Technical Field [001] This invention relates to a method and apparatus for compression molding plastic articles, such as a plastic preform which can subsequently be molded into a plastic container. Background of the Invention [002] Various plastic articles, such as plastic closures for containers, have been formed by a compression molding process. Some compression molding machines have a plurality of tools mounted in a circumferential array on a rotatable turret in a plurality of opposed coacting pairs. The tools of each pair carry opposed male and female mold sections that when closed together form a cavity mold for compression molding the desired articles. The turret rotates adjacent a machine frame that carries cams for moving the tools of each pair toward each other during a portion of each revolution of the turret for compression molding articles between the tool pairs, and away from each other during another portion of the each turret revolution for releasing articles molded between the tools and to receive fresh charges of plastic into the mold cavities. The opposed pairs of tooling have been mounted to the turret by radially extending brackets that carry elongate rods and appropriate bushings and bearings to permit slidable movement of each half of a tooling pair relative to the other half of the tooling pair along the rods. Summary of the Invention [003] A method and apparatus for compression molding plastic articles including a base, a rotatable turret having an annular main body mounted on the base and carrying a plurality of molding tools for compression molding plastic articles, and a drive mechanism coupled to the turret to rotate the turret relative to the base. The drive mechanism may include a driven member coupled to the turret, such as an annular driven gear disposed coaxially with the main body of the turret. [004] The turret main body may be mounted on an annular mounting ring carried by the annular driven gear, wherein the mounting ring and driven gear are coaxially disposed with the main body of the turret for rotation relative to the base. The mounting ring may include a plurality of arcuate segments. A brake carried by the base may selectively engage a portion of the mounting ring to stop rotation of the turret. [005] An annular bearing may be provided between the base and turret to enable rotation of the turret relative to the base. The bearing may include first and second rings coupled together for relative rotation. The rings may be radially inner and outer rings, one carried by the base and the other carried by the mounting ring. [006] The turret main body may include a plurality of arcuate sections, two or more of which may be connected by a tie plate. The tie plate may be an annular tie plate formed by a plurality of arcuate segments, with a gap provided between adjacent sections of the tie plate. Alignment pins may be provided to align the multiple main body sections to the tie plate. Brief Description of the Drawings These and other objects, features and advantages of the present invention will be apparent from the following detailed description of the preferred embodiments and best mode, appended claims and accompanying drawings in which: FIG. 1 is a perspective view of one presently preferred embodiment of an apparatus for compression molding plastic articles; FIG. 2 is a perspective view of a portion of the apparatus showing, among other things, a turret, base and main frame of the apparatus; FIG. 3 is a plan view of the portion of the apparatus shown in FIG. 2; FIG. 4 is a cross-sectional view of the apparatus as shown in FIG. 2; FIG. 5 is a side view of the apparatus shown in FIG. 2; FIG. 6 is a cross-sectional view taken generally along line 6-6 in FIG. 5; FIG. 7 is an enlarged fragmentary sectional view of the encircled portion 7 in FIG. 4; FIG. 8 is an enlarged fragmentary side view of a portion of a drive mechanism of the apparatus; FIG. 9 is an enlarged fragmentary side view of a brake assembly of the apparatus; FIG. 10 is a perspective view of one turret section of the apparatus showing an exterior surface of the turret section; FIG. 11 is a perspective view of one turret section of the apparatus showing an inner surface of the turret section; FIG. 12 is an exploded perspective assembly view showing the turret, 25 base and drive mechanism; FIG. 13 is a fragmentary sectional view of a portion of the turret and adjacent mounting ring; and FIG. 14 is a fragmentary perspective view of a portion of the turret showing portions of a coolant circuit. Detailed Description [007] Referring in more detail to the drawings, FIG. 1 illustrates an apparatus 10 for compression molding plastic articles, such as preforms used in forming plastic containers. The apparatus 10 includes a base 12 and a turret 14 on which a plurality of tooling pairs 16 are mounted in an endless path for rotation with the turret 14 enabling a continuous compression molding process. Each tooling pair 16 includes a first actuator 18 that carries a first mold section, and a second actuator 20 