Abstract:
A conveyor system having an endless conveying surface, a plurality of diverters, and diverting shoes transversely movable across the conveying surface, includes a diverting track network in operational connection with a controller. The controller measures the length of each package, while the diverting track network includes a plurality of upstream diverting tracks and at least one downstream diverting track. The controller selectively actuates a diverter associated with downstream diverting track and at least one diverter along a particular upstream diverting track to engage the package proximate to its leading and trailing end. The diverting track network is configured to initially move the package in a direction generally parallel to the direction of movement of the main conveyor, and out of alignment with the articles traveling therealong, and subsequently rotate the article so that when discharged to a branch conveyor, the leading end of the article is more nearly orthogonal to the direction of motion of the branch conveyor.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates generally to conveyor diverting systems, and, more particularly, to conveyor diverting systems having an endless conveying surface composed of multiple surface members, each one or group of adjacent ones mounted with a laterally movable shoe capable of diverting articles from the conveyor by pushing laterally against the articles as they move down the conveyor. Such lateral pushing thereby diverts a package, such as from the main conveyor to an adjacent branch conveyor, or other receiving structure. 
     Conveyor diverting systems using a moving conveying surface consisting of a plurality of parallel surface members, the conveying surface being propelled, such as by being mounted to endless chains, have been known for a number of years. Such diverting systems utilize a diverter shoe movably mounted on one or more surface members for lateral movement with respect to the conveying surface under the guidance of a track network. The track network is located generally under the conveying surface and guides the diverter shoes via pins descending from the diverter shoes and engaging the track network. Diverters in the track network selectively transfer guidance of each diverter shoe from a track running in the direction of the movement of the conveying surface to a diagonal track, or plurality of diagonal tracks, in order to cause lateral movement of the diverter shoes. An example of a diverting gate used to selectively transfer guidance of diverter shoes between tracks is disclosed in U.S. Pat. No. 5,409,095, issued to Hoshi et al., and U.S. Pat. No. 5,039,912, issued to Cotter. In order to avoid wasted spacing between variable-length packages, such diverting systems may include manual or automatic measuring means at an infeed point to cause the diverter gate associated with the selected branch conveyor to divert a selected number of shoes corresponding in general to the length of the package. Exemplary of this type of conveyor are U.S. Pat. No. 3,361,247, issued to James N. Lauzon et al. and U.S. Pat. No. 4,738,347, issued to Brouwer, and commonly assigned with the present invention. 
     With increased demands for the number of packages to be conveyed by such conveying systems, the inter-package spacing distance has become a critical factor in the design of conveying systems. Decreasing the spacing between packages on the conveyor allows a greater throughput of packages by the conveyor. Conversely, providing more space between the packages results in a diminished efficiency and throughput. 
     A specific minimum inter-package spacing is required in this system as a result of the rotation of the diverted package as it is initially diverted. Because of this rotation, additional inter-package spacing is required to avoid conflict between the diverting package and a closely trailing package. This rotation pushes the trailing corner of the package adjacent the branch conveyor back a distance, which can be estimated using the width (W) of the package and the acute angle (θ) which is formed by the intersection of the material flow on the main conveyor and the diverter shoe diagonal guide track. Using these two variables and assuming that the package rotates about the trailing corner opposite the branch conveyors, it will be observed that: 
     
       
           A=W  sin θ 
       
     
     where A is the distance the trailing corner adjacent the branch conveyor is pushed back by the package&#39;s rotation. It is, therefore, necessary with this system that packages to be diverted are not spaced closer together than the distance W sin θ. 
     By way of example, if a diverting branch is oriented at about 20° with packages 16 inches in width, an inter package distance of approximately 5.5 inches is necessary. If the package is 24 inches long, this results in the need for approximately 23% more empty space on the conveyor. A hypothetical system that could divert packages without any significant space between packages could thus produce a 23% increase in package throughput without any increase in conveyor speed. The high desirability of such a system is thus clear. 
