Scratch seal assembly for ball screw actuator

Abstract

A scratch seal assembly for sealing a ball screw actuator has an annular elastomeric sealing element disposed about a longitudinal axis that separates a grease side from an ambient side. An annular inner support is at least partially disposed within the sealing element. The sealing element has a first arcuate surface configured to be disposed in an inner spiral raceway of the shaft and facing an environment side, a second arcuate surface configured to be disposed in the inner spiral raceway of the shaft and facing a grease side, and an ice scraping seal facing the environment side, an inner helical crest is configured to contact or approach the inner helical crest of the shaft at least 360 degrees about the longitudinal axis. The first and second arcuate surfaces and the ice scraping seal sealingly separate the environmental side from the grease side.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to provisional application 63 / 481,568, filed January 25, 2023, the entire contents of which are incorporated herein by reference in their entirety. Technical Field

[0003] The present invention relates generally to seals and, more particularly, to ball screw seals for ball screw actuators used in aerospace and industrial applications. Background Art

[0004] Ball screw actuators require seals to trap grease within the actuator. Furthermore, these seals must be able to break off external ice formation while preventing intrusion (i.e., entry) of external debris into the actuator and other flight systems. Existing solutions have not been entirely successful in applications with high temperature fluctuations and present drag issues. The present invention overcomes these drawbacks.

[0005] Prior art publications and patents include, but are not limited to: EP3392526B1; EP3428481B1; US4,905,533; US10,612,633; KR101584435B1; US6976399B2; JP4923624B2; JP4923624B2; US20140352470A1; JP3647597B2; US8025128B2; US4905533A; and EP3428481B1. Summary of the Invention

[0006] An exemplary embodiment of the present invention is a wiper seal assembly 20 for a ball screw actuator 1. The ball screw actuator is configured to have a housing 2 with a shaft 3 disposed therein. The housing and the shaft are both disposed about a longitudinal axis 4. A plurality of balls 5 are movably housed within a ball screw thread 6. The ball screw thread has an outer helical raceway 7 separated by outer helical crests 8, the outer helical raceway and the outer helical crests being formed in an inner surface 9 of the housing. The ball screw thread also has an inner helical raceway 10 separated by inner helical crests 11, the inner helical raceway and the inner helical crests being formed in an outer surface 12 of the shaft.

[0007] The wiper seal assembly includes an annular elastomeric sealing element 21 disposed about a longitudinal axis and configured to separate a grease side 14 from an ambient side 15. The wiper seal assembly also includes an annular inner support 22 disposed about the longitudinal axis and at least partially within the sealing element.

[0008] The sealing element includes a first arcuate surface 23 configured to be disposed within the shaft's inner spiral raceway and facing the ambient side; a second arcuate surface 26 configured to be disposed within the shaft's inner spiral raceway and facing the grease side; and an ice scraper seal 29 facing the ambient side, configured to contact or approach the shaft's inner spiral crests for at least 360 degrees around the longitudinal axis. The first arcuate surface, the second arcuate surface, and the ice scraper seal are configured to sealingly separate the ambient side from the grease side when the scraper seal assembly is installed in a ball screw actuator.

[0009] In other exemplary embodiments, the first curved lip 24 extends from the first curved surface toward the environment and is configured to contact the inner spiral raceway of the shaft. The first tapered back surface 25 extends from the first curved surface in a direction opposite to the first curved lip. The first tapered back surface is configured to move away from the inner spiral raceway as it moves further away from the first curved surface.

[0010] In other exemplary embodiments, the second curved lip 27 extends from the second curved surface toward the grease side and is configured to contact the inner spiral raceway of the shaft. The second tapered back surface 28 extends from the second curved surface in a direction opposite to the second curved lip. The second tapered back surface is configured to move away from the inner spiral raceway as it moves further away from the second curved surface. The first tapered back surface merges into and connects to the second tapered back surface. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 is a front view of an exemplary embodiment of a wiper seal assembly of the present invention;

[0012] Figure 2 yes Figure 1 Isometric drawing of the structure shown;

[0013] Figure 3 It is along Figure 2 a cross-sectional view taken along line 3-3;

