Abstract:
A corner clamping apparatus capable of adjustably clamping two joined, mitered corner pieces to form a 90-degree corner with a single clamp. The clamping apparatus includes three rigid L-shaped supports, adjustably mounted relative to one another to accommodate differently sized corner pieces and/or variations in the corner pieces or their mitered edges. Four adjustable clamping feet retained in the rigid L serve to adjust the corner pieces to produce an exact miter joint or seam, and to hold the adjusted corner pieces until they can be more permanently joined.

Description:
RELATED APPLICATIONS/PRIORITY BENEFIT CLAIM 
     This application claims the benefit of U.S. Provisional Application No. 61/209,184 filed Mar. 4, 2009 by the same inventor (Hughey), the entirety of which provisional application is incorporated herein by reference. 
    
    
     FIELD 
     The subject matter of the present application is in the field of clamping apparatus for use in producing corners from mating corner pieces with mitered mating edges, by securely retaining the corner pieces in a corner arrangement. 
     BACKGROUND 
     Devices relating to frame and corner clamps and miters are known. U.S. Pat. No. 4,056,030 to Hahn is directed to a combination miter box, corner clamp, and measuring gauge based on a machined metal, V-shaped structure. However, the Hahn apparatus is not capable of generating longitudinal axis compression of framing strips or corner pieces. Further, the arrangement of the clamping screws in the Hahn apparatus limits its capability for clamping wide frame strips. Finally, the Hahn apparatus is a complex design requiring customized metal machining. 
     U.S. Pat. No. 4,247,090 to Hahn et al teaches a corner clamp using a similar machined metal, V-shaped structure. This apparatus adds a z-plane member capable of clamping to a work bench. However, the apparatus is otherwise subject to the same limitations as the prior Hahn device. 
     U.S. Pat. No. 7,168,693 to Sjuts et al is directed to an adjustable angle clamp. This apparatus uses adjustable clamping jaws disposed on opposing arm members to provide adjustable-angle clamping of two pieces to be joined along a seam. However, the Sjuts et al reference is limited in the width of material it will clamp, and does not readily allow for adjusting the miter seam. 
     BRIEF SUMMARY 
     What is disclosed and claimed herein is an adjustable corner clamping apparatus including, in combination, first, second, and third rigid L supports and first, second, third, and fourth clamping feet. A first rigid L support includes first and second legs. A second rigid L support also includes first and second legs. The first legs of the first and second rigid L supports are slidingly coupled together. As a result, the second legs of the first and second rigid L supports are held in parallel. Further, the distance between the second legs of the first and second rigid L supports is adjustable. 
     A third rigid L support includes first and second legs. The second legs of the first and third rigid L supports are slidingly coupled together. As a result, the first legs of the first and third rigid L supports are held in parallel. Further, the distance between the first legs of the first and third rigid L supports is adjustable. 
     A first clamping foot is adjustably retained in the first leg of the first rigid L support. A second clamping foot is adjustably retained in the second leg of the first rigid L support. A third clamping foot is adjustably retained in the second leg of the second rigid L support. A fourth clamping foot is adjustably retained in the first leg of the third rigid L support. As a result of this unique arrangement of supports and clamping feet, cooperative action between the first, second, third, and fourth clamping feet is operative to receive and securely retain a pair of frame strips or similarly mitered pieces in a corner arrangement. 
     While the terms “frame strips” or “framing strips” has been used so far to generally describe the pieces held together by my clamping apparatus, the term “corner piece” will be used in their place hereafter. All of these terms should be construed to include any mating frame or corner pieces with opposingly-angled or mitered mating edges with which it is desirable to form a tight, clean, even seam where the pieces are joined to form a right-angle corner. For example, the preferred use of my clamping apparatus is in securing, aligning, and retaining mitered wood stock, for example common “1×” or “2×” wood stock used to form right-angle corner trim on a house or a cabinet. Another possible use of the clamping apparatus, without implying limitation, is in forming square newel posts. 
