Clock spring connector

A clock spring connector which has a shorter length of a flexible cable and can suppress noises. In a ring-shaped space between an outer cylindrical portion of a first housing and an inner cylindrical portion of a second housing, there are disposed a flexible cable wound in opposite directions with a reversely looped portion being at a U-turn point, and a carrier member rotatable following the reversely looped portion. A spacer as part of the carrier member slides over a rib provided on a bottom plate of the first housing.

FIELD OF THE INVENTION 
The present invention relates to a clock spring connector for use in an 
automobile steering device or the like to make electrical connection 
between a stationary member and a movable member by utilizing a flexible 
cable. 
DESCRIPTION OF THE RELATED ART 
A clock spring connector is arranged such that a stationary member and a 
movable member mounted rotatably with respect to the stationary member are 
interconnected by a flexible cable, and it has been employed as electrical 
connecting means between the stationary member and the movable member 
which is rotatable an infinite number of revolutions relative to the 
former as encountered in an automobile steering device. 
In that type clock spring connector, the flexible cable takes a substantial 
part of the total cost. For this reason, U.S. Pat. No. 3,763,455 proposes 
a clock spring connector which is aimed at reducing the length of a 
flexible cable required and cutting down the cost. 
FIG. 9 is a top plan view showing the schematic construction of the clock 
spring connector disclosed in the above-cited U.S. Patent. As shown in the 
figure, a movable member 101 is mounted rotatably with respect to a 
stationary member 100 having a cylindrical shape, and flexible cables 103, 
104 are stored in a ring-shaped space 102 defined between the movable 
member 101 and the stationary member 100. More specifically, these 
flexible cables 103, 104 are led out of the space 102 with their end 
portions fixed to the movable member 101 and the stationary member 100, 
respectively, and are stored in the space 102 such that they are wound in 
opposite directions upon an outer cylindrical portion as part of the 
stationary member 100 and an inner cylindrical portion as part of the 
movable member 101, with a reversed portion in a U-shape being formed at 
each position where the direction of winding of the flexible cable is 
reversed. Further, two groups of rollers 105, 106 are arranged within the 
space 102 to roll in the circumferential direction. The reversed portion 
of the flexible cable 103 is looped around one roller of the one group of 
rollers 105, and the reversed portion of the flexible cable 104 is looped 
around one roller of the other group of rollers 106. 
In the clock spring connector thus constructed, when the movable member 101 
is rotated in the clockwise direction, for example, in FIG. 9, the 
reversely looped portions of the flexible cables 103, 104 are moved within 
the space 102 in the clockwise direction through a smaller amount of 
revolutions than that of the movable member 101, thus bringing the 
flexible cables 103, 104 into a wound-up state that they are wrapped in a 
larger amount of revolutions upon the inner cylindrical portion of the 
stationary member 100. On the contrary, when the movable member 101 is 
rotated in the counterclockwise direction, the reversely looped portions 
of the flexible cables 103, 104 are moved in the counterclockwise 
direction through a smaller amount of revolutions than that of the movable 
member 101, thus bringing the flexible cables 103, 104 into an unwound 
state that they are wrapped in a larger amount of revolutions upon the 
outer cylindrical of the movable member 101. When wound-up and unwound, 
the rollers 105, 106 are moved in the counterclockwise and clockwise 
direction, respectively, while receiving forces from the reversely looped 
portions of the flexible cables 103, 104. 
With the above conventional clock spring connector, because the flexible 
cables are each wound in opposite directions upon the inner and outer 
cylindrical portions, the length of the flexible cable required can be cut 
down remarkably in comparison with a clock spring connector of the type 
that the flexible cable is wound (into the spiral form) upon the inner and 
outer cylindrical portions in the same direction. Also, because a 
plurality of rollers are disposed between those loops of the flexible 
cable wound upon the inner cylindrical portion and those loops of the 
flexible cable wound upon the outer cylindrical portion, the flexible 
cable can be restricted in the radial direction almost the entire 
circumference of the ring-shaped space, making it possible to smoothly 
wind up or unwind the flexible cable. 
