The present invention relates to gas-operated firearms and, more particularly, to an improved bolt and bolt carrier for use in such firearms.
The AR15/M16 family of weapons and their derivatives, including all direct gas operated versions, have been in use by the military and civilian population for many years. An essential part of this firearm's design is the bolt carrier which typically includes a bolt mounted in the carrier for axial sliding movement and rotation, a firing pin slidably mounted within the bolt and bolt carrier for restricted reciprocating axial movement, and a cam pin for producing relative rotation between the bolt and the bolt carrier.
The bolt carrier is generally cylindrical in shape with a longitudinally extending circular bore throughout its length. An elongated opening is provided in the top and bottom of the carrier to allow the hammer to extend into the interior of the bolt carrier and strike the firing pin. The rear of the carrier is received within the firearm receiver and the front of the carrier houses the bolt. The upper surface of the carrier immediately adjacent the front face includes a flat shelf for engagement with a charging handle. About the exterior of the bolt carrier are a series of lands and accompanying grooves, usually four, which extend from the forward end of the bolt carrier rearwardly over a distance of about one half the length of the bolt carrier. There are openings on the bolt carrier to mount a gas key, an opening which serves as a gas receiving port and an opening to receive the cam pin. Typically the gas key is secured to the bolt carrier through the use of two screws while the firing pin is retained in place through the use of a retaining or cotter pin.
Like the bolt carrier, the bolt has a body that is generally cylindrical in shape and is provided with a circular bore throughout its length which is designed to accommodate a firing pin. Located radially about a forward portion of the bolt are a series of lugs and an extractor. The exterior of the bolt has a recess provided therein with an extractor bearing surface that houses the extractor. The forward end of the extractor includes a gripping element, or claw, which catches and holds onto the rim of the case head of an ammunition cartridge.
The extractor rotates about a pin received by both the bolt body and the extractor. Located at the rearward end of the extractor is a spring and internal buffer. The extractor spring and buffer press against the extractor bearing surface thereby resisting rotation of the extractor about its axis and facilitates the extraction of a used ammunition cartridge.
Present on the front face of the bolt is an ejector that is located opposite the side of the front face adjacent the extractor. The ejector consists of a spring-loaded pin which is retained in place on the bolt through the use of a roll pin. The ejector assists in pushing an ammunition cartridge away from the bolt face when the firearm is being fired or otherwise unloaded.
The bolt carrier group is responsible for stripping, chambering, locking, firing, extraction and ejection of ammunition cartridges for the host rifle. The energy to perform these functions is provided in the form of hot, expanding gases which travel through the host firearm's gas tube, through the gas key and into the bolt carrier. A secure union between the gas key and bolt carrier is important to the proper operation of a direct gas operated firearm. Should the gas key become loose or be removed, the associated firearm will not properly function due to resulting gas leakage.
As shown in
The retaining pin or cotter pin 64 found in the prior art is retained within an opening 63 that provides no method to orient the pin 64. As a result the pin 64 can be placed either by the user, or through rotation during normal use of the rifle, into a position which orients the thinnest profile of the cotter pin towards the firing pin. This deficiency in the prior art reduces the service life of the cotter pin 64 resulting in several critical issues. The cotter pin can become bent such that maintaining the rifle is difficult since the cotter pin should be removed to service the bolt and bolt carrier properly. Removing a bent cotter pin 64 through the provided opening 63 is difficult, often requiring tools such as pliers to accomplish. Once the cotter pin 64 is removed, the user must be able to reinsert the cotter pin 64 back into the opening 63 of the bolt carrier 60. If the cotter pin 64 is bent, this operation is often virtually impossible. The cotter pin 64 can also break or bend sufficiently thereby rendering the rifle inoperable. The terms “cotter pin” and “retaining pin” are used interchangeably herein.
The prior art bolt has several points of deficiency. First, there are seven bolt lugs placed radially about the forward end of the bolt. These lugs are evenly spaced apart except for the gap created on the exterior of the bolt to accommodate the extractor, which gap is referred to herein as the extractor pocket. When the extractor pocket is machined, a portion of the bolt's face is removed, resulting in the case head of the cartridge not being fully supported.
Second, the lugs located on either side of the extractor pocket are not fully supported, rendering them the weakest lugs on the prior art bolt. As such, these two lugs experience the highest rate of failure. Further, the lugs themselves are machined with sharp edges or geometric corners about their exterior. These geometric corners often accumulate material stress which can result in micro fractures that limit the service life of the bolt.
