EP2109125A1

EP2109125A1 - Spring drive unit comprising a spring state indicator, operating device comprising such spring drive unit, and a spring state indicator

Info

Publication number: EP2109125A1
Application number: EP08103481A
Authority: EP
Inventors: Mats Holman
Original assignee: ABB Technology AG
Current assignee: ABB Technology AG
Priority date: 2008-04-10
Filing date: 2008-04-10
Publication date: 2009-10-14
Also published as: CN102017035A; WO2009124814A1; EP2277186A1

Abstract

The invention relates to a spring drive unit comprising a motor for driving a spring charging mechanism (5), a gearbox (6) connected to the motor (4), a camshaft (7) connected to the gearbox, said gearbox transmitting rotational energy from the motor via a gearbox shaft and the spring charging mechanism to the camshaft, and comprising a closing spring unit (2) coupled to the spring charging mechanism, via the camshaft and being charged by the spring charging mechanism. The spring drive unit also comprises a spring state indicator (14) mounted on the camshaft (7), which indicator indicates the state of charging of the closing spring (2).

The invention also relates to a spring state indicator and an operating device for an electrical switching apparatus, comprising such a spring drive unit with a spring state indicator.

Description

Technical field of the invention

The present invention relates to a spring drive unit comprising a spring state indicator, e.g. for driving and controlling the opening and closing of an electrical switching apparatus, such as a switch or a circuit breaker. The said switching apparatus is meant to be used in a high or medium voltage transmission or distribution network and is thus used at voltages ranging from one kilovolt to several hundreds of kilovolts. The spring drive unit may operate circuit breakers of all types, e.g. gas, oil or vacuum insulated circuit breakers of the live tank or dead tank type.
Spring drive units can also be used in other applications. In principle, they may be used anywhere where there is a need to move something very fast.
The present invention also relates to an operating device for an electrical switching apparatus comprising such spring drive unit, and also to a spring state indicator.

Background of the invention

In a power transmission or distribution network, switching apparatuses are incorporated into the network to provide automatic protection in response to abnormal load conditions or to permit opening or closing (switching) of sections of the network. The switching apparatus may therefore be called upon to perform a number of different operations such as interruption of terminal faults or short line faults, interruption of small inductive currents, interruption of capacitive currents, out-of-phase switching or no-load switching, all of which operations are well known to a person skilled in the art.
In switching apparatuses the actual opening or closing operation is carried out by two contacts where normally one is stationary and the other is mobile. The mobile contact is operated by an operating device which comprises an actuator and a mechanism, where said mechanism operatively connects the actuator to the mobile contact.
