Patent Publication Number: US-4649237-A

Title: Power line/transformer switch

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to an overhead power line/ transformer switch of the isolator type having knife-blades for the respective phases, 
     Switches on the market today for use on overhead power lines are usually based on the use of porcelain insulators (pin- type insulators or massive porcelain insulators). These are normally disposed at a 90° angle on a shaft. The switch is normally used as an isolating switch, or a contact (sweep) is provided in addition for switching unloaded lines or unloaded transformers. A load head can also be mounted for switching load currents. 
     This type of equipment either has limited applicability, or it is expensive, because the switch is cumbersome to operate and the contact system is not independent of the reaction time of the switch. 
     In recent years, remote control of overhead power line networks has become more common. Automatic sectional switches have also been installed in the network for reducing the interruption intervals, which can be lengthy if only one centrally disposed power switch is provided per line. This places demands on the switch, which should be operable by means of a relatively inexpensive motorized drive means and mechanisms for connecting and switching loads. 
     BRIEF DESCRIPTION OF THE INVENTION 
     This is provided according to the invention with an isolating switch of the general type defined above, which is characterized in that the respective contacts for the knives of the switch are disposed on an opposing fixed shaft composed of insulation material. 
     The advantage of this system is that the moment of rotation is reduced because the center of rotation is located in closer proximity to the center of the shaft. This permits the use of simple rotary means or motor drive means. 
     The device is also a simpler and lighter weight construction, and it is therefore easier to install on the towers or supports for the power lines. 
     Another advantage of this switch is that it can be disposed independently of direction. Pin-type insulators, for example, cannot be placed upside-down. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will be described in greater detail in the following with reference to the accompanying drawings, wherein: 
     FIG. 1 shows the switch in cross section, 
     FIG. 2 shows the switch in side view, and 
     FIG. 3 shows an exemplary cross-sectional configuration of the shaft of the switch. 
     FIG. 4 shows a top perspective view of the switch. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The switch consists of knives 1 clamped to a rotatable shaft 2, the shaft being made of insulating material such as fiberglass-reinforced polyester, for example. The shaft 2 may have a cross-sectional configuration as shown in FIG. 3. 
     The knives 1 cooperate with opposing contacts 3 disposed on a shaft 4 corresponding to the shaft 2. 
     On the shaft 2 and 4 between the respective knives 1 and contacts 3, shrink-fitted insulator jackets 6 made of weather resistant plastic or rubber material are provided as a safeguard against leaking current. 
     The shafts 2 and 4 are mounted on the ends of supports 5 and 10 which are joined at the opposite ends thereof so that they form a &#34;V&#34;, and the base or point of the V is fixedly attached to a longitudinal support bar 11 which is parallel with the shafts 2 and 4. The longitudinal support bar 11 is provided with fastening means 9 for attachment to the power line tower 8. 
     The knives 1 are guided into positions of connection or disconnection with the contacts by rotating the shaft 2 by means of a manual actuator provided at the end 12 of the shaft 2 or by means of a suitable motor drive means connected thereto.