Note: Descriptions are shown in the official language in which they were submitted.
'J7 I~S Ll:~2 F.-'~ SllS i71 SOdl ~IU'~ES.~ILLl.~15 ET .~L ~1002
- 02 1 99 33 5
SPRING TRIP S~IANK ASSEMBL~f E~AVIN~ QTJICK-DROP~ING
1~-O7JT FORCE ~'51D ~IPROVE~ RESETTING ABILITY
TEC]~NICAL F~ELD
This irlvention rolates to ~ ,, ! ~ ' ' "~...., ' I~, tillage tools a d, morc
particularly, to tillage shank as~ blics of the spdng trip type which hold a tillage
sht~ or other tool in the grcur d with a rslatively high tri~out force but which relea6e
thc tool to prevent dan~gs when an obstacle is ~'.."A~ t~f~, thercaflter '( ' ~Iy
res ttmg the tool to its wcrking po6ition after cloanng tùe obstacle.
B~CKGRGU~I)
Spring cushion 6b~nk ssst~nblies hold the shanl i~ the ground with a yieldable
spring for.,e so that the shank can relicve~ itself by swingillg up out of the workin~
position in tho event that a hard obstruction is x' Ho veverl in nuny sprmg
cushic,n assemblies, ~e restcring forco of the spring agaiDst tbe tool prcg~
ineroase6 ~c the tool swmgs up, thu6 making it moro di~icult for the sbaDk to clear the
obstacle at the very tune it is needed the most. If the restoring force is set loweT, the
spriD g rnay yield too easily and not be able to keep the shank from bourcin~ as h i9
dragged through thc soil.
Spdrg tnp assemblies, on tbc oth~ hand, are desi~,ued IO hold tho shank ir.
plaoe with a relative!y high trip-out forco, which then drops offquickly once trip-out
n occurred. The îorce required to mako tbe shtnk trip-out is set at a much highcr
levcl than the dT3lft force experienced by the shank in Dormal working conditions. Thus,
the shank remsins firmly in the soil withcut bouncirg. Howevcr, if an obstacle is
~, a ~ , the unyielding resistance of the obstaclo causes tho trip-oul force îo be
reacbed ' ~ ~, whereupon the 9bank i5 raisct oy the obsttcle at a lower trip force
to tho extont necesssry to clear thc obstacle. 0noe the obstaclo has been passed, the
sloreo energy in the stretched or compre4sed sprtn~s resets the shsnk in its workin~
pcsititln.
rhus~ in a sprirl~ trip assernbly the shank actually becQrnes eeSicr to raise afh,r
its inhial high trip-out force has beon exceeded. This is very desirable, since it helps
assure tbtt tbere will nct bo too much spring fotce to prevent tho shenk from risin~ up
03~0~/a7 I~l 11:43 F.~I 81~ ~74 aos7 ~lol~Y.l;lLLl.~lS ET aL 0003
0 2 1 9 9 3 3 5
;md uver the obstraction to the full extent necessary ss the machine contirlues to move
forwardly
In tbe past, a vsnety of li~ksges, latohes snd geotnetries have been used for tnis
purpose, includiug the arrsagement disclosed in e~ired US Patent 3529,673 which is
S own~d by the assignee of ~he pr sent invention. While the spring trip mcchanism of
that patcnt does an exccllent job of providi~g a qrack-dropping trip force, rn some
cond itions tne restonDg foree of the spring for pushirlg the shaT lc baok dowr, into the
grouad raay fall below thst necesssry to positively snd rehsbly accornplish thst job.
Thus, otlce tripped, thc shs k tnay not quite fully r~et.
SUMMARY OF THE PR~SENT INVENIION
Accordingly, one iraportant object of The present inv-ation is to provido a spring
lS trip tillsge ~ool assembly, psrticularly but nat exelusively for chisol sharks, whioh is
eapahlG of a relative h gh trip-out force SD as to keep the shsnlc steady and 'lockod
do~" d~ing mos~ field operations, y-t which c,m t~ip4ut quacXly snd oesily when an
obstrwtion i6 sbruptly ', and which hss the abiliy to rcliably snt
depentsbly reset the shanX fully into the working position ~er the obstruction has been
cleared.
