Lever arrangement for transmitting limited tilting motions

A lever arrangement comprises a bearing pin and a supply space arranged next to the bearing opening of at least one of the levers and which contains a high-viscosity lubricant. In the operation of the lever arrangement with alternating tilting direction, the lubricant arrives, due to its inertia, in the respectively unstressed part of the bearing gap between the levers. The arrangement is suited particularly for highly stressed parts in the mechanism of circuit breakers which must be designed for space saving due to the small space available. The service life of such lever arrangements is increased substantially by arranging the lubricant in the supply space. The supply space can be part of a sleeve braced on the bearing pin.

BACKGROUND OF THE INVENTION 
The present invention relates to an articulated lever arrangement for 
transmitting limited tilting motions with alternating direction with at 
least one pivot and one lever provided with a bearing opening for the 
pivot. 
Lever arrangements of this type are a component of many technical devices 
and are used, for instance, in low-voltage circuit breakers for 
transmitting forces to the contact members. As long as the forces are 
small, parts with the simplest design are sufficient to meet the intended 
purpose. If, however, the forces are larger and if the motions are 
executed with very high acceleration, considerable mechanical problems can 
be expected. It therefore presents difficulties, even if the parts are 
designed strong and carefully, to keep the wear so small that a specified 
number of operation cycles is possible. This problem applies, for 
instance, in low-voltage circuit breakers, e.g., according to U.S. Pat. 
Nos. 3,301,984 or 3,849,619 to the joint between a thrust lever 
transmitting the force of a spring accumulator, a driver lever mounted on 
a control shaft and to a coupling organ transmitting the motion to a 
contact arrangement, since at this point, not only the actuating energy 
leading to a contact member is passed-on in the case of multi-pole circuit 
breakers, but also the actuating energy for further contact members 
connected to the control shaft. 
In mechanical engineering, various designs and components are known per se 
which are suitable for the low-wear and low-friction transmission of large 
forces under unfavorable conditions. Lever arrangements of such design, 
however, require a larger amount of space which cannot be made available 
in view of the extremely compact design of modern circuit breakers. Also 
lubricating the lever arrangements turned out to be a problem because the 
lubricants cannot be brought to bear in the desired manner due to design 
conditions. If oil-like lubricants are chosen, for example, they wet the 
bearing surfaces due to their creep behavior, and protect the bearings 
insufficiently because of the limited toughness and load-carrying capacity 
of the lubricant. In addition, there is the danger, because of the jerky 
motions with high acceleration as they occur in circuit breakers, that 
oil-like lubricants are flung from the parts to be lubricated and cause 
undesired soiling in the interior of the circuit breaker. If, on the other 
hand, lubricants with a greasy or fatty constitution are chosen, i.e., 
with greater viscosity, they are effective only for a few operating cycles 
because the lubricant is then displaced and used up and cannot flow back 
due to its great viscosity. 
SUMMARY OF THE INVENTION 
Starting therefrom, it is an object of the present invention to develop a 
lever arrangement of the type mentioned, having a design as simple as 
possible of its cooperating parts such that the wear is reduced 
substantially and the number of possible operating cycles is increased 
accordingly. 
The above and other objects of the present invention are achieved by an 
articulated lever arrangement for transmitting limited tilting motions 
with alternating direction, having at least one pivot pin and a lever 
provided with a bearing opening for the pivot pin, a supply space being 
provided laterally next to the bearing opening for receiving a 
high-viscosity lubricant which is in connection with the bearing gap 
between the lever and the pivot pin. 
The lateral position of the supply space can be chosen radially as well as 
axially with respect to the pivot of the arrangement. By placing the 
lubricant in a limited space, it is thereby achieved that the lubricant 
cannot escape freely due to the jerky accelerations and decelerations in 
each operating cycle, but rather gets into the bearing gap on that side 
which was unstressed during the preceding motion. In this manner, the 
lubricant is now available where it is required in the subsequent 
operating cycle with the reversed direction of motion. It has been found 
that lubricants with so high a viscosity can be used which would not be 
suitable for the normal, open application for lubricating lever 
arrangements. 
Due to the new arrangement, however, the high-viscosity lubricant becomes 
fully effective and increases the service life of lever arrangements of 
the type considered above substantially. 
