Method of manufacturing a self-propelled physical skateboard

Abstract: A footboard of a skateboard is with respect to a respective reference plane which at riding straight (= x plane) is parallel to the riding path (= the ground), and at turning (= x '' plane) is with respect to the direction of riding slanted to one or the other side, is rhythmically swung around a longitudinal axis ( O ) of swinging lying in suspensions (4, 5) of the skateboard. The amplitude ( A ) and the frequency of swinging are mutually coordinated in a manner that swinging does not result in such meandering of the skateboard, which was felt inconvenient. To a socket shaft housing (8) of a suspension (4, 5) of the skateboard, said housing encasing a roller shaft (11), there is to each end thereof attached a gearing (9, 10), the gearings designed mirror-symmetrically. The gearing (9, 10) is composed of an essentially three-part housing assembly, which comprises a mounting casing (13), an upright intermediate wall (16) and a mounting cover (17), as well as of a train-type gearing composed of a toothed rack (19) as a driving constituent and a gear (25) bound to the roller shaft (11), as a driven constituent. In addition to the roller shaft (11) which passes through, two further, inner shafts (14, 15) constitute said gearing, the lastmentioned shafts each supporting two gears (20, 21; 23, 24), the first one (20) thereof mating the toothed rack (19) and the last one (24) mating the gear (25) driven. The second one (21) of the gears is indirectly connected to the respective shaft (14) by means of an overrunning clutch (22), and shaft (14) is by means of a suitably pre-stressed helical torsion-spring (28), which encompasses the shaft (14), rotationally-elastically bound to the stationary mounting casing (13) of the gearing.

Description: The present invention belongs to the field of sports/games/recreation, and relates to skateboards, particularly the ones which provide special, integrated measures for physically driving the skateboard. ( Int . Cl . 4 : A 63 C 17/12, B 62 M 1/08) In a primary configuration of a skateboard the latter comprises an elongated, suitably designed footboard from which two pairs of rollers are suspended. Optionally, a skateboard can further comprise supplementary equipment, e.g. a brake, a flywheel, a lamp, a marker a buffer, etc. Normally, in the course of skateboarding, curving is made possible with the footboard of the skateboard parallel to the skateboarding path at riding straight, the footboard slanted to either side with respect to its longitudinal axis. This action can be realized by means of specific suspension of the rollers, and at performing a curve the inclination of the footboard results in that a front and a rear roller, the "inner" rollers with respect to the curve, are mutually approached, whereas the other two rollers, the "outer" ones with respect to the curve, are mutually drawn apart. It is obvious that here proper propelling of the skateboard is performed by the rider's pushing off the ground (and/or by riding downhill) so that a skateboard/rider-system as a physical phenomenon, i.e. at skateboard and rider functionally united into a combined, independent unit, can be discussed merely within the period of the consumption of mass forces previously accumulated (or - in the case of riding downhill: by using the gravity force). Known are attempts to assign to a skateboard/rider-system the character of a physical phenomenon without using gravity force or a special source of energy, respectively, i.e. solely on the basis of physical engagement of the rider. From US patent specification 4,915,403 to Wild et al. a "skateboard with mechanical drive" is known, whose footboard is in the area of the middle of the longitudinal extension of the footboard transversely divided to a front, fixed section, and a rear, pedal section. Said, footboard sections are interconnected by a skateboard frame. Hereby, the pedal section is by means of linkages comprising a push rod, a crankshaft and a toothed segment, as well as by means of a gear train bound to said toothed segment and comprising four pairs of toothed wheels and a termination toothed wheel, which is bound to a roller shaft of the rear skateboard rollers, motion-transferably interconnected with respective skateboard rollers, each of the latter being connected to the shaft by means of an overrunning clutch. From US 1,784,761 to J.T. Smith and DE 33 15 856 A1 to R. Brzoska two basically the same inventions of a roller skate with mechanical drive are known. The footboard is interconnected in the front wheel range by a bearing, which enables the footboard to turn with the centre in the said bearing. The rear part of the footboard comprises a rachet bar, which