WO2001065581A1

WO2001065581A1 - A magnetic actuator

Info

Publication number: WO2001065581A1
Application number: PCT/IB2001/000287
Authority: WO
Inventors: Kevin Posen; Lindy Kim Finn; Craig Elle Miller
Original assignee: Cruise, Rupert, John
Priority date: 2000-03-02
Filing date: 2001-03-01
Publication date: 2001-09-07
Also published as: AU3590101A

Abstract

This invention relates to a magnetic actuator which includes a plunger having a leading end and a trailing end, and a core which together with the plunger provides a magnetic flux path along which the plunger is displaceable. The plunger is displaceable between a first operative position in which a trailing airgap between the trailing end of the plunger and the core is closed, and a leading airgap between the leading end of the plunger and the core is open, and a second displaced operative position in which the trailing airgap is open and the leading airgap is closed. The magnetic actuator also includes a plunger holding magnetic flux source for holding the plunger in either of its operative positions, and a pair of simultaneously energizable plunger displacing magnetic flux sources of the same polarity spaced along the magnetic flux path for displacing the plunger between its two operative positions.

Description

A MAGNETIC ACTUATOR

THIS INVENTION relates the operation of a magnetic actuator. It also relates to a magnetic actuator, to a magnetic actuator assembly, and to electrical switch gear incorporating such an assembly.

The applicants have found that magnetic actuators of which they are aware use heavy currents on activation. The applicants believe that an actuator having a more modest activation current requirement may be devised.

Accordingly, in a magnetic actuator which includes a plunger having a leading end and a trailing end and which is movable along a magnetic flux path provided by a magnetic core and the plunger, between a first operative position in which a trailing airgap between the core and the trailing end of the plunger is closed, and a leading airgap between the core and the leading end of the plunger is open, and a second operative position in which the leading airgap is closed and the trailing airgap is open, the invention according to a first aspect, provides a method of operating the actuator which includes the steps of providing a plunger holding magnetic flux source between the airgaps for holding the plunger in one or other of its two operative positions; and simultaneously energizing a pair of plunger displacing magnetic flux sources of the same polarity and spaced apart along the magnetic flux path, thereby to displace the plunger between its first operative position and its second operative position, and thereby to open and close the trailing and leading airgaps.

The simultaneous energizing of the plunger displacing magnetic flux sources may take place momentarily. The energizing of the plunger displacing magnetic flux sources may last at the most until closure of the leading or trailing airgap, as the case may be.

According to another aspect, the invention provides a magnetic actuator which includes a plunger having a leading end and a trailing end; a core which together with the plunger provide a magnetic flux path along which the plunger is displaceable relative to the core, the plunger having a first operative position in which a trailing airgap between the trailing end of the plunger and the core is closed, and a leading airgap between the leading end of the plunger and the core is open, and a second displaced operative position in which the trailing airgap is open and the leading airgap is closed; a plunger holding magnetic flux source between the airgaps for holding the plunger in one or the other of its two operative positions; and a pair of simultaneously energizable plunger displacing magnetic flux sources of the same polarity spaced along the magnetic flux path for displacing the plunger between its two operative positions. The plunger may be elongate, its leading end being axially spaced from its trailing end. The core may define a compartment axially longer than the plunger, within which the plunger is held captive and is axially displaceable between its operative positions.

The plunger holding flux source may be provided by at least one permanent magnet, eg. a toroidal permanent magnet, mounted between ends of the plunger.

In a preferred embodiment the plunger holding flux source is provided by a pair of permanent magnets mounted on opposite sides of the plunger between its ends.

The permanent magnets may be arranged to have like poles on opposite sides of the plunger.

The plunger displacing magnetic flux sources of the same polarity, may be provided by a pair of coils axially spaced proximate the ends of the compartment and coaxial with the plunger. There may also be provided energizing means for energizing them simultaneously. The energizing means may be operable momentarily. The coils may be connected in series.

The invention extends also to a magnetic actuator assembly which includes a plurality of magnetic actuators as described, arranged such that their plungers are spaced and in alignment; mechanical connecting means mechanically interconnecting at least two of the plungers, thereby ensuring that they are displaceable in unison; and electrical connecting means, electrically interconnecting at least two of the plunger displacing magnetic flux sources, to ensure that they are all simultaneously energizable. It is to be appreciated that , although it is advantageous to energize the displacing magnetic flux sources at substantially the same time, they can be energized at slightly differing times provided that at some point in time they are all energized at the same time or substantially simultaneously. This however is not a preferred situation.

