Patent Abstract:
A clamping head assembly for clamping a first member to a second member at a miter joint, where the clamping head assembly includes a first fence member with a first positioning edge for positioning an edge of the first member and a second fence member that is movable and includes a second positioning edge for positioning an edge of the second member. The second positioning edge is arranged at an angle with respect to the first positioning edge. Additionally, the first fence member and the second fence member are configured and arranged so that the angle is approximately bisected by the miter joint formed between the first and second members. The second fence member is movable in a direction that is approximately perpendicular to the miter joint, whereby a normal force is generated upon the miter joint. Furthermore, the present invention also relates to a frame making machine that includes the clamping head assembly just described.

Full Description:
BACKGROUND OF THE INVENTION 
     The present invention relates generally to a machine for joining two members at a miter joint, a clamping head assembly for use in such a machine, and a method of retrofitting an existing joining machine to include the present clamping head assembly. More particularly, the preferred embodiment of the present invention relates to a frame making machine used for joining two frame members at a miter joint, where the machine includes a clamping head assembly with two fence members, at least one of which is movable, which are used to align the frame members in the proper orientation. The present invention also relates to such a clamping head assembly, as well as to retrofitting a machine that includes a conventional head assembly with the present head assembly. It should be noted that although the preferred embodiments of the present invention will be shown and described as being intended for use in the frame making industry, uses of the present invention in other industries that require members to be joined together at a miter joint are also contemplated as being within the scope of the invention, for example the woodworking industry. 
     A miter joint is a corner joint formed by fitting two members together at their respective edges, wherein each edge is cut at some angle; the line defined at the joint between the adjacent edges is the miter angle. Conventionally, for adjacent edges cut at the same angle, if the included angle between the two members is 90 degrees, the miter angle will be 45 degrees, and if the included angle is 60 degrees, the miter angle will be 30 degrees. Therefore, a miter angle by definition is an oblique angle. 
     Machines for joining two frame members at a miter joint are known in the art. One popular machine, which is shown in an exploded view in FIG. 1, is the “Mitre-Mite VN 4 Electronic,” which is manufactured and distributed by Alfamachine-ITW/AMP of Vernon Hills, Ill. The frame making machine  10  includes a work table  12  with a preferably horizontal work surface  14 . Briefly, as known to those of ordinary skill in the art, the machine  10  operates as follows. First, one frame member is aligned along each one of the two fence members ( 22 ,  24 ) with a miter joint therebetween. Next, the frontal clamp  18  (optional) moves horizontally in a direction that is generally coincident with the miter joint, and pushes each of the two frame members against its respective fence member ( 22 ,  24 ). Third, the vertical clamp ( 20 ) engages the frame members from the top, pushing them downwardly against the work surface  14 . Finally, the two frame members are nailed together at the miter joint by one or more nails (e.g., V-nails, corrugated fasteners or other fasteners) that are driven upwardly into the miter joint from a nail driving mechanism that is seated below the work surface  14 . After the nailing operation, the two frame members (which are now a single unit) can be removed from the machine since they have been joined together at the miter joint. 
     Since the present invention relates primarily to the methods and apparatuses used to clamp the frame members in place, these features of the prior art machine will be described next in more detail. The machine  10  includes three primary clamping subassemblies: (1) a stationary clamping assembly  16 ; (2) a movable frontal clamp assembly  18 ; and (3) a movable vertical clamp assembly  20 . It should be noted that since these features are known to those of ordinary skill in the art, only the major components of each subassembly will be described below. 
     The stationary clamping assembly consists primarily of two stationary fence members  22  and  24  that are relatively rigidly affixed to the work surface  14  by a plurality of screws  26  extending through a plurality of associated holes  28 . The holes  28  are in the form of elongated slots to allow for some adjustment of the positioning of the stationary fence members  22 ,  24 . Knobs  30  are useful for adjusting the vertical angle of the edge of the fence members to better accommodate and achieve a tight fit between frame members having angled or non-uniform edges. A shown in the FIG. 1 view, the inner (or left) side of each of the stationary fence members defines a positioning edge upon which a respective edge of one of the frame members intended to be joined together is seated against. 
     The second subassembly, the movable frontal clamp assembly  18 , includes a movable frontal clamp member  32 , which is configured to move within track  34 . The position of the frontal clamp member  32  may be varied by moving the securing knob  36  to another one of the holes  38 . In operation, the movable front clamp member  32  is moved from a first position in which it is drawn backward (toward the left-hand side of FIG. 1) to a second position (toward the right-hand side of FIG. 1) in which it is clamping against the frame members intended to be joined together. The direction of travel of the frontal clamp member  32  is essentially coincident with the miter between the two frame members being joined together. 
