Straight-hydraulic mold clamping system in molding machine

A straight-hydraulic mold clamping system in an injection molding machine, which comprises:

• a mold clamp cylinder having an inner chamber;
• a reciprocating piston slidably mounted within said inner chamber for dividing said inner chamber into two chamber parts;
• a rod having a rear end connected to said piston and a leading end extending out of said mold clamp cylinder, said mold clamp cylinder having a bearing portion slidably supporting said rod and having an inner circumference having at least one sealing member in sealing engagement with said rod;
• a movable platen attached to said leading end of said rod and having thereon one mold half of a pair of mold halves constituting an injection mold;
• a stationary platen disposed opposite to said movable platen and having the other mold half of said injection mold mounted thereon;
• and
• tie bars extending between said mold clamp cylinder and said stationary platen and slidably supporting said movable platen,
• said bearing portion of said mold clamp cylinder having an inner circumferential surface having therein a plurality of narrow annular outwardly divergent V-shaped oil grooves, said inner circumferential surface and said rod having a clearance therebetween through which said narrow annular oil grooves communicate with one of said chamber parts of said inner chamber in said mold clamp cylinder, and said piston having an outer circumferential surface having therein a plurality of further narrow annular outwardly divergent V-shaped grooves, said outer circumferential surface of said piston and the inner circumferential surface of said mold clamp cylinder having a clearance therebetween through which said further narrow annular grooves communicate with said chamber parts of said inner chamber in said mold clamp cylinder.