Structural unit for an electric vehicle

A structural unit for an electric vehicle which includes a box-like slide-in unit containing the electrical, electronic, and electro-mechanical structural elements for the control and regulation of the operating currents and voltages. The slide-in unit which is adapted to be securely connected with the vehicle, consists of a box-shaped slide-in tray provided with guide arrangement and of a support frame also provided with guide arrangement and adapted to be securely fastened at the vehicle. For purposes of establishing the electrical contacts, complementary plug-in contacts are arranged at corresponding places of the support frame and of the box-like slide-in unit whereby the top cover plate is removable at the slide-in unit and the front plate thereof is adapted to be tilted down while the slide-in unit itself is held in the support frame by means of clamping bolts.

The present invention relates to a structural unit for an electric vehicle, 
which includes a slide-in unit containing the electrical, electronic and 
electromechanical structural elements for the control and regulation of 
the operating currents and voltages. 
A structural unit of this type is described in the publication ETZ-A Volume 
94, 1973, issue 11, pages 691 et seq. This prior art structural unit is 
constructed as a console installed in lieu of the engine into the engine 
space of a series-produced vehicle, on which are secured a number of 
protective circuit breakers, a D.C. regulator of semi-conductor 
construction, a number of diodes and further structural elements necessary 
for the control and regulation of the driving and braking operation of the 
vehicle. The feed or supply cables coming from the battery and the control 
lines coming from the command elements initiating the acceleration or 
braking operation, are connected in the prior art structural unit by means 
of customary connector lugs and threaded connections with the regulating 
and control elements of the structural unit. This entails the disadvantage 
that for purposes of removing the structural unit, for example, for the 
examination thereof or exchange of a damaged structural element accessible 
from the outside only with difficulty, numerous threaded connections have 
to be removed before the console can be removed out of the vehicle. A 
further disadvantage of the prior art structural unit resides in that the 
supply cables coming from the battery may come into contact with their 
cable connectors with the vehicle ground during the removal of the 
console, which may lead to short-circuits. Additionally, during the 
re-connection of the cables to the structural elements of the re-installed 
console, the danger exists that the connections are mixed up, which in 
connection with semi-conductor structural elements that are very sensitive 
against an incorrect polarity of the connections, may lead easily to the 
destruction thereof. Additionally, there also exists the danger of 
electrical injuries during the connection or disconnection of structural 
elements which are arranged at places of the structural unit that cannot 
be readily viewed or seen, since the battery voltages used for electric 
vehicles already at present are within the 200 volts range and therewith 
are of an order of magnitude which may lead to fatal injuries. The 
servicing and possibly the repair of the prior art structural unit can 
therefore be undertaken only by specially schooled personnel and 
therebeyond involves a great amount of work and is costly so that it is 
hardly suitable for series manufacture or mass production. 
Accordingly, the aim of the present invention resides in providing a 
structural unit of the aforementioned type whose servicing is simple and 
reliable and can at least be prepared by unschooled personnel, and which 
also makes it possible to rapidly exchange in a simple manner the 
individual structural elements. 
The underlying problems are solved according to the present invention in 
that for purposes of establishing the electrical contacts of the 
structural elements contained in the slide-in unit with a supply battery 
and with the motor, fixedly arranged complementary parts of plug-in 
contacts are provided at the slide-in unit, on the one hand, and at the 
vehicle, on the other, which come into engagement with one another when 
the slide-in unit is pushed into the vehicle whereby the supply current 
sources can be fixedly wired to the plug-in contact parts fixedly arranged 
at the vehicle, on the one hand, and the structural elements can be 
fixedly wired to the plug-in contact parts arranged at the slide-in unit, 
on the other, so that no electric lines can come into contact with the 
vehicle ground when pulling out the slide-in unit out of the vehicle and 
might lead to undesired short-circuits. It then becomes unnecessary for 
purposes of taking out the slide-in unit, that an installer comes into 
contact with the customary current-carrying parts since the pulling out of 
the slide-in unit already leads to a disengagement of all electrical 
connections so that with a subsequent separation of electrical connections 
between structural elements of the structural unit, it is assured in every 
case that the same are no longer alive, i.e., are no longer connected with 
the electrical voltage source. A subsequent examination of the individual 
structural elements by means of a special diagnostic apparatus as is 
customary at present in the automotive industry in order to simplify the 
servicing of vehicles, can thus also be prepared by unschooled personnel 
and also possibly be carried out by the same, which may lead to a 
considerable reduction of the costs connected with the servicing. The 
present invention also offers the advantage that upon re-insertion of the 
slide-in unit, the correct connection is assured in every case by an 
unequivocal coordination of the complementary parts of the plug-in 
connections. 