Another importent object of the present mvbntion is to provide a way of
combining the best at~ibutcs of spring cushion assemblies with those of spring trip
assenmblies in a single new unit. while rarnimizing thc ne~ative ' of each.
A further irnportaat object of the present invention is to provide a rpring tripshaT.~ s$sembly ~vhjch irnprovcs u,oon the principles disclosed in prior US ~alent
3,$29,673 imcluding, for example, rotairling the quick-dropping tri~out force feature
of th~ patellted design whih~ makilg more restoratiOn force aYailable for pushing the
shank bsck down into the soil as it returns to its worki~lg position. It is also irnportant
to provido a rnore compact assembly which can be rclatively quickly and easily
installed or removed ftom the machiDe, a longer wearing product requiring less
~i - and repair, a more efficient use of spring force permitting a lighter duty
spnng to accomplish the sarr.e job, a design which will acce,ot and i5 compatible with
stand;rd industry chjsel shanks, and a dwign which permits the removal and
rc~,la~.c~l. of the skat~k and/or sprin~ unit ' ' " withol~t dismantlin~ the
entire assembly from the tool bar of the machirl-.
-2-
os~s8/9s 1~ Ll:~S FA~ 81S 47~ s7 I~OS~ LLl.~S ET .~L 1~1004
02 199 335
The foregorag arld othcr rn~portant objects of the present iDveDtion arr carriedout througn tbe provisiorl of a shatik asscmbly which makts QSC of efficient le-wr
meohaDism a~ranOod in combulation witb a double-actrn~ spriDg unit m which botb
cnds of the spring are ach~tod - ' '~ by thc shank as it rises to pass over an
S obsttuction. The geometry of the lever mechar~ism causes the me~hanical advantage
of the spring OD the shaDk to dccrease rapidly as the shatlk s~vings up, thus causing thc
trip force to . . ' _'~ drop off r{uiclsly oncs the shenk has tripped out. However,
because the amouttt of poteDti l energy stored up in the spring iDcreasea rapidly as both
ends of the spting are actuatet '~, thc trip force does not drop down as far
as it otherwise would. C~ , the atrlOUDt of rcstoratioD force available to
retum the shank into the grou~ is s',~ , highcr tharl would other~vise be true.
The g eometry of ~o vatiouS parts and the particular len~ths of various mom~at arms
~ld levers ean bc selected to achieve a return Ol scatol~t;u l force that never drops below
the levcl typically required to completely remsert thc potnt of the chisel shs~k back
] S dowD into thc soil and to pusb it into the working position against the resistancc of the
soil.
The gevmctrf of tho parts of thc csembly is such that thc shanlc can achieve a
substantial tnp heigbt without causing othet parts of the asse~r.bly to move through
extensive ram7es of motion. thus reducing wear aDd prolonging the uscful life of the
assen Ibly. The asserably is arranged in A relatively upright orientatloD~ having as its
ptimary supportiDg eornponeDt a bracket or housiDg th~t mounts to the baclcside of the
tool bar or tubolar beam ofthe machine. A block-like shank holder is pivott d to the
lowcr end of thc bracket while a rocker lever is pivoted to the upper end of thc brackct.
A coiie~, helical cn~nr~tCci~n sptiDO uuit is çaptured betwe~ the shank holder and the
inDer end ofthe tocker leverl while a ~ - " r.~ ~11 lirlk is captoreLt betwcten the holder
and the opposite end of the rocker lever. Consc~ucntly, as ~e shar k holder is raised
after trippi,ag out, the compression lirlk pushes up aga.nst tbe outer cnd of the rocker
lever which, in turn, oornp~ses ~c s.oriDg v~th the inner end ofthe lever, Because the
momcnt arm increases for the V~ 7 ' "~ link as the sbalLk f~ swings
upwardly, and tbe moment arms for the spring ~.o".~rd,~_'r decreasc, ~he spring
bccon~es ~l o~ .ly casier and easier to cornpress, asSurir.g that the shank will slip
over the enoountered obstmction. At the rame time, the rapid loading up of the spring
by actuatmg it *o~ both eads ~ " preferably in c~- ~"~ ' - ., prevents the
trip force from droppi~g too low, which results in rnore available retwn force.
