U.S. patent application number 12/096058 was filed with the patent office on 2008-11-06 for drive system for a cleaning head disposed in a tank.
This patent application is currently assigned to ALFA LAVAL TANK EQUIPMENT A/S. Invention is credited to Leon Hjorslev, Hans Erik Jorgensen.
Application Number | 20080272205 12/096058 |
Document ID | / |
Family ID | 37667291 |
Filed Date | 2008-11-06 |
United States Patent
Application |
20080272205 |
Kind Code |
A1 |
Jorgensen; Hans Erik ; et
al. |
November 6, 2008 |
Drive System for a Cleaning Head Disposed in a Tank
Abstract
When, according to the invention, constructing a drive system
for rotating the cleaning head in a tank and allowing the system to
comprise a hysteresis coupling having two magnetic parts which are
present inside the liquid space (4) and outside this, respectively,
a completely liquid-tight separation between the housing (2) and
the gear (14) may be ensured. The magnetic part (8, 18) of the
hysteresis coupling may be formed by electromagnets, and with a
displaceable (13) position of the one part relative to the other
part (11, 19) the coupling may be adjusted with respect to the
transferred torque and/or speed.
Inventors: |
Jorgensen; Hans Erik;
(Ishoj, DK) ; Hjorslev; Leon; (Ishoj, DK) |
Correspondence
Address: |
WILLIAM J. SAPONE;COLEMAN SUDOL SAPONE P.C.
714 COLORADO AVENUE
BRIDGE PORT
CT
06605
US
|
Assignee: |
ALFA LAVAL TANK EQUIPMENT
A/S
Ishoj
DK
|
Family ID: |
37667291 |
Appl. No.: |
12/096058 |
Filed: |
November 20, 2006 |
PCT Filed: |
November 20, 2006 |
PCT NO: |
PCT/DK2006/000642 |
371 Date: |
June 24, 2008 |
Current U.S.
Class: |
239/240 ;
239/263.3; 310/103 |
Current CPC
Class: |
B63B 57/02 20130101;
H02K 49/065 20130101; B08B 9/0936 20130101; B05B 3/0422
20130101 |
Class at
Publication: |
239/240 ;
239/263.3; 310/103 |
International
Class: |
B05B 3/04 20060101
B05B003/04; H02K 49/06 20060101 H02K049/06; B08B 9/093 20060101
B08B009/093; B63B 57/02 20060101 B63B057/02 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 30, 2005 |
DK |
PA2005 01853 |
Claims
1. A drive system for rotating a cleaning head in a tank, said
drive system comprising a housing (2) having a propeller (7)
mounted in a liquid channel (4) to which cleaning liquid is
supplied under pressure, as well as a gear which is driven by the
propeller (7), and which is mounted separated from the cleaning
liquid in the housing (2), said gear transferring the rotation
produced by the propeller (7) to a reduced rotation of the cleaning
head in the tank (1), wherein the rotation produced by the
propeller (7) is transferred to the gear via a magnetic coupling
having coupling parts, the one coupling part of which being
disposed inside the housing in the liquid channel and the other
coupling part of which being disposed outside the housing, and
wherein the rotation from the propeller (7) is transferred to the
gear via a hysteresis coupling comprising a rotating magnetic
inductor (18) driven by the propeller (7) or a hysteresis part (19)
in the housing (2) which drives a rotating part mounted outside the
housing (2), either of a ferromagnetic hysteresis material (19) or
a magnetic part (18) which is connected with the input shaft (12)
of the gear characterized in that the coupling parts are configured
as two concentrically mounted cylinders (16,19) with magnets (18)
mounted on the cylinder (16) around the shaft (6) extending from
the propeller (7) and hysteresis cylinder (19) placed on the
outside of the cylinder (16) and connected to the gear thereby
achieving a more compact and efficient coupling and drive
system.
2. A drive system according to claim 1, characterized in that the
coupling part (19) outside the housing (2) may be displaced (13)
for variably changing the distance to cooperating coupling part (8,
9 and 11) and thereby for variably transferring the torque and/or
speed in the hysteresis coupling.
3. A drive system according to claim 1, characterized in that the
magnetic inductor is provided with a plurality of permanent magnets
(18) for generating the necessary magnetic field strength and
polarity.
4. A drive system according to claim 1, characterized in that the
magnetic inductor (16, 18) is provided with electromagnetic magnets
for variable adjustment of the magnetic field strength instead of
moving the hysteresis cylinder.
