FIELD OF THE INVENTION
[0001] The present invention relates to a motorized air pumps and especially to low-pressure
air pumps without an air tank.
BACKGROUND OF THE INVENTION
[0002] Installed pipelines in buildings and underground can be rehabilitated without opening
structures or digging the ground. The trenchless rehabilitation allows a quick and
durable rehabilitation of pipes within buildings and underground pipelines. A resin
impregnated liner is installed in a pipe with an inversion drum using air pressure
to invert the liner into the pipe. Once the liner is installed air pressure is maintained
on an elevated level until the resin within the liner settles and the liner forms
a rigid pipe against the inner surface of the old pipe. A drop in air pressure inside
the pipe during a settling period may cause collapse of the liner which blocks or
at least severely restricts the flow of fluids in the pipe.
[0003] Air compressors have been used both for inverting the liner and to maintain air pressure
inside a newly installed liner. Air compressors typically produce compressed air having
high pressure but low output volume whereas high volume of low-pressure air would
be desirable. Pressure regulators are mandatory during lining operations due to the
high output pressure of air compressors. Typically about 50 kPa over the atmospheric
pressure is needed in lining operations and typical compressor produces output of
700 to 1000 kPa. A pressure level like that in a liner would tear the liner instantly
and it can happen due to malfunction in the pressure regulator.
[0004] Another problem is the output volume of air compressors. Typical portable electric
air compressors produce 20 to 100 litres/min of air. If there is a minor leak in a
newly installed liner, the air compressor might have to either run constantly or start
and stop every minute or so. Air compressors are not designed for that and their operating
life shortens significantly is this type of use. This either causes significant delays
or requires a spare unit at hand all the time.
[0005] There is also another problem when lining pipes of residential buildings. Air compressors
make a loud noise which tends to annoy residents of the building and sometimes one
of the residents unplugs the air compressor at night. This leads to a failed lining
and requires significant effort to remove the failed lining and reline the pipe.
BRIEF DESCRIPTION OF THE INVENTION
[0006] An object of the present invention is to provide a device for producing compressed
air that is more suitable for pipe lining operations than current air compressors.
[0007] One aspect of the present invention is an air pump system based on the idea of having
an air cylinder and a disc moving inside the cylinder along a rotatable shaft to provide
pumping action. The pumping action is achieved with a motor rotating the shaft and
a motor controller driving said motor. Both ends of the cylinder have inlet and outlet
valves so that back and forth movement of the disc is used for pumping air during
both movement directions of the disc.
[0008] The object of the invention is achieved with an air pump system of independent claim
1. Advantageous embodiments are presented in dependent claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] In the following the present invention is described in greater detail by means of
preferred embodiments with reference to the accompanying drawings, in which
Figure 1 illustrates an isometric view of an air pump system according to an embodiment
of the invention;
Figure 2 illustrates an isometric view of an air pump system according to an embodiment
of the invention without protective cover;
Figure 3 illustrates an isometric section view of an air pump system according to
an embodiment of the invention; and
Figure 4 illustrates detail A of Figure 3.
DETAILED DESCRIPTION OF THE INVENTION
[0010] Figures 1 and 2 illustrate an air pump system according to an embodiment of the invention
and Figures 3 and 4 are section views showing insides of the air pump system.
[0011] An air pump system according to an embodiment of the present invention comprises
an air cylinder which is delimited by a tubular side wall 10, a first end portion
11 and a second end portion 12. The tubular side wall is preferably a tube having
a circular cross-section and is made of metal or plastic, such as polyethylene or
HDPE. The tubular side wall can be for example HDPE pipe having an inner diameter
of 150-300 mm, e.g. 200 mm. The first end portion 11 and the second end portion 12
are made of metal or plastic, such as polyethylene or HDPE and attached to opposite
ends of the tubular side wall to create an air cylinder. A seal or gasket can be used
between the tubular side wall and said end portions to minimize leaking of air.
[0012] The air pump system also comprises a rotatable shaft 20. The shaft has a helically
grooved or threaded surface and the shaft extends from said first end portion 11 to
said second end portion 12 within the air cylinder. A motor 80 is provided and configured
to rotate the shaft 20. Power from rotating shaft of the motor 80 is delivered to
the rotating shaft 20 of the air pump system using conventional means, such as a belt,
a chain, a set of pinions or any combination of the previously mentioned.
