Patent Application
20080223989
Not Applicable
Not Applicable
Not Applicable
1. Field of Invention
This invention relates to control systems for kites, especially for, but not limited to traction kites used in the sport of kite surfing, snow kiting and other sports involving a person operating a kite as a means for propulsion.
2. Prior Art
Kite control systems for use with multi-line traction kites commonly consist of
(a) a center rope (8) which operatively connects a kite operator's harness (15) to the supporting flying lines (3) and (4) of a kite (1), which are connected to the leading edge (2) of the kite, and
(b) a movable control handlebar (11) which slides along the center rope, guided by a hole in the center of the bar. The left end of the bar is linked to a left control line (5), and the right end to a right control line (6). The control lines are attached either directly to the bar, or in an improved design linked indirectly through a pulley.
The handlebar is held by a human kite operator (14) with both hands and is used for a dual purpose: (a) to steer the kite to either side and (b) to adjust the angle of the kite relative to the wind in order to increase or decrease the lifting power generated by the kite, commonly referred to as powering or depowering the kite, or in sailing terms: “sheeting in” or “sheeting out” respectively.
To steer the kite, the control handlebar has to be pulled with one hand while releasing the other hand. To power or depower the kite, the handlebar needs to be either pulled or released with both hands simultaneously.
These actions require a significant amount of effort by the kite operator because part of the lifting power of the kite is distributed to the control lines. It is a common complaint among kite boarders that their arms and hands get prematurely tired when practicing their sport.
The french patent FR2762583 ‘Systeme de controle d'une aile ellipsoidal generalment en forme de fuseau spherique et retenue par des lignes’ describes a prior art system as illustrated above.
Another french patent FR2873093 ‘Dispositif de controle pour ailes de traction’ describes a 2:1 advantage steering system where each control line goes around a pulley (12a) and (12b) attached to each end of the handlebar. This recent development dramatically improves the maneuverability of the kite on the one hand, but on the other hand even increases the problems described above, due to an increased force on the handlebar. Some manufacturers therefore have abandoned the 2:1 steering system already.
Several attempts have been made to reduce the amount of effort necessary to control the kite. One such attempt is an extra harness loop (13) attached to the handlebar, which simply can be hooked to the harness and by doing so fixing the handlebar in place. The problem with this attempt is that it takes too long to unhook in case of a sudden need to depower, for instance because of a wind gust or a change in the moving direction of the kite operator, and thus looses its flexibility to adjust power.
Another attempt to solve the problem is by using a stopper ball (21) resting on a fixed member on the center rope. The stopper ball prevents the handlebar from sliding through the center rope, unless the force applied to the handlebar is beyond a certain amount. In order to depower, the handlebar has to be pushed forward vigorously which will push the stopper ball through. The disadvantages are: (a) only limited power adjustment is possible while the handlebar is resting on the stopper ball, (b) the stopper ball has to be reloaded manually, and (c) sometimes the stopper ball slides through unintendedly, and vice versa.
U.S. Pat. No. 6,514,115 ‘Line system for steering a kite’ teaches a different configuration of flying lines, using deflecting pulleys which link flying lines together. As a further ramification, it shows a pulley on the harness side of the control system, which has the purpose to take away the pulling force on the control handlebar. This solution unfortunately does not work on kite control systems which don't use the special line system described in said patent. If the full force of the supporting lines of the kite was redirected to the control handle bar, the kite would uncontrollably power up in a wind gust, and make the operation of the kite very unsafe.
The invention provides a kite control system which balances the main lifting force of the kite and the force on the control handles under changing wind conditions. It comprises a proportional mechanical redirection device, which redirects the main lifting force of the kite to the control handles, and thus significantly reduces the force thereon and assists with holding and pulling said control handles. The proportional mechanical redirection device can be, in accordance with the embodiments shown here, but are not limited to: (a) a compound pulley system which redirects the main lifting force of the kite to the center of the control handlebar, or (b) control handles configured as levers with a pivot in between the two ends of the lever, proportionally redirecting the movements of the supporting flying lines on the first end to the control lines on the second end.
a shows a compound pulley system used as a proportional redirection device.
b shows a lever used as a proportional redirection device.
Different ratios of redirection are possible with different configurations of the compound pulley system.
The system in
(a) The fixed portion is operatively connected to the kite operator's harness and comprises a triple pulley block (24) with a cleat. The first end of the rope (28) of the compound pulley system goes through the cleat on the triple pulley block and can be used as a fine trim end (30) of the system. A hook (23) is attached to the triple pulley block and can be connected to a quick release shackle (22) on the harness side. This quick release shackle must be operable under load, and it is connected via a swivel (20) to the harness bracket (16). The harness bracket is fixed on the kite operator's harness. If a safety leash is used, a leash connector (31) must be attached to a point located between the swivel and the quick release shackle, so the safety leash will rotate together with the kite control system and the kite. The other end of the safety leash is usually connected to one of the supporting lines (safety leash not shown).
(b) The first moving portion is operatively linked to the main lifting force of the kite, and comprises a double pulley block (25). A center rope (8) connects the double pulley block to a central connector (7), where the supporting flying lines (3) and (4) are attached. The length of the center rope can be adjusted with one end of the center rope (10) going trough a pulley and V-cleat combination (9).
