Apparatus for the production of hollow bodies from thermoplastic material by an extrusion blow molding process

In an apparatus for the production of hollow bodies from thermoplastic material by use of extrusion blow molding, having at least two blow molding units and an extrusion system, in an operating cycle each blow molding unit is movable between a receiving position in which the opened blow molding mold receives a preform and at least one other position in which the expanded hollow body is removed from the blow molding mold. Each blow molding unit is firstly moved from a station remote from the removal station in at least one direction into the removal station and opened after reaching the removal station, whereupon the hollow body previously produced in the blow molding mold is removed. The respective blow molding unit is then moved by use of a second movement in another direction, with the blow molding mold open, into the receiving position which is arranged laterally displaced relative to the path of movement along which the blow molding unit is moved into the removal station.

BACKGROUND OF THE INVENTION 
A number of operating procedures for the production of hollow bodies from 
thermoplastic material by an extrusion blow molding process, particularly 
in the case of producing relatively large hollow bodies such as barrels or 
motor vehicle tanks, involve the use of at least two blow molding molds 
associated with an extrusion head. The blow molding molds are moved 
selectively into a receiving position, for example beneath an extrusion 
head, in order to receive preforms which are extruded from the extrusion 
head. In that operation it is necessary for the blow molding molds to be 
arranged movably relative to the extrusion head, in such a way that, after 
a preform has been received by a blow molding mold, that mold is moved 
away in order to liberate the space beneath the extrusion head for the 
other blow molding mold to receive the respective following preform. 
In continuous extrusion of the preforms, it is generally usual for the 
movement of the blow molding mold between the receiving station beneath 
the extrusion head and a station which is spaced away from the receiving 
station to take place substantially parallel to the separation surface of 
the blow molding mold. When the blow molding mold parts are of a 
symmetrical configuration, that separation surface is the vertical plane 
of symmetry of the mold, being at any event a surface which extends not 
parallel but mostly perpendicularly to the directions of the mold opening 
and closing movements. The need for the movements of the blow molding mold 
between the receiving position and a position spaced therefrom to take 
place approximately parallel to the above-mentioned plane makes it 
possible for the two parts of the blow molding mold, in the opened 
condition thereof, upon movement into the receiving position, to be guided 
laterally past the preform which is in the process of being formed and 
which may already involve the major part of its required length. In that 
respect, it is also possible for the blow molding mold to move along an 
arc portion as long as the radius of that arc is of such a size that the 
above-indicated requirements are met. Nonetheless, in a continuous 
extrusion procedure, the possible movements as between the blow molding 
mold and the preform which is in the receiving station are limited, unless 
particular additional steps are taken, for example by introducing the 
preform into the blow molding mold in the receiving station, by means of a 
gripper device for firstly removing the preform from the extrusion head 
which is disposed at a certain spacing from the receiving station. Thus, 
when such a mode of operation is employed, the extrusion head could be 
arranged at a spacing above the blow molding mold which is in the 
receiving station, that spacing approximately correspondingly to the 
target or reference length of the preform. 
The limitations in regard to performance of the movements of the blow 
molding molds, which are imposed in continuous extrusion of the preform, 
can have a disadvantageous effect insofar as the operation of removing the 
hollow bodies which are produced by being expanded in the blow molding 
molds cannot be effected in a position which is common to the two blow 
molding molds and which is selectively adopted by the respective blow 
molding molds. On the contrary, in the above-indicated apparatuses the 
usual practice is that the blow molding molds, upon removal of the hollow 
bodies therefrom, adopt different positions, with the consequence that the 
devices required for removal of the hollow bodies and for further 
transportation thereof into some downstream-disposed treatment stations 
must be duplicated. That gives rise to a not inconsiderable level of 
expenditure, which increases with the size of the hollow bodies, as the 
transportation distances, removal devices, and downstream-disposed 
transportation means and other devices must inevitably be adapted to the 
size of the hollow bodies. 
Moreover, when dealing with hollow bodies of relatively large size, for 
example motor vehicle tanks, it, is frequently necessary to introduce 
additional parts into the blow molding mold prior to closure thereof, for 
receiving the preform; such insertion parts when introduced into the mold 
are joined to the hollow body in the mold in the course of the operation 
of expanding the preform to constitute the hollow body. The insertion 
parts for example may involve installation components which are to be 
mounted in the interior of a tank, but they may also be reinforcing parts 
which are to be mounted on the outside. At any event the use of such 
insertion parts which must be introduced into the mold prior to closure 
thereof is of great practical significance, insofar as those parts must be 
correctly positioned in the blow molding mold with a great deal of care 
and generally in a very short time. The endeavor here is also that the at 
least two blow molding molds use a common station in which they are 
provided with the insertion parts to be introduced into the molds, so that 
essential members of the devices which are required for that operation can 
be jointly used by at least two blow molding units. 
In discontinuous extrusion using an accumulator or storage head, the 
limitations and disadvantages described hereinbefore in relation to 
continuous extrusion are less pronounced, as there is greater freedom in 
regard to the movements of the at least two blow molding units. It is also 
possible for the two blow molding units to have a common station in which 
the hollow bodies are removed from the respective blow molding unit 
disposed at that station. A similar consideration applies in regard to the 
operation of introducing any parts which are to be joined to the hollow 
body in the blow molding mold. However discontinuous extrusion also 
requires the fulfilment of certain conditions, if for example the 
arrangement provides for both blow molding units a single common position 
in which the operation of removing the hollow bodies is effected. 
SUMMARY OF THE INVENTION 
An object of the present invention is to provide an apparatus for the 
production of hollow bodies from thermoplastic material by means of 
extrusion blow molding, such that in every case and including therefore in 
a continuous extrusion procedure, it is possible to provide for at least 
two blow molding units a single station in which the hollow bodies are 
removed from the blow molding units. 
Another object of the present invention is to provide an apparatus for the 
production of thermoplastic hollow bodies by extrusion blow molding with 
the incorporation of at least one insertion part, which is so designed 
that the operation of feeding the insertion part to be joined to the 
hollow body in the blow molding mold is effected at a single position 
which is common to the two blow molding units. 
