WO1996005024A1

WO1996005024A1 - Grating fastener

Info

Publication number: WO1996005024A1
Application number: PCT/US1995/009682
Authority: WO
Inventors: Kenmore E. Mccauley
Original assignee: Harsco Corporation
Priority date: 1994-08-10
Filing date: 1995-08-07
Publication date: 1996-02-22

Abstract

An improved fastener for clamping a bar grating sheet (12) to an underlying structural support member (14) includes a saddle clamp (20) extending between and supported on the top surface of two adjacent load support bars (16) of the grating and a threaded fastener (28) extending through the saddle clamp (20) and engaging a threaded opening (38) in the top arm (40) of a generally C-shaped friction clamp (42). The friction clamp (42) includes a lower arm (44) spaced from the upper arm for extending beneath a flange or leg of a metal structural member, whereby turning the threaded fastener (28) in the opening in the top arm provides a clamping pressure between the grating sheet (12) and the support member (14). A bearing pad (48) having a planar top surface (50) of predetermined area is formed on the top surface of the lower arm (44) to provide a fixed unit clamping pressure between the bearing pad (48) and the structural member (14) upon application of a predetermined torque to the threaded fastener (28).

Description

GRATING FASTENER

BACKGROUND OF THE INVENTION Field of the Invention

This invention relates to fastener devices, and more particularly to an improved fastener device useful in attaching bar grating sheets to underlying structural support members such as to a flange of a metal beam or to the leg of a structural angle. Description of the Prior Art Conventional bar gratings are normally manufactured in relatively large rectangular sheets assembled as open grids consisting of spaced parallel load support bars, typically flat metal bars arranged on edge, joined by spaced cross bars extending transversely of and welded or otherwise rigidly connected thereto. Specifications for standard gratings are published by the National Association of Architectural Metal Manufacturers, reference to which may be had for more detailed information on such bar gratings.

Bar gratings are used to form floors and decks by positioning bar grating sheets on an underlying structural frame and attaching the sheets to the frame members to prevent shifting or movement in use. One common practice is to weld the bottom edge of selected ones of the load support bars directly to the underlying frame member, although this practice is not entirely satisfactory for various reasons. For example, the welding step requires substantial skill and is difficult to perform from above the grating. Also, welding destroys the paint or other corrosion resistant coating on the frame member at the weld joint, thereby creating a corrosion problem unless the weld area is repainted or otherwise treated after installation is completed. Such corrosion treatment generally requires access from beneath the bar grating, and generally is only partially effective. It is also a common practice to employ clamping devices including a saddle or similar clamp for engaging the top of selected load support bars and threaded fastener means extending through the clamp and engaging the structural member, either directly or through another clamping or attaching member. Clamps of this general type are illustrated, for example, in U.S. Patent Nos. 4,362,422 and 5,118,147.

The saddle clamping element illustrated at 24 in U.S. Patent No. 4,362,422 is typical of that used in many of the known clamping devices, and includes a pair of spaced, downwardly directed channels adapted to fit over the top edge of two adjacent load support bars and a recessed central web joining the channel portions. A threaded fastener extends through an opening in the central web for securing the grating sheet to the underlying support structure. The threaded member may be a bolt as shown in U.S. Patent No. 4,362,422, and the bolt may be threaded to a second clamp member which in turn engages the support structure, or the bolt may be received in an opening in the support member and secured by a nut, or by threads in the opening of the support member. Also, the threaded member may be a stud welded to the support member and projecting upwardly through the central web for receiving a nut. The clamping device of U.S. Patent No.

5,118,147 employs a saddle element which is generally rectangular and has a recessed rectangular central panel dimensioned to fit between two adjacent load support bars. An opening in the central recessed panel receives a fastener for threadably engaging a jaw assembly or a hook assembly for anchoring the device to an underlying support element. The jaw connector 22 includes a pair of spaced legs each having a plurality of pointed teeth adapted to engage and bite into a downwardly directed substantially flat surface of the support member to clamp the grating sheets.