Such an unequivocal coordination of the plug-in contact parts with respect 
to one another may be assured, for example, in that the plug-in contacts 
are arranged asymmetrically so that they can be joined only in one way. 
However, also if the contacts are grouped approximately symmetrically 
about a center axis so that in principle two plug-in possibilities exist, 
or in cases in which a repeating arrangement of contacts is provided along 
an axis so that different plug-in possibilities exist offset about the 
division in question, whereby then respectively a portion of the contacts 
would remain free, or non-connected, an unequivocal coordination of the 
contact parts can be achieved with advantage in that a guidance is 
provided in which the slide-in units can be displaced in the direction 
toward the connecting parts fixedly arranged at the vehicle and can be 
brought into engagement with the same in an unequivocal coordination. For 
example, for that purpose, guide rails may be secured at the vehicle, on 
which the slide-in unit is movably or slidingly displaceably guided in the 
direction toward the contact parts rigidly connected with the vehicle, for 
example, by means of rollers. 
According to one particularly advantageous construction of the present 
invention, the sockets of the plug-in contacts are arranged at a plate 
extending perpendicularly to the guide direction and provided at a support 
frame which is adapted to be connected with the vehicle and is provided 
with guide means for the slide-in unit, whereas the contact pins are 
arranged at an inner side wall of the slide-in unit extending parallel to 
this plate. The support frame may then be manufactured in a very simple 
manner outside of the vehicle in a form matched very accurately to the 
form of the slide-in unit and to the arrangement of the plug-in contact 
parts and may be connected with the vehicle by means of suitable fastening 
members. This offers the advantage that a very precise guidance of the 
slide-in unit and of its contact pins in the direction toward the contact 
sockets arranged at the support frame is assured also, when the support 
frame cannot be secured quite accurately in the vehicle at the place 
provided for its fastening. A further advantage of this construction of 
the present invention resides in that the structural unit including the 
slide-in unit and the support frame can be adapted in a simple manner to 
very different types of vehicles by a mere change of the connecting means 
of the support frame with the vehicle. 
It is, however, also understood that the sockets of the plug-in contacts 
may also be arranged at the slide-in unit and the contact pins at the 
support frame or some of the sockets as well as some of the contact pins 
could also be provided at each of the slide-in unit and the support frame. 
However, since the contact pins as a rule are more exposed to the danger 
of damage than the contact sockets, it is appropriate to arrange all of 
the contact pins at the slide-in unit adapted to be pulled out so that 
they are readily interchangeable in case of need. 