Yet another object of the present invention is to provide an apparatus for 
producing hollow bodies from thermoplastic material by extrusion blow 
molding, which is of such a configuration that hollow bodies are removed 
from at least first and second blow molding units thereof at a single 
station at which an additional part to be joined to a hollow body produced 
in a molding unit can also be fed to the molding unit. 
Still a further object of the invention is an apparatus for producing 
hollow bodies from preforms of thermoplastic material for blow molding 
wherein the major parts of the apparatus are easily accessible and easy to 
maintain. 
According to the present invention the foregoing and other objects are 
attained by the apparatus set forth herein. 
With this apparatus, it is readily possible for the hollow bodies to be 
removed from the blow molding molds of all blow molding units at one 
location and to be guided away from that location by suitable means such 
as a conveyor belt. A similar consideration applies in regard to the feed 
of insertion parts. In other words, in comparison with prior apparatuses, 
the means required for removal of the expanded hollow bodies and 
transporting them away can be concentrated at one location. A similar 
point also applies in regard to the means for feeding any additional 
insertion parts to be fitted and/or introducing them into the molds. 
When reference is made herein to `blow molding mold` and `blow molding 
unit`, that is intended to include the possibility that each blow molding 
mold may contain two or more blow molding cavities. Consequently, the term 
`extrusion head` is also to be interpreted as meaning that it may include 
a plurality of discharge openings, the number of which corresponds to the 
number of blow molding cavities. 
The term `blow molding unit` also includes for example the structure 
carrying the blow molding mold parts, drive means and synchronising 
devices for the opening and closing movements of the blow molding mold 
parts, blowing mandrels or tubes or other means for the supply of 
compressed air for expanding the preforms in the blow molding mold. 
The term `continuous extrusion` used in this specification is not intended 
to exclude the possibility of the extrusion procedure being briefly 
interrupted, but rather it is to be interpreted as meaning that the 
procedure is such that, at the moment at which the blow molding mold is 
moved into the receiving station, for example beneath the extrusion head, 
the blow molding mold would collide with the at least one preform unless 
particular precautions are taken, for example by a suitable arrangement of 
the blow molding mold relative to the preform, for example along the lines 
of the above-mentioned arrangement of the blow molding mold parts in such 
a way that, upon moving into the receiving station, they are guided past a 
preform which is possibly already to be found there. 
Particularly in the production of hollow bodies with a multi-layer or 
laminate wall, use is increasingly made of continuous extrusion of the 
preform. In that procedure, the preform which is also of a multilayer or 
laminate structure is produced by a co-extrusion process which, in the 
case of batch-wise extrusion, requires particular precautions in order to 
guarantee uniform and undisturbed formation of the individual layers of 
the preform and, in that respect, the article to be produced therefrom. 
The requirement for the additional measures mentioned above is due in 
particular to the point that batch-wise extrusion involves the occurrence 
of pressure fluctuations in the extrusion system, that is to say in the 
extrusion storage head and in the extruders associated therewith, and such 
pressure fluctuations can result in irregularities in distribution of the 
material forming the individual layers in the preform. In comparison, when 
continuous extrusion is used, the entire system consisting of extruders 
and extrusion head is maintained in a condition involving constant and 
uniform operating conditions, over prolonged periods of time, without 
serious difficulty, as the pressure and the flow speeds in the systems 
vary, if at all, only slowly and within close limits. Therefore for 
example certain layers can be formed substantially more uniformly and thus 
thinner. In addition an extrusion system for continuous extrusion is 
substantially cheaper.

DESCRIPTION OF PREFERRED EMBODIMENTS 
The fundamental structure of the apparatus is firstly described hereinafter 
with reference to FIGS. 1 through 3. The embodiment illustrated therein 
comprises two blow molding units 10 and 12 which are arranged reciprocably 
in a horizontal plane. Each of the two blow molding units 10, 12 is 
provided with a carriage or slider 14 and 16 respectively which is movable 
for example on rails 38 in the direction indicted by the arrows 17 and 18. 
The to blow molding units 10 and 12 are each in the form of a push-pull 
clamping system comprising three plates, as will be described below. Each 
of the two mold halves 10a, 10b and 12a, 12b is carried by a carrier plate 
20a, 20b and 22a, 22b respectively. The carrier plates 20a, 20b are 
mounted on approximately diagonally extending supports 24, 25, each of 
which represents one of the two plates of the push-pull clamping system. 
The third plate is formed by a support 26 which extends substantially 
parallel to the support 24 and which is connected by way of two spars or 
struts 28, 30 to the support 24 forming the first plate. A piston-cylinder 
unit 32 is arranged between the support 25 carrying the mold half 10a, and 
the support 26 representing the third plate, in such a way that, when the 
cylinder of that unit 32 is actuated, starting from the position of the 
parts shown in FIG. 2 of the drawings, the support 25 with the blow 
molding mold half 10a carried thereby moves towards the left, that is to 
say in the direction of the arrow 17, and the support 24 with the blow 
molding mold half 10b carried thereby moves towards the right, that is to 
say in the direction indicated by the arrow 18. In that situation the 
movement is transmitted to the support 24 from the support 26 by way of 
the two struts 28, 30 and a synchronization device (not shown) which is 
arranged between the supports 24 and 25. In the course of the 
above-described movement of the parts, the blow molding mold 10a, b is 
opened. 
Actuation of the piston-cylinder unit 32 in the opposite direction results 
in closure of the blow molding mold 10a, b. FIG. 2 of the drawings shows 
both blow molding molds 10a, 10b and 12a, 12b respectively in the closed 
position. 
In order to be able to produce the above-described opening and closing 
movements, the three supports 24, 25 and 26 are mounted displaceably in 
the directions of the arrows 17 and 18 on a support frame structure 34 
which in turn is mounted on the carriage 14 pivotably approximately in a 
horizontal plane. In particular FIG. 3 shows that the supports 24, 25 and 
26 can each be provided with a lateral strut 35. The supports 24, 25, 26 
and the respective struts 35 are provided at their lower ends with wheels, 
rollers or the like 27 which are movable on guides 29 mounted on the frame 
structure 34 on the top thereof. 
