CA1080758A - Mechanical shock arrestor - Google Patents

Abstract

MECHANICAL SHOCK ARRESTOR
Abstract Relative axial motion of a pair of strut members is converted into rotation of a shaft which drive a rotatably mounted inertia element. Rotation of the shaft in the opposite direction drives a second rotatably mounted inertia element. The inertia elements are interconnected by a coil spring with the result that the inertia element driven directly by the shaft drives the other inertia element. At a predetermined acceleration, the inertia element driven by the spring will lag, and this change the spring diameter causing the spring to engage a surrounding housing causing a braking action to limit the acceleration, In a second embodiment, the axial strut load is translated through a fixed shaft into rotation of a nut which drives the inertia element The nut also transfers the axial load through the inertia element and a single ball bearing set to the other strut member.

Description

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19 ~ ~his invention relates to apparatus ~or limiti~ acceleration 20 1f two relatively movi~g members to a preaetermined thre~hol~,-ana 21 Imore particularly, to an improved all mechanical shock arrestor 221 or motion snubbing device~
23 ¦ In U.S. Patent No. 3,876,040, there is disclosed an 24 ¦acceleration sensitive motion snubber tha~ is particularly useful 2B ¦in snubbing motion which occurs from earthguakes or other rapid~
26 laccelerating forces. Such devices permit slow accelera~ion such 27 las that which occurs due to temperature changes bu~ will p~evenk 28 ¦rapid acceleration while still permi~ting continued movemen~ at 29 . .
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~2 !I ~ V75~ 1 1 the lower acceleration levels The device sho~m in ~aten~ ~o 3,87G,040 is particularly useful in connection ~Jith atomlc ener~y ~
3 el~ctric genera~ing plants because it is hicJhly reliable an~ s , 4 not afected by radiation, as'are hydraulic snu~bers The present inventi~n relates to improvem~n~s in an 6 acceleration sensitive mechanical shock arrestor o~ tho senerz?
type disclosed in the above-m~ntioned pa~ent. Such shoc~ arrestor o has been ve_y successful, particularly in the smaller sizes_ However, with struts fox handling exceedingly lar~e l~aas suc~ 25 ' 11 that which might be,imposed on stru~s attachea ~irectly ~o major 12 components within a nuclear reactor, the design shown i~ ~he ~ove-men~ioned patent can become larger than aesired w~en ha~in~
;jadequate strength. Thus, the present invention emplays 14 .
arrangemQntS which are more compact ana also highly reliable_ 16 In accoraance with the invention, a pair of members moun~e~ - , 17 for relative movement are connected ~o a pair oE iner~ia elemen,s 18 which are mounted to be ~reely rotated. The connec~in~ means lg between the members and the inertia elements is so arranged ~at 20 relative movement o the members in one airection will only airecly 21 or positivel~ drive one of the inertia elements ana x~la~ive 22 movement of the member in an opposite direction will only direc~ly 23 or positively drive the other inertia element These inertia 24 elements are in turn connected in a manner such,that ~he elemen~
25 being rotated by the drive means will rotate the other inertia 26 element. This second inertia elem2nt Will sense the accelera~ion ~ `
27 land will follo~ the first one below a predetermined mo~ion 23 ,threshold; but i~ acceler~tion,is attempted beyond that threshola,j his second inertia element t~ill initiate a braking actio~ ~o -30!l~imit motion to said threshold.

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1 ¦ In ~ne form of the invention, the inertia elements are

2 ¦cylindrical or somewhat disc shaped and are mounted coaxially

3 ¦with two of their ends in face to face relation. Motion is 41 transmitted bekween the inertia elements by means of a coil spring 5¦ which surrounds the interfacing portions of the elements. If the 61 force applied to the inertia elements exceeds a predetermined 7¦ acceleration threshold, the inertia of the elements being driven ~¦ by the coil spring will cause the element to impose a lagging 9¦ force on the springs which in turn will cause it to increase its 10¦ diameter so that it will brake against a surrounding housins wall.
11¦ This braking action prevents acceleration beyond the threshold.
2¦ In another form of the invention, the axial length of a strut 13¦ employing the acceleration sensitive means has been cleverly 14¦ minimized. A very short strut is needed in certain applications 15¦ such as interconnecting fuel rod support tubes in a nuclear ~61 reactor. In such an axially short snubbing device, the inertia 17 elements are made axially short so that they are somewhat disc shape d~
18 The drive sha~t Eor rotating the inertia elemen~s is forme~ with 19 high lead -khreads on opposite enas which coopera-te with members 201 to be attached to the fuel rod tubes or o~her structure whose 221 motion is to ~e arrested. These connecting members are sli~ably mounted for axial movement in the ends o~ a hvusing containlng 23 the inertia elements and the slidable mounting arrangement preven~

24 rotation of ~he connecting me~bers. The threaded connections 26 between the members and the shaf-~ are such that moving the -¦
connecting members -towards each other will produce rotation o 28 the shaEt in one airection and moving the connecting members awayj -29 from each o-ther will rotate the shaE~ in the opposite directio~ ¦
30 This is pre~erabl~ accomplished by having the threads on opposi~e¦
ends of the sha-Et extend in opposite directions, Tnus, bot~

