Automated Mold Height Adjusting Mechanism For Hydraulic Tire Curing Press

Field of the invention

The present invention relates generally to hydraulic tire curing press, and more particularly, to an arrangement involved for adjusting the mold height automatically through Programmable Logic Controller (hereinafter referred to as PLC).

Background of the invention

Mold height adjusting arrangement is generally done for accommodating tire molds of different heights in a tire curing press, whereby a range of tire sizes can be optimally processed in a single tire curing press. Various approaches have been used over the years to improve mold height adjustment in tire curing press to accommodate upper and lower mold sections having different combined heights when in the fully closed position.

Generally, mold height adjusting mechanisms of the prior art have employed spacers of different thicknesses or adjusting screw with nut arrangements or indexing mechanism with spacers or with long stroke press cylinder and floating column arrangement to achieve required positioning of press components to optimize operating with mold sections of different heights. In some cases, cylindrical spacers of different thicknesses are placed between cylinder rods and rod extensions of the curing press so that mold sections get closed while applying squeeze pressure. However, to achieve different adjusted positions of the mold, a variety of spacers required to be stored. Also, changing of the spacers takes a lot of time and results in significant downtime and resultant loss of production for the presses. Specifically, the mold change with some spacer installations may take several hours and approach eight hours in the case of some large truck presses.

An alternative to the spacer arrangement is a squeeze cylinder rod or rod extension provided with a number of axially or vertically spaced annular grooves and a removable stop collar selectively positioned in one of the grooves to engage a stop tube which surround the cylinder rods or rod extensions. This arrangement has the same features and disadvantages as the conventional cylindrical spacer arrangement except that it need only replacement or repair parts to be maintained in the inventory.

Another type of the mold height adjusting arrangement includes an adjusting screw and a nut arrangement which operates in conjunction with the positioning of the upper mold section of the mold. A crossbeam of the press is connected to an upper bolster supporting a top mold section by a single central adjusting sleeve which is externally threaded. An internally threaded ring engages the threads of the adjusting sleeve and is rigidly attached to the crossbeam so that it cannot rotate. A ring gear attached to the adjusting sleeve is used with other gearing to facilitate the rotation of the adjusting sleeve and it results in selective vertical positioning of the upper mold section relative to the lower mold section.

Yet another type of adjusting screw and nut arrangement operates in conjunction with the positioning of the lower mold section of the tire mold. In this arrangement, blind ends of the squeeze cylinders are supported on an adjusting screw or stud which is externally threaded. An internally threaded nut engages the external threads on the adjusting screw and is journaled in the press frame. Each nut has an attached sprocket. A drive chain extending around the sprocket on each of the nuts for each squeeze cylinder permits simultaneous, equiangular rotation of each of the nuts to adjust the vertical position of each of the squeeze cylinders and thus the lower mold section. The above adjusting screw and nut arrangements have the advantage that they are relatively easy to operate and set
up in comparison with the previously discussed spacer arrangements. However, the clearance in the threads of the screw and nut seriously compromise the vertical location accuracy and concentricity of the mold part that is supported thereby, as compounded by wear. Also, the complexity and precision required for achieving acceptable accuracy in adjusting screw and nut mechanisms add substantially to the manufacturing and maintenance cost.

Yet another type of mold adjusting arrangement includes an adjusting screw which goes through a bottom of a lower part of steam chamber. Adjusting screw is fixed by its upper end in the mold clamping plate. The lower end of the adjusting screw is placed in a hollow of the piston that is the part of hydraulic cylinder. The barrel of the hydraulic cylinder is attached to the steam chamber by means of bolts. A nut is threaded onto the adjusting screw, the nut adjoins a top surface of the piston. The nut can be turned by the action of worm gearing. Simultaneous motion of a plurality of worms associated with the plurality of adjusting screws is induced by gearing. The gearing are connected to a source of torsional moment, which is usually an electric motor. The torsional moment is transmitted to the side worms by means of a system of sprockets and chains. By powering the electric motor the adjusting nut can be raised and lowered which bring the mold height adjustment over a height range. However the use of more number of interconnected components and use of an additional electric drive adds more to the manufacturing and maintenance cost of the tire curing press. And also the curing force generated is transferred to the steam chamber through adjusting screw's threads which in due course cause shearing of threads. And also presence of thread clearances affects the positional accuracy of the steam chamber.