One practical embodiment for forming the supply space is to provide a 
sleeve which surrounds the pivot pin and adjoins the lever. Such a sleeve 
can also be supported in a simple manner at the pivot in that the hole of 
the sleeve is given a part fitting the diameter of the pivot pin as well 
as a part made larger in comparison for receiving the lubricant. In this 
connection it is advantageous to design the sleeve as a spacer between 
levers arranged in pairs. Here, the sleeve fulfills a double function 
since it braces on the one hand the levers arranged in pairs against each 
other and prevents jamming and changes in spacing, and in addition, takes 
up the supply of lubricant. 
As already mentioned, the difficulties described occur, for instance, in 
low-voltage circuit breakers. In such devices, the life of the most highly 
stressed parts can be improved by the provision that the pivot pin is the 
connecting element for transmitting the force between two drive levers 
arranged on a control shaft, two support levers acted upon by a spring 
accumulator, of a thrust lever and a coupling member connected to a 
contact arrangement of the circuit breaker, and that the sleeve is 
designed in accordance with the distance between the partial levers and 
the latter are arranged adjacent to the driving levers. At this point, the 
full driving energy for all contact members of the switch is transmitted. 
Therefore, the flow of energy is extremely high at this point in a three 
or four hole switch. In view of the small space available, it is not 
possible on the other hand, as explained above, to employ costly joint 
designs of great strength and durability. Rather, only joint arrangements 
of a simple design can be used which have smooth cylindrical pins and 
straps consisting of sheet steel with bearing openings made by stamping or 
drilling. This bearing point is given substantially longer life by the 
invention. 
As mentioned above, the supply space for the lubricant can be arranged 
radially as well as axially next to the bearing gap. A radially lateral 
arrangement can be realized to particular advantage by a hole leading into 
the bearing opening. With a lever having two bearing openings, such a hole 
can be arranged so that it connects the two bearing openings. Thereby, 
lubricant is fed to both bearing openings if the lever moves alternatingly 
in the direction of the connecting line of the bearing openings. A lever 
of this type is likewise suitable for electric circuit breakers, 
especially in the area of the driving parts. 
As already mentioned, the new lever arrangement is particularly well suited 
for use in low-voltage circuit breakers in such a manner that the bushing 
is arranged between the lever sections of a thrust lever. In order to 
achieve the greatest effectiveness, it is desirable that the bushing rests 
against the lever sections as free of play as possible. According to one 
embodiment of the invention, this can be achieved by the feature that the 
bushing consists of two sections, each of which have a supply space 
adjoining the lever sections and the total length of both sections is made 
smaller than the spacing of the lever sections by the interposition of 
washers for dimensionally correct matching to the spacing of the lever 
sections. Identical sections can be used here for forming the bushing. 
The installation of the bushing in the lever arrangement can further be 
facilitated over the embodiment just described by the feature that the 
bushing is composed of two parts which are axially movable in an 
interlaced manner relative to each other, and that at least one axially 
active spring element is arranged between two oppositely arranged ring 
areas of the parts. In the assembly, such a bushing acts like an ordinary 
one-piece bushing but adapts itself without play to the spacing of the 
lever sections due to the springiness of the spring element. 
The substantially same property of adaptation of the lever parts without 
play can also be achieved by a further embodiment of the bushing which has 
an inner part with a lathe cut provided approximately centered at the 
circumference, and a part of the jacket extending beyond the one end face 
of the bushing which has a region which can radially be deformed 
permanently. Such a region can be formed, for instance, by recesses which 
are arranged distributed over the circumference and by which the cross 
section of the jacket piece is reduced. 
Approximately the same properties as the mentioned embodiment of the 
bushing equipped with a spring element can be accomplished by the 
provision that the bushing, if made of one piece of plastic, has an 
axially elastically deformable region arranged approximately in the 
center. This can be achieved, in a manner known per se, also by a region 
with reduced cross section approximately so that two or more arms 
extending in the circumferential direction are formed as a connection of 
the end pieces of the bushing. Thermoplastic materials are particularly 
well suited for making such bushings.

