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CROSS-REFERENCE TO THE RELATED APPLICATIONS 
   This application is a continuation-in-part of U.S. patent application Ser. No. 09/735,386, filed Dec. 12, 2000, now abandoned. 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates generally to clamping and leveling tools and procedures, and in particular to a cased opening trim installation tool and method. 
   2. Description of the Related Art 
   In construction, wall openings are commonly formed for various purposes, e.g. to accommodate doors and windows. Sometimes wall openings are formed and left open to provide relatively free access between adjacent rooms in a structure. A relatively large number of interior partitions in residential and commercial construction are assembled in this manner. Many interior residential partitions have overall thicknesses of about 4½ inches. One of the advantages of having relatively uniform-thickness partitions is that I sizes of millwork for trimming same can be relatively uniform and standardized. Such standardization can be desirable because of the efficiencies involved in utilizing common trim sizes which are sized for the most popular wall thicknesses. 
   Such openings are often edged with trim pieces to conceal the framing members which surround and frame the opening, and also to provide a finished, aesthetically pleasing appearance which can be relatively uniform throughout the structure. A typical opening trim system might include, for example, a pair of jamb trim pieces each mounted on a respective side of the opening on a respective framing member framing same, a header or transom trim piece mounted on the underside of a header assembly constructed of structural framing members, and casing trim consisting of both jamb and header casing trim pieces for mounting on the wall faces on both sides around the opening. Additional trim pieces can be added, e.g., door stops for door openings, etc. 
   The widths of wall openings encountered in constructions vary considerably, but headers are normally placed at about 6′-8″ to 7′ above the floor, whereby standard doors with heights in the range of about 6′-8″ to 7′ can be accommodated. Since the trim around such an opening is typically a conspicuously visible part of the finished building interior, relatively precise installation can be highly desirable. However, rough-in or frame carpentry can be relatively inaccurate, with the framing lumber bordering the opening being somewhat out-of-plumb, out-of-square, etc. 
   To accommodate for such inaccuracies, the opening trim pieces are often carefully positioned within the wall openings to provide same with square and plumb configurations. The fine positioning of the jamb and header trim pieces can be accomplished with wedge-shaped shims inserted between the trim pieces and the opening framing members. The relative spacing between the trim pieces and the opening framing members can be adjusted by varying the number of shims and their thicknesses. However, such procedures tend to be relatively time consuming and awkward, particularly for unassisted workers. Difficulties can be encountered in installing such trim pieces in a square, plumb manner, particularly with respect to temporarily positioning the shims and casing trim pieces for nailing. During nailing, the shims and the trim pieces can shift, causing misalignment. Such problems can be compounded when a door is hingedly mounted on one of the jamb trim pieces. 
   Therefore, conventional methods of installing cased opening trim pieces tended to produce results which were sometimes lacking in uniformity and neatness of appearance. 
   Certain types of construction, particularly commercial and institutional facilities, involve the use of steel door frames and steel studs in lieu of wood, which is commonly used in residential construction. Steel door frames are often prefabricated for placement in the wall openings prior to installing the wall panels. It is desirable for such door frame assemblies to be properly positioned when fastened to the wall structures in which they are mounted. 
   A previous solution to the problem of positioning and holding trim in door and window openings during installation utilized a tool with a level adapted for mounting in an opening with set screws. With the installation tool in place, the jam and header trim could be properly positioned and nailed in place. However, the set screws used for attaching the tool tended to slow installation and removal. Moreover, the previous tool did not accommodate standard, commercially-available levels and was not readily adjustable for various wall thicknesses. 
   The present invention addresses the aforementioned problems with previous equipment and techniques for trimming wall openings. 
   BRIEF DESCRIPTION OF THE INVENTION 
   In the practice of the present invention, a trim installation tool is provided which includes a base having first and second ends, inner and outer faces, and opposite side edges. First and second clamp assemblies are mounted on the base first and second ends respectively. Each clamp assembly includes first and second clamp brackets connected by a bridge. Each first clamp bracket mounts a toggle clamp with an over-center plunger mechanism. The clamp assemblies have engaged positions adapted for engaging a wall and disengaged positions disengaged therefrom. An elongated level with orientation-display assemblies is mounted on the base inner face and extends generally between the ends thereof. Optional spacers are provided for spacing the base to provide clearance for a door trim piece. 
   OBJECTS AND ADVANTAGES OF THE INVENTION 
   The principle objects and advantages of the present invention include: providing a wall opening trim installation tool; providing such a tool which is adapted for installing trim in a relatively square and plumb configuration; providing such a tool which is adapted for installing trim around various types of openings including door openings, clear openings and window openings in walls; providing such a tool which facilitates installing trim by a single worker; providing such a tool which can be adjusted for various wall thicknesses; providing such a tool which provides relatively accurate placement for trim systems in wall openings of various sizes; providing such a tool which is adapted for firmly clamping casing trim in place prior to being permanently nailed; providing such a tool which accommodates nailing of casing trim permanently in place with nail guns and the like; providing such a tool which utilizes commercially-available levels; and providing such a tool which is economical to manufacture, efficient in operation, capable of a long operating life, designed for fabrication from common materials and components, and which is particularly well adapted for the proposed usage thereof. 
