U.S. patent application number 10/694790 was filed with the patent office on 2004-06-03 for ejector with gas propulsion.
This patent application is currently assigned to J. Schmalz GmbH. Invention is credited to Eisele, Thomas, Schmalz, Kurt.
Application Number | 20040105760 10/694790 |
Document ID | / |
Family ID | 32335741 |
Filed Date | 2004-06-03 |
United States Patent
Application |
20040105760 |
Kind Code |
A1 |
Eisele, Thomas ; et
al. |
June 3, 2004 |
Ejector with gas propulsion
Abstract
Ejector with driver gas comprising at least one primary nozzle
branch (12) with a driver nozzle (36) having a cross-sectional
narrowing and an adjacent receiving nozzle (32), wherein a suction
line (24) terminates in the narrowing, characterized by at least
one connectable secondary nozzle branch (14) having a driver nozzle
(38) with a cross-sectional narrowing and an adjacent receiving
nozzle (34), wherein the narrowing of the secondary nozzle branch
(14) is connected to a suction line (24) when the secondary nozzle
branch (14) is opened, and with a closing instrument (20) connected
upstream, with respect to the flow direction of the gas propellant,
of the at least one secondary nozzle branch (14) to connect and
disconnect the secondary nozzle branch (14) in dependence on the
inlet pressure of the driver gas entering the ejector (20).
Inventors: |
Eisele, Thomas;
(Flourn-Winzeln, DE) ; Schmalz, Kurt;
(Dornstetten, DE) |
Correspondence
Address: |
Dreiss, Fuhlendorf, Steimle & Becker
Postfach 10 37 62
Stuttgart
D-70032
DE
|
Assignee: |
J. Schmalz GmbH
Glatten
DE
|
Family ID: |
32335741 |
Appl. No.: |
10/694790 |
Filed: |
October 29, 2003 |
Current U.S.
Class: |
417/151 |
Current CPC
Class: |
F04F 5/466 20130101;
F04F 5/52 20130101 |
Class at
Publication: |
417/151 |
International
Class: |
F04F 005/00 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 29, 2002 |
DE |
102 50 532.2 |
Claims
We claim:
1. An ejector having a driver gas at an inlet pressure, the ejector
comprising: at least one primary branch; a primary driver nozzle
disposed within said primary branch, said primary driver nozzle
having a primary driver cross-sectional narrowing; a primary
receiver nozzle disposed downstream of and adjacent to said primary
driver nozzle; a primary suction line in vacuum communication with
said primary driver narrowing; at least one secondary branch; a
secondary driver nozzle disposed within said secondary branch, said
secondary driver nozzle having a secondary driver cross-sectional
narrowing; a secondary receiver nozzle disposed downstream of and
adjacent to said secondary driver nozzle; a secondary suction line
in interruptable vacuum communication with said secondary driver
narrowing; and a closing instrument disposed upstream of said
secondary driver nozzle to connect and disconnect said secondary
branch in dependence on the inlet pressure of the driver gas into
the ejector.
2. The ejector of claim 1, wherein said closing instrument is held
in a first position through a biasing force means, said biasing
force means counteracting the inlet pressure of the driver gas.
3. The ejector of claim 2, wherein said closing instrument
comprises a piston.
4. The ejector of claim 3, wherein said biasing force means
comprises a spring which acts on said piston.
5. The ejector of claim 1, wherein said closing instrument is
transferred to a second position when a switching pressure is
reached by the inlet pressure of the driver gas.
6. The ejector of claim 5, wherein said at least one secondary
branch is disconnected when the inlet pressure is lower than said
switching pressure.
7. The ejector of claim 5, wherein said at least one secondary
branch is disconnected when the inlet pressure is higher than said
switching pressure.
8. The ejector of claim 1, further comprising a common driver gas
feed line communicating with said primary and said secondary
branches, wherein said closing instrument is disposed in said feed
line.
9. The ejector of claim 1, wherein said primary suction line and
said secondary suction line coincide, and further comprising a
check valve disposed in said primary and secondary suction line
between said secondary branch and said primary branch to prevent
leakage of vacuum generated by said primary branch when said
secondary branch is disconnected.
