Patent Publication Number: US-2011047915-A1

Title: Clamp for fastening concrete rebar intersections

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     Not Applicable 
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not Applicable. 
     BACKGROUND OF THE DISCLOSURE 
     This disclosure relates to static structures which engage and support elongated reinforcing bars for embedding in a hardening material such as concrete, and in a particular to rebar support chairs and clips for crossed reinforcing bars. 
     FIELD OF DISCLOSURE OR TECHNICAL FIELD 
     Elongated reinforcing steel bars or rods (“rebar”) crossed and connected to form a horizontal grid or mat are used in the construction of poured concrete structures, such as foundation slabs, roadways, side walks, tilt up building walls and the like, to prevent the hardened concrete from separating along crack lines caused by the curing process, from load induced stress, from weather conditions, and from other causes. The rebar grid or mat holds the cracks tight, facilitates load transfer across the cracks, and restrains end movement, providing stiffness. For length, width, thickness (height) and intended use of each concrete structure, engineers determine, inter alia (i) the optimum spacing separating longitudinal bars laid out in parallel across bars laid perpendicularly to the length of the structure (cross or “transverse”) bars, (ii) the optimal spacing separating transverse bars, and (iii) the optimum height of a grid of transverse bars and longitudinal bars within a concrete form and within the formed concrete solid, all so the rebar mat functions correctly for its design purposes. In order for transverse and longitudinal reinforcing steel to effectively perform their engineered function, the rebar mat must be elevated to the design height above the pour surface before the pour, and the reinforcing steel must remain at its correct height, spacing and shape within the pour and after the pour. It is thus necessary to prevent movement of the reinforcing bars and the mat of bars during the pour. 
     For pours on a horizontal surface such as a roadway, the traditional method is to erect the mat in place, and then prop the mat to the design height above the pour surface. To do this, one of the lengths of rebar steel, for example the transverse rebar, is laid out on the pour surface at the specified intervals. Other lengths of rebar, in this example, longitudinal rebar, is then laid out on top of the transverse bars, and these transverse and longitudinal bars are wire tied together to form a template for the completed mat. Then the template rebar is lifted up, and supports for the template, colloquially called “chairs”, are placed under the lower bars, in the example, transverse bars, at the ends of the bars and at locations between the ends of the bars in a number sufficient to support the weight of the steel mat when it is completed, in the example, by adding remaining longitudinal rods at the design spacing and wire tying them to the transverse bars. 
     Plastic chairs have been developed in recent years with the goal of eliminating the need to wire tie the intersections where the chair is placed. The typical chair includes an openwardly open lower rod support for receiving a first rebar lowered into it (a “bottom bar”), and above it, at the sides of the rod support, either hook members opening in the same direction for orthogonally receiving a second rebar (a “top bar”) from one side (e.g., U.S. Pat. No. 3,673,753, Anderson), or upwardly open receivers higher than the rod support for orthogonally receiving a top bar lowered into the receivers to rest above the bottom bar. The higher upwardly open receivers generally have some means for restraining dislodgment of the top bar. Examples of the upwardly open rebar receivers include U.S. Pat. Nos. 5,893,252, 6,112,494 and 6,837,017 issued to Applicants, and U.S. Pat. Nos. 6,276,108 (Padrun), 6,557,317 (Sorkin), 6,684,595 (Sorkin), 6,962,029 (Lowrey), 7,322,158 (Sorkin), and 7,461,491 (Sorkin). These chairs position separate bottom bars and top bars in place orthogonally. 
     Other chairs have been described for attaching to already united crossed wires (welded wire mesh) to stand the mesh a planned distance from a pour surface: U.S. Pat. Nos. 3,378,981 (Horne) and 6,212,848 (Cooper) and International Patent Application PCT/US99/10962 (Nicol). 
     Cement pours are also made within upright forms to form a vertical structure, such as a barrier. A traditional method for erecting a vertical rebar mat is to cross the rebar lengths and wire tie them together at their intersections, a tedious process. Plastic clips have been described for connecting rebar. Same side opening plastic clips have been used to join rebar longitudinally (U.S. Pat. No. 4,617,775—Padrun) or at intersections: U.S. Pat. No. 3,694,988 (Skold), U.S. Pat. No. 4,110,951 (Padrun), U.S. Pat. No. 7,469,515 (Minor). Orthogonal clips have been used to join rebar: U.S. Pat. No. 5,371,991 (Bechtel et al.), U.S. Pat. No. 5,878,546 (Westover). Stirrup clips have been described for replacing wire ties for rebar runs at the corners of wire stirrups (U.S. Pat. No. 4,900,184, Cleveland). 
