Field of the Invention

[0001] The present disclosure relates to means for transporting a user employing a mechanism attached to one or both of the user's feet. The mechanism preferably has the appearance of ordinary shoes and propels the user through one or more battery powered actuators.

Background

[0002] A number of forms of iransporting or assistance in moving humans are known. For example, a moving sidewalk includes a moving walking platform where the user either may stand stationary to be propelled by the movement of the platform or may walk along the platform where its movement assists the walking movement. The speed of the moving walkways has varied over the years. The first successful high-speed walkway was installed in 2002 at the Montparnasse - Bienvemte Metro station in Paris. At first it operated at 7 miles per hour (MPH) but due to people losing their balance, the speed was reduced to 6 MPH. (See http://en.wikipedia.org/wiki/Moving_walkway.)

Summary of the Invention

[0003] In one aspect of the disclosure, power shoes for transport of a user are provided, the shoes each include a body portion for individually securing to a user's foot. Each body portion includes one or more actuators, such as powered motors, and transport means, such as belt driven rollers, connected to and driven by the actuators. The transport means is supported on the body portions for moving contact with a ground surface. A control means is provided for activating and controlling the actuators and for driving the transport means. Upon activation of the actuators, the body portions provide moving transport to the user's feet.

[0004] In a further aspect of the power shoes sensors may be connected to the control means. The sensors may be provided to detect the position of the user's foot within the associated body portion. An obstacle sensor or other sensor type may further be provided for sensing objects or the like in a forward direction relative to the user.

[0005] In a further aspect of the powered shoes the body portions may each comprise a sole portion for supporting a user's foot. The sole may comprise a heal portion and a toe portion, with the heal portion being pivotably connected to the toe portion. A sensor may be provided in both the heal portion and the toe portion for determining the force of the user's foot on the relevant portion of the sole. The sensor signals are directed to the control means for assisting in controlling the powered movement of the user's feet.

[0006] In a further aspect of the powered shoes, the control means may be capable of operating the actuators in one or more ways, such as a walking mode, a striding mode, a surfing mode, and/or a riding mode. Preferably, when active, the powered shoes can provide rapid transport beyond the capability of standard striding movement of the user's feet.

[0007] Walking Mode. The powered shoes are able to safely accelerate the user to a speed greater than noraial walking speed. As such, the walking mode of the powered shoes preferably incorporates the user's normal walking stride and increases the user's speed to a value greater than normal walking speed associated with the user's stride. In the walking mode, the user's feet preferably lift off the ground briefly as in normal walking.

[0008] Striding Mode, This mode is similar to the walking mode, but the user does not need to lift their feet from the surface. This movement is similar to a user on an elliptical machine in the gym or on cross country skis. Though their feet may partially lift by flexing, their feet don't fully lift off the ground as they are propelled by the powered shoes over the surface in a gliding motion. [0009] Surfing Mode. In this mode, the user is preferably standing with their feet in a fixed position. The user would be able to ride the powered shoes without moving their feet. In some implementations means may be included to physically or electronically constrain the two shoe bodies together to aid the user in maintaining balance and control.

[0010] Riding Mode. In this mode a user can control movement, such as by adjusting speed and direction, by leaning forward, back, left, or right in logical combinations. The user ^' s attitude will effect the acceleration, speed, and jerk of the shoes. The user can also control the same functions directly using more conventional controls such as joysticks, switches, touch screen (such as through a phone or tablet app) and/or potentiometers. The user controls and sensory controls can also be used in combination in some cases.

[0011] In some implementations, sensors and controls can be used to help provide safety functions such as balance for the wearer and to control the speed, acceleration, and the like regardless of the surface material and slope. The controls may be a combination of user settings and/or computer control based on sensors and the environmental conditions (including slope and ground material).

[0012] Other features of the present invention will become apparent from the detailed description to follow, taken in conjunction with the accompanying drawings.

Brief Description of the Drawings

[0013] For the purpose of illustrating the invention, there is shown in the drawings a form which is presently preferred: it being understood that the invention is not limited to the precise arrangements and instrumentalities shown.

[0014] Fig. 1 shows a perspective view of a shoe-like article having a movement mechanism built therein.

[0015] Fig. 2 shows a top view of the shoe-like article of Fig. 1.