Actuators of known operating devices for medium and high voltage switches and circuit breakers are of the spring operated, the hydraulic or the electromagnetic type. In the following, operating devices will be described operating a circuit breaker but similar known operating devices may also operate switches.
The spring operated actuator, or spring drive unit as it is also called, generally uses two springs for operating the circuit breaker; an opening spring for opening the circuit breaker and a closing spring for closing the circuit breaker and reloading the opening spring. Instead of just one spring for each one of the opening spring and the closing spring, sometimes a set of springs may be used for each one of the opening spring and the closing spring. For example, such a set of springs may include a small spring arranged inside a larger spring or springs arranged in parallel, side by side. In the following, it should be understood that when reference is made to the spring of the respective opening spring and the closing spring, such a spring could include a set of springs, and the term spring unit is also used to indicate this. In addition to the opening spring and the closing spring, the spring drive unit includes an electrical motor, a gearbox and a camshaft connected to the gearbox, said gearbox transmitting rotational energy from the motor, via a gearbox shaft and a spring charging mechanism, to the camshaft. Another mechanism converts the motion of the springs into a translation movement of the mobile contact. In its closed position in a network the mobile contact and the stationary contact of the circuit breaker are in contact with each other and the opening spring and the closing spring of the operating device are charged. Upon an opening command the opening spring opens the circuit breaker, separating the contacts. Upon a closing command the closing spring closes the circuit breaker and, at the same time, charges the opening spring. The opening spring is now ready to perform a second opening operation if necessary. When the closing spring has closed the circuit breaker, the electrical motor in the operating device recharges the closing spring. This recharging operation takes several seconds.
In order to have safe and reliable functionality of the spring drive unit, it is desirable to have some kind of arrangement that offers the possibility to obtain information about the charging status of, in particular, the closing spring. An operator may want to know if the spring is fully charged and ready for operation, is charging under way or has something happened that has stopped the charging process, has perhaps the charging process been interrupted and the spring is only partly charged, etc.
There does exist some examples of spring state indicators in prior art, but they are complicated and therefore also costly. As an example, from US 6,144,002 is known a mechanical visualization means with three different positions indicating the state of charging of a closing spring. This means involves a complicated arrangement with a number of kinematically linked parts, linking the indicator to the spring loading mechanism, the opening latch and the movable contact. The indicator itself involves a lever with a visualization face passing in front of a window. The obvious drawback is the number of kinematically linked parts that have to be added to the spring drive, making it expensive and complicated.

