Pump with transfer tube
A pump uses tubular transfer members for transferring intake and/or exhaust air into the crankcase and/or between valve head chambers. The pump has compact 180° opposed pistons that minimize axial spacing between the pistons on the drive shaft and thereby reduces the shaking couple and noise from reciprocation. Each piston has its own eccentric element press-fit into the connecting rods so as not to occupy space between the pistons. The shaking couple can be further reduced for pistons of different masses by selecting the mass of the cup retainers to compensate for the difference in overall piston masses. The pump includes an improved cylinder sealing arrangement having a circumferential groove in an angled surface at the end of the cylinder. The pump also has a special cover and seal for closing the open neck of the pump crankcase and a multi-lobed valve stop.
This is a divisional of U.S. patent application Ser. No. 10/338,950 filed Jan. 8, 2003, now issued as U.S. Pat. No. ______.
STATEMENT OF FEDERALLY SPONSORED RESEARCH OR DEVELOPMENTNot applicable.
BACKGROUND OF THE INVENTIONThe present invention relates to pumps and in particular to compact piston pumps.
Pumps for medical applications, such as used in oxygen concentrators, generally need to be compact and quiet to operate indiscreetly in homes and hospitals. It is thus important to properly muffle the working air as well as to reduce vibration during operation of the pump.
One problem with conventional pumps is that they can create excessive noise and vibration as the piston(s) are reciprocated, especially if they are improperly balanced. One reason for this in opposed piston pumps is that the pistons may be coupled to the drive shaft by a single retainer or eccentric element between the connecting rods of the piston. Ordinarily, an eccentric element is mounted to the drive shaft and two nibs or bosses extend axially from each side of the eccentric element to mount the pistons to the drive shaft. A moment, or shaking couple, arises as the drive shaft is turn because of the axial spacing between the pistons.
Another problem with conventional pumps is sealing the crankcase and cylinder(s). Improper sealing of the cylinders to the crankcase or the valve head(s) can cause pressurized air to leak to the outside of the pump, which both reduces pumping efficiency and makes noise. Typical sealing arrangements are either prone to leakage or require costly machining operations on the valve plate or other valve mounting member. Also, many crankcases are made with open necks to allow the pistons to be slid into the crankcase easily during assembly. Typically, the openings in the neck terminate at the cylinders, which have curved exterior surfaces. This makes sealing the crankcase difficult and typically requires separate seals in addition to that sealing the end of the crankcase, thus increasing assembly complexity and creating a potential leak path between the neck seals and the end seal.
Yet another problem confronting the design of low-noise pumps is properly muffling the working fluid chambers, e.g., the intake and/or exhaust chambers of the valve heads. This can be done by attaching a muffler element to the valve head either directly or via suitable hoses. Another technique is to run the exhaust air into the crankcase on the non-pressure side of the piston head. In this case, if the crankcase is closed and the pistons are in phase, the crankcase will usually be vented through a muffler to avoid generating pulsations in the pump. Even using the later technique, the valve heads are usually exhausted through hoses leading to the crankcase, which is vented through a muffler directly mounted to the crankcase or at the end of a hose.
Accordingly, an improved pump is needed which addresses the aforementioned problems.
SUMMARY OF THE INVENTIONThe invention provides a pump with one or more transfer tubes that communicate through one or more passageways in the crankcase for passing working fluid from one or more valve head chambers to the crankcase or to another valve head chamber. This provides integrated connections that are resistant to leakage and vibration, and provides opportunities for muffling, communication with the crankcase chamber and communication between chambers of multiple valve heads of the pump.
In one useful form, a pump of the invention has a crankcase defining a pumping chamber and a transfer opening. A valve mounting member mounted to the crankcase over the pumping chamber has at least one port in communication with the pumping chamber that is opened and closed by a valve mounted to the valve mounting member. At least one working fluid chamber defined at least in part by the valve mounting member on a side of the valve mounting member opposite from the pumping chamber is in communication with the pumping chamber through the port when the valve is open. A transfer port is in communication with the working fluid chamber outside of the pumping chamber. A transfer tube is connected at one end to the transfer port and at the other end to the crankcase transfer opening.