     The present invention is directed to a clamping structure for fastening separate concrete reinforcing rods together to form a clamped intersection. The invention is useful for clamping together rods crossing in adjacent horizontal planes and for clamping together bars crossing in adjacent vertical planes. The clamping structure may comprise a support (chair) or a free standing clip. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an isometric view of a chair clamp embodiment of this invention. 
         FIG. 2  is a top view of the chair of  FIG. 1 , showing by dashed lines bars captured mutually perpendicularly in the chair clamp. 
         FIG. 3 . is a side view of the chair of  FIG. 1  along the direction of axis Y. 
         FIG. 4 . is a side view of the chair of  FIG. 1  along the direction of axis “X”. 
         FIG. 5 . is an isometric view of another chair embodiment of this invention. 
         FIG. 6 . is a side view of the chair of  FIG. 5  along the direction of axis “X”. 
         FIG. 7  is the same as  FIG. 1  showing positioning of the chair below crossed bars indicating movement of the chair upwardly to engage the lower of the crossed bars. 
         FIG. 8   a  is a top view of the chair of  FIG. 1  engaged with the lower of the crossed bars ready for rotational movement to capture the bars, the arrows indicating a direction of rotation. 
         FIG. 8   b  is a top view of the chair of  FIG. 1  engaged with the lower of the crossed bars rotated in the direction of the arrows and entering engagement with the upper of the crossed bars. 
         FIG. 8   c  is a top view of the chair of  FIG. 1  showing the crossed bars of  FIGS. 6   a  and  6   b  captured in the chair. 
         FIG. 9  is an isometric view of an assembly of the chair of  FIG. 1  and crossed rods. 
         FIG. 10  is an isometric view of a mat of intersecting longitudinal reinforced rods supported and held in mutually perpendicular arrangement by chairs of the embodiment depicted in  FIG. 1 , embedded within a slab of concrete. 
         FIG. 11  Is an isometric view of a clip clamp embodiment of this invention. 
         FIG. 12  is a side view of the clamp of  FIG. 5  along the direction of axis “X”. 
         FIG. 13  is an isometric view of an assembly of the clamp of  FIG. 11  clamping crossed rods. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     In the following detailed description of embodiments, reference is made to the accompanying drawings, which form a part hereof and in which are shown, by way of illustration, specific embodiments in which the invention may be practiced. Specific details disclosed herein, including what is described in the Abstract, are in every case a non-limiting description and embodiment representing concrete ways in which the concepts of the invention may be practiced. This serves to teach one skilled in the art to employ the present invention in virtually any appropriately detailed system, structure or manner consistent with those concepts. It will be seen that various changes and alternatives to the specific described embodiments and the details of those embodiments may be made within the scope of the invention. It will be appreciated that one or more of the elements depicted in the drawings can also be implemented in a more separated or integrated manner, or even removed or rendered as inoperable in certain cases, as is useful in accordance with a particular application. Because many varying and different embodiments may be made within the scope of the inventive concepts herein described and in the specific embodiments herein detailed, it is to be understood that the details herein are to be interpreted as illustrative and not as limiting. 
     Reference throughout this specification to “one embodiment”, “an embodiment”, or “a specific embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, the appearances of phrases such as “in one embodiment”, “in an embodiment”, or “in a specific embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. 
     The concepts embodied in the embodiments described herein have application to any system in which rods need to be clamped together in a mutually transverse arrangement to fix the rods in a clamped intersection. The terms “rod”, “bar” and “rebar” are used interchangeably herein. 
     The various directions such as “upper,” “lower,” “bottom,” “top,” “back,” “front,” “transverse,” “perpendicular”, “vertical”, “horizontal,” “length,” “width, “downwardly”, “laterally” and so forth used in the detailed description of embodiments are made only for easier explanation in conjunction with the drawings. The components may be oriented differently while performing the same function and accomplishing the same result as the embodiments herein detailed embody the concepts of the invention, and such terminologies are not to be understood as limiting the concepts which the embodiments exemplify. 
     The term “transversely” means at a crossing angle, which is not necessarily but may be a perpendicular angle. The terms “orthogonally” or “perpendicularly” means substantially at a right angle to a reference to a degree that if not absolutely a right angle will not materially adversely affect the arrangement and function of the element described as perpendicular. The terms “vertical” or “vertically” include but are not limited to literal vertical and generally mean oriented up and down with respect to the earth&#39;s horizon to a degree that if not absolutely vertical will not materially adversely affect the function of the element described as vertical. Similarly, the terms “horizontal” or “horizontally” include but are not limited to literal horizontal and generally mean not out of level with respect to the earth&#39;s horizon to a degree that will materially adversely affect the function of the element described as horizontal. “Downwardly,” “upwardly” and “laterally” have their normal meanings; i.e., “downwardly” means: toward a lower place, point or level; “upwardly” means: toward a higher place, point or level; and “laterally” means: of, at, toward, or from the side or sides. When the term “vertically” is used in the phrase “rotationally vertically received” with regard to a rod, it is meant that where the rod is disposed in a generally horizontal plane, the rod is received by an upwardly generally horizontal movement of a structure receiving the rod or a downwardly horizontal movement of the rod with respect to the receiving structure. 