that carries a second mold section, with the first and second mold sections defining at least part of a mold cavity in which a plastic article is compression molded. The first and second actuators 18, 20 are preferably slidably carried by the turret 14 for movement toward each other to a closed position to form a plastic charge in the mold cavity, and away from each other to permit removal of a formed plastic article and delivery of a fresh plastic charge into each mold cavity. Formed plastic articles are removed from the mold cavities by an appropriate take-out mechanism (not shown). An extruder 22 provides molten plastic charges that are delivered to each of the mold cavities by a distributor 23 during a portion of the rotation of the turret 14 wherein the first and second actuators 18, 20 are separated or opened. In FIG. 1, the turret 14 is shown with some tooling pairs 16 removed. In the presently preferred embodiment, the tooling pairs 16 are disposed around the entire perimeter of the turret 14. [008] As best shown in FIGS. 2, 4, 5 and 10, the base 12 is preferably formed by spaced apart upper and lower plates 24, 26 interconnected by a plurality of support ribs 28 that may be welded to each of the plates. To facilitate forming and processing a large base for a large apparatus, the upper and lower plates 24, 26 are preferably formed in two halves each having a semicircular inner surface 30, 32, respectively, providing a generally annular base 12. Outwardly extending flanges 34 facilitate mounting the base 12 to a floor, or the base 12 may include appropriate nonslip or vibration or shock dampening feet 36 so that the base 12 can be free standing on a floor without being secured or fixed thereto. A key plate 38 and associated keys 39 may be provided on the base 12 to facilitate alignment of adjacent machines or devices, such as, byway of examples without limitation, a takeout apparatus and a plastic charge distributor. [009] As best shown in FIGS. 2 and 3, a frame 40 is preferably fixed to the base 12, although it may be fixed to a floor upon which the base 12 rests. In one presently preferred embodiment, the frame 40 includes three posts 42, 44, 46 fixed to the outwardly extending flanges 34 of the upper plate 24. A main beam 48 spans and is connected to two of the posts 42, 44 and is interconnected to the third post 46 by a pair of cross beams 50, 52 fixed at one end to the main beam 48 and at their other end to the third post 46. The main beam 48 and the base 12, in the area between the two posts 42, 44, are constructed and arranged to carry upper and lower cam plate assemblies 54, 56 that engage appropriate cam followers carried by the first and second actuators 18, 20. The cam plates and followers open or separate the first and second actuators 18, 20 so that a formed article can be removed by the take-out mechanism and to permit a fresh charge of plastic to be received in each mold cavity, and close the first and second actuators 18, 20 to compression mold a plastic charge in the mold cavities. Accordingly, the frame 40 provides support against the reactive forces on the cam plates 54, 56 generated by manipulating the first and second actuators 18, 20 and providing the compression molding force to the first and second actuators 18, 20 to form aplastic article. [0010] The turret 14 includes a main body 60 which is preferably generally annular and carried by the base 12 for rotation about an axis 61 (FIG. 6). The main body 60 has a lower end 62 adjacent to the base 12 and extends axially to an upper end 64 that is preferably generally planar. The main body 60 includes a radially outer surface 66 about which the mold tooling pairs 16 are preferably disposed, and a radially inner surface 68. As best shown in FIGS. 10-12, the main body 60 of the turret 14 is preferably formed by a plurality of sections 70 arranged side-by-side to form the annular main body 60. Each turret section 70 includes an axially upper end 72 and a lower end 74 as well as axially extending and circumferentially spaced side walls 76. Each section 70 is preferably arcuate so an outer surface 78 of each section is equally radially spaced relative to the axis 61 about which the turret 14 rotates, hi the embodiment shown, eight separate sections 70 are mounted adjacent to each other with each side wall 76 of each section 70 disposed adjacent to a side wall 76 of an adjacent section 70 of the turret 14. Accordingly, in this embodiment, each turret section 70 spans an arc of about 45 degrees so that when placed side-by-side the eight sections 70 span 360 degrees and provide a complete annulus. To facilitate assembly and account for manufacturing and assembly tolerances, each turret section 70 is preferably circumferentially spaced from adjacent turret sections 70 providing a gap 80 between the side walls 76 of adjacent turret sections 70. [0011] As best shown in FIG. 11 , an inner surface 82 of each turret section 70 may be substantially hollow including a plurality of radially inwardly extending support walls 84 