Note: Descriptions are shown in the official language in which they were submitted.
- ' ' ' ' !` . ~;) ~
PLUG-IN CONNECTOR WITH ANTI-DI~CHARGE ELEM[ENT
' ' '"',
Field of the Invention
The invention relates to the field of connectors for computer devices? and
in particlllar to a plug-in connector capable of preventing damage from
accidental electrostatic discharges in such devices.
Back~round of the lnvention
Plug-in connectors are well-known in the art, being used to facilitate
coupling of computer devices to one another. A typical plug-in connector, such
as a "SUB-D" plug-in connector, generally includes a number of contact
elements (e.g., contact tubes) whose contact ends may be directed against a
mating connector having compatible contact elements (e.g., contact plugs). Such
15 a plug-in connector generally includes an electrically-insulating body in which the
contact elements are positioned. A common application for a plug-in connector
of this type is as an interface for a stored-program controller, facilita~ing the
coupling of a programming device to the controller.
In most common applications, the plug-in connector is freely accessible
to promote ease of connectivity, often being installed in the back of a computerdevice to which a peripheral device may be connected and thus exposed to the
- . :
, .. : ,' ' , ., ' ~
, . .
,, , i
- 2 -
environrnent. This accessibility, however, creates the possibility that a personmay touch the plug-in connector either purposely or inadvertently. If this person
is statically charged, an electrostatic discharge, or "spark-over," may occur. In
many instances such a discharge is harmless, being dissipated by a screen
5 laterally surrounding the plug-in connector; however, in some cases a spark may
flash-over onto one of the contact elements of the plug-in connector with
potentially damaging results. For example, a spark striking a contact element
of a plug-in connector installed in a stored-program controller may actually
disturb a program run. Such an electrostatic discharge is especially undesirable10 in stored-program controllers used for safety-related applications where perfect
functioning of the controller is typically an operational requirement.
One known approach for avoiding electrostatic discharge in plug-in
connectors is to provide a removable cover for the plug-in connector to prevent
inadvertent contact during operation. This approach is inadequate bec~use the
cover must necessarily be removed in order to connect a device to the plug-in
connector. The plug-in connector is thus left unprotected at the very time when
the likelihood of touching the connector is greatest.
:
Another known approach is to provide protective circuits for the contact
elements of the plug-in connector. While effective in protecting the contact
elements from electrostatic discharge, such circuits are undesirable due to their
complexity. Each contact element must be individually screened from static
discharges. Moreover, the protective circuits undesirably re~uire additional
space on the device in which the plug-in connector is installed.
Accordingly, there is a need for a reliable means for shielding a plug-in
connector from undesirable electrostatic discharge that is simple, cost-effective
and space-efficient.
, '
,,
Summar~ of the Invention
The present invention provides a plug-in connector that eliminates the
danger of undesirable electrostatic discharge more effectively than known
shielding approaches and without the complexity of known protective circuit
5 approaches. The plug-in connector is advantageously simple in design, and
therefore cost-effective to produce. Furthermore, it is fully-compatible with
existing connectors with which a plug-in connector according to the present
invention would mate.
In one embodiment of the present invention, a plug-in connector includes
a metal strip arranged between two rows of external openings for the contact
tubes into which corresponding contact plugs of a mating connector are inserted.This metal strip comprises an electrically-conductive anti-discharge element, and
is connected to ground through, ~or example, the frame of the plug-in connector.15 The metal strip may be a distinct part that is secured to a lateral screen of the
plug-in connector, or may be integrally formed as part of the lateral screen.
In another embodiment, the anti-discharge element comprises a metallic
coating over the front surface of the plug-in connector. As with the metal strip20 in the first embodiment, the metallic coating is connected to ground.
The plug-in coMector of the present invention is adapted to eliminate the
risk of undesirable electrostatic discharge in computer devices. The plug-in
connector is especially well-suited to installation in stored-program controllers,
25 particularly those used ~or safety-related applications, but may be advantageously
used in many types of telecommunications engineering applications.
A plug-in connector constructed in accordance with the present invention
and installed in a device such as a stored-program controller satisfies the
30 stringent safety requirements of International Electrotechnical Comrnission
(IEC) regulation 801-2. In addition, the present invention is fully compatible,
both mechanically and electrically, with previously-used standard plug-in
~, ,, . ; , ~ , . ., ,, - , ,, ~ , . - " . .
