Note: Descriptions are shown in the official language in which they were submitted.
130;~144
. E~ 04
MATEFiIAL-~DNTF~oL--~F~Fi~NGE~ME-NT-EuF~ uL-~ OF_~fl_EF~I~L
This invention rel~tes to ~ feed control ~rr~ngentent
for bul~ n)-~teri-~ls, ~nd is especi411y directed to ~rr-~ngen~ents
for in,proving the feeding of rot-~ting Ib~teri-~ls~ such ls
~sph~lt or other m-~teri~ls in ro~d p~vers, wideners, etc.
While the invention will be described with p~rticul~r
reference to such ~pplic~tions, it will be ~pp.~rent th-~t the
concept of the invention, ~s discussed herein, is not so
limited.
In ro~d p~ving equipn,ent of one type, p~ving n,~teri~l
such ~5 l~sphl~lt is fed rel~rwl~rdly on the equipn,ent, for
e~:~n,ple by ~ conveyor ch~in or the li~e, ~s the equipment i5
n,oved forw-~rdly l~long l~ rol~d or rol~d bed, the p~ving n,-~teri-~l
being fed to l~ device for distributing the n,~teriql
tr~nsversely, such l~6 ~n ~uger in the c~se of 1~ p~ving device,
or ~ belt in the c-~se of ro~d widening equipn,ent. The p-~ving
m-xteri-~l is deposited in front of 1 screed, which n,~y be ~
flo-~ting screed, to effect the leveling ~nd con~p~ction of the
n,-lteri-~l. Typic-~l p~ving devices ~re disclosed, fnr ex-~n,ple,
in U.S. F-~tent No. 3,584,547, ll~vin, ~nd typic~l rol~d wideners
~re disclosed, for e~ mple, in U-S- F-~tent No. 3,636,~31,
Il-~vin et al.
1302~44
In order to enl~ble the l-~ying of ~ sn,ooth ro~d surf~ce
by such equipn,ent, it is necess~ry to n,~int,~in control over
the l~n,ount of ml~teril~l deposited l~long the front of the
tr~nsverse feed device, such ~s ~n ~uger. The ~sphl~lt piled
~nd distribu-ted in front of the screed ,~pplies forces to the
screed, c~using the screed to v~ry its level in response to
the ~n,ount of n"~teri,~l distribllted thereto. It is therefore
~pp~rent th~t v~ri~tions in the height of the p~vins n,~teri,~l
in front of the screed results in v,~ri,~tions in the thic~ness
of p~ving n,~teri~ pplied to ,~ road sur~,lce ~nd, hence, in
reduction o4 sn,oothness of the s~lrf-~ce.
This problem h~s been recognized in the p~st, l~nd ~
sollltion thereof i5 sllggested, for e~ mple, in U-S- Fl~tent No-
3,678,817, M~rtenson et l~l, wherein pl~ddles ,~re n,o~nted on the
p,~ving equipment ~d.j~cent e~ch side thereof, the p-~ddles
riding on the surf,~ce of the ~sph~lt ~s it is conveyed to the
ouger- The p~ddles ,~re coupled to ~rn,s of potention,eters,
thereby providing sign-~ls responsive to the height of the
p,~ving n,~teri~l ~t the p,~ddles, ~ function of the feed of
p,~ving m,~teri~l to the screed. This reference discloses th~t
such signl~ls n,-~y be en,ployed to control v~rious feed functions
of the equipn,ent, such ~5 the speed of rot,~tion of the ~uger,
the speed of n,ovement of the conveYor device conveying
13~144 ~ 04
m~teri,~l from .~ hopper to the ~luger, or controlling the ~eight
of ~ g,~te to .~dJust the pern~iss.~ble thic~ness of p.~ving
n~terilll on the conveyor. While~p.~ddle controlled
-potention,eters of this type sin,plified the-~utonl~tic control
of feed of p.~ving n,~teri.~l, to in,prove:the snoQthness of the
ro4d surf~ce, they h~ve been sub.ject to prQblems~ The
p~ddles, resting directly on the p~ving nll~teri41, such ~s hot
~sph.~lt or the li~e, .~re sub.ject to buildup of n~.~teri.~l
~dhering thereto, thereby resultiny in erroneous indic.~tions
of the qctu.~l height of the p.~ving nl.~teri.~l in front of the
screed. On occ~sion, the p.lddles n~.~y even beconle buried in
the .~sph.~lt n,~teri.~l, thereby resulting in thè pro~uction of
sign~ls th~t h~ve no rel~tinn to nl~teri~l thic~ness.
The problem is con,pounded when screed extensions ~re
en,ployed, for es:~nlple ~s disclosed in U.S. F.~tent No.