While known grating clamps have been widely used, particularly in areas where it may be necessary or desirable to releasably mount the grating sheets to the support structure, these known devices have not been entirely satisfactory for various reasons. For example, the fastener assembly disclosed in U.S. Patent No. 4,362,422 is relatively complex and expensive to manufacture, and is not easily manipulated for installation or removal from above the grating. Other disadvantages include the inefficient clamping force applied by the inclined, class three lever clamping element in the absence of an interlocking groove formed in the support member for engaging the tongue element 65 on the clamping end of the lower member. Further, this interlocking tongue, when engaging a flat surface, can damage any corrosion resistant coating on the support structure.

While the parallel leg jaw structure of the fastener shown in U.S. Patent No. 5,118,147 overcomes some of the shortcomings of the clamping device discussed above, the pointed teeth provided on the spaced narrow legs of the hook inherently tend to break through the corrosion resistant coating on the structural member. Further, the nature of these sawtooth serrations on the two parallel legs makes repair of the corrosion resistant coating, or paint, very difficult. Accordingly, it is an object of the present invention to provide an improved bar grating fastener device which overcomes the shortcomings of the prior art.

Another object is to provide such a fastener assembly having a support structure bearing surface which will provide an adequate, uniform clamping load without damaging any paint or other corrosion resistant coating on the support member.

Another object is to provide such a fastener which is easy to install and remove from above the bar grating, and which is easy and economical to manufacture. SUMMARY OF THE INVENTION

In the attainment of the foregoing and other objects and advantages of the invention, an important feature resides in providing a clamp assembly employing a saddle clip adapted to engage a pair of load bearing bars at their top surface, with a threaded bolt extending through the central web of the saddle clip to be threaded into an opening in a first or top arm of a generally C-shaped friction clamp member. The friction clamp has a pair of arms extending in spaced parallel relation to freely receive a flange or leg of a structural support member therebetween, with the arms being joined at one end by a central web. The second arm has a raised bearing pad formed thereon, with the bearing pad having a substantially flat surface in axial alignment with the threaded bolt received in the first arm whereby only the raised bearing surface engages the surface of the flange or leg of the support element. The axial alignment of the bolt and bearing pad assures that, upon tightening the bolt to secure the grating sheet to the support element, a uniform pressure is applied over the entire surface of the bearing pad. The surface area of the bearing pad is such as to apply a predetermined unit pressure upon application of a predetermined torque to the fastening bolt to thereby assure that the friction clamp applies adequate clamping pressure to secure the grating sheet without damaging the surface coating of the structural support member.

In a preferred embodiment of the invention, the C-shaped friction clamp is formed from a length of flat metal bar, preferably a corrosion resistant steel, bent into the required generally C-shaped configuration with the two arm portions extending in spaced parallel relation to one another. One of the two arms, hereinafter the upper arm, is then drilled and tapped at a location adjacent its free end for receiving a threaded bolt. The other, or lower arm is then subjected to a die-forming operation which includes positioning the upper surface of the lower arm over a shallow, generally disc-shaped or cylindrical die cavity and applying a concentrated force to the opposite or bottom surface to cause a cold forming, or plastic flow, of metal into the die cavity to form a generally cylindrical raised platform or bearing pad on the top surface of the lower arm in axial alignment with the threaded bore in the upper arm. The platform has a substantially planar top surface parallel to and spaced slightly above the top surface of the lower arm to engage a flat surface of a support element such as a flange or web of a metal structural support member, with the remaining top surface of the lower arm being spaced from the support member flat surface. The top bearing surface of the raised pad is dimensioned to provide a predetermined unit bearing force to the support member upon application of a predetermined torque to the threaded bolt extending through a saddle clip mounted on and engaging the top edge surface of a pair of load support bars in the bar grating sheet in the manner described above. The smooth, flat bearing surface thus applies the desired clamping and retaining force without the risk of concentrated loads which could mar or damage a corrosion resistant surface coating on the support element. BRIEF DESCRIPTION OF THE DRAWINGS

Other features and advantages of the invention will be apparent from the detailed description contained hereinbelow, taken in conjunction with the drawings, in which: Fig. 1 is a fragmentary isometric view of a section of bar grating sheet attached to a structural angle support member using the improved grating fastener assembly of the present invention; Fig. 2 is an enlarged elevation view of the grating fastener assembly shown in Fig. 1 with portions of the support structure shown in broken line; Fig. 3 is a fragmentary sectional view taken along line 3-3 of Fig. 2; and

