Abstract:
The present invention is an apparatus and method for detecting foreign material in containers in a product stream. Two X-ray emitters and two sensor arrays are positioned in a constellation to improve the detection of foreign material. A first x-ray emitter is positioned so that it projects an x-ray beam in a downward manner through the product stream. A second x-ray emitter is positioned so that it projects an x-ray beam in an upward manner through the product stream. Two sensor arrays are each positioned in receiving relation to each of the x-ray beams to receive and provide signals from each of the beams after they have interacted with the product stream. Signals from each of the two sensor arrays are processed and compared with user defined thresholds to detect and indicate the presence of foreign material in containers.

Description:
TECHNICAL FIELD 
     The present invention relates to an apparatus and method for identifying foreign materials in a container. 
     BACKGROUND OF THE INVENTION 
     For many years, the food industry has employed x-ray scanning devices and detectors to inspect cans or containers for foreign or undesirable material to ensure the safety and quality of their products. Often, each type of container presents its own unique challenges for optimizing the accuracy of the detection of foreign material. Containers are built using a variety of materials, and come in many shapes and sizes. 
     One device in the art that has been specifically optimized for the detection of foreign material within a bottle is disclosed in U.S. Pat. No. 7,106,827. Here the invention utilizes one or two X-ray sources and one detector array positioned so that some of the x-rays travel in a direction that is approximately tangential to a maximum slope of a bulge of on a bottom of a container. 
     Such an approach, however, is of limited use when detecting foreign material in containers such as cans. Here, various features of the cans including seams, pull-tops and folds can confound the detection process, and decrease the overall effectiveness of an apparatus. 
     So, what is needed is an apparatus and method for detecting foreign material in a container including cans which can effectively identify and detect foreign material despite confounding features of the container such as seams, pull-tops and folds. 
     SUMMARY OF THE INVENTION 
     A first aspect of the present invention is to provide an apparatus for detecting the presence of a foreign object in a container with a top surface that is positioned in a first horizontal plane, and a bottom surface that is positioned in a second horizontal plane. The apparatus includes a conveyor configured to transport the container, and a first x-ray emitter located proximate to the first horizontal plane, and configured to project a first diverging x-ray beam in a first vertical plane through the container, and a first sensor array positioned in receiving relation to the first x-ray beam after the first x-ray beam has interacted with the container. The apparatus also includes a second x-ray emitter located proximate to the second horizontal plane, and configured to project a second diverging x-ray beam in a second vertical plane through the container, and a second sensor array positioned in receiving relation to the second x-ray beam after the second x-ray beam has interacted with the container, and wherein the first and second vertical planes are oriented in non-parallel relation. 
     Another aspect of the invention is a method for detecting the presence of a foreign object in a container, which includes providing a container having a top surface bound by a first horizontal plane and a bottom surface bound by a second horizontal plane, and providing a first x-ray emitter located proximate to the first horizontal plane, and providing a second x-ray emitter located proximate to the second horizontal plane. The method further includes transporting the container, and directing a first x-ray beam from the first x-ray emitter in a first vertical plane, and toward the second horizontal plane in a diverging manner; and directing a second x-ray beam from the second x-ray emitter in a second vertical plane, and toward the first horizontal plane in a diverging manner. 
     These and other aspects of the present invention will be discussed in greater detail hereinafter. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Preferred embodiments of the invention are described below with reference to the following accompanying drawings. 
         FIG. 1  is an isometric view of the apparatus for detecting foreign material in a product stream of filled and sealed cans. 
         FIG. 2  is an isometric view of a preferred embodiment of the inspection station of the apparatus with an optional actuator. 
         FIG. 3  is a plan view of a preferred embodiment of the inspection station. 
         FIG. 4  is a partial cross sectional view of the inspection station with the first x-ray emitter projecting a first x-ray beam through a can containing foreign material to the first sensor array. 
         FIG. 5  is a partial cross sectional view of the inspection station with the second x-ray emitter projecting a second x-ray beam through a can containing foreign material to the second sensor array. 
         FIG. 6  is an isometric view of an alternate embodiment of the inspection station of the apparatus. 
         FIG. 7  is a plan view of an alternate embodiment of the inspection station. 