3,702,578~ vin~ or when telescoping screeds .~re en~ployed,
for ex.~nlple, .~s described in U.S. P~tent No. 4,379,b53, ~rown.
It is convention.~l to provide .~n end pl.1te .~t the sides of the
screed, for n~int.~ining the level of p~ving nl~teri~l ~t the
extren,ities of the screed. The sensing p~ddles, for sensing
the height of the upper surf~ce of the p.~ving n,.~teri.~l,
however, ,~re fis:ed to the p.~ving equipn~ent. If the screed
width is reduced, it is ~pp.~rent th.~t the end pl.~tes thereof
-- 3 --
1302144
E~ 04
n,~y effect the burying of the sensing paddle in the p~ving--
n"~teri.~l, by forcing paving nlaterial inwardly fron, the outer
ends of the screed.
:- Paddle controlled potention,eters, directly cont~cting
the-h`ot asph31t,-were~en,ployed prinlirily in`~i`èw~o~he ;i
extremely adverse conditions for the sensing of the height of
the top level of the asphalt. Thus, any sensing arr-~ngen,ent
n,ust be capable of functioning properlY under conditions of
extren,e ten,perature variation, as well as being resist~nt to
~brasion ~nd shoc~- It h-~s further been heretofor considered
necessary that the sensing arrangen,ent not be sensitive to
loc~l conditions other th~n the heiyht of the nlateri~l. The
fact that the sensing devices are en,ployed on road n"~ing
equipn,ent therebY necessitates that they be e~:tremelY rugged.
In the p~st it has been considered that, even though n"~ny
other sensing ~rrangements n,~Y be useful for other
applic-~tions, p-~ddle controlled potention,eters of the type-
disclosed in U.S. P~tent No.3,678,817 provided the only
~a~`isfactory solution in paving equipn,ent. As above
discussed, howe~er, the provision of paddles physic~lly
contacting the ~sphalt, generally in regions ad.jacent the ends
of the augers, does not provide an optimun, solution to the
problem.
1~02i44
~ 04
The present invention is therefore directed to the
provision of ~n in,proved sensing ,~rr-~ngement for bulK n"~teri~l
conveying equipment, especil~lly ro~d equipment such ,~ p.~vers,
which overcon,es the ~bove discused problen,s of prior
,lrr-~ngen,ents.
~ riefly st~ted, in-~ccor~,~nce with the invention,
sensing ~rr~ngen,ent is provided for bul~ n"~teri,~l conveying
equipn,ent such l~5 p~vers or the li~e, wherein the sensiny
qrr~ngen~ent con,prises ,~ non-cont-~cting sensor fi~edlY n,ounted
to the equipn,ent, for sensing the dist~nce between the level
of the bul~ n"~terinl ~nd the sensor. The ren,ote loc~tion of
the sensing device fron, the bul~ ~"~teri,~l, such ~5 hot ~sphl~lt
in ,1 p,~ving mqchine, reduces the requirements of the sen6ing
device to withst~nd e~treme environmentl~l conditions, the
sensing device thus no longer being sub.ject to the he,~t of the
l~sph~lt or to ~br,~sion fron, the ml~teril~l. The provision of
the ren,ote sensing device in ~ccord-~nce with the invention
further prevents the outputting of erroneous control sign~ls
due~ for e.-:~mple, to buildup of the n,~teri~l on the sensor, or
to l~ctuql burying of the sensing device within the nll~teri~l.
Contr-~ry to previous belief, it h~s now been found th-lt non-
cont,~cting sensing ~rr,~ngen,ents not only overcon,e the ,~bove
discussed dis,~dv-~nt~lges of prior ,~rr~ngen,ents, but l~lso
1302144 ~-'~
provide sl~tisf-~ctory perforn,~nce under the e~:trenle1y h,~r~h
environn~ent,~l conditions 1~5 re~lllired.
