EP0871244A2

EP0871244A2 - Paint penetrating ground clamp for painted raised floor pedestal

Info

Publication number: EP0871244A2
Application number: EP98870044A
Authority: EP
Inventors: Keith F. Mello; David P. Gouveia
Original assignee: Framatome Connectors International SAS
Current assignee: FCI SA
Priority date: 1997-03-10
Filing date: 1998-03-04
Publication date: 1998-10-14
Also published as: CA2228669A1; EP0871244A3

Abstract

An electrical grounding connector (28) comprising a U-bolt (30), an upper clamp part (32) and a lower clamp part (34). The upper clamp part (32) is connected to the U-bolt (30) to clamp a floor pedestal (14,54) therebetween. The lower clamp part (34) is connected to the U-bolt (30) to clamp a conductor (24) between the upper (32) and the lower (34) clamp parts. The upper clamp part (32) has a stepped surface (38) therein to penetrate through paint on the floor pedestal (14).

Description

The present invention relates to electrical connectors, and more specifically to grounding connectors.

US Patent No. 5 004 437 discloses an electrical connector comprising a base member and a clamp member for clamping a wire therebetween. A requirement has arisen to properly ground newly designed painted raised floor pedestals used in earthquake and other critical applications. These pedestals are used to raise flooring for computer rooms and telecommunications equipment areas, in addition to other applications.

A set number of pedestals per square area is required to be bonded using copper conductor with a range of # 6 awg to 2/0 awg. A single conductor or two conductors are attached perpendicularly to the pedestal. Currently these pedestals are being bonded with the use of the Burndy GAR1726 ground clamp connector which is attached to the bare metal surface, thus enabling an effective electrical connection. The removal of the paint from the pedestals is time consuming and costly for the installers of these connectors. It was desired to develop a connector that would make such removal of paint unnecessary. This connector would have some means that would penetrate the paint when installed, making a proper connection. The connector must meet all requirements of UL standard 467 Grounding and Bonding Equipment for the intended conductor range. The connector is also required to stand up to the rigors of the extreme conditions of an earthquake and still maintain electrical contact.

There may also be a need to ground rectangular unpainted raised floor pedestals. No paint penetrating device would be needed for this application, only a connector that would accommodate its rectangular configuration.

The present invention provides a solution to this problem by modifying a standard GP type connector such that the groove that accepts the pedestal is machined creating a series of steps. The sharp edge formed by these steps contact the surface of the pedestal. When U-bolt of the connector is tightened to its proper torque, these edges penetrate through the paint enabling contact with the metallic pedestal and the connector. The profile of steps can be configured such that it would also accommodate a rectangular raised floor pedestal.

The present invention comprises a cast copper alloy ground clamp that attaches to painted metallic raised floor pedestals which permits during installation, connection to stranded or solid copper conductors. The surface of the groove of the connector, which accepts the painted metallic raised floor pedestal, has a series of machined steps that run parallel to the length of the pedestal. These steps form sharp edges. The steps are dimensioned such that when the pedestal is placed in the groove, each edge is in contact with the surface of the pedestal. When the connector is assembled, and is tightened to the required torque, these edges penetrate through the painted surface of the pedestal thereby making contact with the metallic portion of the pedestal, thus enabling an electrical connection with relatively low resistance.

In accordance with one embodiment of the present invention, an electrical grounding connector is provided comprising a U-bolt, an upper clamp part and a lower clamp part. The upper clamp part is connected to the U-bolt to clamp a floor pedestal therebetween. The lower clamp part is connected to the U-bolt to clamp a conductor between the upper and lower clamp parts. The upper clamp part has a stepped surface therein to penetrate through paint on the floor pedestal.

In accordance with another embodiment of the present invention, an electrical grounding connector is provided comprising a first clamp member, means for clamping the first clamp member to a floor pedestal and conductor retaining means. The conductor retaining means mechanically and electrically connect a conductor to the first clamp member. The first clamp member has a step thereon so that, when the first clamp is clamped against the floor pedestal, the step pierces an exterior surface on the floor pedestal making electrical contact with the floor pedestal.

