Abstract:
The present invention relates to a cavity for a mould-cavity system for the production of hollow mouldings, where the cavity ( 1 ) has an element ( 2 ) which is in essence hollow and cylindrical, where a cooling channel has been provided at the outer side of the hollow cylindrical element ( 2 ). To provide a cavity which is easy to produce and which can increase the effectiveness of cooling of the cavity, the invention proposes provision of the cooling channel with a plurality of cooling-channel sections ( 3 ) extending substantially axially, and with at least one cooling-channel-connector section ( 4 ), where the cooling-channel-connector section ( 4 ) connects two of the cooling-channel sections ( 3 ) extending substantially axially.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The present invention concerns a cavity member for a mold cavity structure for the production of hollow body moldings by means of injection molding. 
         [0002]    In plastic material processing injection molding represents the most important process for the production of moldings. In the injection molding procedure the molding material in powder form or in granulate form is plasticised for example in a screw injection molding machine and then urged into the closed, generally cooled tool, for example a mold cavity structure. When the mold or the mold space provided therein is completely filled with the melt, it hardens by cooling. That generally involves a reduction in volume. That is frequently compensated by melt being further subsequently urged into the mold, from the injection cylinder. In addition the contraction is also generally taken into consideration by a suitable oversize in the mold contour. Finally the tool or the mold cavity structure is opened and the finished molding (injection molding) is removed and ejected. The tool can be closed again and a fresh working cycle can begin, with renewed injection. 
         [0003]    By means of injection molding it is possible to produce hollow bodies which can be inflated in a later working step for example to afford bottles or canisters. Those hollow bodies are also referred to as preforms or parisons. 
         [0004]    Mold cavity structures for the production of parisons which are intended for subsequent inflation to form PET bottles usually comprise a core, a cavity member, a base insert and a neck jaw. 
         [0005]    In the closed condition of the mold cavity structure a mold space, the shape of which corresponds to the molding to be produced, is formed between the core on the one hand and the base insert, cavity member and neck jaw on the other hand. The outside contour of the core thus forms the inside contour of the hollow body molding while the outside contour of the hollow body molding is formed by the cavity member, the base insert and the neck jaw. 
         [0006]    The cavity member has a substantially hollow-cylindrical element. The base of the mold space is formed by the base insert which adjoins the cavity member. The neck jaw adjoins the cavity at the side remote from the base insert. 
         [0007]    In other words, the neck jaw, the cavity member and the base insert afford a hollow space into which the core penetrates. 
         [0008]    In general all parts of the mold cavity structure are cooled. Therefore the cavity member has a cooling passage at the outside of the hollow-cylindrical part. Usually the cooling passage comprises a groove of spiral shape, which is introduced into the outside of the hollow-cylindrical element of the cavity member. In operation the cavity member is fitted with the remaining parts of the mold cavity structure into what is referred to as a cavity plate. The cavity plate has a corresponding recess. The cooling passage is then formed on the one hand by the spiral groove and on the other hand by the inside wall of the corresponding recess in the cavity plate, which closes the spiral groove. In most cases the cavity plate is designed to receive a multiplicity of mold cavity structures, for example 192. 
         [0009]    It has been found that, by virtue of the spiral configuration of the cooling passage, a substantial part of the cooling fluid flowing through the cooling passage does not come into contact with the cavity by virtue of centrifugal force, and therefore also does not contribute to the cooling action. In addition the heat to be dissipated occurs substantially at the groove bottom so that a temperature gradient is formed within the cooling fluid so that the temperature of the cooling fluid decreases from the outside inwardly or from the groove bottom to the inside wall of the cavity plate recess. Accordingly because of their greater density the colder cooling fluid constituents preferably flow in the outside region of the spiral cooling passage so that it is precisely the cooling fluid flow which is particularly preferred for effective cooling that contributes only little to the cooling action. 