Fig. 4 is a fragmentary sectional view taken along line 4-4 of Fig. 2. DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings in detail, a grating clamp assembly according to the present invention is designated generally by the reference numeral 10 and illustrated in Fig. 1 in use to clamp a bar grating sheet 12 to an underlying structural support angle 14. The bar grating sheet 12 includes a plurality of parallel, laterally spaced load support members 16 in the form of flat metal bars arranged on edge and rigidly joined, as by welding, in their fixed spaced relation by transverse metal bars 18. It should be understood, of course, that the load support bar elements may take forms other than that shown and the load support bars may be secured in their spaced relation by other means than by the transverse bars welded thereto. The clamp assembly 10 includes a saddle clamp 20 having a pair of downwardly directed open channels 22, 24 formed one on each end thereof and a central web portion 26 integrally formed with and extending between the channels 22, 24. The saddle clamp 20 is preferably formed, as by a stamping operation, from a single strip of high strength metal such as a corrosion resistant steel strip, with the central web 26 being dimensioned such that the downwardly open channels 22, 24 receive and fit over the top edge surface of an adjacent pair of load support bars 16, with the central web 26 being spaced below the top edges of the load support bars. An elongated cap screw or bolt 28 extends downwardly through a central opening 30 in central web 26, with the bolt head 32, and a lock washer 34 bearing on the top surface of the central web for applying load thereto. The threaded body 36 of the cap screw 28 is received in a threaded opening 38 in the upper arm 40 of a C-shaped friction clamp 42. Clamp 42 includes a lower arm 44 extending in spaced parallel relation to arm 40, with arms 40 and 44 elongated and having one end integrally joined by a web portion 46 and their other ends free.

The friction clamp 42 preferably is formed from a single length of flat metal bar stock such as a corrosion resistant steel which is bent or shaped into the desired C-shaped configuration. The opening 38 in upper arm 40 may be drilled and tapped either before or after forming the bar stock into the desired shape. Also, a bearing pad 48 is formed on the top surface of lower arm 44, again either before or after the bar stock is formed into the C- shaped configuration. In either instance, the normal top or upwardly directed surface of arm 44 is placed in contact with a die element (not shown) having a shallow substantially cylindrical depression therein, and a force is applied as by a generally cone-shaped forming tool to the surface of the lower arm opposite the die cavity. Sufficient force is applied by the forming tool to cause a cold flow of the metal from the top surface portion of arm 44 into the die cavity to thereby form the raised, generally cylindrical bearing pad having a top flat surface 50 slightly offset, for example from about 0.02 to about 0.08 inches, from the top surface of the lower arm 44.

Bearing pad 48 is in axial alignment with the threaded opening 38 for reasons pointed out more fully hereinbelow. Further, the surface area of the bearing pad top surface is designed to provide a predetermined unit force on the bearing pad upon application of a predetermined torque load to the cap screw 28 when the clamp assembly 10 is installed as described hereinbelow. In practice, the area of surface 50 will be selected to provide a predetermined bearing unit clamping pressure between the bearing pad and the support member upon application of a predetermined torque to the threaded fastener. In one embodiment which has been successfully used, the cap screw 28 is a 1/4 - 20 bolt, and the bearing pad 48 has a diameter of 3/16 inches and a height of 1/32 inches. This clamp was formed from 1/4 x 3/4 inch flat steel bar stock and was produced and tested in three sizes in which the spacing between the upper and lower arms was 5/8 inch, 7/8 inch, and 1 1/8 inch, respectively, for use in connection with support member flanges of different thicknesses. In use of the improved bearing clamp assembly, the bar grating sheets 12 are positioned on a support frame structure made up of structural support elements such as the metal angle 14. A lock washer 34 is positioned on the cap screw 28, and the threaded shaft 36 of the cap screw is inserted through the opening 30 in the web 26 of the saddle clamp 20. Cap screw 28 is then threaded into opening 38 in the top arm 40, and the friction clamp 42 is inserted between two adjacent load support bars 16 of the grating sheet and moved downwardly until the channels 22, 24 engage the top surface of the respective load support bars. Cap screw 28 is then rotated until the open side of the C-shaped friction clamp 42 faces an adjacent structural member such as the leg 52 of angle 14 and saddle clamp 20 is moved along the support bars 16 until the leg 52 is received between the top and lower arms 40, 44, respectively. In this position, the top arm is disposed between the pair of load support bars.