Still another mold height adjusting mechanism employs an indexing ring with discrete vertical steps of different vertical heights which are selectively interposed between squeeze cylinder rods and a lower bolster of the press to provide mold height adjustment for at least two mold sizes. The indexing ring contains at least two discrete vertical steps for each squeeze cylinder, whereby rotation of the indexing ring simultaneously provides a desired mold height adjustment at each squeeze cylinder for a particular mold. A locking assembly locks the indexing ring with a selected discrete vertical step aligned with the squeeze cylinder rod, while permitting release of the locking assembly for moving the indexing ring to another discrete vertical step, to be locked thereafter for operating tire molds having a different height dimension. The indexing ring carries at least two attached spacers of differing sizes which are rotated in and out of alignment with piston rods of the squeeze cylinder thus to make the spacers self-storing and thereby eliminate the need to inventory and store a large number of spacers at a location away from the tire curing press. The advantages of indexing ring mechanism over the spacer and adjusting screw and nut methods are lesser time requirement for mold height adjustment and lesser inventory requirement. However, indexing ring mechanism takes approximately 15 minutes to provide the mold height adjustment to accommodate a different mold size and needs additional cylinders for raising bolster relative to the frame to permit the moving of indexing apparatus. Further, infinite mold height adjustment within a wide range is either impossible or tedious exercise in all the above methods.

Yet another mold height adjusting mechanism employs a floating column connected to the press cylinder attached to the bottom of the lower body containing the lower mold .

The upper body with the upper mold slides up/down vertically along the floating columns and gets locked with the lock housing provided in the floating columns. Mold height adjustment is done by varying the stroke of the press cylinder to which the floating columns are attached and thereby enabling the press to accommodate molds over a height range. The advantage of floating column arrangement is that it can reduce the downtime but however the drawbacks associated with it is non-isolation of floating columns from forces during curing due to which maintaining the vertical alignment of floating column with respect to the press may become difficult and tedious and also it may lead to components wear as the upper body is sliding on the floating columns. Furthermore the floating column arrangement is difficult to disassemble for in case of maintenance activity.

Specifically, US Patent No. 6506040 patent discloses a tire curing press having a frame, a bolster for mounting a lower mold section, a cylinder mounted on the frame, a cylinder rod of the cylinder for moving the bolster and the lower mold section between a closed position and a partially open position, moveable indexing apparatus interposed between the cylinder rod and the bolster, and at least two steps of differing thicknesses on the indexing apparatus, whereby moving a selected one of the plurality of steps into alignment with the cylinder rod establishes a different partially open position of the lower mold section.

Another US 4332536 patent discloses a dual cavity hydraulic tire press utilizes a single long stroke piston-cylinder assembly vertically positioned substantially in line with the center of gravity of the vertically movable upper mold sections, the latter being supported on the underside of the outer ends of a shallow V-shaped beam which is mounted for vertical movement on a readily removable column or post. In the closed position of the press the top mold cavities are locked to the base of the press by rotatable bayonet locks.

Four short stroke hydraulic clamp piston-cylinder assemblies are positioned beneath each bottom mold section to achieve clamping pressure during curing. Mechanical stops or other positioning devices are utilized for mold height adjustment and for preventing the molds from separating unduly in the event of the loss of fluid pressure.

Further US Patent No. 6139301 discloses a device for adjustment of the clamping plate height in a curing press steam chamber. The height adjustability allows the clamping plate to be attached to different size tire molds to produce tires of different sizes in a single steam chamber. The device for adjustment of the height of the clamping plate in a steam chamber includes at least two hydraulic cylinders between the upper and/or lower part of the steam chamber and the clamping plate within the steam chamber

Yet another patent WO2010/146554 Al discloses a tire curing press with a mold height adjusting mechanism which uses a long stroke press cylinder attached to the lower body of the tire curing press and a floating column connected to press cylinder. By varying the stroke of the press cylinder the upper body of the tire curing press is locked at suitable height for accommodating molds over a height range.

All the above mentioned patents uses one or more a mechanism of a mold height adjusting arrangement described above which has particular drawbacks associated therewith as described above.

Accordingly, there exists a need provide a mold height adjusting mechanism for hydraulic tire curing press which overcomes drawbacks of the prior art.

Objects of the invention

An object of the present invention is to provide an infinite and accurate mold height adjustments within a specified mold range.

Another object of the present invention is to provide two stage locking provision in a lock ring in order to reduce the down time required for mold height adjustment.

