Note: Descriptions are shown in the official language in which they were submitted.
CA 022~9639 1998-12-18
r~ A ~
~ 'Ll~A,i,T,~ ,1
Process of Manufacturin~ Terminal Sleeves on Plastic Tubes and Apparatus for
Performinq the Process
This invention relates to a process of manufacturing terminal sleeves on plastictubes from hot-forming plastic materials, in particular polyolefins or PVC, wherein
an area at the end of the tube, which approximately has the length of the sleeve,
is heated in a heating station to or above its deformation temperature, is formed to
the sleeve in this condition by means of a sleeve-fitting tool introduced from the
tube end, and before and/or after drawing the sleeve-fitting tool is cooled below
the hot-forming temperature.
Furthermore, the invention relates to an apparatus for performing the process,
comprising a sleeve-fitting station, in which a sleeve-fitting tool designed for in-
stance as a sleeve-fitting arbor conically tapering at the leading end can be intro-
duced under a relative longitudinal adjustment into a portion at the end of a plastic
tube, which for instance in a heating station has been heated to or above its de-
formation temperature and approximately has the length of the sleeve, by expand-ing and deforming this portion to form the sleeve.
Examples for materials for manufacturing such plastic tubes include polyolefins
such as high-pressure and low-pressure polyethylene, polypropylene and further
hot-forming plastics (thermoplastics), in particular PVC. The possible deformability
largely depends on the respective manufacturing material and the temperatures
applicable during the deformation, where the deformability is not only influenced
by the main manufacturing material, but also by the kind, quantity and consis-
tency, e.g. grain size, of used fillers. In general it can be said that the manufacture
CA 022~9639 1998-12-18
of the sleeves becomes easier the smaller the necessary expansion of the tube toform the sleeve, the wall thickness of the tube, and the length of the sleeve to be
manufactured. Depending on the material, such sleeves can therefore be manu-
factured in series and productively only up to limit dimensions, so that for instance
when sleeves with diameters and lengths above this limit value are required for
certain tubes, more expensive manufacturing materials with less fillers and a more
favorable hot-forming property must be used for the entire tube. Special shapes of
the terminal sleeves, e.g. for the connection of thicker tubes or tubes with larger
diameters, can frequently only be provided such that they are manufactured in a
separate injection molding operation and connected with the tube or are molded
directly to the end of an existing tube subsequent to the injection molding opera-
tion. This statement is also true when the basic shape of an attachment, e.g.
sleeve, largely differs from the basic shape of the tube, e.g. when a square sleeve
should be attached to a round tube. In this case, the commonly used procedure
consists in either designing the component to be attached as a fitting provided
with a round socket, which fitting is plugged into a normal terminal sleeve of the
tube, or, as described above, in a large-scale production, designing this compo-nent again as injection-molded component.
Even in the case of relatively easily deformable materials major problems occur in
connection with large sleeve diameters and lengths as compared to the tube di-
ameter. It has so far been common practice to either hold the tube at the end fac-
ing away from the sleeve-fitting zone and press the sleeve-fitting tool into theheated end of the tube, or vice versa let the sleeve-fitting tool, e.g. the corre-
sponding arbor, stand firm and manufacture the sleeve by pushing the tube onto
this stationary arbor. In both cases, the support of the tube for accommodating or
applying the pushing forces is effected in a portion of the tube which has not or
only slightly been heated. When the sleeve portion is heated more to provide for a
greater deformation, introducing the sleeve-fitting tool may lead to corrugations in
that portion in which a heating of the tube has taken place, but which has not yet
been reached by the sleeve-fitting tool when introducing the same. This is unde-sired and virtually leads to the formation of scrap. A very flat conical inclination of
the sleeve-fitting arbor at the leading end promotes and facilitates the introduction
into the tube, but leads to undesired long transition zones between the normal
tube and the sleeve portion having the full terminal diameter. A partial solution to
these problems has so far been achieved in long sleeves in that the portion de-
CA 022~9639 1998-12-18
signed for the formation of the sleeve at the end of the tube is heated to various
degrees according to mostly empirically determined values, i.e. the outer end isheated much more than the inner end, so that the last portion of the sleeve thatcomes into engagement with the sleeve-fitting tool receives a greater rigidity than
the end portion prior to such sleeve-fitting operation. As a result, however, the
deformation force to be applied increases again because of the greater retentioncapacity of the cooler portion. What is disadvantageous in almost all used plastics
and tubes manufactured therefrom also is the so-called memory effect, i.e. the
tendency of a part prefabricated by means of hot forming to wholly or partly return
to the original shape upon heating or also at normal temperature. The memory
effect is noted more and more, the lower the hot-forming temperature must be
kept with respect to the melting temperature because of the other conditions to be
observed when manufacturing the sleeves. In the above example of a long sleeve,
the memory effect will therefore get stronger towards the inner end of the sleeve7
so that due to this effect greater deformations will occur there than in the end por-
tion in the course of time.