Cap screw 28 is then turned into the threaded opening 38 with the clamp 42 being retained against rotation by the opposed side surfaces or faces of the load support bars. Turning screw 28 causes the friction clamp 42 to be raised until the top friction or bearing surface 50 of bearing pad 48 comes into contact with the downwardly directed surface of leg 52. The spacing between upper and lower arms 40, 44, respectively, and the length of cap screw 28 are such that the bottom end of the cap screw does not contact the top surface of the leg 52 so that the clamp assembly is, upon proper tightening of the cap screw, retained in tension, thereby applying a clamping load between the bottom surface of the angle of leg 52 and the top edges of the load support bars 16 of the grating sheets 12 in contact with saddle clamp 20. As the screw 28 is tightened, the assembly is self-aligning, bringing the surface 50 into uniform contact with the surface of the support member. Cap screws of different lengths are used, as appropriate, to accommodate grating sheets of different thicknesses. Since the cap screw 28 and the bearing pad 48 are in axial alignment, with the friction surface 50 of the bearing pad being perpendicular to the axis of the cap screw, the tensile load in the cap screw will maintain a uniform bearing load between friction surface 50 and the bottom surface of the leg of the support angle. Also, since a known bearing surface on lower arm 44 always contacts the support structure, the bearing load or clamping load applied by the clamping assembly can be controlled by applying a predetermined torque to the cap screw by use of a torque wrench during installation. Thus, by limiting the torque, and thereby the unit load applied to the surface of the support structure and by maintaining a uniform load over the entire bearing pad area, damage to the corrosion resistant surface, such as a painted surface, can be avoided while assuring adequate clamping load to maintain the bar grating sheets in position.

It is believed apparent from the simplicity of the structure, as described above, that the improved friction clamp assembly according to the present invention may be repeatedly and easily installed and removed by workmen standing on the grating sheet whereby installation and/or removal of the grating sheets is greatly facilitated.

While a preferred embodiment of the invention has been disclosed and described, it should be apparent that the invention is not so limited and it is thereby intended that all embodiments be included which would be apparent to one skilled in the art and which come within the spirit and scope of the invention.

Claims

WHAT IS CLAIMED IS: 1. In a clamping assembly for fastening a grating sheet to a structural support member in contact therewith, the grating sheet including a plurality of parallel spaced load support bars each having upper and lower edges and generally vertical side surfaces and spacing members rigidly joined to and retaining the load support bars in their spaced relation, said clamping assembly including an elongated saddle clip having a pair of downwardly open channels formed one adjacent each end and an integral web portion joining said channels, said channels being dimensioned and spaced to receive and engage the upper edge portion of a pair of adjacent load support bars, a central opening in said web portion, a threaded fastener passing through the central opening, and a friction clamp for engaging the support member, the improvement wherein said friction clamp comprises, upper and lower generally parallel spaced arms each having one end integrally joined to a central web and a free end, said arms and central web defining a generally C-shaped rigid member open at one side for receiving a web or flange of the structural member between said arms, a threaded opening in said upper arm adjacent said free end thereof for receiving said threaded fastener, and a bearing pad integrally formed on and projecting above an upwardly directed surface of said lower arm adjacent said free end thereof and in axial alignment with said threaded opening, said bearing pad having a planar bearing surface perpendicular to the axis of said threaded opening.

2. The clamping assembly defined in claim 1 wherein said bearing surface has an area less than the cross sectional area of said threaded fastener.

3. The clamping assembly defined in claim 2 wherein said friction clamp is formed from a length of flat steel bar stock bent into said generally C- shaped configuration.

4. The clamping assembly defined in claim 3 wherein said bearing pad is formed on said lower leg by a pressing operation producing a cold metal flow into a die cavity.

5. The clamping assembly defined in claim 4 wherein said clamping surface is spaced from the upwardly directed surface of said lower arm by a distance within the range of about 0.02 to about 0.08 inches.