US 3295091 A
Description (OCR text may contain errors)
Dec. 27, 1966 o. VON MOSSIN 3,295,091
LIQUID CONTACT ARRANGEMENT BETWEEN RELATIVELY ROTATABLE GONDUCTORS Filed Dec. 28, 1964 4 Sheets-Sheet 1 h v 3 5, UM 72 I] ll :L'ff'ijffi LITIMQ Wm HLl I Jnvemor O-SKAR VON Moss! Dec. 27, 1966 o. VON MOSSIN 3,295,091
LIQUID CONTACT ARRANGEMENT BETWEEN RELATIVELY ROTATABLE CONDUCTORS Filed Dec. 28, 1964 4 Sheets-Sheet 2 TiqlA. H
I N VEN T D R OSKAQ VO/Y MOSS/Iv Dec. 27, 1966 O. LIQUID CONTAC VON MOSSIN T ARRANGEMENT BETWEEN RELATIVELY ROTATABLE CONDUCTORS 4 Sheets-Sheet 3 7n venfor O5KAF2 VON Moss! ZTTOQTZZ Dec. 27, 1966 o. VON MOSSIN LIQUID CONTACT ARRANGEMENT BETWEEN RELAT IVELY ROTATABLIE CONDUCTORS 4 Sheets-$heet 4 Filed Dec. 28, 1964 Jnvenlor w S S o M N 0 V Q A w United States Patent 4 Claims. (Cl. 3395) The invention relates to a contact arrangement for transmitting electric currents between relatively rotatable conductors, in which electric conductive discs, insulated from each other, dip into a liquid electric conductor accommodated in annular chambers.
Contact arrangements of the above-mentioned type are known in which the chambers for accommodating the liquid electric conductor are located in a housing of an electric insulating material. On this housing, terminals are mounted each of which projects with one end into its respective chamber and is thereby in electric contact with the liquid electric conductor. In these contact arrangements the capacitance between the individual contact elements assumes different values because the ring formed by the liquid electric conductive material changes according to the position of the arrangement and the speed of rotation. In many cases this is undesirable, especially when the contact arrangement is to be used for transmitting high-frequency measuring currents. In addition the known contact arrangements can as a rule only be used when their axis is horizontal.
The object of the invention is primarily to produce a contact arrangement of the type mentioned at the outset, in which the disadvantages of the known arrangements are avoided.
For this purpose the chambers containing the liquid conductor (contact chambers) each have a substantially closed electric conductive screening.
At the same time the contact chambers themselves may be of electric conducting material.
In this manner it is possible, according to the invention, to keep the: capacitance between the individual contact elements constant independently of the distribution of the liquid electric conductor in the contact chambers.
The annular contact chambers are preferably of such cross-section that each chamber receives and contains the liquid electric conductor independently of the axial position of the arrangement when the arrangement is at a standstill. This enables the contact arrangement to be used in any position.
At the same time the cross-section of the contact chambers can be enlarged at the periphery and narrowed towards the axis. The cross-section of the contact discs is also enlarged within the cross-sectional enlargement of the contact chambers.
It is advisable to make the peripheral edge of the contact discs of substantially semicircular shape in outward direction and the peripheryof the chambers surrounding this edge correspondingly hollow or concave. This en sures the smoothest possible. flow of the contact medium even at high speeds of rotation.
It is also advantageous to arrange rotatable screening discs between the current transmitting contact points. This prevents inductive influences between the measuring circuits.
The part of the arrangement carrying the contact discs 325,091 Patented Dec. 27, 1966 is preferably constructed as a hollow shaft. This hollow shaft may be slip-on or flanged. In the latter case it has a flange at one or both ends.
Several embodiments of the invention are illustrated by way of example in the accompanying drawings, in which FIG. 1 is a diagrammatic longitudinal section showing half the contact arrangement, and
FIG. 2 a longitudinal section of a contact arrangement with a hollow shaft to be slipped on to a measuring shaft, while FIGS. 1a, 3 and 4 show further embodiments of the invention.
In FIG. 1 a hollow shaft designated by 10 is provided with an electrically insulating coating 17. Contact discs 11 are mounted on this shaft and separated from each other by spacers 12 of insulating material. The crosssection of contact disc portion 11b is reduced while the cross-section of portion 11a is again enlarged.