The carriages or sliders 14, 16 are also provided with wheels 36 which are 
guided on the rails 38. The rails 38 are laid on the ground 40. 
The two blow molding units 10 and 12 are of the same configuration so that 
mutually corresponding parts are also denoted by the same references. 
In the embodiment shown in FIGS. 1 through 3, the carriages 14 and 16 which 
each carry a respective blow molding unit 10 and 12 respectively are shown 
as mutually independent components, with the result that the two carriages 
14 and 16 can be moved independently of each other in the direction of the 
arrows 17 and 18. It is however also possible for the two carriages 14 and 
16 to be coupled together or combined together to form a structural unit. 
The apparatus is also provided with a continuously operating extrusion 
system 42 having an extrusion head 44 and two extruders 48 which convey 
the material plasticized therein into the extrusion head 44. The material 
issues at the lower end of the extrusion head 44, in the form of a 
generally tubular preform 46 (see FIG. 3). The preform is not shown in the 
other Figures of the drawings, for the sake of clarity of the drawings. 
Although two extruders are shown in FIG. 2 of the drawings, it is possible 
for only one or more than two extruders to be associated with the 
extrusion head 44. More than two extruders are generally provided when a 
multi-layer or laminate preform is co-extruded. The wall of the hollow 
body to be produced from the preform is then also of a correspondingly 
multi-layer or laminate configuration. 
The extrusion head 44 and the extruder 48 with the associated drive means 
and feed devices are disposed on a platform 50 which in turn is carried by 
two supports 52 in a plane above the blow molding units 10, 12. 
FIG. 3 in particular shows that the extrusion head 44 is arranged laterally 
beside the path of movement which is defined by the two rails 38 and along 
which the two blow molding units 10 and 12 are reciprocated in the 
direction of the arrows 17 and 18. 
FIG. 1 in particular shows that the two frame structures 34 are each 
mounted on the respective carriage 14 and 16 pivotably about a respective 
pivot point 54 and 56 respectively, at the end of the respective frame 
structure 34 which is towards the support 26 serving as the third plate of 
the push-pull clamping system, the pivot mounting being for example by way 
of a pin or in some other suitable manner. As a result of that 
arrangement, the respective blow molding unit 10 or 12 with the frame 
structure 34 carrying it can be pivoted about the respective pivot axis 
thereof in the direction indicated by the arrow 58 into a position which 
corresponds to the position of the blow molding unit 12 in FIG. 1. 
Reference is now made to FIGS. 4 and 5 showing a possible configuration of 
the drive means which are required for producing that pivotal movement. 
The drive means in this embodiment involves a piston-cylinder unit 72 
comprising a cylinder 74 which is mounted pivotably on a suitable support 
75 while the free end of the piston rod 76 can be releasably mounted 
pivotably to the frame structure 34 of the blow molding unit 10 or 12 
which is respectively in the removal station where the hollow body is 
removed from the blow molding mold. For purpose each frame structure 34 is 
provided with an eye 77 to which the free end of the piston rod 76 can be 
mounted using a pin or bolt or the like. In the operating position of the 
blow molding units, as shown in FIGS. 1 and 2, the piston rod 76 is 
connected to the blow molding unit 12. By suitable actuation of the 
cylinder 74 the frame structure 34 with the blow molding unit is pivoted 
out of the position shown in FIG. 4 into that shown in FIGS. 1 and 5 and, 
later, back again into the position shown in FIG. 6. After that, the 
piston rod 76 is released from the frame structure 34 of the blow molding 
unit 12 in order to be connected to the frame structure 34 of the blow 
molding unit 10 after the two blow molding units have been moved into the 
position shown in FIG. 7. In other words, a common drive means is 
associated with all blow molding units, for movement thereof between the 
receiving position and the removal position. 
In the pivoted position, the respective blow molding mold--when the 
components are in the position shown in FIG. 1 this is the blow molding 
mold 12a, b--is disposed beneath the extrusion head 44 which is indicated 
by a circle in FIG. 1. As, in the pivoted position, the blow molding unit 
with the frame structure 34 carrying it, at its end region remote from the 
respective pivot point 54 or 56, projects laterally relative to the 
respectively associated carriage 14 or 16, an additional support means 55 
is arranged for additionally supporting the outwardly pivoted blow molding 
unit in the region beside the path of movement defined by the two rails 
38, in such a way that the additional support means 55 additionally 
supports the end region of the blow molding unit which is remote from the 
respective pivot axis 54 or 56, during the pivotal movement of the blow 
molding unit and in the outwardly pivoted position thereof. For the 
purposes of effecting the pivotal movements, the carriages 14, 16 and/or 
the frame structures 34 and possibly the support means 55 may be provided 
with guide means and means for reducing friction, as is indicated for 
example in FIG. 15. The arrangements and measures required for that 
purpose are familiar to any man skilled in the art so that they do not 
need to be described in greater detail herein. 
The mode of operation of the apparatus is described hereinafter, in 
particular with reference to FIGS. 4 through 9. The starting point taken 
is the position of the two blow molding units shown in FIG. 4, in which 
the blow molding units 10 and 12 extend parallel to each other and to the 
path of movement defined by the rails 38. That position is referred to 
hereinafter as the `linear` position. In that situation, the blow molding 
unit 12 is dispossed laterally beside the extrusion head 44 in the removal 
position, as shown in FIG. 4. The blow molding mold 12a, 12b is in an open 
condition. In other words, the two blow molding mold parts 12a, and 12b 
are moved away from each other and are at a spacing from each other. The 
blow molding mold 12a, 12b was opened so that, in the position of the blow 
molding unit 12 shown in FIG. 4, the hollow body produced in the preceding 
working cycle can be removed from the blow molding mold. 
