SurfSliding method and apparatus for surfing on artificial surfaces

Abstract: A new sport of skill, SurfSliding having an open pipe ramp system covered in artificial turf (14) and a lubricating means. SurfSliding allows a participant to glide downhill by gravity and kinetic energy while maneuvering a lawnboard strapped to the participants feet. The new sport provides for a sport similar to surfing while executing movements similar to skateboarding and snowboarding.

Description: Field of the Invention This invention relates to surfing, specifically to "SurfSliding", a new sport of skill which consists of controlled movements on a short "LawnBoard" strapped to the feet of the surfer who glides downhill by gravity and kinetic energy over a slope covered with artificial turf and lubricated by water. Background - Description of the Prior Art Surfing on waves and skateboarding on land or ramps have been sporting attractions to many people for quite some time. Snowboarding has become a very popular winter sport in mountain areas. Water slide parks are abundant in many areas. Such sports attractions are usually confined to certain geographical locations such as surfing to areas with oceans or lakes with waves, and snowboarding to areas with mountains, snow and cold seasons. The prior art most comparable to the concept of SurfSliding is described in US-A-4 339 122, which discloses an aquatic amusement apparatus comprising "a shaped slope having a plurality of stationary wave-like contours and surface irregularities". The substrate is foam and the covering is vinyl. Technically speaking, water slides are the closest known type of art. They are usually elongated tubes or troughs following a predetermined circuitous path downward from an elevated starting platform. A typical apparatus of this type is described in US-A-4 194 733. A slide apparatus which has a generally parabolic upwardly opening cross section is defined in US-A-5 137 497. Another water slide described in US-A-5 011 134 discloses a water slide apparatus which allows for up-hill movement by the inclusion of a drainage tube. This patent introduces a variation of existing water slides, but it still is characterized by "a trough or chute where adequate water is retained to allow the ride to skim the surface". The user is confined to a narrow predetermined path with little or no control over his speed. Water slides in general need substantial amounts of water, and this particular slide needs to inject and evacuate water from certain points along the trough in order for it to work. GB-A-1 418 668 describes an artificial sleigh run "comprising a substantially U-section track member formed from a synthetic material ... [It] comprises a plurality of interconnected substantially U-section track members molded from glass fiber reinforced plastic material.... The sleighs are constructed in the conventional manner with the exception that the metal runners are replaced by plastic material runners or brushes. Alternatively the metal runners are replaced by roller bearings or ball bearings ...". Again, the apparently narrow U-section confines the rider to a predetermined path unsuitable to develop competitive riding skills. US-A-2 254 482 discloses an artificial skiing track designed to be used without water as the prior art references to this point were unsuccessful in using artificial snow. A means is disclosed to exercise skiing in the off-season on an artificial track, and it is not the same technique or disclosure for surf-like or snowboard-like exercise in the off-season. A different kind of artificial ski slope is described in EP-A-0 303 958, which proposes "a ski slope made of a carpet of upward pointing plastic needles for the purpose of learning to ski". To obtain on his artificial ski slope "friction conditions comparable to those on snow", he applies "a lubricant essentially consisting of water in the form of fog dispensed from spray nozzles". The nozzles are arranged below the ski slope surface and blow their droplets through surface openings in such a way that the fog is only knee deep. In conclusion, all downhill sports utilize the same physical phenomena: 1) that a slope offers downhill force which, under proper conditions, can be translated into downhill motion; 2) that such motion results when the downward force exceeds the friction between the moving body and the substrate and therefore attains a desirable speed, and for this to occur, the friction must be kept low; 3) that the combination of high speed and low friction allows to build up kinetic energy which, in turn, enables the user to move uphill until such energy is expended. These are basic principles of physics and not patentable phenomena. The patentable differences are represented by the means employed to keep the friction low and constant, the vehicle design, the choice of available path, and the degree in variation of the rides and the attainable levels of skill. By contrast to the prior art, the SurfSliding ramps employ engineering techniques that are designed for low and constant friction allowing for active motion with a continued pursuit and challenge for increasing the