     Prior methods of diverting packages that addresses the problem of reducing the required inter-package spacing, is described in commonly assigned U.S. Pat. No. 5,165,515, issued to Michael L. Nitschke et al., which is commonly assigned with the present application. This system increases throughput by not rotating the diverted packages. This non-rotation is accomplished by using a plurality of generally parallel diverting tracks oriented diagonally with respect to the direction of conveyor movement, instead of a single diverting track. Each track has its own diverting gate which is actuated to divert the movement of the diverting shoes from the direction of the conveyor to the lateral diverting direction. By simultaneously activating more than a single diverting gate, a group of diverting shoes corresponding to the measured package length can be moved laterally across the conveyor surface. This group of shoes acts along nearly the entire length of the package to be diverted and, therefore, causes no rotation of the package. Without rotation of the package, the inter-package spacing requirement is reduced to a minimum. 
     However, this technique is not without difficulties. The deliberate non-rotation of the packages means the packages will enter the branch conveyor still aligned parallel to the main conveyor, but oriented generally diagonally with respect to the branch conveyor (i.e., their lengthwise sides are not parallel to the direction of motion of the branch conveyor). This orientation significantly increases the necessary width of the branch conveyors, resulting in an increase in cost and a reduction in the spacing on branch conveyors. 
     Still another method of diverting packages which reduces the required inter-package spacing, is described in commonly assigned U.S. Pat. No. 5,927,465, issued to Shearer, Jr. With this system, an automatic controller oversees the operation of the diverting gates to determine which diverting gates are to be actuated and for how long, depending upon the measured length of the packages on the conveyor. Once the length of the package is determined, the controller determines whether a package will be diverted using one diverting gate or two (or more) diverting gates. For certain situations, such as long packages, a single diverter is activated and as many diverting shoes are diverted as necessary to divert the package through the single diverting gate. Packages diverted in this manner are rotated, with the trailing corner of the package moving in an initial rearward direction. 
     Other packages are diverted with two or more gates in a manner that the packages are initially diverted out of line with other packages without substantially rotating the packages, in the same manner as in Nitschke et al. &#39;515 Patent. After the initial diverting, the package is then rotated prior to discharge to the spur. This has the advantage of the Nitschke et al. &#39;515 Patent of not requiring increased gaps between packages but eliminates the disadvantage of increased spur size. However, some of the packages, such as long packages, are still diverted using conventional techniques and increased gaps must be provided at both ends of such packages. 
     It will thus be observed that there exists a need for a conveyor diverting system that can divert packages with little or no inter-package spacing, and ensure that packages diverted to the branch conveyor are properly aligned, all while keeping costs to a minimum. 
     SUMMARY OF THE INVENTION 
     The present invention provides a sortation conveyor which achieves efficiency gains through reduction of the inter-package spacing. These efficiency gains are especially desirable because they can be achieved without the extra power consumption, noise, and wear that results from increasing the conveyor speed. The present invention increases conveyor diverting system throughput by utilizing a diverting track network having at least one downstream diverting track and a plurality of upstream diverting tracks. The tracks are configured to enable movable pushers to initially divert a package in an orientation which prohibits the article being diverted from interfering with the trailing article. 
     According to one aspect of the invention, a conveyor system includes a conveyor surface having a direction of travel, which conveys articles substantially in a line. Movable pushers are mounted on the conveying surface and are adapted to move transversely thereacross. A diverting track network, positioned beneath the conveying surface, is configured to move at least two movable pushers substantially perpendicular to the direction of travel of the conveying surface for at least an initial distance, and thereafter to guide the movable pushers in a direction which causes the rotation of at least some of the articles being diverted after being placed out of line with the other articles. The ability of the diverting track network to initially move an article from the line of articles in a direction substantially perpendicular to the direction of travel of the conveying surface, and thereafter subsequently rotate at least some of the articles being diverted enables the minimization of space between articles, and hence increases throughput. 
     According to another aspect of the invention, a conveyor system for diverting articles includes a conveying surface moving in a particular direction, and at least one branch conveyor extending from the conveying surface. A plurality of diverters are mounted on the conveying surface and are movable between a diverting state and a non-diverting state, while a plurality of movable pushers, mounted on the conveying surface, are movable across the conveying surface when a particular diverter is in the diverting state. A control system is configured to determine the length of articles conveyed, and is connected to a diverting system having at least one downstream diverting track extending substantially across the conveying surface, and a plurality of upstream diverting tracks which each extend partially across the conveying surface. The diverting system simultaneously diverts at least one movable pusher along the downstream diverting track when the leading end of the article to be diverted is positioned thereover, and at least one movable pusher along an upstream diverting track, proximate to the trailing end of the article. Simultaneously actuating at least a pair of movable pushers to engage an article to be diverted, proximate to both its leading end and trailing end, assures effective diversion of articles from the conveying surface. 
