Slot And Pin Sliding Mechanism For Locking/Unlocking Of The Segment Mold In Hydraulic Tire Curing Press

Field of the invention

The present invention relates to a hydraulic tire curing press, and in more particularly, to a an arrangement involved for opening and closing of the segmented tread tire mold assembly and in particular to a mechanism involved for locking/unlocking the segmented tread tire mold assembly with the press.

Background of the invention

Conventionally, tire curing molds in a tire curing press are of two types: (a) a two-piece mold divided into upper and lower two pieces and (b) segmental mold(segmented tread mold).

The segmental mold includes an upper container plate, a lower container plate, and a plurality of divided segments. These segments expand and contracts in radial direction. For expanding and contracting the segments in the mold an expanding/contracting device is provided in a tire curing press.

The mold in a tire curing press needs to be replaced in accordance with the size of the tire to be produced. For this purpose, an attachment/detachment activity between the expanding/contracting device and the upper container plate of the segment mold is done by means of fasteners arrangement. This brings down the workability and productivity.

To overcome the drawbacks with fastening arrangement , a locking/unlocking mechanism was brought into place between the expanding/contracting device and the upper container plate of the segment mold, so that the segment mold removal/replacement at any point of time is done quickly just by actuating the locking/unlocking mechanism.

The locking/unlocking mean uses a bayonet mechanism which includes a female bayonet lock/bayonet ring bolted between the upper container plate of the segmental mold and the a expansion/contraction device, and has a configuration which consists of a across machines varying mechanism, so as to rotate the male bayonet ring attached to the expansion/contraction device to engage with and disengage therewith.

The expansion/contraction of the segmental mold is then carried out by attaching a piston rod of the hydraulic cylinder to the male bayonet ring.

When a pressure fluid is supplied to the hydraulic cylinder, the piston rod is operated in the extending direction to expand the divided segments in the segmental mold in radial direction. The contracting operation of the divided segments in the segmental mold happens in the same manner but with the piston rod operated in retracting direction.

Associated with the locking/unlocking process, the expansion/contraction device is also intended to trap, sense the bladder leak steam and send the feedback signal to the control. This is carried out by adopting a separate components assembly consisting of sealing rings coupled with this device. In order to install the bladder leak sealing assembly, the hydraulic cylinder has to be raised to a considerable height from its normal mounting level.

Specifically, US patent No. 5466140 discloses a segment mold operator mechanism provided with a pair of fluid cylinder/piston units mounted on a vertical posts and the downwardly extending lower ends of the pistons are secured to a cross-head that extends through the vertical axis. The cross head is linked to an outer tube through a number of interconnected welded and bolted links in-between. The lower end of the outer tube is connected to a vertically adjustable bearing sleeve which is adapted for vertical adjustment through a threaded arrangement within a larger sleeve that is mounted at the bottom of the cross beam. The outer tube is connected to an actuator ring that supports the radial tread segments. The vertical movement of the bearing sleeve relative to the outer tube produces vertical movement of a wedge ring relative to a radial tread segments and horizontally moves the radial tread segments radially inward and outward. However the arrangement uses at least two fluid cylinder/piston units which produces difficulty in synchronizing them , which in turn results in uneven pressures which may produce improper radial inward and outward movement of the segmented tire mold assembly. Moreover this arrangement comprises more number of components and links which increases the production and servicing cost and decreases its reliability in the press.

Another US Patent No 5690970, discloses a split mold opening and closing device , wherein a flange fixed to either one of a top plate of a split mold and a piston rod tip end of a split mold opening/closing cylinder is held by operating fingers. The fingers are assembled in such a manner to be capable of oscillating in the holding direction by the return force of a spring. The top plate is connected to a piston rod of the split mold opening/closing cylinder, thereupon, the split mold is opened and closed by the output of the split mold opening/closing cylinder and the vertical movement of the bolster plat. When the split mold is replaced the holding is released by oscillating the fingers by using a finger driving device, by which the top plate is separated from the piston rod of the split mold opening/closing cylinder. However the oscillating finger mechanism is prone to problems, the compression spring used between the fingers are exposed to hot steam condition, which in due course may alter the property of the spring due to which the clamping and unclamping process may become non viable. Moreover for operating the oscillating fingers , a finger drive device consisting a cam body elevating cylinder and cam rollers are used, along with connecting linkages between the cylinder and fingers ,which increases the overall cost of the assembly . In addition to this , the oscillating mechanism requires more radial space for achieving clearances during clamping and unclamping , which calls for increase in bore diameter in the bolster plate. In addition to these, the use of cam rollers calls for proper lubrication between the rolling surfaces and that too which the presence of hot conditions, frequent lubrication may be required due to drying up of lubricants, which reduces the reliability of the device and moreover the use of lubricants at this juncture is not advisable, since , any leaking of the lubricants may fall on either an uncured tire or on hot cured tire may result in a scrap tire.

