Patent Abstract:
An accessory for providing mechanical communication between a rotatable latching shaft and an actuation device of an electrical circuit breaker includes a lever, a working surface, and a snap fitting. The lever includes an engagement orifice. The engagement orifice is receptive to the rotatable latching shaft. The working surface is in mechanical communication with the actuation device. The snap fitting is securely mated with the rotatable latching shaft.

Full Description:
BACKGROUND OF THE INVENTION  
       [0001]     The present invention relates to an accessory for an air circuit breaker. An accessory is typically designed to fit onto a latching shaft included in the circuit breaker. The accessory is often used to provide communication between a latching shaft and an actuation device within the circuit breaker.  
         [0002]     Air circuit breakers are commonly used in electrical distribution systems. A typical air circuit breaker comprises a component for connecting an electrical power source to electrical power consumer called a load. The component is referred to as a main contact assembly. A main contact is typically either opened, interrupting a path for power to travel from the source to the load, or closed, providing a path for power to travel from the source to the load. In many air circuit breakers, the force necessary to open or close the main contact assembly is provided by an arrangement of compression springs. When the compression springs discharge, they exert a force that provides the energy needed to open or close the main contacts. Compression springs that provide a force to close the main contacts are often called closing springs. Compression springs that provide a force to open the main contacts are often referred to as contact springs.  
         [0003]     In many air circuit breakers, the mechanism for controlling the compression springs comprises a configuration of mechanical linkages between a latching shaft and an actuation device. The actuation device may be manually or electrically operated. An electrically operated actuation device generally operates when a particular electrical condition is sensed, for example, under voltage or remote operation of breaker for closing and opening conditions. The actuation device within the circuit breaker typically imparts a force onto an accessory. The accessory then translates the force from the actuation device into a rotational force exerted on the latching shaft. The latching shaft then rotates. This rotation is translated through the mechanical linkages to unlatch or activate either the closing springs or the contact springs. There is typically a first latching shaft mechanically linked to the closing springs called the closing shaft. A second latching shaft is mechanically linked to the contact springs called the tripping shaft.  
         [0004]     As each actuation device acts upon the latching shaft via a corresponding accessory, the accessory acts as a lever converting a linear force from the actuation device to a rotational force on the latching shaft. The accessory is disposed in contact with the latching shaft and attached to the latching shaft by a fixing mechanism. A common fixing mechanism typically includes a threaded fastener, a rivet joint or a pin assembly. Additionally, the fixing mechanism is normally metallic. Thus, a typical fixing mechanism requires selective local heat treatment of the latching shaft, tapping of the latching shaft and the accessory, riveting, or a pin assembly. These processes add to the cost and time of production. Additionally, the fixing mechanism tends to loosen over time.  
         [0005]     Thus, it is desirable to reduce the time and cost of production by developing a fixing mechanism that eliminates metallic threaded fasteners, rivet joints and pin assemblies. Eliminating metallic threaded fasteners, rivet joints and pin assembly fixing mechanisms may also prevent loosening of fixing mechanisms over time.  
       BRIEF DESCRIPTION OF THE INVENTION  
       [0006]     Exemplary embodiments of the invention include an accessory for providing mechanical communication between a rotatable latching shaft and an actuation device of an electrical circuit breaker. The accessory includes a lever, a working surface, and a snap fitting. The lever includes an engagement orifice. The engagement orifice is receptive to the rotatable latching shaft. The working surface is in mechanical communication with the actuation device. The snap fitting is securely mated with the rotatable latching shaft.  
         [0007]     Further exemplary embodiments of the invention include an accessorized shaft in mechanical communication with an actuation device of a circuit breaker. The accessorized shaft includes a rotatable latching shaft and an accessory. The accessory includes a lever, a working surface, and a snap fitting. The lever includes an engagement orifice. The engagement orifice is receptive to the rotatable latching shaft. The working surface is in mechanical communication with the actuation device. The snap fitting is securely mated with the rotatable latching shaft.  