.,. - : ~ , ., ; :,
. . .
. ,'~ ,.,~ ' . . ' - , . ' . ' ' . '
. j , ,
";
flJ~ 3 ~
-
- 4 -
connectors. Furthermore, the simple design of the plug-in connector promotes
cost-effective production. Since protective circuits for contact tubes are not
necessary, a device in which the plug-in connector is installed will have
additional space available for other features. Finally, the present invention's
5 solution to the problem of undesirable static discharge is robust and resistant to
interference.
Brief Description o~the Drawin~s
Fig. 1 shows the central unit of a stored-program controller equipped with
10 a plug-in connector.
Fig. 2 is a top plan view of a plug-in connector including a longitudinal
anti-discharge element in accordance with an embodiment of the present
invention. -
Fig. 3 is a cross-sectional view of a plug-in connector including a
15 longitudinal anti-discharge element in accordance with an embodiment of the
present invention.
Fig. 4 is a top plan view of a plug^in connector in accordance with an
embodiment of the present invention including a metallic coating.
20 Detailed De~tion
Fig. 1 shows an embodiment of the present invention in which a
modularly constructed stored-program controller includes a housing 1 that holds
a backup battery 2, power supply terminals 3, a plug-in memory submodule 4,
and a RUN/STOP switch S including a status display. The housing 1 also holds
25 a plug-in connector 6, which is connected to an electronic circuit (not shown)
arranged in the interior of the housing 1. The plug-in connector 6 serves as an
interface for connecting a programming device (not shown) to the stored-
program controller.
Referring now to Fig. 2, an embodiment of a plug-in connector 6
comprising a 15-pole SUB-D connector jack constructed in accordance with
German Industrial Standard (DIN) 41652 is shown in top plan view. The plug-in
, ,~,,
~' ' , - ' .
,........... .
_ S _ ,
connector 6 includes a lateral screen 7 connected to grownd through the frame
of the plug-in connector 6. ~ front s~lrface 8 of an electrically-insulating basic
body 9 includes a longitudinal groove 12 (shown in Fig. 3) extending between
two rows 10, 11 of cutouts 15. A metal strip 13 is embedded in the longitudinal
S groove 12 and serves as an anti-discharge element. The metal strip 13 ;s
preferably joined to the screen 7. This joinirlg rnay be accomplished, for
example, by soldering a distinct metal strip 13 to the screen 7 or by forming the
metal strip 13 as an integral part of the screen 7.
Fig. 3 shows a cross-sectional view of the plug-in connector 6 shown in
Fig. 2, with the cutting plane perpendicular to the plane of the top plan view.
The contact tubes 14 of the plug-in connector 6 are directed with their contact
ends 14' towards a mating connector (not shown). The mating connector will
include contact plugs corresponding to the contact tubes 14. The contact tubes
15 14 are secured in an electrically-insulating basic body 9 such that the frontsurface 8 is arranged between the contact tubes 14 and the contact plugs of the
mating connector. The basic body 9, including the front surface 8, has cutouts
15 upstream o~ the contact tubes 14 to accept the plugs of the rnating connector,
thereby facilitating connection to the plug-in connector 6.
Referring now to Fig. 4, another embodiment of a plug-in connector 6
includes a front surface X provided with a metallic coa~ing 16. The metallic
coating 16 serves the same discharge-inhibiting function as the metal strip 13 of
the embodiment shown in ~ig. 2. The metallic coating 16 is joined to the screen
25 7, and thus is connected to ground through the frame of the plug-in connector6. The metallic coating 16 includes a recess 17 for each cutout lS to prevent
short circuits between the metallic coating 16 and the contact plugs of a matingconnector. The diameter D of each recess 17 is greater than the diameter d of
the corresponding cutou~ 15.
While the present invention is described with reference to specific
embodiments, it will be apparent to those skilled in the art that many modifica-
. ... ... ~ . .. .. ...
, ~ . . .
, ., , , , ",
.
:
.
., .... ..... ~............ , .
7 1~J- 6 -
tions and variations are possible. Accordingly, the present invention embraces
all alternatives, modifications and variations that fall within the spirit and scope
of the appended claims, as well as all equivalents thereof.
.. . ~
