5 CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority from and claims the benefit of U.S. Patent Application Serial No. 14/542,765, riled November 17, 2014, which is incorporated by reference herein.

10 BACKGROUND

Field

The disclosed concept pertains generally to vacuum switching apparatus and, more particularly, to vacuum switching apparatus such as for example, vacuum interrupters. The disclosed concept also pertains to contact assemblies for

15 vacuum switching apparatus. The disclosed concept further pertains to methods of securing an electrical contact to an electrode in vacuum switching apparatus.

Background information

Some circuit breaker's such as. for example, power circuit breakers, employ vacuum interrupters as the switching devices. Vacuum interrupters generally

20 include separable electrical contacts disposed on the ends of corresponding electrodes within an insulating housing. The electrical contacts are typically mechanically and electrically connected to the electrodes by brazing. While further components of the vacuum interrupter are being assembled with the electrode/electrical contact assembly, it is important to keep the mating between the electrode/electrical contact

25 secured. Known practices for securing this connection involve employing a contact weight on top of the electrical contact. However, employing a contact weight has disadvantages. For example, while the vacuum interrupter is brazed in a furnace, the contact weight requires an additional expenditure of energy by the furnace.

Additionally, employing a contact weight creates a risk that the electrical contacts will

30 not be properly positioned, which can result in poor brazing of the joint bet ween

them, leading to an undesirable increase in electrical resistance of that joint and of the entire vacuum interrupter. There are also situations when the use of a positioning weight is prohibited, for example and without limitation, when the entire vacuum interrupter is to be brazed in a single vacuum brazing furnace run.

There is, therefore, room for improvement in vacuum switching apparatus, and in contact assemblies and methods of securing an electrical contact to 5 an electrode therefor.

SUMMARY

These needs and others are met by embodiments of the disclosed concept, which are directed to a contact assembly and associated method of securing

10 an electrical contact to an electrode in vacuum switching apparatus.

m accordance with one aspect of the disclosed concept, a contact assembly for a vacuum switching apparatus is provided. The vacuum switching apparatus includes a vacuum envelope. The vacuum envelope has an interior. The contact assembly comprises: a number of electrical contacts disposed in the interior of

15 the vacuum envelope, at least one electrical contact having a hole; and a number of electrodes each engaging a corresponding one of the number of electrical contacts, at least one electrode comprising a base and a protrusion. The protrusion extends from the base into the hole of the electrical contact in order to secure the electrical contact to the electrode.

20 As another aspect of the disclosed concept., a vacuum switching

apparatus comprises: a vacuum envelope having an interior; and a contact assembly comprising: a number of electrical contacts disposed in the interior of the vacuum envelope, at least one electrical contact having a hole, and a number of electrodes each engaging a corresponding one of the number of electrical contacts, at least one

25 electrode comprising a base and a protrusion. The protrusion extends from the base into the hole of the electrical contact in order to secure the electrical contact to the electrode.

As another aspect of the disclosed concept, a method of securing an electrical contact to an electrode in a vacuum switching apparatus is provided. The 30 vacuum switching apparatus includes a vacuum envelope having an interior. The electrode comprises a base and a protrusion extending from the base. The electrical contact has a hole. The electrical contact is disposed in the interior of the vacuum envelope. The method comprises the steps of: inserting the protrusion into the hole of the electrical contact; and deforming the protrusion in order to secure the electrical contact to the electrode.

BRIEF DESCRIPTION OF THE DRAWINGS

A full understanding of the disclosed concept can he gained from the following description of the preferred embodiments when read in conjunction with the accompanying drawings in which:

Figure 1 is a simplified section view of a contact assembly in accordance with an embodiment of the disclosed concept, shown before the electrical contact is secured to the electrode;

Figure 2 is a simplified section view of the contact assembly of Figure 1 , shown with the electrode extending into the electrical contact and with a component of a tooling apparatus;

Figure 3 is a simplified section view of the contact assembly and component of the tooling apparatus of Figure 2, also showing additional features of the tooling apparatus;

