Abstract:
A panel array support assembly has a lower support joist to which are directly connected panel holding devices or clips. The panel clips are configured so that the length of each clip extends along the length of the lower support joist. The panel clips are preferable configured to have a sliding top arm, which holds the upper edge of the panel, and slides back so that they panel can be placed on a lower holding arm.

Description:
PRIORITY INFORMATION 
       [0001]    This invention claims priority to U.S. Provisional Application No. 61/371,370 filed on Aug. 6, 2010, making reference to same herein in its entirety. 
     
    
     FIELD OF THE INVENTION 
       [0002]    This invention relates to support systems for panels and panel-like structures, such as solar energy collection systems, and more particularly to a support system for an array of photovoltaic panels, and a method of quickly assembling the same for activation. 
       BACKGROUND OF THE INVENTION 
       [0003]    A standard photovoltaic (solar) panel array includes a plurality of solar panels optimally arranged for converting light incident upon the panels to electricity. Various support systems are used for attachment to roofs, free-field ground racks or tracking units. Typically, these support systems are costly, labor intensive to install, heavy, structurally inferior, and mechanically complicated. Once the support structure is in place, mounting the solar panels on the support structure can be very difficult. Further, some large solar panels tend to sag and flex, thereby rendering the panel mounting unstable. Panel repair and adjustment are rendered more difficult thereby. 
         [0004]    A conventional two dimensional panel support system generally includes off-the-shelf metal framing channels having a C-shaped cross-section, such as those sold under the trademarks UNISTRUT™ or BLIME™, improvised for use as vertical and horizontal support members. The photovoltaic (solar) panels  12  or other panel-like structures are directly secured to upper support members ( 30  in  FIG. 3 ) and held in place by panel clips or panel holders  45  (as depicted in  FIG. 3 ). These panel clips are found in a wide range of sizes and shapes. The panel clips serve as hold-down devices to secure the panel against the corresponding top support members ( 30 ) in spaced-relationships. The clips are conventionally positioned and attached about the panel edges once each panel is arranged in place. 
         [0005]    For a conventional, free-field ground rack system (for mounting solar panels) as shown in  FIG. 1 , vertical support elements, such as I-beams  14 , are spaced and securely embedded vertically in the ground. Tilt mounting brackets  16 , are installed at the top of each I-beam, and each tilt mounting bracket is secured to the I-beam such that a tilt bracket flange extends above the I-beam at an angle as best seen in  FIG. 2A . As shown in this case, two UNISTRUT™ lower joists  20  span the tilt mounting brackets  16  and are secured thereto. As seen in  FIG. 2B , UNISTRUT™ rails  30  are positioned across and fastened to lower joists  20 . To secure each rail  30  to the corresponding lower joists  20 , a bolt through a bolt hole made in the rail sidewall attaches to a threaded opening in a transverse nut-like plate (not shown) slideably mounted inside the channel of the UNISTRUT™ joist, so that the nut-like plate engages and tightly secures against the upper flange of the joist&#39;s C-channels as depicted in  FIG. 2A . 
         [0006]    Once the bi-directional span  10  is assembled, each solar panel  12  is secured in place by a portion of panel holding clips  45 , which are secured to the support rails about the perimeter of each panel. The panel clips are put in place, and tightened to support rails  30 . This installation process is often costly, inaccurate, dangerous and time-consuming. 
         [0007]    Another example of a support system for panel like structures is shown in U.S. Pat. No. 5,762,720, issued to Hanoka et al., which describes various mounting brackets used with a UNISTRUT™ channel. Notably, the Hanoka et al. patent uses a solar cell module having an integral mounting structure, i.e. a mounting bracket bonded directly to a surface of the backskin layer of a laminated solar cell module, which is then secured to the channel bracket by bolt or slideably engaging C-shaped members. Other examples are shown in U.S. Pat. No. 6,617,507, issued to Mapes et al.; U.S. Pat. No. 6,370,828, issued to Genschorek; U.S. Pat. No. 4,966,631, issued to Matlin et al.; and U.S. Pat. No. 7,012,188, issued to Erling. 