         [0008]     Further exemplary embodiments of the invention include a mechanism that operates a main contact assembly of a circuit breaker via mechanical communication between the mechanism and a spring. The mechanism includes an actuation device, a rotatable latching shaft, a mechanical linkage, and an accessory. The mechanical linkage provides the mechanical communication between the rotatable latching shaft and the spring. The accessory includes a lever, a working surface, and a snap fitting. The lever includes an engagement orifice. The engagement orifice is receptive to the rotatable latching shaft. The working surface is in mechanical communication with the actuation device. The snap fitting is securely mated with the rotatable latching shaft.  
         [0009]     The above, and other objects, features and advantages of the present invention will become apparent from the following description read in conjunction with the accompanying drawings, in which like reference numerals designate the same elements.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]     Referring now to the drawings wherein like elements are numbered alike in the several FIGURES:  
         [0011]      FIG. 1  is an aspect view of an exemplary embodiment of a circuit breaker having accessories and a closing shaft and a tripping shaft;  
         [0012]      FIG. 2  is a side view of a the exemplary embodiment of a circuit breaker of  FIG. 1  showing a shunt coil in communication with a first tripping accessory;  
         [0013]      FIG. 3  is a side view showing the opposite side of the exemplary embodiment of a circuit breaker in  FIG. 1  showing an undervoltage coil in communication with a second tripping accessory;  
         [0014]      FIG. 4  is a perspective view of a tripping shaft from an exemplary embodiment;  
         [0015]      FIG. 5  is a cross section view of first flat surfaces of a tripping shaft from an exemplary embodiment showing a section cut with background removed;  
         [0016]      FIG. 6  is a cross section view of a third flat surface of a tripping shaft from an exemplary embodiment showing a section cut with background removed;  
         [0017]      FIG. 7  is a perspective view of a first tripping accessory from an exemplary embodiment;  
         [0018]      FIG. 8  is a perspective view of a second tripping accessory from an exemplary embodiment;  
         [0019]      FIG. 9  is a perspective view of a third tripping accessory from an exemplary embodiment;  
         [0020]      FIG. 10  is a perspective view of a closing shaft from an exemplary embodiment;  
         [0021]      FIG. 11  is a perspective view of a first closing accessory from an exemplary embodiment;  
         [0022]      FIG. 12  is a perspective view of a second closing accessory from an exemplary embodiment;  
         [0023]      FIG. 13  shows a perspective view of an exemplary embodiment in which the tripping shaft is fully accessorized; and  
         [0024]      FIG. 14  shows a perspective view of an exemplary embodiment in which the closing shaft is fully accessorized. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0025]     An embodiment of the present invention is an air circuit breaker. However, it is contemplated that the method and apparatus described may be implemented in other electrical circuit breakers. Additionally, the method and apparatus described are suited to use in either more complex or simpler designs involving accessories than those discussed with respect to the exemplary circuit breaker below.  
         [0026]      FIG. 1  is an aspect view of an exemplary circuit breaker  10  having an accessory and a rotatable latching shaft. The rotatable latching shaft includes either a closing shaft  20  or a tripping shaft  30 . Closing and tripping shafts  20  and  30  are mechanically communicated to compression springs (not shown) via mechanical linkages  40 . Compression springs include a closing springs and a contact springs. Mechanical linkages  40  allow a rotation of the closing shaft  20  to release the energy stored in closing springs to shut or close a main contact assembly (not shown). When the main contact assembly is closed, electrical power passes from an electrical source (not shown) upstream of the circuit breaker  10  to an electrical load (not shown) downstream of the circuit breaker  10 . Mechanical linkages  40  also allow rotation of the tripping shaft  30  to release the energy stored in contact springs to open the main contact assembly. When the main contact assembly is opened, electrical power is interrupted from an electrical source upstream of the circuit breaker  10  to an electrical load downstream of the circuit breaker  10 .  
