Abstract:
A vacuum interrupter includes end covers having a curved or looped portion, which serves to connect a coil segment of the vacuum interrupter to a ceramic envelope of the vacuum interrupter, and thereby help maintain a vacuum seal for the interrupter. The curved portion acts as a spring when the vacuum interrupter is exposed to heat, thereby absorbing any expansion or contraction in the length of the vacuum interrupter due to the heating or cooling. The curved portion also protects an end of the ceramic envelope from any build-up of metallic arcing products and eliminates the need for elaborate fixturing during assembly. Additionally, a guide may be affixed to the end cover, the guide having ears which ride in a slot in a moving rod of the vacuum interrupter, to thereby prevent a twisting of a bellows of the interrupter during a brazing process. Thus, no elaborate fixturing is necessary to prevent this twisting.

Description:
TECHNICAL FIELD 
   This description relates to vacuum fault interrupters. 
   BACKGROUND 
   Conventional vacuum fault interrupters exist for the purpose of providing high voltage fault interruption. Such vacuum fault interrupters, which also may be referred to as “vacuum interrupters,” generally include a stationary electrode assembly having an electrical contact, and a movable electrode assembly on a common longitudinal axis with respect to the stationary electrode assembly and having its own electrical contact. The movable electrode assembly generally moves along the common longitudinal axis such that the electrical contacts come into and out of contact with one another. In this way, vacuum interrupters placed in a current path can be used to interrupt extremely high current, and thereby prevent damage to an external circuit. 
   SUMMARY 
   In one general aspect, an end cover for a vacuum interrupter includes a substantially annular first portion that is attached to a substantially cylindrical hollow body of the vacuum interrupter. The end cover also includes a concave second portion that is concentric to the first portion and concave with respect to the body, and a substantially annular third portion that is concentric to the first portion. 
   Implementations may include one or more of the following features. For example, the body may be primarily composed of ceramic. 
   At least a first section of the first portion may be substantially in a plane of the third portion. In this case, all of the first portion may be substantially in the plane of the third portion, and substantially perpendicular to the body. Alternatively, the second section of the first portion may be tapered away from the plane of the third portion, in a direction of the concave second portion, and attached to the body. 
   The end cover may also include a fourth portion that extends over the second portion. 
   The third portion may be attached to a substantially cylindrical electrode support structure. The support structure and the body may be concentric. 
   A substantially annular hollow guide may be attached to the third portion. The guide may include protruding portions extending into an interior of the guide. The protruding portions may ride in corresponding slots formed in a moving rod that is slidable through the end cover and the guide and operable to actuate a moving electrode of the vacuum interrupter. The protruding portions may be composed primarily of steel. 
   The third portion may be attached to, and sandwiched between, a support structure for an electrode of the vacuum interrupter and a female-threaded metallic base. 
   In another general aspect, a vacuum interrupter includes an end cover that includes a substantially circular outer perimeter portion and an inner portion that is concentric to the outer perimeter portion. A curved portion protrudes into a body of the vacuum interrupter and joins the outer perimeter portion to the inner portion. 
   Implementations may include one or more of the following features. For example, the inner portion may be substantially within a plane, and at least a first portion of the outer perimeter portion may be substantially within the plane of the inner portion. In this case, substantially all of the outer perimeter portion may be substantially within the plane of the inner portion. Alternatively, a second portion of the outer perimeter portion may be tapered away from the plane of the inner portion, in a direction of the curved portion, and attached to a substantially cylindrical hollow body of the vacuum interrupter. 
   The outer perimeter portion and the inner portion may be substantially perpendicular to a substantially cylindrical hollow body of the vacuum interrupter. The vacuum interrupter may also include a covering portion that extends over the curved portion. 
   The inner portion may be attached to a substantially cylindrical electrode support structure. The support structure and the body may be concentric. 
   A substantially annular hollow guide as discussed above may be attached to the inner portion. 
   The inner portion may be attached to, and sandwiched between, a support structure for an electrode of the vacuum interrupter and a female-threaded metallic base. 
   The details of one or more implementations are set forth in the accompanying drawings and the description below. Other features will be apparent from the description and drawings, and from the claims. 

   
     DESCRIPTION OF DRAWINGS 
       FIG. 1  is a cutaway side view of a vacuum interrupter. 