         [0008]    Foldable support arrays  10  of upper support rails  30  and lower support joists  20  are found in the newer art developed by the inventors of the present application. One such example is depicted in  FIG. 4 . A detailed view of the intersection between upper support rail  30  and lower support joist  20  is depicted in  FIG. 5 . The present inventor has developed a number of foldable support systems for solar panels and other panel like structures. These are listed in attached information disclosure documents. 
         [0009]    The folding support arrays  10  of these support systems solve many problems well known in the art of panel arrays. However, even with a reliable, easily-deployed support array, there are still difficulties in the installation of panel arrays, especially solar panel arrays. In particular, existing support systems require meticulous on-site assembly of multiple parts, performed by expensive, dedicated field labor. Assembly is often performed in unfavorable working conditions, i.e. in harsh weather and over difficult terrain, without the benefit of quality control safeguards and precision tooling. Misalignment of the overall support assembly often occurs, especially when mounting panels to the rails  30  with clips  45 . This can jeopardize the supported solar panels. 
         [0010]    Another problem is spacing of the photovoltaic (solar) panels  12 . This is important to accommodate panel expansion and contraction due to the change of the weather. It is important, therefore, that the panels are properly spaced for maximum use of the bi-directional area of the span. Different spacings may be required on account of different temperature swings within various geographical areas. It is difficult, however, to precisely space the panels on-site using existing support structures and panel clips or holders without advanced (and expensive) technical assistance. 
         [0011]    For example, with one of the existing designs described above (with reference to  FIGS. 2A and 2B ), until the upper rails  30  are tightly secured to the lower joists  20 , each upper rail is free to slide along the lower joists and, therefore, will need to be properly spaced and secured once mounted on-site. Further, since the distance between the two lower joists is fixed on account of the drilled bolt holes through the rails, it is preferred to drill the holes on-site, so that the lower joists can be precisely aligned to attach through the pre-drilled attachment holes of the tilt bracket. Unfortunately, the operation of drilling the holes on-site requires skilled workers, and even with skilled installation, might still result in misalignment of the support structure (i.e. improperly spaced or slightly skewed from parallel) and/or the solar panels supported by that structure. 
         [0012]    An additional degree of difficulty is added by the provision of drilling holes  145  to accommodate connectors for the panel clips or holders  45 . If this is done on site, precise placement of the solar panels becomes extremely difficult. Even if the apertures  145  are precisely drilled at a factory, an additional degree of imprecision is introduced when the panel clips  45  have to be connected to the upper support rails  30  while being positioned to hold panels  12 . This is an awkward arrangement, even in the hands of expert installers. Normally, it is accomplished by connecting one portion of the panel clip  45  to the upper support rail  30 , and then positioning panel  12  to be secured by another portion of panel clip  45 . Of necessity, this adds an additional assembly step for each panel clip  45 , while still offering opportunities to accidently introduce misalignment in the overall panel array  10 . 
         [0013]    Misalignment difficulties are exacerbated by the flexing of the panels and natural sagging permitted by the flexibility of the panels. The sagging of the panels can cause the panels to work out of their holders, whether they would be holding clips or part of the overall structure of the upper support rail. Improper installation, which occurs frequently in conventional systems, can lead to dislocation of the panels due to sagging or atmospheric conditions. The use of a wide variety of different mounting positions and array arrangements also exacerbate the stability problems caused by panel sagging or deflection. Further, certain mounting positions will make the panels more vulnerable to atmospheric disruptions, such as those created by wind and precipitation. All of these variables also complicate electrical connections to the panels. 
         [0014]    One method of correcting misalignment is through the use of larger and more effective panel clips  45 . However, there are drawbacks in this approach. In particular, there are only a limited number of points at which panel clips can be connected. Accordingly, even with enlarged panel clips  45 , only extremely limited portions of the lengths of panels can be secured. 
         [0015]    Therefore, a need exists for a low-cost, uncomplicated, structurally strong support system and assembly method, so as to optimally position and easily attach the plurality of photovoltaic panels, while meeting architectural and engineering requirements. Likewise, there is an urgent need for a panel support system that will maintain the security of the mechanical connections of the solar panels to support rails despite the flexing of the panels (and support structure) caused by any of gravity, vibration, or environmental factors. Likewise, there is an urgent need to simplify the assembly of panel support systems, especially the connections between the upper support rails  30  and panel clips  45 . Such simplification should not compromise the stability or strength of the connections between the panels and the support system. 