level of skill towards daring acrobatic movement and trickery while standing erect. Additionally, more than one user can be on the ramp system at the same time. General Description of the Invention The present invention is a "Surf Slide" that is to provide for a new sport of skill during an extended season. The "SurfSlide Sport" contains the following elements: Starting: The Takeoff! To start a ride, the rider must commit to a given movement. To do so, he must lean forward into the slope to attain speed. Simultaneously, he must choose a path on which to ride. This is called choosing or picking a line. First Turn The rider must lean his body weight to the desired side. This weight translation forces the board's surface to focus on one rail and the center fin. This focused rail becomes the inside rail (the opposing rail is considered the outside rail). Control and movement is achieved by one's command of body position. Subsequent Turns A ride is composed of continuous balancing and weight shifting. A turn is the result of weighting and un-weighting while the rider shifts the board position from rail to rail. By using body torque, the rider's footwork controls the board's positioning as it passes over a given surface. This active control of turns makes the ride. Trickery The power of gravity, the flow of water, and the skill of riders provide for many exciting maneuvers. LawnBoards have foot straps allowing riders to make many such maneuvers, including aerial acrobatics. The continuous advance of maneuvers will drive the technology of the sport. The invention facilitates this new sport of downhill surfing on a water lubricated artificial surface suitable for water-oriented theme parks, additions to ski resorts, or stand alone sporting facilities. The new apparatus is made from commercially available materials, components, and manufacturing processes. The apparatus can be built as an above-ground structure, an in-ground structure, or a combination of the two. The "above-ground apparatus" is a ramp system consisting of large open pipes constructed from high strength / low weight materials cradled in a support structure. The interior surfaces of the open pipes are lined with an artificial surface material similar to those used on golf courses. A gutter system on both sides of the pipes along the rims provides a thin sheet of water or other lubricant to continuously run down over the surface material. In many soil conditions, "in-ground slides" offer advantages. The open pipe is scooped out from the soil, and the planking is replaced by gunited concrete, or sprayed fiber glass walls. The removed soil can be used for landscaping around the SurfSlides. The water collection channel runs at the bottom of the open pipe and is covered with the same grating as in the above-ground structure. The gutter system is built into a pre-cast concrete channel and hidden by a concrete cover. The cover also serves as a safety walkway. It is easy to open for service and adjustment of the gutter system. The advantages of the in-ground slides are: Better fit of the SurfSlides into the landscape, aesthetically more appealing; Rounded turns instead of discrete angles; Great flexibility for varying dimensions and shape of open pipe cross sections; Reduced danger when surfers perform acrobatics above the "gunwales"; Elimination of weight constraints; Lower costs in favorable soil conditions. The lubricant has several functions: 1) it reduces friction for the passing LawnBoard; 2) it acts as a coolant for the LawnBoard; 3) it acts as a shock absorber for the surfer when he falls; and 4) the water reduces the risk of friction burns when the surfer falls and slides on the material. Thus, the sheet of water plus the water retained in the fibers of the turf material provide for an ample supply of water for the smooth gliding of the passing LawnBoard, resulting in a hydroplaning experience like that of skim boarding. At the bottom of the open pipes are gratings of adequate width to allow the water to seep away and run into a collection channel underneath. Depending on the water availability, the water may either run off in a creek or be recycled by means of a pump/filter system. Each installation requires a site-specific water supply and re-circulation solution using commercially available components. In Summary, the invention has the following advantages and objectives deriving from the features of claim 1: a) A new sport similar to surfing and snow boarding; b) Varying slopes and curves for all skill levels, from beginners to experts; c) Suitable for large numbers of surfers; d) Enables ski resorts to utilize large portions of their investment (access roads, ski lifts, lodges, stores) in their off-seasons; and e) Can be installed as a stand-alone or as part of a theme park in areas where there are no oceans, lakes, or mountains, thus bringing the surfing experience to new area. Summary Description of Drawing Figures In the drawings, closely related figures have the same number but different alphabetic suffixes. ELEMENTS OF THE SURFSLIDE SPORT Fig. 1a: shows the SurfSlide trails from beginner to expert slope, all adapted to the natural