Yet another US Patent No.7987697 discloses a method of detecting a leak in a curing bladder during the tire curing process provides a curing bladder and a tire in a tire mold structure. An inert tracer gas is added to the pressurized gas such as nitrogen, with the nitrogen inflating the curing bladder so that the curing bladder engages a portion of the tire. The method detects whether the inert gas is present between the curing bladder and the tire with the curing bladder and tire remain in tire mold structure. A leak detection system with vacuum source, sensors, piping arrangement is provided to detect the leak through a passage provided in the mold. However the leak detection system has to employ many components for sealing and detecting the bladder leak which increases the overall cost and maintenance of the system. Further the sealing and detecting arrangements call for piping provisions on the press which increases the height of the press.

The drawbacks associated with the all the above mentioned patents on presently existing expansion/contraction device also called as segment mold locking/unlocking device or segment mold operator is, less reliability and huge weight which is due to more number of interconnected components for achieving the desired motions through mechanisms, a considerable increment in the overall height of the press, which is due to mounting of hydraulic cylinder at an elevated height, a separate sealing assembly for trapping the bladder leak steam, more space is required on the tire curing press for installing this bulky constructed device, high production cost owing to the increased number of working components and a separate sealing setup. In addition to these , many of the described methods employ direct mounting of hydraulic cylinders to the hot bolster plate, which increases the working temperature of the hydraulic cylinder and thereby reducing the life of seals and fluid.

Accordingly, there exists a need to provide a locking/unlocking mechanism for the segment mold of the hydraulic tire curing press, which overcomes drawbacks of the prior art.
Objects of the invention

An object of the present invention is to provide a reliable and compactly configured segment mold operator in hydraulic tire curing press.

Another object of present invention is to provide a segment mold operator with less number of working components than many other existing mechanisms for the same purpose.

Yet another object of present invention to provide a segment mold operator with an integrated bladder leak trapping setup without requiring separate components assembly for detecting the bladder leak.

Still another object of the present invention to provide a segment mold operator with less overall height thereby bringing down the overall height of the press.

Still another object of the present invention to provide a segment mold operator with provisions to isolate the hydraulic cylinders from the hot bolster plate and increasing the reliability of hydraulic cylinders.

One more object of present invention to provide a less weight and more cost effective segment mold locking/unlocking device.

Summary of the invention

Accordingly, the present invention provides a mechanism for locking/unlocking the segment mold in hydraulic tire curing press. The mechanism includes a guide rod having an upper end secured to a lever and a slider connected to the lower end of the guide rod. The slider includes a slot configured therein. The mechanism further includes a plunger communicating with a hydraulic cylinder for expansion/contraction of the segmental mold. The plunger includes a projection configured at upper portion and a flange configured at lower end thereof. The mechanism furthermore includes a male bayonet ring inserted in the plunger. The male bayonet ring is capable of being rotated about its own axis. Wherein upward movement of the male bayonet ring is arrested by the projection in the plunger and downward motion of the male bayonet ring is arrested with the flange of the plunger. The male bayonet ring includes a pivot pin threaded thereon. The pivot pin is capable of sliding within the slot of the slider. Wherein upon rotating the lever in any one of clockwise direction and counter clockwise direction, the rotation is transferred to the guide rod and then to the slider thereby rotating the slider, thereafter the pivot pin slides within the slot provided in the slider to ensure a rotary motion in the male bayonet ring through which the male bayonet ring gets locked/unlocked with the female bayonet ring attached on to the segment mold.

Brief description of the drawings

Figure 1 shows a front cross section view of a slot and pin sliding mechanism for locking/unlocking of the segment moid in hydraulic tire curing press, in accordance with the present invention;

Figure 2a and 2b shows top view of the mechanism of figure 1 with locked state and unlocked state respectively.

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 slot and pin sliding mechanism for locking/unlocking of the segment mold in hydraulic tire curing press. The mechanism comprises a unique configuration for ensuring the complete rotation of the male bayonet ring provided to the expansion/contraction device cylinder piston rod and a lock provided on an upper container plate of segment mold.

Referring now to figure 1, there is shown a slot and pin sliding mechanism (hereinafter referred to as "the mechanism (100)") for locking/unlocking of the segment mold (60) in a hydraulic tire curing press. The mechanism (100) includes a guide rod (10), a support rod (70), a slider (20), a plunger (30), a male bayonet ring (40), and a pivot pin (50).

The guide rod (10) includes an upper end (12) and a lower end (14). The upper end (12) is secured to a lever (16). In an embodiment, the lever (16) is securely connected with the upper end (12) of the guide rod (10) with an across flat provision. A support lever (72) which allows free sliding of guide rod(10) and support rod(70) is constrained for its upward and downward motion with hydraulic cylinder mounting flange(74) and a clamping unit(76). The top end of the support rod(78) has larger section to constrain the movement of lever( 16). The lower end (14) of the guide rod (10) includes the slider (20) connected thereto. In an embodiment, the guide rod (10) is welded to the slider (20). The slider (20) includes a slot (22) configured therein, on to which the pivot pin (50) is inserted.

