Abstract:
An ink cup ( 10 ) for a printing machine is disclosed as including a body ( 11 ) with a cavity ( 34 ) for containing a solvent ( 35 ) and a cavity ( 28 ) for containing an ink ( 26 ), and a screw valve ( 36 ) movable relative to the body ( 11 ) between a first position in which the two cavities ( 34, 28 ) are in a liquid-non-communicable relationship and a second position in which the two cavities ( 34, 28 ) are in a liquid-communicable relationship.

Description:
TECHNICAL FIELD 
       [0001]    This invention relates to an ink cup for a printing machine (such as an ink cup for a pad printing machine) and an accessory for an ink cup for a printing machine. 
       BACKGROUND 
       [0002]    Existing ink cups for printing machines have a body made of a metal (e.g. aluminum) or metal alloy. The body of such a conventional ink cup has a cavity with an open end. The ink cup is placed on a major surface of a metal printing plate for sliding movement relative to the printing plate. Printing ink is contained with the cavity of the ink cup body and, in use, the ink is held between the ink cup body and the printing plate. 
         [0003]    At least one pattern is engraved on the major surface of the metal printing plate on which the ink cup slides. When the ink cup slides across the engraved pattern, some ink in the cavity of the ink cup body is left in the engraved pattern, to be picked up by a printing head (e.g. a silicone printing pad) of the printing machine for printing purpose. 
         [0004]    To achieve consistent and satisfactory printing effect, the ink in the cavity of the ink cup body should be kept at an appropriate viscosity or within an acceptable range of viscosity, by adjusting the concentration of solvent in the ink. It is known in practice that the solvent in the ink evaporates during use, so that the ink becomes more and more viscous upon use. Operation of the printing machine may have to be stopped to allow addition of solvent, which will slow down the printing process and cause variation in the printing quality. 
       SUMMARY OF THE INVENTION 
       [0005]    It is thus an object of the present invention to provide an improved ink cup for a printing machine and an accessory for an ink cup for a printing machine in which the aforesaid shortcoming is mitigated, or at least to provide a useful alternative to the trade and public. Other advantages of the ink cup for a printing machine and the accessory for an ink cup for a printing machine according to the present invention will become apparent from the following discussion. 
         [0006]    According to a first aspect of the present invention, there is provided an ink cup for a printing machine, said ink cup including a body with a first cavity and a second cavity, and a valve member movable relative to said body between a first position in which said first cavity and said second cavity are in a liquid-non-communicable relationship and a second position in which said first cavity and said second cavity are in a liquid-communicable relationship, wherein, when said valve member is in said second position, a liquid in said first cavity is adapted to enter said second cavity at a first substantially constant rate, wherein said valve member is movable relative to said body to a third position in which said first cavity and said second cavity are in a liquid-communicable relationship, and wherein when said valve member is in said third position, a liquid in said first cavity is adapted to enter said second cavity at a second substantially constant rate which is different from said first substantially constant rate. 
         [0007]    According to a second aspect of the present invention, there is provided an accessory for an ink cup for a printing machine, said accessory including a body with a cavity having a first opening and a second opening, and a valve member movable relative to said body between a first position in which a liquid in said cavity is prevented from exiting said body via said second opening and a second position in which a liquid in said cavity is allowed to exit said body via said second opening, wherein, when said valve member is in said second position, a liquid in said first cavity is adapted to exit said body via said second opening at a first substantially constant rate, wherein said valve member is movable relative to said body to a third position in which a liquid in said cavity is allowed to exit said body via said second opening, and wherein when said valve member is in said third position, a liquid in said first cavity is adapted to exit said body via said second opening at a second substantially constant rate which is different from said first substantially constant rate. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]    An ink cup for a printing machine according to an embodiment of the present invention will be discussed with reference to the accompanying drawings in which: 
           [0009]      FIG. 1  is a longitudinal sectional view of an ink cup for a printing machine according to an embodiment of the present invention; and 
           [0010]      FIG. 2  is an enlarged view of the encircled part in  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0011]    A longitudinal sectional view of an ink cup for a printing machine according to an embodiment of the present invention is shown in  FIG. 1  in an in-use orientation, which ink cup being generally designated as  10 . The ink cup  10  has a body  11  formed of a lower body  12  and an upper body  14 . The lower body  12  is threadedly engaged with the upper body  14 , and the upper body  14  is threadedly engaged with a cover  16 . Each of the lower body  12 , upper body  14  and cover  16  is made of a metal or metal alloy, e.g. aluminum. The material with which each of the lower body  12 , upper body  14  and cover  16  is made may be different or the same. In the present embodiment, the lower body  12  and the upper body  14  are two separate components releasably and threadedly engageable with each other. It is of course possible to form a body  11  in which the lower body  12  and the upper body  14  are integrally formed with each other. 
         [0012]    To a lower circular rim of the lower body  12  is fixedly engaged with a circular ring  18 , which may be made of ceramic or a metal. In use, the ring  18  is in contact with an upper major surface of a metal printing plate formed (e.g. by engraving) with at least one recessed pattern. An ink bowl  20  with a lower open end and an opposite upper wall  22  is engaged with the lower body  12 . In particular, the ink bowl  20  is received within a recess  24  of the lower body  12 . Printing ink  26  is received within a cavity  28  within the ink bowl  20 . In use, the ink cup  10  is slidingly movable on and relative to the printing plate, with the ring  18  being in contact with the printing plate, to leave ink originally in the ink bowl  20  on the recessed pattern on the printing plate for printing purpose. To prevent the ink cup  10  from being accidentally displaced from the printing plate, a number of magnets  30  are enclosed within cavities between the lower rim of the lower body  12  and the ring  18 . These magnets  30  serve to attract the ink cup  10  to the printing plate in use. 