         [0016]    At present, none of the conventional art offers these capabilities. An improved support system would achieve a precise configuration in the field without extensive work at the installation site. The use of such an improved system would facilitate easy placement of solar panels onto the support structure. The shipping configuration of the improved support system would be such so as to be easily handled in transit while still facilitating rapid deployment. Rapid deployment must be facilitated on any type of substrate providing stable support for the panels, without damaging or otherwise compromising the panels, or substrate. Rapid deployment would also include rapid mechanical connection of the panels to panel clips in a manner that would keep the panels secure despite panel flexing, or any number of other factors. 
       SUMMARY OF THE INVENTION 
       [0017]    It is a primary object of the present invention to improve upon conventional photovoltaic solar panel systems, especially with regard to assembly and installation. 
         [0018]    It is another object of the present invention to provide a support and installation system for solar panels in which the panels are less likely to be damaged during installation. 
         [0019]    It is a further object of the present invention to provide a simplified support system for solar panels that is easily installed while still facilitating a precise configuration. 
         [0020]    It is an additional object of the present invention to provide a solar panel support system that can be assembled very quickly on site, due to fewer assembly steps. 
         [0021]    It is still another object of the present invention to provide a solar panel support system that can achieve close tolerances during field installation without the necessity of skilled on-site labor. 
         [0022]    It is still an additional object of the present invention to provide a solar panel support system which can be easily adapted to a wide variety of solar panel array sizes and shapes. 
         [0023]    It is yet another object of the present invention to provide a solar panel support system which minimizes the necessity for precise measurements at the installation site. 
         [0024]    It is again a further object of the present invention to provide a solar panel support system that can be arranged at a variety of different positions and exposure angles. 
         [0025]    It is still an additional object of the present invention to provide a solar panel support system that can be precisely configured to a specific environment. 
         [0026]    It is another object of the present invention to provide a support system for solar panels and other panel-like structures in which degradation caused by metal-to-metal contact is substantially reduced. 
         [0027]    It is again another object of the present invention to provide a support system for panel-like structures in which accommodation is made for movement caused by changes in temperatures, humidity or other environmental considerations. 
         [0028]    It is still a further object of the present invention to provide a simplified connection system for a solar panels using a reduced number of parts. 
         [0029]    It is still an additional object of the present invention to provide a solar panel mounting system that can accommodate easy installation and removal of panels on adjacent frameworks. 
         [0030]    It is yet another object of the present invention to provide a roof interface framework for a solar panel support structure which allows easy installation of adjacent panel support systems, without interfering with previously installed panels. 
         [0031]    It is again an additional object of the present invention to provide a panel support system that permits deployment of multiple support structures on a wide variety of different substrates. 
         [0032]    It is still another object of the present invention to provide a panel support system wherein a wide variety of different sizes and shapes of panel configurations can be accommodated, and easily installed, as well as removed. 
         [0033]    It is again a further object of the present invention to provide a panel support system in which panels can be easily attached to support brackets without incurring damage to the panels. 
         [0034]    It is still another object of the present invention to provide a support system for panels or panel-like structures for a wide range of uses, positions, and configurations. 
         [0035]    It is still a further object of the present invention to provide a panel mounting system which is entirely self-contained with its own installation interface. 
         [0036]    It is again an additional object of the present invention to provide a panel mounting system which facilitates quick, secure mounting of the panels once the support system is deployed. 
         [0037]    It is yet another object of the present invention to provide a panel support system that can accommodate flexing, sagging and other deformation of the panels while maintaining a secure connection thereto. 
         [0038]    It is yet a further object of the present invention to provide a panel mounting system which facilitates increased panel clip capacity. 
         [0039]    It is again an additional object of the present invention to provide a panel mounting system that facilitates safe tightening of panel clips. 
         [0040]    It is yet another object of the present invention to provide a panel clip or connector that can accommodate for flexing of both the panel and the support system. 
         [0041]    It is still a further object of the present invention to provide a panel connection system that can facilitate rapid installation while maintaining a secure hold on the panels or panel like structures. 
         [0042]    It is yet an additional object of the present invention to provide support rails configured to ensure a secure panel connection. 
         [0043]    It is yet a further object of the present invention to reduce the cost of panel support structures by eliminating the overall length of structural aluminum, such as those currently used in conventional systems, without sacrificing the strength of the overall structure. 