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1 connecting men~rs and both ends of the s~laft ar~ involved in 2 converting axial movemen-t of the device into rotation of the 3 inertia elements.
In a form o~ the invention scheduled for production, and 5 which now appears to be the preferred form, axial movement of 6 a fixed shaft on one strut member is transferred to the o-ther 7 ! member by being translated into rotaton of a nu-t; the nut in turn`
8 transfers th~ rotation and the axial load direc~ly to an inertia 9 el.ement which transfers the axial load through ball bearings to the other strut member. Interengaging portions o* -the stru~
11 member surround the inertia members which increases the strength 12 of the strut enabling it to handle lateral or side loads better 13 than with a strut of reduced diameter. ' 1~¦ For a more.thorough understanding of ~he inven-tion reEer now to the following detail description,and c~rawinys in which:
16 Fig. 1 is a cross-sec-tional view on the longitudlnal axis o 17 a strut embodying one form of the invention; .
18 ~ig. 2 is a cross-sectional view on line 2-2 o~ Fi~. l;
19 Fig. 3 is a cross~sectional view on line 3-3 ~f Fig_ .1; ' ~ig. 3a is a side elevational view illustrating,the 21 connection between an inextia elem~nt and -the sp~ing; .
Fig. ~ is a cross sectional view on line 4-4 of Fig, lr .-23 Fig~ 5 is a cross-sectional view on -the longi-tudinal axis o~
2~ a strut embodying another form of the invention; ' Fig, 6 is a view of the strut of Pig 5 on line 6-6;
26 Fig~ 7 is a cross-sectional view o-f the strut of Fig, 5 on 28 line 7-7; ' 29 ~ig~ 8 is a cross-sectional view of the strut of Fig 5 on.
li.ne 8-8;
~0 . t l ~ig. 9 is a schematic perspective view illustratiny the 5~ru-~
3ll `,., ~ c~f Fig 5 in use; and 2 Fig. 10 is a longi.tudinal cross-sectional view of the ~orm of 3 ¦the invention claimed herein.
a of ~ig. 5 in use.
Referring now to Fig. 1, the shocX arrestor show~ inclu~es a 6 pair o support or connec-tiny members generally i~dicatea a~ 10 an 7 12 which are te~escopically moun~ed on each o~her for rela~ive 8 axial xeciprocation. These support members are formea a~ se~eral 9 differen~ componen~s which are xigidly connectea to move as a u~
10 Thus, the support mem~ers 10 and 12 each inclu~e~ an e~ tongue 14 ¦
11 and 16r respectivel~, which are adapted to be connec~ed ~o ~he.
12 structures whose relative motion is being arres~ed_ The tongu~ 14 !
13 is threadably attached to a heavy disc shapea en~ p~ate which in 14 turn is attache~ to a tubular or cylindrical housing 20, Attached to ~he other end of the housing 20 i5 an end pla~e 17 or flange 22 formed integral with a tuhe 24. The ~lange 22 is 18 positioned.a~ainst an annular shoulder in ~he housing wall 20 an~ ¦
19 is axiall~ held in this position by a retaining ring 26~ The ~lan~e 22 is also rotationally ixed with respect ~o ~e housing .
21 wall 20 by means of ~ series of pins 28, one o whic~ i5 ShOWrL in 2Z ~ig. 1.
23 The other end of the tube 24 is threaded to a tubular sleeve .
24 30 which slidably receives an elongated suppor~ ~ube 32~ ~hic~ is 25 threadably attached to the tongue 16 of the support mem~er 1~
2~ Threadabl~ attached to the interior of the o~her end o~ the tube 3 27 is a t~bulax nut 34 which has an outwardly extending flan~e on one 28 end that has a plurality of raaially extending lugs 36, as seen 29 in ~ig~ 4. These lugs fit ~Jithin axially extending groo~es forme~
30 between splines 38 on the interior of the tube ~4 which is attache~
31 to the support assembly 10. Thus, it can be seen that the ~ltelescopic movem~nt of the assemblies 10 and 12 occurs by th~
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l'itube 32 axially sliding within the tu~e ~ and its sleeve 30 Th~
2 ! cooperation bet~;een the nut lu~s 36 and the splined in.erior 38 3 ¦of the tube 24 prevents ro~ation of the assem~lies 10 and 12. Th2 ¦strut is sho-~7n in its fully telescoped position with ~he end of ¦the sleeve 30 engaging the interior end wall of ~he ton~ue ~6_ .
6 ¦ The ;nterior of the tubular nut 34 is ~ormea with a high-leaa 7 ¦thread ~hich mates with a high-leaa ~hread formea on the exterior B ¦of the shaft 40 which extends ~7ithin Lhe ~ube 32 and int~ ~he g ¦housing 20. The portion of the shaf~ ex~ending inLO ~7ne housing .
10 ¦20 has a section 42 with a sl.ightly reduced diameter on which is ¦
11 !thxeadably mounted a tubular load transfer mem~er 4~ The me~ber 12 1~4 is xoLationally and axially locked on the shaft by means o~ a 13 plug sleeve 46 which is forced be~ween an axially ri~ged bore in 14 the member ~4 and an ~xially rid~ed section ~-8 formea on the : :
shaft 40.
16 As seen from Fig. 1, the shaft through its load ~rans~r :~-17 member 44 is ro~atably mounted within the housing 20 on the .
18 support assembly 10. This is accomplished by means o~ a:~
19 schematically illustrated ~earing 50 which ex-ends ~De~J en ihe inner end o~ the ~ube 24 and an annular shoulde~ 52 form~d on one end of the load txans~er member 44. Similarly, a bearin~ 5 ls 22 positioned be~ween the in~e~face o ~he en~ plate 18 an~ an :
23 annular shoulder 56 formea on the other ena of the loaa transfer 25 me~ber 44. The tip 58 of the shaft ~0 is also rotatabl~ moun~ed ;
26 in the end plate 18; however, the axial load on the strut i~ ~
2~ carried on ~he bearings 50 and 54. :
2~ Between the housing wall 20 and the load ~ransfer member 4~, :
29 there is formed an annular cavity in which is positioned a pair of xing shaped or annularly shap~d inertia elements 60 ana 62~ ~s 31 may be seen from ~iy. 1, these members are iden~ical and they are :
axiall~ aligned within the cavi-ty~ Ho~ever, the~ are mounted in 32 . .
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ll¦opposed relation ~ith the end face of one closely positio~ed 2 adjacent the similar end face of the other. A suitable roller 3 bearing unit 64 is positioned in rec~sses formed in the Opposing