Summary of the invention

The object of the present invention is to provide a spring drive unit with a spring state indicator, in particular a spring drive unit arranged in an operating device for driving and controlling the opening and closing of an electrical switching apparatus, such as a switch or a circuit breaker. A further object is to provide an operating device for an electrical switching apparatus, comprising a spring drive unit with a spring state indicator, and also to provide a spring state indicator as such.
The object of the present invention is achieved by means a spring drive unit, an operating device and a spring state indicator as defined in the independent claims.
According to the present invention is defined a spring drive unit comprising a motor for driving a spring charging mechanism, a gearbox connected to the motor, a camshaft connected to the gearbox, said gearbox transmitting rotational energy from the motor via a gearbox shaft and the spring charging mechanism to the camshaft, and comprising a closing spring unit coupled to the spring charging mechanism, via the camshaft and being charged by the spring charging mechanism, characterized in that it comprises a spring state indicator mounted on the camshaft, which indicator indicates the state of charging of the closing spring. By providing a spring state indicator mounted directly on the camshaft of the spring drive unit is obtained a very simple and reliable functionality, since it is directly coupled to the camshaft without any intermediate mechanical link mechanisms. There are fewer components that may fail and it will be less expensive.
According to an aspect of the invention, the spring state indicator is mounted at the free end of the camshaft. This makes the installation very simple.
According to a further aspect of the invention, the spring state indicator comprises a wheel mounted on the camshaft and which rotates together with the camshaft. This spring state indicator wheel has at least one visual indication means for indicating the state of charging of the closing spring. The visual indication means is consequently coupled directly to the rotation of the camshaft performing the charging of the spring, with the result that direct information is obtained about the state of charging. To use a wheel is also a very simple and cost effective solution. It is easy to manufacture, with only one part.
The spring state indicator wheel may also have at least one mechanical indication means for indicating the state of charging of the closing spring which of course also is directly coupled to the rotation of the camshaft.
According to a first embodiment, the wheel has a circumferential surface and at least one of the visual indication means and the mechanical indication means is provided on the circumferential surface for indicating the state of charging of the closing spring.
According to a second embodiment, the wheel has a radial surface and that at least one of the visual indication means and the mechanical indication means is provided on the radial surface for indicating the state of charging of the closing spring.
Naturally, there is nothing that prevents that the two embodiments are combined, such that the wheel can have both a circumferential surface and a radial surface. The visual indication means and the mechanical indication means may be located on either one of the surfaces, and a number of combinations can be foreseen, as will be clear from the following detailed description. The location of the visual and mechanical indication means is determined by practical circumstances, from case to case.
According to a further aspect, the mechanical indication means comprises at least one cam element. This cam element may arranged as a protrusion on the surface, or as a recess extending down into the surface.
According to alternative embodiments, the mechanical indication means may comprise at least one cam element arranged as a protrusion extending axially from the side of a circumferential surface of the wheel, or as a recess extending axially into the side of a circumferential surface of the wheel.
According to a further feature, the spring drive unit may comprise at least one limit switch and the mechanical indication means of the spring state indicator activates a limit switch in order to indicate the state of charging of the closing spring. Through this, not only a visual indication is obtained but also an electrical indication of the state of charging is obtained. The limit switch may for example activate a lamp that will indicate that the spring is fully charged and ready for operation. As above, this mechanical indication means may be a cam element, which cam element triggers at least one limit switch. According to prior art, visual indication means and means for triggering limit switches are two completely separate devices. For example, they often both involve complicated mechanical link mechanisms or they may involve different sensors for determining the positions of different elements of the spring drive unit. Through the present invention, it is possible to provide a simple visual indication and an electrical indication by means of a simple wheel as the major element.
As a further feature, a limit switch may be provided that controls the motor, such that the motor is turned off when the limit switch is activated by the mechanical indication means and the motor is turned on again when the limit switch is deactivated. This offers a simple way of controlling the motor.
As a means to trigger the limit switch, the spring drive unit may comprise a link mechanism comprising a cam follower and a link arm, and the cam follower is influenced by the cam element thereby transferring a movement via the link arm to the limit switch and thereby activating the limit switch.
According to the present invention is also defined an operating device for an electrical switching apparatus, comprising a spring drive unit in accordance with any one of the claims related to the inventive spring drive unit and a mechanism for operatively connecting the spring drive unit with a contact in the electrical switching apparatus.
Finally is defined, according to the present invention, a spring state indicator for a spring drive unit, characterized in that it has the shape of a wheel which has indication means for indicating the charging status of a spring of the spring drive unit.
The indication means may be visual indication means, and/or mechanical indication means presenting the features that have already been described above in relation to the spring drive unit.
The wheel may be made in a lightweight material.
Further features and advantages of the present invention will become apparent from the following detailed description of the invention.

