Note: Descriptions are shown in the official language in which they were submitted.
21 2~0
D PROCESS FOR ~
The invention relates to an electric sur~ace heatin~ means Eor
t~e surface welding of thermoplastic ~ittings and a process for
the production o~ such surf2c~ heatln~ means Erom suppor~ me~-
bers and heating conductors.
Surface heating mea~s are used ~or Joining pipelines and pipe-
line parts~ as well as for producing branch liues, e~g. u~ing
pipe saddles and boring pipe boxes. The heat requlred ~or su~h
a surface ~eatin~ ls produced in the ease of so-called hea~ln~
coil ~eldin~ b~ means o~ a heatin~ wire coil or heatin~ ~at
lnserted in the joi~ing zone by ~eans of Joule's heat. The
te~pe~ature in the heating w~re u~ed and at its ~urface is deter-
mined by s~veral parameters, such as t~e specific ohmic ~esis-
tance, the diameter and len~h of ~he heatin~ wire, ~s ~ell as
the level of t~e vol~a~e applied~ the level o~ the flowln~ cu~r-
ent and t~e ~eat trans~er via the hea~in~ wire sur~ace into the
thermoplastic material ~o ~e melted~
The surfacs heating means for plastic pi~elines presen~ly avail-
~ble on the market ~re mainly desi~ned for use in gas suppl~
systems, i.e. they ~r~ used for small and medium size pipes.
Fo~ e~mple~ ~ran~hes from gas pipes to ~ouse connections tend
to have small pipe d~ameters- The connectlons to the l~rge main
gas su~ply pip~s are corresPondlngly small ~nd co~sequently fit-
tings such as pipe saddles and borl~g plpe boxes h~ve small to
medium drllled diamet~r~.
Plastîc pipes ~d therefore also heating coîl welding technolo~y
ar~ increasingly ~ei~ u~ed in plant constructio~ in the mos~
v~rled fields, such a e.g- in water supply applications- This
multipli~it~ of uses le~d~ to a demand for e~g. larger connec-
ting or joining fi~tingq for la~er br~n~h lines o~ pipes ~han
has be~n the case up to now 1~ gas 5upply ~pplicatiQns and also
l~ads to a demand ~r ~or~ ~le~ibly usable ittln~s.
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The m~nufacture of large b~anch p~pe~ requires much lar~er wel-
ding surfaces on the ou~er surfaces bf larse main pipes. ~hese
welding sur~aces incre~se with the square o~ ~he diameter o~ the
branch ~ipe and therefo~e requi~e oorrqspondingly bigher elec-
tric power levels. ~owever, for saEety reasons the maxim~m per-
mit~ed welding voltages are limited to about 50 V. The Joule's
heat necessary for heatlng coil welding consequen~lY increases
quadratically with the weldi~ surf~ce, whereas ~he Joule's heat
supplied by ~e heati~g wire only i~crea~es li~early with decrea-
sing ohmic resis~ance. Thus~ in the case of l~rge surface hea-
ting means it is necessarY to use long, thick heating wlres with
corresPondlngly lo~ o mic resistances.
K~own heatlng wire coil and heating mat cons~r~ctio~s conse-
quent~y have the fundamental disadvantages of a) hi~h material
costs resul~lng from t~e long and relatively thick heatin~ ~ires
and b~ high inherent rigldity and large sp~in~ tensions ~elastlc
recover~ or sprin~iness when the embeddin~ material is l~elted)
due to the ~lckness of the be~t heating wires. ~he high
inhercnt ri~idi~y not only ~akes it di~ficul~ to design sur~ace
heating means and in~tall them on the buildin~ site, bu~ also
hinder~ t~e ~eldin~ proce8s. ~he inh~rent r~gidity and ~pring
ten~io~s of ben~ ~eatin~ wlres give rise to i~calcul~ble wlre
displacements, so that indl~idual7 ben~ wires or wire loops can
come in~o ~o~tact with one anot~er and be short-circulted, which
lead~ to local hot ~nd cold poi~ts. In addition, during ~he
weldlng process ther~ can be incalcul~ble~ radial bending and
stre~ching movements of curYed wire coils, wh~ch displace ~e
heat su~ply out o~ the joillinB zone into ~e pipe wall or into
~he ehaped article . Such distur4ed welded i~ oints ~ave an
lnherent ris~ o~ welding ~aults and ~a~ directly ~ive r~se ~o
:~ leak5 and reduced lollg-term ch2~acteristi~s.
!
Ap~rt :Erom the above dif f icultl~s encountered with ~cnow~ heating
`~ wire c~ arld he~ti~ mati$ ~ith reSpect to the size of the
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weldin~ surfaces, ~hey suffer from ~e disadvantage tha~ the
shape and surface extensio~ o~ the weld-~ree zo~es of the fi~-
i~gs, such as e.g. pîpe saddles and boring pipe boxes, ~ot being
freely selectable. Thus, the~e are products on the market,
where lt is necessary to accept tha~ individual hea~ ~ire~
are mechanical~ cut ~hrough if, fallowing the welding proces~,
the main pipe ~s drilled in the vicinity of the borin~ pipe box
for producing a pipe connection^ This rec~uires not only an
undesira~ly hi~h force expendi~ure, but also makes it ~ore dif~-
icult to subsequently check or re~air the pipe connection and
renders impossible any subsequent rewelding.
S~iss patent C~ 57Q5577 discloses a rectangular, ~hole-surface
heatl~g me~ns ~or an approxima~e ~ipe-embracin~ welding, ~hich
comyrises mea~der-like~ stI-un~ ~ogether, pla~ic-coated heati~g
wires. ~par~ ~rom the lar~e amount of wire needed and the chick,
sti~ ~nd expensive ~eating wire needed for such large weldi~g
surfa~es, ~here is the furcher dis~dvantage tha~ the hea~lng
wire~ must be separa~ed or drilling in t~e drilled area.
Europe~ patents 119061 and 160536 describe circular surface
heati~g means wlth spiral heatlng coils. O~e ~eati~g wire e~d
lo~ated on the ou~ermost circumference can ea-~ily be connected
~o a contact elemen~. ~owe~er, t~e other heating ~ire end loca-
ted on the innermost circu~fere~oe must pass throug~ all the
~î~e ~oils in order to be led to the outside, where it is i~
turn connected ~o a co~tact element. A disad~antage of this
surfa~e heatin~ mea~s ~g that although t~e traversing heatin~
wire has a safet~ distance with respect to the wi~e coils, ~here
is a co~ider~ble short-cirouit risk during the welding process.
This is due to the ~ct that the insula~in~ ~hermoplastie mater-
ial iu the ent~e heatin~ ~oil area ~ust be deliberately t~ans-
formed into th~ molte~ st~te, as ~ ~elding zone~ the immobiliza-
tiou oE the individual heati~g co~duotor p~rts and there~ore
al50 ~he a~ety dista~ce being lar~ely lo~.
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An ~mprovement with respect to the said s~ort-circuit risk dur-
i~g the welding process is described in Europe~n pa~ent }84658.
This improvement consists o~ a heating coil being wound fro~ the
outslde to t~e inside on one surface of a connecting fitting,
being passed through ~he latter on t~e innermost circumference
aud then wound from the lnside to t~e outside on a second surf-
ace. In addition ~o the tech~ically difficul~ly perfor~able
passage of the heatin~ wire in t~e central area of a connecting
~ieting, this arr~ngement~ compared with a sl~le coil, requires
twice the amount of heating wlre- In addition, it leads to two,
îndependen~ weldin~ surfaces, thereby doubling the risk o a
welding fault in the func~io~ally crit~eal joining aIea. This
procedure ls unsult~ble for large welding surfaces.