-- While it hns been found th~t ultr~sonic sensiny -
~,~rr,~ngements ~re especi~lly useful in ,~ccord~nce with the
invention, in p,~rticul~r for ro~d p,~ving equipn~ent, the
invention l~lso conten,pl~tes other ren.ote sensing l~rrl~ngen~ents
of ~nown types, for ex,~n-ple, emploYing light or other
r~di,~tion to detern,ine the dist,nce between the sensor ~nd the
p~ving n.,~teri~l, for exqnlple bY tri,~ngul.~tion. The invention
thereby en,~bles the more ,~ccur,~te ~uton-~tic control of
n-~teri~l height, ~nd i5 especil~lly useful in equipn~ent such ~s
p~ving n~qchines wherein control of this p~r~n,èter is essenti~l
in the use of the equi.pnler)t~
In order thl~t the invention n~Y be n~ore cle,~rly
understood, it will now be disclosed in gre,~ter det~il with
reference to the ,~ccon,p,~nying dr,~wings, wherein:
FIB. 1 is ,~ sin.plified side view of ,~ pl~ving n,~chine
incorpor.~ting the invention, the p,~ving n"~chine being
illustr~ted p,~rti~llY in section:
FIG. 2 is ~ sin,plified top view of ~ portion of
p,~ving n"~chine with extend4ble screeJs~ lllustrl~ting the
~d~pt.~tion of the sensing ~rr.~ngen~ent of the invention to such
~ device
1302144
0
. FIG. 3 is a sin,plified bloc~ di~gr,~nl of-,~ sensi-ng
arr~ngen,ent in accord~nce with one embodin,ent of the
invention, for ~pplic,~tion to a p,~ving machine: .-
- -- FIG. 4 is-q-sin,plified-cross sectional view of ~
sensing he-~d thl~t n~Y be emploYed in the arr~ngen,ent~ of FIG. 3
qs well qs in the arr~ngement of FIG. 6 . . - ..;. -
FIG. 5 illustrates various timing signals for thecircuit of FIG.3;
FIG. 6 is ~ n,ore detailed circuit of ,~ preferred
enbodiment of the invention:
FIG. 7 illustrates various timing wl~ve fornls of the
circuit of FIG. 6.
FIG. 1 illustr~tes ~ paving machine h~ving ,~ fr,~n,e 10
with a hopper 11 for receiving p~ving m~terial and ~ body 12
mounted thereon. The paving n"~chine is adapted to nlove on
endless tr-~c~s 13 although it is ~pparent that it nl~Y
~lternatively be n~ounted to move on wheels (not shown). fl
screed 14 is supported pivot~lly rearwl~rdlY of the fr~n~e by a
screed arn, 15. Pl~ving materi~l deposited in the hopper 11 is
conveyed by a conveyor (not illustrated~ in FIG. 1, to ~
tr-~nsverselY es:tending auger 16 in front of the screed, the
p~ving m~teri.~l 17 being trQnsversely distributed by the ~uger
16 for con~paction in a l.~Yer of even thic~ness by the screed
130Z144 }~ ol~
14. The p~ving n"1chine illustr-1ted in FIG. 1 n,1y thus be, for
ex~n,ple, ~ device of the type disclosed in U.S. F~1tent No.
3,700,~88.
In ~ccord~nce with the inventlon, ~ sensor. for
e~x~mple, ~n ultr1sonic sensor 20 is mounted to the p~ving
n,~chine, or screed, ~nd directed in the direction of ~rrow 21
to sense the top surf-~ce of the p-1ving n,~teril11 17. The
sensor 21, which n,-~y be con,prised of ~n ultr~sonic tr~nsducer
~s will be disclosed in gre-lter det~il in the following
p~r~gr-~phs, nl~y be rigidlY ~ffixed to the p-~ving nl~chine, ~nd
prefer~bly sep.~r.~te such tr.~nsd-lcers .~re provided ~t e.~ch side
of the p~ving n,~chine to sense the height of the top surf~ce
of the p~ving m~teri-~ d.j-~cent eQch end of the ~uger 16.
While the dr~wing illustr~tes the sensing of the height of the
p-1ving m-~teri-~l inlmedi-~tely to the front of the ~uger, it will
be ~pp-~rent thl~t the tr~nsducer nlay be directed to sense the
height of the top surf~ce of the p~ving nlQteril~l ~t ~ny other
convenient loc.~tion.
The tr~nsducer ~0 is connected to provide ~n output
signl11 corresponding to the tin,e of trlvel of sound wlves
between the trl~nsducer ~nd the top surf~ce of the p-lving
n,-~teri-~l, this dist-~nce hence constituting ~ n~e~sure of the
dist-~nce between the tr~nsducer ~nd the surf~ce 22 upon which
i302144 ~ 4
the paving n,~chine is driven, lnd, hence. the thic~ness of the
paving n,ateri~l in front of the screed. FIG. 1 thus
illustr.~tes generally the sensing arrangen,ent in accordance
with the invention, and its relationship to the poving machine
in general. The paving nlateri-ll piled in front of the screed
...., . .. .. . . ~ ., . ;. .~ .....
directs forces onto the screed in ~nown manner, wherebY the
~ngular orientation of the screed, and hence the thic~ness of
the con,pacted layer ~3 behind the screed, n,ay v-~ry ~s a
function of the an~ount of n"~terial in front of the screed~
FIG. ~ illustrates a simpiified top view of a portion
of a paving n,~chine having a telescoping screed, for e~ n,ple,
of the type disclosed in U.S. Patent No. 4,379,653. In this
arrangen~ent the p.~ving n,aterial is conveyed on a conveyor 30,
in the direction of arrow 31, to a rotl~tqble auger 3~
e~:tending trl~nsverselY of the direction of n,oven,ent ~arrow 33)
of the paving n"~chine- The paving n,achine is provided with a
p~ir of fi~ed n,ain screeds 34 rearwardly of the auger, ~nd ~
: .......