Brief description of the drawings

Fig. 1 illustrates schematically a spring drive unit according to an embodiment of the present invention,
Fig. 2 shows a first embodiment of a spring state indicator according to the invention,
Fig. 3 shows a variant of the first embodiment of the spring state indicator,
Fig. 4 shows a second embodiment of a spring state indicator according to the invention, and
Fig. 5 shows a variant of the second embodiment.

Detailed description of the invention

In Fig. 1 is shown the major parts of a spring drive unit according to the present invention. For example, this spring drive unit may be used in an operating device for an electrical switching apparatus, such as a switch or a circuit breaker for medium and high voltages. The main parts and the operation of a spring drive unit as well as an operating device used for circuit breakers and switches have already been described above.
The spring drive unit includes two spring units, one closing spring unit 2 for closing the circuit breaker and one opening spring unit (not shown) for opening the circuit breaker. Each spring unit includes a spring or sometimes a set of springs. For the sake of simplicity, in the following only the shorter terms closing spring and opening spring will be used, but it should be understood that what is intended is a spring unit that may comprise one spring or a set of springs. Furthermore, it includes a motor 4 for driving a spring charging mechanism 5. It includes a gearbox 6 connected to the motor 4, and a camshaft 7 connected to the gearbox shaft. The gearbox transmits rotational energy from the motor via the gearbox shaft and the spring charging mechanism to the camshaft. The closing spring 2 is coupled to the spring charging mechanism, via the camshaft 7. The closing spring is connected to the camshaft by means of a pullrod 8. In Fig. 1 the closing spring 2 is very close to its fully charged position, which occurs when the pullrod 8 is in its uppermost position on the camshaft 7.
Different types of spring charging mechanisms are possible, for example the spring charging mechanism described in European patent application No. 08101862 by the same applicant as for the present application. The closing spring is charged by the spring charging mechanism controlling rotation of the gearbox shaft and the camshaft. The charging is a fairly slow process, typically it takes less than 15 seconds. When the closing spring has been fully charged, a latch means 10 on the camshaft is engaged with an external catchgear (not shown), and this catchgear keeps the camshaft 7 locked in the fully charged position of the closing spring. The motor is then shut off. The closing spring can now be discharged at any time by releasing the external catchgear that engages with the latch means 10 on the camshaft. When the closing spring is discharged, the camshaft rotates and thereby the cam 12 on the camshaft moves to influence a mechanism that closes the circuit breaker.
The spring drive unit in Fig. 1 also comprises a spring state indicator 14, according to the present invention. The spring state indicator is designed as a wheel that is mounted on the free end of the camshaft 7. The wheel is secured to the camshaft by means of a shaft key way or spline arrangement, for example. The wheel rotates with the camshaft. The illustrated spring state indicator wheel 14 has a visual indication means 20 and a mechanical indication means 22 for indicating the state of charging of the closing spring. The spring state indicator wheel 14 may be designed according to several different embodiments, as will be described below with reference to Figs. 2, 3, 4 and 5.
Furthermore, in Fig. 1 is shown a set of limit switches 16 mounted on a plate close to the wheel 14, and a link mechanism 18 by means of which the limit switches may be activated.
The details of a first embodiment of the spring state indicator wheel are shown in Fig. 2. The circumference, or outside, of the wheel has an axial extension that is wide enough to provide a circumferential surface that can be used for visual marking with symbols that indicate the state of charging of the closing spring. In the illustrated example, the wheel has a visual indication means 20 on the circumferential surface in the form an area of differing colouring illustrating that charging is under way. This area gets wider as the charging continues until it extends over the entire width of the wheel, thereby illustrating that the closing spring is fully charged. Alternatively, or additionally, the wheel has some other type of marking, such as the illustrated letter marking, where a small size C indicates that the spring is only in the beginning of the charging phase and a bigger C is used to illustrate that the charging is completed. The marking of the wheel should naturally be adapted to the location from where the marking should be visible in order to obtain direct reading of the state of the closing spring. Also, in this context it must be mentioned that it is very important that the orientation of the wheel on the camshaft axis is coordinated with the spring charging mechanism and in particular the latch 10, such that the marking for fully charged closing spring really corresponds to the position where the latch 10 is engaged with the external catchgear and the catchgear keeps the camshaft 7 locked in the fully charged position of the closing spring.