4 end ~aces to facilitate the rota-tion of the i~ertia elem~n~s Wlt~
~ respeet to the otherO The inertia element 60 is fur-ther ro~a~ly 6 mounted by a roller bearing 66 positioned beLween the inner wall 7 of the element 60 adjacent its a~ially outer end ana the exterior 8 of the tube 24 adjacen~ its end within the housing 20 Simil~rly, .
9 a bearing 68 is positioned between the inner wall of the ine~tia element 62 adjacent its axi~lly outer end ~nd the ex~erior of a 11 cylindrical axial projection 18a on the end pla-~e 18.
12 A coil spxin~ 70 surrounds the poxtions of ~he inertia e~em n~s 13 60 and 62 adjacent their opposing ends An annular recess 63 is 14 ~ormed in the elements 60 and 62 for receiving the spring_ As 15 may be seen from ~ig. 1, the coil spring 70 is closely spaced fram~
16 the surrounding housing wall 20~ A shallow annular recess 72 17 may be formed in the wall 20 for xeceiving the coil spring ~7i~
_8 the desired spacing, although it is no~ critical, 19 The ends of the coil spri~g 70 are intexconnected ta ~he 21 inertia elemen~s 60 and 62 so that rotation o~ one iner~ia elem~
will rotate the other elemen-t through the spring~ ~lore specif1cal .
22 one end 70a of the spring, as shown in ~ig 3a, engages a radial 23 shoulder 62a ~ormed on the inertia elemen~ 62~ The shoulder 62 24 is created by forming the end wall 62b o~ the recess 63 in the 26 inertia element 62 so that it conforms to the spirall~? sloping 27 end sur~ace of the spring 70. The other end of the sprin~ 7Q is 28 similarl~, though reversely, positioned with respec~ to the ..
.inertia element 60.
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The load transfer nut 44 is formed with a plurality of axially -~1 and radially extending teet'n or ribs 74 as may ~e seen in Figs~ 2 32 and 3 which de~ine spaces between them~ The inertia ~lement 60 is _7-, 75~3 1 similarly for~ed ~ith inwardly e~tendin~ rib5 or t~eth 76 ~lhich ~i .
2 within the spaces bet~een the teeth 7~ on ~he loa~ trans~er nut;
3 however, the spaces ~etween the teeth 74 and the spaces be~J~en ¦
4 the teeth 76 are l~ryer than t'ne tee~h posi~io~ea ther2in s~ ~hat ~ in the position shown in Pig. 2, one edge of eac~ ~ooth 7~ is 6 engaged with one edge of each tooth 76 hu~ the other e~ges of the 7 teeth are spaced circum~erentially a dis~a~ce greater than ~he ' 8 width of the teeth.
9 Re~erring to Fig. 3, the inertia element 62~ being i~entica~
10 to the element 60 also has inwardly ex~ending teet~ 78 ~7hich .:
11 engage ~he teeth 74. However, in this instance, it is ~he o~he-1~ edge of each tooth 74 which engages the edg~ o~ the ~ee-~ 7~_ ;
13 This occuxs because of the.reversal o~ the elements 60 and 6~, 1~ The :Location of the teeth 76 and 78 on the iner~ia elemen~ is circumferentially oriented or related to ~he loca~ion of tke ~6 raaial shoulders on the inerti2 elements that are enga~ed ~ ~he :
17 ends of.~he coil spr.ing 70 so that the load trans~er nut ~eeth 7~ :
~8 are oriented with respect to the inertia elemen~ tee~h as shown ~:
19 in ~igs. 2 and 3. . .
20 - Operation .
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21 When an axial force is applied ~o ~he stru~ causin~ ~ ;
22 become shorter or longer, the axial ~orce ~s applied to ~he sha~t :
23 40 by means of the nut 34. The high-lead threads o~ ~he n~t and .
24 shaft will produce rotation of the shaf~ as the stru~ members 10 .
and 12 are axially moving relative to each other~ The ro~a~ion OL ..
26 the shaft 40 of course, rotates the load transfer nuk 44 w~ich ls attached thereto. Relative axial motion o~ the strut members in .
28 one direction will produce counterclocXwi5e rotation, and tho teeth 74 on the load transfer nut 44 will eng~ge ana drive ~he ~1 teeth 76 ~ormed on the inertia element 60 as sho~n in Fig_ 2_ .-. :
~lo~ever, referxing to Fiq. 3, it can be seen ~h~t the load trans~e: .
32 nut does not drive the inertia ele~ent 62 with a coun~ercloc~ise .
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l¦lrotation b-c~usr- the -teet'rl 7~ o~llc~ t~n~ to ~o~e a~7a~ ~rom t~r~
2 teeth 78. , 3 ~otation of the inerti~ ele~ent 60 in a counterclockwise E~
direction also rotates the coil spring 70 since the end o~ the ~''spring en~ages the shoulder on the inertia ~lem9n-~ to cause such

6 rotation. Rotation of the coil spriny 70 in turn dri~es the

7 inertia element 62 through the end 70a of the spring 70 engaging

8 the shoulder 62a as shown in Fig. 3a. So long as the accelara~on o~ the telescoping movement of the stru~ and the resu~ting 11 rotation o~ the shaft and load trans~er nut is slowr ~he iner~a 12 elemen~ 62 simply ~ollcws the movement o~ the inertia elem~ 60 and the xelatio~ship of the com~onents remains as illus~ra~e~ 1~
13 the dr~ings~ Thus~ the strut can acc~mmodate slow movemen~ such 15 as that p~oduced b~ the thermal expansio~ and contraction of t~e 16 components and structures to which the s~rut is attache~
17 However, if the relative movemen. received by the strut . .
appxoaches a predetermined acceleration ~hreshold, the inertia 18 .
19 of the inertia element 62 which is being rotate~ throu~h the coil 20 spring 70 will cause ~he element to lag ro~ationally because o 21 the resiliency of the spring. This lagging rotatio.n ~n be 22 furt~er understood by referring to Fig. 3 and visuali~ing ~he 23 teeth 74 moving in a counterclockwise direction away ~rom the 24 teeth 78. The lagging movement of the i~ertia element 62 in~rodu 5 25 a foxce or load ~7hich trys to compress t'ne spring 70 along i~5 26 spiral axis which causes the diameter of the coils to expand and 27 fric~ionally engage the inner sur~ace of the housing wall 20~ .
28 ~his frictional engagement produces a braking action which limits .
2g the accelexation of the inertia elements, whioh in turn bxakes ~.
30 restricts the rotation of the load transfer nut and the shaf~ 40 31 P~e~erriny to FiyO 3, the ~idth of the slots be~een the -teeth is 32 such that the lagging movement of the inertia element 62 can ~e -:
1 acco~odated ~ hou~ th2 tee~h i8 in~erf~rirlcJ with the teeth 7~ :
hen the acceleratin~ Lorce a~temptirlcJ ~o ~ause movement ~ ! ~e~ond the acceleration thr~shold is snubbe~, t~le coil spring can :
4 rela~ and r~turn the inertia elemen~ 62 ~o its normal pOsi~ion in relation to the load trans~er nut 74 as shown in ~ 3_ The 6 telescoping movement o~ the strut does na~ stop with ~his br2kins 7 action producea by the coil spring and t~e inertia elem~ts~ ~ :
8 Instead, the mo~ion continues but at an acceleration xate w~ich . : :

9 is below the predetermined threshol~.
IX the telescoping force on the s~rut is such as ta px~duce. .
11 rotation of the sha-E~ 40 in the opposite ox clockwlse airec~ion, 12 ~he operation of the strut is the sam~ wi~h the excep~ion tha-~ the :~
13 ine~tia elemen~ 62 becomes the element positively or ~irectly 1~ driven by the load ~ranser nut and the iner~ia element 60 is driven through the coil spring. More specifically, the ~ee~h ~4 :
16 on the load transfer nut positively arive the ~eeth 78 o~ ~he 17 iner~ia elemen~ 62 as shown in ~i~, 3 This orce is the~ in 18 turn transferred to the coil spring 70 by ~irtue of the shoulder :~ .
19 ¦62a on the inertia element shown on Fig 3a engaging -~he ena o~ .
20 tne coil spring 70. The spring then drives the elem~nt 60~ Thus, it can be seen that the load transfer nut positivel~ drives either~

o the inertia elem~nts aepen~ing upon ~he direction o~ ro~a~ion . .
23 but it only positively or directl~ drives one o~ ~hem a~ a time, and the element not directly driven by ~he load ~ransfer nu~ is . -instead rotated by means o~ the coil spring.
26 Emboaiment o Figs. 5 - 9 , . _ . .
27 The embodiment OL Figs. 5 9 i~ similar -to that of the 28 embodiment o~ ~igsO 1 - ~ in that it employs a pair of inertia 29 elements selectively driven by a rotating shaft and interconnected ¦¦by a coil spring. However; th~ structure is otherwise ~rea~ly 31 !l iimodified and simplified to form a very compact and ~xially shor~