     The third subassembly, the movable vertical clamp assembly  20 , includes a pressure plate  37  that is attached to a rod  39 . The rod  39  is attached to a support structure  40 , which is in turn connected to two cylinders  42 . The cylinders  42  are rigidly affixed to the work surface  14  from below so that the attachment plates  44  are below the work surface  14  and the cylinders  42  extend through holes  45  to be situated above the work surface. If necessary, the horizontal location of the pressure plate  37  may be adjusted by loosening handle  46 , and then sliding the threaded dowel  48  within the slot  50 . The vertical height of the pressure plate  37  may be adjusted by manipulating the other handle  52 . In operation, the cylinders  42  are withdrawn to push the pressure plate  37  downwardly upon the top of the frame members being joined together at the miter joint. In this manner, the frame members are firmly held down when the fastener(s) (e.g., V-nails, corrugated fasteners) are inserted from below. 
     One common problem with many frame assembly machines of the prior art, such as the one described above, is that the two frame members being joined together may not be properly held together at the miter joint. There may be a slight space between the two frame members at the miter joint prior to nailing. If this is the case, when the frame members are nailed together, there will be an unsightly gap between the two frame members at the joint. That is, the miter joint may be too wide along its entire length, resulting in a visible air space along the entire length of the miter joint, or the miter joint may be uneven, whereby a portion of the joint has a visible air space and another portion is tight with no visible air space. Neither of these two situations is desirable since the intent is to arrive at a tight miter joint with no visible gap between the two frame members. 
     Accordingly, one object of the present invention is to provide an improved frame assembly machine which is capable of consistently making a tight miter joint. 
     Another object of the present invention is to provide a clamping head assembly for use with a frame assembly machine whereby the resulting miter joints are tight. 
     A third object of the present invention is to provide a clamping head assembly for use with a frame machine where the assembly includes at least one movable fence member for properly positioning the frame member within the machine prior to the nailing operation. 
     A fourth object of the present invention is to provide a clamping head assembly that applies a force to the frame members being joined together at a miter joint, where that force is applied in a direction that is approximately perpendicular to the miter joint. 
     An additional object of the present invention is to provide a method of retrofitting an improved clamping head assembly upon an existing frame assembly machine. 
     These and other objects of the present invention are discussed or will be apparent from the following detailed description of the present invention. 
     BRIEF SUMMARY OF THE INVENTION 
     The above-listed objects are met or exceeded by the present frame assembly machine, which features a clamping head assembly that provides an additional clamping force for maintaining the frame members in position prior to being joined together at a miter joint, where that additional clamping force is applied in a direction that is approximately perpendicular to the miter joint. In the preferred embodiments, the additional clamping force is realized by providing a movable fence member that cooperates with a stationary fence member to retain the two frame members in the proper position prior to being nailed together. 
     More specifically, the present invention provides a clamping head assembly for clamping a first member to a second member at a miter joint, where the clamping head assembly includes a first fence member with a first positioning edge for positioning an edge of the first member and a second fence member that is movable and includes a second positioning edge for positioning an edge of the second member. The second positioning edge is arranged at an approximately right angle with respect to the first positioning edge. Additionally, the first fence member and the second fence member are configured and arranged to that the approximately right angle is approximately bisected by the miter joint formed between the first and second members. The second fence member is movable in a direction that is approximately perpendicular to the miter joint, whereby a normal force is generated upon the miter joint. Furthermore, the present invention also relates to a frame making machine that includes the clamping head assembly just described. 
     Another aspect of the present invention relates to retrofitting an existing frame making machine with an improved clamping head assembly. In particular, the invention relates to a method of retrofitting a frame making machine that originally includes a primary work surface (preferably generally horizontal) and two stationary fence members for positioning first and second frame members intended to be joined together at a miter joint, where the two stationary fence members are seated upon the primary work surface. The first step of the method involves removing at least one of the stationary fence members from the frame making machine. The second step involves installing at least one movable fence member upon the frame making machine, where the movable fence member is capable of being moved in a direction that is generally perpendicular to the miter joint between the first and second frame members. 
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
     Preferred embodiments of the present invention are described herein with reference to the drawings wherein: 
     FIG. 1 is an exploded view of a prior art frame assembly machine, including a prior art clamping head assembly consisting of two stationary fence members; 
     FIG. 2 is a top perspective view of the first embodiment of the clamping head assembly of the present invention; 
     FIG. 3 is schematic view of a second embodiment of the clamping head assembly of the present invention; and 
     FIG. 4 is a schematic view of a third embodiment of the clamping head assembly of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to FIG. 2, a first embodiment of the present clamping head assembly will be described. It should be noted that features of FIG. 2 that are also found in the prior art device of FIG. 1 will be numbered with the same numbers used in FIG.  1 . It should also be noted that in FIG. 2 a portion of the pressure plate  37  has been cut away to allow for a better view of the components below this plate. 