         FIG. 8  is a partial cross sectional view of the alternate embodiment of the inspection station with the second x-ray emitter projecting a second x-ray beam through a can containing foreign material to the second sensor array. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     This disclosure of the invention is submitted in furtherance of the constitutional purposes of the U.S. Patent Laws“to promote the progress of science and useful arts” (Article 1, Section 8). 
     A preferred embodiment of an apparatus  10  for detecting foreign material in a container is shown in  FIG. 1 . The apparatus  10  is mounted to a floor or platform using a plurality of support feet  12 . The support feet  12  are adjustably mounted to a support frame  14 . An enclosure  16  is borne by the support frame  14 . A user interface  20  is mounted to the enclosure  20 . A series of status lights  22  are also mounted to the enclosure  16 . 
     The enclosure  16  has an aperture  18  which provides a path therethrough. An inspection station  24  is contained within the enclosure  16 , and is positioned around the aperture  18  in x-ray transmission relation, and will be discussed in further detail below. 
     A conveyor frame  26  is held by a conveyor support  28  and extends through the aperture  18 . A product stream  30  having a plurality of articles including cans or containers  32  are borne by, and transported with a conveyor belt  34  in a flow direction generally indicated by the numeral  36 . The cans or containers  32  range in height from 15 mm to 220 mm and from a diameter of 20 mm to 180 mm. The cans or containers  32  are transported at a speed having a range, and the range extends from a low value of  2  meters per minute to a high value of 250 meters per minute. In this arrangement, cans or containers  32  are transported by the conveyor belt  34  through the aperture  18  and interrogated by the inspection station  24  to identify the presence of foreign material in the cans or containers  32 . 
     Now referring to  FIG. 2 , the inspection station  24  is positioned within the enclosure  16  ( FIG. 1 ) and is positioned in straddling relation to the conveyor belt  34  where cans or containers  32  are transported. 
     A first x-ray emitter  40  is positioned on adjacent to the conveyor belt  34  and is operable to emit x-ray radiation in a pattern forming a first x-ray beam  42  having a first diverging angle  44 . The x-ray emitter  40  is positioned at a height or elevation that is approximate to a top seam  46  of the can or container  32  so that the first x-ray emitter  40  and the top seam  46  of the can or container  32  both border a first horizontal plane  50  ( FIG. 4 ). 
     The first x-ray emitter  40  is positioned so that an upper edge  48  of the first beam  42  is proximate to the first horizontal plane  50  ( FIG. 4 ). An optional actuator  41  is shown which is utilized to position the emitter  40  at a preset position to enable rapid change over for containers of varying heights. A lower edge  52  of the first beam  42  is positioned in intersecting relation to the can or container  32 . In a preferred embodiment, the first x-ray emitter  40  is an x-ray source having a spectral range of 20 to 70 kV. 
     A first sensor array  54  is positioned in receiving relation to the first x-ray beam  42 . A top  56  of the first sensor array  54  is positioned proximate to the first horizontal plane  50 . A bottom  58  of the first sensor array  54  is positioned below the conveyor belt  34 . In this manner, x-rays originating from the first x-ray emitter  40  are projected through the can or container  32  where they are received and converted into signals by the first sensor array  54 . 
     A second x-ray emitter  60  is positioned adjacent to the conveyor belt  34  that is opposite the first side, and is operable to emit x-ray radiation in a pattern forming a second x-ray beam  62  having a second diverging angle  64 . The second x-ray emitter  60  is positioned at a height or elevation that is approximate to a bottom seam  66  of the can or container  32  so that the second x-ray emitter  60  and the bottom seam  66  of the can or container  32  both border a second horizontal plane  70  ( FIG. 4 ). The second x-ray emitter  60  is positioned so that a lower edge  72  of the second x-ray beam  62  is proximate to the second horizontal plane  70  ( FIG. 4 ). An upper edge  68  of the second beam  62  is positioned in intersecting relation to the can or container  32 . In a preferred embodiment, the second x-ray emitter  60  is an x-ray source having a spectral range of 20 to 70 kV. 
     A second sensor array  74  is positioned in receiving relation to the second x-ray beam  62 . A bottom  78  of the second sensor array  74  is positioned proximate to the second horizontal plane  70  ( FIG. 4 ). A top  76  of the second sensor array  54  is positioned substantially above the top seam  46  of the can or container  32 . In this manner, x-rays originating from the second x-ray emitter  60  are projected through the can or container  32  where they are received and converted into signals by the second sensor array  74 . 
