Electricity: conductors and insulators – Boxes and housings
Reexamination Certificate
2000-01-11
2002-04-02
Dinkins, Anthony (Department: 2831)
Electricity: conductors and insulators
Boxes and housings
C174S058000, C220S004020, C439S535000, C298S02200C
Reexamination Certificate
active
06365831
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to electrical boxes, and more particularly to electrical boxes including clamping devices used for securing electrical cables to electrical boxes in accordance with the National Electrical Code, Section 370-17(c).
Various electrical boxes have been utilized to provide some means for securing an electrical cable to electrical boxes so as to prevent inadvertent disconnection or disengagement of the cable from the box. Various electrical codes and standards have been applied to these electrical boxes. These include the National Electrical Code, Section 370 and the Third Edition of the Standard For Nonmetallic Outlet Boxes, Flush-Device Boxes And Covers, UL 514C. Recently, new requirements have been suggested for nonmetallic outlet boxes by Underwriters Laboratories, Inc. These new requirements are concerned with clamping electrical cables to electrical boxes such that the cables cannot be unintentionally removed from the box. The following are representative of these requirements:
“26 Knockouts
26.1 A force of 10 pounds (44.5 N) shall be applied to a knockout or integral cable clamp for 1 minute by means of a minimum 1½ inch (38.1 mm) long by ¼ inch (6.4 mm) diameter mandrel with a flat end. The force is to be applied in a direction perpendicular to the plane of the knockout or clamp and at the point most likely to cause movement. The knockout or clamp shall remain in place and the clearance between the knockout or clamp and the opening shall not be more than 0.030 inch (0.75 mm) when measured 1 hour after the force has been removed.
26.2 A knockout shall be easily removed by means of a screw driver, used as a chisel, without leaving any sharp edges or causing any damage to the box. The side edge of a screwdriver may be run along the edge of the knockout opening once, to remove any fragile tabs remaining along the edge.
26.3 A box that is constructed of a material that is known to be affected by low temperatures is to be conditioned for 5 hours in air maintained at minus 20±1° C. (minus 4±2° F.). Immediately following this conditioning, the test described in 26.2 shall be repeated on the box.
26.4 For a box employing multi-stage knockouts, there shall be no displacement of a larger stage when a smaller stage is removed as described in 26.1 and 26.2.”
“27.1 Pull Test
27.1.1 A box provided with a nonmetallic-sheathed-cable clamp shall be assembled in accordance with 27.1.2-
27.1.4 The clamp shall secure the cable so that it will withstand for 5 minutes the pull specified in 27.1.5 without:
a) Damage to the cable sheath or the conductor insulation,
b) Displacement of the cable more than ⅛ inch (3.2 mm),
c) Loosening so that the cable is removable by bending or flexing after the pull force is removed, or
d) Cracking, breaking, or other indication that the clamp has been damaged. *27.1 revised and relocated as 27.1.1 Sep. 30, 1998*
27.1.2 A box provided with a nonmetallic-sheathed cable clamp is to be assembled as intended to nonmetallic-sheathed cable that complies with the Standard for Nonmetallic-Sheathed Cables, UL 719. The cable or cables are to be of the size that the clamp is intended to secure. See 86.2.4 and 86.2.5. *27.2 relocated as 27.1.2 Sep. 30, 1998*
27.1.3 Knockout removal is to be in accordance with in 26.2. For an integral clamp, the holding tabs of the clamp, the holding tabs of the clamp, are to be cut. The integral clamp is not to be removed. After assembly, the cut end of the cable sheath is to be in contact with the stop when one is provided. When a stop is not provided, the cut end of the sheath is to extend ¼ inch (6.4 mm) beyond the clamp. The wires of the cable are to project 6 inches (152 mm) inside the box. A screw that has provision for tightening with a screwdriver is to be tightened as specified in 7.5. *27.3 revised and relocated as 27.1.3 Sep. 30, 1998*
