Snowboards and the like having integrated dynamic light displays related to snowboard motion
Selected patterns of lights are displayed on a recreational conveyance such as a snowboard according to the motion of the board. A selection of patterns is stored in a processor memory, the motion of the board is measured (for example with accelerometers) and a pattern is selected from memory based on the measured motion. Then lights on the board are blinked on and off in the selected pattern. Accelerometer inputs are analyzed and a series of states is derived for each accelerometer axis. A series of states can be analyzed as a set to select a different pattern. Also, the magnitude of the states (such as duration, speed, or intensity) may affect the pattern selected. The process may be adaptive, so that the analyzing step further analyzes user weight or past snowboarding style to set adaptive thresholds for selecting patterns.
1. Field of the Invention
The present invention relates to a snowboard or the like having a programmable display of lights which is responsive to the motion of the board. More particularly, the present invention relates to a dynamic snowboard, ski, skateboard, or helmet whereby detection of combinations of velocity, acceleration, impact, shock and or surface flexure and strain, control and initiate a programmable display of lights and sound that is integrated into the snowboard, skateboard, skis and helmet.
2. Discussion of Background Art
Owners of snowboards, skateboards, skis, and the like have long decorated their recreational conveyances with eye-catching elements. These decorative elements also serve a safety purpose as they make the rider more visible. Hence, fluorescent colors, reflectors, and lights have all been used to decorate these sorts of recreational conveyances. For example, U.S. Pat. No. 6,802,636 describes a skateboard having light recessed into the sides of the board. The lights are illuminated in one of a predetermined set of patterns, such as flashing, strobing, twinkling, and solid sequences. The user selects the light sequence by setting the position of a switch.
However, thus far, there has not been a way to generate light patterns from the recreational conveyance that are dependent upon the movement of the recreational conveyance—speed, landing, turning and the like. A need remains in the art for methods and apparatus for snowboards and the like having integrated programmable display of lights which is responsive to the motion of the board.
SUMMARYIt is an object of the present invention to provide snowboards and the like having integrated programmable display of lights which is responsive to the motion of the board. This object is accomplished by providing an integrated visual display of lights or light emitting diodes (LEDs) that when triggered by any of several motion-related inputs shall provide a programmed display that produces light patterns based upon the sensor responses from the snowboard, skateboard, skis or helmet.
Additionally the output may consist of an audible or audio output, that when triggered by any of the motion-related inputs shall provide a programmed audio sequence that follows or produces patterns based upon the sensor responses from the snowboard skis, skateboard or helmet. The audio and visual outputs may be combined or operate independently.
For example a rider hits a jump and the various sensors determine that the snowboard, skateboard or skis are in free space. The proposed system shall detect this condition and trigger a programmed audio and or visual display. Upon contacting the surface again the system shall detect the impact and trigger a new and different display of audio and or visual content.
The device is capable of detecting such data as velocity from sensors placed on the snowboard, skateboard, and skis or via an input from a Global Positioning System (GPS) or the like, and generating a visual display that is functionally related and dynamically adjusts to the sensed velocity. For example two strings of sequential lights located longitudinally along the board surface may flash in sequence down the length of the board and increase in frequency as the speed of the board increases.
A method of displaying selected patterns of lights on a recreational conveyance such as a snowboard includes the steps of:
(a) loading a processor memory on the recreational conveyance with a selection of patterns
(b) measuring the motion of the recreational conveyance;
(c) selecting a pattern from processor memory based upon measured motion; and
(d) selectively lighting lights on the recreational conveyance according to the selected pattern.
The measuring step may be performed by two accelerometers.
Generally the selecting step includes analyzing the accelerometer inputs and deriving a series of states for each accelerometer axis, and performing a matching step which analyzes the derived states and selecting patterns in a lookup table according to the analysis results. analyzing step may further analyzes series of states as a set, for example to determine that the snowboard is performing a spin.
The analyzing step my further analyze the magnitude of states, wherein the magnitude of a state includes duration, speed (or rate), and intensity.
Preferably the analyzing step includes self-learning. It further analyzes adaptive attributes (such as user weight and style of snowboarding over time) and accordingly sets adaptive thresholds for selecting patterns.
The step of selectively lighting the LEDs includes converting the selected pattern into serial data, conveying the serial data to an LED decoder and power driver, decoding the serial data, and alternatively powering and unpowering selected LEDs in LED arrays according to the decoded data.
