Pumps – Motor driven – Fluid motor
Reexamination Certificate
1998-11-10
2001-06-05
Thorpe, Timothy S. (Department: 3746)
Pumps
Motor driven
Fluid motor
C417S393000, C137S625600
Reexamination Certificate
active
06241487
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to pumps and, more specifically, to fluid powered diaphragm pumps. Still more specifically, the present invention relates to design improvements which reduce stalling and sticking of the main fluid valve, which enhance the serviceability of the pump, which improve the efficiency of the exhaust system of the pump and which enable the pump to be easily interfaced with electronic equipment.
BACKGROUND OF THE INVENTION
Fluid powered diaphragm pumps are known. A typical design sold under the SANDPIPER® trademark by Warren Rupp, Inc., a unit of IDEX Corporation, of Mansfield, Ohio is shown in FIG.
1
. Specifically, the pump
10
includes two chambers
11
,
12
which are defined by the diaphragms
13
,
14
. The diaphragms
13
,
14
are connected by a diaphragm rod
15
by way of the diaphragm plate assemblies
16
,
17
. Pressurized fluid is supplied to the inner diaphragm chambers
18
,
19
by way of a main fluid valve
21
. The main fluid valve
21
includes a spool
22
that is slidably accommodated in a housing
23
. The housing
23
may also be equipped with a sleeve-like structure
24
that accommodates the spool
22
. The spool
22
slides back and forth from left to right in the housing
23
and directs pressurized fluid into the inner diaphragm chambers
18
,
19
in a reciprocating fashion. The spool
22
, or the main fluid valve
21
is shifted by a pilot valve which is not shown in FIG.
1
. Typical prior art pilot valves are powered by air bled off of the pressurized fluid supply which drives the pump. This design has been found to be problematic for the following reasons.
Specifically, when the pump
10
is operating at low speeds or with a pressurized fluid supply at a relatively low pressure, the pilot valve can be starved for power as the pump
10
consumes the bulk of the pressurized supply fluid. Accordingly, the pilot valve may not shift properly and, accordingly, will not direct a sufficient amount of pressurized fluid to either opposing end
25
,
26
to properly shift the spool
22
of the main fluid valve
21
. Therefore, there is a need for an improved fluid diaphragm pump which avoids the problem associated with the shifting of the pilot valve, and consequently the shifting of the main fluid valve, when the pump is operating with a pressurized fluid supply of a reduced pressure.
Two other problems associated with the operation of fluid powered diaphragm pumps are stalling and sticking. Stalling typically occurs when the pump is operated at low speeds or at a low pressure differential. Stalling can also occur when the main fluid valve components are worn thereby allowing internal fluid leakage or by-pass. In any event, the spool
22
of the main fluid valve
21
becomes stuck at a midpoint between the first and second positions, or left and right positions, and the only reliable means for restarting the pump requires the operator to shut off the pressurized fluid supply and restart the pressurized fluid supply. Typically, operators in this field will attempt to restart the pump by banging on the main fluid valve housing with a hammer or other heavy object, which can damage the pump. This solution is also ineffective because the spool of the pilot valve, along with the spool of the main fluid valve, is typically located at a midpoint between the two shifted positions. The location of the spool of the main fluid valve in the mid-point position diverts or blocks off the supply fluid and prevents the pump from reciprocating.
Stalling is normally associated when the discharge fluid is compressible or includes air or vapor which results in a lower pressure head. As the discharge fluid is compressed and decompressed in the diaphragm chambers, the pilot valve is pulsed, rather than positively shifted, eventually resulting in the building up of balanced air pressures on either side of the pilot valve spool as well as the main fluid valve spool, causing both spools to obtain a centered position in their respective housings. Stalling can also occur with low flow and low speed applications such as the employment of a diaphragm pump in a filter press or in connection with an on-demand spray service. Both applications have low speed and low flow coupled with a low head or dead head. Both applications can also create air or vapor build-up on the discharge side of the pump.
As a result, there is a need for an improved fluid powered diaphragm pump which results in a positive shift of both the pilot valve spool and main fluid valve spool in low speed, low pressure applications.
A pump is considered to be sticking when it fails to restart or stops in the middle of a stroke. Typically, the main fluid valve spool is seized or stuck in the sleeve or housing. This situation occurs most frequently when the pressurized fluid is contaminated or is of a poor quality. Sticking frequently occurs when diaphragm pumps are employed in mines and the pressurized fluid is a poor quality air supply. Because the main fluid valve spool is typically disposed within a solid sleeve structure that, in turn, is attached to the valve housing, it is very difficult to service the main fluid valves of diaphragm pumps. The entire spool and sleeve must be removed and clean in the event sticking occurs.
Accordingly, there is a need for an improved fluid powered diaphragm pump with a main fluid valve that is easier to disassemble and/or service.
Further, currently available diaphragm pumps typically include inefficient exhaust systems. Exhaust systems are required due to the high noise level associated with these pumps. Further, most diaphragm pumps do not come equipped with a versatile exhaust element, meaning that the pump is equipped with its own exhaust and muffler system or, the pump must be modified if the end users is required to pipe the exhaust away from the pump. Further, many exhaust system designs are difficult to disassemble, and disassembly is required on a relatively frequent basis due to the susceptibility of exhaust systems to freezing.
Further, diaphragm pumps are not easily incorporated into electronic interfaces which monitor the pump frequency. Typically, upgrading an existing pump to be interfaced with electronic manufacturing equipment is time consuming and expensive. Accordingly, there is a need for an improved fluid powered diaphragm pump design which enables the pump to be easily integrated with electronic manufacturing equipment.
Still further, there is a need for an improved fluid powered diaphragm pump which may be easily locked so as to prevent the pump from running accidentally. Currently, the only way to lock out a diaphragm pump is to completely disconnect the pressurized fluid supply.
SUMMARY OF THE INVENTION
The present invention satisfies the aforenoted needs by providing a fluid powered diaphragm pump that comprises a fluid inlet providing communication between a pressurized fluid supply and both a main fluid valve and a pilot valve. The main fluid valve comprises a housing. The pilot valve is disposed between the fluid inlet and the main fluid valve. As a result, the pilot valve is powered directly by the pressurized fluid supply as opposed to bleed fluid. Therefore, the pilot valve is operated as fluid under the same pressure that is used to operate the main fluid valve.
In an embodiment, the main fluid valve further comprises a spool slidably accommodated in a segmented sleeve assembly. The segmented sleeve assembly comprises a plurality of annular sleeve segments or wafers. The annular sleeve segments are fixedly accommodated in the housing. As a result, the sleeve assembly is easily disassembled for servicing of the main fluid valve spool in the event the main fluid valve spool becomes stuck or bound in place. The segmented sleeve assembly enhances the serviceability of the main fluid valve.
In an embodiment, the segmented sleeve assembly further comprises a plurality of spacers. Each spacer is disposed between two of the annular sleeve segments.
In an embodiment, the spool comprises opposing first a
Barnes & Thornburg
Gray Michael K.
Thorpe Timothy S.
Warren Rupp, Inc.
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