Abstract:
The snow bicycle comprises a main frame similar to the one used on a conventional bicycle. It features a rear drive wheel assembly removably connected to the main frame. The rear drive wheel assembly comprises two longitudinally-oriented wheels operatively connected between a two-section frame. A track belt is winded around the two wheels and two parallel sets of rollers are provided on each side of the lower inner side of the free track belt to support the rear of the main frame when the bicycle is on the ground. This provides a versatile arrangement that suitably combines stability and the ability of to reach high speed on various types of grounds, particularly snow or ice.

Description:
BACKGROUND 
     It is well known that human powered wheeled vehicles, like bicycles, are very difficult to use on a loose or slippery ground as, for example, ground covered with snow or ice. Indeed, on such grounds, the driving wheel of conventional bicycles tends to skid. This considerably slows or possibly destabilises the cyclist and provokes a fall. 
     Some prior attempts were made to provide snow bicycles with a drive wheel assembly comprising a track. However, none successfully provides a versatile arrangement that suitably combines stability and the ability to reach high speed on various types of grounds, particularly snow or ice. 
     SUMMARY 
     It is the object of the present invention to provide a snow bicycle that satisfies the above-identified needs. To do so, the present invention provides a snow bicycle comprising: 
     a main frame having a front head tube and a rear chain stay, the rear chain stay comprising a left and a right pipe; 
     a front steerable supporting assembly operatively connected to the head tube to support the front of the frame when the bicycle is on the ground; 
     a pedal drive assembly operatively connected to the frame; 
     a rear drive wheel unit comprising: 
     a drive wheel frame having two parallel sections respectively aligned with the left and the right pipe of the chain stay, each section comprising an oblique member downwardly projecting towards the rear and a horizontal member having a rear end connected to a lower end of the corresponding oblique member; 
     a connecting means for removably connecting the drive wheel frame to the chain stay; 
     a first longitudinally-oriented wheel operatively connected between the two sections of the drive wheel frame; 
     a second longitudinally-oriented wheel operatively connected between the two sections of the drive wheel frame and longitudinally aligned with the first wheel, the front wheel and the second wheel having a substantially identical diameter; 
     a track belt having an inner side winded around the first and second wheel; and 
     two parallel sets of rollers, each set comprising a plurality of spaced-apart rollers operatively connected to and extending downwardly from a respective horizontal member, each roller being in engagement with the inner side of the track belt to support the rear of the frame when the bicycle is on the ground; and 
     a transmission mechanism to mechanically connect the pedal drive assembly to the second wheel. 
     A non restrictive description of a preferred embodiment will now be given with reference to the appended drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side elevational view showing the snow bicycle according to a possible embodiment of the present invention, showing an example of the bicycle with a ski assembly. 
     FIG. 2 is an enlarged side elevational view of the rear drive wheel unit of FIG. 1. 
     FIG. 3 is a cross-sectional view of the rear drive wheel unit taken along line III--III of FIG. 2. 
     FIG. 4 is a cross-sectional view of the rear drive wheel unit taken along line IV--IV of FIG. 2. 
     FIG. 5 is an enlarged view of the front steerable supporting assembly according to a preferred embodiment of the present invention, showing an example of the assembly with a single ice blade. 
     FIG. 6 is an enlarged view of the lower part of the front steerable supporting assembly according to a preferred embodiment of the present invention, showing an example of the assembly with opposite ice blades. 
     FIG. 7 is an enlarged view of the front steerable supporting assembly according to a preferred embodiment of the present invention, showing an example of the assembly with a wheel. 
    
    
     IDENTIFICATION OF THE COMPONENTS 
     The following is a list of the reference numerals, along with the names of the corresponding components, that are used in the appended drawings and in the description. 
