Spring spacer for bladder assembly in a tire curing press

Spacers for bladder assemblies for standing post tire curing presses and bladder assemblies for same are provided having a spacer with first and second parts biased by a spring, so that they are freely slidable relative to one another so as to cover the center post of the tire curing press during its operation.

FIELD OF THE INVENTION
 This invention relates to spacers for standing post tire presses and to
 bladder assemblies for standing post tire curing presses.
 BACKGROUND OF THE INVENTION
 Conventional standing post tire curing presses typically comprise a bladder
 assembly and a tire mold assembly. The bladder assembly typically has a
 bladder, a standing center press post and upper and lower clamp ring
 assemblies that clamp the tire and oppose each other so as to support both
 sides of the tire. By way of definition, "opposing clamp ring assemblies"
 is understood to mean clamp ring assemblies that are opposite each other
 along the center post. The upper clamp ring assembly includes an upper
 mold ring and an upper clamp ring. The lower clamp ring assembly includes
 a lower bead ring and a lower clamp ring.
 In a conventional tire curing process, the bladder clamp ring assemblies
 and spacer are moved relative to each other and pressure or vacuum is
 applied depending upon the point in the tire curing process. First, a
 loader loads a green tire assembly over the center post of the bladder
 assembly so that the lower tire bead is adjacent to the lower bead ring
 with the upper clamp ring assembly raised up to its fully extended
 position, also known as the "primary stacking height", and with a vacuum
 being applied to the bladder. Typically, the upper clamp ring assembly is
 fixed to the center post utilizing a collar. Thus, to raise the upper
 clamp ring, the center post is extended from the well.
 Once the green tire assembly is loaded, the vacuum is typically broken and
 the upper clamp ring is dropped on a fixed-height spacer. The point to
 which the upper clamp ring is dropped to rest on the spacer is known as
 the "secondary stacking height." A shaping pressure is applied to
 pre-shape the tire. The tire loader will release after the tire is
 preshaped. Then the tire mold assembly is closed around the green tire and
 the spacer travels further down the center post to the well.
 During unloading of the cured tire, the bladder assembly is raised up along
 the center post so that stripping arms may be inserted adjacent to the
 lower bead ring and side wall of the tire. As the stripping arms are moved
 into position, the upper clamp ring is moved upward to its primary
 stacking height with the bladder being relaxed. Then, a vacuum is applied
 and the bladder assembly is lowered to the bottom side wall of the tire
 mold. Then the vacuum is broken, and the upper clamp ring is dropped to
 its secondary stacking height. The stripping arms are tilted releasing the
 cured tire to the back of the press.
 While the above steps are the typical steps involved in curing a tire using
 a tire curing press having a standing center post, other sequences or the
 omission or addition of steps are contemplated and understood to be
 incorporated in this disclosure.
 Conventionally, a tubular, fixed height spacer is placed over the center
 post and rests on the center mechanism adjacent to the lower clamp ring
 assembly to limit the extent to which the upper clamp ring assembly drops
 as it moves toward the lower clamp ring assembly. "Fixed height spacer" is
 understood to mean a spacer that maintains is overall height throughout
 the curing process.
 Bladders are frequently pinched during the curing process when conventional
 fixed height spacers are used. The dropping of the upper clamp ring
 assembly and applying a vacuum allows the bladder to slacken and pulls the
 slackened bladder inward adjacent to the exposed portion of the center
 post. As this occurs, the bladder can be pinched between the end of the
 fixed-height spacer and the upper clamp ring, thereby cutting the bladder.
 The bladder may also frequently be pinched if the press malfunctions or
 the power to the press is lost which typically results in the upper clamp
 ring dropping. The bladder may also be pinched if the upper clamp ring is
 dropped through tire curing press operator error. Over time, the bladder
 tends to be cut after repeated pinching causing the bladder to leak, and
 not to hold sufficient pressure during the tire curing process. When the
 bladder leaks, tires tend to be produced which have poor inside finish,
 poor bead formation or other defects which tend to reduce manufacturing
 yields and increase the number of defective tires produced. Thus, when the
 upper clamp ring assembly is raised and the bladder is under vacuum, a
 portion of the center post of the bladder assembly is exposed which allows
 for the bladder to be pinched.
 U.S. Pat. Nos. 5,393,480 to Pizzorno, and 3,976,409 to Athey disclose
 conventional tire curing presses, bladder assemblies and tire curing
 processes and are hereby incorporated by reference. Athey '409 discloses a
 center mechanism for a conventional tire curing press having a single
 piece cylindrical sleeve supported on a ledge on the piston rod below the
 lower clamp ring for limiting the extent of travel of the piston rod.
 Pizzorno '480 discloses a locating sleeve disposed over the press drive
 rod between the clamp rings having a pair of semicircular elements.
 A disadvantage of conventional spacers is that they tend to leave a portion
 of the center post exposed and allow the bladder to be pinched, or they
 tend to require manual adjustment to change the operating position of the
 upper clamp ring assembly relative to the lower clamp ring assembly.