In accordance with still another embodiment of the present invention, an electrical grounding connector is provided comprising a first clamp member, a fastener connector thereto and conductor retaining means. The fastener is connected to the first clamp member to clamp a floor pedestal therebetween. The conductor retaining means connect a conductor to the first clamp member. The first clamp member has a pair of steps forming a recess therebetween. The recess is adapted to receive a rectangular portion of a first type of floor pedestal. When the first clamp member is attached to a cylindrical portion of a second type of floor pedestal, edges of the pair of steps effectuate electrical contact with the cylindrical portion at an exterior surface of the cylindrical portion.

The foregoing aspects and other features of the present invention are explained in the following description, taken in connection with the accompanying drawings wherein :

Fig. 1 is a schematic elevational view of a floor system and grounding system having a grounding connector incorporating features of the present invention ;

Fig. 2 is an exploded perspective view of the ground connection between the floor pedestal, the tap conductor and the grounding connector shown in Fig. 1 ;

Fig. 3 is a perspective view of the upper clamp part of the grounding connector shown in Fig. 2 ;

Fig. 3A is an enlarged elevation view of area 3A of the steps formed in the upper clamp part shown in Fig. 3 ;

Fig. 4 is a cross-sectional view of the upper clamp part shown in Fig. 3 taken along line 4-4 ;

Fig. 5 is a perspective view of the lower clamp part of the grounding connector shown in Fig. 2 ;

Fig. 6 is a cross-sectional view of the lower clamp part shown in Fig. 5 taken along line 6-6 ;

Fig. 7 is a schematic elevational view of an alternate embodiment of a floor system and grounding system ; and

Fig. 8 is a top plan view of the grounding connector clamped to the alternative type of pedestal shown in Fig. 7.

Referring to Fig. 1, there is shown a schematic elevational view of a floor system 10 and a grounding system 20 incorporating features of the present invention. Although the present invention will be described with reference to the embodiments shown in the drawings, it should be understood that the present invention can be embodied in various different types of grounding systems. In addition, any suitable size, shape or type of elements or materials could be used.

The floor system 10 generally comprises a foundation slab 12, a plurality of floor pedestals 14 and a plurality of structural floor portions or tiles 16. The floor pedestals 14 support the floor tiles 16.a spaced distance from the foundation slab 12. The grounding system 20 comprises a main grounding conductor 22, a tap conductor 24, a tap-main connector 26, and a grounding connector 28. The grounding system 20 is attached to the floor pedestals 14. The main conductor 22 spans between floor pedestals 14. The tap conductor 24 extends between the floor pedestals 14 and main conductor 22. The tap conductor 24 is mechanically and electrically connected to the main conductor 22 by the tap-main connector 26. The tap conductor 24 is mechanically and electrically connected to the floor pedestal 14 by the grounding connector 28. Thus, the floor pedestals 14, and hence the floor system 10 is grounded by the grounding connector 28, the tap conductor 24 and the tap-main connector 26 to the main conductor 22 of the grounding system 20.

Referring also to Fig. 2, the grounding connector 28 comprises a U-bolt 30, an upper clamp part 32, a lower clamp part 34, two lockwashers 35 and two nuts 36. The upper clamp part 32 is removably connected to the U-bolt 30 to clamp a cylindrical section 214 to the floor pedestal 14 therebetween. Clamping the upper clamp part 32 to the floor pedestal 14 electrically connects the grounding connector 28 to the floor pedestal 14. The lower clamp part 34 is removably connected to the U-bolt 30 and the upper clamp part 32 to clamp the tap conductor 24 between the upper clamp part 32 and lower clamp part 34. Clamping the tap conductor 24 between the upper clamp part 32 and lower clamp part 34 creates an electrical connection between the conductor 24 and the grounding connector 28. Thus, the floor pedestal 14 is electrically connected by the grounding connector 28 to the tap conductor 24.