terrain of a given hill side. Fig. 1b: shows the stand-up version of a lawn board Fig. 1c: shows a cross-sectional support, consisting of two identical side mounts and a center assembly. THE SURFSLIDE APPARATUS The support structure, usually made from steel or fiberglass, is so large that it takes several levels of magnification to show its make-up. Fig. 2a: shows a side view of the Surf Slide with planking, support structure and slope changes, adapting to the given terrain. Fig. 2b: shows details of a concrete footing. Fig. 2c: shows light-weight hollow core pultrusions with a removable attachment and artificial turf. IN-GROUND SURFSLIDE Fig. 3a: shows the cross section of an in-ground SurfSlide. Fig. 3b: shows a section of the gutter system. LIST OF REFERENCE NUMERALS 14 Artificial Turf 18 Board 20 Center Section Assembly 22 Chair Lifts 24 Clamp 26 Concave Fins 28 Concrete Channel 30 Concrete Footing 36 Control Valve 38 Coping 40 Cover 42 Extension for Fast Turns 44 Flexible Pipe 46 Foot Straps 48 Grating 50 Gunite or Shot-Crete 52 Gutter or Sprinkler 58 Knock-through 60 Lock Strip (Coping) 62 Original Contour 64 Planking (Pultrusions) 68 Railing 70 Removable Attachment 72 Rolled Profile, Steel 74 Room for Utility Conduits 76 Safety Walkway 78 Seal 80 Shim Adjustment 82 Side Trellis 84 Slope Decrease 86 Slope Increase 88 Soil, Gravel 90 Steel Shoe 92 Stiffening Steel Sheet 94 Support Plate 96 Surf Slide 98 Surfer, 6 Foot tall, to scale 104 Trellis Support Structure 106 Water Collection Channel 110 Water Exit Slot 112 Water Return Pipe 114 Water Supply Main Detailed Description of Drawing Figures ELEMENTS OF THE SURFSLIDE SPORT Fig. 1a renders a view of a complete SurfSlide park with SurfSlides (96) of different slopes for different skill levels. The SurfSlides and the chairlift installations (22) follow the natural terrain to minimize the environmental impact. Fig. 1b shows a short light-weight board (18) with concave fins (26) for directional control and with foot straps (46). Fig. 1c illustrates the open pipe - a typical embodiment of the invention - which is constructed of planking (64), supported by a trellis support structure (104) which rests on concrete footings (30). For reason of transport, the pipe support consists of a center section assembly (20) and two side sections (82) which are bolted together. The open pipe can be formed from any material that lends itself to form large sections such as sheet metal, planking, or preformed fiberglass sections. In this example, the open pipes are built from hollow core fiberglass pultrusions (64) which offer high strength at low weight and are highly weather resistant; they are easy to transport, to handle and to cut to size on site. Pultrusion planking (64) offers smooth surfaces suitable for adhesive bonding to the rolled steel L-profile (72) and for the removable attachment of the artificial turf (14) with an adhesive or hook & loop tapes. The cut-outs in the stiffening steel sheet (92) serve for stress relief. They provide room for utility conduits (74) such as the water collection channel (106), the water supply main (114), the water return pipes (112) and others. A fast action vertical extension (42) for the outside of turns can be added to the trellis support structure (104). This extension allows for gravity defying maneuvers as well as keeping the riders in the SurfSlide. In all places without such extension, a protruding coping (38) is installed along the upper rim of the SurfSlide to ensure that anyone surfing beyond the upper rim will fall back into the open pipe. Just below the coping (respectively below the extension) is the gutter (52) located to dispense the water or other lubricant. On the bottom, the water escapes through a grating (48) into the water collection channel (106). To allow for easy service of the artificial turf (14) and for rescue in the event of an accident, a safety walkway (76) is provided on top of the trellis support structure (104), secured by a railing (68). The relation of a 1,8 m (6 foot) tall Surfer (98) and a 9 m (30 foot) diameter open pipe is sketched to scale. THE AERIAL SURFSLIDE Fig. 2a shows a side view of the planked above-ground SurfSlide system (64). The exterior of the open pipe is supported by the trellis structure (104) and mounted on concrete footings (30) with steel shoes (90) comparable to bridge constructions. The slope increases (86) and decreases (84) are mitered between the abutting straight sections. Fig. 2b shows details of a concrete footing (30). The trellis structure (104) rests with a steel shoe (90) on a support plate (94). The space between the two screws has to be calculated to accommodate thermal expansions and contractions. To level out in-accuracies of the footing or to compensate for settlement of the soil, the position of the support plate can be corrected with one or more shim adjustments (80). Fig. 2c illustrates the means of attaching the artificial turf (14) to the inner surface of the SurfSlide. Several commercial turf products are available, mostly manufactured for golf courses, football fields and other sports facilities. The artificial turf (14) shall be selected