DETAILED DESCRIPTION 
The low-voltage circuit breaker 1 shown in FIG. 1 contains a contact 
arrangement 2, the movable part 3 of which can be tilted about a 
stationary bearing 4. The contact arrangement 2 is shown in the opened 
condition; if it is closed, a closed current path is formed which extends 
from an upper connecting conductor 5 via a fixed contact 6, a contact 7 
located at the movable part 3 of the contact arrangement as well as a 
current carrying ribbon 10 to a lower connecting conductor 11. Below the 
contact arrangement 2 fastened to an insulating carrier 12, there is a 
spring accumulator 13 which makes available the switching energy for 
closing the circuit breaker 1. Considering that circuit breakers of this 
type are designed as a rule with several poles, i.e., with three or four 
poles and that, when switching on a short circuit, strong repulsion forces 
must be overcome, the circuit breaker requires much energy. 
In FIG. 1, the spring accumulator is shown in the cocked condition. 
Compression springs 14 contained in the spring accumulator act on a drive 
16 via a thrust rod 15 which cooperates with a lower toggle lever 17 of a 
multi-member lever arrangement. Part of this is a central toggle lever 20 
as well as a lower toggle lever 21 which acts as a thrust lever and is 
connected by means of a pivot pin 22 to a driving lever 23 which is 
fastened on a control shaft 24. As is shown in FIG. 2, three pairs of 
driving levers 23, 23a and 23b are fastened which are provided for 
actuating three contact arrangements 2 arranged next to each other. The 
pivot pin 22 thus transmits the entire mechanical energy required for 
switching. As is further shown in FIG. 2, the upper toggle lever 21 is 
formed by partial levers 25 and 26 which rest against the sides facing 
each other of the two centrally arranged driving levers 23. Against the 
sides of the driving levers 23 facing away from each other rest coupling 
members 27 and 30 which serve for passing-on the driving energy to the 
moveable part 3 of the central contact arrangement 2 shown in FIG. 1. The 
detailed design of the lever arrangement in the vicinity of the pivot pin 
22 is shown in FIG. 3. 
As shown in FIG. 3, there is provided between the lever parts 25 and 26 of 
the upper toggle lever 21 a sleeve 31, the length of which is matched to 
the spacing of the lever parts 25 and 26 and therefore braces these levers 
against each other and prevents them from jamming under the influence of 
the strong forces. The levers 25 and 26 in turn rest against the driving 
levers 23 of the control shaft 24. The central part 32 of the sleeve 31 is 
adapted to the diameter of the bearing pin 22. Near the ends, the inside 
diameter of the bearing sleeve 31 is widened by lathe cuts 33 to form an 
annular space serving as the supply space, in which a lubricant 34 with 
the highest possible viscosity is located. 
Upon the release of the spring accumulator 13 by a closing latch, not 
shown, the toggle switch arrangement explained in connection with FIG. 1 
is stretched, whereby the control shaft 24 with the driving levers 23 
mounted thereon is tilted in a jerky motion via the pivot pin 22. The tilt 
angle is relatively small and may be in the range of 50.degree. to 
60.degree. . The lever parts 25 and 26 rest with their bearing openings, 
of which one (35) is shown in FIG. 4, against the one side of the bearing 
pin 22. If the arrangement now arrives in its end position, the lubricant 
34 is subjected due to its inertia, to an acceleration which is sufficient 
to overcome the viscosity of the lubricant and to transport it into the 
part of the bearing gap which had remained unstressed during the preceding 
motion. This is indicated by arrows 36 in FIG. 3. Vibration or impact 
caused by the sudden breaking of the parts also can contribute to the 
distribution of the lubricant into the bearing gap. 
In opening, the tilting motion described is executed in the reverse 
direction. To this end, the opening latch is released by means of a push 
button 37 (FIG. 1) whereby the support is removed from the stretched 
toggle lever arrangement in a manner known per se. The control shaft 24 
with a driving lever 23 mounted thereon now swings back counterclockwise 
into the position shown in FIG. 1. The energy for carrying out this motion 
is now supplied by springs which are part of the contact arrangement 2 in 
a manner known per se and had been cocked during the preceding closing of 
the circuit breaker 1. In the course of this opening motion, the opposite 
side of the bearing pin 22 is now stressed, on which, however lubricant 
had been deposited from the annular spaces 33 of the sleeve 31 in the 
manner explained. Thereby, the wear is kept low in the desired manner. 
