GB2153473A - Prevention corrosion of screw threaded fastenings - Google Patents

Abstract

A screw-threaded fastener assembly comprises a nut 5 onto which is pushed a grease-filled cap 6. The cap 6 is provided with a vent hole 9 and a ridge 10 for frictionally engaging the nut 5. The cap 6 is made of plastics or synthetic rubber or resilient metal. <IMAGE>

Description

SPECIFICATION Device for prevention of corrosion of threaded fastenings The invention relates to the combination of a cap the said cap containing a protective grease and a threaded fastening such fastening consisting of an internally threaded nut in association with an exter nallythreaded member. At present it is common practice to secure an assembly by means of an externally threaded screw or bolt engaging with an internally threaded nut. The problem which is encountered with such assemblies is that over long periods and in exposure to the atmosphere corrosion may take place making difficult the disassembly of the said assembly.

It is the object of the present invention to provide a means of protecting the exposed area from ingress of moisture or contamination so inhibiting the possibility of corrosion and facilitating disassembly of the said assembly so overcoming the presently existing disadvantage.

According to the invention we provide a combination ofan assembly of an internallythreaded nut engaged on to an externally threaded member and a cap made wholly of resilient synthetic resinous or other material the cap comprising a sleeve closed at one end the internal bore comprising an inner cavity conforming to the plurality of faces on the exterior of the said nut and flexibily disposed so as to engage securely with these faces the said cavity extending axially sufficiently far to accommodate both the said nut and any projecting portion of threaded member and to accommodate additionally at the closed end of the cavity a reservoir able to contain a supply of protective grease.

Preferably the closed end of the sleeve will be penetrated by a vent hole of such diameter as to enable surplus grease to be displaced when the bore of the cap is axially presented to the threaded assembly and engaged to its fullest extent. The axial length of the cavity is sufficiently long to permit the outward face of the open end of the cap to engage with any face of the assembly which is in the same plane as the remote end face of the nut. In fitting the cap to the assembly the cap is driven home such that the outward face of the open end of the cap interengages with the face of any washer or other component on to which the nut has been tightened, so providing a seal which prevents ingress of gas liquid or solids. In so fitting any surplus grease is driven out of the vent hole and between the interengaging faces in such manner that the residue provides an efficient seal.I have found that suitable materials for the cap are polyethylene ethylene vinyl acetate, polypropylene or an admixture of these materials although other materials may be used-if desired and these could include synthetic rubbers or resilient metals.

An embodiment of the invention will now be described in detail by way of example with reference to the accompanying drawings in which Figure 1 is a section through a typical assembly and cap.

Figure 2 is a section on the line AA of Figure 1.

Referring firstly to Figure 1 the assembly as it would normally be made comprises two plates 1 and 2 which it is desired to secure in juxtaposition and this is accomplished by the use of a bolt 4 on to which is tightened a nut 5, with a washer 3 interposed to reduce friction. In this assembly the bolt end 8 protrudes from the nut and would be exposed to atmosphere and possible corrosion. In this embodiment of the invention the cap 6 is driven home against the face of the washer 3 and is held in this position by the frictional engagement of the hemispherical annular protruberance 10.This prot ruberancefulfils no other function than to ensure that engagement is near the open end of the cap and not near the closed end and facilitates injection moulding of the cap than if the bore were to be provided with a slightly greater diameter at the closed end than at the open end. In an alternative construction the internal bore of the cap could be produced in parallel form and could rely on an interference fit with the faces 13 of the nut by virtue of the flexibility of the material used to construct the cap.

The spaces 12 and 7 between the cap and the assembly are pre-filled with a suitable grease and the act of driving home the cap forces surplus grease through the vent hole 9. It will be seen that the grease provides a residue in vent 9 and between the interengaging faces 14 of the cap and washer, effectively excluding any contaminant.

1. Acombination ofafastenerassemblycom- prising an externally threaded member and an internally threaded securing nut in which the securing nut is received into the bore or cavity of a cap such cap being frictionally engaged with the exterior of the nut the said cap being provided with an internal reservoir containing a suitable grease such that when the cap is driven home the assembly displaces grease through any clearances between the said cap and the said assembly in such manner as to provide a seal against any ingress of contaminants.

2. A combination according to Claim 1 wherein the cap is provided with a small vent hole to facilitate displacement of surplus grease.

3. A combination according to Claim 1 wherein a hemispherical internal ridge is provided disposed towards the open end of the bore of the cap so as to engage frictionally with the flat outwardly facing faces of the nut.

4. A combination according to Claim 1 wherein the cap is made of synthetic resinous material or synthetic rubber or a resilient metal.

