U.S. patent number 3,775,025 [Application Number 05/222,824] was granted by the patent office on 1973-11-27 for constant pressure pumping unit.
This patent grant is currently assigned to Maher Corporation. Invention is credited to Edward John Maher, Denis L. Maher, Jr..
United States Patent |
3,775,025 |
Maher, Jr. , et al. |
November 27, 1973 |
CONSTANT PRESSURE PUMPING UNIT
Abstract
A pumping unit is disclosed for use with water delivery systems
where the demand is variable. The unit has first and second pumps
with the drive of the first pump variable and operable to provide a
constant pressure at any speed while the drive of the second pump
provides a constant speed therefor. The drive of the first pump is
responsive to the pressure established by it in the system so that
its speed varies with the demand as measured by said pressure. A
control for the drives includes control circuitry having a switch
responsive to pressure in the system established by the unit and
having high and low pressure limits and placing the second pump in
service only when a predetermined high pressure cannot be
maintained by the first pump.
Inventors: |
Maher, Jr.; Denis L. (Woburn,
MA), Maher; Edward John (Woburn, MA) |
Assignee: |
Maher Corporation (North
Reading, MA)
|
Family
ID: |
22833842 |
Appl.
No.: |
05/222,824 |
Filed: |
February 2, 1972 |
Current U.S.
Class: |
417/7; 417/216;
417/426; 417/12; 417/287 |
Current CPC
Class: |
F04B
49/08 (20130101); F04D 15/0066 (20130101); G05D
16/2073 (20130101); F04D 15/0072 (20130101) |
Current International
Class: |
F04D
15/00 (20060101); F04B 49/08 (20060101); G05D
16/20 (20060101); F04b 041/06 () |
Field of
Search: |
;417/2,5,7,12,286,287,216,426 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Croyle; Carlton R.
Assistant Examiner: Sher; Richard
Claims
We claim:
1. A pumping unit for a water delivery system where the demand is
variable, said unit comprising first and second pumps, a drive for
each pump, the drive for the first pump including a constant speed
motor and pressure responsive means operable to vary the drive
speed to provide a constant pressure throughout a wide range of
system demands, the drive for the second pump including a constant
speed motor, a delivery conduit section with which the outlets of
both pumps and the pressure responsive means of the first pump
drive are in communication, a control circuit for said drives
including a pressure responsive switch having low and high pressure
positions and said conduit section includes means in communication
with said pressure responsive means of said first pump drive and
with said switch utilizing the pressure in said section as a
measure of the demand on said system, said control including
circuitry in control of both motors and operable to place said
second pump in service only when a predetermined high pressure
cannot be maintained by the operation of said first pump and means
responsive to a zero speed of the variable drive to de-energize it
for a predetermined interval.
2. The pumping unit of claim 1 and means operable to terminate the
operation of the second pump after a predetermined time interval
when the switch is brought into its high pressure position to
ensure that the predetermined high pressure is re-established and
not the result of a surge.
3. The pumping unit of claim 1 and a vacuum pump connected to the
delivery system at the intake side of said pump, and said third
section includes an additional lead including a normally open
switch, a connection with the intake side of said system operable
to close said switch in response to suction, and a relay in said
additional lead operable to place the vacuum pump in operation.
4. A pumping unit for a water delivery system where the demand is
variable, said unit comprising first and second pumps, a drive for
each pump, the drive for the first pump including a constant speed
motor and pressure responsive means operable to vary the drive
speed to provide a constant pressure throughout a wide range of
system demands, the drive for the second pump including a constant
speed motor, a delivery conduit section with which the outlets of
both pumps and the pressure responsive means of the first pump
drive are in communication, and circuitry including a first section
including the motor (9) of the first pump, a second section
including a pressure responsive switch (26) having a low-pressure,
high-demand position and a high-pressure low-demand position, and
means (24) in control of said switch effective to operate it to be
responsive to the pressure in said system as a measure of the
demand on said system, said third section including means (68, 68A,
68B, 68C, 69, 69A, 56) responsive to a zero demand and operable to
open the first section relative to its motor, a relay (67) included
in the third section in the high-pressure, low-demand position of
said switch and operable to open the second section relative to its
motor and means (66) and (55) in the low-pressure, high-demand
position thereof operable to close the first and second sections of
the circuit relative to their motors.
5. The pumping unit of claim 4 in which the first section includes
a lead (39) provided with a normally open switch (55A), the second
section includes a lead (42) provided with the normally open switch
(66A) and a normally closed switch (67A), the means included in the
third section of said low-pressure, high-demand position include
first and second parallel elements (55, 66), the first element (55)
operable when energized to close the normally open switch (55A) of
the first section and the second element (66) operable when
energized to close the normally open switch (66A) of the second
section, and the means (67) included in the third section in said
high-pressure, low-demand position operable when energized to open
the normally closed switch (67A) of the second section.
