Patent Publication Number: US-6220784-B1

Title: Method and apparatus for forming a trench

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     Applicant hereby claims priority to and incorporates by reference U.S. Provisional Application Ser. No. 60/075,065, filed Feb. 18, 1998. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates generally to the construction industry and more specifically to apparatus used in constructing grate-covered trenches. 
     BACKGROUND OF THE INVENTION 
     The use of concrete lined, grate or solid covered trenches are well known in the road, parking lot, and manufacturing plant construction industry. The typical trench construction includes a pair of spaced rails, wherein each rail has a grate supporting surface upon which a central grate rests. FIGS. 1 and 2 illustrate a typical prior art trench-forming assembly  10 . Each rail  12 ,  14  is made of a rigid material which preferably can be easily and inexpensively molded, cast, extruded, or stamped into a desired rail shape. As indicated in these figures, each rail  12 ,  14  can be Z-shaped in cross-section and connected by a connecting rod  16  which typically is attached to the rails by welding to an inside surface  17  of each rail. When such connecting rods  16  are used, at least two such connecting rods are placed between each set of rails, typically with one rod positioned at the end of each rod pair. The connecting rods  16  are used to maintain the rails  12 ,  14  in a fixed position relative to each other prior to and during the curing of the hardenable material used to form the completed trench. 
     Adjustable anchoring means typically are used to adjust the slope and height of the rails  12 ,  14 . As indicated in FIGS. 1 and 2, one such means includes a connecting member  18  that extends outwardly from an outside surface  20  of the rails  12 ,  14  to connect to an anchor rod  22  that is adapted to be driven into the ground at the bottom of the excavated trench. As is further indicated in the figures, the connecting member  18  includes a collar  24  through which the rod  22  can be passed. Each collar  24  includes a fastening member such as a thumb screw  26  which is threadingly inserted into an aperture formed within each collar so that, when the fastening member is tightened, the connecting member  18  can be fixed relative to the rod  22  such that the rails  12 ,  14  can be supported by the rods in the desired position. 
     The prior art assembly  10  of FIGS. 1 and 2 further includes a form  28 . Although capable of alternative construction, the form  28  typically is made of an expanded polystyrene foam which is adapted to be held in a fixed position between the rails  12 ,  14 . The form  142  normally includes an upper surface  30  and a shaped lower surface  32 . The lower surface  32  can be shaped into any contour, but preferably is tapered from the upper surface  30  to facilitate simple removal from the final trench. In the embodiment illustrated in FIGS. 1 and 2, a plurality of grooves  34  are formed in the upper surface  30  of the form  28  to receive each connecting rod  16  provided along the rails  12 ,  14 . The grooves  34  allow each connecting rod  16  to laterally traverse the form  28  to secure the form  28  in position while held between the rails  12 ,  14  as shown in FIG.  2 . Once the assembly is arranged as illustrated in FIG.  2  and the anchoring means adjusted into the desired position, hardnenable material (typically concrete) is poured into the excavated trench to surround the form  28 . After the hardenable material has cured, the form  28  can be removed to reveal a completed trench having the contours of the lower surface  32  of the form  128 . To facilitate removal of the form  28 , however, the connecting rods  16  first must be removed from the rails  12 ,  14 . In that the connecting rods  16  usually are welded to the rails, the rods typically must be cut from the rails with an electric grinder or saw. 
     Although adequately functional in design, there are several disadvantages associated with the prior art forming system set out in FIGS. 1 and 2. First, the upward buoyancy forces exerted on the form  28  often is sufficient to deepen the grooves  34  which receive the connecting rods  16 . As a result, the form  28  can be displaced upwardly, resulting in an uneven trench bottom surface. This result is particularly disadvantageous to the liquid displacing function of the trench in that it can create stagnant puddles of liquid therein. Furthermore, the connecting rods  16  can deform into an upwardly convex orientation, especially in wider form applications, due to the buoyancy forces imposed by the hardenable material. This deformation can cause misalignment or twisting of the frames, and can result in an uneven bottom trench surface, as described above. 