for good water retention of the fibers. The artificial turf (14) must withstand the full temperature range of the region where it is installed, which often means a range from -25° F to 120° F (-32 °C to 52 °C). It must also be highly UV light resistant to avoid embrittlement. The attachment (70) to the planking (64) must be removable to rotate artificial turf (14) sections or to replace worn areas. This can be accomplished with hook & loop strips or with a suitable water resistant, removable sticky adhesive. WATER SUPPLY AND RE-CIRCULATION The water supply system is entirely composed of commercial components such as flexible water pipe, T-connectors, clamps, tubes slotted for water dispersion, adjustment valves, and so on. Similarly, the water re-circulation system uses commercial drain grates and sewer pipes for the water collection, as well as pump-filter aggregates to clean and pump the water back up-hill for re-use in the water supply system. The water system can be adapted to any form and length of the ramps as they are fitted into the natural terrain of the site. The water supply and re-circulation system is an integral part of this invention, but the system components which can be purchased from any local plumbing supply house, are not. For this reason the water system is not shown. THE IN-GROUND SURFSLIDE Fig. 3a shows an in-ground version of the SurfSlide. In this version, the trellis support structure is replaced by the surrounding soil (88), and the planking is replaced by a gunite cement, by a sprayed fiberglass wall (50). The gutter system (52), the water collection channel (106) with the grating (48) above it, and the artificial turf (14) are all arranged like in the aerial version. The safety walkway (76) in this version consists of concrete slabs covering the gutter system. Fig. 3b shows a section of such gutter system housed in a pre-cast concrete channel (28) for use with an in-ground SurfSlide structure. The water main (114) is connected by a flexible pipe (44) with water exit slots (110). The dispensed water forms a uniform sheet on the artificial turf (14). The amount of exiting water is controlled by the control valve (36). The lock strips (60), made in bright color from an elastic plastic or rubber, make for a clean looking band which runs along the top of the ramp and also serves as coping. The concrete gutter channel (28) rests on soil or gravel (88) which is level with the upper end of the gunite (50). The concrete cover (40) protects the gutter arrangement and also serves as safety walkway. Operation of the Invention 1) CONSTRUCTION: AERIAL STRUCTURE The SurfSlide Structure To facilitate manufacturing, transport, and assembly, the aerial structure consists of standardized straight and angled sections that are bolted together on-site. A center assembly (20) (Fig. 1c) is placed on the lowest set of prepared concrete footings (30). The bottom beams are attached to the center section and rest on the second pair of footings. The next center section (20) (Fig. 1c) is put in place, bolted to the resting beams. A diagonal brace completes the first bottom trellis (not shown). The bottom trellises required for a given run are built first and must be measured carefully to make sure that all levels, angles and distances are correct. The side sections (82) (Fig. 1c) are bolted to both sides of the center sections (20)(Fig. 1c) and braced together with straight and diagonal beams to complete the side trellises shown in (Fig. 2a). To complete the structure, end caps for shoeing surfers into the slide and for safe exit at the end must be built to fit the terrain. If extensions for fast turns are used (42) (Fig. 1c), sprinklers (not shown) may be installed on the safety walkway (76) (Fig. 1c) on the opposite side to shoot a jet of water onto the extension which is located above the gutter (52)(Fig. 1c). Also, a "traffic signal system" (not shown) may be installed to avoid one surfer from plowing into another one who has fallen with his board. The support structure (104) (Fig. 2a) must be dimensioned to support the highest load expected. In mountainous areas in the North, this could be 0,9 m (3 feet) of wet snow. In the South, high side winds could be the primary concern. Water Supply and Evacuation Prior to planking, the water collection channel (106) (Fig. 1c) is placed in the center section (20) (Fig. 1c) and connected to the water return pipe (112) (Fig. 1c) in regular intervals. Above the water collection channel (106) (Fig. 1c), a grating (48) (Fig. 1c) is placed and lined up parallel to the trellis beams. Then, pultrusions or other planks (64) (Fig. 1c) are placed on both sides of the grating to plank the open pipe. The highest positioned "plank" on either side is the gutter (52) which can be a water carrying poltrusion or another water supply pipe with water exit slots in order to lubricate the walls from top to bottom. They are connected to the water supply main (114) (Fig. 1c) at regular intervals. Other utility pipes are put in place (74) (Fig. 1c) and supported as needed with braces attached to the bottom trellises. Each connection to the water supply main must have a flow