Abstract:
This mounting clamp is used as a truss adapter for support of fixtures, electrical and otherwise, from a truss ceiling. The clamp comprises a plate suspended by a pair of upstanding arms, each of which is formed by a bolt connected to an inverted U-shaped rectangular hanger member. The hangers and their associated bolts are inserted upwardly between the spaced beams of a bar joist from below and then the hangers are rotated 90 degrees before they are lowered into place to rest on both of the spaced beams, spreading the load, as the hanger arms are tightened to the plate. The plate carries a connector for mating to the object to be mounted. Leveling screws provide adjustment for orienting the mounted object. A vibration damping pad is included when appropriate. Variations of the clamp may be used in wall or parapet mount configurations.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS  
       [0001]     Not Applicable.  
       STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT  
       [0002]     Not Applicable.  
       FIELD OF THE INVENTION  
       [0003]     The present invention relates generally to a device for overhead mounting of an article such as an electrical fixture or appliance to a ceiling, eave or wall. The described invention is particularly suited for ease of installation when suspending a surveillance camera to an open truss ceiling by a person working alone.  
       BACKGROUND OF THE INVENTION  
       [0004]     As low cost construction techniques have developed for commercial buildings, there has been a greater utilization of bar joists and trusses, enabling the use of considerably greater unsupported spans than had been allowed by older construction methods. It is becoming commonplace for office and retail building space to be constructed in manners formerly reserved for wholesale or warehousing environments. The appearance of suspended or dropped ceilings has been replaced by open ceilings. In parallel with the development of these construction techniques has been the availability of, and apparent need for, more gadgetry, mostly electronic, that is best mounted overhead. The ceiling-mounted or suspended plumbing, lighting and HVAC components have been joined by requisite smoke detectors, sprinkler systems, and intrusion detection systems, including surveillance cameras. A need has developed for a means of mounting these additional components securely with minimal installation effort and time.  
         [0005]     Bar joists in most buildings comprise a pair of angle beams spaced slightly apart and disposed so that a vertical leg of each beam faces a corresponding vertical leg of the opposing related beam to form a chord. Additional support to the bar joists are provided by coupling a chord pair into a truss type arrangement with braces fastened to and between the pairs of angle beams of one chord to and between the angle beams of the second chord. Items to be suspended from the bar joist are commonly attached to the bar joist by clamps. Lighter weight loads are generally carried by clamps having a C-shape, similar to C-clamps. A series of these C-shaped clamps may be used to support elongated items such as conduit and plumbing. Such clamps are connected to one of the chords, often only to the angle beam on one side of that chord, and have a threaded receiver for reception of the threaded rod of a pipe-hanging element.  
         [0006]     For heavier loads, or discrete rather than elongated loads, the capacity of the C-shaped clamps is often insufficient. Where weight or integrity of the support is an issue, a more substantial clamping system is required. For these situations a common form of truss adapter is available from many suppliers. This common truss adapter comprises a rectangular plate which is typically supported by a pair of inverted U-bolts attached to the corners of the plate by threaded couplers. The U-bolts provide for attachment of the plate to square, round, rectangular or I-beam trusses. Since many of the fixtures that will be suspended from these adapters are fitted by their manufacturers with a threaded pipe stub to enable their mounting, the plate generally has a centrally located hole to which a 1½ inch diameter pipe coupler is fitted for attaching the load.  
         [0007]     Another type of truss system is constructed from a product known as Unistrut®. This is a rectangular channel, open on one side with inturned edges, and often with holes spaced along the opposite side. Mounting of devices to a Unistrut® system may be accomplished by the use of special nuts captured between the inturned edges on the open side of the channel. Another approach to mounting in these systems involves use of one or more plates, at least one of which is inserted into the channel to form a sandwich through which bolts are inserted.  
