Information
-
Patent Grant
-
6761203
-
Patent Number
6,761,203
-
Date Filed
Monday, March 31, 200321 years ago
-
Date Issued
Tuesday, July 13, 200420 years ago
-
Inventors
-
Original Assignees
-
Examiners
Agents
- Ohlandt, Greeley, Ruggiero & Perle, L.L.P.
-
CPC
-
US Classifications
Field of Search
US
- 160 170
- 160 171
- 160 172 R
- 160 8404
- 160 8405
- 160 192
- 185 37
- 185 39
- 185 45
- 242 373
-
International Classifications
-
Abstract
A window blind includes a head rail, a bottom rail, and an expandable window covering. A pair of pull cords interconnect the head rail, the bottom rail and the expandable window covering. A spring motor includes a drive drum, a pair of cord spools, a spiral spring, and a friction imposing mechanism. The drive drum is mounted rotatably on the head rail. Each of the cord spools is mounted to rotate with and is disposed on a respective side of the drive drum, and is connected to a respective one of the pull cords. The spiral spring provides a biasing force acting on the drive drum. The friction imposing mechanism provides a friction force acting on one of the drive drum and the pull cords. The biasing force and the friction force cooperate to retain the bottom rail at a desired vertical distance relative to the head rail.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a window blind, more particularly to a window blind having a spring motor for concealed pull cords thereof.
2. Description of the Related Art
In U.S. Pat. No. 6,289,965, there is disclosed a conventional window blind that comprises a head rail, a bottom rail, and an expandable window covering therebetween. A pair of pull cords interconnect the head rail, the bottom rail, and the expandable window covering. A spring motor includes a frame, a drive drum, an idler gear, a take-up drum, a pair of cord spools, and a coil spring. The frame is mounted on the head rail. The drive drum is mounted rotatably on the frame and is provided with a drive gear. The idler gear is mounted rotatably on the frame and meshes with the drive gear. The take-up drum is mounted rotatably on and is concentric with the idler gear. The idler gear rotates independently of the take-up drum. Each of the cord spools is mounted rotatably on one end of the frame adjacent to a respective one of the idler gear and the drive drum, is provided with a driven gear that meshes with the respective one of the idler gear and the drive drum, and is connected to a respective one of the pull cords. The coil spring is wound on the take-up drum, has opposite ends connected to the take-up drum and the drive drum, and provides a biasing force for biasing the take-up drum to rotate in a direction for winding the pull cords on the cord spools.
The aforementioned conventional window blind achieves the purpose of concealing the pull cords with the deployment of the spring motor, and the bottom rail does not slant while being raised or lowered. However, the drive and take-up drums rotate at different speeds. In addition to this, the idler gear and the take-up drum rotate independently of one another. Further, the drive drum, the idler gear and the cord spools rotate at the same speed. This rotational speed relationship among the drive and take-up drums, the idler gear, and the cord spools results in a complicated construction for the spring motor of the conventional window blind:
SUMMARY OF THE INVENTION
Therefore, the object of the present invention is to provide a window blind that has a relatively simple spring motor for concealed pull cords thereof.
According to the present invention, a window blind comprises a head rail, a bottom rail, and an expandable window covering between the head rail and the bottom rail. A pair of pull cords interconnect the head rail, the bottom rail and the expandable window covering. A spring motor includes a frame, a drive drum, a pair of cord spools, a spiral spring, and a friction imposing mechanism. The frame is mounted on one of the head and bottom rails. The drive drum is mounted rotatably on the frame and is provided with a drive gear. Each of the cord spools is mounted rotatably on the frame, is disposed on a respective one of opposite sides of the drive drum, is provided with a driven gear that meshes with the drive gear, and is connected to a respective one of the pull cords. The spiral spring is wound on the drive drum, has opposite ends connected respectively to the drive drum and the frame, provides a biasing force for biasing the drive drum to rotate in a direction for winding the pull cords on the cord spools, and deforms from an initial state to an extent corresponding to vertical distance of the bottom rail from the head rail. The friction imposing mechanism is mounted on the frame and is operable so as to provide a friction force that acts on one of the drive drum and the pull cords. The biasing force of the spiral spring and the friction force attributed to the friction imposing mechanism cooperate to support the weight of the bottom rail and the weight of the expandable window covering that acts on the bottom rail so as to retain the bottom rail at a desired vertical distance relative to the head rail.
