Abstract:
A grounding clip is a shelf-grounding device includes a resilient conductive clip that installs onto a fully assembled shelving unit, providing a plurality of electrical connections between the shelf and post to reduce the risks from electrostatic discharge, or ESD. The clip can be installed and removed without the use of tools and is held securely in place when attached. Since the clip is attached after the shelving unit is assembled, less skill is required by the installer during the installation or reconfiguration process. The clip is reusable and provides electrical connectivity between the shelf and post regardless of whether the shelving unit was assembled with conductive or plastic split sleeves.

Description:
FIELD OF THE INVENTION 
   This invention relates to electrostatic discharge (“ESD”) and in particular, the grounding of shelving and transport carts with apparatus and methods used to reduce risk of damage from electrostatic discharge for electronic circuits and other areas where electrostatic discharge may cause hazards. 
   BACKGROUND 
   Conventional shelving units typically include a plurality of vertically standing support posts and at least one shelf horizontally supported by the posts. For example, U.S. Pat. No. 3,523,508, issued to Maslow 1972, and No. 3,757,705, issued to Maslow 1970, disclose a shelving unit formed from four support posts, and one or more horizontal shelves provided with a frustro-conically shaped collar at each corner for receiving one of the support posts. A split sleeve is secured to each support post and fits into the frustro-conically shaped collar at each corner of the shelf. The positions of the split sleeves on the support posts are vertically adjustable so the height and relative spacing of the horizontal shelves can be chosen when assembling the shelving structure. These adjustable shelving structures are sold and marketed under the trademark SUPER ERECTA SHELF by InterMetro Industries Corporation, of Wilkes-Barre, Pa. Other similar adjustable shelving structures are offered under brand names such as EAGLE and others. 
   Static electricity is commonly defined as an electrical charge resulting from the imbalance of electrons on the surface of a material. Most people are quite familiar with the everyday effects of static electricity—it is the shock one receives when touching a doorknob after walking across a carpet. The technical name for the electrical shock just described is electrostatic discharge. ESD is technically described as the transfer of electrical charge between bodies—for instance, a human hand and a doorknob—that are at different electrical potentials. 
   In most everyday situations, ESD can be a bother but rarely a problem. However, the problems resulting from ESD are magnified in industrial settings, where ESD is a major concern. Among the many problems that static discharge can cause are the unintentional ignition of flammable materials, damage to electronic components and systems, and the attraction of contaminants such as charged dust particles in clean room environments. Even centuries ago military forces were aware that ESD could cause the unintentional ignition of black powder. To alleviate this sometimes-catastrophic problem, ESD control measures were used as early as the 14th century to protect black powder stores. Today, many industries—from high tech manufacturing plants to businesses commonly thought of as “smoke stack” industries—are concerned with ESD and its control, since controlling ESD can lead to a safer work environment and reduction or elimination of damage resulting from ESD. 
   While nearly all industries are or should be concerned with controlling ESD, the concern is most acutely felt by businesses in the electronics industry. To give just a few examples of the damage that ESD can cause in the electronics industry, it can destroy or degrade semiconductor devices by changing operational characteristics. It can cause disruptions to the normal operation of an electronic system—sometimes leading to equipment failure, and in clean rooms it can cause charged particles to adhere tightly to the surface of a silicon wafer, resulting in distinct problems with wafer production and efficiency. 
   Given these problems and the economic damage that can result from them, control of ESD is a major concern and a complete industry has grown up around the field of ESD control. 
   Some very common ESD protective measures are to use conductive floors, benches, containers, storage shelves, and transport carts, and then connect each of these, as well as products and people, to a common electrical ground. Connecting them to a common electrical ground reduces any build-up of electrical potential between objects, thereby reducing the risk of an ESD event. 
   A critical component of an ESD control program is dissipating and neutralizing ESD during handling, transporting and storing of ESD sensitive materials. 
