Over-center self-closing hinge having a spring biased cam thruster

Over-center hinge (10) whose jamb-related part is in the form of a supporting arm (16) coupled by two links (18 and 20) to the door-related part (14) in the manner of a four-joint hinge. In the linkage end of the supporting arm (16) there is provided a thruster (26) whose one end is mounted so as to be longitudinally displaceable under resilient bias and rotatable about the fixed pivot (28) of one of the hinge links (18), and whose other end, which is provided with a cam (42-44), is urged against a crosspiece (36) in the supporting arm (16). By way of studs (50) on the other hinge link (20), which are guided by a cam (48), the thruster (26) is swung during the hinge movement, while in the vicinity of the closed position a ramp surface (44) cooperates with the crosspiece (36) in such a manner that the thruster (26) is swung towards the second hinge link (20 ) and exerts a force thereon acting in the closing direction.

BACKGROUND OF THE INVENTION 
The invention relates to an over-center, self-closing hinge for cabinet 
doors, having two hinge links pivoting in the manner of a four-joint hinge 
on a door-related hinge part at one end and on a jamb-related hinge part 
in the form of an elongated supporting arm at the other, and having a 
biased spring one end of which thrusts against the jamb-related pivot of 
the outer hinge link, i.e., the link more remote from the jamb, and whose 
other end thrusts against the inner hinge link, i.e., the link nearer the 
jamb, at a point at a distance froom its jamb-end pivot, so as to produce 
a hinge closing torque when the hinge is close to its closed position. 
An over-center, self-closing hinge of this kind is known from U.S. Pat. No. 
4,065,829, in which the spring under bias is an arcuately curved spring 
whose one end thrusts against the pivot of the outer hinge link while its 
other end engages a pin disposed transversely between two side plates 
formed on the inner hinge link. As a result of the distance between the 
transverse pin and the pin mounting the inner hinge link, the bias of the 
spring engages the inner hinge link with mechanical advantage, such that, 
as the hinge nears the closed position, a torque acting in the closing 
direction is produced by the bias, and, as it nears the open position, a 
torque acting in the opening direction is produced. The known hinge thus 
has an over-center characteristic which forces the hinge to one of its end 
positions depending on the angle of the hinge. For certain uses, however, 
over-center hinges are needed which produce a closing torque only in the 
vicinity of the closed position, while otherwise the hinge, along with the 
door mounted on it, can be moved to and fro without force or torque being 
applied by the spring. 
It is therefore the object of the invention to create an over-center, 
self-closing hinge of this kind, namely one in which a closing torque acts 
only in the vicinity of the closed position, and to make the over-center 
mechanism producing this torque so compact that it can be disposed out of 
sight in the interior of the supporting arm. 
SUMMARY OF THE INVENTION 
Setting out from a hinge of the kind mentioned above, this problem is 
solved in accordance with the invention in that the spring is disposed in 
a swiveling thruster which is displaceable longitudinally relative to the 
fixed pivot pin of the outer hinge link and whose end remote from the 
pivot pin is in the form of a cam thrusting against a cross piece provided 
in the supporting arm; in that during the closing movement the thruster is 
coupled with the inner hinge link by studs provided on the latter, which 
engage cam surfaces provided on the sides of the thruster so as to rock 
the cam-end of the thruster toward the inner hinge link, and that the cam 
on the end of the thruster has an arcuate section which is concentric with 
the axis of the fixed pivot pin of the outer hinge link, and a ramp 
section onto which the crosspiece passes from the arcuate cam section as 
the hinge comes near to the closed position. This construction of the 
over-center hinge of the invention makes it possible to dispose the 
over-center mechanism invisibly within the supporting arm without the need 
for making the supporting arm larger or of different dimensions than those 
of normal parallelogram hinges. The hinge can therefore be combined with 
normal hinges, i.e., hinges having no over-center mechanism, without it 
being apparent that the hinges are different. If, for example, the closing 
force of the hinge suffices for a small or light door leaf, the door leaf 
can be fitted with one hinge made in the manner of the invention and with 
another, normal hinge matching it in appearance. A reduction in cost is 
thus achieved by using one instead of two over-center hinges. In the case 
of large door leaves fitted to the cabinet carcass with more than two 
hinges, it then also becomes possible to use only two over-center hinges 
for two of the three or four hinges that are to be used for the mounting 
of the door. 
