Glass container forming machine plunger assembly

A plunger assembly (10) for a glass container forming machine of the I.S. type, the plunger assembly having a plunger (12) that is open it one end and is non-threadably secured at its open end to a free end of an annular cylinder rod (14) that operates to reciprocate the plunger relative to a blank mold of the forming machine. A perforated cooling air inlet tube (20) is positioned within the plunger, and the free end of the air inlet tube is held against a free end of an annular extension (22) of the cylinder rod, an opposed end of which is threadably received in the cylinder rod, by a split locking ring (30) an inwardly facing recess (36, 38) of which traps a radially outwardly extending flange (40) of the plunger to axially position the plunger relative to the split ring. The split ring abuts an endless ring (24) and is axially positioned thereagainst by a flange (44, 46) of the split ring that is received in a recess (42) of the extension. Cooling air flows into the cooling air inlet tube through the cylinder rod and the extension and exit from the plunger through apertures (54) in the split ring, an annular cavity (76) in the endless ring, openings (52) in the endless ring, openings (78) in the sleeve, an annulus (18) between the cylinder rod and the sleeve and an annulus (48) at the base of the sleeve.

BACKGROUND OF THE INVENTION
 1. Field of the Invention
 This invention relates to a plunger assembly of the type used in a glass
 container forming machine of the individual section (I.S.) type when used
 to produce containers according to the narrow neck press and blow (NNPB)
 process.
 2. Description of the Prior Art
 Production of glass containers on an I.S. machine by the NNPB process is
 generally described in U.S. Pat. No. 5,707,414 (Leidy), which is assigned
 to the assignee of this application, the disclosure of which is
 incorporated by reference herein. In conventional NNPB glass container
 manufacturing, container preforms, which are often called parisons or
 blanks, are formed from gobs of molten glass in blank molds of an I.S.
 machine by pressing, by a reciprocating plunger that is powered by a
 pneumatic cylinder, and this process, conventionally, requires that the
 plunger and cylinder rod elements of the plunger assembly be separate
 pieces. These separate pieces conventionally are removably joined to one
 another by a specially designed threaded fastener that is used to join
 plunger and cylinder rod clips to one another. Such threaded fasteners,
 when new, tend to work loose, and, when old, tend to fuse to one another
 by rusting that occurs in the inherently high temperature environment of a
 glass container forming machine. Further, a typical plunger is internally
 air cooled by way of an air inlet pipe that extends into the plunger
 through the plunger cylinder rod, and this air inlet pipe is subject to
 breakage in use in the region of the free or distal end of the plunger
 because of misalignment that can occur in service between the plunger and
 the plunger cylinder.
 The misalignment of the plunger and the air inlet tube contained therein
 can also lead to contact between the tip of the air inlet tube and the
 inside of the plunger, and this can lead to an undesirable non-uniform
 temperature condition on the interior of the plunger.
 An alternative glass container forming machine plunger assembly is
 described in U.S. Pat. No. 3,314,775 (DeShetler et al.), which was
 assigned to a predecessor of the assignee of the present invention, the
 disclosure of which is also incorporated by reference herein.
 SUMMARY OF THE INVENTION
 The aforesaid and other problems associated with prior art pneumatically
 actuated glass container parison plunger assemblies is overcome by the
 plunger assembly according to the present invention in which the plunger
 to cylinder connection permits the plunger to float freely relative to the
 cylinder rod to which it is removably secured, a factor that reduces
 plunger cooling tube breakage and helps to maintain plunger surface
 temperature uniformity; this factor also reduces the time involved in
 changing a plunger in such a plunger assembly. These results are obtained
 by connecting the plunger to the cylinder rod by a split locking ring with
 an inwardly extending flange at an end that engages an outwardly extending
 flange of the plunger. The split ring is aligned, at its other end, but is
 not connected to, an endless ring which has an inwardly extending flange
 that engages an outwardly extending flange of an extension of the cylinder
 rod, and the cylinder rod extension has an internally threaded free end
 that is threadably received in the cylinder rod of the plunger assembly.
 The plunger air inlet tube floats within the plunger, but is maintained in
 alignment with the extension to the cylinder rod, by the engagement of the
 plunger by the split ring. The split ring has a series of openings passing
 therethrough, and these openings are aligned with corresponding openings
 in the fixed ring. In the normal operating positions of the plunger, the
 split locking ring is always surrounded by an annular sleeve to keep the
 locking ring segments from separating; however, to change a plunger, the
 plunger cylinder is advanced to move the split locking ring to a position
 external to the annular sleeve, to thereby permit the locking ring
 segments to be separated, without the need for any-special tool, and
 thereby remove the plunger from engagement with the cylinder rod. A
 cooling air seal is formed between the endless ring and the split locking
 ring thereabove by an O-ring contained in an annular groove of the endless
 ring, at a location radially inwardly of the openings in the fixed ring
 and in alignment with an annular surface of the split ring when the
 segments of the split ring are closed. At this location, the O-ring
 expands when heated, which increases its sealing effectiveness.
 Accordingly, it is an object of the present invention to provide an
 improved glass container forming machine plunger assembly. More
 specifically, it is an object of the present invention to provide an
 assembly of the foregoing character in which a plunger element may be
 readily disconnected from the cylinder element to which it is connected in
 service, and without the requirement for any special tool, to facilitate
 replacement of a plunger.