interconnecting the upper, lower, and side walls 72, 74, 76, respectively, of the turret section 70. As shown, the support walls 84 extend axially and circumferentially although any suitable orientation can be employed where support walls 84 are desired. To facilitate mounting the tooling pairs 16 on each turret section 70, a plurality of radially outwardly and axially extending flanges 86 are preferably provided on the outer surface 78 of each turret section 70. In one presently preferred embodiment, each flange 86 carries a rail of a linear bearing about which the mold tooling pairs 16 reciprocate axially relative to the turret sections 70. Desirably, the radially outwardly extending flanges 86 provide a gap between the mold tooling 16 and the outer surface 78 of the turret 14 enabling coolant lines to be routed between the mold tooling and turret. The gaps may also facilitate access to the mold tooling 16 such as through one or more holes 88 provided through each section 70 of the turret 14. [0012] When stacked adjacent to each other, the turret sections 70 provide a substantially circumferentially continuous turret main body 60 adapted to carry a plurality of mold tooling pairs 16 for rotation relative to the cam plates 54, 56, the base 12 and frame 40 generally. In one presently preferred embodiment, each turret section 70 is adapted to carry five tooling pairs 16 so that with eight turret sections 70, forty mold tooling pairs 16 are provided in an endless path along the turret 14. In the presently preferred embodiment, each mold tooling pair 16 includes four mold cavities to simultaneously form four plastic articles. Accordingly, for each revolution of the turret one hundred and sixty plastic articles are formed. [0013] The lower axial end 74 of each section 70 of the turret 14 is disposed on a mounting ring 90 and is preferably fixed thereto, such as by bolts. The mounting ring 90 is preferably annular and underlies substantially the entire lower end 74 of each turret section 70. The mounting ring 90 preferably extends radially outwardly from the exterior surface 66 of the turret 14, as best shown in FIGS. 2, 3, 5 and 6. To facilitate forming and processing the mounting ring 90, it is preferably formed in two halves 90a, 90b, although the mounting ring 90 may be formed in one or any number of segments. When formed in more than one segment, it is desirable that the ends 92 of the segments are not circumferentially aligned with a gap 80 between adjacent turret sections 70. Preferably, each gap 80 between adjacent turret sections 70 is spanned by a portion of the mounting ring 90. [0014] The mounting ring 90 in turn is received on and is connected to a driven gear 94 that is rotatably carried by the base 12. The driven gear 94 is preferably annular, coaxially aligned with the mounting ring 90 and the turret main body 60, and has a plurality of radially outwardly extending teeth 96 about its outer surface. The driven gear 94 may be formed in one or more than one section as desired. The driven gear 94 is mated with a drive mechanism 97 including a drive gear 98 that is driven for rotation by a suitable motor and gearbox 100. The drive gear 98 has radially outwardly extending teeth 102 that mesh with the teeth 96 of the driven gear 94. To reduce the need for lubrication, and the wear on the driven gear 94, the drive gear 98 may be formed of a polymeric material, such as a nylon. In the embodiment shown, the drive gear 98 is a pinion gear that is much smaller than the driven gear 94 and much easier to form, so preventing wear to the driven gear 94 is desirable as the drive gear 98 can be easily replaced at comparatively low cost. The mounting ring 90 is preferably bolted to the driven gear 94 for co-rotation of the turret main body 60, mounting ring 90 and driven gear 94. [0015] To facilitate rotation of the turret 14 relative to the base 12, a bearing 104 is preferably disposed between them. The bearing 104 is preferably annular, may be formed in one or more than one section, and preferably includes radially inner and outer rings 106, 108, respectively. The radially inner ring 106 is preferably fixed to the base 12, such as by a plurality of bolts or screws. The outer ring 108 is preferably received within and adjacent to the driven gear 94 and fixed to the mounting ring 90, also preferably by a plurality of bolts or screws as best shown in FIGS. 4 and 7. The outer ring 108 rotates relative to the inner ring 106, and with the driven gear 94. To enable the relative rotation between the inner and outer rings 106, 108, the outer ring 108 preferably includes a circumferentially continuous race 110 formed in its radially inner surface and aligned with a circumferentially continuous race 112 formed in the radially outer surface of the inner ring 106. A plurality of balls 114 are preferably received in the races 110, 112 between the inner and outer rings 106, 108 to support the outer ring 108 relative to the inner ring 106 and permit the relative rotation of the rings. [0016] The axial upper end 72 of