     As used herein, the use of the word “a” or “an” when used in conjunction with the term “comprising” (or the synonymous “having” or “including”) in the claims and/or the specification may mean “one,” but it is also consistent with the meaning of “one or more,” “at least one,” and “one or more than one.” In addition, as used herein, the phrase “connected to” means joined to or placed into communication with, either directly or through intermediate components. 
     Certain embodiments are disclosed for a chair structure for clamping two rods mutually transverse to one another above a pour surface. In these embodiments, the chair comprises a support; an upwardly open seating surface supported by the support and having a longitudinal direction for rotationally vertically receiving a first rod in the longitudinal direction; and a pair of side opening rod retainers each supported by the support above and on opposite sides of the upwardly open longitudinal seating surface, the side openings of the retainers opening in opposite directions for rotationally laterally receiving opposite sides of a second rod along a direction transverse to the longitudinal direction, the retainers each including a top portion spaced from the lower seating surface a distance effective to cause a second rod rotationally laterally received in the side openings to exert a compressive force against a first rod rotationally vertically received on the lower seating surface, thereby clamping the two rods mutually transversely to each other. 
     In an embodiment of the invention, and referring to  FIGS. 1-4  and  7 - 9  for illustrations, a chair structure  10  for clamping two rods  100  and  200  mutually transversely to one another above a pour surface comprises a support  11 , suitably comprising a base  12  and pedestal  13 , and an upwardly open lower seating surface  24  supported by support  11  and having a longitudinal direction  26 . The upwardly open lower seating surface may have any generally upwardly open shape, as for non-limiting example, a hollow or rod support. 
     In the chair, a pair of side opening rod retainers  48 ,  66  rise vertically from support  11  above and on opposite sides of upwardly open seating surface  24 . Each side opening retainer comprises a vertical shank portion ( 15  in retainer  48 ,  19  in retainer  66 ) and terminates at top in an outwardly extending top portion; for shank portion  15 , it is top portion  17 , for shank portion  19 , it is top portion  21 . The term “retainer” is used without regard to configuration other than an upright shank portion and a top portion extending outwardly from the shank to cap a side opening. For non-limiting example, retainers can take the shape of an inverted “L”, a sideways “J”, a “C”, or a “G.” All these shapes are side opening and all have a vertical shank ( 15  in retainer  48 ,  19  in retainer  66 ) capped with an outwardly extending top portion ( 17  for shank portion  15 ,  21  for shank portion  19 ). In the illustrations, a side opening in the general form of a “C” ( FIGS. 1-4 ,  7 - 13 ) or a sideways “J” ( FIGS. 5-6 ) is depicted, namely a side opening having an bowed shape for the shank. While these are the side opening modes illustrated, the scope of the invention is not limited to the bowed shaped of the side opening. 
     Whether the retainers take the general shape of a sideways “J”, an inverted “L”, a “C” or a “G”, the side openings bounded by the shanks and top portions face in opposite directions for rotationally laterally receiving opposite sides of a rod  200  in them. Vertical shank portions  15  and  19  are on opposite sides of a plane extending upwardly from the members supporting the retainers ( 14 ,  16  in  FIG. 1-6  and  94   a ,  94   b  in  FIGS. 11-13 ). Top portions  17  and  21  extend outwardly in opposite directions in general paralleling the longitudinal direction  26 . In other words, retainer  48  is open on the side of the vertical shank  15  in the direction pointed by the top portion  17  of retainer  48 , and retainer  66  is open on the side of the vertical shank  19  in the direction pointed by the top portion  21  of retainer  66 . Top portions  17  and  21  point in opposite directions, so the side openings of the retainers are on opposite sides of their respective shanks. 