Preferably, the invention includes a sleep mode. Thus, steps (c) and (d) are suspended and no patterns are displayed if nothing is happening and hence step (b) indicates activity below a predetermined level.
The lighting step may also select the brightness of lighted lights, or a clock rate for patterns
Apparatus for selectively displaying light patterns on a recreational conveyance such as a snowboard comprises a memory for storing a set of lighting patterns, an array of lights affixed to the recreational conveyance, sensors for determining the motion of the recreational conveyance and providing sensor output, input circuitry for generating data signals based upon the sensor output, a processor for decoding the data signals and for retrieving patterns from the memory based upon the decoded data signals; and an LED driver circuit for alternatively lighting and extinguishing lights in the array according to the retrieved patterns.
Generally, the sensor output is analog and the input circuitry includes a low pass filter for filtering the sensor output and an analog to digital converter for converting filtered data into digital data. As a feature, an input port may be provided for downloading patterns into the memory from an external device. Also, an output port may be included for uploading data based upon the sensor output for external processing.
BRIEF DESCRIPTION OF THE DRAWINGS
The following reference numbers used in the Figures are associated with the following elements of the invention:
-
- 1 Snowboard
- 2 Flexible printed circuit layer
- 3 Color graphic layer
- 4 Board binding sub-plate for electronics and batteries
- 5 Multi color LEDs
- 6 Self adhesive laminate comprising 2+3+5
- 7 Three-axis accelerometer
- 8 Skateboard
- 9 Ski
- 10 Truck housing for batteries and electronics
- 20, 40 Strain gage signals
- 22, 34, 122 Accelerometer signals
- 24, 36, 124 Filters
- 26, 30, 38, 126, 130 Signal processing
- 28, 128 Audio input
- 32, 132 A/D converters
- 42, 142 External program input
- 44, 144 Memory
- 46, 146 Processors
- 48, 148 Software
- 50, 150 Power drivers
- 52, 54, 152, 154 LEDs
- 55, 155 LED signal decode
- 58 Batteries
- 60, 160 Control circuitry
- 62 Programmer interface
- 64 External programming
- 202-226 Software processes
All of the recreational conveyances include at least one sensor, usually an accelerometer 7, which is placed on the conveyance. Sensors placed on the conveyance detect the normal loaded condition, which is the steady state condition of the conveyance with a rider in a static state. These sensors might be accelerometers 7 mounted on the surface of the conveyance such that they differentially measure the movement of the conveyance. As an alternative, the sensors could comprise strain gages, or GPS receivers, or other detectors capable of determining motion of the conveyance. When a change is a detected in the state of the conveyance, a programmable display sequence is initiated where a sequence of lights and is triggered that will flash according to the programmed sequence.
The entire system can be manufactured using a multi layer flexible sheet. The sheet consists of multiple layers with adhesive between them. The layers comprise one or more flexible printed circuit layers that utilize a silkscreen technology to create the circuit traces. These printed circuit layers may contain all or some of the electronics components used in the system. The electronic components including the light emitting diodes are surface mount devices that can be attached directly to the printed circuit layers. A plastic top protective layer is back screen printed with a graphic overlay that provides protection for the printed circuit layer and has clear areas for the LEDs to shine through. The graphic screened layer is easily changed to accommodate different graphics in production. Additionally users can design custom graphics displays for their personal system.
The entire system can be assembled onto a snowboard, skateboard, or pair of skis at the time of manufacture, or can be manufactured as an aftermarket kit that can be easily applied to an existing snowboard, skateboard or pair of skis. Some additional of the product are for bicycles, motorcycles, snowmobiles and automobiles.
In the preferred embodiments, the graphics portion of the device consists of a plastic layer 3 including a graphic design that is screen printed, painted or the like, and is illuminated by a series of Light Emitting Diodes (LEDs) 5 of sufficient brightness to be seen clearly in daylight and bright sunshine. The series of LEDs can be mounted on a surface of the conveyance using a plastic and metal flexible circuit 2 or by embedding in the physical material of the conveyance. The color graphic layer 3, flexible printed circuit layer 2, and multicolor LEDs 5 can be combined in a complete self adhesive laminate 6 that can be applied to existing or new snowboards, skis, skateboards and helmets. This may be applied on the top or bottom surface of the snowboard, ski, or skateboard. The graphic can form a backdrop for the illuminating light system. For example the graphic may portray a pinball machine, and the LEDs fire off in sequences to simulate a pinball bouncing from bumper to bumper. Audio output could be generated in synchronization with the visual display to simulate a pinball machine.
