US2762016A - Rotary distributors - Google Patents

Description

United States Patent ROTARY DISTRIBUTORS Angelo Montani, Baltimore, Md., assignor of one-half to Communication Measurements Laboratory, New York, N. Y., a partnership Application May 15, 1952, Serial No. 287,993

3 Claims. (Cl. 333-7) This invention relates to rotary distributors of the type used in multiplex signalling apparatus.

A rotary distributor may be used, for example, to obtain, in an output channel, a signal which is a series of samples of signals present in a plurality of input channels.

A widely used rotary distributor is a segmental contact device in which a rotary contact or brush passes successively over a plurality of stationary contacts. Distributors of the rotary contact type have some inherent drawbacks which have been a cause of considerable trouble.

' One of these drawbacks is the unavoidable chatter of the contacts. Another drawback is the wear of the contacts. A third drawback is a limitation on the speed of the rotary distributor, as both chatter and wear increase with speed. A fourth drawback is the possible deposit, at the contacts, of metallic particles which may bridge two segments and introduce objectionable crosstalk.

It is an object of the present invention to provide a signal distributor which avoids using segmental contact devices.

It is another object of the present invention to eliminate transient effects due to chatter in high speed rotary distributors.

It is a further object of the present invention to eliminate the effects of contact wear in rotary distributors.

According to the present invention, these drawbacks are eliminated through the use of a rotary distributor in which signal coupling is effected capacitively, the segmental contacts having been eliminated.

Other and incidental objects of the present invention will be apparent from a reading of the following specification and an inspection of the accompanying drawings in which:

Figure 1 is a cross-sectional view of one embodiment of the present invention, and

Figure 2 is an exploded view of another embodiment of the present invention.

Referring to Figure 1, there is shown a surface of conductive material 5. This surface 5 is mechanically and electrically connected to a hollow cylinder 7 by means of arm 9. A cylinder 11 is concentrically located inside cylinder 7, the common center being designated as 12. Both cylinders 7 and 11 are made of conductive material, and are separated by an air gap 13. Cylinder 7 is mounted so as to rotate about cylinder 11, which is stationary.

A lead 15 electrically connects cylinder 11 to a terminal of a resistor 17, the other terminal of which is grounded. The terminals of resistor 17 are the input terminals of utilization circuit 19.

Eight surfaces 21 through 28, made of conductive material, are arranged around a circumference which is concentric with cylinders 7 and 11, and has a radius 29. Radius 29 is larger than the radius between center 12 and surface 5, the difference between these radii forming an air gap 31. The surfaces 21 through 28 are mechanically mounted on an insulating member 33 by means of stems such as 35. Surfaces 21 through 28 are electrically connected to input channels 41 through 48 respectively.

Eight surfaces 51 through 58, made of conductive material, are arranged around a circumference having its center at 12, and having a radius 59. Radius 59 is slightly greater than radius 29. Surfaces 51 through 59 are mechanically mounted on insulating member 33 by means of Stems such as (it). Surfaces 51 through 59 are electrically grounded by means of common ground connection 61.

The surfaces 21 through 28 may be called input plates, while the surfaces 51 through 58 may be called ground plates. Surface 5 may be called an output plate. It can be seen that input plates and ground plates are so disposed that, as the output plate 5 rotates around center 12, the output plate 5 alternately faces an input plate and a ground plate.

The input plates 21 through 28, and the ground plates 51 through 5%, are in spaced relationship from each other, so that there is no electrical contact between a ground plate and an input plate. The ground plates are shown to be wider than the input plates; they are also shown to be provided with ridges such as 63 and 65. These ridges may extend to the circumference of radius 29.

The operation of the distributor shown in Figure 1 is as follows. derived from input channels 41 through 48 are applied to the input plates 21 through 2%. A synchronous motor (not shown) makes output plate 5, arm 9 and hollow cylinder 7 rotate about stationary cylinder 11 and center rated by air gap 13, also form a coupling condenser, so I that the signal present on plate 24 is capacitively coupled to resistor 17 and to the utilization circuit 19.

When output plate 5 faces one of the grounded plates, such as 54, the output plate 5 is momentarily grounded. This grounding is due to the capacitive coupling between the output plate 5 and the grounded plate, there being no physical contact therebetween. This grounding avoids crosstalk between input channels due to the carrying over of electrostatic charges from one channel to another. This momentary grounding of plate 5 by means of the grounded plates is helped by the fact that the maximum (or fully meshed) capacity between the output plate 5 and any of the grounded plates 51 through 58, is considerably smaller than the maximum (or fully meshed) capacity between the output plate and any of the input plates 21 through 28.

