F O R M 2

THE PATENTS ACT, 1970
(39 of 1970)
&
The Patents Rules, 2003
COMPLETE SPECIFICATION
(See section 10; rule 13)

1. Title of the invention: MECHANICALLY ADJUSTABLE VARIABLE FLUX SOLENOID

2. Applicant(s):

(a) NAME : LARSEN & TOUBRO LIMITED
(b) NATIONALITY : An 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 THE INVENTION

The present invention relates to solenoid devices or electromagnetic actuators. Particularly, the present invention relates to a linear electromagnetic actuator/solenoid, which can be used where linear mechanical force is required by the application of electrical energy. More particularly, the present invention relates to a solenoid/actuator constitutes of a set of rotating disk arrangement type of end plates, which by the virtue of differential air gap arrangement, offers the flexibility to modify/adjust the plunger force.

BACKGROUND AND THE PRIOR ART OF THE INVENTION

US 5389910 discloses a set up in which the plunger can be toggled between two position by varying the reluctance of the encasement by the rotation of whole yoke for permanent magnet.

US 6392516 discloses a solenoid in which the plunger force is improved by using magnetic shunt structure which reduces the existing air gap between plunger and pole phase.

US4635683 discloses the variable force solenoid devices in which the varying plunger force is achieved by use of new integrated design of metallic plate springs.

The disadvantages of the above mentioned prior art is that when different amount of plunger force required the flux is varied by varying the input current supply or by changing number of turns in coil. This process is time consuming and requires a design change and may also be difficult if variable source is not available. Some designs are also there which uses permanent magnets and give variable reluctance feature. In case of permanent magnets extra means are required to shield them from external environment. Some devices require movement of whole yoke/core to vary the reluctance which may cause some difficulties in assembling them on site.

Thus there is a need to provide mechanically adjustable variable flux solenoid/actuator that would provide different amount of plunger force without varying the input current supply or without changing number of turns in coil.

OBJECTS OF THE INVENTION

An object of the present invention is to overcome the problems/disadvantages of the prior art.

Another object of the present invention is to provide a mechanically adjustable variable flux solenoid.

Yet another object of the present invention is to provide a solenoid/actuator for flux variation by only rotating a ferromagnetic disk or bush.

These and advantages of the present invention will become readily apparent from the following detailed description taken in conjunction with the accompanying drawings.

SUMMARY OF THE INVENTION

According to one aspect of the present invention there is provided a linear electromagnetic actuator or solenoid device, said device comprising
a core/yoke means forming the outer casing of said device having a substantial cut;
a coil means partially or wholly enclosed within said core means;
a plunger means substantially sits within said coil means adapted to provide plunger force;
a lower bush means substantially placed on the lower side of said device;
an energy storing element means operatively connected with said plunger adapted for up and down motion of said plunger ;
an air gap arrangement adapted to offer flexibility to modify/adjust the plunger force;

wherein said air gap arrangement when decreased , the effective reluctance of path also decreases and increases the flux which causes more amount of force on the plunger;

a top plate arrangement ,said arrangement comprising
outer top plate means having an inner profile and an outer profile;
wherein said inner profile comprising:
plurality of teeth having substantial inward profile;
plurality of slots having substantial outward profile and

inner top plate means having an inner profile and an outer profile ;
wherein said outer profile comprising
plurality of teeth having substantial inward profile ;
plurality of slots substantial outward profile
a handle means having a substantial projection mechanically connected with said inner top plate means adapted to rotate said inner top plate means manually and
a upper bush means having a substantially ring shaped modular profile secured inside said inner profile means
wherein said air gap arrangement substantially located in-between said plunger means and outer top plate means;

wherein said inner top plate means is rotated such that its teeth fall substantially below the teeth of the outer top plate means to define a position where angle θ= 0°
wherein θ= angle between said inner top plate means and outer top plate means
and generate predetermined amount of magnetic flux and produce predetermined amount of force on plunger such that rotating flux faces a large air gap between outer top plate means and inner top plate means and air gap increase the effective reluctance of path and reduce the flux which causes less amount of force on the plunger;

wherein said inner top plate means is rotated such that angle θ start to increase from angle θ= 0° position and the teeth of inner top plate means come in front of slots of outer top plate means due to which the air gap arrangement generated by the slots of outer top plate means is substantially covered by teeth of inner top plate means.