Another object of the present invention is to keep the guide columns isolated from the curing forces.

Yet another object of the present invention to provide a lesser number of working components for mold height adjusting arrangement by eliminating spacers, indexing mechanism, floating column and lift cylinders.

Still another object of the present invention is to provide lowest machine downtime for mold height adjustment.

Further object of the present invention is to minimize the squeeze cylinder stroke length requirement with two stage mold locking arrangement.

Furthermore, object of the present invention is to eliminate additional electrical drive for mold height adjustment.

Summary of the invention

Accordingly, the present invention provides a hydraulic tire curing press with automated mold height adjusting mechanism. The hydraulic tire curing press includes an upper housing, an upper mold and a lower mold. The upper mold is rigidly attached to the upper housing through a top steam platen and the lower mold rigidly attached to a bottom platen support. Further, the hydraulic tire curing press includes a lock ring having a top groove and a bottom groove configured on inner side thereof. The lock ring is capable of receiving a flange of the upper housing either in the top groove or in the bottom groove for locking the upper housing therein and adjusting the height of the upper mold.

Furthermore, the hydraulic tire curing press includes a squeeze support plate for holding the lock ring in a position during the curing process by accommodating a flange portion thereof in the bottom groove of the lock ring and at least two squeeze cylinders attached to the squeeze support plate. The squeeze cylinders are capable of moving the squeeze support plate up and down for fine adjustment of the mold. The hydraulic tire curing press also includes at least two squeeze cylinder rods secured to the bottom platen support for moving the bottom platen support up and down, and a programmable logic controller (PLC) capable of selecting/adjusting the mold height based on the vertical position of the upper housing, wherein, the flange of the upper housing is held either in the top grove or in the bottom groove of the lock ring and stroke of the squeeze cylinders are varied for accommodating molds of different heights within a particular range.

Brief description of the drawings

Figure 1 shows a schematic drawing of the mold height adjusting mechanism with the flange of the upper housing locked in the top groove of the lock ring, in accordance with the present invention; and

Figure 2 shows a schematic drawing of the mold height adjusting mechanism with the flange of the upper housing and the flange of the squeeze support plate locked in the bottom groove of the lock ring, in accordance with the present invention.

Detailed description of the invention

The foregoing objects of the present invention are accomplished and the problems and shortcomings associated with the prior art, techniques and approaches are overcome by the present invention as described below in the preferred embodiments.

The present invention provides a hydraulic tire curing press with automated mold height adjusting mechanism. The hydraulic tire curing press provides two stage locking of an upper mold in a lock ring in order to reduce the down time required for mold height adjustment which improves the productivity of the tire curing press. Further, two stage locking provision in the lock ring along with a squeeze support plate and a squeeze cylinder arrangement isolates the guide columns from getting loaded during curing. The hydraulic tire curing press is fully automated by the use of programmable logic controller (PLC).

Referring now to figure 1 and 2, there is shown a hydraulic tire curing press (100) with automated mold height adjusting mechanism, in accordance with the present invention.
The hydraulic tire curing press (100) includes an upper housing (10), an upper mold (not shown), a lower mold (not shown), a lock ring (20), a squeeze support plate (30), at least two squeeze cylinders (40), at least two squeeze cylinder rods (50) and a programmable logic controller (PLC) (not shown).

The upper housing (10) includes a flange (12) extending out from a lower portion thereof.

The upper housing (10) includes the upper mold rigidly attached thereto through a top steam platen (14). Further, the lower mold is rigidly attached to a bottom platen support (16). Specifically, the lower mold is rigidly attached to a bottom platen support (16) through bottom steam platen (16a). In an embodiment, the attachment of the upper mold to the upper housing (10) and attachment of the lower mold to the bottom platen support (16) is by means of suitable securing mechanism known in the art. The upper housing (10) is engaged with lock ring (20).

Specifically, the lock ring (20) includes a top groove (22) and a bottom groove (24) configured on inner side thereof. In an embodiment, the lock ring (20) is having an "E" shaped cross section defining the top groove (22) and the bottom groove (24). The lock ring (20) is capable of receiving the flange (12) of the upper housing (10) either in the top groove (22) or in the bottom groove (24) for locking the upper housing (10) therein and adjusting the height of the upper mold. In an embodiment, the upper housing (10) is held either in the top groove (22) or in the bottom groove (24) depending on the mold height range to be accommodated by the tire curing press (100). Specifically, figure 1 shows the flange (12) of the upper housing (10) locked in the top groove (22) of the lock ring (24), in accordance with the present invention. The lock ring (20) is held in place by the squeeze support plate (30).