         [0010]    Such a mold cavity structure is known for example from WO 2005/051632. 
       BRIEF SUMMARY OF THE INVENTION 
       [0011]    The object of the present invention is to provide a cavity member which is simple to produce and which permits more effective cooling of the cavity member. 
         [0012]    According to the invention that object is attained in that the cooling passage has a plurality of cooling passage portions extending substantially in the axial direction and at least one connecting portion, wherein the connecting portion connects two cooling passage portions extending substantially in the axial direction. 
         [0013]    More particularly, the invention includes a cavity member for a mold cavity structure for the production of hollow body moldings, wherein the cavity member has a substantially hollow-cylindrical element, wherein a cooling passage is provided at the outside of the hollow-cylindrical element and the cooling passage has a plurality of cooling passage portions extending substantially in the axial direction and at least one cooling passage connecting portion and wherein the cooling passage connecting portion connects two cooling passage portions extending substantially in the axial direction. 
         [0014]    There are at least four, preferably at least eight and particularly preferably at least twelve cooling passage portions extending substantially in the axial direction. 
         [0015]    The cooling passage connecting portion is desirably arranged substantially in the peripheral direction at the outside of the hollow-cylindrical element and the cavity member desirably has a collar portion with a through opening and wherein the hollow-cylindrical element is in part arranged in the through opening so that the through opening is filled in part by the hollow-cylindrical element. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         [0016]      FIG. 1  shows a perspective view of a first embodiment of a cavity member, 
           [0017]      FIG. 2  shows a sectional view of the  FIG. 1  embodiment in the condition of being fitted into the tool, 
           [0018]      FIG. 3  shows a sectional view along line A-A in  FIG. 2 , 
           [0019]      FIG. 4  shows a sectional view of the cavity member of  FIG. 1 , 
           [0020]      FIG. 5  shows a diagrammatic view of the fluid flow configuration in the cavity member, 
           [0021]      FIG. 6  shows a side view and a view from below of a second embodiment of the invention, 
           [0022]      FIG. 7  shows the side view of  FIG. 6  with diagrammatically illustrated fluid flow configuration, 
           [0023]      FIG. 8  shows a sectional view of the second embodiment of  FIGS. 6 and 7  in the condition of being fitted into the tool, 
           [0024]      FIG. 9  shows a third embodiment of the cavity member according to the invention, 
           [0025]      FIG. 10  shows a portion from  FIG. 9  with the diagrammatically illustrated fluid flow configuration, 
           [0026]      FIG. 11  shows a side view on to a deflection element, 
           [0027]      FIG. 12  shows a sectional view along line A-A in  FIG. 11 , 
           [0028]      FIG. 13  shows a sectional view along line B-B in  FIG. 11 , 
           [0029]      FIG. 14  shows a sectional view of the third embodiment in the condition of being fitted into the tool, wherein the deflection element has been modified, 
           [0030]      FIG. 15  shows a plan view of the modified deflection element with illustrated fluid flow configuration, 
           [0031]      FIG. 16  shows a sectional view along line A-A in  FIG. 15 , 
           [0032]      FIG. 17  shows a sectional view along line B-B in  FIG. 15 , 
           [0033]      FIG. 18  shows a sectional view along line C-C in  FIG. 15 , 
           [0034]      FIG. 19  shows a sectional view of a fourth embodiment of a cavity member according to the invention, 
           [0035]      FIG. 20  shows a sectional view of a cavity member enlargement, 
           [0036]      FIG. 21  shows a sectional view of the fourth embodiment of  FIGS. 19 and 20  in the condition of being fitted into the tool, 
           [0037]      FIG. 22  shows a sectional view of a fifth embodiment and a diagrammatic representation of the fluid flow configuration, 
           [0038]      FIG. 23  shows a perspective view of a sixth embodiment of the invention, 
           [0039]      FIG. 24  shows a longitudinal section through the embodiment of  FIG. 23 , 
           [0040]      FIG. 25  shows an exploded view of the embodiment of  FIG. 23 , 
           [0041]      FIG. 26  shows a further exploded view of the embodiment of  FIG. 23 , 
