Note: Descriptions are shown in the official language in which they were submitted.
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TITLE OF THE INVENTION
TRANSFORMER STUD MOUNTING BLOCK AND MULTI-CONDUCTOR
CONNECTOR ASSEMBLIES
FIELD OF THE INVENTION
The present invention relates to a transformer stud mounting block
assembly. The present invention also relates to a connector assembly
comprising a mounting block to connect a conductor connector to a
transformer stud.
BACKGROUND OF THE INVENTION
Electrical connections to the primary and secondary windings of a
power transformer are generally provided by means of a number of
cylindrical, splined or threaded, and electrically conductive studs protruding
from the housing of the transformer. Typically, conductors are connected to
a given stud through an adapter made of an electrically conductive and
readily machined material such as brass or aluminium. The adapter is
fixedly mounted to the stud and includes a series of conductor-receiving
assemblies into which one or more individual conductors may be
introduced and secured.
A variety of adapters for connecting electrical conductors to a
transformer stud have been developed. These adapters are typically
fabricated from a single piece of conductive metal which is appropriately
machined to accept both the transformer stud and at least one electrical
conductor. These known adapters use either:
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(a) a thread on the transformer stud and a complementary threaded hole in
the adapter to screw the adapter onto the transformer stud; or
(b) a hole in the adapter, which is oversized with respect to the transformer
stud to slip-fit the adapter on the stud of the transformer.
Adapters of type (a) suffer from the drawback that they have to be
screwed onto the transformer stud which may be quite long. Additionally,
the region of electrical contact between the threaded outer surface of the
transformer stud and the threaded inner surface of the hole in the adapter
is subject to oxidisation since adequate spacing between these two
surfaces is required to allow the adapter to be screwed onto the stud. This
may lead to poor electrical conductivity between the stud and the adapter.
Also, removal (by unscrewing) of the adapter from the transformer stud
requires disconnection of every conductor.
Adapters of type (b) suffer from the drawback that the stud of the
transformer is typically secured in the hole of the adapter by means of one
or more retaining screws which intersect with the hole and, once tightened,
force the stud into contact with the inner surface of the hole. As the stud is
forced against one side of the inner surface of the hole, an air gap is
formed between the stud and the hole surface on the side of the stud
opposite to the region of contact, leading to reduced conductivity and
increasing the potential for oxidisation.
Also known are adapters comprised of a conductor connecting pad
and a mounting block wherein the connector connecting pad is removably
secured to the mounting block through a suitable fastener arrangement,
typically, as discussed above, a screw-on or slip-on fastener arrangement.
However, these adapters require another separate arrangement to secure
the mounting block to the transformer stud, thereby increasing the
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complexity of the machining of the adapter and the number of components
necessary to assemble that adapter.
SUMMARY OF THE INVENTION
The present invention overcomes the above and other drawbacks by
providing a mounting block assembly for interconnecting a conductor
connector with a transformer stud comprising:
- a mounting block made of electrically conductive material;
- a deformable stud-receiving hole in the mounting block, the stud-
receiving hole having an inner surface and dimensions suitable to
receive the transformer stud;
a first connector-and-block interconnecting fastener dedicated, when
tightened, to connect the conductor connector to the mounting block;
and
- a second fastener having both a connector-and-block interconnecting
portion and a hole-deforming portion, said second fastener, when
tightened, simultaneously connecting the conductor connector to the
mounting block and deforming the stud-receiving hole such that its inner
surface grips the transformer stud.
The present invention also relates to a connector assembly for
attaching at least one conductor to a transformer stud, comprising:
- an electrically conductive conductor connector comprising at least one
conductor attachment point for said at least one conductor;
- a mounting block made of electrically conductive material;
- a deformable stud-receiving hole in the mounting block, this stud-
receiving hole having an inner surface and dimensions suitable to
receive the transformer stud;
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- a first connector-and-block interconnecting fastener dedicated, when
tightened, to connect the conductor connector to the mounting block;
and
- a second fastener having both a connector-and-block interconnecting
portion and a hole-deforming portion, said second fastener, when
tightened, simultaneously connecting the conductor connector to the
mounting block and deforming the stud-receiving hole such that its inner
surface grips the transformer stud.
