U.S. patent number 3,924,207 [Application Number 05/531,517] was granted by the patent office on 1975-12-02 for variable attenuator apparatus.
This patent grant is currently assigned to Precision Electronics Components Ltd.. Invention is credited to Arnold Simoni.
United States Patent |
3,924,207 |
Simoni |
December 2, 1975 |
Variable attenuator apparatus
Abstract
The invention provides a variable attenuator apparatus for high
frequency application comprising fixed and variable resistance
elements moulded together as an integral part on an insulating base
supported within an insulating housing, the variable resistance
elements being operated in unison from a common rotatable shaft
extending inwardly of the housing. A pair of spaced apart
stationary insulating substrate elements are supported within the
housing, one of the elements including a shaft-receiving aperture
through which the rotatable shaft extends, and a contact brush
carrier is disposed between the substrate elements and mounted on
the rotatable shaft for rotation therewith. Each of the substrate
elements has an arcuate resistance track and a conducting collector
track, and one substrate element also has a pair of fixed resistors
connected between one end of the arcuate resistance track and
respective first and second terminals of said element. A pair of
spring-loaded contact brushes are mounted on opposite faces of the
contact brush carrier, each contact brush being spring biased into
sliding bridging engagement with the arcuate resistance track and
collector track of the respective substrate element to define a
variable resistor. Three external terminal connections to the
attenuator network are provided.
Inventors: |
Simoni; Arnold (Don Mills,
CA) |
Assignee: |
Precision Electronics Components
Ltd. (Toronto, CA)
|
Family
ID: |
24117957 |
Appl.
No.: |
05/531,517 |
Filed: |
December 11, 1974 |
Current U.S.
Class: |
333/81R; 338/132;
338/174 |
Current CPC
Class: |
H03H
7/24 (20130101) |
Current International
Class: |
H03H
7/24 (20060101); H03H 007/26 () |
Field of
Search: |
;323/74,81,94R,96
;333/81R,81A ;338/170 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Gensler; Paul L.
Claims
What I claim as my invention is:
1. A variable attenuator apparatus comprising:
a housing;
a rotatable shaft extending inwardly of the housing;
first and second spaced-apart, stationary insulating substrate
elements supported within the housing, one of said elements
including a shaft-receiving aperture through which the rotatable
shaft extends, each substrate element supporting a pair of first
and second terminals, the first and second terminals of one pair
being connected respectively to the first and second terminals of
the other pair;
a contact brush carrier disposed between the substrate elements and
mounted on the rotatable shaft for rotation therewith;
first and second arcuate resistance tracks and first and second
collector tracks supported respectively by the first and second
substrate elements;
a pair of fixed resistors supported by the second substrate element
and connected respectively between one end of the second arcuate
resistance track and the first and second terminals of the second
substrate element;
the terminals of the first substrate element being directly
connected to one end of the first arcuate resistance track and to
the collector track, respectively;
a pair of spring-loaded contact brushes mounted on opposite faces
of the contact brush carrier for rotation therewith, each contact
brush being spring-biased into sliding bridging engagement with the
arcuate resistance track and collector track of the respective
substrate element to define therewith a variable resistor, said
variable resistors varying in opposite senses upon rotation of the
shaft;
a first terminal connection to said interconnected first terminals
of the substrate elements;
a second terminal connection to said interconnected second
terminals of the substrate elements; and
a third terminal connection to said second collector track.
2. A variable attenuator apparatus according to claim 1, wherein
the pair of fixed resistors are of equal resistance value.
3. A variable attenuator apparatus according to claim 1, wherein
the housing provides a front wall having a shaft-receiving aperture
through which the rotatable shaft extends and a rear wall from
which the terminal connections extend.
4. A variable attenuator apparatus according to claim 1, wherein
the contact brush carrier is integral with said shaft.
5. A variable attenuator apparatus according to claim 1, wherein
the contact brushes are constituted by resilient plates keyed to
opposite faces of the brush carrier.
6. A variable attenuator apparatus according to claim 5, wherein
the opposite faces of the brush carrier are formed with
parallel-sided recesses, each resilient plate having a pair of
parallel edges engaging in the respective recess and a raised
medial portion providing a pair of projecting contact regions
respectively engaging the arcuate resistance track and the
collector track of a respective substrate element.
Description
BACKGROUND OF THE INVENTION
This invention relates to a variable attenuator apparatus, and is
concerned primarily with a variable bridged-T attenuator intended
for high frequency operation and including both fixed resistors and
variable resistors which are operated in unison from a common
rotatable shaft.
Variable attenuator apparatus of the type including a pair of
variable resistors mounted for dual operation from a common control
shaft have been previously proposed. One such apparatus is
described in U.S. Pat. No. 3,579,169 issued on May 18, 1971 to
Allen-Bradley Company. The apparatus provides a variable resistor
assembly for dual operation comprising a pair of arcuate resistance
track elements in axially spaced, face-to-face relationship and
having interposed therebetween a single insulating rotor or brush
carrier including oppositely facing cavities, the brush members
being located in the cavities. The brush members are spring-biased
into electrical contact with the respective resistance elements,
and terminal assemblies are provided for each of the resistance
track elements. The apparatus can be adapted for bridged-T or
bridged-L operation, external terminals being provided for the
connection of fixed resistors according to the type of operation
required. The internal construction of the apparatus makes it
necessary that the fixed resistors be connected externally to the
resistance track elements to complete the attenuating network, thus
adding to the overall dimensions of the apparatus and limiting its
usefulness for high frequency operation.
