Acceleration sensitive motion snubber

Abstract

Relative axial movement of telescopically mounted support members is converted to rotation of an inertia mass by means of a ball-screw arrangement and a capstan spring loosely surrounding a portion of one of the support members. Slow acceleration of the inertia mass is accommodated, but rapid acceleration causes the inertia mass to lag which winds the capstan spring enough to grip one of the support members, which are rotationally fixed, and thereby snub movement until acceleration forces decrease. A spring band clutch positioned within the inertia mass and linked to the capstan spring ends enables the mass to slip in the event high velocity movement of the support members occurs and is then interrupted.

What is claimed is: 
     
       1. A motion snubbing device comprising: a pair of members mounted for relative movement with respect to each other; and   acceleration sensitive means connected to said members for limiting movement of either of the members relative to the other member in either of two opposite directions to a predetermined threshold acceleration rate .Iadd.while permitting continued relative movement at said threshold and .Iaddend.including means for preventing operation of said limiting means below said predetermined acceleration thus permitting repeated or continuous relative movement below said predetermined threshold both before and after said predetermined acceleration has been reached.   
     
     
       2. The device of claim 1 wherein said acceleration sensitive means includes: brake means for restricting said relative movement and an inertia mass connected to sense the acceleration of said relative movement and to actuate said brake means so as to prevent acceleration beyond said threshold rate.   
     
     
       3. A motion snubbing device comprising: a pair of members mounted for relative movement with respect to each other; and   acceleration sensitive means connected to said members for limiting the relative movement of the members to a predetermined threshold acceleration rate, said acceleration sensitive means including a torsion spring loosely surrounding a brake surface and an inertia mass connected to be driven by the relative movement of said members through said torsion spring in a manner such that rapid acceleration of the inertia mass in either of two opposite directions causes said inertia mass to lag with respect to the driving force producing a winding force on said spring causing it to grip the brake surface to limit acceleration of said members.   
     
     
       4. The device of claim 1 wherein said members are mounted to reciprocate with respect to each other. 
     
     
       5. The device of claim 4 wherein said members comprise a telescopically movable strut. 
     
     
       6. The device of claim 5 wherein said acceleration sensitive means includes a rotatably mounted inertia mass, means for converting telescopic movement of the strut into rotation of the inertia mass in a manner to enable the mass to lag in its movement when the telescoping acceleration of said strut reaches said threshold, and brake means responsive to said lagging to limit the acceleration at said threshold rate. 
     
     
       7. A device for snubbing rapid pipe movement in a power generating station that might be caused by sudden forces such as that occurring during an earthquake, the device comprising: a pair of support members mounted to reciprocate on each other while being restrained from relative rotation;   a rotatably mounted torque carrier;   means for translating relative axial movement of said support members into rotation of said carrier;   a rotatably mounted inertia mass;   a brake surface positioned inwardly from the torque carrier; and   spring means positioned within said carrier loosely surrounding said brake surface, said spring means being connected to the carrier and the inertia mass in a manner to cause the spring and the inertia mass to rotate with the carrier during slow acceleration of the carrier, while during rapid acceleration, the inertia mass lags the carrier causing the spring diameter to be reduced so that it grips the brake surface and locks the carrier, and thereby locks the support members.   
     
     
       8. The device of claim 7 wherein said spring means has a generally cylindrical configuration with a plurality of turns which surround the brake surface and extend along the brake surface so as to provide considerable gripping area on the brake surface. 
     
     
       9. The device of claim 8 wherein the ends of said spring engage the torque carrier and the inertia mass to cause the torque carrier to drive the inertia mass. 
     
     
       10. The device of claim 9 wherein said torque carrier has a cylindrically shaped portion with a window formed therein and the ends of said spring extend through said window, the spring ends normally engaging opposite edges of the window, said spring ends being connected to said inertia mass in a manner such that when the inertia mass lags behind the carrier the inertia mass causes the spring ends to be moved in a spring winding direction thereby causing the spring to grip the brake surface. 
     