           [0042]      FIG. 27  shows a perspective view of the cover element of the embodiment of  FIG. 23 , 
           [0043]      FIG. 28  shows a diagrammatic view of the cooling agent flow in the embodiment of  FIG. 23 , 
           [0044]      FIG. 29  shows a perspective view of a seventh embodiment, 
           [0045]      FIG. 30  shows a perspective view of the peripheral casing element of the embodiment of  FIG. 29 , 
           [0046]      FIG. 31  shows a perspective view of the base element of the embodiment of  FIG. 29 , 
           [0047]      FIG. 32  shows an exploded view of the embodiment of  FIG. 29 , 
           [0048]      FIG. 33  shows a perspective view of the peripheral casing element of the seventh embodiment in the flat condition, and 
           [0049]      FIG. 34  shows diagrammatic sketches of an eighth embodiment. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0050]    The cooling passage portions that extend in the axial direction preferably provide for highly efficient cooling as no centrifugal forces here provide for a separation of colder and hotter cooling fluid. In addition the main loading of the mold cavity structure desirably occurs in the axial direction so that grooves extending in the axial direction limit the strength characteristic, by virtue of a notch effect, much less than grooves extending in a peripheral direction. It is therefore possible and even advantageous by virtue of the improved wetting effect for the cooling passages arranged in the axial direction, to be formed with a flat base or even with an inwardly curved base. 
         [0051]    The connecting portion preferably extends substantially in the peripheral direction. 
         [0052]    It will be appreciated that the improved cooling effect is correspondingly greater, the greater the proportion of cooling passage portions extending in themselves substantially in the axial direction, in relation to the total cooling passage length. Preferably, the totalled length of all substantially axially extending cooling passages is at least twice as great and preferably at least five times as great and particularly preferably at least ten times as great as the totalled length of all connecting portions. 
         [0053]    Therefore it is provided in a preferred embodiment that there are at least four, preferably at least eight and particularly preferably at least twelve cooling passage portions extending substantially in the axial direction. They are then connected by cooling passage portions extending substantially in the peripheral direction. 
         [0054]    The cooling passage is thus of a substantially meander-form configuration. 
         [0055]    There are embodiments in which the cavity member has a collar portion with a through opening, wherein the hollow-cylindrical element is in part arranged in the through opening so that the through opening is filled in part by the hollow-cylindrical element. The part of the through opening, that is not filled by the hollow-cylindrical element, then serves to receive an external cone of the neck jaw. 
         [0056]    In a particularly preferred embodiment the arrangement according to the invention of the cooling passage portions allows that at least some of the cooling passage portions extending in the axial direction at least partially extend into the collar portion. In contrast to the state of the art therefore the collar portion itself can be cooled directly with cooling fluid. In the case of the known cavity members, cooling of the collar portion was effected only by heat conduction within the cavity member, which led to a markedly reduced cooling efficiency. 
         [0057]    In a further particularly preferred embodiment at least some of the cooling passage portions extending substantially in the peripheral direction are arranged at an end of the hollow-cylindrical element, wherein preferably there is provided a closure element which at the end closes the cooling passage portions which are arranged at the end of the hollow-cylindrical element and which extend substantially in the peripheral direction. 
         [0058]    Thus it is possible for example for the cooling passage portions extending substantially in the axial direction to be in the form of axial bores which extend for example into the collar portion. Then, at the end of the hollow-cylindrical element, recesses are produced in the hollow-cylindrical element, the recesses respectively connecting each two adjacent substantially axially extending cooling passages. The end of the hollow-cylindrical element is then covered with the closure element. The closure element can be for example soldered to the hollow-cylindrical element. 
         [0059]    The recesses which respectively connect two adjacent substantially axially extending cooling passage portions here form the connecting portions arranged substantially in the peripheral direction. 