     Another disadvantage associated with the assembly illustrated in FIGS. 1 and 2, and other similar known systems, pertains to the attachment and removal of the connecting rods. Specifically, additional labor is required to weld each of the rods between the rails, which increases the cost and complexity of the assembly and makes it less economical to manufacture. In addition to the unnecessary labor associated with attachment of the connecting rods, additional labor is needed to remove them. Because the connecting rods normally must be cut away from the rails, the welded rod feature requires the presence of electrical power on a construction site or the use of gasoline powered tools. In the absence of such equipment, a hack saw must be used, making the removal of the form extremely labor intensive and quite expensive. 
     From the above, it can be appreciated that it would be advantageous to have a form assembly which is more resistant to the buoyancy forces imposed by the hardenable material, and which is less difficult to use. 
     SUMMARY OF THE INVENTION 
     Generally speaking, the present invention relates to an apparatus for forming a trench which is adapted to receive at least one grate that will cover the trench. The apparatus comprises first and second frame rails that are connected by at least one removable spacer. The spacer is sized and configured to maintain proper alignment and spacing between the first and second frame rails during the formation of the trench. The removable spacer is connected to the first and second frame rails with spacer securing means. 
     Once the first and second frame rails have been connected with the spacer securing means, the frame rails can be positioned within the excavated trench in a desired orientation. At this point, a hardenable material such as concrete can be poured into the excavated trench to surround the first and second frame rails. Once the hardenable material has cured to an adequate degree, the at least one removable spacer can be removed from the first and second frame rails and replaced with one or more grates. Typically these grates are fixedly secured to the first and second frame rails by using at least a portion of the securing means that was used to releasably secure the at least one spacer to the first and second frame rails. In that the securing means is used to secure both the at least one spacer and the one or more grates, the apparatus of the present invention can be more economically manufactured and more easily used. 
     The objects, features, and advantages of the present invention will become apparent upon reading of the following specification when taken in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF TIE DRAWINGS 
     The accompanying drawings incorporated in and forming a part of the specification illustrate several aspects of the present invention, and together with the description service to explain the principles of the invention. The components in the drawings are not necessarily to scale, emphasis instead being placed upon clearly illustrating principles of the present invention. In the drawings appended hereto, like numerals illustrate lie parts throughout the several views. 
     FIG. 1 illustrates an exploded perspective view of a prior art trench-forming assembly. 
     FIG. 2 illustrates a perspective view of the assembly of FIG. 1, shown in an assembled state. 
     FIG. 3 illustrates an exploded perspective view of a first embodiment of trench forming apparatus constructed in accordance with the present invention. 
     FIG. 4 illustrates a partial cross-sectional end view of the apparatus of FIG. 3, shown in a partially assembled state. 
     FIG. 5 illustrates a partial cross-sectional end view of the apparatus of claim  4 , shown in a fully assembled state. 
     FIG. 6 illustrates a completed trench formed with the apparatus of FIG.  3 . 
     FIG. 7 illustrates an exploded perspective view of a second embodiment of trench forming apparatus constructed in accordance with the present invention. 
     FIG. 8 illustrates a partial cross-sectional end view of the apparatus of FIG. 7, shown in a fully assembled state. 
     FIG. 9 illustrates a completed trench formed with the apparatus of FIG.  7 . 
     FIG. 10 illustrates a first alternative spacer securing means. 
     FIG. 11 illustrates a second alternative spacer securing means. 
     FIG. 12 illustrates a third alternative spacer securing means. 
     FIG. 13 illustrates a fourth alternative spacer securing means. 
    
    
     Reference will now be made in detail to the description of the invention as illustrated in the drawings. While the invention will be described in connection with these drawings, there is no intent to limit it to the embodiment or embodiments disclosed therein. On the contrary, the intent is to cover all alternatives, modifications, and equivalents included within the spirit and scope of the invention as defined by the appended claims. 