     In the FIG. 2 embodiment, the clamping head assembly  52  includes two fence members—a stationary fence member  54  and a movable fence member  56 . The stationary fence member  54  includes a positioning edge  58  for aligning the edge of one of the frame members intended to be joined at a miter joint, and the movable fence member  56  also includes a positioning edge  60  for aligning the other frame member. The stationary fence member  54  is preferably rigidly affixed to the work surface  14  via several bolt and slot arrangements, only one of which is shown. These arrangements each include a bolt, such as bolt  62 , and a slot, such as slot  64 . The elongated slots  64  allow for some adjustment of the position of the stationary fence member  54 . 
     In this preferred embodiment, the movable fence member  56  is attached to a cylinder rod  66  of a pneumatic cylinder  68  via a pivotable connection  70  made through a block  72 . The block  72  is rigidly affixed to the top of the movable fence member  56 . One end of the cylinder  68  is preferably affixed to a cylinder base  73  such that the cylinder extends horizontally from the base so that the cylinder rod  66  is aligned with the pivotable connection  70 . Instead of using a pneumatic cylinder to move the movable fence member  56 , it is also contemplated that electromechanical means, e.g., electronic, mechanical, pneumatic controls and parts, may be used. 
     Two guide rods  74 , each of which are slidable between a corresponding guide block  76 , are preferably provided to guide the movable fence member  56  along a straight horizontal path that is perpendicular to the miter joint that will be found between the two frame members being joined together. The guide rods  74  are preferably notched at areas  75 , which is a simple method of affixing them to the raised shoulder  79  of the movable fence member  56 . A stop bar  78  is preferably provided on the ends of both guide rods  74  in order to prevent the rods from extending too far. The guide blocks  76  and the cylinder base  73  are preferably rigidly affixed to a supplemental work surface  77 . 
     Optionally, additional guidance for the movable fence member  56  may also be provided by a pair of bearings  80  seated within a pair of slots  82  (only one of which are shown). It should be noted that each bearing  80  passes through one of the slots  82 , and is affixed to the work surface  14 , and this bearing/slot combination allows for the movable fence member  56  to slide across the work surface  14 . 
     Another optional feature of the present invention is the inclusion of a ridge  84  on the stationary fence member  54 . The ridge functions to align the frame members prior to clamping and fastening the members together. The ridge further facilitates the centering of the fastener with respect to the miter joint. A notch  86  may also be included the movable fence member  56 . The notch provides clearance for the moveable fence to move inwardly toward the stationary fence, while applying pressure perpendicularly to the miter joint. This notch/ridge configuration thereby facilitates the formation of the miter joint. 
     In operation, the steps related to the clamping head assembly of the present invention are simply incorporated into the operating steps of prior art frame making machines. Thus, first the operator sets one frame member against each of the positioning edges  58  and  60 . Next, the movable frontal clamp  32  moves towards the frame members in a direction that is essentially coincident with the miter joint. Third, the cylinder  68  activates to move the movable fence member  56  in the direction of the arrow, creating a force upon the frame members that is approximately perpendicular to the miter joint. Such a force is useful in reducing the size of the gap between frame members at the miter joint. Next, the pressure plate  36  is lowered, creating a downward force upon the frame members. Finally, the frame members are affixed together at the miter joint, for example, by one or more fasteners that are driven upwardly from below the work surface  14 . Accordingly, the two frame members are now affixed together at a miter joint, and can be removed from the machine. 
     Another important aspect of the present invention is that the present clamping head assembly may be retrofitted to a frame making machine with two stationary fence members, such as that shown and described above while referring to FIG.  1 . The basic retrofitting procedure is as follows. First, one of the stationary fence members, such as fence member  22  of FIG. 1, is removed from the machine. Then, the movable fence member  56  is positioned upon the primary work surface  14  in the appropriate area. The movable fence member  56  preferably includes the block  72 , but the fence member is not connected to the cylinder rod  66  or the guide rods  74  yet. Either before or after the movable fence  56  is installed, a supplemental work surface (such as surface  77  of FIG. 2) is affixed to the machine. Upon the supplemental work surface  77  are seated the components used to move the movable fence member  56 , such as the pneumatic cylinder  68 , the guide blocks  76 , etc. At this point the guide rods  74  are connected to the movable fence member  56  via the notched area  75  and the raised shoulder configuration  79  mentioned above. The cylinder rod  66  is connected as well, via the pivotable connection  70 . The pneumatic tubes  81  are then connected to the cylinder  68 , and the machine is in condition to be operated. If desired, the other stationary fence member (member  24  of FIG. 1) may also be replaced by a fence member with a ridge (such as member  54  of FIG. 2 with ridge  84 ) in order to facilitate the substantial alignment of the frame members prior to clamping and fastening operations. 