The foregoing and other objects, advantages and features of the
present invention will become more apparent upon reading of the following
non restrictive description of illustrative embodiments thereof, given by way
of example only with reference to the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
In the appended drawings:
Figure 1 is a perspective view of a first illustrative embodiment of the
transformer stud mounting block according to the invention, disposed on a
transformer stud;
Figure 2 is a front, elevational and cross sectional view of the
transformer stud mounting block of Figure 1;
Figure 3 is a perspective view of an illustrative embodiment of an
assembly according to the present invention for attaching electrical
conductors to a transformer stud;
Figure 4 is a bottom view of the assembly of Figure 3; and
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Figure 5 is a perspective view of a second illustrative embodiment of
the transformer stud mounting block in accordance with the present
invention.
5 DETAILED DESCRIPTION OF THE ILLUSTRATIVE EMBODIMENTS
Illustrative embodiments of the transformer stud mounting block will
now be described.
Referring to Figure 1, a transformer stud mounting block 2 is
illustrated. The mounting block 2 is fabricated from an electrically
conductive material which lends itself well to casting and/or machining,
such as aluminium, brass or copper. To provide enhanced resistance to
corrosion and oxidisation while maintaining conductive properties following
machining, the outer surface of the mounting block 2 can be plated with a
conductive protective coating 4. For example, the protective coating 4 can
be deposited on the outer surface of the mounting block 2 by means of well
known techniques such as anodising or electroplating techniques.
A transverse cylindrical stud-receiving hole 6 is machined through
the mounting block 2 from the front face 8 to the rear face 10 thereof. The
stud-receiving hole 6 has a diameter so adjusted that a stud 12 of a
transformer can be freely inserted into the hole 6, fitting snugly against the
inner surface 14 of the hole 6.
The transformer stud 12 is generally cylindrical and made of a
conductive material such as aluminium. Stud 12 is typically embedded in
the transformer housing 16, and protrudes therefrom. The outer surface 18
of a transformer stud 12 is often machined with a thread (not shown), or
with a series of longitudinal, parallel and equally spaced apart grooves 20
arranged around the circumference of the transformer stud 12. The
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grooves 20 improve the grip exerted by the inner surface 14 of the stud-
receiving hole 6 on the transformer stud 12. In an alternative embodiment,
the inner surface 14 of the stud-receiving hole 6 may also be machined
with a similar complementary grooved pattern.
Referring to Figure 2 in addition to Figure 1, in order to securely
fasten the mounting block 2 onto the transformer stud 12, a crimping slot
22 is machined in the mounting block 2 from the side face 24 to the stud-
receiving hole 6 in such a manner that the median plane of the slot 22
intersects with the axis of the hole 6. A first cylindrical bolt-receiving
hole 26
extends through the mounting block 2 from the lower face 28 to the upper
face 30. Hole 26 is perpendicular to both the hole 6 and the crimping slot
22. The inner surface 32 of the upper section of hole 26 located above the
crimping slot 22 is threaded. The surtace 34 of the lower section of hole 26
located below the crimping slot 22 is smooth and presents a diameter
slightly larger than the threaded inner surface 32. A first bolt 36 having a
head 38 and a threaded shank 40 is freely inserted through the lower
section of hole 26 and is screwed into the threaded inner surtace 32 of the
upper section of hole 26.
