Electricity: electrothermally or thermally actuated switches – Electrothermally actuated switches – Fusible element actuated
Reexamination Certificate
2001-07-16
2003-03-11
Vortman, Anatoly (Department: 2835)
Electricity: electrothermally or thermally actuated switches
Electrothermally actuated switches
Fusible element actuated
C337S168000, C337S216000, C337S208000, C337S284000, C081S003800
Reexamination Certificate
active
06531948
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a device for handling fuses and in particular, but not exclusively, to a device for safety inserting and extracting electrical fuses used in a three phase electrical fuse unit.
Fuse units are used in low voltage distribution and supply networks. Low voltage supply distribution from indoor and outdoor sub-stations include a fuse board, fuse pillar or fuse cabinet, incorporating a fuse unit, as part of the network and as appropriate to the particular application. Conventionally, four or five supply bus bars are provided, one for each of the three phases and either a common earth neutral bar or separate earth and neutral bars. Each three phase output taken from the supply has each power carrying cable connected to the bus bar of the respective phase by way of a fuse, the three fuses being mounted together in a fuse unit on a distribution unit. Each fuse is designed to engage and bridge a pair of contacts, one electrically connected to the respective bus bar, and the other to the respective output.
Two different types of fuse are used in such applications: UK style fuses with additional contact members and European style fuses. UK and European style fuses differ in their geometry and the contact members that they present to the pair of contacts in the fuse unit. UK style fuses have additional contact members providing a generally U shaped configuration and tend to be presented to contacts in a fuse holder in an inverted U manner with the contact members providing the legs of the U which engage the pair of contacts of the fuse holder. The legs of the U extend laterally to provide an extended region of contact between the fuse contact members and the fuse holder contacts adapted to receive them. European style fuses have fuse terminals providing integral flat planar contact members extending from either end of a main body and are inserted vertically into fuse unit contacts adapted to receive them.
In order to handle the supplied electrical currents and to provide good electrical and mechanical contact, the contact members of a European fuse are extended vertically. In contrast the contact members of UK style fuses extend laterally.
In order to allow for the safe handling of live fuses they must be rapidly and firmly inserted or removed form the live contacts. Owing to the U shaped configuration of UK style fuses this can be achieved quite readily. However, owing to the fact that European style fuses extend substantially further in the direction of their insertion or removal a greater stroke is required in order to safely effect their removal or insertion. European style fuses are becoming prevalent in a number of countries and the safety requirements for their handling are becoming more stringent. Hence there is a need for a device for effecting the safe handling of European style configured fuses in live fuse units.
European style configured fuse handling devices integral to a fuse unit can be provided but at increased cost and complexity to the fuse unit. A removable device suitable for use with a fuse unit allows the safe handling of all live fuses by a single device providing economies of cost and simplicity of fuse unit manufacture. A compact handling device is to be preferred, owing to the proximity of fuse units on fuse boards, pillars or cabinets and their ease of use by workmen.
SUMMARY OF THE INVENTION
According to a first aspect of the invention there is provided a fuse handling device for use with a fuse unit having a pair of contacts between which a fuse with integral switching contacts may extend in use, the handling device having an actuating lever operable into a first position and a second position, a charging means operably connected to the actuating lever and a drive means operably connected to the charging means, in which when the handling device in use is mounted on the fuse unit, the drive means attaches to the fuse and operation of the actuating lever into the first position charges the charging means to causes the drive means to extract the fuse from the pair of contacts and operation of the actuating lever into the second position charges the charging means to cause the drive means to insert the fuse into the pair of contacts, in which the fuse moves in a direction parallel to a plane defined by its switching contacts.
The device is for use in safely extracting and inserting European style configured fuses as used in fuse units. Both a European style fuse and a UK fuse without additional contact members, i.e. with integral fuse terminal/switching contacts, are considered to fall within the scope of a European style configured fuse. The invention allows fuses with integral switching contacts to be safely manipulated while the fuse unit is still live. The handling device is actuated by a throw lever. With the actuating lever in a first neutral position the device is mounted on a fuse unit and a drive means attaches to a fuse located between a pair of contacts in the fuse unit. Operation of the actuating lever into a first position charges up a charging means until sufficient energy has been stored to effect rapid and safe removal of the fuse from its pair of contacts. The device can also be used to safely insert a fuse between a pair of live contacts. The device with a fuse can be mounted on the live fuse unit and the actuating lever operated into a second position. Charging means are charged until sufficient energy is stored to effect the rapid and safe insertion of the fuse between a pair of contacts in the fuse unit. The device can move the fuse in a plane substantially parallel to the plane defined by the switching contacts of a European style configured fuse.
Preferably, the device has a housing and an axle extending across the housing and the actuating lever pivots about the axle. The provision of a housing improves the safety of the device and also provides a robust device capable of withstanding the mechanical forces exerted during extraction and insertion of a fuse.
The drive means of the device may include a member having a fuse engagement formation slidingly mounted on the device. The fuse engagement formation of the member securely attaches the fuse to the drive means for either insertion or extraction. Slidingly mounting the member on the device helps to robustly guide the motion of the fuse during extraction or insertion ensuring the fuse moves along a preferred path.
Preferably, the member slides in a direction parallel to a plank defined by the pair of contacts of the fuse unit. In this way frictional forces between the pair of contacts and the fuse are minimised and the fuse moves through the minimal possible distance thereby increasing the efficiency of the insertion of extraction of the fuse.
The charging means may include a pair of springs. The charging means may include two pairs of springs. Preferably, the springs of a pair of springs are wound in opposite senses.
An outer end of the first spring of the pair may be connected to the actuating lever and an outer end of the second spring of the pair may be connected to the drive means and the inner ends of the first and second springs are connected in series. This provides for charging the springs to a predetermined amount before they discharge to extract or insert the fuse. The predetermined amount should be sufficient to safely extract or insert a fuse in a live fuse unit.
Preferably the pair of springs are mounted concentric to the axle. In this manner the springs can be easily and simply operably connected to the actuating lever. The pair of springs may be connected in series via a square shaft mounted concentric to the axle.
Preferably a motion transformation device is mounted on the axle and engages the drive means. The motion transformation device can include members arranged to convert rotational motion to linear motion. The motion transformation device is preferably in the form of an arm which may be pivotally mounted on the axle and engage the drive means. In this way the rotational movement of the actuating lever and ch
Merchant & Gould P.C.
Schneider Electric Limited
Vortman Anatoly
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