In an embodiment, the guide rod (10) has an across flat on its top end to which the lever (16) having an across flat cut is inserted and is held in firm position with cover plate (not shown) and fastener (not shown). The guide rod (10) together with the lever(16) slides up and down along the support rod(70) with respect to different mold sizes and in case of tire curing process.

The hydraulic cylinder(80) is mounted on to a hydraulic cylinder mounting flange (74). The hydraulic cylinder(80) is kept isolated from the hot bolster plate(82) by placing an effective insulator(84) in-between the hydraulic cylinder mounting flange(74) and bolster plate(82) and thereby preventing the hydraulic cylinder(80) from getting damaged due to increase in temperature from bolster plate(82).

The plunger (30) communicates with a hydraulic cylinder (not shown) for expansion/contraction of the segmental mold. Specifically, the plunger (30) is threaded to the hydraulic cylinder. The plunger (30) is provided with a projection (32) configured at upper portion thereof, and a flange (34) configured at lower end thereof. The plunger (30) includes the male bayonet ring (40) inserted therein.

The male bayonet ring (40) is capable of being rotated about its own axis. Specifically, the upward movement of the male bayonet ring (40) is arrested by the projection (32) of the plunger (30) and downward motion of the male bayonet ring (40) is arrested with the flange (34) of the plunger (30).

The pivot pin (50) in the slot (22) of the slider (20) is threaded to the male bayonet ring (40) so as to achieve the desired rotation of male bayonet ring(40) as and when the pivot pin (50) slides on the slot (22). The pivot pin (50) is capable of sliding within the slot (22) of the slider (20). Specifically, the male bayonet ring (40) rotates about its axis while keeping the guide rod (20) in a fixed position.

Referring now to figure 2a, there is shown a mechanism (100) in locked state. When the lever (16) is rotated in clockwise direction, the rotation is transferred to the guide rod (10) and then to the slider (20) thereby rotating the slider (20). The pivot pin (50) slides within the slot (22) provided in the slider (20) to ensure a rotary motion in the male bayonet ring (40). The rotary motion causes through which the male bayonet ring (40) to get locked with the female bayonet ring (86), attached on to the segment mold (60). Similarly, the mechanism (100) get unlocked when the lever (16) is rotated in counterclockwise direction as shown in figure 2b.

The curing bladder leak is detected by trapping the high pressure curing gas which escapes through the a passage (not shown) provided on the upper container plate of segment mold (88), within the central bore (90), since both the ends of the bore (92 & 94) are being covered with, hydraulic cylinder mounting flange (74) on one end (92) and upper container segment mold plate(88) on another side(94). A humidity sensor/pressure switch (not mentioned) is provided on the opening (96) provided in the hydraulic cylinder mounting flange(74). As the escaped gas gets trapped between the ends (92 and 94) of the central bore , the pressure/temperature builds up, and when it reaches the limiting values of humidity sensor/ pressure switch, the device gets activated and a signal is given to the operator and the curing process is halted.

Advantages of the invention

1. The mechanism (100) provides a new reliable and compact segment mold operator arrangement with less number of components.

2. The mechanism (100) provides an integrated curing bladder leak detection arrangement with less number of components and simple method.

2. The mechanism (100) provides a cost effective means with minimum number of components for achieving locking/unlocking of segment mold .

3. The hydraulic cylinder is mounted on with an insulator in place , so as to prevent the failure of hydraulic cylinder due to rise in temperature.

3. The compact mechanism (100), reduces the overall height of the press, due to which the press can be installed in the compact space.

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 mechanism for locking/unlocking the segment mold in hydraulic tire curing press, the mechanism comprising:
a guide rod having an upper end and a lower end, the upper end secured to a lever;
a slider connected to the lower end of the guide rod, the slider having a slot configured therein;
a support rod with support lever for allowing vertical up/down movement of guide rod;
a plunger communicating with a hydraulic cylinder for expansion/contraction of the segmental mold, the plunger having a projection configured at upper portion and a flange configured at lower end thereof;
a male bayonet ring inserted in the plunger, the male bayonet ring capable of being rotated about its own axis, wherein upward movement of the male bayonet ring is arrested by the projection in the plunger and downward motion of the male bayonet ring is arrested with the flange of the plunger;
a pivot pin threaded to the bayonet ring, the pivot pin capable of sliding within the slot of the slider;
wherein upon rotating the lever in any one of clockwise direction and counter clockwise direction, the rotation is transferred to the guide rod and then to the slider thereby rotating the slider, thereafter the pivot pin slides within the slot provided in the slider to ensure a rotary motion in the male bayonet ring

through which the male bayonet ring gets locked/unlocked with the female bayonet ring attached on to the segment mold.

2. The mechanism as claimed in claim 1, wherein the lever is securely connected with the guide rod with an across flat cut on the lever and guide rod.