OSOU, 97 1}1~ 4 FA:~ 81~ s7~ 905'i ~IOS'E~ .WILLI.UI9 ET 51 0005
0 2 1 9 9 3 ~ 5
Thc spring nnlt is ~csi~ed to be a self-contairled subassembly ~hich can be
readily remv~ed ~m tho mounti~g bracket ~itb or u~thout first removing the ~rsc~et
from tb~ tool bar. LL1~e vise, the ~a~ o., hnk hss ccncave retaining saddles at its
opposite ends instead of closed cyelcts for the CU.~ v~i ng pivot sh4fts of the
S assemblies so thst, ~on relea~ng the c , force in the link by ~ghtening dov~n
a bo] t assocjJted with the spnng, tho ~ ~ssion link may be essily ren~.oved without
first rcmovtng any other psrts of the assembly. ~y pulling a cotter pin in the upper
pivol of the rocker leYer, the pivor may be Icmored from the ~rackct to relesse the rest
of th-: YoriCing ~ , , except for tbe sbsnlc holder.
BEUi;,F DESCR~PTION OF TB DRAWINGS
Figure I is a ri~ght frc~t perspective view of A spring trip shank assombly
consiructed ncccordstlcev,iththeprinciplesvf~epresentinvenrionandadaptedto
b~ ;nuunted onto the frame member or tool bar of a tilla~e implemerlt;
Fig, 2 is an exploded, perspe~: ve view of tho shanlc assanbly;
Fig. 3 is a left side elevatiorlal vie~v of the shank assembly mounted on the ~oot
bar with the near side wall of the mounting bracket remc ~ e~ and pslts shown in cross-
section for clarity, the shank being illustrated in its working position;
Fig. 3a is a schematic diagram illustrating the geutne'rical relationsbip of thecomponentS of the assembly in tho Fig. 3 position;
Fig. 4 is a lef~ side elevational vie~Y ofthe s~anlc asstmbiy similar to Fig. 3 but
showing the shank trippe~ out and partially raised;
Fig. 4a is a schematic diagr~ illustrating thc components in the Fig. 4 posiion;Fig. 5 is a fragmc~tary cross-sectional vjew ufthe assembly talcen substantiallyalong linc S-5 of Fig. 3;
Fig. 6 is aTear elevational view oftbe assernbly taken b~ ' "y alonQ sight
line 6-6 of Fig. 3; and
Fig. 7 is a graph of spring trip forcc ver6us tr:.p height for thc shank assembly
of the present invention~ together with a graph of return force versus trip height.
~ETAILED ~ESCRlPTION
3~
03 05,~97 I~l[ ll: l i F~3 815 4. ~ ~057 ~O~ ',WlLL~ S Er .~L lzluo~
02199 33 5
Altho~gh the invention as hereinafter descnbed is embodied in a chi5el shanlc
assa ~bly, it rnay be ' . ' i~to other types of tillage tool assclnblies as well.
The shar~ assembly 10 nfthe pre5ent ~verltion, as shown particularly in Figs.
I amt 2, includes all elongated, normally generally uplight, slightly reatwardly inc~ined
housing or mounting bracket 12, havit~ an upper end 14, a lower end 16, a front 18,
arld a rear 20. Tbe bracket also includes a pair of opposite sid s 22 ant 24 extending
between upper ard lower ends 14,16. The two sides 22 and 24 are defined by a pair
of laterally spaced apatt side plates 26 and 28 that coopetatc to defLne ~n interior space
within which the ,~ - spring and other components o~ thc assembly ~re
housod, aS WLll be desctibed below. The two sides plates 26 and 28 are çotnp'otely open
across the rear 20 of the bracket, as well as across thc upper eDd 14 and the lower cnd
16. rhe front 18, however is partially closod by a front plate 30 that spans the side
plates 26 and 28 from a point somewbat below the upper ond 14 down to almost themidpoint of the bracket. A cross strap 32 sFans the side plates 26 and 28 ' ~ 'ybelow the front plate 30 and is slightly recessed with respect theteto as illustrated bost
rn Figs.2, 3 and 4. The cross strap 32 has a pair of bolt koles 34, (Fig. 2) for receivin3
4VII~ r '' _ mounting bolts 36 used in att~chod dle bracket 12 to a twl bar 38 as
shown in Figs. 3 and 4. T ' ~ below the cross strap 32, the side plates 26 and
28 aro nor~ev ou~ to present a receivir g notch 40 in bracket 12 that; , ' ~'.,,recei~res the bsck side and lower face of the tool bar 38. A se_ond crvoss strap 42
below the notch 40 and spam~ulg the side p]abs 26,28 has a p~ur of bolt
holes 44 for receiving ~ mounting bolts 26, ~he bolts 36 and 46 comprise
parts of stmcture for secu~ing the brscket 12 to the tool bearn 38, the remainder of such
stnwtureincludmgapairofan31edclampingstraps48 and501Oopedoverthefrontand
topsidesofthetoolbar3B,andbolts36,46andnuts52,54(Figs.3and4)forthecross
strsps 32 and 42.