The problem o~ the presen~ inven~ion is to p~ovide a surface
heating means ~ith low sho~t-circuit risks ~or the sur~ace wel-
dlng of fit~in~s~ as well as a process for the productlon thereof
in ~ number o~ differen~ constructional embodiments wit~ respec~
to the sha~e and size. T~ese surface ~eating means are conse-
quently usa~le for joinin~ ~lascic pipelines, must be ~eldable
in ~ull-surface manner a~d can have weld-free partial sur~aces
in use-specific ~anner. Apart fro~ a ~ood shor~-circu~t pro~-
eceion, t~ese sur~a~e heatin~ means must have an additio~al con-
s~ru~tionall~ caused mlnimiza~ion o~ the s~ort-circuit ef~ects
duri~g the welding process, i.e. in th~ case of (a possibly
~tlll occ~rring~ cont~ct between two hea~in~ wires o~ly a mini-
mum of the e~tire hea~ing wire~ resis~ance is bridgcd a SO that
on~ y a minlmum o~ the heati~g po~er is disconnected. The sur-
face heatlng means must be deslgn~d in suc~ a ~ay that a plur-
alic~ o~ diferently di~en~oned fitti~gs can be i~terconnec~ed.
It mu~t be a~le to have homo~eneou~ thermal f~elds (identical
hea~ing r~nges) and deliber~tely inhomogeneous therm~l fields
(di~erent he~ing ranges) in the heati~g z~es. It ~s in~ended
to use ~upport m~terial o~ tings for heatl~g ~lement~ whieh,
f~llowi~g welding, ~orm part of the definl~lve joini~g zone a~d
whi~h ~re selec~ed in such a way that the weld has ~ptimum ch~ra-
cteristlcs.
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Accordin~ to the invention this problem is solved b~ the ; nven-
~on given in the claims. Particularly advantageous develop-
men~s of the i~vention are characterized in the dependent claim~.
~he solution according to the invention is based o~ consldera-
tions that a connectin~ or joining fitting ~itherto designed and
made as a functional unit, together with ~he heating means for
surf ace welding can be reduced to its elemen~ary, topological
obJects and to i~s elementary, electrical components. Such a
reduction leads ~o a novel idea o~ concept of a sur-face hea~lng
means, namel~ that from matched, eleme~tary fittings, it ls pos-
sible ~ form sur~a~ h~3~ti~s T~C~ or ~uLL~lectlng flttin~
T~is movin~ away from the principle o~ n~itary produced connec
ting fi.ttings, so-~o-speak fro~ a cast metal, and the ~oving
away rom the principle of the unitary ~uided ~eating wire coil,
lead to che surface heatin~ means and the produc~ion process
accordin~ to t~e present invention. ~ process is used for the
~echnicall~ simple manu~acture of a sur~ace heating means, w~ich
either compri~es se~e.ral matched heating elements with ~eating
wîres and heati~g zoncs ~or form~ng a heating mat, or w~ich
comprises the insert.;nn ~f h~atin~ wir~ roo~ diL~etly t.n
the fîtting~ so that directly in s~ld ~ittlngs are ~ormed ~eat-
in~ 20nes, so that the fittings are heated from themsel~es. ~he
h~atins wir~3 of ea~h of ~e ~ hea~n~ ele~ents ca~ be made
fro~ ~h~ sa~e or dife~ent material, can h~ve the same or dif~-
erent lengths or thick~esse~ ~tc. The suppor~ bodies or fit-
ti~gs to which th~ he~lng wires can be fit~ed are freely s~aped
and are e.g. gao~etrical objec~s of ~ low topological o~der
~order 0~. ~his leads to a great freedom ln choosing the compo-
slt~on of fitti~gs for forming po~ibly a pluralit~ of diffe~ent
connec~ing fitCi~gs from el~m~ntary fi~tings and sur~ace ~eating
means. The he~ing mats compris~ se~eral identical or dif~erent
heatin~ elements. The heatin~ mats or self-heated fi~cin~s c~n
be connected in ~cc~rda~ce wi~h electrlc circuit patterns ~ln
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series or parallel~ to provi~e surface ~ea~in~ means and in this
~ay form ~eating mats ~th ~omo~eneous or in~omogeneous ther-
mal fiel~s ~heating ~ones). ~his leads to an enor~ous flexi-
bili~y wîth respect to uses and appllcarions~
The sur~ace heating mea~s ~nd ~he process for the productio~
thereof according to the inventio~ are descri.bed in detail here-
lnafter relative to preferred embodime~s~ ~ ~e~ns of ~igs.
la to le the problems of the prior ar~ are referred to .
Fi~ la ~howc ~ ~rior art pi~ ddle ~o~ connec~ing ~o plastic
plpes havl~g dif~erent dia~eters.
Fig. lb shows a ~nown construct~on of the beating wire config- -
uration in the heatln~ ~at for use ~ccording to fig. la,
in which the heatins ~ire ends have a reciprocal saEet~
distance.
Fig. lc s~ows another known construction of the haati~ wlre
con~iguration ~n ehe heating ma~ ~or use accordin~ eo
~ig. la, in whic~ the heating wire en~s have no rec~pr-
ocal s~fe~y dls~ance~ .
Fig. ld s~ows another known co~stru~tio~ of the ~eating wire
conflgura~lon in the he~tlng mat for use according ~o
fi~. la, in which the heatln~ ~ire ends are on di~fere~e
sides o~ the hea~ln~ mat by pa~sin~ on~ of them throu~h
a hole,
Fi~. le shows the pipe saddle acoording ~o fi~. lz broken down
ineo its geometri~al compone~ts.
g . 2a shows a f irs~, advantageous e~bodi~en~ of a support body
i~ ~he form of a half-r~n~-shaped sup~ort pl~e, a~ a
semifi~ished produo~ for ~ ~rst embodimen~ o;E a surface
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heating means according to the invention wit~ a weld-
free zone.
Fig. 2b ~hows a cut groove pattern for inserting heatin~ wire
on o~e side o~ ~e support plate according to fi~. 2a.
Fig. 2c shows a first embodiment of a heat.ing ~lement produced
by inserting the heating w~re in a su~port plate accor-
ding to ~i~. 2b.
Fig. 2d shows t~o heating elements according ta fig. 2c, which
are asse~bled in suc~ a way as to form a first embodi-
ment of a ~ur~ace heating means according to c~e
invention with a central, ~eld-free zone.
Fig. 3a shows a second embodiment of a heati~g element with a
cut ~roove pattern and heating wire embedded the~ein.
Eig. 3b shows four heating ele~ents according to ~g. 3a, ~hich
are ~ssembled so as to form a second embodi~en~ of a sur-
~ace heating means aocording to the inVentiOn with a
central, weld-~ree zone.
Fi~. 4a shows a third em~odiment of a ~eati~g element wit~ a
cut groove pattern and heatln~ wire e~bedded therein.
~ig. 4b ~hows ~w~ heating elements according to fig. 4a, which
are assem41ed in such a way as to fGrm a third embodi-
men~ of a su~face heating mea~s acco~ding eo the ~nven-
tion w~ a cent~al~ ~eld-free zone and wh~re o~ce agai~
assembly or joini~g can take place in ths man~er shown
in fig. 3.
Fig. 5a shows a fourth~ pre~exred embodiment o~ a heating
element wi~h ~ut groove patter~ and embedded heating
~i~e.
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2:~2~ao
Fi~. Sb s~o~s two hea~ing elements according to fig. 5a, which :: .
are joined so as ~o form a ~ourt~ e~bodi~e~ o~ a sur-
~ace heating means according to the inve~tio~ with a
central a weld-free zone and ~hi~ cau be assembled in the
manner ~own in fi~. 3.
Fig. ~a shows a ~ifth, pre~erred embodiment of a heating element
with a cut groove pattern and heating uire e~bedded
therei~.