Due to the flexible properties of the self-adhesive laminate this system can be readily adapted to operate in a similar fashion on other moving devices such as bicycles, motorcycles and automobiles.
The flexible sheet 6 that comprises the upper surface mounting system can be applied (retrofitted) to existing snowboards, skis or skateboards in addition to being applied by a manufacturer of said devices. The unit power may be provided by a rechargeable battery system of sufficient power to last a minimum of 8 hours of operation. This battery may be enclosed in a waterproof enclosure that is part of the flexible membrane system.
Another important feature of the present invention is its ability to automatically adapt to the user. For example, a light user who snowboards slowly and carefully needs different thresholds for setting off patterns than a heavy, intense boarder. The present invention self calibrates such that over time each user will see a similar range of patterns. A user switch may also be provided to allow the user to bias the self calibration, for example to require that the board motion reach a certain level of intensity to set off patterns.
The signal /display controller module and LED display modules are mounted on a snow board providing daylight viewable entertaining light patterns on the board in response to actions the snow boarder takes. As an example, a snow boarder does a flip, the LEDs illuminate in a dancing pattern indicating the flip to the viewing audience. If the snow boarder wipes out and crashes, then the lights perform a different pattern representing the accident (yard sale). The pattern, the speed the pattern changes and length of the pattern is varied to match the intensity of the action. The invention is not limited in the application for a snowboard—it may be used for entertainment or scientific purposes in a variety of other applications.
The prototype LED arrays 52, 54 are 10-inch by 10-inch assemblies that hold 32 LEDs 5 each. The LEDs are sunlight visible. Two LED Display modules 52, 54 are used on snowboard 1—one on the front (designated Front Flip) and one on the back (Back Flip). LED selection is critical to achieve the conflicting goals of visibility in sunlight and low power. These display modules may be built entirely on a flexible printed circuit card that is part of the entire graphics circuit assembly.
The system may be personalized through the use of a personal computer software program via interface 42. This software program allows individual users to program the threshold levels, intensity and sequence of the light display patterns. The software program permits the user to “dry run” the light display programs on the computer monitor prior to transferring it to the recreational conveyance. Multiple custom sequences may be programmed and stored in the system memory 44. For example a rider may run one sequence for downhill riding and a different sequence for the snowboard park that involves different motions and threshold levels.
For example a rider is accelerating downhill in a normal left-right motion, the accelerometers will produce continuous positive vertical and a positive longitudinal component on both front and rear devices while alternate positive and negative horizontal components that are relatively slow in changing will be observed from the 2 measuring devices. The “set of events” can be then used to trigger a specific light pattern. If the rider for example during a normal descent rotates the snowboard around an axis at the rear end of the board the sequence set will change accordingly and a different pattern of lights will be triggered.
If we examine the accelerations generated from a normal descent there is an initial condition setting where we will see a positive vertical acceleration (due to gravity) vectored with a longitudinal positive acceleration as the board points down the hill. As speed increases the longitudinal accelerations will increase and at some point the rider will make either a heel or toe turn (left hand or right hand motion) generating a horizontal acceleration. This will then be followed by a short vertical descent and then transition into a horizontal component of the opposite direction.
Using the acceleration notation as shown in
{Yf+&Yb+&Zf+&Zb+} then t1+{>Yf+&>Yb+&Zf+&Zb+}
then t2+{<Yf+&<Yb+&<Zf+&<Zb+&>Xf−&>Xb+}
then t3+{>Yf+&>Yb+&>Zf+&>Zb+}
then t4+{<Yf+&<Yb+&<Zf+&<Zb+&>Xf+&>Xb−}
Where t1, t2, t3, and t4 are time intervals between the detected accelerations.
In one embodiment, controller 60 is programmed in the ‘C’ programming. The Controller provides debug capability without adding hardware in the form of an In Circuit Debugger (ICD). In Circuit Debugging capability is built into every Signal Processor and Display Controller. This also enables the product to be programmed after it is assembled. The user of this system is able to input to programs of different patterns and levels of sensitivity into the system by a simple electronic connection from a computer or other electronic device such as a PDA or a memory chip similar to those used in digital cameras and USB memory devices. These patterns can be pre-programmed using a personal computer program and demonstrated on a computer screen to simulate the real time responses of the system. Then this data set is exported to the system on the recreational conveyance.
