Blow station bottom plug actuating mechanism

ABSTRACT

The upper and lower halves of a blow mold define a blow mold cavity when the halves are closed together. A bottom plug which serves to form a dome in the bottom of the blown bottle is shifted into and out of a cooperating relationship with the two mold halves by cam mechanism that operates in response to raising and lowering of the upper die set upon which the upper mold half is mounted. The actuating mechanism comprises a pair of mutually opposed cam rods having a follower trapped therebetween that is in turn coupled with the bottom plug so that as the cam rods are shifted with the upper die set, the follower reacts to cam surfaces on the rods to impart a corresponding extension and retraction motion to the bottom plug. To handle multiple, side-by-side blow mold cavities, the bottom plugs for such cavities are ganged together on a common support bar that is in turn provided with operating shanks, each provided with a cam follower operated by a cam assembly. In an alternative embodiment, the bottom plug is split into two upper and lower halves, with each half being provided with its own actuating mechanism. Sets of upper plug halves can be ganged together for actuation in unison, as can sets of lower plug halves.

INFORMATION

DETAILED DESCRIPTION OF THE INVENTION

DETAILED DESCRIPTION

Prior Art

FIGS. 1-4 show a prior art unit cavity blow mold having an upper mold half and a lower mold half . Mold halves and are mounted on respective upper and lower die sets (not shown) for vertical movement of upper half toward and away from lower half to open and close the mold defined by halves , . A plurality of external nipples such as nipples on halves , communicate with internal cooling passages such as passages in halves , for the purpose of supplying a cooling liquid such as water to the mold.

When the mold halves , come together as illustrated in FIG. 3, a blow mold cavity becomes defined between halves and corresponding in shape and size to the final blown bottle. A major portion of the bottom of cavity is defined by a cylindrical plug having a convex or dome-shaped leading surface . Plug is adapted to be actuated horizontally between an extended position in FIG. 3 and a retracted position in FIG. 4 by interacting cam wedges and .

The upper cam wedge is fixed to the outer end of upper mold half for vertical reciprocation therewith and has a downwardly and inwardly facing bevel at its lower extremity. Upper wedge also has an inverted, generally U-shaped notch in its lower extremity.

On the other hand, lower wedge is affixed to plug for horizontal reciprocation therewith and is guided in such movement by a pair of lower outwardly projecting guide pins on lower mold half and a pair of upper outwardly projecting guide pins on lower mold half . A coiled return spring surrounding each upper guide pin yieldably biases lower wedge and thus also plug outwardly to the retracted position determined by the enlarged head of each lower guide pin . Lower wedge has an outwardly and upwardly facing bevel on its upper end having the same inclination as bevel of upper wedge . A cooling tube for water or the like is threaded into the outboard end of plug and projects outwardly through a hole in bevel to support a fitting at its outer end, to which is connected one of the nipples .

The notch in upper wedge is aligned with the tube associated with lower wedge so that as upper half moves downwardly toward lower half to close mold , tube slips into clearance notch . Bevels and come into engagement with one another, causing a horizontal reaction force directed rightwardly viewing FIGS. 4 and 3, causing plug to be shifted into its extended position of FIG. 3 as mold halves , fully close. Springs become compressed at this time. As mold halves , are then reopened, bevel rises from bevel and return springs push lower wedge leftwardly viewing FIGS. 3 and 4 to the extent permitted by heads of guide rods . Thus, plug becomes shifted outwardly to its retracted or withdrawn position.

In practice, production molds typically comprise a multiplicity of side-by-side blow mold cavities, each provided with their own pair of upper and lower mold halves and their own bottom plug. Each mold is also provided with its own pair of upper and lower cam wedges for actuating the corresponding bottom plug during raising and lower of the upper die set to which the upper mold halves are commonly attached.

A Preferred Embodiment of the Present Invention

The present invention is susceptible of embodiment in many different forms. While the drawings illustrate and the specification describes certain preferred embodiments of the invention, it is to be understood that such disclosure is by way of example only. There is no intent to limit the principles of the present invention to the particular disclosed embodiments.