transfers an up-down movement of the footboard to a gear, placed between the wheels and transforming this longitudinal movement to the rotation of said wheels. From DE 193653 to H. Stephan another type of a roller skate with mechanical drive is known. Both wheel pairs are driven by gears, which are by toothed segments connected to the footboard, which is swung by foot downwards alternatively in the front and rear part, while it is mounted on a frame by a bearing in its middle part. According to the above references (US 4, 915, 403), the skateboard essentially provides the same height as the skateboards without propelling gearings, and there are aimed to be retained diverse operational possibilities, such as ease in negotiating curves and maneuverability. However, with the antecedent solution, the height of the skateboard can only be a matter of discussion in connection with the front, i.e. fixed, footboard section of the skateboard, not in connection with the rear, i.e. pedal section, except at a position when its pedal function is arrested which, however, is not in conformity with the primary aim or object of the solution. Analogously, regarding the "diverse possibilities" there has to be noted the following: The curves can easily be negotiated and the skateboard easily handled under the condition only that the pedal function is arrested, i.e. both footboard sections straightened (= coplanar). In the state when the skateboard is physically pushed, merely the rider's foot resting on the front footboard section of the skateboard is left to accomplish normal riding ("normal" - possibilities offered by the skateboards without propelling gears). Thus, the maneuverability is obviously and considerably affected. So, e.g., the possibility of making jumps, when the pedal section is lifted, is totally excluded. With the antecedent solution the length of the footboard of the skateboard is limited down to a size of at least (= not less than) two feet. Besides, there is imminent the danger of toppling on one or the other side with respect to the direction of riding as well as backwards over the rear rollers (as a consequence of the circumstance that propelling as such tends to jerk the skateboard from under the rider's feet). From the functional point of view the known solution show a further disadvantage, which cannot be neglected, namely the driving torsional moment is enforced intermittently: a driving phase is followed by an idle one, the latter is followed by a driving phase, etc. Further there is known a skateboard according to FR 2 666 780 to Mariet. This skateboard is powered by pushing directly with one foot off the ground. It is characterized by a tilting footboard along its longitudinal axis to steer the skateboard, while the footboard is connected by steering rods to a pair of wheels, which are swung around the vertical axis according to the angle of the tilted footboard, which corresponds to a negotiating curve. However, this construction makes it impossible to arrange on a skateboard any propelling gear powered by a person directly by tilting the footboard along its longitudinal axes. It is now an object of the invention to overcome the disadvantages set forth above, and to provide a skateboard which can physically be driven by means of movements proper to a rider used to apply skateboards without driving gears. Considering the circumstance that for negotiating curves, a footboard of a skateboard is tiltable within limits, whose extreme values are defined by constructional measures, and that reasonably rapid swinging of the footboard, limited to a correspondingly small angle, with respect to a given plane which is horizontal at straight riding and is at negotiating a curve tilted to the direction of the geometrical center of the curve, practically generates no perceivable meandering of the skateboard, the invention is based on the problem how to convert said swinging of the footboard to propelling of the rollers of a skateboard. According to the invention this is achieved by claim 1. Advantageously the gearboxes belonging to the front and/or rear roller shaft are designed mirror-symmetrically with respect to the longitudinal upright plane placed through the suspensions. Preferably said skateboard is characterized in that the gearbox is composed of: a mounting casing attached to the shaft housing which in the direction towards the respective roller is closed by an upright wall to which is connected a mounting cover bearings both in the mounting casing and the mounting cover being foreseen for journalling the roller shaft and gear shafts, a vertical toothed rack guided by a guide, the latter being a constituent of the intermediary wall, the rack extending through a recess of the ceiling wall of the