p.~ir of laterally nlovable screeds 35 in front of the n,ain
screeds, the e~ttendable screeds being n,ovable in the
directions of the arrows 36. End plates 37 are affi~:ed to the
.... .
lateral extren,ities of the e~:tendable screeds. In this
arr.~ngen,ent, the non-cont-~cting sensors or transdllcers 38 in
qccordance with the invention ~re n,ounted above and to the
13~Z~44
front of the ends of the nuger 32, to detect the height of the
pnving n..~terinl in this~ region. The control sign-~ls o~t-lined
fron, the sensing devices nre employed ~o control the speed of
rot~tion of the drive 39 of the ~uger ~nd/or the speed of
moven,ent of the conveyor 31 nnd/or the height of ~ g-lte for
pnssing mnteri~l ~long the hopper ns disclosed, for e~:ample,
. -
in ~-S- Pntent No. 3,678,817.
It is ~pp~rent th~t if the non-cont~cting sensors of
the invention h-~d been repl-~ced bY pnving n,nteri-~l contncting
p~ddles, ns in the prior nrt, inwnrd nlovement of the end
pl~tes 37 would force the p.~ving mnterinl inwnrdlY .~g~inst the
sensing pnddles, to effect the buri~l of the p-~ddles within
the p~ving mnteri~l. The provision of the non~cont-~cting
tr-~nsducer 38 of the invention, nbove the pnving mnteri-~l,
elin,in~tes this problem. FIG. 2 thus illustr~tes further, in
~ sin,plified n,-~nner, the ~pplic-~tion of the non-cont-~cting
sensors or tr~nsducers of the invention to 4 paving mnchine.
FIG. 3 is ~ simplified bloc~ dingrnm of one en,bodiment
of ~ feed control nrrnngen~ent of the invention, especi~lly
~dnpted for n pnving m.~chine or the li~e. As illustrnted in
FIG. 3, n n,~ster cloc~ 40 ~pplies tin,ing si~nnls to ~
tr-~ns~it/receive device 41 coupled to n tr-~nsducer 42. The
tr~nsducer n,-~y be ~n ultr.~sonic trnnsducer- The
~ 10 --
1302144
E~ 04
trQnsn,it/receive device 41 hence comprises ~ circuit
responsive to the control sign-~ls fronl the m-~ster cloc~ fDr
energi~ing the tr~nsducer to tr~nsn,it .~n ultr~sonic pulse.
The tr~nsn,it/receive device .~lso receives echo sign~ls
. .. . . . . . .
responsive to the receipt of ultr~sonic echoes by the
tr~nsducer 42, for ~pplying ~n echo responsive sign.~l to ~
logic circuit 43 by w.~y of ~ control line 44. The ultr~sonic
pulses ~re directed to the p.~ving n"~teri.~l sl~ch .~s ~sph~lt 45
forw~rdly of the ~uger 46 of the plving nl~chine, so th.~t the
el~psed tin,e between the pulse tr~nsmitted by the tr.~nsdllcer
42 qnd the ultr~sonic echo pulse received by the tr~nsducer 42
is ~ function of the dist.~nce between the tr~nsducer 42 ~nd
the top surf-~ce of the ~sph-~lt. The tr~nsducer 42 is .~d-~pted
to be fixedly nlounted to the p~ving n,~chine, or screed, so
th-lt this tinle del~y is ~lso ~ n,e.~sure of the height oF the
top surf.~ce of the ~sph~lt, .~nd hence of the thic~ness of the
~sph~lt l.~yer.
In order to en~ble the mounting of the tr~nsducer 4
in .~ rugged m.~nner, the tr~nsducer 42 m.~y be ~ commerci.~lly
.~v.~ ble ultr-~sonic tr-~nsducer fi~edly mounted in ~n open-
ended pl.~stit housing 50 for inst.~ tion .~nd support, the
pl-lstic housing S~ being fixedly nlounted in ~n ~lunlinun,
housing S1 for n,ech.~nicl~l strength, the hol.lsing 51 being
~302~44
3K-2ii4
shaped~as clesire~ to cnable its ready ir.ountin~3:to the paving
~achi'ne. Tl-e o?en end of the ~lasti'c~'ho'usi'ncJ S~'is'covered
~itn a layer 52 of acoustically :'tran~~'pàr'ent' foa.ti,'~rot~cted by
an external layer 53 of screen wire. The transducer ~2 ~lay.be
Electrostatic ~rransducer number 6~4l42 manufactured by the
Polaroid Cor~oration.