Third, extraction of a spent cartridge by the extractor, extractor spring and buffer can be disrupted due to a variety of conditions including a fouled barrel chamber, an over pressured gas system, an improperly annealed cartridge rim, as well as others. To compensate for this deficiency, various remedies have been developed to include, for example, the use of o-rings which increase the force the extractor is capable of placing on the rim of an ammunition cartridge.
Fourth and fifth, problems persist with the present method of securing the gas key to the bolt carrier using two screws as described above, and with the method by which the cotter pin that retains the firing pin is able to rotate into a structurally weak position. Finally, there is a deficiency in prior art methods of manufacturing the bolt. It would be highly advantageous, therefore, to remedy the foregoing and other deficiencies inherent in the prior art.
In view of the foregoing, one object of the present invention is to overcome the shortcomings in the design of bolt carriers and bolts for self-loading firearms as described above. Another object of the present invention is to provide a bolt carrier having an integral gas key with a removable nozzle which is constructed to be in communication with a gas tube of the host firearm.
Yet another object of the present invention is to provide a bolt carrier in accordance with the preceding objects in which the nozzle is threadedly secured to the gas key and held in place with a cross pin that relies on tension and the structure of the upper receiver to retain the cross pin in place.
A further object of the present invention is to provide a bolt carrier in accordance with the preceding objects in which the bolt carrier is constructed to orient the cotter pin that retains the firing pin such that the widest profile of the cotter pin is always oriented towards the firing pin.
A still further object of the present invention is to provide a bolt carrier in accordance with the preceding objects which includes a bolt with a fully supported bolt face and an improved structure for incorporation of the extractor.
Another object of the present invention is to provide a bolt carrier in accordance with the preceding objects in which the extractor engages a larger portion of the rim of the cartridge case as compared to prior art extractors.
A still further object of the present invention to provide an improved bolt carrier in accordance with the preceding objects that is not complex in structure and which can be manufactured at low cost but yet increases the reliability and safety of the firearm.
In accordance with these and other objects, the present invention is directed to a direct gas operated firearm of the AR15/M16 variety having an improved bolt carrier assembly. This improved bolt carrier assembly can be retrofitted to an existing direct gas operated AR15/M16 type rifle without the need for any modification to the receiver of the rifle or any other part thereof.
The improved bolt carrier includes an integral gas key which is threaded to receive an extension nozzle which is constructed to receive a portion of the host firearm's gas tube. The extension nozzle is held in place through the use of a cross pin which prevents loosening of the nozzle during use of the firearm.
The present invention also provides an improved bolt carrier that includes a machined structure on the exterior of the bolt carrier which optimally orients the cotter pin that retains the firing pin retaining pin so as to maximize the service life of the cotter pin. In particular, the retaining pin is oriented in a vertical profile so that the widest profile of the retaining pin is always oriented toward the firing pin.
In addition, the improved bolt carrier according to the present invention has a bolt with a fully supported bolt face, eliminating the machining of a gap into the bolt face in order to accommodate an extractor. By fully supporting the bolt face, the lugs located on either side of the extractor pocket are not undercut, resulting in a more durable bolt.
Still further, the present invention includes a bolt carrier with a bolt including an extractor having an extractor claw that grabs or engages approximately 17% more of an ammunition cartridge's rim as compared with prior art extractors. By spreading the forces related to extraction over a larger area of the rim of the cartridge, the likelihood of failed extraction is substantially diminished.
These together with other improvements and advantages which will become subsequently apparent reside in the details of construction and operation as more fully hereinafter described and claimed, reference being had to the accompanying drawings forming a part hereof, wherein like numerals refer to like parts throughout.
In describing a preferred embodiment of the invention illustrated in the drawings, specific terminology will be resorted to for the sake of clarity. However, the invention is not intended to be limited to the specific terms so selected, and it is to be understood that each specific term includes all technical equivalents which operate in a similar manner to accomplish a similar purpose.
The present invention is directed towards a bolt and bolt carrier group or bolt carrier assembly for use with the M4/M16/AR15 family of firearms and their derivatives. As used herein, the phrases “bolt carrier assembly” and “bolt carrier group” are used interchangeably.