         [0044]    It is still an additional object of the present invention to provide a panel support system admitting to substantial flexibility of configuration. 
         [0045]    It is the overall goal of the present invention to provide a comprehensive panel mounting system that facilitates rapid, secure installation, including deployment of the panel support structure, and placement of the panels on that support structure. 
         [0046]    These and other goals and objects of the present invention are provided by a mounting system having lower support joists and upper support rails constituting panel clips with at least one adjustable arm. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0047]    Having generally described the nature of the invention, reference will now be made to the accompanying drawings used to illustrate and describe the preferred embodiments thereof. Further, the aforementioned advantages and others will become apparent to those skilled in this art from the following detailed description of the preferred embodiments when considered in light of these drawings, in which: 
           [0048]      FIG. 1  is a perspective view of an assembled conventional field ground rack support system for securing a plurality of solar panels; 
           [0049]      FIG. 2A  is a side view of a conventional tilt bracket mount with prior art C-shaped sectional channels secured back-to-back to form support joists to which upper support rails, also shown in  FIG. 2B , are secured; 
           [0050]      FIG. 2B  shows an end view of prior art upper support rails, each with a C-shaped sectional channel; 
           [0051]      FIG. 3  is a perspective view of a previously-disclosed support system in a configuration as used with solar panels arranged in a column and in spaced relationship thereon; 
           [0052]      FIG. 4  is a top view illustrating the bi-directional support frame collapsed to an intermediate folded position; 
           [0053]      FIG. 5  is an end elevation and partial sectional view depicting a conventional arrangement of a lower support joist, and upper support rail, and a panel clip; 
           [0054]      FIG. 6A  is an end view of a support clip of the present invention, with a sliding arm in a first position; 
           [0055]      FIG. 6B  is a top view of  FIG. 6A ; 
           [0056]      FIG. 6C  is an end view of  FIG. 6A  with the sliding arm in a second or withdrawn position; 
           [0057]      FIG. 7  is a top view of a section of the sliding arm; and 
           [0058]      FIG. 8  is a side view depicting a first installed panel and a partially installed second panel. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0059]    As has been previously discussed, conventional panel (solar and other types) support systems tend to be constituted by two dimensional arrays having lower support joists  20  and upper support rails  30 . Panel clips or holders  45  are then mounted on the upper support rails so that the panels  12  can be placed thereon, and secured with additional portions of the clips. Even with factory pre-alignment and set up, conventionally there is little that can be done about the many assembly steps required to place both the panel clips  45  and the panels on the upper rails. 
         [0060]    The present invention, as depicted in  FIGS. 6(   a - c ),  7  and  8 , is a departure from this arrangement. Reinforced clip structure  400 , as depicted in detail by  FIGS. 6(   a )- 6 ( c ), provides a reinforced structure to serve as a clip, and as a substitute for upper support rail  30 , such as that provided in the conventional art previously described herein. This substitution is performed without detriment to the strength and stability of the overall panel array system  10 . The structural stability of the conventional tubular upper support rail  30  depicted in  FIG. 5  is provided by tubular support structure  405  constituting the main body of inventive support clip  400 . The tubular support structure  405  includes two side walls  405 ( a ),  405 ( b ), a lower wall  405 ( c ) and an upper thickened wall  405 ( d ). The upper thickened wall  405 ( d ) includes a threaded portion  405 ( e ) to receive an external connecting screw  406 . 
         [0061]    Inventive support clip  400  is held to a conventional lower support joist  20  (as depicted in  FIG. 8 ) through the use of a U-shaped structure, which operates as a kind of hinge. This structure includes two extending legs  402 ( a ),  402 ( b ), which extends on either side of the sidewalls of support joist  20  (not shown in  FIG. 6(   a  &amp;  c )). The two extending legs  402 ( a ),  402 ( b ) are attached to the rest of support clip  400  through horizontal shoulders  401 ( a ),  401 ( b ), respectively. Besides forming the U-shaped structure to attach support clip  400 , to a lower support joist  20 , the two shoulder structures  401 ( a ),  401 ( b ) also serve as supports for external panels  12  (as depicted in  FIG. 8) . 