In addition to the visual indication means 20 in the form of markings along the circumference of the wheel, the wheel may also have mechanical indication means 22 for indicating the state of charging of the closing spring. For example, these mechanical indication means may be used for activation of a limit switch 16. For this purpose, the circumferential surface of the wheel may also be provided with a cam element 22, that is coaxial with the wheel axis, and which constitutes a mechanical indication means. When the cam element 22 enters into contact with the link mechanism 18, the "bump" represented by the cam moves the link mechanism such that the link mechanism activates one or several limit switches 16 that are so located that they can be influenced by the movement of the link mechanism. The coordination of the location of the cam element 22 and the position of the wheel 14 on the camshaft 7 in relation to the spring charging mechanism and in particular the latch 10 is even more important in this case, when the cam is used to trigger limit switches 16, via an actuator such as the link mechanism 18.
In the illustrated embodiment, the link mechanism 18 includes a link arm 24 and a cam follower 26. Naturally, it would also be possible to use other types of devices for transferring a movement, caused by the cam element, to a limit switch and thereby activating the switch.
The limit switches can be used to give an electrical spring state indication. A number of different states can be indicated, for example that the spring is fully charged. The limit switches may also be used to activate certain functions, as the result of a certain state of the spring. For example, a limit switch may be used to trigger the shut off of the motor when the charging of the closing spring has been fully achieved. In that case, the location of the cam element 22 must be meticulously coordinated with the position of the wheel on the camshaft when charging has just been fully achieved. The shut off of the motor should be triggered when the cam follower 26 climbs up on the cam element 22. When the closing spring is discharged, the cam follower falls down on the other side of the cam element 22 and this should trigger the restart the motor.
As a further example, another limit switch may be used to indicate electrically that discharging is now allowed, for example by means of activating a lamp.
The wheel can also be used to indicate other states of the closing spring.
An example of another possible use of a limit switch is for fault detection. After discharging, the closing spring should automatically be charged again. If this does not occur within a given time limit, i.e. if the cam element does not reach the cam follower and does not activate the switch turning on the lamp indicating that charging is allowed, then a fault indication switch and/or lamp is activated.
With regard to Fig. 2, the cam element 22 is illustrated as protruding from the surface, but it may alternatively be designed as a recess in the surface.
In Fig. 3 is illustrated a variant of the embodiment in Fig. 2. In this figure, as well as in the Figs. 4 and 5, elements that are the same or similar to elements in Fig. 1 have been given the same reference number. Regarding the variant of the wheel 14 in Fig. 3, the cam element 32 is a protrusion extending axially from the side of a circumferential surface of the wheel 14. As an alternative, it may be designed as a recess extending axially into the side of a circumferential surface of the wheel. This wheel may also have visual indication means 20 similar to the wheel in Fig. 2.
In Fig. 4 is illustrated a second embodiment of a springs state indicator wheel 14 for a spring drive unit, according to the present invention. This wheel has a radial surface on which visual indication means 40 are provided. For example, this visual indication means 40 may be an area of differing colouring illustrating that charging is under way, similar to Figs. 2 and 3. The area gets wider as the charging continues until it extends over a major part of the width of the wheel, thereby illustrating that the closing spring is fully charged. Alternatively, or additionally, the wheel has some other type of marking, such as letter marking or any other suitable marking. The wheel in this second embodiment also has a mechanical indication means designed as a cam element 42 on the circumference of the wheel. The cam element is illustrated as a protrusion but may alternatively be a recess and functions in the same manner as the cam element 22 of the first embodiment.
A variant of the second embodiment is illustrated in Fig. 5. Here, the wheel has a radial surface with a visual indication means 40, similar to Fig. 4. However, the cam element 52 in this variant is also located on the radial surface, instead of the circumferential surface. The cam element 52 is illustrated as being a recess in the surface, but it may equally be made as a protruding cam element.
It should be mentioned that the different designs of the visual indication means and the mechanical indication means described in connection with the figures may be combined freely, for example the cam element of Fig. 3 may be combined with the visual indication means of Fig. 4. It is also conceivable to have a wheel with only mechanical indication means, such as a cam.
It would be conceivable to have switches at different locations along the wheel, with their own link mechanisms, in order to be able to electrically indicate other states in the spring charging process. It may also be possible to have more than one cam element on the wheel, in order to trigger different switches. The cam elements could then be offset in relation to each other and only extending over part of the width of the wheel.
The wheel may be a lightweight wheel.
The present inventions is not limited to the described embodiment, given as example only, but can be modified in various ways by a person skilled in the art within the scope as defined in the appended patent claims.

