Steering wheel spring assembly

An improved mechanical linkage may be used in devices such as a non-powered PC gaming steering wheel controller. In one embodiment, the linkage is part of a steering wheel assembly. The assembly provides a steering wheel shaft having a flange extending radially from the shaft. A first coil spring and a second coil spring are attached to the flange to return the flange and the steering wheel shaft to a neutral position. The coil springs typically are mounted between a base of the steering wheel assembly and the flange portion of the shaft. The flange is sized to facilitate rotation of the steering wheel shaft without causing the coil springs to bend about the shaft. The coil spring preferably has an elongate portion that is offset from the centerline of the coil spring. This offset distance preferably allows the shaft to rotate to at least 120.degree. in the clockwise or counterclockwise direction from its neutral position without causing the elongate portion of the spring to bend. Eliminating bending in the spring improves the lifespan of the spring.

BACKGROUND OF THE INVENTION
 The present invention relates generally to mechanical linkages, and more
 specifically to mechanical linkages for use in computer peripherals such
 as a steering wheel controller and the like.
 On non-powered, non-force feedback personal computer (PC) gaming steering
 wheel devices, springs are sometimes used to provide rotational resistance
 to the turning of the steering wheel. In part, the resistance is used to
 simulate the turning resistance of a steering wheel used in actual cars
 and racing machines. Additionally, however, the springs are also used to
 create a self-centering steering wheel which will return the wheel to a
 neutral, center position when the steering wheel is ungripped. This
 self-centering quality facilitates game play and further simulates real
 life driving conditions where the steering wheel tends to be somewhat
 self-centering when ungripped by the driver.
 Most of these non-powered PC gaming steering wheels as shown in FIG. 1,
 typically have a steering wheel W mounted onto a shaft S that is contained
 within the controller housing H. The self-centering mechanisms which
 control the rotational position of the shaft S and the wheel W, are
 preferably contained within the housing H.
 In conventional steering wheel devices, the typical spring loaded device is
 restricted to approximately 180.degree. of total wheel rotation (i.e.
 90.degree. rotation in clockwise and counterclockwise direction) if a long
 spring life and self-centering of the wheel is desired. This is because
 the extension springs used to self-center the steering wheel shaft must
 first be stretched straight and then bent around the main shaft of the
 steering wheel to complete rotation greater than 90.degree. in a clockwise
 or counterclockwise direction for a total of 180.degree. of rotation. For
 example, FIG. 2 shows a conventional steering wheel shaft S with an
 elastomeric spring E. FIG. 2 shows the shaft rotated 90.degree. from its
 neutral or resting position. As seen in FIG. 2, the elastomeric spring E
 remains in a substantially straight configuration. As the steering wheel
 shaft S is rotated further, to 120.degree. from its neutral position, the
 elastomeric spring E is bent at location B as shown in FIG. 3. It is this
 type of bending that shortens the life span of the spring. Although a
 variety of different types of springs such as coil springs, elastomeric
 cords, or similar bias members have been used, the lateral stress posed on
 the spring due to the bending around the steering wheel shaft eventually
 leads to early spring failure in these conventional assemblies.
 Accordingly, it would be desirable to provide an improved self-centering
 steering wheel assembly which allows for a greater degree of wheel
 rotation, such as a total of 240.degree. rotation, while maintaining a
 long lifespan for the springs in the assembly. Such a self-centering
 steering wheel assembly would improve lifespan of the spring by preventing
 the bending of the spring about the steering wheel shaft while increasing
 the range of rotational motion.
 SUMMARY OF THE INVENTION
 The present invention provides a self-centering steering wheel assembly
 having a unique flange and bias member combination as described below. The
 flange is mounted radially about a steering wheel shaft. The bias member,
 which is typically a coil spring, is pivotally coupled to the flange and
 has a substantially straight elongate portion offset from a center axis of
 the bias member by an offset distance. By offsetting the substantially
 straight portion of the bias member from its center axis (i.e., a straight
 portion from a side of a coil spring, instead of the center), the offset
 distance advantageously allows the steering wheel shaft to rotate at least
 about 120.degree. in a clockwise or counterclockwise direction without
 causing the straight portion to bend. The offset distance allows the
 spring to move to the "other side" of the steering wheel shaft centerline
 without causing the substantially straight portion of the bias member to
 bend. This allows for the long spring life and self-centering quality of
 the steering wheel assembly.