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1 strut 79 haYin~J ~ minin~um num~r o~ pClrts- 'rher~ i5 shot~n a 2 tub~ r or cylindrical housing 80 clam~ed ~et~Jeen a pair of en~
3 ¦ ~la~s B2 and ~3 by a plura~ity of bol-ts 8~ extendin~ through the .~ ¦ corners of the plates.
5 ¦ Attached to and ex-tending out~7ardly ~rom the ena o~ each plat~
~¦ is a pair of guide pins ~6. ~ pair o~ identical suppor~ or 7 attachment n~embers 88 are slidably mountea on the guide pins 86 8 for axial movement while beins preventea from rotation~ Tne 9 member3 88 are each provided wi~h a pair of bores 8~ ~or.receivl~S

10 ¦ the guide pins 86~ The members 88 are fur~her provided wit~ an

11 ¦ opening 90 through which connection is ~ade to ~he s~ructure tJhose

12 ¦ motion is being snu~bed or arrested. Each of the m~m~exs 88 is

13¦ further provided with a tubular extension ~2 which extends into

14 ¦ the end plates 82 and 83. The tubular extensions are i~ternally

15¦ threaded to mate with the threads on the end o~ a shaft ~4 ~Jhich-

16¦ extends through ~he housing coaxial with the cylindrical WAll B0_ ~71 The threads on the tubular extensions 92 and on the enas o~ -the 18 shaft 94 are of the high-lead type so that axial movemen~ o~ ~he 1~ members 88 will produce rotation of the sha~t. ~o~e from Fig~ 5 2.0 that the threads on one end of the shaft are le~-hana and the 21 threads on the other end o~ the shaft are righ~-hand, Wi~h ~his 22 a~rangement~ the end members 88 can have the iden~ical in~e~nal 23 thread and movement of the me~bers 88 towards each other will 24 produce rotation of the shaft 34 in one direction and moveme~t o~
25 ¦ the members 88 away from each will ro~ate the shaf~ g4 i~ the 2 I opposite direction. ¦
7,~ Positioned within the housing 80 are a pair o~ inertia elemen~s 2~ and 98 which have a generally tubular or ring shape surroundin~
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the sha~t 9~. Tne inerti~ clc~ nts 9G ~nd 9~ are ro.~tably 2 mount~d, but this is ac-:omplished without the use oE an~ roller ~ or ball ~earings The inertia elements 96 and 98 ~r~ identical : ~ in shape and are axially aligned. Ho~JeverO they are positione~
5 with their simil~r.faces in op~osins relation. A washe~ or rLn~ .
.,: shaped spacer 100 extends between these opposing faces ~o givc . 7 ¦ them a slight clearance and keep the inertia elemen~ 96 and ~8 :~ 8 ¦ on the relative center of the shaf~ 94 . The housing is also g ¦ thereby centrall~ positioned between the members 88~ The o~h~r :
10 ¦ axial ends of the inertia elem3nts are f~rmed tJi~h axially 11 ¦ extending tubular portions 102 which fit within sockP~s 104-~or~ed 12 ¦ in the end plates 82 ana 83. The tubular portions 102 ana ~he '. ~3 ¦ sockets 104 provide bearing su~fac2s for the inertia ele~e~s .
¦ which rotationa:Lly and axially position the elements~
.. ¦ A spirally shaped coil spring 106 is positioned within an~ula.
16 recesses form~d on the exterior of the inertia elements ~ajacen~
; 17 the opposing faces. The ends of the coil spring engage shoul2ers, ~:
~.: 18 ~not shown) on the inertia elements in a ~anner similar to that -:. 19 explained in connection with the embodimen~ o Pigs 1 - 4_ Tne :.~. 2p outer periphery of the coil spring 106 is closely spaced ~rom the .
~1 inner suxface of the cylindrical wall 80 22 A load trans~er nut 108 is ixed to the centxal sec~ion o~
the shaft 94 to rotate with the shaft. ~s wi~h the arran~emen~
24 of ~igs. 1 - 4, the load txansfer nut 108 is provi~ed with a .~ 25 plurality of radially extending teeth llQ ~Jhich cooperate with 26 radially extending teeth form~d on the inertia elements 96 and 98.
j. . 271l ~loxe specifically, the teeth 110 of the loaa transfer nut are . ~Zl~ oriente~ to drivingly engage the tee.h 112 of the inertia element .
2~ ~! 96 when the load transfer nut is rotated in a coun~ercloc~wise 3~ !~ direction as viewed in Fi~. 7. By contrast, the teeth ~10 ~7ill i 3~