     Each retainer  48  and  66  is adapted to rotationally laterally receive opposite sides of a rod  200  under their respective outwardly extending top portions  17 ,  21  such that, when captured inside the side openings under the top portions, the rod ends up transversely oriented to the longitudinal direction  26 . Shank  15  of retainer  48  blocks lateral movement of a rod  200  rotationally received under outwardly extending top portion  17  except in the direction in which top portion  17  extends. Shank  19  of retainer  66  blocks lateral movement of a rod  200  rotationally received under outwardly extending top portions  21  except in the direction in which top portions  21  extends. Each retainer ( 48  or  66 ) is spaced from the other retainer ( 66  or  48 ) on opposite sides of the lower longitudinal seating surface  24  with the top portions  17 ,  21  spaced from the lower seating surface  24  a distance effective to cause a rod  200  rotationally laterally received under the top portions  17 ,  21  to exert a compressive force against a rod  100  rotationally vertically received on the lower seating surface  24 , thereby clamping the rods mutually transversely to each other. This spacing locks the rods  100  and  200  together and restrains upper rod  200  from being displaced laterally from retainers  48 ,  66 . 
     In one embodiment, the shanks  15 ,  19  of retainers  48 ,  66  each take the form of an arch about an included concavity or recess, respectively recesses  50 ,  68 . In this configuration, the recesses  50 ,  68  share a common axis “X”, that is both retainers  48 ,  66  are centered upon and in a circumferential relationship with axis “X.” Axis “X” is transverse to the longitudinal direction  26  of the seating surface  24  and is spaced above surface  24  a distance effective to cause a rod  200  rotationally laterally received in retainers  48 ,  66  coaxial to axis “X” to exert a compressive force against a rod  100  rotationally vertically received on the lower seating surface  24 . In the embodiments illustrated in  FIGS. 1-13 , axis “Y” occupies the longitudinal direction  26 . Axis “X” is perpendicular to axis “Y”. An additional axis, axis “Z” (indicated by reference numeral  96 ) is centered on the union in the embodiments of  FIGS. 1-9  where the pedestal legs  14 ,  16 ,  18 ,  20  described below centrally join, and in the embodiment of  FIGS. 11-13 , axis “Z” is centered where the cross members  91 ,  92  unite. Axes “X”, “Y” and “Z” are mutually perpendicular to one another. 
     In another embodiment, as in  FIGS. 5 and 6 , the retainer shanks  15 ,  19  each comprise a shape in the general form of an sideways “J” in which the shank  15 ,  19  is an arched part of the general form of the “J.” In shorthand rendition this retainer as well as a shank in which the shanks  15 ,  19  and top portion  17 ,  21  are linear in form (an inverted “L”) sometimes is referred to herein as a “finger clip”, and is described in further detail below. 
     In the embodiments of  FIGS. 1-4 ,  7 - 9  and  11 - 13 , additional basal structure is provided to the shank and top extension of the retainers by forming the retainer in a general “C” shape. The additional basal structure assists in retaining rod  200  in place. More particularly, in the embodiments depicted in  FIGS. 1-4  and  7 - 9 , the retainers  48 ,  66  each comprise a jaw structure in the general form of the letter “C”, centered on axis “X”, the retainers  48 ,  66  providing a basal seating surface as hereinafter described in detail for a rod  200  rotationally laterally received in the retainers, the basal seating surface of the retainers having an elevation above the lower seating surface  24  effective to cause the compressive force against a rod  100  rotationally received in the lower seating surface. 
     In a shorthand rendition, the general form of the retainers  48 ,  66  in the general shape of a “C” (for example, as depicted in  FIGS. 1-4 ,  7 - 9  and  11 - 13 ) sometimes is herein called a “C-clip.” The term “C-clip” is intended also to include a “C” shape with the additional structure of an inwardly deflectable resilient member disposed at the end portion of the top or base of the opening (giving a generally inverted “G” shape or a general “G” shape, respectively) to deflect for entrance of rod  200  and spring back to press laterally against rod  200  and provide additional retention structure for holding transverse bar  200  in the retainer. 
     There is provided in an embodiment a chair structure for clamping two rods mutually transverse to one another in which the upwardly facing seating surface includes sides. In this embodiment, the chair comprises a longitudinal seat having a first seating surface between seat sides. The seat is oriented in a first direction for longitudinally rotationally vertically receiving and seating a first rod inside the sides. The chair includes first and second resilient retainers each comprising a recess about a common axis transverse to the first direction. The recesses have side openings oppositely facing in the first direction. The retainers are spaced apart along the mentioned axis above and to the sides of the longitudinal seat. The recesses each have a second seating surface for seating a second rod rotationally laterally received in the recess and an opposite top surface for pressing the second rod against the second seating surface. A deepest portion of the second seating surfaces of the recesses is spaced from a deepest portion of the first seating surface a distance equal to or less than the thickness of the first rod. 