Figure 4A is a simplified section view of the contact assembly of Figure 2, modified to show the electrical contact secured to the electrode;

Figure 4B is a simplified top plan view of the contact assembly of

Figure 4A;

Figure 4C is an enlarged section view of a portion of the contact assembly of Figure 4A;

Figure 5 is a section view of a vacuum switching apparatus and contact assembly therefor, in accordance with an embodiment of the disclosed concept; and

Figure 6 is a section view of a vacuum switching apparatus and contact assembly therefor, in accordance with an alternative embodiment of the disclosed concept.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

For purposes of the description hereinafter, directional phrases used herein such as, for example "up", "down' ⁵ , "top", "bottom' ⁵ , and derivatives thereof shall relate to the disclosed concept, as it is oriented in the drawings. It is to be understood that the specific elements illustrated in the drawings and described in the following specification are simply exemplary embodiments of the disclosed concept. Therefore, specific orientations and other physical characteristics related to the 5 embodiments disclosed herein are not to be considered limiting with respect to the scope of the disclosed concept.

As employed herein, the term "number" shall mean one or an integer greater than one {i.e., a plurality).

As employed herein, the statement that two or more parts are

10 "connected" or "coupled" together shall mean that the parts are joined together either directly or joined through one or more intermediate parts. Further, as employed herein, the statement that two or more parts are "attached" or "affixed" shal l mean that the pans are joined together directly.

As employed herein, the statement that two or more parts or

15 components "engage" one another shall mean that the parts touch and/or exert a force against one another either directly or through one or more intermediate parts or components.

As employed herein, the term "coupling member" refers to any suitable connecting or tightening mechanism expressly including, but not limited to,

20 screws, rivets, bolts and the combinations of bolts and nuts (e.g., without limitation, lock nuts) and bolts, washers and nuts.

As employed herein, the term "vacuum envelope" means an envelope employing a partial vacuum therein.

Figure 1 shows a contact assembly 100 (shown in simplified form) for

25 a vacuum switching apparatus such as, for example and without limitation, a vacuum interrupter 400 (shown in simplified form in Figure 5). In the example of Figure I, the contact assembly 100 includes an electrical contact 110 and an electrode 120, before the electrical contact 1 10 has been secured to the electrode 120. As seen, the electrical contact 1 10 has a hole (e.g., without limitation, thru hole 1 12), and the

30 electrode 120 includes a base 122 and a protrusion 124 extending from the base 122.

The protrusion 124 has a cavity 126, the purpose of which will be described below. In operation, the protrusion 124 extends into the thru hole 1 12 in order to secure the electrical contact 1 10 to the electrode 120 (see for example Figure 2, which shows the electrode 120 engaging the electrical contact 110).

Figure 3 shows a tooling apparatus 2 mounted on the contact assembly 100. The tooling apparatus 2 generally includes a component (e.g., without

5 limitation, rivet tool 4), a body portion 6.. a cap 8, and a housing 10. The body portion 6 has a thru hole 12. In order to assemble the tooling apparatus 2, the rivet tool 4 is inserted through the thru hole 12. The cap 8 has a thru hole 16. The tooling apparatus 2 further includes a number of coupling members (three coupling members 18,26,28 are shown). To secure the cap 8 to the rivet tool 4, the coupling member 18 is

10 inserted into the thru hole 16 of the cap 8 and an aperture 14 (shown in hidden line drawing in Figure 2) of the rivet tool 4. In order to secure the housing 10 to each of the body portion 6 and the cap 8, and therefore to the rivet tool 4, the housing 10 is placed on the cap 8 such that the cap 8 extends through a corresponding thru hole 20 {three thru holes 20,22,24 are shown in Figure 3). Similarly, the coupling members

15 26,28 are inserted through the respective thru holes 22,24 and engage the body

portion 6.

The tooling apparatus 2 includes a spring 30 that extends from the body portion 6 to the cap 8. The rivet tool 4 extends through the spring 30. The spring 30 exerts a force on the body portion 6 and on the cap 8. In operation, the

20 tooling apparatus 2 secures the electrical contact 1 10 to the electrode 120. For

example and without limitation, when the rivet tool 4 moves into the thru hole 112 toward the base 122 of the electrode 120, and the rivet tool 4 pushes into the protrusion 124, the protrusion 124 plastically deforms.

