Actuator with compression seal

Abstract

An actuator includes a housing having an inner surface, a proximal end, and a distal end. A gas generator is coupled to the proximal end of the housing. The actuator also includes a piston rod slidably engaged with the inner surface of the housing, the piston rod having a proximal end and a distal end opposite the proximal end. A piston head is coupled to the proximal end of the piston rod and a seal is disposed between the piston rod and the piston head. The piston head is movable relative to the piston rod from a first position prior to deployment of the gas generator to a second position after deployment of the gas generator, wherein movement of the piston head from the first position to the second position compresses the seal.

Description

ACTUATOR WITH COMPRESSION SEALCross Reference To Related Applications

[0001] This application claims the benefit of U.S. Provisional Patent Application No.63 / 701.091 filed September 30, 2024, the entire contents of which are incorporated herein by reference.Technical Field

[0002] The present disclosure relates to safety devices for passenger vehicles. In particular, the disclosure relates to an actuator with a compression seal. Passenger vehicles may include, for example, automobiles, boats, trains, aircrafts, and spacecrafts.Background

[0003] Actuators in vehicles are capable of moving vehicle components and therefore have many potential uses, including for safety. In one example, an actuator can be used to lift a portion of a hood of an automobile (e.g., a rear portion of the hood proximate the windshield) in a situation during which the vehicle collides with a pedestrian. When actuated, the actuator raises the hood portion from its normal rest position to an elevated position to increase the space between the hood and rigid structures beneath the hood(e.g., an engine). When a pedestrian impacts the elevated hood, the extra space helps to"cushion" the pedestrian, lowering the likelihood of injury from impacting the rigid structures beneath the hood.

[0004] To ensure optimum performance of the actuator, a reliable seal needs to be maintained between the internal components of the actuator. If a seal is not properly maintained, the actuator may leak pressurized gases and be unable to fully perform the required function, such as lifting the hood of the vehicle, as noted above. For example, if too much pressurized gas leaks from the actuator during deployment, the actuator may not be able to raise the hood to an appropriate level for optimum cushioning during apedestrian impact. Therefore, there is a continuing need for improving the sealing of actuators white minimizing the number of components to encourage increased adoption by vehicle manufacturers.Summary

[0005] In some implementations, an actuator comprises a housing comprising an inner surface, a proximal end, and a distal end. A gas generator is coupled to the proximal end of the housing and a piston rod is slidably engaged with the inner surface of the housing. The piston rod comprises a proximal end and a distal end and a piston head is movably coupled to the proximal end of the piston rod. A seal is disposed between the piston rod and the piston head. The piston head is movable relative to the piston rod from a first position prior to deployment of the gas generator to a second position after deployment of the gas generator and movement of the piston head from the first position to the second position compresses the seal.

[0006] In some implementations, the housing further comprises a central axis extending from the proximal end to the distal end, wherein the piston head moves from the first position to the second position along the central axis. In some implementations, the seal is compressed in a direction parallel to the central axis. In some implementations, the proximal end of the piston rod defines a proximal end wall extending at least partially radially outwardly away from the central axis. In some implementations, the piston head defines a shoulder extending at least partially radially outwardly away from the central axis.In some implementations, the seal is compressed between the proximal end wall of the piston rod and the shoulder of the piston head as the piston head moves from the first position to the second position.

[0007] In some implementations, the piston rod defines a blind hole extending from the proximal end towards the distal end and along the central axis. In some implementations, the piston head defines an extension, wherein the extension extends into the blind hole ofthe piston rod when the piston head is in the first position and the second position. In some implementations, the piston rod defines at least one pressure relief hole extending radially outwardly from the central axis from the blind hole to an inner volume of the housing to enable fluid communication between the blind hole and the inner volume of the housing.

[0008] In other implementations, the piston rod comprises a hollow tube. In some implementations, the piston head defines an extension, wherein the extension extends into the hollow tube when the piston head is in the first position and the second position.

[0009] In some implementations, the piston head comprises a body portion and defines an extension extending away from the body portion. In some implementations, the piston head further comprises a transition portion extending between the body portion and the extension and comprising a curved surface.

