Injection molding methods and apparatus

Abstract

An injection molding apparatus for hollow parts comprises first and second co-operating dies, each die including a first male die core and a female die recess. One of the dies is rotatable about an axis. In a first angular position of the rotatable die, the male die core of the first die co-operates with the female die recess of the second die and the male die core of the second die co-operates with the female die recess of the first die, to define first and second molds in which half-components may be formed. In a second angular position of the rotatable die, the respective female dies recesses of the first and second dies co-operate to form a third mold in which the half-components may be joined. The apparatus makes use of a single injector differentially controlled for each stage.

1 . An apparatus for producing molded articles comprising: 
 first and second dies, movable towards and away from one another in a direction parallel to an axis, the first and second dies each having one or more female die cavities and one or more male die cores, the number of female die cavities and the number of male die cores of each die being equal;    means to rotate the second die about the axis between a first angular position in which only the first and second molded parts are formed and a second angular position in which the first and second molded parts are joined together; and    a single injection device communicating with first and second runner drops defined in the first die;    wherein, in the first angular position, the one or more female die cavities in the first die receive a respective male die core of the second die to create one or more first molds, the one or more female die cavities in the second die receive a respective male die core of the first die to create one or more second molds, and the first and second molds are in communication with the first and second runner drops respectively to receive molten material from the injection device to create one or more first and second molded parts; and    in the second angular position, the female die cavities of the first and second dies are aligned with one another to create one or more third molds which communicate with a runner drop to receive molten material from the injection device which surrounds and joins the molded parts together to produce a whole molded article.    
   
   
       2 . An apparatus according to  claim 1 , wherein the second die comprises a backing member and a body pivotally attached thereto for rotation about the axis relative to the backing member and the first die, the body defining the one or more female die cavities and the one or more male die cores.  
   
   
       3 . An apparatus according to  claim 2 , wherein the body further includes a first runner associated with the one or more male die cores and second and third runners associated with the one or more female die cavities of the body; wherein, in the first angular position, the first runner connects the one or more first molds to the first runner drop in the first die and the second runner connects the one or more second molds to the second runner drop in the first die, and, in the second angular position, the third runner connects the one or more third molds to the first runner drop in the first die.  
   
   
       4 . An apparatus according to  claim 2 , wherein the body attached to the second die is sized so that in the second angular position the one or more male die cores of the first die are located beyond the marginal edge of the body and the one or more male die cores of the second die are located beyond the marginal edge of the first die.  
   
   
       5 . An apparatus according to  claim 1 , wherein, in the second angular position, the second runner in the first die is blanked off by a portion of the second die.  
   
   
       6 . An apparatus according to  claim 5 , wherein the blanking portion of the second die comprises a heated plate.  
   
   
       7 . An apparatus according to  claim 1 , wherein the first and second dies each have a recess for receiving the one or more male die cores of the other die in the second angular position.  
   
   
       8 . An apparatus according to  claim 2 , wherein the means to reciprocally rotate the body between the first and second angular positions comprises a piston pivotally secured to the body and a cylinder fixedly secured to the backing member.  
   
   
       9 . An apparatus according to  claim 1 , wherein the second die is movable towards and away from the first die along the axis under the action of a plurality of cylinders and cooperating pistons.  
   
   
       10 . An apparatus according to  claim 1 , further comprising a plurality of co-operating dowels and bores formed in the first and second dies to hold the dies in alignment in the first and second angular positions.  
   
   
       11 . An apparatus according to  claim 1 , wherein in the first angular position, the injection device is operable to inject a first quantity of molten material sufficient to fill the one or more first and one or more second molds and, in the second angular position, the injection device is operable to inject a second, smaller quantity of molten material sufficient to join the molded parts together.  
   
   
       12 . An apparatus according to  claim 11 , wherein the injection device comprises a screw-driven piston and cylinder.  
   
   
       13 . An apparatus according to  claim 1 , further comprising means to inject material or add a further component between or into one or both molded parts before joining the molded parts together to form a whole article.  
   
   
       14 . A method of producing one or more molded articles using the apparatus of  claim 3  comprising: 
 with the first and second dies spaced from one another, rotating the second die to the first angular position;    contacting the first and second dies whereby the one or more female die cavities of the first die receives the one or more male die cores of the second die and the one or more female die cavities of the second die receives the one or more male die cores of the first die to form the one or more first and one or more second moulds respectively;    injecting molten material from the injection device through the first and second drops into the one or more first and one or more second moulds to form one or more first and second molded parts;    separating the first and second dies;    rotating the second die to the second angular position;    contacting the first and second dies whereby the one or more female die cavities, each containing a molded part, are aligned with one another to form one or more third molds;    injecting molten material through the first runner drop to join the molded parts together to create one or more whole molded articles; and    separating the first and second dies to allow removal of one or more molded articles.    
   