[0016] Fig. 3 shows a schematic bottom view of the show-like article of Figs. 1 and 2 wherein the drive mechanism is illustrated.

[0017] Figs. 4 and 5 show a preferred planetary gear arrangement for the actuator portion of powered shoes. Detailed Description

[0018] Referring now to the drawings, where like numerals identify like elements, there is shown in Fig. 1 an article having the outward appearance of a shoe. The shoe-like article is designated with the numeral 10 and is contemplated to one of a pair of articles to be worn on a user's feet. As will be described in further detail below, the powered shoe 10 includes a drive mechanism for assisting in the movement of the user. For purposes of the present discussion, the operation of a pair of powered shoes 10 and their associated drive mechanism will be described with reference to the structure of the single shoe shown in the figures.

[0019] Each of the powered shoes 10 preferably have the same form, fit and function as standard shoes so that they appear to an observer to be a standard set of shoes. It is also preferred that the powered shoes 10 have a weight similar to that of an ordinary set of shoes, such that they may be comfortably worn and used with or without engagement of the drive mechanism.

[0020] The shoe 10 as shown in Fig. 1 includes a body having an upper body portion 12, a base or sole portion 14, a foot receiving opening 16 adjacent a heel portion 18 of the sole 14, and a toe portion 20, positioned opposite of the heel portion 18 and covered by the upper body 12. A shown in Fig. 1 , an obstacle sensor 22 is positioned adjacent the toe portion of the sole 14. Multiple obstacle sensors 22 may be provided for covering different positioned adjacent the toe portion 20, or other portions, of the sole 14 of the powered shoe. The obstacle sensors may be of a type produced by Sharp Electronics (part no. GP2Y0A21 YK). As an alternative or supplement, an ultrasonic sensor produced by MaxBotix LV, called MaxSonar-EZl , may be used to measure the distance between the toe and objects within a variable range and resolution. In some of the modes for automatic operations, it may be necessary for sensors to measure the relative position of the shoes to one another, and/or to the ground surface. The outside sensor 22 may include one or more sensor for this purpose. The sensors may take any number of forms or combinations thereof, including optical means, acceleroraeters, magnetometers., angular rate sensors, etc. [0021] As illustrated in Fig. 2, a toe force sensor 24 and a heel force sensor 26 are also provided. In addition, the heel portion 18 and toe portion 20 of the sole 14 are pivotable connected to one another at hinge 28. The hinged connection of the heel portion 18 and toe portion of the sole 14 enables flexing of the sole 14 during use of the shoe 10. The hinge connection or operation may be omitted, if desired.

[0022] The drive mechanism 30 is shown in Fig. 3. Two drive belts 32A, 32B are provided and extend in opposite directions from the central shaft 36. Two center rollers 34A, 34B are provided on the shaft. The center shaft 36 and axis of the center rollers 34A, 34B are aligned with the axis of the hinge 28. The front drive belt 32A extends between a front shaft 38 and the center shaft 36. The front drive shaft 38 includes two front rollers 40A, 40B and is mounted on the toe portion 2(5 of the sole 14. The rear drive belt 32B extends between the center shaft 36 and a rear shaft 42, with the rear shaft 42 having two rear rollers 44A, 44B thereon. The rear shaft 42 and its rollers 44 A, 44B are mounted on the rear portion 20 of the sole 14. The user is propelled by the three roller sets 34, 40 and 44 that are driven by the belts 32A, 32B.

[0023] The drive belts 32A, 32B serve as timing belts for the three sets of rollers 34, 40 and 44. The belts 32 include inside notches which engage a toothed portion of the shafts. As an alternative, a chain drive or similar device may be used to direct movement to the multiple rollers or other propulsion devices, another alternative includes a traction or propulsion belt (tread) mounted on and/or supported by rollers. The traction belt would serve as the ground engaging surface and create the movement of the shoes upon engaging drive actuators 50. A tensioning roller or its associated structure may also be included.

[0024] A magnet 46 is shown on one of the front rollers 40B. The magnet 46 communicates with a Hall effect sensor 48 mounted on an adjacent portion of the sole 14. (The Hall effect sensor may be of the type produced by Diodes, Inc., part no. ATS177-PG-A-B.) The Hall effect sensor is a transducer that provides an output signal in response to the passage of the magnetic field of the magnet 46 as it rotates with the rollers 40. The signal from the sensor 48 provides an indication of the speed of the roller and the shoes. The sensor 48 provides a speed control for the drive mechanism 30. Other forms of speed indicators and controllers may be provided. In addition, the location and number of sensors may be changed from that shown in the drawings. A belt encoder or similar device may also be used as pari of the control system to control speed of the rollers.