FIGS. 5-12 show various aspects of one embodiment of blow mold apparatus constructed in accordance with the principles of the present invention. Although the mold halves are adapted to open vertically, and the upper mold halves are the movable ones while the lower halves are stationary, other arrangements are possible within the scope of the present invention. As illustrated in those figures, the apparatus includes an upper die set member adapted to be attached to an upper platen (not shown) of a suitable injection blow molding machine, a lower die set member adapted be attached to the machine bed of the machine, and a plurality of upright guide posts that guide upper die set during vertical reciprocation toward and away from lower die set . A series of blow molds comprising respective pairs of upper mold halves and lower halves are mounted on upper die set and lower die set respectively for opening and closing of the molds as illustrated in FIGS. 5, and , , for example.

Each mold defines its own internal blow mold cavity when mold halves , are closed, and each mold is provided with its own bottom plug that provides a closed bottom for the cavity . The convex or domed leading surface of each plug provides the desired domed or recessed bottom of the blown bottle, and each set of mold halves , is provided with the usual type of cooling passages such as internal passages shown in FIGS. 9 and 10. Such passages communicate with external nipples such as nipples shown in FIGS. 5-8. Although not shown in the drawings, it will be understood that plugs may be provided with means for circulating cooling fluid through the interior thereof.

The foregoing components of the blow molding apparatus of FIGS. 5-12 are substantially the same as corresponding conventional components. The difference between such apparatus and the prior art resides in the manner in which bottom plugs are ganged for actuation in unison, and in the particular actuating mechanism used for carrying out such actuation. In this respect, the apparatus of FIGS. 5-12 further includes a transverse mounting bar that extends along behind the row of bottom plugs and serves as a common mounting and support bar for all of the plugs of that particular gang. Additional bottom plugs may be ganged together on additional bars as desired, to accommodate additional sets of mold cavities. In a preferred embodiment, each bar is rectangular in cross sectional configuration, although this may vary, and each plug is secured to the front side of bar by a pair of upper and lower screws . Bar may be provided with suitable conditioning means (not shown) for cooling or heating purposes.

In the illustrated embodiment, each mounting bar has a pair of cylindrical operating shanks projecting rearwardly therefrom (although more than two maybe provided) at a pair of spaced locations along its length somewhat inboard from opposite ends thereof. Each shank is secured to the rear face of mounting bar by a mounting plate . Each plate traps an enlarged head (see FIGS. 9 and 10) up against mounting bar , while the rest of shank projects rearwardly through plate for interaction with other structure as subsequently described. Each mounting plate is releasably attached to mounting bar using suitable fasteners such as screws (not shown) which may be recessed within countersunk bores in plate as illustrated, for example, in FIG. .

As illustrated particularly in FIG. and also in FIGS. 9 and 10, each operating shank has a vertical through slot intermediate its opposite ends of the shank. Within slot , disposed centrally thereof in a fore-and-aft direction, is cam follower structure in the nature of a roller journaled for rotation on a transversely extending, horizontal cross pin . Slot is of such length and roller is of such diameter that spaces are defined on opposite sides of roller between the latter and the corresponding end of slot . Roller is slightly smaller in diameter than the diameter of shank and its axis of rotation defined by cross pin is located on the central axis of shank so that roller is symmetrical with respect to shank and does not project above or below the same.

The apparatus of FIGS. 5-12 further includes a pair of upstanding guide blocks that are secured to lower die set at locations spaced behind mounting bar in alignment with operating shanks . Each guide block has a fore-and-aft extending, horizontal passage that slidably receives the corresponding shank of mounting bar . Shank may thus slidably reciprocate within passage between the two extreme positions illustrated in FIGS. 9 and 10. Each guide block is secured to lower die set by suitable fasteners not shown which pass through vertically extending, countersunk bores at the four corners of the block as illustrated by the two countersunk bores in FIG. 12, for example.