BRIEF DESCRIPTION OF THE DRAWINGS
Other features and advantages of the present invention will become apparent in the following detailed description of the preferred embodiments with reference to the accompanying drawings, of which:
FIG. 1
is a schematic view of the first preferred embodiment of a window blind according to the present invention;
FIG. 2
is an exploded perspective view of a spring motor of the first preferred embodiment of a window blind according to the present invention;
FIG. 3
is a sectional view of the spring motor illustrating a pair of pull cords wound on a pair of cord spools and trained on a pair of friction roller sets;
FIG. 4
is a schematic view of the spring motor illustrating a spiral spring being deformed, and the pull cords being unwound from the cord spools;
FIG. 5
is a schematic view of the spring motor illustrating the spiral spring being restored to an initial state on a drive drum, and the pull cords being wound on the cord spools;
FIG. 6
is an exploded perspective view of a spring motor of the second preferred embodiment of a window blind according to the present invention; and
FIG. 7
is a schematic view of the spring motor illustrating operation of a friction imposing mechanism thereof.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Before the present invention is described in greater detail, it should be noted that like elements are denoted by the same reference numerals throughout the disclosure.
Referring to
FIGS. 1
to
3
, the first preferred embodiment of a window blind
9
according to the present invention is shown to include a head rail
91
, a bottom rail
92
, and an expandable window covering
93
therebetween. A pair of pull cords
94
interconnect the head rail
91
, the bottom rail
92
and the expandable window covering
93
. In this embodiment, the expandable window covering
93
includes a plurality of parallel slats suspended between the head rail
91
and the bottom rail
92
in a conventional manner with the use of ladder cords (not shown). A spring motor
100
of the window blind
9
includes a frame
10
, a drive drum
20
, a pair of cord spools
30
, a spiral spring
22
, and a friction imposing mechanism
60
.
While the frame
10
is mounted on the head rail
91
. In this embodiment, it is apparent to one skilled in the art that the frame
10
can be mounted instead on the bottom rail
92
. The drive drum
20
is mounted rotatably on the frame
10
and is provided with a drive gear
212
. Each of the cord spools
30
is mounted rotatably on the frame
10
, is disposed on a respective on one of opposite sides of the drive drum
20
, is provided with a driven gear
311
, and is connected to a respective on one of the pull cords
94
. The spiral spring
22
is wound on the drive drum
20
, has opposite inner and outer ends
222
,
221
connected to a respective one of the drive drum
20
and the frame
10
, provides a biasing force for biasing the drive drum
20
to rotate in a direction for winding the pull cords
94
on the cord spools
30
, and deforms from an initial state to an extent corresponding to vertical distance of the bottom rail
92
from the head rail
91
. In this embodiment, the friction imposing mechanism
60
is mounted on the frame
10
and is operable so as to provide a friction force that acts on the pull cords
94
. The frame
10
is formed with left and right compartments
111
and a middle compartment
112
therebetween. The drive drum
20
is disposed in the middle compartment
112
, and has a drive shaft
211
that is connected to the drive gear
212
and that is formed with a slit
213
for engaging the inner end
222
of the spiral spring
22
. The middle compartment
112
is formed with a pair of slits
14
for engaging selectively the outer end
221
of the spiral spring
22
. The drive gear
212
extends radially out of the middle compartment
112
. Each of the left and right compartments
111
has an axle
12
disposed therein for mounting rotatably a respective one of the cord spools
30
in the left and right compartments
111
. Each of the cord spools
30
has a driven shaft
312
that is connected to a respective one of the driven gears driven gears
311
and that is journalled to a respective one of the axles
12
. Each of the driven gears
311
extends radially out of a respective one of the left and right compartments
111
and meshes with the drive gear
212
. Preferably, the frame
10
includes a casing part
101
that is formed with the left, middle and right compartments
111
,
113
and that has an open side, and a cover part
102
that is mounted on the casing part
101
to cover the open side of the casing part
101
and to retain the cord spools
30
and the drive drum
20
in the casing part
101
.
With further reference in
FIG. 3
, the friction imposing mechanism
60
of this embodiment includes a pair of friction roller sets. Each of the friction roller sets is mounted on one end of the frame
10
adjacent to a respective one of the cord spools
30
, and includes three friction rollers
61
,
62
,
63
arranged in a triangular formation. Each of the pull cords
94
is trained on the friction rollers
61
,
62
,
63
of a respective one of the friction roller sets.