mounting cover up to the footboard, a pinion mating the toothed rack as well as pairs of gears which constitute a trainkind interconnection of the toothed rack and the roller shaft, the last one of the gears mentioned being arranged on the roller shaft, and a suitably pre-stressed retracting helical torsion-spring interconnecting the shaft of the pinion and the mounting casing in a manner such that on lowering the toothed rack the spring is tightened, the gear next to the spring being indirectly connected by means of the overrunning clutch to the shaft which is common to the spring and the gear. The preferred exemplary embodiment of the invention will hereinafter be described in conjunction with the appending drawing, wherein like designations denote like elements, and: Fig. 1 is a schematic, pictorial representation of a skateboard provided in accordance to the invention, with the footboard of the skateboard prevailingly broken to expose the substructure of the skateboard, Fig. 2 is a side-view of a skateboard of Fig. 1, with the left end section of the skateboard (i.e. the front end section of the skateboard) represented as a vertical sectional elevation of a gearbox, Fig. 3 is the view of a skateboard of Fig. 2 from the left (i.e. the front view), with the section relating to the front right roller represented as a vertical sectional elevation which corresponds to line III-III of Fig. 2, and shows a corresponding toothed rack not covered by said sectional plane (one of axles and accompanying two gears omitted to improve the clearness of the drawing), Fig. 4 is a sectional elevation corresponding to line IV-IV of Fig. 3, Fig. 5 is a schematic, pictorial representation of a couple of gearboxes (without respective toothed racks) belonging to an axle (front or rear) of the skateboard, Fig. 6 is a schematic, pictorial representation of the gearbox, the right one with respect to the riding direction, partly taken apart, Fig. 7 is a schematic front view (or rear view - it makes no difference) of the skateboard, whose footboard is at negotiating a curve extremely tilted, there being shown the geometry of swinging, and Fig. 8 is a view analogous to Fig 7, yet showing the contrary tilting of the footboard. The skateboard comprises a footboard 1 which is composed and designed in accordance with the respective object and on whose lower side a front substructure assembly 2 and a rear substructure assembly 3 are suspended at the front and the rear end sections, respectively. The connection of the footboard 1 and the substructure assemblies 2, 3 is a direct one, similar to that at the skateboards without incorporated driving gearboxes. The substructure assembly 2, 3 is designed by a two-column suspension 4 (front); suspension 5 (rear) which, as such, belongs to the prior art. The two suspensions 4, 5 constructionally equal each other, yet are arranged in known manner mirror-symmetrically with respect to a vertical central plane positioned transversely to the direction of the movement of the skateboard. When observing the representation of Fig. 1, the constructional feature just mentioned appears such that of the two-column suspension 4 of the front substructure assembly 2 a rigid, internally rotatable and breakable column 6, and of the two-column suspension 5 of the rear substructure assembly 3, respectively, an elastically flexible column 7 is visible. The columns 6,7 of either suspension 4, 5 are arranged in a V -relation in the central longitudinal vertical plane of the skateboard, which feature in the combination with other features of the suspensions 4, 5 makes it possible that at tilting of the footboard 1 to the left or to the right, respectively, with regard to the direction of riding the skateboard, the front substructure assembly 2 and the rear substructure assembly 3 are definitely swung in opposite directions - each assembly around its own vertical axis, which coincides with the axis of the rigid column 6, which shiftings in functional meaning result in turning of the skateboard. Except in view of the mentioned feature that the suspensions 4, 5 are arranged mirror-symmetrically, the front substructure assembly 2 and the rear substructure assembly 3 being constructionally equal each other. In order to simplify the description of the skateboard, merely the front substructure assembly 2 and the front suspension 4 will hereinafter be referred to, but including the rear substructure assembly 3 and the rear suspension 5. According to the invention to each side (= end) of a shaft housing 8, the latter arranged crosswisely to the columns 6, 7 at the root section of the V -arrangement of said columns of the suspension 4, there are attached gearboxes 9, 10, said gearboxes being preferably designed so as to