Starting from the linear position shown in FIG. 4, the blow molding unit 12 
with the blow molding mold in the open condition is pivoted about the 
associated pivot axis 56 in the direction indicated by the arrow 58 into 
the receiving position indicated at 45 in FIG. 5 in which the opened blow 
molding mold 12a, 12b is disposed beneath the extrusion head 44. Although, 
in a continuous extrusion process, at the moment of the pivotal movement 
into the receiving position shown in FIG. 5, the preform which is to be 
received by the blow molding mold 12a, 12b will be of almost its target or 
reference length which is required for the production of a hollow body, 
the pivotal movement can be produced without involving any contact between 
the preform and any components of the blow molding unit. The strut 28 
which is at the front in the direction of movement as indicated by the 
arrow 58 is arranged so low that it passes beneath the free end of the 
preform which hangs from the extrusion head. The strut 30 which is the 
upper strut and which is the trailing strut in the direction of movement 
as indicated by the arrow 58 remains outside the region within which the 
preform is disposed. The two blow molding mold parts 12a and 12b are moved 
apart to such an extent that, in the receiving position, they are disposed 
laterally of the preform which hangs from the extrusion head 44, as can be 
clearly seen from FIG. 5. 
When the preform has reached at least its target or reference length, and 
this will generally be the case immediately after termination of the 
pivotal movement in the direction indicated by the arrow 58, the blow 
molding mold is closed by moving the two blow molding mold parts 12a, 12b 
together. In that operation, the preform is received by the blow molding 
mold and at least partially pressed together and closed at its top and its 
bottom. FIG. 1 shows in solid lines the positions of the parts when the 
blow molding mold unit 12 is pivoted and the mold is closed, that is to 
say immediately after the mold has received the preform. After that, the 
preform is expanded by means of an increased internal pressure. It will be 
noted in that respect that air or another gas may also already be 
introduced into the preform when it is still suspended from the extrusion 
head 44. The man skilled in the art is familiar with the procedures and 
steps relating to closure of the mold and resulting enclosure of the 
preform in the blow molding mold. After the blow molding mold 12a, b is 
closed, the closed mold is pivoted out of the receiving position shown in 
FIG. 5 into the position shown in FIG. 6, in the direction indicated by 
the arrow 60, back into the removal position in which the blow molding 
unit 12 again adopts its linear position. 
After that, the two blow molding units 10 and 12 are displaced in the 
substantially horizontal plane in the direction indicated by the arrow 18 
(see FIG. 2), that is to say towards the right into the position shown in 
FIG. 7 in which the blow molding unit 10 is in the removal station, that 
is to say beside the extrusion head 44. The position which the blow 
molding unit 12 adopts in that situation is shown in broken line on the 
right in FIG. 1. Normally, the preform in the blow molding mold 12a, 12b 
will be expanded at the time of reaching the position shown in FIG. 7, so 
that the operation of cooling the hollow body which has been produced from 
the preform and which bears against the wall of the mold cavity of the 
blow molding mold 12a, 12b is already effected here. These procedures are 
also generally known to the man skilled in the art so that there is no 
need of further description thereof herein. 
After the arrangement reaches the removal position shown in FIG. 7 the blow 
molding mold 10a, b of the blow molding unit 10 is opened, as shown in 
FIG. 7, so that the hollow body which was produced previously can be 
removed from the blow molding mold 10a, b. For that purpose, associated 
with the removal station B is a removal device 62 (see FIG. 1) which is 
provided with a gripper 64. The gripper 64 is carried by a guide 66 along 
which the gripper 64 is reciprocable approximately perpendicularly to the 
linear directions of movement indicated by the arrows 17 and 18. FIG. 1 
shows the gripper 64 in the closed condition. In other words, the two 
members forming the gripper 64 are bearing against each other. More 
specifically, the operation of removing the hollow body from the blow 
molding mold 10a, b which is disposed in the station B in a linear 
position, that is to say the removal position, can be effected by a 
procedure whereby, as soon as the components have reached the positions 
shown in FIG. 7, the gripper 64 is moved into the position shown in FIG. 1 
in order to grip the waste portion, which projects upwardly out of the 
blow molding mold, of the hollow body which is disposed in the mold. That 
waste portion had been squeezed off the preform by the two mold ports when 
the blow molding mold was closed around the preform in the receiving 
station 45. After the gripper 64 has engaged the above-mentioned waste 
portion, the blow molding mold 10a, b can be opened so that the mold parts 
10a and 10b occupy the position shown in FIG. 7. The gripper 64 can now be 
moved along the guide 66 into the position shown in broken lines in FIG. 1 
and indicated at 64a. In the course of that movement, the hollow body is 
removed from the open blow molding mold 10a, b. Preferably prior to that 
movement .taking place any parts which project into the hollow body 
through openings in the wall thereof, such as a blowing mandrel or tube or 
the like, are pulled out of the hollow body. When the gripper 64 is in the 
position 64a, the hollow body carried thereby is disposed above a conveyor 
68 on to which the hollow body is deposited in order to be passed for 
further subsequent processing by any items of equipment. 
As soon as the hollow body has been gripped by the gripper 64 and the blow 
molding mold has been opened, the blow molding unit 10, with the blow 
molding mold in the open condition, is pivoted into the receiving station 
beneath the extrusion head 44. The pivotal movement of the blow molding 
unit 10 can therefore begin before the removal gripper 64 has reached the 
position 64a. That pivotal movement corresponds to the pivotal movement of 
the blow molding unit 12 in the direction of the arrow 58, as described 
with reference to FIG. 5. For that purpose, after the arrangement reaches 
the position shown in FIG. 7, the piston rod 56 of the piston-cylinder 
unit 72 (see FIGS. 4 and 5) has been connected to the frame structure 34 
of the blow molding unit 10. 