 In one embodiment, the present invention provides a steering wheel shaft
 having a flange extending radially from the shaft. A first coil spring and
 a second coil spring are attached to the flange to return the flange and
 the steering wheel shaft to a neutral position. The coil springs typically
 are mounted between a base of the steering wheel assembly and the flange
 portion of the shaft. The flange is sized to facilitate rotation of the
 steering wheel shaft without causing the coil springs to bend about the
 shaft. The coil spring preferably has an elongate portion that is offset
 from the centerline of the coil spring. As mentioned previously, this
 offset distance allows the shaft to rotate to at least about 120.degree.
 from its neutral position without causing the elongate portion of the
 spring to bend. Preferably, the elongate portion of the coil spring has a
 length sufficient to allow the shaft to rotate to about 120.degree. in
 either clockwise or counterclockwise direction without the coil portion of
 the spring contacting the flange and interfering with the rotation of the
 steering wheel shaft. Additionally, when the steering wheel shaft is in a
 neutral position, the coil springs are mounted at a pre-load angle which
 provides sufficient force to overcome losses in bearings of the steering
 wheel shaft while the angle is also small enough to prevent the straight
 portion of the coil spring from interfering with the shaft when the shaft
 is rotated to 120.degree. from its neutral position.
 A further understanding of the nature and advantages of the invention will
 become apparent by reference to the remaining portions of the
 specification and drawings.

DESCRIPTION OF THE SPECIFIC EMBODIMENTS
 The present invention provides a mechanical linkage for use in devices such
 as a non-powered PC gaming steering wheel controllers. The present
 invention provides an apparatus that adds a self-centering quality to the
 steering wheel controller while allowing for a greater degree of
 rotational motion without reducing the lifespan of bias members used in
 the steering wheel controller. The self-centering quality causes the
 steering wheel to return to a neutral rotational position when the user is
 not turning or gripping the steering wheel. This return force of the
 self-centering steering wheel assembly provides for a more realistic
 gaming experience and also provides resistance that simulates the steering
 wheel "feel" associated with real cars and driving vehicles. The present
 invention advantageously allows the lifespan of the steering wheel to
 exceed 300,000 cycles while increasing the total rotational motion from
 180.degree. to 240.degree..
 Referring now to FIGS. 4 and 5, a self-centering steering wheel assembly
 according to the present invention will be described in further detail.
 FIG. 4 shows a view of the steering wheel assembly 10 as viewed when
 looking longitudinally down the shaft S. A flange 12 is mounted radially
 about the shaft S. The flange 12 may be integrally formed with the shaft
 S, interference fit with the shaft, or otherwise attached to the shaft.
 The flange 12 is coupled to at least one bias member. The embodiment of
 FIG. 4 uses a first coil spring 20 and a second coil spring 22 as the bias
 members. For a steering wheel assembly to be "self centering," two bias
 members or extension springs of equal spring rate are preferably attached
 to moment arms extending from the main shaft on one end, and then angled
 down on both sides to create an initial force in each spring with a
 component of the force pointing down on each side of the main shaft of
 equal magnitude. These springs create equilibrium due to opposite and
 equal moments being applied to the shaft. If the wheel is turned either
 way the springs are stretched to create a moment force which acts to
 restore the wheel to the centered position.
 In the embodiment of FIG. 4, the first coil spring 20 has a coiled portion
 24 and a substantially straight elongate portion 26. This straight portion
 26 is preferably long enough to prevent the coils from interfering with
 the shaft when the spring is extended as shown in FIG. 5. In the
 embodiment of FIG. 4, the distal end of the elongate portion has a eye
 hook which pivotally mounts to a connection point 30 on the flange 12. The
 connection point 30 may be a pin, stud, or similar protrusion located on
 the flange 12. The connection has a center 32. The flange 12 and shaft S
 define a moment arm 40 which extends from a center 42 of the shaft S to a
 center 32 of the connection point 30. The arm length of the moment arm 40
 preferably allows the coil spring 20 to move from a neutral position, as
 illustrated in FIG. 4, to a rotated position, as shown in FIG. 5, without
 causing the substantially straight elongate portion 26 to bend about the
 steering wheel shaft S. The moment arm 40 is preferably long enough to
 allow for space between the long straight section and the main shaft at
 rotations greater than about 90.degree. while being short enough to
 prevent interference with the coils on the spring when extended.