5. A drive system according to claim 1, characterized in that the
rotation of the gear is transferred to a drive shaft (15) for the
cleaning head via a further hysteresis coupling.
6. A drive system according to claim 2, characterized in that the
magnetic inductor is provided with a plurality of permanent magnets
(18) for generating the necessary magnetic field strength and
polarity.
7. A drive system according to claim 2, characterized in that the
magnetic inductor (16, 18) is provided with electromagnetic magnets
for variable adjustment of the magnetic field strength instead of
moving the hysteresis cylinder.
8. A drive system according to claim 3, characterized in that the
magnetic inductor (16, 18) is provided with electromagnetic magnets
for variable adjustment of the magnetic field strength instead of
moving the hysteresis cylinder.
Description
THE PRIOR ART
[0001] The invention relates to a drive system for rotating a
cleaning head in a tank, said drive system comprising a housing
having a propeller mounted in a liquid channel to which cleaning
liquid is supplied under pressure, as well as a gear which is
driven by the propeller, and which is mounted separated from the
cleaning liquid in the housing as a safeguard against leakage of
cleaning liquid, said gear transferring the rotation produced by
the propeller to a reduced rotation of the cleaning head in the
tank, wherein the rotation produced by the propeller is transferred
to the gear via a magnetic coupling having coupling parts, the one
coupling part of which being disposed inside the housing in the
liquid channel and the other coupling part of which being disposed
outside the housing, and wherein the coupling parts are configured
either as mutually parallel discs or as two cylindrical,
concentrically mounted discs.
[0002] As a safeguard against leakage it is known to separate the
driving propeller shaft, which extends in the liquid flow, from the
gear itself, which is mounted outside the liquid flow. This may
take place by means of various gaskets and stuffing boxes, but it
has been found that these do not always operate reliably, in
particular after wear, liquid exposure and ageing.
[0003] To improve these conditions, it is known to separate the
parts completely by a wall between the liquid channel and the outer
side of the housing when transferring the torque via a magnetic
drive system, where the magnetic part driven by the propeller is
mounted inside the liquid flow, while the driven magnetic part
mounted outside the housing is connected with the gear. Thus, the
parts are coupled together magnetically to transfer the torque and
the rotation caused thereby.
[0004] Such a drive system for a tank cleaning system is disclosed
in the European Patent EP 0 723 909 A1, where it may be seen in
FIG. 2 that the propeller inside the liquid channel drives a
disc-shaped magnetic part, which is seated internally in the
channel, and which is coupled magnetically to another disc-shaped
magnetic part outside the channel. It is stated in claim 2 of the
document that both magnetic parts are composed of permanent
magnets. It is moreover stated that the magnetic parts may have
another configuration than the shown parallel discs, it being
stated that the one magnetic part may be disposed inside the other.
Speed adjustment may be performed by manually adjusting a counter
nut, so that the position and the spacing of the propeller from the
walls in the channel are displaced, thereby causing a change in the
speed of rotation of the propeller.
[0005] Another European Patent EP 0 084 342 A2 discloses a washing
machine for cleaning surgical instruments, such as e.g. endoscopes
and the like. The washing machine is equipped with a set of
rotatable washing nozzles which are driven by a motor arranged
outside the washing machine, said motor transferring its rotation
via a magnetic coupling to the rotatable set of washing nozzles. No
gear mechanisms are included in the system, and its speed cannot be
adjusted. The document mentions parallel disc-shaped magnetic parts
as well as cylindrical, concentrically arranged magnetic parts. It
is stated that the magnetic parts are equipped with permanent
magnets, but that they may also be constructed as electromagnets.
No great torque has to be transferred in order to start the washing
machine, and the reaction force of the nozzles will contribute to
rotating the washing nozzles in the washing machine.
[0006] In practice, however, it is difficult to make such a
magnetic coupling having permanent magnets work in connection with
cleaning heads for tanks, especially because of a relatively great
starting torque and the high speed of rotation of the driving
magnetic part at the moment of start. These conditions may have as
a result that the driven part does not enter into magnetic
engagement and thus cannot transfer the torque. Such a situation
occurs when the starting torque exceeds the maximum torque of the
coupling. The coupling slips in a jerky and shaking manner, because
the magnetic forces are interrupted and can then only transfer very
small torques. Couplings of this type having permanent magnets are
called synchronous couplings for the same reason, precisely because
it is a requirement that the coupling parts can move together. In
other words, it is necessary to dimension the coupling such that
its maximum torque is considerably greater than its starting torque
if the system is to be able to start. Synchronous couplings having
a torque of up to 1000 Nm are known.
