Patent Application
20130305915
The invention generally relates to a gas strut assembly, and more specifically to an internal detent module for increasing a hold-open force of the gas strut assembly.
Gas strut assemblies include a housing that defines an interior space, with a rod moveably disposed within the interior space. The rod is slideably moveable along a central axis between a retracted position, i.e., a shortened position, and an extended position, i.e., a lengthened position. A piston is disposed at an axial end of the rod within the interior space of the housing. The housing includes a closed end, and includes a volume of gas, such as but not limited to air, trapped within the interior space of the housing, between the piston and the closed end of the housing. Movement of the rod from the extended position into the retracted position compresses the air between the closed end of the housing and the piston, thereby generating a resulting axial force urging the piston and the rod back into the extended position. As such, the rod is continuously biased toward the extended position.
Because the gas strut assemblies are biased toward the extended position, the gas strut assemblies are often utilized to provide an opening force and/or to provide a hold-open force to door, trunk lid, hood, etc. However, the gas strut assemblies rely on the compressed gas to provide the axial force urging the piston and the rod into the extended position. Changing ambient temperatures change the temperature of the gas, which changes the density of the gas. For example, when the temperature decreases, the density of gas also decreases, which lowers the resulting axial force that urges the rod into the extended position.
A gas strut assembly is provided. The gas strut assembly includes a housing having a wall that extends along a central axis. The wall defines an interior space. A rod is coupled to the housing. The rod is slideably moveable within the interior space along the central axis between an extended position and a retracted position. A flexible member is secured in position relative to the housing. A rigid member is coupled to and moveable with the rod. The flexible member includes at least one displaceable portion that moves radially away from the central axis in response to a first radial force component of an opening force when engaged by the rigid member moving from the retracted position into the extended position. The displaceable portion moves radially away from the central axis in response to a second radial force component of a closing force when engaged by the rigid member moving from the extended position into the retracted position. The second radial force component is greater than the first radial force component.
Accordingly, the interaction between the rigid member and the flexible member resists movement of the rod along the central axis. In order to move the rod from the extended position into the retracted position, the interaction between the flexible member and the rigid member must generate the second radial force component from the closing force. The second radial force component must be sufficient to move the displaceable portion away from the rigid member to allow the rigid member to pass thereby and continue into the refracted position. As such, the mechanical interaction between the rigid member and the flexible member increases the force required to move the rod out of the extended position and into the retracted position, thereby increasing the hold-open force of the gas strut assembly.
In order to move the rod from the retracted position into the extended position, the interaction between the flexible member and the rigid member must generate the first radial force component from the opening force. The first radial force component must be sufficient to move the displaceable portion away from the rigid member to allow the rigid member to pass thereby and continue into the extended position. As such, the mechanical interaction between the rigid member and the flexible member increases the force required to move the rod into the extended position. The interaction between the flexible member and the rigid member is designed so that the first radial force component is significantly less than the second radial force component so that the axial opening force generated from the compressed gas within the housing is able to generate the first radial force component and move the rod into the extended position.
The above features and advantages and other features and advantages of the present invention are readily apparent from the following detailed description of the best modes for carrying out the invention when taken in connection with the accompanying drawings.
Those having ordinary skill in the art will recognize that terms such as “above,” “below,” “upward,” “downward,” “top,” “bottom,” etc., are used descriptively for the figures, and do not represent limitations on the scope of the invention, as defined by the appended claims.
Referring to the Figures, wherein like numerals indicate like parts throughout the several views, a gas strut assembly is generally shown at 20. Referring to
The housing 22 includes a first open end 30 and a second closed end 32. A rod 34 is coupled to the housing 22, and extends through the open end of the housing 22. The rod 34 extends along the central axis 26, and is concentric with the housing 22 about the central axis 26. The rod 34 is slideably moveable within the interior space 28 of the housing 22 along the central axis 26. The rod 34 moves between a retracted or shortened position, shown in
A sealing pack 36 is attached to the housing 22, adjacent the first open end 30 of the housing 22. The sealing pack 36 seals between the rod 34 and the housing 22 to trap gas, such as but not limited to air, within the interior space 28 of the housing 22. The sealing pack 36 slideably supports the rod 34 relative to the housing 22.
The first open end 30 of the housing 22 is flared radially inward toward the central axis 26. The housing 22 includes a first rim 38 that extends radially inward toward the central axis 26. The first rim 38 is spaced from the flared open end of the housing 22 an axial distance 40 along the central axis 26 equal to a length 42 of the sealing pack 36 measured along the central axis 26. The sealing pack 36 is disposed between the first rim 38 and the flared open end of the housing 22, and is secured in position relative to the housing 22 by the flared first open end 30 of the housing 22 and the first rim 38.