[0014] Figure 4 It is from Figure 3 The structure is an enlarged view taken along line 4-4;

[0015] Figure 5 yes Figure 3 a side view of the structure shown;

[0016] Figure 6 is similar to Figure 4 Another enlarged cross-sectional view of the , but from a slightly different perspective;

[0017] Figure 7 yes Figure 1 an enlarged view of the illustrated structure, more clearly showing the first and second seals adapted to the inner spiral raceway of the shaft;

[0018] Figure 8 yes Figure 7 An enlarged isometric view of the structure shown from the opposite side, more clearly illustrating the grease sealing surface;

[0019] Figure 9 is a simplified cross-sectional view of a ball screw actuator without the wiper seal assembly installed;

[0020] Figure 10 is a simplified cross-sectional view of a similar ball screw actuator, now installed with an embodiment of the wiper seal assembly of the present invention;

[0021] Figure 11 is a theoretical cross-sectional view taken along the helical thread of the ball screw actuator for better understanding the first and second arcuate surfaces. DETAILED DESCRIPTION

[0022] Reference is now made to provisional application 63 / 481,568 Figure 1-8 . The inventive design is a ball screw seal that uses high durometer rubber to achieve environmental sealing, grease sealing, sealing against the outer diameter of the housing bore, and also features a rubber ice scraper with a Shore A hardness range of 75-90. The seal also includes a solid metal shell to assist in supporting the sealing of the housing bore. The rubber portion of the seal follows the helical design of the screw thread, with the ice scraper rotating a full circle (360°) around the thread and sealing against the main diameter of the thread in the axial direction (environmental side). In addition to the ice scraper, the design also features a mirrored double lip sealing portion, one side for sealing against the environment and the other side for sealing against grease. This portion of the seal seals along the minor diameter of the thread and features a cupped lip design with both sides gradually sloping away from the sealing surface. This allows the rubber lip to have a certain flexibility, thereby reducing the friction and drag caused by the sealing lip. The mirrored double lip only extends around approximately 20° of the circumference. By using rubber in this design, the seal can maintain flexibility to reduce friction while also accommodating larger tolerances within the hardware.

[0023] Figure 1 1 is a front view of the wiper seal of the present invention.

[0024] Figure 2 yes Figure 1 Isometric drawing of the structure shown.

[0025] Figure 3 yes Figure 1 Cross-sectional view of the structure shown.

[0026] Figure 4 It is from Figure 3 Enlarged image of the capture.

[0027] Figure 5 yes Figure 3Side view of the structure shown.

[0028] Figure 6 yes Figure 1 An enlarged view of the structure shown inside the housing.

[0029] Figure 7 It is from Figure 1 A magnified view of the section showing the scraper more clearly.

[0030] Figure 8 yes Figure 1 An enlarged isometric view of the structure shown, more clearly illustrating the grease seal and environmental seal.

[0031] like Figure 1-8 As shown, the elastic contact scraper is supported by a metal shell (i.e., a frame, a support member), as shown in FIG. Figure 3-6 Best shown. Rubber OD creates an OD grease seal. Cup-shaped scrapers remove ice along the ball screw threads. This invention is designed for minimal surface contact to achieve a low-drag seal.

[0032] The metal shell provides structural support to the wiper seal assembly. The metal can be made from a variety of metals known to those skilled in the art. Furthermore, the shell can be made from plastic, composite materials, metal, or any combination thereof. The shell can be bonded or attached to the elastomeric contact wiper, or the elastomeric contact wiper can be overmolded onto the shell.

[0033] The seal is designed with a spiral shape to seal on the outer diameter of the seal and along the screw threads through elastomeric contact. The seal will have a sealing lip on the minor diameter to seal against the environment and a mirrored sealing lip on the other side to seal out grease. The design will also have a wiper lip along the major diameter of the thread, which will remove ice in the axial direction.

[0034] The wiper seals approximately 360°, but the secondary seal, which seals along the minor path on the ambient and grease sides, only seals approximately 20° around the circumference.

[0035] This design differs from the prior art in that it uses elastomeric contacts to achieve sealing and wiping (at different locations) in the application, and to allow for flexibility in the seal.