 What is desired, therefore, is a bladder assembly for a tire curing press
 that limits the extent to which the upper clamp ring assembly is dropped,
 but does not leave the center post exposed so as to allow the bladder to
 be pinched between the upper end of the spacer and the upper clamp ring. A
 spacer that substantially covers the center post of a bladder assembly so
 as to not leave the center post so exposed is also desired.
 SUMMARY OF THE INVENTION
 Accordingly it is an object of the present invention is to provide a spacer
 that extends to cover the center post of a tire curing press bladder
 assembly during its operation, yet which limits the extent to which the
 upper clamp ring is dropped.
 Another object of the invention to provide a spacer for the center post of
 the tire curing press bladder assembly that covers the center post during
 operation of the tire curing press, yet which limits the extent to which
 the upper clamp ring is dropped.
 Still yet another object of the invention is to provide a bladder assembly
 for a standing post tire curing press having a spacer with the above
 characteristics.
 These and other objectives are achieved by the invention which provides
 bladder assembly and a spacer for the bladder assembly. More particularly,
 the invention provides: at least two opposing clamp rings, at least one of
 which being movably disposed on a center post and having a bladder clamped
 to them, a first spacer part disposed on the center post and slidable with
 the movement of the opposing clamp ring assembly to a fully returned
 position relative to said second spacer part, a second spacer part
 disposed on the center post adjacent to an opposing clamp ring, and a
 spring for biasing said first spacer part toward one opposing clamp ring
 to minimize pinching of said bladder; a first clamp ring placed over the
 post, a second clamp ring slidable along the post, a bladder clamped to
 said first and second clamp rings, a first spacer part disposed on the
 post adjacent said first clamp ring, a second spacer part disposed on the
 post and slidable within said first spacer part to fully extended and
 returned positions, and a spring for biasing said second spacer part
 toward the other of said first and second clamp rings to minimize pinching
 of said bladder; and at least first and second parts slidable relative to
 one another having substantially tubular shapes, at least one of said
 parts having an outer diameter such that at least a portion of said part
 is returnable within the other of said parts to a fully returned position,
 and a spring with a spring potential and an inner diameter that is
 sufficiently large so as to allow one of said parts to extend and return
 relative to one of said other parts, said spring being disposed so that
 the spring potential is at its maximum when one of said parts is retracted
 and is at its minimum when one of said parts is fully extended from the
 other of said parts.
 The invention and its particular features will become more apparent from
 the following detailed description considered with reference to the
 accompanying figures.

DETAILED DESCRIPTION OF THE INVENTION
 Spacer 10 is shown in FIG. 1, in its extended position, disposed over
 center post 12 of tire curing bladder assembly 14 having upper and lower
 clamp ring assemblies 22 and 23, the upper clamping ring assembly 22
 having upper clamp ring 20 and upper mold ring 21, respectively. Collar 11
 fixes upper clamp ring assembly 22 to center post 12. When extended, upper
 end 16 of the upper spacer part 18 is adjacent to the upper clamp ring 20
 and which is adjacent to lower spacer part 24. As can be seen in FIG. 1,
 when spacer 10 is extended, center post 12 is substantially covered by
 spacer 10 and bladder 28 cannot contact center post 12 or upper end 16
 adjacent to upper clamp ring 20. It is critical that inner surface 19 of
 upper spacer part 18 has an inner diameter such that upper spacer part 18
 is slidable along center post 12. It is also critical that upper spacer
 part 18 has a diameter such that upper spacer part 18 is slidable within
 lower spacer part 24.
 It is understood, however, that lower spacer part 24 may be slidable within
 upper spacer part 18, and that the function of the spacer parts 18 and 24
 relative to each other in FIG. 1 is by way of example only. It is further
 understood that any type of press may be used having a center post 12 that
 is oriented in any direction, be it standing or oriented horizontally or
 other than standing. Thus, this disclosure and the figures for the
 invention depict clamp ring assemblies 23 and 23 in terms of upper and
 lower clamp ring assemblies 22 and 23 by way of example only, and it is
 understood that the function of the clamp rings assemblies 22 and 23 could
 be reversed, or that the clamp ring assemblies 22 and 23 could be oriented
 differently than as shown and discussed herein so long as they are capable
 of supporting a tire 52 and a bladder 28 and of automatically allowing for
 loading and unloading of the tire 52.
 Preferably, as shown in FIG. 1, spring 34 is used as a means for allowing
 upper spacer part 18 and lower spacer part 24 to extend and return
 relative to one another and clamp ring assemblies 22 and 23. It is
 critical that spring 34 has an inner diameter 36 so as to allow spring 34,
 and, accordingly, upper spacer part 18 to move or slide on post 12 as the
 clamp ring assemblies 22 and 23 are extended and returned relative to each
 other. In particular, when upper clamp ring 22 is extended to its primary
 stacking height, spring 34 forces upper spacer part 18 toward upper clamp
 ring assembly 22 thereby covering center post 12. Accordingly, when upper
 clamp ring 22 is dropped to its secondary stacking height, spring allows
 upper spacer part 18 to return. Spring 34 is disposed between upper and
 lower spacer parts, 18 and 24, so that the spring potential is at its
 maximum when upper spacer part 18 is fully returned and is at its minimum
 when the upper spacer part 18 is fully extended. FIG. 1 shows spring 34
 disposed on center post 12 with upper end 35 adjacent to upper spacer part
 lower end 17, and lower spring end 37 adjacent to flange 30.