Referring also to Figs. 3 and 3A, the upper clamp part 32 of the grounding connector 28 has an upper surface 37 with a recess 40 formed therein. The bottom surface 60 of the recess 40 is substantially flat. On each side of the recess 40, stepped surfaces 38 step upward and outward away from the recess 40 to the upper surface 37 of the upper clamp part 32. Each stepped surface 38 has a first step 41 adjoining the recess 40 and steps or teeth 42 rising between the first step 41 and the upper surface 37. The

steps

41, 42 of each stepped surface 38 have sharp interior edges 62, as shown in Fig. 3A. In the preferred embodiment, the sharp edges 62 are substantially straight extending parallel to the floor pedestal 14 when the upper clamp part 32 is clamped thereon. In alternate embodiments, the steps may be aligned so that their sharp edges extend perpendicularly to the floor pedestal 14, when the upper clamp part 32 is clamped thereon. The sharp edges 62 of

steps

41, 42 are located in a curved pattern conforming to the circumference of the cylindrical section 214 of the floor pedestal 14. In the preferred embodiment, each first step 41 has a rising portion 41A aligned generally perpendicular to the bottom surface 60 of the recess 40. The risers 42A of the adjoining steps 42 are aligned generally parallel to rising portion 41A and the transverse sections connecting the steps 42 are aligned generally perpendicular to the risers 42A so that the

steps

41, 42 have a general right angle profile (see Fig. 3A). In alternate embodiments, the alignment of the risers and transverse sections of the steps may vary with respect to each other so that the steps have an obtuse angle or acute angle profile.

Referring also to Fig. 4, the upper clamp part 32 has a lower surface 100 with two conductors receiving channels 102. In the preferred embodiment, the channels 102 are aligned generally perpendicular to the recess 40 in the upper surface 37. The channels 102 are located proximate the longitudinal sides 104 of the upper clamp part 32. The conductor receiving channels 102 are separated sufficiently from each other so that when the tap conductor 24 is located in one channel 102A, and a second conductor (not shown) is located in the other channel 102B, the U-bolt 30 inserted through the bolt holes 33 in the upper clamp part 32 extends between the conductors in the

channels

102A, 102B. In alternate embodiments, the number and alignment of conductor receiving channels in the upper clamp part may vary. For example, the upper clamp part may have one or more conductor receiving passageways aligned generally parallel to the recess 40 in the upper surface 37. Each

longitudinal side

104A, 104B of the upper clamp part 32 has a

recess

106A, 106B extending thereinto form the lower surface 100 (see Fig. 3). Each

recess

106A, 106B communicates with the

conductor receiving channel

102A, 102B proximate the corresponding

sides

104A, 104B of the upper clamp part 32. The lower surface 100 has a key section 110 projecting therefrom between the

conductor receiving channels

102A, 102B.

Referring now to Figs. 5 and 6, the lower clamp part 34 has an upper surface 70 with a keyway 72 formed therein. The keyway 72 is adapted to receive the keyed section 110 of the upper clamp part 32 when it is mated to the lower clamp part 34. The lower clamp part 34 has two

conductor receiving channels

74A, 74B longitudinally astride the keyway 72. The

conductor receiving channels

74A, 74B are located in the lower clamp part 34 to generally align with the corresponding

conductor receiving channels

102A, 102B in the upper clamp part 32, when the key section 110 of the upper clamp part 32 is located in the keyway 72. Outer side supports 76A, 76B extend upward from each longitudinal side 78A, 78B of the lower clamp part 34. The outer supports 76A, 76B are adapted to be admitted in the corresponding side recesses 106A, 106B of the upper clamp part 32, when the upper clamp part 32 and the lower clamp part 34 are joined.