[0010] In other implementations, the piston head further comprises a transition portion extending between the body portion and the extension and comprising a linear surface. In some implementations, the piston rod comprises a linear surface which contacts the linear surface of the piston head when the piston head is in the second position. In some implementations, the contact between the linear surface of the piston head and the linear surface of the piston rod creates an interference fit that prevents the piston head from moving from the second position to the first position.

[0011] In some implementations, the piston head is comprised of a material having a melting temperature in the range of 120-200 degrees Celsius. In some implementations, the piston head is formed from plastic.

[0012] In other implementations, the piston head is formed from metal.

[0013] In some implementations, the seal comprises an elastic material.Brief Description of the Drawings

[0014] The drawings are merely exemplary to illustrate steps, structure, and certain features that can be used singularly or in combination with other features. The disclosureshould not be limited to the implementations shown. Similar reference numerals (e.g., 101,201, etc.) represent similar steps, structures, and features throughout the implementations shown.

[0015] FIG. 1 is a side view of an actuator in a retracted position.

[0016] FIG. 2 is a side view of the actuator of FIG. 1 in an extended position.

[0017] FIG. 3 is a cross-sectional view of the actuator of FIG. 1 as taken along the plane A-A.

[0018] FIG. 4 is a side view of a piston head of FIG. 3.

[0019] FIG. 5 is a perspective view of the piston head of FIG. 4.

[0020] FIG. 6 is a perspective view of the piston head of FIG. 5 with a seal.

[0021] FIG. 7 is a perspective view of the seal of FIG. 6.

[0022] FIG. 8 is a zoomed-in cross-sectional view of a portion of the actuator of FIG. 3 with the piston head in a first position.

[0023] FIG. 9 is a zoomed-in cross -sectional view of a portion of the actuator of FIG. 3 with the piston head in a second position.

[0024] FIG. 10 is a perspective view of a portion of a piston rod of FIG. 3.

[0025] FIG. 11 is another perspective view of the piston rod of FIG. 10.

[0026] FIG. 12 is a side view of a second implementation of a piston head for use with the actuator of FIG. 1.

[0027] FIG. 13 is a perspective view of the piston head of FIG. 12.

[0028] FIG. 14 is a perspective view of the piston head of FIG. 13 with a seal.

[0029] FIG. 15 is a zoomed-in cross- sectional view of a portion of the actuator of FIG. 3 with the piston head of FIG. 12 in a first position.

[0030] FIG. 16 is a zoomed-in cross-sectional view of a portion of the actuator of FIG. 3 with the piston head of FIG. 12 in a second position.

[0031] FIG. 17 is a perspective view of a portion of a second implementation of a piston rod for use with the piston head of FIG. 12.

[0032] FIG. 18 is another perspective view' of the piston rod of FIG. 17.Detailed Description

[0033] The devices, systems, and methods disclosed herein provide for an actuator having a movable piston head with a compression seal. The actuator can be included in a hood lifting mechanism for lifting the hood of a vehicle, for example. The actuator includes a housing and a piston rod slidably engaged with an inner surface of the housing, wherein the piston rod comprises a proximal end and a distal end. A piston head is coupled to the proximal end of the piston rod and a seal is disposed between the piston rod and the piston head. The piston head is movable relative to the piston rod, whereby movement of the piston head from a first position to a second position compresses the seal. As used herein, the verb"seal" (and correlative nouns, adjectives, etc.) means to limit, including fully prevent, fluid communication between two or more locations, structures, surfaces, components, etc., as well as to limit, including fully prevent, the movement of solid material (e.g., dirt or dust) between two or more locations, structures, surfaces, components, etc.