       FIG. 2  is a perspective view of coil segments of the vacuum interrupter of FIG.  1 . 
       FIG. 3  is a perspective view illustrating a technique for increasing a current path between coil segments and electrical contacts of the vacuum interrupter of FIG.  1 . 
       FIG. 4  is a block diagram illustrating current flow in the vacuum interrupter of FIG.  1 . 
       FIG. 5  is a cutaway side view of a vacuum interrupter. 
       FIG. 6  is a perspective view illustrating current flow through the vacuum fault interrupter of FIG.  5 . 
       FIG. 7  is a block diagram illustrating current flow through the vacuum interrupter of FIG.  5 . 
       FIG. 8A  is a cutaway side view of a vacuum interrupter. 
       FIG. 8B  is a block diagram illustrating current flow through the vacuum interrupter of FIG.  8 A. 
       FIG. 9A  is a cutaway side view of a vacuum interrupter. 
       FIG. 9B  is a block diagram illustrating current flow through the vacuum interrupter of FIG.  9 A. 
       FIG. 10  is an alternate implementation of a vacuum interrupter. 
       FIG. 11A  is a sectional view of a first end cap for use with the vacuum interrupter of FIG.  10 . 
       FIG. 11B  is a sectional view of a second end cap for use with the vacuum interrupter of FIG.  10 . 
       FIG. 11C  is a sectional view of a third end cap for use with the vacuum interrupter of FIG.  10 . 
       FIG. 12  is an alternate sectional view of the vacuum interrupter of FIG.  10 . 
       FIG. 13  is a cross-sectional view of the vacuum interrupter of  FIG. 12  taken along section  13 — 13 . 
   

   DETAILED DESCRIPTION 
     FIG. 1  demonstrates a vacuum interrupter  100  that includes a vacuum vessel  102 . Vacuum vessel  102  is designed to maintain an integrity of a vacuum seal with respect to components enclosed therein. Part of vacuum vessel  102  is a ceramic material  104 , which is generally cylindrical in shape. Vacuum vessel  102 , including ceramic material  104 , contains a movable electrode structure  106 , which, as described below, is operable to move toward and away from a stationary electrode structure  108 , to thereby permit or prevent a current flow through the vacuum interrupter  100 . A bellows  110  within vacuum vessel  102  is composed of a convoluted, flexible material, and is used to maintain the integrity of the vacuum vessel  102  during a movement of the movable electrode structure  106  toward or away from the stationary electrode structure  108 , as discussed in more detail below. 
   The stationary electrode structure  108  further includes a tubular coil conductor  124  in which slits  128  are machined, and an electrical contact  130 . The electrical contact  130  and tubular coil conductor  124  are mechanically strengthened by a structural support rod  122 . An external conductive rod  116  is attached to the structural support rod  122  and to conductor discs  118  and  120 . 
   The movable electrode structure  106  has many functionally-similar parts as the stationary electrode structure  108 . In particular, structure  106  includes a tubular coil conductor  140  in which slits  144  are machined, and an electrical contact  142 . Structure  106  also includes a conductor disc  138  attached to the bellows  110  and to the movable coil conductor  140  such that the electrical contact  142  may be moved into and out of contact with the electrical contact  130 . The movable electrode structure  106  is mechanically strengthened by support rod  146 , which extends out of the vacuum vessel  102  and is attached to a moving rod  134 . The moving rod  134  and the support rod  146  serve as a conductive external connection point between the vacuum interrupter and an external circuit, as well as a mechanical connection point for actuation of the vacuum interrupter. 
   A vacuum seal at each end of the ceramic portion  104  is provided by metal end caps  112  and  113 , which are brazed to a metallized surface on the ceramic. Along with the end cap  112 , an end shield  114  protects the integrity of the vacuum interrupter, and is attached between conductor discs  118  and  120 . Similarly, an end shield  115  is positioned between bellows  110  and end cap  113 . 
   In the vacuum fault interrupter of  FIG. 1 , current may flow, for example, from coil conductor  124 , electrical contact  130 , and electrical contact  142  to coil conductor  140 , so that, with respect to contacts  130  and  142 , the current may flow straight through from the ends of slots  128  and  144 . This current becomes an arc current when electrode structure  106  is separated from electrode structure  108 . 