Tightening the first bolt 36 with the head 38 applied to the lower face
28 of the mounting block 2 causes the upper and lower inner faces 52, 54
of the crimping slot 22 to be deflected towards one another, thereby
reducing the diameter of the stud-receiving hole 6. By placing the mounting
block 2 on a transformer stud 12 and tightening the first bolt 36, the
transformer stud 12 can be gripped by the inner surface 14 of the stud-
receiving hole 6. A curved middle portion of the upper face 30 of block 2 is
coaxial with the stud-receiving hole 6, and allows deformation of the inner
surface 14 of the stud-receiving hole 6 caused by tightening of the first bolt
36 to remain uniform over a larger portion of the circumference of the inner
surface 14. By distributing the deformation over a larger region, as opposed
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to concentrating it in one localised zone (which is typically the effect of
using retaining screws as disclosed in the prior art), the pressure exerted
by the inner surface 14 on the outer surface 18 of the transformer stud 12
remains even over a larger region, thereby improving contact between the
two surfaces. This additionally decreases the possibility of oxidisation build-
up between the two surfaces thereby improving electrically conductive
performance.
A second cylindrical bolt-receiving hole 42 has an inner threaded
surface 44 to receive a second bolt 46. Hole 42 is generally parallel to hole
26 and extends from lower face 28 to upper face 30. This second bolt 46 is
also provided with a head 48 and a threaded shank 50 which can be
screwed into threaded hole 42.
Referring now to Figures 3 and 4, the second bolt 46 is dedicated to
secure the electrical pad-mount connector 56 to the mounting block 2. The
first bolt 36 also contributes to secure this electrical pad-mount connector
56 to the mounting block 2. As shown in Figure 3, the pad-mount connector
56 presents the general configuration of a parallelepiped and is fabricated
from a piece of electrically conductive material which lends itself well to
casting and machining, such as aluminium, brass or copper. To provide
enhanced resistance to corrosion and oxidisation following machining while
rnaintaining the required electrically conductive properties, the outer
surface of the pad-mount connector 56 can be plated with a conductive
protective coating 58, the protective coating 58 being deposited on the
outer surface by well known techniques such as, for example, anodising
and electroplating techniques.
Two parallel series of conductor attachment points 60 are machined
in the pad-mount connector 56. Each conductor attachment point 60
comprises a conductor-receiving hole 61 extending from the upper face 62
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of the pad-mount connector 56 to the lower face 64 thereof. Additionally,
each conductor attachment point 60 comprises a threaded screw-receiving
hole 66 extending through the pad-mount connector 56 from a side face 68
(or 70) thereof to the corresponding hole 61. The axes of the corresponding
holes 61 and 66 are perpendicular and intersect with each other. A set
screw such as 72 is engaged with the thread of each hole 66. The
diameters of the conductor-receiving holes 61 and screw-receiving holes
66 are approximately the same, although the inner surfaces of the screw-
receiving holes 66 are formed with a thread for accepting the set screws
72. In the illustrative embodiment of Figure 3, the set screws 72 are
headless Allan-type machine screws.
As illustrated in Figure 4, a conductor such as 74 is connected both
mechanically and electrically to the pad-mount connector 56 by first
stripping the dielectric covering 76 from the conductor 74 thereby exposing
a short end section of wire 78. The short end section of wire 78 is inserted
into one of the conductor-receiving hole 61 and the set screw 72 tightened.
The set screw 72 has a raised nipple 80 on the end thereof which comes
into contact with the short end wire section. As the set screw 72 is
tightened the section of wire 78 is pressed between the raised nipple 80
and the inner surface 82 of the conductor-receiving hole 61. The short end
section of wire 78 is then deformed, thereby increasing the surface and
quality of the contact with the inner surface 82. Through further tightening
of the set screw 72 the short section of wire 78 is held firmly within the
conductor-receiving hole 61 of the conductor attachment point 60. In an
illustrative embodiment the conductor 74 is stranded to facilitate
deformation, thereby improving the quality of contact.
Additionally, further conductor attachment points such as 84 for
smaller gauge wires are included to increase the versatility of the
assembly.