     My clamping apparatus optimally addresses several critical issues typical to corner clamping. These issues include the need (1) to adjust for different corner piece lengths, (2) to adjust for different corner piece widths, (3) to generate adequate compression between the mated corner pieces, (4) to compensate for variations in the miter seam, and (5) to provide an economical and easy to manufacture clamping apparatus. 
     The clamping apparatus functions by receiving corner pieces therein to form a corner or by being applied to already-mated corner pieces to secure them in place while they are more permanently fastened, for example by allowing previously-applied adhesive to set, and/or by nailing or screwing the joined corner pieces together. 
     These and other features and advantages of the invention will become apparent from the detailed description below, in light of the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a top view of a corner clamping apparatus according to a preferred example of the present invention. 
         FIG. 2  is a perspective view of the corner clamping apparatus of  FIG. 1 . 
         FIG. 3  is a top view of the corner clamping apparatus of  FIG. 1 , further showing the clamping apparatus receiving and retaining a pair of corner pieces in a corner arrangement. 
         FIG. 4  is a partially exploded perspective view of several corner clamps according to  FIGS. 1-3  applied to the corner trim of a house. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIGS. 1 through 4 , a corner clamping apparatus is shown in exemplary form in order to teach how to make and use the claimed invention. 
     In  FIG. 1 , a corner clamping apparatus  10  includes a first rigid L support  14 , a second rigid L support  26 , a third rigid L support  38 , a first clamping foot  50 , a second clamping foot  66 , a third clamping foot  78 , and a fourth clamping foot  94 . The rigid L supports  14 ,  26 , and  38  are so named for their general “L” shapes. The first rigid L support  14  has a first leg  18  and a second leg  22 . The second rigid L support  26  also has a first leg  30  and a second leg  34 . 
     The first leg  18  of the first rigid L support  14  and the first leg  30  of the second rigid L support  26  are slidingly coupled together. For example, the rigid L supports may be fabricated from square steel tubing. In the illustrated embodiment, the first rigid L support  14  is fabricated tubing stock of somewhat larger cross section than the second rigid L support  26 . As a result, the first leg  30  of the second rigid L support  26  slides into the first leg  1  of the first rigid L support  14 . Alternatively, the second rigid L support  26  could be made larger such that the first rigid L support  14  could slide into the second rigid L support. The position of the coupling of the first and second rigid L supports  14  and  26  may be fixed using, for example, a set screw  36  that is retained in one of the legs while frictionally coupled to the other. As a result of such a coupling, the second leg  22  of the first rigid L support  14  and second leg  34  of the second rigid L support  26  are held in parallel. Further, the distance between the second leg  22  of the first rigid L support  14  and the second leg  34  of the second rigid L support  26  is adjustable based on the position of the sliding coupling as fixed by the set screw  36 . 
     A third rigid L support  38  has a first leg  42  and second leg  46 . The second leg  22  of the first rigid L support  14  and the second leg  46  of the third rigid L support  38  are slidingly coupled together. In the illustrated embodiment, the second leg  46  of the third rigid L support  38  slides into the second leg  22  of the first rigid L support  14 . Alternatively, the first rigid L support  14  may be made to slide into the third rigid L support  38 . The position of the coupling of the first and third rigid L supports  14  and  38  may also be fixed using a set screw  48  retained in one of the legs while frictionally coupled to the other. As a result of such a coupling, the first leg  18  of the first rigid L support  14  and first leg  42  of the third rigid L support  38  are held in parallel. Further, the distance between the first leg  18  of the first rigid L support  14  and the first leg  42  of the third rigid L support  38  is adjustable based on the position of the sliding coupling as fixed by the set screw  48 . 
     A first clamping foot  50  is adjustably retained in the first leg  18  of the first rigid L support  14 . A second clamping foot  66  is adjustably retained in the second leg  22  of the first rigid L support  14 . A third clamping foot  78  is adjustably retained in the second leg  34  of the second rigid L support  26 . A fourth clamping foot  94  is adjustably retained in the first leg  42  of the third rigid L support  38 . The first, second, third, and fourth clamping feet  50 ,  66 ,  78 , and  94  are preferably each attached to a separate threaded spindle  54 ,  70 ,  82 , and  98  to provide a means both for retention in their respective legs and for making adjustments to the feet positions. The position of each threaded spindle may be adjusted by turning the spindle clockwise or counterclockwise. As each spindle is turned, the relative positions of each clamping foot may be adjusted to accommodate a work piece, not shown. 