In the receiving station, the blow molding mold 10a, b is closed around the 
preform 46 in the manner already described above in relation to the blow 
molding mold 12a, b, and then, by actuation of the piston-cylinder unit 
72, pivoted in the direction indicated by the arrow 60 back into the 
linear position in which the blow molding mold 10a, b is disposed in the 
removal station. That position is shown in FIG. 9. After that, the two 
blow molding units 10 and 12 are moved in the direction indicated by the 
arrow 17 into the starting position shown in FIG. 4. In this case however, 
unlike the situation shown in FIG. 4, the blow molding mold 12a, b is 
still closed. In other words, the blow molding mold 12a, b is now disposed 
in the removal station. The previously produced hollow body is then 
removed in the manner already described in connection with the blow 
molding mold 10 with reference to FIG. 7, the parts then again occupying 
the positions shown in FIG. 4. 
FIG. 1 in particular shows that the blow molding unit 10 is reciprocated 
between the stations A and B and the blow molding unit 12 is reciprocated 
between the stations B and C. It will be seen that this arrangement 
therefore provides that it is not only the same receiving station that is 
used by the two blow molding units for receiving the preform, as is 
hitherto generally conventional practice. On the contrary, the arrangement 
has only one common position for also effecting removal of the hollow 
bodies which have been expanded in both the blow molding units 10 and 12, 
so that the devices required for removal of the hollow bodies, such as for 
example including the piston-cylinder unit 72, need to be provided only 
once. A further major advantage of the apparatus according to the 
invention is that the supply of any parts into the blow molding mold can 
be effected at the same location for both blow molding units, more 
specifically when the blow molding mold is in the removal and/or the 
receiving position. FIG. 1 more particularly shows that the blow molding 
mold which is in the receiving position is accessible both from the side 
at which the strut 28 is disposed and also from the side at which the 
support 24 is disposed. It is therefore readily possible for any insertion 
parts which are to be joined in the blow molding mold to the hollow body 
to be produced from the preform therein to be introduced into the mold, as 
long as the mold is still open, while the mold is in the receiving 
position. The step of mounting such additional parts to the hollow body 
within the blow molding mold is frequently required in particular in 
relation to large-size containers, for example motor vehicle tanks. 
It will be noted that the invention is not restricted to a construction 
with only two blow molding units. Thus FIGS. 10 through 12 show an 
embodiment having three blow molding units 110, 111 and 112 which are also 
arranged and disposed as was described hereinbefore in connection with the 
embodiment shown in FIGS. 1 through 9. Accordingly the same components are 
also denoted by the same references which however are higher by 100 in 
relation to the embodiment shown in FIGS. 10 through 12. 
At the beginning of the operating procedure, described hereinafter, of an 
apparatus having three blow molding units 110, 111 and 112, the blow 
molding unit 112 which is disposed at the right in the views shown in 
FIGS. 10 through 12 is disposed in the station B in which the preform is 
received by the blow molding mold when the latter is in its pivoted 
position and the expanded hollow body is removed from the blow molding 
mold when the latter is in its linear position. In FIG. 10 the blow 
molding unit 112 is pivoted into the receiving position so that the blow 
molding mold 112a, 112b is disposed beneath the extrusion head 144. FIG. 
10 shows the position of the apparatus components immediately after the 
blow molding mold 112a, 112b has closed around the preform hanging from 
the extrusion head 144. Immediately thereafter, the blow molding mold is 
pivoted beck in the direction indicated by the arrow 158 into its linear 
position in which it extends parallel to the other blow molding units 110 
and 111. The return pivotal movement into that linear position is 
generally effected immediately after closure of the blow molding mold in 
order to provide space beneath the extrusion head for the preform which is 
continuously issuing therefrom. The preform is separated from the 
extrusion head in the pivotal movement from the receiving position into 
the linear position. 
After the blow molding unit 112 has reached its linear position, the three 
blow molding units 110, 111 and 112 are displaced by approximately the 
length of a blow molding unit in the direction indicated by the arrow 118, 
that is to say, towards the right, so that the middle blow molding unit 
111 passes into the station B while the blow molding unit 112 which has 
now received the previously produced preform is now in station C in which 
the step of cooling the hollow body which in the meantime has been 
expanded in the blow molding mold 112a, 112b begins. 
As, in a preceding working cycle, the blow molding unit 111 had already 
received a preform and expanded it to constitute a hollow body, the blow 
molding mold 111a, 111b contains a hollow body which first has to be 
removed from the blow molding mold before the mold can receive the 
following preform which is being extruded in the meantime. Therefore, when 
it passes into the station B, the blow molding mold 111a, b firstly opens 
so that the apparatus components are in the position shown in FIG. 4 in 
relation to the blow molding unit 12. Then, the expanded hollow body is 
removed from the mold and possibly transported to downstream-disposed 
treatment stations in the manner already described with reference to FIG. 
1, using a gripper or other means. The blow molding unit 111 with the 
emptied open blow molding mold is then pivoted into the position shown in 
FIG. 11, that is to say into the receiving position, in the direction 
indicated by the arrow 160, and pivoted back into the linear position in 
the direction indicated by the arrow 158, after having received the 
preform. 
In the course of the subsequent further displacement of the three blow 
molding units 110, 111 and 112 in the direction of the arrow 118, that is 
to say towards the right, the third blow molding unit 110 passes into the 
station B, in which case the blow molding unit 112 is displaced out of the 
station C into the station D and the blow molding unit 111 is displaced 
out of the station B into the station C. The hollow body which in the 
meantime has been expanded in the blow molding mold 111a, b begins to be 
subjected to the cooling procedure in the station C. At the same time 
time, cooling of the hollow body in the blow molding mold 112a, b is 
continued in the station D. 
In station B, with the blow molding unit 110 initially in the linear 
position, the hollow body which was produced in the previous working cycle 
is removed in the manner already described above. The opened blow molding 
mold is then pivoted into the receiving position shown in FIG. 12. FIG. 12 
also shows the blow molding mold 110a, b in the condition of already being 
closed, that is to say immediately before the beginning of the pivotal 
movement in the direction of the arrow 158 back into the linear position. 