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~OB~3'758 1 1 ~ri~e the t~e-th 11~ on the inerti~ ~lemerlt 98 when the loa~
211 tr~nsfer nut 108 is ro~ated in -the opposi~e or c~ock~Jise direotio 3j ~s shown in ~ig. 8 ~,¦ Operation l . _ . .
~ It will be appaxent that movement o~ ~he en~ memhers 88 6 towards each other will permit -~he m~mbers 88 to slide tow~rds 7 the end plates on the guide pins 86~ ~his movement ~`7ill ro~ate 8 the shaft 94 in one direction due to ~he ~hreads on t~e sh2~ an~
9 the members 88. If the motion is in, say, a countercl~c~se directi~n, the loa~ trans~er nut 108 will positivel~ drive.or 11 ratate ~he inertia element 96 in a coun~erclock~ise ~ir~c~on as .
12 shown i~ FigO 7. ~lem~n~ 96 will in tur~ ro~ate elemen~ 98 b~
13 means of the coil spring 106~ So long as the accelera~ion rema~ns 14 helow a prede~ermined threshold, the inertia elements will simply xotate as the strut ~elescopes How2ver, if accelera~ion reaches 16 the prede-termined threshola, the inertia elemen~ 98 will lag by 1~ vir~ue of its resilient connection t~rough the coil spring an~ wil 18 cause the coil spring diameter to expand ana ~ric~ionally en~a~e 19 the cylindrical wall 80 producing a ~xakLng action on movement~ .
2.0 As with the embodiment of Figs 1 - 4, ~o~emen~ o~ ~he 21 s~ruk mem~ers in the ~pposite direction will produce ~he oppo~i~e 22 rotation of ~he sha~t 94. T~is in turn ~ill cause ~he ~oa~
trans~er nut 108 to drive the other inertia elemen-t ~8 b~ mo~ement 24 in ~he clock~7is-e direction as shown in Fig, 8, The inertla elemen 96 then becomes the elemen~ driven throug~ the coil sprin~ 106 and 26 the combination o~ the spring and the ele~ent 106 will sense t~e 27 acceleration threshold to prevent acceleration be.yond the :
28 threshold D
2~ The device in Fig. 5 is particularly useful in situations ~0 I
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wher~in th~r~ is very limit~cq a~ial space in :hic~l to posi~io~
2 snub~er. ~n e~ampl~ o~ -thi~ is in connection ~ h ~he fuel ro~
guide tubes ~ithin a power yenera-tincf nuclear reac~or It h~s been determined ~ha-t it is desirable ~rom a sae~ st2n~poin~ ~o 5 in~erconnect the fuel ro~ tubes with devices ~Jhich t7ill s~u~ or.
~¦ arrest rapidly ocllitating forces such as that t~hich ~igh-~ occur 7 during an earthquake. The amoun-t o~ rela~ive movamen~ which ~he 8 device will be subjected to as a result o~ normal thermal c~a~ges 9 is quite small, and thus the travel o~ the attachmen-~ members 88 wikh respect to ~he housing is liml~ed, as ~eterminea by t~e gui~e;
11 pins 86 and retaining rings 116 positioned on the exterior o~ ~e 12 ~ubular extension 92 on the attachment memkers 88~ ~
13 The snubbing de~iee of Fig. 5 is shown in ~ig. g connected ~ .
14 to such nuclear reactor fuel rod tubes. More specificallyr there , is shown a mounting bracket or structure 120 attached ~o ~
16 plurality of vertically oriented, closely spac2a, parallel ~uel :
1~ xod tubes 122. The attachment bracket 120 has an out~Jaral~
18 extending lug 124 as best seen in ~ig~ 6J on which is ~oun~ed a 19 stud 130~ The snubbing device is positioned so tha~ the S~a 13~ .
extends through the hole 90 in the connecting member 88. A -21 suitable xe~aining elem~nt 132 ~i ~ting over the stud is show~ oin 22 the o~hex end o~ the device in ~ig. 5, T~us, several s~ubbing 23 devices 79 ma~ be attached between a group of fuel rod tubes ag 2~ shown in Fig. 9 to pro~ide the necessar~ capabili~y ~or prevsnking 25 the fuel rods from whipping violently and ~angerously during ,:
rapid movement such as tha. in an earthquake~
271 . Embodiment of Figure 10 ~ it - ~
28 1¦ Fig. 10 shows a variation of the arrangem2nt shown in ~igs~
r~f 2~ he form of the invention shown in Fig. 10 is scheduled ~0l, for production and hence, is presently the preferred form~ The ~ 3~
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1 shoc~ arrestor shown includes a pair of strut members generally 2 indicated at 210 and 212 which are -telescopically mounted on each 31 otiher for relative axial reciprocationO These strut members are formed of several different components which are rigidly connecte~
I to move as a unit. Thus, the support member 210 includes an end 61 tongue (not shown) adapted to be connected to the structure 71 whose relative mo-tion is being arrested. Such tongue is ~hreadably ~¦ attached to a heavy disc-shaped end plate 218 which in turn is 9¦ threaded to a tubular or cylindrical housing or casing 220 having 10¦ inner bearing surfaces 220a and 220b~ Fixed to the end plate 218 ~1¦ is an elongated shaft 240 which extends through a centxal opening 12¦ in the end plate 218 and is threaded on the exterior o~ an enlarged 13¦ head which mates with internal threads fo~ned on the bore through t~ e 141 end plate. A xetaininy element 241 further locks the shaft in 15l position.
~ The support member 212 includes an enlarged tongue 216 which i~

17 formed with an end plate 217. Surrounding the end plate and slidinc

18 within the tubular casing 220 is an elongated tubulax housing membe~

19 2~4. The housing 224 is axially Eixed to the end plate by a ~lange

20 2~4a which is captured between a shoulder 217a on the end plate and

21 a retaining ring 226~ This arrangement permits the tongue 2~6 to

22 be rotated for alignment purposes in mounting. The other end o~ th

23 tube 224 is threaded on its intexior and mates with a tubular bearir

24 support member ~28. The bearing support member 2~8 includes an

25 enlarged end portion or plate which mates with the tube 224 and

26 further includes a tubular portion of reduced di~neter ~hich suxrour ds

27 the shaft 240. Pinned in a recess in the right end of the bearing ~8 support member 228 is a spline follower 230 having a plurality of 29 circ~nferentially spaced grooves which slidabl~ ma-te with axially 30 extending spline teeth 241 on the ex-terior of the shaft 240~ This 31 spline teeth and groove arrangement pe m its axial movement of one 32 stru-t member relative to the other but prevents relative rotation.

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On the other end of the bearing support member 228 is !positioned a bearing race 2~2, which is h~ld in ~lace b~ a 3 ¦retaining rin~ 244. Thus, it can be seen that the bearing support rnember 22~ along with the bearing xace 2~2 and the spline follo~er 230 are fixed to the tubular member 224 which is attached 6 to the mounting tongue 216. In addi-cion the strut member 212 7 incluaes a bearing support member 246 on the stru~ left e~d ~7hich is threadably attached to internal threads on a recess in 9 the support plate 217. This bearing s~pport member 2a6 ~i~e the support member 228 carries a bearing xace 24~ on the exterior 11 surface of the inner end of the member and is held in position 12~ by a retaining xing 250. Thus, the strut member~l2 forms a 13 closed end structure which can slide axially relative to the 14 stxut member 210.
Positionedwithin the housing 224 is a tor~ue transfer nut 16 254 which is threadably mounted on the threads 243 on ~he shaft 17 240. The threads on the shaft and the mating threads on ~he 18 torque transfer nut 254 are of the high-lead type such that 1~ axial movemen~ of the shaft 240 relative to the transfer nuL
20 will cause the nut to rotate.
21 Surrounding the transfer nut 254 and extending wi~hin the 22 annular space formed by the bearing supports 246 and 228 in ~3 co~bination with the surrounding housing 224 are a pair vf 24 elongated inertia elements 256 and 258. The inertia element 256 25 is actually ormed of two components, a central portion ~56ar 26 ~ich is threaded to an end portion 256b. The element 25B is 27 sîmilarly formed with the portions258a and 258b. Captured between

28 the two portions of each inertia element are bearing races 260

29 and 262 which mate with the races 2~8 and 242 respectively.