Of the order of 30 to 50 plug-in contacts are required for the connection 
of the structural elements contained in the slide-in unit with the supply 
battery, which may be dimensioned differently depending on the different 
current magnitudes in the individual structural elements. Whereas the 
D.C./A.C. converters and/or the D.C. regulator used for feeding the 
driving motor require contacts which must be able to withstand a starting 
current of several hundred amperes and therefore must be dimensioned 
mechanically very sturdily, the contact pins for the control and 
regulating electronics which control the power electronics and which are 
constructed as typical low-current electronics, may be constructed as 
relatively thin contact pins and may be arranged within a narrow space at 
a distance of only a few millimeters from one another. It is then 
necessary that the contact pins are guided very accurately in the 
direction toward the coordinated contact sockets during the displacement 
of the slide-in unit. Though the plates customarily made of synthetic 
resinous material such as "Pertinax", at which are arranged the contact 
sockets and the contact pins, may be made aligned very accurately 
mirror-image-like and the complementary elements of the plug-in contacts 
can be constructed corresponding accurately, the guidance for the slide-in 
unit will exhibit, as a rule, a certain play, so that the danger exists 
that the contact pins which are disposed very closely adjacent one another 
and are not constructed mechanically very sturdily, do not reach 
accurately the coordinated sockets during the sliding-in of the unit and 
may possibly be bent. It is therefore particularly advantageous, as is 
provided according to one embodiment of the present invention, if 
especially the sturdily constructed contact pins and sockets for the 
connection of the power electronics are constructed additionally as guide 
elements for the slide-in movement since the arrangement thereof with 
respect to the other more weakly constructed contact pins can be readily 
attained with the requisite accuracy and therewith an exact centering of 
all contact pins with respect to the associated sockets can be assured. 
Consequently, according to one embodiment of the present invention, the 
openings of the sockets are arranged in a common plane, and the base 
points of the contact pins of the slide-in unit are arranged in a plane 
arranged parallel thereto, whereby the lengths of the contact pin for the 
power electronics is greater than the length of the contact pins for the 
control electronics which then, in their turn, are adapted to be 
accurately centered when sliding-in the slide-in unit, with the aid of the 
sturdy contact pins for the power electronics within the scope of the 
guide clearance of the guidances of the support frame. 
In order that the plug-in contacts do not become disengaged during the 
driving operation, it is necessary to suitably fix the slide-in unit in 
its end position. For example, automatic locking devices with latches or 
catches which retract during the slide-in movement, may be provided which, 
when the slide-in movement has arrived in its end position in which the 
plug-in contacts are joined together, drop into recesses or apertures of 
the side walls or come into abutment at a front plate of the slide-in unit 
and thereby prevent a return movement of the slide-in unit. If, however, 
as in the instant case, numerous plug-in contacts are present whose 
sockets include springy contact elements which abut under a considerable 
spring-stress at the contact pins, then as a rule, considerable forces are 
necessary in order to displace the slide-in unit into its end position. It 
is then often difficult to displace the slide-in unit into its end 
position against these forces which on the average may be of the order of 
magnitude of up to 1 kp per plug-in contact, whereby it should be noted 
that the insertion of the contact pins into the sockets should not take 
place jerk-like in order to avoid damages. It is therefore particularly 
advantageous, as is provided according to a preferred embodiment of the 
present invention, if clamping means engaging at the support frame in the 
direction of the guidance or of the axis of the plug-in contacts, are 
provided for fastening the slide-in unit at the support frame, which 
clamping means may be realized according to a further feature of the 
present invention in that the guidances of the support frame include 
U-shaped profile rails with legs pointing toward one another, in which the 
slide-in unit is displaceably guided by means of hollow profiles fixedly 
arranged at the side walls thereof, within which are rotatably arranged 
tension rods which include at their one, inner end a threaded section 
cooperating with a nut member of the support frame and which at their 
other outer end are supported against the outside of the slide-in unit. 
These torsion rods may then be utilized both for the displacement of the 
slide-in unit into the engaging position of the plug-in contacts as also 
for the fixing thereof, whereby the forces necessary for the sliding-in 
movement can be metered very finely by means of rotary handles or knobs 
arranged at the outer ends of the torsion rods so that the contacts are 
protected in an optimum manner during the sliding-in movement. 
It is further advantageous if the slide-in unit according to a further 
feature of the present invention, is supported with respect to the support 
frame in an end portion of its slide-in movement which is somewhat greater 
than the greatest length of the contact pins, by way of spring-elastic 
elements whose spring constant may be so dimensioned and selected that 
upon disengagement the slide-in unit moves outwardly automatically and 
uniformly under the influence of these spring-elastic elements against the 
tensional forces exerted on the contact pins by the springy contact 
elements of the sockets and jerk-like movements are avoided when taking 
out the slide-in unit. 
