Abstract
Flux shift trip device to prevent demagnetization of magnet from external field by providing a low reluctance path to the external field flux lines and protects it from shocks and vibrations by strengthening pull of magnet with optimum utilization of the magnetic energy comprises frame means (1), controller means (3) operatively located on top surface (1a) of the frame means (1) and ergonomically constructed such that desired air gap generated during assembly of actuator means co-operatively connected to the controller means is maintained. The actuator means comprises armature means (11), spring means (4), flux shunting means (8) and support means (7).
Specification
FORM2
THE PATENTS ACT, 1970
(39 of 1970)
&
The Patents Rules, 2003
COMPLETE SPECIFICATION
(See section 10; rule 13)
1. Title of the invention - ACTUATING DEVICE FOR CIRCUIT BREAKERS
2. Applicant
(a) NAME : LARSEN & TOUBRO LIMITED
(b) NATIONALITY : Indian Company
(c) ADDRESS : L & T House, Ballard Estate, Mumbai 400 001,
State of Maharashtra, India
3. PREAMBLE TO THE DESCRIPTION
The following specification particularly describes the invention and the manner in which it is to be performed :
Field Of Invention
The present invention relates to a sensitive flux shift trip device for operating switching mechanism/apparatus as circuit breaker mechanism and the like. More particularly, the invention relates to a flux shift trip device comprising specific constructional arrangements with the advantage of accommodation in miniaturized circuit breakers preventing demagnetization of magnet by providing low reluctance path to the external field flux lines and making the device immune to shocks and vibrations by strengthening pull of magnet with optimum utilization of the magnetic energy.
Background And Prior Art
A trip device for tripping a circuit breaker is generally an electromagnetic device, which mechanically trips a circuit breaker mechanism to open the electrical contacts when the device is pulsed by a momentary low energy electrical signal supplied under abnormal or overload conditions.
US 4251789 discloses a flux shift device having feature of remote
indication of tripping of circuit breaker. A "bell alarm" switch is
incorporated in the circuit breaker. The trip alarm remotely indicates
tripping of circuit breaker.
US 3693122 discloses a flux diverter element which interfaces between the actuator and the magnet This element insures immediate response to a flux canceling electrical signal and prevents possible demagnetization of permanent magnet when the trip signal becomes exceptionally large.
Generally, a sensitive flux shift trip device is required to be provided for reliable tripping of circuit breaker mechanism under the worst set of conditions where low energy is available, and not to be accidentally activated or triggered due to shock or vibration in the circuit breaker.
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Also the device should be compact so that it can be accommodated in miniaturized circuit breakers.
Objects Of Invention
Thus the basic object of the present invention is to provide a reliable sensitive flux shift trip device of relatively small in size without its permanent magnet being demagnetized by external fields.
Another object is to provide tripping operation by relatively small amounts of electrical energy.
The other object is to provide device immune to shocks and vibrations in an industrially applicable environment by optimum utilization of permanent magnetic energy.
Summary Of Invention
Thus according to the basic aspect of the present invention there is provided a flux shift trip device adapted to prevent demagnetization of magnet from external field by providing a low reluctance path to the external field flux lines and protects it from shocks and vibrations by strengthening pull of magnet with optimum utilization of the magnetic energy, the said device comprising:
(i) frame means;
(ii) controller means operatively located on top surface of said frame means wherein said controller means being ergonomically constructed such that desired air gap generated during assembly of actuator means cooperatively connected to said controller means is maintained; and
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(iii) said actuator means comprising (a) armature means operatively disposed in controller means, (b) spring means wound around the armature means and operatively rested on said controller means such that it provides resilient motion to the armature means, (c) flux shunting means to limit tripping flux in operative connection with said armature means and (d) support means operatively engaged with the flux shunting means and comprising means to trip.