As soon as that position is reached, the blow molding units 110, 111, 112 
are moved from the position shown in FIG. 12 back into the position shown 
in FIG. 10, that is to say into the starting position, in the direction 
indicated by the arrow 117. Thereafter, the hollow body which was 
previously produced is then removed from the blow molding mold 112a, b 
which is now disposed in the station B, and the blow molding unit 112 is 
then pivoted again in the direction indicated by the arrow 160 into the 
receiving position shown in FIG. 10, whereupon the above-described 
operating procedures are repeated. 
FIG. 24 depicts a modified version of the apparatus of FIGS. 1-12 in which 
a single carriage 714 is provided carrying at least two of the blow 
molding units 10 and 12. It will be appreciated that a single carriage 
carrying multiple blow molding units can be provided in any of the 
subsequently described embodiments of the invention. 
The embodiment shown in FIGS. 13 and 14 corresponds in respect of its 
fundamental structure to the embodiment shown in FIGS. 1 through 9 so that 
corresponding components are also denoted by the same references but 
increased by 200. This apparatus also has two blow molding units 210, 212 
which are moved alternately into the removal station and then pivoted into 
the receiving position. The essential difference in relation to the 
embodiment shown in FIGS. 1 through 9 is that the carriage 214 and 216 
respectively is greater in width so that each frame structure 234, in its 
condition of being pivoted into the receiving position 245, is also 
supported by the respective carriage 214, 216 to such an extent that it 
does not need any additional support or guide means. Accordingly, the two 
rails 238 which form the track for the carriages 214, 216 are also at a 
greater spacing from each other. In this case also, similarly to the 
embodiment shown in FIGS. 1 through 9, the apparatus may have a common 
drive means for producing the pivotal movements between the removal 
position and the receiving position. It is however also possible to 
envisage other arrangements as are described hereinafter in connection 
with further embodiments. 
In the embodiment shown in FIG. 15 which, for the sake of simplicity, shows 
only one carriage whose fundamental structure however is also the same as 
that shown in FIGS. 1 through 9 so that the same components are denoted by 
the same references but increased by 300, associated with each blow 
molding unit 310, 314 is its own drive means in the form of a 
piston-cylinder unit 372 for producing the pivotal movements between the 
removal position and the receiving position. In this embodiment, the two 
carriages 314, 316 are coupled together by suitable releasable means 378 
so that only the carriage 314 is provided with a drive motor 380 for the 
drive to a pair of wheels 336. The electric motor 380 drives a gear 381 
which is fixedly mounted on a shaft 382 carrying the pair of wheels 336. 
The arrangement however may also be such that the gear 381 is engaged with 
a stationary rack disposed between the two rails 338, and in that way 
produces transportation movement of the two carriages 314, 316 in the 
directions indicated by the arrows 17 and 18. Such a drive arrangement, 
simple means, permits highly accurate positioning of the carriages in the 
station B. That is important for precise positioning of the blow molding 
mold, when receiving the preform. 
The frame structures 334 which carry the blow molding units 310 and 312 
respectively are provided at their ends remote from the respective pivot 
points 354 and 356, with wheels or rollers 384 which run on a support 
means 355. At its end remote from the rails 338, the support means 355 is 
provided with a stop 386 determining the position of the frame structure 
334 and therewith the respectively associated blow molding unit, in the 
receiving position. The blow mold unit is not shown in FIG. 15, for the 
sake of clarity of the drawings. 
The above-described push-pull clamping system comprising the three plates 
is particularly advantageous when using the pivotal movement for bridging 
over the distance between the linear position and the receiving position, 
as the off-center arrangement of the blow molding mold, which is employed 
or possible in that system, makes it possible, at just a small amount of 
pivotal movement along the arcuate path, to move the blow molding mold 
into the region of the receiving station and thus out of the region of the 
removal station, in order to afford good accessibility from the end at 
which the support 24 is disposed. The only requirement in that respect is 
that the pivot axis 354 or 356 respectively is arranged near that end of 
the frame structure 334 from which the blow molding mold is most remote. 
The presence of the support 24 will in general not hinder accessibility to 
the internal region of the opened blow molding mold since, as not least 
FIG. 3 shows, there is sufficient room beneath the support 24 to have 
access to the region under the actual blow molding mold parts. The 
above-mentioned insertion parts to be fitted into the hollow body are 
mainly to be positioned in that region in order then to connect them to 
the preform or to the hollow body which is being formed therefrom. 
It is also possible for the individual blow molding units to be moved from 
the linear removal position into the receiving position not by a pivotal 
movement, but rather by a movement which takes place perpendicularly to 
the directions of movement 17, 18 and which is thus approximately parallel 
to the guide 66 (see FIG. 1). In that case, when in the receiving 
position, the blow molding units also each adopt a position parallel to 
the linear position, in the removal station. Such an embodiment also 
enjoys all the above-mentioned advantages in regard to only one removal 
station and in regard to the possibility of using only one station for the 
introduction of any insertion parts to be fitted into the preform or the 
hollow body. However, the devices for producing reciprocating transverse 
movements in parallel relationship possibly involve a somewhat higher 
level of machine expenditure and also require a larger amount of space. 