     DETAILED DESCRIPTION 
     Referring now in more detail to the drawings in which like numerals indicate corresponding parts through the several views, FIGS. 3-6 illustrate a first embodiment of trench-forming apparatus  100  constructed in accordance with the present invention. As is most clearly apparent from FIG. 3, the apparatus  100  generally comprises first and second frame rails  112  and  114 , and a removable form  116 . Typically, each frame rail  112 ,  114  comprises a vertical first portion  118 , a horizontal portion  120 , and a second vertical portion  122 . The first vertical portion  118  extends upwardly from the horizontal portion  120  and the second vertical portion  122  extends downwardly from the horizontal portion such that each frame rail  112 ,  114  is substantially Z-shaped in cross-section. Although a substantially Z-shaped cross-section is preferred, it is to be understood that alternative shapes could be used in lieu of the Z-shape, as desired. 
     The frame rails  112 ,  114  normally are constructed of a rigid material such as a metal or a polymeric material. Preferably, the rigid material is galvanized, painted, or unpainted steel, cast or extruded aluminum, or cast iron. The horizontal portion  120  of each frame rail  112 ,  114  is provided with a plurality of openings  124 , the purpose for which will be described below. Each opening  124  extends from a top surface  126  of the horizontal portion  120  to a bottom surface  128  of the horizontal portion so as to pass completely through the horizontal portion of each frame rail  112 ,  114 . Normally, the openings  124  are arranged in pairs  130  along the length of the horizontal portion  120  to facilitate lock-down of grates which will be placed atop the trench when completed. 
     Attached to the bottom surface  128  of each frame rail  112 ,  114  in the first embodiment is a plurality of support members  132  which are fixedly attached thereto. As indicated in FIG. 3, each of these support members  132  is positioned incrementally along the length of each frame rail  112 ,  114  and extends outwardly therefrom. Typically, each support member  132  extends perpendicularly outward from its associated frame rail  112 ,  114 , although alternative configurations are possible. In a preferred embodiment, each support member  132  can be configured as a support bracket  134 . Normally, each support bracket  134  is formed of flat bar and is welded to the underside of each frame rail  112 ,  114 . The support brackets  134  shown in FIG. 3 each includes at least a first and second horizontal portions  136  and  138 , as well as at least one vertical portion  140 . Each of the horizontal portions  136 ,  138  is provided with a support rod opening  142  which is adapted to receive a support rod  144 . Usually, each support rod comprises a steel rod commonly known as rebar, although alternative rigid materials could be used with similar results. In addition to the support rod openings  142 , each support bracket  134  further is provided with a threaded fastener opening  146 . Preferably, the fastener opening  146  is provided in the vertical portion  140  of each support bracket  134  and is sized and configured to receive a fastener  148  such as a screw or bolt. 
     As is further indicated in FIG. 3, the form  116  is substantially elongated in shape and comprises an upper surface  150  as well as a lower surface  152 . Typically, the upper surface  150  is substantially flat in shape and the lower surface  152  is substantially U-shaped. It is to be understood, however, that the shape of the lower surface can be varied to produce any resultant trench shape that is desired. Accordingly, the lower surface alternatively could be substantially square shaped in cross-section, substantially V-shaped in cross-section, or arranged in substantially any other shape. In a preferred configuration, the removable form  116  is composed of expanded polystyrene (EPS) and comprises two separate sections, an inner core  154  and an outer shell  156 . This material and the above-described construction facilitates simple removal of the removable form  116  after the hardenable material has been poured into the excavated trench. In that it typically is desirable to have a sloped trench bottom, the lower surface  152  of the form normally is not parallel to the upper surface  150  of the form as shown in FIG.  3 . 