Fig. 6b shows two heating elemen~s according to fi~. 6a, which
are ~oined to~ether so as to for~ a fifth ~mbodiment of
a surface hea~iug means according t~ the inv~tion wi~h-
out a central weld-free zone.
p~g. 6c sho~s a pluralit~ of heating ele~ents according to ~ig.
6a in parallel interco~nection so as to form a randomly
large h~atin~ mat and where at the contact points P with
the same ~lectric potential possible con~acts have no
influence on the heating power of the indivldual ele-
ment. ~e parallel connectio~ o~ such heating elem~ts
be~aves i~ the same way as ~he pa~allel guidance of ~8
plurality o~ u~insulated wires or conduct~r~ of a
stra~ded cable~ ~ich are in electric con~act wit~ o~e
ano~er 7 without in~luencing the conducti~g character-
is~ic of the i~dividual conductor in the stra.nd.
Fi~. 7~ shows a si~th7 preferred embodiment of a heating element
in plan vlew with a cut groove pattern a~d ~eating wire~
part~ally e~bedded therein and wh~ch fo~ms a si.xth e~bo~-
ime~t of a surface heati~ means according to the ~nven-
tio~ with a ce~tral, weld-free zone.
~ig. 7b s~ows a perspec~ire seetlon A~' accordi~g to ~ig. 7a,
with a cu~ groove pattern ~nd heating wires partially
embedded therein wî~ a weld-free zone. The heati~g
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wlres are partiallY embedded because they project in the
turning are~s on the surface of the heati~g element.
Fig. 7c shows a larger-scale, perspective section BB' acco~-
ding to fig. 7a with a cut groove pat~ern a~d hea~ing
w~res partially embedded therein ~ith a weld-free zone.
T~is vie~ makes it clear ho~ the heating wires adva~-
tageously project fro~ the heating element sur~ace in
the ~urning areas.
Fi$. 7d shows a seven~h, pre~erred embodiment of a sur~ace
heating ~eans after pressin~ ~nd melting in the pro~ec-
tin~ tur~ing or reversing areas o~ the heatin~ wiFes
directly into a flttin~ and wi~ a weld-free zone. ~is
surface heating means has the complex geometry o~ the
not shown ittiu~ to be connect~d.
~or ~he discusslpn of the prior art ~igs. la to le show a~
example of the ~onnectio~ of a pi~e saddle of two plast~c pipes
having dlfferen~ diameter~ in accordance ~ith ~uropean patent~
11~061 and 1~4658.
~ig. la show~ a pipe support having a pipe length 2 sh~ped ~o a
q~ddle 3 ~aving a cîrcular c~lindrical openin~ 1. Two elect-
rical contac~ 5 ~ laterally fitted to the heati~g mat 4 on
one surface of the ~addle~ A pipe support ha~ a very complex
geo~etry. ~us, the saddle 3 and t~e heat~g mat 4 are shaped
in ~ccorda~ce with the ex~rnal diameter of the lar~er plas~cic
~ipe ~not show~) to be connected and as ~ r~sul~ of the numerous
parts to be used i~ the manufacture of the pipe support said
shapi~g must be ~rried out in the factory. For ex~mple, the
gui~ance of the heating wire and the ele~trical co~tactl~g of
che heat~n~ mat 4 take place in several plane~, as ca~ be seen
in flgs. lb to ld.
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Figs. lb to ld sho~ three dlfferent construction6 of the heating
wire con~iguration, in which there are curved ~eas 6, l.e. in
whlch the unitary guided heating wire 7 changes its space orien-
tation or spati~lization. As a resul~ of the length of the
wound hea~ing wire 7, particularly in ~he case of ~ lar~e wel-
ding surface, said wire 7 mu~t have a certain thickness in order
to have a lo~ ohmic resistance and is the~efore relatively rigld.
Difficulty is encountered in manufac~uring such ~e~ting mats 4
because the mec~anical windin~ of the ~eating wire 7 onto ~he
mats 4 is complicated a~d in particular in areas with spaca
orienta~ion changes of the wire 7 the said wire 7 ~nd the hea-
ti~g mat 4 must be moved during ~he win~ing process, which
increases costs. In fi~. lb the heatin~ wixe 7 is ln two planes,
the heat~ng wire ends having a reciproc~l safety dis~ance or
spaci~g- In one plane the heating wire 7 is wound from the o~
side ~o the inside ~nd chen at t~e innermost circumlerence in
the second plane in the c~ossed area 8 is guided tG the outside
agai~. The heatin~ wire 7 has curved are~s 6, where it changes
its space or~entation in one plane by 90~ In ~he embodi~en~
accordin~ to flg. lc the heating wire 7 has hi~hly curved Qreas
6, where it chan~es its space orientatio~ in one plane by 180 A
In thi~ e~40d~ment there is no sa~ety distan~e between the
heatiu~ wire ends. The u~e o~ such lon~, thick and theref ore
rigid heating wires 7, re~uired ~or a lar~e weldin~ surface, o~
the heati~g mat 4 i~ che pipe support accordlng ~o fig. la con-
sequently le~ds to di~ iculties. The risks of incalculable
he~tin~ wire shifts durin~ the welding process due to th2
exist~ng bending stresses o~ ~he heating wire~ 7 in th~ curved
~re~5 6, ~ich then lead ~o hot points due to the ~losely juxta-
posed heatin~ wires ~nd finally to a pa~tial o~ ~omplete s~ort-
circuit, are si~ific~nt due to t~e ~uidance of the heating mat
4. Eln~ , in the embodiment according to ~i~. ld ~his problem
is obviated ~.n that the ~e~ting wire ls passed through a hole
bi in t~e support to the o~he~ side ~nd conse~uen~ly the ends
are eeparated ~om one another ~ short-cic~ proof ~nner.
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~owever, the threading of the heating wire through au opening is
an u~desired a~d avoidable measure.
Fig. le shows the pipe support according to fig. la broken down
lnto several simple, ~eo~etrical objects The pipe support ca~
be looked upon as a pipe leng~h 2 wich a clrcular ~ylind~lcal
opening 1~ i.e. ~he aceual saddle 3, t~e heatl~g mat ~ and the
two electric contacts ~. ~hls does not solve the pro~le~ of
the potential shor~-circuit risk due to the heati~g m~ts 4 used.
The assembly and manufacturing p~ocess are also not made simple~.
Thus, what is soug~t is a novel geo~etrical reduction o~ heating
elements e.g, used on such a pipe support or saddle to simple,
geomet~ical objects, linked w~th a ~ovel concePt of a ~rface
~eatin~ means. This geomet,rical re~uc~ion is e.g. carried out
on the drawin~ board~ in that there the deslred thermal fields
are defined and correspo~ding support bodles for the heating w~n-
ding determined. ~hey ~an be prefab~icated in t~ determ~ned
skeleton form as semifini~hed p~oducts and kept in s~o~e. It is
advaneageous to find standardlzed sh~pes a~d keap ~hem in store
~d they ca~ then be prov~ded w~th the desired heatin~ powers.
~si~g the example of th~ ~ipe saddle or support~ this is s~own
in sta~es in t~e followin~ drawin~s.