[0007] To this should be added that such a magnetic coupling cannot
readily be set to transfer a variable torque or a variable
speed.
THE OBJECT OF THE INVENTION
[0008] The object of the invention is to remedy these many
drawbacks, and this is achieved by means of a drive system, wherein
the rotation from the propeller is transferred to the gear by a
hysteresis coupling comprising a rotating magnetic inductor driven
by the propeller, or a hysteresis part in the housing which drives
a rotating part mounted outside the housing, either of a
ferromagnetic hysteresis material or a magnetic part which is
connected with the input shaft of the gear.
[0009] Such a hysteresis coupling provides for an unprecedented
possibility of ensuring a quite certain torque transfer of the
rotating movement also at the start phase for cleaning heads for
tanks. It has been found that in spite of the great difference in
the speed of rotation at the moment of start between the driving
and the driven magnetic parts, the hysteresis coupling is capable
of supplying a torque which is sufficiently great to accelerate the
driven magnetic part and thereby the gear in terms of speed, if it
is dimensioned correctly, that is that it can transfer a torque
which is greater than the starting torque. The advantageous
properties of the hysteresis coupling include e.g. its ability to
transfer an almost constant torque independently of the relative
speed between the coupling parts, and the ability of the coupling
to operate with a continuous or varying slip, said slip being
"soft" and without any detrimental effect on the structure.
[0010] The mutual position of the inductor and the hysteresis part
may be selected freely in dependence on the conditions, so that the
one part may be placed either "dry" in the gear or in the liquid
flow in the housing. This hysteresis coupling will operate in a
housing of a non-magnetic material, such as stainless steel, which
is a preferred material for use in connection with cleaning
equipment of this type.
[0011] The drive system is maintenance-free and will therefore not
require any form of service.
[0012] When, as stated in claim 2, the gap between the coupling
parts may be varied, it is possible to adjust the energy content in
the gap and thereby the magnetic forces between the coupling parts,
whereby the coupling may be adjusted to transfer a given torque
and/or a given speed.
[0013] When, as stated in claims 3 and 4, the magnetic field is
produced either by means of permanent magnets or by means of
electromagnets, desired magnetic properties may be achieved, and as
far as the electromagnets are concerned, also a variable field
strength.
[0014] Finally, it is expedient, as stated in claim 5, to transfer
the rotating movement of the gear to the cleaning head via a
further magnetic or hysteresis coupling, as a total separation
between the liquid part and the gear may be achieved thereby.
THE DRAWING
[0015] Preferred exemplary embodiments according to the invention
will be described more fully below with reference to the drawing,
in which
[0016] FIG. 1 shows a sectional view of a drive system having
magnetic parts mounted in parallel,
[0017] FIG. 2 shows a similar system having concentrically mounted
magnetic parts, and
[0018] FIG. 3 shows a sectional view of a drive system with a
reverse position of the magnetic parts relative to the example in
FIG. 1.
DESCRIPTION OF THE EXEMPLARY EMBODIMENTS
[0019] Three exemplary embodiments shown in FIG. 1, FIG. 2 and FIG.
3, respectively, will be described below.
[0020] Apart from the hysteresis coupling itself, a section through
the driving part of the cleaning equipment is shown in the
examples, viz. a housing 2 which has a liquid inlet 3 for cleaning
liquid under pressure, said liquid flowing past a propeller 7 which
is thereby caused to rotate with a speed of rotation of several
thousand revolutions per minute. The rotation of the propellers 7
is transferred via a shaft 6 to the magnetic part placed in the
housing 2. The liquid flow is conveyed through the channel 4 as
liquid which is conveyed via a pipe (not shown) to the cleaning
head, which is present down in the tank 1.
[0021] The cleaning head is rotatable by means of a rotary shaft
15, and it is also provided with rotating nozzles to eject cleaning
liquid under pressure and thereby to clean the entire internal
surface of the tank.
[0022] Since the rotation of the cleaning head takes place at low
revolutions, a gear must be interposed between the driving
propeller 7 and the rotary shaft 15.
[0023] This gear is mounted on the housing 2, as indicated by a
simple line 14. The input shaft of the gear is indicated at 12, and
its output shaft having a reduced speed of rotation is indicated at
15.
[0024] The housing 2 with the gear is mounted externally on the
tank 1, as indicated.