Horizontal passage within each guide block intersects with a pair of vertical, fore-and-aft spaced guide bores and . Such bores , are, in turn, adapted to slidably receive corresponding vertically disposed, generally cylindrical cam rods and of a cam assembly secured to and carried by upper die set . Thus, the cam assemblies comprise another part of the blow mold apparatus of FIGS. 5-12.

The cam rods and of each cam assembly are secured to upper die set by a circular mounting plate which is itself secured to die set by fasteners not shown passing through bores in plate (FIG. ). Each mounting plate has a pair of countersunk bores and for receiving the corresponding cam rod and respectively and capturing the enlarged heads and thereof up against the bottom surface of upper die set . As shown in FIGS. 9 and 10, lower die set is provided with a pair of horizontally spaced, vertical bores and aligned with bores and of each guide block for the purpose of receiving and clearing the lower ends of cam rods and when upper die set is in its lowered position as illustrated in FIG. .

Each cam rod is an “extend” cam, while each cam rod is a “retract” cam. Extend cam rod is generally cylindrical, but has a forwardly facing cam surface that includes a flat, upright, follower-engaging segment extending upwardly from its lowermost tip to approximately its mid-portion. At the upper termination of flat segment , the effective cam surface of extend cam transitions to a radiused, forwardly facing, outwardly extending, concave segment so that the effective working cam surface progressively moves closer to the forward extremity of cam rod during this segment. At the upper extremity of concave segment , just before it would otherwise intersect with the forwardmost portion of the outer periphery of cam rod , the cam surface changes to a short, flat, upright segment . The horizontal, radial distance between flat segment and flat segment in one preferred embodiment is on the order of ten millimeters such that the effective stroke of the bottom plugs from their retracted positions to their extended positions is likewise on the order of ten millimeters. Although in practice the upper flat segment may be produced to have an uppermost arcuate portion, such uppermost arcuate portion is of no particular significance in the functioning of cam rod and, in any event, that portion of cam rod above upper flat segment is cylindrical for the remaining length of rod to its upper end.

Retract cam rod is likewise generally cylindrical. However, this overall cylindrical configuration is deviated from over its lower portion through the presence of the rearwardly facing retract cam surface which includes a long flat, rearwardly facing, upright segment . Flat segment corresponds in length to flat segment of extend cam , although it is somewhat narrower than segment . At the upper extremity of flat segment , the cam surface face of retract cam transitions to a rearwardly facing concave segment that deepens into retract cam at essentially the same radius as the concave segment of extend cam curves out toward the outer periphery of extend cam . Concave segments and are directly opposed to one another. At the upper and inner termination of concave segment , a short flat upright segment commences in spaced opposition to short flat segment on extend cam . Above short flat segment , a second rearwardly facing concave segment curves outwardly and intersects with the rearmost periphery of retract cam .

In one preferred embodiment, guide blocks are constructed from aluminum that is hard-anodized, while cam rods , , operating shanks , and follower rollers are constructed from hardened steel. Mounting bar and plugs are constructed from a high thermoconductive material such as aluminum.

It will be appreciated that although cams , have been disclosed as being associated with die sets , and follower roller has been disclosed as being associated with bottom plug , it is within the concepts of the present invention for this relationship to be reversed. It is to be understood that, in principle, cams , could be carried by bottom plug while follower roller is carried by the movable one of the two die sets.

Operation

When the upper die set is in its raised position as illustrated in FIGS. 5, , and to open the molds, plugs are in their retracted positions. Cam rods and are fully raised such that the follower roller in each guide block is confined between flat segments and on cam rods and .

As upper die set begins to descend, upper mold halves start moving toward lower mold halves . However, this does not initially result in movement of bottom plugs because cam rods , have no effect on followers even though rods and are moving downwardly into guide blocks at this time. Because segments and are upright and flat, they merely travel vertically along opposite front and rear sides of rollers without imparting any horizontal movement to shanks .