6. The pumping unit of claim 4 in which said second section
includes a second lead (41) provided with a normally open switch
(57B) and the first section includes a relay (57) operable to close
said normally open switch (57B) when the first section is closed
relative to its motor.
7. The pumping unit of claim 6 in which the first lead (42) of the
second section includes a relay (64), the second lead (41) of the
second section includes a normally open switch (64A) closed when
the last mentioned relay is energized, and a connection (65)
between said first and second leads between the two switches of
each of them to provide a holding circuit for said first lead relay
whereby, in said high-pressure, low-demand position, the second
circuit is opened relative to its motor by the relay (67) then
placed in the circuit by said pressure responsive switch (26), said
last named relay being of a time delay type.
8. The pumping unit of claim 4 in which the means responsive to the
zero demand includes a normally closed switch (56A) in the first
section, and a self-setting timer (56) operable to effect a cycle
for said switch whenever a zero speed exists in which said switch
(56A) is opened and then closed after a predetermined interval and
to repeat said cycle as long as said zero demand exists.
9. The pumping unit of claim 8 in which the means responsive to the
zero demand includes a switch (63B) and the second switch includes
a relay (63) operable to open said switch (63B) whenever said
second section is closed relative to its motor.
10. The pumping unit of claim 8 in which the means responsive to
the zero demand includes a normally closed switch (55B) with which
the timer (56) is in series and the first section includes a relay
(55) operable to open said switch whenever the first circuit
section is closed relative to its motor.
11. The pumping unit of claim 4 in which the third section includes
a first lead (46) provided with a relay (68) and closed by said
means at said zero demand, a second lead (43) including first and
second normally closed switches (63B and 68A) and a relay (69), and
a third lead (44) including a normally closed switch (55B), a
normally open switch (69A), and a self-setting timer (56) operable
to open said first section relative to its motor for a
predetermined time interval, means controlled by said switch (26)
in its high-pressure, low-demand position to open said third lead
(44) and means controlled by said second section to open said
second lead (43) whenever said section is closed relative to its
motor.
12. The pumping unit of claim 4 in which both motors include
circuits having a series of pairs of parallel leads each having a
normally open switch, one lead of each pair effecting a voltage
reduction, and each of the first two sections includes a first
relay operable to close the normally open switch of the reduced
voltage leads of the appropriate one of the motor circuits, a
parallel time delay relay and a parallel normally open switch
closed by the time delay relay and a third relay operable to close
the normally open switch of the other lead of each pair of the
appropriate motor circuits.
13. The pumping unit of claim 12 in which each of the first two
sections includes a manually operable switch having two operating
positions in the first of which it is subject to control by the
third section and in the second of which it is independent thereof.
Description
BACKGROUND OF THE INVENTION
In fluid delivery systems, particularly water systems for
relatively tall buildings, the maintenance of a predetermined
pressure has presented problems because widely fluctuating demands
make control by a single pump impractical.
Multi-pump arrangements have been employed with constant speed
drives but these have failed to provide sufficient flexibility to
enable economical and satisfactory operations throughout the range
of expected demands to be effected.
THE PRESENT INVENTION
The objective of the present invention is to provide a pumping unit
that meets, with minimum power requirements, the full range of
demands placed on a water delivery system of which those of tall
buildings are examples.
This objective is attained by providing a pumping unit including
first and second pumps. The drive of the first pump is variable and
provides for a constant pressure at any speed and is responsive to
the pressure in the system as a measure of the demand thereon while
the drive for the second pump provides for a constant pump speed.
The unit includes control cotrol having control circuitry for both
pumps and includes a switch responsive to the pressure in the
system and having high and low pressure limits and providing for
the operation of the second pump at the low pressure limit and the
discontinuance of its operation when a predetermined high pressure
in the system is established.
In operations, where a high pressure demand exists, the second pump
comes into service and control means are provided to permit both
pumps to remain in operation but with the first pump throttled back
as the pressure builds up thus ensuring economy in operation and
maintenance of adequate pressure in the system with extremely
limited variations in the pressure in the delivery system.
THE PREFERRED EMBODIMENT OF THE INVENTION
In the accompanying drawings, the preferred embodiment of the
invention is shown of which
FIG. 1 is a plan view of the pumps, their connections, and their
control valves;
FIG. 2 is a side view thereof; and
FIG. 3 is a schematic view of the control circuitry.
A pumping unit includes a frame 5 on which pumps 6 and 7 are
mounted. These may be, in the disclosed embodiment, vertical
turbine or horizontal centrifugal pumps having one, two, or three
variable speed or constant speed pumps or combinations thereof.
