Tilt-steered rolling device

Abstract: Rolling devices such as roller skates, skateboards, rolling skis, and scooters are known which steer by tilt, but either the wheels do not tilt, or the mechanism is of complex design, or the wheels shift sideways upon tilt. A rolling device shall have tilt-steering wheels which tilt with the device, and which stay in the middle of the platform when steering, and which are cheaply manufactured. This invention comprises a wheel pair, consisting of two wheels (3a, 3b) affixed to wheel-holders (4a, 4b), which are interconnected by two cross-guides (5, 6) thus forming a parallelogrammic link chain. The two cross-guides (5, 6) swivel having their swivel axes (9a, 9b) oriented parallel to each other providing an angle between the set of swivel axes (9a, 9b) and the set of pivot axes (7a, 7b, 7c, 7d) of the four links which constitute the chain. The cross-guides (5, 6) are fixed at the device platform extensions (8a, 8b) using three universal joints. One such tilt-steering wheel pair mechanism together with at least one fixed wheel are attached at opposite ends of the rolling device.

Description: This invention relates to rolling devices that allow individuals to move forwards or backwards such as roller skates, inline skates, skateboards, scooters, skis on wheels, wheel chairs, tricycles etc. Roller skates and skateboards are known which provide two non-tiltable wheel pair mechanisms, one at each end, wherein the platform can be tilted sideways and the wheels steer responding to the tilt by making the mechanisms swivel, having upwardly and downwardly angled swivel axes, thereby changing the direction in which the wheels are pointing. Usually small extra-wide cylindrical wheels are used that cause undesirably high friction. Upon tilting, the mass acceleration forces are directed off the midline of the wheels' tracks, loading the wheels unequally and finally limiting the maximum tilt angle. Inline skates, however, tilt as a whole, comprising the known low friction narrow wheels, but cannot be tilt-steered. DE19803412A1 discloses tiltable and tilt-steered wheel supports, wherein the wheels are fixed to longitudinal guides, the latter functioning as a compound guide system based on two sets of longitudinal fourfold linked chains. Any such solution using longitudinal guides is technically complex. Another problem is that such a solution causes unequal loading on the wheels of each pair. The latter disadvantage was overcome by using cross-guides. WO85/03644A1, on which the preamble of the independent claim 1 is based, describes wheels affixed to holders, which are guided using cross-guides in order to form a parallelogram-like chain having two sets of four links. The entire system is pivotally secured to a base plate, where the pivot axis extends vertically with respect to this base plate, just like a bogie. Steering is coupled to the tilt by a rack and pinion mechanism with the rack attached to the base plate. This solution still requires many parts and is complex. The principal objective of the present invention is to provide a novel steering mechanism to be used in wholly tiltable rolling devices wherein the steering angle is coupled to the tilt angle in a simple and kinematically well defined manner. Another major objective of this invention is to provide a steering mechanism which distributes the radial load equally on the wheels comprised by this mechanism. A further important objective of this invention is to provide a steering mechanism which uses only a few simple or easily manufactured parts or which uses standard components. These objectives are attained as follows. Assume a multitracked tilt-steered rolling device which incorporates pairs of tiltable wheels wherein the wheels are guided in form of a parallelogram. The simple steering mechanism described by the present invention comprises generally two obliquely swiveling cross-guides 5, 6. Their swivel axes are 9a, 9b. These two cross-guides 5, 6 attach pivotably to two separate wheel holders 4a, 4b where the pivot axes 7a, 7b of the first cross-guide 5 and the pivot axes 7c, 7d of the second cross-guide 6 are preferably oriented longitudinally and parallel, in a way that the known parallelogrammic link chain is formed. One wheel 3a is rotatably affixed to one wheel holder 4a and the other wheel 3b is rotatably affixed to the other wheel holder 4b. The two cross-guides 5, 6 are allowed to swivel with regard to the platform (2), their swivel axes being 9a, 9b. Alternatively the axial swivelling 9b is replaced by and included in a universally swivelling capacity which is provided by a universal joint 12 which attaches to the platform. The kinematics of the whole mechanical system is then well defined. The oblique swivel axis 9a of the first cross-guide 5 is at an angle α (alpha) with respect to the pivot axes 7a, 7b, 7c, 7d. This angle, called the steering factor angle, influences the capability of the rolling device to be tilt-steered. The advantages of this invention are that it provides the rolling device with an overall tilting capability combined with a steering effect, where the steering is directly coupled with the tilt, and that only a few simple parts are used. The invented rolling device combines smooth low friction rolling as known from inline skates with the excellent maneuverability of skateboards or roller skates. The several views of