Referring now to the embodiment shown in FIGS. 16 and 17, insofar as the 
components correspond to those of the embodiment shown in FIGS. 1 through 
9, they are denoted by the same references but increased by 400. The two 
blow molding units 410, 412 are also each carried by a respective frame 
structure 434 which however is not pivotable but is displaceable 
perpendicularly to the transportation directions 17, 18 of the two 
carriages 414, 416, on respective linear guides 488 carried by the 
carriages. In FIG. 16 the carriages 414, 416 occupy a position 
corresponding to the position of the carriages 14, 16 in FIG. 4 of the 
embodiment shown in FIGS. 1 through 9. In other words, the carriage 416 
with the blow molding unit 412 disposed thereon is in the removal 
position, and therefore beside the receiving position which is determined 
by the extrusion head 444. After opening of the blow molding mold 412a, 
412b and removal of the hollow body produced in the preceding working 
cycle, the frame structure 434 with the blow molding unit 412 thereon and 
with the blow molding mold still in the open condition is moved out of the 
position shown in FIG. 16 into that shown in FIG. 17, in order to receive 
the preform there. In that respect, it is also possible, in the receiving 
position and possibly additionally or alternatively also in the removal 
position, for any additional parts which are to be joined to the hollow 
body to be produced from the preform in the blow molding mold, to be 
fitted into the blow molding mold or mounted in position in some other 
way. After the blow molding mold 412a, 412b has been closed around the 
preform in the receiving station, the frame structure 434 with the blow 
molding unit 412 is moved along the guides 488 back into the position 
shown in FIG. 16 again, whereupon the other working steps then take place 
within the working cycle, in the usual way. In other words, the two 
carriages 414, 416, driven by a common drive or by separate drives, are 
moved towards the right so that the blow molding unit 410 moves into the 
removal position. The further working steps then take place in the manner 
already described above. In this case also, similarly to the embodiment 
shown in FIGS. 13 and 14, the two carriages 414 and 416 are of such a 
width that the transverse movements of the respective frame structure 434, 
with the blow molding unit carried thereby, are produced on the respective 
carriage in the directions indicated by the arrows 493 and 494 
respectively. 
The embodiment shown in FIGS. 18 and 19 which show only one carriage and in 
which parts corresponding to those of the embodiment shown in FIGS. 1 
through 9 are denoted by the same references but increased by 500 differs 
from all the above-described embodiments in that it is not just the 
respective blow molding unit that is reciprocated relative to the 
carriage, between the removal position and the receiving position. On the 
contrary, the carriage is moved in its entirety. In the embodiment shown 
in FIGS. 18 and 19, this movement involves a pivotal movement. For that 
purpose, the track which is formed by the rails 538 and on which the 
carriages are moved in the directions indicated by the arrows 17 and 18 is 
provided in the region of the removal station with a track portion which 
is arranged pivotably in a horizontal plane about a pivot point 554, 
relative to the other stationary track portions. Desirably, disposed 
beneath the pivotable track portion is a platform 590 or the like on which 
the pivotable track region 591 is supported by way of rollers or runners 
584 carried thereby. The runners or rollers 584 run on a rail or other 
guide 595 which extends in a curved configuration, corresponding to the 
pivotal movement. The rail portion 591 is provided with an electric motor 
572 which by way of suitable means, drives at least one of the two wheels 
584. The end positions of the track portion 591 are determined by stops 
586 and 587. This embodiment does not require a particular support frame 
structure or a particular frame assembly to carry the respective blow 
molding unit. 
The embodiment shown in FIGS. 18 and 19 also has two or three carriages. 
However, if the carriages are connected together for the purposes of 
transportation movement in the directions 17 and 18, the carriages must be 
uncoupled for the purposes of performing the pivotal movements between the 
removal station and the receiving station, unless the arrangement uses 
special coupling means which permit such pivotal movements to take place. 
The blow molding unit is not shown in FIGS. 18 and 19, for the sake of 
clarity of the drawing. 
The embodiment shown in FIGS. 20 through 23 differs from that shown in 
FIGS. 18 and 19 in particular by virtue of the fact that the distance 
between the removal station and the receiving station is not covered by a 
pivotal movement, but, similarly to the embodiment shown in FIGS. 16 and 
17, by a linear displacement which takes place transversely relative to 
the rails for transportation of the carriages in the directions 17 and 18. 
Components corresponding to the embodiment shown in FIGS. 1 through 9 are 
denoted by the same references but increased by 600. The movements in the 
directions of the arrows 693 and 694 make it necessary to provide a 
correspondingly displaceably arranged track portion 691 which is carried 
by a carriage 695. As FIGS. 20 and 21 in particular show, the arrangement 
is such that the rollers 636 for transportation movement of the blow 
molding units in the directions 17 and 18 are mounted on the component 634 
which corresponds to the frame structure 34 of the embodiment shown in 
FIGS. 1 through 9. The position occupied by the two blow molding units in 
FIGS. 20 and 22 corresponds to the position of the corresponding blow 
molding units in FIG. 4. In other words, one of the two blow molding 
units, namely the blow molding unit 612, is in the removal station 
laterally beside the receiving position. In that station, the blow molding 
unit 612 with the associated frame structure 634 is carried by the 
displaceably arranged track portion 691, the rail portions of which are 
aligned with the stationary rail portions 638. As soon as the blow molding 
unit 612, in the course of the transportation movement in the direction of 
the arrow 17 or 18, has reached the removal station shown in FIGS. 20 and 
21, a piston 696 which is arranged in a cylinder 697 is displaced, so that 
a pin carried by the piston 696 is introduced into a recess 698 of 
corresponding cross-section, in the carriage 695. As the piston 696 and 
the cylinder 697 are mounted on the frame structure 634, the 
above-mentioned pin, when in its lower operative position in the recess 
698, produces a positively locking connection between the frame structure 
634 and the carriage 695 so that those two components are no longer 
movable relative to each other. After the hollow body produced in the 
preceding working cycle has been removed from the blow molding unit 612 
and possibly after any necessary insertion portions have been fitted into 
the blow molding mold in the removal station, the blow molding unit 612 is 
moved into the position shown in FIGS. 21 and 23, by suitable displacement 
of the carriage 695 in the direction of the arrow 693. In that position as 
shown in FIGS. 21 and 23, the opened blow molding mold is disposed beneath 
the extrusion head 644. Then, in the receiving station, after insertion 
portions have possibly there been introduced into the blow molding mold, 
the preform which is hanging from the extrusion head 644 is received by 
the closing blow molding mold, whereupon the blow molding unit 612 is 
moved back into the starting position shown in FIGS. 20 and 22 in the 
direction indicated by the arrow 694 (see FIG. 22). After the locking 
engagement of the pin into the recess 698 has been released, there then 
occurs the displacement in the direction indicated by the arrow 18, as has 
already been described above in connection with the other embodiments. In 
the course of that movement, the other blow molding unit 610 passes into 
the removal station and thus on to the track portion which is carried by 
the carriage 695. 