30 Large ball bearings 264 are mounted within the bearing races.
~1 As can be seen, the inertia element portions 256b and 258b , ~; ~ ,, . ... ~ #~ ~Y~
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1 Ihave annular recesses on their radially inner sur~aces, that o~en : 2 ¦to their opposin~ ~ial faces, and which together define a recess 3 Ifo r axially capturing the torque transfer nut 254. The torque 41 trans~er nut 254 has a circular exterior cross-section that is separated radially by an annular space 274 frorn the surrounding I circular walls of the inertia elements 256 and 258. The torque 71 transfer nut is axially confined by the annular shoulders 256c 81 and 258c on the inertia elements. However, there is a slight 9¦ clearance between the shoulders and the torque -transfer nu~ so 10¦ that one inertia element can rotate relative to the torque transfer 11¦ nut when the other element is being driven by the nutO
121 Surrounding the adjacent ends of the inertia elements 256 13¦ and 258 is a coil spring 270 similar to the spring 70 in Fig. ~.
141 The ends of the coil spring 270 mate wi-th shoulders on the inertia 15¦ elements in a manner similar to that described in connection with 161 Fig. 3a. In addition, one end of the spring 270 is restrained by 171 a screw or pin 272 which extends with slight clearance into a ho~e 181 in the inertia element 256 which permits the spring to wind and 19¦ unwind but yet prevents the co~ponents from separating~ A similar 201 screw or pin 273 extends into a hole in the inertia element 25g~
21¦ In operation of the strut of Fig. 10, the overall result 22¦ obtained is similar to that o the strut in Fig. 1. ~owever, there 231 are a number of operational and structural differences that 2~1 provide certain advantages. The strut is shown in its most fully 251 collapsed position. If a tension load is applied to the strut, 26¦ the load is transmitted directly through the shaft 240 and the 271 torque transfer nut 254 into the shoulder 258c of the inertia 28¦ element 258. The load path is through the ball bearings 265 ~ and 29 into the bearing support member 228, the surrounding housing 22 30 and the tongue 216 oE the support member 212.
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Since the nut 254 is axially ~ng~giny the inertia elernent 2 258 and cannot move furtner axially in that dire_tionr the high lead thread connection with the shaft causes the nut 254 to rotate which in turn ro-tates the inertia element 258 through the friction of the interengaging axial surfaces on the nut an~ the the iner-tia element. The inertia element 258 which is ariven 7 by the nut 254 rotates the spring 270, which in turn rotates ~he 8 inertia element 256. A slight axial clearance between ~he nu~
9 ¦and the inertia element 256 being driven by the sprin~ permits ~he 10 ¦spring driven element to rotate independently of the nu~ an~
11 ¦the inertia element 256. When rotation of the nut 254 and ~h2 12 ¦inertia elements is below a predetermined acceleration level, 13 the rotating components have no significant effect on the 14 telescoping movement of the strut. However, with accelera~ion 15 beyond a pxedetermined threshold, the inertia of the eleme~t :L6 being driven through the coil spring causes the spring to unwin~
17 a small amount such that the diameter of the spring increases 18 causing the spring to brake against the interior of the 19 surrounding support housing 22~, thus, imposing a br~king ~oxce 20 on the telescoping strut. As soo~ as the acceleration is brak~a, 21 the spring diamete,r will relax to its normal condition.
22 With the strut in compr~ssion the load is again thxough the 23 shaf~ and the nut but it passes from the nut through the inertia 2~ element 256 and ball bearing 264 into the strut mem~er 212. The 25 compressio~ load rotates the nut which rotates the element 256, 26 that in turn drives the element 258 through the spring 270, The 27 braking ac-tion at the threshold acceleration is comparable to 28 that which occurs with a tension load.

29 OnP of the advantages of the arrangemen-k of Fig. 10 is that 30 only a single set of large ball bearings is required for each

31

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`"; 1 inertia elelnent. Such bearinc~s handle both the radial forces ~nd ; the axial thrust forces. The size of the bearings are such ti~a~
3 the very large thrust components can be accorl~odated~ The 12rge 4 single sets of bearing also provide considerable manufacturing convenience in that the~ are easier to install than the small roller bearings shown in Fig. 1.
7 The use of the large ball bearing enables the nut 254 to 8 transmit the axial load directly to one of the inertia elements 9 and enables the nut to rotate the inertia element without the need ~or teeth connecting the nut to the inertia elements as in ll Fig. 1. This eliminates lost angular motion between the components 12 Also, the manufacture and assembly is simplified~ Further, 13 the number of components is minimized in tha~ the nut 254 14 serves the function of translating the axial force of the stxut into rotation~ in combination with the s~aft as well as the 16 device which transfers the torque to the inertia elements, This 17 is in contrast with the arrangement o~ Fig, 1 wherein the xotating 18 shaft was used and one threaded member was used ~or rotating the 19 shaft and a torque transfer nut was attached to the shaft for 20 rotating the inertia element.
21 Another advantage of the arrangement of Fig, 10 is that the 22 reciprocating stru-t components are of relativel~ large ~i~meter 23 throughout the length of the strut. This enables the strut to withstand lateral forces more effectively than can a strut of 25 smaller diameter. Yet the overall size of the s-tructure is not 26 prohibitive in terms of installation problems in that the radial 27 thickness of the t~bular members forming the strut is not large 2~ relative to the overall diameter of the strut.

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Claims (35)

WHAT IS CLAIMED IS:

1. A motion snubbing device compressing:
a pair of members mounted for relative movement;
a pair of inertia elements mounted to be freely rotated;
means connecting said members to said elements so that relative movement of said members in one direction will drive one of said inertia elements, and relative movement of said members in an opposite direction will drive the other inertia element; and means connecting said inertia elements in a manner such that rotating either of the elements below a predetermined motion threshold causes such element rotate the other inertia element, and attempting to rotate said other inertia element above said threshold initiates braking action on said elements and said members which limits motion to said threshold.

2. The device of Claim 1 including a housing surrounding said inertia elements; and wherein said elements are mounted in axial alignment, with an end of one element facing an end of the other element; and said element connecting means comprises a coil spring surrounding a portion of said elements adjacent said housing with the spring being arranged to transmit torque between the elements, the inertia of the spring driven element causing it to lag and increase the spring diameter so that it engages said housing to produce said braking action.

3. The device of Claim 1 wherein said inertia elements are mounted on one of said members.

4. The device of Claim 1 wherein said members are telescoping strut members and said means connecting said members to said elements includes means for translating the relative axial movement of said strut members into rotation of said inertia elements.

5. The device of Claim 4 includes an axially fixed shaft rotatably mounted on one of said strut members and said inertia elements are axially fixed and are ring shaped and surround said shaft.

6. The device of Claim 1 including a shaft rotatably mounted on one of said members and wherein said inertia elements are ring-shaped and surround said shaft, further including means fixed to said shaft and positioned within said inertia elements for selectively driving the other of said inertia elements including axially extending outwardly facing ribs which fit within axially extending slots on said inertia elements, said ribs drivingly engaging the edges of said slots on one of said inertia elements when said shaft is rotated in one direction and the edges of said slots on the other of said inertia elements being engaged by said ribs when the shaft is rotated in the opposite direction, said means connecting said inertia elements positioning said inertia elements so that said ribs are oriented so that only one inertia element at a time is directly driven by said torque transfer member.