         [0060]    Basically the closure element can be of any desired form and can also be of a multi-part configuration. In a particularly preferred embodiment the closure element is of a substantially annular configuration and in a particularly preferred embodiment has an internal cone at the side remote from the cooling passage portions. That is advantageous in particular when using a cavity member with a collar portion as the collar portion can be more easily produced thereby. In principle the through opening in the collar portion, that is not filled by the hollow-cylindrical element, must have a portion with an internal cone so that it can co-operate with a corresponding external cone portion of the neck jaw. The conical configuration of the closure element can provide that the through opening can be formed in the collar portion in the form of a through bore, the internal cone then being formed by the closure element. 
         [0061]    In an embodiment the cooling passage is substantially formed by grooves provided in the outside in the hollow-cylindrical element. By way of example the grooves can be milled into the material of the hollow-cylindrical part. 
         [0062]    In an alternative configuration the cooling passage is formed by separating elements arranged on the outside of the hollow-cylindrical element. It has been found that introducing grooves into the outside of the cavity member leads to a considerable reduction in the stability of the cavity member. So that the cavity member does not fracture in operation therefore the remaining wall thickness between the groove base and the hollow space formed by the cavity member must be suitably large. 
         [0063]    In principle however it is desirable for the cooling fluid to be passed as closely as possible to the mold space in order to ensure very effective cooling of the parison. 
         [0064]    For that reason it is advantageous for the outside of the cavity member to be left as smooth as possible, that is to say without cooling grooves therein. The cavity member itself can then be of a very thin-walled structure. More specifically it was surprisingly found that a thin-walled cavity member with a smooth outside surface enjoys higher stability than a thick-walled cavity member with cooling grooves in the outside surface, more specifically even when the wall thickness in the region of the cooling grooves is greater than the wall thickness of the thin-walled cavity member. 
         [0065]    Those separating elements must be fixed to the outside of the hollow-cylindrical element. It has also been found here that fixing directly to the outside leads to a reduction in stability. Therefore a further particularly preferred embodiment provides that the hollow-cylindrical element has at its outside and substantially at its ends a respective ring element projecting beyond the outside of the hollow-cylindrical element, wherein the separating elements are fixed to the ring elements and preferably not to the hollow-cylindrical element. It will be appreciated that, by virtue of the absence of any fixing between the separating element and the outside surface of the hollow-cylindrical element, no fluid-tight separation of adjacent cooling passage portions is possibly achieved. That however is of subordinate significance for the purpose according to the invention. 
         [0066]    In a particularly preferred embodiment the separating elements are substantially bar-shaped, and are particularly preferably oriented in the axial direction. The axial orientation of the separating elements provides that a respective substantially axially extending cooling passage portion is provided on both sides of the separating elements. 
         [0067]    In a particularly preferred embodiment the cooling passage portions arranged in the peripheral direction are formed by through openings provided in the separating elements, wherein preferably the through openings are provided substantially in the region of an end portion of the separating element. The cooling fluid then flows along the substantially axially arranged cooling passages between two adjacent separating elements, then passes through the through opening in the separating element into the adjacent axially extending cooling passage portion and there flows in opposite relationship along the axial cooling passage portion. The through opening provided alternately in the end portions of the separating elements can thus provide a cooling passage which is of a meander configuration or a zig-zag configuration. 
         [0068]    In a preferred embodiment the separating elements are of a substantially rectangular cross-sectional area. That means that the separating elements can be quite inexpensively produced. For many situations of use however it may be advantageous for the separating elements to be of a substantially triangular cross-sectional area. 
