Abstract:
An injection moulding machine that incorporates a centering linkage for producing unequal strokes during the opening and closing of the mould sections. The centering linkage mechanism is adjustable so that the stroke lengths of the mould sections can be adjusted from time to time

Description:
CROSS-REFERENCE 
       [0001]    This application claims priority to U.S. Provisional App. No. 62/148,717 filed Apr. 16, 2015. 
     
    
     FIELD 
       [0002]    The subject matter hereof relates generally to the field of injection moulding machines. 
       BACKGROUND 
       [0003]    An example of a moulding machine having a centering linkage that enables unequal strokes of the mould sections is disclosed in U.S. Pat. No. 6,099,784 to Husky Injection Moulding Systems. The issue with the mechanisms described in this reference is that the centering linkage mechanism is not easily adjustable. A more robust solution is desired. 
       SUMMARY OF INVENTION 
       [0004]    In one aspect of the invention an injection moulding machine is provided that incorporates a centering linkage for producing unequal strokes during the opening and closing of the mould sections. The centering linkage mechanism is adjustable so that the stroke lengths of the mould sections can be adjusted from time to time. 
         [0005]    According to this aspect, there is provided an injection moulding machine which includes a stationary platen with a mould plate and a moveable platen with a mould plate. A primary drive axially reciprocates the moving platen between an open position and a closed position. The machine further includes at least one moveable center section having first and second mould plates on opposing sides thereof, the first mould plate facing the stationary platen mould plate so as to define a first mould half, the second mould plate facing the moving platen mould plate so as to define a second mould half. A centering linkage mechanism converts the reciprocating movement of the moveable platen to corresponding reciprocating movement of the center section. The centering linkage mechanism includes a central link member pivotally connected to the center section, a first link arm pivotally connected to the central link member and pivotally connected to the stationary platen, and a second link arm pivotally connected to the central link member and pivotally connected to the moving platen. At least one of the first link arm and the second link arm includes a central piece that is threadingly engaged with two end pieces such that the depth of engagement between the center piece and each end piece is manually adjustable, thereby enabling adjustment in stroke length of at least one of the mould halves. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0006]    The foregoing and other aspects of the invention will be more readily appreciated having reference to the attached drawings wherein: 
           [0007]      FIG. 1  shows a portion of a stack mould, including centering linkage according to a first embodiment of the invention, in an open position; 
           [0008]      FIG. 2  shows the portion of the stack mould of  FIG. 1  in a closed position; and 
           [0009]      FIGS. 3A, 3B and 3C  shows elevation, plan and cross-section views of a portion of the centering linkage. 
       
    
    
     DETAILED DESCRIPTION 
       [0010]      FIGS. 1 and 2  show a portion of a stack mould  10 , which has two moulding stations A and B. Station A is provided by a mould plate  12  mounted on a stationary platen  14  and a mould plate  16  mounted on a immediately adjacent side of a center section  20 . When juxtaposed or closed together these two mould plates  12 ,  16  define a first set of mould cavity spaces into which molten material is injected. Likewise, Station B is provided by a mould plate  22  mounted on a moving platen  24  and a mould plate  26  mounted on the immediately adjacent side of the center section  20 . When juxtaposed or closed together these two mould plates  22 ,  26  define a second set of mould cavity spaces into which molten material is injected. 
         [0011]    The mould sections are mounted on and translate over tie bars  30 . The primary drive means for moving the mould sections is not shown as it is a conventional mechanism. 
         [0012]    As the moving platen  24  reciprocates between open and closed positions to open and close the mould, the center section  20  must also move relative to the stationary and moving platens  14 ,  24  in order to open the stations A and B for ejection or removal of the moulded articles. In particular, in a balanced or symmetrical mould the center section  20  moves half the distance or half the stroke of the moving platen  24 , relative to the stationary platen  14 , so the opening width of stations A and B are equal. In some circumstances, for example, where stations A and B mould articles of different sizes, it may be desirable for the center section  20  to have a different stroke ratio so that the opening widths of stations A and B are different. 
         [0013]    The stack mould  10  is provided with a centering linkage mechanism  40  to cause the mould stations A and B to have different or unequal opening strokes. The linkage mechanism  40  includes a central link member  42  pivotally connected to the center section  20 , a first link arm  44  which is pivotally connected at one end to the central link member  42  and pivotally connected at the other end to the stationary platen  14 , and a second link arm  46  which is pivotally connected at one end to the central link member  42  and pivotally connected at the other end to the moving platen  24 . 
         [0014]    The first and second link arms  44 ,  46  may have different lengths, whereby mould stations A and B may have different or unequal opening strokes. 
         [0015]    The link arms  44 ,  46  may be identically constructed and  FIGS. 3A, 3B and 3C  show various views of one link arm. The link arm  44  or  46  is preferably constructed from three parts: a center piece  50  and two end pieces  52 ,  54 . The link arm  44  or  46  is adjustable in length because the center piece  50  is threadingly engaged with the end pieces  52 ,  54  such that the depth of engagement between the center piece  50  and each end piece  52 ,  54  can be manually adjusted. 
         [0016]    In the illustrated embodiment the center piece  50  has two opposing threaded shafts  62 ,  64  which jut out from opposites ends of a casing  60 . In practice the casing  60  can be provided by an internally threaded cylinder which has a centrally situated tooling profile  66  on the outer surface thereof for receipt of a gripping tool head such as a wrench. The threaded shafts  62 ,  64  may be releasably locked in position by lock nuts  68 . The end pieces  52 ,  54  each include threaded apertures  70 ,  72 , respectively, for receipt of the threaded shafts  62 ,  64 . The end pieces  52 ,  54  may be releasably locked against the threaded shafts  62 ,  64  by lock nuts  69 . 
         [0017]    Loosening the lock nuts  68 ,  69  allows the operator to adjust depth of engagement of the threaded shafts  62 ,  64  within the end pieces  52 ,  54 , thus enabling adjustment of the mould station stroke distance. 
         [0018]    The opposite end of the end pieces  50 ,  52  include apertures  74 ,  76 , respectively, for pivotal connection to the central link member and moving or stationary platen. As the end pieces  52 ,  54  are precluded from rotating, rotation of the center piece  50  will cause a corresponding translation of the end pieces  52 ,  54  relative to the center piece  50 . The orientation of the shaft threads  62 ,  64  and threaded apertures  70 , 72  can be arranged such that rotation of the center piece  50  in one direction causes the end pieces  52 ,  54  to simultaneously move away from one another and rotation of the center piece  50  in the opposite direction causes the end pieces  52 ,  54  to simultaneously move toward one another. 
         [0019]    Those skilled in the art will appreciate that a variety of other alternations or modifications may be made to the embodiments discussed herein without departing from the scope of the invention as defined by the appended claims.