult as the ring gear diameter is made smaller. Solar epicycle gear trains are adapted to provide gear ratios between 1.2:1 to 1.7:1 with the higher ratios being more difficult as the ring gear diameter is made smaller. Star epicycle gear trains are adapted to provide gear ratios between 2.1:1 to 11.1:1 with the lower end being more difficult as the ring gear diameter decreases. It should be understood that the above ranges of gear ratios are considered by those skilled in the art as practical limits for simple epicycle gear trains. Gear ratios outside of the specified ranges could be achieved. However, to do so requires that undesirable sacrifices be made to cost, performance, each of manufacture/assembly and/or strength.
Referring to
As described above, the optimum gear ratio based on balance of chain travel and force reduction is 2:1 for a jointed chain. Since this ratio is not practical with a standard epicycle gear train, the manual roller shade 10 of the present invention includes a component sizing arrangement having the effect of trading off gear ratio otherwise achievable with the star gear train such that an effective gear train ratio of 2:1 is achieved. More particularly, the gear ratio trade off is achieved by selecting the input wheel sprocket diameter such that the ratio of the sprocket wheel diameter to the roller tube diameter (i.e., a “sprocket ratio”) creates an overall combined gear ratio of 2:1. In other words, some of the mechanical advantage associated with the star epicycle gear train is offset by the sprocket ratio to achieve the desired gear ratio of 2:1. As described above, the force reduction system of the present invention can be applied to any manual roller shade to achieve a desired effective gear ratio. However, for a jointed chain, the desired ratio is 2:1 for the reasons described above.
The foregoing describes the invention in terms of embodiments foreseen by the inventor for which an enabling description was available, notwithstanding that insubstantial modifications of the invention, not presently foreseen, may nonetheless represent equivalents thereto.
This application claims priority from U.S. Provisional Application No. 60/859,317, filed Nov. 16, 2006, and is a divisional of U.S. application Ser. No. 11/985,418, filed Nov. 15, 2007, the entire disclosures of which are hereby incorporated by reference herein.
Number | Date | Country | |
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60859317 | Nov 2006 | US |
Number | Date | Country | |
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Parent | 11985418 | Nov 2007 | US |
Child | 12769069 | US |