These spring-elastic elements, according to one embodiment of the present 
invention, are constructed as spiral springs concentrically surrounding an 
inner end section of the tension rods having a small cross section, 
whereby these springs supported with their one end against a 
shoulder-shaped end surface of the outer section of the tension rod and 
with their other end at the support frame, and are arranged protected 
against soiling in the guide elements for the slide-in unit. 
Such springy support elements additionally provide a further protection for 
the contact pins since they brake the forward movement of the slide-in 
unit when they come into abutment at the support frame so that the contact 
pins can come into engagement with the sockets in their engaging position 
only by actuation of the clamping means. 
The structural unit according to the present invention by reason of the 
conveniently disengageable electrical plug contacts, distinguishes itself 
by a particularly high ease of servicing which according to a further 
development of the present invention can be increased also by a special 
configuration and construction of the slide-in unit, in which the slide-in 
unit is constructed as parallelepiped, flat box guided in horizontal guide 
means which extend up to the immediate vicinity of its outer front plate, 
whereby the box includes a top plate which is displaceable in guide means 
parallel to these guide means and adapted to be removed. The box-like 
slide-in unit can then be pulled out by a predetermined distance which 
corresponds nearly to the entire length of the box, and the top plate can 
be pulled out within its guide means, in case of need, only a certain 
distance or completely in order to enable access to the individual 
structural elements from above which, in this construction of the box, are 
preferably threadably secured at the bottom thereof so that they can be 
conveniently disengaged from above. 
Such a slide-in unit constructed as flat box is suited not only as a 
horizontal slide-in unit but can also be constructed that it may also be 
arranged in trough-shaped recesses of the vehicle floor or approximately 
under the seat bench of a passenger motor vehicle by means of vertical 
guide means whereby the contact pins may then be arranged projecting 
downwardly from the bottom of the slide-in unit and the contact sockets 
may be arranged at the bottom of the trough or recess or vice-versa. 
Accordingly, it is an object of the present invention to provide a 
structural unit for electric motor vehicles which avoids by simple means 
the aforementioned shortcomings and drawbacks encountered in the prior 
art. 
Another object of the present invention resides in a structural unit for 
electric vehicles which is relatively simple in construction and easy to 
install and remove. 
Still another object of the present invention resides in a structural unit 
for electric vehicles in which the electrical connections are established 
by the mere slide-in movement of a slide-in unit in such a manner that 
short-circuits as well as danger of injury to the personnel are avoided. 
A still further object of the present invention resides in a structural 
unit for electrically driven vehicles in which the plug-in contacts are 
protected in a far-reaching manner against damage due to incorrect plug-in 
or as well as against external influences. 
Another object of the present invention resides in a structural unit of the 
type described above in which the structural elements thereof are readily 
accessible for servicing, thereby also minimizing the time required by 
schooled personnel. 
Still another object of the present invention resides in a structural unit 
for electrically driven vehicles whose service is simple and can at least 
be prepared by relatively untrained personnel. 
A still further object of the present invention resides in a structural 
unit of the type descibed above in which the individual structural 
elements can be rapidly exchanged in a simple manner in case of need, 
without danger that any of them are still connected to the power supply at 
the time the service operations are undertaken. 
Still another object of the present invention resides in a structural unit 
for electric vehicles which can be readily adapted to most different types 
of vehicles. 
Another object of the present invention resides in a structural unit for 
electric vehicles in which the installation and removal of the slide-in 
structural unit can be undertaken in a simple manner, protecting all parts 
involved therein.

Referring now to the drawing wherein like reference numerals are used 
throughout the various views to designate like parts, the structural unit 
illustrated in FIGS. 1 to 4 includes a slide-in unit generally designated 
by reference numeral 1 constructed as relatively flat, parallelepiped box 
for the accommodation of the power electronics and control electronics of 
an electrically driven vehicle, which box-like unit is displaceable within 
guide means in a support frame generally designated by reference numeral 2 
(FIG. 2) and secured at the vehicle, and which is arranged to be fixed in 
its completely pushed-in position. 