     10 snow bicycle 
     12 main frame 
     14 down tube 
     16 seat tube 
     18 seat 
     20 front head tube 
     21 fork 
     22 handlebars 
     24 rear chain stay 
     30 side plates 
     32 lockable hinge (of the main frame) 
     34 pedal drive assembly 
     36 pedals 
     38 pivot (of the pedal drive assembly) 
     40 rear drive wheel unit 
     42 drive wheel frame 
     44 left section 
     46 right section 
     48 oblique member (of the left section) 
     50 oblique member (of the right section) 
     52 horizontal member (of the left section) 
     54 horizontal member (of the right section) 
     56 slots 
     58 fasteners 
     60 first wheel 
     62 pivot (of the first wheel) 
     64 second wheel 
     66 pivot (of the second wheel) 
     68 track belt 
     70 inner side (of the track belt) 
     72 outer side (of the track belt) 
     74 screw mechanism (of the track belt) 
     78 brackets (of the rollers) 
     80 pivots (of the rollers) 
     82 front rollers 
     84 intermediary rollers 
     86 rear rollers 
     88 hub 
     90 first sprocket gear(s) 
     92 second sprocket gear 
     94 third sprocket gear 
     96 fourth sprocket gear 
     98 first sprocket chain 
     100 second sprocket chain 
     102 front derailleur 
     104 lever (of the front derailleur) 
     105 cable 
     106 rear derailleur 
     108 V-shaped knife 
     110 pivot (of the knife) 
     112 ski 
     114 leaf spring 
     116 single ice blade 
     117 shock absorber 
     118 opposite ice blades 
     120 transverse bar (of the opposite ice blades) 
     122 steering system (of the opposite ice blades) 
     124 tie rods (of the opposite ice blades) 
     126 front wheel 
     128 rear attachment 
     130 steering tube 
     132 lower sleeve tube 
     134 fastener 
     136 releasable fastener 
     DESCRIPTION 
     FIG. 1 shows a snow bicycle (10) according to a possible embodiment of the present invention. The bicycle (10) comprises a main frame (12) which may be, as illustrated, substantially similar to a conventional bicycle frame. This main frame (12) comprises a down tube (14), a seat tube (16) for supporting a seat (18), a front head tube (20) , handlebars (22) and a rear chain stay (24). The rear chain stay (24) comprises a left and a right pipe extending towards the rear. The main frame (12) may also comprise a lockable hinge (32) located on the down tube (14) for collapsing the main frame (12). 
     The snow bicycle (10) is called as such because it is primarily designed for the winter season. However, it is possible to use the bicycle (10) during other seasons. For instance, it is possible to use the bicycle (10) on conventional dry pavement, mud or grass. It must be understood that the term &#34;snow&#34; should not be interpreted as being restrictive. 
     The front of the main frame (12) is supported by a front steerable supporting assembly that is operatively connected to the head tube (20). This assembly is actuated by the user through the handlebars (22). Depending on the nature of the ground on which the bicycle (10) will travel, it is possible to choose among a plurality of removable implements such as a ski assembly (FIG. 1), a single ice blade assembly (FIG. 5), a pair of opposite ice blades assembly (FIG. 6) and a wheel (FIG. 7). Those implements will be described later. 
     Since the bicycle (10) is human-powered, it comprises a pedal drive assembly (34) operatively connected to the main frame (12). The pedal drive assembly (34) comprises opposite pedals (36) that are operatively connected to a pivot (38) located in the lower side of the main frame (12). 
     The bicycle (10) further comprises a rear drive wheel unit (40) that is preferably removably connected to the main frame (12) for easing the storage or the transportation by hand. Alternatively, one can construct the bicycle (10) without making the rear drive wheel unit (40) removable. 
     The rear drive wheel unit (40) comprises a drive wheel frame (42) having two parallel sections (44,46) respectively aligned with the left and the right pipe of the chain stay (24). Each section (44,46) comprises an oblique member (48,50) downwardly projecting towards the rear and a substantially horizontal member (52,54). The rear end of each horizontal member (52,54) is connected to a lower end of the corresponding oblique member (48,50). Preferably, the left section (44) and the right section (46) are substantially symmetrical with reference to a vertical plane. 
     The drive wheel frame (42) is removably connected to the chain stay (24). One possible way is to provide a plurality of slots (56) and corresponding fasteners (58). It is then possible to connect the upper end of the oblique members (48,50) to the chain stay (24) and to connect the front end of the horizontal members (52,54) to vertical side plates (30) that are extending downwardly and rigidly connected to the left pipe (26) or the right pipe (28), respectively. 
     The drive wheel frame (42) further comprises a first longitudinally-oriented wheel (60) operatively connected between the two sections (44,46) by means of a pivot (62). Then, a second longitudinally-oriented wheel (64) is provided and is operatively connected between the two sections (44,46) by means of a pivot (66). The second wheel (64) is longitudinally aligned with the first wheel (60) and an endless track belt (68) is winded around them. The front wheel (60) and the second wheel (64) have a substantially identical diameter so that the path of the track belt (68) be as uniform as possible during the rotation thereof. The track belt (68) comprises a tread design on its outer side (72) to improve the traction. It may also comprise studs (not shown). The tension in the track belt (68) may be adjusted by a screw mechanism (74) that moves the second wheel (64) longitudinally. 