Claims

A spring drive unit comprising a motor for driving a spring charging mechanism (5), a gearbox (6) connected to the motor (4), a camshaft (7) connected to the gearbox, said gearbox transmitting rotational energy from the motor via a gearbox shaft and the spring charging mechanism to the camshaft, and comprising a closing spring unit (2) coupled to the spring charging mechanism, via the camshaft and being charged by the spring charging mechanism, characterized in that the spring drive unit comprises a spring state indicator (14) mounted on the camshaft (7), which indicator indicates the state of charging of the closing spring (2).
A spring drive unit according to claim 1, characterized in that the spring state indicator (14) is mounted at the free end of the camshaft (7).
A spring drive unit according to any one of claims 1-2, characterized in that the spring state indicator (14) comprises a wheel mounted on the camshaft (7) and which rotates together with the camshaft.
A spring drive unit according to claim 3, characterized in that the spring state indicator wheel (14) has at least one visual indication means (20, 40) for indicating the state of charging of the closing spring.
A spring drive unit according to claim 3 or 4, characterized in that the spring state indicator wheel (14) has at least one mechanical indication means (22, 32, 42, 52) for indicating the state of charging of the closing spring
A spring drive unit according to any one of claims 4 and 5, characterized in that the wheel (14) has a circumferential surface and that at least one of the visual indication means (20) and the mechanical indication means (22, 42) is provided on the circumferential surface for indicating the state of charging of the closing spring.
A spring drive unit according to any one of claims 4, 5 and 6 characterized in that the wheel (14) has a radial surface and that at least one of the visual indication means (40) and the mechanical indication means (52) is provided on the radial surface for indicating the state of charging of the closing spring.
A spring drive unit according to any one of claims 5-7, characterized in that the mechanical indication means comprises at least one cam element.
A spring drive unit according to claim 8, characterized in that the cam element is arranged as a protrusion on the surface.
A spring drive unit according to claim 8, characterized in that the cam element is arranged as a recess extending down into the surface.
A spring drive unit according to claim 5, characterized in that the mechanical indication means comprises (32) at least one cam element arranged as a protrusion extending axially from the side of a circumferential surface of the wheel (14).
A spring drive unit according to claim 5, characterized in that the mechanical indication means comprises at least one cam element arranged as a recess extending axially into the side of a circumferential surface of the wheel.
A spring drive unit according to any one of claims 5-12, characterized in that it comprises at least one limit switch (16) and that the mechanical indication means (22, 32, 42, 52) of the spring state indicator activates a limit switch.
A spring drive unit according to claim 13, characterized in that a limit switch (16) is provided that controls the motor (4), such that when the limit switch is activated by the mechanical indication means (22, 32, 42, 52) the motor is turned off and when the limit switch is deactivated the motor is turned on.
A spring drive unit according to any one of claims 13-14, characterized in that a limit switch (16) is provided that indicates the state of charging of the closing spring.
A spring drive unit according to any one of claims 13-15, characterized in that it comprises a link mechanism (18) comprising a cam follower (26) and a link arm (24), that the mechanical indication means (22, 32, 42, 52) comprises at least one cam element, and that the cam follower is influenced by the cam element thereby transferring a movement via the link arm to at least one limit switch (16) and thereby activating the limit switch.
An operating device for an electrical switching apparatus, comprising a spring drive unit in accordance with any one of claims 1-16 and a mechanism for operatively connecting the spring drive unit with a contact in the electrical switching apparatus.
A spring state indicator for a spring drive unit, characterized in that it has the shape of a wheel (14) which has at least one indication means (20, 40; 22, 32, 42, 52) for indicating the charging status of a spring of the spring drive unit.
A spring state indicator according to claim 18, characterized in that the indication means comprises at least one visual indication means (20, 40).
A spring state indicator according to claim 18 or claim 19, characterized in that the indication means comprises a least one mechanical indication means (22, 32, 42, 52).
A spring state indicator according to claim 19 or claim 20, characterized in that the wheel has a circumferential surface and that at least one of the visual indication means (20) and the mechanical indication means (22, 32, 42) is provided on the circumferential surface for indicating the state of charging of the closing spring.
A spring state indicator according to any one of claims 19, 20 and 21, characterized in that the wheel has a radial surface and that at least one of the visual indication means (40) and the mechanical indication means (52) is provided on the radial surface for indicating the state of charging of the closing spring.
A spring state indicator according to any one of claims 20-22, characterized in that the mechanical indication means comprises at least one cam element.