 It is understood, however, that spring 34 may be disposed on one of said
 spacer parts, 18 and 24, rather than on the center post 12, and that the
 configuration shown in FIG. 1 is by way of example only. Thus, any
 combination of spring 34 and spacer parts 18, 24 may be used so long as
 parts 18, 24 extend and return relative to one another and clamp ring
 assemblies 22 and 23.
 As shown in FIG. 1, spring 34 may be supported with a spring potential
 between upper spacer part end 17 adjacent to lower spacer part flange 30.
 Upper spring end 35 may also be supported at any point along upper spacer
 part 18 so long as enough spring potential is provided to allow upper
 spacer part 18 to extend as upper clamp ring assembly 22 extends and to
 return as upper clamp ring assembly 22 returns. For example, spring 34 may
 be supported by a step or second flange located at a point other than end
 32 or flange 30, determined by the size of spring 34 (i.e., number of
 coils and diameter of spring 34).
 Lower spacer part 24 preferably has a step 38 provided in its inner surface
 40. Step 38 is an annular groove provided on inner surface 40 and
 determines the overall height of spacer 10 in its fully returned position
 and which prevents spring 34 from being crushed when upper clamp ring
 assembly 22 is returned. In particular, upper spacer part 18 abuts step 38
 when it is returned within lower spacer part 24. Height B of step 38 must
 be at least the height of spring 34 when it is completely compressed.
 Preferably, height B is the height of spring 34 when it is completely
 compressed plus approximately 5.0 mm.
 Lower spacer part end 42 adjacent to upper spacer part 18 may have an
 arcuate edge 44 so as to provide a smooth interface between upper spacer
 part 18 and lower spacer part 24. Arcuate edge 44 is further desirable so
 as to further prevent bladder 28 from being pinched, worn or caught by
 spacer 10. Further, upper spacer part 18 may have a center portion 46
 having a slightly smaller diameter than opposing end portions 48 and 50
 which further provide a smooth outer surface, in addition to arcuate edge
 44. This variation in diameter provided by center portion 46 and opposing
 end portions 48 and 50 further allows upper spacer part 18 to extend and
 return and tends to prevent resistance that may arise due to suction or
 friction. It is understood that the lower spacer part may return within
 the upper spacer part and if that is so, in that instance, the lower
 spacer part may have a smaller center portion, and larger end portions,
 and upper spacer part may have an arcuate edge.
 Thus, it is preferred that the outer surface of upper spacer part 18 that
 is in contact with the lower spacer part 24 be minimized so as to minimize
 friction and resistance to relative sliding of upper and lower spacer
 parts 18 and 24. It is also preferred that upper spacer part end portion
 48 has a larger diameter than lower spacer part portion 50. This is
 preferable so that spacer 10 can be inserted into the press in one
 direction only. More preferably, end portion 50 and inner surface 40 of
 lower spacer part 24 are machined so that they are smooth and have
 relatively low resistance to sliding relative to each other.
 To prevent pinching of bladder 28, spacer 10 is placed over center post 12.
 Upper spacer part 18 extends so as to substantially cover center post 12
 during operation of the tire curing press. When pressure is applied to
 bladder 28, bladder 28 extends while the tire 52 is being cured. When the
 upper clamp ring assembly 22 is in its extended position or its primary
 stacking height so as to receive a green tire assembly, a vacuum is
 applied to the bladder 28 and spacer 10 is fully extended so as to prevent
 bladder 28 from contacting center post 12 when center post 12 is moved
 down to move the upper clamp ring assembly 22 to the secondary stacking
 height. Thus, when the bladder assembly 14 is in its retracted position
 after the tire loader has been removed, spacer 10 also retracts. Lower
 clamp ring assembly 23 is typically threaded to the lower bead ring
 support 56 which is movable relative to the center post 12 to allow the
 lower clamp ring assembly 23 to be raised so as to allow the stripping
 arms to be placed under the cured tire 52 to remove it. Thus, in this
 manner, spacer 10 protects the bladder 28 each time a vacuum is applied
 and the upper clamp ring assembly 22 is dropped.
 Spacer parts 18, 24 are preferably tubular in shape and preferably
 cylindrical. It is understood, however, that spacer parts 18, 24 may be
 rectangular tubes or any other shape so long as they fit within the
 bladder 28. Spacer part 24 shown in FIG. 1 rests on the center mechanism
 floating ring 54 and is adjacent to lower clamp ring assembly 23.
 Although the invention has been described with reference to particular
 dimensions and shapes and the like, these are not intended to exhaust all
 possible arrangements or features, and indeed many other modifications and
 variations will be ascertainable to those of skill in the art.