     Each of the clamping feet  50 ,  66 ,  78 , and  94  are preferably each further attached, via the spindles, to operating ends  58 ,  74 ,  86 , and  102 . The operating end preferably includes a transverse pin handle  62 ,  90 , or equivalent, to provide a means for the operator to create torque on the spindle—torque that is converted into compression force as the clamping feet cooperatively couple onto or engage a work piece, i.e. two corner-forming pieces. 
     Each of the clamping feet  50 ,  66 ,  78 , and  94  are each preferably operative to swivel on their respective spindles to accommodate uniquely shaped corner pieces and to accommodate deviations in the miter joint or the assembled corner pieces. Also, each of the clamping feet  50 ,  66 ,  78 , and  94  preferably includes treading  106 , or knurling, to provide frictional coupling between the foot and a work piece. This feature promotes accommodation of uniquely shaped work pieces. 
     Referring now to  FIG. 2 , a full isometric view of the corner clamping apparatus  10  according to the exemplary and currently preferred embodiment of the present invention is shown. Steel square tubing, which is the preferred support material, allows the second and third rigid L supports  26  and  38  to slide into the first rigid L support  14 , as shown in phantom lines. 
     Referring now to  FIG. 3 , a full top view of the corner clamping apparatus according to the preferred embodiment of the present invention is shown. The clamping apparatus  10  is shown receiving and retaining a work piece—a pair of corner pieces C that could be a pair of frame strips or could be a pair of corner trim pieces—for example serving when held together to form a right angle corner on a finished item such as a window frame or the corner trim of a house. As a result of this unique arrangement of supports  14 ,  26 , and  38 , and of clamping feet  50 ,  66 ,  78 , and  94 , cooperative action between the first, second, third, and fourth clamping feet is operative to receive and securely retain a pair of frame strips in a corner arrangement. 
     It can be seen from  FIG. 3  that the four clamping feet all put pressure on the mitered joint in a direction tending to force and hold the mitered edges of the corner pieces tightly together. The interior clamping feet  50  and  66  that engage the corner at the seam are believed to be the most important for aligning the seam. 
     Referring to  FIG. 4 , several clamps  10  are shown in use with corner pieces C, here shown forming a corner trim  104  on a house  100 . Once corner pieces C are joined with their mitered inside edges abutting to form a miter seam  104   a , clamps  10  are applied at multiple locations along the corner  104  to retain the corner pieces in a tight fit until they can be permanently joined, for example by allowing previously-applied glue to set or by nailing or screwing them together. The mitered edges  104   e  of the corner pieces C are mitered at 45-degree angles to form a 90-degree corner as shown in  FIGS. 3 and 4 . The infinite adjustability of the clamping feet on clamps  10  allows small variations in the end or outside faces of the corner pieces to be accommodated. The four-point adjustable clamping pressure of the feet also allows corner pieces C to be minutely adjusted to overcome variations or imperfections in the alignment or evenness of their mitered edges, so that seam  104   a  can be adjustably clamped as tightly and evenly as possible. The number of clamps  10  applied to a given work piece or corner is in the discretion of the user. 
     It will finally be understood that the disclosed embodiments are representative of presently preferred examples of how to make and use the claimed invention, but are intended to be explanatory rather than limiting of the scope of the invention as defined by the claims below. Reasonable variations and modifications of the illustrated examples in the foregoing written specification and drawings are possible without departing from the scope of the invention as defined in the claims below. It should further be understood that to the extent the term “invention” is used in the written specification, it is not to be construed as a limiting term as to number of claimed or disclosed inventions or the scope of any such invention, but as a term which has long been conveniently and widely used to describe new and useful improvements in technology. The scope of the invention is accordingly defined by the following claims.