According to another aspect of the present invention there is provided a A linear electromagnetic actuator or solenoid device, said device comprising
a core means forming the outer casing of said device having a substantial cut;
a coil means partially or wholly enclosed within said core means;
a plunger means substantially sits within said coil means
a lower bush means substantially placed on the lower side of said device;
an energy storing element means operatively connected with said plunger adapted for up and down motion of said plunger ;
an air gap arrangement adapted to offer flexibility to modify/adjust the plunger force;

wherein said air gap arrangement when decreased , the effective reluctance of path also decreases and increases the flux which causes more amount of force on the plunger;

a top plate arrangement ,said arrangement comprising:
a top plate means having inner profile and outer profile ;
said inner profile comprising teeth having substantial inward profile and
slots having substantial outward profile and

a bush means having inner profile and outer profile;
said outer profile comprising teeth substantial outward profile;
slots substantial inward profile and
a handle having a substantial projection mechanically connected with said bush means adapted to rotate said bush means manually;
wherein said air gap arrangement substantially located in-between said plunger means and top plate means;

wherein said bush means is rotated such that the teeth of bush means come in front of slots of top plate to define a position where angle Ø = 0° and generate predetermined amount of magnetic flux and produce predetermined amount of force on plunger such that rotating flux faces a large air gap between top plate and bush and air gap increase the effective reluctance of path and reduce the flux which causes less amount of force on the plunger;

wherein said bush means is rotated such that angle Ø start to increase from angle Ø = 0° position and teeth of rotating bush come in front of teeth of plate adapted to cover out the air gap between plate and bush and provide a minimum reluctance path to flux to get higher amount of flux will flow and generate higher force on plunger.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to a linear electromagnetic actuator, which can be used where linear mechanical force is required by the application of electrical energy.

An Electromagnetic actuator or a solenoid consists of a ferromagnetic casing /core, a free moving plunger that sits within a wound coil of conductive material wire. When an electric current passes through the coil wire (energized), a magnetic field is created. The magnetic field then applies a force to this plunger, either attracting or repelling it. The direction of movement of the plunger dependent on the design of actuator whether it is push type or pull type plunger is holded back to its initial position by a spring mechanism which provides the restraining force.

So, when the magnetic field is turned off, the spring returns the plunger to its original state. The magnetic field generated around the solenoid is based on two laws. One is Ampere’s Law and the other is Biot-Savart Law.

The coil creates an MMF which drives flux downward through the plunger, then around the frame of the solenoid to the upwards side, then through the air gap and back into the plunger (X sectional view with component is shown in Fig 1). The reluctance of this path is mostly made up by the air gap as the casing and plunger offer a low reluctance path for the rotating magnetic field.

The present invention relates to a solenoid/actuator as described above, constitutes of a set of rotating disk arrangement type of end plates, which by the virtue of differential air gap arrangement, offers the flexibility to modify/adjust the plunger force.

FEATURES:

• Flux variation by only rotating a ferromagnetic disk or bush.

• Any combination of rotating /sliding toothed profile (with any number of teeth) which varies the effective air gap will modulate the plunger force.

• Can be used in any kind of electromagnetic actuator (solenoid) , where force variation is required without changing the burden on supply.

• Number of teeth and slots may any number depending upon the application and variation in force required.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING

Other features as well as the advantages of the invention will be clear from the following description.
In the appended drawings:
Figure 1 illustrates a solenoid device.
Figure 2 illustrates outer top plate with slotted profile.
Figure 3 illustrates first case of the assembly having complete top plate assembly which has total three components.
Figure 4 illustrates upper bush.
Figure 5 illustrates lower bush.
Figure 6 illustrates inner top plate.
Figure 7 illustrates the plunger.
Figure 8 illustrates second case of the assembly having complete top plate assembly which has total two components.
Figure 9 illustrates the teethed plate.
Figure 10 illustrates the bush with teeth and slot.
Figure 11 illustrates the cut provided in the yoke.
Figure 12 illustrates the cross sectional view of the solenoid device.