   With respect to shelving units there is a real need therefore for an easier method of providing ESD safety. 
   SUMMARY 
   This device is a clip that easily installs onto a fully assembled shelving unit, without the use of tools, and provides electrical connection between the shelf and post to reduce the risks from electrostatic discharge, or ESD. 
   This device is a resilient electrically conductive clip that quickly and easily attaches externally to the shelf and the post, rather than internally as does the split sleeve that is the currently available solution. This clip installs to a shelving unit and is held in place by the resiliency of the material, but is easily removed and reused if the configuration of the shelving unit changes. Each clip provides a plurality of electrical contact points to both the shelf and post to assure electrical connection and can be installed or removed without tools and without disassembling the shelving unit. 
   Besides the objects and advantages of the electrically conductive metal split sleeves described in the above patent, several objects and advantages of the present invention are: 
   Easy to retrofit shelving units that are already assembled; 
   Can be installed without any disassembly of the shelving unit; 
   Can be installed and removed without the use of tools; 
   Attaches externally to the post and shelf, rather than attaching by means of wedging the split sleeve in-between the shelf collar and post; 
   Provides a visual indication that the shelf is electrically connected to a post, unlike the metal split sleeve which is mostly hidden from view when it is installed Reduced errors and rework during shelving unit assembly or modifications because grounding clips are attached after assembly rather than during the assembly process; 
   Provides a plurality of points of contact between the shelf and post. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a partial perspective of an exploded view showing one corner of the conventional shelving unit according to the prior art and as shown in  FIG. 3 . 
       FIG. 2  is a partial perspective view showing one corner of the prior art shelving structure shown in  FIG. 3 . 
       FIG. 3  is a perspective view of portion of a prior art adjustable shelving unit. 
       FIG. 4  Shows front perspective view of one illustrated embodiment of the clip according to the present invention. 
       FIG. 5  is a left-rear perspective view of the clip shown in  FIG. 4 . 
       FIG. 6  is a partial left view of the clip shown in  FIG. 4  mounted in the lower position to a conventional adjustable shelving unit. 
       FIG. 7  is a partial top view of the clip according to the embodiment of the present invention illustrated in  FIG. 4 , mounted in the lower position to a conventional adjustable shelving unit. 
       FIG. 8  is a partial perspective view of the clip according to the embodiment of the present invention illustrated in  FIG. 4 , mounted in the lower position to a conventional adjustable shelving unit. 
       FIG. 9  is a partial left view of the clip of  FIG. 4  mounted in the upper position to a conventional adjustable shelving unit. 
       FIG. 10  is a partial top view of the clip of  FIG. 4  mounted in the upper position to a conventional adjustable shelving unit. 
       FIG. 11  is a partial perspective view of the clip illustrated in  FIG. 4  mounted in the upper position to a conventional adjustable shelving unit. 
       FIG. 12-A  is a partial perspective view of a first alternative embodiment of the illustrated invention mounted in the standard position to a conventional adjustable shelving unit. 
       FIG. 12-B  is a perspective view of the first alternative embodiment of the present invention shown in  FIG. 12-A . 
       FIG. 13-A  is a partial perspective view of a second alternative embodiment of the illustrated invention mounted in the standard position to a conventional adjustable shelving unit. 
       FIG. 13-B  is a perspective view of the second alternative embodiment of the present invention shown in  FIG. 13-A . 
   

   DETAILED DESCRIPTION 
   Description of the Prior Art 
     FIGS. 1 through 3  show in detail a conventional adjustable shelving unit  60  of the type disclosed in U.S. Pat. No. 3,757,705 and as known in the art. A formed-wire shelf  28  has a frustro-conically shaped shelf collar  26  at each corner for receiving a support post  25 . The wire shelf is defined by a plurality of longitudinally extending wire shelf members  31  and  32  and a plurality of transversely extending wire members  29  and  30 , all welded, and therefore electrically connected, to one another at their respective intersecting points to form a rigid structure. 