     In addition to the frame rails  112 ,  114  and the removable form  116 , the form assembly  100  further includes rail spacing means. In the embodiment depicted in FIG. 3, these spacing means include a spacer such as a cross-member  158  which is configured to maintain the proper separation distance between the first and second frame rails  112  and  114 . In a preferred arrangement, each cross-member  158  is provided with a vertical portion  160  and a horizontal portion  162  and therefore is configured as an angle member. In particular, each cross-member  158  is configured to be releasably secured to the top surface  126  of the horizontal portion  120  of each frame rail  112 ,  114 . The cross-members  158  preferably are releasably secured in place with spacer securing means  164 . Specifically, the cross-members  158  are secured with fasteners  164  that are adapted to pass through openings  166  provided in the horizontal portion  162  of the cross-member  158  and through the openings  124  provided in each frame rail  112 ,  114  to thread into a backer bar  168  which includes at least one threaded opening  170 . Each backer bar  168  is substantially rectilinear in shape and is formed of a substantially rigid material such as steel. Normally, each backer bar  168  includes a pair  172  of threaded openings  170  which corresponds to one of the pairs  130  of openings  124  provided in the frame rails  112 ,  114 . As indicated most clearly in FIGS. 4-6, each backer bar  168  can be provided with an oblique edge  174  which facilitates close contact between the backer bar and its associated frame rail  112 ,  114 . Additionally, depicted in FIG. 3 are fastener end caps  176  which protect the threads of the fasteners  164  from contamination by the hardenable material which is poured to form the completed trench. 
     FIG. 4 depicts the trench forming apparatus  100  in a partially assembled state prior to its positioning in the excavated trench. As indicated in this figure, each frame rail  112 ,  114  is positioned adjacent the lateral edges of the upper surface  150  of the removable form  116 . To maintain the frame rails  112 ,  114  in this position, the cross-members  158  are used to support the frame rails  112 ,  114 . In particular, the fasteners  164  are passed through the openings  166  provided in the cross-members  158  and are threaded into their respective backer bars  168 . In that the openings  166  provided in the cross-member  158  are positioned such that the distance between the frame rails  112 ,  114  is less than the width of the upper surface  150  of the removable form  116  when the fasteners  164  are threaded into their backer bars  168 , the frame rails and their associated support brackets  134  tow outwardly as indicated in FIG.  4 . However, when the fasteners  164  are fully tightened into their backer bars  168 , the frame rails  112 ,  114  rotate inwardly towards the removable form  116  and compress the form therebetween (FIG. 5) to hold the form in place prior to pouring of the hardenable material. In addition to this compressive action, the form  116  can be secured with polymeric push pins (not shown) or other such fasteners that extend from the second vertical portion  122  of the frame rails  12 ,  114  into the form. 
     FIG. 5 shows the trench-forming apparatus  100  disposed in an excavated trench T apparatus prior to the pouring of the hardenable material such as concrete. Before being so disposed, however, the apparatus is fully assembled by completing tightening of the fasteners  164  such that the removable form  116  is held in place in compression between the two frame rails  112 ,  114 . Configured in this manner, the removable form  116  is held in place between the frame rails  112 ,  114  prior to pouring of the hardenable material into the excavated trench T. After the fasteners  164  have been fully tightened, the end caps  176  can be placed over the exposed ends of the fasteners as shown in FIG.  5 . Once placed in the trench, the apparatus  100  is supported by its support brackets  134  and the support rods  144  that extend through each respective bracket. At this point, the height and slope of the apparatus  100  can be adjusted by varying the points at which the fasteners  148  are tightened along the length of the support rods  144 . Normally, the height of the form  116  exceeds that of the surrounding ground surface GS so that when the hardenable material is poured it will cover the ground surface, as well as meet the top edge of each frame rail  112 ,  114 . 