As the upper mold halves are close to closing on top of lower mold halves , however, concave segments and of cam rods and come into registration with follower rollers . Continued downward movement of upper die set thus causes concave segment of each extend cam rod to exert a horizontal, forwardly directed force against the corresponding roller , resulting in shifting of all plugs simultaneously toward their extended positions further into the mold halves. Such actuation is permitted at this time by virtue of the relief provided by concave segments on the retract cam rods . By the time upper mold halves have fully closed on lower mold halves and cam rods , have fully descended into blocks , follower rollers have climbed up concave segments of extend cam rods and onto short flat segments . In this position the bottom plugs are fully extended as illustrated in FIG. and are retained against rearward movement out of such position by short flat segments . Short flat segments on retract cam rods preclude further inward movement of bottom plugs beyond their fully extended positions at this time.

Upon completion of the blow cycle, upper die set begins to lift away from lower die set . This immediately starts to separate upper mold halves from lower mold halves and also immediately starts to retract bottom plugs under the positive action of retract cams . As cam rods , move upwardly with upper die set , follower rollers leave short flat segments and and enter the region between concave segments and . Thus, as cam rods and continue upwardly, the concave segments of retract cam rods lift against the front sides of follower rollers and exert rearwardly directed horizontal forces thereto, causing shanks to slide rearwardly within their passages in guide blocks and retracting bottom plugs . By the time flat segments , are reached by follower rollers , bottom plugs are fully retracted, and continued upward movement of cam rods , merely results in bottom plugs holding stationary as upper mold halves continue to rise with upper die set . When upper die set is fully raised, the condition of FIG. 9 is once again established with mold halves , fully opened and bottom plugs fully retracted.

It will thus be seen that the actuating mechanism in accordance with the present invention achieves positive actuation of the bottom plugs in both directions. No springs are relied upon to return the plugs to extended positions as in conventional, prior art arrangements. Furthermore, the thrust from the vertically moving cam rods in the present invention is directly in line with the operating shanks for the bottom plugs such that no canting or cocking of the plugs occurs during their actuating movement, which results in smooth, positive travel without risk of jams and damage to the equipment. And, by mounting all of the bottom plugs on a common mounting bar, only a pair of cam assemblies are needed to actuate the entire set of plugs, instead of having a separate wedge mechanism for each plug. This greatly increases reliability and reduces the likelihood of maintenance problems and consequential downtime. Moreover, the present design can be readily retrofitted onto existing blow molding apparatus.

Alternative Embodiment

FIG. 13 shows an alternative embodiment wherein the bottom plugs are split into two upper and lower halves with one half carried by the upper die set and the other half supported on the lower die set. When the mold halves close, the plug halves also come together to present a complete plug, but each half (or series of halves) is moved through its extension and retraction strokes by its own actuating mechanism. Details of construction of each actuating mechanism remain the same as in the embodiment of FIGS. 5-12 and will not be described again at this juncture. However, due to the split nature of the bottom plugs, the actuating mechanisms are arranged differently than in the earlier embodiment, and more of such mechanisms are necessary.

Specifically, it will be seen that each plug in the embodiment of FIG. 13 now comprises a top half and a bottom half . The top plug halves are secured to a common top mounting bar , while the bottom plug halves are secured to a common bottom mounting bar . In the illustrated embodiment, the top mounting bar has three operating shanks projecting rearwardly therefrom, which are identical to shanks , although that number may vary. Likewise, bottom mounting bar has three operating shanks . Top shanks are reciprocably received by three top guide blocks secured to and depending downwardly from upper die set , while bottom shanks are reciprocably received by three bottom guide blocks secured to and projecting upwardly from lower die set .