         [0008]     A large building, or a cluster of buildings such as a shopping mall, may require hundreds or even thousands or more of truss adapters for the mounting of a variety of fixtures. Although each adapter is relatively inexpensive, its installation can be quite time consuming and thus costly. In the previously mentioned adapters, the installation of each requires tightening of multiple threaded couplers, or insertion of one or more nuts and plates into a channel, in order to properly connect the adapter to the truss, and then the object to be suspended must be connected to the adapter. Over a period of time, vibration in the building may cause the adapter to become loose from the truss, or may cause the suspended object to loosen from its mount.  
       BRIEF SUMMARY OF THE INVENTION  
       [0009]     The disclosed invention relates generally to a clamp for secure mounting of an article such as an electrical fixture or appliance to a ceiling, eave or wall. In its preferred embodiment the described clamp is particularly well-suited for suspending a surveillance camera to a split lower chord of a bar joist in an open truss ceiling. Because ease of installation was among the design criteria, the invented clamp allows a person working alone to easily install the clamp and its supported device using no more than a couple of commonly available tools. It will be shown that further provisions have been made for leveling of the suspended load, and damping against vibration.  
         [0010]     In its most basic form the present invention comprises a rigid rectangular flat plate having sets of holes to receive threaded fasteners. Two of these holes lie along a centerline near opposite ends of the plate. Typically, four additional holes will be disposed near the corners of the plate. A mounting flange suitable for the object which will be supported is attached to a front side of the plate near its center, with a hole behind the flange to allow any necessary wiring to pass through the plate.  
         [0011]     The preferred embodiment of the present invention adds two brackets to the basic form. These brackets are cut from rectangular channel that has an inside width sufficient to span the vertical facing angles of the bar joist. The channel is cut into lengths slightly shorter than the spacing between the angles of the bar joist so that the brackets may be slipped between the angle beams.  
         [0012]     Assembly of the preferred embodiment is accomplished by passing a bolt through the plate at each of the two holes lying along a centerline, entering the plate from the side on which the flange is mounted. Each of these bolts then enters a threaded hole at the center of a corresponding instance of the previously described bracket. The brackets are oriented so that their open side faces the backside of the plate. The threaded connection between the bolts and brackets includes a locking mechanism to prevent the bolts from working loose after the installation is completed.  
         [0013]     Installation of the clamp begins by orienting the two brackets so that their longer dimensions are parallel to the centerline of the plate. The two brackets are then pressed upward so as to pass between the spaced apart bar joists that form the lower chord of the truss. After the brackets are inserted far enough so that their downward facing angles clear the top side of the bar joist angles, each of the brackets is rotated 90-degrees so as to cross both angle beam members of the bar joist. The brackets are then allowed to drop into place coming to rest upon and capturing the upward facing angles of the bar joist. As the two bolts are tightened into their respective brackets, the plate will be drawn into close proximity with the underside of the outward facing angles of the bar joist. With the clamp firmly in place, the object to be supported can be installed into the downward facing flange to complete the operation.  
         [0014]     Each of the four holes at the corners of the plate in the preferred embodiment is threaded to receive a bolt or screw. This hardware is installed for fine-tuning the orientation of the clamp and its supported object. In a general sense these are leveling adjustment screws, but in a specific case these screws may be used to adjust to some other orientation to accommodate the supported device. Given the purpose of these screws, an optimal choice in many situations is cupped-point socket head setscrews.  
         [0015]     An additional feature of the preferred embodiment is the inclusion of a pad of resilient material at the back of the plate that comes to rest against the truss as the bolts are tightened. This resilient pad serves to dampen vibrations that may otherwise be transmitted from the truss to the supported object. Reducing vibration also serves to avoid a problem sometimes encountered with the U-bolt mounts in the prior art whereby over time the bolts could work loose from their points of contact at the top of the bar joist angles allowing the entire mount to wander from its original position.  