In the assembly the cores may be integral with one another and may have plunger compartments which are spaced and aligned. Each plunger may be held captive and may be displaceable in its own compartment; and the mechanical connecting means may include a plunger rod connected to at least two of the plungers, the plunger rod being displaceable with the plungers relative to the core. The core may have a guide passage intersecting the compartments to accommodate the plunger rod.

The invention extends also to electrical switch gear which includes a pair of spaced contactors having open and closed operative positions, at least one of the contactors being movable relative to the other; a magnetic actuator as described above; and interconnecting means interconnecting the plunger to the contactors, for operative displacement of the contactors when the plunger is displaced.

The interconnecting means may include a lever pivotally mounted relative to the core, and having its working arm connected to at least one of the contactors, and having its effort arm connected to the plunger.

The invention extends further to electrical switch gear which includes a pair of spaced contactors having open and closed operative positions, at least one of the contactors being movable relative to the other; a magnetic actuator assembly as described above; and interconnecting means interconnecting the mechanical connecting means to the contactors, for operative displacement of the contactors when the plungers are displaced in unison.

The interconnecting means may include a lever pivotally mounted relative to the core, the lever, having its working arm connected to at least one of the contactors, and having its effort arm connected to the mechanical connecting means.

Further features of the invention will become apparent from the following description by way of example, of a magnetic actuator assembly, with reference to the accompanying diagrammatic drawings.

In the drawings,

Figure 1 shows a longitudinal sectional view through part of a magnetic actuator assembly, in accordance with the invention; Figure 2 shows a longitudinal sectional view corresponding to Figure 1 , including an indication of the polarities of the magnetic flux sources;

Figure 3 shows a three dimensional view of the assembly shown in Figures 1 and 2 of the drawings, in which its core windings are visible;

Figure 4 shows a view corresponding to Figure 3 with the core windings removed;

Figure 5 shows a schematic circuit diagram of a switching arrangement for energizing the core windings or coils of a magnetic actuator assembly in accordance with the invention;

Figure 6 shows the flux distribution in a longitudinal sectional view of the assembly, with the plungers in their first operative position and the coils unenergized; Figure 7 shows a view corresponding to Figure 6, but immediately after the coils have been energized and momentarily before displacement of the plungers;

Figure 8 shows a view corresponding to Figure 7, but with the coils now fully energized and the plungers about to move; Figure 9 shows a view corresponding to Figure 8, but immediately after the plungers have been displaced to their second operative position;

Figure 1 0 shows a view corresponding to Figure 9, but with the plungers held in their second operative position, and with the coils unenergized; and

Figure 1 1 shows electrical switch gear in accordance with the invention, which incorporates a magnetic actuator assembly, also in accordance with the invention. Referring to the drawings, in Figures 1 and 2 of the drawings, reference numeral 1 0 generally indicates part of a magnetic actuator assembly, in accordance with the invention. The magnetic actuator assembly shown, has three magnetic actuators, also in accordance with the invention, generally indicated by reference numeral

1 2. Each actuator 1 2 has a magnetic flux path defining means which is in the form of a ferromagnetic core 1 4, e.g. a steel core, and ferromagnetic plungers 1 6. Each plunger 1 6 has a trailing end 1 8 and an opposed leading end 20. The plungers 1 6 are displaceably mounted relative to the core 14 within core compartments 22. The compartments

22 have opposed end walls 22.1 and 22.2, the end wall 22.1 being a trailing end wall, and the end wall 22.2 being a leading end wall. The plungers 1 6 are displaceable within the compartments 22, in the direction shown by arrow 23. The spacing between the trailing ends 1 8 and the leading ends 20 of the plungers 1 6 is smaller than the spacing between the end walls 22.1 and 22.2. In other words the compartments 22 are axially longer than the plungers 1 6.