[0013] The air pump system also comprises a disc 22 inside the air cylinder dividing the
air cylinder into two chambers, a first chamber 17 and a second chamber 18. The disc
22 is configured to move along said rotatable shaft 20 inside the air cylinder when
said rotatable shaft 20 is rotated. The disc is substantially the same size in diameter
as the inner diameter of the tubular side wall of the air cylinder. The space between
the disc 22 and the inner tubular side wall can be sealed or made small enough to
minimize air leak from one chamber to the other inside the air cylinder. The disc
22 is made of metal or plastic, such as polyethylene or HDPE. Preferably any contacting
parts between the disc 22 and the tubular side wall 10 of the air cylinder are metal-plastic
pairs so that metal always contacts and slides against plastic surface and plastic
always contacts and slides against metal surface. Sliding metal-metal and plastic-plastic
contacts are preferably avoided or eliminated.
[0014] The motor 80 is controlled and driven with a motor controller 90 which is preferably
a frequency converter. The motor controller 90 has preferably a using interface for
switching it on and off but also for changing settings, such as a desired pressure
level or air volume output. The motor controller 90 has preferably one or more inputs
for controlling the motor 80 based on external sensor data.
[0015] For example in an embodiment, the air pump system further comprises one or more sensors
for detecting location of the disc 22 inside the air cylinder. The motor controller
90 is configured to receive said location of the disc 22 and configured to control
the motor 80 based on said location of the disc 22. The motor controller e.g. detects
that the disc 22 is coming close to the first end portion and slows down rotating
speed and prepares to briefly stop the motor 80 and then change rotating direction
and accelerate again in order to move the disc 22 close to the second end portion
before returning back again. These functions can also be programmed into the motor
controller 90 to function without external sensors.
[0016] In another example that can be used with or without the functionality of the previous
example, the air pump system further comprises a pressure sensor configured to measure
air pressure within an outlet air channel 46, 48. The motor controller 90 is configured
to control the motor 80 based on the measured air pressure. A user of the air pump
system can e.g. set a desired pressure level using the motor controller 90 and the
motor controller drives the motor until the set pressure level is achieved based on
the air pressure sensor data or until the pressure level reaches a certain threshold
value based on the set pressure level.
[0017] The disc 22 that is driven with motor 80 changes volumes of the two chambers inside
the air cylinder as the disc 22 moves along the rotatable shaft 20. Thus, air has
to be provided into the air cylinder and moved out from the air cylinder. The air
pump system comprises inlet air valves 40 on the first end portion 11 and the second
end portion 12. The inlet valves 40 allow air to flow into the air cylinder when air
pressure inside the air cylinder is lower than air pressure outside the air cylinder.
Similarly, the inlet valves 40 prevent the flow of air from the air cylinder into
outside the air cylinder, even when air pressure inside the air cylinder is higher
than air pressure outside the air cylinder. The inlet valves 40 can consist of one
or more orifices on the first and second end portions and an elastic or a flexible
sheet or panel on the air cylinder side covering the orifices. Difference in air pressure
over the sheet or panel twists the sheet or panel and allows air to flow into the
air cylinder. Also other suitable well-known valve structures can be used instead.
[0018] The air pump system further comprises an outlet air channel 48 for output of pumped
air through air outlet 49. The air outlet 49 can be equipped with a Camlock connector
or some other type of connector for attaching a pipe liner to the air outlet 49. The
pumped air flows into the outlet air channel through outlet air valves 44, 45 on the
first end portion 11 and the second end portion 12. The outlet air valves allow air
to flow from the air cylinder into the outlet air channel 48 when air pressure inside
the air cylinder is higher than air pressure inside the outlet air channel 48. Similarly,
the outlet valves 44, 45 prevent the flow of air from the outlet air channel into
the air cylinder, even when air pressure inside the air cylinder is lower than air
pressure inside the outlet air channel. Said outlet air valves can comprise, for example,
an elastic element 45 outside the air cylinder and one or more orifices 44 in the
air cylinder, preferably on the tubular side wall. The elastic element can be for
example a rubber or silicone ring. In rest, or in balance state, the elastic element
45 blocks the one or more orifices 44 and prevents air flow through the orifices.