     
       11. The device of claim 10 including clutch means positioned within said inertia cooperating with the spring ends so that the inertia mass is driven through the clutch means. 
     
     
       12. The device of claim 7 including clutch means positioned within said inertia mass to normally rotate with the inertia mass, said clutch means connecting the inertia mass to said spring means such that if the inertia mass is subjected to high velocity and the support members are suddenly stopped, the inertia mass will slip with respect to the clutch means and the spring means so as not to damage the spring means. 
     
     
       13. The device of claim 12 wherein said inertia mass has an inwardly facing cylindrical surface and said clutch means comprises a band of spring material having a generally cylindrical shape confined within the inertia mass to engage the inner cylindrical surface of the inertia mass due to the spring force of the clutch material, said clutch band extending considerably around the interior surface of the inertia mass but terminating in a pair of circumferentially spaced, inwardly extending flanges adapted to cooperate with said spring means. 
     
     
       14. The device of claim 7 wherein said support members are generally cylindrically shaped members, said carrier is a cup-shaped member rotatably mounted on one end of one of the support members, said spring is positioned between said one support member and said torque carrier, and said inertia mass is a cup-shaped member enclosing the torque carrier, the spring ends extending through a window in the torque carrier to co-operate with the inertia mass. 
     
     
       15. A device for snubbing rapid acceleration of one element relative to another comprising: a pair of telescoping support members to be connected between a support surface and the object whose movement is to be snubbed;   an inertia mass rotatably mounted with respect to the support members while being axially fixed; and   means for converting relative axial movement of the support members into rotation of the inertia mass including a capstan spring surrounding a brake surface with the ends of the spring connected to drive the inertia mass, the connection between the spring and the inertia mass permitting limited relative movement so that rapid acceleration applied to the inertia mass will cause it to lag and wind the spring causing the spring to grip the brake surface, while slow acceleration will be accommodated.   
     
     
       16. The device of claim 15 wherein a capstan spring surrounds one of the support surfaces and the brake surface is the exterior of that support member. 
     
     
       17. A device for snubbing rapid movement of one element relative to another comprising: a pair of support members mounted to reciprocate on each other while being restrained from relative rotation;   a torque carrier rotatably mounted within one of said support members while being axially fixed;   means connecting said carrier and the other support member in a manner to translate relative axial movement of said support members into rotation of said carrier;   an inertia mass rotatably mounted adjacent a portion of said carrier;   a capstan spring mounted to rotate in response to rotation of said carrier;   a brake surface positioned within said capstan spring closely spaced from the spring, such that a reduction in diameter of the spring causes the spring to grip the brake surface and prevent the carrier from rotating; and   the ends of said spring being connected to said inertia mass in a manner such that slow rotational acceleration of the carrier will cause the inertia mass to move with the carrier whereas during rapid acceleration of the carrier the inertia mass will lag behind the carrier and thus wind the spring causing it to grip momentarily the brake surface and thus prevent relative axial movement of said support members.   
     
     
       18. An acceleration sensitive device for snubbing motion when it reaches a predetermined acceleration threshold, comprising: a brake surface;   a rotationally mounted inertia mass;   spring means surrounding the brake surface and being connected to drive said inertia mass for slowly accelerating movement in either of two opposite directions while rapid acceleration causes the inertia mass to lag and apply a force on the spring means causing it to grip the brake surface.   
     
     
       19. The device of claim 18 including a rotationally mounted torque carrier surrounding said brake surface and wherein said spring is positioned between the brake surface and the torque carrier and includes a plurality of coils normally loosely surrounding the brake surface, said spring having a pair of end tangs which extend outwardly through a window in the torque carrier to cooperate with the inertia mass, the spring being rotated by the torque carrier through the engagement of the window edges with the spring tangs. 
     
     
       20. The device of claim 19 including a pair of support members mounted to reciprocate on each other and means for converting such reciprocation to rotation of the torque carrier. 
     