         [0016]     Alternate embodiments of the present invention allow for securing objects either interior or exterior to a building, under eaves, on walls, or on rooftops behind parapets. The resilient pad may be used to accommodate an irregular mounting surface. For exterior use the pad may also provide the function of weatherproofing. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0017]     The particular features and advantages of the invention as well as other objects will become apparent from the following description taken in connection with the accompanying drawings, in which:  
         [0018]      FIG. 1  is a perspective view of the present invention securing a surveillance camera to an overhead bar joist truss;  
         [0019]      FIG. 2  is an example of a mounting adapter in the prior art;  
         [0020]      FIG. 3  shows in perspective a clamp in the present invention as viewed from the supported object;  
         [0021]      FIG. 4  is a perspective view of the present invention from the truss side;  
         [0022]      FIG. 5  is a side elevational view of a clamp as described in the present invention;  
         [0023]      FIG. 6  depicts an end elevation of a clamp as described in the present invention;  
         [0024]      FIG. 7  shows a bottom elevation of an instance of the presently described clamp;  
         [0025]      FIG. 8  is a top elevational view of a clamp as described in the present invention;  
         [0026]      FIG. 9  shows a perspective view of a clamp according to the present invention at the beginning of its installation into the space between the bar joists at the lower chord of a truss;  
         [0027]      FIG. 10  depicts in perspective a clamp in the present invention which is midway through the installation process as its brackets have been inserted into the space between the bar joists and beyond;  
         [0028]      FIG. 11  is a perspective view of a presently invented clamp following completion of its installation onto bar joists with bracket bolts securely tightened so as to compress a vibration-damping pad;  
         [0029]      FIG. 12  shows a clamp in accord with the present invention that has been secured to bar joists and then had an electrical item attached to the mounting flange along with a section of conduit to accommodate wiring from the mounted item; and  
         [0030]      FIG. 13  depicts an alternate embodiment of a clamp described by the present invention mounted under an eave.  
     
    
       [0031]     The following Reference Numbers will be used in conjunction with the accompanying  FIGS. 1-13  of the drawings: 
     100 . Clamp      110 . Plate      112 . Hole to accommodate wiring      113 - 114 . Holes for Bracket Bolts      115 - 118 . Holes for Leveling Screws      120 . Mounting Flange      125 . Threaded Interior of Mounting Flange      130 - 131 . Bracket Bolts      135 - 136 . Lockwashers      140 . First Bracket      142 . Threaded Hole in Bracket      144 . Center Section of Bracket      146 - 147 . Angled Ends of Bracket      150 . Threaded Fitting of Bracket using an optional nut      160 . Second Bracket      162 . Threaded Hole in Bracket      164 . Center Section of Bracket      166 - 167 . Angled Ends of Bracket      170 . Threaded Fitting of Bracket using an optional nut      180 - 183 . Leveling Screws      185 - 188 . Lock Nuts for Leveling Screws      190 . Resilient Pad      200 . Truss      210 ,  220 . Angles of Bar Joist forming Lower Chord of Truss      230 ,  240 . Angles of Bar Joist forming Upper Chord of Truss      250 . Braces of Truss      300 . Mounted Object Assembly      310 . Surveillance Camera as example of Mounted Object      320 . Mounting Stub      330 . Electrical Conduit Assembly      332 . Electrical Conduit      334 . Conduit Fitting      336 . Conduit Nut    
 
       DETAILED DESCRIPTION OF THE INVENTION  
       [0065]     Refer to  FIG. 1  where a truss is illustrated, comprising one pair of angle beams  210  and  220  acting as bar joists which form a lower chord, a second pair of bar joist angle beams  230  and  240  forming an upper chord, and braces  250 . While dimensions will vary in keeping with different loads, typically the pair of angle beams forming each chord will be spaced apart by approximately one-half to one inch; that is, the vertical legs of angle beams  210  and  220  will be separated by this amount, and similarly with the vertical legs of angle beams  230  and  240 . This small gap allows for connection of the braces  250  between a pair of angle beams. Whether the braces  250  are welded or bolted into place, they are inclined so as to form a truss for reinforcement of the bar joists. While rods may be used for the chords  210 - 240 , and can be accommodated by the clamp of the present invention, angle beams are more common and will be assumed here for descriptive purposes. A clamp  100  of the present invention is attached to the angle beams  210  and  220  of the lower chord of the truss. The object  300  to be supported comprises the object itself  310 , depicted here as a surveillance camera, attached by a mounting stub  320  to the threaded interior  125  of mounting flange  120  of the clamp  100 . As shown, any pipe-hung equipment, such as a camera, speaker, stage light, or radiant heater, to name just a few, may be mounted directly to the flange  120 .  