FIGS. 20 through 23 show two alternative configurations in regard to the 
drive for producing the movements of the carriage 695. In FIGS. 20 and 21, 
disposed in the carriage 695 is an electric motor 672 which by way of a 
chain or the like, drives one of the wheels 684 or pairs of wheels of the 
carriage 695. 
In FIGS. 22 and 23 which each show only one carriage for the sake of 
simplicity, the transverse movement is produced by a piston-cylinder unit 
672 whose cylinder 674 can be mounted on a suitable support and whose 
piston rod 676 can be fixedly connected to the carriage 695. There is no 
need for the piston rod to be releasably mounted, in a manner 
corresponding to the embodiment shown in FIGS. 1 through 9, as both or 
possibly also all three blow molding units are reciprocated with the 
respectively associated frame structure by the same carriage 695 between 
the removal station and the receiving position. It will be appreciated 
that in this case also, if the carriages are provided with a common drive 
for producing the transportation movements in the directions of the arrows 
17 and 18, the carriages must be uncoupled in order to permit the 
transverse movement of the respective carriage in the removal station. The 
blow molding unit is not shown in FIGS. 22 and 23 for the sake of clarity 
of the drawing. 
In the embodiment shown in FIGS. 1 through 9, all blow molding units of an 
extrusion blow molding apparatus are arranged on the carriage 14, 16 and 
the frame structures 34, in such a way that the pivotal movements between 
the removal position and the receiving position each occur in the same 
direction. It will be appreciated that it is also possible to use an 
arrangement in which, unlike the illustrated embodiment, the pivot axis 
for example of the blow molding unit 12 would be arranged at the 
right-hand end region of the carriage 16, in which case it would then also 
be advantageous for the blow molding unit to be arranged on the associated 
frame structure 34, in a position of being pivoted in total through 
180.degree. about a vertical axis. In that case the blow molding unit 12 
would perform a movement in a clockwise direction upon pivoting from the 
removal position into the receiving position, whereas in the case of the 
blow molding unit 10, the pivotal movement would still be in the 
counter-clockwise direction. That would not be an optimum arrangement if, 
as is frequently the case, the discharge opening of the extrusion head 44 
for the preform is of a different configuration in the peripheral 
direction and is thus not of a symmetrical profile. In general it is 
desirable and possibly even necessary for the blow molding mold and thus 
the blow molding cavity, in the receiving position, to be adapted in a 
specific manner to a peripheral profiling of the tubular preform in order 
to be able to produce a hollow body which is of the optimum configuration. 
The embodiment of FIGS. 10 through 12 shows that the concept of the present 
invention not only permits an arrangement in which certain operations and 
manipulation steps of a given kind, which are to be carried out on a blow 
molding mold or in connection with a blow molding mold, can be performed 
for all blow molding molds in a working region that is common to the blow 
molding molds, but that in addition the degree of flexibility, in regard 
to the number of blow molding molds, is substantially greater than is the 
case with known machine designs. 
Thus, it is also possible for two extrusion blow molding apparatuses 
according to the invention to be arranged in side-by-side relationship, in 
such a way that the removal stations of the two apparatuses are disposed 
opposite each other, and therefore both would be arranged in the station B 
in the case of the above-described embodiments. In that case, it is only 
necessary that, at any event in the station in which the expanded hollow 
bodies are removed from the respective blow molding molds, the distance 
between the two apparatuses which advantageously extend substantially 
parallel to each other is such that removal grippers or other removal 
devices can be disposed between the two apparatuses. In that case, a con, 
non transportation means is sufficient for the two apparatuses, for 
transporting the produced hollow bodies away. It would even be possible 
for a common removal device to be associated with both the apparatuses. 
However, this and other details of the design configuration adopted depend 
on the respective circumstances involved, for example the time required 
for removal of the hollow body from a blow molding mold and for deposit of 
the hollow body on a conveyor. It is also possible for the two apparatuses 
to be arranged somewhat displaced relative to each other in the 
longitudinal direction, that is to say, parallel to the directions in 
which the individual blow molding units are moved between the stations, in 
such a way that the blow molding molds are not disposed precisely opposite 
each other in the common removal station, but are somewhat displaced 
relative to each other; in that way, for example with a small spacing 
between the two apparatuses, the two removal devices can be arranged in 
such a way that they are then displaced by the appropriate dimension in 
the direction of the arrows 17 and 18. 
When two such apparatuses are arranged in substantially parallel 
relationship, as described above, the blow molding units would be pivoted 
into the receiving station from the removal station in an outward 
direction, that is to say in each case away from the respective other 
apparatus. 
It is further possible if necessary for the extrusion blow molding 
apparatus to be operated only with one blow molding unit. In that case the 
respective carriage or slider would only perform movements between a 
receiving position and a removal position. That is important in particular 
for the reason that, for example in all the above-discussed embodiments, 
it would be possible for the overall assembly to continue with operation, 
with only one blow molding unit, in a breakdown situation or when carrying 
out maintenance operations, when only one blow molding unit can be used. 
Although, in the above-described embodiments of the invention, the position 
in which the blow molding mold receives the preform is associated with the 
extrusion head in such a way that the blow molding mold is closed around 
the preform when it is hanging from the extrusion head, the invention is 
in no way restricted to that configuration. It is also possible for the 
receiving station to be arranged independently, that is to say spaced away 
from the extrusion head. It will be appreciated that in that case means 
would have to be provided for transporting the preform from the extrusion 
head into the receiving station. Such a means could be for example a 
gripper which engages the preform at the extrusion head and, after the 
preform has been separated or severed from the extrusion head, moves the 
preform into the receiving station. That may involve a movement in a 
horizontal or a vertical plane, but possibly also a combination of such 
movements. 
It will be appreciated that the above-described embodiments of the 
apparatus according to the invention have been set forth purely by way of 
example and illustration thereof and that various modifications and 
alterations may be made therein without thereby departing from the spirit 
and scope of the invention.