 As seen in FIG. 4, the coil springs are preferably mounted at pre-load
 angle 50 which provides a return force when the shaft is in the neutral
 position. When in the neutral position, the downward force as indicated by
 arrows 52 and 54 are substantially equivalent. The pre-load angle on the
 coil springs 20 and 22 preferably provide sufficient force to overcome
 losses in the bearings of the steering wheel shaft. The pre-load angle is
 also preferably small enough to prevent the straight portion of the coil
 spring from interfering with the rotation of the shaft. An excessively
 strong or high pre-load angle will reduce the range of motion of the shaft
 S before the substantially straight elongate portion 26 begins to bend.
 The main shaft diameter of assembly is preferably small enough to provide
 space between the straight section of the spring and the main shaft beyond
 90 degrees and large enough to provide the needed strength.
 As seen now in FIG. 5, the steering wheel shaft S may be rotated at least
 120.degree. from the neutral position shown in FIG. 4. As seen in FIG. 5,
 at this 120.degree. position, the substantially straight portion 26 of the
 coil spring 20 remains in a substantially straight configuration. Hence,
 the coil spring is simply extended and then compressed during the rotation
 of the shaft S. Rotation which causes the portion 26 to bend will decrease
 the life span of the coil spring 20. Hence, it is desirable to maintain
 this linear extension and compression of the coil spring 20. As seen in
 FIG. 5, the elongate portion 26 is offset from a center axis 60 of the
 coil spring 20 by an offset distance 62. It is this offset distance that
 allows the steering wheel shaft S to rotate 120.degree. without causing
 the coil spring to bend about the shaft. As seen in FIGS. 2 and 3, most
 known steering wheel assemblies can move to a 90.degree. position, but
 further rotation will cause their spring member to bend about the shaft S.
 The greater the offset distance 62, the larger the rotational movement is
 available to the steering wheel shaft S. It should be understood, however,
 that the offset distance cannot be overly increased so as to cause the
 elongate portion 26 to bend when the spring is located underneath the
 steering wheel shaft S, as illustrated by the position 22. Overly
 increasing the offset distance may cause bending at point 64. Preferably,
 the offset distance 62 allows the steering wheel shaft S to rotate at
 least 90.degree. clockwise or counterclockwise beyond the neutral
 position, and more preferably, at least 120.degree. in the clockwise and
 counterclockwise direction. Preferably, the elongate portion 26 also has a
 length sufficient to allow the steering wheel shaft to rotate to its
 maximum rotational position, such as 120.degree., without causing the coil
 portion 24 to contact the flange 12. Such contact may interfere with the
 rotation of the steering wheel shaft and also reduce the life span of the
 coil spring.
 Referring now to FIG. 6, in another embodiment of the present invention,
 the coil spring 69 has a protrusion 70 located at the distal end of the
 elongate portion 72 to provide the desired offset distance. The protrusion
 70 functions similarly to the eye hook in FIGS. 4-5. Protrusion 70 is
 pivotally mounted at connection point 73 to the flange 12 and is used to
 space the elongate portion 72 apart from the center line 60. The spring 69
 is preferably mounted between connection point 73 on the flange 12 and a
 connection point 74 on a base 75. The same can be said of spring 76. The
 offset distance in spring 69 may be measured from the centerline of the
 elongate portion 72 to the center axis 60 of the spring member, or the
 offset distance may be measured from the outer surface of the elongate
 portion to the center line 60 of the bias member. Additionally, the
 elongate portion 72 is not necessarily parallel to the longitudinal center
 axis of the spring member. The elongate portion 72 may be angled relative
 to the center axis 60 so long as sufficient offset distance remains to
 allow the steering wheel shaft S to rotate beyond about 90.degree. from
 the neutral position and preferably at least about 120.degree. from the
 neutral position.
 While the above is a complete description of the preferred embodiments of
 the invention, various alternatives, modifications, and equivalents may be
 used. For example, the spring assembly is applicable to devices outside of
 the computer industry. In some embodiments, the spring may also be angled
 upward, instead of downward as shown in the figures, so long as they
 provide a return force to center the shaft. While the above description is
 complete, it should not be taken as limiting the scope of the invention
 which is defined by the appended claims.