     According to yet another aspect of the invention, a conveyor system for converting articles includes an array of movable surface members defining a conveying surface, and a plurality of diverting shoes mounted on the surface members. A guide track is positioned below the surface members and adapted to guide the diverting shoes. A plurality of diverters are positioned along and interrupt the guide track, and assume either a non-diverting state or a diverting state. When in the non-diverting state, the diverting shoes move along the guide track uninterrupted, while in the diverting state, the diverting shoes are diverted from the guide track. A diverting track network, positioned underneath the conveying surface, meets the diverters, and includes at least one downstream diverting track extending substantially across the conveying surface and a plurality of upstream diverting tracks, each of which extends partially across the conveying surface. A controller, in operational connection with at least one sensor, simultaneously actuates a first diverter to divert a diverting shoe along the downstream diverting track when the first diverter is proximate to the leading end of the article, and a second diverter proximate to the trailing end of the article. Actuating a first diverter farthest downstream, and proximate to the leading end of the article and a second diverter upstream and proximate to the trailing end of the article effectively enables the diversion of articles onto a branch conveyor. 
     The present invention also advances a method for diverting articles which includes the steps of conveying articles substantially in a line with the conveying surface, and applying a perpendicular force component to substantially all the articles to be diverted. The perpendicular force component is substantially perpendicular to the direction of conveyor motion and diverts the article initially out of line with the other articles traveling along the conveying surface. The perpendicular force component is then altered for at least some of the articles after the article is diverted out of line, by including a rotational force component during a subsequent portion of the diverting motion. Initially diverting an article out of a line of articles, and subsequently rotating the article after it has been diverted from the line, permits the spacing between articles to be minimized, and therefore enhances the efficiency and throughput of the conveyor system. 
     According to yet another aspect of the invention, a method for diverting articles includes measuring the length of the articles conveyed along the conveying surface, and providing a diverting track network positioned beneath the conveying surface which includes at least one downstream diverting track laterally traversing substantially the entire conveying surface, and a plurality of upstream tracks partially laterally traversing the conveying surface. A plurality of diverters are provided which cause the movable pushers to move along the associated track, at least partially across the conveying surface when a diverter is activated to a diverting state. The method also includes simultaneously activating at least two of the diverters wherein one of the diverters is associated with the downstream diverting track and positioned proximate to the leading end of the article, and the other diverter is positioned proximate to the trailing end of the article. Diverting articles from a conveying surface by activating at least two diverters wherein one diverter, associated with the downstream track, is actuated when the leading end of the article is positioned thereover, and the other diverter is proximate to the trailing end of the article provides an efficient method for diverting articles onto a secondary conveying surface. 
    
    
     These and other objects, advantages, and features of this invention will become apparent upon review of the following specification in conjunction with the drawings. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a top plan view of a conveyor system according to the invention; 
     FIG. 2 is a top plan view of the conveyor system of FIG. 1, with a center portion of the conveying surface removed to illustrate the underlying structure; 
     FIG. 3 is the same view as FIG. 2 of an alternative preferred embodiment thereof; 
     FIG. 4 is the same view as FIG. 2 of another alternative preferred embodiment thereof, 
     FIG. 4 a  is the same view as FIG. 2 of yet another alternative preferred embodiment thereof; 
     FIG. 5 is the same view as FIG. 2 of still another alternative preferred embodiment thereof; 
     FIG. 6 is a diagram of a single package in various stages of divert, along a downstream track and an upstream track; 
     FIG. 7 is a diagram of a single package in various stages of divert, along a pair of downstream tracks; and 
     FIG. 8 is a flow chart of a method for diverting a package according to the invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring specifically to the drawings and the illustrative embodiments therein, a conveying system  10  includes a main conveyor  9  and a plurality of branch conveyors  5 , of which only one is shown. Although the invention is illustrated for use with a unidirectional divert conveyor, it should be understood that its principles may also be used with bi-directional divert conveyors. Branch conveyor  5  is positioned adjacent to main conveyor  9 , and at an angle, as is conventional. The arrows illustrate the direction of conveyance for both main conveyor  9  and branch conveyor  5 . 