     Now referring to  FIG. 3 , the first x-ray beam  42  is oriented in a first vertical plane  82  and the second x-ray beam  62  is oriented in a second vertical plane  84 . 
     Referring now to  FIGS. 3 and 4 , a can or container  32  is positioned on the conveyor belt  34  and is interrogated by radiation that projects from the first x-ray emitter  40  as the first x-ray beam  42 , and through the can or container  32  to the first sensor array  54 . A section line  4 - 4  ( FIG. 3 ) provides an indication of the location and direction of a partial cross sectional view shown in  FIG. 4 . 
     Referring now to  FIG. 4 , the first x-ray emitter  40  provides radiation forming the x-ray beam  42  having the upper edge  48  and lower edge  52 . The upper edge  48  lies proximate to the first horizontal plane  50 . 
     The can or container  32  contains desirable contents  110  having a top surface  111  inside the can or container  32 . The container is formed having a cylindrical wall  116 , a bottom  114 , and a lid  112 . The bottom  114  and lid  112  each have concentric grooves formed therein to provide rigidity. The lid  112  often includes a pull tab (not shown) to facilitate opening. The cylindrical wall  116  includes a series of corrugations formed therein to strengthen the container  32 . The lid  112  is sealably attached to the wall  116  by means of a seam  118 . 
     The x-ray beam  42  is composed of a plurality of rays, each projecting from the first x-ray emitter  40 . Several of these rays are enumerated as  130 ,  132 ,  134 ,  136 , and  138  for discussion purposes, and will be discussed in more detail below. 
     Referring to  FIGS. 3 and 5 , a can or container  32  is positioned on the conveyor belt  34  and is interrogated by radiation that projects from the second x-ray emitter  60  as the second x-ray beam  62 , and through the can or container  32  to the second sensor array  74 . A section line  5 - 5  ( FIG. 3 ) provides an indication of the location and direction of a partial cross sectional view shown in  FIG. 5 . 
     Referring now to  FIGS. 4 and 5 , several pieces of undesirable or pieces of foreign material are shown suspended or submerged in the contents  110  of the can or container  32  and are represented by the numerals  120 ,  122 ,  124 ,  126 , and  128 . These undesirable or foreign materials includes, but is not limited to, shards of glass, metal fragments, stones, rubber pieces, hard plastic, or bones. 
     Referring now to  FIG. 5 , the second x-ray emitter  60  provides radiation that projects the x-ray beam  62  forming the upper edge  68  and lower edge  72 . The lower edge  72  lies proximate to the second horizontal plane  70 . 
     The second x-ray beam  62  is composed of a plurality of rays, each projecting from the second x-ray emitter  60 , several of which are enumerated as  140 ,  142  and  144 , and will be discussed in more detail below. 
     Now referring to  FIG. 6 , an alternate embodiment of the inspection station  24  is positioned within the enclosure  16  ( FIG. 1 ) and is positioned in straddling relation to the conveyor belt  34  where cans or containers  32  are transported. 
     A first x-ray emitter  240  is positioned on a first side of the conveyor belt  34  and is operable to emit x-ray radiation in a pattern forming a first x-ray beam  242  having a first diverging angle  244 . The x-ray emitter  240  is positioned at a height or elevation that is approximate to the top seam  46  of the can or container  32  so that the first x-ray emitter  240  and the top seam  46  of the can or container  32  both border the first horizontal plane  50  ( FIG. 8 ). The first x-ray emitter  240  is positioned so that an upper edge  248  of the first beam  242  is proximate to the first horizontal plane  50  ( FIG. 8 ). A lower edge  252  of the first beam  242  is positioned in intersecting relation to the can or container  32 . In a preferred embodiment, the first x-ray emitter  240  is an x-ray source having a spectral range of 20 to 70 kV. 
     A first sensor array  254  is positioned in receiving relation to the first x-ray beam  242 . A top  256  of the first sensor array  254  is positioned proximate to the first horizontal plane  50 . A bottom  258  of the first sensor array  254  is positioned below the conveyor belt  34 . In this manner, x-rays originating from the first x-ray emitter  240  are projected through the can or container  32  where they are received and converted into signals by the first sensor array  254 . 