     The foregoing aspects of an embodiment are now described in greater detail with respect to  FIGS. 1-4  and  7 - 9 , in which an intersectional rod support or chair  10  is depicted, suitably constructed of relatively resilient plastic material, for clamping two rods mutually transverse to one another (see  FIG. 9 ) a predetermined distance above a pour surface such as a foundation or fabricated form on which the chair  10  may stand. Chair  10  comprises a base  12  and pedestal  13  comprising four legs  14 ,  16 ,  18 ,  20  extending vertically from base  10 . Legs  14 ,  16 ,  18  and  20  are horizontally equidistantly spaced apart, i.e. each is spaced 90 degrees from the next adjacent leg. A first pair of legs  14  and  16  is horizontally spaced 180 degrees apart and a second pair of legs  18 ,  20  is horizontally spaced 180 degrees apart. Second pair  18 ,  20  extends vertically higher than first pair  14 ,  16 . First leg  14  of pair  14 ,  16  supports a first segment  22  of a upwardly open longitudinal seat  24  oriented in a first direction  26 . Segment  22  has a first single side  28  and an interior bottom seating surface  30  for rotationally vertically receiving and seating a first portion of a first rod  100  in first direction  26 . First rod  100  is sometimes referred to herein as lower or bottom rod  100 . Second leg  16  of pair  14 ,  16  supports a second segment  32  of seat or bottom rod support  24 . Second segment  32  has a second single side  34  and an interior bottom seating surface  36  for rotationally vertically receiving a second portion of the first rod in the first direction. First and second segments  22  and  32  unite at juncture  38  where bottom surfaces  30 ,  36  merge, segments  22 ,  32  centering about a common axis “Y” running in the stated first direction  26 . Seat sides  28 ,  34  each have a runner, respectively  40 ,  42 , that slopes at respective chamfers  44 ,  46 , toward sides  28 ,  34  of seat segments  22 ,  32 . 
     Leg  18  of pedestal second pair  18 ,  20  supports a first resilient rod retainer  48  above and laterally adjacent runner  40  and single side  28  of first segment  22  of bottom rod support  24 . Rod retainer  48  comprises lower jaw  47  and upper jaw  49 . An interior side  45  of lower jaw  47  is adjacent runner  40 . First rod retainer  48  includes a first recess  50  with surfaces about an axis “X” transverse to first direction  26  axis “Y.” The surfaces of the first recess  50  include a lower seating surface  52  on the topside of lower jaw  47  for seating a first portion of a second rod  200  rotationally laterally received in first recess  50  and an upper surface  54  on the underside of upper jaw  49  for pressing the first portion of second rod  200  against lower seating surface  52  of first recess  50 . Second rod  200  is sometimes referred to herein as upper or top rod  200 . The bottom  56  of lower seating surface  52  is a predetermined distance higher than the bottom surface  30 ,  36  of bottom rod support  24 . That predetermined distance is a distance equal to or less than the thickness of first or lower rod  100  and will vary according to the planned application for the chair. For example, in a road construction of 6-8 inches concrete depth, the centerlines for a mat of the rods would be about 3 inches. Lower or transverse rod may be ½ inch thick (½ inch diameter if the rod is round, as in most instance of rebar rods, it is) so the low point of the mat would be 2.5 inches above the pour surface and the high point of the mat would be 3.5 inches above the pour surface. For an application such as a tilt up wall, the pour height is typically less high and smaller transverse rods are used, for example, ⅜ inch thickness. 
     A first ramp  58  comprising an upper part of pedestal leg  18  slopes vertically from adjacent the interior side  45  of first rod retainer  48  toward juncture  38  of longitudinal bottom rod support  24 . First ramp  60  suitably has substantially the same slope as chamfer  44 . 
     First rod retainer  48  has upper and lower projections or detents  60 ,  62  extending toward each other at side opening  64  ( FIG. 3 ) of recess  50  for laterally retaining the first portion of second rod  200  within first rod retainer  48 . A web  51  interconnects members  53 ,  55  of upper jaw  49  to provide additional structural rigidity. 
     Second leg  20  of second pair  18 ,  20  supports a second resilient rod retainer  66  spaced from first rod retainer  48  above and adjacent the runner  42  and single side  34  of the second segment  32  of bottom rod support  24  and longitudinally spaced from but opposite the single side  28  of first segment  22 . Rod retainer  66  comprises lower jaw  65  and upper jaw  67 . An interior side  69  of rod retainer  66  is adjacent runner  42 . Second rod retainer  66  has the same configuration as first rod retainer  48 , and comprises a second recess  68  with surfaces about axis “X” common to first recess  50 . The surfaces of second recess  68  include a lower seating surface  70  for seating a second portion of the second or upper rod  200  rotationally laterally received in second recess  68  and an upper surface  72  for pressing the second portion of upper rod  200  against seating surface  70 . The same as for first rod retainer  48 , the bottom  74  of lower seating surface  70  of second recess  68  is a predetermined distance higher than the bottom surface  30 ,  36  of bottom rod support  24  equal to or less than the thickness of first rod  100 . Similarly, second rod retainer  66  has upper and lower projections or detents  76 ,  78  extending toward each other at a side opening  80  of second recess  68  for laterally retaining the second portion of the second rod  200  within second rod retainer  66 . A web  57  interconnects members  59 ,  61  of upper jaw  67  to provide additional structural rigidity. 