[0025] There is no connection between the driving propeller 7
mounted in the liquid channel 4 and the driven part in that the
housing 2 is completely closed off as a safeguard against leakage
at the wall part 10.
[0026] Moreover, the leakage safeguard may be enhanced by
establishing a physical separation (not shown) between the gear and
the rotary shaft 15 by mounting, in a quite similar manner, a
further hysteresis coupling for transferring the rotary movement.
This coupling (not shown) may be constructed similar to the
coupling which is shown, and which will be described below.
[0027] The first exemplary embodiment, which is shown in FIG. 1,
will be described now.
[0028] The propeller 7 is secured to a shaft 6, which, at the top,
is provided with a disc-shaped magnetic inductor 9 provided with a
plurality of permanent magnets 8.
[0029] These magnets 8 produce a magnetic field, and few magnets
having a great polarizing face of e.g. the AlNiCo magnetic type may
be used, or a large number of small permanent magnets having a
great magnetic force and small surface areas may be selected.
[0030] Instead of the magnets 8, electromagnets may be mounted,
which have the advantage that the strength of the magnetic field
may be varied steplessly by changing the voltage. This provides for
the option of a variable adjustability of the torque and/or the
speed which is to be transferred via the coupling.
[0031] As shown in FIG. 1, the housing 2 is closed by means of a
wall part 10.
[0032] The hysteresis part in the form of a disc 11 is mounted on
the outer side of this wall part 10, said disc extending in
parallel with the disc-shaped inductor 9 and such that they are
both rotatable about the same axis of rotation. The disc 11 is
preferably made of a magnetic material containing metal oxides,
such as Fe 203 powder which is electrically insulated. This
material has a high isotropic electrical resistance which
effectively prevents the generation of eddy currents in the
hysteresis part. Further, the magnetic properties are good, even at
relatively high temperatures.
[0033] Instead of this embodiment, it is conceivable to use a
laminated material having layers of a ferromagnetic hysteresis
material, which is insulated from each other by means of dielectric
films.
[0034] The structure of this coupling is such that it can transfer
a torque generated by the propeller 7 to the input shaft 12 of the
gear in a manner which comprises parts that are separated from each
other by means of an air gap and a wall.
[0035] Experience has shown that a relatively large gap between the
magnetic parts results in a lower torque and/or a lower speed
transferred via the coupling.
[0036] In order to be able to adjust the coupling and thereby the
torque, the hysteresis part is mounted on the shaft 12 such that it
may be adjusted in an axial direction, as indicated by arrows 13.
In a generally known manner, the coupling may be made adjustable
from the outside, e.g. externally on the housing 14.
[0037] A second embodiment of the hysteresis coupling is shown in
FIG. 2. The coupling part comprises two concentrically mounted
rings, viz. an internally secured magnetic ring 16 with magnets 18
mounted on the shaft 6 and a ring mounted externally on the housing
and extending externally on the partition 17.
[0038] The cooperating hysteresis ring 19 extends around the
partition 17 and the ring 16 with magnets 18, said hysteresis ring
being in turn secured to the input shaft 12 of the gear.
[0039] This coupling, too, may be adjusted by an axial movement of
the outer hysteresis ring 19, thereby changing the torque and/or
the speed, as indicated by arrows 13.
[0040] This embodiment of the coupling is very compact and can
transfer high torques because of the radially extending air gap,
which gives a very high torque. Thus, great torques may be
transferred with a relatively low magnetization.
[0041] In the exemplary embodiments shown in FIGS. 1 and 2, the
magnetic part is arranged in the liquid space.
[0042] An example of a reverse arrangement of the magnetic parts is
shown in FIG. 3, from which it appears that the hysteresis part 11
is disposed in the housing, while the inductive magnetic part 8, 9
is disposed externally on the housing 2.
[0043] This position of the inductive part is particularly
advantageous where electromagnets are used, as, technically, it is
easier to establish the necessary electrical connections in a dry
atmosphere. Moreover, it is also possible to utilize the liquid for
the cooling of the hysteresis part.
[0044] Also the structure shown in FIG. 2 may be "reversed" so that
the magnetic part 16, 18 extends externally on the hysteresis
part.
[0045] Finally, the drive system may be extended with a further
magnetic coupling to transfer the rotary movement of the gear to
the rotary shaft 15 of the cleaning head.
[0046] Total liquid separation between the liquid in the housing 2
and the gear may be achieved hereby, as the housing is thus closed
completely and thereby protected against leakage of liquid, caused
e.g. by wear of the shaft seals.
* * * * *