Referrin~;~ again to FIC. 3, the output of tne ~aster
clock 4~ is also a~plieci to a divider or counter circuit 55
for ~ro~ucins a 2lurality of timinc3 signals for the loc~ic
circuits ~,3. I'he logic circuit, u~on recei~t of a si~nal
either from the ~3ivider 55 or t'ne trans~it/receive device 41,
signallins tt1e energization of the transducer, ?rovides a
control circuit for a ra~p generator 56 to initiate a ra~?
signal. The time of the initiation of the ra~p sisnal, with
respect to the time of the trans~m.it pulse, ~ay `oe controlled
in order that tt;e interval c'urin~ which the ra~.p sic3nal
occurs, corres?onc3 to a ~ieterl~ined ranc3e of thicknesses oL the
as~halt. UFon the receipt o~ the echo si~3nal, the lo~ic
circuit opens a ~ate 57 to pass the instantaneous air?litude of
the ra;nn si;Jnal to an inte.;ratcr anci po~er a.~.olificr 58. r'ne
lo;3ic circuit ~3 fur~her controls the su?ression of tnc ra;n?
si~;nal ~JI1en no echo is receiv2.1 witi~in a nrecletcr~ine' rar~c
ot intere.;t. i~enen-~in;J upon the ti~in~J c~r)l~?y~d in the 10~ic
i30Zi44
~K-2~4
circuit, the echo signal may occur prior to the initiation of
the ramp, in which case a zero or ].ow level signal is applied
to the integrater. The ramp generator may hàve a maxlmum ramn
level, attained after a given time following its energizàtion,
so that this maximum level is passed to the integrater in
response to the receipt of an echo signal after the attaining
of its full level by the ramp generator.
5'his operation is illustrated in the timing diagrams
of FIG. 5, wherein line A illustrates an enable signal from
the master clock to the transmit/receive device 41 controlling
the device 41 to transmit the ultrasonic pulse 60 as
illustrated on line B. The logic circuit may develop a listen
gate 61, as illustrated in line C, during which time the logic
circuit 43 is responsive to the receipt of echo pulses from
the device 41, as illustrated on line ~, the time 64 being a
predet:ermined time following the initiation of the transmit
puls~ 60.
Upon receipt of the echo signal 65, as illustrated on
line D, the generation o the aforementioned ra~p signal 63
ceases as shown on line E, and the gate 57 is opened by the
logic circuit 43, as illustrated by the rise at 66 of line F,
to pass the then occurring signal level of the ramU to the
integrater and power amplifier 58.
,:
', .. '
1302~44
~ 04
received sign~l over ~ nunlber of cycles~ for e~ mple, 4bout 10
pulses of ultr~sonic energy, in order to ~void erroneous
output sign~ls resulting from such conditions, for e~:~mple? ~s
uneven surfl~ces of the ~sph.~lt or vibr~tion of the tr~nsducer.
The intern,edi~te sign~ls ~re ~nlplified ~nd ~pplied to ~ motor
speed control device 69 for controlling the ~uger motor 70
The n,otor speed control 69 m~y convention~llY constitute ~
torque n,otor on l~ servo vllver for controlling the speed of
rot.~tion o4 the n)otor 70, when ~n hydr.~ulic motor is emploYed.
In the ~rr~ngement of the invention .~s illustr.~ted in
fIGS. 3 ~nd 5, the r~mp 6~ is positioned in the timing di~gr~m
to occur when the top of the sensed l~sph~lt is within ~
detern,ined r~nge of distl~nces fron, the tr~nsducer in which
v~ri~ble speed control of the ~uger motor is to be effected.
This r.~nge m~y be, for e~:~mple, llbout 2 inches. Thus, if ~n
echo sign~l is received before the initi~tion of the r~n,p,
indic~ting th-~t the top of the ~sph~lt is too close to the
trqnsducer, the level on line E before the initi~tion of the
r~n,p is p~ssed to the i.ntegr~ter, indicl~ting th~t further
m~teri~l should not be fed bY the ~uger. If the echo sign~l
is received ~t the time or ~fter tl-e m-~:imum level of the
r~n,p, indic~ting th~t the level of ~sph~lt is below the 2 inch
control r~nge thereof, the n"~:~imum sign l level is p~ssed to
~302i44 ~ 04
the i.ntegr.~ter, ~nd the motor speed control 69 controls the
n,otor to its f~stest speed r-~te. The n,otor speed control 69
n,~y, of course, ~ddition~llly be employed to control the eed
of n~teriql by w~y of the conveyor. When the height~of the
top of the ~sph~lt f~lls in the two inch r~nge .~s determined
.