The top plug halves are actuated by three bottom cam assemblies that are secured to and project upwardly from lower die set (only two of such assemblies being visible in FIG. ). Cam assemblies are identical to cam assemblies and are reciprocably received within the three corresponding top guide blocks to interact with the followers (not shown, but identical to followers ) of the corresponding top shanks . Likewise, the bottom plug halves are actuated by three top cam assemblies that are secured to and depend downwardly from upper die set . Cam assemblies are identical to cam assemblies and are reciprocably received within the three corresponding bottom guide blocks to interact with the followers of the corresponding bottom shanks

As the top mold halves approach the bottom mold halves and top plug halves approach bottom plug halves , the upper shanks are actuated by the bottom cam assemblies and the bottom shanks are actuated by the top cam assemblies . By the time mold halves and have completely closed, and plug halves and have come together, cam assemblies and will also have fully extended plug halves and into the mold. After the blow cycle, the mold halves , and plug halves , start to separate, and the cam assemblies , withdraw plug halves , to their retracted positions. Upper die set continues its upward movement until reaching its fully raised position of FIG. .

The inventor(s) hereby state(s) his/their intent to rely on the Doctrine of Equivalents to determine and assess the reasonably fair scope of his/their invention as pertains to any apparatus not materially departing from but outside the literal scope of the invention as set out in the following claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an isometric view of a prior art unit cavity blow mold employing cam wedge actuating mechanism for the bottom plug, the mold halves being shown in a closed condition;

FIG. 2 is a side elevational thereof;

FIG. 3 is a slightly enlarged, vertical cross sectional view of the prior art unit cavity blow mold;

FIG. 4 is a vertical cross sectional view of the prior art unit cavity blow mold but with the mold halves in an open condition and the bottom plug in its retracted position;

FIG. 5 is a rear isometric view of blow mold apparatus constructed in accordance with the principles of the present invention and showing the mold halves open and the bottom plugs retracted;

FIG. 6 is a front isometric view thereof with the mold halves open and the bottom plugs retracted;

FIG. 7 is a rear isometric view of blow molding apparatus constructed in accordance with the principles of the present invention showing the mold halves closed and the bottom plugs in their extended positions;

FIG. 8 is a front isometric view thereof with the mold halves closed and the bottom plugs in their extended positions;

FIG. 9 is an enlarged, fragmentary vertical cross sectional view through the apparatus in an open condition revealing details of construction;

FIG. 10 is an enlarged, fragmentary vertical cross sectional view through the closed apparatus revealing details of construction;

FIG. 11 is a isometric view of the two cam rods that comprise the major components of each cam rod assembly of the apparatus;

FIG. 12 is an exploded, fragmentary isometric view with various components shown in cross section to reveal details of construction of the apparatus; and

FIG. 13 is a rear isometric view of another embodiment of the invention wherein the bottom plugs are split into two halves.

CLAIMS

1. In blow molding apparatus including a pair of opposed members wherein at least one of the members is movable toward and away from the other member to open and close a pair of cooperating blow mold halves carried on the members and further including a bottom plug shiftable transversely of the path of travel of the members between an extended position when the mold halves are closed in which the plug cooperates with the mold halves to form a blow cavity and a retracted position when the mold halves are open, improved actuating mechanism for the bottom plug comprising: follower structure movable with said plug; extend cam surface structure operatively coupled with said follower structure for shifting the plug to its extended position as the mold halves close; and retract cam surface structure operatively coupled with said follower structure for shifting the plug to its retracted position as the mold halves open, said plug including an operating shank, said shank having a slot and said follower structure being disposed within said slot, said cam surface structures being located on cams reciprocably received within said slot on opposite sides of said follower structure.

2. In blow molding apparatus as claimed in claim 1, further including a support that reciprocably receives said shank of the plug, said support having a pair of bores within which said cams reciprocate during said movement of said one member.

3. In blow molding apparatus as claimed in claim 2, said follower structure comprising a roller.

4. In blow molding apparatus as claimed in claim 1, said follower structure comprising a roller.

5. In blow molding apparatus as claimed in claim 2, said cams being on said one member, said support being on said other member.

6. In blow molding apparatus as claimed in claim 2, said support being on said one member, said cams being on said other member.