In describing a preferred embodiment of the invention illustrated in the drawings, specific terminology will be resorted to for the sake of clarity. However, the invention is not intended to be limited to the specific terms so selected, and it is to be understood that each specific term includes all technical equivalents which operate in a similar manner to accomplish a similar purpose. Unless otherwise specified, the various components which make up the trigger mechanism, upper receiver assembly, lower receiver assembly, buttstock assembly, bolt and bolt carrier assembly are those found on the prior art M4 and M16 family of firearms.
As used herein, “front” or “forward” and “distal” correspond to the end of the bolt carrier 20 where the gas key is located and nearest the muzzle of the firearm (i.e., to the left as shown in
As shown in
As shown in the exploded view of the bolt carrier assembly 10 provided in
Also present on the bolt carrier 20 is a hammer clearance slot 22, which permits the hammer (not shown) to extend into the bolt carrier 20 and strike a firing pin 29. An opening 41 for a cotter pin 40 and an opening 24 for a bolt 21 (shown in
The opening 24 in the bolt carrier 20 for the bolt 21 includes a longitudinal bore which extends from the forward end of the bolt carrier 20 rearwardly for a distance sufficient to accommodate the rearward portion of the bolt 21. A smaller bore 39 (see
Located rearwardly of the charging handle contact point 38 is a cam slot 26 which provides a contained area for the cam pin 27 to rotate, thus allowing the bolt 21 to move rearward and rotate axially within the bolt carrier 20. The cam pin 27 retains the bolt 21 within the bolt carrier 20.
The bolt carrier 20 is also provided with a series of bearing surfaces 37. These bearing surfaces 37 are located on the front half, top and bottom sides of the bolt carrier 20, and are in direct contact with the interior of the upper receiver 13. The bearing surfaces 37 located along the bottom portion of the bolt carrier 20 are interrupted along there length by a series of sand cuts 23. The sand cuts 23 are longitudinal cuts, having a generally rectangular shape, which reduce the exterior dimensions of the bolt carrier's bearing surfaces 37 when present. If any foreign material, including material resulting from the discharge of a firearm, accumulates within the upper receiver 13, the sand cuts 23 provide an exit for the accumulating debris.
The bolt carrier 20 is further provided with a series of flat surfaces 43 machined onto the forward portion of its exterior. These flat surfaces 43 are present on both the right and left sides of the bolt carrier 20 and machined so that they come to an apex 143. The apex 143 at which point these flat surfaces 43 meet protrudes from the exterior of the bolt carrier 20. These “flats” 43 provide additional space for the accumulation of debris. By providing space and egress points for the accumulation of debris, the static and kinetic friction forces between the bolt carrier 20 and the interior of the upper receiver 13 will not increase as rapidly during prolonged use of the host firearm. Also present is a door opener 28 which provides room for the door latch (not shown) to close.
As best shown in the isolated views in
More particularly,
A timing washer 32, which is located between the extension nozzle 50 and the forward face of the gas key 30, may be placed over the threaded member 52 of the extension nozzle 50 and used as a means to orient the extension nozzle 50 when it is threadedly secured to the gas block 30. More particularly, a series of wrench flats 55 are provided about the exterior of the extension nozzle 50 and provide a means by which torque may be applied during installation of the extension nozzle 50. A crescent wrench or a wrench of similar design is used to rotate the nozzle 50 by engaging with the wrench flats 55. When the extension nozzle 50 is being threaded into the gas block 30, the indexing notch 51 of the extension nozzle 50 is aligned with the indexing notch 33 of the gas key 30. The timing washer 32, which allows for a predetermined torque value to be applied, is selected during assembly to facilitate alignment of the two separate indexing marks 33 and 51 and application of the proper torque range. The timing washer 32 is machined from stainless steel but other materials suitable for use in the manufacture of washers would also be acceptable. Alternatively, modern manufacturing techniques and technologies make it possible to time the threads, thereby eliminating the need for a timing washer 32.
Another method of securing the extension nozzle 50 to the gas block 30 includes press fitting them together. This can be achieved by manufacturing an extension nozzle 50 without a threaded member and a gas block which has a non-threaded opening. The threaded portion of the threaded member 53 shown in the illustrated embodiment would be replaced by a smooth exterior, shaped to be received by the non-threaded opening in the gas block. Such a non-threaded extension nozzle would need to be manufactured such that it required substantial force to be pressed into the opening of the gas block. Once pressed into place, the extension nozzle could then be further secured into place through the use of a roll pin such as roll pin 31 or alternatively, welded.