         [0027]     Circuit breaker  10  includes an actuation device. The actuation device typically responds to an electrical control input or a mechanical control input. Examples of the actuation device include but are not limited to a shunt coil  12 , a closing coil  14 , and an undervoltage coil  16 , a trip free assembly (not shown), a trip coil (not shown), a racking interlock (not shown), and a manual device (not shown). In an exemplary embodiment shunt coil  12 , closing coil  14 , and undervoltage coil  16  are mounted on a top portion of the circuit breaker  10 . The shunt coil  12  is actuated by an electrical input signal. When actuated, shunt coil  12  outputs a linear mechanical force that is capable of translation to the tripping shaft  30 . The closing coil  14  is also actuated by an electrical input signal. When actuated, closing coil  14  outputs a linear mechanical force in a direction shown by arrow  19  that is capable of translation to the closing shaft  20 . Although an exemplary embodiment discloses the actuation device imparting a linear mechanical force on the accessory, other methods of imparting a force are also contemplated. The undervoltage coil  16  is actuated by a low voltage condition of the electrical source. When actuated, undervoltage coil  16  outputs a linear mechanical force in a direction shown by arrow  19  direction that is capable of translation to the tripping shaft  30 . An accessory  50  is a typical component used to translate linear mechanical forces into rotational forces. As referred to in  FIG. 1 , the accessory  50  refers generally to any accessory. In an exemplary embodiment, accessory  50  includes for example a first tripping accessory  51 , a second tripping accessory  52 , a third tripping accessory  54 , a first closing accessory  56 , or a second closing accessory  58 . The accessory  50  acts as a lever to translate linear mechanical forces into rotational forces. The accessory  50  may also be used for other functions involving control and use of the circuit breaker. The accessory  50  is disposed at the closing or tripping shaft  20  or  30  and fixably secured to the closing or tripping shaft  20  or  30 . The accessory  50  is also disposed such that a working surface of the accessory  50  is in communication with the actuation device. In an exemplary embodiment, each accessory  50  is made of molded plastic.  
         [0028]      FIG. 2  shows a side view of circuit breaker  10  in an exemplary embodiment. Shunt coil  12  is shown in communication with a first tripping accessory  51 . First tripping accessory  51  is also fixably secured to the tripping shaft  30 . When shunt coil  12  actuates, a linear force in a direction shown by arrow  19  is exerted on first tripping accessory  51  and translated into rotational force on tripping shaft  30  causing tripping shaft  30  to rotate in a direction shown by arrow  44 . Rotation of the tripping shaft  30  causes the mechanical linkages  40  to release energy in the contact springs to open the main contact assembly.  
         [0029]      FIG. 3  shows an opposite side view of circuit breaker  10  in an exemplary embodiment. Undervoltage coil  16  is shown in communication with a second tripping accessory  52 . Second tripping accessory  52  is also fixably secured to the tripping shaft  30 . When undervoltage coil  16  actuates, a linear force in a direction shown by arrow  19  is exerted on second tripping accessory  52  and translated into rotational force on tripping shaft  30  causing tripping shaft  30  to rotate in a direction shown by arrow  44 . Rotation of the tripping shaft  30  causes mechanical linkages  40  to release energy in the contact springs to open the main contact assembly.  FIG. 3  also shows a first closing accessory  56 . First closing accessory  56  is fixably secured to closing shaft  20 .  
         [0030]      FIG. 4  shows the tripping shaft  30  in an exemplary embodiment. The tripping shaft  30  is substantially cylindrical in shape. Although the tripping shaft  30  of the exemplary embodiment shown is substantially cylindrical, other shapes are also contemplated. Tripping shaft  30  includes a first end  60  and a second end  62 . A diameter of the tripping shaft  30  is substantially constant near both first and second ends  60  and  62 . Near a center of the tripping shaft  30  a raised portion  64  has a larger diameter than the diameter at first and second ends  60  and  62 . Raised portion  64  includes two notches  66  that provide for mechanical communication to mechanical linkages  40  to translate an unlatching force to the contact springs. First end  60  has a first flat surfaces  68  disposed on opposing sides of the tripping shaft  30 .  FIG. 5  shows a cross section of the tripping shaft  30  taken at the first flat surfaces. There is also a first groove  70  disposed near the first end  60 . First groove  70  extends over a circumference of the tripping shaft  30 . Second end  62  also has a second flat surfaces  72  disposed on opposing sides of the tripping shaft  30 . Second flat surfaces  72  form a plane substantially parallel to a plane formed by first flat surfaces  68 . A cross section of the tripping shaft  30  taken at the second flat surfaces  72  is identical to that shown in  FIG. 5 . A second groove  74  is disposed near the second end  62 . Second groove  74  extends over the circumference of the tripping shaft  30 . Raised portion  64  includes a third flat surface  76  which forms a plane substantially parallel to a plane formed by first and second flat surfaces  68  and  72 .  FIG. 6  shows a cross section of the tripping shaft  30  taken at the third flat surface. Raised portion  64  also includes a third groove  78 . Third groove  78  extends over the circumference of the tripping shaft  30 . In an exemplary embodiment, first, second and third flat surfaces  68 ,  72  and  76  and first, second and third grooves  70 ,  74  and  78  are formed by machining of the tripping shaft  30 , however, it is envisioned that other methods including but not limited to die casting and molding could be used.  