   A common type of shelving unit and transport cart used in the electronics and other industries is a type of wire shelving shown in  FIG. 1  through  FIG. 3  and discussed in the Description of Prior Art. One reason for its popularity is that both the shelves  28  and posts  25  are metal, and therefore conductive, allowing them to be electrically connected, providing a means to connect the shelving and therefore the material stored on the shelves to a common ground. Another reason for their popularity is that the shelves can be adjusted to various spacing. 
   Shelving units such as those in  FIG. 1  through  FIG. 3  (hereafter referred to as shelving units) are typically shipped with split sleeves  27  that are made out of an insulative petroleum based material, hereafter referred to as plastic, although metal (or other conductive material) split sleeves  27  can be special ordered, at additional cost, to electrically connect the metal shelves  28  to the metal posts  25 . If assembled correctly, the shelving units can then be grounded to a common ground using wire, conductive feet, or conductive wheels. 
   Where ESD is a concern, the minimum configuration required to electrically connect all shelves to a common ground is to pick one corner post of a shelving unit as a ground post and then install one metal split sleeve  27  on the same corner of each shelf  28 , connecting one corner of each shelf to the selected ground post  25 . The selected ground post  25  is then typically connected to the common ground using a conductive foot, wheel, or wire. In an effort to reduce costs, it is a common practice to use only one metal split sleeve  27  per shelf rather than install them on multiple corners of each shelf. 
   A common problem occurs when shelving units are assembled incorrectly, using plastic split sleeves  27  instead of metal, or installing metal split sleeves  27  in the wrong locations, effectively insulating one or more shelves  28  from the posts  25  and therefore not providing an ESD safe solution. 
   In addition to causing ESD risk when a shelving unit is initially assembled, of each time it is reconfigured, there is a high probability that the split metal sleeves  27  will be installed incorrectly, rendering one or more shelves  28  non-ESD safe. 
   To make a misassembled shelving unit ESD safe, it must be disassembled and all plastic sleeves must be replaced with metal sleeves on at least one post  25 . The disassembly/reassembly process typically requires unloading the shelves, tipping the shelving unit on its side, hammering it apart, replacing plastic sleeves with metal sleeves, reassembling the shelving unit, and then reloading the shelves. 
   Although some of the newer shelving unit designs are easier to disassemble, the replacement process still requires unloading, partially disassembling, reassembling, and then reloading of the shelves. 
   Replacing the split sleeves is difficult due to the frusto-conical design of the shelving collar and split sleeves. Essentially the more weight that the shelf has had on it and the more settling the shelf has done over time, the more difficult it is to disassemble. Since the split sleeves are tapered, covered, and wedged into the space between the shelf collar  26  and the post  25  when they are assembled, the split sleeves are not easily moved from one location to another. 
   Other solutions have been installed in the field, such as 1) installing wires with screws and clamps to electrically connect one shelf to another and 2) drilling a hole through the shelf collar  26  and into the post  25  and driving a screw into the hole. Both of these solutions are effective, but both methods are inflexible and labor-intensive. Drilling a hole and driving a screw into the post  25  often results in a broken drill bit or screw, resulting in a shelf  28  that is no longer adjustable until the broken drill bit or screw is removed. Another potential problem with drilling holes and driving screws into them is that it leaves the shelves and posts with holes that will not align if a shelf location is changed. 
   While using the metal split sleeves  27  does provide a sufficient electrical connection between a shelf  28  and post  25 , they are difficult to install after a shelving unit  60  has already been assembled and are difficult and time consuming to move if they were installed in the wrong location. They are also mostly hidden from view when installed, not making it obvious whether they were correctly installed. 
