Abstract:
A safety razor has a handle and a cartridge selectively detachable from the handle. The cartridge has at least one blade with a sharp cutting edge and an expected shaving utility. A connecting structure is coupled to the handle and attaches or detaches the cartridge from the handle in response to a detachment action performed by a user. A detector within the handle has an actuator coupled to the connecting structure and a sensor for generating a signal, wherein the actuator applies an action on the sensor during the action and the sensor generates the signal in response to the action.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims priority under 35 U.S.C. §119(e) from U.S. Provisional Patent Application Ser. No. 60/994,075, filed Sep. 17, 2007. 
    
    
     BACKGROUND 
     This invention relates to safety razors for wet shaving and, more specifically, to powered wet shaving systems with disposable blade cartridges. 
     Some wet shaving razors have been provided with battery-powered devices such as motors for vibrating a shaving cartridge. One such vibrating wet shaving razor is that sold by The Gillette Company under the trade name the Gillette Fusion™ razor. This razor features a battery disposed in a chamber within its handle, and a motor coupled to the distal tip, on which is mounted a replaceable cartridge, and electronic controls for razor operation. 
     Some wet shaving razors attempt to track blade wear and indicate when the cartridge should be replaced. In the course of shaving hundreds of hairs on a daily basis, the blades of a shaving cartridge inevitably grow duller. This dullness is difficult to detect by visual inspection. In too many cases, by the time a user realizes that a blade is too dull to use, he has already begun what will be an unpleasant shaving experience. 
     Some wet shaving razors have mechanical shave counters for manual counting of each shave. Other wet shaving razors have electronic shave counters that track shaving action (e.g., exposing the razor to moisture, contacting skin with blades, moving or applying forces on the blades or cartridge, gripping the handle, activating a vibration source) as a proxy for blade wear. Some electronic shave counters count discrete shaving uses (e.g., activation of a vibration source) while others count time that the razor is active (e.g., vibrating) or the time that the razor spends shaving (e.g., detecting skin contact or cartridge movement). Some wet shaving razors estimate a remaining cartridge life based on the tracked shaving use. 
     Some wet shaving razors have an indicator to inform a user that the cartridge should be replaced. Some indicators are numeric displays, either mechanical or electronic, showing a count of accumulated shaving uses. The user must learn by experience what number of shaves to expect from a cartridge and must remember to change the cartridge at that number of shaves. Some indicators abruptly inform the user that the cartridge should be replaced, such as by changing vibration (e.g., changing vibration frequency, vibrating in a pattern), emitting an audible sound, or activating a light source, without a warning that the suggested replacement is approaching. 
     One wet shaving razor includes an indicator having a series of seven LEDs. When the razor senses that a cartridge has been attached, the entire series is lit to indicate the cartridge has all of a predetermined initial shaving time remaining. As the razor is used, the initial shaving time is counted down and LEDs are extinguished in proportional sharp steps. When all the LEDs are extinguished, no shaving time remains and the cartridge should be replaced. Indicators with more LEDs tend to consume more power and cost more than indicators with fewer LEDs. 
     Mixing colors of light, also called additive color mixing, is known. Some applications of additive color mixing, such as signs, ornamental displays, and decorative lighting, for example, mix light of two or more LEDs to create light colors different than either LED. 
     Using materials that change electrical properties in response to a change in applied forces in switches are known. 
     A need exists to overcome the shortcomings aforementioned. 
     SUMMARY 
     In one aspect, the invention features a safety razor having a handle and a cartridge selectively detachable from the handle. The cartridge has at least one blade with a sharp cutting edge and an expected shaving utility. A connecting structure is coupled to the handle and attaches or detaches the cartridge from the handle in response to an action performed by a user. A detector within the handle has an actuator coupled to the connecting structure and a sensor for generating a signal, wherein the actuator applies an action on the sensor during the action and the sensor generates the signal in response to the action. 
     Certain implementations of the invention may include one or more of the following features. The sensor may be conductive, capacitive, magnetic, resistive, proximity, pressure sensitive, chemical, inductive, electrical, mechanical, electromechanical, electromagnetic, and combinations thereof. The sensor is convertible between a first level and second level in response to the action. 