         [0031]      FIG. 7  shows a perspective view of the first tripping accessory  51  in an exemplary embodiment. First tripping accessory  51  is a lever that includes an engaging orifice  80 . Engaging orifice  80  is a tubular cuff formed to match a shape of the tripping shaft  30  at the first end  60 . Although a tubular cuff is used in an exemplary embodiment, it is contemplated that the engaging orifice could take on other forms of a hole in the lever. Engaging orifice  80  includes substantially circular portions  81  and flat portions  82 . Circular portions  81  are disposed on opposing sides of the engaging orifice  80 . Flat portions  82  are also disposed on opposing sides of the engaging orifice  80  to contact first flat surfaces  68  when the first tripping accessory  51  is fixably secured to the tripping shaft  30 . Snap protrusions  84  extend from the engaging orifice in a direction substantially perpendicular to a diameter of the engaging orifice  80 . Snap protrusions  84  include one protrusion from each of the circular portions  81  of the engaging orifice  80 . Thus, the snap protrusions  84  are disposed on opposite sides of the engaging orifice  80 . Snap protrusions  84  include a detent  85  at an end of each protrusion. The detent  85  engages the first groove  70 . First flat surfaces  68  in contact with flat portions  82  prevent a rotation of the first tripping accessory  51  with respect to the surface of the tripping shaft  30 . First tripping accessory  51  also includes an L bracket assembly formed by a first operating surface  86  and a second operating surface  88 . First and second operating surfaces  86  and  88  are planar surfaces disposed substantially perpendicular to each other. First and second operating surfaces  86  and  88  are also disposed such that the planar surfaces of first and second operating surfaces  86  and  88  lie substantially perpendicular to the diameter of the engaging orifice  80 . A tail piece  87  extends from the first operating surface substantially perpendicular to the second operating surface  88 . Thus, tail piece  87  and first operating surface  86  form a T shape with the second operating surface  88  being the base of the T. First operating surface  86  is in communication with the shunt coil  12 . Tail piece  87  is in communication with the racking interlock (not shown). Second operating surface  88  is in communication with the trip coil (not shown). The trip coil causes a rotation of the tripping shaft when a certain electrical fault condition is detected.  
         [0032]      FIG. 8  shows a view of the second tripping accessory  52  in an exemplary embodiment. Second tripping accessory  52  includes an engaging orifice  80 . Engaging orifice  80  is a tubular cuff formed to match a shape of the tripping shaft  30  at the second end  62 . Thus, engaging orifice  80  includes substantially circular portions  81  and also includes flat portions  82 . Circular portions  81  are disposed on opposing sides of the engaging orifice  80 . Flat portions  82  are also disposed on opposing sides of the engaging orifice  80  to contact second flat surfaces  72  when the second tripping accessory  52  is fixably secured to the tripping shaft  30 . Snap protrusions  84  extend from the engaging orifice in a direction substantially perpendicular to a diameter of the engaging orifice  80 . Snap protrusions  84  include a protrusion from each of the circular portions  81  of the engaging orifice  80 . Thus, the snap protrusions  84  are disposed on opposite sides of the engaging orifice  80 . Snap protrusions  84  include a detent  85  at the end of each protrusion. The detent  85  engages the second groove  74 . Second flat surfaces  72  in contact with flat portions  82  prevent a rotation of the second tripping accessory  52  with respect to the surface of the tripping shaft  30 . Second tripping accessory  52  also includes an operating surface  90 . Operating surface  90  is disposed substantially perpendicular to the diameter of the engaging orifice  80 . Operating surface  90  includes two portions substantially planar in shape with a bent portion  92  separating the two portions substantially planar in shape. Operating surface  90  is in communication with the undervoltage coil  16 .  