[0036] This seal design allows for a degree of flexibility in the seal, allowing the design to adapt to the tolerances of the application for sealing and scraping. Another advantage is that by tapering the sealing lip away from the sealing point, it provides the benefits of an elastomeric contact seal with reduced contact, thereby reducing friction.

[0037] The wiper will be an elastomeric seal that seals against the crest (major diameter) of the screw threads and seals axially. As the screw rotates, the wiper will scrape ice from the major diameter as it rotates. There will also be a secondary seal / scraper component that acts radially against the root (minor diameter) of the screw threads. This will scrape ice and debris from the minor diameter of the seal as the screw rotates.

[0038] Compared to existing designs, this invention is designed to minimize surface contact, resulting in a low-resistance seal. The radially acting sealing lip at the thread root is designed to gradually move away from the sealing edge. This allows the seal to deform slightly, reducing friction and drag as the ball screw rotates.

[0039] Reference is now made to the drawings of the present application, which are very similar to the drawings of the '568 provisional application. Figure 1-8 An embodiment of the scraper seal assembly 20 of the present invention is shown. To help further understand the present invention, Figure 9-11 Additional views are shown. Figure 9 is a simplified cross-sectional view of a ball screw actuator without the wiper seal assembly installed. Figure 10 is a simplified cross-sectional view of a similar ball screw actuator, now installed with an embodiment of the wiper seal assembly of the present invention. Figure 11 is a theoretical cross-sectional view taken along the helical thread of the ball screw actuator for better understanding the first and second arcuate surfaces.

[0040] Come and see Figure 9 , a ball screw actuator 1 is configured to have a housing 2, with a shaft 3 disposed within the housing. The housing and the shaft are both disposed about a longitudinal axis 4. A plurality of balls 5 are movably housed within a ball screw thread 6. The ball screw thread has an outer helical raceway 7 separated by outer helical crests 8, the outer helical raceway and the outer helical crests being formed in an inner surface 9 of the housing. The ball screw thread also has an inner helical raceway 10 separated by inner helical crests 11, the inner helical raceway and the inner helical crests being formed in an outer surface 12 of the shaft. An annular channel 13 is formed in the housing, in which the wiper seal assembly of the present invention may be placed. Figure 10 The wiper seal assembly 20 of the present invention is shown installed in the annular channel 13 .

[0041] The wiper seal assembly includes an annular elastomeric sealing element 21 disposed about a longitudinal axis and configured to separate the grease side 14 from the ambient side 15. The wiper seal assembly also includes an annular inner support 22 disposed about the longitudinal axis and at least partially within the sealing element. The sealing element can be made of polytetrafluoroethylene (PTFE), unfilled PTFE, hybrid PTFE, glass-molybdenum-filled PTFE, polyetheretherketone (PEEK), and / or thermoplastic materials.

[0042] The sealing element includes a first arcuate surface 23 configured to be positioned within the inner spiral raceway of the shaft and facing the environment. A first arcuate lip 24 extends from the first arcuate surface toward the environment and is configured to contact the inner spiral raceway of the shaft. A first tapered back surface 25 extends from the first arcuate surface in a direction opposite to the first arcuate lip. The first tapered back surface is configured to gradually move away from the inner spiral raceway as it moves further away from the first arcuate surface.

[0043] The second curved surface 26 is configured to be positioned within the shaft's inner spiral raceway and face the grease side. A second curved lip 27 extends from the second curved surface toward the grease side and is configured to contact the shaft's inner spiral raceway. A second tapered back surface 28 extends from the second curved surface in a direction opposite to the second curved lip. The second tapered back surface is configured to gradually move away from the inner spiral raceway as it moves further away from the second curved surface. The first tapered back surface merges into and connects to the second tapered back surface.

[0044] The ice scraper seal 29 faces the ambient side and is configured to contact or be in proximity to the inner helical crest of the shaft for at least 360 degrees around the longitudinal axis. The first arcuate surface, the second arcuate surface, and the ice scraper seal are collectively configured to seal the ambient side from the grease side when the scraper seal assembly is installed in a ball screw actuator.