each turret section 70 is preferably connected to at least one other turret section 70 by a tie plate 120. The tie plate 120 may be annular, and may be formed in one or more than one segment, and is preferably formed in two halves 120a, 120b. When formed in more than one segment, the ends 122 of each segment 120a, 120b preferably are not circumferentially aligned with a gap 80 between adjacent turret sections 70. Accordingly, each gap 80 between adjacent turret sections 70 is preferably overlied by or spanned by a portion of a tie plate 120. Also preferably, the ends 122 of the tie plate segments 120a, 120b are circumferentially offset from the ends 92 of the mounting ring segments 90a, 90b disposed adjacent the axial lower ends 74 of each turret 5 section 70. hi the presently preferred embodiment, the tie plate 120 is preferably formed by two semi-annular halves 120a, 120b, and the mounting ring 90 is likewise formed by two semi-annular halves 90a, 90b. The adjacent ends 122 of the tie plate halves 120a, 120b are preferably circumferentially offset from the adjacent ends 92 of the mounting ring halves 90a, 90b by ninety degrees, as best shown in FIG. 12. This increases the strength and stability of the turret main body 60 which includes at least the turret sections 70, the mounting ring halves 90a, 90b and the tie plate halves 120a, 120b. [0017] To facilitate mounting the tie plate halves 120a, 120b to the turret sections 70, a plurality of holes 126 are provided in the each tie plate half and are adapted 15 to align with a plurality of complementary holes 128 in the upper ends 72 of each turret section 70. To facilitate aligning the upper ends 72 of the turret sections 70 relative to the tie plate 120, tapered alignment pins may be driven through various alignment holes 130 in the tie plate 120 and into corresponding alignment bores 132 in the turret sections 70. Thereafter, bolts can be placed through the 20 tie plate 120 and upper walls 72 of each turret section 70 and nuts can be secured on the bolts. Likewise, as shown in FIGS. 12 and 13, to facilitate aligning the turret sections 70 relative to the mounting ring 90, keys 134 are preferably disposed in aligned slots 136, 138 respectively formed in the lower end 74 of each turret section 70 and on the upper face of the mounting ring 90. As best 25 shown in FIG. 13 the slots 136, 138 formed in the mounting ring 90 and the lower end 74 of the turret sections 70 are preferably cross shaped to ensure precise alignment of the turret sections 70 relative to the mounting ring 90. [0018] To stop the rotation of the turret 14 relative to the base 12, as best shown in FIGS. 3, 6 and 9, a brake assembly 140 is provided and includes at least one and preferably a pair of brake calipers 142 and associated brake pads 144 adapted to engage the portion of the mounting ring 90 that extends radially outwardly away from the turret. The brake calipers 142 include upper and lower brake pads 144 which clamp the upper and lower surfaces of the mounting ring 90 to slow and stop the rotation of the turret 14 as desired. [0019] As best shown in FIGS. 2 and 14, a rotatable fluid coupler 150 is preferably carried by the frame 40, and in one presently preferred embodiment is carried by a plate 152 fixed to the beams 50, 52. The fluid coupler 150 preferably includes a hub 154 that rotates with the turret and includes a plurality of outlets 156. Each outlet 156 communicates with a separate supply conduit or hose 158 that in turn communicates with a manifold 160 mounted on the turret, such as on tie plates 120. The manifold 160 may be formed in one or more than one sections. Each manifold 160 communicates with one or more hoses or conduits 162 that communicate with, for example, the tooling pairs 16 to circulate coolant therethrough. A return circuit may also pass through the coupler 150 via separate hoses or conduits to facilitate carrying heated coolant away from the tooling pairs 16. [0020] While certain preferred embodiments and constructions and arrangements of particular components of the compression molding apparatus 10 have been shown and described herein, one of ordinary skill in this art will readily understand that modifications and substitutions can be made without departing from the scope of the invention as defined by the appended claims. While the drive mechanism in the preferred embodiment includes mating drive and driven gears, any suitable drive mechanism or assembly may be used, for example, without limitation, a belt and pulley or chain and sprocket arrangement 5 may be used. Also, for example and without limitation, while the drive mechanism in the preferred embodiment is shown adjacent the lower end 62 of the turret 14 main body 60, the drive mechanism could also be located adjacent the upper end 64 of the turret 14 main body 60 with the driven gear carried adjacent to the upper end 64 of the turret 14 sections 70. Of course, other 10 modifications and substitutions will be apparent from the detailed description of the presently preferred embodiment.