     A second x-ray emitter  260  is positioned on second side of the conveyor belt  34  that is opposite the first side, and is operable to emit x-ray radiation in a pattern forming a second x-ray beam  262  having a second diverging angle  264 . The second x-ray emitter  260  is positioned at a height or elevation that is approximate to the bottom seam  66  of the can or container  32  so that the second x-ray emitter  260  and the bottom seam  66  of the can or container  32  both border the second horizontal plane  70  ( FIG. 8 ). The second x-ray emitter  260  is positioned so that a lower edge  272  of the second x-ray beam  262  is proximate to the second horizontal plane  270  ( FIG. 8 ). An upper edge  268  of the second beam  62  is positioned in intersecting relation to the can or container  32 . In a preferred embodiment, the second x-ray emitter  60  is an x-ray source having a spectral range of 20 to 70 kV. 
     A second sensor array  274  is positioned in receiving relation to the second x-ray beam  262 . A bottom  278  of the second sensor array  274  is positioned proximate to the second horizontal plane  70  ( FIG. 8 ). A top  276  of the second sensor array  254  is positioned substantially above the top seam  46  of the can or container  32 . In this manner, x-rays originating from the second x-ray emitter  260  are projected through the can or container  32  where they are received and converted into signals by the second sensor array  274 . 
     Now referring to  FIG. 7 , the first x-ray beam  242  is oriented in a first vertical plane  282  and the second x-ray beam  262  is oriented in a second vertical plane  284 . The first x-ray beam  242  and the second x-ray beam  262  are arranged at an angle  280  relative one to another. 
     The can or container  32  is positioned on the conveyor belt  34  and is interrogated by radiation that projects from the first x-ray emitter  240  as the first x-ray beam  242 , and through the can or container  32  to the first sensor array  254 . The section line  44  ( FIG. 7 ) provides an indication of the location and direction of the partial cross sectional view shown in  FIG. 4  referred to earlier in this specification. 
     Referring to  FIGS. 7 and 8 , the can or container  32  is positioned on the conveyor belt  34  and is interrogated by radiation that projects from the second x-ray emitter  260  as the second x-ray beam  262 , and through the can or container  32  to the second sensor array  274 . A section line  8 - 8  ( FIG. 7 ) provides an indication of the location and direction of a partial cross sectional view shown in  FIG. 8 . 
     Referring now to  FIG. 8 , the second x-ray emitter  260  provides radiation that projects the x-ray beam  262  forming the upper edge  268  and lower edge  272 . The lower edge  272  lies proximate to the second horizontal plane  70 . 
     Also shown in  FIG. 8 , are corresponding views of the undesirable or foreign material represented by the numerals  120 ,  122 ,  124 ,  126 , and  128 . 
     The second x-ray beam  262  is composed of a plurality of rays, each projecting from the second x-ray emitter  260 , several of which are enumerated as  290 ,  292  and  294 , and will be discussed in more detail below. 
     Operation 
     The operation of the present invention is believed to be readily apparent and is briefly summarized in the paragraphs which follow. 
     In operation, the product stream  30  having the plurality of cans or containers  32  is conveyed or transported by the conveyor belt  34  in the flow direction generally indicated by the numeral  36 . The cans or containers  32  are conveyed through an aperture  18  in the apparatus for detecting foreign material  10  so that they can be interrogated by the inspection station  24 . 
     The inspection station  24  is operable to interrogate cans or containers  32  in the product stream  30  using through-transmission and reception of X-rays that have been propagated through the containers  32  as that are transported by the conveyor belt  34 . The inspection station  24  includes a first X-ray emitter  40  that is located proximate to the first horizontal plane  50  which coincides with the top seam  46  of the container  32 . The position of the first X-ray emitter  40  is optionally set by the actuator  41 . A second x-ray emitter  60  that is located proximate to the second horizontal plane  70 . The first x-ray beam  42  originates from the first x-ray emitter  40  and is aligned with the first vertical plane  82 , and is directed in a diverging manner toward the second horizontal plane  70 . 
     The second x-ray beam  62  originates from the second x-ray emitter  60  and is aligned with the second vertical plane  84 , and is directed in a diverging manner toward the first horizontal plane  50 . 
