Patent Application
20050173216
This invention relates to axial positioners capable of functioning under impact as energy absorbers.
Self-locking telescoping devices for energy absorption and including axial positioning means are known in the art. A proposed use includes positioning a vehicle bumper for maximum energy absorption prior to impact. However, these devices appear complex and maybe expensive to manufacture.
The present invention provides simplified axial positioners combined with expanding spring energy absorbers. The positioners are capable of fixing a positioned external object and absorbing energy while maintaining the load limit. Energy absorbers for either compression or tension loads may be included. The external object may be of any type for which positioning and restraint with energy absorption of impact loading is desired. Such objects may include vehicle bumpers, roll bars, knee bolsters, seat belt restraints and others.
An axial positioner according to the invention preferably includes an outer tube with first and second ends. A threaded actuator rod extends between the first and second ends of the outer tube. In an exemplary embodiment, the threaded actuator rod has shearable teeth. A drive connected to one end of the outer tube operates to rotate the actuator rod.
An axially movable self-loading restraint assembly threadably engages the actuator rod. The restraint assembly includes a positioning and load initiating internally threaded member threadably engaging the actuator rod, a radially extending load ring spaced axially from the member, and a radially expandable spring, such as a wave spring or a conic spring, positioned between the threaded member and the load ring.
The threaded member includes a radial flange extending toward the outer tube. The radially extending load ring directly engages the threaded member when moved axially in one direction and indirectly engages the threaded member through the spring positioned between the flange and the load ring when the load ring is moved in an opposite direction. When the load ring engages the spring with sufficient force, the spring becomes compressed. Compression of the spring between the flange and the load ring expands the spring radially outward against the outer tube. The resulting engagement of the spring with the outer tube creates resistance to axial motion, which absorbs energy when the restraint assembly is moved with sufficient force.
Tension or compression loads are transmitted to the load ring through a plurality of axially extending force transmitting elements extending through one end of the outer tube. The force transmitting elements may be connected outside the tube with a movable object that exerts either tension or compression loads on the restraint assembly of the axial positioner through the force transmitting elements.
The axial position of the movable object may be altered by rotating the actuator rod with the drive. Depending upon the direction of rotation, the actuator rod can move the restraint assembly in an extension direction, which extends the force transmitting elements from the outer tube, or a retraction direction, which retracts the force transmitting elements into the outer tube.
In an alternative embodiment, a yieldable stop such as a shear pin acts between the threaded member and the load ring to yieldabley retain the load ring a distance from the spring. Under normal tension or compression loads, the stop prevents the load ring from compressing the spring against the flange to prevent the restraint assembly from engaging the tube. When an excessive compression or tension load is exerted on the restraint assembly, the stop yields to allow the load ring to compress the spring against the flange and absorb energy upon motion of the movable object.
In another alternative embodiment, the threaded member is an assembly including a flange with a threaded insert. The insert threadably engages the actuator rod and is retained within the flange with a shear pin. Under normal tension or compression loads, the shear pin retains the insert within the flange. Under excessive compression or tension loads, the load ring compresses the spring against the flange. As the spring is compressed, the load is transferred through the spring to the flange, which in turn exerts pressure on the shear pin causing it to shear and allow the flange to separate from the insert. This prevents the teeth of the actuator rod from shearing and allows the restraint assembly to move within the outer tube resisted by the expansion and engagement of the spring with the outer tube.
These and other features and advantages of the invention will be more fully understood from the following description of certain specific embodiments of the invention taken together with the accompanying drawings.
Referring first to
An axially movable self loading restraint assembly 22 threadably engages the actuator rod. The restraint assembly 22 includes a radially extending positioning and load initiating internally threaded member 24, a radially extending load ring 26 and a radially expandable spring 28 which preferably takes the form of a spring pack.
The threaded member 24 threadably engages teeth 30 of the actuator rod 18 so that, as the rod rotates, it drives the restraint assembly 22, in an axial direction. The threaded member 24 includes a radial flange 32, extending outward toward the outer tube 12, and a retainer cap 34 axially spaced from the flange 32.
The radially extending load ring 26 is retained between the retainer cap 34 and the flange 32. A plurality of force transmitting elements 36 extend axially from the load ring 26 through one end of the outer tube 12.