Metal discs 13 are separated by spacers 14 of an electric insulating material and have a close leak-proof fit in the device. After insertion of the respective contact discs 11, metal discs 13 may, for example, be screwed into place in a leak-proof manner. The metal discs 13 are composed of parts 13a and 13b and contain contact chambers, indicated generally by reference numeral 15, which have an annular part 15b of narrowed cross-section and an outer part 15:: of widened cross-section. These chambers contain a liquid electric conductor 16 such as mercury or gallium, into which the contact dis-cs 11 dip, with the result that the electric contact is established between the contact discs and the annular discs 13 containing the contact chambers. Any good conductive liquid which retains its liquid state in the temperature range coming into question can be used as contact medium. Mercury orgallium is preferably used as the contact medium. The chemical composition of the medium should be such that both when standing idle and also in the case of slow and high speed rotation, any chemical change in the contact material is as far as possible avoided for a long period. The conductive liquid 16 may be filled into the contact chambers 15 by means of bore-holes (not shown) in discs 13. The bore-holes preferably have inside threads and are plugged upon insertion of the conductive liquid by means of threaded screws which prevent leakage of the fluid back through the bore-holes.
Measuring current is tapped for example at terminals 50, indicated in broken lines, while the leads for the current to be measured are designated by 51. They are located in the hollow shaft 10 and extend to the contact discs 11.
As is shown in FIGS. 14, the cross-section of chambers 15 shown therein is bottle-like, with the neck portion of the bottle toward the hollow shaft and the interior edges of the neck portions substantially parallel to one another. As is shown in FIG. 1, chambers 15 are so dimensioned that the liquid electric conductor does not flow out of the chambers even when the arrangement is at a standstill, irrespective of the arrangements axial position. Thus, when the device is at a stand-still, the liquid 16 accumulates in the lowest portion of the chamber. The liquid 16 in the chamber at the left side of FIG. 1 illustrates the level of the liquid when the arrangement is at a stand-still and the device is horizontal. The liquid conductor 16 in the chamber at the right side of FIG. 1 illustrates the level of the liquid when the device is vertical and rotating rather than at a stand-still; and the liquid conductor 16 in the chamber at the center of FIG. 1 illustrates the level of the liquid when the device is horizontal and rotating. It will be noted that in each case the liquid conductor 16 is in contact both with its respective contact disc 11 and also with its respective conductive disc 13.
The contact discs 11 are rounded at their outer end and the contact chambers are correspondingly hollow or concave. Owing to this rounding, smooth flow of the contact medium is ensured, even in the case of higher speeds of rotation. The narrow part 11b of the contact discs and the narrowed gap of the contact chambers prevent the contact medium from flowing out from the contact chambers both when the contact arrangement is in vertical position and when it is subjected to tremors and vibration.
The arrangement can be used for transmitting currents of any kind. It is particularly suitable for transmitting electric measuring currents of high frequency which are liable to be influenced by different capacitive values between the contact elements. As in the case of the subject matter of the invention the outer shape of the screenings between the contact chambers always remains the same, the capacities also remain constant.
If inductive influencing between the measuring currents is also to be eliminated, additional elements 18 are provided which are grounded and arranged, for example, between each two current-conducting contact elements as shown in FIG. 1a. In FIG. 1a, grounded, rotatable shielding discs 18, of a conductive material, are shown on either side of conductive discs 13 which have terminals 50, shown in broken lines, for tapping current from the discs. Leads 52 are electrically connected to the contact discs 11 which extend within discs 13, and leads 52 are electrically connected to the contact discs 11 which extend within the grounded discs 18. Except for the addition of grounded elements 18 between the conducting contact discs 11, the arrangement of FIG. 1a generally corresponds to that of FIG. 3. For example, it includes an insulation coating 17 and spacers 12 as in the arrangement of FIG. 3, and a hollow shaft 30.
FIG. 2 shows an embodiment of the contact arrangement with four contact points for transmitting measuring currents influenced by two elongation measuring strips or strain gauges 22 which serve to measure the torque transmitted by shaft 21. As is shown in FIG. 2, the contact for one of the strain gauge leads is electrically connected to the first contact disc 11 from the left of FIG. 2, and the contact for the other of the strain gauge leads is electrically connected to the third contact disc 11 from the left of FIG. 2. Other contacts are provided in a corresponding manner for the second and fourth contact discs 11 from the left. The hollow shaft designated by reference numeral 20 carries contact discs 11 which are separated from each other by insulating spacers 12. The contact chambers are defined by conductive discs designated by reference numeral 13. They are separated from each other by insulating spacers 14. The hollow shaft 20 is provided with a coating 17 of insulating synthetic resin. 29 are end caps which accommodate the ball bearings 27 with the aid of which the outer part of the arrangement is mounted on the hollow shaft 20.