Fig. 2~ shsws a ~irst exempli~led ~mbodime~t o~ a support bod~
i~ the form o~ a emicircular support plate as a semi~nished
product for producing such surface heatin~ means ~it~ a centralJ
se~ic rcular, weld-f~ee ~one 11 havi~g a radius R21 rela~ e to
the cen.t~al pol~t ~2 (circul~r thermal field~. The suppor~
pl~te 10 is made ~ro~ an eleetrically insula~lng, ther~opl~stic
~terial and ca~ ~e fl~t or spatîall~ curved. For exa~ple, a
pla~ar support plate can form part of a saddle and ~or this p~r-
~j po~e it must assume the external diameter of ~ large~ plastic
pipe (no~ s~own) to be connected a~d this cz~ e,g. take place, by
pres~ing onto the oute~ wall of su~h a plpe. This adapta~ion
ca~ ~ake place durin~ an~ s~a~e of the manufacture o~ the
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surface heatlng ~eansl i.e. also during inst~llation on a buil-
din~ site. The support place lO essentially comprises a circ-
ular cylindr~cal half-rin~ o~ const~nt width which tbased o~ the
central ~oint ~2)~ is bounded b~ two half-circles having an
internal radius R21 and an e~ernal radius R22. The support
plate lO also has two ~ttachments 12 with ~wo circular openings
13 a~d two se~ici~cular recesses 14~ The ope~ings 13 ~re used
for holding, retaining and fixing the suppo~t plate. The thick-
ness of the suppor~ plate 10 ca~ be freely selec~ed and it is
advan~ageous to have thicknesses of 150 to 500% of the heating
wire diame~er to be inserted^ It is ~lso possible to use flex-
ible support plates~ i.e. bendable out of the pl~ne, so that a
clearly defined pre-tension can be given ~o the heating ~ire as
to its pref~rred direction during ~he melting of the surrounding
material~ e.g. i~ order to reduce ~e risk of reciprocal contact
bet~een individual heating wî~e loops during surace weldin~.
Fi~. 2b shows a groove p~t~ern 15 for insertin~ ~eatiu~ wire cut
in zones on ~he support platq 10 according ~o fi~. 2a. The
groove p~ttern lS co~sists of cut groOves 15.1 on ~he s-lpport
plate 10~ ~he grovve patte~n 15 can be located on one or bo~h
lateral faces of maximu~ surface ex~ension of the support plate
10. ~ereinafter these zo~es are re~erred ~o ~s mai~ faces. In
p~rticular in th~ vicinity of the circular cyli~drical half-
ri~g, the subsequent s~rface welding are~ of the heating wire,
~he ~rooves 15O1 ~re i~ ~he form o~ a group of parallel and 7
considered in o~e planP-~ equi~lstantly spaced depresslons.
~hese depres~ions have a wire arrangement with t~e diam~ter of
the hea~ing w~re to be i~serted thereln. In t~e viclnlty of the
a~t~chments 12 the g~ooves 15-1 are not parallel ~c one anot~er,
this ~ g place în order ~o be able to easily tension the
heatin~ wire to be subsequentl~ inser~ed. ~he ~eating wire
insertion process can take place fully automatlcally when using
~ultable tools. Through a freely pro~r~mmable~ coordina~e-
controlled movement of the wor~piece or tool holder. such
21 21'~ ~
positionally predetermined grooves 15.1 are cut in the groove
pattsrn 15 with a clearly defined depth. They ca~ e.g. be
slmply, rapidly, accura~ely and inexpensively produced by mea~s
of a~ially ro~at~ble tools.
Fig. 2c 5ho~s the support ~late 10 accordiug to ~lg. 2b ~ith
e~bedded wixe 16, 80 that a first embodi~ent of a h~ating ele-
ment 10' is ~ormed. The ~eati~g wire 16 is inserted in unitary
manner, is in one plece, thin and t~erefore not rigid and either
p~eo in one pla~e on t~e fr~nt ~L ~he hea~lng el~mant 10'
(only o~ one main face) or in several planes on t~e front and
b~ck of the he~ti~lg element 10' (i.e. on both sur~ace sides).
At ~e ends of th~ individual grooves 15.1 the ~eatin~ wire 16
is guided from one groove lS.l to the next~ adjacent groove 15.1.
I~ the~e turnin~ or ~eversin~ areas 17 ~he hea~ing wire 16
ch~nges its space orientation or spatialîæation by ~wice ~0~.
The he~ei~ wire 16 is inserted i~ loop-like manner into the
~roo~es 15.1. In the c~se of t~e laying of ~he heating wire 16
in several planes on the front and back of t~e heating element
10 ', during ~hese ~urnin~ move~ents it chan~es ~s plane~ which
~an take place in reg~lar or irregular manner. ~he turning
movement~ of the inserti~g tool~ e.g, an inserti~g c~tterl ~s
well as the wlre insertin~ ~ool are el~her performed outside
the bound~ry ed~es o~ the su~por~ plate o~ withln freed rec-
esses~ 0~ the two attach~ents 12 the hea~ing wire 16 is drawn
over later~ es of the semicircular recesses 14. This takes
pl~ce in order to subsequen~lv be able to carr~ out electrical
con~tin~ here. This insertîon process is uncomplicated and
can be easily perf or~ed with suitable~ known lnser~lng tools,
also becau5e the heatin~ wire 16 is ~hin and fle~ible.
3 what disti~guishes this heating wlre 1~ as compared with
the he~ti~g wires of know~ heati~ mats ~ its sm~ll diame~er,
its freely determinable length a~d the gre2t freedom of bei~g
~ble ~o i~sert i~ in a groo~e pa~t~rn in one or more pla~es~
,
~; ~ ' :' . . , '
21.~1~()()
- 14 -
, ~
~he di~meter o~ the ~eati~g wire 1~ is sm~ller than in the case
of the k~own wires, suc~ as e.g. those o~ the ~hree embod~ments
of known heating mats 4 according ~o fi~s. lb, 1c and ld. Small
di~meter heatlng wires have a limited inhe~ent ri~idity a~d are
less ~igid. ~hus, after insertlng in the t~ermoplast~c mate~lal,
they form lower bending a~d spring tensions, which during sur-
face weld~g processes cause unde5ired b~nding and Stretc~lng
move~entS. ~e potential short-circuit risk, whic~ is e.g.
li~ked with hot and cold poin~s of the sur~ace weld, ls inter
alia avoided by uslng thi~ heating wires, In addition, by a
curvacure in the surface ~t is possible to introduce a pre~en-
sion, which durin~ the mel~i~g of the su~por~ body ~ans out the
~eating loops, i.e. they have a tendeney to ~ove away ~rom one
anothe.r. The hea~,ing wires can be chosen in m~terial-spec~fic
manner, so tha~ the resistance of the heatin$ element 10' used
can be fr~ely adap~ed to the requislte co~dltions.
Fi~. 2d ~ows two heating ele~ents 10' accordi~g to ~ig. 2c
assembled or joi~ed in such a ~ay as to f'orm a su~ace heatlng
~ea~s 18 with a ce~tral, circular, weld-free zo~e 11*. ~his is
a ~irst, exe~pli~ied embodiment o~ a surface hea~ng means ~ccor-
ding ~o the i~veneion. ~his surface heating means }~ is ch~rac-
terized by a thin, flexible heatin~ wire 16 wit~ a lower ohmic
r~sis~ance ~an ~uch wires used in known heati~g co~ls o~ mats.
As a result of th~ thin, fle~îble heating wire used, the surface
he~t~n~ ~eans is also flexible and adapts ~asily to the geome~r~
of a pl~n~r or curved shaped part, such as e~g. a curved pipe
~all. ~awever, it is possible to fsrther process a surfaee
heati"~ mea~s accordin~ to the inven~iO~ to a randomly shaped
co~ectin~ ~ttin~ and for thi~ purpose and ~s ~ ~unction o~ the
subsequentl~ inte~ded use9 it is f~xed by means of suitable
clampin~ mean~, e.g. vacuum (suction-), to the table of a special
m~chine 1~ ~ither a flat or a previousl~ established s~pe.
Accordin~ ~o ~he invention, the ~ur~ace hea~ing means comprîses
.:~, . .
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, ...