     The first X-ray beam  42  propagates through the container  32  and its contents  110 , and is received by the first sensor array  54  where a signal is provided representing the magnitude of received X-rays over the length of the array according to a manner that is well known in the art. These signals are processed with known thresholds to make a determination whether foreign material exists in the container  32 . 
     Referring to  FIG. 4 , the first x-ray beam  42  comprises a plurality of rays, of which several are illustrated for discussion. 
     Ray  130  originates from the first X-ray emitter  40  and travels through a corrugated section of the cylindrical wall  116  of the container  32 . Here, some of the energy is diffracted, but a substantial portion continues to travel in the manner illustrated in the figure as it travels through the contents  110  of the container  32 . The ray  130  interacts with a portion of the foreign material piece  124  where some of the energy is reflected or refracted or absorbed. A portion of the energy continues to travel as illustrated in the figure and passes through the bottom  114  of the container, and finally is received by the first sensor array  54 . 
     Another ray,  132  similarly originates from the first x-ray emitter  40  and interacts with the cylindrical wall  116 , and with the contents  110 , and then encounters a piece of foreign material  128 . Then, a portion of the energy travels through the bottom  114  of the container  32  and finally is received by another portion of the first sensor array  54 . 
     Yet another ray  134  also originates from the first x-ray emitter  40 , and then encounters the cylindrical wall  116 , then traveling through the contents  110  where it interacts with pieces of foreign material  128  and  127 . Then the ray  134  emerges through a corner in the container  32  where it is received by yet another portion of the first sensor array. 
     Another ray  136  is transmitted by the first x-ray emitter  40  and passes through the cylindrical wall  116  and then encounters a piece of foreign material  122  that is floating on the surface  111  of the contents  110 . Then, the ray  136  passes through the contents  110 , and through the cylindrical wall  116 , finally being received by another portion the first sensor array  54 . 
     Finally, a ray  138  is sent by the first x-ray emitter  40 , and through the cylindrical wall  116 , and then it interacts with another piece of floating foreign material  120 . Then, the ray grazes the surface  111  and travels through the cylindrical wall  116  where it emerges and is received by a portion of the first sensor array  54 . 
     Referring to  FIG. 5 , the second x-ray beam  62  comprises a plurality of rays, of which several are illustrated for discussion below. 
     Ray  140  originates from the second X-ray emitter  60  and travels through a corner of the container  32 . Here, some of the energy is diffracted, but a substantial portion continues to travel in the manner illustrated in the figure as it travels through the bottom  114  in a substantially absorbing and diffracting manner. Then, a lesser portion of the original ray  140  interacts with the foreign material piece  126  where some of the energy is reflected or refracted or absorbed. A portion of the energy continues to travel as illustrated in the figure and passes through the cylindrical wall  116  of the container  32  where it is finally received by the second sensor array  74 . One skilled in the art would recognize that the magnitude of X-rays of the ray  140  received at the second sensor array  74  would be greatly attenuated from an original magnitude present as the ray emerged from the second X-ray emitter  60 . A careful inspection of  FIG. 4  in comparison to  FIG. 5  reveals that ray  134  of  FIG. 4  is able to more effectively interrogate and to reveal the presence of the piece of foreign material  126  than the ray  140  as shown in  FIG. 5 . 
     Another ray  142  similarly originates from the second x-ray emitter  60  and interacts with the cylindrical wall  116 , then encounters the piece of foreign material  126 . Then, a portion of the energy travels through the contents  110  and interacts with a portion of the piece of foreign material  128 . Finally, the ray  142  passes through the cylindrical wall  116  of the container  32  and emerges to be received by another portion of the second sensor array  74 . A careful inspection of  FIG. 4  and  FIG. 5  reveals that the ray  142  ( FIG. 5 ) is more effective in indicating the presence of the piece of foreign material  124  than the ray  124  ( FIG. 4 ) because the ray  124  interacts with corrugations in the cylindrical wall  116  and the bottom  114  significantly confounding the signal. 
     Finally, another ray  144  also originates from the second x-ray emitter  60  and encounters a corrugated portion of the cylindrical wall  116 , and then travels through the contents  110  where it interacts with a piece of foreign material  122  that is floating on the surface  111 . Then the ray  144  interacts with a seam  118  of the container  32 , finally emerging where it is received by yet another portion of the second sensor array  74 . A careful inspection of  FIGS. 4 and 5  reveals that the ray  136  ( FIG. 4 ) will more accurately reveal the presence of the piece of foreign material  122  than the ray  144  ( FIG. 5 ) which will be attenuated by a greater degree because of an interaction with a corrugated section of the cylindrical wall  116 , a longer path through the contents  110 , and more importantly, the seam  118 . 