The box-like unit 1 includes a frame 4 welded together of conventional 
metal profiles, at which are secured its rear boundary wall 5 (FIG. 1) as 
viewed in the slide-in direction and its lateral boundary walls 6 and 7 as 
well as a front plate 8 pivotal in hinges (not shown) at the forward lower 
outer edge. 
Hollow profiles 9 and 9' (FIG. 1) which project outwardly beyond the side 
walls 6 and 7 and which have a square cross section, are welded to the 
upper lateral metal profiles of the metal frame 4 which extend along the 
edges of the box; the hollow profiles 9 and 9' extend thereby over the 
full length of the slide-in unit. The box-like unit 1 is displaceably 
guided by means of these hollow profiles 9 and 9' in U-shaped profiles 10 
and 10' (FIG. 2) of the support frame 2 which extend parallel to one 
another and have their legs pointing toward one another; the U-shaped 
profiles 10 and 10' also extend over the full length of the box 1. As 
illustrated in FIG. 3, further angle rails 12 and 12' having short legs 13 
and 13' extending perpendicularly to the upper frame surface and further 
legs 14 and 14' pointing toward one another and extending parallel to the 
upper frame surface are welded to the top side of the upper lateral frame 
profiles 11 and 11'; a top cover plate 15 of the box-like unit 1 is 
displaceably guided between the angle rails 12 and 12'. The cover plate 15 
is retained in its position by means of an edge section 16 (FIGS. 1 and 3) 
bent off at right angle from the upper edge of the front plate 8 (FIG. 1), 
which surrounds the forward end edge of the cover plate 15, when the front 
plate 8 is pivoted in the upper direction whereas the top cover plate 15 
can be pulled out, when the front plate 8 is tilted down. The cover plate 
15 includes a number of ventilating slots 48 (FIG. 3) through which can 
escape air heated by the structural elements of the slide-in unit 1 which 
in part are strongly heat-producing and through which a cooling of these 
structural elements can take place by convection. 
If the slide-in unit 1 is pulled out of the support frame 2, the front 
plate 8 is tilted downwardly and the cover plate 15 is pulled out, the 
interior space of the box-like slide-in unit 1 in which are contained the 
structural elements used for the current supply of the driving motor and 
for the control of the operating condition thereof, such as, thyristors, 
power diodes, shunt, relays, fuses, switching elements, armature and field 
control elements, starting resistance, control installation and the like, 
is conveniently accessible from in front and from above. 
The interior space is subdivided by a partition wall 17 (FIG. 1) extending 
parallel to the side walls 6 and 7 and made of an insulating material such 
as "Pertinax", into a narrower structural space 18 in which are 
accommodated the strongly heat-producing parts of the power electronics 
including a number of power diodes with cooling bodies 19 and a starting 
resistance 20, and into a wider structural space 21 including the larger 
part of the box 1, in which are accommodated the less heat-producing 
structural elements such as relays 22, fuses, measuring elements and the 
low current electronics of the control and regulating system for the power 
electronics. 
This structural space is closed off in the downward direction by a bottom 
plate 23 constructed, for example, as wood-fiber plate, at which the 
different structural elements are fastened by means of impact nuts 
impacted into the bottom plate 23 and a screw or bolt screwed-in from 
above. The bottom plate 23 and the partition wall 17 are so dimensioned 
that they can be inserted together with the structural elements fastened 
at the same in the frame of the slide-in unit 1 and can be fastened 
thereat. 