by the positioning of the r~mp 63, the sign~l p,~ssed to the
integr~ter i5 intern~edi~te its m.l::imulo ~nd n,inin,um levels,
thereby en~bling the v-~ri-~ble speed control of the n,otor 70 by
the motor speed control device 69~
FIG. 6 illustr.~tes .~ n,ore det~iled circuit di.~gram of
~ circuit in .~ccord.lnce with the invention, oper.~tive with .
determined commerci~lly ~v~ ble ultr4sonic r~nging systen"
for controlling the feed of the bul~ m-lteri~l such ~s ~sph.~lt.
FIG. 7 illustr~tes the timing emploYed in v.lrious portions of
the circuit of FIG. 6.
~ s illustr.lted in FIG. 6, ~ m.~ster cloc~ 80 of
convention-~l design, h~ving ~ cloc~ frequencY. for e::~mple, of
163.84 ~ilohert~, h.~s .~n output divided bY the divider 81 to
produce ~n ~ppro::im~tely 10 ~ cYle squ~rew~ve for the control
of the tr.~nsducer system 82. The tr.~nsducer systen. 8~ is
con,prised of ~n Electrost~tic Tr~nsducer No. 604142 produced
by the Pol.lroid corpor.ltion, .~nd n r.lnging bo.~rd No. 607089,
~lso of the Fol~roid corpor~tion. This sYstem is responsive
- lS -
i30Z~4~
E~ 04
to the control squ~rew.lve fron, divider 81 to emit l tr~nsn,it
pulse shortly 4fter the le~ding edge of the:control sign.ll.
The tr.~nsmit pulse i5 ~lbout one millisecond long .~nd consists
of 4bout ~6 cycles of ~9.41 ~H~. The stlrt of this trl~nsmit
sign~l is not ~ccur4tely sp4ced from:the~en~rgizing si-gn~
~pplied thereto from the divide~ 81. The XLOG output of the
tr~nsducer circuit is ln lctive low sign~l st~rting 4t the
beginning of the tr-~nsn,it pulse ~nd ending ~t the end of the
tr~nsn,it pulse. The tr.~nsducer 82 further outputs ~ receive
fl~g FLG which is ln .~ctive low sign~l responsive to the
receipt of .~n echo by the trnnsducer.
hs illustr-~ted in FIG. 6, the tr.~nsmit .~nd receive
outputs of the tr4nsducer 82 ~re ~pplied to the set ~nd reset
inputs respectively of 1~ flip flop 83, ~nd the tr4nsn,it pulse
is ~lso ~pplied to the set input of l flip flop 84. The
output 85 of the flip flop 83 is set low by the tr4nsn,it
pulse, to en~ble the ~pplic~tion of cloc~ pulses to the
counter 86 by w4y of the NO~ g4te 87, wherebY the counter 86
st~rts counting l~t the st4rt of the tr.~nsmit pulse fron, the
tr4nsducer circuit 82.. This 4rr4ngement en4bles
sychroniz.ltion of the counter circuit with the tr.~nsducer, in
view of the instl~bilitY of the st4rt of the trl~nsn,it pulse
from the trlnsducer.
~ 16 -
~302~44
I~K-2~J4
from the transducer.
- The counter 86 has a ~lurality -of outputs...as :o :..:.;.
illu.strated, correspondinc3 to divisions..by the 4th., ~-th-, 9th,
l~:th:and 11th powers of two.. The~e output!s--a.re~mpl~ye~ .to
control the timing in the remain~er of the.c-ircuits. The
relative relationships of the c3ivide by 9th power of two to
the divide by the 10th rpower of two are illustrated in the
first seven lines of the timing diagrams of lIG. 7. The ~LOG
transmit ~ulse is indicated on the ~tn line of FIG. 7.
- The ram~ g~nerator of tne arrangement in FIG. 6
includes a charying capacitor 90 serially connected with a
char~ing resistor 91 by way of a charginc3 diode 92 and the
parallel source-(lrain ~atns of transistors 93 and ~4. The
voltage across the charging ca?acitor 9~ is applie~ to an
integrator circuit 95 by way o~ the source-drain path of
transistor 96, anu the capacitor 9~ is shunted to grounc3 by
way oE the source-drain ath of transistor 97.