10. The ejector of claim 1, wherein each nozzle branch or each
group of nozzle branches is/are associated with a separate suction
line.
11. The ejector of claim 9, wherein said check valve is a
spring-loaded ball valve.
12. The ejector of claim 1, wherein said secondary branch has a
same suction performance as said primary branch.
13. The ejector of claim 1, wherein said secondary branch has a
different suction performance than said primary branch.
14. The ejector of claim 13, wherein said secondary branch has a
larger suction performance than said primary branch.
15. The ejector of claim 1, further comprising a housing, wherein
suction lines are bores in said housing and nozzles and valves are
disposed in said housing in an exchangeable manner.
Description
[0001] This application claims Paris Convention priority of DE 102
50 532.2 filed Oct. 29, 2002 the complete disclosure of which is
hereby incorporated by reference.
BACKGROUND OF THE INVENTION
[0002] The invention concerns a gas driven ejector, i.e. a jet
pump, for generating underpressure, with at least one primary
nozzle branch having a driver nozzle with a cross-sectional
narrowing, an adjacent receiving nozzle, and a suction line
connected to the narrowing.
[0003] Conventional ejectors or jet pumps of this type function
according to the Venturi principle. The filtered and lubricant-free
compressed gas flows via a connecting sleeve and a pressuring gas
feed line into the ejector and reaches the driver nozzle where the
flow velocity of the compressed air serving as the driver gas is
increased to supersonic speed in the narrowing. After exiting the
driver nozzle, the air expands and flows into a diffuser and from
there, optionally via a sound absorber, to the outside thereby
producing a vacuum in a chamber surrounding the driver nozzle with
air being pumped via a suction line feeding into the chamber. The
pumped air and the driver gas introduced into the ejector both exit
the ejector via the expansion section.
[0004] With respect to other vacuum pumps, these jet vacuum pumps
advantageously have no rotating parts and maintenance and wear are
therefore minimum. Moreover, they cannot explode since they
function purely pneumatically. In addition, their construction is
simple and they can be installed at any location. They do not
generate heat and can be connected and disconnected at any time to
save energy. Moreover, the vacuum can be generated quickly using
short lines between e.g. a suction gripper and the ejector. The
compact construction, the low weight and the ability to combine
several functions in one device play an important economic role in
the field of construction, work preparation, purchasing, mechanical
processing, assembly, putting into operation and spare part
supply.
[0005] In view of the above, it is the underlying purpose of the
invention to provide a gas propulsion ejector which ensures good
suction performance in a straightforward manner with low driver gas
consumption.
SUMMARY OF THE INVENTION
[0006] This object is achieved in accordance with the invention in
that at least one connectable secondary nozzle branch is provided
which has a driver nozzle with a narrowing and an adjacent
receiving nozzle, wherein the narrowing of the secondary nozzle
branch is connected to a suction line when the nozzle branch is
connected, with a closing instrument being disposed upstream of the
at least one secondary nozzle branch to connect/disconnect the
secondary nozzle branch in dependence on the input pressure of the
driver gas in the ejector.
[0007] In accordance with an embodiment of the invention, the
second nozzle branch, e.g. the secondary nozzle branch, is only
connected when the inlet pressure is high. The second Venturi
nozzle is then activated to provide a very high suction capacity
and associated high vacuum. In this case, both Venturi nozzle
suction capacities are combined to evacuate e.g. the feed line to a
suction gripper. Since the second Venturi nozzle is connected only
when required, no driver gas is wasted. In this fashion, the
modular connection of one or more additional Venturi nozzles
individually adjusts the suction performance while providing
sufficient flow velocity at high as well as low required suction
performance to always ensure safe operation of the evacuation
process.
[0008] Alternatively, the secondary nozzle branch may be connected
when the inlet pressure is below a certain switching pressure. In
this case, both nozzle branches are used only when the inlet
pressures are low and evacuation takes place only via one nozzle
branch, i.e. the primary nozzle branch when the inlet pressure is
high.