In a particular embodiment, the pump is a 180 degree opposed piston pump with both pistons located to one or the other side of the motor. The pump has a crankcase defining a chamber, a cylinder and a transfer opening. A valve plate type valve mounting member is mounted to the cylinder. The valve plate has at least one port in communication with the working air inside of the cylinder. The port is opened and closed by a valve mounted to the valve plate. A valve head is mounted to the valve plate to define the chamber. The valve plate further has a transfer port located in the chamber. The transfer tube is connected between the valve plate transfer port and the crankcase transfer opening.
Multi-cylinder pumps can have multiple transfer tubes connected to one or more transfer ports in the valve plate for each cylinder. For example, the transfer tubes can couple the intake or exhaust chambers to the inside of the crankcase, or they can couple multiple exhaust chambers together and/or multiple intake chambers together or the exhaust chamber of one valve head to the intake chamber of another valve head.
The crankcase can form integral passageways leading from one or more transfer openings at which the transfer tube(s) are connected. The passageway can open into the crankcase chamber in phase or run between transfer openings to join one or more chambers of one valve head with the chamber(s) of another valve head.
In preferred forms, the passageways and transfer tubes have opposing flat side walls. The transfer tube can be separate from the valve plate and the crankcase or formed as a unitary part of either the crankcase or the valve plate or both. Resilient seals can be disposed between the ends of the transfer tubes and a transfer opening in the crankcase and/or the intake and exhaust transfer ports in the valve plates as needed. The transfer tube(s) can be made of a resilient material and have stepped ends sized to fit into transfer ports. Preferably, the transfer tube(s) are clamped between the valve plate(s) and the crank case.
The invention thus provides a compact pump with considerable noise reduction and improved efficiency. These and other advantages of the invention will be apparent from the detailed description and drawings. What follows is a description of the preferred embodiments of the present invention. To assess the full scope of the invention the claims should be looked to as the preferred embodiments are not intended as the only embodiments within the scope of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
Referring to
Referring to
The plug supports 84 and 85 help maintain the seal of the neck plugs 70 and 71. However, the pointed corners of the neck plugs 70 and 71 can flex away from the crankcase and cylinders somewhat to allow a leak path to relieve transient high pressure situations. The seal is designed primarily for low pressure applications to seal off air leaks for noise reductions. The corners of the neck plugs will unseat slightly when the internal pressure reaches about 15 psi as a pressure relief. The assembly could, of course, be used in higher pressure applications by using a more rigid elastomer or modifying the backing plate to prevent the seal from unseating.
Referring to
Referring to
Importantly, the connecting rods 98 and 99 of the pistons 90 and 91 are mounted on the drive shaft 114 so that the connecting rods 98 and 99 are substantially adjacent to one another, that is within ⅛ inches (preferably less than {fraction (1/16)}″) or as close as possible. Preferably, the pistons are mounted on the drive shaft as close as possible with only air space between the connecting rods. This is to reduce the moment or shaking couple about the drive shaft 114 caused by the axial displacement of the piston assemblies 38 and 39. While some moment remains, this arrangement provides a significant improvement over the prior art in that there is no other element (eccentric or otherwise) on the shaft between the pistons so that their axial displacement is minimized.