     
       21. The device of claim 18 including clutch means connecting the spring means to the inertia mass permitting the mass to slip with respect to the spring when subjected to force greater than the force needed to cause the spring to grip the brake surface. 
     
     
       22. A device for snubbing rapid pipe movement in a power generating station that might be caused by sudden forces such as that occurring during an earthquake, the device comprising: a cup-shaped housing having its closed end adapted to be connected to the pipe or to a support structure;   an elongated tube extending partially into the open end of the housing spaced from the surrounding housing to define an annular space with the housing, the open end of the housing being fixed to the outer periphery of the tube;   a cylindrical support member mounted for axial movement with respect to the tube, means for preventing relative rotation between the tube and the support member, the support member being adapted to be attached to either the pipe or adjacent support structure;   threaded means fixed to the support member;   a torque carrier rotatably mounted on thrust bearings supported on the inner end of the tube positioned within the housing;   a shaft fixed to said carrier and threaded through said threaded means such that unbalanced axial forces on said support member and said housing will cause rotation of the shaft and hence permit axial movement of the support member relative to the housing;   said carrier including a flange which extends radially beyond the free end of said tube and a cylindrical skirt which extends into said annular space between the housing and said tube;   a cup-shaped inertia member positioned in said housing rotatably mounted on said carrier coaxially with the carrier, said inertia member including a cylindrical skirt which is positioned in said annular space between the carrier skirt and the surrounding housing;   a clutch band positioned within the cylindrical skirt of the inertia member said clutch band extending partially around the inner circumference of the inertia member skirt terminating in a pair of spaced opposed flanges which extend towards the carrier skirt, said band being made of springy material biased to tightly engage the interior of the inertia member skirt while permitting rotational slippage between the band and the surrounding skirt; and   a capstan spring positioned between said carrier skirt and said tube with the ends of the spring extending through the carrier skirt and into the space between said clutch band flanges; said carrier skirt having a window through which said spring ends extend, said window and the spaced clutch band flanges permit limited winding and unwinding of the spring caused by relative rotation between the carrier and the inertia member, the construction of the spring being such as to cause the spring to normally engage the interior surface of the carrier skirt spaced slightly from the exterior of said tube so that the spring is free to move with the carrier during slow rotational acceleration whereas rapid acceleration will cause the inertia member to lag behind the drum thereby restraining the spring ends to wind the spring and cause it to reduce its diameter and to grip the tube and hence limit the rate of rotation of the carrier which in turn limits the rate of relative axial movement between the support member and the housing.   
     
     
       23. A method of snubbing rapid acceleration of a fluid conducting pipe in a power generating station as might occur during an earthquake, while permitting slow movement of the pipe, comprising: applying the accelerating movement of the pipe to a support structure by means of a pair of support members mounted for reciprocation relative to each other; and   converting the reciprocal movement of the support members into rotation of an inertia mass driven by a capstan spring loosely surrounding a brake surface, such as the exterior of one of the support members in a manner such that the inertia of the inertia mass winds the capstan spring causing it to grip the brake surface when the capstan spring is rapidly accelerated.   
     
     
       24. A device for snubbing rapidly accelerating movement comprising: a pair of members mounted for relative movement;   acceleration sensitive means connected to said members for limiting the relative movement of the members to a predetermined acceleration including resilient brake means and an inertia mass connected to be driven by the relative movement of said members through said resilient brake means in a manner such that attempted rapid acceleration of the inertia means in either of two opposite directions causes said inertia mass to lag with respect to the driving force and produce a force on said resilient brake means causing it to limit acceleration of said members.   
     
     
       25. The device of claim 24 wherein said resilient brake means is self-restoring to a nonbraking condition as soon as the force produced by the lagging inertia mass ceases whereby relative movement between said members can continue in either of said directions. 
     
     
       26. The device of claim 24 wherein said brake means is a coil spring which grips a braking surface to provide braking action. 
     