5. A combination according to Claim 1 wherein the synthetic resinous material is polyethylene polypropylene ethylene vinyl acetate or an admixture of these materials.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (6)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Device for prevention of corrosion of threaded fastenings The invention relates to the combination of a cap the said cap containing a protective grease and a threaded fastening such fastening consisting of an internally threaded nut in association with an exter nallythreaded member. At present it is common practice to secure an assembly by means of an externally threaded screw or bolt engaging with an internally threaded nut. The problem which is encountered with such assemblies is that over long periods and in exposure to the atmosphere corrosion may take place making difficult the disassembly of the said assembly. It is the object of the present invention to provide a means of protecting the exposed area from ingress of moisture or contamination so inhibiting the possibility of corrosion and facilitating disassembly of the said assembly so overcoming the presently existing disadvantage. According to the invention we provide a combination ofan assembly of an internallythreaded nut engaged on to an externally threaded member and a cap made wholly of resilient synthetic resinous or other material the cap comprising a sleeve closed at one end the internal bore comprising an inner cavity conforming to the plurality of faces on the exterior of the said nut and flexibily disposed so as to engage securely with these faces the said cavity extending axially sufficiently far to accommodate both the said nut and any projecting portion of threaded member and to accommodate additionally at the closed end of the cavity a reservoir able to contain a supply of protective grease. Preferably the closed end of the sleeve will be penetrated by a vent hole of such diameter as to enable surplus grease to be displaced when the bore of the cap is axially presented to the threaded assembly and engaged to its fullest extent. The axial length of the cavity is sufficiently long to permit the outward face of the open end of the cap to engage with any face of the assembly which is in the same plane as the remote end face of the nut. In fitting the cap to the assembly the cap is driven home such that the outward face of the open end of the cap interengages with the face of any washer or other component on to which the nut has been tightened, so providing a seal which prevents ingress of gas liquid or solids. In so fitting any surplus grease is driven out of the vent hole and between the interengaging faces in such manner that the residue provides an efficient seal.I have found that suitable materials for the cap are polyethylene ethylene vinyl acetate, polypropylene or an admixture of these materials although other materials may be used-if desired and these could include synthetic rubbers or resilient metals. An embodiment of the invention will now be described in detail by way of example with reference to the accompanying drawings in which Figure 1 is a section through a typical assembly and cap. Figure 2 is a section on the line AA of Figure 1. Referring firstly to Figure 1 the assembly as it would normally be made comprises two plates 1 and 2 which it is desired to secure in juxtaposition and this is accomplished by the use of a bolt 4 on to which is tightened a nut 5, with a washer 3 interposed to reduce friction. In this assembly the bolt end 8 protrudes from the nut and would be exposed to atmosphere and possible corrosion. In this embodiment of the invention the cap 6 is driven home against the face of the washer 3 and is held in this position by the frictional engagement of the hemispherical annular protruberance 10.This prot ruberancefulfils no other function than to ensure that engagement is near the open end of the cap and not near the closed end and facilitates injection moulding of the cap than if the bore were to be provided with a slightly greater diameter at the closed end than at the open end. In an alternative construction the internal bore of the cap could be produced in parallel form and could rely on an interference fit with the faces 13 of the nut by virtue of the flexibility of the material used to construct the cap. The spaces 12 and 7 between the cap and the assembly are pre-filled with a suitable grease and the act of driving home the cap forces surplus grease through the vent hole 9. It will be seen that the grease provides a residue in vent 9 and between the interengaging faces 14 of the cap and washer, effectively excluding any contaminant. CLAIMS

1. Acombination ofafastenerassemblycom- prising an externally threaded member and an internally threaded securing nut in which the securing nut is received into the bore or cavity of a cap such cap being frictionally engaged with the exterior of the nut the said cap being provided with an internal reservoir containing a suitable grease such that when the cap is driven home the assembly displaces grease through any clearances between the said cap and the said assembly in such manner as to provide a seal against any ingress of contaminants.

2. A combination according to Claim 1 wherein the cap is provided with a small vent hole to facilitate displacement of surplus grease.

3. A combination according to Claim 1 wherein a hemispherical internal ridge is provided disposed towards the open end of the bore of the cap so as to engage frictionally with the flat outwardly facing faces of the nut.

4. A combination according to Claim 1 wherein the cap is made of synthetic resinous material or synthetic rubber or a resilient metal.

5. A combination according to Claim 1 wherein the synthetic resinous material is polyethylene polypropylene ethylene vinyl acetate or an admixture of these materials.

6. A combination according to Claim 1 substantially as herein before described with reference to and as shown in Figures 1 and 2 of the accompanying drawings.