     FIG. 6 illustrates the completed trench in its final configuration. As indicated in this figure, the trench-forming apparatus  100  is surrounded by a hardenable material  178  such as concrete. Prior to the curing of the hardenable material  178 , the cross-members  168  provide the resistance needed by the form to resist the buoyancy forces imposed by the hardenable material. In particular, this resistance is provided by the relatively large contact surface area between the cross-members  168  and the form  116 . As is apparent from the figure, each support bracket  134  and support rod  144  is encased within the hardenable material  178  such that they cannot be reused. At this point, the cross-member  158  shown in FIGS. 4 and 5 has been removed along with the removable form  116 . In particular, each fastener  164  which releasably secured the cross-member in place is removed such that grates  180  can be positioned atop the top surface  126  of the horizontal portion  120  of each frame rail  112 ,  114 . As briefly mentioned above, the openings  126  provided in the frame rails  112 ,  114  (and therefore the threaded openings  170  provided in the backer bars  168 ) are configured so as to facilitate lock-down of the grates  180 . Specifically, these openings are arranged so as to align with lock-down bolt openings  182  provided in each of the grates  180 . Accordingly, when each fastener  164  is removed, a threaded opening remains for each lock-down opening  182  such that grate lock-down bolts  184  can be threaded into each backer bar  168  to fixedly secure the grates  180  in place atop the rails  112 ,  114 . In hat each fastener  164  was covered by a fastener cap cover  176 , the threads of each backer bar  168  are clean and free from contamination by the hardenable material  178  such that the lock-down bolts  184  simply can be threaded into the threaded openings  170  of the backer bars without the need for re-tapping or clearing these openings. 
     FIGS. 7-9 illustrate an exploded perspective view of a second embodiment of the trench-forming apparatus  200  constructed in accordance with the present invention. This apparatus  200  is similar to the apparatus  100  of the first embodiment, however, is configured as a hanging system as will be described below. As with the apparatus  100  of the first embodiment, the apparatus  200  of the second embodiment comprises first and second frame rails  202  and  204 , a removable form  206 , and rail spacing means. The frame rails  202 ,  204  include a first vertical portion  208 , a horizontal portion  210 , and a second vertical portion  212 . As in the first embodiment, the horizontal portion  210  of the frame rails  202 ,  204  are provided with spaced pairs of openings  214 . However, unlike the frame rails  102 ,  104  of the first embodiment, the frame rails  202 ,  204  of the second embodiment are not provided with support members  132 , but are instead provided with stabilizing studs  216  that extend downwardly and outwardly from the horizontal portions  210  of the frame rails  202 ,  204 . The stabilizing studs  216  stabilize the frame rails  202 ,  204  after the hardenable material has been poured around the form  206  in the trench. It is to be noted that, although such stabilizing studs are not shown as included with the form assembly  100  of the first embodiment, that such stabilizing studs could be provided on the frame rails  102 ,  104  of the first embodiment, if desired. 
     Similar to the rail spacing means provided in the first embodiment, the rail spacing means of the second embodiment comprise cross-members  218 . These cross-members  218  normally each include a vertical portion  220  and a horizontal portion  222 . The horizontal portions  222  are provided with a first pair of openings  224  so that the cross-members  218  can be removably secured to the frame rails  202 ,  204  with fasteners  225 . The cross-member  218  further include in similar manner as these in the first embodiment an inner pair of openings  226  which are sized and configured to receive fasteners  228 . The apparatus  200  of the second embodiment further includes backer bars  229  that are of similar configuration to those described in the discussion of the first embodiment and therefore include threaded openings  230 . In addition, the apparatus further includes fastener end caps  232 . 
     As briefly mentioned above, the trench-forming apparatus  200  is configured as a hanging system and therefore is arranged to be suspended within the excavated trench T prior to and during pouring of the hardenable material. To facilitate this suspension, the apparatus  200  also includes suspension members  234 . Typically each suspension member  234  is similar in construction to the cross-members  218  and therefore includes a vertical portion  236 , as well as a horizontal portion  238 . The horizontal portions  238  are provided with a pair of openings  240  which, like the inner pair of openings  226  provided in the cross-member are sized and configured to receive the fasteners  228 . 
     To construct a completed trench, the apparatus is suspended within the excavated trench T as shown in FIG.  8 . To suspend the form assembly  200  within the trench T, the cross-members  218  are connected to the suspension members  234  with the fasteners  228 . Specifically, the fasteners are passed through the openings  226  provided in the cross-members  218  and openings  240  provided in the suspension members  234 , and are secured with nuts  242 . The apparatus  200  can then be suspended as indicated in FIG. 8 by the suspension members  234 . At this point, the hardenable material  244  can be poured around the form  206  as indicated in FIG. 9 to secure the apparatus  200  in place at the work site. Then, in like manner to the apparatus  100  of the first embodiment, a perforated grate  246  can be installed on the formed trench and secured thereto with lock-down bolts  248 . 