The radially expandable spring 28 is positioned between the radial flange 32 and the load ring 26. In exemplary embodiments, the spring 28 may be either a wave spring or a conic spring. As the spring 28 is compressed between the load ring 26 and the radial flange 32, the spring expands radially against the outer tube 12, thereby exerting a radial force against the outer tube and holding the positioner 10 in position until an overload force is reached which forces the restraint assembly axially against a restraining force which absorbs energy.
Referring now to
The member 54 threadably engages teeth 60 of the actuator rod 48 so that, as the rod rotates, it drives the member 54 and the restraint assembly 52 in an axial direction between the ends 44, 46. Threaded member 54 has a radial flange 62 extending outward toward the outer tube 42. The radially extending load ring 56 is spaced axially from the member 54 and flange 62. The radially expandable spring 58 is positioned between the radial flange 62 and the load ring 56 to exert a radial force against the outer tube 42 when compressed between the flange and the load ring to hold the restraint assembly 52 in place until an overload force occurs that causes axial motion of the restraint assembly 52 with consequent energy absorption.
The load ring 56 is connected to a plurality of axially extending force transmitting elements 64 which extend through the member 54 and one end of the outer tube 42. The force transmitting elements 64 have abutments 66 axially spaced a distance from the load ring 56 to allow the load ring to axially slide for a distance until the abutments engage the threaded member 54. The abutments 66 of the force transmitting elements 64 form stops that directly engage the member 54 in one direction of motion and the load ring 56 indirectly engages the member 54 through the spring 58 in the other direction of motion.
In operation, the axial positioner 10, as illustrated in
The length of the positioner 10 may be adjusted by activating the drive 20 to rotate the actuator rod 18, which in turn axially moves the restraint assembly 22. As the assembly 22 moves in an expansion direction, the force transmitting elements 36 are pushed outward from the outer tube 12 to lengthen the positioner 10. Conversely, when the restraint assembly 22 moves in a retraction direction, the force transmitting elements 36 are drawn into the outer tube 12 to shorten the positioner 10.
Under normal compression loads, the teeth 30 of the actuator rod 18 maintain the position of the restraint assembly 22. When an excessive compression load is exerted on the positioner 10, energy is transferred through the force transmitting elements to the load ring 26, causing the load ring to move toward the radial flange 32, thereby compressing the spring 28. As the spring 28 is compressed, it expands radially outward against the outer tube 12 to frictionally load the restraint assembly 22. Under severe compression loads, the outward expansion of the spring 28 may plastically deform the outer tube 12 for a distance as the expanded spring slides within the outer tube.
The force exerted by the spring 28 against the outer tube 12 absorbs energy by converting a portion of the kinetic compression energy into work. Additional kinetic energy may also be absorbed by the positioner 10 by allowing the teeth 30 of the actuator rod 18 to shear sequentially as the member 24 of the restraint assembly 22 is axially driven within the outer tube by the compression load.
The axial positioner 37 illustrated in
In operation, the self-locking telescoping positioner 40, as illustrated in
The length of the positioner 40 may be adjusted by activating the drive 50 to rotate the actuator rod 48, which in turn axially moves the restraint assembly 52. As the restraint assembly 52 moves in an expansion direction, the force transmitting elements 64 are pushed outward from the outer tube 42 to lengthen the positioner 40. Conversely, when the restraint assembly 52 moves in a retraction direction, the force transmitting elements 64 are drawn into the outer tube 42 to shorten the positioner 40.
Under normal tension loads, the teeth 60 of the actuator rod 48 maintain the position of the restraint assembly 52. When an excessive tension load is exerted on the positioner 40, the force transmitting elements pull the load ring 56 toward the flange 62, causing the spring 58 to be compressed and expanded radially outward against the outer tube 42 to load the positioner 40. Under severe tension loads, the outward expansion of the spring 58 may plastically deform the outer tube 42 for a distance as the expanded spring 58 slides within the outer tube.
The force exerted by the spring 58 against the outer tube 42 absorbs energy by converting a portion of the kinetic tension energy into work. Additional kinetic energy may also be absorbed by the positioner 40 by allowing the teeth 60 of the actuator rod 48 to shear sequentially as the threaded member 54 of the restraint assembly 52 is axially driven within the outer tube by the tension load.
The axial positioner 67 illustrated in
The alternative threaded member 69 of
While the invention has been described by reference to certain preferred embodiments, it should be understood that numerous changes could be made within the spirit and scope of the inventive concepts described. Accordingly, it is intended that the invention not be limited to the disclosed embodiments, but that it have the full scope permitted by the language of the following claims.