         [0033]      FIG. 9  shows a third tripping accessory  54  in an exemplary embodiment. Third tripping accessory  54  includes an engaging orifice  80 . Engaging orifice  80  is a tubular cuff formed to match a shape of the tripping shaft  30  at the raised portion  64 . Thus, engaging orifice  80  includes a substantially circular portion  81  and also includes a flat portion  82 . Flat portion  82  is disposed on the engaging orifice  80  to contact third flat surface  76  when the third tripping accessory  54  is fixably secured to the tripping shaft  30 . Snap protrusions  84  extend from the engaging orifice in a direction substantially perpendicular to a diameter of the engaging orifice  80 . Snap protrusions  84  include a protrusion from opposite sides of the circular portion  81  of the engaging orifice  80 . Thus, the snap protrusions  84  are disposed on opposite sides of the engaging orifice  80 . Snap protrusions  84  include a detent  85  at the end of each protrusion. The detent  85  engages the third groove  78 . Third flat surface  76  in contact with flat portion  82  prevents a rotation of the third tripping accessory  54  with respect to the surface of the tripping shaft  30 . Third tripping accessory  54  also includes a contact surface  94 . Contact surface  94  is disposed such that it extends substantially tangentially to a radius of the engaging orifice  80 . Contact surface  94  includes two portions substantially planar in shape with a bend  96  separating the two portions substantially planar in shape. Contact surface  94  is in communication with the trip free assembly (not shown). The trip free assembly functions to prevent closing the main contact assembly following a tripping of the circuit breaker  10  until the circuit breaker  10  has been reset if the trip occurred as a result of a signal from the trip coil (not shown).  
         [0034]      FIG. 10  shows the closing shaft  20  in an exemplary embodiment. The closing shaft  20  is substantially cylindrical in shape. Although the closing shaft  20  of the exemplary embodiment shown is substantially cylindrical, other shapes are also contemplated. Closing shaft  20  includes a first end  100  and a second end  102 . A diameter of the closing shaft  20  is substantially constant near both first and second ends  100  and  102 . Near a center of the closing shaft  20  an elevated portion  104  has a larger diameter than the diameter at first and second ends  100  and  102 . Elevated portion  104  includes a notch  106  that connects to mechanical linkages  40  to act as a latching force on the closing springs. First end  100  has a first flat surfaces  108  disposed on opposing sides of the closing shaft  20 . A cross section of the closing shaft  20  taken at the first flat surfaces  108  is identical to that shown in  FIG. 5 . There is also a first groove  110  disposed near the first end  100 . First groove  110  extends over a circumference of the closing shaft  20 . A second groove  112  is disposed on the elevated portion  104  near a middle of the closing shaft  20 . Second groove  112  extends over the circumference of the closing shaft  20 . A second flat surface  114  extends from near the second groove  112  to near the second end  102 . A cross section of the closing shaft  20  taken at the second flat surface  114  is identical to that shown in  FIG. 6 . Second flat surface  114  forms a plane substantially parallel to a plane formed by first flat surfaces  108 . First and second flat surfaces  108  and  114  and first and second grooves  110  and  112  are formed by machining of the closing shaft  20 .  
         [0035]      FIG. 11  shows a view of the first closing accessory  56  in an exemplary embodiment. First closing accessory  56  includes an engaging orifice  80 . Engaging orifice  80  is a tubular cuff formed to match a shape of the closing shaft  20  at the first end  100 . Thus, engaging orifice  80  includes substantially circular portions  81  and also includes flat portions  82 . Circular portions  81  are disposed on opposing sides of the engaging orifice  80 . Flat portions  82  are also disposed on opposing sides of the engaging orifice  80  to contact first flat surfaces  108  when the first closing accessory  56  is fixably secured to the closing shaft  20 . Snap protrusions  84  extend from the engaging orifice in a direction substantially perpendicular to a diameter of the engaging orifice  80 . Snap protrusions  84  include one protrusion from each of the circular portions  81  of the engaging orifice  80 . Thus, the snap protrusions  84  are disposed on opposite sides of the engaging orifice  80 . Snap protrusions  84  include a detent  85  at the end of each protrusion. The detent  85  engages the first groove  110 . First flat surfaces  108  in contact with flat portions  82  prevent a rotation of the first closing accessory  56  with respect to the surface of the closing shaft  20 . First closing accessory  56  also includes a planar surface  116 . Planar surface  116  is disposed substantially parallel to the diameter of the engaging orifice  80 . A nipple  118  extends from the planar surface  116  to communicate with the trip free assembly and ensure closing shaft  20  returns to its original position when undervoltage coil  16  actuates.  