In a preferred further development of the invention, the hinge links, which 
are made from flat metal stock by the stamping and pressing method, have 
their sides bent up at right angles to form cheeks having pivot bores 
through which the pivot pins on the supporting arm side are passed. The 
thruster has a width corresponding to or slightly smaller than the inside 
distance between the cheeks of the links, and on at least one of the 
cheeks--preferably both of them--of the inner hinge link there is provided 
a short stud extending toward the thruster and engaging a cam slot 
provided in the confronting lateral face of the thruster. 
If the supporting arm is in the usual channel shape, the crosspiece that is 
to be provided on the supporting arm can simply be a pin set in opposite 
bores in the sides of the channel. 
The thruster is desirably provided at its cam end with a nose projecting 
toward the hinge link and engaging this hinge link at a distance from the 
pivot at the supporting-arm end of the inner hinge link. The distance 
between the pivot pin and the point of engagement of the nose with the 
hinge link then constitutes the lever arm at which the deflecting force of 
the thruster becomes effective, which force is produced by the bias of the 
spring when the ramp section engages the crosspiece, as the hinge nears 
the closed position. The longer this lever arm is, the less can be the 
bias required of the spring. 
The spring is preferably a compression coil spring contained under bias in 
a blind hole provided in the thruster at the opposite end form the cam, 
and directly engaging at its outer end the fixed pivot pin at one end of 
the outer hinge link.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT 
The hinge in accordance with the invention, designated generally by the 
number 10 in FIGS. 1 and 2, is a so called four-joint hinge, in which the 
door-related part in the form of a cup 14, designed to be driven or 
otherwise set in a mating mortise in the cabinet door 12, is articulated 
by means of two hinge links 18 and 20 to the jamb-related hinge part which 
is in the form of an elongated supporting arm 16. The supporting arm 16 is 
mounted on the jamb 22 of the cabinet through the medium of a mounting 
plate 24 affixed to the jamb 22 in a known manner. Up to this point the 
hinge 10 corresponds to conventional four-joint hinges. 
The over-center mechanism of the hinge 10 has a thruster 26 represented 
separately in FIGS. 7 to 9, which is disposed in the front-end portion of 
the supporting arm 16 between the fixed pivot pins 28 and 30 on which the 
hinge links 18 and 20 are held on the supporting arm. In a blind hole 32 
in the thruster 26, there is inserted under bias a compression coil spring 
34 whose extremity at the open end of the blind hole engages the fixed 
pivot pin 28 at the end of the outer hinge link 18, i.e., the link farther 
away from the door jamb. The other end of the thruster 26 is accordingly 
urged toward the interior of the supporting arm in contact with a cross 
pin 36 which is disposed in the front end of the supporting arm, parallel 
to the fixed pivot pins 28 and 30 and, like the fixed pivot pins, is 
fastened in bores in the side walls 38 of the supporting arm 16. The 
thruster 26 is provided at its open end with a slot 40 in which the pivot 
pin 28 is engaged when the thruster is in its properly installed position. 
This slot 40 enables the thruster to move longitudinally relative to the 
fixed pin 28 as well as to pivot thereon. 
