Locking device for a rear seat back rest

A locking arrangement for a seat back of a motor vehicle rear seat includes a tongue-shaped locking member which is fastened to a body component and provided with a recess. The latching device includes a plastic housing built into the seat back. The plastic housing accommodates a single-arm latch bar which is adapted to engage into the recess of the tongue-like locking member by way of a latch tab. A slidable pin is mounted for axial displacement in a guide bore of the plastic housing and is seated with its one end on the latch bar. On its other end the slidable pin is provided with an actuating button which is embedded in a trough-like grip member. Upon pressing the actuating button, the latch bar is pivoted against the biasing force of a spring, and the latch tab is moved out of the recess of the tongue-shaped locking member, which will cause unlocking of the seat back.

The invention relates to a locking arrangement for the seat back of a motor 
vehicle rear seat assembly, including a latching device incorporating a 
latch member for locking the same to a locking member of a rearwardly 
disposed body portion. Locking devices of this type are currently employed 
in motor vehicles equipped with foldable rear seat assemblies and are 
generally known in the art. 
Prior art locking arrangements oftentimes have a tendency to rattle and 
require relatively close manufacturing tolerances if reliable locking of 
the seat back is to be effected. A wide variety of locking arrangements 
for various purposes are known in the art, so that the expert should have 
no difficulty in adapting one or the other prior art locking arrangement 
to the seat back of a motor vehicle rear seat assembly. However, the 
requirements to be met in motor vehicles are often incompatible with one 
another. If priority is given to rattle-free and reliable operation, close 
attention must be paid to manufacturing tolerances, not only in regard to 
the individual locking components, but also the rear seat itself and the 
locking members to be attached to the vehicle body. 
For instance, in the German patent DE-PS No. 2 365 250 there is disclosed a 
safety belt buckle in which a tongue provided with a recess is to be 
inserted into an arresting device having a single-arm latch bar. The latch 
bar is spring-biased in the locking direction and is adapted for pivoting 
movement by means of a push button in such a manner that a projecting 
portion of the locking lever is moved out of the recess. 
However, safety belt buckles are not afflicted with the problems dominant 
in seat backs for rear seats, i.e., they are not subject to rattling. 
Furthermore, in the manufacture of safety belt buckles, only the parts 
that are locked to each other must have close tolerances, whereas in the 
case of seat backs for rear seat assemblies, dimensional accuracy must be 
extended to the seat back itself and the locking components to be secured 
to the vehicle body if proper functioning of the seat back lock is to be 
expected. 
It is the object of the present invention to provide a locking arrangement 
of the type mentioned in the foregoing which is reliable in operation and 
not subject to rattling while the cooperating components of the locking 
arrangement may be manufactured at tolerances that are not very critical. 
According to the present invention, this objective is met in that the 
striker member is in the form of a tongue which is provided with a recess, 
and the latch member is in the form of a single arm latch bar which is 
mounted in a plastic housing of the seat back of the rear seat assembly. 
The latch bar is provided with a latch tab for engagement with the recess, 
is spring-biased in the direction of the recess and is actuated by an 
axially displaceable pin. The displaceable actuating pin is in abutting 
relationship with the latch bar and is spaced apart from the pivoting axis 
of the latch bolt at a greater distance than the latch tab. 
In the above-described locking arrangement as proposed by the present 
invention, neither the latching parts nor the seat back of the rear seat 
assembly or the striker parts require close manufacturing tolerances, and 
yet the operation of the locking arrangement is reliable and rattle-free. 
Furthermore, the locking arrangement according to the present invention is 
of relatively low weight and has a relatively long service life due to its 
simplicity of construction. 
The manufacturing costs of the locking arrangement can be reduced 
considerably if the latch bar is made of plastics. In addition to the 
cost-saving factor, the use of plastics reduces the likelihood of rattling 
even further. 
Preferably, the latch bar is mounted by way of a pin in a slot of the 
plastic housing. This arrangement will prevent the seat from becoming 
unlocked in the event of an accident. 
An additional feature of the invention resides in an arrangement in which 
the actuating pin is adapted for axial displacement in a guide bore of the 
plastic housing. This arrangement will ensure that the actuating pin, 
regardless of the dimensional tolerances of the seat back of the rear seat 
assembly, will be properly located upon the latch bar and will thereby 
enable proper functioning of the locking arrangement. 
Errors in alignment between the actuating pin with its control knob and the 
embedded grip body accommodating these two parts can be eliminated if the 
plastic housing is provided with an opening for insertion of the grip body 
into which the actuating pin with its control knob is extending. 
Spring-biasing of the latch bar in the locking direction may be effected in 
a relatively simple manner in that the latch bar is urged in that 
direction by a hairpin spring which is encircling the pivot pin and which 
is arranged such that its one leg is bearing against the latch bar and its 
other leg against a retaining surface provided on the plastic housing. 
According to another feature of the invention, the latch tab is provided 
with an engagement surface which is adapted to make the initial contact 
with the tongue-shaped striker when the seat back of the rear seat is 
folded down, and with an arcuate arresting surface that is arranged 
adjacent the engagement surface whose center of curvature is coinciding 
with the axis of the pivot pin of the latch bar. This arrangement will 
enable easy locking engagement when the seat back is moved into its 
fold-down position and will provide that the push button can be pressed 
down without effort when the seat back is to be unlocked. 
The assembly operation of the locking arrangement may be greatly simplified 
if the latch bar is mounted for pivoting movement in the locking direction 
until it is bearing against a stop surface of the plastic housing, because 
this will enable the latch bar to be retained in a non-interfering 
position prior to the time the thrust pin and the latch body are added to 
the assembly.