Referring to
FIG. 4
, when the bottom rail
92
(see
FIG. 1
) is pulled downwardly so as to lower the same, each of the cord spools
30
rotates in a counter-clockwise direction, which results in unwinding of the pull cords
94
from the driven shafts
312
of the cord spools
30
, in axial rotation of the drive drum
20
, and in radial contraction of the spiral spring
22
. Once the bottom rail
92
is lowered to a lower limit position, the spiral spring
22
is deformed such that the spiral spring
22
wraps around the drive shaft
211
of the drive drum
20
. At this time, the biasing force of the spiral spring
22
is at a maximum, and the weight of the expandable window covering
93
(see
FIG. 1
) that acts on the bottom rail
92
is at a minimum. As such, the external force that is required to initiate raising of the bottom rail
92
to retract the expandable window covering
93
is at a minimum.
In addition, in the absence of the external force, the biasing force of the spiral spring
22
and the friction force attributed to the friction imposing mechanism
60
cooperate to support the weight of the bottom rail
92
and the weight of the expandable window covering
93
that acts on the bottom rail
92
so as to retain the bottom rail
92
at a desired vertical distance relative to the head rail
91
(see FIG.
1
).
With further reference to
FIG. 5
, when the bottom rail
92
is pushed upwardly so as to raise the same, due to the biasing force of the spiral spring
22
and slackening of the pull cords
94
, each of the cord spools rotates in a clockwise direction, which results in winding of the pull cords
94
on the driven shafts
312
of the cord spools
30
, in an opposite axial rotation of the drive drum
20
, and in radial expansion of the spiral spring
22
. Once the bottom rail
92
is raised to an upper limit position, the spiral spring
22
is restored to the initial state such that an outer wound of the spiral spring
22
abuts against an inner wall of the middle compartment
112
. At this time, the biasing force of the spiral spring
22
is at a minimum, and the weight of the expandable window covering
93
that acts on the bottom rail
92
is at maximum. As such, the external force that is required to initiate lowering of the bottom rail
92
to expand the expandable window covering
93
is also at a minimum.
It is noted that the cord spools
30
rotate at the same speed. Therefore, the pull cords
94
are wound on and unwound from the cord spools
30
at equal lengths. As such, the bottom rail
92
does not slant and is maintained in a horizontal orientation with respect to the head rail
91
while being raised or lowered.
FIG. 6
illustrates a spring motor of the second preferred embodiment of a window blind according to the present invention. When compared with the first preferred embodiment, the window blind of this embodiment further comprises a pair of auxiliary pull cords
95
. The spring motor further includes a pair of auxiliary cord spools
40
. Each of the auxiliary cord spools
40
has a driven shaft
412
that is mounted to rotate with a respective one of the cord spools
30
and that is connected to a respective one of the auxiliary pull cords
95
. The construction as such provides adequate support to a bigger and heavier window blind.
In this embodiment, the friction imposing mechanism
80
is mounted on the frame
10
, is operable so as to provide a friction force which acts on the drive drum
20
, and includes an annular member
81
, a braking member
82
, a post
83
, and a coil spring
84
.
The annular member
81
is secured on the frame
10
, is vertically aligned with the drive drum
20
, and has annular inner and rectangular outer wall surfaces
811
,
812
. The braking member
82
is disposed in the annular member
81
, and has a tubular part
821
and a pair of braking parts
822
. Each of the braking parts
822
is connected to, is disposed radially and outwardly on a respective one of opposite sides of the tubular part
821
, and is in friction engagement with the inner wall surface
811
of the annular member
81
. The post
83
is mounted on the drive drum
20
and extends into the tubular part
821
of the braking member
82
. The coil spring
84
is sleeved fittingly on the post
83
in the tubular part
821
of the braking member
82
, is wound in a same winding direction as the spiral spring
22
, and has one end fastened to the braking member
82
.
Referring to
FIG. 7
, since the operation of the auxiliary cord spools
40
and the auxiliary pull cords
95
of the second preferred embodiment is similar to those described hereinabove in connection with the cord spools
30
and the pull cords
94
of the previous preferred embodiment, a detailed description of the same will be dispensed with herein for the sake of brevity.
After raising the bottom rail
92
(see FIG.
1
), the bottom rail
92
tends to move downward when the external force applied to raise the bottom rail
92
is removed. This results in tendency of the drive drum
20
to rotate in a first direction the same as the winding direction. The rotation of the drive drum
20
, which in turn directly rotates the post
83
, enables the coil spring
84
to contract radially and to engage with the post
83
. The coil spring
84
urges the braking member
82
to rotate so that friction force between the braking member
82
and the annular member
81
is transmitted to the drive drum
20
. As such, the bottom rail
92
can be retained at a desired vertical distance relative to the head rail
91
(see FIG.
