Frame rack with module carriers and a ventilating installation

In a cabinet (1) for telecommunications engineering, with a frame rack containing at least one module carrier (2) designed to receive plug-in units, and a ventilating installation for cooling the plug-in units, the ventilating installation comprises at least one fan insert (13) with several vertically blowing axial fans, which can be plugged in and integrated into the module carrier (2). The fan insert (13) is located under transverse supports of the module carrier (2) and has at least one plug connector at the rear, which makes contact with a secondary plug connector provided on the rear wiring panel (10).

TECHNICAL FIELD 
The invention concerns a frame rack with module carriers and ventilating 
installation for telecommunication housings or cabinets. 
BACKGROUND OF THE INVENTION 
A cabinet is known from EP-B-0 485 281, with a built-in swivel frame and 
mounting plates attached thereto, for carrying circuit boards that are 
vertically arranged on the rear side facing the inside of the cabinet, and 
which are separated from each other. If required to cool the heat produced 
by the circuit board components, there are air inlet ducts and fan inserts 
attached to the swivel frame under the mounting plates, each with two 
horizontally blowing axial fans. Deflectors are provided to guide the air 
streams vertically. 
DE-A 27 10 356 also describes an aerated cabinet with a frame containing 
several cross bars, which allow the installation of two instrument 
housings next to each other in several superimposed rows. The instrument 
housings contain the groups of components to be cooled, and have slots in 
their bottom and top plates for the passage of cooling air. The latter is 
produced by two fan inserts placed in the frame rack between the lower row 
of instrument housings and the bottom of the cabinet. As viewed in the 
installation direction, each fan insert contains two vertically blowing 
axial fans placed next to each other. 
Module carriers, for example in a 19" assembly system, are known from the 
publication DE-U-87 14 894; they can be equipped with different components 
and are mounted above each other in a frame, cabinet or housing. In an 
embodiment designed as a table housing, in addition to the side walls of 
the housing which is open on the front and has ventilation slots in the 
bottom and on the top, there are vertical profile rails to which the 
lateral flanges of the module carrier and the front plate of a fan insert 
are bolted, where the latter has an inserted filter mat instead of a 
bottom. Vertical profile rails attached horizontally to the guide rails 
facilitate the installation of the fan insert. Two vertically blowing 
axial fans are arranged next to each other behind the front plate of the 
fan insert, and the space behind them has connecting clamps for external 
lines that are connected to the axial fans' service lines. 
When a defect has been signalled or the end of the service life of an axial 
fan, the replacement is complicated and time-consuming. In addition, this 
presupposes that the fan insert must be accessible from the rear of the 
housing for unclamping the external lines, before the attachment can be 
loosened from the vertical profile rails and the fan insert removed. 
Otherwise the external lines must have an excess length so that they can 
be pulled out of the housing together with the fan insert. This requires 
undesirable additional space for storing the excess lengths in the 
housing. 
SUMMARY OF THE INVENTION 
The object of the invention is to ensure an optimum cooling of the plug-in 
units in module carriers by means of a ventilating installation using 
axial fans, which allows the simple and rapid replacement of axial fans 
when required. The invention achieves this object with a frame rack for 
telecommunications engineering with at least one module carrier containing 
a rear wiring panel which has plug connectors for insertable plug-in 
units, and with at least one ventilating installation containing at least 
one vertically blowing axial fan for cooling the plug-in units, wherein 
the ventilating installation comprises a fan insert which can be plugged 
in and integrated into the module carrier, and with at least one plug 
connector at the rear which makes contact with a secondary plug connector 
on the rear wiring panel. 
Among others, the advantages of this solution include that the replacement 
of the fan insert can be undertaken while the installation is operating, 
since neither connection cables nor attachment screws need to be removed. 
Since the replacement of the fan insert can be carried out with few hand 
movements, only a brief interruption of the cooling stream takes place 
which does not cause any unacceptable heating of the plug-in units being 
cooled. Other achievable advantages can be found in the description.