The roll pin 31 used to assist in securing the extension nozzle 50 to the gas key 30 may, alternatively, be replaced with a non-tensioning type (i.e. dowel pin). This solution works because the gas key 30 of the bolt carrier 20 rides in a channel 14 (shown in
The incorporation of the port 36 through the interior of the bolt carrier 20 is a significant feature related to its manufacture. The bolt carrier 20, in general, is manufactured through the use of lathes and mills to create its general shape along with both its internal and external structures. The bolt carrier may also be cast, with secondary machining operations being performed to bring critical surfaces within the required specifications. After the integral gas block 30 is machined onto the exterior of the bolt carrier 20, a drill press, mill or similar machine is used to machine the opening 42 into the top exterior of the gas block, through to the interior opening 24 for the bolt 21. As previously noted, the resulting port 36 is angled along its length. After the port 36 is drilled, the opening 35 at the forward end of the gas block 30 is threaded to receive the extension nozzle 50.
The bolt 21 of
The cylindrical body 87 portion of the bolt 21 defines an extractor recess 93. The extractor recess 93, formed on the exterior surface 91, is in communication with the longitudinal bore 90, or firing pin bore. A bearing portion 94 for the extractor 80 resides within the extractor recess 93 and is integrally formed with the body 87 of the bolt 21. The extractor bearing portion 94 of the recess 93 includes a mating surface 96 (see
The extractor is shown in
The extractor body 105 extends between the flange 104 and the extractor claw 106, located on the extractor's forward end 108. The extractor body 105 defines a pin receiving portion 99 along its length. The pin receiving portion 99 is a bore that runs perpendicular to the longitudinal axis of the extractor 80. The extractor claw 106 defines a recess 109 having an upper portion or lip 107. The lip 107 portion of the extractor claw 106 is constructed to engage with the rim of an ammunition cartridge. Structurally, the lip 107 portion of the extractor claw 106 is wider than the extractor body 105. Further, the circumferential edge 110 of the lip 107 comes to two forward edges 111 which are located on opposite sides of the extractor claw 106. The extractor 80 is symmetrical about its longitudinal axis, with
Prior art extractors used with U.S. military M16/M4 type rifles and their derivatives, grasp approximately 22% or less of an ammunition cartridges rim. An extractor 80 according to the present invention grasps approximately 26% or more of an ammunition cartridge rim. In the preferred embodiment of the present design, the extractor claw 106 grabs approximately 17% more of an ammunition cartridge's rim as compared to the prior art M16/M4 type extractors.
The bore of the extractor's 80 pin receiving portion 99 is configured to align with the second bore 89 of the bolt 21 when the extractor 80 is positioned within the extractor recess 93. A pivot pin 97 is extended through the second bore 89 of the bolt 21 and the pin receiving portion 99 of the extractor to pivotally engage the extractor 80 to the bolt 21. The extractor 80 and thereby its claw 106 are rotatable between a first and second position (not shown). The first position has the lip 107 engaged with the recess of an ammunition cartridge. The second position has the extractor 80 pivotally biased such that the extractor claw 106 is being forced aside during the initial seating of an ammunition cartridge.
The extractor 80 as a unit is constructed to be received within the extractor recess 92 and the extractor gap 144 located on the cylindrical body 87 portion of the bolt 21. The extractor recess 92 and extractor gap 144 are constructed to position the extractor 80 so that its forward end 108 coincides with the front end 82 of the bolt 21.
The cartridge recess 98 is laterally defined by a round side wall 161. The cartridge recess as a whole is defined by the round side wall 161 and the bolt face 92 (shown in
The extractor mating surface 96 defines a portion of the circumference of the face 92 of the bolt 21. In the preferred embodiment, the circumference of the bolt 21 face 92 is circular. In the preferred embodiment of the bolt 21, the face 92 is in direct contact with the entire end portion, or case head, of a retained ammunition cartridge except for the portion which would be over the circumferential groove 162. This method of manufacturing the extractor mating surface 96 and the face 92 does not require material which supports the bolt lugs 142 to be removed thereby compromising their structural integrity.