[0045] like Figure 11 As shown, the first arcuate surface 23 and the second arcuate surface 26 are disposed opposite each other with an angle 30 therebetween, which is approximately 20 degrees. In other embodiments, the angle 30 may be less than 45 degrees and less than 25 degrees.

[0046] The sealing element material is also disposed on the outer side surface 31 to form a thin layer 32. This thin layer 32 can subsequently form a seal with the inner surface 16 of the annular channel 13. Additionally, the inner support 22 can be L-shaped in cross section, having a first portion 33 perpendicular to a second portion 34. The L-shape of the inner support provides rigidity to the entire wiper seal assembly.

[0047] The sealing element 21 of the wiper seal assembly can also extend to the grease side end and the environment side end, such as Figure 4 Best shown.

[0048] The sealing element 21 of the wiper seal assembly may be overmolded onto the inner support 22 to form a good bond between the different materials. Alternatively, the sealing element 21 may be bonded or attached to the inner support.

[0049] Reference Signs List

[0050] 1 Ball screw actuator

[0051] 2 shell

[0052] 3-axis

[0053] 4 Longitudinal axis

[0054] 5+ ball bearings

[0055] 6 ball screw threads

[0056] 7 External spiral raceway

[0057] 8 external helical crest

[0058] 9Inner surface

[0059] 10 inner spiral raceway

[0060] 11 Internal helical crest

[0061] 12 External surface

[0062] 13 Ring Channel

[0063] 14 Grease side

[0064] 15 Environmental side

[0065] 16Inner surface, annular channel, shell

[0066] 20 Scrape seal assembly

[0067] 21 Sealing element

[0068] 22 internal supports

[0069] 23 first curved surface

[0070] 24 first curved lip

[0071] 25 The first cone back

[0072] 26 second curved surface

[0073] 27 Second curved lip

[0074] 28 Second cone back

[0075] 29 Ice scraper seals

[0076] 30 degrees

[0077] 31 outer surface, inner support

[0078] 32 thin layers, sealing elements

[0079] 33 Part 1, Internal Support

[0080] 34 Part 2, Internal Support

[0081] 35 Grease side end, sealing element

[0082] 36 Environmental side end, sealing element

Claims

1. A wiper seal assembly configured to seal a ball screw actuator, wherein: The ball screw actuator is configured to have a housing with a shaft disposed therein, the housing and the shaft being disposed about a longitudinal axis, and a plurality of balls being movably accommodated within a ball screw thread, the ball screw thread having an outer helical raceway separated by outer helical crests and an inner helical raceway separated by inner helical crests, the outer helical crests and the outer helical raceway being formed in an inner surface of the housing, the inner helical crests and the inner helical raceway being formed in an outer surface of the shaft, the scraper seal assembly comprising: an annular elastomeric sealing element disposed about the longitudinal axis and configured to separate a grease side from an ambient side; and an annular inner support member disposed about the longitudinal axis and at least partially within the sealing element; Wherein, the sealing element comprises: a first arcuate surface configured to be disposed in an inner spiral raceway of the shaft and facing the ambient side; a second arcuate surface configured to be disposed in the inner spiral raceway of the shaft and facing the grease side; an ice scraper seal facing the ambient side and configured to be in contact with or proximate to an inner helical crest of the shaft at least 360 degrees around the longitudinal axis; The first arcuate surface, the second arcuate surface and the ice scraper seal are configured to seal the environmental side from the grease side when the ice scraper seal assembly is installed in the ball screw actuator.

2. The wiper seal assembly according to claim 1, wherein: The sealing element has a Shore A hardness ranging from 75 to 90.

3. The wiper seal assembly according to claim 1, wherein: The sealing element is made of polytetrafluoroethylene (PTFE), unfilled polytetrafluoroethylene (PTFE), mixed polytetrafluoroethylene (PTFE), glass-molybdenum-filled polytetrafluoroethylene (PTFE), polyetheretherketone (PEEK) and / or thermoplastic material.

4. The wiper seal assembly according to claim 1, wherein: The inner support and the sealing element are not made of the same material.

5. The wiper seal assembly according to claim 1, wherein: The inner support is made of metal, plastic, composite material and / or combinations thereof.