   In  FIG. 1 , slots  128  and  144  that are cut into copper coil segments  124  and  140  generate a magnetic field parallel to the common longitudinal axis of the electrode structures (an axial magnetic field). The presence of the uniform axial magnetic field causes a diffuse arc between the electrical contacts when separated, which advantageously produces low electrical contact wear and is easy to interrupt. 
     FIG. 2  illustrates coil segments  124  and  140  and their respective slots  128  and  144 . As shown in  FIG. 2 , current flow between the coil segments generally takes the shortest possible path (i.e., current enters contact  142  after the end of each slot  144 ). This results from the flush end of coil segment  140  being connected directly to contact  142 . As a result of this current flow, magnetic flux (and thereby a magnitude of the corresponding magnetic field) is generally reduced. This reduction in the axial magnetic field reduces an ability of the field to keep the arc diffuse and uniform between the contacts, and is therefore undesirable. 
     FIG. 3  demonstrates a technique for increasing a current path between the coil segments and the electrical contacts. In  FIG. 3 , metal footings or clips  302  and  304  are placed at the ends of the coil segments  124  and  140 . The increased length of the current path leads to a higher magnetic field, but also results in difficulty in aligning the footing segment  302  and  304 . Moreover, although the magnitude of the axial magnetic field is increased by the technique of  FIG. 3 , the fact that the current enters contacts  142  and  130  in concentrated regions may lead to localized heating effects and/or a less uniform axial magnetic field. 
     FIG. 4  demonstrates a typical flow of current through vacuum fault interrupter of FIG.  1 . As shown in  FIG. 4 , current flow is generally uniform through the portions of coil segments  124  and  140  which contact electrical contacts  130  and  144 , respectively. Coil segments  124  and  140  are typically composed of a copper tube. The copper tube should ensure that a cross section between slots  128  and  144  (note that slots  128  and  144 , shown in  FIG. 1 , are not explicitly illustrated in  FIG. 4 ) is sufficient to carry high magnitude fault currents traversing the vacuum fault interrupter. As a result, particularly for high-magnitude fault currents, very thick or “heavy-walled” copper tubes may be employed. 
   However, such heavy-walled copper tubes are generally not ideal for ensuring desirable current flow, that is, current flow which is concentrated as much and as close as possible to an outside diameter of the tube. This is due to the magnitude of the magnetic field being determined by an amount of the current enclosing the field in the copper tubes. That is, since the current is flowing through the walls of the tube, there is less current enclosing the magnetic field at an edge of the tube than there is within an inner diameter of the tube. As a result, the field peaks at a center of the tube, and decreases to zero at the outer perimeter of the walls. In a thin-walled tube, the magnetic field peak is lower and the rate of drop-off towards the outside diameter is less. Also, since the inside diameter is closer to the outside diameter (and is thus larger) in a thin-walled tube, this drop-off occurs closer to the outside diameter of the tube, ensuring a larger area with a uniform magnetic field. Uniformity of the magnetic field is thus generally inversely related to the thickness of the walls of the tube. 
     FIG. 5  demonstrates a vacuum fault interrupter  500  that is similar in structure to the fault interrupter  100  of FIG.  1 . Note that portions of  FIG. 5  not explicitly discussed in the following discussion or above with respect to  FIG. 1  are discussed in more detail below with respect to  FIGS. 10 and 12 . In  FIG. 5 , a stainless steel ring  508  is placed between coil segment  502  and contact  506  (which correspond to coil segment  140  and contact  142 ). Similarly, a stainless steel ring is also placed between coil segments  504  and contact  512 . 
   Coil segment  502  includes a small counterbore that produces a longitudinal protrusion  514  that extends from the end of the coil segment around the perimeter of the coil segment. Similarly, coil segment  504  has a counterbore that produces a longitudinal protrusion  516  at the end of that coil segment. Thus, each coil has a constant outer diameter and an inner diameter that increases at the protrusion. Techniques other than counterboring may be used to produce the same results. For example, the coil segments may be cast or forged using a mold that defines the protrusions. 
   Stainless steel rings  508  and  510  each have a volume resistivity higher than those of their respective coil segments and the electrical contacts, such that current flow through the rings is uniformly spread through the copper at the end of the coil segments, and uniformly enters the contacts. Stainless steel rings  508  and  510  may be composed of for example, a non-magnetic stainless steel, such as AISI 304. 