The pump 6 is coupled to an adjustable speed drive, generally
indicated at 8 and including a constant speed motor 9 capable of
producing full motor torque from full input motor speed to zero
R.P.M. A satisfactory drive, of the hydro-viscous wet clutch type
and utilizing a hydraulic control, is manufactured by Borg-Warner
Corporation of Tulsa, Oklahoma, and sold under its trademark
"Infi-Drive." The details of the device are not shown herein but
are disclosed in a copyrighted print published by the manufacturer.
The pump 7 has, for its drive, a constant speed motor 10.
The water supply system 11 has oppositely opening check valves 12
and 13 between which there is a T 14 connected to the manifold 15
with which the intakes of the pumps 6 and 7 are in communication
when their valves 16 and 17, respectively, are open. The check
valve 12 prevents flow from the manifold 15 to the supply system
11. The manifold 18, to which the outlets of the pumps 6 and 7 are
connected by valves 19 and 20, respectively, is connected by a T 21
to the water delivery system 22 which is provided with a discharge
conduit generally indicated at 23.
The discharge conduit 23 has a hydraulic line 24 connected to the
variable orifice controller of the drive 9 to transmit the pressure
existing in the delivery system 22 thereto thereby causing the
speed of its motor 9 to be automatically varied to maintain the
wanted pressure in the delivery system. The discharge conduit 23
also is provided with a hydraulic line 25 in communication with a
pressure responsive switch generally indicated at 26, see FIG. 3,
in a lead 27 and operable to connect it to a lead 27A when a
predetermined high pressure exists in the delivery system 22 and to
connect the lead 27B to the lead 27 when that pressure is not
maintained.
In accordance with the invention, the pump 6, due to the fact that
it is operative to maintain a constant pressure throughout the
speed range of its drive 8, is able to meet a substantial range of
demands on the delivery system 22. If the demand exceeds the
capacity of the pump 6, the pressure responsive switch 26 closes
the circuit 27B and the pump 7 is brought into service and operates
at its full capacity. The added capacity of the pump 7 is reflected
in a lowered demand on the pump 6 and its drive 8 is accordingly
throttled back as the pressure in the delivery system 22 increases.
Should the demand drop enabling the switch 26 to again connect the
leads 27 and 27A, the pump 7 drops out of service.
The operation of a pumping unit in accordance with the invention is
more fully detailed in connection with the discussion of the
circuitry schematically shown in FIG. 3 which also includes a
vacuum pump, employed when a suction lift is needed. The vacuum
pump is not shown but the motor by which it is driven is generally
indicated at 29 in FIG. 3.
In FIG. 3, a generally indicated circuit 30 includes the circuit 31
for the pump motor 9, the circuit 32 for the pump motor 10, the
circuit 33 for the vacuum pump motor 29, and the primary of a
transformer 34. The circuit 31 has parallel leads 31A and 31B and
the circuit 32 also has parallel leads 32A and 32B. The leads 31B
and 32B are reduced voltage leads.
The secondary of the transformer 34 includes a control circuit,
generally indicated at 35 under the control of a switch 36 and
provided with parallel leads 37, 38, 39, 40, 41, 42, 27, 43, 44,
45, and 46. The lead 37 is provided with a lamp 47 indicating that
the power is "on" while a normally closed temperature responsive,
safety switch 48 controls the other leads.
The leads 38 and 39, which comprise the first section of the
circuit, control the operation of the motor 9 and are under the
control of a common switch 50 having three positions, an "off"
position, a first position in which the control of the operation of
the motor 9 is manual and a second position providing for the
automatic control thereof. For that reason, the leads 38 and 39 are
interconnected at 51 with the lead 38 having a relay 52 and
parallel leads 38A and 38B connected to the lead 39 which then
joins the lead 38. The lead 38A has a timer 53 while the lead 38B
has a lamp 54 to show that the motor 9 is energized and the pump 6
in service which results when the relay 52 is energized as it then
closes its switches 52A in the starter leads 31B of the motor
circuit 31.
The lead 39 has, between the switch 50 and the connection 51, the
normally open switch 55A of the relay 55 located in the parallel
lead 127B of the lead 27B, a normally open switch 52B of the relay
52 in parallel with the switch 55A, and the normally closed switch
56A opened by the timer 56 after a predetermined interval, fifteen
minutes by way of example. The timer 56 is located in the parallel
lead 44A of the lead 44. While the other timing means may be and
desirably are relays, the timer 56 is motor driven and
self-resetting, such a model No. HP518A6, made available by Eagle
Signal, a division of Gulf & Western Industries, Inc.,
Davenport Iowa.
The lead 39 has a normally open switch 53A closed after a brief
delay, 10 seconds by way of example, when the timer 53 is
energized, and the relay 57, which, when energized, closes the
normally open switches 57A of the starter leads 31A of the motor
circuit 31.
