Note: Descriptions are shown in the official language in which they were submitted.
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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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31
~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.
31
4r~32~ ~ 2
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108~)'75~
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
27
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~
~2 ~ 3 -
iO~3'75~ ~
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;
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l ~ig. 9 is a schematic perspective view illustratiny the 5~ru-~
3ll
32
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~ 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
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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.
2~
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-
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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~
22
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
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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~
32
;~ 8 )7~
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~
29i.,
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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~
11 1
:~ ~ 3~, - 12 ~ ~
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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
31 i
321' , 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
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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
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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
32
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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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