     The sensor has a resistive member comprising a polymer and particles of metal or semi-conducting material. The resistive member has a first level of conductance when quiescent and a second level of conductance when the action is applied by the actuator. The sensor has first and second electrodes each electrically coupled to the resistive member. The resistive member is configured to electrically couple the first and second electrodes when having the second level of conductance and to electrically uncouple the first and second electrodes when having the first level of conductance. The sensor includes a pressure sensitive resistor for generating the signal in proportion to the pressure applied by the actuator. 
     The razor has an electrical arrangement for detecting and tracking utility of the razor and determining a remaining shaving utility of the cartridge based on an expected utility and a tracked utility. The electrical arrangement receives the signal and resets the tracked utility when the signal exceeds a threshold value. The sensor includes a microswitch. The connecting structure has a button and the action includes pushing the button through a detachment stroke. The actuator includes a beam member projecting from the button transversely to an axis of the of the detachment stroke. 
     The razor has an electrical arrangement for detecting and tracking utility of the razor, determining a remaining shaving utility based on the beginning shaving utility and the tracked utility, and resetting the tracked utility in response to the signal. Resetting the tracked utility includes attaching or detaching the cartridge with the connecting structure. The electrical arrangement has an input source. 
     The input source detects user activation of an electrical device. The electrical arrangement detects the blade unit contacting a shaving surface. The electrical arrangement tracks a number of contacts between the cartridge and the shaving surface. The electrical arrangement tracks an accumulating time period that the cartridge contacts the shaving surface. 
     The electrical arrangement detects pivotal displacement of the cartridge from a rest position. The electrical arrangement tracks a number of pivotal displacements from the rest position. The electrical arrangement tracks an accumulating time period of pivotal displacement from the rest position. The electrical arrangement detects force acting on the cartridge. The electrical arrangement compares the detected force to a threshold value and tracks a number of occurrences that the detected force exceeds the threshold value. The electrical arrangement compares the detected force to a threshold value and tracks an accumulating time period that the detected force exceeds the threshold value. The electrical arrangement is reset by attaching/detaching the cartridge to/from the connecting structure or by continually depressing the power switch for at least 1 second. 
     Other features and advantages of the invention will be apparent from the description and drawings, and from the claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a top view of a razor according to one embodiment of the present invention, with the cartridge separated from the handle. 
         FIGS. 1A and 1B  are cross sectional views of the razor handle of  FIG. 1 . 
         FIG. 2  is a partial side view of the razor handle of  FIG. 1  showing components therein. 
         FIG. 3  is a circuit diagram for a cartridge detachment sensor. 
         FIG. 4  is a partial bottom view of a razor head of  FIG. 1 . 
         FIGS. 5 and 5A  are partial side views of the razor handle of  FIG. 1  showing components therein. 
         FIG. 6  is an exploded view of a button showing a sensor. 
         FIG. 7  shows a controller for determining and indicating a remaining shaving utility of a shaving cartridge. 
         FIGS. 8A and 8B  shows the signals output by components of a cartridge life indicator. 
         FIG. 9  shows an embodiment of the controller of  FIG. 6 . 
         FIG. 10  shows a method of determining remaining shaving utility of a cartridge and indicating the remaining shaving utility to a user. 
     
    
    
     DETAILED DESCRIPTION 
     Razor Structure 
     Referring to  FIGS. 1 ,  1 A, and  1 B, a razor  1  has a cartridge  18  and a handle  10  that includes a razor head  12 , a grip tube  14 , and a battery shell  16 . Razor head  12  includes a connecting structure  17  for connecting cartridge  18  to handle  10  and a release mechanism  19  for releasing cartridge  18  from connecting structure  11 . The grip tube  14  is constructed to be held by a user during shaving, and to contain the components of the razor that provide the battery-powered functionality (electrical arrangement) of the razor, e.g., an electrical device  28 , a printed circuit board (“PCB”)  30 , an electronic switch  29  and the light  31  mounted on the printed circuit board. The electrical device  28  may be a motor, a vibration generator, a heat source, a pump, a radiation generator, a magnetic field generator, an electrical field generator, an electromagnetic field generator, chemical source, or combinations thereof may be substituted for vibration electrical device  28 . 
     The grip tube  14  includes an actuator button  22  that may be pressed by the user to actuate the battery-powered functionality of the razor via an electronic switch  29 . In some examples, the grip tube may also include a transparent window  24  to allow the user to view a light  31  or display or other visual indicator, e.g., an LED or LCD, which provides a visual indication to the user of battery status and/or other information. As described so far, razor handle  10  is known and described in further detail in U.S. application Ser. No. 11/220,015, filed on Apr. 10, 2005, published as U.S. Pat. App. Pub. No. 2007/0050981. The razor may be powered by various energy sources, including but not limited to, radiant, kinetic, potential, thermal, magnetic, gravitational, sound energy, light energy, electromagnetic, chemical, and combinations thereof. 