DETAILED DESCRIPTION OF THE ACCOMPANYING DRAWING

In the following detailed description, reference is made to the accompanying drawings that form a part hereof, and illustrate the best mode presently contemplated for carrying out the invention. Further functioning of the mechanism has been discussed below to describe the way the mechanism operates. However, such description should not be considered as any limitation of scope of the present unit. The structure thus conceived is susceptible of numerous modifications and variations, all the details may furthermore be replaced with elements having technical equivalence. In practice the materials and dimensions may be any according to the requirements, which will still be comprised within its true spirit.
A solenoid/actuator is a device which gives linear movement of its plunger on the application of electric current. A solenoid (Fig 1) essentially has three basic parts, a magnetic core (Yoke) 1, an energizing coil 2, plunger 3 (Fig 7). As the centralized coil is activated by electric supply, it generates magnetic field, which is predominantly concentrated to its central axis. The magnetic flux thus generated starts flowing through the plunger 3 to air gap 27, to lower bush 26, to outer yoke 1, to circular outer top plate 14 which is also referred as end plate 14 in the present embodiment, to upper bush 8, and returns to plunger 3 again and complete the closed loop.(Fig 1). The lower bush 26 (Fig 5) and upper bush 8 (Fig 4) are made of ferromagnetic material. the shape of bushes may vary depending upon the required force and distance characteristics. Plunger 3 (Fig 7) has two part. Upper part 6 is ferromagnetic to provide less reluctance and part 7 is a non ferromagnetic rod which provide a mean for taping resultant movement. Now, as the yoke of the system is fixed and fastened to assembly, the only part which is free to move under the influence of magnetic force is plunger. The plunger is held at its initial position by a restraining spring 4 (see Fig 1 and Fig 12), so as soon as the force of magnetic field exceeds the fixed spring force, the plunger shows linear motion in direction to minimize the air gap 27.

According to Hopkinson’s Law, the magnetic flux always tries to follow the low reluctance path; In this case the majority of the flux would be impelled through the ferromagnetic core and then the plunger, the only air gap

Considered here would be at the joints and at the interface between the plunger 3 and the top plate 14. In this invention we are trying to modulate this air gap which exists between the end plate 14 and the plunger 3, following assumptions were made in the said analysis:
1. Magnetic field distortion , due to joint profile is negligible.
2. Magnetic permeability of the plunger is considered to be same as that of yoke.
3. Magnetic leakage flux is negligible.
4. Air gap at joints is negligible
5. Plunger force is not enhanced but regulated only below its peak value.
6. Direction of magnetic flux indicated is only representative.

Case I

In first case the assembly shown in Fig 3 is used in place of flat ferromagnetic top plate. The top plate 14 is modified to have a slotted profile (Fig 2) which projects at its centre. The inner profile has both teeth 16 and slots 15 and outer profile is a circular periphery 17. (Fig 3) shows the complete top plate assembly which has total three components. Outer top plate 14, inner top plate 9 and upper bush 8.the inner plate 9 also has teeth 12 and slots 13 but on outer profile while the inner profile is circular periphery 10 ( Fig 6). Profile 11 is a handle like structure which projects out of yoke 1 after complete assembly through a cut 28 provided on yoke (Fig 11) and gives a mean to rotate the inner disk 9 by hand. The Plate/disk 9 is tolerance fitted with upper bush 8. So bush 8 rotates with disk 9 while upper plate/disk is permanently fixed with yoke1.
The impelling magnetic flux generated by the coil 2 passes through the yoke 1 and axially travels into plunger 3 to form closed path. when the flux reaches at joint between yoke1 and the top plate assembly since there is comparatively a larger air gap between disk 9 and yoke 1, it chooses the minimum reluctance path i.e. top plate 14. Since the reluctance of the plate 14 is higher than existing flat ferromagnetic plate due to slots 15. So the amount of flux in plate 14 will also be less as compare to existing case.