   Other objects and advantages of this invention will become apparent from the following description taken in conjunction with the accompanying drawings wherein are set forth, by way of illustration and example, certain embodiments of this invention. 
   The drawings constitute a part of this specification and include exemplary embodiments of the present invention and illustrate various objects and features thereof. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The drawings constitute a part of this specification and include exemplary embodiments of the present invention and illustrate various objects and features thereof. 
       FIG. 1  is a perspective view of a wall with an opening and a trim installation tool embodying the present invention clamped to the wall at a side edge of the opening. 
       FIG. 2  is a cross-sectional view of the trim installation tool and the wall opening side edge, taking generally along line  2 — 2  in FIG.  1 . 
       FIG. 3  is a cross-sectional view of the trim installation tool with a clamp assembly thereof in a disengaged position. 
       FIG. 4  is a fragmentary, enlarged, side elevational view of the trim installation tool, particularly showing a bubble-type orientation-display assembly thereof. 
       FIG. 5  is a cross-sectional view of a trimmed edge of the door opening. 
       FIG. 6  is a cross-sectional view of a trim installation tool fitted with optional spacers for clearing a door stop trim piece. 
       FIG. 7  is a fragmentary, front elevational view of a trim system comprising an alternative embodiment of the present invention, particularly showing a level thereof. 
       FIG. 8  is a horizontal cross-section thereof, taking generally along line  8 — 8  in FIG.  7 . 
       FIG. 9  is an upper, perspective view of a door opening, showing a spacer of the alternative embodiment trim system located therein at top and bottom positions within the opening. 
       FIG. 10  is an upper, perspective view of the spacer. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   I. Introduction 
   As required, detailed embodiments and/or aspects of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments/aspects are merely exemplary of the invention, which may be embodied in various forms. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the present invention in virtually any appropriately detailed structure. 
   I. Introduction and Environment 
   Certain terminology will be used in the following description for convenience in reference only and will not be limiting. For example, the words “upwardly,” “downwardly,” “rightwardly,” and “leftwardly” will refer to directions in the drawings to which reference is made. The words “inwardly” and “outwardly” will refer to directions toward and away from, respectively, the geometric center of the embodiment being described and designated parts thereof. Said terminology will include the words specifically mentioned, derivatives thereof and words of a similar import. 
   Referring to the drawings in more detail, the reference numeral  10  generally designates a trim installation tool. Without limitation on the generality of useful applications of the present invention, the trim installation tool  10  can be utilized for installing a trim system  12  on a wall  20  for finishing or casing a wall opening  18  formed therein with a pair of oppositely-disposed, vertical, jamb edges  15  and a horizontally-disposed head or transom edge  17 . 
   The wall  20  can comprise a conventional wall construction with studs  28  extending vertically in spaced relation (e.g., at 16″ or 24″ on centers) between wall panels  30 . The wall panels  30  can comprise a variety of materials, such as gypsum board, plywood, particle board, etc. A header  31  extends across the top of the wall opening  18  and includes a header plate  32  positioned adjacent to the opening head or transom edge  17  between the wall panels  30 . A pair of cripples or trimmers  33  support the header  31 ; each cripple or trimmer  33  is placed adjacent to a respective wall jamb or side edge  15  between the wall panels  30 . The header plate  32  and the trimmers  33  can comprise common framing lumber, such as 2×4&#39;s with actual cross-sectional dimensions of about 1½″ thick by about 3½″ wide. 
   The wall panels  30  can have thicknesses of, for example, approximately ½ inches each whereby the overall wall thickness would be approximately 4½″. However, structural members  28 , 31 , 32  and  33  with other dimensions, and wall panels  30  with other thicknesses, can be accommodated with the trim installation tool  10  of the present invention. 
   The wall  20  described thus far is of generally conventional construction. For aesthetic purposes, the edges  15  and  17  which form the wall opening  18  can be covered by the casing trim system  12  to provide a cased wall opening  18 . 
   The casing trim system  12  can comprise a pair of side or jamb trim pieces  22  and a head or transom trim piece  24 , which can be attached to the trimmers  33  and the header plate  32  respectively, e.g., by nailing, with shims  25  installed therebetween for proper positioning. Side and top casing trim pieces  26 ,  27  are applied to the jamb and head trim pieces  22 ,  24  and to the trimmers  33  and the header plate  32  through the panels  30 . The casing trim pieces  26 ,  27  thus overlap the panels  30  slightly to conceal the unfinished edges thereof. The tool  10  generally comprises a base  40 , a pair of clamp assemblies  42 , and a level  44 . 
