Note: Descriptions are shown in the official language in which they were submitted.
This invention relates to submersible motors
- and particularly to seals for submersible motors.
Background and Summary of the Invention
In submersible electrical devices such as
motors, it is required that the electrical leads be
insulated or sealed from the surrounding water. It has
` been the practice in the past to use various methods of
bringing out a jacketed electrical lead from inside a
cavity required to be sealed from water or other liquids
and for connection to an outside electrical power source.
,; Such a sealing requirement is common where it is required
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~; to immerse in water an electrical appliance or device
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~ such as a submersible sump pump so that it is necessary
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to seal the lead at the point where it emerges from the
pump internal connection or switch cavity. Any such
method of sealing has also been required to meet a
strain relief pull specification as prescribed by
~ agencies like the Underwriter Laboratories and
,~ Canadian Standard Association.
Past efforts to meet the sealing and strain
pull requirements have largely centered around three
basic approaches all workable but possessing disadvantages
one of which being excessive costs. These current
methods include ~1) the use of the well known threaded
compression screw to effect a seal to the outer diameter of
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the lead which is emerging from a threaded hole in the
cavity, (2) the screwing down of a metal plate to
compress a follower washer against a rubber ring seal
which in turn compresses against the outer diameter of
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the lead and (3) the potting of an epoxy resin around
the lead and bonding to the internal diameter of the
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hole in the cavity.
The costs involved in using threaded components
- 10 is obvious and is amplified by the assembly of multiple
-~ parts. Another disadvantage is the excess of radially
~ inward force due to the high mechanical advantage of the
-~ threads which sometimes create a thinning down of the
lead insulation to the point where it becomes susceptable
to mechanical abuse. Potting processes are at best
inconvenient and often messy creat~ng bottlenecks in
high production assembly due to the need for application
of heat and/or long cure times.
The present invention is intended to eliminate
the aforementioned disadvantages by using unique and
simple means for effecting a suitable strain relief and
seal at the location where it is required to have a
jacketed lead or cord emerge from a cavity wherein
electrical connections are made.
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Description of the Drawinqs
Fig. 1 is a part sectional elevational view
of a submersible pump motor embodying the invention.
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Fig. 2 is a fragmentary sectional view on an
enlarged scale of a portion of the submersible pump motor
in Fig. 1.
` Fig. 3 is a perspective view of a part of a
sealing arrangement according to the invention.
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Fig. 4 is a perspective view of another sealing
arrangement according to the invention.
Fig. 5 is a sectional view showing the method
of assembly of the parts of the motor shown in Fig. 2.
Fig. 6 is a sectional view of a modified sealing
arrangement in accordance with the invention.
- 15 Fig. 7 is a sectional view of a further modified
~ sealing arrangement in accordance with the invention.
; Description
Referring to Fig. 1, the invention relates to
submersible motors such as shown in Fig. 1 which includes
a housing comprising a first part 10 for a motor that
has an output shaft 11 that may operate a pump impeller
- or the like. A second part 12 of the housing is
;~ removably mounted on housing 10 by screws 13a (one
- of which is shown). Part 12 has a cavity in which
electrical connections are made between the leads from
the motor housing 10 and a jacketed outlet cord 13
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that includes wires 13b extending to a power source
and a breather tube 13c. In addition, the cavity of
second housing may include a pressure switch S to
which connections are made from the motor winding and
cord 13. The motor is adapted `to be mounted with
the shaft 11 at any angle.
The parts 10, 12 of housing 10 are preferably
made of water and heat resistant, dimensionally stable
material such as powdered iron or a glass reinforced
styrene modified polyphenylene oxide sold under the
trademark NORYL. It is necessary to provide a seal
between the cord 13 that contains wires 13b and
breather tube 13c and housing part 12 to the exterior
of the housing.
Referring to Fig. 2, the seal is provided
- between the cord 13 and the housing part 12 by a rubber
body or seal 15 that is compressed in an open ended
cavity 16 which has its open end extending inwardly of
the housing 12. The closed end of cavity 16 is formed
by a base 30 having an opening 31 through which cord
13 extends. Body 15 engages base 30. The body 15
is preferably made of acrylonitrile-butadiene rubber
sold under the trademark BUNA N and having a shore
durometer of 35 to 60 on the A scale so that it
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falls within the qualifications of soft rubber.
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Satisfactory results have been achieved with a rubber
having a durometer of 50.
As shown in Figs. 3-5, body 15 is first slipped
over cord 13 and then compressed for assembly by placing
;~ 5 the cavity 16 adjacent a fixture 17 having a tapered
;~ opening 18 and a tubular ram 19 of lesser diameter than
the tapered opening 18 in fixture 17. Since the wall of
the opening 18 tapers from a diameter larger than the
rubber body 15 to a diameter slightly smaller than the
cavity 16 when force is applied to ram 19 the rubber
seal 15 is progressively compressed and therefore easily
stuffed into the cavity 16. The opening 20 in ram 19 is
large enough to provide an outlet for the lead 13. If
desired, a lubricant may be used on the outside of the
; 15 body 15 to reduce the insertion force required.
The rubber seal dimensions and material hard-
ness are selected for a given jacketed lead size to
provide a high integrity sealed entry of the lead to
the cavity and ! due to the gripping action of the seal
on the lead, a pull resistance on the lead from the
outside of up to 35 pounds is attainable.
If greater resistance to pull is desired, a
simple wire hog ring 21 can be crimped to the lead and
against the seal as a final operation of the assembly.
As pull is exerted on the lead, the hog ring pulls into
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the seal creating a greater compression force on the
outer diameter of the lead and engages the seal axially
to prevent movement of the lead axially through the
seal.
Where the motor does not require a chamber
to contain the pressure switch or the like, the second
housing part 12 can be simplified as shown in Fig. 6.
In this form, the second housing part 12' of the motor
is removably mounted on housing part 10 and has a
cavity 26 with both ends open. The connections of
cord 13' to the wires 14 extending to the motor can be
made prior to insertion of the resilient compressible
body 15 in which case the housing 12' is first mounted
on housing part 10. Alternatively, the connections
can be made after insertion of body 15', in which case
the housing 12' is mounted on housing 10 after the
~; connections are made. In either case the body 15' is
inserted from the exterior of housing part 12' by an
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apparatus like that shown in Fig. 5. The resistance
to outward pull of the body 15' from cavity 26 is
achieved solely by the friction between body 15' and
the wall of opening 26. However a significant
resistance to pull can be achieved by use of a hog ring
27 clamped about the cord 13' on the interior of
housing so that it becomes embedded in body 15' when
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~ a force is applied to cord 13', as in the previous
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form of the invention. Further resistance to pull can
be achieved by staking all or portions of the end sur-
face as at 29.
:. 5 Where the motor housing is made in a single
part as shown in Fig. 7, housing 10' has a cavity 26'
for receiving the compressible body 15', as in the form
~,: in Fig. 6.
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