Detailed Description Of Invention
In the present invention flux shift trip device comprises of rectangular close shaped frame of permeable magnetic material comprising aperture in the top wall to locate controller means adapted to take care of excessive air gap, which is generated during assembly due to variation in other components of the device. The controller means comprises cap made up of a permeable magnetic material and comprising ergonomical inner surface construction having small circular opening at top surface and large circular openings at the bottom of the cap, the said small circular opening proceeding downward to form cylindrical hole with diameter greater than that of the circular opening. The device comprises actuator means co-operatively connected to the controller means comprising armature means operatively disposed in controller means, spring means wound around the armature means and operatively rested on said controller means, flux shunting means to limit tripping flux in operative connection with said armature means and support means operatively engaged with the flux shunting means and comprising means to trip. The cap rests on circular plate means made up of magnetic material wherein the circular plate transfers pressure exerted by the cap on flux shunting means through a non magnetic means comprising
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bobbin to ensure an airtight assembly. The bobbin is placed operatively in between the flux shunting means and the frame. The frame comprises circular opening at its top surface wherein the armature means is coaxially disposed passing through the circular opening of the cap in a manner that the armature means is able to perform resilient move-in-move out motion. Straight movement of the armature means is guided by non-magnetic cylindrical member placed concentrically within the cap.
The armature means comprises plunger being ergonomically stepped cut having two surfaces. The said surfaces comprises surface 1 and surface 2 having predetermined diameters wherein the diameter of surface 1 is less than that of surface 2. The plungers is surrounded by spring means, which is wound round the plunger through a specific length covering partially the surface 1 and surface 2. The said spring means comprises compression spring supported between adjustable rotatable knob means attached to the plunger and large circular opening of the cap. The knob is screwed to the plunger and the adjustment of the knob by winding and unwinding results in the adjustment of pre-load of the compression spring. Flux shunting means is provided in operative connection with the surface 2 of the plunger. The flux shunting means comprises diverter plate having shunt path containing non-magnetic gap for limiting the amount of tripping flux passing through it. The diverter is so designed with extrusion that in set position minimum amount of flux passes through the shunt path thereby increasing the hold of magnet on armature i.e. plunger and in actuated position larger amount of flux passes through it thereby reducing the hold of magnet on armature i.e. plunger. The diverter comprises rectangular transversely extending base portion in close spaced relation with the side walls of the frame and is in closed engagement with magnetic member supported in aperture provided in the bottom wall of the frame. The extrusion of the diverter has surface contact with surface 2 of the plunger.
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The device comprises magnetic member located vertically in aperture provided in bottom wall of the frame. The magnetic member comprises cylindrical high induction permanent magnet placed within the non magnetic member having a definite concentricity between them. In another embodiment of the said invention the said permanent magnet member can also be supported by a horizontal member or clamping arrangement made up of non magnetic material and having plurality of stepped holes of predetermined dimensions.
The close engagement of the cylindrical high induction permanent magnet with end wall ensures a further airtight assembly by transferring pressure exerted by the cap through bobbin, circular plate and diverter plate.
Therefore the normal flux path for the flux produced by the permanent magnet is from its one end surface into the flux diverter, into the plunger, from thence into member, from thence into the frame through its side walls, to the top and bottom walls of the frame and back to the end wall of the permanent magnet as this provides the least reluctance path for the flux lines developed by permanent magnet. This holds the plunger in retracted or set position against the bias of the compression spring. For the purpose of causing the release of plunger a trip coil is wound on the bobbin means so as to surround the interface of the plunger and the extrusion of the flux diverter. The bobbin is dimensioned in a manner that the interface of the plunger and the flux diverter is projected in the center along its length where the trip coil is wound. The trip signal to the coil is provided by the electronic circuit of the circuit breaker.
During operation, the occurrence of a trip signal current through the coil in predetermined direction develops a magnetomotive force (MMF) which
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acts in opposite direction to the flux created by the permanent magnet across the interface of the plunger and the projection (extrusion) of the flux diverter. This causes the flux lines developed by the permanent magnet to take an alternate path through the flux diverter transversely extending base member and then through the non-magnetic gap between flux diverter and frame and then through the side walls of frame and back to the end surface of the permanent magnet.