   Description of a First Preferred Embodiment of the Illustrated Invention 
   A first preferred embodiment of the wire shelf ESD connecting clip  20  is shown in  FIGS. 4 through 11 . Clip  20  includes a main body portion  33  having two upward extending members, upper contacts  22 , two downward extending members, lower contacts  23 , and two forward extending members, left hook arm  21 -A and right hook arm  21 -B, one extending from each lateral side of clip  20 . Hook arms  21 -A and  21 -B also have a downward hook formed on each of their ends, left hook  24 -A and right hook  24 -B. Upward extending members  22  and downward extending members  23  also angle forward as shown in  FIG. 5  and  FIG. 6 . 
   Clip  20  is made of any sufficiently strong, electrically conductive, resilient, corrosion resistant, and flexible material such as a spring steel, hardened stainless steel, or conductive plastic material. 
   Clip  20  is typically installed in one of two positions. In the lower position, as shown in  FIGS. 6 ,  7 , and  8 , the left hook  24 -A is hooked on the lower longitudinally extending member  32  and right hook  24 -B is hooked on the lower transversely extending member  30 . As attached, the two upper contacts  22  are compressed against the shelf collar  26  and the lower two contacts  23  are compressed against the post  25 . The two upper contacts  22 , and the left and right hooks  24 -A and  24 -B are making mechanical and electrical connection to various parts of the shelf  28  (specifically at lower longitudinally extending member  32  and lower transversely extending member  30 ). The lower contacts  23  are making mechanical and electrical contact with the post  25 , providing multiple electrical connections between the shelf  28  and the post  25 . 
   With clip  20  installed in the upper position, as shown in  FIGS. 9 ,  10  and  11 , the left hook  24 -A is hooked on the upper longitudinally extending member  31  and right hook  24 -B is hooked on the lower transversely extending member  29 . As attached, the two upper contacts  22  are compressed against the post  25  and the lower two contacts  23  are compressed against the shelf collar  26 . The two lower contacts  23 , and the left and right hooks  24 -A and  24 -B are making mechanical and electrical connection to various parts of the shelf  28  (specifically at upper longitudinally extending member  31  and upper transversely extending member  29 ). The lower contacts  23  are making mechanical and electrical contact with the post  25 , providing multiple electrical connections between the shelf  28  and the post  25 . 
   With the clip  20  installed in either the upper or lower position, resilient upper and lower contacts  22  and  23  are compressed and therefore exert force in the opposite direction against the resilient force of the left hook arm  21 -A and right hook arm  21 -B. Left and right hook arms  21 -A and  21 -B pull the left and right hooks  24 -A and  24 -B back, and force upper contacts  22  and lower contacts  23  against the shelf collar  26  and post  25 , hold the clip in place and promote good electrical and mechanical contacts. 
   With clip  20  installed in either the upper or lower position, resilient left and right hook arms  21 -A and  21 -B pull the left and right hooks  24 -A and  24 -B back, hold clip  20  in place and force clip  20  forward. The force holding clip  20  also forces upper and lower contacts  22  and  23  against the shelf collar  26  and post  25  and improves the reliability of the electrical connections. 
   The design of clip  20  uses an efficient one-piece design that attaches to an assembled shelving unit using 2 hooks  24 -A and  24 -B to hold 2 upper and 2 lower contacts  22  and  23  to provide multiple points of electrical contact between the surface of the shelf  28  and post  25 . 
   Operation of the First Illustrated Embodiment of FIGS.  1 - 11   
   Operation of the clip  20  in the normal position as shown in  FIG. 6  through  FIG. 8  is described below. Operation in the upper position is identical to the lower position except that the left and right hooks are connected to the upper members  29  and  31 . 
