Patent Application
20170011878
This application claims the benefit of German Patent Application No. 102015212801.6, filed Jul. 8, 2015.
The invention relates to an electrical switch and, more particularly, to an electrical switch with a movable armature.
Electrical switches, such as relays, are known in the art. Patents U.S. Pat. No. 6,911,884 B2 and U.S. Pat. No. 8,138,863 B2 each disclose an electrical switch having a solenoid, a movable armature, an armature shaft attached to the movable armature, a contact assembly with a plurality of contacts, and other components. The contact assembly is located in a switching chamber region such that any electrical arcs which may arise can be sealed off from an electromagnetic drive system. The contact assembly is attached to the armature shaft, which penetrates a covering plate at a contact chamber aperture. The armature shaft is attached to the armature such that a movement of the armature is also transmitted to the contact assembly.
Due to mechanical tolerances in the overall design and contact wear from electrical arcs, the contacts of the contact assembly never touch corresponding mating contacts at the same time. Such a premature, one-sided mechanical contact initiates a force eccentric to the axis of a guide guiding motion of the armature. The spacing between the end of the armature shaft and the prematurely contacted contact acts as a lever, which tilts the guide. Since such an electrical switch is used to switch large loads, the contact forces for switching are high, leading to large radial forces transmitted by the lever to the guide. These forces can lead to wear on bearing surfaces of the guide or may even lead to the locking of the guide.
A locking of the guide can be avoided if the lever follows the condition (A/L)×2μ≦1, with A being the lever length, L the bearing length, and μ the friction factor.
Elongating the bearing length can prevent locking but impairs the shock resistance of the electrical switch. The contact chamber aperture can be used as a second bearing surface, however, this would require precise mechanical tolerances to avoid a lateral offset of the two bearing surfaces, which would lead to locking.
Locking may also be prevented by reducing the friction factor. However, reducing the friction factor is only possible to a limited extent and requires expensive bearing coatings such as polytetrafluoroethylene (PTFE). Furthermore, such a coating can become worn over the lifespan of the electrical switch, increasing the friction factor over time.
The disclosed electrical switch comprises a solenoid assembly including a core casing having a first bearing site and a bearing bush having a second bearing site. The electrical switch also includes an armature movably borne in a switching direction at the first bearing site. The electrical switch further includes an armature shaft fixed to and movable with the armature and movably borne in the switching direction at the second bearing site.
The invention will now be described by way of example with reference to the accompanying figures, of which:
The invention is explained in greater detail below with reference to embodiments of an electrical switch. This invention may, however, be embodied in other different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete and still fully convey the scope of the invention to those skilled in the art.
An electrical switch 1, according to the invention, is shown in
The contact chamber 5, as shown in
An armature shaft 15 extends into upper chamber 13 through contact chamber aperture 9. Armature shaft 15 has a diameter d.
A contact plate 17 is affixed to an end 16 of armature shaft 15 within upper chamber 13. Contact plate 17 has two armature contacts 19. By moving armature shaft 15 in a switching direction S, armature contacts 19 can contact electrical contacts 21, closing a current circuit. Electrical contacts 21 are connected to upper housing 7.
The solenoid assembly 3, as shown in
Solenoid 27 is rotationally symmetric relative to a central axis M, which is also the central axis M for armature shaft 15. Solenoid 27 has a pancake coil 29, which is rotationally symmetrical about central axis M. Solenoid 27 also has a solenoid wire 33 with loops 31 circumferentially coiled around pancake coil 29. The loops 31 are symbolically represented in
Solenoid 27 also has an inner space 39. An armature 41 is entirely disposed within inner space 39 of solenoid 27, while a core casing 43 is partially disposed within inner space 39 of solenoid 27. Core casing 43 is formed of a magnetic material, such as pure iron with a galvanic coating of bronze or a Teflon-coated piece of pure iron.
An outer wall 45 of core casing 43 abuts an inner wall 47 of pancake coil 29. A protrusion 49 of core casing 43 rests against the pancake coil 29 in the z direction, and, counter to the z direction, against floor 35 of yoke 23. Both pancake coil 29 and core casing 32 are secured against movement in or counter to the z direction by yoke 23 and contact chamber plate 11.
A lower end of the core casing 43 is received in the circular floor aperture 37. The lower end of the core casing 43 has a casing chamfer 43a which is inclined relative to the central axis M. The lower end of core casing 43 is positioned outside of solenoid 27, but does not project beyond yoke 23, and thus is contained within the outer dimensions of solenoid assembly 3.
Armature 41 and armature shaft 15 are rotationally symmetric about central axis M. Armature shaft 15 has a knurl 51, . . . , The section of armature shaft 15 having knurl 51 is connected to armature 41 at an armature attachment 53. In the shown embodiment, the armature attachment 53 is a laser weld, but one with ordinary skill in the art would understand that other attachments known in the art could be used as the armature attachment 53.