Now initially if the plate/disk 9 is located in such a manner that its teeth 12 fall just below the teeth 16 of the top plate 14 (i.e. θ= 0° ) the certain amount of magnetic flux flows through yoke1 to upper bush 8 via plates 14. and produce some amount of force on plunger. Now when the angle θ start to increase from its initial position the teeth 12 of circular disk 9 come in front of slots 15 of plate 14.due to which the air gap generated by the slots 15 is shunted by teeth 12. Or it can be said that teeth form minimum reluctance paths in place of air gaps in prior case. As a result the amount of flux passed from yoke 1 to plates 14 and 9 will be higher which will cause higher force on plunger. The reduction in air gap reluctance will be proportional to the angle θ and the maximum value of θ which causes maximum force on plunger will be

θ max = 360/2n
where n = No. of teeth on plates.

Case II
The top plate assembly used in case 2 is different from case 1. The assembly has only two components instead of three (Fig 8). Assembly has a teethed plate 18 and a bush 22.plate/disk 18 has teeth 21 and slots 19 and circular outer periphery 20 like plate 14. Profile 25 is provided for handle feature. In this arrangement the teeth and slots of bush 22 rotates in plane of top plate 18 while in case1 disk 9 rotates in lower plane of top plate 14 (Fig 8).

Now when the flux passes through yoke 1 and reaches on top plate 18.at initial state when angle between teeth of top plate 18 and bush 22 is minimum (Ø = 0°) the teeth 24 of bush 22 come in front of slots 19 of top plate 18. So the rotating flux faces a large air gap between top plate 18 and bush 22 to complete the cycle. this air gap increase the effective reluctance of path and reduce the flux which causes less amount of force on the plunger. On the other hand when angle Ø start to increase the teeth of rotating bush 22 come in front of teeth of plate18. this shunted out the air gap between plate and bush and provide a minimum reluctance path to flux. As a result higher amount of flux will flow and generate higher force on plunger 3.

According to the empirical formula derived for this set up change in reluctance (ΔR) is directly proportional to number of teeth (n)
ΔR α n
θ (angular length of each teeth) = π / 2n

Thus by varying the number of teeth on the fixed plate and rotating geometry, change in reluctance and ultimately change in force can be achieved.

WE CLAIM

1. A linear electromagnetic actuator or solenoid device, said device comprising
a core/yoke means forming the outer casing of said device having a substantial cut;
a coil means partially or wholly enclosed within said core means;
a plunger means substantially sits within said coil means adapted to provide plunger force;
a lower bush means substantially placed on the lower side of said device;
an energy storing element means operatively connected with said plunger adapted for up and down motion of said plunger ;
an air gap arrangement adapted to offer flexibility to modify/adjust the plunger force;

wherein said air gap arrangement when decreased , the effective reluctance of path also decreases and increases the flux which causes more amount of force on the plunger;

a top plate arrangement ,said arrangement comprising
outer top plate means having an inner profile and an outer profile;
wherein said inner profile comprising:
plurality of teeth having substantial inward profile;
plurality of slots having substantial outward profile and

inner top plate means having an inner profile and an outer profile ;
wherein said outer profile comprising
plurality of teeth having substantial inward profile ;
plurality of slots substantial outward profile
a handle means having a substantial projection mechanically connected with said inner top plate means adapted to rotate said inner top plate means manually and
a upper bush means having a substantially ring shaped modular profile secured inside said inner profile means

wherein said air gap arrangement substantially located in-between said plunger means and outer top plate means;
wherein said inner top plate means is rotated such that its teeth fall substantially below the teeth of the outer top plate means to define a position where angle θ= 0°
wherein θ= angle between said inner top plate means and outer top plate means
and generate predetermined amount of magnetic flux and produce predetermined amount of force on plunger such that rotating flux faces a large air gap between outer top plate means and inner top plate means and air gap increase the effective reluctance of path and reduce the flux which causes less amount of force on the plunger;

wherein said inner top plate means is rotated such that angle θ start to increase from angle θ= 0° position and the teeth of inner top plate means come in front of slots of outer top plate means due to which the air gap arrangement generated by the slots of outer top plate means is substantially covered by teeth of inner top plate means.

