ACTIVATION MECHANISM FOR OPERATURE OF AT LEAST ONE CONTACT AND OPERATING PROCEDURES FOR THIS

Description

[0001] The invention relates to an operating mechanism for operating at least one contact, such as a vacuum interrupter, which operating mechanism comprises: a base frame; an operating rod linearly guided in the base frame for connection with at least one contact, which operating rod has a closed position and an open position; a contact spring for urging the operating rod to the open position; a rod mechanism of two links each having a first end and a second end, wherein the first ends are hinged to each other at a middle hinge, wherein the second end of one link is hinging with the base frame and the second end of the other link is hinging with the operating rod; a cam follower arranged at the middle hinge of the rod mechanism; a cam arranged on a cam shaft, wherein the cam abuts the cam follower and the cam has a profile with, in rotational direction, a closing section, an opening section and an idle-section; a cam shaft lock for locking the shaft at a rotational position where the cam follower abuts the cam at the end of the closing section; a closing spring arranged between a crank arranged to the cam shaft and the base frame, wherein the closing spring relaxes when the cam follower runs over the closing section towards the opening section and wherein the closing spring has a pretension, when the cam shaft is in the locked position.

[0002] With such an operating mechanism a contact can be closed and opened quickly. The closing spring aids in providing a counter force against the contact spring, such that the cam shaft can be rotated quickly and the contact can be closed within a sufficient short time period.

[0003] In order to open the contact, the cam shaft is released such that the contact spring can push open the contact and bring the operating rod towards the open position. In order to have a sufficient quick opening of the contact, the strength of the contact spring can be increased. This however results in a substantial acceleration and thus speed of the operating rod when moving from the closed position to the open position.

[0004] When the operating rod reaches the open position with high speed, the operating rod will bounce back and the contacts are moved again towards each other, which could lead to undesired sparking.

[0005] It is an object of the invention to reduce or even remove the above mentioned disadvantages.

[0006] This object is achieved with an operating mechanism according to the preamble, which is characterized in that the profile of the opening section is designed such that the cam follower follows the profile of the opening section when the operating rod moves from the closed position towards the open position.

[0007] US 2015 / 311005 A1 describes an operating mechanism for for an electrical switching device according to the preamble of claim 1. US 4,163,133 A, US 6,072,136 A and CN 205,159,204 U relate to further similar operating mechanisms for electrical switching devices.

[0008] With the operating mechanism according to the invention, the opening movement of the operating rod and accordingly the movement of the cam follower is controlled. This ensures that any undesired movements can be counteracted directly. To this end, the closing spring is provided. When a bouncing of the operating rod would cause the cam follower to move in the other direction, the cam would also be urged to counter rotate. This counter rotation will cause the closing spring to tension and this will damp the bouncing effect of the operating rod.

[0009] In an embodiment of the operating mechanism according to the invention the closing spring is pretensioned to urge the cam in contact with the cam follower at least when the operating rod moves from the closed position towards the open position.

[0010] The pretension in the closing spring will urge the crank and accordingly the cam shaft to rotate and cause the cam with the opening profile in contact with cam follower during the opening movement of the operating rod.

[0011] In a preferred embodiment of the operating mechanism according to the invention the path of the cam follower coincides or partially intersects with the opening section, when the cam follower contacts the cam at the transition from the closing section and the opening section.

[0012] This ensures that at the moment the operating rod starts to move from the closed position towards the open position, the cam follower can freely move along the opening section, or, in case the path partially intersects with the opening section, needs to slightly push the cam in counter rotation against the tension of the closing spring. This ensures a reliable contact between the cam follower and the cam during the opening movement and will counteract any bouncing of the contacts.

[0013] In another embodiment of the operating mechanism according to the invention the cam follower urges the cam in counter rotational direction, when the operating rod moves from the closed to the open position.

[0014] As the closing spring acts on the crank and thus via the cam shaft on the cam, there is some force counter acting the opening movement of the operating rod and this will dampen any undesired movements.

[0015] In the operating mechanism according to the invention the profile of the opening section is concave up. Preferably, the profile of the closing section and the idle-section are concave down.

[0016] A profile is said to be concave up on a section if the graph of the function is above the tangent at each point of the section. A profile is said to be concave down on a section if the graph of the function is below the tangent at each point of the section.

[0017] As the movement of the cam follower is along a circular path, the cam follower can freely move when the cam follower reaches the transition from the closing section to the opening section. The concave up opening section allows for the cam follower to more or less move freely, without any substantial rotation of the cam shaft. This allows for a controlled opening movement.

[0018] The invention also relates to a method for operating at least one contact, such as a vacuum interrupter, comprising the steps of: providing an operating mechanism according to the invention; turning the cam shaft, wherein the closing section of the cam contacts the cam follower and pushes the cam follower away from the cam shaft, such that the operating rod is moved to the closed position and the tension in the closing spring is released until a first pre-set tension; locking the cam shaft with the cam shaft lock; releasing the cam shaft and letting the first pre-set tension of the closing spring to rotate the cam shaft further, such that the cam follower reaches the opening section of the cam; allowing the contact spring to move the operating rod towards the open position, while maintaining contact between the cam follower and the cam; when the operating rod is in the open position rotating the cam shaft further to retension the closing spring and positioning the cam with the transition from the idle-section to the closing section in contact with the cam follower.

[0019] These and other features of the invention will be elucidated in conjunction with the accompanying drawings. Figure 1 shows a perspective view of an embodiment of an operating mechanism according to the invention. Figure 2 shows a schematic view of the embodiment of figure 1 in a closing position. Figure 3 shows a detailed view of the cam of the embodiment of figure 1. Figures 4 - 6 show a schematic view of the embodiment of figure 1 in different positions. Figure 7 shows a schematic view of the closing spring of the embodiment of figure 1.