         [0036]      FIG. 12  shows a view of the second closing accessory  58  in an exemplary embodiment. Second closing accessory  58  includes an engaging orifice  80 . Engaging orifice  80  is a tubular cuff formed to match a shape of the closing shaft  20  at the elevated portion  104 . Thus, engaging orifice  80  includes a substantially circular portion  81  and also includes a flat portion  82 . Flat portion  82  is disposed on the engaging orifice  80  to contact second flat surface  120  when the second closing accessory  58  is fixably secured to the closing shaft  20 . Snap protrusions  84  extend from the engaging orifice in a direction substantially perpendicular to a diameter of the engaging orifice  80 . Snap protrusions  84  include a protrusion from opposite sides of the circular portion  81  of the engaging orifice  80 . Snap protrusions  84  include a detent  85  at the end of each protrusion. The detent  85  engages the second groove  112 . Second flat surface  120  in contact with flat portion  82  prevents a rotation of the second closing accessory  58  with respect to the surface of the closing shaft  20 . Second closing accessory  58  also includes a contact surface  124 . Contact surface  124  is disposed such that it extends substantially radially from a center of the engaging orifice  80 . Contact surface  124  is in communication with the trip free assembly.  
         [0037]      FIG. 13  shows an exemplary embodiment in which the tripping shaft  30  is fully accessorized. Third tripping accessory  54  is installed so that flat portion  82  slides over third flat surface  76  until detent  85  of snapping protrusions  84  extends into the third groove  78 . The snapping protrusions  84  in combination with the detent  85  ensure no longitudinal movement of the third tripping accessory  54 . First tripping accessory  51  is installed so that flat portions  82  slide over first flat surfaces  68  until detent  85  of snapping protrusions  84  extends into the first groove  70 . The snapping protrusions  84  in combination with the detent  85  ensure no longitudinal movement of the first tripping accessory  51 . Second tripping accessory  52  is installed so that flat portions  82  slide over second flat surfaces  72  until detent  85  of snapping protrusions  84  extends into the second groove  74 . The snapping protrusions  84  in combination with the detent  85  ensure no longitudinal movement of the second tripping accessory  52 . In an exemplary embodiment, the tripping shaft  30  is accessorized at an assembly line, however, other methods of assembly are also envisioned.  
         [0038]      FIG. 14  shows an exemplary embodiment in which the closing shaft  20  is fully accessorized. Second closing accessory  58  is installed so that flat portion  82  slides over second flat surface  114  until detent  85  of snapping protrusions  84  extends into the second groove  112 . The snapping protrusions  84  in combination with the detent  85  ensure no longitudinal movement of the second closing accessory  58 . First closing accessory  56  is installed so that flat portions  82  slide over first flat surfaces  108  until detent  85  of snapping protrusions  84  extends into the first groove  110 . The snapping protrusions  84  in combination with the detent  85  ensure no longitudinal movement of the first closing accessory  56 . A closing paddle  122  is disposed at the closing shaft  20  from a middle portion of the closing shaft  20  to the second end  102 . Closing paddle  122  forms a bridge over second closing accessory  58 . Closing paddle  122  is in communication with closing coil  14 . When closing coil  14  actuates a linear force is exerted on closing paddle  122  and translated into rotational force on closing shaft  20 . Rotation of the closing shaft  20  causes mechanical linkages  40  to release energy in the closing springs to close the main contact assembly. In an exemplary embodiment, the closing shaft  20  is accessorized at an assembly line, however, other methods of assembly are also envisioned.  
         [0039]     In addition, while the invention has been described with reference to exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to a particular embodiment disclosed as the best or only mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims. Moreover, the use of the terms first, second, etc. do not denote any order or importance, but rather the terms first, second, etc. are used to distinguish one element from another. Furthermore, the use of the terms a, an, etc. do not denote a limitation of quantity, but rather denote the presence of at least one of the referenced item.

Technology Classification (CPC): 7