The elastic element 45 is configured to expand into the outlet air channel 48 and
allow air to flow from inside the air cylinder into the outlet air channel 48 through
said one or more orifices 44 when air pressure inside the air cylinder is higher than
air pressure in the outlet air channel 48. The outlet valves can also have construction
similar to the inlet valves. Also other suitable well-known valve structures can be
used instead.
[0019] When the motor 80 is rotated and the disc 22 moves within the air cylinder along
the rotatable shaft towards the first end portion 11, air pressure in the first chamber
17 tends to rise and air pressure in the second chamber 18 tends to fall as the disc
22 moves away from the second end portion 12. The outlet valves allow compressed air
in the first chamber to flow into the outlet air channel when air pressure rises enough.
Similarly, the inlet valves allow new air to flow in to the second chamber 18 when
air pressure in the second chamber 18 falls enough. As the disc 22 approaches the
first end portion 11, the rotation of the rotatable shaft 20 is stopped and rotation
direction of the motor is reversed and accelerated again. The disc 22 starts to move
back towards the second end portion 12 and the first chamber 17 that pumped air into
the outlet air channel 48 now draws new air in through the inlet valves 40 into the
first chamber 17 of the air cylinder. At the same time the second chamber 18, air
pressure starts to build up as the volume of the second chamber 18 decreases and eventually
air is pumped from the second chamber into the outlet air channel 48.
[0020] Compared to a traditional air compressor, the air pump system of a preferred embodiment
does not have a tank for storing high pressure air. In addition, air pressure in the
whole system, including the air pump system and a pipe liner attached to the air outlet
49, gradually builds up without having a dangerously high air pressure anywhere in
the system. Therefore pressure regulators are unnecessary and problems caused by malfunctioning
pressure regulators are non-existent. The air pump system has higher output volume
than an electric compressor of the same size and air pressure levels remain in the
air pump system remain on safe level during operation. Minor leaks when maintaining
air pressure in an installed liner can be compensated by slowly pumping air with the
air pump system. Noise level can be kept much lower than with an air compressor using
small volume high RPM piston.
[0021] In a preferred embodiment of the invention, the outlet air channel 48 or the air
pump system comprises one or more ducts 46 extending between the first end portion
11 and the second end portion 12 thereby creating a fluid connection between the first
end portion 11 and the second end portion 12 on outlet air channel side of the outlet
air valves 44, 45. Fluid connection in this context means that fluid can freely flow
between parts that have a fluid connection between them. In other words, the outlet
air channel is a continuous space into which air can be pumped from both end portions
11, 12 of the air pump system and from which the pumped air can exit through air outlet
49. Said one or more ducts are preferably rigid tubes attached to the first end portion
11 and the second end portion 12 and thereby forming part of a frame structure of
the air pump system but also delivering pumped air from one end portion to another
end portion. Said rigid tubes can also be used to tighten said end portions 11, 12
against opposite ends of the tubular side wall 10. In an embodiment, said one or more
ducts 46 can be any duct enabling flow of air between the first end portion 11 and
the second end portion 12 outside the air cylinder. Preferably the air outlet 49 connected
via outlet air channel 46, 48 to each of the outlet air valves 44, 45 of the air pump
system.
[0022] In an embodiment of the invention, the air pump system further comprises a safety
valve 42 in the outlet air channel 48. The safety valve is configured to release air
from the outlet air channel 48 if air pressure inside the outlet air channel reaches
a predetermined pressure level. The purpose of the safety valve is to protect a liner
attached to the air outlet 49 of the air pump system and also the air pump system
itself in case of a rare but possible failure that would increase air pressure inside
the outlet air channel.
[0023] In an embodiment of the invention the air pump system further comprises one or more
guides 16 for controlling position of said disc 22 and preventing rotation of said
disc 22. The purpose of the position controlling is to keep the disc 22 in a plane
perpendicular to rotation axis of the rotatable shaft 20. In an embodiment said one
or more guides 16 are rods or tubes extending inside the air cylinder from said first
end portion 11 through said disc 22 to said second end portion 12. Sais one or more
guides can include sleeves, collars or flanges attached to one side or both sides
of the disc 22 around said rods or tubes. Said rods or tubes can also be used to tighten
said end portions 11, 12 against opposite ends of the tubular side wall 10. The rods
or tubes are preferably made of metal or plastic, such as polyethylene or HDPE. Preferably
any contacting parts between the disc 22 (or possible sleeves, collars or flanges)
and the rods 16 in the air cylinder are metal-plastic pairs so that metal always contacts
and slides against plastic surface and plastic always contacts and slides against
metal surface. Sliding metal-metal and plastic-plastic contacts are preferably avoided
or eliminated.