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Referring to both Figures 3 and 4, the pad-mount connector 56
includes a proximal, integral connection tongue 86 through which the pad-
mount connector 56 is secured to the mounting block 2. To this end, tongue
86 is formed with a pair of holes extending perpendicular to this tongue 86
from the top face 92 to the bottom face 88 thereof. The bolts 36 and 46 are
inserted in these holes and screwed into the threaded bolt-receiving holes
26 and 42, respectively. Washers such as 90 are interposed between the
bolt heads 38 and 48 and bottom face 88 of the tongue 86. As the bolts 36
and 46 are tightened, the heads 38 and 48 exert pressure on the washers
90 which in turn brings the top face 92 of the connecting tongue 86 into
contact with the lower face 28 of the mounting block 2, thereby establishing
a conductive path across the interface between faces 28 and 92
(connector-and-block interconnecting portion of the fastener including the
bolt 36 and the threaded bolt-receiving hole 26 (threaded inner surface
32)). Tightening of the bolt 36 further causes the upper and lower inner
faces 52, 54 of the crimping slot 22 to be deflected towards one another,
thereby reducing the diameter of the stud hole 6 and gripping the
transformer stud 12 (hole-deforming portion of the fastener including the
bolt 36 and the threaded bolt-receiving hole 26 (threaded inner surface
32)).
To subsequently remove the mounting block 2 from the transformer
stud 12, one has only to loosen bolt 36 and thereby free stud 12 from hole
6. Then:
- dedicated bolt 46 still secures the pad-mount connector 56 firmly to the
mounting block 2; and
- loosened bolt 36 still contributes to fasten the pad-mount connector 56
to the mounting block 2, as least to prevent the pad-mount connector 56
to rotate about bolt 46.
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Figure 5 illustrates an alternative, illustrative embodiment of a
mounting block 100 in accordance with the present invention. The
mounting block 100 retains the essential characteristics of the mounting
block 2 as described hereinabove with reference to Figures 1-4. However,
5 in addition to first 102 and second 104 bolt-receiving holes, a third bolt-
receiving hole 106 is bored through the mounting block 100. Hole 106 is
parallel to holes 102 and 104 but is perpendicular to the stud-receiving hole
108. Also, hole 106 extends through the mounting block 100 from the lower
face 110 of the mounting block 100 to the upper face 112 thereof. The
10 inner surface 114 of the third bolt-receiving hole 106 located above the
crimping slot 116 is threaded while the lower portion (not shown) of the
third bolt-receiving hole 106 located below the crimping slot 116 has a
smooth surface and a diameter slightly larger than the diameter of the
threaded inner surface 114. A third bolt (not shown) having a head and a
threaded shank freely slides through the lower section of the third bolt-
receiving hole 106 and engages with the threaded inner surface 114 of the
third bolt hole 106.
In the same manner, an additional bolt-receiving threaded hole (not
shown) similar to bolt-receiving hole 104 could be provided. Such a bolt-
receiving hole would be bored through the mounting block 100, parallel to
holes 102 and 104 but perpendicular to the stud-receiving hole 108. Also,
that hole (not shown) would extend through the mounting block 100 from
the lower face 110 of the mounting block 100 to the upper face 112 thereof,
but on the side of hole 108 opposite to the crimping slot 116. An additional
bolt (not shown) having a head and a threaded shank would extend
through an additional hole in the connecting tongue 86 (Figure 3 and 4) and
engage the additional threaded hole to better secure this connecting
tongue 86 to the mounting block 100.
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Tightening the third bolt (not shown) will cause deflection of the
upper and lower inner faces 118 and 120 of the crimping slot 116 towards
one another, thereby reducing the diameter of the stud hole 108. This effect
adds to a similar effect produced by a bolt (not shown) which is inserted in
the bolt-receiving hole 102 and tightened. In this manner, the inner surface
122 of the stud-receiving hole 108 exerts a tighter and more reliable grip on
the transformer stud 124 previously inserted into the stud-receiving hole
108. Also, this produces a larger surface of contact between the mounting
block 100 and the transformer stud 124.
Although the present invention has been described hereinabove by
way of illustrative embodiments thereof, these embodiments can be
modified at will, within the scope of the appended claims, without departing
from the spirit and nature of the subject invention.
