Abstract:
A feed system that is adapted for feeding articles to a sortation system includes at least one feed conveyor upstream of the sortation system feeding articles to the sortation system. The feed conveyor includes a plurality of side rails extending from an initial portion of the feed conveyor to a terminal portion thereof. The side rails are spaced apart a substantially constant distance from the initial portion to the terminal portion to provide a footprint that is substantially the footprint of a transport conveyor. A conveying surface is provided between the side rails. The conveying surface includes at least one article-transporting portion and at least one article-unscrambling portion. The portions are in tandem. The unscrambling portion is made up of a plurality of tapered rollers mounted between the side rails.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This is a continuation of application Ser. No. 09/886,833, filed Jun. 21, 2001, now U.S. Pat. No. 6,390,277, which is a division of application Ser. No. 09/258,380, filed Feb. 26, 1999, now U.S. Pat. No. 6,253,905. 
    
    
     BACKGROUND OF THE INVENTION 
     This invention relates generally to conveyor systems and, in particular to conveyors used to unscramble articles received in random order and orient and align the articles in a single file. The invention is particularly adapted for use upstream of an induction system but may have other applications. 
     Many conveyor operations, especially those used in article distribution centers, receive a variety of articles varying in weight, height, length and depth. These articles are unloaded from trucks en masse and placed on the conveyor system. Once upon the conveyor, the articles are forwarded to a central area in random order and orientation. At this point in the conveyor operation, it becomes necessary to orient and align the articles in a single file for further processing. Normally, such further processing includes scanning a barcode attached to the surface of each article. This barcode contains information which identifies the destination of the article. After scanning the articles, they are sorted using a sortation conveyor to discrete departure destination areas. Once in a particular departure destination, the articles are loaded into a truck or other form of transportation and shipped to their final destination. Failure to properly unscramble and singulate articles prior to reaching the scanner results in shipment of articles to an incorrect destination and reduces the efficiency of the distribution process. 
     Unscrambling and aligning conveyors normally utilize skewed rollers which transport articles longitudinally and laterally toward one side of the conveyor. Often, such systems utilize a discrete number of “zones” which are driven at progressively faster speeds in order to unscramble and align the articles. Each zone of the unscrambling and aligning conveyor is driven by a separate motor and dedicated drive mechanism. Consequently, such unscrambling and aligning conveyors are often expensive and are susceptible to failure due to the number of different motors and drive systems necessary to operate the unit. Thus, these conveyors require frequent maintenance, which in turn increase the costs associated with the distribution process. 
     Furthermore, existing unscrambling and aligning conveyors do not effectively eliminate the occurrence of “side-by-side” articles. “Side-by-side” articles, as they are referred to in the industry, are two or more articles which are positioned laterally adjacent along the unscrambling and aligning conveyor and remain so when transferred to the discharge end. The existence of “side-by-sides” interferes with the scanning procedure, insofar as the scanner is incapable of scanning more than one package simultaneously. If such “side-by-sides” are detected, they are manually removed from the conveyor system and placed in a recirculation line, thereby decreasing the throughput of the conveyor system as a whole. If undetected, one of the articles, specifically, the one which is not detected by the scanner, is often sorted along with the adjacent article and subsequently shipped to an incorrect destination. Furthermore, “side-by-sides” often generate jams during the sortation procedure, and thereby reduces the throughput, or articles sorted per unit time, of the distribution center. 
     Additionally, existing conveyors systems often undergo updating to generate a higher throughput. For example, an existing conveyor system may have the sortation system replaced in order to utilize new technology and thereby increase the efficiency of the system as a whole. Consequently, it often becomes necessary to replace an existing unscrambling and aligning conveyor with one having the ability to handle a larger volume of parcels at a higher speed. Heretofore, replacement of the unscrambling and aligning conveyor has presented problems for the industry. Normally, replacing an unscrambling and aligning conveyor required the same to be torn out and replaced with the updated conveyor. This is a great expense in terms of both cost and downtime. 
