Snap-in resilient emi grounding clip apparatus for computer structures

To reliably maintain an EMI grounding connection between a sheet metal computer chassis wall and a computer cover wall that may be removably placed against the outer side of the chassis wall, a lance structure is formed in the chassis wall, and opposing installation notches are formed in the chassis wall on opposite sides of the lance opening. Transversely enlarged end portions of an elongated arcuate sheet metal grounding strip are inserted inwardly through the wall notches and captively retained within the lance structure with a longitudinally intermediate portion of the arcuate strip body extending outwardly through the chassis wall lance opening. When the cover wall is operatively installed on the chassis wall the grounding strip is resiliently flattened and compressed between the lance strip and the installed cover wall to maintain an EMI grounding path between the contiguous chassis and cover walls.

BACKGROUND OF THE INVENTION 
This invention generally relates to apparatus for creating an EMI grounding 
path between two adjacent electronic system structures and, in a preferred 
embodiment thereof, more particularly relates to EMI grounding clip 
apparatus for maintaining a grounding path between two adjacent computer 
components such as a computer chassis wall and an associated computer 
cover wall. 
In the past, many different spring-type clips have been used to create and 
maintain good electrical grounding contact between a carrier wall portion 
of a first electronic system structure and an adjacent wall portion of a 
second electronic system structure. Many of the existing spring clip 
designs attach to the carrier part by fitting over one of the edges of the 
part, or an edge created by punching a hole in the part. Typically, in 
this type of design, a portion of the spring clip is sandwiched between 
the mating surfaces of the two structures. The biggest disadvantage to 
this class of design is that adjustments must be made to the design of the 
carrier part and the mating part to compensate for the additional material 
thickness of the spring clip between them. Also, if not properly designed, 
the spring clip can be overstressed and permanently deformed. 
An improvement on this general type of grounding clip design is illustrated 
and described in U.S. Pat. No. 5,225,629 to Garrett. This EMI clip snaps 
into place on the carrier part. The key difference in this design is that 
it attaches only to the interior surface of the carrier part without any 
portion of the clip being sandwiched between the mating surfaces of the 
two parts to be grounded by the clip. Spring fingers that protrude through 
holes punched in the carrier part make contact with the mating part, but 
they can displace to a position that is flush with the outer surface of 
the carrier part. 
The main drawback to this EMI clip is that it must be placed in the carrier 
part where there is a bend in the sheet metal. Often, these spring clips 
are complex in shape. Also, the physical shape and size of the clip are 
dependent on the specific geometry of the mating parts. Accordingly, each 
pair of differently configured parts that must be grounded to one another 
may require a separate grounding clip design. 
In view of the foregoing it can be readily seen that it would be desirable 
to provide a grounding clip structure, and associated mounting structure, 
which will eliminate or at least substantially minimize the 
above-mentioned problems, limitations and disadvantages commonly 
associated with conventionally designed grounding clip structures. It is 
accordingly an object of the present invention to provide such an improved 
grounding clip and associated mounting structure. 
SUMMARY OF THE INVENTION 
In carrying out principles of the present invention, in accordance with a 
preferred embodiment thereof, apparatus is provided for creating an 
electrically conductive grounding path between a first structure having a 
wall portion with first and second opposite sides, and a second structure 
positionable against the first wall portion side. 
The apparatus comprises a lance structure formed on the first structure 
wall portion and including an opening extending through the wall portion, 
and a lance strip section of the wall portion outwardly offset from the 
second side thereof over said opening therein. A resiliently deflectable, 
electrically conductive grounding strip is longitudinally curved along its 
length and has opposite end portions captively retained between the second 
wall portion side and the lance strip section for movement toward and away 
from the opposite ends of the lance strip section, and a curved 
longitudinally intermediate portion extending through the wall portion 
opening and projecting outwardly beyond the first wall portion side. 
The grounding strip and the two structures it is used with are 
representatively formed from sheet metal, the two structures 
illustratively being a computer chassis and a cover structure removably 
mounted thereon. In a preferred embodiment thereof, the grounding strip is 
in the form of a resiliently deflectable, electrically conductive 
grounding clip member for use in creating a grounding path between two 
objects. The grounding clip member has an elongated strip-like body 
longitudinally curved about a first axis and concavely facing in a first 
direction transverse to the first axis. The body has opposite end portions 
curved about second and third axes parallel to the first axis and 
concavely facing in second directions generally opposite to the first 
direction. The opposite end portions of the body are transversely 
enlarged, in directions parallel to the second and third axes, relative to 
the balance of the body. To facilitate insertion of the transversely 
enlarged clip member end portions into the space between the wall portion 
and its associated lance strip section, notch means are preferably formed 
in the wall portion, at the periphery of its lance opening, and are 
dimensioned to permit the enlarged clip member end portions to be passed 
inwardly therethrough.