It is the object of the invention to improve a process as described above, in order
to simplify the dimensionally accurate manufacture of sleeves, the manufacture of
sleeves of larger diameter and length as compared to the previous process, and
nevertheless largely or wholly avoid dimensional changes as a result of the so-
called memory effect in tubes of a corresponding material. A partial object of the
invention consists in creating a simple apparatus for performing the improved
process.
In accordance with the invention, this object is solved in that for introducing the
sleeve-fitting tool the tube is held at the outer end of the sleeve portion by means
of clamping devices allowing the introduction of the sleeve-fitting tool and engag-
ing in the tube wall both externally and internally.
The basic idea of the invention - extremely simple after all - consists in that it is
much easier to draw a resilient sleeve onto an arbor when the sleeve is held at
the leading end, than to push the sleeve over this arbor by applying pressure onto
the other end. The tube material can not only be heated to a temperature allowing
the deformation, but can be heated to a much higher temperature, at which in thecrystalline structure of the thermoplastic materials a much larger part of the crys-
CA 022~9639 1998-12-18
- 4
tals producing the memory effect as such has been liquefied than at the tempera-tures admissible for the deformation according to the previous processes. As a
result, the tube portion becomes much more resilient and can be deformed more
easily, so that comparatively larger diameters and lengths of the sleeve portioncan be produced with the same material as compared to the previous process,
and moreover a subsequent deformation of materials subject to the memory effect
is largely avoided, as a major part of the crystals has been liquefied and has
therefore lost "the memory" as to the original shape. By observing the conditionthat the clamping devices must allow the introduction of the sleeve-fitting tool, a
plurality of constructions are possible for these clamping devices. They may basi-
cally have clamping jaws that can be adjusted radially from the starting diameter
to the terminal diameter or have inner members variable in diameter like expand-ing mandrels or folding mandrels, which should be designed such that in the
holding area they only slightly protrude beyond the inside of the tube or are
pressed into the inside of the tube, so that movement through the sleeve-fittingtool is possible.
A preferred apparatus for performing the inventive process is characterized in that
for the outer end of the sleeve portion of the tube a holding device is providedwhich has clamps with expanding members engaging in the inside of the tube
wall, which expanding members can be adjusted from their normal position, which
corresponds to the starting diameter of the tube end, to the outside into a clamp-
ing position, which allows the movement of the sleeve-fitting tool therethrough and
urges the outside of the tube end against counter-holders, by expanding the tubematerial.
It is generally possible to use separate drive means for the expanding members.
However, it is particularly advantageous and simple to directly derive the adjust-
ment of the expanding members from the relative adjustment of the sleeve-fittingtool with respect to the tube. It is also possible to subsequently equip an existing
sleeve-fitting station with a corresponding clamping device. In constructive terms,
this provides for a particularly simple solution, in that the holding device has an
outer sleeve, through which the sleeve-fitting tool can be introduced into the end
of the tube, where on the side of the tube the outer sleeve has an annular seat for
the end of the expanded tube with counter-holders for its outer side, and with adistance from this annular seat expanding arms are held on the outer sleeve at
CA 022~9639 1998-12-18
the leading end and outside the tool guideway, where in the rest position the free
ends of the expanding arms protrude to the inside into the longitudinal portion of
the annular seat under flat angles of attack and can engage into the still unde-formed tube end, where the sleeve-fitting tool moving in spreads apart the ex-
panding arms also forming introduction aids for this tool by expanding the tube
end, so that they allow the passage of the sleeve-fitting tool, and their free ends
press the tube end from the inside of the tube against the counter-holders of the
annular seat and hold the tube during the further sleeve-fitting operation. The
counter-holders are preferably mounted such that they maximally reach to an an-
nular bead determined for accommodating a seal in the case of corresponding
sleeves. The annular bead itself can be produced in a manner known per se,
possibly by additionally using a divisible outer mold, by inflating the bead portion
into the outer mold, or also by using extensible folding mandrels of the sleeve-fitting tool.
According to an embodiment, the expanding arms consist of leaf springs which
are fixed at the outer sleeve under the angle of attack and are mounted so as tobe uniformly distributed about the periphery. The use of springs as expanding
arms has the advantage that no joints are necessary, a favorable course of the
expansion movement is effected, and thin springs may be used, which can easily
be accommodated at the inside of the sleeve or in flat grooves provided there for
introducing the sleeve-fitting tool.
As counter-holders of the annular seat one or more annular combs may be pro-
vided, which in the clamping position, like the ends of the expanding arms, are
pressed into the heated tube material. The end of the sleeve is thereby safely re-
tained and gets a neat appearance similar to the outer edge of a crown cork.
Due to the basic equipment in accordance with the invention it is also possible to
manufacture special shapes of the sleeve. In the case of a corresponding ar-
rangement of the expanding arms, the sleeve-fitting tool and the outer sleeve will
accordingly have a cross-sectional shape differing from the basic cross-sectional
shape of a rotation member at least in the edge portion, e.g. a square or polygo-
nal cross-sectional shape, for producing corresponding sleeves.