As shown in observing the arrangement according to FIGS. 3 and 4, the 
highly stressed surfaces are periodically supplied with new lubricant, 
since at the end of each motion cycle, an acceleration sufficient for 
transporting the lubricant occurs. Therefore, lubricants with high 
viscosity can be used which in normal application would not provide 
sufficient wetting of bearing surfaces due to their low flowability. 
Exactly such lubricants are well suited, however, to protect bearing 
surfaces which are subjected to a high stress with small relative motion. 
In the following, embodiments of bushings will be described which permit 
obtaining contact of the end faces of the bushing as free of play as 
possible, independently of tolerances of the spacing of the lever sections 
25 and 26 and the bushing and thereby to give the arrangement the greatest 
effectiveness. In this connection, FIG. 5 shows, in a view approximately 
corresponding to FIG. 3, the lever sections 25 and 26 as well as the pivot 
pin 22 and a bushing 40 arranged between the lever sections. This bushing 
is composed of two identical parts 41, each of which has a supply space 42 
for the lubricant. The overall length of both pieces 41 is made 
intentionally smaller than the spacing of the lever sections 25 and 26 so 
that close contact of the end faces of the pieces 41 with the lever 
sections 25 and 26 is achieved by inserting conventional washer 43 in 
accordance with the prevailing tolerance. 
In FIG. 6, only a bushing 45 is shown without the adjacent parts. The 
bushing 45 is composed of two parts 46 and 47 which are axially movable 
interlaced and relative to each other. The part 46 contains here the two 
supply spaces for the lubricant, while the part 47 forms a cylindrical 
jacket which is movable on the part 46. Between the oppositely arranged 
annular surfaces 50 and 51 of the parts 46 and 47, several axially 
effective spring elements 52 are inserted, for instance, cup springs or 
corrugated spring washers. In the assembly into the lever arrangement 
according to FIGS. 2 or 3, the end faces of the parts 46 and 47 rest 
against the lever sections 25 and 26 with a certain amount of pretension 
due to this springiness. 
An exact adaptation of the bushing to the spacing of the lever section can 
be achieved, however, also without subdivision into parts or additional 
washers or spring elements, by a one-piece design according to FIG. 7. 
This embodiment has a inner part 56 which corresponds substantially, for 
instance, to the bushing 31 in FIG. 3, but is made shorter than the 
latter. The inner part 56 is provided with a jacket part 57 which extends 
beyond the one end face 58 of the inner part 56. The inner part 56 is 
provided approximately in the center with a lathe cut 61. The latter is 
engaged by a deformable region 62 of the jacket part 57 which, if desired, 
can also be formed by spots of reduced cross section or by recesses. In 
this manner a permanent deformation can be achieved by the action of the 
radially directed force onto the region 62 of the jacket part 57, whereby 
the material of the jacket part 57 is pushed into the lathe cut 61. The 
inner part 56 and the jacket part 57 are thereby joined together in the 
desired position and make a bushing of suitable length. 
Spring contact of the bushing against the lever sections can also be 
achieved in accordance with the embodiment in FIGS. 8 and 9. In contrast 
to the bushings described above, the bushing 65 shown here is made in one 
piece of a suitable plastic, especially thermoplastic material and has a 
central elastically deformable region. The latter is realized, as is shown 
by the cross section IX--IX in FIG. 9, as a resilient connecting disc 66 
which is connected to the adjoining partial bodies of the bushing 65 by 
two arms 67 and 68 arranged on opposite sides. 
A deformation occurring when the bushing 65 is installed in a lever 
arrangement according to FIG. 2 is shown schematically in FIG. 8 by 
dashed-dotted lines. 
In the foregoing specification, the invention has been described with 
reference to specific exemplary embodiments thereof. It will, however, be 
evident that various modifications and changes may be made thereunto 
without departing from the broader spirit and scope of the invention as 
set forth in the appended claims. The specification and drawings are, 
accordingly, to be regarded in an illustrative rather than in a 
restrictive sense.