   Because the current does not enter the contacts immediately at the end of the slots in the electrode structure, a longer current path is created. As a result, a magnitude of the axial magnetic field is increased. Also, because of the uniform spreading of the current upon entering the contacts, localized heating at the contacts is reduced, and a uniformity of the axial magnetic field is correspondingly improved. Finally, the presence of the relatively high resistivity ring also serves to reduce any losses in the axial magnetic field which may result from the presence of eddy currents. For example, in the vacuum fault interrupter  100  of  FIG. 1 , eddy currents may momentarily travel around coil segment  124 , and momentarily skip around slot  128  (via contact  130 ) and back into coil segment  124 ; in the vacuum fault interrupter  500  of  FIG. 5 , the high-resistivity ring(s)  508 / 510  prevent this behavior. Additionally, the presence of the high-resistivity (impedance) ring(s)  508 / 510  in  FIG. 5  reduces a conductive cross section available to eddy currents, by taking up space that is filled by the contacts  130  and  142  and/or the coil segments  124  and  140  in FIG.  1 . 
   Because the above-recited features result from the relatively high resistivity of the stainless steel rings  508  and  510 , other materials with similarly high resistivities may also be used to obtain the advantages. For example, certain copper-chrome or copper-nickel alloys (such as Monel) could also be used. Additionally, another way to increase an impedance (although not a resistivity) presented to the current is to increase a diameter of the counter bore (i.e., use a narrow cross section on the end of the coil sections  108  and  140 ). 
   Additionally, protrusions  514  and  516  force the flow of current to an outside diameter of the coil segments and contacts. As a result, despite the use of heavy-walled copper in constructing coil segments  502  and  504 , a uniform axial magnetic field may nevertheless be obtained. 
     FIG. 6  demonstrates a current flow through the vacuum fault interrupter of FIG.  5 . In  FIG. 6 , it should be understood that current flow occurs uniformly between the coil segments due to the presence of steel rings  508  and  510 .  FIG. 7  demonstrates a cross section of current flow through the vacuum interrupter of FIG.  5 . As shown in  FIG. 7 , current flow is forced to an outside diameter of coil segments  124  and  140 , which increases the uniformity of an axial magnetic field between the electrodes. 
     FIG. 8A  demonstrates a vacuum interrupter  800  that is similar to the vacuum interrupter  500  of FIG.  5 . Each of coil segments  806  and  808  includes a counterbore and a corresponding ring-shaped protrusion  810  or  812 . However, stainless steel rings like the rings  508  and  510  are not included. 
     FIG. 8B  illustrates current flow in the implementation of FIG.  8 A. In  FIG. 8B , as in  FIGS. 5-7 , current is forced to an outside perimeter of coil segment  808  by virtue of portions  810  and  812 . This is true aside from the fact that no stainless steel rings or other impedance is placed between coil segments  806 ,  808  and electrical contacts  802 ,  804 , respectively. In  FIGS. 8A and 8B , it should be apparent that contacts  802  and  804  are shaped differently than contacts  506  and  512 . Specifically, contacts  802  and  804  each have a portion within the counterbore of coil segments  806  and  808  that extends throughout essentially the entire diameter of the counterbore, and has direct contact with all of the interior surfaces at the ends of the coil segments  806  and  808 , including those of ring-shaped protrusions  810  and  812 . 
   Conversely,  FIG. 9A  demonstrates an implementation of the vacuum interrupter of  FIG. 5  in which there is no counter bore in the coil segments  906  and  908 . Rather, coil segments  906  and  908  have flush ends, against which steel rings or other high resistivity rings  902  and  904  are situated between the coil segments  906  and  908  and the contacts  912  and  910 , respectively. 
     FIG. 9B  illustrates current flow in the implementation of FIG.  9 A. In  FIG. 9B , current is dispersed by the presence of rings  902  and  904 , and therefore travels evenly through contacts  910  and  912 , as well as through coil segments  906  and  908 . In this way, the current path is effectively lengthened, resulting in a higher axial magnetic field and less localized heating at the contacts  910  and  912 . 