It will thus be apparent that when the switch 50 is set in its
first or manually position to utilize the entire lead 38, as when
the system is to be filled, the starter leads 31B are first closed
and, after a brief delay, the starter leads 31A are also
closed.
The leads 40, 41, and 42, which comprise the second section of the
circuit, control the operation of the motor 10 of the pump and are
under the control of a manually operable switch 58 that, like the
switch 50, has three positions, an "off" position, a first position
in which the operation of the motor 10 is manually controlled and a
second position in which the operation thereof is automatic.
The lead 40 includes a relay 59 and parallel leads 40A and 40B
connected to the lead 41 which then joins the lead 40. The lead 40A
has a timer 60 and the lead 40B has a light 61 to indicate when the
motor 10 and, accordingly, the pump 7 is in service. The relay 59
is operable, when energized, to close the normally open switch 59A
of the starter leads 32B of the motor circuit 32.
Between the switch 58 and the relay 59 and the parallel leads 40A
and 40B, there is a connection 62 placing the normally open timer
switch 60A and a relay 63 in the lead 41 in parallel with the relay
59 and said parallel leads. The relay 63, when energized, as it is
after a short, say ten second, dwell once the timer 60 is
energized, is operative to close the normally open switches 63A of
the leads 32A of the circuit 32.
Thus, when the switch 58 is set for manual control to utilize the
entire lead 40, as when the delivery system is being filled, the
starter leads 32B are closed in advance of the starter leads
32A.
The lead 41 has, ahead of the switch 58 a pair of normally open
switches, the switch 64A closed when the relay 64 in the lead 42 is
energized and the switch 57B closed when the relay 57 is energized.
A connection 65 between the leads 41 and 42 is located between the
switches 64A and 57B of the lead 41 and between a normally open
switch 66A and a normally closed switch 67A in the lead 42.
The switch 66A is closed for a short predetermined interval, say 30
seconds, when the timer 66 in the lead 27B is energized and the
switch 67A is opened after a short delay, say 15 seconds, after the
timer 67 in its lead 27A is energized.
The leads 27, 43, 44, 45, and 46 comprise a third section and the
lead 43 has the normally closed switches 63B and 68A and a relay
69. The switch 63B is closed when the pump 7 is not in service and
the switch 68A is closed when the speed of the drive 8 is zero. To
this end, the lead 46 is provided with a relay 68 including a
pressure responsive switch 68B held open by oil pressure delivered
through the hydraulic line 68C from the variable orifice controller
of the drive 8. The lead 44 includes the normally closed switch 55B
which is open when the relay 55 is deenergized, the normally open
switch 69A of the relay 69 and the timer 56 which is a self-setting
type and operating on a 15 minute cycle, for example.
The lead 45 includes a vacuum operated switch 70 and a relay 71
which when energized closes the switches 71A in the motor circuit
33.
Assuming that the switches 50 and 58 have been set to provide for
automatic control of the operation of the pumps, i.e., the switch
50 connecting the lead 38 to the lead 39 and the switch 58
connecting the lead 41 to the lead 42 and assuming the pressure in
the system is at the predetermined high pressure level, the switch
26 in the lead 27 connects the lead 27A thereto and the timer 67 is
then enegized, opening the switch 67A in the lead 42 thereby
deenergizing the relay 64. Under these conditions the motor 10 for
the pump 7 is deenergized as the switch 66A is now open.
Assuming that the speed of the drive 8 is then zero, the relay 69
is energized closing its switch 69A in the lead 44 so that the
timer 56 is energized and at the end of the predetermined period,
say 15 minutes, the normally closed switch 56A in the lead 39 is
opened thereby deenergizing the relay 52 and the timer 53. It
should be noted, however, that if the demand increased during the
15 minute period, the switch 56A would close and the timer 56 be
reset.
Assuming that the pressure drops below the predetermined high
level, the leads 27B and 127B become both connected to the lead 27
by the switch 26. As a consequence the relay 55 is energized
closing the relay switch 55A to maintain the pump 6 in operation
with the consequent closing of the switch 52B and the starting of
the timer 66 which for a short period, say 30 seconds, closes the
lead 42 starting the motor 10 in operation since the relay switch
57B is now closed.
As before stated once the pressure reaches the high level the lead
27A is again connected to the lead 27 and the timer 67 started
which will in a few moments open the lead 42 to the relay 64.
It will thus be seen that, in automatic operation, the pump 6 stays
alone in service until the demand is such that it is unable to
maintain the pressure in the delivery system at the required high
level. For the reasons before stated, the motor 10 then is started
and the added capacity of the pump 7 enables the demand to be met
with the speed of the pump 6 dropping back and with the motor 9
remaining in service until the speed of the drive 8 drops to
zero.
* * * * *