In order to more fully understand the ol~eration oE the
circuit of FIG. 6, it will initially be explained that it is
desirable to be able to receive an echo pulse, in one
e~bodi;nent of the invention, in tlle ranye of s~acings from 4
inches to 42 inches from the transclucer, anci not ~o receive
echoes from tar(3ets outside of this range. It is further
- 17 -
i302i44
i-~K-2
desiral~le to control the au~er so that it does not feed
asphalt when the detected top surface of 'the asphalt-is closer
~han about 16.15 inches from the transducer, to control- the
auc3er at its full speed when the distance ~etween the top of
the asphalt and the transducer is about 18.15 inches or
~reater, and to have proportionately intermediate speeds or
detected levels of the top of the asphalt within this range of
a'oout 2 inches. The voltac3e across the capacitor 9~, which is
passed to the inte~rater 95, then must be zero if an echo
signal occurs indicatinc3 a distance less than 16.15 inches,
and ,~ust have a maxi:num value at the ti.~e correspon~ing to a
distance of about 18.15 inches or ~reater. ~ccordincJly, the
charcJing resistor 91 and the capacitor 9~ are selected to have
an RC value permitting this char~3inc3 rate.
ReferrincJ aCJain to E'IG. 6, the receive output of the
transducer 82 is normally high, and goes low upon the receipt
of an ecno siynal, to reset the flip flop 83. Irhe resultant
hi~h level at the output ~5 of the flip flop 83 ~loc~s the ~IOR
3ate 87 to stop countinc3 in the counter, resets the counter,
and renders the transistor 96 conductive to ~ass the charge of
the charcJing capacitor 90 to the intecJrator 95.
The generation of a ramn is controlled by the
transistor 93, which, as indicated, occurs in response to
- 1~3 -
1302~4
~ 2~4
positive levels of the divide ~y the 8th and 9th powers of two
of the clock signal. ~s apparent in FIG. 7, the second
occurrence of this coincidence occurs at a time corresponding
to a spacing of 16.15 inches, and hence the transistor 93 is
rendered conductive at this time to enable the charging of the
capacitor 90. The flip flop 8~ is employed in order to bloc~
charging of the capacitor at the first occurrence of this
coincidence, and during the transmit pulse, by holding the
capacitor at lo~ level by way of the diode 98 at the output of
the flip flop 84. Thus, tne capacitor voltage 90 cannot rise
from the time that the flip flop 84 is set by the transmit
pulse, until the time that the divide by the eighth power of
two signal goes low when the divide by 2 to the 10th power
signal is low (at about 1.6 milliseconds from the start of the
transmit pulse).
The minimum time at which the system can respond to a
receive or echo pulse is deterrnined by the transducer itsel~,
and corresponds to about ~.G milliseconds (about 4 to 5
inches). An echo pulse received anytime subsequent to this
time results in the resetting of the flip flop 83, tne
stop~ing of the counter, the resetting of the counter and the
passing of the charge on the capacitor 50 to the integrator 9S
as discussed.
-- lg --
1~02i44
o~
subst~nti~lly its full ch~rging v~lue in ,~ tin,e period
corresponding to ~bout 2 inches of sp.lce.
While, in 4ccord~nce with the invention, the r.~n,p nl~Y
constitute . continuous ch~rging of the c~p.~citor 90, it is
preferred th4t the c~p~citor be ch~rged in steps, to:h.~ve :
pl~te~u intern,edi4te the steps, 4s illustr.lted by the r~n,p 100
in the 9th line of FIG. 7. Thus, .~s illustr4ted in FI~. 6,
the ch~rging volt4ge the c4p4citor is the divide by the 4th
power of two output of the col~nter. This results in the
ch4rging of the c~p,~citor in 4bout 4 steps, e.~ch corresponding
to ~bout one qu.~rter of the full height of the r~nlp.
In Q preferred enlbodin,ent of the invention, it is
desir4ble to be 4ble to re.~dily ch.~nge the tin~e of initi.~tion
of the r~n,p, in order to en4ble either control of the top of
the .~sph~lt lt .~ different level, or its sin,ple .~pplic.~tion of
the tr4nsducer to different types of equipn,ent. for this
purpose, the g~te of the tr.~nsistor ~3 is held low by w~y of
the diode 110 ~nd resistor 111 by the closing of 4 selection
switch 112. The g~te of the tr.~nsistor ~4 is energi~ed by the
divide by the 10th pow~r of two output of the counter, whereby
the tr4nsistor ~4 is rendered conductive initi411Y 4t 4 tin,e
corresponding to .l sp.~cing fron~ the tr-lnsducer of 21.42
inches, providing the r~n~p 1~0, ~s illustr~ted in the l~st
- 20 -
13021A4 ~ ~o~
line of FIG. 7.