The ridges 63 and 65 reduce considerably the capacity coupling between two consecutive input plates, and help in eliminating crosstalk.

The geometry of the whole arrangement is such that an observer, placed inside the circumference of radius 29, cannot see the insulating member 33. Thus any erratic electrostatic charge on insulating member 33 will not influence the potential on output plate 5.

If an alternating potential is applied to one of the input plates 21 to 28, the frequency of that potential should be such that the duration of one cycle is considerably shorter than the time the output plate 5 and the input plate are etfectively coupled.

If a unidirectional potential is applied to one of the input plates, the corresponding output potential will be a bipolar pulse having a positive and a negative amplitude proportional to the unidirectional potential on the input plate.

In both cases, the potential across resistor 17 comprises a series of samples, each sample being proportional to its corresponding input potential.

Patented Sept. 4, 1956 Alternating or unidirectional potentials,

Referring to Figure 2, there is shown a surface 69 of conductive material. Located within windows of surface 69 are shown six input surfaces or plates 71 through 76. These input plates 71 through 76 are made of conductive material and are electrically connected to input channels 81 through 86 respectively. The input plates 71 through 76 are electrically insulated from surface 69, and surface 69 is grounded.

Facing the input plates 71 through 76 are the output surfaces or plates 91 through 96. These output plates are made of conductive material, and are electrically connected together by means of lead 101. Lead 101 is connected to one terminal of a resistor 103, the other terminal of which is grounded. The output plates 91 through 96 may be mechanically supported by a surface (not shown) similar to surface 69 supporting the input plates 71 through 7 6.

Between the input and output plates which are stationary, there is located a rotating plate 105. Plate 105 may be rotated by means of a synchronous motor (not shown). Plate 105 is made of conductive material. Eccentrically located within .it is a window 107. In this window 107 there may be air or any other dielectric material.

It will be noted that the input plates 71 through 76, the output plates 91 through 96, and the window 107 are located around three circumferences having radii of the same length, and whose centers are on an axis perpendicular to these radii.

As plate 105 revolves, the window 107 couples capacitively and in succession each of the input plates 71 through 78 to each of the corresponding output plates 91 through 98. The potential across resistor 103 comprises a series of samples, each sample being proportional to its corresponding input potential.

It will be noted that Figure 2 .is an exploded view. In practice, the distances 109 and 111 amount to only a few thousandths of an inch.

Crosstalk between the input plates 71 through 76 is avoided by grounding plate 69 as shown. The rotating plate 105 and plate 69 forming a condenser to ground, plate 105 is also grounded for alternating potentials.

It is seen that the previously mentioned drawbacks of segmental contacts are avoided in the rotary distributors constructed in accordance with the present invention.

What is claimed is:

l. A rotary signal distributor comprising: a first set of fixed conductive members defining surfaces mounted on the circumference of a circle perpendicular to and centered on an axis, the members of said first set being electrically connected to a common point of reference potential, a second set of fixed conductive members defining surfaces insulatively supported and mounted on the circumference of a circle perpendicular to and centered on said axis, the surfaces of said second set being interposed between the surfaces of said first set, another conductive member defining a surface parallel to said axis, and means for rotating the surface of said other member about said axis and into spaced parallel relationship successively with each of said fixed surfaces to form a capacitor therewith, the maximum capacitance between the surface of said other member and a surface of the first set being smaller than the maximum capacitance between the surface of said other member and a surface of the second set.

2. A rotary signal distributor according to claim 1 wherein the circumference on which the surfaces of said first set are mounted has a slightly larger radius than that of the circumference on which the surfaces of said second set are mounted.

3. A rotary signal distributor according to claim 2 wherein the surfaces of said first set are provided, near the edges close to the surfaces of said second set, with ridges substantially perpendicular to the surfaces.

References Cited in the file of this patent UNITED STATES PATENTS 1,913,512 Reynolds June 13, 1933 2,402,603 Clark June 25, 1946 2,432,089 Carter et al. Dec. 9, 1947 2,477,635 Marchand Aug. 2, 1949 2,679,551 Newby May 25, 1954

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