Thus in a first operative position, as indicated in Figures 1 and 2 of the drawings, open leading air gaps 24.1 are defined between the leading ends 20 of the plungers 1 6 and the end walls 22.2 of the core compartments 22. As the plungers 1 6 are displaced within the core compartments 22, to a second operative position, the leading airgaps 24.1 close, and trailing airgaps 24.2 between the end walls 22.1 of the compartments 22, and the trailing ends 1 8 of the plungers 1 6 become open. The trailing airgaps 24.2, when open, can be clearly seen in

Figures 9 and 1 0 of the drawings. When the plungers 1 6 are in their first operative position, the trailing airgaps 24.2 are closed, and the leading airgaps 24.1 are open. See Figures 1 , 2, 4, 6, 7, 8, and 1 1 . When the plungers 1 6 are in their second operative position, the trailing airgaps 24.2 are open and the leading airgaps 24.1 are closed. See Figures 9 and 1 0 of the drawings.

The plungers 1 6 are mechanically interlinked via mechanical connecting means in the form of a plunger rod 40, which runs along the length of the actuator assembly 1 0. The rod 40 ensures that the plungers 1 6 are all displaced in unison in the direction of arrow 23 when operated (see Figure 1 1 ). It is to be appreciated that any two or more of the plungers 1 6 may be interconnected and each plunger 1 6, or combinations of plungers 1 6, may dependently or independently drive an associated switching device.

Each actuator 1 2 also includes a plunger holding flux source in the form of pairs of permanent magnets 26 mounted adjacent the core compartments 22 on opposite sides of the plungers 1 6, between the airgaps 24.1 and 24.2. The magnets 26 are arranged with their polarities extending transversely to the direction of displacement of the plungers 1 6, and such that like poles of the magnets 1 6 are on opposite sides of the plungers 1 6, as indicated by way of example, in Figure 2. The result is that each plunger 1 6 provides a magnetic flux path for the magnets

26. These permanent magnets 26 are the plunger holding magnetic flux sources for holding the plungers 1 6 in the one or the other of their operative positions (see in particular Figures 1 and 1 0). It is to be appreciated that each pair of magnets 26 may be defined by a single toroidal permanent magnet. The actuators 1 2 also each have a pair of plunger displacing flux sources in the form of a pair of axially spaced core windings or coils 28, mounted adjacent each of the end walls 22.1 and 22.2 of the compartments 22, and co-axial with the direction of displacement of the plungers 1 6, as shown by arrow 23. The coils 28 can be seen in Figure

3. The coils 28 are wound and connected such that currents flowing through the coils produce plunger displacing fluxes of the same polarity in the plungers 1 6 and core 1 4.

In this example of the invention, the coils 28 are connected as shown in the circuit diagram of Figure 5, in which the pairs of wound coils are generally indicated by reference numeral 30. Here the coils 28 in a pair associated with each actuator 1 2, are connected in series with each other, and the pair of coils 30 of each actuator are connected in parallel with the pair of coils 30 of the other actuators 1 2. The coils 28 are energizable via a DC power source 32 which is applied across the pair of coils 30 through a switching bridge 34. The bridge 34 is configured such that when the switches 34.1 and 34.2 are closed and when the switches 34.3 and 34.4 are open the current will flow in one direction through the coils 28, and when 34.1 and 34.2 are open and 34.3 and 34.4 are closed, the current will flow in the opposite direction.

The operation of the magnetic actuator assembly 1 0 is demonstrated in Figures 6 through 1 0. In Figure 6, the coils 28 are shown to be unenergized and the plungers 1 6 are shown to be held in the first operative position, with the trailing ends 1 8 of the plungers 1 6 adjacent the end walls 22.1 of the compartments 22, the trailing airgaps

24.2 being closed. The leading airgaps 24.1 defined between the leading ends 20 of the plungers 1 6 and the opposing end walls 22.2 of the compartments 20, are in the open position. In this stable position the permanent magnets 26 produce a concentrated flux distribution 36 adjacent the end walls 22.1 and bridging the closed airgap 24.2 (see Figure 6) . The magnets 26 are arranged such that they produce balanced magnetic forces through the plungers 1 6, and core 14. However the flux will flow along the path which provides the highest magnetic permeability, and this is defined by the path through the closed airgaps 24.2. Thus the plungers 1 6 are held in their first operative positions by the magnetic flux concentrations 36 bridging the closed airgaps 24.2. Accordingly, no electrical power is required by the actuator 1 2 to maintain plungers 1 6 in their first operative positions.

