A SEALING ASSEMBLY

Abstract: The seal (1) is adapted to provide a sealing contact with a shaft (3) having a helical groove (4) formed therein. The sealing assembly comprises: a stiffening member (5), and a sealing member (6) disposed with relation to the stiffening member (5) so that the sealing member (6) is sufficiently flexible over at least a part of its length to effect a sealing contact with the shaft (3) of at least one turn or circumnavigation of the helical groove (4). In one particular embodiment the sealing member (6) further includes at least one wiping (9) means that acts to prevent any leakage of oil or grease along the length of the helical groove (4).

Description: A SEALING ASSEMBLY This invention relates to a sealing assembly and, in particular, to a sealing assembly for use with a shaft having a helical groove formed therein. In one known form of sealing assembly for use with a shaft having a helical groove formed in the outer surface thereof, the sealing assembly comprises a castellated stiffening ring and a sealing member. The stiffening ring and the sealing member are formed as separate members which are interlocated, but not interconnected, by the location of the castellations of the stiffening ring in grooves provided in the sealing member. In a second known form of sealing assembly for use with a shaft having a helical groove formed in the outer surface thereof, the sealing assembly comprises a polymeric stiffening ring to which a sealing member is adhesively attached. The sealing member having over a part of its length an internal sleeve which overlies the stiffening ring. With this particular arrangement, over that part of its length which forms the internal sleeve the material of the sealing member is not sufficiently flexible to form a sealing contact with the shaft. Further, in bath of the above described known forms of sealing assembly the sealing member, in order to provide adequate operational characteristics, particularly clearance of oil, dirt etc., is provided with slots. This means that a sealing contact is not provided over a whole or complete turn or circumnavigation of the helical groove. Further, in practice the performance of the sealing assembly is drastically reduced. In accordance with the present invention a sealing assembly adapted to provide a sealing contact with a shaft having a helical groove formed therein comprises: a stiffening member; and - a sealing member disposed with relation to the stiffening ring so that the sealing member is sufficiently flexible over at least a part of its length to effect a sealing contact with the shaft of at least one turn or circumnavigation of the helical groove. Preferably, the sealing member is provided with at least two wiping means. In accordance with a second aspect of the present invention a sealing assembly adapted to provide a sealing contact with a shaft having a helical groove formed therein, comprises: a stiffening member; and - a sealing member disposed with relation ro the stiffening ring so that the sealing member is sufficiently flexible over at least a part of its length to effect a sealing contact with the shaft of at least one turn or circumnavigation of the helical groove, and which is provided with at least one wiping means that acts to prevent any leakage of oil or grease along the length of the helical groove. The helical groove in the shaft in addition to defining a depressed groove defines an upstanding helical land.' In order to enhance the sealing contact between the sealing member and the shaft, the shaft and sealing member may be dimensioned so that they are an interference fit with one another. The sealing contact between the sealing member and the shaft may be achieved by contact between the sealing member and the upstanding helical land. The contact between the sealing member and the shaft will only provide an effective/operational sealing contact if there is sufficient flexibility in the sealing member. If this is not the case a simple scraping non-sealing contact only will be provided. Alternatively, the sealing contact between the sealing member and the shaft or apart thereof may be provided by interaction between the, or a part of the, groove and the sealing member. In a preferred.embodiment, the stiffening member and the sealing member are both provided with an abutment means which co-operates with the helical groove formed in the shaft to effect a sealing contact over at least a part of its length. The sealing member provides sealing contact with the shaft over at least one circumnavigation of the shaft, the actual extent of this sealing contact indirectly determines the height of the sealing member, i.e. the axial length of the sealing member with respect to the shaft. In positioning the wiping means provided in accordance with the present invention, it is important that any deformation caused in the sealing member by engagement of the wiping means with the shaft is taken into consideration. In certain embodiments of the present invention the thread of the groove in combination with the sealing contact required over one circumnavigation means that only one wiping means need be provided. However, preferably the sealing member is provided with two wiping means. The, or each of the wiping means provided in a sealing assembly made in accordance with the present invention may include • one, or more than one, individual wiping devices within the same wiping means. The wiping means provided in accordance with the present invention primarily act to maintain the oil and grease in place, and to keep water etc. out of the equipment. In any event the wiping means are formed in a position on the sealing member so that they form a full contact with the helical groove. If this full contact is not achieved it is possible that a leakage path for oil/grease along the helical groove will exist. In a preferred embodiment of the invention, the or each of the wiping means includes at least one wiping device which comprises an upstanding section that acts against the helical groove to provide a full contact sealing contact therewith. With the embodiment of the invention in which sealing contact, or a part thereof, is provided by interaction of an abutment with the helical groove each of the wiping device preferably comprises an upstanding section