     Referring to  FIGS. 1 ,  1 A, and  2 , an indicator  26  is disposed toward forward end  20  of grip tube  14  and includes, in some examples, LEDs  32  and  34  electrically coupled to a controller  40  through PCB  33 . In other embodiments, the indicator is located any place on or within the razor. Other indicators, e.g., visual, audible, olfactory, sensory, or tactile, can be used. While indicator  26  may include two different colored light sources, three or more light sources could be used. In one example, LED  32  emits blue light and LED  34  emits white light, though any suitable two colors could be used. 
     Indicator  26  further includes a light mixing member  36  enclosing LEDs  32  and  34 . When both LEDs  32  and  34  emit lights of different colors to indicate the remaining shaving utility of cartridge  18 , member  36  mixes the two colors and appears to signal one color, as described in more detail below. In an example, light mixing member  36  is transparent neck portion  38  extending around the circumference of grip tube  14  and completely enclosing end  20 . In other examples, light mixing member  36  could be any portion of handle  10  or cartridge  18  configured to mix light from LEDs  32  and  34  such as a window, lens, light pipe, or some combination thereof, in neck portion  38 , grip tube  14 , or cartridge  18 . Neck portion  38  preferably is molded from a clear Zylar acrylic co-polymer, available from Nova Chemicals Corp., Moon Township, Pa., but could be formed from any suitable clear or translucent material. 
     Razor head  12  includes a release mechanism  19  including button  50  having a base member  52  with forwardly projecting pusher arms  56  for releasing cartridge  18  from connecting structure  17 . A gripping member  54  is disposed on the base member  52  for pushing engagement when releasing cartridge  18 . As described so far, cartridge release mechanism is known and described in further detail in U.S. Pat. No. 7,197,825. 
     Cartridge Detachment Sensor 
     In some examples, the razor head  12  includes a sensor  60  electrically coupled to controller  40  through lines  62  for sensing when the cartridge  18  is attached to or detached from razor head  12 . Referring to  FIGS. 1 ,  2  and  4 , in one example, sensor  60  may include a microswitch  76  disposed in razor head  12  and a pin member  72  projecting from button  50  transversely to forward direction  74 . Microswitch  76  may be a normally closed or normally open switch having a forwardly biased toggle member  78  and is electrically coupled to controller  40  by lines  80 . When button  50  is in a rearward position, pin member  72  urges toggle member  78  rearwardly and maintains microswitch  76  in an “cartridge attached” state (e.g., closed for a normally closed microswitch). When the button  50  is pushed forwardly in direction  74  to detach the cartridge  18 , the forward bias of the toggle member  78  changes the state of microswitch  76  to a “cartridge detached” state (e.g., open for a normally closed microswitch). Alternatively, microswitch  76  may have a rearwardly biased toggle member  78  that is urged forwardly by pin member  72  to change switch from “cartridge attached” to “cartridge detached” state. 
     Referring to  FIGS. 2 and 3 , in other examples, sensor  60  may include a PCB  64  mounted in razor head  12  and having electrodes  66   a  and  66   b  thereon. As best seen in  FIG. 3 , fingers  68   a  of electrode  66   a  are interlaced with but are not electrically coupled with fingers  68   b  of electrode  66   b . Resistive member  70  electrically contacts but generally does not electrically couple electrode fingers  68   a  and  68   b . In some examples, resistive member  70  may be formed of a quantum tunneling composite (QTC) of finely dispersed conductive metallic particles, such as metallic alloy or reduced metal oxide particles, in a non-conductive matrix material, such as an elastomer. In QTCs, the metal particles are dispersed closely to each other but do not make contact to form direct conductive paths through the composite while in a quiescent state. When under pressure, however, the particles move close enough together that highly conductive paths form from quantum tunneling between the conductive particles. When the pressure is removed, the QTC returns to its non-conductive quiescent state. In one example, resistive member may be an about 4 mm by about 2 mm portion of QTC pills available from PeraTech Ltd. North Yorkshire, England. As the button  50  is pushed forward to release cartridge  18 , pin member  72  applies pressure to resistive member  70  changing its state from non-conductive to conductive and electrically coupling electrodes  66   a  and  66   b . Consequently, the change in voltage across electrodes  66   a  and  66   b  may be detected by controller  40 . 
