Curved surfaces, particularly reflectors, and methods of forming same

Abstract

Curved surfaces particularly reflectors such as concave mirror elements for use in astronomical telescopes, solar energy concentrators etc., and methods of forming such surfaces. A rigid body with a curved surface is formed by providing a mould ( 20 ) having a curved surface with a curvature opposite to that of the required curved surface, applying a vacuum to the curved surface of the mould to deform a flexible, generally planar member ( 14 ) to match the curved surface of the mould and bonding a front surface of a structurally rigid base member ( 12 ) to the opposite surface of the planar flexible member while the vacuum is applied. Peripheral casing members ( 16, 18 ) may he bonded to the base member. The base member is formed from a rigid, low-density material such as an aluminium or aluminium alloy honeycomb material. The flexible (reflective) member may comprise a thin metallic sheet such as an anodised aluminium alloy sheet, and any casing members may also be of aluminium or aluminium alloy.

1 . A method of forming a rigid body with a curved surface, comprising: 
 providing a mould having a curved surface with a curvature opposite to that of the required curved surface;    providing a vacuum source communicating with the curved surface of the mould;    applying a flexible, generally planar member that is to form the required curved surface to the oppositely curved surface of the mould;    operating the vacuum source to evacuate the space between the planar member and the mould such that the planar member conforms closely to the curved surface of the mould; and    while continuing to operate the vacuum source, bonding a front surface of a structurally rigid base member to the exposed surface of the planar member opposite the surface in contact with the mould.    
     
     
         2 . The method of  claim 1 , further including deactivating the vacuum source once a bonding agent used to bond the base member to the planar member has been cured.  
     
     
         3 . The method of  claim 1 , further including bonding at least one peripheral casing member to a peripheral surface of the base member and/or at least one generally planar casing member to a rear surface of the base member.  
     
     
         4 . The method of  claim 3 , wherein said at least one peripheral casing member is bonded to the peripheral surface of the base member and/or said at least one generally planar casing member is bonded to the rear surface of the base member while the base member is in situ on the mould.  
     
     
         5 . The method of  claim 4 , wherein said at least one peripheral casing member is bonded to the peripheral surface of the base member and/or said at least one generally planar casing member is bonded to the rear surface of the base member while the base member is in situ on the mould and while the vacuum source is operating.  
     
     
         6 . The method of  claim 1 , wherein the shape in plan of the rigid body formed by the method is circular, or a part-circular segment, or polygonal, or a triangular segment of a polygonal shape.  
     
     
         7 . The method of  claim 1 , wherein the curved surface is at least partially concave.  
     
     
         8 . The method of  claim 1 , wherein the curved surface is at least partially convex.  
     
     
         9 . The method of  claim 1 , wherein the base member is formed from a rigid, low density material.  
     
     
         10 . The method of  claim 9 , wherein the low density material is a honeycomb material.  
     
     
         11 . The method of  claim 10 , wherein the honeycomb material is an aluminium or aluminium alloy honeycomb material.  
     
     
         12 . The method of  claim 1 , wherein the rigid body formed by the method is a reflector.  
     
     
         13 . The method of  claim 12 , wherein the flexible planar member is a reflective member.  
     
     
         14 . The method of  claim 13 , wherein the reflective member comprises a thin metallic sheet.  
     
     
         15 . The method of  claim 14 , wherein the thin metallic sheet comprises a thin aluminium or aluminium alloy sheet.  
     
     
         16 . The method of  claim 15 , wherein the aluminium or aluminium alloy sheet comprises an anodised aluminium or aluminium alloy sheet or an anodised and coated aluminium or aluminium alloy sheet.  
     
     
         17 . The method of  claim 1 , wherein casing members bonded to the base members are formed from aluminium or aluminium alloy.  
     
     
         18 . A rigid body having a curved surface, comprising a generally planar, flexible member that is vacuum formed to a required curvature and bonded to a surface of a structurally rigid base member.  
     
     
         19 . The rigid body of  claim 18 , further including at least one peripheral casing member bonded to a peripheral surface of the base member and/or at least one generally planar casing member bonded to a rear surface of the base member.  
     
     
         20 . The rigid body of  claim 18 , wherein shape in plan of the rigid body is circular, or a part-circular segment, or polygonal, or a triangular segment of a polygonal shape.  
     
     
         21 . The rigid body of  claim 18 , wherein the curved surface is concave.  
     
     
         22 . The rigid body of  claim 18 , wherein the curved surface is be convex.  
     
     
         23 . The rigid body of  claim 18 , wherein the base member is formed from a rigid, low density material.  
     
     
         24 . The rigid body of  claim 23 , wherein the low density material is a honeycomb material.  
     
     
         25 . The rigid body of  claim 24 , wherein the honeycomb material is an aluminium or aluminium alloy honeycomb material.  
     
     
         26 . The rigid body of  claim 18 , wherein the rigid body is a reflector.  
     
     
         27 . The rigid body of  claim 26 , wherein the flexible planar member is a reflective member.  
     
     
         28 . The rigid body of  claim 27 , wherein the reflective member comprises a thin metallic sheet.  
     
     
         29 . The rigid body of  claim 28 , wherein the thin metallic sheet comprises a thin aluminium or aluminium alloy sheet.  
     
     
         30 . The rigid body of  claim 29 , wherein the aluminium or aluminium alloy sheet comprises an anodised aluminium or aluminium alloy sheet or an anodised and coated aluminium or aluminium alloy sheet.  
     
     
         31 . The rigid body of  claim 18 , wherein casing member bonded to the base members are formed from aluminium or aluminium alloy.