[0009] In accordance with an embodiment, the closing instrument may
be held in a first position via a preloading force which
counteracts the inlet pressure of the driver gas. The closing
instrument may e.g. be a bistable 2/2 way valve. In this case, the
preloading force is provided by a spring which acts e.g. on a
piston. Depending on whether the secondary nozzle branch is to be
connected at low or high working pressures, the first position is
defined as the open or closed position. The stop valve or closing
instrument is adapted to the desired switching direction. When the
switching pressure is reached, the inlet pressure can switch the
closing instrument into a second position with that second position
being either that state of the closing instrument with which the
secondary branch contributes to the suction performance or that
state in which it is disconnected, in dependence on the desired
switching direction.
[0010] The two nozzle branches may also have a common feed line
which contains the closing instrument. In most cases, the driver
gas is pressurized air.
[0011] According to a further embodiment, the primary and the
secondary nozzle branch may have a common suction line which may,
in particular, be a continuous suction line which communicates with
the two nozzle branches. A check valve may be disposed in the
suction line between the secondary and primary nozzle branch to
prevent leaking of the vacuum generated by the first nozzle branch
when the secondary nozzle branch is disconnected. When an
underpressure is also generated in the secondary nozzle branch, the
check valve opens and the underpressure of the secondary nozzle
branch also contributes to the suction performance in the suction
line.
[0012] Alternatively, at least the secondary nozzle branch, a
further nozzle branch, or a group of nozzle branches may each have
its own separate suction line. Towards this end, several suction
circuits may be connected or disconnected independently of each
other.
[0013] The check valve may preferably be a spring-loaded ball
valve. The spring forces may be adjusted such that even a small
force is sufficient to overcome the spring. In this case, the check
valve may already lift off during low suction performance of the
secondary nozzle branch. The low spring force is sufficient, since
the stop ball is additionally pressed against the closure seat by
the underpressure generated when the first nozzle branch is
operated to thereby safely prevent leakage. If the spring has a low
spring constant, two nozzle branches of equal suction performance
may also be operated, since, in this case, the closing element is
in a bistable state and the suction line is opened for the second
nozzle branch.
[0014] The secondary nozzle branch may have the same or a different
suction performance than the primary nozzle branch and preferably a
higher suction performance, since this ensures complete and simple
opening of the check valve. By providing different Venturi nozzles
of different types or performance classes, the suction performance
effected in the suction line and exhaust connection may be varied
to permit reliable adjustment of the required underpressure and
evacuation time.
[0015] In addition to the above-described two nozzle branches,
several primary and secondary nozzle branches, which are connected
in parallel, may also be provided, with all primary nozzle branches
being connected at the same time and all secondary nozzle branches
being connected or disconnected at a common switching pressure. In
addition to the secondary nozzle branch, a tertiary or quaternary
nozzle branch may be provided which is disconnected or connected at
a further switching pressure other than the first switching
pressure, to further improve the regulation and control of the
suction performance in accordance with the requirements.
[0016] All nozzle branches may be connected to one single suction
line, preferably in that the nozzle branches intersect that suction
line.
[0017] The check valves may be preferably provided only between
branches of different connection pressures. In this manner, no
check valves are provided between different primary nozzle branches
and only one check valve is provided between a group of primary
nozzle branches and a group of secondary nozzle branches. If, in
addition to primary and secondary nozzle branches, tertiary nozzle
branches are also provided, a check valve may be disposed between
the primary and the secondary and tertiary nozzle branches.
[0018] All components and nozzle branches of the ejector can
thereby be disposed within a common housing. The housing may
consist e.g. of a material block into which all lines are
introduced as bores with the nozzles and valves being inserted into
the block and fixed therein with remaining openings being closed by
caps. This provides particular advantages for maintenance,
configuration, and replacement of individual components.
[0019] Further advantages and features of the invention can be
extracted from the disclosure. The drawing gives a detailed
description of a particularly preferred embodiment.
