U.S. patent application number 11/827551 was filed with the patent office on 2008-01-24 for pumping apparatus having a piston with a diamond-like carbon coating.
Invention is credited to Hans-Georg Haertl.
Application Number | 20080019854 11/827551 |
Document ID | / |
Family ID | 37571307 |
Filed Date | 2008-01-24 |
United States Patent
Application |
20080019854 |
Kind Code |
A1 |
Haertl; Hans-Georg |
January 24, 2008 |
Pumping apparatus having a piston with a diamond-like carbon
coating
Abstract
A pumping apparatus is provided, which comprises a piston (1)
for reciprocation in a pump working chamber (3), a valve, coupled
to said pump working chamber (3) in order to permit liquid flow
only unidirectional and a drive unit for reciprocating said piston
(1). The liquid in said pump working chamber (3) is compressed to a
high pressure, at which compressibility of the liquid becomes
noticeable. The piston (1) is at least partially coated with a
diamond-like carbon coating (2), adapted to provide a reduced
abrasion of said piston (1).
Inventors: |
Haertl; Hans-Georg;
(Karlsruhe, DE) |
Correspondence
Address: |
PERMAN & GREEN
425 POST ROAD
FAIRFIELD
CT
06824
US
|
Family ID: |
37571307 |
Appl. No.: |
11/827551 |
Filed: |
July 12, 2007 |
Current U.S.
Class: |
417/545 |
Current CPC
Class: |
G01N 2030/326 20130101;
F04B 53/14 20130101; F05C 2203/0808 20130101 |
Class at
Publication: |
417/545 |
International
Class: |
F04B 39/10 20060101
F04B039/10 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 19, 2006 |
EP |
06117516.2 |
Claims
1. A high performance liquid chromatography pumping apparatus
adapted to perform liquid pumping in a high performance liquid
chromatography device, the pumping apparatus comprising: a first
piston for reciprocation in a first pump working chamber, a valve,
coupled to said first pump working chamber, to permit only
unidirectional liquid, and a drive unit for reciprocating said
first piston, wherein: the liquid in said first pump working
chamber is compressed to a high pressure, at which compressibility
of the liquid becomes noticeable, and said first piston is at least
partially coated with a diamond-like carbon coating, adapted to
provide a reduced abrasion of the first piston.
2. The pumping apparatus of claim 1, wherein the first pump working
chamber has an inlet port and an outlet port.
3. The pumping apparatus of claim 1, wherein the valve is an inlet
valve.
4. The pumping apparatus of claim 1, wherein the drive unit
comprises a piston holder to which the first piston is mounted.
5. The pumping apparatus of claim 1, comprising: a second piston,
wherein the first and second pistons are arranged in one of a dual
serial or dual parallel mode, adapted to provide a continuous
pumping by performing pump cycles,
6. The pumping apparatus of claim 1, wherein the first piston is
made of one of the following: sapphire, ceramics and metals.
7. The pumping apparatus of claim 6, wherein the metal is
steel.
8. The pumping apparatus of claim 1, wherein the diamond-like
carbon coating has a coating thickness ranging from 0.1 to 10
micrometers.
9. (canceled)
10. The pumping apparatus according to claim 1, wherein said high
pressure ranges from 200 to 2000 bar.
11. The pumping apparatus according to claim 1, wherein the liquid
is pumped at a selectable flow rate.
12. (canceled)
13. The pumping apparatus of claim 1, comprising a second piston
for reciprocation in a second pump working chamber having a second
inlet port and a second outlet port, wherein the first pump working
chamber includes a first inlet port and a first outlet port.
14. The pumping apparatus of claim 13, comprising a conduit
coupling between the first outlet port of the first pump working
chamber and the second inlet port of the second pump working
chamber to provide a liquid communication from the first pump
working chamber into the second pump working chamber.
15. The pumping apparatus of claim 13, comprising a first inlet
valve connected to the first inlet port of the first pump working
chamber to permit only unidirectional liquid flow into said first
pump working chamber.
16. The pumping apparatus of claim 13, comprising a first outlet
valve connected to the first outlet port of the first pump working
chamber to permit only unidirectional liquid flow into said second
pump working chamber.