7. In blow molding apparatus including a pair of opposed members wherein at least one of the members is movable toward and away from the other member to open and close a pair of cooperating blow mold halves carried on the members and further including a bottom plug shiftable transversely of the path of travel of the members between an extended position when the mold halves are closed in which the plug cooperates with the mold halves to form a blow cavity and a retracted position when the mold halves are open, improved actuating mechanism for the bottom plug comprising: follower structure movable with said plug; extend cam surface structure operatively coupled with said follower structure for shifting the plug to its extended position as the mold halves close; and retract cam surface structure operatively coupled with said follower structure for shifting the plug to its retracted position as the mold halves open, said plug including a pair of plug halves, one of said plug halves being disposed for movement the said one member and the other of said plug halves being disposed to remain with said other member.

8. In blow molding apparatus as claimed in claim 7, said extend cam surface structure including a pair of extend cam surfaces, one for each of said plug halves, said retract cam surface structure including a pair of retract cam surfaces, one for each of said plug halves.

9. In blow molding apparatus as claimed in claim 8, one of said extend cam surfaces and one of said retract cam surfaces being disposed for movement with the one member for actuating said other plug half that remains with said other member, another of said extend cam surfaces and another of said retract cam surfaces being disposed to remain with said other member for actuating said one plug half that moves with said one member.

10. In blow molding apparatus as claimed in claim 9, each plug half including an operating shank, said shank having a slot, said follower structure including a follower disposed within each slot, the extend cam surface and the retract cam surface for a plug half being located on cams reciprocably received within the slot of the shank of that plug half and on opposite sides of the follower.

11. In blow molding apparatus as claimed in claim 10, each plug half being provided with a support that reciprocably receives the shank of the plug half, each support having a pair of bores within which the cams for the plug half are reciprocably received.

12. In blow molding apparatus as claimed in claim 11, said follower comprising a roller.

13. In blow molding apparatus including a pair of opposed members wherein at least one of the members is movable toward and away from the other member to open and close a pair of cooperating blow mold halves carried on the members and further including a bottom plug shiftable transversely of the path of travel of the members between an extended position when the mold halves are closed in which the plug cooperates with the mold halves to form a blow cavity and a retracted position when the mold halves are open, improved actuating mechanism for the bottom plug comprising: follower structure movable with said plug; extend cam surface structure operatively coupled with said follower structure for shifting the plug to its extended position as the mold halves close; and retract cam surface structure operatively coupled with said follower structure for shifting the plug to its retracted position as the mold halves open, said one member being disposed for vertical movement, said plug being disposed for horizontal shifting.

14. Blow molding apparatus comprising: a pair of opposed members; a series of side-by-side first blow mold halves carried by one of said members and an opposed series of side-by-side second blow mold halves carried by the other of said members, at least said one member being movable toward and away from the other member to open and close the mold halves; a series of side-by-side bottom plugs for cooperating with the mold halves when the mold halves are closed in forming a corresponding series of side-by-side-blow cavities; mounting structure supporting said plugs for shifting in unison in a direction transverse to the direction of movement of said one member between extended positions for forming blow cavities when the mold halves are closed and retracted positions when the mold halves are open; followers carried by said mounting structure; and cam assemblies operably coupled with said followers for shifting the mounting structure and the plugs to said extended positions as the mold halves close and for shifting the mounting structure and the plugs to said retracted positions as the mold halves open.

15. Blow molding apparatus as claimed in claim 14, each of said cam assemblies including an extend cam surface and a retract cam surface on opposite sides of a corresponding follower.

16. Blow molding apparatus as claimed in claim 15, each of said followers comprising a roller.

17. Blow molding apparatus as claimed in claim 15, said mounting structure including a mounting member having a pair of operating shanks projecting rearwardly therefrom at spaced locations along the length thereof, further comprising a pair of guide blocks secured to said other member and reciprocably receiving respective ones of said operating shanks, said followers being mounted on respective ones of said shanks and disposed within a corresponding guide block, each cam assembly being reciprocably received within a corresponding guide block in operable interengagement with a follower.