More specifically, when the cap 8 moves toward the electrical contact

25 1 10 (i.e., movement initiated by an operator), the cap 8 pushes into the rivet tool 4, which in turn is driven into the cavity 126 of the electrode 120, plastically deforming the protrusion 124 of the electrode 120 to form an electrode 120', as shown in Figure 4A (it will be appreciated that like reference numbers are used to represent like features in Figure 4 A). This process is known as ''staking" the rivet (i.e., the

30 protrusion 124), and it provides a mechanism to attach two components (i.e., the

electrode 120' is attached to the electrical contact 1 10). In other words, by deforming (i.e., staking) the protrusion 124, the electrical contact 1 10 is secured to the resulting electrode 120', which is advantageously prevented from being pulled through the electrical contact 1 10.

As the cap 8 moves toward the electrical contact 1 10, the force exerted by the spring 30 on each of the body portion 6 and the cap 8 advantageously

5 increases. In this manner, the amount of plastic deformation can be relatively

controlled, for example and without limitation., although it is within the scope of the disclosed concept for the rivet tool 4, or a similar suitable alternative tool (not shown), to perform the desired deforming function without the other components of the tooling apparatus 2 (see for example Figure 2, in which only the rivet tool 4 is

10 shown), employing the tooling apparatus 2 allows the amount of force exerted on the protrusion 124 to be controlled. Specifically, by having the opposing force of the spring 30 on the cap 8, and by having that, force increase as the cap 8 moves toward the electrical contact 1 10, the tooling apparatus 2 advantageously provides a controlled mechanism to deform the protrusion 124, as desired.

15 When the rivet tool 4 is performing the desired deforming function, the body portion 6 of the tooling apparatus 2 is advantageously aligned with the contact assembly 100. As seen in Figure 3, the thru hole 1 12 of the electrical contact 1 10 has a receiving portion 1 13, and the body portion 6 of the tooling apparatus 2 includes a securing portion 7 that fits in the receiving portion 1 13. When the securing portion 7

20 is located in the receiving portion 1 13, the rivet tool 4 is positioned directly on top of the cavity 126. As a result, when the rivet tool 4 drives down into the cavity 126 of the protrusion 124, the rivet tool 4 is advantageously able to plastically deform the protrusion 124 to form a consistent annular-shaped retaining portion 125'. It is, however, within the scope of the disclosed concept for an electrical contact (not

25 shown) and body portion (not shown) to have any suitable alternative shape and/or configuration in order to perform the desired function of aligning the rivet tool 4 with the cavity 126.

Referring to Figures 4B and 4C, the electrical contact 1 10 includes an annular-shaped internal ledge 114 located adjacent the thru hole 1 12 (Figure 4C). As 30 seen in Figure 4C, the protrusion 124' extends from the base 122' past the internal ledge 114. The retaining portion 125' substantially overlays and engages the internal ledge 114. The retaining portion 125' has an outer diameter 127' that is larger than an inner diameter 1 15 of the interna! ledge 1 14. In this manner, the retaining portion 125' advantageously prevents the electrode 120' from becoming detached from (i.e., pulled through) the electrical contact 1 10, thus securing the electrical contact 110 to the electrode 120'.

5 This connection advantageously allows the electrode 120' and the electrical contact 1 10 to be brazed in a single furnace run with the rest of the vacuum interrupter 400 (Figure 5). Additionally, employing the disclosed riveting concept allows the electrical contact 1 10 and the electrode 120' ιο be more tightly mated together. As a result, the quality of the vacuum brazing is advantageously improved,

10 because when the braze melts, it weeps up better along the tighter joint. Furthermore, known methods of securing an electrical contact (not shown) to an electrode (not shown) involving contact weights (not shown) can be eliminated. Consequently, when the vacuum interrupters 400,500 undergo brazing, undesirable expenditures of energy previously associated with contact weights (not shown) can be eliminated.