The structural elements used in the control unit are mounted on and/or 
soldered to printed circuit boards or plug-in cards 24. The plug-in cards 
are inserted into associated socket strips provided with card guide means 
25 (FIG. 1) which are secured at a separate light metal frame 26, at which 
is also secured a fuse plate 27. This light metal frame 26 is arranged in 
the forwad part of the larger structural space 21 directly to the rear of 
the front plate 8 and more particularly in that part thereof which is 
farthest away from the heat-producing elements 19 and 20. Inside of this 
frame 26, the plug-in cards or circuit boards are arranged parallel to one 
another in planes extending perpendicular to the front plate 8 and to the 
bottom plate 23 so that they are also readily accessible after folding 
down the front plate 8, when the box-like unit 1 remains pushed-in in the 
support frame 2. Each of the plug-in boards 24 is provided at its end face 
facing the front plate 8 with a diagnostic socket 28 (FIG. 1) so that a 
testing of the plug-in board is possible also with a pushed-in box 1. 
Similarly, the fuses and corresponding control lamps for the control unit 
are arranged at the end thereof facing the front plate 8. 
The electrical lines, by means of which the structural elements contained 
in the box 1 are adapted to be connected with the supply battery, are 
connected with connecting lugs or terminals projecting into the box-like 
unit of pin-contacts 29 (FIG. 3) of plug-in connections arranged at the 
rear boundary wall 5 of the box 1, whose complementary sockets 30 are 
secured in a corresponding arrangement at the support frame 2 in such a 
manner that the axes of the contact pins 29 projecting a right angle from 
the outside of the boundary wall 5 and the axes of the contact sockets 30 
are aligned with one another and extend parallel to the guide means 9 and 
10, when the box-like unit 1 is inserted by means of its guide profiles 9 
and 9' into the U-shaped profiles 10 and 10' of the support frame 2. 
The sockets 30 are embedded in a thick synthetic plastic plate 31 (FIG. 2) 
and are so arranged in the same that their openings are disposed in the 
forward plane of the synthetic plastic plate 31 facing the insert unit 1. 
The plate 31, in its turn, is secured at a rectangular frame part 32 of 
the support frame 2 which is welded together at its two upper corners with 
the rear end sections of the U-shaped profile rails 10 and 10' of the 
support frame 2. The two U-shaped profile rails 10 and 10' are connected 
at their forward end facing the box with a cross strut 35 (FIG. 2) for the 
stable fixing of their mutual spacing, which cross strut 35 is welded to 
the upper legs of the U-shaped profiles 10 and 10'. 
Two rubber pads or buffers 36 (FIG. 2) are mounted at a distance from one 
another at the respective lower legs of the U-shaped profiles 10 and 10' 
which are supported on suspensions mounted at the vehicle. It is assured 
thereby that hard shocks are dampened. In order to protect the cable 
fastening means at the rear socket parts opposite the insert unit 1 
against dirt, the side of the rectangular frame member 32 which faces the 
insert unit 1 is covered off over the entire width with PVC plates 37 so 
that only the socket openings remain free. Furthermore, sheet metal cover 
means 38, 38' and 39, 39' are installed at the lower and upper frame leg 
of the rectangular frame part 32 and at its lateral legs which protect the 
rearward parts of the contact sockets mechanically and against soiling. 
The contact pins 29 which are also fastened at a synthetic plastic plate 33 
forming a part of the rear boundary wall 5 of the box 1, are dimensioned 
differently, corresponding to the electric power to be transmitted 
thereby, as illustrated in FIG. 3, whereby the contact pins 29' and 29" 
connected with the structural elements of the power electronics and with 
the motor as well as with a ventilating fan have a greater length and 
thickness than the contact pins 29'" connected with the electronic control 
system which is constructed as low-current electronic system, which 
contact pins 29'" are combined into a thirty-terminal unit 34. If the 
slide-in unit 1 is pushed in into the support frame 2 by means of handles 
40 (FIG. 1) arranged at the front end of the metal frame 4, then at first 
the sturdily constructed and longer contact pins 29' and 29" for the 
electronic power system come into engagement with the contact sockets 30' 
and 30" coordinated thereto, as a result of which the contact pins 29'" of 
the electronic control and regulating system arranged at a very small 
distance from one another are centered very accurately with respect to 
their coordinated sockets 30'" so that these contact pins 29'" are not 
damaged when they finally come into engagement with the contact sockets 
coordinated thereto during a further slide-in movement of the slide-in 
unit 1. 