Armature shaft 15 is disposed in inner space 39 of solenoid 27, penetrates armature 41 at armature attachment 53, and projects out of solenoid assembly 3 through contact chamber aperture 9. In the shown embodiment, armature shaft 15 is made of a steel such as Cr—Ni steel, but one with ordinary skill in the art would understand that other materials, such as brass, are possible. Armature shaft 15 may have a rounded or angled cross-section.
Armature 41 has a cylindrical armature body 55 sealed by an armature floor 57 at an end situated counter to switching direction S. Armature floor 57 has a groove 60 extending annularly around central axis M. In the shown embodiment, groove 60 of armature floor 57 has a V-shaped cross-section, but groove 60 of armature floor 57 may alternatively have a rectangular or semicircular cross-section. Armature 41 also has an armature flange 59 positioned at an opposite end in switching direction S. In the shown embodiment, armature flange 59 is materially bonded to armature body 55, but armature flange 59 may alternatively be integrally formed with armature body 55.
Armature body 55 is partially surrounded by core casing 43 and is guided within core casing 43 in switching direction S over a bearing length L. Armature body 55 is guided and movably bears on a first bearing site 61 of core casing 43, which forms a first bearing surface 62.
Armature flange 59 is located in a cavity 63 formed by pancake coil 29 and contact chamber plate 11. Cavity 63 has a height h and armature flange 59 has a flange height hF. Flange height hF is measured in switching direction S from the position at which armature flange 59 abuts pancake coil 29 up to a portion of armature 41 which projects furthest in the switching direction S.
Armature shaft 15 is fixed to armature 41 and extends from armature floor 57 through cavity 63. Armature shaft 15 is surrounded by a spring 67 such that the spring 67 abuts both armature floor 57 and a side of contact chamber plate 11 which points counter to the switching direction S.
At an end of solenoid assembly 3 opposite contact chamber 5, a bearing element 68 in the form of a bearing bush 69 is inserted and form-fit into core casing 43. The bearing bush 69 is shown in
Bearing bush 69 has an inner bearing section 71, an outer bearing section 73, and an annular disc 75 connecting inner bearing section 71 and outer bearing section 73. Inner bearing section 71, outer bearing section 73, and annular disc 75 are symmetrical about central axis M and are connected to one another by material bonding at a side of bearing bush 69 counter to the switching direction S. Bearing bush 69 also has an annular trench 77 formed between inner bearing section 71 and outer bearing section 73.
Bearing bush 69 has a bearing flange 76. In the shown embodiment, bearing flange 76 is monolithically formed with annular disc 75, but the bearing flange 76 could alternatively be attached to annular disc 75. Bearing bush 69 may be formed by injection-molding or by other forms of production known to those with ordinary skill in the art.
Bearing flange 76 extends away from the central axis M, projecting past outer bearing section 73. Bearing flange 76 abuts an end of core casing 43 facing counter to switching direction S and prevents bearing bush 69 from being inserted deeper into core casing 43. Bearing flange 76 has a bearing chamfer 76a complementary to casing chamfer 43a, such that casing chamfer 43a abuts bearing chamfer 76a along a surface inclined away from central axis M. In the shown embodiment, both bearing chamfer 76a and casing chamfer 43a have a 45° angle.
Bearing bush 69, as shown best in
Armature shaft 15 is received in and movably bears on second bearing site 83. A length of second bearing site 83 in switching direction S is at most half of a diameter of armature shaft 15. Insertion slopes 81 simplify the introduction of armature shaft 15 into bearing bush 69 by centering armature shaft 15 with respect to bearing bush 69.
The assembly and use of electrical switch 1 will now be described with reference to
Contact chamber 5 forms a cover 6 which is attached to and seals off solenoid assembly 3. Cover 6 may be attached to solenoid assembly 3 by welding, gluing, screwing, riveting, or other forms of fastening known to those with ordinary skill in the art. Cover 6 separates solenoid assembly 3 from armature contacts 19, shielding solenoid assembly 3 from electrical arcs. Contact chamber aperture 9 is the sole connection between solenoid assembly 3 and upper chamber 13.
The movement of armature 41 and armature shaft 15 is transmitted to contact plate 17. As shown in contact position K in
The initial mechanical touching of the contact plate 17 with second electrical contact 21b leads to the transverse force F, which is transmitted from the magnetic field of solenoid 27 to armature 41 and armature shaft 15, acting on contact plate 17 along a direction counter to switching direction S. Transverse force F is transmitted over a lever length A onto armature shaft 15, tilting armature 41 within core casing 43. Lever length A is measured from central axis M to second armature contact 19b. Since the second armature contact 19b bears against the second electrical contact 21b over a large area, a mechanical point of application 19c is located centrally on the second armature contact 19b in the x-direction.
Advantageously, the electrical switch 1 according to the present invention, due to the first bearing site 61 and the second bearing site 83, resists tilting and locking of the armature shaft 15 without reducing shock resistance or requiring a costly bearing coating.
| Number | Date | Country | Kind |
|---|---|---|---|
| 102015212801.6 | Jul 2015 | DE | national |