the drawing are now briefly described. FIG. 1 is a front view of the invented tilt-steering parallelogrammic link chain in the tilted position. FIG. 2 is a side view of a skate which incorporates three wheels. FIG. 3 is a front view of the invented parallelogrammic link chain in the upright position. FIG. 4 is a side view of this embodiment. FIG. 5 is an exploded perspective view of part of the tilt-steering mechanism. FIG. 6 is an enlarged view of a possible embodiment of the universal joint which connects the cross-guides with the extensions of the platform. FIG. 7 is a detailed view of another embodiment showing the spring used to return the mechanism into the neutral position. The invention is now described in detail; a skate serves as an example. FIG. 3 shows the front view of a parallelogrammic link chain, which consists of the two wheel holders, left 4a and right 4b, and the two cross-guides, the first on top, 5, and the second below, 6. The parallelogrammic link chain, described by its four pivot axes 7a, 7b, 7c, 7d is rectangular, as shown in FIG. 3, or is a non-rectangular parallelogram, as shown in FIG. 1. The invention also includes the possibility that the four axes define a trapezium (not drawn). The kinematics is shown in FIG. 1, viewed in the direction of the axes 7a, 7b, 7c, 7d. The platform 2 is then seen at a shallow perspective angle. Although FIGS. 2 to 5 anticipate that the axes 7a, 7b, 7c, 7d are oriented longitudinally with respect to the rolling device and are oriented parallel to the ground, this is not necessarily a prerequisite of the present invention. The essential condition for ensuring the tilt-steering function is the presence of an angle α (alpha, steering factor angle) which is described by the intersection of the parallel set of pivot axes 7a, 7b, 7c, 7d and the parallel set of swivel axes 9a, 9b. Shown in FIG. 5 are the two cross-guides 5, 6, the right wheel holder 4b, one wheel 3b and its bolt and axle 11b. The respective symmetrical wheel and wheel holder from the left side are omitted. The cross-guide 5 incorporates a bridge 5b which has a cross-sectional area large enough to ensure high torsion stiffness. In this embodiment the cross-section of the bridge 5b is a triangle. The preferred embodiment of the invented obliquely swiveling parallelogrammic link chain contains six links, where the first cross-guide 5 has four holes and the second cross-guide 6 has two holes. Six bolts (three bolts 21 are shown in FIG. 5) or axles connect the two cross-guides 5, 6 with the two wheel holders 4a, 4b which accordingly have three eyeholes each to accommodate said six bolts or axles. These six links pivotally connecting the cross-guides with the wheel-holders can easily be designed in a way which is common and well known to a person skilled in the art. Steel bolts can also be combined with standard cylindrical bearings made from brass or plastic, which fit into the eye-holes (not drawn). Referring to FIG. 2 the rolling device is able to steer along a curved track if the device has rotatably affixed to the platform at least one guiding wheel 16 which has a distance r (wheel base) to the wheels 3a, 3b of the wheel pair. Another parallelogrammic wheel pair mechanism can be used instead of the one guiding wheel 16. Its steering factor angle α (alpha) may be designed to be zero. In this case this wheel pair does not steer. The device's ability to curve is only determined by the steering function of the wheel pair mechanisms whose steering factor angles are not zero. The invented obliquely swiveling parallelogrammic link chain mechanism only consists of a few simple parts. Design components can be cheaply molded, formed or machined. Materials used may include light metal such as aluminum or other strong or reinforced (e.g. glass or carbon fiber resin) plastic. Certain applications e.g. roller skates, require the wheels to be placed underneath the platform 2. Upon tilting the platform, one wheel of the wheel pair 17 moves upwards approaching the platform 2, and the other wheel moves away from it. The space between the wheels and the platform needed for this movement increases with both the maximum tilt angle and the track widths between the two wheels 3a, 3b of the wheel pair. In order to minimize the space required i.e. to avoid an excessive "high-heeled" design, it is desirable to design the track s to be as small as possible. As can be seen in FIG. 1 the lateral space between the two parallelogrammically guided wheels reduces upon tilting. In addition, space is required for affixing the wheels' axles 11a, 11b. This additional space can be reduced, if necessary, if the said axles are fixed to the wheel holder only from the outer side of the wheels. However, the single sided wheel axle fixation is an optional feature. An embodiment is preferred, in which the wheels' rotation axes are kept parallel. This is achieved by making the distance between the pivot axis 7a and the pivot axis 7b of the first cross-guide 5 the same as the distance between the pivot axis 7c and the pivot axis 7d of the second cross-guide 6. If, upon tilting, the track width alters, at least one of the two wheels 3a, 3b will slide sidewards on the ground, causing friction and wear. An embodiment is therefore preferred which stabilizes the track, avoiding friction or wear, by having the distance between the pivot axes 7a and 7b of the first