I'he mounting bracket 12 has a pait of axiaTly aligncd pivot ruFport rings 56 and
58 at its lower cnd 16, each of which is inLeo to a r ~ C. one of the side plates,
26,28 in such a roanner as to p~senl a transverse lower pivot axis. ~he t vo ril~gs 56,58
serveasameansforsupportingatrarlsversepivotpin50tha~spallsthetwonngsS6,58
and is held against rotation by a keeper 62 (Fig.2) at onc end thereof. The keepa 62
usesaboltandnutassembly64toanchortbepjvotpin60tothepro~nalsidoplate28.
Ibe p;vot pin 60 serves as a mo~ting pivot for a generally block-shaped shank holdes
66 having a pair of axially a]igned sleeves 68 and 70 at its front end provided v ith a
pair of internal, ~~ , plastic busbings 72 and 74 wlu'ch rotatably receive the
u3is3 s7 T~ IA~; 51~ ~7~ 8057 1~OS~ ILLI.4115 ~1 .4L b~oO7
02199 33 5
pivoi pin 60. Thus, the shank holder 66 csn sv~ng up and down rbout the pivot pin 60
relativo to the bracket 12. A generally U-shaped, rigid strap 76 depending from the
bracket 12 is looped under ~te sharik holder 66 and serves as a lower lilnit stop for
d~Yllward swingir g of the holder 66.
The holder 66 is gerterally cha~el shaped alor;g its bottom surface in a fore-
and- aft direction to c , ' "~ reccive and locate z gcnerally C-shapcd chiscl
shank 78. The shank 78 is provided with mountma holcs 80 at its lower end for
attachmentofaruitabletillagetoolsuchrsasweep ~2 ororhorpointshowninFig. 3.
Inordcrtosecuretheupperendofthesharlk78totheholder66,thecentralbodyofthe
1 0 hold~ r 66 has a bolt hole 8J. re~eiving a bolt 86 that also passes thrcugh a hole 88 in thc
upper end cftke shrnk 78. A nut 90 on thc upper end of the bolt 86 is ~ , '- "~
received within a hexagonal upper extremit,Y of the bolt hole 84 to preclude rotation of
the nut 90~ The sharlk 78 is also held in place by a lower transverse strap 92 behtnd the
bolt 86 which clamps the shanlc 78 up against the bottom of the holder 66 rhrough the
use of 1 pair of bolt assemblies 94.
Atthcupperend 140fthebracketi2,arockerlever96isswmgablyrrounted
betw~en the two sido plates 2c, and 28. An upper transverse piVQt 98 spans the side
platea Z6 and Z8 at this location to seive as a pivot for the rocker le~er 96. The pivot
98 is removably retained within thc side plates by a cotter pin 97. The rocker lever 96
iscomprisedofapairoflaterallyspacedapart,bellcrankshapedplatcslOOandlO2
that Pre secu~d together along ~eir lower extrernity by a cross pin 104. A pair of
axially aligned sleeves 106 and 108 are fixed to respective ones ofthe plates 100,102
at thLir upper apexos, each of wbich rece.ves a plastic bushing 110 that rotatably
receives the pivot 98. A keeper 112 on one end of the p;vot pin 98 prevents the later
from rotating during swinging of the rocker lever 96 about the pivot 98.