control valve to fine tune the amount of water released. - The water supply and the re-circulation system must be designed individually for every installation. Planking For the above ground SurfSlide, a trellis support structure (104) (Fig. 1c) made from steel with fiberglass pultrusions as planking material has been chosen for the following reasons: the steel structure for the ease of pre-manufacture, transport and on-site assembly; the pultrusions for their high strength-to-weight ratio and climatic resilience, their ease of transportation and of cutting them to length in their final position. Both materials offer high strength at reasonable costs. The pultrusions (64) (Fig. 1c) are placed on both sides of the grating (48) (Fig. 1c), each pultrusion being oversized in length by 0,15 m to 0,3 m (6" to 1 to 12") for the final cut. As the pultrusions are put in place, they are glued to the rolled steel L-profiles (72) (Fig. 1c). The adhesive must withstand the entire temperature range of the geographic area where the SurfSlide is installed; it must be resistant to water and dampness, and it must remain elastic to accommodate differences in thermal expansion between the steel support structure and the fiberglass pultrusion planking. Lined-up pultrusions (64) (Fig. 2a) are cut either straight or mitered for angled turns and connected with thermoplastic inserts. Fig. 22 also shows slope decreases (84) and slope increases (86) which are obtained by the same miter cut technology. The Turf The artificial turf (14) (Fig. 2c) is installed on the inner surface of the SurfSlide. To facilitate replacement of worn sections, it is recommended to install the artificial turf (14) (Fig. 2c) in manageable sizes, referred to as "turf tiles", and to attach them to the pultrusions with either a hook and loop tape as shown in Fig. 2c or with a water-resistant, removable adhesive. The requirements for such adhesive are that the turf tiles solidly adhere to the pultrusions, irrespective of temperature and water influence to assure that under no circumstances the edges lift off and a lawn board gets caught underneath a turf tile; on the other hand, the adhesive must be removable for replacement or rotation of turf tiles. Design Constraints The rigidity of the pultrusions imposes a rigid design and precision manufacturing of the trellis support structure (104) (Fig. 1c) and the concrete footings (30) (Fig. 2b) on which the structure rests. To balance out inaccuracies of the concrete footings or to compensate for settlement in the soil, the concrete footings (30) (Fig. 2b) provide for shim adjustments (80) (Fig. 2b). 2) CONSTRUCTION: IN-GROUND STRUCTURE In sloped areas with soft, stable ground and without bedrock, the SurfSlide construction can be simplified by scooping out the soil and shaping it into an open pipe, then guniting the shell with "pool building" techniques (Fig. 3a). Prior to guniting, the water collection channel (106) (Fig. 3a) made from pre-cast concrete, is inserted in the bottom of the excavated open area. Similarly, the gutters (52) (Fig. 3a), water mains (114) (Fig. 3b) and other utility conduits can be housed in profiled concrete channels (28) (Fig. 3b) positioned on level soil or gravel (88) (Fig. 3b) on both sides of the open pipe. The artificial turf (14) is attached as described above. Similarly, all other design features are identical to the aerial structure. In fact, both versions should be combined to take the best advantage of a given terrain. 3) CONCLUSIONS, RAMIFICATIONS AND SCOPE The reader will see that the SurfSlide invention provides for a new SPORT OF SKILL that consists of controlled movements on a LawnBoard over an open pipe ramp system covered with artificial turf. Such sport is usually not limited by geography, terrain or climate. While the above description contains many specifities, these should not be construed as limitations on the scope of the invention but rather as an explanation of preferred embodiments. Many variations of aerial and in-ground SurfSlides are possible. Also, other types of vehicles such as inner tubes, sleds or toboggans can be used for a ride on the SurfSlide. SurfSliding is a sport similar to surfing while executing movements similar to skateboarding and snowboarding. SurfSliding can be experienced in various geographical locations and is not confined to the topographical layout of the land. It differs from water slide amusements in that the "patron participates actively in the ride". It inspires repeat visits to a facility so the patron can improve his/her skills. The configuration of this ramp system can reflect a wide variety of designs and layouts for various skill levels of surfers. The arrangement of the ramps is only limited by the imagination of the designer. Depending on the terrain and the desired degree of SurfSlide challenge, different cross-sectional designs may be used, ranging from flat to circular to elliptical or parabolic, lifting or lowering the side walls. All components of the SurfSlide ramp system and component parts are constructed from commercially available materials. Each project engineer can make changes to use materials available