   
       15 . A method according to  claim 14 , further comprising: 
 injecting material or adding a further component between or into one or both of the first and second molded parts before injecting molten material to join the one or more molded parts together to form one or more whole articles.    
   
   
       16 . A hollow article produced by the apparatus of  claim 1 .  
   
   
       17 . A hollow article produced by the method of  claim 14 .  
   
   
       18 . A method of molding one or more articles comprising: 
 (a) bringing together a first die with a second die in a first relative position to form one or more first molds and one or more second molds, the one or more first molds being defined between one or more male die cores of the second die and one or more female die cavities of the first die, and the one or more second molds being defined between one or more male die cores of the first die and one or more female die cavities of the second die;    (b) using a single injection device to deliver a first amount of molten material which is relayed to the one or more first and one or more second molds respectively via first and second runner drops defined in the first die, to form one or more first molded parts and one or more second molded parts;    (c) separating the first die from the second die to remove the male die cores from the female die cavities while retaining the first and second molded parts in the female die cavities;    (d) moving the second die relative to the first die to a second relative position so that one or more third molds are formed, the one or more third molds being defined when the one or more female die cavities of the first die align with the one or more female die cavities of the second die;    (e) bringing together the first and second dies in the second relative position to bring together facing surfaces of the one or more first molded parts situated in the female die cavities of the first die and the one or more second molded parts situated in the female die cavities of the second die, the female die cavities of the first and second dies together defining one or more third molds in which previously molded parts are located;    (f) using the injection device to deliver a second amount of molten material to the one or more third molds via the first runner drop, which molten material surrounds a part at least of each previously molded part and then solidifies to connect and joint together the previously molded parts to form one or more whole molded entities;    (g) removing the one or more whole molded entities from the separated first and second dies; and    (h) moving the first and second dies back to the first relative position and bringing the fist and second dies together to commence a further cycle and form one or more further whole molded entities.    
   
   
       19 . A method according to  claim 18  further comprising: 
 delivering the molten material to the one or more first and one or more second molds by first and second runners in the second die, the first and second runners aligning with the first and second runner drops in the first die to receive molten material therefrom only when the first and second dies are in the first relative position; and    delivering the molten material to the one or more third molds by a third runner in the second die, the third runner aligning with a first runner drop in the first die to receive molten material therefrom only when the first and second dies are in the second relative position.    
   
   
       20 . A method according to  claim 18  further comprising:. 
 moving the first and second dies from the first relative position to the second relative position and subsequently back from the second relative position to the first relative position by rotating the second die about an axis.    
   
   
       21 . A method according to  claim 20  further comprising: 
 using a single actuator to rotate the second die about the axis.    
   
   
       22 . A method according to  claim 18  further comprising: 
 using the same single injection device to deliver molten material of the same composition to the one or more first and one or more second molds and to the one or more third molds.    
   
   
       23 . A method according to  claim 18 , further comprising: 
 using a part of the surface of the second die to seal off at least one of the runner drops in the surface of the first die while molten material is delivered to the one or more third molds.    
   
   
       24 . A method according to  claim 18 , further comprising: 
 heating the part of the surface of the second die used to seal off an aperture in the surface of first die.    
   
   
       25 . A method according to  claim 18 , further comprising: 
 controlling the single injection device by using electronic control means to control the amount of molten material delivered by the single injection device such that the first amount of molten material delivered by the single injection device to the one or more first and one or more second molds is different from the second amount of molten material delivered by the injection device to the one or more third molds.    
   
   
       26 . A method according to  claim 18 , further comprising: 
 injecting material or adding a further component between or into one or both of the first and second molded parts before injecting molten material to join the molded parts together to form one or more whole molded articles.    
   
   
       27 . A hollow article produced by the method of  claim 18 .  
   