[0034] Referring to FIGS. 1-11, an actuator 100 comprises a housing 101 comprising a proximal end 102, a distal end 103, and a wall 106 extending from the proximal end 102 to the distal end 103. The wall 106 comprises an inner surface 107 and an outer surface 108.The housing 101 further comprises a central axis 109 extending from the proximal end 102 to the distal end 103. The distal end 103 defines a distal end wall 104 extending at least partially radially inward toward the central axis 109. An opening 105 is defined by the distal end wall 104 and is configured for allowing a piston rod 117 to extend from the housing 101, as described below. An inner volume 110 is defined within the housing 101, bounded by the inner surface 107, the proximal end 102, and the distal end 103. In some implementations,the housing 101 may be formed from metal, such as stainless steel, and may be formed by a deep drawing process.

[0035] The piston rod 117 comprises a proximal end 118 and a distal end 120 opposite the proximal end 118. The proximal end 118 of the piston rod 117 defines a proximal end wail119 extending at least partially radially outwardly away from the central axis 109. In a retracted position, for example as shown in FIGS. 1 and 3, the distal end 120 of the piston rod 117 is adjacent the distal end 103 of the housing 101 and the piston rod 117 is substantially disposed within the inner volume 110 of the housing 101. In an extended position, as shown in FIG. 2, the proximal end 118 of the piston rod 117 is adjacent the distal end 103 of the housing 101 and the piston rod 117 is substantially disposed outside the inner volume 110 of the housing 101. The piston rod 117 may take the form of a hollow' tube defining an inner volume 122, as shown in FIG. 3. In other implementations, the piston rod may take the form of a mostly solid rod, as further described below. In some implementations, the piston rod 117 may be formed from metal, such as stainless steel, and be formed by a deep drawing process.

[0036] A piston head 123 is movably coupled to the proximal end 118 of the piston rod 117.The piston head 123 comprises a body portion 125 and defines an extension 124 extending away from the body portion. The extension 124 of the piston head 123 extends into the inner volume 122 of the piston rod 117. The extension 124 is sized such that the fit is tight enough to keep the piston head 123 from dislodging from the piston rod 117, but not so tight as to prevent movement of the piston head 123 relative to the piston rod 117. The piston head 123 further defines a shoulder 128 extending at least partially radially outwardly away from the central axis 109. A transition portion 126, extending between the extension 124 and the body portion 125, comprises a curved surface 127. A pressure surface 129 faces a gas generator 112.

[0037] In some implementations, the piston head 123 may be formed from metal or plastic, by way of nonlimiting example, depending on the requirements of the practical application. and may be formed by machining or 3D-printing, for example. In some use cases, it may be advantageous for the piston head 123 to decompose and open a venting path for pressurized gases to leave the actuator 100 through the opening 105 of the housing 101.This can be particularly useful during transportation of large quantities of actuators 100 prior to their finai assembly into vehicles. In the event of a fire, the actuators 100 may deploy safely and prevent injury to bystanders and first responders.

[0038] The actuator 100 must be able to operate normally and not automatically deploy under temperature conditions normal to a vehicle, for example up to 120 degrees Celsius when installed as a hood lifter in an automobile (i.e., under the hood and near the engine).In some implementations, the piston head 123 must be able to withstand these temperatures but also decompose before the gas generator 112 will deploy in a fire, for example in the range of 160-200 degrees Celsius. Therefore, the piston head 123 may be comprised of a material (e.g., plastic) having a melting temperature in the range of 120-200 degrees Celsius, and more preferable in the range of 120-160 degrees Celsius.

[0039] A seal 130 is disposed around the body portion 125 and between the shoulder 128 of the piston head 123 and the proximal end wall 119 of the piston rod 117. The seal 130 may comprise an elastic material, such as a rubber. The seal 130 may take several forms, including an o-ring toroid as known in the art having, for example, a circular cross-section or, as shown throughout the FIGURES, a rectangular shaped cross-section (the cross section taken through a plane parallel to the axis of revolution of the toroid). The compression ratio of the seal 130 may be selected such that, when the piston head 123 is coupled to the piston rod 117 with the seal 130 disposed therebetween, a space 131 is maintained between the piston head 123 and the piston rod 117. Specifically, the space 131 is maintained between the curved surface 127 of the piston head 123 and a corresponding curved surface 121 of the piston rod 117.