As noted in Figs. 3 and 4, for example, the rocker lever 96 is generally inversely
L-shaped, presenting one cnd defined by a short leg 114 that projects generally into the
interior of the brackct 12, aud an opposite end def~ned by a long~ leg 116 projecting
genaally outwardly away fiom the intetior of the bracket 12. The inn~ end of therockes lever 96 as defined by the leg 114 calries a pair of axially tligned, cylindrical
tips 118 and 1'~0 (~ig. 2) on respective ones of the plates 100,102, while the opposite
cndoftherockerleverg6aspresentedbytheleg 116carriesthecrosspin 104,1ikevwise
defini~g a cylindrical tip.
The mounting bracket 12, ~he shank holder 66, thc rocker lever 96 and the
attaching structure 55 co]lectively define ~vhat may be collectively described as a
03~0s,a7 TilO' 11:45 F.~3 815 474 û067 II~ ~Y.S'lLLï.~gS ET .~L l~boo8
02199 33 5
mouating bracket - ' ' 'y. The shaDk 78 and its sweep 82 or otber tool may be
considered a sh~k ' ' '" ~.' ' can be attached to or coupled with the mormting
bracket ' ' ~y ViA the shar,k holder 66. Although tbe rocXer lever 96 has becn
descJibedascoalprisin~partofthemountiogbraclcet ' 'l~,it~illbcnotedthat
S tbe r~xker lever 96 is detachable from the bracket 12 by simply pulling the cotter pir
97 and relessi~g the keeper 112
The shank assembly 1~ also tncludes a sprLng suba6sernbly compnsed by s
rnn gn~c~irm s~ing unit 122 located betweerl t~e sbar~ holder 66 and the inner end of
tbe nlcker leveT 96. The spring unit 122 irlcludes a pair of axially spaced spart end caps
124rndl26atoppo5tcerldsofahelical- . spmlgl28(ifdesiredasccond,
disposed, smalleT diameter, inner: tl spring 128a may be used
to in~ease the stren~th of tbe s7pring unit as shown in Fig. 2). A ~eusion bolt mesnber
130 ~'y disposed within the 5p~iDg 128 is telescoped loosely throu~ the
upper end cap 124 and is secured ~qa threads into an upstanding, cylindrical sprirlg
IS guidt 132fixedtotheiowerendc~pl26. Theoolt130ha Imerllargedhead134atits
upper end which is disposed on the upper side of the erld cap 124 so that when the bolt
130 is threaded down into the Sprin~ guide 132, the upper er.d csp 124 is drawn
downwardly toward the lower end cnp 126 to adjustably compress and preload the
sprirl~ 128. On the other hand, the upper end cap 124 is fr~ to slide axially up and
down along the bolt 130 when a cormpressive force i5 applicd to the upper end cap 124.
The upper end cap 124 has a concave, upwnrdly f~cing saddle 136 thst
cun.~.,' ' ty and pivotally receives tbe r,~nvex tip of the iDner end of tbe rocker
lever 96 defined by the two cylindrical tips 118 and 120. Tbe saddle 136 is rnore
particularlytefinedbyapairofzlignod,arcuatedepressionsl3Bandl40~ig.2)on
opposite sides of a cent~aL generally triangular boss 142 on the upper end cap 124. llle
two cylindrical tips 118.120 tbus straddle the boss 142, and the bolt 130 passesupwardly through thc boss 142 witb a be~d 134 at the uppen~ost extremity of the boss
142. rbealignedtipsll8arldl20defneaupperspringpivotforthespringl28and
serve to operably conr ecl the spring 128 with tbe lever 96.