The housing 22 further includes a second rim 44 spaced along the central axis 26 from the first rim 38. A flexible member 46 of an internal detent module 48 (described in greater detail below) is disposed between the sealing pack 36 and the second rim 44. As such, the flexible member 46 of the internal detent module 48 is secured in position relative to the housing 22 by the sealing pack 36 and the second rim 44.
The internal detent module 48 interconnects the housing 22 and the rod 34 when the rod 34 is disposed in the extended position to increase a closing force of the gas strut assembly 20. The closing force is the force required to move the rod 34 from the extended position into the retracted position. Accordingly, the internal detent module 48 increase the force required to move the rod 34 from the extended position into the retracted position.
Referring also to
The flexible member 46 includes an annular base 54 defining a central aperture 56. The rod 34 extends through the central aperture 56 of the annular base 54. The outer periphery of the annular base 54 extends radially outward into abutting engagement with an interior surface 58 of the exterior wall 24 of the housing 22. The displaceable portion 52 extends axially along the central axis 26 from the annular base 54, with the displaceable portion 52 disposed between the annular base 54 and the sealing pack 36. The displaceable portion 52 includes a first leg portion 60 extending substantially along the central axis 26, a wall portion 62 extending from the first leg portion 60 and substantially away from the central axis 26, and a second leg portion 66 extending from the wall portion 62 and substantially along the central axis 26.
The rigid member 50 includes a body 68 that defines a central bore 70. The body 68 is disposed about and concentric with the rod 34 such that the rod 34 passes through the central bore 70. As shown, the rod 34 includes a ridge 72 that engages the body 68 of the rigid member 50 and prevents the rigid member 50 from moving axially along the rod 34 in a first axial direction 74 beyond the ridge 72. A clip 76 is coupled to a recess 78 in the rod 34 to prevent movement of the rigid member 50 relative to the rod 34 in a second axial direction 80, i.e., opposite the first axial direction 74. As such, the rigid member 50 is secured in place on the rod 34 between the ridge 72 and the clip 76. The internal detent module 48 may further include a first washer 82 and a second washer 84 disposed at opposite axial ends of the rigid member 50. The body 68 includes detent 86, which extends radially away from the body 68 and the central axis 26. The detent 86 is disposed at an axial end of the body 68 facing the first open end 30 of the housing 22. As shown, the detent 86 includes an annular ring that extends away from the body 68 of the rigid member 50, and completely encircles the rod 34. However, it should be appreciated that the detent 86 need not completely encircle the rod 34, and that the detent 86 may include multiple detents, with each of the detents spaced about the body 68 of the rigid member 50.
The detent 86 includes a first cam surface 88 and a second cam surface 90. As shown, the first cam surface 88 and the second cam surface 90 are defined by rounded or chamfered axial edges of the detent 86. The first cam surface 88 is defined by an axial edge of the detent 86 facing the first open end 30 of the housing 22. The second cam surface 90 is defined by an axial edge of the detent 86 facing the second closed end 32 of the housing 22.
Referring to
The first leg portion 60 of the displaceable portion 52 includes a radially inner surface 94 that contacts and/or engages the first cam surface 88 of the detent 86. The radial inner surface 94 of the first leg portion 60 is angled relative to the central axis 26. The first cam surface 88 engages the radial inner surface 94 of the first leg portion 60 to define a first engagement angle 96 there between. When the opening force FO is applied to the rod 34, the engagement or interaction between the first cam surface 88 and the radial inner surface 94 of the first leg portion 60 at the first engagement angle 96 relative to the central axis 26 generates a first axial force component FA1 and the first radial force component FR1. The first axial force component FA1 is directed along or parallel with the central axis 26, and the first radial force component FR1 is directed perpendicularly away from the central axis 26, and against the displaceable portion 52. The degree of angle of the first engagement angle 96 relative to the central axis 26 determines how much of the opening force FO is directed into the first axial force component FA1 and the first radial force component FR1 respectively. A greater value of the first engagement angle 96 directs more of the opening force FO into the first axial force component FA1 than a lesser value of the first engagement angle 96, thereby decreasing the first radial force component FR1 and requiring a greater opening force FO to move the displaceable portion 52 radially away from the detent 86 and allow the rigid member 50 to move into the extended position. The radial inner surface 94 of the first leg portion 60 is preferably oriented relative to the central axis 26 so that the first engagement angle 96 includes a smaller or lesser value so as not to greatly increase the required opening force FO. For example, the first engagement angle 96 may vary between the range of 0° and 45°. However, it should be appreciated that the first engagement angle 96 may differ from the values described herein, and may be defined based upon the particular uses of the gas strut assembly 20.