CA 022~9639 1998-12-18
In the above-mentioned example of the manufacture of a long sleeve of HD-PE
heating to different temperatures would be effected under corresponding difficul-
ties, if a sleeve with an inside terminal diameter of 122 mm and a length of 400mm would be required for a tube of 104 mm inside diameter and a wall thickness
of 5 mm, where the inner end of the sleeve portion would reach a maximum of
120~C, and the outer end would reach a maximum of 140~C. In the process in ac-
cordance with the invention, the same tube is maintained above 140~C over its
entire length, and is preferably heated up to the range of 200~C, i.e. very close to
the melting point, and is then deformed.
Further details and advantages of the subject-matter of the invention can be taken
from the following description of the drawing.
In the drawing, the subject-matter of the invention is represented by way of ex-ample, wherein:
Fig. 1 shows a view of a tube with a terminal sleeve manufactured in accor-
dance with the inventive process,
Fig. 2 shows a section of the inventive holding device of a sleeve-fitting sta-
tion with an introduced tube end before the sleeve-fitting operation, and
Fig. 3 shows the holding device with fixed tube end and sleeve-fitting arbor of
the sleeve-fitting station partly introduced into the tube in a representa-
tion corresponding to Fig. 2.
As shown in Fig. 1, at the end of a tube 1 a sleeve 2 is formed, which is very long
as compared to the tube diameter and has a large diameter, and which during the
sleeve-fitting operation was held at its end 3, and at a distance from the end 3carries an annular bead 4, which was made for instance by inflating into an outer
mold, for accommodating a sealing ring. During the manufacture, the sleeve por-
tion 2, 3, 4 of the tube was heated to a relatively high temperature over its entire
length, so that the memory effect in the finished sleeve is virtually excluded even
if it is made of a susceptible material.
For the sleeve-fitting station shown in Figs. 2 and 3 there are provided known
holding or feeding devices for the tube 1 and a sleeve-fitting arbor 5 with a conical
end portion 6, which can be extended relative to the tube in longitudinal direction
CA 022~9639 1998-12-18
thereof, where said sleeve-fitting arbor can have blow nozzles in the portion that
will later on form the bead 4, which blow nozzles blow the corresponding sleeve
area into a divided outer mold, which upon making the bead can again be sepa-
rated for releasing the bead. For making the bead there may also be used foldingmandrels in the arbor 5.
What is essential for the invention in the embodiment is the holding device 7
shown in Figs. 2 and 3. The same substantially consists of an outer sleeve 8,
which at the outer end 9 and beside an annular seat 10 at the inner end 11 is kept
only slightly larger in diameter than the arbor 5 and from the inner end 11 slightly
conically expands up to a re-entrant portion 12.
The re-entrant portion 12 constitutes an annular groove of triangular cross-
section, whose outer flank is inclined towards 12. At the inclined flank of the
groove 12, which is inclined towards the end 11, there are mounted spring
tongues 13 serving as expanding arms with an angle of attack sloping flat against
the end 11 and the annular seat 10 in the rest condition. The free ends of the
spring tongues 13 are Iying close to each other on a circle. The spring tongues
may for instance have a width in the order of magnitude of 10 mm and a thicknessin the order of magnitude of 1 mm.
As shown in Fig. 1, the heated tube 1 with its corresponding end has been intro-duced into the outer sleeve 8 such that the terminal edge slightly protrudes be-yond the annular seat 10, where the ends of the spring tongues 13 engage in thistube end 3. Now, the sleeve-fitting arbor 5 is introduced from the right and thereby
spreads the spring tongues 13 to the outside until they almost abut against the
inner wall of the outer sleeve 8, where the free ends of the spring tongues or leaf
springs 13, which engage in the tube end 3, expand this tube end and press into
the annular seat 10. In the annular seat 10, one or more annular combs 14 are
provided parallel to the edge, which with fully spread leaf springs 13 press from
the outside into the tube end 3 now forming the end of the sleeve. The ends of the
leaf springs, too, are outwardly pressing into the sleeve end 3. From this position
onwards, the sleeve end, which by swivelling out the leaf springs has been ex-
panded anyway, is retained at the outer sleeve 8, so that the sleeve-fitting arbor
further moving in not only receives an introduction aid via the leaf springs 13, but
also a compression of the sleeve portion of the tube upon drawing the same onto
CA 022~9639 1998-12-18
the arbor 5 is safely prevented. Upon completion of the sleeve-fitting operationand upon mounting the annular bead 4 in the manner described above, there can
at best be effected a precooling of the sleeve portion, until the sleeve 2 has the
necessary stability, whereupon the sleeve-fitting arbor is drawn out, or the tube 1
with the finished sleeve 2 is withdrawn from the sleeve-fitting arbor.