     Two parallel sets of rollers are provided to support the rear of the frame when the bicycle (10) is on the ground. Each set comprises a plurality of spaced-apart rollers (82,84,86) operatively connected to and extending downwardly from a respective horizontal member (52,54) by means of individual brackets (78) with corresponding pivots (80). Each roller (82,84,86) is in engagement with the inner side (70) of the track belt (68) and is significantly smaller than the first (60) and the second wheel (64). An example of a suitable type of roller (82,84,86) is a roller such as used on an in-line skate. 
     Preferably, each set of rollers comprises a front roller (82) juxtaposed to the first wheel (60), which means that the roller (82) is laterally offset with the first wheel (60) and that the bottom of the first wheel (60) and the bottom of the roller (82) are substantially side-by-side. This allows the weight to be divided between the front rollers (82) and the first wheel (60). Then, a rear roller (86) is juxtaposed to the second wheel (64) and at least one intermediary roller (84) is located between the corresponding front (82) and rear rollers (86) and substantially longitudinally aligned therewith. Two intermediary rollers (84) are provided on each set in the preferred embodiment shown in FIGS. 1 and 2. 
     A transmission mechanism is used to mechanically connect the pedal drive assembly (34) to the second wheel (64). Various arrangements are possible. Preferably, the transmission mechanism comprises a set of at least two first sprocket gears (90) rigidly connected to the pedal drive assembly (34). A hub (88), operatively connected between the upper end of the oblique members (48,50), is provided to bear a second (92) and a third sprocket gear (94). A first sprocket chain (98) has one end winded around one of the first gears (90) and another end winded around the second gear (92). A front derailleur (102) may be used to selectively align the first chain (98) with one of the first gears (90). The user controls the front derailleur (102) with a lever (104) and through a corresponding cable (105). A fourth sprocket gear (96) is rigidly connected to and coaxial with the second wheel (64). Then, a second sprocket chain (100) is winded around the third gear (94) and around the fourth gear (96) to complete the mechanical connection. 
     Preferably, a stretching means may be used for tensioning the first chain (98). This may be done by using a conventional rear derailleur (106) without the ability of shifting gears. A similar additional rear derailleur (107) may be provided for tensioning the second chain (100). 
     A guarding device may be provided to prevent snow or ice debris from accumulating in front of the second wheel (64) and the rear rollers (86). Preferably, the guarding device comprises an inverted V-shaped knife (108) operatively connected in front of the second wheel (64) between the horizontal members (52,54) by means of a pivot (110). The knife (108) pushes away snow or ice debris to help prevent a possible jam between the second wheel (64) and the track belt (68), or between the rear rollers (86) and the track belt (68). 
     As aforesaid, it is possible to choose among a plurality of removable implements such as a ski assembly, a single ice blade assembly, opposite ice blades assembly and a wheel (126). The ski assembly is shown in FIG. 1. It may comprise a ski (112) and a leaf spring (114) to absorb the shocks. 
     FIG. 5 shows an example of a single ice blade assembly to be used on an icy surface. The blade (116) is connected to the conventional fork (21) that is steerable using the handlebars (22). The fork (21) comprises an upper tube (130) that is inserted upwardly in the head tube (20) and connected to the handlebars (22) by a fastener (132). The blade assembly may comprise a front shock absorber (117) to damp the irregularities of the ground while riding thereon. The upper end of the shock absorber (117) is removably connected to the fork (21) by means of a cotter pin. 
     FIG. 6 shows another possibility for the front steerable supporting assembly. It consists of an opposite ice blades assembly that comprises a transverse static bar (120) connected to the main frame (12) and two opposite and parallel ice blades (118) operatively connected to a respective end of the bar (120). A steering system (122) is provided to steer the ice blades (118). This system (122) comprises tie rods (124) connected to the handlebars (22) by means of the steering tube (130) inserted and pivoting in the head tube (20). The bar (120) is connected to the main frame (12) by a lower sleeve tube (132) connected to the lower part of the head tube (20) by a fastener (134), such as a cotter pin. The upper end of the steering tube (130) is connected to the handlebars (22) by means of a releasable fastener (136). 
     FIG. 7 shows a front wheel (126) operatively connected to the fork (21). This wheel (126) may always be transported on the bicycle (10) by connecting it to the main frame (12) using an appropriate rear attachment (128), as shown in FIG. 1. This may be very useful in case the ice or snow surface is discontinued. One may also use the wheel (126) permanently if desired. 
     Although a preferred embodiment of the invention has been described in detail herein and illustrated in the accompanying drawings, it is to be understood that the invention is not limited to this precise embodiment and that various changes and modifications may be effected therein without departing from the scope or spirit of the present invention.