     Also, it is relatively common to add an unscrambling and aligning conveyor to an existing conveyor system. For example, it may be desirable to add an unscrambler upstream of an induction system in order to significantly reduce the number of side-by-side articles fed to the induction system. Such side-by-side articles tend to interfere with proper operation of the induction system and have previously required an operator to manually remove such packages. In such instances, a length of conveyor must be torn out and replaced with an unscrambling and aligning conveyor. The procedure of adding an unscrambling and aligning conveyor may also be costly, resulting in a large amount of downtime as the existing conveyor section must be completely torn out and the unscrambling and aligning conveyor installed. 
     Consequently, there exists a need for an unscrambling and aligning conveyor which can effectively singulate a large volume of packages delivered thereto in a close packed order at a rate which is commensurate with the existing high speed conveyor equipment, and can be retrofitted onto an existing conveyor system with a minimal amount of labor and changeover costs. 
     SUMMARY OF THE INVENTION 
     Accordingly, the present invention advances an unscrambling and aligning conveyor having an input end which receives articles from an input conveyor in random order and alignment, and an opposing discharge end from which singulated, unscrambled articles are discharged. The unscrambling and aligning conveyor has an article transport surface, supported by a first and second side support, which is configured to transport articles longitudinally from the input end to the discharge end. According to an aspect of the invention, the article transport surface produces a linear speed decrease towards an alignment region of the conveyor in order to cause articles positioned laterally remote from the alignment region to accelerate in front of articles positioned proximate to the alignment region. 
     In one particular form, the linear speed decrease is provided by a plurality of tapered rollers supported by the side supports. Each tapered roller decreases in diameter toward the alignment region. The tapered rollers are preferably skewed with respect to the first and second side supports to thereby urge articles towards the alignment region. Also, preferably, the tapered rollers are parallel, while each tapered roller rotates upon a substantially horizontal axis of rotation to thereby create a slightly declining, or downwardly sloped article transport surface which in turn provides a gravitational force to move articles towards the alignment region. 
     According to another aspect of the invention, when articles contact the input end of the unscrambling and aligning conveyor, a separation distance or gap is generated between a particular article and the preceding article. These gaps between articles provide the space necessary for an article to move ahead of a laterally adjacent article and thereby facilitates article alignment and singulation. This may be accomplished by the input conveyor being driven at a speed less than the speed of the unscrambling and aligning conveyor. 
     According to another aspect of the invention, the plurality of tapered rollers are driven at a single speed by a power mechanism in operational connection with drive equipment such as an endless padded conveyor chain, belt or the like. Powering the unscrambling and aligning conveyor using one power source reduces the energy costs associated with its operation and simplifies the installation and maintenance of the conveyor. 
     The present invention also provides a method for controlling a conveyor system. The method comprises monitoring the movement of articles, preferably by photo-detectors, on the accumulation conveyor which receives singulated articles from the unscrambling and aligning conveyor. When the photo-detectors detect the lack of movement of articles along the accumulation conveyor for a predetermined period of time, a signal is issued to a controller in electrical communication with the power mechanism of the unscrambling and aligning conveyor. Upon receipt of this signal, the controller deactivates or decelerates the unscrambling and aligning conveyor. Preferably, the controller is also in electrical communication with the input conveyor and thereby either shuts down or reduces the speed of the input conveyor upon receipt of the signal from the photo-detectors. Shutting down or decelerating the unscrambling and aligning conveyor as well as all conveyors upstream thereof prevents the unscrambling and aligning conveyor from becoming blocked by articles encroaching upon the discharge end. 
     The present invention also provides a method for retrofitting an unscrambling and aligning conveyor and transforming a length of conveyor into an unscrambling and aligning conveyor. The method includes removing the existing article transport surface and replacing the same with the tapered rollers. An unscrambling and aligning conveyor, or a length of a conveyor, normally includes a pair of side supports generally arranged parallel and spaced a preselected distance apart. The side supports contain a plurality of sets of apertures, wherein an aperture on the first side support is axially aligned with an aperture on the second side support. Subsequent to removal of the existing article transport surface, the tapered rollers of the present invention may be positioned within the apertures of the side supports such that each tapered roller occupies an aperture in one side support and is received on the opposing side support by an aperture which is not axially aligned with the opposing aperture. Insertion of the tapered rollers of the present invention in this manner provides a skew, with respect to the first and second side support, which urges articles toward one side. Once the tapered rollers of the present invention are installed, a vertical guide surface is positioned proximate to the alignment region of the tapered rollers. The vertical guide surface prevents articles from being propelled laterally from the article transport surface and facilitates the forward progression of articles. 