The present invention provides a novel construction of bridged-T
attenuator wherein the dual operation of the variable resistors
does not preclude the internal mounting of fixed resistors, thus
avoiding the need for external terminals for their connection and
so reducing the overall size of the assembly. The device has just
three terminal pins making contact directly with the internal
resistors, thereby eliminating the need to make troublesome
adjustments as is the case with a device having external terminals
to which the fixed resistors are soldered. A bridged-T attenuator
apparatus in accordance with the invention, by reason if its
internal construction, is particularly well adapted for high
frequency operation.
One embodiment of the invention, as applied to a variable bridged-T
attenuator apparatus, will now be described by way of example with
reference to the accompanying drawings, in which:
FIG. 1 is a schematic wiring diagram of the attenuator network;
FIG. 2 is an exploded perspective view of the apparatus, a part of
the housing being broken away to show internal structure; and
FIG. 3 is a vertical section taken along the axis of the
apparatus.
Referring to FIG. 1, the bridged-T attenuator network is of
conventional form and comprises a pair of fixed resistors r.sub.1,
r.sub.2, of equal resistance value, connected between first and
second terminals 10, 11, a first variable resistance element
r.sub.3 being connected between the terminals and in parallel with
the fixed resistors. A second variable resistance element r.sub.4,
having the same resistance value as r.sub.3, is connected between
the junction of resistors r.sub.1 and r.sub.2 and a third terminal
12. By varying the resistances r.sub.3 and r.sub.4 in unison so
that their resistance values are varied in opposite senses, the
resistive impedance of the network can be maintained at a specified
value for different amounts of attenuation.
Referring now to FIGS. 2 and 3, the apparatus embodying the
bridged-T attenuator network comprises an insulating housing 13,
the housing having a front wall 14 including an aperture 15 through
which a rotatable shaft 16 extends inwardly of the housing. A first
insulating substrate element 17, including a shaft-receiving
aperture 18 through which the rotatable shaft 16 extends, is
supported within the housing adjacent to the front wall 14, a
resilient gasket 19 being located in a recess 20 of the front wall
and bearing against the substrate element 17. A second substrate
element 21 is supported within the housing and is spaced from the
first element 17 by spacer elements such as 22 which are an
integral part of the housing structure. The second substrate
element 21, when so located, constitutes a rear wall of the
housing.
The substrate element 17 supports a pair of first and second
terminals 23, 24, an arcuate resistance track 25 (r.sub.3)
connected at one end to the first terminal 23, and a conducting
collector track 26 which is connected to the second terminal 24.
The second substrate element 21 supports a corresponding pair of
first and second terminals 27, 28, an arcuate resistance track 29
(r.sub.4), a conducting collector track 30, and a pair of fixed
resistors 31 (r.sub.1) and 32 (r.sub.2). It will be observed that
one end of the resistance track 29 is connected to the collector
track 30, and the fixed resistors 31, 32 are connected respectively
between the other end of the resistance track 29 and the terminals
27, 28. The terminals 23, 24 are conductively connected to the
terminals 27, 28 respectively, by internal conductors 33.
A contact brush carrier 34 is mounted on the shaft 16 with which it
is integral, and is disposed between the substrate elements 17, 21.
The opposite faces of the carrier 34 are formed with parallel sided
recesses of generally rectangular form 35, and contact brushes 36,
37 constituted by resilient plates are keyed to the opposite faces
of the carrier 34 by means of the recesses 35. Each resilient plate
is of generally rectangular shape having an elongated central
aperture, the parallel vertical edges of the plate engaging in the
respective recess to locate the plate. It will be noted that the
plate is bent about a vertical media line so as to provide a pair
of outwardly projecting contact regions 38, 39 which respectively
engage the collector track and the arcuate resistance track of the
respective substrate element.
When the apparatus is assembled, as shown in FIG. 3, the contact
brushes 36, 37 are spring-biased into sliding bridging engagement
with the respective arcuate resistance tracks and collector tracks
so as to define therewith a pair of variable resistors arranged for
dual operation, the variable resistors varying in opposite senses
upon rotation of the rotatable shaft 16. The assembly is therefore
compact, all the resistance components of the network being mounted
internally of the housing. Only three external terminals are
required, for connecting the attenuator in circuit with a network
or transmission line, and these are provided by the three terminal
pins 40, 41 and 42 which project rearwardly from the rear wall of
the housing 13. The terminal 40, corresponding to the terminal 10
of FIG. 1, provides an external connection to resistance elements
31 and 25 via terminals 27 and 23. The terminal 41, corresponding
to the terminal 11 of FIG. 1, provides an external connection to
the resistance element 32 and the collector track 26 via the
terminals 28 and 24. The third terminal 42, corresponding to
terminal 12 of FIG. 1, provides an external connection to the
collector track 30 and therefore to the slider of resistance
r.sub.4.
The attenuator construction permits great ease of manufacture and
assembly, is very compact and therefore especially suitable for
high frequency operation, and above all, overcomes the problem of
mounting fixed resistors internally in a unit having ganged
resistors arranged for dual operation.
* * * * *