Referring now to Fig. 2, the ground connection between the floor pedestal 14 and the ground conductor 24 is established by clamping the grounding connector 28 on the floor pedestal 14 and connecting the conductor 24 to the conductor 28. The grounding connector 28 is clamped on the cylindrical section 214 of the floor pedestal 14. The upper clamp part 32 of the connector 28 is placed against the cylindrical section 214, so that the sharp edges 62, of the

steps

41, 42 of each stepped surface 38 contact the floor pedestal 14. The U-bolt 30 is positioned around the cylindrical section 214 and inserted into the bolt holes 33 of the upper clamp part 32 to capture the floor pedestal 14 between the U-bolt 30 and the upper clamp part 32. The connection between the tap conductor 24 and the connector 28 is formed by clamping the conductor 24 between the upper clamp part 32 and the lower clamp part 34. The conductor 24 is placed in one of the

conductor receiving channels

102A, 102B in the upper clamp part 32. The lower clamp part 34 is mated to the upper clamp part 32 capturing the conductor 24 therebetween. When the upper clamp part 32 and the lower clamp part 34 are mated, the key section 110 of the upper part 32 is located in the keyway 72 in the lower part 34. Thus, the respective

conductor receiving channels

74A, 74B in the lower clamp part 34 are generally aligned with the

conductor receiving channels

102A, 102B in the upper clamp part 32, so that the corresponding

conductor receiving channel

74A, 74B in the lower clamp part 34 cooperates with the

conductor receiving channel

102A, 102B in the upper clamp part 32 wherein the conductor 24 is located to hold the conductor 24. The U-bolt 30 is inserted through holes 160 in the lower clamp part 34. The lock washers 35 are placed on the U-bolt 30 and the nuts 36 are threaded on. Threading the nuts 36 on the U-bolt 30 urges the lower clamp part 34 against the upper clamp part 32, and thus clamps the tap conductor 24 between the two clamp part. The upper surface 70 of the lower clamp part 34 seats against the lower surface 100 of the upper clamp part 32 so that the lower clamp part 34 may directly press upon the upper clamp part 32 while maintaining sufficient but limited clamping pressure on the tap conductor 24, in the

conductor receiving channels

102A, 102B, to prevent excessive damage to the conductor 24. As the upper clamp part 32 and the lower clamp part 34 are drawn together, the side supports 76A, 76B on the lower clamp part 34 enter the

recesses

106A, 106B in the upper clamp part 32, one of the side supports 76A, 76B contacting the conductor 24 in the

conductor receiving channel

102A, 102B. The contacting

support

76A, 76B laterally guides the conductor 24 as it is clamped between the upper clamp part 32 and the lower clamp part 34. This ensures that the conductor 24 does not deform and exit the conductor receiving channels. Clamping the conductor 24 between the upper clamp part 32 and lower clamp part 34 creates the electrical and mechanical connection between the connector 28 and conductor 24.

The pressure transmitted by the lower clamp part 34 on the upper clamp part 32 as the nuts 36 are threaded on the U-bolt 30 presses the upper clamp part 32 into the cylindrical portion 214 of the floor pedestal 14 and correspondingly draws the U-bolt 30 into the upper clamp part 32 generating clamping forces on the cylindrical portion 214. Under these clamping forces, the sharp edges 62 of the

steps

41, 42 are driven through the exterior surface and into the metal substrate of the floor pedestal 14 electrically and mechanically connecting the grounding connector 28 to the pedestal 14.

Referring now to the Fig. 7, an alternate embodiment of the floor system 50 is shown. The floor system 50 is substantially the same as the floor system 10 shown in Fig. 1. However, floor pedestal 14 has been replaced with floor pedestal 54. Referring also to Fig. 8, the floor pedestal 54 has a main shaft 56 with a rectangular cross-section. The floor system 50 is grounded to grounding system 20 in substantially the same manner as floor system 10 is grounded to grounding system 20 (see Fig. 1). The difference is that the main conductor 22 in this embodiment is located proximate to or in the foundation slab 12. The floor pedestal are electrically connected to the tap conductor 24, and hence to the grounding system 20, by the grounding connector 28. The rectangular main shaft 56 is received in the recess 40 of the upper clamp part 32.The U-bolt 30 is connected to the upper clamp part 32 to clamp the grounding connector 28 to the floor pedestal 54. The exterior of the rectangular main shaft 56 is not painted so that clamping the grounding connector 28 thereon electrically connects the pedestal 54 to the connector 28.