create mutual mirror-symmetry with respect to the intermediate vertical longitudinal plane of the skateboard. A roller shaft 11, bearing at its free end sections skateboard rollers 12, is inserted through the shaft housing 8 and the gearboxes 9, 10. For the solution of the problem of the invention it is really indispensable to foresee a couple of gearboxes 9, 10 for each shaft 11. In principle, the installation of gearboxes at both shafts, i.e. at the front and at the rear roller shaft, is optional, but the tests performed as well as diverse practical aspects (which will be discussed in more detail later) lead to the conclusion that it is convenient to foresee two couples of gearboxes as represented in Fig. 1. Possible initial doubts to the effect that the gearboxes in the arrangement mentioned might result in an aimless constructional jamming of the skateboard, disappear at becoming aware of the circumstance that according to the invention the suspensions which, as generally known, are "critical" (and therefore expensive) components of skateboards, need not be divided to front/rear and left/right ones, respectively, as this is the case in the prior art analyzed. The gearbox 9 according to the invention is composed of a box-shaped mounting casing 13 which is attached to the free end of the shaft housing 8 and in which, beside the roller shaft 11, a shaft 14 for carrying gears, conveniently disposed above the roller shaft 11, and an intermediate shaft 15 also for carrying gears, disposed vertically between the shafts 11 and 14, but shifted rearwards with respect to the direction of riding the skateboard, are mounted. On the side oriented to the roller 12 of the skateboard, the mounting casing 13 is closed by a vertical adapted wall 16 (cf. Fig. 6). Finally attached to the latter, is a mounting cover 17, which provides another series of bearings for pivoting the shafts 11, 14, 15. In the ceiling part of the wall of the mounting cover 17 there directly at the wall 16 foreseen a recess 18 for conveying a toothed rack 19 as explained below, is foreseen. The shaft 14 supports a pinion 20 which is directly bound to the former and is foreseen to co-operate with the toothed rack 19, as well as a further gear 21, which by means of an overrunning clutch 22 (= a grip roller and expanding friction clutch) is connected to the shaft 14. Hereby, the pinion 20 resides inside the mounting cover 17 and projects into an appropriate circular recess 26 of the wall 16, whereas the gear 21 accompanied with its overrunning clutch 22 resides inside the mounting casing 13 and is arranged at an axial distance from the journal of the shaft 14. The intermediate shaft 15 supports a gear 23 designed to mate the gear 21, whose diameter is greater than that of the former one, and on the side oriented to the vertical wall part of the mounting casing 13, supports a further, larger gear 24. The two gears 23, 24 are directly connected to the intermediate shaft 15. The roller shaft 11 supports a gear 25, driven and designed to mate the gear 24, whose diameter is larger than that of the former one. The interconnection of the gear 25 and the shaft 11 is a direct one as well. Naturally, analogously to the recess 26, in the wall 16 there also are foreseen adapted recesses to convey shafts 11, 15. Besides, the wall 16 provides an upright trough-shaped guide 27 (Fig. 6) for the accommodation and guiding of the upright toothed rack 19, the inner cross-section of the guide 27 coinciding with the recess 18. On the shaft 14 in the axial interspace between the gear 21 and its overrunning clutch 22, respectively, and the bearing of the shaft 14 is arranged a suitably prestressed helical torsion-spring 28, whose one end is formed like a hinge and by means of tangential approaching to the surface mantle of the shaft 14 is connected to the latter, and whose other end is designed like a special hook and thereby connected to the mounting casing 13. Hereby, the windings of the spring 28 pass in a manner that they are tightened when the toothed rack 19 is moved down, i.e. they accumulate potential energy necessary for returning (lifting) the toothed rack 19. It is clearly evident from Fig. 5 that in the case of existence of two gearboxes 9, 10 bound to a respective roller shaft 11, one of the two springs 28 is coiled right-hand and the other one is coiled left-hand. An embodiment of a left-hand coiled helical torsion spring 28 is pictorially represented in Fig. 6. The gearbox is designed on the principle that one stroke of the toothed rack 19 results in one revolution of the shaft 14. Naturally, at a complete revolution of the shaft 14 the windings of the spring 28 do not thoroughly clamp the mantle surface of the latter, and the ability of spring force accumulation