BEST MODE FOR CARRYING OUT THE INVENTION 
FIG. 1 designates the cabinet with its door by 1. This is a configuration 
with a frame rack whose vertical spars are made e.g. of separate L-shaped 
rails, or also of profile rails bent out of the cabinet sheet metal, to 
which for example five module carriers 2 are attached in a superimposed 
manner. As illustrated in FIGS. 2 and 3, such a module carrier 2 usually 
comprises two lateral walls 3 with attachment flanges 3' facing outward, 
and several transverse supports which connect the lateral walls. In the 
lower part these are a first front and a second rear transverse support 4, 
5, as well as a third and fourth transverse support 6, 7 which 
interconnect the upper corners of the lateral walls 3 in the front and in 
the back. Both lower and upper transverse supports 4, 5 and 6, 7 have 
guide strips 8 attached at predetermined distances for plug-in units 9 
(FIG. 3) which are at least partially equipped with cooling ribs, and make 
contact with plug connectors 11 installed on the front of the module 
carrier 2 located on a rear panel 10. The rear panel 10 is designed in the 
well known manner as a wiring panel, and is attached to the rear 
transverse supports. 
In the design of the module carrier 2 of the present configuration, the 
rear wiring panel 10 has a reduced height in order not to block the air 
circulation. For that reason a fifth transverse support 12, to which the 
upper end of the rear panel 10 is attached, is provided between the second 
and the fourth rear transverse supports 5, 7. In addition, in this case 
the lateral walls 3 are designed to be vertically longer and protrude from 
under both transverse supports 4, 5, which creates a laterally limited 
space for storing fan inserts 13 (FIGS. 3 and 4) which are built like 
drawers. Guide rails are attached to the underside of both lower 
transverse supports 4, 5 to hold the fan inserts 13. If only a single fan 
insert 13 is integrated in the module carrier 2 and occupies the entire 
width, only two guide rails 14 are needed, one of which is placed directly 
next to the lateral walls 3 in each instance. In this case the guide rails 
14 have a Z-shaped cross section. Of course, guide rails 14 with L-shaped 
cross sections can also be provided, which are then attached to the inside 
of the lateral walls 3. If two half-wide fan inserts 13 are provided, an 
additional guide rail 15 which is built as a cap rail, is placed in the 
center of the lower transverse supports 4, 5. 
To better adapt the cooling output to different requirements, the module 
carrier 2 preferably has three identically designed fan inserts 13 which 
are arranged next to each other in one plane. In that case two cap-shaped 
guide rails 15 are attached between the two Z-shaped guide rails 14 at a 
suitable distance from each other (FIG. 3). The guide rails 14, 15 are for 
example simple bent parts made of sheet metal, which can be 
cost-effectively produced and attached by spot-welding e.g. to the 
transverse supports 4, 5, which are also made of sheet metal. Since the 
fan insert 13 is designed as a plug-in unit which has a plug connector 16 
at the rear, the lateral wall 10 of the module carrier 2 protrudes 
somewhat in the vertical direction under its lower transverse support 5, 
and carries the secondary plug connectors 17. 
The drawer 18 of the fan insert 13 is a one-piece injection-molded plastic 
part. When viewed in the insertion direction it is designed as two 
sequential vents 19 with open tops, where each is able to receive a 
vertically blowing axial fan 20, and each vent 19 has at least one air 
inlet opening on the bottom. In addition, each of the two outer sides of 
the lateral walls of the drawer 18 has a slide strip for holding and 
guiding, where its flush closing top corresponds to the guide rails 14, 15 
in the module carrier 2. To prevent any involuntary manual access into a 
module carrier 2 with activated plug-in units 9 and running axial fans 20, 
the vents 19 are covered with a plastic screen which is attached to the 
drawer 18 for safety. A convenient hand-grip 21 is formed on the front of 
the drawer 18, which also has at least one abutment suitably placed to 
lock the fan insert 13 in the module carrier 2. The locking can also be 
coupled to the hand-grip 21, so that an automatic interlock takes place 
when the fan insert 13 is installed, which can be unlocked by means of the 
hand-grip 21 (not illustrated). 