The decrease of the net flux across the interface of the plunger and the cylindrical projection (extrusion) of the flux diverter reduces the hold of permanent magnet on plunger. Hence when a trip current of sufficient predetermined amplitude flows through the trip coil the plunger is released and moves outwardly under the force of compression spring. The plunger engages with the trip member of the circuit breaker and trips the breaker. The plunger is then reset from the actuated position to its set position by suitable means (not shown).
In set position the portion of the flux developed by the permanent magnet can also take an alternate path through flux diverter. Its desired that in set position the maximum portion of the flux developed by the permanent magnet flows through the plunger and thus reluctance to the flux path along the transversely extending portion of flux diverter is comparatively high. However to achieve the tripping action by consuming low energy, demands, that the reluctance of the flux path along the transversely extending portion should be less. So to meet the contradictory requirements the members along the two paths should be dimensioned properly.
Also the reliability of the flux shift device in the presence of external fields is maintained by keeping the cylindrical portion (extrusion) of the diverter and the plunger in saturation. The illustrated construction of the
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frame of preferred embodiment helps in optimizing the size of device. Being a close construction it offers minimum reluctance to the flux lines flowing through it and hence helps in optimum utilization of the flux developed by permanent magnet.
Brief Description Of Accompanying Figures
Figure 1 illustrates the front view of a sensitive flux shift trip device of the present invention.
Figure 2 illustrates the front view, partly in section, of the device in set position.
Figure 3 illustrates the front view, partly in section, of the device in actuated position.
Figure 4 illustrates the scaled isometric view of the device.
Detailed Description Of Accompanying Figures
Referring to figure 1 the device comprises close shaped frame (1) made up of permeable magnetic material comprising an aperture (2) (not visible in figure 1) in the top wall (la) to locate the component i.e cap (3). The cap (3) is fitted in the aperture (2) in a vertical manner. The front view of the flux shift assembly unit further discloses compression spring (4) and adjustable knob (5).
Referring to figure 2 circular plate (6) made up of a magnetic material is supported by bobbin (7). The cap (3) rests on said circular plate (6) wherein the plate (6) transfers the pressure exerted by cap (3) on the diverter (8) and permanent magnetic member (9) through bobbin (7) to ensure an airtight assembly. Magnetic member (9) is supported in the end wall (lb) by suitable locating means comprising predetermined aperture in the end wall (lb) (not visible in figure 2). The close
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engagement of the member (9) with end wall (lb) ensures a further airtight assembly by transferring pressure exerted by cap (3) through the said components (6, 7 and 8).
In the figure component (10) made up of non-magnetic material is placed concentrically with member (9) to shield the magnetic member (9) from foreign particles. Cylindrical armature (plunger) (11) is supported for reciprocal straight-line movement through a corresponding opening in the end wall (la) of frame (1) and hence through the circular opening (3a) in cap (3). The armature (plunger) (11) comprises surface 1 (15) and surface 2 (16) having predetermined diameters wherein the diameter of surface 1 (15) is less than that of surface 2 (16). Straight movement of the plunger (11) is guided by cylindrical member (12). The plunger (11) is biased for the outward movement through the frame member (1) by compressing spring (4). The said spring (4) is supported between the knob (5) and circular opening (3c) of cap (3). The flux-diverter (8) comprises rectangular transversely extending base portion (8b) and is in close spaced relation with the side walls of the frame (1). The flux diverter (8) has a cylindrical extension (8a). The said cylindrical member (12) is concentrically arranged with cylindrical extrusion (8a) of diverter (8) and is supported partly in the cylindrical hole (3b) of cap (3). Trip coil (13) is wound on the bobbin (7) so as to surround the interface of the plunger (11) and the extrusion (8a) of the flux diverter (8).
In figure 3 the front view, partly in section, of the device in actuated position is illustrated. The plunger (11) is detached from diverter (8) with a predetermined space (14) in the between the extrusion (8a) of diverter (8) and the plunger (11).
Apart from the actuating device for circuit breaker the device can also be used in remote operations for other actuating mechanisms
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While only one specific embodiment of the invention has been revealed and described, it will be obvious that many modifications there of may readily be made. It is therefore, intended by the appended claims to cover all such modifications as fall within the true spirit and scope of the invention.