The present invention provides a grounding connector 28 that, when installed on the cylindrical section 214 of floor pedestal 14, effects and electrical connection between the floor pedestal 14 and connector 28 without prior preparation of the surface of the pedestal 14. The exterior surface of pedestal 14 may be painted. When grounding the floor pedestal 14 with connectors known in the art, the paint had to be removed in order to provide clean contact surfaces. In contrast, the present invention allows the user to ground the floor pedestal 14 by merely clamping the grounding connector 28 to the floor pedestal 14. Prior removal of the paint from the pedestal 14 is no longer required. This is because, when the connector 28 is clamped on, the sharp edges 62 of the

steps

41, 42 on the upper clamp part 32 penetrate through the painted surface into the metal of the pedestal 14 effecting an electrical connection. The present invention also provides a grounding connector 28 that forms a positive mechanical connection when clamped to the cylindrical section 214 of floor pedestal 14 to withstand the rigors of the extreme vibrations of an earthquake and still maintain electrical contact. The

steps

41, 42 of the connector 28 penetrate into and engage the metal of the floor pedestal 14 to form the positive mechanical connection which overcomes the limitation of present grounding connectors that rely on friction to maintain the electrical connection. The vibrations generated during a seismic event adversely impact frictional connections, thus severely degrading the electrical connection of these connectors. However, seismic vibrations have negligible effect on a positive mechanical connection, and hence the electrical connection between the floor pedestal 14 and the connectors 28 of the present invention is maintained under such vibrations. Finally, the present invention provides a single grounding connector 28 capable of being mechanically and electrically connected to either a floor pedestal 14 with a cylindrical section 214, or to a floor pedestal 54 with a rectangular main shaft 56. Consequently, the user no longer needs carry with him two types of grounding connectors, one for grounding structure with a rectangular cross-section and another for grounding structure with a cylindrical cross-section.

It should be understood that the foregoing description is only illustrative of the invention. Various alternative and modifications can be devised by those skilled in the art without departing from the scope of the invention. Accordingly, the present invention is intended to embrace all such alternative, modifications and variances which fall within the scope of the appended claims.

Claims

An electrical grounding connector (28) to be attached to a painted floor pedestal (14), comprising :

a U-bolt (30) ;

an upper clamp part (32) connected to the U-bolt (30) to clamp the floor pedestal (14) therebetween ; and

a lower clamp part (34) connected to the U-bolt (30) to clamp a conductor (24) between the upper (32) and lower (34) clamp parts ;

