Lift control device for a roller shade

A lift control device for a roller shade includes a support rod having one end containing an insert socket, a spring mounted on the support rod, a roller cap rotatably mounted on the support rod and containing a retaining opening to secure the spring therein such that the spring is rotated by the roller cap, and a follower spool secured on the roller cap to rotate therewith.

BACKGROUND OF THE INVENTION
 1. Field of the Invention
 The present invention relates to a lift control device, and more
 particularly to lift control device for a roller shade.
 2. Description of the Related Art
 The closest prior art of which the applicant is aware is disclosed in U.S.
 Pat. No. 4,433,765 to Rude et al., filed on Sep. 13, 1982, entitled
 "Spring Clutches". However, the springs are separately mounted on a limit
 rod, and the lugs for each of the springs has to align with each other so
 as to be fit into the slot of the cap, thereby making the assembly more
 difficult. In addition, the inner wall of the slot of the cap only
 contacts the lug of some of the springs, and cannot contact all of the
 springs such that the force exerted on the springs is not evenly
 distributed, thereby decreasing the retaining effect between the springs
 and the limit rod such that the force is concentrated on the springs which
 contact the cap causing elastic fatigue during long-term utilization,
 thereby greatly reducing the lifetime of the springs. The present
 invention has arisen to mitigate and/or obviate the disadvantage of the
 conventional spring clutch.
 BRIEF SUMMARY OF THE INVENTION
 In accordance with one aspect of the present invention, there is provided a
 lift control device for a roller shade comprising a support rod, one end
 containing an insert socket therein, a spring mounted on the support rod,
 a roller cap rotatably mounted on the support rod and containing a
 retaining opening to secure the spring therein such that the spring is
 rotated by the roller cap, and a follower spool secured on the roller cap
 to rotate therewith.
 In accordance with another aspect of the present invention, there is
 provided a lift control device for a roller shade comprising a support
 rod, and a spring mounted on the support rod and including at least two
 coiled portions each having a bent distal end, and a connecting lug
 connecting the two coiled portions, the connecting lug being separated
 from the bent distal end of each of the two coiled portions.

DETAILED DESCRIPTION OF THE INVENTION
 Referring to the drawings and initially to FIGS. 1-3, a lift control device
 for a roller shade in accordance with the present invention comprises a
 support rod (11) with a cruciform shaped insert socket (112) in one end,
 an insert piece (30) detachably received in the insert socket (112), a
 spring (18) rotatably mounted on the support rod (11), a roller cap (12)
 rotatably mounted on the support rod (11) and containing a retaining
 opening (122) to secure the spring (18) therein such that the spring (18)
 is rotated by the roller cap (12), and a follower spool (16) mounted on
 the roller cap (12) and secured to the spring (18) to rotate with it.
 The roller cap (12) includes a chain retaining wheel (124) mounted on one
 end thereof, and the lift control device comprises a loop-shaped chain
 (20) having a plurality of beads (22) secured to the chain retaining wheel
 (124) to rotate the chain retaining wheel (124), and a side cover (14)
 rotatably receiving the chain retaining wheel (124) of the roller cap (12)
 therein, and containing a chain outlet (142) to allow passage of the chain
 (20). The side cover (14) contains an axial hole (140) therein, and the
 support rod (11) extends through the axial hole (140) and includes an
 annular shoulder (110) formed on the end with the socket (112) and is
 pressed into the axial hole (140). The axial hole (140) of the side cover
 (14) contains an arcuate slot (146) defined in the periphery thereof, and
 the annular shoulder (110) includes a boss (111) movably received in the
 arcuate slot (146).
 The follower spool (16) includes an annular flange (160) formed on one end
 and contains a retaining hole (161) therein, and the end of the support
 rod (11) away from the socket (112) extends through the retaining hole
 (161) and includes two hooks (116) abutting the annular flange (160). An
 elongated slot (114) is formed between the two hooks (116) such that the
 end of the support rod (11) is flexible.
 The spring (18) includes two coiled portions (182) each having a bent
 distal end (183) abutting a one side of the retaining opening (122), and
 an inverted U-shaped connecting lug (186) connecting the two coiled
 portions (182) and abutting the other side of the retaining opening (122).
 The bent distal end (183) of the two coiled portions (182) aligns with
 each other. The connecting lug (186) is separated from the bent distal end
 (183) of each of the two coiled portions (182).
 The follower spool (16) includes an elongated rib (162) formed on the inner
 wall thereof and movably located between the connecting lug (186) and the
 distal end (183) of each of the two coiled portions (182).
 In assembly, referring to FIG. 4 with reference to FIGS. 1-3, two brackets
 (40) are attached to a vertical wall, and each contains a locking slot
 (42) therein, the insert piece (30) of the lift control device (10) is
 inserted into the locking slot (42) of a bracket (40), and a roller tube
 (not shown) having a shade cloth (not shown) mounted thereon includes one
 end securely fit on the follower spool (16) of the lift control device
 (10) to rotate therewith, and the other end rotatably attached to another
 bracket (40).
 In operation, the support rod (11) is held in position by the insert piece
 (30) which is held in position in the retaining slot (42) of the bracket
 (40). The bent distal end (183) of each of the two coiled portions (182)
 of the spring (18) abuts the first side of the retaining opening (122),
 and the connecting lug (186) abuts the second side of the retaining
 opening (122) such that the spring (18) is rotated with the roller cap
 (12). The elongated rib (162) is located between the distal end (183) of
 each of the two coiled portions (182) and the connecting lug (186) such
 that the follower spool (16) is rotated with the spring (18) by the distal
 end (183) or the connecting lug (186).
 When the a user exerts a drawing force on the loop-shaped chain (20), the
 chain retaining wheel (124) is rotated by the chain (20) to rotate the
 roller cap (12) which rotates the spring (18) which rotates the follower
 spool (16) which rotates the roller tube, thereby lifting or lowering the
 shade cloth. When the drawing force exerted on the chain (20) is removed,
 further movement of the follower spool (16) is limited by the spring (18)
 due to the friction between the coiled portions (182) and the support rod
 (11) such that the follower spool (16) will not be reversed by the weight
 of the shade cloth.
 Referring to FIG. 5 with reference to FIGS. 1-3, in accordance with another
 embodiment of the present invention, two brackets (50) are attached to a
 vertical wall, and each includes an insert piece (52). The insert piece
 (52) of a bracket (50) is inserted into the insert socket (112) of the
 support rod (11) of the lift control device (10), and a roller tube (not
 shown) having a shade cloth (not shown) mounted thereon includes one end
 securely fit on the follower spool (16) of the lift control device (10) to
 rotate therewith, and the other end rotatably attached to the other
 bracket (50).
 The springs bodies (182) are integrally formed with each other, thereby
 increasing the precision of alignment. In addition, the force is evenly
 distributed on the coiled portions (182) of the spring (18) which mate
 with the support rod (11) to provide an even retaining effect to the
 follower spool (16), thereby preventing elastic fatigue due to the coiled
 portions (182) being unevenly stressed so as to increase the lifetime of
 the spring (18). Further, the insert piece (30) received in the insert
 socket (112) is inserted into the locking slot (42) of the bracket (40) as
 shown in FIG. 4, or the insert socket (112) is used to receive the insert
 piece (52) of the support bracket (50) as shown in FIG. 5, thereby
 increasing the versatility of the lift control device (10) and decreasing
 the cost in fabrication.
 It should be clear to those skilled in the art that further embodiments may
 be made without departing from the scope of the present invention.