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We Claim
1. A flux shift trip device adapted to prevent demagnetization of
magnet from external field by providing a low reluctance path to
the external field flux lines and protects it from shocks and
vibrations by strengthening pull of magnet with optimum
utilization of the magnetic energy, the said device comprising:
(i) frame means;
(ii) controller means operatively located on top surface of said frame means wherein said controller means being ergonomically constructed such that desired air gap generated during assembly of actuator means cooperatively connected to said controller means is maintained; and
(iii) said actuator means comprising (a) armature means operatively disposed in controller means, (b) spring means wound around the armature means and operatively rested on said controller means such that it provides resilient motion to the armature means, (c) flux shunting means to limit tripping flux in operative connection with said armature means and (d) support means operatively engaged with the flux shunting means and comprising means to trip.
2. A flux shift trip device as claimed in claim 1, wherein the controller
means comprises cap having lateral inner surface such that small
circular opening are located on top surface of the cap and large
circular openings at bottom part of the cap wherein said small
circular opening proceeds downward to form cylindrical hole.
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3. A flux shift trip device as claimed in claims 1 and 2, wherein the diameters of small circular opening, large circular opening and the cylindrical hole are in stepped relation in a manner that the armature means is operatively disposed to perform move-in-move out motion.
4. A flux shift trip device as claimed in claims 1 to 3, wherein armature means comprises plunger being ergonomically stepped cut in a manner to have two surfaces comprising surface 1 and surface 2 having predetermined diameters wherein the diameter of surface 1 being less than that of surface 2 such that the plunger is co-operatively disposed in the cap to perform move-in motion to meet the flux shunting means and move-out motion to trip the device.
5. A flux shift trip device as claimed in claims 1 to 4, wherein spring means comprises compression springs operatively located between the cap and load adjustable means connected to the plunger whereby said compression springs being wound around the plunger in a manner that part of its length covers surface 1 and remaining part covers surface 2.
6. A flux shift trip device as claimed in claim 5, wherein the load adjustable means comprises rotatable knob such that winding and unwinding of the knob provides adjustment of pre-load of the compression spring.
7. A flux shift trip device as claimed in claims 1 to 6, wherein the flux shunting means comprises diverter plate designed in a manner comprising rectangular transversely extending base portion having extrusion on top surface being dimensioned in a manner that there
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is a surface contact between the extrusion and surface 2 of the plunger such that in set position minimum amount of flux passes through the shunt path thereby increasing the hold of magnet on plunger and in actuated position larger amount of flux passes through it thereby reducing the hold of magnet on plunger.
8. A flux shift trip device as claimed in claims 1 to 7, wherein the extrusion of the diverter and the transversely extending base portion resting on permanent magnet fixed to the end walls of the frame such that the extrusion is operatively disposed in the cylindrical hole in alignment with the plunger adapted to achieve diversion of flux lines and subsequent tripping consuming low energy.
9. A flux shift trip device as claimed in any of the preceding claims, wherein the support means for supporting the diverter comprises bobbin ergonomically designed and dimensioned in a manner that the interface of the plunger and the flux diverter is projected in the center along its length where the means for tripping comprising trip coil is wound.
10. A flux shift trip device substantially as herein described and illustrated with reference to the accompanying figures.
Dated this 8 th day of August, 2005.
Abhishek Sen
of S. Majumdar & Co.
Applicant's agent
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ABSTRACT
Title : Actuating Device For Circuit Breakers
Flux shift trip device to prevent demagnetization of magnet from external field by providing a low reluctance path to the external field flux lines and protects it from shocks and vibrations by strengthening pull of magnet with optimum utilization of the magnetic energy comprises frame means (1), controller means (3) operatively located on top surface (la) of the frame means (1) and economically constructed such that desired air gap generated during assembly of actuator means co-operatively connected to the controller means is maintained. The actuator means comprises armature means (11), spring means (4), flux shunting means (8) and support means (7).
Figure 2