     In other examples, resistive member  70  may be formed from a pressure sensitive polymer having conductive (e.g., carbon) or semi-conductive (e.g., silicon) particles dispersed therein. Generally, a pressure sensitive polymer would electrically couple electrodes  66   a  and  66   b  and has a base resistance while in a quiescent state and increase or decrease resistance as a function of pressure applied thereto. In other examples, the resistive member  70  is made of a polymer, metallic particles, a semi-conductive material, combinations thereof, or other materials suitable for the intended purpose. 
     Referring to  FIGS. 5 and 5A  in still other examples, sensor  60  may include a magnetic member  82  disposed on button  50  and reed switch  84  electrically coupled to controller  40  in a “cartridge attached” state (e.g., closed) ( FIG. 5 ). As the button  50  is pushed forwardly along direction  74  to release cartridge  18 , the magnetic field of member  82  changes reed switch  84  to a “cartridge detached” state (e.g., open) ( FIG. 5A ). When button  50  is released and moves rearwardly, reed switch  84  returns to a “cartridge attached” state. Other switches can be used in place of reed switch  84 , e.g. a Hall effect switch. 
     Referring to  FIG. 6 , in still other examples, sensor  60  may be disposed on the base member  52  of button  50 , which may be formed of a relatively hard material, such as an acetyl polymer. In another embodiment, a gripping member  54  covers button  50 . Gripping member can be made of any suitable material, e.g. relatively soft material, elastomer, hard material, or combinations thereof. Sensor  60  will sense the force applied to the gripping member  54  to overcome the rearwardly biasing force of spring  58  ( FIG. 1A ) and move the button  50  forward for cartridge release as well as possible additional forces when detaching cartridge  18  and bottoming out of the stroke of button  50 . 
     In one example, sensor  60  may be a pressure sensitive resistor  90  electrically coupled to controller  40  by lines  92  that changes resistance in proportion to the force applied to active portion  94  disposed under the gripping portion  54 . A suitable pressure sensitive resistor  90  is an Interlink FSR400 force sensitive resistor, available from Interlink Electronics, Inc., of Camarillo, Calif. In another example, sensor  60  may include a QTC resistive member and electrodes similar to those described above. 
     In other examples, the sensor may be of the type selected from conductive, capacitive, magnetic, resistive, proximity, pressure sensitive, chemical, inductive, electrical, mechanical, electromechanical, electromagnetic, and combinations thereof. Other sensors suitable for the intended purpose could likewise be used. In some examples, the sensor is convertible between a first level and second level in response to the action being applied. The sensor can be converted from the second level to the first level in response to the action being removed. 
     Cartridge Life Indication 
     New shaving cartridges have a finite quantity of expected life, use, or utility (“expected utility”), including, but not limited to, blade sharpness, lubrication, cleanliness, or other deteriorating qualities. Blades eventually dull and shaving performance deteriorates to a point at which a cartridge should be replaced. While the expected utility may vary from user to user for a number of reasons, assumptions may be made about the expected utility after which a cartridge should be replaced and consumer testing may provide data for maximizing expected utility across a broad range of users. Even if an individual user has a different expected utility than what is assumed, knowing the difference between the expected utility and that user&#39;s actual use (i.e., “remaining shaving utility”) may guide the user in deciding when to replace a cartridge. 
     Referring to  FIG. 7 , in some examples, razor  1  includes a cartridge life detection system  100  for tracking shaving utility of cartridge  18  and indicating remaining cartridge life. Controller  40  receives input from input source  102  when a user is shaving. In some examples, the input may be activating electrical device  28  by actuating switch  22 . In other examples, the input could be the time that electrical device  28  is active. In still other examples, the input could be instances of time spent with contact between a user&#39;s skin and cartridge  18 . One method of detecting skin contact is detailed in U.S. application Ser. No. 11/799,843. In still other examples, the input could be instances of or accumulated time of detected movement between the cartridge  18  and handle  10  or detected gripping of handle  10  by a user. In still other examples, one or more of the above inputs could be combined to determine when a user is shaving and cartridge  18  is being used. 