     The present invention also provides a conveyor system having at least one induction line which receives articles in single file from an unscrambling conveyor. Preferably, an accumulation conveyor is positioned between the induction line and the unscrambling and aligning conveyor. Placement of the unscrambling and aligning conveyor upstream of the induction system assures proper orientation of the articles during the induction process, and thereby increases the efficiency or throughput of the conveyor operation. 
     The present invention facilitates a high volume unscrambling and aligning of articles because of its effective means for providing gaps between the articles and conveying the articles laterally toward the alignment region. As it is driven by one power mechanism, the unscrambling and aligning conveyor of the present invention provides a low cost and effective conveyor for singulating articles which requires less maintenance than existing unscrambling and aligning conveyors. 
     Furthermore, the present invention provides an effective method for retrofitting an existing unscrambling and aligning conveyor or transforming a length of conveyor into a unscrambling and aligning conveyor by removing the existing article transporting surface and replacing it with the tapered rollers of present invention. This method permits existing conveyor systems to achieve greater throughput at a reduced cost. 
     These and other objects, advantages and features of the present invention will become apparent upon review of the following specification in conjunction with the drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a plan view of an unscrambling and aligning conveyor according to the present invention; 
     FIG. 1 a  is a plan view of a conveyor system according to the present invention; 
     FIG. 2 is a sectional view taken along line I—I of FIG. 1; 
     FIG. 3 is a fragmentary perspective view of the power mechanism of the unscrambling and aligning conveyor of FIGS. 1 and 2; 
     FIG. 4 is a schematic plan view of the unscrambling and aligning conveyor illustrating the alignment and singulation of articles therealong; 
     FIG. 5 is a schematic plan view of the unscrambling and aligning conveyor illustrating the rotation and alignment of an article therealong; 
     FIG. 6 is a schematic plan view of the unscrambling and aligning conveyor illustrating the gapping and aligning principal of the present invention; and 
     FIG. 7 is a plan view of a method of retrofitting a conveyor with the article transport surface of the unscrambling and aligning conveyor according to the present invention, with the rollers of the existing conveyor depicted in phantom. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now specifically to the drawings, and the illustrative embodiments depicted therein, an unscrambling and aligning conveyor  10  includes a vertical first side support  20  and an opposing vertical second side support  30 . First side support  20  and second side support  30  are parallel and placed a preselected distance apart. An article transport surface  40  is attached to and supported by first side support  20  and second side support  30 . The articles or packages to be separated from a laterally adjacent position to single file on unscrambling and aligning conveyor  10  are delivered to input end  22  of unscrambling and aligning conveyor  10  from an input conveyor  14 . The articles delivered to unscrambling and aligning conveyor  10  by input conveyor  14  are randomly arranged and of varying dimension and may be laterally adjacent. As the articles contact input end  22  of unscrambling and aligning conveyor  10 , they are accelerated and moved laterally across article transport surface  40  of the unscrambling and aligning conveyor  10 , and aligned in single file in alignment region  42  of article transport surface  40 . Alignment region  42  is proximate to first side support  20 . Articles positioned in alignment region  42  of article transport surface  40  are positioned against or immediately adjacent a vertical guide surface  44  which, in the illustrated embodiment, is plurality of guide rollers positioned adjacent to and above article transport surface  40 . Vertical guide surface  44  could, alternatively, be a vertical belt, a series of vertically arranged travelling belts or a stationary surface. Guide surface  44  forms an upstanding vertical alignment surface to allow articles to align against in alignment region  42  of article transport surface  40 . The articles that get arranged in single file along unscrambling and aligning conveyor  10  are discharged therefrom at discharge end  24  to an accumulation conveyor  26  and are transported downstream for further processing. 
