Towable innertube accessory with rudder

An innertube accessory that facilitates towing an innertube by a boat. The accessory includes a shell for receiving any size innertube and attaching it. The accessory is suitable for being towed by the boat, by a track and trolley mechanism that adapts to different towing angles away from the boat center line. The innertube rider can steer the accessory by operating a rudder. The rudder is a steering rope that controls pivoting of a rudder fin relative to the shell. Additional fins provide stability.

BACKGROUND OF THE INVENTION
 1. Field of the Invention
 The present invention is related to the field of water sports, and more
 specifically to watercraft of the type towed behind a boat or other
 vessel.
 2. Description of the Related Art
 A fun water sport is to be towed behind a boat on an innertube, that is
 also known as a ski biscuit. A rider sits in the innertube, which is
 attached to a speeding boat by a towline, and thus gets pulled wherever
 the boat goes.
 A problem with this sport is that the rider lacks control over where the
 innertube goes. Every time the boat turns, the innertube tends to continue
 in its original direction, unless pulled in a different direction. A large
 body of water is required to make turns safely at high-speed. If such is
 not the case, the innertube might approach the shore, or undesirable
 debris. In addition, this sport remains unchallenging compared to similar
 water sports, where the rider can steer.
 There has been some interest in making steerable innertubes. For example,
 in U.S. Pat. No. 5,819,680, a steerable towcraft is taught. The floating
 device is triangular, which does not make it exactly a ski biscuit. The
 rider can pull on a steering line with respect to the towline, which
 rotates the floating device. A fin that is fixedly attached to the
 underside of the floating device converts the rotation into changed
 direction.
 A problem in this invention is that steering can be performed only when
 there is active towing by the boat, i.e. with the towline being taut. When
 the towline is slack, there is no steering control. Plus, it is not
 adaptable to existing ski biscuits.
 Moreover, as per U.S. Pat. No. 5,899,782 to Martin, a flotation device is
 provided that can be towed behind a speeding boat, and can change
 direction. The rider pulls on handle with respect to the taut towline,
 which rotates the flotation device with respect to the direction that it
 is being pulled. Again, a fin-like apparatus provided under the flotation
 device converts this rotation into a changed direction of motion for the
 flotation device.
 This invention has the same problem of lack of steering control when the
 towline is not taut. In addition, the handle may fall into the water, in
 which case the rider loses control.
 BRIEF SUMMARY OF THE INVENTION
 The present invention overcomes these problems and limitations of the prior
 art.
 Generally, the present invention provides an innertube accessory that
 facilitates towing an innertube by a boat. The accessory is a device that
 includes a shell for receiving the innertube, that is also suitable for
 being towed by the boat. While the innertube provides flotation, a rider
 of the innertube can also steer the device. The rider steers by operating
 a rudder of the device, that controls pivoting of a rudder fin relative to
 the shell.
 The rudder is operated independently of the towline, and cannot fall into
 the water, which makes the device of the invention safer to use. The
 foregoing and other features and advantages of the invention will become
 more readily apparent from the following detailed description of a
 preferred embodiment which proceeds with reference to the drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)
 As has been mentioned, the present invention provides a ski biscuit
 accessory. The accessory is a device for facilitating towing an innertube
 on a surface of water by a pulling watercraft traveling in a boat
 direction. The device is steerable by a rider riding in the innertube, for
 attaining a second direction different from the boat direction.
 The invention is now described with reference to FIG. 1. A body of water 20
 has a surface 22, on which the boat 24 is pilot and by a driver 26 along a
 boat direction B. The boat is towing, via a towline 30, a rider 32. Rider
 32 rides on an innertube 34, a.k.a. ski biscuit 34. Innertube 34 is
 attached to accessory 50, made according to the present invention.
 Referring now to FIGS. 2 and 3, the preferred embodiment of accessory 50 of
 the invention is described in more detail. Accessory 50 includes a shell
 60 for receiving innertube 34, and for riding substantially on the water
 surface. Shell 60 is preferably shaped to present low drag, and its
 underside 61 is slick. The whole shell 60 is preferably semi rigid and
 lightweight. It can be made of the suitable material, such as fiberglass
 or high density plastic, and be 3/16" to 1/4" thick. It can be built using
 injection molding, or using sheet plastic over a vacuum form mold. The
 sheet is heated and formed over a mold via vacuum holes in the mold.