     Shave detector  104  determines whether the input from input source  102  should be counted and filters out inadvertent input. In one example, shave detector  104  times how long electrical device  28  remains active. After a period of time, such as 15 seconds, for example, it is likely that shaving is occurring and shave detector  104  allows the input from source  102  to be counted. In some examples, controller  40  includes a lockout timer  106  that counts down a period of time during which shaving input is not counted. For example, a user may momentarily switch off electrical device  28  during use or switch  22  may be inadvertently pressed while razor  1  is being stored between uses. Treating these inputs as separate and distinct “shaves” that reduce the remaining shaving utility of a cartridge would make system  100  less precise. In one example, lockout timer  106  disregards input from shave detector  104  for four hours after electrical device  28  is activated. 
     Shave counter  108  receives and tracks the shaving input received from shave detector  104 , storing the accumulated shaving input (i.e., actual utility) in memory  110  while sensor  60  remains in a “cartridge attached” state. Shave counter  108  compares the tracked shaving input against an expected shaving utility, stored in memory  110 , for example, and determines the remaining shaving utility of cartridge  18 . In one example, counter  108  compares the number of electrical device  28  activations, filtered by shave detector  104  and lockout timer  106 , as described above, and compares that to an expected number of activations. In some examples, the expected number of activations is greater than about 8, between about 8 and about 20, and about 14. 
     Controller  40  clears the accumulated shaving input from shave counter  108  and memory  110  when sensor  60  is in a “cartridge detached” state. In some examples, the cartridge detached state may be closing of a circuit, such as by closing microswitch  76  or reed switch  84  or by applying pressure to a resistive member  70  formed of QTC. In other examples, the cartridge detached state may be the opening of a circuit, such as by opening microswitch  76  or reed switch  84 . In still other examples, the cartridge detached state may be a voltage across a resistive member  70  formed from a pressure sensitive polymer or across a pressure sensitive resistor  90  that exceeds a threshold value. In another example, the cartridge detached state may be achieved by continually depressing the power switch for at least 1 second. 
     Although the expected shaving utility may be programmed in controller  40  during manufacture, it need not be a fixed value. In some examples, system  100  could be configured to permit a user to adjust the expected shaving utility. In other examples, system  100  could automatically adjust the expected shaving utility based on a user&#39;s history of utility per cartridge. For example, shave counter  108  could remember the number of counted electrical device  28  activations for the prior five cartridges and adjust the expected shaving utility of the next cartridge to the average utility of the prior five. 
     Referring to  FIGS. 7 ,  8 A, and  8 B, in some examples, controller  40  indicates the remaining shaving utility of cartridge  18  with output light  113  emitted by LEDs  32  and  34  and mixed in light mixing member  36 . Preferably, LEDs  32  and  34  emit contrasting colored lights, such as blue and white, for example. Pulse width modulator generates signals  114  and  116  to illuminate LEDs  32  and  34 , respectively, at low and high voltage levels. When the signal pulses (i.e., higher voltage) are relatively long compared to the time between pulses (i.e., lower voltage), such as signal  114 , the LED emits a relatively bright light. Conversely, when the pulses are relatively short compared to the time therebetween (e.g., signal  116 ), the LED emits a relatively dim light. 
     By mixing two lights of contrasting color and variable brightness, system  100  is able to communicate a wide and gradual range of colored output light  113  representing remaining cartridge life to a user with few light elements and low power consumption. In some examples, the color of LED  32  represents remaining shaving utility, with the full brightness representing full remaining shaving utility (i.e., expected utility). The color of LED  34  represents the absence of remaining shaving utility, with the full brightness representing no remaining shaving utility and that the cartridge should be replaced. For example, sending signal  114  to a blue LED  32  (i.e., producing a bright blue light) and signal  116  to a white LED  34  (i.e., producing a pale white light) results in color mixing member  36  emitting a relatively deep blue output light  113 , indicating more remaining shaving utility. Sending signal  118  to a blue LED  32  (i.e., producing a pale blue light) and signal  120  to a white LED  34  (i.e., producing a bright while light) results in member  36  emitting a relatively pale blue output light  113 , indicating less remaining shaving utility. The two lights may be mixed so that output light  113  maintains steady brightness or varies in brightness over the range of colored light output. The two lights may be changed proportionally to the remaining shaving utility or non-proportionally (e.g., exponentially). Each light may be changed dependently or independently of the other. In other examples, light sources other than LEDs could be used. In still other examples, more than two light sources could be used. Additive light mixing of three primary colors could be used to generate the entire range of visible colors, for example. 