cross-guide 5, which is equal to the distance between the pivot axes 7c and 7d of the second cross-guide 6, made now equal to the track width s by design. This means that the pivot axes 7a and 7c lie in the center plane of wheel 3a and the pivot axes 7b and 7d lie in the center plane of the other wheel 3b. The present invention allows that each of the two cross-guides 5, 6 has a cylindrical bored hole, both parallel to each other but obliquely oriented with respect to the set of pivot axes 7a, 7b, 7c, 7d where the said holes serve to accommodate axles to be affixed to extensions 8a, 8b of the platform. This embodiment is possibly kinematically overdefined, as (in brief) the two cross-guides are forced to move in a parallel orientation by two independent mechanisms, first by the said two axles, secondly by the parallelogrammic link chain, both mechanisms possibly interfering with each other, if design tolerances are unfavorable. In order to avoid such interference, an embodiment is preferred wherein only one cross-guide 5 is supplied with a swivel axis 9a as mentioned, affixing this swivel axis 9a at extensions 8a, 8b of the platform 2, but supplying the second cross-guide 6 with a universal joint 12, e.g. in form of a spherical bushing, a ball-head bearing or the like, connecting the cross-guide 6 with the extension 8a of the platform 2 using the said universal joint 12 (see FIG. 4). This invention may also imply that the swivel axis 9a is directed obliquely with respect to most of the component parts' edges and faces. Technically any skew angled drilling, washers, axles etc. cause considerably high manufacturing costs. The preferred embodiment saves costs, as it ensures the function of an oblique swivel axis combined with hole drilling to be simply perpendicular to the part surfaces by use of universal joints 13a, 13b. The obliquity of the swivel axis 9a is ensured by designing a (preferably) vertical offset h in placing the two universal joints 13a and 13b at the first cross-guide 5. Altogether the universal joints 12, 13a, 13b can now fit into drilled holes, which are at right angles to the surfaces of the cross-guides 5, 6 and extensions 8a, 8b of the platform 2. The swivel axis 9a is now defined by the straight line through the centers of the two universal joints 13a, 13b. Another advantage of using universal joints instead of full-length axles is that the full-length axle produces space restrictions due to the limited track width condition. This is shown in FIG. 1 and FIG. 4. It is noted that the universal joint 12 of the second cross-guide 6 should preferably be vertically offset with respect to the middle of its pivot axes 7c, 7d and that the said offset in millimeters (mm) equals the vertical offset in mm of the universal joint 13a of the first cross-guide 5 with respect to the middle of its pivot axes 7a, 7b. FIG. 6 shows how parts can be connected using a spherical bushing as universal joint. A threaded bolt 22 having a cylindrical portion is placed through the spherical bushing 12, 13a, or 13b. The parts to be connected are the cross-guide 5, respectively 6, with extension 8a, respectively 8b, of the platform 2. The bolts 22 have design axes 14a, 14b, 14c. Many rolling devices like roller skates or scooters need to be functionally right-left symmetrical. This symmetry is preferably realized by having the oblique swivel axis 9a lie in the longitudinal vertical symmetry plane of the device, i.e. triangle 7c, 7d, 14c and triangle 7a, 7b, 14a are isosceles triangles. As the center parallel line 7m between axes 7a and 7b is lying within the symmetry plane, there exists a point K where the axes 9a and 7m intersect. One of the objects of this invention is to avoid shifting of the wheel pair out of the center line upon tilting. The wheels 3a, 3b of the wheel pair will, upon tilt, stay within the center line, if by design the said intersection point K is positioned vertically above the common axis of the axles 11a, lib, as shown in FIG. 4. Certain rolling devices, e.g. roller skates, are alternatively lifted of the ground and put back down again. When touching the ground, one wheel grips first, initiating the tilt-steering action. Finally the second wheel of the wheel pair touches down, stabilizing the tilt-steered curve. During this short interval the steering function is not defined. An embodiment is preferred which ensures that the device, e.g. a roller skate, assumes a neutral position i.e. the upright non-tilted position, when lifted from the ground. This objective is met by introducing a flexing means, which returns or maintains the wheel pair in the neutral position using the force of this flexible material or of a spring. FIG. 7 shows an embodiment, wherein a preformed spring wire 15 is affixed at the extension 8a, acting on the cross-guide 5 so that it is forced to assume the desired position. A multitude of alternative design possibilities exist, which are easily applied by a person skilled in the art. FIG. 2 illustrates that the device additionally incorporates a wheel 16 which is affixed longitudinally at a certain distance, the wheel base r, in order to be able to be steered. Alternatively another tilt-steering wheel pair which is designed according to this invention can be affixed. The curve radius depends on the steering factor angles α (alpha), which pertain to the one or two tilt-steering mechanisms. It also depends