 For a further understanding of the present invention and the objects
 thereof, attention is directed to the drawing and the following brief
 description thereof; to the detailed description of the preferred
 embodiment and to the appended claims.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
 A plunger assembly according to the preferred embodiment of the present
 invention is generally illustrated by the reference numeral 10. The
 plunger assembly 10 has a plunger 12, which is open at one end, and an
 annular rod 14 of a pneumatic cylinder or other prime mover. The open end
 of the plunger 12 is removably secured to an end of the rod 14. The rod 14
 reciprocates within an annular sleeve 16, the interior of which defines an
 annulus 18 with the exterior of the rod 14. The rod 12 reciprocates
 relative to a blank mold (not shown) of an I.S. glass container forming
 machine to press gobs of molten glass into preforms, often called parisons
 or blanks; consequently, the plunger 12 is always operating in a high
 temperature environment. To keep the plunger 12 from overheating during
 service, a perforated cooling air inlet tube 20 is positioned within the
 plunger 12, extending from the open end of the plunger 12 to nearly its
 opposed end, to continuously discharge cooling air into the interior of
 the plunger 12.
 The air inlet tube 20 is in engagement with an annular surface at an end of
 an annular extension 22 to the cylinder rod 14, and the opposed end of
 cylinder rod extension 22 is threadably received in the interior of a free
 end of the cylinder rod 14. The exterior of the free end of the cylinder
 rod 14 is surrounded by an endless or annular ring 24, and the annular
 ring 24 has an inwardly projecting flange 26 that seats against an
 outwardly projecting flange 28 of the cylinder rod extension 22 to
 accurately axially position the annular ring 24 relative to the cylinder
 rod extension.
 A split locking ring 30 with semi-cylindrical segments 32, 34 disposed end
 to end during normal operation of the plunger assembly 10 is positioned in
 axial alignment with the annular ring 24. The segments 32, 34 have
 radially inwardly facing recesses 36, 38, respectively, and the recesses
 36, 38 engage a radially outwardly projecting shoulder 40 at an inlet of
 the plunger 12 to accurately axially position the plunger 12 relative to
 the cylinder rod 14 when the segments 32, 34 are disposed in end to end
 relationship, as they will be at all times during normal operation of the
 plunger assembly 10 because of the presence of the sleeve 16. However, to
 change a plunger 12, the cylinder rod 14 is advanced to move the split
 ring 30 beyond the outer limits of the sleeve 16, whereupon the segments
 32, 34 can be freely separated from one another to permit the plunger 12
 to be removed from the cylinder rod 14. The split ring 30 is also
 maintained in accurate axial position relative to the cylinder rod during
 normal operation of the plunger assembly 10 by providing the cylinder rod
 extension 22 with an outwardly facing recess 42 and by providing the
 segments 32, 34 with inwardly facing flanges 44, 46, respectively, that
 are received in the recess 42 when the segments 32, 34 are disposed in end
 to end relationship to one another.
 Cooling air flows upwardly, in the orientation depicted in FIGS. 1 and 2,
 through the cylinder rod 14 and the cylinder rod extension 22 into the
 perforated air inlet tube 20, from which it flows outwardly through the
 perforations therein to cool the interior of the plunger 12. The cooling
 air then flows downwardly in the space between the plunger 12 and the air
 inlet tube 20 to exit through openings 70 in an annular base 72 at an
 opposed end of the air inlet tube 20, the openings 70 being arranged in a
 circumferentially spaced array of individual openings. The air then flows
 through an annular cavity 74 that is formed by the segments 32, 34, and
 from the cavity 74 the air then flows through openings 54 in the inwardly
 facing flanges 44, 46 of the segments 32, 34. The air then flows into an
 annular cavity 76 in the endless ring 24 from which it exits through
 openings 24 in the endless ring 52, the openings 52 being arranged in a
 circumferential array of individual openings. The air then flows into the
 annulus 18, through openings 78 in the sleeve 16, and then into an annulus
 48 at the base of the sleeve 16, from which it is vented to atmosphere.
 The escaping air from the plunger 12 is now at an elevated temperature, for
 example, a temperature of the order of 400.degree. F., and the metal
 elements of the plunger assembly are now substantially expanded. However,
 the expanded elements must still have sufficient play to accommodate
 misalignment of the air inlet tube 20 relative to the cylinder rod 14.
 This misalignment is frictionally accommodated by an O-ring in an annular
 recess 58 of a face at the end of the cylinder rod tube 14 that is engaged
 by an annular surface of the annular base 72 of the cooling air inlet
 tube, this arrangement permitting the cooling air inlet tube to move
 radially with respect to the cylinder rod 14. Further, frictional radial
 movement of the segments 32, 34 relative to the annular ring 24 is
 permitted by an O-ring in a annulus 56 in a face of the annular ring 24
 that is engaged by the flanges 44, 46 of the segments 32, 34.
 Any shock loads that may be encountered by the plunger assembly 10 in its
 normal operation are absorbed by a compression spring 58 that is trapped
 between an annular shoulder 60 of an annular sleeve 62 of the plunger
 assembly 10 that slidably surrounds the sleeve 16 and an annular shoulder
 64 of the sleeve.
 The annular base 72 of cooling air tube 20 has a circumferentially spaced
 apart plurality of radially outwardly extending tabs 72a, and the plunger
 14 is provided with a flange 14a that has a plurality of circumferentially
 spaced apart plurality of radially inwardly extending tabs 14b. The
 cooling air tube 20, then, may be rapidly removably secured within the
 plunger by an insert and turn motion, to bring the annular base 72 into
 engagement with the flange 14a and to bring the tabs 72a and 14b into
 overlapping relationship with one another. Preferably the tabs 72a and 14b
 have tapered faces that engage one another to frictionally, but smoothly,
 secure the cooling air tube 20 and the plunger 14 to one another.
 Although the best mode contemplated by the inventor for carrying out the
 present invention as of the filing date hereof has been shown and
 described herein, it will be apparent to those skilled in the art that
 suitable modifications, variations and equivalents may be made without
 departing from the scope of the invention, such scope being limited solely
 by the terms of the following claims and the legal equivalents thereof.