7. The device of Claim 1 wherein the means connecting said members to said elements includes a rotatably mounted shaft which is rotated in either direction by relative movement of said members;
said inertia elements are annularly shaped and surround said shaft; and including means mounted on said shaft cooperating with means on the interior of said inertia elements for driving one of the inertia elements when the shaft is rotated in one direction and driving the other one of said elements when the shaft is rotated in the opposite direction.

8. The device of Claim 7 wherein said inertia elements are identical in shape but are positioned in opposing relation surrounding said shaft; and wherein said means connecting said inertia elements angularly orients said elements so that only one of the elements is directly driven by the means on said shaft when the shaft is rotated in one direction and only the other inertia element is directly rotated when the shaft is rotated in the other direction.

9. The device of Claim 1 wherein said members are a pair of strut members mounted for telescopic movement on each other;
said means for connecting said members to said elements includes a shaft rotatably mounted on one of said strut members and means to convert axial movement of said strut members into rotation of said shaft, said inertia elements being rotatably mounted on said one strut member adjacent said shaft, and said means for connecting said members-to said elements further includes means mounted on said shaft cooperating with said inertia elements for rotating the inertia elements; and said means interconnecting said inertia elements includes means for angularly orienting the inertia elements so that rotation of the shaft in one direction drives one element and rotation of the shaft in the opposite direction drives the other element.

10. The device of Claim 1 wherein said means for interconnecting said members to said inertia elements includes housing with a drive shaft mounted therein, the ends of said shaft being threaded and said members having threaded portions which mate with the threads on said shaft, the threads on said shaft and said threaded portions being arranged so that with one member threaded to one end of the shaft and the other member threaded to the other end of said shaft, relative movement of said members toward each other or away from each other produces rotation of said shaft, and means on said shaft for rotating said inertia members.

11. The device of Claim 10 wherein said inertia members are annularly shaped and surround said shaft.

12. The device of Claim 11 wherein said means interconnecting said inertia elements includes a coil spring surrounding the mating portions of said inertia elements, one end of the coil spring being connected to drive or be driven by one of the inertia elements while the other end of the spring is connected to drive or be driven by the other of said elements.

13. The device of Claim 10 including guide means extending outwardly from the opposite ends of said housing and slidably received in said members with one member on one end of the housing and the other member on the other end of the housing, said members being movable on the housing toward and away from each other, while being prevented from rotating.

14. A motion snubbing device comprising:
a pair of members mounted for relative movement with respect to each other;
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, said acceleration sensitive means including a pair of rotatably mounted inertia members and means responsive to said relative movement in one direction for rotating one of said inertia elements and responsive to said relative movement in the opposite direction for rotating the other one of said elements, means interconnecting said inertia elements in a manner such that rotation of the element being driven by said relative movement will further rotate the other one of said elements so long as the rotational acceleration is below said threshold, and attempted acceleration above said threshold will cause the inertia element driven by the other inertia elements to lag because of its inertia, and means responsive to said lagging movement prevent acceleration beyond said threshold.

15. The device of Claim 14 including a housing connected to one of said members, said inertia elements being annularly shaped and being rotatably mounted within said housing with the periphery of the inertia elements being closely spaced from the interior wall of the housing, said means interconnecting said inertia elements comprises a coil spring surrounding said inertia elements and being closely spaced from said housing, said coil spring being arranged with respect to said inertia members in a manner such that said lagging movement causes the coils of said spring to increase their diameter and engage the interior of said housing to provide said braking action which limits the acceleration.

16. A motion snubbing device comprising:
a pair of telescoping strut members, each of the strut members having means for attachment to structures whose relative movement is to be snubbed;
a cylindrical housing attached to one of said members and having a tubular portion extending outwardly therefrom toward the other member;
a shaft rotatably mounted in said housing with a portion of the shaft extending out of the housing through said tubular portion, said shaft portion having high-lead threads formed on its exterior, the other of said strut members having a tubular portion which is slidably received within the tubular portion on said one member and surrounds said shaft portion, threaded means formed on said last mentioned tubular portion for cooperating with the threads on said shaft so that axial movement of said strut members rotates said shaft;
a pair of inertia elements rotatably mounted in said housing, said inertia elements being ring-shaped and surrounding a portion of said shaft within said housing, said inertia element being similar in shape and being axially aligned in face to face opposed relation, each of said elements having an annular recess on its outer cylindrical surface adjacent the ends of the inertia elements which are in face to face relation; and a coil spring positioned in said recess and surrounding said inertia elements, the spring being closely spaced from the surrounding housing, said coil spring being arranged such that rotation of one inertia element rotates the spring and transmits torque to the other inertia element, said spring being closely positioned to said housing so that when the acceleration of the inertia element to lag and introduce an unwinding force on said threshold, the inertia of the element will cause the element to lag and introduce and unwinding force on said spring causing it to expand and engage a surrounding surface on said housing, thus produce a braking action which limits the movement of said strut members to a predetermined threshold acceleration.

17. A mechanical shock arrestor comprising:
a housing having a cylindrical wall and a pair of end walls;
a pair of spaced guide-pins mounted in each of said end walls and extending axially, outwardly, parallel to the axis of said cylindrical wall;
a pair of members connected to said end plates for mounting the shock arrestor to structure whose shocks are to be arrested;
guide means on said mounting members and on said plates for slidably mounting the member axial movement with respect to said housing while preventing rotation of said members, each of said mounting members further including tubular portions which extend through said end plates and into said housing;
a drive shaft axially positioned within said cylindrical housing wall having threads formed on opposite ends of the shaft which threadably connected to said tubular portions, the thread connection being arranged so that when said members are moved toward each other, both members transmit torque to the shaft in the same direction and when said members are moved away from each other, torque is transmitted to the shaft in the opposite direction;
a pair of annularly shaped inertia members positioned within said housing surrounding said shaft, the inertia elements being mounted for free rotation while being axially fixed, said inertia elements being closely spaced from each other with the end face of one inertia element opposing the end face of the other element; and a coil spring surrounding the portion of said inertia elements adjacent the opposing end faces of the elements, the ends of said springs being arranged to respectively engage a shoulder on each of said elements so that rotation of either element in one direction will drive the other element in the same direction through the means of said spring, the exterior of said coil spring being closely positioned adjacent the interior cylindrical surface of said housing;
and means on the exterior of the central portion of said shaft and means on the inertia elements surrounding said shaft central portion for selectively engaging and driving only one of said element when the shaft is rotated in one direction and selectively engaging and driving the other of said elements when the shaft is rotated in the opposite direction.