As shown in
Air flow through the cylinders is controlled by the valving on the valve plates 44 and 45. Referring to
The intake 120 and exhaust 122 ports are controlled by respective flapper valves 130 and 132. The flapper valves 130 and 132 are identically shaped thin, metal valves. The valves 130 and 132 each have a middle section 134 defining an opening 136 and an alignment tab 139 as well as two identical paddles 140 extending from the middle section 130 in opposite directions approximately 30 degrees from vertical. The paddles 140 have narrow necks 142 and relative large flat heads 144. The heads are sized slightly larger than the intake and exhaust ports and the necks are narrow to let the valves flex more easily under the force of the pressurized air, and thus reduce power consumption. Each flapper valve 130 and 132 is mounted to the valve plate 44 by a fastener 146 inserted through the opening 136 in the middle section 134 of the valve and threaded into bores in the valve plate. The intake valve 130 is mounted at the inside of the cylinder 40 and the exhaust valve 132 is mounted in the exhaust chamber 128.
Referring to
Another feature of the pump 30 is the use of transfer tubes 158 with air passageways formed in the body of the crankcase 36 (outside of the internal chamber) to either couple an intake or exhaust chamber to the inside of the crankcase or to couple the valve heads together (in parallel between exhaust chambers and/or between intake chambers or in series with the exhaust chamber of one valve head connected to the intake chamber of the other valve head) without the need for hoses. Referring now to
As mentioned, the crankcase 36 has two sets of interior passageways 170 and 171 in the walls of the crankcase opening at the transfer openings 164 and 165. Depending on the desired operation of the pump, there can be only one of these passageways 170 and 171 or one set of these passageways in one side of the crankcase. One or both of these passageways may also open to the channels 78 and 79, which open to the interior of the crankcase. This can be done by boring through section 174 or by casting the crankcase to block off or connect passageways as needed. In the parallel pressure embodiment of the pump shown in
Since the pistons are of different sizes, they have different masses. The difference in masses will make the pistons out of balance and thus effect unequal moments on the drive shaft, which would cause vibration, noise and lower pump efficiency. Preferably, the retainers 96C and 97C are selected to have different masses, substantially equal to the difference in the masses of the other parts of the pistons (such as the connecting rods and the heads/pans). This can be accomplished by making the retainers 96C and 97C from disparate materials or of different thicknesses. For example, the retainer 96C could be made of a suitable zinc composition so that it has a greater mass (despite its smaller diameter) than retainer 97C, which could be made of an aluminum. Thus, the heavier retainer 96C would make up the difference in mass of the smaller piston 90C. The result is equally balanced piston assemblies and improved operation of the pump when the application requires different flow volumes in the cylinders.
The pump also differs from that described above in that it has only one transfer tube 158C connecting the exhaust side of valve head 47C to passageway 171C (through a transfer opening) in the crankcase 36C. Passageway 171C intersects with channel 78C (as shown in
This embodiment of the pump is thus constructed so that air can be drawn from the load (through a hose (not shown) connected to barb 200) and into the intake chamber of valve head 47C. Surrounding air can also be brought in through barb 202 (to which preferably a muffler (not shown)) is mounted. Air from the higher pressure side valve head 46C exhaust chamber will be exhausted through barb 204 to the load (after passing through hoses and valves as needed). The exhaust chamber of the vacuum side valve head 47C will exhaust through the transfer tube 158C and the crankcase passageway 171C to the non-pressure side of the inside of the crankcase 36C, which is vented through barb 206 and another muffler (not shown). Passing the exhaust through the crankcase prior to the muffler provides further (two-stage) sound attenuation beneficial in low-noise applications, such as when used with medical devices.
It should be appreciated that preferred embodiments of the invention have been described above. However, many modifications and variations to these preferred embodiments will be apparent to those skilled in the art, which will be within the spirit and scope of the invention. For example, while only two-cylinder embodiments were shown, the principles of the invention could apply to a single-cylinder pump or to three or four cylinder pumps, such pumps having a double shafted motor and additional crankcases, cylinders, pistons and valve heads. For multi-cylinder pumps, the valve heads of all of the cylinders could be coupled in series or parallel through the transfer tubes and integral crankcase passageways, like those described above. Shared valve heads for multiple cylinders could also be incorporated into such a pump. The pump of the present invention could also include transfer tubes which connect directly to the valve heads/plates to join air chambers without connected to passageways in the crankcase.