However, the clock spring connector constructed as mentioned above has 
suffered from the problem that since the rollers are moved within the 
space in the circumferential direction while being held at their lower end 
faces closely against a member defining the bottom surface of the space, 
there cause large noisy sounds of sliding due to friction therebetween. If 
a sufficient clearance is set to be left between upper end faces of the 
rollers and a member defining the top surface of the space, the above 
noisy sounds of sliding could be reduced to some extent. But the presence 
of such a clearance causes the rollers to move up and down, which has 
raised the problem that the rollers strike against the members defining 
the top and bottom surfaces of the space and collision noises are 
produced. 
SUMMARY OF THE INVENTION 
The present invention has been made in view of the above-mentioned state of 
art, and an object of the invention is to provide a clock spring connector 
which is inexpensive and can suppress noises. 
To achieve the above object, a primarily feature of the present invention 
resides in a clock spring connector comprising a stationary member, a 
movable member mounted rotatably with respect to the stationary member, a 
flexible cable stored in a space between an inner cylindrical portion 
provided on one of the stationary member and the movable member and an 
outer cylindrical portion provided on the other, and a carrier member 
disposed in the space and having an opening, the flexible cable being 
reversely looped to provide a U-turn point in the opening of the carrier 
member and wound in opposite directions upon the inner cylindrical portion 
and the outer cylindrical portion, wherein a projection is provided 
between the carrier member and at least one of a top surface and a bottom 
surface of the space for making smaller a contact area between the carrier 
member and one of the top surface and the bottom surface. 
Another feature of the present invention is in that the projection is 
provided on at least one of the carrier member and the top surface and the 
bottom surface of the space, and more particularly in that the projection 
is provided on the carrier member. 
Still another feature of the present invention is in that a ring-shaped 
recessed groove is provided on at least one of the the top surface and the 
bottom surface of the space in facing relation to the carrier member for 
guiding the carrier member in the circumferential direction. Additional 
feature of the present invention is in that the projection is provided on 
at least one of the top surface and the bottom surface of the space in 
facing relation to the flexible cable. 
Yet another feature of the present invention is in that the projection is 
in the form of a radial rib and/or an annular rib. 
When the movable member is rotated in one direction with respect to the 
stationary member, the flexible cable is wound up upon the inner 
cylindrical portion or unwound upon the outer cylindrical portion through 
the reversely looped portion. At this time, the reversely looped portion 
is moved within the space in the same direction through a smaller amount 
of revolutions than that of the movable member, and the carrier member is 
also moved within the space to revolve in the same direction following the 
reversely looped portion. Because of the projection being provided between 
the carrier member and the stationary member to make smaller a contact 
area therebetween, noises due to sliding of the carrier member are 
suppressed and the carrier member can be smoothly moved within the space 
with no need of leaving a clearance between the carrier member and the top 
surface of the space.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Hereinafter, preferred embodiments of the present invention will be 
described with referent to the drawings. 
FIG. 1 is a vertical sectional view of a clock spring connector according 
to a first embodiment of the present invention, FIG. 2 is an exploded 
perspective view of the clock spring connector, FIG. 3 is a top plan view 
of principal parts of the clock spring connector, and FIG. 4 is an 
enlarged sectional view taken along line 4--4 in FIG. 3. 
As shown in these figures, a clock spring connector according to this 
embodiment primarily comprises a first housing 1, a second housing 2 
mounted rotatably with respect to the first housing 1, a flexible member 3 
stored between both the housings 1, 2, and a carrier member 4 rotatably 
disposed between both the housings 1, 2. 
The first housing 1 comprises a lower case 7 provided with an outer 
cylindrical portion 6 upstanding at the peripheral edge of a base plate 5, 
and an upper cover 8 integrally joined to an upper end of the outer 
cylindrical portion 6. Center holes 9, 10 are bored at the centers of the 
bottom plate 5 of the lower case 7 and the upper cover 8, respectively. A 
guide groove 11 having a ring-shaped shape as viewed from above is 
provided in the bottom plate 5 and an annular rib 12 is projected at the 
center of the guide groove 11. 
The second housing 2 comprises a cylindrical member having a shaft 
insertion hole 13 at the center. The second housing 2 is rotatably coupled 
to the first housing 1 in such a manner that the outer peripheral edge of 
the second housing 2 is guided at its upper and lower ends by the center 
holes 9, 10 in the lower case 7 and the upper cover 8, respectively. As 
will be seen from FIGS. 3 and 4, a space 15 having a ring-like shape as 
viewed from above is defined by the bottom plate 5, the outer cylindrical 
portion 6 and the upper cover 8 on the side of the first housing 1, as 
well as by an inner cylindrical portion 14 which is part of the second 
housing 2 and provides a circumferential surface of the same. 