   In operation, a shelving unit is assembled or an existing shelving unit is modified to its desired configuration using either plastic or metal split sleeves  27  to support the shelves  28 . One uses the clips  20  of the present invention according to the following steps: 
   To install a clip  20 : 
   1) pick one or more corner posts  25  of a shelving unit  60  to serve as a ground post; 
   2) install one clip  20  to each shelf  28  on the corner or corners selected as the ground post(s)  25  as follows:
         a) grasp the clip by the left and right hook arms  21 -A and  21 -B with the hooks pointing down;   b) squeeze left and right hook arms  21 -A and  21 -B together to form the main body portion  33  of the clip  20  so that it curves around the shelf collar  26  (as best shown in  FIG. 7 );   c) connect the left hook  24 -A over member  32  and connect right hook over member  30 ;   d) confirm that upper and lower contacts  22  and  23  are being forced against the shelf sleeve  26  and the post  25 ; and   e) Check electrical continuity between the shelf  28  and post  25  using an ohmmeter.       

   To remove a clip  20 : 
   1) grasp the clip by the left and right hook arms  21 -A and  21 -B; 
   2) squeeze left and right hook arms  21 -A and  21 -B together while pressing the clip  20  toward the shelf collar  26 ; 
   3) lift clip  20  upward to disengage the left hook  24 -A from member  32  and right hook from member  30 ; and 
   4) remove clip  20   
   Description of a Second Illustrated Embodiment 
   A second illustrated, alternative embodiment of a wire shelf ESD connecting clip  40  according to the present invention is illustrated in  FIG. 12-A  and  12 -B. Clip  40  is similar to clip  20  described in detail above, except that clip  40  can be made from a less resilient material than clip  20 . A material such as non-hardened stainless steel, aluminum, conductive plastic, or other similar material, will do, as spring  43  provides most of the resiliency to hold clip  40  in place and assure electrical contact. Clip  40  is defined by a main body portion  47 , left and right retaining hooks  41 -A and  41 -B, and spring  42 . Clip  40  makes electrical and mechanical contact with the post  25  by way of spring  43 . Clip  40  makes contact to the shelf  28  by means of left retaining hook  41 -A and right retaining hook  41 -B to engage members  30  and  32 . Hooks  41 -A and  41 -B are held against member  30  and  32  by means of the force from spring  43  against post  25 . 
   Clip  40  can also be inverted and installed with hooks  41 -A and  41 -B connected on the upper frame members  29  and  31 . This is optional can be used as needed to accommodate specific shelving unit configurations. 
   Operation of the Second Illustrated Embodiment 
   This operation describes operation of clip  40  in the normal position as shown in  FIG. 12-A  and  12 -B. Operation in the inverted position is nearly identical except that the left and right hooks  41 -A and  41 -B are connected to the upper members  29  and  31 , and one presses down to engage hooks  41 -A and  41 -B rather than up. 
   First, assemble a shelving unit or modify an existing shelving unit to its desired configuration using either plastic or metal split sleeves  27  to support the shelves  28 . In operation, one uses the clip  40  as follows: 
   To install a clip  40 : 
   1) pick one or more corner posts of a shelving unit  60  to serve as a ground post; 
   2) install one clip  40  to each shelf  28  on the corner(s) selected as ground posts  25  as follows:
         a) grasp the clip with hooks  41 -A and  41 -B pointing up as in  FIG. 12-B ;   b) bring clip  40  toward the post  25  with spring  43  just below shelf collar  26  and hooks  41 -A and  41 -B just under members  30  and  32 ;   c) press the main body of clip  40  toward the shelf collar  26 , which stretches spring  43  around post  25 ;   d) press upwards on clip  40  to engage left hook  41 -A over member  32  and right hook  41 -B over member  30 .       

   3) Check electrical continuity between the shelf and post  25  using an ohmmeter. 
   To remove a clip  40 : 
   1) grasp the clip  40  by the main body; 
   2) press clip  40  toward the shelf collar  26 ; 
   3) lower clip to disengage the hooks  41 -A and  41 -B from members  32  and member  30 ; and 
   4) remove clip  40 . 