provided on the abutment of the sealing member. Further, with a sealing assembly having two wiping means it is possible to provide the abutment on the sealing member only between the two wiping means. In this case the full circumnavigation of the shaft's sealing contact with the sealing member is provided by a combination of contact between the upstanding land of the helical groove, and the sealing member, and the helical groove and the abutment on the sealing member. Under certain operational criteria which may be placed upon the sealing assembly, in order to enhance the quality of the sealing contact between the sealing assembly and the shaft. The sealing assembly may be provided with energising/loading means. In a particular embodiment of the present invention it is envisaged that the sealing member of the sealing assembly will have two arm sections, one of which forms the sealing contact with the shaft ant the other of which forms a static seal with the body into which the sealing assembly is mounted, between which is formed a space. With this type of arrangement the energising/loading means is preferably provided in the space between the two arm sections of the sealing assembly. In one form of the present invention the energising/loading means comprises filling, or partially filling, the space between the two arm sections with an elastomeric material, or a material which exhibits elastic type behaviour, which is of softer texture than the material of the sealing member of the sealing assembly. Alternatively, a C-shaped member of resilient material for example, a metal or metal alloy, may be housed in the space between the two arm sections. It is envisaged that sealing assemblies made in accordance with the present invention will be used in aircraft flap and slat control systems. In this particular case, a section of the shaft would normally be exposed to the environment, and in flight this will cause a build up of ice etc. in the helical groove of that section of the shaft. Preferably, in this case, the sealing assembly is disposed so that the abutment on the stiffening member engages with the helical groove on the shaft prior to the abutment on the sealing member so as to remove the ice etc.. Therefore, the abutment on the stiffening member acts as a scraper which removes the unwanted extraneous matter in the helical groove. The (D removal of the extraneous matter is important, in order to maintain the sealing contact integrity and thereby the sealing assembly efficiency. Preferably, the stiffening member is made from a metal, for example phosphor bronze, stainless steel, etc.. Where the stiffening ring is made from a metal or other load bearing material the sealing assembly has the added advantageous feature in that in the event that the associated working apparatus should fail in a manner which will exact a load on the sealing assembly, the stiffening ring is generally capable of sustaining said load. This can be a particular advantage where the use of the sealing assembly is in an aircraft flap or slat control system. In a preferred embodiment of the invention, the sealing member is directly attached to the stiffening member so that effectively the sealing member does not overlay any part of the stiffening member. (I Preferably, the stiffening member and the sealing member are mechanically keyed together or mechanically interlocked so as to form a unitary sealing assembly. In a preferred embodiment this is achieved by moulding the sealing member into position with respect to the stiffening member in a single operation. Preferably, the stiffening member and the sealing member are mechanically keyed together or mechanically interlocked by through moulding. In this case, preferably, the stiffening member is • provided with means, for example a series of holes, which enables the sealing member material during moulding to pass into an expanded means, for example a groove, and thereby lock the sealing means into position with respect to the stiffening member. Preferably, additionally the stiffening member and the sealing member are adhesively locked together. IZ The material from which the sealing member is manufactured is preferably a natural or synthetic polymeric material. The actual choice of material used is dependent upon the operational conditions which prevail on the system. In particular, where use is envisaged in an aircraft flap or slat system, the sealing assembly may be subjected to severe fluctuations/differences in temperature. Therefore, it is highly important that the polymeric material is correctly chosen, so as to enhance/ensure integrity of the sealing contact. In the above mentioned possible use, the polymeric material may be a fluoro-silicone polymer or a low nitrile polymer. This invention also includes apparatus having a shaft with a helical groove formed therein which incorporates a sealing assembly made in accordance with the present invention. The invention will now be illustrated,, by way of description, of an example, with reference to the accompanying drawings, in which: IS Figure 1 shows a cross-sectional side view of a sealing assembly made in accordance with the present invention mounted in a casing; Figure 2 shows a schematic cross-sectional side view of the sealing member of the sealing assembly shown in Figure 1; Figure 3 shows a plan view of the sealing member of the sealing assembly shown in Figure 1; Figure 4 shows a sectional through cut of the sealing member shown in Figure 3; Figure 5 shows a layout view of the sealing assembly shown in Figure 1; Figure 6 shows a plan view of the stiffening member of the sealing assembly shown in Figure 1; •t Figure 7 shows a sectional through cut of the stiffening member shown in Figure 5; Figure 8 shows a schematic cross-sectional side view of an alternative sealing member made in accordance with the present invention; Figure 9 shows a plan view of the sealing member shown in Figure 8; Figure 10 shows a schematic cross-sectional side view of a second alternative sealing member made in accordance with the present invention; and Figure 11 shows a plan view of the sealing member shown in Figure 10. Now referring to Figure 1 of the drawings, a sealing assembly 1 made in accordance with the present invention is shown mounted in the casing 2 of a ball screw arrangement (not shown), for example, a ball screw arrangement of an aircraft flap or slat system, and is disposed with relation to a shaft 3. The shaft 3 has a helical groove 4 formed therein, and with respect to which the sealing assembly is disposed so that it forms a sealing contact therewith. The sealing assembly 1 comprises: a stiffening ring 5 made from metal or other load bearing material, for example, phosphor bronze, stainless steel etc., and - a sealing member 6 made from a suitable natural or synthetic polymeric material, for example a fluoro-silicone polymer. Now referring to Figures 2 to 5 of the drawings, the sealing member 6 is formed as a ring, and comprises: - an inwardly facing sealing surface 7 on which a sealing abutment 8 is formed with a wiping means having two spaced apart upstanding sections 9; an outwardly facing sealing surface 10 shaped and dimensioned so that it forms a static seal with the casing 2 into which the sealing assembly is mounted; - a central body section 11; two upwardly extending arm members 12, 12a, one arm member 12 of which forms a continuation of the inwardly facing sealing surface 7 and the other of which (arm member 12a) forms a continuation of the outwardly facing sealing surface 10; a series of web members 13, which are circumferentially disposed between the two upwardly extending arm members 12, 12a, and which act to strengthen the sealing member 6 and enhance the quality of the π seal between the sealing member 6 and the shaft 3 about whic it is disposed; and - a downwardly extending locking means 14. The wiping means is formed in a position on the sealing abutment so as to ensure a full sealing contact with the helical groove 3. The wiping means is positioned on the sealing member so that it is in the vicinity of the stiffening member. Normally, the wiping means is positioned on the sealing abutment 8 so as to provide a full sealing contact with the helical groove. In this way any leakage path which may exist along the helical groove is blocked. With the provision of two upstanding sections 9 in the wiping means, one acts to prevent the passage i.e. egress, of oil/grease along the helical groove, whilst the other acts to prevent the ingress of water etc. into the apparatus along the helical groove. In the preferred embodiment of the invention the sealing abutment 8 has been reduced in profile t fr i.e. wasted, to form a flat surface 21 except between the two upstanding sections 9. This reduces the drag friction between the sealing assembly i and the shaft 2. Now referring to Figures 6 and 7 of the drawings, the stiffening member is formed as a substantially circular ring, and comprises: a body section 15; - two, diametrically opposed, location members 16 which engage in recesses (not shown) in the casing 2; an inward shaft engaging face 17; a circumferentially extending series of holes 19, which interconnect the groove 18 with the other side of the stiffening member 5. The inward shaft engaging face 17 is provided with an abutment 20 which co-operates with the helical groove 4 of the shaft 3 so as to act as a scraper n which removes dirt, ice, etc. present in the helical groove 4. The sealing abutment 8 in the sealing member 6 and the abutment 20 in the stiffening ring 5 are shaped and dimensioned so as to form a complementary engagement with the helical groove 4 formed in the shaft 3. The sealing assembly is manufactured by: locating and positioning the stiffening ring 5 in a mould, so that the surface of the stiffening ring 5 not having the groove 18 formed therein will be in contact with the body section 11 of the sealing member 6; and - injection moulding for example, transfer moulding the sealing member 6. During, the injection moulding operation the polymeric material is caused to flow into the groove 18 and through the holes 19. Thereby, lo the sealing member 6 is locked into position relative to the stiffening ring 5. Further, in order to enhance the quality of the locking together of the sealing member 6 and the stiffening ring 5 a suitable chemical bonding agent can be applied to the stiffening ring 5 prior to the injection moulding of the sealing memb r 6. With the arrangement of the sealing assembly 1 shown', there is sufficient flexibility in the sealing member 6 to ensure a sealing contact between the sealing abutment 8 of the sealing member 6 and a shaft 3 about which it is disposed, over a majority of the length of the contact between the sealing member and the shaft. This sealing contact extends over at least one turn or circumnavigation of the helical groove 4 in the shaft 3. In practice the sealing member flexibility is at its least in the area thereof immediately adjacent the stiffening ring. Now referring to Figures 8 and 9 of the drawings, there is shown an alternative form of sealing member in accordance with the present invention. The sealing member 6 shown in Figures 8 and 9 of the drawings is substantially the same as that previously described therefore like numerals have been used to show like components. The only difference between the two forms of sealing member is that the space between the arm sections 12, 12a of the sealing members is filled with a resilient material 22, for example , to energise/preload the sealing member and enhance the sealing contact between the sealing member 6 and the shaft 3. Now referring to Figures 10 and 11 of the drawings there is shown a second alternative form ' of sealing member made in accordance with the present invention. 01 The sealing member 6 shown in Figures 10 and 11 of the drawings is substantially the same as that previously described with reference to Figures 2 and 3 of the drawings and therefore like numerals have been used to show like components. The only difference between the two forms of sealing member is that the space between the arm sections 12, 12a of the sealing member has a web section 23 bridging the two arm sections immediately adjacent to the wiping means 9. Further a C-shape member 24 of resilient material is disposed in the space defined by the two arm sections 12, 12a. In this particular arrangement the web section 23 provided adjacent to the wiping means provides rigidity in this area, whilst the C-shaped member 24 acts to energise/preload the sealing member and therefore enhance the quality of the sealing contact.