BRIEF DESCRIPTION OF THE DRAWING
[0020] FIG. 1 shows a diagram of connections of an inventive
ejector;
[0021] FIG. 2 shows an exploded view of an inventive ejector;
and
[0022] FIG. 3 shows a section through an inventive ejector.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0023] FIG. 1 shows a circuit diagram of an ejector or jet pump,
designated in its entirety with 10. The ejector 10 has a primary
nozzle branch 12 and a secondary nozzle branch 14. The two nozzle
branches are connected to a feed line 16 for a driver gas, wherein
in FIG. 1, a common air supply branch 16 branches into the air
supply branches 16' and 16" for the primary nozzle branch 12 and
the secondary nozzle branch 14, respectively. The air supply branch
16' for the primary nozzle branch supplies driver gas to a first
Venturi arrangement 18 of the first supply branch 12. A switching
valve 20 is disposed in the second air supply branch 16" to pass
air to the second Venturi arrangement 22 of the second nozzle
branch 14 or to close off the air supply line 16" of the second
arrangement 22.
[0024] The valve 20 is a bistable 2/2 way valve and is explained in
more detail below.
[0025] The primary nozzle branch 12 and the secondary nozzle branch
14 are connected to a suction line 24. One single suction line 24
connects to the two nozzle branches 12, 14 in the region of their
respective cross-sectional narrowings of the Venturi arrangements
18, 22. A further line, e.g. for a suction gripper, may be
evacuated via the suction line 24 which feeds to a suction nozzle
26. A check valve 28 (a spring-loaded ball valve) is disposed in
the suction line 24 between the primary nozzle branch 12 and the
secondary nozzle branch 14 to prevent leakage of the vacuum of the
first nozzle branch 12 in the event that the secondary nozzle
branch is not connected.
[0026] In the circuit of FIG. 1, the ejector 10 is operated only
with respect to the primary nozzle branch 12 as soon as it is
loaded with driver gas (compressed air). The valve 20 is thereby
held in the blocking position. Acceleration of the compressed air
to supersonic speed in the primary nozzle branch 12 generates an
underpressure in the region of its cross-sectional narrowing in a
chamber surrounding the narrowing, through which the suction line
24 is evacuated. The check valve 28 prevents leakage of vacuum in
the chamber.
[0027] As soon as the supply pressure in the feed line 16 of the
compressed air reaches a predetermined switching pressure for the
valve 20, the second, i.e. secondary nozzle branch 14 is opened. At
this moment, the air consumption is doubled, as is the suction
volume.
[0028] As soon as the inlet pressure is reduced, the valve 20
switches back to the blocked position.
[0029] A certain switching hysteresis of the valve 20 must thereby
be taken into account.
[0030] The switching pressure is thereby predetermined by the valve
20.
[0031] The structure is explained below using an exploded view of
an inventive ejector 10. The ejector 10 is mounted in a housing 29
and can be fixed through the housing 29 to a base e.g. via mounting
locations 30.
[0032] The two nozzle branches 12 and 14 thereby consist
essentially of a receiver nozzle 32 or 34 and a driver nozzle 36 or
38, which are connected to each other via an O-ring 40 and form the
Venturi arrangements 18, 22. The cross-sectional narrowing in the
driver nozzle 36 or 38 accelerates the compressed air introduced
into the feed line 16 to supersonic speed.
[0033] A check valve 28 comprising a ball 42 as the closing body
and a spring 44 with a low spring constant is disposed between the
two nozzle branches 12 and 14 in the suction line 24 which connects
the two nozzle branches 12 and 14 and which feeds to a suction
nozzle 26. The vacuum generated in the primary nozzle branch 12 is
thereby protected from leakage with respect to the secondary nozzle
branch.
[0034] The suction line 24 is closed on both sides of the housing
29 through which it penetrates using cover flaps 46, in particular
plastic lids.