   Use of the vacuum interrupters of  FIGS. 5 ,  8  and  9  is governed by particular needs of a user of the interrupter. For example, the assembly of the formation of  FIGS. 8A and 8B  may obviate any cost and assembly-related difficulties associated with rings  508  and  510 . Conversely, machining of the coil segments  906  and  908  of the vacuum interrupter of  FIGS. 9A and 9B  may be eased by the nature of the flush end of the coil segments  906  and  908  with respect to steel rings  902  and  904 . 
     FIG. 10  illustrates an alternate implementation of a vacuum interrupter  1000 . In  FIG. 10 , an end cap  1005  serves to help maintain an integrity of a vacuum seal of vacuum interrupter  1000 . End cap  1005  is attached to ceramic  1010  (which forms a substantially cylindrical hollow body), cylindrical structure  1015 , and conductive segment  1020 . In this implementation, conductive segment  1020  is a female-threaded connector for connecting to a male-threaded connector and thereby to an external circuit. Compared to external conductive rod  116  of  FIG. 1 , segment  1020  provides a more stable base upon which the vacuum interrupter of  FIG. 10  may need to rest during an assembly of the vacuum interrupter. 
   Additionally, end cap  1005  includes a loop or continuously curved portion  1022  that provides several advantages. For example, in the vacuum interrupter of  FIG. 1 , end caps  112  and  113  are generally fixtured during assembly of the vacuum interrupter, and thereby held in place while being brazed to the metallized surface on ceramic  104 . This is necessary since the brazing is a fluid process, and the end caps  112  and  113  might float out of position if not held in place by fixtures. Nonetheless, such fixtures are often elaborate and, particularly with respect to a level of cleanliness that must be preserved throughout the brazing process, extremely difficult to maintain. Moreover, such fixtures are often difficult to maintain mechanically as well, often loosening over time until they fail to secure their associated portions of the vacuum interrupter tightly enough to ensure functionality. 
   As the vacuum interrupter cools from the brazing cycle (approximately 700-800° C.), a difference in the coefficients of linear thermal expansion between ceramic  104  (approximately 6-8×10 −6  inches/inches° C.) and end cap  112  (approximately 1-2×10 −6  inches/inches° C.) may cause end cap  112  to bow inward, thereby changing the overall length of the vacuum interrupter. Moreover, the amount of this bowing tends to vary, making it difficult to predict a final length of a vacuum interrupter being assembled. 
   Additionally, end shield  114 , which may be either attached to end cap  112  as shown in  FIG. 1  or integral to end cap  112 , serves to protect the triple joint (ceramic, metal, and vacuum) at each end of ceramic  104 . Because the tip of end shield  114  has a relatively sharp point, end shield  114  tends to focus electrical stress (electric field), such that any burrs or discontinuities on the surface of end field  114  may cause a failure of the vacuum fault interrupter at high voltage. 
   In contrast, the rounded surface of the loop  1022  of the end cap  1005  in the vacuum interrupter of  FIG. 10  produces a much lower electrical stress and thereby reduces the probability of a failure at high voltage. Furthermore, this loop acts as a radial spring that absorbs any differences in the coefficients of linear thermal expansion between the ceramic  1010  and metal end cap  1005 . Since the end caps do not bow, the end length of the vacuum interrupter of  FIG. 10  does not vary significantly. In anther example of an advantageous feature of the vacuum interrupter of  FIG. 10 , the loop-associated angles and radii leading to the loop from the outer flange surface (i.e., a flat area outside the loop) tend to be self aligning at braze temperature, so that elaborate fixturing is not necessary to hold the end cap in place until the end cap is brazed. 
     FIGS. 11A ,  11 B, and  11 C illustrate three examples of loops that may be formed in the end caps  1005  of the vacuum interrupter of FIG.  10 . In  FIG. 11A , a loop  1105  is essentially perfectly rounded, so that portions  1110  and  1115  are substantially symmetrical, and define a distance “d 1 ”  1120  that exists between a bottom of loop  1105  and a top plane of end cap  1005 . 
   In  FIG. 11B , a loop  1125  is less rounded and comes to a somewhat sharper point. In this case, portions  1130  and  1135  may be of different lengths, as shown. Also, a distance “d 2 ”  1140  may be relatively larger than distance d 1   1120 . Increasing or decreasing the distance d 1   1120  or d 2   1140  may impact a spring constant of loop  1105  or  1125 , respectively, as well as an amount of triple joint protection and shielding. Similarly, increasing or reducing a symmetry of loops  1105  and  1125  may also affect their respective spring constants, so that these factors may be adjusted as needed to obtain a desired result. Thus, as long as the loop does not form such a sharp point as to begin to act as an area of electric field concentration, thereby causing electrical discontinuities, a degree of concavity may be chosen by a designer in any manner thought to optimize the use of end cap  1005 . 