The axial fans 20 are wired to the inside of the fan inserts 13 via their 
rear plug connectors 16. The axial fans 20 obtain their power through the 
plug connector 16. Control and monitoring lines are also connected there. 
The three auxiliary plug connectors 17, with their fronts suitably 
attached to the rear panel 10 of the module carrier 2, are in turn wired 
back among other things to a control module 22, which can preferably be 
plugged in between two plug connectors 11 for plug-in units 9. The rear 
panel wiring can comprise connecting wires, as well as conducting paths of 
the rear wiring panel 10, or a suitable combination of both types of 
electrical connections. 
The pluggable arrangement of the control module 22 has the advantage that 
it can be replaced if necessary, after removing the plug-in unit 9 located 
before it. The control module 22 is equipped with a bus connection via 
which a control unit 23 can check the position of each axial fan 20 in 
every module carrier 2 of the frame rack. In this way defects can be 
detected, and the speed can be individually controlled in accordance with 
the cooling requirement, so that the front row of fans within a module 
carrier 2 e.g. can run at a different speed than that of the rear row of 
fans, or the axial fans 20 arranged on the bottom of the frame rack can 
rotate slower than those placed in the fan inserts of a module carrier 2 
that is positioned at a higher level in the frame rack. Incidentally, the 
plug connectors 16 of the fan inserts 13 can be encoded by means of a wire 
or diode bridge, so that the coding contains e.g. the year the fan insert 
13 was manufactured. 
This information can also be read by the central control unit 23 via the 
bus connection of the control module 22, and the near end of the 
approximately 5.5 year service life of the axial fans can be signalled. 
The central control unit 23 is e.g. part of a mobile radio system and is 
stored in a base station cabinet 1. 
Each of the vertical spars of the frame rack in such a base station has a 
row of holes at a predetermined spacing pattern for the attachment of the 
module carriers 2. As shown in FIG. 1, the height of the cabinet 1 is for 
instance 2 meters, which allows the full installation of five module 
carriers. Depending on the power loss produced by the plug-in units 9 and 
the position of the module carriers in the frame rack, module carriers 2 
which are fully equipped with fan inserts 13 and module carriers 2' 
without fan inserts and without control module are arranged in the frame 
rack, but can be retrofitted without difficulty if required. The 
integrated arrangement of three adjacent fan inserts 13 in the module 
carriers 2, which can be plugged in or activated independently of each 
other, make it possible to lead incoming and outgoing HF cables vertically 
on the front of the plug-in units 9 and therefore via a short path between 
the different insertion planes, since only a minimal lateral displacement 
of the front cables is needed to replace the relatively small fan inserts 
13. 
In the illustrated embodiment of the base station, the cabinet 1 has a 
mixed installation as seen from the bottom to the top. The first lower 
module carrier 2, which is equipped with fan inserts 13, is followed by a 
second module carrier 2' without fan inserts, and the empty space is 
covered with a snap-in front shutter 24. A plate forms the bottom of an 
air intake compartment 25 located above this module carrier 2', and 
deflects rising warm air into a rear air exhaust duct in the cabinet 1. A 
third module carrier 2, which again is equipped with fan inserts 13, is 
located above the air intake compartment 25, and above that a fourth 
module carrier 2' covered by a front shutter 24, which is followed by a 
further air intake compartment 25 and a fifth module carrier 2 with fan 
inserts 13. Finally, the part of the cabinet 1 which is located above that 
contains among other things the central control unit 23 of the base 
station, and three further fan inserts 13 (top fans) with the same control 
electronics (control module 22). In this way a frame rack, in which five 
module carriers 2 that are fully equipped with fan inserts are mounted, 
can therefore contain thirty-six individually controllable axial fans 20.