Referring to
Extractor bounce is a phenomenon whereby the extractor slips off of a seated cartridges rim when the bolt comes under a heightened recoil force generated by the host firearm's discharge, resulting in a failure to extract. When the extractor 80 is engaged to the bolt 21 as previously described above, each one of the nipples 103 on the flange 104 engages a spring 101 while it is housed in a spring well 100. In operation, the springs 101 place pressure on the flange 104 of the extractor 80, thereby pivotally biasing the extractor 80 radially inward. This allows the claw 106 of the extractor to engage the rim of an ammunition cartridge. The springs 101 used for this purpose must also have sufficient flexibility to allow the extractor 80 to pivot radially outward during the recoil cycle so that the ammunition cartridge may be ejected.
As shown in
Each of the bolt lugs 142 defines a corresponding end wall 150A, 150B, 151A, 151B, 151C, 151D and 151E (collectively referred to as “end walls 152”) and a pair of side walls 153. At the junction where the side walls 153 meet with at least one of the end walls 153, all sharp angles have been rounded and reinforced with radii removing potential stress risers and concentrators.
In the prior art, bolt lugs 140A and 140B had a portion of the material which would have supported them removed to accommodate the extractor 80 body, a process that is referred to as undercutting the bolt. Additionally, a portion of the bolt's face was removed in order to accommodate the forward end 108 and claw 106 portions of the extractor 80. Structurally, undercutting the bolt constitutes removal of the material under the plane of sidewall 160A of lug 140A and the plane of the sidewall 160B of the lug 140B. This does not apply to the portion of the lugs 140A and 140B which protrudes above the face 92 of the bolt 21.
The preferred embodiment of the bolt 21 as described herein does not rely on removing structural material which would otherwise strengthen the bolt 21. Specifically, lugs 140A and 140B are not undercut by the extractor recess 93. Further, the portion of the extractor gap 144 which accommodates the claw 106 portion of the extractor 80 is wider than the extractor's body 105 and the extractor recess 93. The extractor recess 93 is defined as the relevant area and structural features as set forth above that are located below the horizontal plane defined by the face 92 of the bolt 21. The extractor gap 144 is defined as the relevant opening located above the plane defined by the bolt face 92 and between lugs 140A and 140B of the bolt 21 (shown in
Best shown in
At its other end, the annular structure 163 terminates into two side walls 170B and 171B. Side wall 170B is adjacent the extractor gap 144 while side wall 171B is adjacent the extractor recess 93. Side wall 170B forms one side of the extractor gap 144 while side wall 171B forms a portion of the side wall which is defined by the extractor recess 93.
The side wall 171A of the extractor recess is coplanar with the side wall 160A of the first bolt lug 140A. Both side walls 171A and 160A occupy the same plane which is indicated in
Side walls 170A and 170B occupy parallel planes. Further, side walls 170A and 170B define the width of the extractor gap 144 that is located above the face 92 of the bolt 21. The extractor gap 144 is wider than the extractor recess 93 that is located below the face 92 of the bolt 21.
Side wall 170A lies on a plane which is indicated in
The bolt 21 of the present invention is turned, machined and precision ground from 9310 steel-alloy bar stock. The bolt 21 is then carburized for case hardness and tempered to increase core toughness. The bolt 21 is steel shot-peened by blasting selected surfaces with steel pellets to induce compressive stresses and improve fatigue life. A coating of nickel with TEFLON®, polytetrafluoroethylene a fluoropolymer, is applied to the bolt 21 to reduce the friction coefficient between the bolt 21 and the bolt carrier 20, and the bolt 21 and the barrel extension (not shown) of the barrel 12.
The bolt carrier 20 is machined from an 8620 steel alloy and carburized or case hardened for wear resistance. A coating comprised of nickel and TEFLON®®, polytetrafluoroethylene a fluoropolymer, is applied to the bolt carrier 20. Electroless Nickel provides wear resistance for the bolt carrier 20 and makes the part easier to clean as carbon and other fouling resulting from the use of the host firearm is easier to remove. The coating also provides the parts with a natural lubricity. Even with the specificity provided above, it should be understood that the entire bolt carrier 20 and bolt 21 of the present invention could be made of conventional materials, preferably hard structural material such as steel or stainless steel and coated with prior art surface finishes such as an electrochemical phosphate conversion coating.