         [0069]    As the cavity member including the separating elements are fitted in operation into a corresponding sleeve or a cavity plate with corresponding recess, a further preferred embodiment provides that the separating elements are of a shape that is rounded at their side remote from the hollow-cylindrical element. That curved surface preferably follows substantially the peripheral surface of a cylinder. 
         [0070]    The present invention also concerns a mold cavity structure having the described cavity member as well as a tool having such a mold cavity structure. 
         [0071]    In that respect, in the tool in a particularly preferred embodiment, a cooling fluid feed and a cooling fluid discharge are arranged in such a way that two parallel cooling circuits are formed by the cooling passage structure of the cavity member. In other words, the cooling fluid flow fed from one side to the cavity member is divided and flows in two separate fluid flows around the cavity member in each case over a peripheral angle of about 180°. Then, arranged on the side of the cavity member, that is approximately opposite to the cooling fluid feed, is the cooling fluid discharge where the two cooling fluid flows come together again. 
         [0072]    In a further particularly preferred embodiment arranged in a recess in the cavity plate is a cooling fluid distributor which connects together at least two substantially axially extending cooling passage portions of the hollow-cylindrical element by way of a connecting passage arranged within the cooling fluid distributor so that the connecting passage forms a cooling passage portion arranged substantially in the peripheral direction. 
         [0073]    Further advantages, features and possible uses will be apparent from the description hereinafter of preferred embodiments and the accompanying drawings. 
         [0074]      FIG. 1  shows a perspective view of a first embodiment of the cavity member  1  according to the invention. The cavity member  1  has a hollow-cylindrical portion  2  and a collar element  5 . As can be seen in particular from the sectional view in  FIG. 2  the collar element  5  has a through opening into which the hollow-cylindrical element  2  partially penetrates. A cooling passage  3 ,  4  is milled in the hollow-cylindrical element at the outside thereof. The cooling passage  3 ,  4  comprises cooling passage portions  3  extending substantially in the axial direction and connecting portions  4  extending substantially in the peripheral direction. On the side remote from the hollow-cylindrical element  2  the collar element  5  has a recess  6  which serves to receive a neck jaw. 
         [0075]      FIG. 2  shows a sectional view of the embodiment of the cavity member illustrated in  FIG. 1 , in the condition of being fitted into the tool. 
         [0076]    The tool here includes a cavity plate  14  which generally has an entire row of recesses, for example 48 or 96, into each of which a respective cavity member  1  is fitted. 
         [0077]    In the tool adjoining the hollow-cylindrical portion  2  is the base insert  9 ,  10  which here is of a two-part configuration. Because the cooling passage in the outside wall of the hollow-cylindrical element is fitted into the cavity plate  14 , the cooling passage is formed on the one hand by the milled cooling grooves and on the other hand by the inside wall of the recesses in the cavity plate  14 . 
         [0078]    The cavity plate  14  has a fluid feed  11  and a cooling fluid discharge  12 . It can be clearly seen that the axially oriented cooling passage portions  3  extend into the collar portion  5 . It is provided that the cooling fluid flows around the cavity member  1  in a meander form or in a zig-zag configuration. Recesses  7  are provided in the material in order to interconnect axially extending cooling passage portions  3  which are adjacent to each other at the end of the cavity member  1 . 
         [0079]    For closing the cooling passage, there is provided a closure element  13  which sits at the end on the hollow-cylindrical element. The closure element  13  is of a substantially annular configuration and has an internal cone provided for receiving a corresponding external cone of a neck jaw. 
         [0080]    It can be clearly seen from  FIG. 2  that the hollow-cylindrical element  2  of the cavity member  1  together with the base insert  9 ,  10  forms a mold space  8  in which the molding to be produced is formed. 
         [0081]    A sectional view along line A-A in  FIG. 2  is shown in  FIG. 3 , to clearly illustrate the connecting passages  7 . 