On tbe otber hand. the lower end cap 126 has a geDerally C-shaped, downwardly
faculg saddle 144 that is ~ teceived on a cross pin 146 supportcd bchveal
a pnir of laterally spaced zpart, upstanding cradles 148 ~md î 50 on tbe top side of the
sharLl~ holder 66. A stabilizer kcy 152 ~Fig 2) fixed to the undersidc of tbe CroSs pin
146 is received wi~in a roati~g groove 154 ~ the top surfacc of thc holdcr 66 behveen
the cradles 148 and 150 to preclude rotation of the cross pin 146 and prevent axislly
~7
05~0~7 TH[ 11:45 F.~ 81d 47~ 9057 E;O~ Y.I~ILLI.~'IS E:T aL ~boos
0 2 1 9 9 ~ ~ 5
shifiinethereof I~ecrosspin146definesalowersprin~pi~otforthespnng128and
serves to operably i ,1~ n ,~ the spnng 128 and the holder 66
Due to the open-ended nature of the saddle5 136 and 144 at OppoSite ends oi'the
sprLn7 unit 122, the spring unit 122 is removzbly captured behyeen the rocker lever 96
S on the one b~d and tbe sha~k holder 66 on the other hand As long as the cylindt ic /~
nps]l8,1200fthctockalcYer96aremaintamedwithinthedepres5ionsl38,1400fthc
up,oer cnd czp 124 and thc cross pin 146 of thc shank holdcr 66 is maintaincd within the
saddlel440fthelowerendcap 126,thespringunitl22aillrer~ninplsce~Yithtnthe
shz;ll; assembly 10 HoweYer, if the rocker Icver 96 is unseated frcr,rn the uppor end cap
124, the entire spring untt 122 may be lifted off the shank holda 66 and out of the
brac~et 12
The shanlc assembly 10 further include5 a ~ Oll lillk me~nber 156
betw3en the outer cnd oftbe rocker bver 96 r~d the shank holder 66 in the form of a
pairoflinkslS8andl60~ Ihetvolinlcsl58andl60are ' , ~'byacrossbolt
162 ~Fig ~, while a tubular spacer 164 ~ia 2) cncirclcs the cross bolt 162 and is
disposedbetveenthelinks 158,160tomatntsintheirseparationandprovidestructursl
integritytothe~, ~ss.onmemberl56 Theupperendofthelinkl58hasaconcave
saddle 166thatrotat~1yreceivestbeproximalendofthecrosspivot 104Oftherocker
lever 96, while the lower end of the 1i~ 158 has a concavo seddle l 68 that re9ts upon
and rotatzbly receives the cv~ end of the cross pivot l 46 zssociated with the
shanl; holder 66 The other link 160 has similar upper and lawor s~ddlcs 1 70 and 172
rcspcctivcly
As a ~ of this construction of the ~ - - n~ member 156 it wi11
be seen that the member 156 comprises another rernovable au~ ..bl.y ofthe shanlcassembly 10. As long as the cross pi~ot 104 of rocker lever 96 is sested within the
uppersadd1cs 166,170Ofthe. . ' member156andthelowercrosspivotl46
is seated within the lower saddles 168 ard 172 ofthe i , ' member 156, the
;VII member 156 will remain in place bctween the rocl~er lever 96 snd the
shanl; holder 66. However, due to the open ended nature of the saddles of the
OO.III~.G~;OII memb~ 156, thc member is ea5ily removed frorn the assembly when
compressiYc loading is removod from its opposite 0ds, such as by tightening down the
draw bolt 130 to such an extent that the 1, ' spring 128 no longer exerts an
upwzrd force against tho rockor lever 96 when the shank 78 is in its lowered wo~king
position against the stop 76 as in Fig 3
05;013~37 TIIG Ll:~5 Fsl 8tL1 17~ ~os7 IlO~ liLI.~Yj ET dL ~010
0 2 1 9 9 3 3 5
OPER~TION
Refemng particularly to Figs. 3 aDd 4, it v~ill be seerL that when the sb~lc
t~nbly l 0 is placed iD USO, the, . spring 128 pushes the shaLk holdet 66
S ~L .. _JI~ about pivot 60 to the extent permiffed by the stop 76. tn this respect, tho
lower end of the spri~g 128 pushcs dowmvardly through the lower eDd cap 126 a~t~nst
t~v lowa srmin~ piYot 144 ~hile the u,oper e~LLt of the spring 128 pushes upwatdly
thtoughtheupperendcap 124agairLstthcuppLrsFnDgpivotderLnedbytips 118,!2Q,
w~Lich in tum exctts downward fott e against the lowet spnng p jvot 146 via tho roc;cet
levet96andthc; . ~ lillklsvO. TheshatlkholdL,r66,theenmrr~sc~nlinkl56,
and ~he tocket bYer 96 thus broadly sorve as ap,orratlLs operably i..t~..w._~c.~ g thc
sptin~ 12? and the shank 78.