     As shown in FIG. 1 a , accumulation conveyor  26  transports articles to an induction system  100 . In normal conveyor operations, there is usually more than one conveyor line  110  conveying articles to induction system  100 . Consequently, FIG. 1 a  illustrates two conveyor lines  110 , each of which presents articles to the induction system  100 . Each conveyor line  100  includes an input conveyor  14 , an unscrambling and aligning conveyor  10  and an accumulation conveyor  26 . Induction system  100  includes induction conveyors  112 , each of which receives articles from the respective accumulation conveyor  26  and forwards the same to a combiner  114 . Induction conveyors  112  controllably release articles to combiner  114  so as to provide a gap between each successive article positioned on combiner  114 . Induction system  100  may be of the type disclosed in commonly assigned U.S. Pat. Nos. 5,038,911; 5,341,916; and 5,267,638, the disclosures of which are hereby incorporated herein by reference. Once articles are inducted by induction system  100 , further processing includes scanning of the barcode contained on each article and the subsequent sortation of these articles by a sortation system  115  which forwards the articles to a particular destination area. 
     Article transport surface  40  is comprised of a plurality of tapered rollers  50 . Each tapered roller  50  is generally parallel to the adjacent tapered roller  50  and may be skewed or canted to side support  20  and side support  30  at a preselected angle. The skew or cant angle of each roller  50  is such that the axis of each tapered roller  50  converges toward side support  20 . As shown most clearly in FIG. 2, each tapered roller  50  is formed having a tapered surface with a maximum diameter end  52  positioned adjacent side support  30  and a minimum diameter end  54  positioned adjacent side support  20 . 
     In the preferred construction, each tapered roller  50  is an axleless roller. Tapered rollers  50  are rotatably attached to side supports  20 ,  30  by axle adapters  57 . However, tapered rollers  50  could be supported by a central shaft, or by a pair of shaft sections, one at each end, aligned along the same axis as the axle adapters  57 . In either construction, the ends of the shaft projecting from each tapered roller  50  are received by apertures  58  formed in side support  20  and side support  30  (FIG.  3 ). In the illustrated embodiment, axle adapters  57  are positioned within apertures  58  such that the centerline of each tapered roller  50  is horizontal. Consequently, top surface  53  of each tapered roller  50  slopes downwardly or declines from side support  30  to side support  20 . As a result, article transport surface  40  slopes downwardly towards alignment region  42 . This downwardly sloping article transport surface  42  results in a slight gravitational force being imparted upon articles positioned on article transport surface  42  to thereby move the same into alignment region  42 . Alternatively, top surface  53  of each tapered roller  50  could be set substantially horizontal such that the skew of the rollers alone urge articles toward alignment region  42 . 
     Each tapered roller  50  is independently driven by endless driving member  60 . Driving member  60  is trained around a gear  62  having a shaft  63  operably connected to a gear  64 . Gear  64  is operationally connected to a power mechanism or motor  65  by endless belt  66 . Motor  65  drives each tapered roller  50  at a single, preselected speed. 
     In the illustrated embodiment, driving member  60  is a padded chain of the type disclosed in commonly assigned U.S. Pat. No. 4,074,805, the disclosure of which is hereby incorporated herein by reference, but could also be a flat belt, a circular belt, a linked belt of the type disclosed in commonly assigned copending application, Ser. No. 60/115,146, filed Jan. 8, 1999 by Nguyen et al., the disclosure of which is hereby incorporated herein by reference. Endless driving member  60  could, alternatively, be a belt of the type disclosed in commonly assigned U.S. Pat. No. 5,415,281, the disclosure of which is hereby incorporated herein by reference, which drives rollers  50  through intermediate pulleys and O-rings. 
     Side support  20  and  30  may be joined at suitable lengths by one or more cross supports  70 . An L-shaped bracket  72  is attached to exterior surface  21  of side support  20 . L-shape bracket  72  has a horizontal member  74  and a vertical member  76  extending upwardly from horizontal member  74 . Attached to end  74 ′ horizontal member  74  is a horizontal flange  75  extending in a direction towards article transport surface  40  and positioned thereabove. End  75 ′ of horizontal flange  75  contains an aperture through which the shaft of rollers  44  extends. Exterior surface  31  of side support  30  carries an L-shaped bracket  78  having a horizontal member  79  and a vertical member  80  extending upwardly from horizontal member  79 . Attached to end  80 ′ of vertical member  80  is a flange  82  extending in a direction towards article transport surface  42 . Abutment member  84  is attached to end  82 ′ of flange  82 . Abutment member  84  is generally “C” shaped and is preferably made of a material having a low coefficient of friction. Abutment member  84  and flange  82  provide a barrier preventing articles from being propelled laterally off tapered rollers  50  while the low coefficient of friction abutment member  84  enables articles to continue their forward progression along unscrambling and aligning conveyor  10 . Attached to and depending from horizontal member  74  and  79  are legs  86 . Legs  86  support unscrambling and aligning conveyor  10  a preselected distance above the floor. 