[0024] In an embodiment, said one or more guides comprise a longitudinal recess or groove,
parallel to the rotatable shaft, on the inner wall of the tubular side wall 10 and
a matching protrusion on the periphery of the disc 22. In an embodiment, said one
or more guides comprise a longitudinal protrusion, parallel to the rotatable shaft,
on the inner wall of the tubular side wall 10 and a matching recess or a groove on
the periphery of the disc 22.
[0025] It will be obvious to a person skilled in the art that, as the technology advances,
that the inventive concept can be implemented in various ways. The present invention
and its embodiments are not limited to the examples described above but may vary within
the scope of the claims.
1. An air pump system comprising:
an air cylinder delimited by a tubular side wall (10), a first end portion (11) and
a second end portion (12);
a rotatable shaft (20) having a helically grooved or threaded surface and extending
from said first end portion (11) to said second end portion (12) within the air cylinder;
an outlet air channel (48, 49) for output of pumped air;
a motor (80) configured to rotate the rotatable shaft (20); and
a motor controller (90) for controlling the operation of the motor (80), wherein the
air pump system is characterized in that it further comprises:
a disc (22) inside the air cylinder dividing the air cylinder into two chambers (17,
18), which disc is configured to move along said rotatable shaft (20) inside the air
cylinder when said rotatable shaft (20) is rotated;
inlet air valves (40) on said first end portion (11) and said second end portion (12)
allowing air to flow into the air cylinder when air pressure inside the air cylinder
is lower than air pressure outside the air cylinder; and
outlet air valves (44, 45) on said first end portion (11) and said second end portion
(12) allowing air to flow from the air cylinder into the outlet air channel (48) when
air pressure inside the air cylinder is higher than air pressure inside the outlet
air channel (48).
2. An air pump system according to claim 1, wherein the outlet air channel (48) further
comprises one or more ducts (46) extending between said first end portion (11) and
said second end portion (12) thereby creating a fluid connection between said first
end portion (11) and said second end portion (12) on outlet air channel side of said
outlet air valves (44, 45).
3. An air pump system according to claim 1 or 2, wherein the air pump system comprises
an air outlet (49) connected via outlet air channel (46, 48) to each of the outlet
air valves (44, 45) of the system.
4. An air pump system according to any one of claims 1 to 3, wherein the outlet air channel
(48) further comprises a safety valve (42) configured to release air from the outlet
air channel (48) if the pressure inside the outlet air channel reaches a predetermined
pressure level.
5. An air pump system according to any one of claims 1 to 4, wherein the air pump system
further comprises a pressure sensor configured to measure air pressure within the
outlet air channel (48), wherein the motor controller (90) is configured to control
the motor (80) based on the measured air pressure.
6. An air pump system according to any one of claims 1 to 5, wherein the air pump system
further comprises one or more guides (16) for controlling position of said disc (22)
and preventing rotation of said disc (22).
7. An air pump system according to any one of claims 1 to 6, wherein said one or more
guides (16) are rods or tubes extending inside the air cylinder from said first end
portion (11) through said disc (22) to said second end portion (12).
8. An air pump system according to any one of claims 1 to 7, wherein said outlet air
valves comprise an elastic element (45) outside the air cylinder, wherein the elastic
element (45) is configured to expand into the outlet air channel (48) and allow air
to flow from inside the air cylinder into the outlet air channel (48) through one
or more orifices (44) of the air cylinder.
9. An air pump system according to any one of claims 1 to 8, wherein the air pump system
further comprises one or more sensors for detecting location of the disc (22) inside
the air cylinder.
10. An air pump system according to claim 9, wherein the motor controller (90) is configured
to receive said location of the disc (22) and configured to control the motor (80)
based on said location of the disc (22).
11. An air pump system according to any one of claims 1 to 10, wherein the tubular side
wall (10) of the air cylinder is made of plastic.
12. An air pump system according to any one of claims 1 to 11, wherein the tubular side
wall (10) of the air cylinder has a circular cross-section.