 Shell 60 is also for coupling to the towline 30, for being towed by the
 boat. The preferred embodiment of accessory 50 further includes a track
 and trolley system, which is described below. The track 62 is attached to
 a front side of the shell 60.
 Device 50 preferably further includes skegs 64, 66 also known as fins,
 fixedly attached to the underside of the shell 60. Only skeg 64 is seen in
 FIG. 2; skeg 66 is obscured by skeg 64. These skegs 64, 66 provide
 stability in the chosen direction, especially for when the device of the
 invention is running parallel to the pulling boat, but not behind it. If
 not provided as stand out skegs, the shell 60 can have raised surfaces for
 providing a similar guiding effect. When using standing out skegs such as
 those shown, a kit can come with replaceable skegs of different sizes, for
 different performances at different speeds.
 Device 50 of the invention further includes a rudder 70, and at least one
 rudder fin 72. Rudder fin 72 is attached pivotably to shell 60, and
 preferably at the rear. It is to be under the water surface at least in
 part. Rudder 70 is operable by the rider, for pivoting rudder fin 72
 relative to shell 60. This will cause rudder 70 to steer shell 60 by
 rudder fin 72 engaging the water.
 The preferred embodiment of device 50 further includes a dash 80 and two
 eyeholes 82 for the rudder, as a seen below.
 FIG. 4 is a view of device 50 as it appears before inserting and attaching
 an innertube. Two aluminum strips 92, 94, accommodate series of screws
 support the track (not seen in FIG. 5) that is on the outside.
 Two sets of straps 98 are attached to the inside of shell 60. They are
 preferably attached by the aforementioned strips 92, 94. The straps are
 for attaching the innertube to shell 60. The straps can terminate in
 belt-like buckles, or use Velcro. The straps can either go around the
 innertube, or attach to handles of the innertube. The straps can be
 adjustable to accommodate various sizes innertubes.
 The rudder 70 of the invention is now described in more detail, referring
 to FIG. 4 and also to FIG. 5. A rudder according to the invention is any
 mechanism that will rotate rudder fin 72 with respect to shell 60
 according to arc 102.
 The preferred rudder includes at least one steering rope 104 that coupled
 with rudder fin 72, and is operable by the rider to pivot the rudder fin
 72. As seen in FIG. 4 and in FIG. 5, steering rope 104 terminates at the
 two eyeholes 82.
 Preferably steering rope 104 includes steering handles 106. These can be
 made from plastic tubing or foam rubber around steering rope 104. They are
 preferably made from foam rubber tubes with a plastic tube in the core for
 rigidity. These left and right steering handles 106 serve both to steer
 the craft, and also to maintain a constant positive grip on the vessel.
 The steering handles are held in place on steering rope 104 via knots tied
 in steering rope 104 at each end of steering handles 106. Then steering
 rope 104 passes through two eyeholes 108 provided in dash 80.
 Device 50 preferably further includes tubes 112. Steering rope 104 runs
 through tubes 112 at least in part. Tubes 112 can be made from nylon, and
 be mounted to dash 80 and to a rudder station 120. The nylon tubes can be
 allowed to lay along the floor of the shell from the dash to the rudder
 station. Alternatively, they may also be inlayed into the fiberglass, when
 the shell is produced. The nylon tubes protect the steering rope from
 being pinched down by the weight of the ski biscuit during operation.
 Steering rope 104 continues through rudder station 120. Steering rope 104
 is engaged with rudder fin 72. Engagement can be by threading through the
 rear portion of rudder station 120. A knot can be tied and recessed into a
 receiving hole, which keeps the rope fixed to the controlled end of the
 rudder.
 As the rider pulls on the left steering handle, the rudder will turn the
 craft to the left. The opposite is true if the rider pulls on the right
 handle. Whichever handle is pulled, the opposite handle must be relieved,
 as steering rope 104 is continuous in this embodiments. Other embodiments
 can have a plurality of ropes, or levers, etc.