Controller circuitry 60 has a micro controller that interprets the output of two three-axis accelerometers 7. Depending on the accelerations detected, the micro controller selects a display pattern. This pattern is output to the LED Display modules 52, 54 over a four-wire interface. The LED Display module consists of a 32 bit serial shift register, one register bit per LED, one drive transistor per LED and 32 sunlight visible LEDs 5. Each LED has a single dropping resistor from the positive supply voltage. For debug purposes, the Controller has an RS232 interface and an ICD interface. Both may be accessed simultaneously. In normal use, neither is required. The RS232 interface continuously outputs accelerometer and status information during normal operation.
A second software program 64 for the personal computer allows the user to playback logged data from the system. The system controller logs all of the state changes detected by the system during operation. This log may be transferred out of the system via a memory device or computer interface and replayed out on the computer using playback software. This software program when used with a ski area map or skateboard park layout can overlay the motion, and path of the snowboard, skis or skateboard and show the resulting display on the computer monitor.
The Initialization Process configures internal micro controller peripherals to:
-
- 1. Setup the master oscillator to be the internal RC at 4 MHz
- 2. Setup the A/D inputs, set the A/D range and converter clock
- 3. Setup the periodic interrupt rate for the Sample and Output processes
- 4. Setup the serial interface to the board LEDs
- 5. Turn on the interrupts!
- 6. Signal “Ready” over the serial interface.
After initialization, five processes are at work in the software—digitizing accelerometer 7 outputs 22, 34 every 100 msec in Accelerometer Sampling step 202, analyzing the accelerometer outputs to determine states in State Process step 204 (see
The State process is shown in
The Pattern Match process takes the output of the state analyzer, matches these inputs to “events”, and sets Pattern, Pattern Speed and Pattern Length values to match the intensity of the event. The speed of the LED pattern is proportional to the maximum velocity that the state analyzer reports. The duration of the LED pattern is proportional to the maximum velocity*elapsed time that the state analyzer reports. This corresponds to distance. These parameters are converted to LED driving signals by the Output Process.
The pattern matcher overwrites patterns, so the last pattern matched is displayed. Consequently, the lowest priority states are analyzed first. If they have a match and a higher priority state also has a match, the higher priority state over writes the lower priority state. The following states are listed in order of priority, lowest first:
-
- Axes are showing<1 g
- An axis is in takeoff TKOFF (2) state
- An axis is in landing LNDNG (5) state
The Match process initiates a new LED pattern if we have a takeoff or a landing, LNDNG or TKOFF states. To do this, it must first generate an integer that uniquely represents the board state. Then, this integer indexes into a list that maps unique board state to a LED pattern. Finally, Pattern Speed and Length are calculated based on maximum velocity and elapsed time.
To generate the integer we analyze the state, per axis. We define a threshold below which we consider the axis to be not accelerating. Assign ‘0’ to mean no acceleration above the threshold, ‘−’ to mean negative acceleration above the threshold and ‘+’ to mean a positive acceleration above the threshold. In the board long axis Y, there are only three states the board can be in:
-
- not accelerating (0)
- accelerating forward (+)
- accelerating backward (−)
In the vertical Z and cross X axes, there are two independent accelerometers to detect motion. In these axes, there are nine acceleration states
-
- none (0/0)
- “front up” with “back up” (+/+)
- “front up” with “back pivot” (+/0)
- “front pivot” with “back up” (0/+)
- “front down” with “back down” (−/−)
- “front down” with “back pivot” (−/0)
- “front pivot” with “back down” (0/−)
- Counter Clock Wise rotation (+/−)
- Clock Wise rotation (−/+).