27.1.4 The box is to secured so that the plane of the face of the box is vertical and the clamp being tested is located in the bottom surface. The free end of the cable is to be formed into a loop and securely fastened to itself by tape or equivalent means. The pull is to be applied to the loop by a hook or other convenient method. A clamp that is intended to secure more than one cable is to have the pull applied separately to each cable. *27.4 relocated as 27.1.4 Sep. 30, 1998*
27.1.5 A box with a nonmetallic-sheathed cable clamp is to be subjected to either:
a) A direct pull of 60 lbs (267 N); or
b) A direct pull of 25 lbs (110 N) and the tests specified in Aging and Dielectric Voltage-Withstand Test, Section 27.2, and Pull Test of 25 lbs (110 N), Section 27.3. *27.1.5 added Sep. 30, 1998*”
“27.3 Pull Test of 25 lbs (110 N)
27.3.1 With reference to 27.1.5(b), a clamp shall comply with 27.1.1 when tested as described in 27.32 and 27.3.3. *27.3.1 added Sep. 30, 1998*
27.3.2 Three sample boxes with clamps are to each be assembled to a nonmetallic-sheathed cable sample. Each clamp is then to be subjected to a direct pull of 25 lbs (110 N). *27.3.2 added Sep. 30, 1998*
27.3.3 Three sample assemblies consisting of a box with clamp and a nonmetallic-sheathed cable are to be conditioned for 24 hours in air at a temperature of minus 25±1° C. (minus 13±2° F.). Immediately after removal from the conditioning, the assembly is to be subjected to a direct pull of 25 lbs (110 N). *27.3.3 added Sep. 30, 1998*”
Certain other requirements have been proposed upon nonmetallic outlet boxes in 1999 to ensure that the outlet box will function as designed in relatively cold temperatures. Representative of these requirements are:
“27.4 Assembly At Low Temperature Test
27.4.1 When tested as described in 27.4.2, an integral cable clamp shall remain usable and stay in place during installation of nonmetallic-sheathed cable at low temperatures. *Added 27.4.1 effective May 1, 2000*
27.4.2 A box provided with an integral cable clamp for nonmetallic-sheathed cable is to be assembled in accordance with 27.1.2 and 27.1.3 after being conditioned in air maintained at minus 20±1° C. (minus 4±2° F.) for 5 hours. The sample is to be assembled in the conditioned air or within 15 seconds after removal. *Added 27.4.2 effective May 1, 2000*”
The methods heretofore used to secure the cable in accordance with the above requirements use clamps retained by screws to the box to grip the electrical cable inserted through openings in the box. These electrical boxes have the shortcoming that the installation is relatively cumbersome and the clamps require use of a screwdriver in the confines of an electrical box. Another variety of electrical box eliminates the use of a screwdriver and utilizes wedges which must be forced in place after the electrical cable is inserted into the confines of the box. See U.S. Pat. No. 4,724,282. Provisions must be made in distributing and selling the boxes for packaging the wedges such that they remain with the box and for providing for the separate generation of both boxes and wedges.
It is therefore highly desirable to provide a new and improved electrical outlet box. It is also highly desirable to provide a new and improved electrical outlet box which retains electrical cables in securance therewith without the use of screws. It is also highly desirable to provide a new and improved electrical outlet box which retains electrical cables in securance therewith without the use of clamps or wedges which have to be tightened or set. It is also highly desirable to provide a new and improved electrical outlet box by which electrical cables can be retained in securance therewith totally from the exterior of the box and without manipulation within the box. It is also highly desirable to provide a new and improved electrical outlet box which may be shipped without the fear of loss or special packaging or distribution of screws or wedges or clamps.
It is also highly desirable to provide a new and improved electrical outlet box which is easy to use and which presents little risk of damage to the electrical c
Knecht Thomas D.
Rupp Bradford D.
Allied Moulded Products, Inc.
Dinkins Anthony
Krieg DeVault Lundy LLP
Patel Dhiru R
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