     A second ramp  82  comprising an upper part of pedestal leg  20  slopes vertically from adjacent the interior side  69  of second rod retainer  66  toward juncture  38  of longitudinal bottom rod support  24 . Second ramp  82  suitably has substantially the same slope as chamfer  46 . 
     A realization of the invention includes a methodology for clamping two rods transversely together. The method comprises (a) placing a second rod transversely against a first rod to form an intersection; (b) placing a rod support structure adjacent said intersection, the rod support structure comprising a support, an upwardly open lower seating surface supported by the support and having a longitudinal direction, the structure further having a pair of side opening rod retainers supported by the support above and on opposite sides of the upwardly open longitudinal seating surface, the side openings of the retainers opening in opposite directions for rotationally laterally receiving opposite sides of a second rod along a direction transverse to the longitudinal direction, the retainers including a top portion spaced from the lower seating surface a distance effective to cause a rod rotationally laterally received in the side opening to exert a compressive force against a rod rotationally vertically received on the lower seating surface, thereby clamping the rods mutually transversely to each other; and (c) rotating the structure into the intersection to vertically receive the first rod in the longitudinal seat and to laterally receive opposite sides of the second rod under the top retainer portions to press the second rod forcibly against the first rod in the longitudinal seat, clamping the two rods together. 
     This method is now more particularly described in respect to the rod support embodiments of  FIGS. 1-4  and in which reference is made to  FIGS. 7-9  to illustrate the method. 
     Referring to those figures, side openings  64 ,  80  of first and second recesses  50 ,  68  respectively of first and second retainers  48 ,  66  open outwardly in opposite directions to each other, recess  50  facing and opening to the “south” (arbitrarily assigning “south” to the left as  FIGS. 1 and 7  are viewed) and the recess  68  facing and opening to the “north” (arbitrarily assigning “north” to the right as  FIGS. 1 and 7  are viewed). First, an intersection of first and second rods  100  and  200  is created. Referring to FIG.  7 , the orientation of recess side openings  64 ,  80  in oppositely facing retainers  48 ,  66  allows chair  10  to be positioned and raised under the intersection of first and second rods  100 ,  200 , as indicated by the up-pointing arrows  84 ,  85  in  FIG. 5 . Referring to  FIGS. 8   a ,  8   b , and  8   c , and as indicated by  FIG. 7  and  FIG. 8   a , as chair  10  is raised under an intersection of rods  100  and  200 , chair  10  is rotated about the “Z” axis in the direction of arrow  86  (counterclockwise) and comes into contact first with rod  100  at ramps  58  and  82  above respectively sides  45  and  69  of lower jaws  47  and  67  of retainers  48  and  66 . As shown in  FIG. 8   b , as chair  10  comes into contact with ramps  58 ,  82  and as chair  10  continues being rotated about the “Z” axis counter-clockwise in the direction indicated by arrow  86 , detent  60  of first rod retainer  48  and detent  76  of second rod retainer  66  are rotated over upper rod  200  and detents  62  and  78  are rotated under rod  200 , forcing upper and lower jaws  49 ,  47  of first rod retainer  48  apart, and similarly, forcing upper and lower jaws  67 ,  65  of second rod retainer  66  apart. This same rotation moves lower rod  100  down ramps  58 ,  82  and closer to alignment with bottom rod support  24 . Further counter-clockwise rotation of chair  100  in the direction of arrow  86  presses upper rod  200  through detents  60 ,  62  of first rod retainer  48  and detents  76 ,  78  of second rod retainer  66  into recesses  50 ,  68  respectively onto seating surface bottoms  56 ,  74 , while at the same time aligning lower rod  100  with bottom rod support  24  into which lower rod  100  is pressed by the force of upper rod  200  acting on it. Because the bottom seating surfaces of retainers  48 ,  66  are higher than the bottom surfaces  30 ,  36  of bottom rod support  24  only a distance equal to or less than the thickness of said lower rod  100  and because upper surfaces  54 ,  72  on the underside of upper jaws  49 ,  67  presses the first and second portions of second rod  200  against lower seating surfaces  52 ,  70  of first and second recesses  50 ,  68 , rotation of chair  10  into the intersection of rods  100  and  200  forces upper rod  200  down onto lower rod  100 , clamping rod  100  against its seating surfaces  30 , 36 , top portions  17  and  21  of retainers  48 ,  66  holding rod  200  against lower rod  100 . Detents  60 ,  62  and  76 ,  78  assist in retaining rod  200  laterally in place. An assembly of an upper rod  200 , a lower rod  100  and a chair  10  is thus formed when the recesses  50 ,  68  of chair  10 , each respectively having an side opening  64 ,  80  facing oppositely in a direction parallel to the Y axis, rotationally laterally receive opposite sides of second or upper rod  200 . 