We can summarize the states as:
-
- 0, +, −; The 3 linear accelerations states (Y)
- 0/0, +/+, −/−, +/−, −/+, +/0, 0/+, −/0, 0/−; The 9 linear and rotary acceleration states (X and Z)
There are 243 states as a result (9*3*9 states). Assign a value of 0 to ‘0’, 1 to ‘+’ and 2 to ‘−’ for the Y axis. Assign a value of 0 to (0/0), 1 to (+/+), 2 to (−/−), 3 to (+/−), 4 to (−/+), 5 to (+/0), 6 to (0/+), 7 to (−/0) and 8 to (0/−) for the X and Z Axes. The unique integer=27*X_Value+9*Y_Value+Z_Value. It is easy to see that all states are decoded and that different patterns may be displayed on the front and back of the board. The states the Match Process can detect are shown in Table 1.
The Sample Process 202 digitizes the accelerometers ten times per second. It uses a firmware divide-by-ten counter to increase the interval between accelerometer digitization to 100 mS, a ten times per second rate. After the accelerometers are digitized, a global flag is set in step 222 to signal the Match Process 206 in the main body of the code that new accelerometer values are available for pattern matching. Digitized Accelerometer values are passed as globals.
Two independent but identical output processes run—one for the Front and one for the Back LED flip boards. The LED Processes 210 use separate firmware divide-by-N counters to set the interval between when the output processes run to be longer than the 10 mS one-hundred times per second rate, in step 224. The interval multipliers, NFront and NBack, are set in the main body of the code by the Match Process. Low values of N means the process runs more often. This process calculates the next set of LEDs 5 to illuminate and instructs the Serial Peripheral Interface (SPI) to output that stream to the Front Flip and Back Flip boards. In addition to the interval counter, the LED Process 210 also is instructed how many times it is to run before turning off the LEDs 5. This sets the length of the displayed pattern.
After the hardware setup is complete and the interrupts are enabled, the timer 2 interrupt occurs, the Sample Process occurs, accelerometer data is digitized and the “System Ready” pattern of LEDs is output. The final act of the interrupt is to signal to the software operation that new samples are ready for interpretation. Step 226 causes the process to pause or sleep until the 10 mSec interval is over.
We can describe these six states as:
- S0 REST—no velocity, no acceleration, initial resting condition
- S1 ACCEL—during this time, the velocity is increasing. Upon entry the time and initial acceleration is stored. Upon exit, store max velocity.
- S2 TKOFF—signal to the Pattern Match process acceleration is done, do takeoff pattern match
- S3 COAST—during this time, the velocity is constant, coasting
- S4 DECEL—during this time, the velocity decreases to zero
- S5 LNDNG—signal to the pattern match section deceleration is done, do landing pattern match
States S2 and S5 are transient; they signal the Pattern Match process to analyze the state and output a pattern if there is a match. State S2 corresponds to takeoff. State S5 corresponds to landing.
Match process 206 plugs the output of the State Analyzer of
Match Process
These patterns may correspond to the more familiar terms: Buying Lift ticket, Standing in line, Getting on lift, Getting off lift, Start a run, Going fast, Grinding, Wipe out, Yard sale, Weightless, Hard impact, Stopping, Carving, Spinning, Flips, Misty, Tree bashing, Grabs, Bumping, Transporting board, Wake Up . . .
There is no reason to limit the application to a fixed threshold in the state detector. Variable acceleration thresholds may be used to ensure that riders experiencing lower g-loads experience the same range of visual effects as riders taking high g-loads. To do this, the maximum detected acceleration is low pass filtered with a slow decay. As the time between events passes, this value drops. A fixed percentage of this value is then used to set the acceleration thresholds described above. This sets the rate of visual effects to be based on the tricks thrown, not the weight of the rider. This also calibrates out short and long term drift of the sensing components.
While the present invention has been shown and described in the context of specific examples and embodiments thereof, it will be understood by those skilled in the art that numerous changes in the form and details may be made without departing from the scope and spirit of the invention as encompassed in the appended claims.
Some alternative embodiments include the following. The system may also be programmed either automatically, if serious and dangerous conditions occur, or manually to display an “emergency” or help mode. For example if the light display is set to repetitively and alternately flash Red circles at each end of a snowboard this can signal to other skiers and the ski patrol that the rider is in trouble. Additionally the audio output can be made to generate continuous emergency alternating tones to attract attention This will aid in saving lives on the ski slopes by attracting immediate attention to the rider in trouble. This feature is of particular benefit in backcountry snowboarding or skiing where there is considerable risk of avalanches.