characterised in
that the upper clamp part (32) has a stepped surface (38) therein to penetrate through paint on the floor pedestal (14).
An electrical grounding connector as in claim 1, wherein the upper clamp part (32) has two of the stepped surfaces (38) to penetrate through paint on the floor pedestal (14).
An electrical grounding connector as in claim 1, wherein edges (62) on the stepped surface (38) are aligned generally parallel to a longitudinal axis of the floor pedestal (14), when the floor pedestal is clamped between the U-bolt (30) and upper clamp part (32).
An electrical grounding connector as in claim 2, wherein a first one of the two stepped surfaces (38) is separated from a second one of the two stepped surfaces to form a recess (40) therebetween.
An electrical grounding connector as in claim 4, wherein when the upper clamp part (32) is clamped to the pedestal (14), a portion of a cylindrical section of the floor pedestal is located between the two stepped surfaces (38), so that edges (62) on the first stepped surface (38) contact the portion of the cylindrical section (214) and edges (62) on the second stepped surface (38) contact the portion of the cylindrical section (214) generally opposite the edges on the first stepped surface.
An electrical grounding connector as in claim 1, wherein the upper clamp part (32) has a lower surface (100) with a conductor receiving channel (102) formed therein for locating a portion of the conductor (24) therein when the conductor is clamped between the upper clamp part (32) and the lower clamp part (34).
An electrical grounding connector as in claim 6, wherein the upper clamp part (32) has two of the conductor receiving channels (102A, 102B) aligned generally parallel to a longitudinal axis of the upper clamp part (32) and located, so that, when a conductor (24) is received in each one of the conductor receiving channels, the U-bolt (30) passes between the conductors (24).
An electrical grounding connector as in Claim 7, wherein the upper clamp part (32) has two longitudinal sides (104A, 104B) exterior to the two conductor receiving channels (102A, 102B), each one of the longitudinal sides having a recess (106A and 106B) extending thereinto from the lower surface (100) of the upper clamp part (32) and wherein the recess (106) in each one of the longitudinal sides (104) communicates with the corresponding conductor receiving channel (102).
An electrical grounding connector as in claim 1, wherein the lower clamp part (34) has an upper surface (70) with conductor lateral supports (76A, 76B) extending upward therefrom, so that, when the two conductors (24) are clamped between the upper clamp part (32) and lower clamp part (34), the conductor lateral supports (76A, 76B) laterally support a portion of each of the two conductors (24) outside the conductor receiving channels (74,102).
An electrical grounding connector as in claim 9, wherein the conductor lateral supports (76A, 76B) on the lower clamp part 34 are adapted to be admitted within the corresponding recesses (106) in the longitudinal sides of the upper clamp part (32).
An electrical grounding connector (28) to be attached to a floor pedestal (14) comprising :

a first clamp member (32) ;

means (30, 35, 36) for clamping the first clamp member (32) to a floor pedestal (14,54) ; and

conductor retaining means (34) for mechanically and electrically connecting a conductor (24) to the first clamp member (32) ;

wherein the first clamp member (32) has a step (41.) thereon so that, when the first clamp member (32) is clamped against the floor pedestal (14), the step (41) pierces an exterior surface of the floor pedestal (14) making electrical contact with the floor pedestal.
An electrical grounding connector as in claim 11, wherein the first clamp member (32) has a plurality of the steps (41,42) forming a first stepped surface (38) and a second stepped surface (38) with a recess (40) therebetween.
An electrical grounding connector as in claim 12, wherein the first stepped surface (38) and the second stepped surface (38) have edges (62) contacting the floor pedestal (14) when the first clamp member (32) is clamped to the floor pedestal, the edges (62) being aligned generally parallel to a longitudinal axis of the floor pedestal (14).
An electrical grounding connector (28) to be attached to a floor pedestal (14,54) comprising :

a first clamp member (32) ;

a fastener (30) connected to the first clamp member to clamp a floor pedestal (14,54) therebetween ; and

conductor retaining means (34) for connecting a conductor (24) to the first clamp member (32) ;

wherein the first clamp member (32) has a pair of steps (38) forming a recess (40) therebetween, the recess (40) being adapted to receive a rectangular portion (56) of a first type of floor pedestal (54), wherein, when the first clamp member (32) is attached to a cylindrical portion (214) of a second type of floor pedestal (14), edges (62) of the pair of steps (41,42) effectuate electrical contact with the cylindrical portion (214) at an exterior surface of the cylindrical portion.
An electrical grounding connector as in claim 14, wherein the first clamp member (32) has a pair of stepped surfaces (38) on opposite sides of the recess (40), each stepped surface (38) comprising one of the pair of steps (41) forming the recess (40).
An electrical grounding connector as in claim 15, wherein the pair of stepped surfaces (38) have outer edges (62) contacting the cylindrical portion (214) of the second type of floor pedestal (14), when the second type of floor pedestal is clamped between the first clamp member (32) and the fastener (30).
An electrical grounding connector as in claim 15, wherein each stepped surface (38) from the pair of stepped surfaces is stepped upward and outward from the recess (40).
An electrical grounding connector as in claim 14, wherein the recess (40) is generally centered on the first clamp member (32).