   
       28 . A method of molding one or more articles comprising: 
 (a) bringing together first and second dies in a first relative position to form one or more first and one or more second molds, the one or more first molds being defined between one or more male die cores of the second die and one or more female die cavities of the first die, and the one or more second molds being defined between one or more male die cores of the first die and one or more female die cavities of the second die;    (b) injecting molten material into both the one or more first and one or more second molds, respectively via first and second runner drops defined in the first die to form one or more first and one or more second molded parts;    (c) separating the first and second dies to remove the male die cores from the female die cavities while retaining the one or more first and one or more second molded parts in the female die cavities;    (d) moving the first die relative to the second die to a second relative position;    (e) bringing together the first and second dies in the second relative position to bring together facing surfaces of the one or more first molded parts situated in the one or more female die cavities of first die and the one or more second molded parts situated in the one or more female die cavities of the second die, the one or more female die cavities of the first and second dies together defining one or more third molds in which both previously molded parts are located;    (f) injecting molten material into the one or more third molds via the first runner drop, the molten material surrounding a part at least of each previously molded part and solidifying to connect together the previously molded parts to form one or more whole molded entities;    (g) separating the first and second dies and removing the one or more whole molded entities from the separated first and second dies;    (h) moving the first and second dies back to the first relative position and bringing the first and second dies together to commence a further cycle and form one or more additional whole molded entities;    wherein the method comprises additionally:    delivering the molten material to the one or more first, one or more second, and one or more third molds through a first and second runner drop which extend through the first die;    delivering the molten material to the one or more first and one or more second molds by first and second runners in the second die, the first and second runners aligning with first and second runner drops of the first die to receive molten material therefrom only when the first and second dies are in the first relative position; and    delivering molten material to the one or more third molds by a third runner in the second die, the third runner aligning with a runner drop of the first die to receive molten material therefrom only when the first and second dies are in the second relative position.    
   
   
       29 . A method according to  claim 28  further comprising: 
 moving the first and second dies from the first relative position to the second relative position and subsequently back form the second relative position to the first relative position by rotating the second die about an axis.    
   
   
       30 . A method according to  claim 28  further comprising: 
 using a single runner drop to deliver molten material to one of the first and second runners and also to the third runner in the second die.    
   
   
       31 . A method according to  claim 28  further comprising: 
 using a part of the surface of the second die to seal off at least one of the runner drops in the surface of the first die while molten material is delivered to the third mold.    
   
   
       32 . A method according to  claim 31  further comprising: 
 heating the part of the surface of the second die used to seal off the aperture in the surface of the first die.    
   
   
       33 . A hollow article produced by the method of  claim 28 .  
   
   
       34 . A method of molding one or more articles each comprising two first components conjoined by a second component using apparatus which comprises: a first die; a second die; means to rotate the second die about an axis; means to move at least one of the first and second dies translationally parallel to the axis; and injection means for delivering molten material under pressure; the method comprising: 
 (a) bringing the first and second dies together in a first rotational position in which the first and second dies define between them n first molds, where n is an even number;    (b) using the injection means to deliver a first amount of molten material;    (c) relaying the first amount of molten material to the n first molds via a first runner provided in the second die;    (d) allowing the molten material to cool and solidify in the n first molds to form n first components of the article;    (e) separating the first and second dies by moving at least one of the dies translationally;    (f) rotating the second die relative to the first die once separated therefrom;    (g) bringing the first and second dies together in a second rotational position in which the first and second dies define between them m second molds in which the previously formed components are located, where m=n/2;    (h) using the injection means to deliver a second amount of molten material to the m second molds;    (i) relaying the second amount of molten material to the m second molds via a second runner provided in the second die;    (j) allowing the molten material to cool and solidify in the m second molds to form m second components conjoining m pairs of first components in order to produce m articles.    
   
   
       35 . A method according to  claim 34  wherein: the apparatus used comprises at least one runner drop extending through the first die which receives molten material delivered from the injection means; the first runner in the second die aligns with a runner drop in the first die only in the first rotational position of the second die; and the second runner in the second die aligns with a runner drop in the second die only in the second rotational position of the second die.  
   
   
       36 . A method according to  claim 34  where the first amount of molten material delivered by the injection means is different to the second amount of molten material delivered thereby.  
   
   
       37 . A method according to  claim 35  wherein the injection means comprises first and second injectors and wherein the first injector is used to deliver the first amount of a first molten material to the n first molds and the second injector is used to deliver the second amount of second molten material to the m second molds, the second molten material being different to the first molten material.  
   
   
       38 . A method according to  claim 37  wherein: the first molten material is delivered through a first runner drop in the first die which aligns with the first runner in the second die in the first rotational position of the second die; and the second molten material is delivered through a second runner drop in the first die which aligns with the second runner in the second die in the second rotational position of the second die.  
   
   
       39 . A method according to  claim 34  wherein: the injection means comprises a single injection; the first die comprises first and second runner drops; the first amount of molten material is delivered through the first runner drop which aligns with the first runner in the first rotational position of the second die; and the second amount of molten material is delivered through the second runner drop which aligns with the second runner in the second rotational position of the second die.  
   
   
       40 . A hollow article produced by the method of  claim 34.