The flexible cable 3 comprises a so-called flat cable of the type that a 
plurality of conducting wires parallel to each other are laminated by 
using a pair of insulating films. This embodiment uses a flat cable for 
five lines in which five conducting lines are embedded. One end of the 
flexible cable 3 is connected to a first connector 16 fixed to the outer 
cylindrical portion 6 and led out of the first housing 1 via the first 
connector 16. Meanwhile, the other end of the flexible cable 3 is 
connected to a second connector 17 fixed to the inner cylindrical portion 
14 and led out of the second housing 2 via the second connector 17. 
Further, the flexible cable 3 is stored in the space such that it is wound 
in the clockwise direction along an inner wall of the outer cylindrical 
portion 6 from the first connector 16, reversely turned while making a 
U-shaped loop (hereinafter referred to as a reversely looped portion 3a), 
and then wound in the counterclockwise direction along an outer wall of 
the inner cylindrical portion 14 from the reversely looped portion 3a to 
reach the second connector 17. 
The carrier member 4 comprises a ring-shaped spacer 19 provided with a 
plurality of pins 18 upstanding on its upper surface, and rollers 20 
rotatably fitted over the respective pins 18. The carrier member 4 is 
disposed in the space 15 such that the spacer 19 is restricted by the 
guide groove 11 in radial movement and upper end faces of the rollers 20 
are held in contact with a lower surface of the upper cover 8. In 
addition, the reversely looped portion 3a of the flexible cable 3 is 
positioned in an opening space between two adjacent rollers among a group 
of the rollers 20. 
Operation of the clock spring connector according to this embodiment will 
now be described taking, as an example, the case where the first housing 1 
is used as a stationary member and the second housing 2 is used as a 
movable member. 
When the second housing 2 is rotated in the clockwise direction from a 
neutral position where the flexible cable 3 is wound upon the outer 
cylindrical portion 6 of the first housing 1 and the inner cylindrical 
portion 14 of the second housing 2 in almost the same amount of 
revolutions, the reversely looped portion 3a of the flexible cable 3 is 
moved in the clockwise direction through a smaller amount of revolutions 
than that of the second housing 2. The group of the rollers 20 and the 
spacer 19 are also moved in the clockwise direction following the 
reversely looped portion 3a, whereby the flexible cable 3 is let out from 
the side of the inner cylindrical portion 14 and wrapped on the side of 
the outer cylindrical portion 6 by a length corresponding to about twice 
the amount of revolving movement of the reversely looped portion 3a. At 
this time, since the spacer 19 and the first housing 1 are held in contact 
with each other via the rib 12 provided on the base plate 5 with a small 
coefficient of friction, the spacer 19 is smoothly revolved to slide in 
the space 15 while being guided by the guide groove 11. As a result, noisy 
sounds of sliding generated upon the movement of the spacer 19 are 
diminished. 
To the contrary, when the second housing 2 is rotated in the 
counterclockwise direction from the aforesaid neutral position, the 
reversely looped portion 3a of the flexible cable 3 and the carrier member 
4 are moved through a smaller amount of revolutions than that of the 
second housing 2, whereby the flexible cable 3 is let out from the side of 
the outer cylindrical portion 6 and wrapped on the side of the inner 
cylindrical 14 by a length corresponding to about twice the amount of 
revolving movement of the reversely looped portion 3a. In this case, too, 
since the spacer 19 and the first housing 1 are contacted with each other 
via the rib 12 with a small coefficient of friction, the spacer 19 is 
smoothly revolved to slide in the space 15 while being guided by the guide 
groove 11. As a result, noisy sounds of sliding generated upon the 
movement of the spacer 19 are diminished similarly. 
With the clock spring connector according to the first embodiment explained 
above, since the flexible cable 3 is wound in opposite directions upon the 
outer cylindrical portion 6 and the inner cylindrical portion 14 with the 
reversely looped portion 3a being at a U-turn point, the length of the 
flexible cable 3 required can be shortened. As a result, the present clock 
spring connector is able to cut down the total cost and is advantageous in 
making the connector size smaller. 