6. The wiper seal assembly according to claim 1, wherein: The sealing element is an overmoulding surrounding the inner support.

7. The wiper seal assembly according to claim 1, wherein: The sealing element is bonded and / or adhered to the inner support.

8. The wiper seal assembly according to claim 1, wherein: The inner support is L-shaped in a cross-section taken along the longitudinal axis.

9. The wiper seal assembly according to claim 1, wherein: The wiper seal assembly includes a first arcuate lip extending from the first arcuate surface toward the ambient side, the first arcuate lip being configured to contact an inner spiral raceway of the shaft.

10. The wiper seal assembly according to claim 9, wherein: The scraper seal assembly includes a first tapered back surface extending from the first arcuate surface in a direction opposite to the first arcuate lip, wherein the first tapered back surface is configured to move away from the inner spiral raceway as it moves farther away from the first arcuate surface.

11. The wiper seal assembly according to claim 10, wherein: The wiper seal assembly includes a second arcuate lip extending from the second arcuate surface toward the grease side, the second arcuate lip being configured to contact an inner spiral raceway of the shaft.

12. The wiper seal assembly according to claim 11, wherein: The scraper seal assembly includes a second tapered back surface extending from the second arcuate surface in a direction opposite to the second arcuate lip, wherein the second tapered back surface is configured to move away from the inner spiral raceway as it moves farther away from the second arcuate surface.

13. The wiper seal assembly according to claim 12, wherein: The first tapered rear surface is connected to the second tapered rear surface.

14. The wiper seal assembly according to claim 13, wherein: The first arcuate surface and the second arcuate surface are spaced apart at an angle of less than 45 degrees about the longitudinal axis.

15. The wiper seal assembly according to claim 13, wherein: The first arcuate surface and the second arcuate surface are spaced apart by an angle less than 25 degrees about the longitudinal axis.

16. The wiper seal assembly according to claim 13, wherein: The first arcuate surface and the second arcuate surface are spaced apart at an angle of 20 degrees around the longitudinal axis.

17. The wiper seal assembly of claim 1, wherein: The wiper seal assembly includes a sealing element layer disposed on an outer side surface of the inner support.

18. A wiper seal assembly configured to seal a ball screw actuator, wherein: The ball screw actuator is configured to have a housing with a shaft disposed therein, the housing and the shaft being disposed about a longitudinal axis, and a plurality of balls being movably accommodated within a ball screw thread, the ball screw thread having an outer helical raceway separated by outer helical crests and an inner helical raceway separated by inner helical crests, the outer helical crests and the outer helical raceway being formed in an inner surface of the housing, the inner helical crests and the inner helical raceway being formed in an outer surface of the shaft, the scraper seal assembly comprising: an annular elastomeric sealing element disposed about the longitudinal axis and configured to separate a grease side from an ambient side; and an annular inner support member disposed about the longitudinal axis and at least partially within the sealing element; Wherein, the sealing element comprises: a first arcuate surface configured to be disposed in the inner spiral raceway of the shaft and facing the ambient side; a first arcuate lip extending from the first arcuate surface toward the ambient side and configured to be contactable with the inner spiral raceway of the shaft; a first tapered back surface extending from the first arcuate surface in a direction opposite to the first arcuate lip, the first tapered back surface being configured to move away from the inner spiral raceway as it moves farther away from the first arcuate surface; a second arcuate surface configured to be disposed in the inner spiral raceway of the shaft and facing the grease side; a second arcuate lip extending from the second arcuate surface toward the grease side and configured to be contactable with the inner spiral raceway of the shaft; a second tapered back surface extending from the second arcuate surface in a direction opposite to the second arcuate lip, the second tapered back surface being configured to move away from the inner spiral raceway as it moves farther away from the second arcuate surface; wherein the first tapered back surface is connected to the second tapered back surface; and an ice scraper seal facing the ambient side and configured to be in contact with or proximate to an inner helical crest of the shaft at least 360 degrees around the longitudinal axis; The first arcuate surface, the second arcuate surface and the ice scraper seal are configured to seal the environmental side from the grease side when the ice scraper seal assembly is installed in the ball screw actuator.

Images