FIG. 1 illustrates the side portion of a rear seat assembly 1 which is 
comprised of a seat back 2 and a seat bottom 3. The seat bottom 3 is 
adapted to be lifted up by means of a loop-type handle 4 attached to the 
rear thereof and to be pivoted into a vertical position. For this purpose, 
hinges 5 are provided on the front of the seat bottom. 
The dash-dotted lines in FIG. 1 represent a locking arrangement for the 
seat back of a rear seat which can be unlocked by means of an actuating 
device 7 built into the seat back of the rear seat. The unlocked seat can 
be knocked down forwardly through swinging movement about an axis 8. 
FIG. 2 shows in greater detail the basic components employed in the locking 
arrangement according to the invention. One will notice again the seat 
back 2 of the rear seat assembly. The seat back 2 has a rear panel 9 which 
has a plastic housing 10 secured to its inner side by means of threaded 
bolts 11, 12. A tongue member 13, which is attached rearwardly of the rear 
panel 9, as for instance by welding, to a body component 14 is arranged so 
as to extend into the plastic housing 10. This tongue-like member 13 is 
provided, just like the tongue of a seatbelt buckle, with a recess 15 
adapted to be engaged inside of the plastic housing 10 by a latch tab 16 
of a latch bar 17 which will cause the seat back 2 of the rear seat 
assembly to be locked to the tongue-like member 13. 
The latch bar 17 is mounted on a pin 18 inside the plastic housing 10 and 
is spring-biased by a hairpin spring 19 in the locking direction, i.e., 
clockwise as viewed in the drawing. A slidable pin 20, which is spaced 
apart from the pivot pin 18 at a greater distance than is the latch tab 
16, is provided and arranged so as to bear against the latch bar 17. The 
slidable pin 20 has an actuating button 21 on its upper end which is 
accommodated inside a trough-like grip member 22. It is apparent from FIG. 
2 that the slidable pin 20 is guided in a guide bore 23 of the plastic 
housing 10. The trough-like grip member 22, too, is retained by the 
plastic housing 10 as it is seated with its lower end inside a plug-in 
opening 24 formed in the plastic housing 10. 
FIGS. 3 and 4 illustrate the plastic housing in greater detail. One will 
note in these figures a transversely and downwardly extending slot 25 
which is defined on the bottom by a slanted stop surface 26 and which 
merges on the top into a considerably wider horizontal slot 27 which is 
designed to accommodate the tongue-like locking member 13. It should be 
noted, however, that the slot 27 does not extend through the entire 
plastic housing 10, so that the slot 25, too, is defined on the top by a 
stop surface 27 and by sides of side surfaces of the housing 10. 
As shown in FIG. 2, the guide bore 23 also mentioned in the foregoing 
extends generally vertically and is terminating from above into the 
horizontal slot 27. One will also note in FIGS. 3 and 4 the plug-in 
opening 24 which extends coaxially of the guide bore 23 and which, like 
the guide bore, is of square cross-section. The pivot pin 18 for the latch 
bar is mounted in a horizontal bore 28 the sides of the housing 10 and 
extends transversely through the slot 25 in the plastic housing 10. 
The latch bar 17 illustrated in FIGS. 5 and 6 is also provided with a bore 
designated by the numeral 29 so that it can be mounted on the pin 18. Its 
latch tab 16 is defined by a standard engagement surface 30 and an arcuate 
locking surface 31, with the center of curvature of the locking surface 31 
coinciding with the center of the bore 29 and thus with the center of pin 
18. 
The hairpin spring 19 illustrated in FIGS. 7 and 8 has two coil portions 
32, 33 with which it is trained about the pin 18. It also has a cross 
member 34 for connecting the two coil portions 32, 33 which engages the 
latch bar 34 from below, and a pair of leg ends 35, 36 which abut against 
the engagement surface 26. 
The manner of operation of the subject locking arrangement is very simple. 
When the seat back 2 of the rear seat is swung from a horizontal position 
into an upright position, the tongue-like locking member 13 will become 
seated in the horizontal slot 37 and will be caused to engage with the 
engagement surface 30 of the latch bar 17. This will cause the latch bar 
17 to be pivoted counterclockwise against the force of the hairpin spring 
19. Once the seat back 2 has assumed its final upright position, the latch 
tab 16 will snap into the recess 15 of the tongue-like locking member 13 
and will thus lock the seat back into position. 
In order to fold the seat back 2 down, the actuating button 21 is pressed 
downwardly into the trough-like grip member 22. The slidable pin 20 will 
then cause the latch bar 17 to be pivoted counterclockwise, so that the 
latch tab 16 is being urged out of the recess 15, which will enable the 
seat back to be folded forwardly.