         [0082]      FIG. 4  shows a longitudinal section through the cavity member  1 . The cavity member  1  comprises a portion  15  which is intended to be fitted into the cavity plate  14  and a portion  16  which remains outside the cavity plate  14 . In this case the collar element  5  rests on the surface of the cavity plate  14 . 
         [0083]      FIG. 5  diagrammatically shows the fluid flow configuration along the outside of the cavity member  1 . Cooling fluid is fed by way of the fluid feed  11  and is divided into two cooling fluid paths disposed in parallel. The cooling fluid now follows the meander arrangement of the cooling passage and flows alternately through axially directed cooling passage portions  3  and peripherally directed cooling passage portions  4 ,  7 . The two cooling fluid paths come together again at the cooling fluid discharge  12 . 
         [0084]    It can be clearly seen that the proportion of the substantially axially directed cooling passage portions  3  is in total substantially longer than the cooling passage portions  4 ,  7  which are oriented substantially in the peripheral direction. According to the invention a flow configuration parallel to the axis of the hollow-cylindrical element  4  is advantageous. 
         [0085]      FIG. 6  shows a side view and a view from below of a second embodiment of a cavity member according to the invention. Here the cooling passage portions are not provided in the outside wall of the hollow-cylindrical element  2  but are formed by separating elements  17 ,  17 ′,  17 ″ which connect to the outside wall of the hollow-cylindrical element  2 . As shown by way of example in relation to the separating element  17 ′, the separating elements can have a through opening  18  providing a connection with adjacent axially extending cooling passage portions. The separating elements  17 ,  17 ″ can be bar-shaped of rectangular cross-section or, as shown by way of example with reference to the separating element  17 ″, they can be substantially triangular. 
         [0086]      FIG. 7  shows once again the second embodiment of the cavity member  1 ′, the pattern of the cooling fluid flow additionally being shown diagrammatically here. The cooling fluid meets the hollow-cylindrical element  2  at the location marked with the dotted-line circle. The cooling fluid flow is divided by virtue of the separating elements  17  and flows both towards the left and towards the right along the axially extending cooling passage portion. At the end of that axially extending cooling passage portion the cooling fluid flows over through a corresponding through opening into the adjacent axially extending cooling passage portion and there flows again in the axial direction in opposite relationship. That accordingly provides a zig-zag structure or meander structure for the cooling fluid flow. 
         [0087]    It can be clearly seen that the hollow-cylindrical element  2  has ring elements  21 ,  22  projecting at both sides at its end portions. The separating elements  17  are fixed for example by means of weld points  19  only to those ring elements  21 ,  22  so that no force or stressing is exerted on the hollow-cylindrical element  2  by the separating elements  17 . That freedom from forces makes it possible for the wall thickness of the hollow-cylindrical element  2  to be very small without the stability of the cavity member being limited. As a result the cooling fluid can be taken closer to the mold space  8  and cooling can thus be effected more efficiently, and that leads to a reduction in the cycle time, that is to say the time during which the parison must be in the mold space  8 . 
         [0088]      FIG. 8  shows a sectional view of the second embodiment in the fitted condition. Here the base insert is of a one-part structure and is denoted by reference  23 . It will be seen that the separating elements  17  are arranged only at the portion of the hollow-cylindrical element  2 , that is outside the collar element  5 . The collar element  5  or the ring element  21  is of a configuration as already described in relation to the first embodiment. In other words, the connection between adjacent axially directed cooling passage portions is made by a recess which is formed in the peripheral direction and which is covered over by means of the closure element  13 . 
         [0089]      FIG. 9  shows a third embodiment of a cavity member according to the invention. Here the separating elements are formed by the deflection element  24  which was pressed into the cavity plate between the base insert  9 ,  10  on the one hand and the cavity member  1 ″ on the other hand. That deflection element  24  is shown once again separately in  FIG. 10  in the installed condition, the direction of the fluid flow being shown here by means of arrows. 
