Method of and means for producing a helical band

A method of producing an insulator for use in an overhead electric power transmission line, which comprises the steps of:

• applying a layer of at least potentially electrically-insulating, fluid, heat-settable, material onto a rotating support to one side of an axis of rotation of the support,
• applying heat to the layer while rotating the support and the layer applied thereto for a length of time sufficient for the material in the layer to set in shape to a required extent to form a helical electrically-insulating band,
• removing the set-in-shape band from the support before the band comes into contact with the material being applied onto the support, a speed of rotation of the support, a distance travelled by the layer/band on the support and the heat applied to the layer/band being such as to cause the required setting in shape of the material in the layer, and,
• applying the band helically around a substantially cylindrical rod of electrically-insulating material and bonding the band to the rod to form the rod with a helical flange such as to define a corresponding helical trough and, along a base of the trough, a helical leakage path of substantially uniform width.

A device for producing a helical band, comprising:

• a support rotatable about a substantially vertical axis,
• means for applying a layer of fluid heat-settable material onto an upper side of the support at one side of the axis of rotation of the support,
• means for applying heat to the layer while rotating the layer on the support for a length of time sufficient for the material in the layer to set in shape to a required extent to form the band, and
• means for removing the band from the support before the band comes into contact with the material being applied onto the support, the support being rotated at a speed and affording the layer/band a dwell time on the support such as to cause the required setting of the material in the layer for a given layer-heating temperature.

Apparatus for producing an insulator for use in an overhead electric power transmission line, comprising:

• a rotatable support,
• means for applying a layer of fluid heat-settable material onto the support to one side of an axis of rotation of the support,
• means for applying heat to the layer while rotating on the support for a length of time sufficient for the material in the layer to set in shape to a required extent to form the band, and
• means for removing the band from the support before the band comes into contact with the material being applied onto the support and for applying the band helically round a substantially cylindrical rod of electrically-insulating material with a set pitch, and bonding the band to the rod to provide the rod with a helical flange such as to define a corresponding helical trough and, along a base of the trough, a helical leakage path of substantially uniform width, the support being rotated at a speed and affording the layer/band a dwell time such as to cause the required setting in shape of the material in the layer for a given layer-heating temperature.