[0025] As shown in the drawings, the belts 32 are centrally positioned between two roller parts. Other formations and positions may be used without departing from the intended operational result. The drive mechanism or actuator means 30 as shown comprises two drive motors 50 located on the heel portion 18 of the sole 14. The drive motors are connected to one another by a shaft 52. The shaft 52 is connected to a gear box 54. The rear shaft 42 is also connected to the gearbox 54. Hence, the drive motors 50 drive the rear rollers 44A, 44B through the gearbox 54. Rotation of the rear shaft 42 causes a similar rotation of the other rollers 34, 40 through the drive belts 32. Although two drive motors are shown, the number of motors may be changed as desired. Preferably, the actuators or motors are battery powered. Other forms of power generation for the actuator means may include fuel cells, small gasoline or similarly fueled engines, or the like.

[0026] A controller will typically be provided for activating the driving motion of the motors 50. The controller may be provided on one or more of the shoes or may be a separate implement. The control signals may, for example be directed to the shoes by an application (app) provided on a smart phone or the like. The shoe 10 is shown to include control electronics 56, which may include an electronic speed control, such as a Mamba Max Pro by Castle. The controller electronics 56 may further include an Arduino Mini Pro microcontroller and be connected to a Bluetooth transceiver, such as Bluetooth Mate Gold (part no. WRL-12580), and to a (5 VDC) voltage regulator.

[0027] The toe and heel sensors 24, 26 are further connected to the controller electronics 56. These sensors may include force sensitive resistors having an approximately 0.5 inch diameter (for example a SparkFun sensor, part no. SEN-09375) and provide force/weight feedback to indicate the user's phase in the movement cycle. Force sensitive resistors of the type preferred will vary resistance depending on how much pressure is being applied to the sensing area. The more force, the lower the resistance. When no force is being applied to the sensor, its resistance will be relatively large. The sensors are contemplated to sense range of an applied force and output a corresponding signal. Other types of sensors and switches may be used as desired. Preferably, at least two sensor/switch structures are provided, one on the toe portion 20 of the sole 14 and another on the heel portion

[0028] The additional functions and hardware may be included as part of the controller electronics 56 for balancing the user during driving of the rollers 34, 40, 44. For example, an accelerometer (such as a digital accelerometer produced by Analog Devices, part no. ADXL345) and/or an angular rate sensor or gyro (such as a triple-axis digital -output gyro from InvenSense, part no. ITG-3200) may be provided. These devices sense position/motion in three axis directions. However, it is possible that only one axis (pitch) is required for balancing. A second axis (roll) may be used for steering, as may a third axis (yaw). It may also be appropriate to add a magnetometer and GPS sensor to provide additional navigational features, Again, a remote control device may be used for manual activation or for drive control through the electronics positioned on or adjacent the shoe.

[0029] The drive motors 50 are preferably three phase, brushless DC motors, such as part no. AX-4008Q-620KV from Hobby King. The motors 50 are preferably positioned on the same shaft 52 and are wired in series. The motors 50 are preferably combined with a planetary gear set known as a compound planetary differential reduction. This type of gearing was developed by the US Army for portable radar dishes in World War II and is contemplated to provide a compact and efficient structure, in addition to a self-locking feature. An alternative motor structure may be a brushless motor is the Novak Timbuk2 Ballistic Crawling Brushless motor System, part no. 13.5T, #3223.