   II. Base  40   
   The base  40  includes first and second ends  45 ,  46  and a rectangular cross-sectional configuration. The base  40  further includes an outer, contact or trim engagement face  37 , and an inner face  38 . The base  40  has a pair of side edges  49  and a plurality of nailing holes  43 . 
   III. Clamp Assemblies 
   Each clamp assembly  42  is mounted on the base inner face  38  in proximity to a respective end  45 ,  46  and includes first and second clamp brackets  52   a,b . Each bracket  52   a,b  includes a respective base leg  54   a,b  mounted on the base inner face  38  and projecting laterally from a respective base side edge  49 . Each bracket  52   a,b  also includes an extension leg  56   a,b  extending outwardly from a respective base leg  54   a,b . Each first clamp bracket  52   a  includes a toggle clamp  58  with an over-center plunger mechanism  60  with retracted and extended positions. A handle  62  is provided for moving the toggle clamp  58  between its retracted and extended positions. A foot  64  is mounted on the end of the plunger mechanism  60  by a threaded shaft  61  with a set nut  63  in spaced relation from and parallel to the first extension leg  56   a . A clearance  78  is defined between the foot  64  and the second extension leg  56   b  for receiving the wall  20  adjacent to the wall opening  18 . Each clamp assembly  42  also includes a bridge  66  connected to and extending between the base legs  54   a,b  for securing same together in fixed relation corresponding to the thickness of the wall  20 . 
   The toggle clamp  58  can be adjusted to accommodate different wall thicknesses by threadably retracting and extending the foot  64  on the shaft  61 . Alternatively, greater variations in wall thickness can be accommodated by providing different clamp brackets  52  with various spacings between their respective extension legs  56   a,b . For example, wall thicknesses can vary considerably depending upon their construction with studs of different widths. Stud widths varying from 1½ inches to 7½ inches are common. Clamp brackets  52   a,b  for various wall thicknesses can be provided for interchangeably mounting on the base  40  as needed. 
     FIG. 6  shows an optional configuration of the tool  10  with spacers  70  mounted on the base outer face  37  by screws  72  extending through receivers  74  formed in the base  40  at regular intervals. The spacers  70  space the base  40  inwardly from the trim pieces  22 ,  24  to clear a door stop trim piece  76 . It will be appreciated that the spacers  70  can easily be installed and removed as needed, and different thicknesses of spacers can be provided to provide clearance for different thicknesses of door stop trim pieces  76 . 
   IV. Level  44   
   The level  44  includes a total of three orientation-display assemblies; two end display assemblies  102  and a middle orientation display assembly  104  mounted in the level  44 . Each display assembly  102 ,  104  includes a liquid-filled tube  106  with a bubble  108 , the tube  106  being mounted in an annular rum  110  and extending more or less diametrically thereacross. The rims  110  can be rotatable for reorienting the tubes  106 . 
   The level  44  can comprise a standard, commercially-available level of the type commonly used in construction. The overall length should preferably be under six feet in order to fit within commonly-encountered door openings. Shorter-length levels can be utilized for mounting head/transom trim pieces  24 , for trimming window openings, etc. 
   V. Operation and Trim Installation Method 
   In operation, the tool  10  can be used for placing a variety of members and holding them in predetermined positions. The level  44  can provide the user with a relatively accurate indication of the orientation of a member clamped by the tool  10 . For example, the tubes  106  can be placed in longitudinal alignment with the tool  10  for indicating the horizontal orientation of the tool  10  and a horizontal member (e.g., head or transom trim piece  24 ) clamped thereby, or can be oriented substantially transversely with respect to the tool  10  for indicating a vertical orientation of the tool  10  and a vertical member (e.g., side or jamb trim piece  22 ) clamped thereby. The end orientation-display assemblies  102 ,  104 , with their tubes  106  oriented substantially transversely to the tool  10 , can be positioned near the top and bottom of the wall opening  18  ( FIG. 1 ) for reference by a worker in proximity to the clamp assemblies  42 . 
   The clamp assembly clearances  78  receive the wall  20  and can be closed by the feet  64 . The nailing holes  43  provide openings for nails  100  or other fasteners to be driven through the respective trim pieces  22 ,  24  and into respective framing members such as the header plate  32  and the trimmers  33 . Pneumatic nail guns could be employed for nailing the trim pieces  22 ,  24  in place through the nailing holes  43 . 
