Seals and a method of making seals

Abstract

A seal and method of making seals utilises folds in order to form creases in a length of material such that the creases reinforce individual seal elements or surfaces whilst perforations or slots in a seal edge allow air leakage from one side of the seal element or surface to the other. Thus, air pressurisation can take place between spaced seal elements or surfaces and this allows air flotation or riding of a rotating component relative to a static housing component. The perforations are typically graduated from the seal edge in order to provide the best pressurisation and air-riding effect for proximity or gap control between the sealing edge and the rotating component surface. The slots effectively provide flexibility to the sealing edge such that the seal component emulates a brush seal.

I claim:  
     
         1 . A seal comprising a seal edge to be held in close proximity in use to a relatively rotating surface, the edge being reinforced by creases extending away from the edge, characterised in that a desired distribution of perforations is provided above the edge to facilitate air pressure differential across the edge as the rotating surface rotates in relation to the edge and the rotating surface rides upon an enhanced pressure created by air leakage through the perforations.  
     
     
         2 . A seal comprising a seal edge to be held in close proximity to a rotating surface in use, the edge being reinforced by creases extending away from the edge, characterised in that between the creases the edge includes slots to facilitate flexibility in the edge when held in close proximity to the rotating surface.  
     
     
         3 . A seal as defined in  claim 1  and  claim 2 .  
     
     
         4 . A seal as claimed in  claim 1  wherein the seal includes a plurality of edges in a seal assembly and these edges are presented upon respective spaced seal elements of the seal assembly.  
     
     
         5 . A seal as claimed in  claim 1  wherein the perforations are graded outwardly from the edge.  
     
     
         6 . A seal as claimed in  claim 5  wherein the perforations nearer to the edge are relatively small compared to perforations further displaced from the edge.  
     
     
         7 . A seal as claimed in  claim 5  wherein the perforations nearer to the edge have a greater population density per unit area compared to perforations further displaced from the edge.  
     
     
         8 . A seal as claimed in  claim 1  wherein the perforations are configured from one side to the other to facilitate airflow to achieve the desired air pressure differential across the edge.  
     
     
         9 . A seal as claimed in  claim 1  wherein the creases are angular relative to the edge in order to form a ring with sails defined between respective adjacent creases.  
     
     
         10 . A seal as claimed in  claim 4  wherein creases in the adjacent spaced seal elements are in a respectively opposed relationship relative to each other.  
     
     
         11 . A seal as claimed in  claim 2  wherein the slots extend substantially perpendicular to the major axis of the edge.  
     
     
         12 . A seal as claimed in  claim 2  wherein the slots terminate in one of a keyhole and a bulbous end to inhibit crack propagation due to flexing of the edge.  
     
     
         13 . A seal as claimed in  claim 2  wherein the slots are of varying lengths extending from the edge.  
     
     
         14 . A seal as claimed in  claim 2  wherein the slots have a length at least equivalent to the expected wear depth in use of the seal.  
     
     
         15 . A seal as claimed in  claim 1  wherein the edge is substantially straight between respective creases.  
     
     
         16 . A seal as claimed in  claim 1  wherein the edge is curved between respective creases.  
     
     
         17 . A seal as claimed in  claim 1  wherein one of a stiffener fold and a stiffener element is secured to the seal to further reinforce each edge.  
     
     
         18 . A seal as claimed in  claim 1  wherein the seal is associated with an air deflector in order to further facilitate air pressure differential across the edge.  
     
     
         19 . A seal as claimed in  claim 1  wherein the edge is formed upon a spiral which extends for a number of cycles to form the seal.  
     
     
         20 . A method of forming a seal element including the steps of taking a length of material and forming a number of creases to define a seal edge and characterised in that there is perforation of that length of material such that when formed there is a specific distribution of perforations above the seal edge for air leakage in use.  
     
     
         21 . A method of forming a seal element including the steps of taking a length of material and forming a number of creases to define a seal edge and characterised in that slots are formed in the length of material which when the seal is formed extend from the seal edge to render that edge more flexible.  
     
     
         22 . A method of forming a seal element as claimed in  claim 20  and  claim 21 .  
     
     
         23 . A method as claimed in  claim 20  wherein the ends of the length of material are welded or otherwise secured together to form a ring.  
     
     
         24 . A method as claimed in  claim 21  wherein the ends of the length of material are welded or otherwise secured together to form a ring.  
     
     
         25 . A method as claimed in  claim 20  wherein the perforations are formed such that there is a size graduation away from the seal edge.  
     
     
         26 . A method as claimed in  claim 25  wherein the perforations near to the edge are formed smaller than those at more displaced positions.  
     
     
         27 . A method as claimed in  claim 25  wherein the perforations nearer to the edge are formed with a greater population density per unit area than those at more displaced positions.  
     
     
         28 . A method of making a seal assembly wherein a number of seals in accordance with  claim 1  are secured in alignment with the respective seal edges of the seals presented towards the relatively rotating surface.  
     
     
         29 . A method as claimed in  claim 28  wherein spacing elements are located between adjacent seals.  
     
     
         30 . A method as claimed in  claim 28  wherein the respective seals are secured in one of a recess and an aperture to form the seal assembly.