17. The pumping apparatus of claim 13, wherein the drive unit is
operable to reciprocate the first and the second piston, wherein:
the liquid in the first pump working chamber is compressed to said
high pressure before delivery of the compressed liquid into the
second pump working chamber, and at least one of said first and
second pistons that are reciprocated into said first and second
working chambers, respectively, is at least partially coated with a
diamond-like carbon coating, adapted to provide a reduced abrasion
of the piston.
18. The pumping apparatus of claim 1, wherein the diamond-like
carbon coating has a coating thickness ranging from 0.2 to 5
micrometers.
Description
[0001] The present invention relates to a pumping apparatus.
BACKGROUND ART
[0002] A number of pumping devices is described in the state of the
art, said pumping devices being used for transfer of liquid in low-
or high pressure apparatuses. Piston- or plunger pumps adapted for
usage in said low- or high pressure devices comprise one or more a
pistons which are arranged to perform reciprocal movements in a
corresponding pump chamber, thereby compressing the fluid within
said pump chambers. The reciprocation is repeated thousand fold
during the lifetime of the pump, thereby causing wear, abrasion
and, hence, changes of the material and surface properties to the
piston.
[0003] A liquid chromatography pumping system is described in EP
0,309,596 B1 to Strohmeier and Witt, e.g., depicting a pumping
apparatus comprising a dual piston pump system for delivering
liquid at high pressure, e.g., for solvent delivery in liquid
chromatography.
[0004] Further pumping systems with coated components are disclosed
in the state of the art: WO 06,005,399 A1 to Beck et al. refers to
an axial piston engine with a wear-resistant carbon-containing
layer on one of the sliding faces.
[0005] JP 2004,239,191 A2 to Kato et al. describes a hydraulic
piston pump motor with a DLC (diamond-like carbon) coated film on a
sliding surface of a shoe which slidably contacts said swash plate
for reciprocally moving the pistons.
[0006] JP 2004,019,464 A2 to Narato discloses a hydraulic piston
pump motor with a piston ring being coated with a thin film of DLC
on its sliding surface to improve wear resistance.
[0007] DE 102,004,032,342 A1 to Fischer et al. discloses a method
providing the outside extent surface of a piston ring base with a
coating comprised of two layers, one of which being a wear
protection layer.
[0008] US 2004,258,547 AA to Bayer et al. refers to a pump piston
and a sealing ring with an additionally applied coating,
predominantly formed of halogen-, silicon-, carbon-containing
and/or metal-organic monomers.
[0009] WO 03,078,679 A1 to Teer concerns a coating and apparatus
and method for its application. The coating is applied by chemical
vapour deposition using a pulsed DC biased power supply, the
coating having an initial metal layer followed by a transitional
metal carbide layer and a DLC layer.
[0010] JP 2,000,320,670 A2 to Kitago et al., a piston with a
hardening layer is described, comprising a DLC layer which is
applied succeeding to soft nitriding and polishing of a steel
piston.
DISCLOSURE
[0011] It is an object of the invention to provide an improved
pumping apparatus. The object is solved by the independent claims.
Further embodiments are shown by the dependent claims.
[0012] According to embodiments of the present invention, a pumping
apparatus is described which is adapted to deliver liquids under
high pressure in devices such as, e.g., devices for analysis of
chemical or biochemical compounds, working with liquids or liquid
samples being injected under high pressure. Said pumping apparatus
is composed of one or more pistons, each of which being movably
arranged in a corresponding pump working chamber. Moving of a
piston is performed by a drive unit having a piston holder;
accordingly the reciprocal movement of the piston in the chamber
can be carried out for a plurality of strokes. Each strike provides
a liquid compression; the plurality of strikes demanding an
increased material resistance with respect to the piston wear. A
diamond-like carbon (DLC) coating on the piston surface
advantageously provides an improved wear resistance, adapted to
provide a reduced abrasion of the piston. Said improved wear
resistance is based on a hardening of the surface due to the
coating, associated with an optimized surface smoothness and
evenness leading to friction reduction.