[0035] In a particularly simple fashion, the housing 29 is not
merely a cover for the individual parts but a material block into
which the individual recesses for the feed line etc. such as e.g.
the suction line and the compressed air lines of the nozzle
branches 12, 14, which intersect the suction line, are machined,
wherein only components such as the driver nozzle, the receiving
nozzle, and the valves are separate and are inserted into and fixed
in the housing block. In this fashion, replacement of the
individual component or insert is particularly easy. A jet pump 10
of this type can be easily adjusted to different types or
performance classes without having to replace the entire jet pump
10. For cleaning and/or inspection, the individual nozzles 32-38
can be easily removed, cleaned or examined and be subsequently
re-installed. Faulty individual parts may be particularly easy to
replace.
[0036] A 2/2 way valve 20 may be provided in the region of the feed
line which comprises a piston 48 which forms a unit together with a
piston seal 50 and an O-ring seal 52. The piston is pressed by a
spring 54 in the direction of its longitudinal axis, whose spring
constant and bias permits adjustment of the switching point. The
O-ring 52 thereby seals the compressed air line of the secondary
nozzle branch 14 when the piston 48 is in a closed position, i.e.
in its first or resting position.
[0037] The side of the spring 54 facing away from the piston 48
abuts a plug 56 via which the spring bias can be adjusted.
[0038] When the valve 20 is closed, compressed air for the primary
nozzle branch 12 can flow unhindered past the switching piston 48.
The switching piston has different cross-sections along its length,
with the pressure of the flowing compressed air acting on the
piston 48, via an annular surface of larger cross-section formed at
a front side of the piston 48 in the region of the larger
cross-section to oppose the loading direction of the spring 54. The
compressive forces of the pressurized air thereby depend on the
circular area 51 of the piston 48 at which those forces act as well
as on the absolute pressure.
[0039] The smaller cross-sectional surface of the piston 48 which
corresponds to a corresponding smaller bore in the housing 28 is
thereby disposed in the direction of the second 14 nozzle
branch.
[0040] If there is compressed air in the feed line 16, the piston
48 is loaded with pressure at its surface 51. This force acts
against the bias of the spring 54. As the pressure is increased and
as soon as the force exerted by the compressed air exceeds the
spring force, the piston 48 is moved against the spring force in
the direction of the plug and up to a predetermined stop. The feed
line to the secondary nozzle branch 14 is thereby opened and the
secondary nozzle branch contributes to the suction performance.
This doubles the air consumption and the suction volume.
[0041] If the supply pressure on the inlet line 16 is reduced, the
piston 48 moves back towards the second nozzle branch 14 until the
O-ring 52 of the piston seal 50, piston 48 and O-ring 52 assembly
abuts the corresponding bore 53 and the associated surface in the
housing block 29 to seal the piston 48 in the position on the
conical surface 53.
[0042] FIG. 3 shows the ejector 10 of FIG. 2 in an assembled state
illustrating the position of the check valve between the nozzle
branches 12 and 14.
[0043] The pressure forces of the compressed air thereby act on the
annular surface 51. The spring force of the spring 54 opposes these
pressure forces produced by compressed air. If the pressure forces
exceed a switching pressure, the piston 48 is pressed downwards (in
the illustration) against the spring 54 and permits passage of
compressed air to the second nozzle branch 14.
[0044] As soon as the second nozzle branch also produces a vacuum,
the ball 42 of the check valve is moved against the spring force of
the spring 44 by the vacuum in the second nozzle branch 14 and
towards the second nozzle branch 14 to open the passage in the
suction line 24, wherein additional vacuum is generated on the
suction nozzle 26, e.g. for a suction gripper. The suction
performance of the secondary nozzle branch 14 must be greater than
or equal to that of the primary branch 12 in order to hold the
check valve 28 in the open position.
[0045] As soon as the pressure in the feed line 16 decreases, and
the piston 48 closes the feed line to the second nozzle branch 14,
the ball 42 is pressed back into its valve seat by the force of the
spring 44 to close the suction line 24 in the region of the
narrowing of the first nozzle branch 12, thereby preventing
leakage.
[0046] In this fashion, a second nozzle branch 14 can be connected
only when increased suction performance is required and in all
other cases, air consumption can be reduced. The air consumption
and suction performance can thereby be efficiently controlled.
* * * * *