         [0090]      FIGS. 11 through 13  show the deflection element  24  once again as a side view and as two sectional views, to clearly illustrate same. 
         [0091]    In this case the cooling fluid flow is illustrated by arrows or circular symbols. 
         [0092]    In  FIG. 12  the symbol comprising a circle in which an ‘X’ is enclosed is intended to represent a direction of flow into the plane of the drawing while the symbol comprising a circle arranged in a circle is intended to denote a direction of flow out of the plane of the drawing. 
         [0093]      FIG. 14  shows a sectional view of this embodiment in the condition of being fitted into the tool. This arrangement however uses a somewhat longer deflection element  24 ′ which is shown once again as side and sectional views in  FIGS. 15 through 18 . 
         [0094]    Finally  FIGS. 19 through 21  show a fourth embodiment of the cavity member  1 ″′ according to the invention. The cavity member  1 ″′ again comprises a hollow cylindrical element  2  which is adjoined by a collar element  5 . Provided on the outside of the hollow-cylindrical element  2  within the collar element  5  are corresponding bores which extend in the longitudinal or axial direction and which in part form the axially extending cooling passage portions. Respective adjacent axially extending cooling passage portions are connected by means of the recesses  7 . At the side of the cavity member, that is remote from the tool or the cavity plate, this embodiment corresponds to the embodiment shown in  FIGS. 1 through 3 . Unlike the embodiment of  FIGS. 1 through 3 , no cooling grooves are provided here at the outside of the hollow-cylindrical element  2 . In addition no separating elements are welded in place here. Instead, there is provided a cavity enlargement  25  which is fitted in the form of a sleeve on to the outside surface of the hollow-cylindrical element  2 . The cavity enlargement  25  has corresponding separating elements  17  at its inside. Those separating elements  17  provide for the meandering cooling fluid flow according to the invention, which occurs substantially in the axial direction.  FIG. 21  shows the cavity member  1 ″′ in the condition of being fitted in the tool. This embodiment further has the advantage that the cooling fluid feed  11  and the cooling fluid feed  12  is provided both for the cooling fluid feed for the cavity member  1 ″′ and also for the cooling fluid feed for the base insert  9 ,  10 . 
         [0095]    As it is possibly desired for the molding to be produced to be altered, for example for a somewhat different length to be selected, then it is only necessary for the cavity  1 ″′ including the cavity enlargement  25  to be replaced by suitably modified parts. The cavity plate and the base insert can be retained. In other words the cavity plate can be used for a large number of different tools. Usually the manufacturers of such injection molding machines offer those for a large number of different parison geometries. 
         [0096]    If the customer wants an injection molding system for the production of parisons of a different length, with the systems in the state of the art adaptation of the cavity plate is required. The cavity plate can therefore only be manufactured when the exact length of the parison is known. Use of the cavity enlargement according to the invention means that the thickness of the cavity plate is independent of the length of the parison to be produced, so that the cavity plate can already be produced as a standard part before it is in any way known what the parison to be produced looks like. Then, it is only necessary to produce the corresponding cavity enlargements, in dependence on the length of the parison to be produced. 
         [0097]      FIG. 22  shows a sectional view of a fifth embodiment. This embodiment substantially corresponds to the embodiment of  FIG. 8 , wherein here the connecting passages are not afforded by a recess disposed in the peripheral direction, which is covered by a closure element, but by two blind bores which are inclined with respect to the axial direction, wherein two blind bores meet and thus embody a V-shaped connecting passage. 
         [0098]    That therefore affords the flow configuration shown at the left in the Figure, for the flow of cooling fluid. 
         [0099]    Efficient cooling of the cavity member is achieved by the measure according to the invention. 
         [0100]      FIGS. 23 through 28  show a sixth embodiment of the invention.  FIG. 23  shows a perspective view and  FIG. 24  shows a sectional view. The cavity is of a two-part construction and comprises a cover element  26  and a main part  27 . The main part  27  substantially comprises a hollow cylinder in which there is a row of axially extending bores serving as axially extending cooling passage portions  3 . It can be clearly seen that the axial bores are in the form of blind bores, the bores opening towards the end, at the end towards the cover element  26 . 