The means for fastening the slide-in unit 1 at the support frame 2 which 
are illustrated in FIG. 4 in partial cross section along the center plane 
of the hollow profile 9, include a tension rod 41 rotatably supported in 
the hollow profile 9 whose diameter to corresponds approximately to the 
clear inner diameter of the hollow profile 9. The tension rod 41 includes 
at its inner end facing the rectangular frame part 32 of the support frame 
2, a threaded section 42 of smaller diameter which engages into a threaded 
member 43 which is rigidly arranged in the end section of the guiding 
U-shaped profile 10 welded together with the rectangular frame part 2. The 
length of the threaded section 42 of the tensional rod 41 is slightly 
larger than the greatest length of the contact pins 29. The threaded 
section 42 is concentrically surrounded by a spiral spring 44 whose one 
end is supported under elastic stress at the end face of the threaded 
member 43 facing the slide-in unit 1 and whose other end is supported 
under elastic stress at the inner end surface 45 of the section with 
larger cross section of the tension rod 41. At its outer end, the tension 
rod 41 includes a cross-like handle 46 with four equispaced arms which is 
supported at the forward end surface 47 of the square hollow profile 9 
welded to the frame 4 of the slide-in unit. 
If the slide-in unit 1 is displaced within the guide rails 9 in the 
direction toward the plug-in sockets, then at first the spiral spring 44 
whose length in the unstressed condition is somewhat greater than the 
length of the threaded section 42, comes into abutment with the end 
surface of the threaded member 43 so that during the further sliding-in 
movement of the slide-in unit 1, until the threaded section 42 is able to 
come into engagement with the thread of the threaded member 43, a 
spring-force braking the slide-in movement is exerted by the spiral spring 
44. This spring-force can then be overcome in an easy and well-metered 
manner by rotation of the tension rod 41 with the aid of the cross-handle 
46 whereby the contact pins 29 of the slide-in unit 1 come into engagement 
with the sockets coordinated thereto in the course of a continuous forward 
movement. When turning back the tension rod 41, the slide-in unit 1 is 
then pushed back and out again in a continuous movement under the stress 
of the spiral spring 44 without the need for the assembler to pull at the 
slide-in unit 1. 
In a further embodiment of the present invention which is not illustrated 
in the drawing, and which is particularly suited for an installation 
underneath a seat bench of a passenger motor vehicle, the structural unit 
includes a box-like slide-in unit having a metallic frame in which is 
mounted or embedded a base plate, in the center area of which is arranged 
the socket plate of the plug-in connections; the contact pins 
corresponding to the sockets in the socket plate are fixedly arranged in a 
trough-shaped recess of the sheet metal floor of the vehicle. 
The slide-in unit is provided at its bottom side with rubber legs which 
keep the same at a distance from the sheet-metal floor member of the 
vehicle so that supply cables can be laid out in the intermediate space 
between the sheet metal floor member and the base plate of the slide-in 
unit. The contact pins are surrounded on all sides by a PVC covering. The 
guidance of the slide-in unit in the direction toward the contact pins is 
provided by two cylindrical rods which are surrounded concentrically by 
helical springs which, in the unstressed condition, keep the slide-in unit 
at a distance from the contact pins so that the electrical contacts of the 
plug-in connections are disengaged. It is possible by means of a bolt or 
screw centrally arranged in the socket plate, which is provided at its top 
side with a star-shaped handle, to clamp the socket plate in the vertical 
direction downwardly against the plug-in plate and to keep the slide-in 
unit in the engaging position of its sockets with the pin contacts of the 
plug-in plate. 
While we have shown and described only one embodiment in accordance with 
the present invention, it is understood that the same is not limited 
thereto but is susceptible of numerous changes and modifications as known 
to those skilled in the art, and we therefore do not wish to be limited to 
the details shown and described herein but intend to cover all such 
changes and modifications as are encompassed by the scope of the appended 
claims.