     A second embodiment of the present invention will now be described while referring to the schematic view of the top of the machine shown in FIG.  3 . Once again, like components from FIGS. 1 and 2 will be numbered with the same index numbers in FIG.  3 . 
     One of the main features of the FIG. 3 embodiment is that the work surface  14  is split into two sections—section  14 A and section  14 B. In this embodiment, the movable fence member  56  is rigidly affixed to work surface section  14 A, and the entire section  14 A of the work surface is configured to move in the direction of the arrow, i.e., in a direction that is approximately perpendicular to the miter joint between the two frame members. 
     In order to be able to move, the movable section  14  of the work surface is connected to a support structure  88  that is situated below the work surface  14 . The support structure  88  preferably includes four mounting blocks  90 , which are used to mount two rods  92 . A bearing  94 , such as a Thompson bearing, is slidably mounted upon each rod  92 . The tops of the bearings  94  are rigidly connected to the bottom of section  14 A of the work surface. The bearings  94  are preferably connected to each other via a bar  96 , which is connected near a center portion thereof to a cylinder  98 . The cylinder  98  is configured to move the bar  96  in the direction of the arrow, and accordingly also moves the bearings  94  and work surface section  14 A in the same direction, since these components are all rigidly connected to the bar  96 . 
     In the FIG. 3 embodiment, as well as in the FIG. 2 embodiment, only a slight movement of fence member  56  is required to provide sufficient pressure upon the miter joint. For example, travel of approximately 0.25 inches is sufficient. Since only a minimal amount of movement required, it is also contemplated that section  14 A of the work surface may be hingedly mounted to a mechanism for moving it with respect to the other section (section  14 B). Although movable fence member  56  would then be moved in an arc (instead of perfectly perpendicular to the miter joint as in the embodiments of FIGS.  2  and  3 ), the movement distance is so minimal that it can be considered to be moving in a straight line. 
     In the FIG. 3 embodiment, the movable vertical clamp assembly  20 , which includes the pressure plate  37 , is preferably configured in a similar manner to that shown in FIG.  1 . However, since section  14 A of the work surface is movable (along with the associated cylinder  42 ), the left side of the horizontal bar  41  of the support structure  40  needs to be connected to the left cylinder  42  with a horizontally slidable connection, such as with a bearing. In the alternative, the components supporting the pressure plate  37  may all be positioned upon the movable section  14 A, in which case a horizontally slidable connection between horizontal bar  41  and the left cylinder  42  is unnecessary. 
     The FIG. 3 embodiment may also be retrofitted to an existing frame making machine, such as machine  10  shown in FIG.  1 . Basically, the work surface  14  (FIG. 1) is removed from the work table  12 , and is divided into two sections  14 A and  14 B (FIG. 3) along a line that is coincident with the location of the miter joint between the two frame members intended to be joined together. The support structure  88  is installed within the work table  12 , section  14 A of the work surface is seated above the support structure, and the bottom of section  14 A is connected to the tops of bearings  94 . The other section of the work surface, section  14 B, is then reinstalled upon the work table  12  so that it remains stationary with respect to the work table. The fences  54  and  56  may be installed upon their respective sections ( 14 A and  14 B) of the work surface either before or after the work surface is reinstalled upon the table  12 . The movable vertical clamp assembly  20  (FIG. 1) may also be reinstalled upon the appropriate work surface section  14 A (or upon both sections  14 A and  14 B if desired) either before or after the section(s) have been reinstalled upon the table  12 . 
     Referring now to FIG. 4, a schematic view of the top of the machine of a third embodiment is shown. In this embodiment, both fences  54  and  56  are fixed to the work surface  14 , and the additional pressure is applied by pads  100 . In this schematic, arrows  102  represent cylinders, or other similar pressure means, that apply pressure to the pads  100  in the direction of the arrows. As in the other embodiments, each of the pads  100  apply pressure in a direction that is approximately perpendicular to the miter joint between the two frame members being joined together. In this way, the frame members are moved together to form the miter joint, while being held against the work surface, resulting in a tighter miter joint. Preferably, the cylinders  102  are arranged to apply forces in the vertical direction as well as in the horizontal direction. This combination force can be accomplished by arranging the cylinders  102  at an angle with respect to the work surface  14 . The suggested range for the angle is between 30° and 60°, with 45° being most preferred. This embodiment may also be retrofitted upon an existing machine, such as the machine of FIG.  1 . 
     While particular embodiments of the clamping head assembly and method of retrofitting a frame making machine to include the assembly have been shown and described, it will be appreciated by those skilled in the art that changes and modifications may be made thereto without departing from the invention in its broader aspects and as set forth in the following claims.

Technology Classification (CPC): 1