   VI. Alternative Embodiment Door Trim System and Method 
     FIGS. 7-10  show a trim installation system  202  comprising an alternative embodiment or aspect of the present invention and generally including a level  204  and a trim piece spacer  206 . The level  204  can be constructed with a single-piece, unitary extrusion  206  forming a combined base  210  and level flange  212 . The base  210  mounts a pair of clamp assemblies  214  positioned in spaced relation and each comprising first (inner) and second (outer) L-shaped brackets  218 ,  220 . The general configuration and operation of the level  204  are similar to those of the trim installation tool  10  described above. 
   Each first bracket  218  includes a first base leg  222  mounted on the base  210  and a first extension leg  224  extending from a respective base leg  222  and forming a right angle with respect thereto. The first base leg  222  is slotted at  225 . The first extension leg  224  mounts a compressible engagement pad  226 . Each second bracket  220  includes a second base leg  228 , which is slotted at  230 , and a second extension leg  232  forming a right angle with respect thereto. The second base legs  228  overlie the first base legs  222 , with their respective slots  225 ,  230  aligned and receiving fasteners  234 ,  235 , which can comprise suitable machine screws, washers and nuts for releasably clamping the base legs  222  and  228  onto the base  210 . For example, a locking-type crown nut  244  can be provided for one of the fasteners  234 , and a handwheel  246  can be provided for the other fastener  235  whereby loosening and tightening adjustments can be made quickly and manually. 
   The base legs  222  and  228  are thus adapted to slide with respect to each other and with respect to the base  210 , whereby the openings or jaws defined by the clamp assemblies  214  can be adjusted. For example, adjustments in the range of about 4½ inches to about 11¼ inches will accommodate most wall thicknesses commonly encountered in construction. Each second bracket extension leg  232  mounts a plunger assembly  236 , which includes a foot  238  mounting a compressible engagement pad  240 . Spacer clips  242  are clipped on the edges of the base  210  for spacing same from the jamb of a door and for providing clearance over a door stop  76 . 
   The spacer  206  includes a body  252  with a lower bar  254  having an upwardly-open channel  256  and an upper bar  258  with a longitudinally-extending slot  260 , which generally aligns with the channel  256 . A set screw assembly  262  is mounted on a lower bar inner end  264  and is slidably received in the upper bar slot  260 . A disk-shaped nut  266  of the set screw assembly  262  is adapted for tightening and loosening same by hand whereby the bars  254  and  258  are selectively clamped together or adjustably slidable with respect to each other. 
   The lower and upper bars  254 ,  258  include outer ends  268 ,  274  respectively, each mounting a cross brace  270 . Each cross brace  270  includes transversely, slidably adjustable brace spacers  272 , which function like the spacer clips  242  described above to provide clearance over the door stop  76 . 
   In operation, the clamp assemblies  214  are adapted for adjustment by sliding the brackets  218 ,  220  with respect to each other whereby the thickness of a wall can be approximated. In many construction jobs, similar wall thicknesses are encountered repeatedly whereby a number of openings can be trimmed without readjusting the clamp assemblies  214 . When different wall thicknesses are encountered, readjustment can be easily accomplished with the clamp assemblies  214 . 
   The clamp assembly plungers  236  likewise facilitate fine adjustments to accommodate different wall thicknesses. The feet  238  thereof can be threadably adjusted to tighten or loosen the clamp assemblies  214 . The level  204  is used in a similar manner to the trim installation tool  10  described above. The spacer  206  is adapted for squaring the trim within an opening by calibrating a constant spacing between parallel trim members, such as the jambs. For example, as shown in  FIG. 9 , the spacer  206  can be placed at the top of a door frame to gauge the spacing of the jamb trim pieces. The spacer  206  is readily adjustable by loosening and tightening the set screw assembly  262  by manually tightening and loosening the disk-shaped nut  266 , permitting the bars  254 ,  258  to reciprocably slide with respect to each other whereby the cross brace  270  engages the jamb trim pieces on either side of the opening. The spacer  206  can then be repositioned by, for example, placing it at the bottom of the opening as shown in FIG.  9 . The trimmed opening can thus be held to relatively precise tolerances, which facilitate proper fit and operation of doors, windows and other finish constructions. 
   It is to be understood that while certain embodiments and/or aspects of the invention have been shown and described, the invention is not limited thereto and encompasses various other embodiments/aspects.

Summary:
A trim installation tool includes a base with first and second ends, inner and outer faces, and opposite side edges. First and second clamp assemblies are mounted on the base in proximity to its first and second ends respectively. The clamp assemblies have engaged and disengaged positions for respectively clamping and releasing a wall edge adjacent to the wall opening. An elongated level with an orientation-display device is mounted on the base inner face and extends generally between the ends thereof. The orientation-display device indicates a level or plumb orientation of a trim piece clamped in position by the tool for attachment to the frame members surrounding the wall opening. In an alternative embodiment or aspect of the invention, a trim installation system and method are provided, which include a level and a trim piece spacer.