[0030] The preferred planetary gear arrangement is shown in more detail in Figs. 4 and 5. A normal planetary reduction has a sun gear 60, one or more planets gears 62 that orbit the sun and a ring gear 64 that orbits the planet gears 62, The compound differential planetary reduction has a second ring gear 66. The two ring gears 64, 66 included an identical pitch diameter but a different pitch and number of teeth. For example, the first ring gear 64 may have a pitch of 32 and the second ring gear 66 may have a pitch of 48, both with a pitch diameter of 1.5 inches. The first ring gear 64 is fixed in position on the motor frame, with the other ring gear 66 connected to a bearing (not shown) that will rotate with the output shaft 68, [0031] The planets gears 62 are also formed by two gear parts stacked and locked together. These two gear parts are, again, of the same pitch diameter but of different pitches (and thus a different number of teeth). The two parts of the planet gears 62 line up with the ring gear of the same pitch. As the planet gears 62 orbit the sun gear 60, one part is engaged with the fixed ring gear 66 and orbit inside it. Hence, the ring gear 64 stays engaged with the planets because it is fixed to the motor frame. Since the planet pairs themselves are locked together as one, they both orbit around inside the two ring gears, but the second set of planets that is lined up with the second ring gear 66, the one that is free to rotate as the output, will force that second ring gear 66 to rotate the proportionate difference in the number of teeth between the fixed ring gear 64 and the free ring gear 66.

[0032] This planetary structure of the motor drive 50 creates a reduction as well as having the property of not being back drivable. The second ring gear 66 is only able to move via the difference that is obtained by the teeth counts in the two ring gears 64, 66 as the planets gears 62 orbit the sun gear 60. If the planets do not orbit, there is no differential and second ring gear 66 cannot move. This arrangement provides a desirable speed reduction and a proportionate torque increase, while being automatically self-locking. It also enhances the ability of the motor to resist increasing its revolutions per minute (rpm) if the wearer is walking down hill. The motor does not have to use power to limit speed, and the structure automatically resists the changes in loads occurring during a walk cycle.

[0033] As an alternative to the preferred power transmission structure of the motor drives 50 as shown in Figs. 4 and 5, a manual or electromechanical lock is required for normal walking mode. In addition, in the enhanced walking mode the motor would consume a great deal more power to limit the speed of the user on a down hill slope or during the load changes of the walk cycle. These additional complexities, while feasible, are not preferred as they may decrease operational efficiency of, add weight to and/or add cost to the shoes.

[0034] Each shoe 10 contains a battery 72 for powering the geared motors 50 and the control electronics 56. An electronic speed control is incorporated into the electronics 56, along with a wireless transceiver 58 for each shoe 10 in the pair to communicate with one another. The motors 50 are connected to the drive belts 32 for rotation of the rollers 34, 40 and 44. Further, a number of sensors 22, 24 and 26 provide input into the logic within the electronics 56. At least one sensor 22 is directed forward of the shoe for identification of obstacles. As indicated, there may be more than one obstacle sensor 22 with one aimed above the horizon, for example at 12 degrees above the horizontal position of the shoe on the ground. A second sensor, if provided, may be aimed below the horizontal position, such as at an angle of 12 degrees. The toe sensor 24 and heel sensor 26 are contemplated to be weight sensors and provide feedback on the position of the user's foot within the show during the walking or striding motion.

[0035] When the shoes 10 are first powered up, they start out in a "stop" mode. A command signal insures that the motors and belts are off and locked. The two shoes 10 men establish communication and determine, by reading the toe sensor 24 and heel sensor 26, if both shoes are on the ground. Once both shoes are on the ground, the system will move to a desired movement mode. The weight sensors 24, 26 and wireless coordination of the shoes 10 via the wireless transceiver 58, determine the user's movement by a separation of the two shoes 10. The user status conditions will also be determined and measured by the toe sensor 24 and heel sensor 26 in the two shoes 10. Further, the controller 56 determines the phase of each shoe 10 in the movement cycle, including the heel strike HS, foot flat FF, mid-stance MS, heel rise HR and toe- off TO. This information is available in both shoes and is preferably shared via the wireless transceiver 58. Other devices may be used for communication between the two shoes, such as an infrared range sensor or similar device. The sensors may be included as part of a sensor array within obstacle sensor 22 or otherwise positioned on the shoes.

[0036] The controller may also determine if the stride is "normal" and measure the cadence of the user. Normal may vary from user to user, but typically it has been found that each shoe touches the ground about 60% of the walking cycle, and is in the air 40% of the time. Both feet overlap and are touching the ground about 20% of the cycle. If the sensors 24, 26 detect that the user is walking normally, and no obstacles or safety issues are detected in front of either shoe by the sensor 22, the controller 56 will start the motors 50. A typical startup is performed slowly moving the belts 32 and rollers 34, 40, 44 in the forward direction. In the "walking mode" each step or stride will produce an increase speed until a set maximum speed is reached. The maximum speed may be pre-set or sellable by the user via a remote or switch (not shown) connected to the controller electronics 56. Hence, the speed and operation cycle may vary from user to user depending on user preferences and physical characteristics.