     As indicated above, another embodiment of a chair structure is depicted in  FIGS. 5 and 6 . The same reference numerals as used in  FIGS. 1-4  and  7 - 9  are used in  FIGS. 5 and 6  to indicate like structure. The embodiment depicted in  FIGS. 5 ,  6  is essentially the same as the one depicted in  FIGS. 1-4  and  7 - 9 , except the basal structure forward of seating portion  56  inclusive of lower jaw  47  and detent  62  of retainer  48  and the basal structure forward of seating portion  70  inclusive of lower jaw  65  and detent  78  of retainer  66  in the embodiment of  FIGS. 1-4  and  7 - 9  is absent. In this embodiment, each retainer  48 ,  66  comprises a raised shank portion  15 ,  19  terminating in a top portion respectively  17  and  21 . Each top portion  17  or  21  extends laterally outwardly in a direction opposite from the other top portion  21  or  17  and generally parallel to direction  26 . Each shank portion  15 ,  19  is adapted to receive a rod  200  under the outwardly extending top portions  17 ,  21 , transverse to the longitudinal direction  26  of upwardly open lower seating surface  24  supported by support  11 . Each shank  15 ,  19  blocks lateral movement of rod  200  rotationally laterally received under the top portions  17 ,  21  except in the directions of the outwardly extending respective top portions  17 ,  21 . Each retainer  48 ,  66  is spaced from the other retainer  66  or  48  on opposite sides of the lower longitudinal seating surface  24  with the top portions  17 ,  21  spaced from the lower seating surface  24  a distance effective to cause a rod  200  rotationally laterally received under the top portions  17 ,  21  to exert a compressive force against a rod  100  rotationally vertically received on the lower seating surface  24 , clamping the rods  100 ,  200  mutually transverse to each other. 
     Using chair  10 , a method is provided for assembling a mat  300  of concrete reinforcement rods for a concrete pour, comprising (i) laying out a plurality of first or lower rods  100  spaced substantially parallel to one another in a first rod direction; (ii) laying out a plurality of second rods  200  spaced substantially parallel to one another atop the first rods in a second rod direction transverse to the first rod direction, to provide intersections  350  of first and second rods  100 ,  200  at predetermined intervals; (iii) placing a chair  10  under an intersection  350  of a first rod  100  and a second rod  200  such that the longitudinal bottom rod support  24  is under the first rod  100 , and raising and rotating chair  10  to align first rod  100  longitudinally with said longitudinal bottom rod support  24  and at the same time rotationally laterally receive second rod  200  through the side openings  64 ,  80  of first and second retainers  48 ,  66  into recesses  50 ,  68  of the retainers to clamp second rod  200  down onto first rod  100  lodged in longitudinal seat  24 ; and repeating step (iii) for a plurality of the intersections  350 . 
     A method of constructing a concrete slab  500  is provided using chair  10 , comprising (i) conducting the operations described in the next previous paragraph to construct a mat  300  of intersecting longitudinal rods  100 ,  200  and lock the intersections  350  of rods  100 ,  200  a predetermined height above a pour surface  400  on which the slab is to be laid, using a plurality of chairs  10 ; and (ii) laying a pour of concrete over the mat of locked intersections of rods  100 ,  200 . 
     Thus there is also provided a concrete slab  500  having a top  502  and bottom  504  and comprising between top and bottom  502 ,  504  a mat  300  of intersecting longitudinal reinforced bars  100 ,  200  the intersections  350  of which are locked a predetermined height above the surface  400  and bottom  502  of the slab  500  by a plurality of chairs  10 . 
     The foregoing chair structures are useful where crossing rods are disposed in adjacent horizontal planes, as depicted in  FIG. 10 . In another embodiment of the invention, the same superstructure as used in the embodiments shown in  FIGS. 1-4  and  7 - 9  is used without a pedestal and base and is useful for clamping rods in adjacent planes of any orientation from horizontal to vertical. This embodiment is shown in  FIGS. 11 ,  12  and  13 ,  FIG. 13  showing the use of the structure to clamp two rods in adjacent vertical planes transversely together. Thus, referring to  FIGS. 11 and 12 , and continuing use of the same reference numerals as in  FIGS. 1-4  and  7 - 9  for identical structure, there is provided an embodiment of a structure  90  for clamping two rods mutually transversely to one another, comprising first cross members,  93   a ,  93   b  and second cross members,  94   a ,  94   b . Cross members  93   a ,  93   b  extend transversely from cross section members  94   a ,  94   b  to end portions  95   a ,  95   b  from a central union  96  along a first axis “Z” in the line of union  96 . 