Once the coils 28 have been energized with a suitable polarity to oppose the polarity of the flux at the closed airgaps 24.2, as shown in Figures 7, 8, 9, plunger displacing magnetic fluxes are produced in the plungers 1 6 and the core 1 4 by the coils 28 which overpower the holding flux 36 produced by the permanent magnets 26 adjacent the end walls 22.1 and adjacent the trailing ends 1 8 of the plungers 1 6. The coils 28 when energized, provide a high flux density across the open leading airgaps 24.1 and a low flux density across the trailing airgaps

24.2. This results in a magnetic force from left to right in the drawings in the direction of arrow 23 which causes displacement of the plungers 1 6 from their first operative positions into their second operative positions.

As the leading ends 20 of the plungers 1 6 approach the end walls 22.2 defining the second operative positions, the higher magnetic permeability associated with the now diminished leading airgaps 24.1 tends to increase the concentration of flux adjacent the end walls 22.2, thereby to cause accelerated displacement of the plungers 1 6. It is therefore possible to de-energize the coils 28 before the leading ends 20 of the plungers 1 6 reach the end walls 22.2 and before they close the leading airgaps 24.1 . The coils 28 therefore need only be energized momentarily, to achieve displacement of the plungers 1 6. That is the coils 28 are typically energized for a period lasting at the most until the leading airgaps 24.1 are closed.

Once the leading ends 20 of the plungers 1 6 reach the end walls 22.2, the plungers 1 6 are once again held in position by the holding fluxes of the permanent magnets 26 in the second operative position. The holding fluxes in this operative position is indicated by reference numeral 38, bridging the now closed airgaps 24.1 . It will be noted that adjacent magnetic actuator 1 2 shares a common wall of the core 14.

Further, the core 1 4 may have different shapes and configurations dependent upon the selected design of the actuator 1 2.

It is possible to displace the plungers 1 6 back into the first operative position by reversing the direction of current flow through the coils 28 which will produce a magnetic force in the plungers 1 6 and core

14 in the opposite direction, that is from right to left in the drawings. For such reverse operation, the leading ends 20 of the plungers 1 6 then become trailing ends, and the trailing ends 1 8 become leading ends.

In Figure 1 1 , reference numeral 50 generally indicates electrical switch gear assembly, also in accordance with the invention, including an actuator assembly 1 0. The assembly includes contactors 42 and mechanical connecting means in the form of a plunger rod 40, mechanically interconnecting the plungers 1 6 of the actuator 10 via a guide passage 43. The rod 40 is displaceable in the direction of arrow 23, relative to the core 1 4. The rod 40 is in turn coupled by a lever 41 to the contactors 42. The coils 28 may therefore be energized to cause the connecting rod 40 to either open or close the contactors 42, as indicated by arrows 23.1 .

The inventors believe that the invention, as described, provides an improved magnetic actuator 1 0 and magnetic actuator assembly 50 which make efficient use of the actuator core material and reduces the required current carrying winding material. The use of a pair of simultaneously momentarily energizable coil windings 30 which spread and re-distribute the flux in the core 1 4 makes effective use of the core material. Thus the overall flux densities throughout the core 1 4 are reduced over that which would normally be required. The volume and hence the cost of the core material are thus reduced. Furthermore, the use of spaced simultaneously energizable coil windings 28 reduces the maximum magnetomotive force required to cause displacement of the plungers 1 6. This results in a reduction in the volume of current carrying coil material (e.g. copper) in each of the coil windings. This further reduces the cost of the manufacture of the actuator.

Claims

CLAIMS:

1 . In a magnetic actuator which includes a plunger having a leading end and a trailing end and which is movable along a magnetic flux path provided by a magnetic core and the plunger, between a first operative position in which a trailing airgap between the core and the trailing end of the plunger is closed, and a leading airgap between the core and the leading end of the plunger is open, and a second operative position in which the leading airgap is closed and the trailing airgap is open, there is provided a method of operating the actuator which includes the steps of providing a plunger holding magnetic flux source between the airgaps for holding the plunger in one or other of its two operative positions; and simultaneously energizing a pair of plunger displacing magnetic flux sources of the same polarity and spaced apart along the magnetic flux path, thereby to displace the plunger between its first operative position and its second operative position, and thereby to open and close the trailing and leading airgaps.

2. A method as claimed in Claim 1 , in which the simultaneous energizing of the plunger displacing magnetic flux sources takes place momentarily.