[0040] To deploy the actuator 100 and therefore move the piston rod 117 from the retracted position to the extended position, the gas generator 112 is coupled to the proximal end 102 of the housing 101. The gas generator 112 may be coupled to a vehicle electronic control unit (ECU, not shown) via a lead wire 113 to form an electrical connection between the gas generator 112 and the ECU. In some implementations, the gas generator112 may be a pyrotechnic gas generator, such as an initiator or micro gas generator, both well known in the art. In other implementations, the gas generator may comprise a source of stored, pressurized gas that is released upon actuation.

[0041] When the ECU sends an actuation signal to the gas generator 112, the gas generator112 introduces high-pressure gas into a pressure volume 111 that pushes against the pressure surface 129 of the piston head 123 as represented by FIG. 9. Before the piston rod117 moves from the retracted position to the extended position, the piston head 123 will move from a first position prior to deployment of the gas generator 112, as shown in FIG. 8, to a second position after deployment of the gas generator 112, as shown in FIG. 9, along the central axis 109. When the piston head 123 is in the second position, the space 131 is either reduced in volume or eliminated entirely by contact between the curved surface 127 of the piston head 123 and the curved surface 121 of the piston rod 117.

[0042] As the piston head 123 moves from the first position to the second position, it compresses the seal 130, in a direction parallel to the central axis 109, between the shoulder 128 of the piston head 123 and the proximal end wall 119 of the piston rod 117.This compression toward the proximal end wall 119, as represented in FIG. 9, will cause the seal 130 to expand radially both inwardly toward and outwardly away from the central axis109, increasing its compression ratio and thereby improving the seal between the body portion 125 of the piston head 123 and the inner surface 107 of the housing 101. As shown in FIG. 9, the shoulder 128 may be sized such that a gap is maintained between the shoulder128 and the inner surface 107 of the housing 101. Therefore, the pressurized gas from the gas generator 112 may also directly impinge on the seal 130 causing even greater compression toward the proximal end wall 119 of the piston rod 117.

[0043] The extension 124 of the piston head 123 extends into the piston rod 117 (i.e., inner volume 122 / hollow tube) when the piston head 123 is in the first position and the second position. As a result of the interaction between the piston head 123, the piston rod 117, the seal 130, and the inner surface 107 of the housing 101, the piston rod 117 is reliably kept centered along the central axis 109 such that it will deploy through the opening 105 in the distal end wall 104 of the housing 101 without issue. Additionally, a small space (or alternatively minimal contact) may be maintained between the inner surface 107 of the housing 101 and the proximal end wall 119 of the piston rod 117 to ensure that piston rod117 may slide easily in and out of the housing 101. This allows the piston rod 117 to be slidably engaged with the inner surface 107 of the housing 101 with minimal friction and resistance.

[0044] To mount the actuator 100 to a vehicle, a mounting bracket may be used. For example, a first bracket 115 and a second bracket 116 may be coupled to the distal end 103 of the housing 101. The first bracket 115 and the second bracket 116 may define holes for extending fasteners, such as screws or rivets, through the first bracket 115 and the second bracket 116 and into a corresponding vehicle hole. The first bracket 115 and the second bracket 116 may be coupled to the actuator 100 via a weld, an adhesive, an interference fit, or any other suitable method. An environmental cap 114 may also be coupled to the second bracket 116 to provide a seal between the outside environment and the inner volume 110 of the housing 101. As the piston rod 117 moves from the retracted position to the extended position, it may break through the environmental cap 114 or dislodge the environmental cap 114 from the second bracket 116.

[0045] Referring now to FIGS. 12-18, a second implementation of a piston head 223 is movably coupled to a piston rod 217. An extension 224 of the piston rod 217 extends into an inner volume 222 of the piston rod 217. The extension 124 is sized such that the fit is tight enough to keep the piston head 223 from dislodging from the piston rod 217, but not so tight as to prevent movement of the piston head 223 relative to the piston rod 217. The piston head 223 comprises a body portion 225 and defines a shoulder 228 extending at least partially radially outwardly away from the central axis 109. A transition portion 226, extending between the extension 224 and the body portion 225, comprises a linear surface227. A pressure surface 229 faces the gas generator 112.