in his area. The open pipes of the invention can be made of straight, hollow fiberglass pultrusions that are easy to transport over the road. Since the open pipe size requirements depend on the customer specifications, the support structure can become very large. If so, it should be designed for pre-manufacture of sections which can be transported on regular trucks (no oversize permits and escorts) and bolted together on-site on prepared concrete pilings. The basic riding concepts required to SurfSlide are hybrids from skateboarding, skimboarding, surfing and snowboarding which means that the basic movements are well established but now applied in a novel manner. A combination of skill and balance are used to perform maneuvers along a ski slope, an ocean swell, a city street, or now, along a SurfSlide ramp. The primary mechanics of riding are as follows: Balance Constant body weight shifting is required to keep on top of and maintain control of a board. In a fluid and dynamic medium, balance is crucial. Skill Persistent efforts to ride eventually become learned skills, whereby riders constantly make maneuvers based on given situations. Skilled riders spontaneously change their body dynamics to adapt to surface conditions. Body 1. Stance Using bent knees, a rider puts one foot forward (steering control) and one foot back (power and balance). The rider and board form an A-frame for stability and control. 2. Torque To turn, a rider uses twisting movements of the body, ultimately controlling the board with the feet. This footwork allows the rider to change directions, using a rail-to-rail transition flow for board and path control. Grace Controlled movements allow for the aesthetic flow of turns. This graceful pattern of riding is known as "style". Each individual rider develops his or her own personal style. The fascination of young people with "boarding" skills leads to competition and offers a sense of accomplishment that attracts repetitive business for the surf slide operator. Accordingly, the scope of the invention should be determined not by the illustrations provided but by the attached claims and their legal equivalents.

Claims: A SurfSlide apparatus comprising: a) a fixed ramp system having a top and a bottom and having an inner side and outer side; b) said ramp system having an upwardly opening cross section, sloping downwardly and forwardly from said top to said bottom; c) a lubricant which flows over a surface of said inner side of said ramp system; d) said ramp system having an entrance at said top whereby a user or a conveyance carrying a user enters, travels on said ramp system downwardly over said surface until the user exits said ramp system at said bottom of said ramp system; and e) a lubricant collection channel; characterized in that f) said ramp system consists of open pipes which are large enough to allow the user to develop skills in controlling direction, speed, movement and vertical ability while traveling downwardly on said ramp system; g) an artificial turf material forming said surface and working as a friction control surface consisting of material fibers having the ability to retain said lubricant is disposed on said surface on said inner side of said ramp system. A SurfSlide apparatus as claimed in claim 1 in which said lubricant controls the friction between said friction control surface and a user or conveyance carrying a user sliding over said friction control surface. A SurfSlide apparatus as claimed in claim 1 which further comprises a means for supporting said ramp system. A SurfSlide apparatus as claimed in claim 1 which further comprises a lubricant re-circulation system. A SurfSlide apparatus as claimed in claim 1 which further comprises an attachment means for adhering said friction control surface to the inner side of the said ramp system. A SurfSlide apparatus as claimed in claim 1 which further comprises said ramp system having a plurality of curves and slope increases and decreases as said ramp system is constructed downwardly and forwardly from top to bottom. A SurfSlide apparatus as claimed in claim 1 which further comprises a conveyance carrier for allowing a user to travel downwardly through said ramp system either standing erect, sitting, lying, or kneeling. A SurfSlide apparatus as claimed in claim 1 which further comprises a plurality of open pipe structures connected together to form said ramp system. A SurfSlide apparatus as claimed in claim 1 in which said ramp system has a first upper wall disposed on the left of the longitudinal axis of said open pipe and a second upper wall disposed on the right of the longitudinal axis of said open pipe which allows for a user or conveyance carrying a user to stand or sit and travel upwardly upon said first upper wall and downwardly again to the center of the ramp system and then upwardly upon said second upper wall, causing a back and forth motion as the user travels in a generally downwardly motion to the bottom of said ramp system.

Inventors: GRIMES MARTIN O JR, GRIMES, MARTIN O., JR.
Applicants: HAUSEN GUENTHER G, HAUSEN, GUENTHER G.
Application year: 1998
Main classification: A63C19
IPC codes: A63C19