0
- 15 -
at least two hea~ng ~ires 16 separately guided on the two hea-
ting elements 10' and ~hich are wired according to k~own elec-
tric circuit patterns, ~referably in perallel or ln serles and
in combined for~, l.e. in par~llel and in ser~es. In the case
of wiring in series lt is not Possible to use a bare h~ating
wire 16, and t~e lat~er must instead be sealed, e g. enamel-
insulate~. ~he ~eating wire 16 of the assembled heating elemen~
10' can contact the co~tact points P in the turning areas 7 and
can in this way for~ electric contactS. In the ~ase of parallel
wirin~ the contact poi~ts P have the same electric potential,
whleh in ~he case of an electrically conduetive contact ~as no
in~luence on the feeding in o~ power. The el~ctrically conduc- -
tive contac~ at ~he cont~ct points P can also be used ir. ~he
case o-E a par~llel connec~lon of the sle~ents in a planned man-
ner ~or power bra~ching between elements having a dif~erent
h~ti~ power.
Tho Po~ ~r3.nchi~ mc;~o~S~c ~'ill bc di.~ L-~ ~L`d;/lL~dS~ 1;3
Et~:~ relatlve 10 ~ r ~l.L~lWlT~gS. ~ne essel:LClal poin.t is
~hat the electric con~uctor areas ~wl~e are~s~, which were kept
apart in the prio~ art to avoid shor~-circuit~, can now be short-
c~cui~ed in un~ritical or~anizatlon, in that o~l~ co~tact~
bet~een ldent~cal electrlc pot~ntials (voltages) are possible
a~d ~ power ~ranc~ng can take place if dlffere~t heatin~ powers
axe brought together in this way.
This hea~ing mat compri~es ~e least two heatin~ elements 10'.
~e electric po~er ~ecessary ~or welding purpos~s is supplied to
the heatln~ wires 16 by me~ns of ~he connection points 19, 19'
(~ormed from th~ s~micirc~lar r~ e 14 and the e~bcdded he~-
~ing w~re 16 of di~erenC adiacen~ heating ~lements). The
recesses 14 and th~ embedded heatin~ wlres lG of adjacent hea-
ti~g eleme~ts 10' ~n therefore Coincide or ~ot. The ~wo
heating wires 16 of the t~o ad~ent ~eating el~men~s 10' o~ the
~irst embodim~t of a sur~ace ~eatin~ ~eans 1~ are i~ contact i~
r;'.'~
:,., . , :
'',., ~ " '
.''. .'' '
2 ~
_ - 16 -
~he two connection points 19, 19' and consequently for~ a para-
llel circuit, so that unll~e in fig. lc the con~ections are far
ap~rt, which ensures a 100~ short-circu~t avoidance- On ~pply-
ing power the latter simultaneously E~o~s through the two ~eat-
ing elements LO'. If ~wo ~d~cent recesses 14 o~ two ~oined
~ogether heating eleme~s 10' coincide at a con~ec~ion point 19,
~hen this leads to a series co~nec~on or circuit. The current
~hen successively ~lows throu~h the he~ting wires 16 of ~he
he~ting elemen~s 10'. According to ~he i~v~ntion, it is n~tur-
ally also possible ~o join together more than two hea~ing ele- -
ments ~lt~ a correspondi~g geometr~ for formlng a sur~ace
he~tin~ means. On joining more than two heating elements to
form a surface heatin$ mean~ several suc~ ~ontact points can be
for~ed and, freel~ selectable b~ the designer and in each case
in local manner, serie~ or parallel connections can be formed
with the hea~i~g elements (cf. ~ig. 3).
Following welding, the support material is ~ homo~eneous co~po-
nen~ o~ the fi~ished support zone. ~he prereq~isite for t~e
m~erial choice of said support plate is the weldin~ compati-
blli~y with the bodles ~o ~e welded. With a planned selection
o~ the ma~erial ~or the support pla~es with respec~ ~o the parts
~o be u~lded or their materials (e.~. different types of poly-
ethylene~, it îs ~ossible to select in pl~n~ed manner tha qual~
it~ of the fi~ished ~eld by the choice of ~e sup~ort plate
material with compensating ~ara~teristicS (e.g. rel~tive to the
fi~ln~ ~aterial and the pipe material).
In order eo avoid ~hort-clrcuit ef~ects during ~eldin$ as a res-
ult of undesired co~t~c~lng of hea~n~ wi~e are~ in contac~
with one another ~uri~g the weldl~g of the thermopl~stic mater-
ial as a resul~ of ~eat evolution in ~he heatin~ wires, the
lagou~, ~he circuit desi~n a~d the wire gu~dance in accorda~ce
with the ~rooYe ~at~ern are c~osen ln such ~ ~y ~hat as a
result of u~des~red c~n~actin between heating wire areas in
co~tact onl~ a minimu~ of t~e overall hea~lng w~re resistance is
.:' ~'.-
.~,
2 1 ~ 0
- 17 -
bridged The~efore a hea~ing mat, which is formed ~rom a sur-
face heating mea~s comprisin~ several parallel-co~nec~ed heatin~
elements, is advancageous, ~n that if ol~e of the heating ele-
ments fails duri~g the welding proce~s, the other heating ele-
me~t continues to ~unction- I~ series connection~ the elec~rlc
current flow in the surface heacing means is inter~upted as a
resul~ of the failure of a single heating element. In addition,
a heating wire guidance in a groove patteru is advan~ageous, in
which in the case of contact of heating wire areas o~ly a short
length of ~he laid heating wire is short-circuited. This is ~he
case with the advantageous embodiments of the haating elements
according to the prese~t ~nvention, because th~ heatin~ wire is
inserted in 2 plurality of grooves with equidistant spaci~g on
one or ~wo main ~aces of a support plate and is turn~d or
reversed in turniug or reversing area. The~efore the shor~-
circui~ only occurs be~ween two such s~ort, adJacent heati~g
wire areas and consequently o~ly leads to the ~ailure of a small
part, e.g. 1~ of the overall heati-ng wire len~t~ a~d conse-
~uenel~ only to a small reduction i4 the overall ohmic resist-
ance o~ the s~r~ace heatin~ means.
By checking ~he applied voltage a~d ~he electric current wh~ch
is flowing during ~he welding proces~ is possible to carry
o~t a quaLity check on the completed surface ~eld. T~is per~its
a fa~ter checking of the quality of the surf~e weld In the
case of a ~ailure, e.~. due to a ~hort-circuit, of a hea~ing
wire a~ea, the overall ohmic resistance of ~he heating mat,
correspo~din~ to t~e size of ~he ohmic partial resistance o~ ~he
heating wire area which has failed, ls onl~ sli~htl~ reduced,
whlch is not ~he case with a short-circui~ of a u~itary guided
heati~g wire of a known heating coil or mat (c. figs. lb, lc
and ld), where there is a much greater reduction of the ohmic
resistance due to the short-circuit.
I For producing a firs~ embodim~nt of a surface heating means ~wo
.
;: ~ : - : : . . : ,
`! `:~ ~
'~: . ,
.: ' ., .
2 1 ~
- 18 -
iden~ically worked heaClng elemen~s having identical o~mic resis-
tances ~ere joined to~ether, so that t~e overall o~mic ~esist-
ance of the surCace heating means is cons~ituted by the indivi-
dual oh~ic resistances of th~ heatln~ wires of the ~wo heacin
elements. The resulting heating mat h~s a homogeneous thermal
Lield, t~e two ~eating wires are identically ~orked and duri~g
current passa~e produce a uni~orm heatin~ zone or range, in
which the t~er~oplastic materlal melts ln a melting zone. ~his
is not a necess~ty and ~hen uslng di~ferent heating powers of
the heatin~ elements 10' 7 e-~. t~roug~ using di~ferenc mate~-
ials, copper and constan~an i~ t~e two heatin~ eleme~ts 10', or
when using varyingly thick heaeing wire~ 16 o~ varyingly long
wîres 16 of the two joined heatin~ eleme~ts 10', a heating ~at
ha~in~ a non-homogeneous or inhomogeneous therm~l field is
obtained (non-uniform he~tin~ zones). Such di~fere~t ~eating
powers can e.g. be obtained by ~ea~s o~ different groove pat-
terns 1;, in which the heating elements 10' e.g. ha~e varyiug
groove spacings on ~he ~ain faces. Layi4g on both main faces
(front and b~ck) or on onl~ one main face can also be chosen
~reely and increases the range o~ applications of the surface
heatin~ means formed from such heating eleme~ts to a con~ider-
able extent. ~hus on laying the heating wire on two main faces
there is a different heating and melting behaviour of the heat-
ing ~t as co~pared with layins on only a si~gle main face.