   In  FIG. 11C , a loop  1143  forming a continuously curving concave second portion is similar to the loop  1125  of  FIG. 11B , with respect to a shape of portions  1145  and  1150 . However, in  FIG. 11C , an outer portion  1155  (i.e., an outer sealing flange of the end cap  1005 , also referred to as a substantially annular first portion, or a substantially circular outer perimeter portion) is not completely co-planar with an inner portion  1160  (also referred to as a substantially annular third portion) of the end cap  1005 , as is shown in  FIGS. 11A and 11B . Rather, only a first section of the outer portion (i.e., first portion)  1155  is co-planar with the inner portion (i.e., third portion)  1160 . A second section of the outer portion  1155  tapers away from a plane of the inner portion  1160 , to define a distance “d 3 ”  1165 , and thus forms the outer portion  1155  into a slightly conical shape. In practice, the distance d 3   1165  may be, for example, approximately 0.001 inches to .010 inches, and may not be visible to the naked eye (in  FIG. 11C , a magnitude of the distance d 3   1165  with respect to a size of the end cap  1005  is exaggerated for the sake of illustration). Although a portion of the outer portion  1155  is co-planar with the inner portion  1160  in  FIG. 11C , the outer portion  1155  could also be formed so as to have no portion that is co-planar with the inner portion  1160 , regardless of whether the outer portion  1155  is tapered in the manner of FIG.  11 C. 
   Referring again to  FIG. 10 , cover portions  1025  may optionally be used to cover an open area formed by the presence of the loop in end cap  1005 . This cover may be useful in situations in which the vacuum interrupter of  FIG. 10  is to be molded within a solid dielectric (e.g., an epoxy material). In this way, an air cavity is maintained within the concavity formed by the loop in end cap  1005 , so that the advantageous compression of end cap  1005  discussed above may also be realized for absorbing stresses associated with solid dielectrics, i.e., molding stresses. In other situations, such as when the vacuum interrupter is encased in oil, cover portions  1025  may not be necessary. In the context of, for example.  FIG. 11C , the cover portions  1025  may be used to form a fourth portion that extends over the second portion  1140 . 
   As referred to above with respect to  FIG. 1 , a motion of a moving rod  134 , and its associated electrical contact  142 , is maintained with a bellows  110 . While very flexible, bellows  110  may also be quite fragile. Thus, after the vacuum interrupter of  FIG. 1  is brazed together, there must be assurance that the moving rod  134 , and thus the bellows  110 , are not twisted, as this would damage the bellows  110 . 
   To help avoid damage to bellows  1030  of  FIG. 10 , a slot  1050  is formed in a tubular portion of moving rod  1035 . A substantially annular hollow guide  1045  having a plurality of ears ( 1302  in  FIG. 13 ) is affixed to the end cap  1005 , and these ears ride in the slot  1050  in the moving rod  1035 , which extends along moving rod  1035  into the vacuum interrupter, past the end cap  1005 .  FIG. 13  demonstrates a cross-section view of moving rod  1035  showing guide  1045  taken along sectional line  13 — 13  shown in  FIG. 12 , and illustrating ears or protruding portions  1302 . In  FIG. 13 , other elements of  FIG. 12  are not shown, to thereby better illustrate the slotted nature of moving rod  1035  and guide  1045 . 
     FIG. 12  illustrates the addition of a compression spring  1205  that is added and held in place via a spring holder  1210  that in turn is held in place by a roll pin  1215 . The roll pin  1215  sits in slot  1050  (not seen in this figure). Actuation of the vacuum interrupter is transmitted through compression spring  1205 . Through the assembly as described above and shown in  FIGS. 10 ,  12 , and  13 , the moving rod  1035  is prevented from twisting and damaging the bellows during subsequent assembly operations, e.g., current exchange assembly or epoxy encapsulation, and little or no fixturing may be required to achieve this result. 
   A number of implementations have been described. Nevertheless, it will be understood that various modifications may be made. Accordingly, other implementations are within the scope of the following claims.