         [0101]    To form the complete cooling passage, connecting grooves  28  are provided in the proximity of the end of the main part  27 , that is remote from the cover element  26 . Those connecting grooves  28  form peripherally extending cooling passage portions and in the illustrated embodiment always connect four axial bores  3  extending in parallel relationship. 
         [0102]    The cover element  26  in turn has milled-out portions  29  also extending in the peripheral direction. They are so arranged that they prolong and partially connect the axially extending cooling passages which open at the end of the main part  27 . Here too four cooling passages are always connected together. It will be noted however that the cover element respectively connects two cooling passages which extend in parallel and which are connected by a groove  28 , to two cooling passages which extend in parallel and which are connected by an adjacent groove  28 . The cover element can be clearly seen as a perspective view in  FIG. 27 . 
         [0103]    There are further provided a cooling fluid feed  11  and discharge  12 . When the cavity member is supplied with cooling fluid by way of the cooling fluid feed  11  the result is the configuration diagrammatically shown in  FIG. 28 . Here too the entire cooling passage is of a meander-shaped configuration, wherein, to increase the through-flow of cooling agent, cooling agent always flows through two adjacent axially extending passages in parallel relationship (and in opposite relationship to the nearest two adjacent axially extending cooling passages). 
         [0104]      FIGS. 29 through 33  show a seventh embodiment. This essentially differs from the preceding one in that the axially extending cooling agent passages are only partially provided within the main part. Instead, there is a peripheral casing portion  30  having recesses (grooves) which extend axially and which are provided at one side. When the casing portion  30  is placed around the cylindrical outside surface of the main part  27  the recesses in the casing portion  30  form axially extending cooling passages. At the side remote from the cover element  26 , the axially extending cooling passages are connected together in paired relationship by a peripherally extending connecting passage forming the cooling passage portion  4  which extends in the peripheral direction. The connecting passage  4  is formed by adjacent grooves in the casing portion being connected together, that is to say the land formed between the grooves is shortened. 
         [0105]      FIG. 33  shows the casing portion in the unrolled, that is to say flat condition, so that production of the connecting portions  4  can be clearly seen. 
         [0106]    The cover element  26  substantially corresponds to the cover element of the previous embodiment, but in this case only two respective adjacent axially extending cooling passage portions are connected together. 
         [0107]      FIG. 34  shows an eighth embodiment of the invention. Here the casing portion  30  comprises a flexible material such as for example POM. A cross-sectional view is shown at top left in  FIG. 34 . It will be seen that the casing portion  30  has on both sides incisions  31  which alternately engage into each other so that basically the casing portion  30  is of a meander-shaped configuration. The result of this, as shown at top right in  FIG. 34 , is that the casing portion can be pulled apart somewhat by virtue of its elasticity so that it can be pulled on to the main part  27 . The casing portion  30  is drawn on to the cylindrical outside surface of the main part  27 , by virtue of the elastic characteristics of the casing portion. 
         [0108]    The casing portion  30  can thus be easily produced in one piece and can be fitted without a tool. 
       LIST OF REFERENCES 
       [0109]      1  cavity
 
 2  hollow-cylindrical portion
 
 3  cooling passage portions extending in the axial direction
 
 4  cooling passage portions extending in the peripheral direction
 
 5  collar element
 
 6  recess in the collar element
 
 7  recesses
 
 8  mold space
 
 9 ,  10  base insert
 
 11  fluid feed
 
 12  cooling fluid discharge
 
 13  closure element
 
 14  cavity plate
 
 15  portion within the cavity plate
 
 16  portion outside the cavity plate
 
 17 , 17 ′, 17 ″ separating elements
 
 18  through opening
 
 19  weld points
 
 20  fluid flow pattern
 
 21 ,  22  ring elements
 
 23  base insert
 
 24  deflection element
 
 25  cavity enlargement
 
 26  cover element
 
 27  main part
 
 28  connecting grooves
 
 29  milled-out portions
 
 30  peripheral casing portion
 
 31  incisions