     Another further example of the operation of the inspection station  24  includes a discussion of the alternate embodiment shown in  FIG. 6 . Here, the inspection station  24  includes a first X-ray emitter  240  that is located proximate to the first horizontal plane  50  and a second x-ray emitter  260  that is located proximate to the second horizontal plane  70 . The first x-ray beam  242  originates from the first x-ray emitter  240  and is aligned with the first vertical plane  282 , and is directed in a diverging manner toward the second horizontal plane  70 . 
     The second x-ray beam  262  originates from the second x-ray emitter  260  and is aligned with the second vertical plane  284 , and is directed in a diverging manner toward the first horizontal plane  50 . 
     The first X-ray beam  242  propagates through the container  32  and its contents  110 , and is received by the first sensor array  254  where a signal is provided representing the magnitude of received X-rays over the length of the array according to a manner that is well known in the art. These signals are processed with known thresholds to make a determination whether foreign material exists in the container  32 . 
     The interaction of the first x-ray beam has been previously discussed as described in  FIG. 4 . 
     Referring now to  FIG. 8 , the second x-ray beam  262  comprises a plurality of rays, of which several are illustrated for discussion below. 
     Ray  290  originates from the second X-ray emitter  260  and travels through a corner of the container  32 . Here, some of the energy is diffracted, but a substantial portion continues to travel in the manner illustrated in the figure as it travels through the bottom  114  in a substantially absorbing and diffracting manner. Then, a lesser portion of the original ray  140  interacts with the foreign material pieces  126  and  128  where some of the energy is reflected or refracted or absorbed. A portion of the energy continues to travel as illustrated in the figure and passes through the cylindrical wall  116  of the container  32  where it is finally received by the second sensor array  274 . One skilled in the art would recognize that the magnitude of X-rays of the ray  290  received at the second sensor array.  274  would be greatly attenuated from an original magnitude present as the ray emerged from the second X-ray emitter  260 . A careful inspection of  FIG. 4  in comparison to  FIG. 8  reveals that ray  134  of  FIG. 4  is able to more effectively interrogate and to reveal the presence of the piece of foreign material  126  than the ray  140  as shown in  FIG. 8 . 
     Another ray  292  similarly originates from the second x-ray emitter  260  and interacts with the cylindrical wall  116 , then encounters the piece of foreign material  124 . Then, a portion of the energy travels through the contents  110  and interacts with a portion of the piece of foreign material  128 . Finally, the ray  292  passes through the cylindrical wall  116  of the container  32  and emerges to be received by another portion of the second sensor array  274 . A careful inspection of  FIG. 4  and  FIG. 8  reveals that the ray  292  is more effective in detecting the presence of the piece of foreign material  124  than the ray  130  ( FIG. 4 ) because the ray  130  interacts with corrugations in the cylindrical wall  116  and the bottom  114  significantly confounding the signal. 
     Finally, another ray  294  also originates from the second x-ray emitter  260  and encounters a corrugated portion of the cylindrical wall  116 , and then travels through the contents  110  where it interacts with a piece of foreign material  122  that is floating on the surface  111 . Then the ray  294  interacts with a seam  118  of the container  32 , finally emerging where it is received by yet another portion of the second sensor array  74 . A careful inspection of  FIGS. 4 and 8  reveals that the ray  136  ( FIG. 4 ) will more accurately reveal the presence of the piece of foreign material  122  than the ray  294  ( FIG. 8 ) which will be attenuated by a greater degree because of an interaction with a corrugated section of the cylindrical wall  116 , a longer path through the contents  110 , and more importantly, the seam  118 . 
     In compliance with the statute, the invention has been described in language more or less specific as to structural and methodical features. It is to be understood, however, that the invention is not limited to the specific features shown and described, since the means herein disclosed comprise preferred forms of putting the invention into effect. The invention is, therefore, claimed in any of its forms or modifications within the proper scope of the appended claims appropriately interpreted in accordance with the doctrine of equivalents.