This can be utilized in order to e.g. bu~t-join two fittin~s v~a
sa~d sur~ce welding 2reas on the two main faces.
Accordin~ to the invention, the 5urface heating means comprises
several, simple, geometrical obj ects with a low topologlcal
order~ ~ mathematically precise desc~iption of the deformation
of geometrical objec~s can be obtalned by their imaging in topo-
logical spaces. An importa~t part is hereby played by the
quality posi~ion rel~tions o~ the parts of the said objects.
The heating elemen~s 10' of the ~irst embodi~ent of th~ surf ace
heatin~ means 18 according to flg. 2d are in the bottom topolo-
: . ,
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2~2~ ~0
- 19 -
~ical order and of $reat si~pliclt~. This ls made apparent by
the fact that the support body 10 is only a simple plate, so
~hat ~he cutting of grooves, the inse~tion of hea~in~ wires,
the adaptation of the inis~ed su~Lace heatin~ mea~,~ 18 to
external sh~pes is neither prevented, nor made difficult. ~or
exa~le, the heating wire 16 duri~g t~e manufacture OL the hiea-
ting element 10' can be laid either in one plane (on one main
face) or in several planes (on both main ~aces). This is very
si~ple i~ the case of the present semifinished p~oduct in ~e
form of a support plate lO, which has no opening through which
it is necessary to wl~d the heatin~ wire. ~owever, it should be
n,o~ed that surface heating means 18 formed ~rom suc~ heatin~
ele~ents 10' do indeed ha~e an openi~g in the form o~ a weld-
free zone ll*, throu~h which the hea~in~ wires 16 are wound.
~hus, the heating wire can be laid on t~is ultra-simPle,
topological object in the form o~ a sur,port plate ~opological
order = O) lO accordin~ to the groove patter~, without, after
each winding throu~h an o~ening, the insertion tool ha~ing to
engage round it, such as is e.~ the case when p~odueing a ring-
llke heating mat (topolo~ical order = l). The simple further
processing of this semifinished product or, in o~er words, the
simple manu~acture o a surface heating ~e~ns 18 is due ~o this
low topolo~ical orde~ of the semi~inished product.
Fig . 3 shows a second embodi~ent o~ heating elements SO' ~ig.
3a) and a second e~bodime~t of a su~Lace heating means 58 accor-
ding to the i~vention (Çi~. 3b) ~ormed by the assembly or ~oin-
ing o~ four suc~i heating elemen~s 50' and h~ving a central,
circular, weld-~ree ~one 51*. The surface heating means 5~
comPri~es four symmetrical heati4g elements 50' ~aving ~he shape
of quarter arcs with w~ld-free zones ll, with zonally cut groo~e
pat~erns 55 and heati~g wires 56 e~bedded therein. ~hese hea~iug
eleme~ts 50 ' are m~de from electrically insulati~g, thermo-
plas~ic ~aterial a~d ca~ be pla~ar or spa~ially curved. The
thickness of the support plates 50, servin~ as semifinished
, -:: .
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".:
0
- 20 -
products for producing the heating elements 50', is freely sel-
ec~able and as a rule of thumb it is 1.5 to 5 times thicker ~han
the heating wire 56 used. Each of the hea~ing elements 50' has,
as i~ the first embodiment of fig. 2, two at~achments 52 ~ith
Cwo circular openings 53 and C~o semicircular recesses 54. The
heating wire 5~ is inserted i~ uni~ar~ form in each heacing
ele~enC 50', is formed by a sin~le piece, is thin ~nd there~ore
not rigid and either runs in one vlane on the front of ~he
heating element 50' (only on one main face) or ln several
planes on t~e front and bac~ o~ the heating element 50' ~i.e. on
both maln faces). ~t the ends of the individual grooves 55.1
the h~ating wire 56 is gulded from 04e groove 55.1 to the next,
adjacent groove 55.1. In these turning or reversing areas 57
~he heating wire 56 changes its space orie~tation by ~wiee ~0.
~he heating wire 56 is lnserted in looped ~orm ln the $rooves
55.1. The curren~ necessary for welding p~rposes is supplied
to the hea~ing wires 56 by means of the four connec~ion points
59, S9', 59" and 59"' (formed by ~he se~icircular recesses 54
a~d the embedded heating wire 56 of different adjacent heatin~
elements). Thus, there are Eour con~ection poin~s 59, 59', 59'~,
59"' to wh~c~ a voltage can be applied. If ~his takes place
between the connection points 59 a~d 59" or 59' and 59~'', then
the curren~ flows in parallel through ln each case two heating
eleme~ts 50'.
The second embodiment of a surface heating means 58 differs from
~he other embodiment~ throu~h the forma~ion of a thermal field
of four heating elements 50' to a heating ~at. ~he leng~h of
the hea~ing wire 50' between the conne~ion points 59 of the
surface hea~ing means 58 is roug~ly hal~ as lo~g as in the f irst
embodiment of a surface heating means 28. Therefore these short
heating wires have lower troughly half as high~ oh~ic resist-
ances, which can be utîlîzed b~ a corresponding wiring for the
surLace weldi~g process. ~ere again the connectio~s can be
spaced. The use of several he~ing elements 50' can be del~b-
: . . .
. . , ~ :
,: : .
.
.
21 21~
- 21 -
e~ately utili2ed in order to produce different weldin~ ~emper-
atu~es in di~feren~ areas of the surface heating means 5~ in ~e
case of a surface weldin~ with differen~ heatin~ elements 50'.
This can e.g. take place by uslng dif~eren~ heating wlre mater-
ials. On applyin~ a voltage i~ a parallel connection, the
different ohmic resistances can lead to a higher Joule's heat
being formed in one than in the other element, so that these
heating zo~es of the heati~ mat b~co~e hocter and there is an
inho~ogeneous ~hermal field allowi~g ne~ welding procedures.
Fig. 4a shows a third, preferred e~bodime~t of a heati~g elemen~
20' with zonally cut groove pattern 25 and hea~ing wire 26
embedded therein. The rectangular heatin~ element 20' has a
rectangular, weld-Çree zone 21 with the shortest diameter D3
based on a central poin~ ~3. The heating element 20' is made
from an electrically insuLating ~her~oplastic material and can
be planar or spatiall~ curved. The ~ic~ness of the support
plate 20, which serves as a semi~inished product for producing
the hea~ng element 20', is ~reely selectable and ~s a rule of
thumb is 1.5 to 5 ~imes thicker than the heating wire 26 used.
As in the first embodiment according to fig. 2, the heating
element 20 ' has two a~tachments 22 with two ~ircular openings
23 and two æe~icircular recesses 24. ~nlike in the embodiment
according to ~ig. 2, the heatin~ wire 26 is not onl~ laid
waL~1y ~ounal~g tne s~pport plate 20
ln accordance ~1~h a pre~abrlcated groove pattern 25, but is
also wound over two lnner, rec~angular openings 20~1 of the
support plate 20. ~his ~akes place in order ~o keep to the
mini~um the amount of heating wire 26 used. Thus, the heating
wire 2~ does no~ have to be wound up to the outex edge of the
s~ifinished product and instead its path is reversed in freely
selectable 9 rectan~ular openings 20.1 thereiu. ~owever~ a~ a
result of this measure, ma~ufac~ure ~s only not ~ore compl~cated
if there is no windin~ round o~ t~e sup~ort body. ~owever, as
discussed hereinbefore, it is also possible to use a multiple
element solution here.