Reference numerals 25 and 25' respectively designate the terminals connected to the contact chambers to which the leads 26 and 26' are connected. These leads 26 and 26 serve, for example for feeding and conducting high frequency strain gauge measuring currents. One of the two strain gauges shown in FIG. 2 is shown in circuit with elements 25 and 26, and the other is shown in circuit with elements 25 and 26'.
In the hollow shaft 20, a measuring or testing shaft 21 is arranged, the fluctuations in torque of which are to be measured, for example, with the aid of the elongation strips 22. The hollow shaft has a part 20a with enlarged internal diameter in which the testing shaft 21 provided with a collar 21:: is inserted. This collar 21a may be provided with a bore 21b if the measuring point is located outside the hollow shaft 20. Reference numeral 22a designates a screw-threaded bore for a grub screw by means of which the measuring shaft 22 is connected with the hollow shaft 20.
In the embodiment illustrated in FIG. 3, the contact discs are arranged on a hollow shaft 30, the end 30a of which is mounted on the housing containing the contact chambers, Whereas the other end of the hollow shaft is constructed as a flange 30b to which some rotating part can be rigidly connected. Reference numerals 50 designate the terminals and leads, shown in broken lines, for tapping the testing current, and reference numerals 51 designate the leads for the current to be measured in the torque tube. The openings from the inside of the torque tube past insulation 17 to contact discs 11 are designated by reference numeral 53, and the electrical connectors at the contact discs are designated with reference numeral 52. r
The contact arrangement is built up like a box of bricks, that is, more or fewer contact elements can be arranged side-by-side so that a large number of currents can be transmitted, for example, measuring values for power, torque, work, output, speed, acceleration, temperature, hydrogen ion concentration, and so forth. All other conceivable signals of electronic circuits can also be transmitted, for example, signals of radar installations or television plants, also in the case of different carrier frequencies.
The number of contact elements arranged in series in a contact arrangement cannot be increased indiscriminately on account of the relatively narrow permissible length tolerances. This disadvantage can be overcome by arranging several self-contained contact arrangements in series. For this purpose the hollow shaft 40 as shown in FIG. 4 is provided with a flange at each end. The flange 40a can, for example be connected with a rotary measuring shaft and the flange 41 with another contact arrangement.
What I claim is:
1. A contact device for the transmission of electrical currents between relatively rotatable conductors comprising:
(1) a plurality of electrically conductive, mutually insulated members each of which forms an annular chamber,
(2) an electrically conductive liquid within the chambers,
(3) a plurality of electrically conductive, mutually insulated disc-like members, at least a portion of each of said disc-like members entering a chamber and contacting said liquid therewithin,
each chamber having a portion opposite to the side of the chamber through which a disc-like member enters which is wider than the portion of the chamber adjacent to the side of entry of said disc-like member, and
each disc-like member having (a) an edge portion which is within a chamber and is wider than said portion of the chamber adjacent to the side of entry of said disc-like member, and
(b) a portion outside of any of the chambers which is wider than and overlies a said portion of the chambers adjacent to the side of entry of said disc-like member.
2. A contact device according to claim 1 wherein a portion of the periphery of said edge portions of said disc-like members is substantially semicircular in crosssection and wherein a portion of the inner periphery of the chambers is concave and substantially semicircular in cross-section.
3. A contact device according to claim 1 wherein the chambers are bottle-like in cross-section and each have a neck portion with sides substantially parallel to one an- FOREIGN PATENTS other, and an outside portion which is proportioned such 815 989 10/1951 Germany that a portion of said electrically conductive liquid re- 676106 7/1952 Great Britain mains Within the chambers when the contact device is 176576 9/1961 Sweden stationary, irrespective of the attitude of the chambers. 5 361'043 5/1962 switzerl'and 4. A contact device according to claim 1 further characterized by a rotatable screening disc between each pair OTHER REFERENCES of adjacent disc-like members- Rohrbach, c, VDI Zeitschrift Band 100, August 1,
1958, 1041-2. References Cited by the Examiner 1 pp 0 UNITED STATES PATENTS EDWARD C. ALLEN, Primary Examiner. 1,460,037 6/1923 Pierson 339 118 X ALFRED S. TRASK, Examiner.