18. Blow molding apparatus as claimed in claim 17, each shank having an operating slot, each follower being disposed within said slot, each cam assembly comprising an extend cam and a retract cam disposed within said slot on opposite sides of the follower.

19. Blow molding apparatus as claimed in claim 18, each of said followers comprising a roller.

20. Blow molding apparatus as claimed in claim 14, each of said followers comprising a roller.

21. Blow molding apparatus as claimed in claim 14, each plug including a pair of plug halves, said mounting structure including a pair of mounting members, one disposed for movement with the one member and the other disposed to remain with the other member, each mounting member supporting a series of plug halves.

22. Blow molding apparatus as claimed in claim 21, each mounting member having a pair of operating shanks projecting rearwardly therefrom at spaced locations along the length thereof, each operating shank being reciprocably received by a guide block secured to the member with which the mounting member is disposed, said followers being mounted on respective ones of said shanks and disposed within a corresponding guide block, each cam assembly being reciprocably received within a corresponding guide block in operable interengagement with a follower.

23. Blow molding apparatus as claimed in claim 22, each shank having an operating slot, each follower being disposed within said slot, each cam assembly comprising an extend cam and a retract cam disposed within said slot on opposite sides of the follower.

24. Blow molding apparatus as claimed in claim 23, each of said followers comprising a roller.

25. Mechanism for use in actuating a bottom plug of blow molding apparatus between extended and retracted positions, said mechanism comprising: a guide block; an operating shank reciprocably received within said block, said shank carrying a cam follower; and a cam assembly reciprocably received within said block for reciprocation along a path of travel disposed at an angle to the path of travel of the shank, said cam assembly including a pair of cam surfaces on opposite sides of said follower and configured to cause reciprocation of the shank in response to relative reciprocation between the block and the cam assembly.

26. Mechanism as claimed in claim 25, said shank having a slot, said follower being disposed within said slot, said cam surfaces reciprocating through said slot on opposite sides of the follower.

27. Mechanism as claimed in claim 26, said follower comprising a roller.

28. Mechanism as claimed in claim 26, said cam assembly including a pair of separate cam rods, said cam surfaces being on said rods.

29. Mechanism as claimed in claim 25, said cam assembly including a pair of separate cam rods, said cam surfaces being on said rods.

30. In blow molding apparatus including a pair of opposed members wherein at least one of the members is movable toward and away from the other member to open and close a pair of cooperating blow mold halves carried on the members and further including a bottom plug shiftable transversely of the path of travel of the members between an extended position when the mold halves are closed in which the plug cooperates with the mold halves to form a blow cavity and a retracted position when the mold halves are open, improved actuating mechanism for the bottom plug comprising: follower structure; extend cam surface structure operably coupled with said follower structure; and retract cam surface structure operably coupled with said follower structure, said follower structure and said cam surface structures coupled with said plug and said members in such a manner that the plug is shifted to its extended position as the mold halves close and to its retracted position as the mold halves open, said cam surface structures being movable with said one member, said plug being disposed on the other member, said follower structure being movable with the plug.

31. In blow molding apparatus including a pair of opposed members wherein at least one of the members is movable toward and away from the other member to open and close a pair of cooperating blow mold halves carried on the members and further including a bottom plug shiftable transversely of the path of travel of the members between an extended position when the mold halves are closed in which the plug cooperates with the mold halves to form a blow cavity and a retracted position when the mold halves are open, improved actuating mechanism for the bottom plug comprising: follower structure; extend cam surface structure operably coupled with said follower structure; and retract cam surface structure operably coupled with said follower structure, said follower structure and said cam surface structures being coupled with said plug and said members in such a manner that the plug is shifted to its extended position as the mold halves close and to its retracted position as the mold halves open, said plug including a pair of plug halves, one of said plug halves being disposed for movement with the one member and the other of said plug halves being disposed to remain with said other member, said follower structure including a follower movable with each plug half, said extend cam surface structure including an extend cam surface for each plug half, said retract cam surface structure including a retract cam surface for each plug half, there being an extend cam surface and a retract cam surface mounted on each of said members.

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