[0020] Figure 1 shows a perspective view of an embodiment of an operating mechanism 1 according to the invention. The operating mechanism 1 has a base frame 2 with an operating rod or bridge 3 (also describes as an "operating rod") to operate simultaneously three contacts, which are each provided with a contact spring 4.

[0021] A rod mechanism consisting out of two links 5, 6 is provided arranged between the base frame 2 and the bridge 3 (or "operating rod"). A cam follower 7 is provided between the two links 5, 6 at the mutual hinge.

[0022] A cam shaft 8 is arranged rotatably in the base frame 2. A cam 9 is arranged on the cam shaft 8 and the cam 9 is in contact with the cam follower 7. The cam shaft 8 has on an end a crank 10 to which a closing spring 11 is arranged.

[0023] Figure 2 shows a schematic view of the operating mechanism 1 of figure 1. By rotating the cam shaft 8, the cam 9 pushes the cam follower 7, such that the links 5, 6 "stretch" and the bridge 3 is moved down to close one or more contacts.

[0024] Figure 3 shows the cam 9 in more detail. The outer profile of the cam 9 has three sections: a closing section 12, an opening section 13 and an idle-section 14.

[0025] Figure 4 shows the operating mechanism 1 in closed position, where the cam follower 7 contacts the cam 9 at the end of the closing profile 12. In this position the cam shaft 8 is locked by a cam shaft lock.

[0026] When the contacts need to open, for example as a result of a short-circuit or the like, the cam shaft lock is released and the closing spring 11, which is under some residual tension and because the crank 10 is not yet aligned with the closing spring 11 (as shown in figure 7), the cam shaft 8 will be rotated to the position, where the cam follower 7 passes the transition of the closing section 12 and the opening section 13, as shown in figure 5.

[0027] At this moment the cam follower 7 is free to move along its path and along the concave up opening section of the profile, as shown in figure 6.

[0028] When the bridge 3 would bounce back, the cam follower 7 is withheld by the concave up opening section 13 of the cam 9. Only by rotation in counter direction of the cam shaft 8, which will tension the closing spring will allow for movement back of the cam follower 7 and the bridge 3, but this will dampen the undesired movement.

[0029] After the opening movement is completed, the cam shaft 8 can be rotated further, where the cam follower 7 rolls over the idle-section 14, which does not impose any displacement of the cam follower 7, but will tension the closing spring 11 to a maximum, such that the closing spring 11 can cause the closing movement, when the cam shaft is rotated to the position shown in figure 2.

Claims

1. Operating mechanism (1) for operating at least one contact, such as a vacuum interrupter, which operating mechanism (1) comprises: - a base frame (2); - an operating rod (3) linearly guided in the base frame (2) for connection with at least one contact, which operating rod (3) has a closed position and an open position; - a contact spring (4) for urging the operating rod (3) to the open position; - a rod mechanism of two links (5, 6) each having a first end and a second end, wherein the first ends are hinged to each other at a middle hinge, wherein the second end of one link (6) is hinging with the base frame (2) and the second end of the other link is hinging with the operating rod (3); - a cam follower (7) arranged at the middle hinge of the rod mechanism (5, 6); - a cam (9) arranged on a cam shaft (8), wherein the cam (9) abuts the cam follower (7) and the cam (9) has a profile with, in rotational direction, a closing section (12), an opening section (13) and an idle-section (14); - a cam shaft lock for locking the shaft (8) at a rotational position where the cam follower (7) abuts the cam (9) at the end of the closing section (12); characterized by a closing spring (11) arranged between a crank (10) arranged to the cam shaft (8) and the base frame (2), wherein the closing spring (11) relaxes when the cam follower (7) runs over the closing section (12) towards the opening section (13) and wherein the closing spring (11) has a pretension, when the cam shaft (8) is in the locked position; wherein the profile of the opening section (13) is concave up and configured such that the cam follower (7) follows the profile of the opening section (13) when the operating rod (3) moves from the closed position towards the open position.

2. Operating mechanism (1) according to claim 1, wherein the closing spring (11) is pretensioned to urge the cam (9) in contact with the cam follower (7) at least when the operating rod (3) moves from the closed position towards the open position.

3. Operating mechanism (1) according to claim 1 or 2, wherein the path of the cam follower (7) coincides or partially intersects with the opening section (13), when the cam follower (7) contacts the cam (9) at the transition from the closing section (12) and the opening section (13).

4. Operating mechanism (1) according to any of the preceding claims, wherein the cam follower (7) urges the cam (9) in counter rotational direction, when the operating rod (3) moves from the closed to the open position.

5. Operating mechanism (1) according to claim 1, wherein the profile of the closing section (12) and the idle-section (14) are concave down.

6. Method for operating at least one contact, such as a vacuum interrupter, comprising the steps of: - providing an operating mechanism (1) according to any of the preceding claims; - turning the cam shaft (8), wherein the closing section (12) of the cam (9) contacts the cam follower (7) and pushes the cam follower (7) away from the cam shaft (8), such that the operating rod (3) is moved to the closed position and the tension in the closing spring (11) is released until a first pre-set tension; - locking the cam shaft (8) with the cam shaft lock; - releasing the cam shaft (8) and letting the first pre-set tension of the closing spring (11) to rotate the cam shaft (11) further, such that the cam follower (7) reaches the opening section of the cam (9); - allowing the contact spring (4) to move the operating rod (3) towards the open position, while maintaining contact between the cam follower (7) and the cam (9); - when the operating rod (3) is in the open position rotating the cam shaft (8) further to retension the closing spring (11) and positioning the cam (9) with the transition from the idle-section (14) to the closing section (10) in contact with the cam follower (7).