         [0066]     A mounting adapter from the prior art is depicted in  FIG. 2 . In use, such an adapter has a pair of inverted U-bolts that span the lower chord of the truss. Nuts are tightened onto the U-bolts in order to draw the plate against the underside of the lower chord of the truss. It is time consuming to connect each such clamp to the truss. A typical installation process might be to place a first U-bolt over the lower chord, align two holes along one side of the plate with the threaded ends of the U-bolt, slip the plate over the U-bolt ends, hold the plate in place while threading nuts onto the first U-bolt, then place the second U-bolt over the lower chord aligning it with the open holes in the plate, and attach a pair of nuts to finish the process. It will be shown that the present invention offers a significant advantage with regard to ease of installation.  
         [0067]     Detailed views of the clamp  100  of the present invention are shown in perspective in  FIGS. 3 and 4  and in the various elevations of  FIGS. 5-8 . The foundation of the clamp  100  is plate  110  which in the preferred embodiment is a steel plate having a typical thickness of 3/16-inch. This is sufficient to carry the loads that are anticipated to be supported in the environments under consideration. Other materials, known to those skilled in the art to have suitable structural and load-carrying properties, may be used where they are deemed appropriate.  
         [0068]     Attached to a proximal side of the plate  110  is a mounting flange  120 . This attachment will generally be welded, though other means known in the art are to be allowed. Most of the objects that will be mounted to the clamp  100  will have a mounting stub  320  that terminates in a 1¼ inch diameter male pipe thread. The largest devices to be considered are likely to require mounts that are no larger than 1½ inches in diameter. Use of a mounting flange  120  having the larger diameter of 1½ inches allows for insertion of reducer bushings to accommodate any smaller size of mounting stub  320 . Furthermore, adapter fittings may be inserted into the mounting flange  120  for acceptance of bayonet or other styles of mount. A hole  112 , best seen in  FIG. 3 , centrally located in the plate  110 , allows access of wiring from the mounted object  310  through the mounting stub  320 . An optional electrical conduit assembly  330  (shown in  FIG. 1 ) may be fitted into hole  112 . The details of a conduit connection are shown in  FIG. 5  wherein the conduit  332  is fitted with a male adapter  334  which is inserted into hole  112  and locked in place by conduit nut  336 .  
         [0069]     In its preferred embodiment the clamp  100  further comprises two brackets  140  and  160 . These brackets are identical and interchangeable. They are made from rectangular channel having a typical width of 3 inches. The exact dimension is unimportant here, provided that the bracket  140  is sufficiently broad to allow the inside faces of its angled ends  146  and  147  to span and to comfortably clear the vertical legs of the angle beams  210  and  220  in a bar joist. To make the brackets the channel is cut into lengths slightly shorter than the spacing between the angles of the bar joist so that the finished brackets will be able to slip through that space.  
         [0070]     Each bracket  140  and  160  has a threaded fitting  142  and  162  located at the center of its central section  144  and  164 . In the preferred embodiment bracket fittings  142  and  162  are holes that have been drilled and tapped with threads.  FIG. 3  shows an alternate embodiment in which holes have been drilled without tapping at locations  142  and  162  over which hex nuts  150  and  170  have been welded to provide the threaded fitting. Regardless of how the bracket fittings  142  and  162  are manufactured, the described clamp includes a locking mechanism that will prevent the bolts  130  and  131  from working loose after an installation has been completed. Many such locking mechanisms are known by those skilled in the mechanical arts and include plastic inserts, or crossed threads as well as lockwashers and other means. While a locking mechanism at the bracket  140  and  160  is preferred so as to create a connection to bolt  130  and  131  that exhibits high rotational friction, an alternative embodiment might use lockwashers  135  and  136  placed between the heads of bolts  130  and  131  and mounting plate  110  as shown in  FIG. 3 .  