Also, since the carrier member 4 is disposed between those loops of the 
flexible cable 3 wrapped upon the outer cylindrical portion 6 and those 
loops of the flexible cable 3 wrapped upon the inner cylindrical portion 
14 and the reversely looped portion 3a is positioned between a pair of the 
rollers 20 provided as parts of the carrier member 4, the flexible cable 3 
can be prevented by the group of rollers 20 from so expanding outwardly in 
the radial direction as to buckle on the way to reach the reversely looped 
portion 3a, when the flexible cable 3 is unwound. It is thus possible to 
positively carry out the unwinding operation. 
Further, since the annular rib 12 is provided on the bottom plate 5 of the 
first housing 1 so that the spacer 19 and the bottom plate 5 are contacted 
with each other via the rib 12 with a small coefficient of friction, 
sounds of sliding generated upon the spacer 19 being revolved to slide in 
the space 15 can be diminished to suppress resultant noises. 
Additionally, since the guide groove 11 is provided in the bottom plate 5 
of the first housing 1 to guide the spacer 19 in the circumferential 
direction, the spacer 19 can be prevented from radially moving to strike 
against the flexible cable 3 wound upon the outer cylindrical portion 6 or 
the inner cylindrical portion 14. From this point as well, suppression of 
noises can be achieved. 
FIG. 5 is a top plan view of principal parts of a clock spring connector 
according to a second embodiment of the present invention, and FIG. 6 is a 
sectional view taken along line 6--6 in FIG. 5. In these figures, the 
components corresponding to those in FIGS. 1 to 4 are denoted by the same 
reference numerals. 
This embodiment is different from the above first embodiment in that a 
plurality of other ribs 21 radially extending are provided on the bottom 
plate 5 at locations other than the guide groove 11. The remaining 
construction is basically the same between these two embodiments. In this 
case, since the flexible cable 3 and the bottom plate 5 of the first 
housing 1 are contacted with each other via the ribs 21 with a small 
coefficient of friction, noisy sounds generated upon the flexible cable 3 
sliding over the bottom plate 5 can be diminished, hence noises can 
further be suppressed. 
FIG. 7 is a top plan view of principal parts of a clock spring connector 
according to a third embodiment of the present invention, and FIG. 8 is a 
sectional view taken along line 8--8 in FIG. 7. In these figures, the 
components corresponding to those in FIGS. 5 and 6 are denoted by the same 
reference numerals. 
This embodiment is different from the above second embodiment in that a 
plurality of still other ribs 22 are provided in the guide groove 11 to 
extend in the radial direction as with the outer ribs 21. The remaining 
construction is basically the same between these two embodiments. In this 
case, there can also be obtained a similar advantage to that in the second 
embodiment. 
It should be noted that while the above embodiments have been explained as 
interposing the annular rib 12 or the radial ribs 22 between the bottom 
plate 5 of the first housing 1 an the spacer 19, a plurality of separate 
projections may be provided instead of the continuous ribs 12, 22. As an 
alternative, those ribs or projections may be provided on the underside of 
the spacer 19. 
Moreover, while the above embodiments have been explained in connection 
with the case where the first housing 1 serves as a stationary member and 
the second housing 2 serves as a movable member, it is conversely also 
possible to use the first housing 1 as a movable member and the second 
housing 2 as a stationary member. Further, the configurations of the first 
and second housings 1, 2 are not limited to those illustrated in the above 
embodiments. For example, the upper cover 8 may be integral with the 
second housing 2 and the first housing 1 may have an upwardly open shape 
provided with the bottom. 
Additionally, while the flat cable is illustrated as one example of the 
flexible cable 3 in the above embodiments, a flexible cable called a round 
wire cable in which a leading wire is coated with an insulating tube can 
be used instead of the flat cable. In this case, a plurality of round wire 
cables corresponding to the number of lines required are held together in 
the form of a belt. 
According to the present invention, as described above, the length of the 
flexible cable required can be cut down remarkably and noisy sounds 
generated upon the carrier member moving in the space can be diminished. 
Consequently, there can be provided a clock spring connector which is 
inexpensive and produces less noises.