The squeeze support plate (30) holds the lock ring (20) in a position during the curing process by accommodating a flange (32) thereof in the bottom groove (24) of the lock ring (20). In an embodiment, the height of the bottom groove (24) of the lock ring (20) is higher than the height of the top groove (22) for accommodating the flange (12) of the upper housing (10) as well as the flange (32) of the squeeze support plate (30) for the smaller mold. Specifically, figure 2 shows the flange (12) of the upper housing (10) and the flange (32) of the squeeze support plate (30) locked in the bottom groove (24) of the lock ring (20), in accordance with the present invention. At least two squeeze cylinders (40) are attached to the squeeze support plate (30).

The squeeze cylinders (40) moves the bottom platen support (16) up and down for fine adjustment of the lower mold during adjusting of height for the mold. Specifically, vertical position of the lower mold fixed on the bottom platen support (16) changes depending on the squeeze cylinder (40) stroke.

Further, at least two squeeze cylinder rods (50) are secured to the bottom platen support (16). The squeeze cylinder rods (50) moves the bottom platen support (16) up and down.

The programmable logic controller (PLC) adjusts the upper mold height after receiving a signal for the position of upper housing( 10) and then it computes and adjusts the stroke of the squeeze cylinder(40) required to hermetically close the mold

During height adjustment for mold, the flange (12) of the upper housing (10) is held either in the top groove (22) or in the bottom groove (24) of the lock ring (20) and stroke of the squeeze cylinders (40) are varied for accommodating molds of different heights in the hydraulic tire curing press (100). The top groove (22) and the bottom groove (24) of the lock ring (20) are used for selecting the mold height range and the squeeze cylinders (40) are used for fine adjustments within the selected range.

Advantages of the invention

1. The mechanism of the hydraulic tire curing press provides two stage locking of the upper mold in the lock ring which reduces the time required for mold height adjustment and also number of components required are less.

2. The mechanism of the hydraulic tire curing press is fully automated by use of the programmable logic controller (PLC).

3. The mechanism of the hydraulic tire curing press provides an improved productivity by reducing the machine downtime.

4. The mechanism of the hydraulic tire curing press do not use spacers and hence less inventory to be maintained

5. With the use of mechanism, infinite adjustments possible with in a particular tire range and has good repeatability.

6. Two stage locking provision in the lock ring along with the squeeze support plate and squeeze cylinder arrangement isolates the guide columns from getting loaded during curing.

The foregoing descriptions of specific embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the present invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the present invention and its practical application, to thereby enable others skilled in the art to best utilize the present invention and various embodiments with various modifications as are suited to the particular use contemplated. It is understood that various omission and substitutions of equivalents are contemplated as circumstance may suggest or render expedient, but such are intended to cover the application or implementation without departing from the spirit or scope of the present invention.

We Claim

1. A hydraulic tire curing press with automated mold height adjusting mechanism, the hydraulic tire curing press comprising:

an upper housing;

an upper mold and a lower mold, the upper mold rigidly attached to the upper housing through a top steam platen and the lower mold rigidly attached to a bottom platen support;

a lock ring having a top groove and a bottom groove configured on inner side thereof, the lock ring capable of receiving a flange of the upper housing in either in the top groove or in the bottom groove for locking the upper housing therein and adjusting the height of the upper mold;

a squeeze support plate for holding the lock ring in a position during the curing process by accommodating a flange portion thereof in the bottom groove of the lock ring;

at least two squeeze cylinders attached to the squeeze support plate, at least two squeeze cylinders capable of moving the bottom platen support up and down for fine adjustment of the lower mold;

at least two squeeze cylinder rods secured to the bottom platen support, at least two squeeze cylinder rods capable of moving the bottom platen support up and down; and

a programmable logic controller (PLC) capable of adjusting the upper mold height after receiving a signal for the position of upper housing which then computes and adjusts the stroke of the squeeze cylinder required to hermetically close the mold,

wherein, the flange of the upper housing is held either in the top groove or in the bottom groove of the lock ring and stroke of the squeeze cylinders are varied for accommodating molds of different heights.

2. The hydraulic tire curing press as claimed in claim 1, wherein the lower mold is rigidly attached to a bottom platen support through bottom steam platen.