The closed end of the thruster is in the form of a two-section cam composed 
of a first, circularly arcuate section 42 adjoined at its upper end by a 
second, ramp-like section 44. The arc of the first cam section 42 is 
concentric with the fixed pivot pin 28, i.e., its center coincides with 
the longitudinal central axis of the fixed pin 28. As long as the 
thruster, therefore, has its cam section 42 in contact with the cross pin 
36, no component of force of the bias of the coil spring 34 will develop 
seeking to rotate the thruster about the pivot pin 28. When the cross pin 
36, however, comes within reach of the ramp section 44, the slope of the 
ramp causes a strong component of the spring force to seek to turn the 
thruster 26 clockwise. The cam end of the thruster 26 then swings toward 
the inner hinge link 20 and, by means of a nose 46 prolonging the arcuate 
cam section 42, presses against the inner hinge link 20. Since the point 
of engagement of the nose 46 is at a distance from the fixed pivot pin 30, 
the inner hinge link 20 will be rotated counterclockwise, and thus the 
closing torque is produced which forces the hinge toward the end position 
when it nears the closed position. Since a component of force seeking to 
rotate the thruster is produced, as mentioned, only when its ramp surface 
44 is engaged with the cross pin 36, the thruster is coupled to the inner 
hinge link 20 by a coupling which positively turns the thruster 26 during 
that portion of the hinge movement during which the hinge turns freely. 
This coupling is formed by a cam 48 formed in a recess in each of the 
lateral surfaces of the thruster, and this cam is engaged by short studs 
50 projecting towards the thruster from two cheeks 52 bent up at right 
angles from the supporting-arm end of the inner hinge link 20 which is 
made from flat material. In FIGS. 3 and 4 can be seen the configuration of 
the cheeks 52 bearing the studs 50, and it also can be seen that the 
cheeks 52 contain the pivot bores 54 for the pivot pin 30 of the hinge 
link 20. 
The outer hinge link 18 (FIGS. 5 and 6) also has cheeks 56 turned up from 
its sides at its supporting-arm end, so that the fixed pivot pin 28 is 
exposed between the cheeks 56 to receive the thrust of the coil spring 34. 
The operation of the above described over-center mechanism is such that, 
when the hinge swings from the open position shown in FIG. 1 to the closed 
position (FIG. 2), the studs 50 pass into the recesses containing the cams 
48 in the lateral faces of the thruster 26 and, in cooperation with its 
lower edges defining the cam 48, which curve in the manner represented, 
swing the thruster 26 clockwise, at first without the nose 46 pressing 
against the hinge link 20, i.e., the curvature of the said cam 48 is such 
that the thruster 26 at first only loosely, though positively, follows the 
changes of the angular position of the inner hinge link 20 during the 
closing of the hinge. At the same time the arcuate section 42 of the 
thruster cam slides on the cross pin 36, while all of the compressive 
force of the spring 34 is exerted against the cross pin 36, since the cam 
section 42 is concentric with the axis of the pivot pin 28. As soon as the 
cross pin, however, passes over onto the ramp section 44, a force 
component of the coil spring 34 turns the thruster 26 toward the hinge 
link 20 as a result of the change in the shape of the thruster cam, and is 
transmitted by the nose 46 to the hinge link 20. The studs 50 which have 
been controlling the thruster up to that point then come away from the cam 
48 and stop at a distance from the cam surface in the end 60 of the cam 
recess, which is sufficiently wide to permit the stud 50 to disengage 
(FIG. 2). The force component acting through the nose 46 on the inner 
hinge link 20 then produces on the latter a closing torque which moves the 
hinge to the closed position and holds it there. The distance between the 
point of engagement of the nose 46 with the inner hinge link 20 and its 
fixed pivot axis (pivot pin 30) is, as it can be seen in FIG. 2, 
relatively great, so that the closing torque resulting from the product of 
this distance and the closing force component of the spring force 
achieves, even when relatively weak springs are used, a sufficient 
magnitude to pull even heavy doors persistently toward the closed position 
and keep them closed. 
When the closed hinge is opened (FIG. 2), the inner hinge link 20 turns the 
thruster 26 counter-clockwise by its nose 46, while the ramp section 44 
slides onto the cross pin 36. As soon as the cross pin 36 passes over onto 
the cam section 42, the force component, which until then has been seeking 
to turn the thruster clockwise, vanishes, and the hinge can then be turned 
effortlessly to the open position shown in FIG. 1. The inner hinge link 20 
turns the thruster 26 by its nose 46 positively to the position 
represented in FIG. 1, i.e., in the return of the thruster the studs 50 on 
the inner hinge link do not need to cooperate with the upper edge of the 
recess of cam 48.