1
).
Further, when the bottom rail
92
is raised, this results in rotation of the drive drum
20
in a second direction opposite to the first direction. The rotation of the drive drum
20
, which in turn directly rotates the post
83
, enables the coil spring
84
to expand radially and not to rotate with the post
83
. Accordingly, the friction force between the braking member
82
and the annular member
81
is not transmitted to the drive drum
20
. As such, the friction force that is provided by the friction imposing mechanism
80
does not act on the drive drum
20
while the bottom rail
92
is being raised.
It has thus been shown that the window blind
9
of this invention includes a spring motor
100
that dispenses with an idler gear and a take-up drum. As such, the spring motor
100
utilized in this invention is relatively simple to construct as compared to the aforesaid prior art. While the present invention has been described in connection with what is considered the most practical and preferred embodiments, it is understood that this invention is not limited to the disclosed embodiments but is intended to cover various arrangements included within the spirit and scope of the broadest interpretation so as to encompass all such modifications and equivalent arrangements.
Claims
- 1. A window blind comprising:a head rail; a bottom rail; an expandable window covering between said head rail and said bottom rail; a pair of pull cords interconnecting said head rail, said bottom rail and said expandable window covering; and a spring motor including a frame mounted on one of said head rail and said bottom rail, a drive drum mounted rotatably on said frame and provided with a drive gear, a pair of cord spools mounted rotatably on said frame and disposed on opposite sides of said drive drum, each of said cord spools being provided with a driven gear that meshes with said drive gear and being connected to a respective one of said pull cords, a spiral spring wound on said drive drum and having opposite ends connected to said drive drum and said frame, respectively, said spiral spring providing a biasing force for biasing said drive drum to rotate in a direction for winding said pull cords on said cord spools, and a friction imposing mechanism mounted on said frame and operable so as to provide a friction force that acts on one of said drive drum and said pull cords; wherein said spiral spring deforms from an initial state to an extent corresponding to vertical distance of said bottom rail from said head rail; and wherein said biasing force of said spiral spring and said friction force attributed to said friction imposing mechanism cooperate to support the weight of said bottom rail and the weight of said expandable window covering that acts on said bottom rail so as to retain said bottom rail at a desired vertical distance relative to said head rail.
- 2. The window blind as claimed in claim 1, wherein said expandable window covering includes a plurality of parallel slats.
- 3. The window blind as claimed in claim 1, wherein said frame is formed with left and right compartments, and a middle compartment between said left and right compartments, each of said left and right compartments having an axle disposed therein for mounting rotatably a respective one of said cord spools in said left and right compartments, said drive drum being disposed in said middle compartment.
- 4. The window blind as claimed in claim 3, wherein said drive drum has a drive shaft connected to said drive gear and formed with a slit for engaging one of said opposite ends of said spiral spring.
- 5. The window blind as claimed in claim 3, wherein said frame includes a casing part formed with said left, middle and right compartments and having an open side, and a cover part mounted on said casing part to cover said open side of said casing part and to retain said cord spools and said drive drum in said casing part.
- 6. The window blind as claimed in claim 1, wherein said friction imposing mechanism includes a pair of friction roller sets, each of which is mounted on one end of said frame adjacent to a respective one of said cord spools, each of said friction roller sets including three friction rollers arranged in a triangular formation, each of said pull cords being trained on said friction rollers of a respective one of said friction roller sets.
- 7. The window blind as claimed in claim 1, wherein said friction imposing mechanism includes:an annular member secured on said frame and vertically aligned with said drive drum, said annular member having an annular inner wall surface; a braking member disposed in said annular member and having a tubular part and a braking part connected to and disposed radially and outwardly of said tubular part, said braking part being in friction engagement with said inner wall surface of said annular member; a post mounted on said drive drum and extending into said tubular part of said braking member; and a coil spring sleeved fittingly on said post in said tubular part of said braking member and wound in a same winding direction as said spiral spring, said coil spring having one end fastened to said braking member; wherein rotation of said drive drum in a first direction the same as the winding direction enables said coil spring to contract radially so that friction force between said braking member and said annular member is transmitted to said drive drum; and wherein rotation of said drive drum in a second direction opposite to the first direction enables said coil spring to expand radially so that the friction force between said braking member and said annular member is not transmitted to said drive drum.
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