Referring to
The wall portion 62 of the displaceable portion 52 extends from an axial end of the first leg portion 60 and radially away from the central axis 26. The wall portion 62 includes an axial end surface 98 that engages and/or contacts the second cam surface 90 of the detent 86. The axial end surface 98 of the wall portion 62 is angled relative to the central axis 26. The second cam surface 90 engages the axial end surface 98 of the wall portion 62 to define a second engagement angle 100 there between relative to the central axis 26. When the closing force FC is applied to the rod 34, the engagement between the second cam surface 90 and the axial end surface 98 of the wall portion 62 at the second engagement angle 100 relative to the central axis 26 generates a second axial force component FA2 and the second radial force component FR2. The second axial force component FA2 is directed along or parallel with the central axis 26, and the second radial force component FR2 is directed perpendicularly away from the central axis 26, and against the displaceable portion 52. The degree of angle of the second engagement angle 100 relative to the central axis 26 determines how much of the closing force FC is directed into the second axial force component FA2 and the second radial force component FR2 respectively. A greater value of the second engagement angle 100 directs more of the closing force FC into the second radial force component FR2 than a lesser value of the second engagement angle 100, thereby requiring a greater closing force FC to move the displaceable portion 52 radially away from the detent 86 and allow the rigid member to move into the retracted position. The axial end surface 98 of the wall portion 62 is preferably oriented relative to the central axis 26 so that the second engagement angle 100 includes a higher or greater value so as to significantly increase the required closing force FC. For example, the second engagement angle 100 may vary between the range of 0° and 45°. However, it should be appreciated that the second engagement angle 100 may differ from the values described herein, and may be defined based upon the particular uses of the gas strut assembly 20. When the second engagement angle 100 is defined to include a higher value than the first engagement angle 96, it should be appreciated that the second radial force component FR2 is greater than the first radial force component FR1.
The second leg portion 66 of the displaceable portion 52 extends from the wall portion 62, axially along the central axis 26 and away from the first leg portion 60. The second leg portion 66 includes an inner surface 102 that contacts and/or engages a radial outer surface 104 of the detent 86. Engagement between the radial outer surface 104 of the detent 86 and the inner surface 102 of the second leg portion 66 limits radial movement of the displaceable portion 52 inward toward the central axis 26 when the rod 34 is in the extended position. As such, when the rod 34 is in the extended position, the engagement between the radial outer surface 104 of the detent 86 and the inner surface 102 of the second leg portion 66 ensures proper engagement between the second cam surface 90 and the axial end surface 98 of the wall portion 62, and prevents the displaceable portion 52 from flexing radially inward toward the body 68 of the rigid member 50 and becoming wedged in place.
The flexible member 46 may include and be manufactured from a polymer, such as but not limited to nylon or a plastic. The characteristics of the material used to form the flexible member 46, particularly the stiffness or resistance to bending of the material, affects the force required to move the displaceable portion 52 radially away from the body 68. As such, the specific material chosen for the flexible member 46 is dependent upon the particular use for the strut assembly.
A band 106 may be disposed radially about and encircle the displaceable portions 52. In order for the displaceable portions 52 to flex radial outward away from the detent 86 of the body 68, the band 106 must expand in circumferential length 42. Accordingly, the band 106 increases the force required to move the displaceable portions 52 radially outward away from the detent 86 of the body 68. The material characteristics of the material used to form the band 106, particularly the strain resistance or resistance to stretching, affects the force required to stretch or expand the band 106, and thereby affects the force required to move the displaceable portions 52 radially away from the body 68.
The band 106 may include and be manufactured from a material having a resistance to expansion that is variable with temperature. As such, the band 106 may include a resistance to expansion that increases with a decrease in temperature. Accordingly, as the temperature decreases, the resistance of the band 106 to expanding, i.e., stretching, increases, thereby increasing the force required to move the displaceable portions 52 radially away from the detent 86 of the rigid member 50. As such, the specific material chosen for the band 106 is dependent upon the amount of resistance the band 106 is required to provide, which is dependent upon the particular use of the gas strut assembly 20. However, the band 106 may include and be manufactured from, for example, one of a thermoplastic elastomer or a thermoplastic rubber.
The detailed description and the drawings or figures are supportive and descriptive of the invention, but the scope of the invention is defined solely by the claims. While some of the best modes and other embodiments for carrying out the claimed invention have been described in detail, various alternative designs and embodiments exist for practicing the invention defined in the appended claims.