18. In an nuclear power generating plant, the combination comprising:
a plurality of fuel rod support tubes vertically oriented in closely spaced parallel relation; and an axially short mechanical shock arrestor connected to and extending between two of said tubes that are positioned adjacent to each other, said arrestor including an axially short housing having a tubular side wall and a pair of end plates, a pair of attachment members adapted to be connected to said pair of tubes, said members being respectively slidably mounted on one of said end plates to permit some horizontal movement of said members toward each other, a shaft positioned within said housing with one end of the shaft being threaded onto one attachment member and the other end of the shaft being threaded onto the other attachment member, the threads on said shaft and on said attachment members being arranged such that when a force urging said pair of tubes together is applied on said arrestor, the threaded connection between the attachment members and the shaft will rotate the shaft in one direction and when a force urging said pair of tubes apart is applied to the arrestor, the connecting members will rotate the shaft in the opposite direction, and means positioned in said housing and driven by said shaft for limiting the relative movement of the tubes to a predetermined threshold.

19. The combination of Claim 18 wherein said limiting means includes an inertia element rotatably mounted in said housing and arranged to respond to the acceleration at said threshold to initiate a braking action to prevent acceleration beyond said threshold.

20. The combination of Claim 18 wherein said limiting means includes a pair of axially short somewhat disc-shaped inertia members surrounding said shaft within said housing, the end of one inertia member being positioned in face to face relation with the end of the other inertia element, a coil spring surrounding said inertia elements adjacent the ends that are in face-to-face relation, the ends of the coil spring being arranged to transmit torque between said inertia elements, the exterior of said coil spring being closely space from surrounding cylindrical wall of the housing so that when a force is applied to the spring, causing its coils to increase in diameter, the coils will brake against said wall.

21. The combination of Claim 20 wherein the outer ends of said inertia elements are formed with a bearing surface which slidably engages the end plates of said housing to position the inertia elements both axially and rotatably.

22. The combination of Claim 20 wherein each of said inertia elements is formed with an outwardly extending annular collar and said end plates are each formed with a socket on their inner wall for slidably receiving the collar on said inertia element.

23. An acceleration sensing motion snubbing mechanism comprising:
a pair of inertia elements mounted for free rotation;
means resiliently interconnecting said inertia elements in a manner such that rotation of either element will produce rotation in the other element although with a predetermined acceleration the rotation of the driven element will lag that of the driving element because of the resilient connection;
means for either driving one of said elements in one direction or driving the other of said elements in the opposite direction; and means responsive to the lagging movement of the element driven through said resilient connections for limiting the acceleration of said elements.

24. A motion snubbing device comprising:
first and second strut members mounted for relative movement;
a pair of inertia elements rotatably mounted on said first strut member;
a threaded shaft fixed to said second strut member;
a nut mounted on said shaft to be rotated by the shaft when the shaft is moved axially relative to said nut;
means connecting said nut to said elements so that relative movement of said members in one direction will drive one of said inertia elements, and relative movement of said members in an opposite direction will drive the other inertia element; and means connecting said inertia elements in a manner such that rotating either of the elements below a predetermined motion threshold causes such element to rotate the other inertia element, and attempting to rotate said other inertia element above said threshold initiates braking action on said elements and said members which limits motion to said threshold.

25. The device of claim 24 wherein said inertia elements have means for axially restraining said nut.

26. The device of claim 24 wherein said inertia elements include tubular portions which are axially aligned in end to end relation with each of said portions having an annular, inner shoulder forming an annular recess in which said nut is positioned so that axial loads applied to said shaft are transmitted through said nut and into one or the other of said inertia elements depending on whether the strut is in tension or compression and the inertia element engaged by the nut is frictionally rotated by the nut through the interengaging axial surfaces.

27. The device of claim 26 including a set of ball bearings mounting each of said inertia elements on said first strut member arranged to receive the axial load on said strut members as well as the radial load of the rotation of said inertia elements.

28. The device of claim 27 wherein said first strut member includes a pair of spaced end plates each having a tubular bearing support with one of said ball bearing sets being mounted on the exterior of each of said bearing supports, and with each of said inertia elements surrounding a respective one of said bearing supports, and said first strut member further includes a tubular housing surrounding said inertia elements and fixed to said end plates, and wherein said shaft extends through one of said end plates.

29. The device of claim 28 wherein said second strut member includes an end plate to which said shaft is fixed, and a tubular casing attached to said second strut end plate and surrounding said housing of said first strut member.

30. A motion snubbing device comprising:
a first strut member including a tubular support housing and an end plate attached to each end of said housing, and a tubular bearing support attached to each end plate which extends into said housing toward the other of said bearing supports, the housing being spaced from the bearing supports to define an annular space;
a second strut member including an end plate and a tubular casing attached to said end and slidably mounted on said housing, a threaded shaft attached to said end plate of said second strut member and extending through one of the end plates on said first strut member and through said bearing supports, means on the end plate through which the shaft extends for supporting said shaft for axial movement while cooperating with the shaft to prevent rotation of the shaft;
a pair of tubular inertia elements positioned within said housing annular space in end to end relation, bearing means rotatably mounting each of said elements on a respective one of said bearing supports;
means for translating axial movement of said shaft relative to said first strut member into rotation of one of said inertia members; and means connecting said inertia elements in a manner such that rotating one of said elements in one direction causes such element to rotate the other of said inertia elements below a predetermined motion threshold, and attempting to rotate either of said elements above said threshold initiates braking action on said inertia elements and said strut members.

31. The device of claim 30 wherein the means connecting said inertia elements comprises a coil spring surrounding the inertia elements adjacent the inner wall of said housing, said inertia elements and said spring being arranged such that attempting to rotate an inertia element above said threshold will cause the spring diameter to increase and frictionally engage the wall of the surrounding housing to produce said braking action.

32. The device of claim 30 wherein said translating means comprises a nut mounted on said shaft and axially restrained by said inertia elements to axially engage and rotate one or the other of said inertia elements depending upon whether the strut is under compression or tension.

33. A motion snubbing device comprising:
first and second strut members mounted for relative movement;
a pair of inertia elements rotatably mounted on said first strut member in axially spaced relation;
load transfer means captured between said inertia elements axially engaged by one of said inertia elements while the other element is free to rotate relative to said load transfer means;
means for transmitting the axial load on said strut members through said load transfer means and for translating some of the axial load into rotation of said load transfer means and rotation of the inertia element axially engaged by said load transfer means; and means connecting said inertia elements in a manner such that rotating either of the elements below a predetermined motion threshold causes such element to rotate the other inertia element, and attempting to rotate the other inertia element, and attempting to rotate said other inertia element above said threshold initiates braking action on said elements and said members which limits motion to said threshold.

34. The device of claim 33 wherein said load transfer means includes a nut axially captured between said inertia elements, and said transmitting and translating means includes a shaft on which said nut is mounted, said shaft being connected to receive the axial load on said strut and to cause rotation of said nut.

35. The device of claim 33 wherein said inertia elements are tubular elements axially aligned in end to end relation, and said load transfer means includes an internally threaded nut which is axially captured between axially opposing faces of said elements.