         [0062]    T-slot  409  is provided between shoulders  401 ( a ),  401 ( b ) to accommodate a bolt head (not shown) that passes through the lower support joists  20  (depicted in  FIG. 8 ). By using T-slot channel  409 , the panel clip structure can be held securely to the lower support joists  20 , an advantage that was not easily achieved in the conventional art where the panel clip had to be attached separately to the upper support rail  30 . By incorporating both the panel clip  45  and the upper support rail  30  into the same structure, (support clip  400 ), the present invention has achieved superior structural integrity, as well as greater simplicity. Further, enhanced stability is added by the extending legs  402 ( a ),  402 ( b ), of the U-shaped structure so that even greater stability between the two structures (support clip  400  and lower support joists  20 ) is achieved than has previously been possible with the conventional art. 
         [0063]    It should be noted that support clip  400  is preferably made of aluminum. Conventional support joists  20 , upon which the support clip  400  is mounted, are preferably made of steel. Accordingly, provision must be made for some kind of barrier to prevent a metal-to-metal contact between the aluminum support clip and the steel support joist. One way of affecting this is through the use of a nylon gasket (not shown) formed over the interior of the U-shaped structure formed by legs  402 ( a ),  402 ( b ), and shoulders  401 ( a ) and  401 ( b ). The gasket can have a hole, to accommodate the bolt (not shown) which will interact with T-slot  409 . The gasket can be formed of nylon, and be contiguous over the U-shape of the support clip  400 . 
         [0064]    In the alternative, the gasket, or gaskets, can be made to be discontiguous, in a variety of shapes and sizes. Further, while nylon has been proven to work admirably as an insulator, to prevent metal-to-metal contact between aluminum and steel, other materials can also be used. Thus, while some type of gasket is necessary between support clip  400  and support joists  20 , virtually any arrangement is permissible with the concept of the present invention. 
         [0065]      FIG. 6(   b ) depicts a top view of support clip  400 . Included in the view is an external tightening screw  406 . The entirety of the width of support clip  400  is approximately 1¾ inches. However, while this is one preferred size, other sizes can be used within the concept of the present invention. Also, the length of support clip  400  is shown to be foreshortened, and contain only a single tightening screw  406 . While this is suitable for one embodiment of the present invention, not all embodiments of the present invention are so limited. 
         [0066]    In a first embodiment of the present invention, support clip  400  can be the approximate length of a conventional clip  45  (as depicted in the conventional art drawings). However, with this configuration, the present invention would still suffer from some of the drawbacks of the conventional art. For example, there would still be a very limited number of points at which the panels  12  could be connected to an underlying support array. While this is adequate for some panel support arrangements  10 , this is not always the case. 
         [0067]    In another embodiment of the present invention, the length of support clip  400  can be much greater than that suggested in  FIG. 6(   b ). For example, the length of support clip  400  can extend for the entire length of the underlying support joists  20 . An appropriate number of tightening screws  406  and accompanying threaded portions could also be provided based upon the requirements of the specific panel array to be mounted. A continuous connection between the support clip  400  and the panel that the clip is holding for a major portion of the length of that panel provides a much more secure connection than is currently available with conventional art. As a result, many panel flaws and eccentricities (such as sagging, warping, or the like) can be adequately addressed with the present invention. 
         [0068]    Secure, contiguous connections are only part of the advantage provided by the present support clip  400 . The present invention further addresses the difficulties normally occurring with placement and securing of panels during the assembly process, and any subsequent repair or maintenance operations that might require removal or adjustment of panels  12 . In order to appreciate the advantages of the present invention, it is necessary to consider the parts of support clip  400  that hold or otherwise address external panels  12 . Normally, the panels  12  would rest upon shoulders  401 ( a ) or  401 ( b ). The upper part of the panel would interface with an upper fixed arm such as  408 . In order for support clip  400  to hold an external panel  12  using shoulder  401 ( b ) and fixed arm  408 , the panel  12  would have to be slid between these two arms. While this may be suitable for one side of the panel, the opposite side would present severe problems if there is an attempt to mount the panel in the same manner. Normally, a panel would have to be slid perpendicularly (in the Z axis extending out of the drawing) in order to be fit into two clips on either side of it, having fixed upper and lower arms, such as shoulder  401 ( b ) and fixed arm  408 . While this may be practical in some arrangements, it is very often not practical, so that even if the sliding of multiple panels  12  is possible, it can be very awkward. 