 Referring now to FIG. 6, underside 61 of shell 60 is seen. A rudder pivot
 point 124 is the center of arc 102.
 A trolley 130 is used for attaching to the towline. Trolley 130 has an
 opening 144 for tying therethrough the towline. Trolley 130 is movably
 engaged in track 62. As such, trolley 130 can move freely along arc 132,
 depending on where device 50 is with respect to the towing boat. It will
 be appreciated that, While the combination of rudder fin 72 and skegs 64,
 66, may move around device 50 with respect to the towing boat, the fact
 that the trolley 130 is free to move will keep device 50 from being forced
 to return behind the boat.
 Referring now to FIGS. 7 and 8, the track and trolley system are described
 in more detail. Track 62 defines an oblong channel that extends
 horizontally along the front side of shell 60. The channel has a wide
 portion 140, and a constricted neck portion 142. Trolley 130 is movable
 within the channel.
 Track 62 can be made from plastic such as ultra high molecular weight
 ("uhmw") plastic. It can be made starting from round stalk having a 3"
 radius at 180.degree., with rounded ends. In the event that the shell is
 produced via injection molding, the track and shell can be produced as a
 single component. Track 62 is attached to shell 60 by screws 138, that go
 through strips 92, 94.
 Seen better in FIG. 8, trolley 130 has a body 146, that can be 1/2" thick,
 and can be made from umhw plastic. Body 130 has an expanded portion 148,
 that is confined by the constricted neck portion 142 of the channel into
 the wide portion of the channel. Trolly 130 includes bearings at the
 expanded portion 148, for rolling within the wide channel portion 140. The
 bearings can have 3/4" outer diameter and 1/4" inner diameter. The
 bearings are preferably made from a rust resistant material, such as
 stainless steel. Trolley 130 also includes rollers 152, such as nylon
 rollers, for rolling within the constricted neck portion 142 of the
 channel. The bearings and the rollers are supported by shafts and pins.
 Referring now to FIGS. 4, 5, 9 and 10, a steering method of the invention
 is described
 As seen in FIG. 9, if unsteered, an innertube connected with device 50 of
 the invention ordinarily is towed behind pulling watercraft 24, and in the
 same direction B. The method of the invention is for a rider riding in the
 innertube to steer the innertube to a direction C different from B.
 The method is for the innertube rider to pivot a rudder fin 52 of device 50
 with respect to shell 60. Rudder fin 52, being under water surface 22,
 steers shell 60 by engaging water 20.
 Preferably pivoting is accomplished by operating a rudder 70 that is
 coupled with rudder fin 72. Preferably, where the rudder uses a steering
 rope, operating the rudder is performed by pulling on the steering rope
 with respect to the shell.
 After steering, device 50 will have been placed to the right side of line
 160, which is also the centerline of boat 24. Then the rider can adjust
 the angle of steering, and end up being towed along a line 162, parallel
 to line 160, and in the same direction. The rider can experiment switching
 positions according to their comfort level.
 Another advantage of the invention is that it can be used with an existing
 ski biscuit. A user does not need to buy a new ski biscuit, or adapt an
 old one.
 A person skilled in the art will be able to practice the present invention
 in view of the present description, where numerous details have been set
 forth in order to provide a more thorough understanding of the invention.
 In other instances, well-known features have not been described in detail
 in order not to obscure unnecessarily the invention.
 While the invention has been disclosed in its preferred form, the specific
 embodiments thereof as disclosed and illustrated herein are not to be
 considered in a limiting sense. Indeed, it should be readily apparent to
 those skilled in the art in view of the present description that the
 invention can be modified in numerous ways. Applicant regards the subject
 matter of the invention to include all combinations and subcombinations of
 the various elements, features, functions and/or properties disclosed
 herein. The following claims define certain combinations and
 subcombinations, which are regarded as novel and non-obvious. Additional
 claims for other combinations and subcombinations of features, functions,
 elements and/or properties may be presented in this or a related
 application for patent. Such additional claims are also regarded as
 included within the subject matter of applicant's invention irrespectively
 of whether they are broader, narrower, or equal in scope to the original
 claims.