     A conveying surface  1  of main conveyor  9  is defined by a series of surface members  13  which define a product conveying surface. The lengthwise direction of surface members  13  is oriented perpendicular to the direction of movement of main conveyor  9 . Surface members  13  are supported on either side by side members  2  and  3 . The details of the interconnections of the surface members with each other are disclosed in U.S. Pat. No. 5,127,510, issued to Cotter et al., the disclosure of which is hereby incorporated herein by reference and will not be repeated. 
     A series of movable pushers, or diverting shoes,  14  are located along main conveyor opposite branch conveyor  5  and proximate to side member  2 . When diverting shoes  14  are not being utilized to push an article off main conveyor  9  and onto branch conveyor  5 , they travel in sequence along a shoe guideway  8 , adjacent the longitudinally extending guide track  12 . Guide track  12  prevents diverting shoes  14  from moving transversely across main conveyor  9  except at the point along main conveyor  9  at which diverters  25 a through  25   i  are located, or along similar points where a branch conveyor connects to main conveyor  9 . Diverting gates  25   a  through  25   i  can be seen attached along side member  2  of main conveyor  9 , and in the path of diverting shoes  14 . Diverters  25   a  through  25   i  are preferably of the type disclosed in U.S. Pat. No. 5,038,912, issued to Cotter, the disclosure of which is hereby incorporated herein by reference. Alternately, diverters  25   a  through  25   i  may be of the type disclosed in U.S. Pat. No. 5,409,095, issued to Hoshi et al., the disclosure of which is hereby incorporated herein by reference. 
     With reference to FIG. 2, a section of conveying surface  1  has been removed from the central portion of main conveyor  9  to illustrate the structure of a diverting track network  30 . Diverting track network  30  includes a plurality of first, or upstream diverting tracks  40 , and one or more second, or downstream, diverting tracks  50 . Although there are seven upstream diverting tracks  40  and two downstream diverting tracks  50  illustrated in FIG. 2, it is within the spirit and scope of the invention to have any number of upstream diverting tracks  40  and downstream diverting tracks  50 . In general, diverting tracks  40 ,  50  span the maximum article length to be transported by conveyor system  10 , as will be discussed in detail hereinbelow. Downstream diverting tracks  50  traverse substantially the entire conveying surface  1  at a preselected angle to the direction of movement of main conveyor  9 . Each downstream diverting track  50  may be generally straight or linear throughout its length. Each upstream diverting track  40  terminates partway across conveying surface  1 , at a location that generally relates to the width of the package stream conveyed by conveyor  10 . In the illustrated embodiment, each diverting track  40  includes a linear, or first section  42  which is generally parallel to downstream diverting tracks  50 , and a second section  44  projecting from the end of first section  42 , and extending downstream at an obtuse angle to first section  42 . Each second section  44  of upstream diverting tracks  40  is operably coupled to the second section  44  of the adjacent upstream diverting track  40 . Second section  44  of the upstream diverting track  40  adjacent to, and immediately upstream of, first downstream diverting track  50   a  is operably connected to downstream diverting track  50   a , a preselected distance below end  54 . Upstream diverting tracks  40  may be integrally formed with second section  44  bent to achieve the preselected angle. Alternatively, second section  44  may be a separate member, operably coupled to first section  42  by any means commonly employed in the art. Collectively, second sections  44  form an upwardly curved path, toward side member  3 , as they approach downstream diverting track  50   a.    
     Downwardly depending portions of diverting shoes  14  are diverted to specific upstream diverting tracks  40   a  through  40   g , and downstream diverting tracks  50   a  and  50   b  by a dedicated diverter  25   a  through  25   i . Diverters  25   a  through  25   i  are electrically actuated, for example, by shoe divert solenoids, in electrical connection with a divert control module  26  as disclosed in Cotter &#39;192 or by magnetic attraction of a portion of the diverting shoe as disclosed in Hoshi et al. &#39;095. It will be recognized by those with ordinary skill in the art that diverters  25   a  through  25   i  may be controlled by any means commonly recognized in the art without departing from the spirit and scope of the invention. 