.~, . ~, .
.:
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2 l ,7. ~ a
_ - 22 -
~he heating wire 26 is inserted in unitary form, ls consti~uted
by one p~ece, is thin and non-rlgid a~d advantageouqly runs i~
one plane on ~e fronC of the heating element 20'. In accor-
dance with tha groove pattern 25 the wire 26 runs in grooves
25.1, na~ely in a group of ~arallel depressions ~hich, l~ one
plane, are equidis~an~ly spaced. These depressions ~ave wire
arrangements ~ith the diameter of the heating wire 26 inserced
therein. At the ends of said lndividual grooves 25.1, ~he
heating wire 26 is guided from one groove to the ne~t, adJacent
groove. In t~ese turni~g areas 27 the heating w~re 26 changes
its space orie~tation by ~wice 90. As in fig. 2~ the heating
wire 26 on one main Eace of the heating element 20' is inserted
by an appropriate insertion ~ool in accordance ~ith the groove
pattern 25 located in one plane and does not have to be d~awn
throug~ the openin~s 20' in the sUpporc body.
Fig. 4b shows t~o heating elements 20' according to fig. 4a,
which are asse~bled i~ such a way as to ~orm a t~lrd embodimen~
o~ a surface heating means 28 according to the invention with a
c~n~al, square, weld-freç zone 21*. Accordi~g to the inven~ion,
the ~urface heating means 2~ comprises two heating wires 26
separately guided on ~he ~wo heating elements 20'. ~n the thi~d
embodiment of a sur~ace heating means in fig. 4b there is a
parallel connection a~d bet~een the connection points 29~ 29'
(forme~ by the semioireular recesses 24 and the embedded heatiug
wire 26), ~e current flows t~rough the identica~ly worlted supp-
ort plates 20. In the parallel connec~lo~ according to fig. 4b
the indi~idual resistance of th~ thin heating wires 26 is çon-
s~que~tly e.g. twice as high as ln the comparable, known ~ea~ing
coils and ma~
~i~. Sa sho~s a ~ourth, preferred e~bodi~ent of a hea~in~
element ~ith zonally cut groo~e pa~tern and heating uire embed-
ded eherein. ~he descrip~on of the heating element 30' l~
fig 5a substantially correspondq ~ith that o~ the ~lrst and
third embod~ment~ of heating elemen~ according to f igs . 2 and 4.
:~.~: .. : .
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,-
. 'f
~121~QI,~
-~ - 23 -
Whereas the heating element 10' is based on a semicircul~r
geometry a~d the heating element 20' on a rectangular geometry,
ehe heating element 30' is based on a polygonal ~eometry. In
~his fourth embodiment, the ~eld-free zone 31 has a central
point M4 bou~ded by equidlstant edges arranged wlth che spacing
of the diameter D4. The support ~late 30 serving ~s the se~i-
~ini~ed product for producing the hea-ting element 30' is made
from an electrically i~sulating, thermoplastic ~aterial and can
be flat or spatially curved. The thickness o~ the support plate
30 is freely selectable a~d as a rule of thumb is 1.5 to 5 times
thicker than the heating wire 36 used. The heating element 30'
has t~o at~achments 32 with two circular openings 33 and two
semicircular x-ecesses 34- The ~eating wire 36 is inserted i~
unitary man~er, co~prises one piece, is ~hin and ~on-rigid and
eithe~ passes in one nlane on the ~ront of the ~eating element
30' or ln several planes on the two ~ain faces (front and back)
of the ele~ent 30'. The heati~g w~re 36 is inserted in grooYes
35.1 according to the groove p~tter~ 35. It runs in a plurali~
of depressions, which are parallel and, co~sidered in a plane,
equidistantly spaced. ~hese depressions have t~e diameter of
the heatl~ wire 36 tO be in~erted therein. On the ends of the~e
indiYidual $roQVes 35.17 the heating wire 36 is guided from one
grnove 35.1 to ~he next, adjacent groove 35.1. In ~his turni~g
area 37 the heating wire 36 chan~es its space orientat~on ~wlce
by 90.
Fig. 5b shows two support plates according to ~ig. 5a, ~hich are
so assembled as to form a fourth e~bodiment of a surface heating
me~ns 38 accordi~g to the lnven~lon with a centralj, hexagonal,
weld-free zone 31*. According to the invention, t~e surface
heacing means 38 is assemb~ed f~om at least two heating wires
36 separa~ely guided on the two ~eating elements 30'. T~e
fourth embodiment of a surface hea~ng ~eans is also parallel-
connec~ed via con~ecting poin~s 39, 39'. With the knoule~ge of
i~he present inven~ion, the e~per~ ~an ~aturally imple~ent
.i',:: .. . :
~12:~00
. .
- 24 -
numerous e~bodi~ents o~ support body shapes and therefore heat-
ing elements ~or random, sur~ace-cove~ing surfac~ heating means.
At least two ~eating ele~ents are joined together so as ~o ~orm
a surface heating means. ~hus, for forming larger surface hea-
ting means, it is e.g. possible to connect in parallel four
heating elemqnts, so t~ac the individual heating wi~e length
per heating element used can be kept the same. T~us, accordlng
to the invention a pluralitY of different embodiments thereof
are Possible~
Fig. 6a shows a fifth, pre~erred embod~ment of a heating element
40' with zonally cut ~roove pattern 45 and ~eating ~-ire 46
embedded therein. It di~fers through the omissio4 of ~ weld-
free zone. The heating wi~e 46 is inser~ed in unitary rQanner,
compriseS one piece, is thin and no~-rigid and run~ either in
one plane on the front of the heati~g element 40' or i4 several
planes on the two mai~ faces (front and back) of the hea~ing
element 40'. It is inserted in grooves 45.1 according to a
groave pattern 45 of clearly defined depth and extensio~, runs
in an ordered manne~, namely in a group of par~llel depressions
which, considered in o~e plane, are equidistantly spaced. In
the turning areas 47 a~ the ends of ~rooves 45.l the heating
wire 4~ is looped, 50 that the wire 46 ls guided in arcs from
one groove 45.1 to the next, adj~c~nt groove 45.l. In these
~urnin~ areas 47 the heatin~ wire 46 changes its space orien-
tatio~ twice by ~o. A5 also i~ the embodlments accordi~g to
fi~sn 2 to 5, the hea~in~ wire 46 is inser~ed by a matching
insertion tool on the heating element 40' in aocordance with the
groove pat~ern 45 a~ranged in one or more planes, so t~at it
does not h~ve to be drawn thxou~h the ~eating element 4Q'.
Flg. 6b shows ~wo heating elements 40' accordi~g to fig. 6~,
which are asse~bled to form a fifth e~bodiment of a surface
he~t~ng means 48 accordin~ to the inventlOn without formin~ a
cent~al w~ld-free zone- According tO the in~e~tion, the surface
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heaCin$ means 48 comprlses at least t~o heating wires 46 guided
separately on the ~o heating elements 40'. In each case two
semicircular rece~ses 44 of in each case oue of the heat~ng
elements 40' of the surface heating means 48 face one another
and ~or~ ~air~. Eleccrlc circuits can now be desizned in such a
way that pairs of semicircular recesses 44 of in each case one
support plate 40 of th~ surface he~ting means 48 are brought
into ele~tric contact ~eonnection points 49, 49').
Fig. 6c shows a plurality of heating elements accordi~g to flg.