     As articles enter unscrambling and alignment conveyor  10  at input end  22 , the skewed, tapered rollers  50  urge articles toward alignment region  42  of article transport surface  40 . As is illustrated in FIG. 1, alignment region  42  is along the region of tapered rollers  50  having the minimum diameter  54 . Further, the downwardly sloping angle of article transport surface  40  achieved by securing tapered rollers  50  to side supports  20  and  30  such that the centerline of each tapered roller  50  is horizontal, also contributes to the movement of articles toward alignment region  42 . If tapered rollers  50  are not skewed, then the downwardly sloping angle of article transport surface  40  will urge articles toward alignment region  42 . 
     As earlier described, each tapered roller  50  has a maximum diameter end  52  and an opposing minimum diameter end  54 . The minimum diameter end  54  of tapered rollers  50  is positioned against side support  20  and defines alignment region  42  of article transport surface  40 . As articles move longitudinally across tapered rollers  50 , articles positioned proximate to side support  30  will move at a speed greater than articles positioned proximate to side support  20 . This is so because the maximum diameter end  52  of each tapered roller  50  has a greater surface speed than the minimum diameter end  54 . As a result, articles moving transversely from input end  22  to discharge end  24  of unscrambling and aligning conveyor  10  will experience a linear, lateral speed decrease across article transport surface  42  from side support  30  to side support  20  with alignment region  42  exhibiting the slowest speed. This linear, lateral speed decrease enables unscrambling and aligning conveyor  10  to singulate articles in alignment region  42 . 
     As depicted in FIG. 4, an article A laterally remote from alignment region  42  will travel at a faster speed and thereby move ahead of article B which is positioned proximate to or in alignment region  42 . Thus, article A that is laterally farthest from the alignment region  42  will be accelerated in front of an article B laterally adjacent thereto. This lateral speed decrease rapidly reorganizes laterally adjacent articles into a single file stream in alignment region  42 . 
     As shown in FIG. 5, the linear, lateral speed decrease across article transport surface  42  also results in the rotational movement of articles in alignment region  42  such that their major dimension is substantially parallel to side support  20 . This beneficial rotation of articles, which facilitates their subsequent induction and sortation, occurs when a particular article is oriented at input end  22  such that its major dimension is substantially perpendicular to side supports  20 ,  30 . For example, article A of FIG. 5 is rectangular with its major dimension being substantial perpendicular to cross supports  20  and  30 . As article A moves along article transport surface  40 , the different surface speeds imparted by tapered rollers  50  will result in end  90  of article A moving at a faster rate than end  92 . This speed differential between ends  90 ,  92  of article A will tend to cause the rotation of the article A such that end  90  will move transversely along article transport surface  40  and rotate ahead of end  92  towards alignment region  42  such that when in the alignment region  42 , the major dimension of article A will generally parallel to side supports  20  and  30 . This rotation of packages is particularly beneficial when unscrambling and aligning conveyor  10  is used in the separation and organization in single file of a large number of articles of differing shapes and weights. 
     Unscrambling of articles within alignment region  42  of unscrambling and aligning conveyor  10  is further enhanced by providing a gap, or separation distance, between articles such that a laterally adjacent article may move into the space provided between the trailing end of a lead article and the forward end of a rear article. In the illustrated embodiment, this gap is achieved by creating a speed differential between end  15  of input conveyor  14  and input end  22  of unscrambling and aligning conveyor  10 . Specifically, unscrambling and aligning conveyor  10  is run at a speed greater than input conveyor  14 . In a preferred embodiment, unscrambling and aligning conveyor  10  is run at a speed of 270 feet per minute and input conveyor  14  is run at a speed of 180 feet per minute. 
     As articles are conveyed from input conveyor  14  to unscrambling and aligning conveyor  10 , articles contacting input end  22  of unscrambling and aligning conveyor  10  will be accelerated to thereby create a space, or gap, between it and the article behind it. As illustrated in FIG. 6, once article B traverses the intersection between input conveyor  14  and input end  22  of unscrambling and aligning conveyor  10 , it is accelerated to thereby create a gap between it and the article A positioned therebehind. An article C, laterally adjacent to article A, and positioned proximate to side support  30  will be accelerated ahead of article A. As article C accelerates ahead of article A, the gap generated between article A and article B enables article C to singulated therebetween. 