[0037] If an obstacle, such as a set of stairs or another person, i.s detected by the sensor 22 in front of and in close proximity of either shoe 10, the motors 50 in both shoes 10 will come to a stop controlled by the controller 56. Typically, the signal of the obstacle sensor 22 will be given more weight when the shoe 10 is on the ground, as measured by the toe sensor 24 and/or heel sensor 26. The deceleration of the motors 50 will be based on the distance of the obstacle from the shoe 10. The ideal deceleration is 0.1 g or less, but the shoes may be programmed to decelerate at whatever rate is needed to avoid contact with the obstacle.

[0038] The shoes 10 may also decelerate if both shoes are on the ground at the same time outside of a normal walking stride, or if both shoes are off the ground at the same time. As noted earlier, in a normal stride, both shoes are on the ground at the same time about 20% of the cycle time within the stride. The controller 56 will recognize normal walking and will stop the motors 50 in the situation where the amount of time both feet are on the ground simultaneously is determined to be abnormal or not part of a normal stride. Once stopped, when the user again enters a normal walking mode by striding, the motors will once again begin to move as described previously.

[0039] To aid the user in turning or changing directions while walking, especially sharp litmus or turns on steep hills, software may be included within the controller 56 to read the systems sensors (such as the toe sensor 24 and the heel sensor 26) to help determine when the user is making the turn and to assist the user by adjusting the speed of the belts according to the type of turn. For example, if the user is making a u-tura to the left, the bell on the left shoe will typically slow down, while the belt on the right shoe may stay at a constant speed. As an alternative, the motors 50 may simply stop when the control system determines that the user is making a turn, allowing the user to control the turn motion, as they would while walking without the powered shoes.

[0040] The speed of the shoes in the walking mode is preferably controlled by the pace of the user's stride. The shoes amplify the speed of the user's walking motion. In the walking mode, the shoes do not serve as a powered vehicle and further do not create a free rolling operation, such as - π - in roller skates. The control system preferably provides a transparent interface so that the user is does not have to consciously control the shoes, but merely walks normally. The assistance or benefit received by the user of the shoes is similar to that of walking on an airport moving walkway. While the user is walking normally, his/her actual ground speed is faster, without expending extra effort. In walking mode, the ground speed of the powered shoe user may be on the order of 7 MPH. The user's normal walking motion would be contributing about half of this speed rate, while the powered shoes provide the additional speed.

[0041] The control system of the powered shoes in the walking mode will further provide a change in speed, responsive to the users change in stride. The shoes will transparently accelerate and decelerate at 0.1 g or less based in input from the sensors. For example, when coming up to a doorway or curb that requires the user to stop, the user simply reacts normally and slows down the walking pace. In addition, the shoes will sense this change in cadence and the proximity of the doorway or curb will be detected by the obstacle sensor(s) and, as a result, the controller will slow the motor(s) and the belt driven rollers to a comfortable halt. Again, in a normal walking operation the shoes provide velocity amplification. The amount of the increase in speed can be varied to suit conditions either by automatic sensing or through direct user control.

[0042] The riding mode for the shoes 10 is initiated when the shoes are side by side, as measured by the transceiver 58 of by added optical sensors on each shoe. A further condition prior to initiation is using the toe sensors 24 and the heel sensors 26 to determine that the user is balanced. The user will control direction and speed by leaning forward, backward, left and right, with the toe and heel sensors 24, 26 (possibly along with other sensors, such as an accelerometer and/or an angular rate sensor/gyro). When the user is standing balanced evenly, the motors 50 will be off or otherwise disconnected from driving the rollers 34, 40, 44. When the user leans forward, the motors 50 will energize and rotate to cause a forward movement. Speed will be based on how far forward the user leans, the more pressure on the toe weight sensors, the faster the motors will move forward.