   Description of a Third Illustrated Embodiment 
   A third illustrated, alternate embodiment of a wire shelf ESD connecting clip according to the present invention is illustrated in  FIG. 13-A  and  13 -B as clip  50 . Clip  50  is similar to clip  20  described in detail above, except that clip  50  utilizes two resilient C-shaped clips  51  and  52  connected with a conductive backing that defines a main body portion  53  of clip  50 . C-shaped clips  51  and  52  must have adequate resiliency and flexibility to accommodate the post  25  and the larger size of the shelf collar  26 , or one c-shaped clip  51  or  52  can be made larger than the other to accommodate the larger shelf collar  26 . 
   Clip  50  can also be inverted and installed with c-shaped clip  51  attached to post  25  below shelf  28  rather than above and c-shaped clip  52  attached to the shelf collar. This inverted installation is optional and can be used as needed to accommodate specific shelving unit configurations. 
   Operation of the Third Illustrated Embodiment 
   This operation describes operation of the clip  50  in the normal position as shown in  FIG. 13-A  and  13 -B. Operation in the inverted position is nearly identical except that the upper c-shaped clip  51  is connected to the post  25  below the shelf collar rather than above it. C-shaped clip  52  is installed in the same location over shelf collar  26 , but the entire clip  50  is inverted. 
   First, assemble a shelving unit or modify an existing shelving unit to its desired configuration using either plastic or metal split sleeves  27  to support the shelves  28 . In operation, one uses the clip  50  as follows: 
   To install a clip  50 : 
   1) pick one or more corner posts of a shelving unit to serve as a ground post; 
   2) install one clip  50  to each shelf on the corner or corners selected with the ground post  25  of the shelving unit  60  as follows:
         a) grasp clip  50  with the c-shaped clip  51  on top and the open portion of the clips pointed toward the post  25  and shelf sleeve  26  as in  FIG. 13-B ;   b) bring clip  50  toward post  25  and shelf collar  26  with c-shaped clip  52  engaging shelf collar  26  at a vertical height of approximately half-way between upper members  29  and  31  and lower members  30  and  32  and c-shaped clip  51  engaging post  25  just above shelf collar  26 ;   c) press the main body of clip  50  toward the shelf collar  26  and post  25  until c-shaped clips  51  and  52  snap firmly into place over shelf collar  26  and post  25 .       

   3) Check electrical continuity between the shelf  28  and post  25  using an ohmmeter. 
   To remove a clip  50 : 
   1) grasp the clip  50  by the main body; 
   2) pull clip  50  away from the shelf collar  26  and post  25 ; and 
   3) remove the clip  50 . 
   Based on the foregoing description and the drawings it will be apparent that the various embodiments of clips comprise several structural elements that have functional purposes. These include for example post contact means for establishing an electrically conductive path from the post  25  to the main body of the clip (e. g., contacts  23  in  FIGS. 6-8 ; contacts  22  in  FIGS. 9-11 ; spring  43  in  FIGS. 12-A  and  12 -B; and clip  51  in  FIGS. 13-A  and  13 -B), shelf contact means electrically connected to the main body of the clip for establishing an electrically conductive path from the shelf to the clip (e. g., hook arms  21 -A and  21 -B in  FIGS. 4-11 ; hooks  41 -A-and  41 -B in  FIGS. 12-A  and  12 - B; and clip  52  in FIGS.  13 -A-and  13 - B), and retaining means for retaining the post contact means in electrical contact with the shelf (e. g. ,the resilient main body portion  33  and contacts  22  and  23  in  FIGS. 4-11 ; spring  43  in  FIGS. 12-A  and  12 -B; and clip  51  and  52  in Gigs.  13 -A and  13 -B). 
   Having here described illustrated embodiments of the invention, it is anticipated that other modifications may be made thereto within the scope of the invention by those of ordinary skill in the art. It will thus be appreciated and understood that the spirit and scope of the invention is not limited to those embodiments, but extend to the various modifications and equivalents as defined in the appended claims.