         [0013]    The upper body  14  has a central cylinder  32  which is surrounded by an annular cavity  34  with an open upper end. A solvent  35  for the ink  26  may be introduced into the cavity  34  of the upper body  14  through its open upper end. The cylinder  32  has a central threaded bore which is threadedly engaged with a screw valve  36 . The screw valve  36  is movable relative to the upper body  14  (and thus the ink cup  10 ) up and down, i.e. in the directions indicated by the bi-directional arrow B-B in  FIG. 1 . The screw valve  36  has an end pin  38  and a threaded portion  39 : The diameter of the end pin  38  is smaller than the diameter of the threaded portion  39 . The cover  16  is releasably engageable with the upper body  14  to prevent or at least reduce evaporation of the solvent  35  received within the cavity  34  to the outside environment. 
         [0014]    As can be seen more clearly in  FIG. 2 , a channel  40  in the upper body  14  leads from a lower portion of the annular cavity  34  of the upper body  14  to a tunnel  42 , which in turn leads to an opening  43  at the bottom of the upper body  14 . The channel  40  is slanted relative to a longitudinal axis L-L of the ink cup  10 , and the tunnel  42  is parallel to the longitudinal axis L-L of the ink cup  10 . Thus, in the absence of the screw valve  36 , the solvent  35  in the cavity  34  will flow (under its own weight, and in the direction indicated by the arrow A in  FIG. 2 ) through the channel  40 , then through the tunnel  42 , and exit the upper body  14  via the opening  43 . 
         [0015]    The end pin  38  of the screw valve  36  is of a diameter of 3 mm and the tunnel  42  is of a diameter slightly larger than 3 mm. When the screw valve  36  is rotated relative to the upper body  14  to its lowermost position, the screw valve  36  will close a lower end of the channel  40 , thus blocking liquid communication between the channel  40  and the tunnel  42 , i.e. no solvent  35  can flow from the cavity  34  via the channel  40  to the tunnel  42 . 
         [0016]    When the screw valve  36  is rotated to move upwardly relative to the upper body  14  to an upper position, a gap is opened between the channel  40  and the tunnel  42 , thus allowing the solvent  35  in the cavity  34  to flow through the channel  40  to the tunnel  42 , eventually exiting the upper body  14  via the opening  43 . The small difference between the diameter of the tunnel  42  and the diameter of the end pin  38  has the effect of ensuring that the solvent  35  exits the tunnel  42  at a constant rate and in drops. 
         [0017]    When the screw valve  36  is rotated to move further upward relative to the upper body  14  to a further upper position, a wider gap is opened between the channel  40  and the tunnel  42 . Therefore, solvent  35  in the cavity  34  will flow through the channel  40  and the tunnel  42 , and exit the upper body  14  via the opening  43  of the tunnel  42  at a higher constant rate, also in drops. Thus, by adjusting the position of the screw valve  36  relative to the upper body  14  (and thus relative to the body  11 ), one may (a) selectively allow or prevent the solvent  35  in the annular cavity  34  from exiting the upper body  14  via the opening  43  of the tunnel  42  and (b) adjust the rate at which the solvent  35  in the annular cavity  34  exits the upper body  14  via the opening  43  of the tunnel  42 . It should also be understood that adjusting the position of the screw valve  36  relative to the upper body  14  will also bring about a corresponding adjustment of the position of the end pin  38  within and relative to the tunnel  42  (which may alternatively be a separate steel sleeve). 
         [0018]    In use, the opening  43  of the tunnel  42  of the upper body  14  is vertically above a hole  44  through the upper wall  22  of the ink bowl  20  in the lower body  12 . The solvent  35  exiting the upper body  14  via the opening  43  of the tunnel  42  will thus fall, on its own weight and in drops, through the recess  24  in the lower body  12 , and subsequently enter, through the hole  44 , the cavity  28  within the ink bowl  20 , and be mixed with the ink  26  in the ink bowl  20 . Thorough mixing of the solvent  35  with the ink  26  in the ink bowl  20  is facilitated, in use, by movement of the ink cup  10  on and relative to the printing plate. 
         [0019]    It can thus be seen that an advantage of the ink cup  10  according to the present invention is that the solvent  35  in the cavity  34  can be added to the ink  26  in the ink bowl  20  below the cavity  34  automatically and in a controlled manner. It is also possible for an operator to adjust the rate at which the solvent  35  is added to the ink  26  by simple operation and adjustment of the screw valve  36 . 
         [0020]    Although the upper body  14 , the screw valve  36  and the cover  16  have so far been disclosed as forming part of the ink cup  10 , it is envisaged that the upper body  14 , the screw valve  36  and the cover  16  may form a separate accessory releasably engageable with a conventional ink cup to provide the automatic viscosity control/adjustment function. 
         [0021]    It should be understood that the above only illustrates an example whereby the present invention may be carried out, and that various modifications and/or alterations may be made thereto without departing from the spirit of the invention. It should also be understood that various features of the invention which are, for brevity, described here in the context of a single embodiment, may also be provided separately or in any appropriate sub-combinations.