DETAILED DESCRIPTION 
The present invention provides a specially designed resilient EMI grounding 
clip member 10 (see FIG. 1) that may be used to provide a reliable 
electrical grounding contact connection between two computer structures 
(or other structures needing a grounding path therebetween) such as a 
chassis portion 12 shown in FIGS. 2-5 and an associated computer cover 
wall portion 14 shown in FIGS. 4-5 and positionable against the chassis 
portion. 
Referring to FIG. 1, the grounding clip member 10 is formed from a 
resiliently bendable sheet metal material and has an arcuate, elongated 
rectangular body portion 16 with a longitudinally intermediate outer side 
surfaced portion 18, and a width W. Disposed at the opposite ends of the 
arcuate body 16 are arcuately cross-sectioned end portions 20 of the clip 
member that extend transversely to the body 16 and have lengths L greater 
than the body width W. As illustrated, the open sides of the end portions 
20 generally face in the same direction as the outer body side surface 18. 
As illustrated in FIGS. 2 and 4, the chassis portion 12 is formed from 
sheet metal and includes a horizontal base wall 22, and a vertical side 
wall 24 having inner and outer side surfaces 26,28. The computer cover 
wall portion 14 (see FIG. 4) is representatively of a sheet metal or 
metal-clad plastic construction and is removably positioned against the 
outer side 28 of the chassis wall in a parallel relationship therewith by 
sliding the cover wall portion 14 outwardly along the chassis wall 24 
during installation of the overall computer housing cover structure. 
The vertical chassis side wall 24 has a lance structure 30 formed therein 
and including a horizontally elongated rectangular wall opening 32, and a 
corresponding metal lance strip section 34 projecting inwardly beyond the 
inner chassis wall side surface 26 over the wall opening 32. The vertical 
width of the wall opening 32 is slightly greater than the clip body width 
W, but is less than the end portion lengths L. Vertically opposed arcuate 
installation notches 36 are formed in the chassis wall 24 at horizontally 
intermediate portions of the top and bottom sides of the wall opening 32. 
Referring now to FIG. 3, the grounding clip member 10 is installed on the 
lance structure 30 by pushing the transversely enlarged clip member end 
portions 20 inwardly through the installation notches 36 to captively 
retain the end portions 20 between the wall 24 and the metal lance strip 
34, and the arcuate clip member body portion 16 projecting outwardly 
through the wall opening 32. As viewed in FIG. 3, this clip member 
installation may be effected by, for example, pushing the right clip 
member end portion 20 inwardly through the notches 36, sliding the 
inserted right end portion 20 toward the right end of the lance strip 34, 
slightly bending the clip member, inserting the left clip member end 
portion 20 inwardly through the notches 36, and then releasing the bent 
clip member 10 to permit it to spring back to its original position shown 
in FIG. 3. With the clip member 10 installed in this manner, the convex 
sides of the curved clip member end portions 20 face the lance strip 34. 
The clip member 10 and the lance structure 30 are relatively configured in 
a manner such that the distance between the clip member end portions 20 is 
less than the distance between the opposite ends 34a of the lance strip 
34. Accordingly, when the computer cover wall 14 is slid along the outer 
side of the chassis wall 24 to its installed position as shown in FIGS. 4 
and 5, the previously mounted grounding clip member 10 is pushed by the 
cover wall 14 inwardly toward the lance strip 34 in a manner flattening 
the clip body 16 and pushing its captively retained transverse end 
portions 20 toward the opposite ends 34a of the lance strip 34 as best 
illustrated in FIG. 5. 
With the clip member 10 in this resiliently bent operating orientation, the 
clip member ends 20 are held in forcible engagement with opposite end 
portions of the lance strip 34, and the central outer side surface portion 
18 of the clip member body 16 forcibly engages the inner side surface of 
the cover wall 14 which is positioned against the outer side surface 28 of 
the chassis wall 24. The resiliently deformed clip member 10 thus reliably 
maintains an EMI grounding path between the chassis and cover walls 24 and 
14. When the cover wall 14 is removed from the chassis portion 12, the 
grounding clip 10 springs back to its FIG. 3 position. 
The grounding clip 10, and its associated lance mounting structure 30, are 
simple and inexpensive to fabricate and install, and provide a variety of 
advantages over conventional grounding clip designs. For example, the 
grounding clip 10 does not have to be mounted on an angled portion of the 
wall 24 - it may be mounted on any flat portion thereof. Additionally, as 
may be best seen in FIG. 5, the clip member 10 is not interposed between 
the mating surfaces of the contiguous walls 14 and 24 during use of the 
clip. Accordingly, these walls do not have to be specially contoured to 
provide clip clearance space therebetween. Moreover, due to the method 
used in mounting the clip 10, it is not permanently deformed during use 
thereof. It will spring back to its original FIG. 3 configuration when the 
cover wall 14 is removed from the chassis portion 12. 
The foregoing detailed description is to be clearly understood as being 
given by way of illustration and example only, the spirit and scope of the 
present invention being limited solely by the appended claims.