     The number of upstream diverting tracks  40  utilized in conveyor system  10  is dictated by the maximum length of a package to be handled by the conveyor system. Preferably, the distance between downstream diverting track  50   b  and upstream diverting track  40   a  farthest upstream is approximately equal to, or greater than, the maximum length of packages to be diverted along conveyor system  10 . The longitudinal spacing between upstream diverting tracks  40  and downstream diverting tracks  50  may be substantially equal to the longitudinal distance of a single surface member  13 , so that each diverting shoe  14  positioned over upstream diverting tracks  40  and downstream diverting tracks  50  may be selectively actuated by the associated diverter  25   a  through  25   i . Alternatively, the longitudinal spacing between upstream diverting tracks  40  and downstream diverting tracks  50  may be some multiple, such as twice the width of a surface member  13 , such that every other diverting shoe  14  may be selectively actuated when positioned over diverting tracks  40 ,  50  without departing from the scope of the invention. 
     Conveyor system  10  is equipped with at least one sensor  58 , operably connected to a control system  60 , to thereby determine the length of each package being transported along conveyor system  10 . Sensor  58  may be any sensor commonly used in the art, and is positioned in proximity to, or along main conveyor  9 , upstream of diverting track network  30  or upstream of main conveyor  9 . Control system  60  is in electrical communication with divert control module  26 . 
     When a particular package  70  is to be diverted onto branch conveyor  5 , a signal is sent from control system  60  to divert control module  26  to thereby cause the selective actuation of diverter  25   a , and at least one of diverters  25   b  through  25   i  to thereby divert at least two diverting shoes  14 . One diverting shoe will be diverted along a downstream diverting track, preferably track  50   b , and one along another track thereof, such as the other downstream diverting track  50   a , or an upstream diverting track  40 . Specifically, the divert control module  26  will effect actuation of diverter  25   a  farthest downstream along main conveyor  9 , which corresponds to downstream diverting track  50   b , and the leading end  68  of package  70  to be diverted. Simultaneously, control divert module  26  will actuate a diverter  25   b  through  25   i  along a downstream diverting track  50   a  or along a particular upstream diverting track  40 , whichever is most proximate to the trailing end  69  of package  70 . 
     Consequently, diverting shoes  14  will be diverted along downstream diverting track  50   b , and along downstream diverting track  50   a , or a particular upstream diverting track  40 . This will effect non-rotational movement of package  70  out of line with other packages traveling along conveyor surface  9 . If the upstream one of diverting shoes  14  is diverted to an upstream diverting track  40 , the particular diverting shoe  14  urges trailing end  69  of package  70  and contacts second section  44 . Subsequent movement of diverting shoe  14  along second section  44  imparts a rotational force upon package  70  to thereby orient leading end  68  of package  70  in a direction substantially orthogonal to the direction of movement of branch conveyor  5 . The lateral speed of the diverting shoes actuated along downstream diverting track  50   b  and on an upstream diverting track  40  will be substantially equal while the diverting shoe traveling along upstream diverting track  40  is located in linear section  42 . Once the diverting shoe engages second section  44 , however, the lateral speed of the diverting shoe traveling along downstream diverting track  50   b  increases compared to the lateral speed of the diverting shoe traveling on successive second sections  44 . This difference in lateral speed rotates leading edge  68  of package  70  towards branch conveyor  5 . Once diverting shoe  14 , travelling on successive second sections  44 , converges into downstream diverting track  50   b , the rotational movement of package  70  ceases, and it is thereafter diverted in a direction substantially parallel to the direction of main conveyor  9 . The degree of rotation of package  70  may be degrees less than or equal to the angle α, formed at the intersection of main conveyor  9  and branch conveyor  5 . Preferably, the degree of rotation of package  70  is substantially equal to the angle α, formed at the intersection of main conveyor  9  and branch conveyor  5 . 
     A conveyor system  10 , illustrated in FIGS. 1 and 2. depicts a pair of downstream diverting tracks  50   a  and  50   b . If a package  70  to be diverted has a length less than the distance between diverters  25   a  and  25   b , the package will be diverted by the actuation of diverters  25   a  and  25   b  to thereby diverting a pair of diverting shoes  14  along downstream diverting tracks  50   a  and  50   b . Packages of this lenght will be transported substantially parallel to the direction of movement of main conveyor  9  and will not experience a rotational force. For packages having a length greater than the distance between diverters  25   a  and  25   b , control system  60  will cause the simultaneous diversion of a diverting shoe along the farthest downstream diverting track  50 , and at least one along an upstream diverting track  40 . 