of the spring is thereby not thoroughly exhausted. The interconnection of the shaft 11 and the roller 12 is taken from prior art and designed by providing a roller bearing 29 (Fig. 3) and an overrunning clutch 30. In a preferred embodiment of the invention there with respect to the overrunning clutch 30 belonging to the roller 12, as well as with respect to the overrunning clutch 22 belonging to the gear 21, among known overrunning clutches chosen, the one designed on two mutually movable rings is inserted one into another and each of them carries an appropriate series of roller needles, whereby the inclination sections are foreseen in the outer ring. The two overrunning clutches 22 of rollers 12 bound to a common shaft 11 thus work in the same direction of rotation. Figs. 1 through 6 of the drawing represent a state of a skateboard which is neutral with respect to the footboard 1 and is balanced with respect to the spring 28. The four toothed racks 19 are forced upwards to the footboard 1 under the influence of the returning forces of the springs 28. Contrary to the above mentioned state, Fig. 7 schematically represents a state of a skateboard, which corresponds to a footboard 1 tilted to one of two limiting positions by force, Fig. 8 representing a state corresponding to tilting thereof into another limiting position. The two springs 28 referring to the toothed racks 19, which are pushed down by the footboard 1, are then tightened (stressed), the other ones are then slack (loose). Evidently, at riding, the states of Figs. 7-8 mean negotiation of curves by the skateboard to one or the other direction. Fig. 7 comprises three plane coordinate systems bound to the swinging axis O of the footboard 1. The x-y system denotes the position of the footboard 1 when riding straight, the x'-y' system denoting the position thereof at extreme turning to one direction (an analogous position as to extreme turning to the other direction being represented in Fig. 8), and the x''-y'' system denoting an optional intermediary position of turning the skateboard, i.e. slight turning. Arched arrows A added to the ordinate planes y, y', y'' in Fig. 7 indicate the possibility of performing the swinging of the footboard with respect to the respective ordinate planes in the course of riding on a skateboard, with the amplitude of swinging each reasonably measured off. In principle or advantageously, respectively, it is foreseen that in the case of all arrows A, essentially the same angle of swinging is applied although the choice of the extent of swinging as such is within the individual discretion or the user's mastering of the rolling technique, and said extent both depends on the embodiment and riding features, respectively, and is constructionally limited to one or the other side merely by the extremely possible tilting position here indicated by the x'-y' system. The swinging of the footboard 1 as explained above is in accordance with the fundamental conception of the invention, as defined in the introduction, exploited in the range of angles indicated by the arcuate arrows A for generating the propelling of skateboard. Namely, the experiments have shown that swinging generated by a reasonably high frequency and reasonably small amplitude with respect to an optionally chosen plane y, y'', naturally without exceeding the limit plane y', does not result in a risky uneven riding of the skateboard (in fact, swinging essentially means creating miniature curves, i.e. meandering), it, however, can be exploited as an appropriate basis for generating an appropriate propelling moment of rotation. The circumstance that the gearbox 9 is unavoidably embodied as a "light" one, is actually an obvious accompanying feature of the concept as set forth above. Having provided both roller shafts 11 with gearboxes 9, which means that the driving load is every time divided to two gearboxes 9, the skateboard as a whole meets the requirements regarding solidity, typical for articles of this type. By the skateboard according to the invention possibilities are given to start riding either by pushing off the ground (similarly to skateboards without a driving mechanism) or by treading on the footboard and starting swinging of the footboard of the skateboard. When pushing the toothed rack 19 of the gearbox 9 downwards, the shaft 14 rotates; the overrunning clutch 22 is engaged and hence the gear 21 rotates as well. The rotation of the shaft 14 is followed by tightening of the spring 28. From the gear 21 the rotational moment is conveyed to the gear 23, by means of the latter it is conveyed to the gear 15 and hence to the gear 24, which gears are thus turned dextrorotatorily. From the gear 24 the rotational moment is conveyed to the gear 25 now