[0046] The piston rod 217 comprises a distal end 220 and a proximal end 218 that defines a proximal end wall 219 extending at least partially radially outwardly away from the central axis 109. The piston rod 217 may take the form of a mostly solid tube defining an inner volume 222, as shown in FIGS. 15-17. For example, the inner volume 222 may be sized depending on required characteristics, such as weight and cost, such that the piston rod 217 defines a blind hole extending from the proximal end 218 toward the distal end 220 and along the central axis 109, provided there is enough room for the extension 224 of the piston head 223 to be inserted.

[0047] To ensure the piston head 223 can move relative to the piston rod 217 from the first position to the second position, the piston rod 217 defines at least one pressure relief hole232 extending radially outwardly from the central axis 109 from the inner volume 222 (i.e., blind hole) of the piston rod 217 to the inner volume 110 of the housing 101 to enable fluid communication between the inner volume 222 and the inner volume 110. This ensures there is no back-force caused by pressurizing any gas present in the inner volume 222 as the piston head 223 moves from the first position to the second position.

[0048] The seal 130 is disposed around the body portion 225 and between the shoulder 228 of the piston head 223 and the proximal end wall 219 of the piston rod 217. The compression ratio of the seal 130 may be selected such that, when the piston head 223 is coupled to the piston rod 217 with the seal 130 disposed therebetween, a space 231 is maintained between the piston head 223 and the piston rod 217. Specifically, the space 231 is maintained between the linear surface 227 of the piston head 223 and a corresponding linear surface 221 of the piston rod 217.

[0049] When the ECU sends an actuation signal to the gas generator 112, the gas generator112 introduces high -pressure gas into the pressure volume 111 that pushes against the pressure surface 229 of the piston head 223 as represented by FIG. 16. Before the piston rod 217 moves from the retracted position to the extended position, the piston head 223 will move from the first position prior to deployment of the gas generator 112, as shown inFIG. 15, to the second position after deployment of the gas generator 112, as shown in FIG.16, along the central axis 109. When the piston head 223 is in the second position, the space 231 is eliminated entirely by contact between the linear surface 227 of the piston head 223 and the linear surface 221 of the piston rod 217. This contact between linear surfaces produces a locking effect (i.e., interference fit) which prevents the piston head 223 from moving from the second position to the first position.

[0050] As the piston head 223 moves from the first position to the second position, it compresses the seal 130, in a direction parallel to the central axis 109, between the shoulder 228 of the piston head 223 and the proximal end wall 219 of the piston rod 217.This compression toward the proximal end wall 219, as represented in FIG. 16, will cause the seal 130 to expand radially both inwardly toward and outwardly away from the central axis109, increasing its compression ratio and thereby improving the seal between the body portion 225 of the piston head 223 and the inner surface 107 of the housing 101. As shownin FIG. 16, the shoulder 228 may be sized such that a gap is maintained between the shoulder 228 and the inner surface 107 of the housing 101. Therefore, the pressurized gas from the gas generator 112 may also directly impinge on the seal 130 causing even greater compression toward the proximal end wall 219.

[0051] The extension 224 of the piston head 223 extends into the piston rod 217 (i.e., inner volume 222 / blind hole) when the piston head 223 is in the first position and the second position. As a result of the interaction between the piston head 223, the piston rod 217, the seal 130, and the inner surface 107 of the housing 101, the piston rad 217 is reliably kept centered along the central axis 109 such that it will deploy through the opening 105 in the distal end wall 104 of the housing 101 without issue. Additionally, a small space (or alternatively minimal contact) may be maintained between the inner surface 107 of the housing 101 and the proximal end wall 219 of the piston rod 217 to ensure that piston rod217 may slide easily in and out of the housing 101. This allows the piston rod 217 to be slidably engaged with the inner surface 107 of the housing 101 with minimal friction and resistance.