     With respect to FIG. 3, conveyor system  10  is shown having only one downstream diverting track  50 . In this embodiment, packages of any length will be moved laterally without rotation out of line with other packages traveling along conveyor&#39;s surface  9  and will experience a rotational force as it is further diverted, toward the branch conveyor  5  because, in all instances, a diverting shoe will be diverted along both downstream diverting track  50 , and at least one upstream diverting track  40 . 
     Turning now to FIG. 4, in an alternative preferred embodiment, each upstream diverting track  40  has a second section  44  which, rather than being coupled to an adjacent second section  44  of an adjacent upstream diverting track  40 , are each separately connected to a downstream diverting track  50 . In all other aspects, conveyor system  10 ′ is structurally and functionally similar to conveyor system  10 . Individual attachment of second section  44  to downstream diverting track  50  reduces the noise produced by conveyor system  10 ′ by minimizing the number of mechanical gaps that a diverting shoe  14  must traverse as it is diverting a package toward branch conveyor  5 . 
     FIG. 4 a  shows another preferred alternative embodiment with the same configuration as FIG. 4, but only one downstream diverting track  50 . It will be recognized that in the embodiments of FIGS. 4 and 4 a , each second section  44  of upstream diverting tracks  40  may be curved upwards towards downstream diverting track  50  as are the second sections  44  depicted in FIGS. 1 and 2. 
     Referring now to FIG. 5, conveyor system  10 ″ illustrates an embodiment wherein once initially diverted in a substantially parallel direction, the package experiences a continuous rotational force until it is discharged onto branch conveyor  5 . This is achieved by each second section  44  of upstream diverting tracks  40  being operably connected to a second section  44  of an adjacent upstream diverting track  40 . The second section  44  of the upstream diverting track  40 , positioned adjacent to downstream diverting track  50 , is operably connected to downstream diverting track  50 , proximate to end  54 . Consequently, once the diverting shoes  14  are diverted along downstream diverting track  50  and a particular upstream diverting track  40 , package  70  will be urged towards branch conveyor  5 , but will not begin to rotate until a diverting shoe contacts second section  44  of upstream diverting track  40 . Thereafter, package  70  will continue to rotate until being discharged onto branch conveyor  5 . In all other aspects, conveyor system  10 ″ is structurally and functionally similar to conveyor system  10 . 
     FIG. 6 illustrates the diversional sequence of a package being diverted by diverting track network  30 . As can be seen, the package will travel in a substantially parallel to the direction of travel of main conveyor  9 , indicated by the directional arrow, as the package is diverted out of line with other packages traveling along conveying surface  1 , until a rotational force is subsequently imparted upon the package as a diverting shoe  14  contacts second section  44 , and continues travel therealong. 
     FIG. 7 illustrates the diversional sequence of a package being diverted by downstream diverting track  50   a  and  50   b  of diverting track network  30 . As can be seen, the package being diverted will travel in a substantially parallel direction of travel of main conveyor  9 , throughout the length of main conveyor  9 , until it is discharged onto a branch conveyor. 
     Turning now to FIG. 8, there is shown a diagrammatic representation of the control sequence necessary to divert a package according to the present invention. The control sequence includes determining at  70  the length of a package to be diverted. Thereafter, once the package is positioned over the farthest downstream diverting track  50 , the diverting associated with the farthest downstream diverting track  50  and at least one diverting gate associated with an upstream diverting track  40 , are simultaneously diverted at  72 . The choice of which upstream diverting gate is to be activated along with the downstream diverting gate is dictated by the length of the package to be diverted. Specifically, the upstream diverting gate most proximate to the trailing end of the package will be actuated. 
     Although the invention is illustrated with two shoes diverting each package, it could be implemented with three or more shoes diverting each package. The invention is not intended to be limited by the configuration of the diverting shoe  14 , the surface members  13  or diverters  25   a - 25   i.    
     Having described the invention in connection with certain specific embodiments thereof, it is to be understood that the description is meant to be interpreted as illustrative only, and that various modifications may also be made by those skilled in the art without departing from the spirit and scope of the invention as expressed in the accompanying claims.