If the point 82 hits ID obsttuction 174 (Pi~. 3) and the rcsistance of the
obstnLctionl74ishigherLou~htot~ip-oi-Ltthesharlk78,sha~k78 vills~yir~guFwt~dly
in a . 1 '~ d~;tion about thc shank pivot 60 to the L~aent necesst~ty to clear
theobsttuction,sndwillthenrvsetitselfhackdownintheworkingpositiorlofFig. 3.
In tbo process, the two end CApS 124 ~.d 126 compress the spring 128 from opposite
oirectior~s to auickly store up potential energy within ~he spring, which is then exerted
against tbe shank 78 as it is rL~ned to its workirLg position.
In tho workihg poL;ition of Fig. 3, the spring 128 is under ~ -tl ~ The
arnol~t of ~ . detennLncs ~e trip-out forcc for the shank 78 snd ct~n bc varied
by sclecting different spring resistances and dimensions for Tl2e rocker lever 96 and
Cv~ link 156. Prefer~bly, Lhe tlip-out forcc IS establi5hed at a rc!stirely highlcvel compared to t~Le typical draft force exened by thc ground OD the sh~c 78 so that
in nonrLal conditio~s the s~ank vrill stay down in it~ workin~ position
As shc wn ih Fi~. 3A, wherL tbe shank 78 is in its workin,g position Ihe momeDt
artr~oftheiirLeofactionofthespnngactirLgtlhroughpirotl46hasaleng~L"X':whilc
the moment arm o~ the line of sction of the sprir,g actin~ throagh the rocker lever pivot
98 has a length "~'. Additionally, the a nount of "o~set" of the lever pivot 104 to an
irna~na y liDe g the lowcr spr~lg pivot 146 and rhe uppcr lever pivot 98
has a value "Z".
As the shank 78 is tripped-out, the offset of the outcr lev~ pivu; 104 i~crcasesrapidly to an amount '-ZI ", whilc the moment a~ns X and ~ both decre2~ce to the values
"Xl " and "Yl ". Iherefore, although potential ener~y is being stored up in the sprin3
128 at this tirne, thc mcchaDical advantage of the spri~7g over the ~hanlc decreases
03, 05, ~7 TN~ FA~ SlS i71 3us7 iiO-EY,WlLLl.USS ~1' AL 12loll
0 2 1 9 9 3 3 5
L~ul..L~,~lly so that tsle net effect is to decrease the trip force required to move the
shank upwardly, once the initial trip-out level has been reached. Thi5 is ilh:strated in
F;QV 1 by Ule descending curve 1?6, which is a plot of the trip out force v-rses the
hd ~ht of the shank as it 6wing6 up vardly about the shs~llc pivot 60. Although the
numbers associated with the graph iD ~ig. 7 are for il;ustrative purposes only, it will be
seell tbat the trip-out force is ~l, ~ I} 750 pounds whcn the sharik is fillty down
in Ule worldng poSition at "0" height. However, by the tiole the sharik h~s raised only
I iDch, the amount of force rcquired to swing the sharlk upwardly has dropped to 600
pou~v~. Ihereafter, ~he srip force stays fairly flat, gradually dreppin~ dowr~ to
~1~11 ~ ' '.~,450poundsatalOinchtripheight. Thusjratherthal~thoc,.",~
loaeirlg on the spring msking it harder for the shar k to clesr tt e obstruction. there is
actuasly an immeoiate drop-offof the effective holding force of the spru~g against the
sharX to make it easier for the sharX to s]ip up over the obss le.
It will be noted that, a'sthough the trip force drups offvery quickly, it does not
drop too far. This is due in palt to the fact that althou~h the ~eornetry of thccor~ponents of the t~p assembly cause the mechaDical afsvarltage of the sprrng on the
shar~k to be decreased as the shank swines upwardly, the sprmg 128 is loaded up at a
rapirl rate due to the fact that it i9 being actuated from both ends as U~e shsnk rises. In
prior known spring cur~ion assembliesl only the bottom and of the spring has been
compressed while the upper end rernained statioD~y. In the present i~ -- a~
how- ver, the upper end i5 comprcssed as wel's, reslllting in a rate of ener~ build-up that
is, for example, twicc as fast as in pr:om~ ~ - 6~ - ~ for ~he sasne arnount oftrip hei iht
of th v shank. C~ ~ 'y, althongh the spring, in effect, loses some of its leverage
over the sha;Lk as the shanlc rises, thi5 is offset by the rapid build-up of ener~ within
the sPring 128 to keep thc trip foree from dropping too low.