[0043] In the riding mode, a reverse movement is also possible. Reverse movement will be created in essentially the same manner as a forward motion except with a shift of weight (lean) in the direction of the user's heels. Again, the amount the user leans backwards will determine the - 3 z - speed of movement. Other alternative movement reaction may be based different lean signals being received by shoes. Whether the shoes are moving forward or in reverse, if the user leans left or right, as determined by the weight differences In the toe sensors 24 and the- heel sensors 26 in both shoes 10, the controller 56 will send the signals to the left and right shoes to change speed relative to one another, creating a turning motion, sometimes referred to differential or skid steering. In the same manner, the control system 56 may be used to provide balance to the user. The controller 56 will attempt to physically keep the shoes under the center of gravity of the user, providing balance, by adjusting the speed and relative of the shoes.

[0044] Another method that may be used for the riding mode, in place of, or in conjunction with the sensors 24. 26, is to use an accelerometer and/or an angular rate sensor/gyro, to provide balance, steering and forward / reverse motions and velocity control. The accelerometer and gyro may be located on the user or on the shoes and connected to the controller 56. The accelerometer and gyro will measure the user's attitude relative to vertical and adjust the speed of the motors 50. The gyro provides the basic angle of the user's center of gravity relative to vertical, and the accelerometer is used to eliminate the gyro's drift error that is inherent to such sensors. Based on this sensor data, the controller will provide commands as needed to perform the desired movement function.

[0045] A number of other operational variations are possible using the structures described herein or with additional elements incorporated therein. As one non-limiting example, the two shoes may be constrained to one another, either physically or electronically. The constraint insures that the user's feet are in acceptable proximity and orientation to one another. In the electronic mode, sensors may be employed to form an electronic interlock that prevents the system from operating outside a set distance.

[0046] As part of the control system or operation software for the controller 56, a sensor or algorithm may be used to determine the skill or current ability of the user (e.g., measuring erratic use, wobbling, uneven balance, etc.). In addition, the rolling conditions of the environment and/or surface (e.g., rough, slope, rocky, icy, etc.) may be determined by sensors or other operational parameters. Further, a maximum speed (which could be zero mph in some cases) may be determined or otherwise set based on sensor or user input. [0047] As noted above, a remote control or control panel may be provided to set and regulate the speed or other operational parameters of the shoes, making adjustments in real time or in response to set parameters or personal information (e.g. height, weight, age, skill, etc.). This remote controller could be an app or program running on a cell phone, computer, tablet, or similar device. Preferably, a single controller is used to control both shoes simultaneously.

[0048] The motors in the two shoes are preferably coordinated to run at the same speed or load, even with varying input from left or right side shoe. The shoes preferably need to communicate with one another for coordination. As indicated above, this coordination can be performed through wireless communication and/or optical sensor means.

[0049] As shown in the figures, the hinge 8 permits the sole portion 14 to ilex. As shown, the hinge is located adjacent (and preferably behind) the ball of the user's foot. Other flexing arrangements are possible. The shoes may alternatively include a rigid sole. In the preferred structure, the shoes may allow for natural foot abduction or out-toeing at an angle comfortable and natural for the user. This may be accomplished by the alignment of the rollers or otherwise. The angle is typically 6 degrees from center, but can vary from one user to another. Hence, a rotational control within the rollers may create an appropriate adjustment.

[0050] The provided batteries will ideally be light weight and compact, such as lithium polymer structure, mounted on or within the shoes in such a location and configuration that they can be removed or charged. The batteries may also be mounted on the user's legs or body and connected through wires. The batteries may preferably be mounted at or above the ankle to reduce the effect of their weight on the foot.

[0051] As discussed above, the drive system is preferably self-locking. If the shoe unit is not powered up or in an active mode, it will not be able to roll. The drive system further will resist movement from momentum or gravity. The gear reduction provided by the gear box (54) may be self-locking, such as the planetary gear set described, which is considered more efficient than a worm drive. [0052] A further modification of the powered shoes may serve to reduce power consumption by turning off the motors when they are off the ground during each walk cycle. A further modification to the control of the powered shoe may result from adjustment of the speed of belts based on the phase of the walking cycle. For example, as the shoe is about to enter the toe-off phase, the motor may stop momentarily to allow the user to push off the ground within the normal stride. The present disclosure shows and describes one or more exemplary embodiments.

[0053] It should be understood by those skilled in the art from the foregoing that various other changes, omissions and additions may be made therein, without departing from the spirit and scope of the contemplated invention, with the scope of the invention being defined by the foregoing claims. Further, the terms herein are used in a generic and descriptive sense and are not necessarily for purposes of limitation. The scope of the invention is set forth in the following claims.