15 Referring again to Figure 4A, the base 122' of the electrode 120'

includes an engaging surface 128' that engages the electrical contact 1 10 and faces in a direction 132. The engaging surface 12S' is located in a plane 130 and the internal ledge 1 14 is located in a plane 1 16 that is parallel to the plane 130. The direction 132 that the engaging surface 128' faces is perpendicular to the planes Π 6, 130. More

20 precisely, the engaging surface 128' is substantially flush with the electrical contact 1 10 and exerts a force on the electrical contact 110 in the direction 132. The retaining portion 125' exerts an opposing force on the electrical contact 1 10 in a direction opposite the direction 132. Because the planes 1 16,130 are parallel to each other, the retaining portion 125' and the engaging surface 128' are advantageously able to

25 provide a maximum clamping force on the electrical contact 1 10 to secure the

electrical contact 1 10 to the electrode 120'. This configuration advantageously provides a relatively strong securement of the electrode 120' and the electrical contact 1 10 to prevent them from moving out of position while the contact assembly 100 is further processed. Additionally, the configuration provides a relatively tight

30 geometric fit between the electrode 120' and the electrical contact 1 10,

advantageously allowing for a relatively void free mechanical and electrical connection. Figure 5 shows the aforementioned vacuum interrupter 400, including the contact, assembly 100 and a vacuum envelope 402. The contact, assembly 100 further includes another electrical contact 210 and a corresponding electrode 220' engaging the electrical contact 210. As seen, the vacuum envelope 402 has an interior 5 404 and each of the electrical contacts 1 10,210 are located in the interior 404. The electrical contact 210 is opposite the electrical contact 1 10. Additionally, it will be appreciated that the electrical contact 210 is secured to the electrode 220' in substantially the same manner as the electrode 120' and the electrical contact 1 10. Thus, advantages associated with the relatively secure mechanical/electrical

10 connection between the electrode 120' and the electrical contact 1 10 likewise apply to the electrode 220' and the electrical contact 210.

Figure 6 shows another electrical switching apparatus (e.g., without limitation, vacuum interrupter 500) that includes a vacuum envelope 502 having an interior 504, and a contact assembly 300. The contact assembly 300 includes the

15 electrical contact 1 10 and the corresponding electrode 120'. In addition, the contact assembly 300 includes another electrical contact 310 and an electrode 320 engaging the electrical contact 310. The electrical contacts 1 10,310 are opposite each other and are located in the interior 504 of the vacuum envelope 502. The electrode 320 does not extend into the electrical contact 310. It will be appreciated that the electrical

20 contact 310 may be secured to the electrode 320 by any known method (e.g., without limitation, brazing). Thus, the contact assembly 300 and associated vacuum interrupter 500 include the electrical contact 1 10 and associated electrode 120' secured in accordance with the disclosed staking concept, as well as the electrical contact 310 and associated electrode 320 secured in accordance with known methods.

25 Accordingly, it will be appreciated that the disclosed concept provides for an improved (e.g., without limitation, easier to manufacture, more energy efficient, stronger mechanical/electrical connection between electrode/electrical contact) vacuum switching apparatus (e.g., without limitation, vacuum interrupters 400,500), and contact assembly 100,300 and method of securing an electrical contact

30 1 10,210 to an electrode 120' ,220' therefor, which among other benefits, deforms (i.e., stakes) the protrusion 124 of the electrode 120 in a controlled manner, as desired. Thus, a portion (i.e., retaining portion 125') of the resulting electrode 120' advantageously prevents the electrode 120' from being pulled through the electrical contact 1 10, thus securing the electrical contact 110 to the electrode 120'.

While specific embodiments of the disclosed concept have been described in detail, it will be appreciated by those skilled in the art that various modifications and alternatives to those details could be developed in light of the overall teachings of the disclosure. Accordingly, the particular arrangements disclosed are meant to be illustrati ve only and not limiting as to the scope of the disclosed concept which is to be given the full breadth of the claims appended and any and all equivalents thereof