(c) The second moving portion comprises a stopper ring (27) at the second end of the rope of the compound pulley system. The stopper ring connects to a snap shackle (26) which is attached to the center of the control handlebar (11). The stopper ring must be large enough to be stopped by the triple pulley block when the snap shackle is opened and the rope of the compound pulley system is retracted.
A left hand pulley (12a) linked to the left control line (5) is connected to the left end of the handlebar, and a right hand pulley (12b) linked to the right control line (6) is connected to the right end of the handlebar. The ends of the control lines lead to the central connector.
An array of rope guides (29) for the rope of the compound pulley system is located centrally between the two ends at the bottom of the handlebar.
The redirection system as described above redirects the force of the main supporting flying lines to the control handle. To depower the kite, the bar simply needs to be pushed forward—no unhooking or other actions are necessary. The compound pulley system as used in this embodiment has a 4:1 mechanical advantage. In this application, the compound pulley system divides the magnitude of the force which is present at the center rope by 4. The reduced and redirected force is effective on the handlebar, and it significantly diminishes the force necessary to keep the kite powered.
To determine the suitable ratio of the proportional redirecting system, the following things need to be considered: When the control handle is not held, the kite should be in a partially powered state. To fully power the kite, the control handle needs to be pulled slightly. To fully depower the kite, the control handle needs to be pushed away slightly. The redirection system can be compared to a power assisted steering in a car which doesn't do all the work but leaves some steering feel to the driver for better and safer driving properties, and which will straighten the wheels automatically if the steering wheel is not held.
For different kites or different applications, there may be a different mechanical advantage of the redirection system necessary, depending on kite design, kite size, number and location of flying line attachment points on the kite, existence of a 2:1 advantage steering system, and personal preference. For common traction kites on the market, a ratio of 1:4 may be suitable to achieve the goals described above.
There are 2 trimming features according to this embodiment. Both features are used to adjust the distance between the kite operator and part of the kite control system in order to keep the control handle at a convenient position in changing wind conditions. At light wind conditions the distance can be increased to allow the full range of movement of the control handlebar. In stronger winds the distance can be shortened to make it easier to push the control handle forward when depowering the kite. The two trimming options are:
(a) The trim end of the center rope can be used to make rough adjustments. Because it is far away from the kite operator it can't be used easily while “on the go”. Also to operate this trim easily, the kite should be partially depowered in order to decrease the load on the center rope.
(b) The fine trim end of the compound pulley system's rope can be operated “on the go”, as it is in a convenient location, and, because of the 4:1 advantage of the compound pulley system, it can easily and quickly be operated under load. The end of this rope should be attached with an elastic stretch cord (not shown) to the central connector, to keep it out of the way and prevent it from entanglement.
There are 2 safety features in this embodiment:
(a) The snap shackle on the control handle can be opened. The control handle is then freely movable and the kite control system will work like a prior art control system. This safety feature is needed to temporarily minimize the power of the kite in order to correct a problem, for instance an entanglement of lines. This feature is also useful when the wind speed increases dramatically and the kite size is becoming too large for the present wind condition, so a kite surfer could reach the shore with minimal power of the kite.
(b) The quick release shackle on the harness side can be opened in all other cases of emergencies. By opening this shackle the whole kite system is separated from the kite operator and the kite will depower. A safety leash can be used to prevent the loss of the kite.
Tests show very satisfactory results: (a) Arms and Hands don't become tired, (b) when the bar is released: the kite will still hover in the air, it doesn't fall or power up uncontrollably, (c) in strong gusts, no extra effort is necessary to hold the handlebar (d) the handlebar can be held one handed without losing control over the kite. This is necessary when the other hand is busy with something else, i.e. holding the board while trying to start, (e) the fine trim can be adjusted with minimal effort because of the the compound pulley system, and it can therefore be done in an instant, (f) the overall travel distance of the control handlebar from a depowered state to a maximum powered state is shorter than on conventional systems, and therefore the range of power adjustment is increased with the same arm movement distance.
b shows a basic configuration of a force redirecting lever (47) as used in the context of these embodiments, having a fixed portion (48) at the lever's pivot, a first moving portion (49) at one end of the lever, and a second moving portion (50) at the other end of the lever, wherein the pivot is located in between the two moving portions, and whereas the mechanical force is redirected from one moving portion to the other. The ratio of the distance from the pivot to the first portion and the distance from the pivot to the second portion is inversely proportional to the ratio of the redirected force from one end to the other.
In
In
An additional ramification is shown if
Accordingly the reader will see that the kite control systems of the various embodiments have many advantages, and allow for the operation of the kite in a more convenient, flexible, versatile and safe manner, as the control handles can be released or pushed away without any additional action necessary, while still providing a substantial relief of the force on the control handle and avoiding exhaustion in arms and hands. Furthermore, greater steering control of the kite is possible, no loss of control is experienced when only one hand is holding the bar, and additionally, the control system can easily be trimmed.
While the above description contains many specificities, these should not be construed as limiting the scope of any embodiment, but as exemplifications of the presently preferred embodiments thereof. Many other ramifications and variations are possible within the teachings of the various embodiments, for example by using alternative redirection mechanisms, using different ratios of redirection, combining redirection systems of different types, etc.
Thus the scope of the invention should be determined by the appended claims and their legal equivalents, and not by the examples given.