         [0071]     Although these brackets  140  and  160  bear some resemblance to toggle bolts that have expanded into their supportive positions, the brackets herein described have significant advantage over toggle bolts. One advantage is that being manufactured from solid sections of rectangular channel the described brackets  140  and  160  are capable of supporting significant loads, whereas toggle bolts would tend to sag under comparable loads. Another advantage of the presently described bracket design is that it allows for the use of shorter bolts  130  and  131  than would be required if toggle bolts were to be used. This difference in bolt length amounts to an allowance for half of the expanded span of the toggle bolt when it is folded back along the length of the bolt prior to clearance of the distal side of the bar joist during installation. These factors allow the brackets described in the present invention to be manufactured at lower cost.  
         [0072]     The clamp  100  may be preassembled prior to installation. Assembly involves using a pair of bolts  130  and  131  to connect a pair of brackets  140  and  160  to plate  110 . The threaded ends of the bolts  130  and  131  are inserted into the plate  110 , from the proximal side on which the flange  120  is mounted, at holes  113  and  114 , respectively, lying along a longitudinal centerline of plate  110 . Bolts  130  and  131  are then threaded into bracket fittings  142  and  162  on their respective brackets  140  and  160  so that the open sides of the brackets face the distal side of the plate  100 . The bolts  130  and  131  should sufficiently engage bracket fittings  142  and  162  for a snug fit, exhibiting sufficient rotational friction that an unimpeded bracket  140  could be rotated by turning the attached bolt  130 , but need not extend beyond that prior to being installed.  
         [0073]     The process of installing the clamp  100  is depicted in a sequence beginning at  FIG. 9 . To begin installation the two brackets  140  and  160  are oriented so that their lengths are parallel to the centerline of the plate  110 . The two brackets  140  and  160  are then pressed into the space between bar joists  210  and  220  that form the lower chord of the truss  200  as shown in  FIG. 10 . The brackets  140  and  160  are inserted far enough for the open ends of the downward facing angles  146  and  147 , and  166  and  167 , to clear the distal (top) side of the bar joist angles  210  and  220 . Each of the brackets  140  and  160  is then rotated 90-degrees so as to cross both members  210  and  220  of the bar joist so that each will contribute to the support of the load after the mounted object  300  is installed. This rotation is facilitated by the high friction connection between the brackets ( 140  and  160 ) and their bolts ( 130  and  131 ) mentioned previously. The brackets  140  and  160  are then allowed to drop downward and are pulled into place against the upward facing angles  210  and  220  of the bar joist so as to capture the joist. Tightening of the bolts  130  and  131  into their respective brackets  140  and  160  draws plate  110  toward the underside of the outward facing angles of the bar joist  210  and  220  (see  FIG. 11 ). After the clamp  100  has been thusly secured, the installation process is completed, as seen in  FIG. 12 , by connecting the supported object  300  by means of its mounting stub  320  to the flange  120 . If desired an optional electrical conduit  330  may be added. In that case, referring to  FIG. 5 , conduit  332  would be fitted with a male adapter  334  which would be inserted through hole  112  and secured by a nut  336  from inside the mounting flange  120  prior to the mounting of the supported object assembly  300 .  
         [0074]     The above installation procedure also allows the presently described mounting clamp to be used with Unistrut® beams in addition to the previously described bar joist truss. A rectangular U-shaped channel with inturned edges on its open side, Unistrut® beams are available with rectangular slot cutouts. The brackets  140  and  160  may be inserted through the slots in a suitable Unistrut® beam and then rotated 90-degrees transverse to the beam before the bracket bolts  130  and  131  are tightened to capture the beam within the mounting clamp  100 . In situations where the brackets  140  and  160  are not accommodated by the slots in a particular Unistrut® beam, the brackets  140  and  160  may need to be removed from the bracket bolts  130  and  131  before the bolts are inserted into the beam and then reattached afterward. In either case, this installation procedure is much simpler, and less time-consuming, than a typical mount to a Unistrut® system which requires that special nuts and/or at least one plate be inserted into the channel to form a sandwich that will accept mounting bolts.  