6a, whl~h are assemble~ to form a further embodiment of the
surface heati~g means 48 aocordi~g to the invention, i.e. show a
randomlY large heaei~g mat- According to the inve~t~on, the
surface heating ~eans 48 co~p~ises heating wires 46 separatel~
g~i~ed on the heating eleme~ts 40'. In eac~ case two semi-
circular recesses 44 of irl each case one of t~e heating elemen~s
40' of the surLace heating means 48 face one another and form
pairs (connection points 4~, 49'). Electric ci~cuits can now
be designed in such a way that one or both pairs o~ semicir-
cular recesses 44 o~ în each.case one support plate 40 o~ tha
surface hea~ing means 48 can be brought into elect~ic~l contact.
At ~he ~ontact polnLs P contac~s can occur without a~fecting the
heatin~ power of the individu~l ele~ent, because with identical
heatin~ e~eme~ts the same electric Potential occurs at the con-
tact points P. The indl~idual. par~llel-con~eceed heat~ng
elements ~eed not havé ~e same heating power and c~n have
diferent oh~ic resistanceS. so that ~ith a planned electrical
con~act between the points P a branching oE the hea~lng power
occurs, because along a row o~ contact points P ~ such as for the
tap on a potentiometer) different individual resistances of
dlf~erent potentials occur. Thus, the current at certaln con-
t~ct poi~ts P will seek the path across the adjacent ~eating
element, i e- will bra~ch This ef f ect is in~errupted as soon
as the sof tening o~ t~e support separates the contacts at the
points ~ and t~e current flow between -two elements i~ interr-
upted .
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Fig. 7a shows a si~th, preferred e~bodiment of a heati~g element
60' with zonally cu~ groove pattern 65 and ~eating wires 66
embedded therein, toge~her with a ce~tral, weld-free zone 61*.
This e~bodiment differs from t~e prevlous embodiments ln that
here two ~eatiug wire ~6 are laid in grooves 65.1 on a common
support plate 60 a~d f o~m two heating zones in which the fit-
tings ca~ be welded in weldin~ zones. The topological problems
when la~ing the heating wire are solved i~ this sixth embodiment
in that ~he wires 66 are turned in turn~ng areas 67 on the sa~e
size of the suppo~t pla~e 60. ~hus, the heating wires 66 do no~
have eo be drawn throu~h the weld-free zone 61*. This embodi-
ment also differs in that the heating wires 66, projecting from
the surface of the support plate 60, run in turning ar~eas 67.
Thus, only the turnin~ areas 67 of the heating wires G~ of the
sur~ace heating means 68 ~re visible from the outside, whereas
the other areas of the wire 66 are located in the grooves ~5.1.
Finally, ~he wires 66 have no contact p~ints.
Other~ise this embodiment follows t~e characteristics of the
previously discussed embodiments according to fi~s. 2 to 6.
The surface heati~g means 68 co~sequently co~prises two heat~n~
wire~ 6~ separatel~ gulded on the hea~ing ele~ent 60'. In each
case two semicircular recesses 64 of in each case one of the
heating elements 60' of the surface heating means 68 face one
anothe~ and form pairs. Electric circuits can now be clesigned
in such a ~ay that pairs of semicirc~lar recesses 64 of ~he
surface ~eating means 68 are brought into electric eo~t~ct
(connectio~ points 6~, ~9'). The hea~ing wire 66 is once again
inserted in unitarv ma~ner, comprlses one piece, is th~n and
non-rigid~ I~ certain zones it is inser~ed in grooves 65.1
accordin~ to a ~roove pattern 65 of clearly defiued depth and
exte~sion, it runs in a~ o~d~red manner, namely i~ a plur~lity
o~ pa~allel depressions which, considered in a plane, are equi-
distantly spaced. Through groups of smaller and larger wire
spa~i~gs i~ is possible to crea~e ~ea~ing zones wî~h different
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energy densities. I~ turning areas 67 at the end~ of the
grooves 65.1, the heating wire 66 projects out of the support
material 60, so that the wlre 66 is guided on the su~ace from
one groove 65 1 to the ~ext, adJaoen~ groove 65.1. As ln the
embodiments according to figs. 2 to 6 the heating wl~e 66 is
inserted by a matching insertion tool on the heating element
60' i~ acoordance with the groo~e pattern 65 arranged i~ a
planar or curved face.
~ig. 7b is a persp~ctive section AA' of this preferred embodi-
~en~ according to flg. 7a. The heating wires ~6 are only partly
d~ ~d i~:L thc turnin~ rc:lc 67 project out o tho E:ur~ac~
of the suvpore ~late 60~ ~hus, follouing the welding of the
grooves these points aopear as a seam. In thi5 embodiment of a
heati~g elemenc 60' and surEace hea~ing means 68 use iS made of
a "double" support bod~ 60 with two separa~ely inserted heating
~ires 66.
Fig. 7c shows a larger-scale~ perspective section BB' of ~his
pr~f~rred ~boctim~nt ~ rdi~ to fig. 7a and i~ is Po~;sible to
see how the heati~g wire5 66 i n the turning areas 67 acLva~tage-
ously come flat o~ the surlace of the hea~in~ element 60' and
are then again inse~ted in the ne~t groove. This lnsertion
prooess cons~qùently differs fro~ the preceding embodi~ents,
where the hea~ing wire 66 is inser~ed in looped form.
Fi~. 7d shows a seventh, preferred embodiment of a heatin~
clcment 70' and a su~f~r~ .ing means 78. ~ollowing the pres-
sing and meltln~ in of ~h~ projecting turning a~ea 77 of the
heating wire 76 and give a weld-ree zone 71*. This surface
heating means has a comPlex geometry and is shaped a5 a portion
of a larger plastic pipe to be connected (not show~ d~a~-
tageously the procedure is su~h t~a~ t~e groove pattern 75 or
~he heat~ng zo~es are brought directly onto the fiteln~s 70 to
b~ connected. ~his has the ad~anta~e that the heaeing zones are
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directly connecte~ to the fitting and can therefore be welded
wi~hout insertin~ ~ heatlng mat. ~he shor~-circuit risk is
eliminated, because che heati~g wires 76 pass at an adequate
distance from one another and in meander-like manner on one side
of the fitting 70.
This surface heating mea~s is characteriæed i~ t~at eac~ of the
heating wires 76 is inserted in accorda~ce with a g~oove pattern
75 in grooves 7S.1 of the fittings 70 and ~hat the wires 76, at
~he ends of said grooves 75.1, aIe guided în t~rning areas 77
~rom one groove 75.1 to the next, adjacen~ ~roove 75.1 and
thereby under~o a space orientation cha~ge. ~he grooves 75.1
in which the hea~ing wires 76 pass in ~e heating 20ne comprise
a plurality of depressions associated with one ano~her in one
surf ace and having a predetermined dep~h and which are cut in
o~e side of the fi~ting 70. In the turning a~eas 77, the
heatin~ ~ires 76 come flat ~o the surface o~ the ~i~tin~s 70
and then are introduced into the next groove 75.1. The heati~g
zone of the surface heating ~ea~s 76 can have di~ferent groove
pat~erns 75 wlth different equidi~tant grooves 75.1, so that
said heating zones have dif~erent heating powers for sur~ace
w1din~ in welding zones. ~he ends of the heating wires 76
are electrically contac~able on attachme~t 72 by means of
recesses 74 at connec~ion poin~s 79, 79'.
Thus, also in ~his e~bodl~ent there is no UnitarY produced conn-
eceing fittin~ only usable in a specific construction and h~re
again there is no connectin~ fitti~g produced from a cast
materlal~ e.g. a plastic pipe and it can be a random sur ace
o~ a thermoplastic fitti~g. ~his leads to a considerable free-
oom ln the ~hoice of the ascembly of the fitti~s for for~in~
numerous di~ferent co~nectin~ fitti~gs from elem~ncary fi~ting$
and su~f ace he~t~n~ m~ans It is naturall~ also possible to use
surface heating means without a central, weld-free zone 71
i8 ~lso ~ossible to have ~ombinatlo~s and assemblies ~ith othe
embodiment~ of surLace heati~ means.
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