2. Device as claimed in claim 1 wherein said top plate means is slotted.

3. Device as claimed in claim 1 wherein said outer profile of said outer top plate means is having substantially circular periphery.

4. Device as claimed in claim 1 wherein said inner profile of said inner top plate means is having substantially circular periphery.

5. Device as claimed in claim 1 wherein said handle means that projects out of yoke through the cut provided on yoke.

6. Device as claimed in claim 1 wherein said core means is magnetic.

7. Device as claimed in claim 1 wherein said plunger means comprising
upper part adapted to provide less reluctance and
lower part adapted to provide a mean for taping resultant movement .

8. Device as claimed in claim 7 wherein said upper part is ferromagnetic.

9. Device as claimed in claim 7 wherein said lower part is a non ferromagnetic rod.

10. Device as claimed in claim 1 wherein said an energy storing element means comprises restraining spring.

11. Device as claimed in claim 1 wherein said upper bush made of ferromagnetic material.

12. Device as claimed in claim 1 wherein said lower bush made of ferromagnetic material.

13. Device as claimed in claim 1 wherein said outer top plate means is fixed with said yoke.

14. Device as claimed in claim 1 wherein said inner top plate means is fitted with said upper bush means and said plate means rotates with said bush means.

15. A linear electromagnetic actuator or solenoid device, said device comprising
a core means forming the outer casing of said device having a substantial cut;
a coil means partially or wholly enclosed within said core means;
a plunger means substantially sits within said coil means
a lower bush means substantially placed on the lower side of said device;
an energy storing element means operatively connected with said plunger adapted for up and down motion of said plunger ;
an air gap arrangement adapted to offer flexibility to modify/adjust the plunger force;

wherein said air gap arrangement when decreased , the effective reluctance of path also decreases and increases the flux which causes more amount of force on the plunger;

a top plate arrangement ,said arrangement comprising:
a top plate means having inner profile and outer profile ;
said inner profile comprising teeth having substantial inward profile and
slots having substantial outward profile and

a bush means having inner profile and outer profile;
said outer profile comprising teeth substantial outward profile;
slots substantial inward profile and
a handle having a substantial projection mechanically connected with said bush means adapted to rotate said bush means manually;
wherein said air gap arrangement substantially located in-between said plunger means and top plate means;
wherein said bush means is rotated such that the teeth of bush means come in front of slots of top plate to define a position where angle Ø = 0° and generate predetermined amount of magnetic flux and produce predetermined amount of force on plunger such that rotating flux faces a large air gap between top plate and bush and air gap increase the effective reluctance of path and reduce the flux which causes less amount of force on the plunger;

wherein said bush means is rotated such that angle Ø start to increase from angle Ø = 0° position and teeth of rotating bush come in front of teeth of plate adapted to cover out the air gap between plate and bush and provide a minimum reluctance path to flux to get higher amount of flux will flow and generate higher force on plunger.

16. Device as claimed in claim 15 wherein said handle means that projects out of yoke through the cut provided on yoke.

17. Device as claimed in claim 15 wherein said core means is magnetic.

18. Device as claimed in claim 15 wherein said plunger means comprising
upper part adapted to provide less reluctance and
lower part adapted to provide a mean for taping resultant movement .

19. Device as claimed in claim 18 wherein said upper part is ferromagnetic.

20. Device as claimed in claim 18 wherein said lower part is a non ferromagnetic rod.

21. Device as claimed in claim 1 wherein said outer profile of said top plate means is having substantially circular periphery.

22. Device as claimed in claim 1 wherein said an energy storing element means comprises restraining spring.

23. Device as claimed in claim 1 wherein said top plate means is fixed with said yoke.

24. Device as claimed in claim 23 wherein said bush means is fitted with said top plate means and said bush means rotates.

25. Device as claimed in claim 1 wherein said lower bush made of ferromagnetic material.

26. A linear electromagnetic actuator or solenoid device as herein substantially described and illustrated with the accompanying drawings.