     
       27. The combination comprising: a supporting structure in a power generating station;   a pipe supported by said support structure;   a pair of members mounted for relative movement with respect to each other, one of said members being connected to one of said pipes and the other of said members being connected to said support structure; and   means connected to said members for limiting the relative movement of the members to a predetermined threshold acceleration while permitting .Iadd.further .Iaddend.relative movement of said members .[.at acceleration rates below.]. .Iadd.under continued application of a substantial amount of the force applied to said members in reaching .Iaddend.said threshold.   
     
     
       28. The device of claim 27 wherein said members are telescopically mounted with respect to each other to form a strut connected between said pipe and said support structure. 
     
     
       29. A motion snubbing device comprising: a strut having two members mounted for movement relative to the other to be connected between the structures whose relative movement is to be snubbed;   an inertia mass which is rotatably mounted and axially fixed;   means connecting said inertia mass to be rotated by relative movement of said strut members in a manner such that the inertia mass can lag rotationally with respect to the force rotating it; and   means responsive to a predetermined amount of said lagging for limiting the relative movement of said strut members to a predetermined acceleration.   
     
     
       30. A method of automatically snubbing the motion of pipes in a power generating station relative to the structure supporting the pipes such as the surrounding building, comprising the steps of: connecting a strut formed of two relatively movable members between one of said pipes and said support structure;   sensing the relative acceleration of said members; and   preventing .[.relative motion.]. .Iadd.acceleration .Iaddend.above a predetermined acceleration threshold, while permitting .[.unrestricted.]. .Iadd.further relative .Iaddend.motion .[.below the threshold.]. .Iadd.of said members under continued application of force applied to the member in reaching said threshold.   
     
     
       31. The method of claim 30 wherein: said sensing step includes converting the relative movement of said members into movement of an inertia mass through a resilient connection in a manner such that the movement of the inertia mass will lag with respect to the relative movement of said members; and   said preventing step includes utilizing the lagging of said inertia mass to restrict relative movement of said members to said predetermined threshold acceleration.   
     
     
       32. The method of claim 31 wherein said resilient connection is a spring surrounding a braking surface and the lagging of said inertia mass causes the spring to tighten on the braking surface when said predetermined accleration is reached and thereby restrict said relative movement. .Iadd. 33. A motion snubbing device comprising: a pair of support members mounted to reciprocate on each other while being restrained from relative rotation;   a rotatably mounted torque carrier;   means for translating relative axial movement of said support members into rotation of said carrier;   a cylindrical brake surface concentrically positioned adjacent said carrier; and   means including an inertia mass and a torsion producing spring connected to rotate with said carrier in a manner to sense the relative acceleration of said carrier and to cooperate with said brake surface to limit said acceleration to a predetermined threshold. .Iadd. 34. The device of claim 33 wherein said spring is connected to said carrier to drive said inertia mass, the spring permitting said inertia mass to lag the movement of the carrier, said lagging movement being utilized to initiate braking action with respect to said brake surface. .Iadd. 35. A motion snubbing device comprising:   a pair of support members mounted to reciprocate on each other while being restrained from relative rotation;   a rotatably mounted torque carrier;   means for translating relative axial movement of said support members into rotation of said carrier;   a brake surface positioned adjacent to said carrier; and   means including an inertia mass and a spring connected to said carrier to drive said inertia mass, the spring permitting said inertia mass to lag the movement of the carrier at a predetermined acceleration, said lagging movement being utilized to initiate braking action with respect to said brake surface. .Iadd. 36. A motion snubbing device comprising:   a pair of support members mounted to reciprocate on each other while being restrained from relative rotation;   a rotatably mounted torque carrier;   means for translating relative axial movement of said support members into rotation of said carrier;   brake means; and   means for sensing the relative acceleration of said carrier to initiate action of said brake means to limit said acceleration to a predetermined threshold, the accuracy of said sensing and brake initiating action being independent of frictional losses in said translating means.