     Referring to  FIG. 9 , a configuration of controller  40  may be implemented in a programmable-system-on-chip, such as CY8C21634, available from Cypress Semiconductor Corp., of San Jose, Calif. Controller  40  includes a microcontroller U 1 . The integrated switched mode pump (SMP) in conjunction with L 1 , D 4  and C 2  boosts a 1.4V alkaline battery coupled by VBATT to 3.3V (VCC). Razor  1  is turned on by switch  22  (SW 1 ) which has a weak pull up resistor R 1 . Microcontroller U 1  detects the activation of switch  22  through a General Purpose Input Output (GPIO). Microcontroller U 1  turns electrical device  28  on and off though transistor Q 1 . D 3  is used to protect controller  40  from back EMF from electrical device  28 . Microcontroller U 1  directly powers the LEDs  32  and  34  through small current limiting resistors R 2  and R 3 . As discussed above, controller  40  controls the brightness of the LEDs  32  and  34  through Pulse Width Modulation (PWM). The output for the LED  32  (pin P 2 [ 1 ]) is also fed back into the microcontroller U 1  to create the inverse PWM for the LED  34  output (pin P 0 [ 6 ]). A low battery indicator light  31  is provided by the red LED (D 2 ) and its current limiting resistor R 5 . Microcontroller U 1  can detect the removal of cartridge  18  through cartridge detachment sensor  60  using the potential divider formed by R 6 . The microcontroller U 1  monitors this activity using another GPIO (pin P 0 [ 1 ]). Capacitor C 4  provides filtering on the signal from cartridge detachment sensor  60 . Of course, controller  40  could be implemented in other ways, such as by using discrete components (e.g., transistors, diodes, resistors, and capacitors) or customized ASIC configured for the functionality described herein. 
     Referring to  FIG. 10 , in some examples a method  200  of controlling razor  1  begins with razor  1  being powered up at step  202  when a user presses switch  22 . Electrical device  28 , e.g. motor, starts at step  204  and pulse width modulation of a blue LED  32  and a white LED  34  begins ( 206 ,  208 ) to bring razor  1  into “running” mode at step  210 . If razor  1  is in running mode for more than 15 seconds ( 212 ) and more than four hours have passes since the last razor power up ( 214 ) then razor  1  has accumulated a shaving utility. Accordingly, pulse widths to blue LED  32  are incrementally decreased, slightly dimming LED  32  ( 216 ) and pulse widths to white LED  34  are incrementally increased ( 218 ), slightly brightening LED  34 . This results in a slight fading of blue colored output light  113  emitted by light mixing member  36 . As more shaving utilities are accumulated, output light  113  eventually becomes entirely white, at which time cartridge  18  should be replaced. 
     While in running mode, if switch  22  is actuated at step  220 , razor  1  enters power down mode at step  222 , in which the motor ( 224 ) and LEDs  32  and  34  ( 226 ,  228 ) are stopped, and then enters sleep mode at step  230 . While in sleep mode, switch  22  and sensor  60  are monitored ( 232 ,  234 ). If cartridge  18  is detached, pulse width modulation for blue LED  32  is set to 100% at step  236  and modulation for white LED  34  is set to 0% modulation at step  238 . If switch  22  is actuated during sleep mode at step  232 , razor  1  re-enters power up mode at step  202 . 
     The dimensions and values disclosed herein are not to be understood as being strictly limited to the exact numerical values recited. Instead, unless otherwise specified, each such dimension is intended to mean both the recited value and a functionally equivalent range surrounding that value. For example, a dimension disclosed as “40 mm” is intended to mean “about 40 mm.” 
     Every document cited herein, including any cross referenced or related patent or application, is hereby incorporated herein by reference in its entirety unless expressly excluded or otherwise limited. The citation of any document is not an admission that it is prior art with respect to any invention disclosed or claimed herein or that it alone, or in any combination with any other reference or references, teaches, suggests or discloses any such invention. Further, to the extent that any meaning or definition of a term in this document conflicts with any meaning or definition of the same term in a document incorporated by reference, the meaning or definition assigned to that term in this document shall govern. 
     While particular embodiments of the present invention have been illustrated and described, it would be obvious to those skilled in the art that various other changes and modifications can be made without departing from the spirit and scope of the invention. It is therefore intended to cover in the appended claims all such changes and modifications that are within the scope of this invention.