The system can also be used as a training device for people learning to snowboard and ski. The system can determine through the use of the sensors the relative position of the board to the snow surface and indicate that position through the illumination of the appropriate lights or LEDs. An example of this is a snowboarder learning to set a toe or heel edge on the snowboard. The system can detect when the board has been angled correctly and illuminate the appropriate edge side of the board. So for example if the rider makes a correct edge the lights along the side of that edge will illuminate correctly allowing the instructor to determine if the rider has achieved the correct action. Alternatively the snowboard can intelligently determine when a change in position or direction is needed and output an audible tone to aid the beginner snowboarder or skier in learning to correctly operate the board or skis.
Claims
1. A method of displaying selected patterns of lights on a recreational conveyance such as a snowboard comprising the steps of:
- (a) loading a processor memory on the recreational conveyance with a selection of patterns
- (b) measuring the motion of the recreational conveyance;
- (c) selecting a pattern from processor memory based upon measured motion;
- (d) selectively lighting lights on the recreational conveyance according to the selected pattern.
2. The method of claim 1 wherein the measuring step is performed by two accelerometers.
3. The method of claim 1 wherein the selecting step includes the substeps of:
- analyzing the accelerometer inputs and deriving a series of states for each accelerometer axis;
- a matching step for analyzing the derived states and selecting patterns in a lookup table according to the analysis results.
4. The method of claim 3, wherein the analyzing step further analyzes series of states as a set.
5. The method of claim 3, wherein the analyzing step further analyzes the magnitude of states, and wherein the magnitude of a state includes one or more of the following magnitude attributes:
- duration;
- speed;
- intensity.
6. The method of claim 5, further wherein the analyzing step further analyzes one or more of the following adaptive attributes and sets adaptive thresholds for selecting patterns based upon analysis of adaptive attributes:
- user weight;
- past history of motion;
- a user defined style setting.
7. The method of claim 1 wherein the step of selectively lighting comprises the steps of:
- converting the selected pattern into serial data;
- conveying the serial data to an LED decoder and power driver;
- decoding the serial data
- alternatively powering and unpowering selected LEDs in LED arrays according to the decoded data.
8. The method of claim 1, further including the step of suspending steps (c) and (d) if step (b) indicates activity below a predetermined level.
9. The method of claim 1 wherein the lighting step further includes the step of selecting the brightness of lighted lights.
10. The method of claim 1 wherein the lighting step further includes the step of selecting a clock rate for patterns.
11. Apparatus for selectively displaying light patterns on a recreational conveyance such as a snowboard comprising:
- a memory for storing a set of lighting patterns;
- an array of lights affixed to the recreational conveyance;
- sensors for determining the motion of the recreational conveyance and providing sensor output;
- input circuitry for generating data signals based upon the sensor output;
- a processor for decoding the data signals and for retrieving patterns from the memory based upon the decoded data signals;
- a driver circuit for alternatively lighting and extinguishing lights in the array according to the retrieved patterns.
12. The apparatus of claim 11 wherein the sensor output is analog and wherein the input circuitry includes a low pass filter for filtering the sensor output and an analog to digital converter for converting filtered data into digital data.
13. The apparatus of claim 11, further including an input port for downloading patterns into the memory from an external device.
14. The apparatus of claim 11, further including an output port for uploading data based upon the sensor output for external processing.
15. The apparatus of claim 15 wherein the lights are LEDs.
16. A kit for displaying patterns of lights on a recreational conveyance such as a snowboard comprising:
- a memory for storing a set of lighting patterns;
- an array of lights to be affixed to the recreational conveyance;
- sensors for determining the motion of the recreational conveyance and providing sensor output;
- input circuitry for generating data signals based upon the sensor output;
- a processor for decoding the data signals and for retrieving patterns from the memory based upon the decoded data signals;
- an LED driver circuit for alternatively lighting and extinguishing lights in the array according to the retrieved patterns.
17. The kit of claim 16 wherein the sensors comprise a 3-axis accelerometer.
18. The kit of claim 16 wherein the kit is contained in a multilayer flexible sheet for adhesion to the board.
19. The kit of claim 18 wherein the sensor, circuitry, processor, and driver comprise a flexible printed circuit board.
Type: Application
Filed: Feb 21, 2006
Publication Date: Aug 23, 2007
Inventors: Christopher Stone (Lafayette, CO), Robert Schaefer (Boulder, CO)
Application Number: 11/358,491
International Classification: A63C 5/00 (20060101);