Claims: CLAIMS 1. A sealing assembly with a sealing member adapted to provide a sealing contact with a shaft having a helical groove formed therein, comprises: a stiffening member; and .- a sealing member disposed with relation to the stiffening ring so that the sealing member is sufficiently flexible over at least a part of its length to effect a sealing contact with the shaft of at least one turn or circumnavigation of the helical groove. 2. A sealing assembly as claimed in claim 1, which also comprises at least one wiping means provided on the sealing member. 3. A sealing assembly adapted to provide a sealing contact with a shaft having a helical groove formed therein, comprises: a stiffening member; and - a sealing member disposed with relation to the stiffening member so that the sealing member is sufficiently flexible over at least a part of its length to effect a sealing contact with the shaft of at least one turn or circumnavigation of the helical groove, and which is provided with' at least one wiping means that acts to prevent any leakage of oil or grease along the length of the helical groove. 4. A sealing assembly as claimed in any one of the preceding claims, in which the stiffening member and the sealing member are both provided with an abutment means which co-operates with the helical groove formed in the shaft to effect a sealing contact over at least a part of its length. 5. A sealing assembly as claimed in any one of the preceding claims, in which one wiping means is provided on the sealing member. 6. A sealing assembly as claimed in any one of claims 1 to 4, in which two wiping means are provided on the sealing member. 7. A sealing assembly as claimed in any one of claims 3 to 6, in which the or each of the wiping means includes at least one wiping device which comprises an upstanding section that acts against the helical groove to provide a full contact sealing contact therewith. 8. A sealing assembly as claimed in any one of claims 3 to 6, in which sealing contact, or a part thereof, is provided by interaction of an abutment with the helical groove each of the wiping devices comprise an upstanding section provided on the abutment of the sealing member. 9. A sealing assembly as claimed in any one of the preceding claims, in which the sealing member has two arm sections, one of which forms the sealing contact with the shaft and the other of which forms a static seal with the body into which the sealing assembly is mounted and between which is defined a space, wherein an energising/loading means is provided in the space between the two arm sections of the sealing assembly. 10. A sealing assembly as claimed in claim 9, wherein the energising/loading means comprises filling the space between the two arm sections with a material which exhibits elastic type behaviour and which is softer in texture than the material of the sealing member of the sealing assembly. 11. A sealing assembly as claimed in claim 9, wherein the energising/loading means comprises a C-εhaped member of resilient material housed in the space between the two arm sections. 12. A sealing assembly as.-claimed in any one of the preceding claims, where in use it can be disposed so that the abutment on the stiffening member engages with the helical groove on the shaft prior to the abutment on the sealing member so as to remove the ice and dirt build-up in the groove . 13. A sealing assembly as claimed in any one of the preceding claims, wherein the stiffening member is made from a metal material. 14. A sealing assembly as claimed in any one of the preceding claims, wherein the sealing member is directly attached to the stiffening member so that effectively the sealing member does not overlay any part of the stiffening member. 15. A sealing assembly as claimed in any one of the preceding claims, in which the stiffening member and the sealing member are mechanically keyed together or mechanically interlocked so as to form a unitary sealing assembly. 16. A sealing assembly as claimed in claim 15, wherein this is achieved by moulding the sealing member into position with respect to the ' stiffening member in a single operation. 17. A sealing assembly as claimed in any one of Z8 claims 1 to 13, in which the stiffening member and the sealing member are mechanically keyed together or mechanically interlocked by through moulding. 18. A sealing assembly as claimed in claim 17, in which the stiffening member is provided with means which enables the sealing member material during moulding to pass into an expanded means, and thereby lock the sealing means into position with respect to the stiffening member. 19. A sealing assembly as claimed in claim 18, in which the stiffening member and the sealing member are also adhesively locked together.

Inventors: SMITH ROBERT MILES, SMITH, ROBERT, MILES
Applicants: DOWTY SEALS LTD, DOWTY SEALS LIMITED
Application year: 1989
Main classification: F16H25
IPC codes: F16H25, F16J15