The bolt 21 and bolt carrier 20 of the present invention may be used in conjunction with each other or independently with prior art AR15/M4 bolt carriers or bolts. The method of securing the bolt 21 to the bolt carrier 20 is substantially similar to the methods used in the prior art. Initially the springs 101 and their buffers 102 are inserted into the spring wells 100 located within the extractor recess 93 of the bolt 21. The extractor 80 is placed within the recess 93 so that the two nipples 103 located on its flange 104 are in direct contact with the springs 101. With the pin receiving portion 99 of the extractor 80 aligned with the second bore 89 of the bolt 21, a pivot pin 97 is inserted therethrough to secure the extractor 80 to the bolt 21.
The ejector 120 and spring 122 are received within a bore 121 present on the cylindrical body 87 of the bolt 21, and retained in place through the use of a roll pin 123 as is common throughout the prior art. The roll pin 123 is received in a bore 124 present near the front end 82 of the bolt 21. The gas rings 85 are flexed so that they may be received within the groove 84 present near the rear end 81 of the bolt 21. After the bolt 21 and bolt carrier 20 are assembled as described above, the bolt 21 is inserted into an opening 24 found on the carriers 20 forward end. The first bore 88 of the bolt 21 is oriented so that it aligns with the cam slot 26 of the bolt carrier 20. The cam pin 27 is then inserted through the cam slot 26 and into the first bore 88 of the bolt 21 and rotated so that an opening present along its bottom side is aligned with the bore 39 of the bolt carrier 20, the specifics of which are well known in the prior art. Next the firing pin 29 is inserted through the bore 30 of the bolt carrier 20 and into the longitudinal bore 90 of the bolt 21. The firing pin 29 is secured in placed through the use of a cotter pin 40. The cotter pin 40 is inserted into an opening 41 located on the bolt carrier's exterior and oriented within the opening 41 as described above.
Thus the assembly of the bolt 21 and bolt carrier 20 has been described. By reversing the steps detailed above the bolt carrier 20 and bolt 21 may be disassembled for maintenance and repair as required.
In sum, the present invention provides an improved means for securing a gas nozzle to the bolt carrier of an M16 type rifle. By integrating the gas key 30 onto the bolt carrier 20, the problems associated with the prior art attachment methods are eliminated. By threadedly securing the extension nozzle 50 to the gas key 30 and retaining the extension nozzle 50 in place through the use of a roll pin 31, a superior attachment method is provided. This method of manufacturing a bolt carrier eliminates the extraction and ammunition feeding problems associated with gas leakage linked to the compromised union between the prior art gas key 61 and bolt carrier 60.
The present invention also provides an improved structure on the bolt carrier 20 which orients the cotter pin 40 in a position that optimizes its service life. The opening 41 for the cotter pin 40 holds it in a vertical orientation which places its widest profile towards the back side of the annular flange 44 of firing pin 29. The use of this feature is not limited to rifles using the direct gas operating system seen on the rifle 300 shown in
Additionally, there is provided a bolt 21 which provides an extractor recess 93 which does not rely on undercutting the face 92 of the bolt 21 in order to accommodate an extractor 80. Also provided is an extractor which has been designed to grasp at least 26% of an ammunition cartridge's rim.
In an alternate embodiment the extractor's flange 104 could be modified to use a prior art spring and buffer without departing from the significant advantages offered by the herein disclosed apparatus.
In still another alternate embodiment, the bolt face 92 could be machined without the inclusion of the circumferential groove 162.
The foregoing descriptions and drawings should be considered as illustrative only of the principles of the invention. The invention may be configured in a variety of shapes and sizes and is not limited by the dimensions of the preferred embodiment. Numerous applications of the present invention will readily occur to those skilled in the art. Therefore, it is not desired to limit the invention to the specific examples disclosed or the exact construction and operation shown and described. Rather, all suitable modifications and equivalents may be resorted to, falling within the scope of the invention.
This is a divisional of U.S. patent application Ser. No. 14/575,923, filed Dec. 18, 2014, granted as U.S. Pat. No. 9,810,495, which is a divisional of U.S. patent application Ser. No. 13/588,294, filed Aug. 17, 2012, granted as U.S. Pat. No. 8,950,312, which claims priority to U.S. Provisional Application No. 61/524,500, filed Aug. 17, 2011, the disclosure of each of which is incorporated herein by reference.
Number | Date | Country | |
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61524500 | Aug 2011 | US |
Number | Date | Country | |
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Parent | 14575923 | Dec 2014 | US |
Child | 15806137 | US | |
Parent | 13588294 | Aug 2012 | US |
Child | 14575923 | US |