[0052] The description in the present disclosure has been presented for purposes of illustration but is not intended to be exhaustive or limited to the implementations disclosed.It will be understood that various modifications and variations will be apparent to those of ordinary skill in the art and may be made without departing from the spirit and scope of the following claims. Accordingly, other implementations are within the scope of the claims.The implementations described were chosen in order to best explain the principles of the actuator and its practical application, and to enable others of ordinary skill in the art to understand the assembly for various implementations with various modifications as are suited to the particular use contemplated.

[0053] The terms "coupled," "connected," and the like as used herein to mean the joining of two members directly or indirectly to one another. Such joining may be stationary (e.g., permanent) or moveable (e.g., removable or releasable). Such joining may be achieved with the two members or the two members and any additional intermediate members being integrally formed as a single unitary body with one another or with the two members or the two members and any additional intermediate members being attached to one another.

[0054] The terminology used herein is for the purpose of describing particular implementations only and is not intended to be limiting of the disclosure. As used herein, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context dearly indicates otherwise. It will be further understood that the terms"comprises" and / or "comprising," when used in this specification, specify the presence of stated features, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, operations, elements, components, and / or groups thereof.

Claims

CLAIMSWhat is claimed is:

1. An actuator comprising: a housing comprising an inner surface, a proximal end, and a distal end; a gas generator coupled to the proximal end of the housing; a piston rod slidably engaged with the inner surface of the housing, the piston rod comprising a proximal end and a distal end; a piston head movably coupled to the proximal end of the piston rod; and a seal disposed between the piston rod and the piston head; wherein the piston head is movable relative to the piston rod from a first position prior to deployment of the gas generator to a second position after deployment of the gas generator, and wherein movement of the piston head from the first position to the second position compresses the seal.

2. The actuator of claim 1. wherein the housing further comprises a central axis extending from the proximal end to the distal end, and wherein the piston head moves from the first position to the second position along the central axis.

3. The actuator of claim 2, wherein the seal is compressed in a direction parallel to the central axis.

4. The actuator of claim 2, wherein the proximal end of the piston rod defines a proximal end wall extending at least partially radially outwardly away from the central axis.

5. The actuator of claim 4. wherein the piston head defines a shoulder extending at least partially radially outwardly away from the central axis.

6. The actuator of claim 5, wherein the seal is compressed between the proximal end wall of the piston rod and the shoulder of the piston head as the piston head moves from the first position to the second position.

7. The actuator of claim 2, wherein the piston rod defines a blind hole extending from the proximal end towards the distal end and along the central axis.

8. The actuator of ciaim 7, wherein the piston head defines an extension, and wherein the extension extends into the biind hoie of the piston rod when the piston head is in the first position and the second position.

9. The actuator of ciaim 8, wherein the piston rod defines at least one pressure relief hoie extending radiaiiy outwardly from the central axis from the blind hole to an inner volume of the housing to enable fluid communication between the blind hole and the inner volume of the housing.

10. The actuator of claim 9, wherein the piston rod comprises a hollow tube.

11. The actuator of claim 10, wherein the piston head defines an extension, and wherein the extension extends into the hollow tube when the piston head is in the first position and the second position.

12. The actuator of claim 1, wherein the piston head comprises a body portion and defines an extension extending away from the body portion.

13. The actuator of claim 12, wherein the piston head further comprises a transition portion extending between the body portion and the extension and comprising a curved surface.

14. The actuator of claim 12, wherein the piston head further comprises a transition portion extending between the body portion and the extension and comprising a linear surface.

15. The actuator of claim 14, wherein the piston rod comprises a linear surface which contacts the linear surface of the piston head when the piston head is in the second position.

16. The actuator of claim 14, wherein contact between the linear surface of the piston head and the linear surface of the piston rod creates an interference fit that prevents the piston head from moving from the second position to the first position.

17. The actuator of claim 1, wherein the piston head is comprised of a material having a melting temperature in a range of 120-200 degrees Celsius.

18. The actuator of ciaim 17;wherein the piston head is formed from plastic.

19. The actuator of claim 1. wherein the piston head is formed from metal.

20. The actuator of claim 1. wherein the seal comprises an elastic material.

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