[0013] A further embodiment of the present invention comprises two
pistons arranged in a dual serial or dual parallel mode in order to
provide continuous pumping by performing pump cycles. Due to an
advantageously provided coating of the piston surfaces, which
coating reduces friction of the pistons and optimizes surface
durability, an optimized performing of pump cycles can be carried
out.
[0014] A further embodiment refers to a high pressure liquid
chromatography device to perform injecting of liquid into a
chromatograph. The herein used pumping apparatus has a piston for
repeated reciprocation into a pump working chamber, which piston is
advantageously coated with a diamond-like carbon coating, providing
a hard and even piston surface which helps prolonging the lifetime
of the piston. Furthermore, the highly precise pumping of said
device, which is used for injecting micro-volumes pumping, is
further optimized since the piston cay move nearly
friction-free.
[0015] Further embodiments of the present invention refer to a high
pressure liquid chromatography device comprising a liquid pumping
apparatus having a DLC coated piston, which may be made of
sapphire, being chemically inert and having an improved surface
with respect to abrasion, and showing a reduced brittleness.
DETAILED DESCRIPTION
[0016] Other objects and many of the attendant advantages of
embodiments of the present invention will be readily appreciated
and become better understood by reference to the following more
detailed description of embodiments in connection with the
accompanied drawings. Features that are substantially or
functionally equal or similar will be referred to by the same
reference signs.
[0017] FIG. 1 schematically shows a pumping apparatus comprising a
coated piston.
[0018] In the following, generally pumping apparatuses for
delivering liquid at a high pressure are described. The pressure
which affects the liquid provides a noticeable compressibility of
the liquid, which noticeable compression is achieved in that a
piston of the pumping apparatus is reciprocated in a pump working
chamber containing the respective liquid. The pump working chamber
may be coupled to a valve in order to permit liquid flow
unidirectional only. Driving of the piston may be performed by a
drive unit which permits pressurizing of the liquid in said pump
working chamber to high pressure. Advantageously, a diamond-like
carbon coating covers the parts of the piston which are the most
susceptible to abrasion; the smooth and even DLC coating reduces
friction and damages due to friction.
[0019] FIG. 1 depicts a pumping apparatus comprising a piston 1,
which is reciprocated in a pump working chamber 3, having a
cylindrical inner bore 9 and having an inlet port 4' and an outlet
port 5'. An inlet valve 13 is connected via a capillary 5, which
has an inner bore 4, to said inlet port 4' of the pump working
chamber 3, to permit liquid flow only unidirectional into the pump
working chamber 3. The reciprocating movements are driven by a
drive unit (not shown herein), which operates the piston holder 6
via the ball 8 which is embedded in a recess 10. The ball 8 is
operated by an actuator 7. Since the piston holder 6 is mounted to
the piston 1, the drive unit may affect the piston 1 via the piston
holder 6 to perform said moving of the piston into the pump working
chamber 3. Furthermore, a seal 11 is provided for sealing off the
pump working chamber 3 at the opening, through which the piston 1
moves into said pump working chamber 3, so that unwanted liquid
flow-out is prevented. Guiding of the piston1 into the pumping
chamber 3 is supported by the guiding element 12.
[0020] The liquid in said pump working chamber 3 is compressed to a
high pressure before being delivered via an outlet port 5' and via
a capillary 5 with an inner bore 4 being attached to said outlet
port 5', into a liquid receiving device.
[0021] Generally, wear and abrasion are well known phenomena
causing material destruction of a plurality of components in
driving units, pumps and other devices. Since the piston 1 performs
said reciprocating movement manifold during its lifetime, it is
subjected to said abrasion due to friction loading, accordingly
risking to be damaged from wear. Advantageously reducing of said
destructive effects is achieved by optimizing the surface
durability.
[0022] Therefore, the piston 1 is provided with a diamond-like
carbon (DLC) coating 2, which herein covers the piston 1 along its
length, leaving the top and the bottom of the piston 1 uncovered.
The diamond-like carbon (DLC) coating 2 might as well cover the
piston 1 completely. Due to its abrasion reducing effects, the DLC
coating 2 may advantageously prolong the lifetime of the piston
1.