     End portions  95   a ,  95   b  of the first cross member support a seating surface  24  crossing at juncture  38  over the union  96  along a second axis “Y” perpendicular to the first axis “Z.” Seating surface  24  has at least on side portion, in the embodiment, a side portion  28  on one side of junction  38  above the line of cross members union  96  and another side portion  34  on the other side of the junction  38 . Seating surface  24  also has a basal portion  30  adjacent side portion  28  and a basal portion  36  adjacent side portion  34 . Basal portions  30 ,  36  face away from the union (“away” is upwardly in the side views of  FIGS. 11 and 12 ). 
     End portions  97   a ,  97   b  of second cross members  94   a ,  94   b  support a pair of retainers  48 ,  66  separated from each other on opposite sides of the seating surface  24 . Retainer  48  has a shank portion  15  and a top portion  17  defining a side opening  64  under top portion  17 . Retainer  66  has a shank portion  19  and a top portion  21  defining a side opening  80  under top portion  17 . Side openings  64 ,  80  are co-aligned along a third axis (“X”) that is perpendicular to the first axis (“Z”) and second axis (“Y”). Side openings  64 ,  80  face opposite directions, as seen in  FIGS. 11 and 12  and to best advantage in  FIG. 13 . Top portions  17 ,  21  respectively of retainers  48 , 66  are spaced from respective basal portions  30 ,  36  of the seating surface  24  by an extent effective to cause a second rod  200  received in retainer openings  64 ,  80  to press on a transverse first rod  100  received in the seating surface  24  upon rotation of structure  90  about the first axis (“Z”) to clamp the two transverse rods together, as seen in  FIG. 13 . The embodiment  90  of  FIGS. 11-13  is useful in clamping together crossing rods in any orientation. Thus structure  90  can clamp rods in adjacent vertical planes as well as rods in adjacent planes other than vertical planes.  FIG. 13  depicts a first rod disposed vertically, and in an adjacent vertical plane, a second rod perpendicular to the first rod. 
     Use of embodiment  90  comprises: (a) placing a second rod  200  transversely against a first rod  100  to form an intersection; (b) placing clamping structure  90  adjacent the intersection, clamping structure  90  comprising first cross members  93   a ,  93   b  and second cross members  94   a ,  94   b  each extending transversely to one another to end portions from a central union  96  along a first axis “Z”, the end portions  95   a ,  95   b  of the first cross member supporting a seating surface  24  crossing over the union  96  along a second axis “Y” perpendicular to the first axis “Z”, the seating surface  24  having a basal portion  30  facing away from the union, the end portions  97   a ,  97   b  of the second cross member  94   a ,  94   b  supporting a pair of retainers  48 ,  66  separated from each other on opposite sides of the seating surface  24 , each retainer  48 ,  66  having a shank portion ( 15  on retainer  48 ,  19  on retainer  68 ) and top portion ( 17  on retainer  48 ,  21  on retainer  66 ) defining a side opening ( 64  on retainer  48 ,  80  on retainer  68 ) under the respective top portions, the side openings  64 ,  80  being co-aligned along a third axis “X” that is perpendicular to the first and second axes (“Z” and “Y” respectively), the side openings  64 ,  70  facing opposite directions, the top portions  17 ,  21  of the retainers being spaced from the basal portion  30  of the seating surface  24  only to an extent effective to cause a second rod  200  received in the retainer openings  64 ,  80  upon rotation of structure  90  about first axis “Z” to press normally on first rod  100  received in the seating surface  24  upon the rotation to clamp the two rods  100 ,  200  transversely together at an intersection of the first, second and third axes, and (c) rotating the clamping structure  90  into the intersection to vertically receive the first rod  100  in the longitudinal seat  24  and to laterally receive opposite sides of the second rod  200  under the top retainer portions  17 ,  21  to press the second rod  200  forcibly against the first rod  100  in the longitudinal seat  24 , clamping the two rods  100 ,  200  together. 
     The above disclosed subject matter is to be considered illustrative, and not restrictive, and the appended claims are intended to cover all modifications, enhancements, and other embodiments that fall within the true scope of the present invention, which to the maximum extent allowed by law, is to be determined by the broadest permissible interpretation of the following claims and their equivalents, unrestricted or limited by the foregoing detailed descriptions of embodiments of the invention