     Under certain operating conditions, accumulation conveyor  26  may be in the accumulation mode, with articles accumulated at or near end  27  of accumulation conveyor  26 . It is disadvantageous to have articles backed up or being accumulated on article transport surface  40 . In order to prevent such accumulation on the unscrambling and aligning conveyor  10 , a pair of photo-detectors  94  and  96  are positioned approximate to end  27  of accumulation conveyor  26  (FIG.  1 ). Photo-detectors  94  and  96  are in electrical communication with a controller  98  which is in turn operably connected to motor  65  of unscrambling and aligning conveyor  10 . When photo-detectors  94  and  96  detect the presence of accumulated and articles at or near end  27  of accumulation conveyor  26  that have become stationary, a signal is sent to controller  98  to thereby shutdown or deactuate motor  65 . Alternatively, controller  98  may issue a signal to motor  65  to thereby decrease the speed at which the unscrambling and aligning conveyor  10  is operated. Also, preferably, controller  98  is operationally connected with the power mechanism of input conveyor  14 . Thus when articles have accumulated approximate to discharge end  24 , a signal is sent which deactivates both unscrambling and aligning conveyor  10  and input conveyor  14 . It will be understood by those with ordinary skill in the art that input conveyor  14  may be a series of different conveyor sections, all of which may be controlled by controller  98  to be deactivated, or operated at a reduced speed, upon receipt of a signal from controller  98 . 
     Unscrambling and aligning conveyor  10  may be retrofitted onto an existing conveyor  110  having generally parallel, side supports  120  and  130 . Conveyor  110  may be an existing live roller conveyor. In order to retrofit an existing conveyor  110  with article transport surface  40  of unscrambling and aligning conveyor  10 , it is first necessary to remove existing rollers  140  from side supports  120  and  130 . As shown in FIG. 7, existing rollers  140  are depicted in phantom. Side supports  120  and  130  have a plurality of sets of apertures  160  placed a preselected distance apart. Each set of apertures  160  includes an aperture  162  positioned in side support  120  which is axially aligned with an aperture  164  positioned in support  130 . Once existing rollers  140  are removed, tapered rollers  50  are positioned in sets of apertures  160 . If it is desired to provide a skewed or canted article transport surface with respect to side supports  120  and  130 , each tapered roller  50  is positioned in apertures which are axially offset. Specifically, this is achieved by positioning axle adapter  57 , extending from minimum diameter end  54 , into an aperture  162 . Thereafter, axle adapter  57 , extending from maximum diameter end  52 , is inserted in an aperture  164  of an adjacently forward set of apertures  160 . In order to provide tapered rollers  50  with a speed that is higher than the speed of input conveyor  14 , thereby creating gaps at the input of conveyor  110 , the power mechanism and drive system of existing conveyor  110  may be modified to thereby enable article transport surface  40  to be driven at a speed greater than the conveyor positioned upstream thereof. Modification of the power mechanism and drive system is a routine task within the knowledge of those of ordinary skill in the industry. 
     Many scanning and sorter conveyors located downstream of accumulation conveyor  26  are incapable of operating efficiently at speeds commensurate with the speed at which unscrambling and aligning conveyor  10  may be operated. Accumulation conveyor  26  is therefore operated at a speed less than the speed of unscrambling and aligning conveyor  10 . Thus, articles singulated along alignment region  42  of unscrambling and aligning conveyor  10  will enter accumulation conveyor  26  and decelerate to a speed at which scanning and subsequent sortation may be achieved with minimum error. In a preferred embodiment, accumulation conveyor  26  is driven at a speed of approximately 135 feet per minute. 
     The above description is considered that of the preferred embodiments only. Modifications of the invention will occur to those skilled in the art and those who make or use the invention. Therefore, it is understood that the embodiments shown in the drawings and described above are merely for illustrative purposes and are not intended to limit the scope of the invention, which is defined by the following claims as interpreted according to the principles of patent law, including the doctrine of equivalents.