driven, and by means of the latter conveyed to the roller shaft 11. Evidently, the gear 25 and the shaft 11 obtain levorotation; the overrunning clutch 30 of the roller 12 is engaged. It is a result of the transmission disclosed that a stroke of the toothed rack 19 is converted into propelling rotation of the roller 12. At realizing the above disclosed working stroke of the toothed rack 19 of the gearbox 9, the toothed rack of the gearbox 10 belonging to the same roller shaft 11 follows the lifting of the footboard of the skateboard under the influence of the force of unwinding the respective spring. Hereby, the connection of the shaft 14 and the gear 21 of the gearbox 10 is broken by means of the overrunning clutch. At turning, particularly at sharp turning, the difference between the number of revolutions of the outer rollers and the inner rollers 12 cannot be neglected, in principle. There is not excluded the possibility that in the case of realizing the above disclosed swinging, also in the course of turning of the skateboard the drive actively influences merely the inner roller 12, which rotates slower, i.e. the number of revolutions of the outer roller might exceed the one really attained by the gearbox. In this case the overrunning clutch 30 of the outer roller enables free rotation of the latter. Naturally, the overrunning clutches 30 are also necessary for riding a skateboard backwards, in that case without engaging the gearboxes. From the above elucidations it follows that with respect to the lower side of the footboard 1 the tip portion of each toothed rack 19 performs a motion (Fig. 8) composed of a straight, radial component R created by tilting the footboard 1 as such, i.e. swinging the footboard 1 around the longitudinal axis O, and also composed of a circular component C created at swinging the substructure assembly 2, 3 to perform turning, i.e. at swinging around the vertical main axis of the suspension 4, 5. In order to avoid the risk of possible non-reversibility of the footboard 1 and the toothed rack 19, there is at the top of each toothed rack 19 foreseen a ball bearing 31, known per se, not represented in the drawing.

Claims: A skateboard comprising a footboard (1) having on its lower side a front and rear substructure assembly (2,3) suspended by suspensions (4,5) from front and rear sections of the footboard, respectively, the suspensions comprising socket shaft housings (8), the skateboard further comprising rollers indirectly connected to a roller shaft by means of an overrunning clutch, the roller shafts being encased by said socket shaft housings and each clutch being part of a gearbox (9,10), at least one of said socket shaft housings having a gearbox (9, 10) attached at each end. Skateboard according to claim 1, characterized in that the gearboxes (9, 10) belonging to the front and-or rear roller shaft (11) are designed mirror-symmetrically with respect to the longitudinal upright plane placed through the suspensions (4, 5). Skateboard according to claim 2, characterized in that each gearbox (9, 10) is composed of: a mounting casing (13) attached to the shaft housing (8), which in the direction towards the respective roller (12) is closed by an upright wall (16), to which is connected a mounting cover (17), bearings both in the mounting casing (13) and the mounting cover (17) being foreseen for journalling the roller shaft (11) and gear shafts (14, 15), a vertical toothed rack (19) guided by a guide (27), the latter being a constituent of the intermediary wall (16), the rack (19) extending through a recess (18) of the ceiling wall of the mounting cover (17) up to the footboard (1), a pinion (20) mating the toothed rack (19) as well as pairs of gears (21, 23; 24, 25) which constitute a train-kind interconnection of the toothed rack (19) and the roller shaft (11), the last one (25) of the gears mentioned being arranged on the roller shaft (11), and a suitably pre-stressed retracting helical torsion-spring (28) interconnecting the shaft (14) of the pinion and the mounting casing (13) in a manner such that on lowering the toothed rack (19) the spring (28) is tightened, the gear (21) next to the spring (28) being indirectly connected by means of the overrunning clutch (22) to the shaft (14) which is common to the spring and the gear. Skateboard according to one of the preceding claims characterized in that each suspension (4, 5) has two columns, one rigid (6) and the other elastically flexible (7) which columns of either suspension are arranged in a V -relation in the central longitudinal vertical plane of the skateboard.

Inventors: SOBOCAN BORIS, SOBOCAN, BORIS
Applicants: SOBOCAN BORIS, SOBOCAN, BORIS
Application year: 1992
Main classification: A63C17
IPC codes: B62M1, A63C17