         [0075]     To accommodate situations in which the truss  200  is not level, disposed near the corners of plate  110  in the preferred embodiment are four threaded holes  115 - 118  to accept leveling screws  180 - 183 . Cupped-point socket head setscrews are a preferred choice for these screws which may be used to fine tune the orientation of the mounting clamp  100  with respect to the surface on which it is mounted. In many cases this adjustment will allow for leveling of the mounted object  310  where the underside of the truss  200  has a slope to it, whether that slope is intentional or not. In other cases leveling screws  180 - 183  may be used to accommodate other angles, for instance where it is desired that a scanning surveillance camera sweep through an arc that does not have a uniform height. Though not typically necessary, each of the leveling screws  180 - 183  may be fitted with an optional lock nut  185 - 188  to keep the screws from becoming loose.  
         [0076]     Truss systems are designed to be capable of absorbing shock and vibration, and yet they are still good transmitters of those mechanical effects. Traffic generates vibrations of a very low-frequency nature, whether it&#39;s vehicular traffic outside of the building or foot or equipment traffic inside. Objects suspended from the truss, such as fans and plumbing also contribute to a variety of vibrations. To alleviate the effects of these vibrations, the preferred embodiment of the presently disclosed mounting clamp  100  additionally includes a vibration-damping pad  190  of resilient material as a backing to the plate  110 . Damping pad  190  will typically be made of rubber or a rubber-like product, such as neoprene, or a high-density foam. As the bolts  130  and  131  pull the brackets  140  and  160  into tight contact against the angle beams  210  and  220  of the truss  200 , the pad  190  is somewhat compressed to aid in damping vibration transmitted through the truss before it reaches the supported object assembly  300 .  
         [0077]     The preferred embodiment of the present invention includes all of the features described above, which are shown in  FIGS. 3 and 4 , namely brackets, leveling screws and vibration-damping pad. It will be recognized by those skilled in the related arts, that some of these features may be set aside to accommodate use of the described mounting clamp  100  in alternate embodiments. A variety of subsets of the invention allow for its use in many different environments, including those that are exterior as well as interior to a building or other structure, whether the mounted object is to be placed on a wall, against a soffit under an eave, or on a rooftop behind a parapet.  FIG. 13  depicts one such alternate embodiment in use for securing an object, such as the surveillance camera shown here, to a soffit under an eave. In this case the brackets  140  and  160  have been set aside, and bolts  130  and  131  have been replaced by lag screws for a secure attachment into a wooden beam structure. Depending upon the mounting surface, the leveling screws  180 - 183  may be more or less useful. For softer mounting surfaces such as lumber products, the leveling screws may be of little utility, in which case broader support of the mounting plate  110  can be gained by replacing the leveling screws  180 - 183  with wood screws or lag screws, with or without using a pair of lag screws in place of the bracket bolts  130  and  131 .  
         [0078]     In another alternate embodiment of the described invention the resilient pad  190  may be useful as a gasket to accommodate an irregular mounting surface. Another alternative use of the mounting clamp  100  in exterior conditions allows for replacement of the vibration-damping pad  190  with a weatherproofing material to maintain environmental integrity of the mount.  
         [0079]     While the present invention has been described with respect to a preferred embodiment, there is no implication to restrict the present invention to preclude other implementations that will be apparent to those skilled in the related arts. It is easily recognized that the described invention may be implemented with a variety of materials so as to adapt to a multitude of applications. Therefore, it is not intended that the invention be limited to the disclosed embodiments or to the specifically described details insofar as variations can be made within the spirit and scope of the appended claims.