Thus, after the obstacle has been cleared, there is moro than ample force
available frorn the spring 128 to reset the shank down in its wori~ing position. Evec~
thuugh the soil resists the re-entry of the point 82 down into the ~ruund and forvvard
mov ment 2to the fully rcset posi~ion of Fig. 3, the additional energy stured up within
the spring 128 by virtue of tlle present design can ovorcome such resistance.
The "trip force" as that term is wed hcroin is defined as the arnount of force
requi red at ~y given trip height to make the s~nlc s ving up. The graph in Fi~, 7
shows that trip force, represented by cun e 176, is generally higher at all points of shank
height than return force which is d~oted by the cu~vc 178. This disparity oehveen trip
force aDd ~ fotce arisos from frictiou ~bat exist5 within &e shank assembly. If the
-1~
03~0~97 ~}11.1 11:4d F.~ 81C 171 ~057 aO'~EY.~lLLl.~lS E~ AL lalûl~
02199 33 5
frictbm force v,-ere zero at the pivot points 60, 120, 98, 104 and 146 and other places,
the trip force and the retum force vould substalltially coincide. However, since this is
notdlecsse,thetripforceatallpointsalol~gthecurvel76isthetotaloftheeffective
resistive force off~ed by the Spring 128 plus the resistivc force provided by thc friction
S i~t the joints.
On lhe other hand, the "retuTn force" as that terra is used herein, i5 the forceav~;ihlble at my giYen tdp hd~ht to push the shank bacl~ dow~.t into the ~round. T~us,
the total retum force available at each trip hcight to push down on the shank is thc force
from the spritlg 128 minus dhe resistive drag exerteded by friction in the joints.
C~ y~ aS shovm ia ~ig. 7, the retuTn fiorce represeated by curve 178 rur~s e-elow
the trlp-out force aT every individual ttip h~ight 'exce,ot the 10 inch heigltt which is the
fully Lrippcd positior ~. Since 400 1 ~0 pouads at the 1 inch depth is typically needed
in onler to keep the shank in the ground, it will be seen that there is more than a~nple
return force available in the present inverltion to assure filll resetting of the shank 78
once rhe obstruction has been cleared.
It vrill be noted that the preferred, ' - ' of the shank assembly as
disclosed herein is easy to service in the event that parts need replacing. For example,
the sbarlk itself can rea~ily cbe removed and rcplaced by loosenmg the bol~s 86 and 94.
Thespringunitl2Zcanbereraovedbyfusttighteningdovmthedrawboltl30until
such lime as the spnng 128 loses its . , ~., force in oppositc dircctions against
thelowerpivotl46andtheupperpivotll8,120. Theatherockerlever96isremoved
from Ihe bracket 12 by pulling the cotter pin 97 (Fig. Z~ and ~ ;LI.L_ .. illg the pivot 98.
Once rocker lever 96 is gonc, the self-contsihled spring unit 122 c2Dt simply be lifted off
the holder 66 due to the open saddle 144 at the lower end of the SpriD~ unin
II it i5 dcsired to remove Ihe - , linkl 56 without also removing the
spring unit IZ2 and the rocker lever 96, that can be readily ~~ r' by first
tighte~ingdownonthcdrawboltl30toremove , ~1oadingontheLiDk156.
After removirlg the cross bolt 162, either nr both of the Links 158, 160 may be pulled
out of the assembly.
Thus, there is no need to completely remove the shank assembly 10 from the
tool beam 38 in order to replace thc major working parts of the trip mechanism. In
addition, the spring unit 122 a~d the ~ -r link 156 can be readily removcd
without 9rst removiDg the sbaDk holder 66 and the rocker leva 96~ This greatly
faciLit Ites servicing and T~luces do~n time, whicb is alvvays sîl importallt
in fartning operations.