[0023] The pumping apparatus of the embodiments of the present
invention may be comprised of one or more pistons: A pumping
apparatus being comprised of two pistons might be constructed such
that said two pistons are arranged in a dual serial mode,
permitting thereby to provide a continuous pumping by performing
pump cycles. A pumping apparatus with two pistons accordingly
comprises two pump working chambers, such that the first piston can
be reciprocally moved into, a first pump working chamber having an
inlet port and an outlet port, and that a second piston can be
reciprocally moved into a second pump working chamber, having an
in- and an outlet, too. A conduit coupling is arranged between the
outlet port of the first pump working chamber and the inlet port of
the second pump working chamber, thus a liquid communication from
the first to the second pump working chamber is provided.
[0024] An inlet valve, which is connected to the inlet port of the
first pump working chamber, permits liquid flow only unidirectional
from a liquid source such as, e.g., a sample reservoir, into said
first pump working chamber, whereas an the outlet valve, which is
connected to the outlet port of said first pump working chamber,
prevents returning of a liquid into said first pump working
chamber. Thus, only unidirectional liquid flow from the first into
said second pump working chamber is permitted.
[0025] Reciprocation of a the first and the second pistons is
performed by usage of a driving unit which is provided with a
piston holder per piston, said piston being mounted on the
corresponding holder and being coated with DLC in order to have an
optimized resistance with respect to abrasion.
[0026] The pumping apparatuses of the embodiments of the present
invention are adapted to work under high pressure, they may be
designed to stand pressures of up to 200 bar, any may be
constructed to stand even 2000 bar, and they may be equipped with
an additional option to perform pumping at a selectable flow rate.
Said pumping apparatuses may be used in liquid chromatography
devices, in particular in high pressure liquid chromatography
(HPLC) devices. In an HPLC device, the pumping apparatus may serve
to perform injecting of liquid into the chromatograph.
[0027] Generally, the pistons of the herein referred embodiments
can be made of materials such as sapphire, ceramics and metals such
as steel. The choice of the piston material depends on the
technical application which is carried out using the pumping
apparatus: A pumping apparatus used for pumping oil or oily liquids
may be equipped with a piston made of steel, or made of another
metal or material having a rough surface. It must be noticed, that
"rough" herein means a roughness provided by micro- or nanoscale
recession. The pumped oil molecules fill even the tiniest micro- or
nano-pores or scratches being present in the rough materials'
surface and, hence, smoothens it.
[0028] On the contrary, other liquids, in particular solvents such
as Acetonitril, Tetrahydrofurane, Hexane or other solvents used
particularly in HPLC technology have properties which rather clean
the surfaces of the aforementioned rough piston materials since
they are strong solvents, dissolving and removing molecules being
present in said micro recesses. Accordingly, the surface roughness
becomes even rougher.
[0029] So, sapphire is a well known and popular material for
producing pistons for usage in the above HPLC pumping apparatuses:
The sapphire material is very even and smooth, hard and chemically
inert, therefore an ideal material for the use in HPLC technology,
but it inheres a certain brittleness. Applying of an at least
partial DLC coating on the sapphire piston might therefore reduce
abrasion, increase wear resistance, and, might additionally reduce
the tendency of being damaged by brittle fraction. Furthermore, the
surface roughness remains even and smooth since the sapphire
material provides an ideal under-surface for the DLC coating.
[0030] On the other hand, the sapphire material is an exclusive
material which needs a careful processing. Thus, another option to
obtain an optimized HPLC piston might be the use of the above
materials ceramics and steel: These materials have to be prepared
using an intense smoothing and polishing in case of usage for HPLC
technologies, what can be done easily due to the good
processibility of these materials. The polished material is very
smooth then, but prone to wear. Applying DLC can lead to an
advantageously increased wear resistance, but the DLC layer should
be applied to a well polished surface; otherwise the roughness
would be set forth through the DLC layer. A well polished and
DLC-coated surface of a piston comprises furthermore the advantages
of chemical inertness and of having a low friction.
[0031] The DLC coating can have a thickness ranging from 0.1 to 10
micrometer, a preferred range of thickness is 0.2 to 5 micrometer,
depending on the piston base material and depending on what the
piston is intended to be used for. After all, advantageously the
minimum thickness of 0.1 should be provided in order to obtain a
homogeneous and tightly closed coating layer.
* * * * *