Therefore, the invention should not be limited to the described embodiments. To ascertain the full scope of the invention, the following claims should be referenced.
Claims
1. A pump, comprising:
- a crankcase defining a pumping chamber and a transfer opening;
- a valve mounting member mounted to the crankcase over the pumping chamber and having a port in communication with the pumping chamber, the port being opened and closed by a valve mounted to the valve mounting member;
- a working fluid chamber defined at least in part by the valve mounting member on a side of the valve mounting member opposite from the pumping chamber, said working fluid chamber being in communication with the pumping chamber through the port when the valve is open;
- a transfer port in communication with the working fluid chamber, said transfer port being outside of the pumping chamber; and
- a transfer tube connected at one end to the transfer port and at the other end to the crankcase transfer opening.
2. The pump of claim 1, wherein the transfer tube has opposite flat side walls.
3. The pump of claim 1, wherein the transfer tube is separate from the valve mounting member and from the crankcase.
4. The pump of claim 1, wherein the transfer tube is formed as a unitary part of the valve mounting member.
5. The pump of claim 1, wherein the crankcase defines an integral passageway leading to the transfer opening.
6. The pump of claim 5, wherein the passageway leads to a crankcase chamber.
7. The pump of claim 5, wherein the passageway leads to a second transfer opening in the crankcase.
8. The pump of claim 7, further including a second transfer tube connecting the passageway to a second working fluid chamber of the pump.
9. The pump of claim 5, wherein the passageway has two flat side walls.
10. The pump of claim 8, wherein the transfer tube is formed as a unitary part of the valve mounting member.
11. The pump of claim 10, further including a resilient seal disposed between the transfer opening and the transfer tube.
12. The pump of claim 11, wherein the transfer tube is separate from the valve mounting member and from the crankcase.
13. The pump of claim 12, wherein the transfer tube is a resilient material.
14. The pump of claim 12, further including resilient seals at each end of the transfer tube.
15. The pump of claim 12, wherein the transfer tube is clamped between the valve mounting member and the crank case.
16. The pump of claim 1, wherein the valve mounting member is a valve plate.
17. The pump of claim 16, wherein the working fluid is air.
18. The pump of claim 1, wherein the working fluid chamber is an intake chamber.
19. The pump of claim 1, wherein the working fluid chamber is an exhaust chamber.
20. A pump, comprising:
- a crankcase defining two pumping chambers in which a working fluid is pumped and defining a passageway opening at at least two transfer openings at opposite sides of the crankcase;
- two valve mounting members mounted to the crankcase that close the pumping chambers, each valve mounting member having a valve port in communication with the pumping chamber, the valve port being opened and closed by a valve mounted to the valve mounting member, each valve mounting member further having a transfer port;
- at least two working fluid chambers, each said working fluid chamber defined at least in part by one or the other of the valve mounting members on a side of said valve mounting member opposite from the pumping chamber of the pump that is adjacent to said valve mounting member, each said working fluid chamber being in communication with the adjacent pumping chamber when the valve port of the adjacent valve mounting member is open; and
- a transfer tube connected between the transport ports of the valve mounting members and the crankcase transfer openings to connect each working fluid chamber to the passageway.
21. The pump of claim 20, wherein:
- said at least two working fluid chambers are connected to each other through the transfer tube.
22. The pump of claim 20, wherein:
- said at least two working fluid chambers are connected to a chamber of the crankcase through the transfer tube.
23. The pump of claim 20, wherein:
- the chambers are intake chambers.
24. The pump of claim 20, wherein:
- the chambers are exhaust chambers.
25. The pump of claim 20, wherein:
- at least one of the chambers is an intake chamber and at least one of the chambers is an exhaust chamber.
Type: Application
Filed: Dec 8, 2004
Publication Date: May 12, 2005
Inventor: Shawn Leu (Newton, WI)
Application Number: 11/007,111