3. A method as claimed in Claim 2, in which the energizing of the plunger displacing magnetic flux sources lasts at the most until closure of the airgap.

4. A magnetic actuator, which includes a plunger having a leading end and a trailing end; a core which together with the plunger provide a magnetic flux path along which the plunger is displaceable relative to the core, the plunger having a first operative position in which a trailing airgap between the trailing end of the plunger and the core is closed, and a leading airgap between the leading end of the plunger and the core is open, and a second displaced operative position in which the trailing airgap is open and the leading airgap is closed; a plunger holding magnetic flux source between the airgaps for holding the plunger in one or the other of its two operative positions; and a pair of simultaneously energizable plunger displacing magnetic flux sources of the same polarity spaced along the magnetic flux path for displacing the plunger between its two operative positions.

5. A magnetic actuator as claimed in Claim 4, in which the plunger is elongate, its leading end being axially spaced from its trailing end, and in which the core defines a compartment axially longer than the plunger, and within which the plunger is held captive and is axially displaceable between its operative positions.

6. A magnetic actuator as claimed in Claim 5, in which the plunger holding flux source is provided by at least one permanent magnet mounted between ends of the plunger.

7. A magnetic actuator as claimed in Claim 5 or Claim 6, in which the plunger holding flux source is provided by a pair of permanent magnets mounted on opposite sides of the plunger between its ends.

8. A magnetic actuator as claimed in Claim 7, in which the permanent magnets are arranged to have like poles on opposite sides of the plunger.

9. A magnetic actuator as claimed in any one of the preceding claims 5 to 8 inclusive, in which the plunger displacing magnetic flux sources of the same polarity, are provided by a pair of coils axially spaced proximate the ends of the compartment and coaxial with the plunger; and in which there is provided energizing means for energizing them substantially simultaneously.

10. A magnetic actuator as claimed in Claim 9, in which the energizing means are operable momentarily.

1 1 . A magnetic actuator as claimed in Claim 9 or Claim 1 0, in which the coils are connected in series.

1 2. A magnetic actuator assembly, which includes a plurality of magnetic actuators as claimed in any one of the claims 9 to 1 1 inclusive, arranged such that their plungers are spaced and in alignment; mechanical connecting means mechanically interconnecting at least two of the plungers, thereby ensuring that they are displaceable in unison; and electrical connecting means, electrically interconnecting at least two of the plunger displacing magnetic flux sources, to ensure that they are all simultaneously energizable.

1 3. A magnetic actuator assembly as claimed in Claim 1 2, in which the cores are integral with one another and have plunger compartments which are spaced and aligned, and in which each plunger is held captive and is displaceable in its own compartment; and in which the mechanical connecting means includes a plunger rod connected to at least two of the plungers, the plunger rod being displaceable with the plungers relative to the core.

14. A magnetic actuator assembly as claimed in Claim 1 3, in which the core has a guide passage intersecting the compartments to accommodate the plunger rod.

1 5. Electrical switch gear, which includes a pair of spaced contactors having open and closed operative positions, at least one of the contactors being movable relative to the other; a magnetic actuator as claimed in any one of the claims 4 to 1 1 inclusive; and interconnecting means interconnecting the plunger to the contactors, for operative displacement of the contactors when the plunger is displaced.

1 6. Electrical switch gear as claimed in Claim 1 5, in which the interconnecting means includes a lever pivotally mounted relative to the core, and having its working arm connected to at least one of the contactors, and having its effort arm connected to the plunger.

1 7. Electrical switch gear, which includes a pair of spaced contactors having open and closed operative positions, at least one of the contactors being movable relative to the other; a magnetic actuator assembly as claimed in any one of the claims 1 2 to 14 inclusive; and interconnecting means interconnecting the mechanical connecting means to the contactors, for operative displacement of the contactors when the plungers are displaced in unison.

1 8. Electrical switch gear as claimed in Claim 1 7 in which the interconnecting means includes a lever pivotally mounted relative to the core, the lever, having its working arm connected to at least one of the contactors, and having its effort arm connected to the mechanical connecting means.

1 9. A method of operating a magnetic actuator, substantially herein described and illustrated.

20. A magnetic actuator, substantially as herein described and illustrated.

21 . A magnetic actuator assembly, substantially as herein described and illustrated.

22. Electrical switch gear, substantially as herein described and illustrated.