         [0069]    The problem of mounting and dismounting panels  12  within support clip  400  is solved through the use of sliding arm  410 , a top view of which is depicted in  FIG. 7 . Sliding arm  410  is attached to the rest of the support clip  400  by means of slot  410 ( b ) and tightening screw  406 . This means that the entirety of sliding arm  410  is capable of being moved from the position depicted in  FIG. 6(   a ) to the position depicted in  FIG. 6(   c ). In the  FIG. 6(   c ) position, sliding arm  410  is entirely clear of side wall  405 ( b ). This allows a panel  12  (not shown therein) to be placed atop shoulder  410 ( a ) from the top of the support clip  400 , rather than being slid sideways. 
         [0070]    Movement of sliding arm  410  is controlled through tension generated by spring  407  and tightening screw  406 . The spring tension generated can render movement of sliding arm  410  to be very difficult. This difficulty can be easily overcome by means of beveled shoulder  410 ( a ) which allows sliding arm  410  to slide easily over the top surface of structure  405 ( d ). The movement of sliding arm  410  is further facilitated by the beveled shoulder  408 ( a ) of fixed arm  408 . The result of this arrangement is that sliding arm  410  can be effectively controlled so that it can be slid back from its extended position (as depicted in  FIG. 6(   a )) to a retracted position (as depicted in  FIG. 6(   c )), and held there without any difficulty. Replacement of the sliding arm  410  into its  FIG. 6(   a ) position is easily facilitated by the same structures that permitted easy sliding and retention in the retracted position. Once sliding arm  410  is returned to the extended position (as depicted in  FIG. 6(   a )), the panel  12  can be tightened in place with little additional effort by simply operating tightening screw  406  to increase the tension of spring  407  on sliding arm  410  (and thus the panel  12  being held firmly by sliding arm  410 ). 
         [0071]    An example of the aforementioned operation is depicted in  FIG. 8 . In this arrangement, lower support joists  20  are arranged on a substrate  100  (which can be constituted by any surface from a concrete slab, to a roof, to a metal mounting bracket, for example, atop a tilt bracket for an extended length of joist). The lower support joists  20  are held to the substrate by any number of different, conventional mounting techniques, which has been elaborated on in a substantial number of conventional art examples. Further details of these mounting techniques are not necessary for an understanding of the present invention. Support clips  400  are mounted to the lower support joists  20  as previously described, using the U-shaped structure of the lower support clip, and if desired, bolts extending through the support joists and into the T-slot  409  of support clip  400 . As depicted in  FIG. 8 , the right-hand panel  12  has been fit into a first support clip  400 , and the right-hand side of the panel is about to be lowered onto the far right-hand support clip  400  from above. The sliding arm  410  of the far right-hand support clip  400  has been retracted, and is in the same position as depicted in  FIG. 6(   c ). 
         [0072]    The arrangement depicted in  FIG. 8  allows for very easy and rapid deployment of panels  12 , in a wide variety of different configurations. The ease of mounting and dismounting panels  12  for arrangements as depicted in  FIG. 8  renders the installation and maintenance of solar panel arrays much less expensive than is the prevailing condition for conventional arrays. 
         [0073]    A further advantage of the present invention is that the sliding arm can be arranged in virtually any length that is considered desirable for a particular panel array, or even individual panel. Accordingly, a single panel array can contain any number of different lengths and configurations of sliding arms  410  to better facilitate ease of installation and security of the panels for a particular place in the panel array, or even a particular panel. Likewise, because support clip  400  is arranged parallel to the lower support joists  20 , the numbers of tightening screws  406  can be changed as needed for a particular place or position in the panel array. For example, a three foot length of support clip  400  could have two feet of sliding arm  410  arranged at different positions along the length of the support clip  400 . The lengths of sliding arm could be manufactured to have different numbers of slots for increasingly secure connections between the sliding arm  410  and the panel  12  to be held. 
         [0074]    While a number of preferred embodiments have been described by way of example, the present invention is not limited thereto. Rather, the present invention should be understood to include any and all variations, modifications, adaptations, permutations, derivations, and embodiments that would occur to one skilled in this art in possession of the teachings of the present invention. Accordingly, the present invention should be construed to be limited only by the following claims.