     FIGS. 10-13 illustrate various alternatives for the spacer securing means used to removably secure the cross-members (or other such spacers) to the frame rails. In particular, FIGS. 10-12 show alternatives to the backer bars described in the discussion of the first two embodiments. In FIG. 10, the backer bar is replaced with a support bracket  300  that is similar in form to the support brackets  134  of the apparatus  100  of the first embodiment. Similar to those support brackets, the support bracket  300  includes first and second horizontal portions  302  and  304  and a vertical portion  306 . In this arrangement, however, the first horizontal portion  302  is provided with a threaded opening  308  that is adapted to receive a fastener  310  that passes through the cross-member  312  and the frame rail  314 . When the support bracket  300  is used, the cross-member  312  as well as the support bracket can be securely fastened to the frame rail  314  by tightly threading the fastener  310  through the support bracket. 
     In FIG. 11, the backer bars are replaced with stabilizing bars  400 . Although the stabilizing bars  400  can be used in either the apparatus of the first embodiment or of the second embodiment, the stabilizer bars are particularly well suited for a hanging system similar to that of the second embodiment. Like the support bracket  300 , the stabilizing bar  400  receives the fastener  402  in a threaded opening  404  to fasten both the cross-member  406  and the stabilizer bar in place relative to the frame rail  408 . 
     In FIG. 12, a nut  500  is welded to the bottom surface  502  of the horizontal portion  504  of the frame rail  506 . Like the support brackets  300  and the stabilizing bar  400 , this nut receives a fastener  508  which passes through the cross-member  510  and the frame rail  506  to fasten the cross-member to the frame rail. Although a nut  500  is depicted in FIG. 12, it will be understood that the frame rail  506  could equivalently be provided with its own threaded opening that is adapted to threadingly receive the fastener  508 . 
     FIG. 13 illustrates an embodiment in which a separate fastener is not needed to secure a cross-members to the frame rails. Instead, threaded studs  600  are welded to the horizontal portion  602  of each frame rail  604 ,  606 . In this manner, the cross-member  608  can be releasably secured to the frame rails  604 ,  606  by seating the cross-member in place on the rails with the threaded studs  600  passing through openings  610  provided in the cross-member. The cross-member  608  can then be secured to the rail  604 ,  606  by threading nuts  612  onto the threaded studs  600 . 
     One advantage of the various embodiments of the present invention includes the relative low cost associated with trench construction with these embodiments. For instance, the same securing means used to secure the spacers such as the cross-members can be utilized to lock-down the trench grates. This feature is desirable since it reduces manufacturing costs of the frame rails for applications in which locking-down of the grating is required. Furthermore, this feature avoids some of the manufacturing difficulties associated with providing lock-down means in conventional trench-forming systems. Because several of the components of the systems described herein can be removed, further savings can be achieved by reusing these removed components. The present invention further lowers costs by eliminating the labor associated with welding connecting rods in place, and cutting these connecting rods off after completion of the trench. 
     In addition to the above-recited advantages, the systems described herein provide the benefit of a more rigid connection between the frame rails for increased precision of alignment and spacing of the form rails. Moreover, due to the compressive forces imposed on the removable form from the frame rails, the form can be maintained in correct orientation relative to the frame rails until the hardenable material has cured. Due to these factors, the resultant trench is more precisely formed, therefore avoiding the typical drainage problems encountered with known conventional trench-forming systems. 
     While preferred embodiments of the invention have been disclosed in detail in the foregoing description and drawings, it will be understood by those skilled in the art that variations and modifications thereof can be made without departing from the spirit and scope of the invention as set forth in the following claims. For instance, although described as comprising horizontal and vertical portions, the cross-members could be formed, for example, as flat bars or substantially rod-shaped members, if desired. The cross-members could be arranged in any configuration which ensures correct alignment and spacing of the frame rails. Indeed, it is to be appreciated that the grates themselves could be used to provide the alignment and spacing normally provided by typical spacers such as the herein described cross-members.