The integr~ter 95 is con,prised of ~ convention~l
integr-~ted circuit h~ving circuit-component6.en-~bling -the.;... :.
integr~ion of input sign~ls for .~ peri.od of ~bout 1 second,.
corres~onding to .~bout:10 cYcles of:the ultr~son~ic systenl~-
the output of the integr~ter 9S is-~pp.lied to ~ tr~n~istor.
power ~mplifier 116 supplied by ~ const-~nt current source 117
of convention~l construction. The tr~nsistor ~n~plifier 116 is
provided with ~ p-~r-~llel ~C feedb.~c~ networ~ 118 to provide
f~st response slow dec-~Y ch~r~cteristics, .~nd ~ diode 120 m4y
be connected in series with the collector resistor for spi~ed
protection. The outpllt of the ~n~plifier 116 is directed to
the servo v~lve 130, of convention~l construction. for control
of the .~uger nlotor 131.
The devices en~ployed in the circuit of FIG. 6 ~re
convention~ nd it n~.~y be convention~l CMOS devices. The
tr~nsistors enlployed in the timing control.circuitrY nl.~y
constitute convention~l tr~nsnlission gl~tesr ~nd the counter 86
~nd divider 81 4re convention~l CMOS devices.
The c.~p.~citor ~0 i5 disch.~rged everY cycle of the
ultr~sonic pulse, when no echo is received within r~nge of
interest, by the divide by the 11th power of 2 sign~l, bY the
tr~nsistor 97.
- 21 -
i3~2~44 ~-204
While it is preferred th~t the tr.lnsducer be ~n
ultrQsonic trqnsducer for ~pplic.~tions where high he~t c-ln be
expected in the n,~teri~l to be distr.ibuted, such ~5 ~sph~lt
p.~ving m.lteri41s, it is .~pp.~rent th~t the concept of:the
-i*~ention is ~lso qpplic~ble to other~tr~ns-d~cer dë~ices, such
~s pie~o electric devices. Further, in ~ccord~nce-with the
invention, it i5 ~pp~rent thqt other dist~nce me~suring
~rr~ngements m~y be employed, such.-~s tri~ngul-~tion devices
employing v.~rious forn,s of r~di.~tion. It is still further
~pp.lrent th-lt me.~ns .lre prefer~bly provided for overriding the
qutom~tic control of the invention for m~nu~l oper.~tion. in
the event thqt ~utom.~tic'control is not desired. This m.~y be
effected by conventional devices, for e~.~mple, upon the
dis~blement of the circuit of the invention. It is of course
further ~pp~rent th~t the output of the circuit c4n be
en,ployed, inste.~d of or in .~ddition to ~utom~tic~llY
controlling the ~uger 4nd/or conveYor feed, to control ~n
indic~tor~ wherebY ~n oper~tor n,~y view such indic~tor to
effect the m~nu~l control of the feed.
~ n electronic tr~nsducer of the ~bove disclosed tYpe
provides the .~dv.lnt.~ge of subst.~nti.~l inlm'nity to e~ttern~l
influences, since the tr4nsducer is direction.~l. The immunity
is incre-~sed bY inhibiting ~ny response to sign~ls received
- 22 -
` 1302i44 ~ 04
fron~ dist.~nces gre~ter th~t 4bout 40 inches. The device i5
hence subst.~nti.~llY in,n.une to control by humps or ridges in .
the:surf~ce being p~ved, n,~teri~l spilled from-the:truc~.or
hopper, or n,.~teri.~l pulled in bY n~rrowing of the p~ving-
width.~ The tr~nsducer n.~y be mounted ~t-~ loc~tion wher.e it :-
does not interfere with inst~ tion or remov~l o~ con,ponents
of the p~ving m~chine. The circuit of the invention is .~lso
re~dily ~d~ptc~ble to .~uton~tic or remote control of n~.lteri.~l
feed.
. It is q further adv~nt~geous fe.~ture of the invention
th~t the .~uger or other feed device controlled bY the sYsten
is turned off when the first echo received corresponds.to Q
dist.~nce of .~bout 16 inches or less, corresponding to .~n over
supply of .~sph~lt . This fe~ture thereby renders the sYsten,
oper.~tive to shut off the ~uger in the event of other ob.jects
between the luger ~nd the tr~nsducer~ .~nd c.~n prevent in.jury
to oper.~ting personnel if theY .~re intention-~llY or
~ccident~lly present in this sp~ce, by effecting the turning
off of the ~uger.
While the invention h-~s been disclosed ~nd described
with reference to .~ linlitecl nun~ber of en,bodin,ents, it is
1pp-~rent th~t v.~ri.ltions .~nd n,odific.~tions n~y be nl.~de
therein, .~nd it is therefore intended in the following cl~ims
- 23 -
~30214A
~ 04
to cover el~ch such vllri,~tion ,lnd modific~tion ~s follows
within the spirit qnd scope of the invention.
: . .
- -- 24 --