on the wheel base r. The curve radius becomes small when by design the angles α (alpha) are chosen to be large and the wheel base r is small. For this new tilt-steering skates, α (alpha) may range from 0.05 to 0.2 radian to be useful. The wheel base r may range from 20 to 35 centimeter, dependent on the preferred use of the skate. For example the designer of high speed skates may allow for smooth long curves. The mentioned ranges for α (alpha) and r are not meant to exclude other values. It is just this variability which opens ways to commercialize a wide variety of rolling devices specifically intended for different uses. The most economic embodiment of the invention combines one tilt-steered wheel pair with one fixed wheel. Embodiments are preferred where the tilt-steering wheel pair is arranged at the rear end of the device and the single wheel is affixed at its front end and vice versa. If four wheels are preferred because of improved weight distribution or because of better tracking then a preferred embodiment would combine two tilt-steering wheel pairs 17 affixed at either end of the rolling device. It is to be noted that the rearmost affixed wheel pair should have its swiveling axis 9a be designed to be declining, and that the front wheel pair should have its swiveling axis 9a be designed to be inclining, both viewed from behind. An alternative cheap four-wheels embodiment within the scope of this invention is defined by the combination of one tilt-steering wheel pair with one pair of wheels in-line, both pairs being affixed at opposite ends of the rolling device (not drawn). If the preferred use of the invented rolling device implies its use on rough surfaces, suspension and damping qualities are desired in order to protect the ankles and to keep the device on track. A suspension with or without damping can be realized by affixing the tilt-steering wheel pair in such a manner to the platform, that it can be shifted essentially at a right angle to the platform and by introducing a springy and vibration damping element into the space reserve needed for shifting. For example, DE19715706A1 discloses appropriate features, describing technical solutions for non-steering wheel suspensions which can also be applied to tilt-steering mechanisms like the one invented here.

Claims: A tilt-steered rolling device, consisting of an optional application part (1), a platform (2) including extensions (8a, 8b), and at least three wheels (3a, 3b, 16), two of said wheels being arranged side by side as a wheel pair, the wheels (3a, 3b) of the at least one wheel pair each being rotatably affixed at a separate wheel holder (4a, 4b), the two wheel holders being interconnected via two cross-guides (5, 6) using at least four pivot links (7a, 7b, 7c, 7d) forming a trapezium-like or a parallelogram-like link chain, characterised in that the said two cross-guides (5, 6) are each linked with the extensions (8a, 8b) of the platform (2) in such a way that the first cross-guide (5) swivels having a defined first swivel axis (9a) and the second cross-guide swivels allowing a second swivel axis (9b), where the said first swivel axis (9a) and the said second swivel axis (9b) are oriented in parallel, and wherein the direction of the set of said first and second swivel axes (9a, 9b) make an angle α (alpha) to the common and parallel direction of the pivot axes (7a, 7b, 7c, 7d) of the at least four links of the said trapezium- or parallelogram-like link chain. A device as defined in claim 1, characterised in that each axle (11a, 11b) of the two wheels (3a, 3b) of the wheel pair is attached only to one side of the respective wheel holder (4a, 4b). A device as defined in claim 1, characterised in that the pivot axes (7a, 7b) of the first cross-guide (5) are separated by a distance which is equal to the distance between the pivot axes (7c, 7d) of the second cross-guide (6). A device as defined in claim 3, characterised in that the distances as described in claim 3 are both equal to the track width (s) of the two wheels (3a, 3b) of the wheel pair. A device as defined in claim 1, characterised in that the second cross-guide (6) is linked to one of the extensions (8a) of the platform using a universal joint (12). A device as defined in claim 1, characterised in that the first cross-guide (5) is linked to the extensions (8a, 8b) of the platform using two universal joints (13a, 13b). A device as defined in claim 6, characterised in that the middle parallel line (7m) between the two pivot axes (7a, 7b) of the first cross-guide (5) has an intersection point (K) with the swivel axis (9a) of said first cross-guide (5) and where the intersection point K is located vertically above the axes of the wheels (3a, 3b) of the wheel pair. A device as defined in claim 1, characterised in that a flexing means (15) is comprised which forces the wheel pair to return from the tilt or which maintains it in a preferred neutral position. A device as defined in claim 1, characterised in that a tilt-steering wheel pair mechanism is mounted at one end of the device and a single wheel (16) is affixed at the other end of the device. A device as defined in claim 1, characterised in that the device has tilt-steering wheel pairs at both ends.

Inventors: GORISCH WOLFRAM, GORISCH, WOLFRAM
Applicants: GORISCH WOLFRAM, GORISCH, WOLFRAM
Application year: 2001
Main classification: A63C17
IPC codes: A63C17