Tyre loaders are used for loading so-called "green tyres'1 into the various moulds fitted to tyre curing presses. The most important requirements of such tyre loaders includes concentric loading of the tyre in the mould and repeatability of concentricity. This is important to ensure that the tyres are uniformly cured and to minimize bead damage and distortion during the loading cycle.

Tyre loaders of this type generally include a loader assembly having a frame and a number of shoes or paddles which depend from below the frame in a concentric arrangement. The paddles are arranged to move radially relative to the central axis of the frame. In use, the shoes are retracted to a position in which they can be placed within the inner diameter of the uncured tyre, and then extended radially until they engage the bead of the tyre. The engaged and supported tyre is then loaded into the tyre press for curing.

Because the shoes are required to move radially between retracted and extended positions, there is a limit to the number of shoes which can be used which still allow the shoes to retract sufficiently to receive an uncured tyre.

In one such tyre loader assembly, manufactured by National Feedscrew and Machining Inc., six shoes are arranged for radial movement.

A further example of a tyre loader assembly of this type using radially movable shoes is described in US patent 4,608,219 to NRM Corporation.

The loader basket comprises a series of circularly arranged loader or chuck shoes which are connected to a radially extending adjusting bar about a horizontal pin. The shoes are arranged to engage the bead of a tyre by radial movement of the adjusting bar.

US patent no. 2,997,738 to The McNeil Machine and Engineering Company discloses a loader assembly having a number of segments which are increased in diameter to engage the bead of a curved tyre. Each segment is mounted to a frame about a horizontal pin such that it can pivot towards and away from the central axis of the assembly to engage and release a tyre.

Once again there is a limit to the number of segments that can be used.

Since there is a limit to the number of shoes which can be used with conventional tyre loaders, concentricity is not always achievable as the uncured tyres, which are relatively soft and easily deformable, tend to be "squared-off" or deformed by the shoes. As a result, when the uncured tyre is loaded onto the mould, it is not always concentric, resulting in imperfections when the tyre is cured. Repeatability of concentricity, therefore, is not always achievable.

Besides the limitations imposed by the shoe configurations, the conventional tyre loader assemblies use a linkage system of levers and slides which tend to have cumulative play due to machine intolerance, resulting in greater wear and less likelihood of repeatability. In addition, due to wear and malfunction parts of these may become dislodged during a loading cycle and fall into the mould and cause a great deal of damage as a result. SUMMARY OF THE INVENTION According to one aspect of the invention there is provided a tyre loader assembly for a tyre press, comprising a support frame defining a central axis, a plurality of gripping arms mounted on the frame for pivotal movement about respective axes substantially parallel to the central axis, and drive means for pivoting the gripping arms, the arms being arranged to engage and support an uncured tyre upon being pivoted by the drive means.

The support frame may be an annular body defining a substantially vertical central axis, the gripping arms being pivotally mounted on the annular body about the central axis so that an uncured tyre, coaxially aligned with the annular body, may be gripped and supported upon pivoting of the gripping arms.

The gripping arms are preferably pivotable towards and away from the central axis in a horizontal swinging motion between an inoperative position in which the uncured tyre may be positioned about the gripping arms and an operative position in which the beard of the uncured tyre is engaged by the gripping arms to support the uncured tyre in a substantially concentric orientation.

Preferably, the inoperative position corresponds to an inner limit of movement of the gripping arms and the operative position corresponds to an outer limit of movement of the gripping arms, the drive means being arranged to set the inner and outer limits in accordance with the internal diameter of the tyre to be cured.

The drive means preferably includes a plurality of pre-determined settings corresponding to the respective internal diameters of conventionally sized tyres.

The gripping arms are preferably mounted on the support frame by respective spaced apart shafts or rods depending from below the support frame, each gripping arm comprising a substantially horizontal swing bar connected at one end to its respective shaft and arranged to pivot upon rotation of the respective shaft, and a substantially vertical leg section depending from an opposite end of the swing bar, the vertical leg section being arranged to engage the bead of a tyre to be cured.

The vertical leg section conveniently terminates in a foot adapted to engage the bead of the tyre.

The support frame is typically in the form of an annular housing, a plurality of interconnected pivoting means being arranged concentrically within the housing to pivot the respective gripping arms.

The pivoting means preferably comprises a plurality of spaced-apart planetary gears interconnected by a ring gear arranged to rotate within the housing, each planetary gear being arranged to pivot a respective gripping arm upon rotation of the ring gear.

The drive means typically comprises a lever connected to at least one of the planetary gears to rotate it, and consequently the ring gear, upon being pivoted and an actuator means arranged to pivot the lever so as to pivot the gripping arms in a synchronised manner.

According to a further aspect of the invention a tyre press comprising a loader assembly of the invention is provided.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will now be described in more detail, by way of example only, with reference to the accompanying drawings in which: Figure 1 shows a perspective view of a tyre loader assembly of the invention; Figure 2 shows a cross-section on the line 2-2 of Figure 1; Figure 3 shows a partial plan view of the housing of the tyre loader assembly of Figure 1; Figure 4 shows an underplan view of the tyre loader assembly of Figure 1; Figure 5 shows a supported "green tyre"; Figure 6 shows a detailed plan view of a portion of the drive mechanism of the tyre loader assembly of Figure 1; Figure 7 shows a side view of a paddle of a tyre loader assembly of the invention; Figure 8 shows a plan view of the paddle of Figure 7; Figure 9 shows a perspective view of a retaining clip used with the paddle of Figure 7; and Figure 10 shows the retaining clip of Figure 9 in use.

DESCRIPTION OF A PREFERRED EMBODIMENT The tyre loader assembly 10 seen in Figure 1 consists of an annular support frame or housing 12, a number of gripping arms or paddles 14 depending from below the housing 12, and a drive mechanism 16.

The housing 12 includes a channel 18 in which a number of gears 20 and guide rollers 22 are housed. Each paddle 14 is connected to a gear 20. The channel 18 is enclosed by a lid 24 which is held securely in place by four releasable clip locks (not shown). The assembly 10 includes a mounting bracket 26 extending from the side of the housing 12 for mounting it on a conventional tyre loader. Alternatively, the mounting bracket 26 can extend from above or below the housing if necessary for mounting it to a convention tyre loader or press.

Referring to Figure 2, it can be seen that the paddle 14 is shaped like a crank, having a generally horizontal arm section or swing bar 28 and a vertical leg section 30 ending in a foot 32. The end 34 of the arm 28 includes a bore (not shown) for connecting the paddle 14 to a shaft 36 depending from the gear 20. The paddle 14 is secured on the shaft 36 by a pair of cap screws 38. This arrangement allows the horizontal position of the paddle 14 to be altered relative to the shaft 36. The shaft 36 is undercut to prevent the paddle 14 from moving up or down when secured.

Turning to Figure 3, it can be seen that each gear 20 is positioned in engagement with a ring gear 40 arranged to move along the periphery 19 of the channel 18. Typically, at least three guide rollers 22 are provided for supporting or guiding the ring gear 40 in the channel 18.

The drive mechanism 16, as illustrated in Figure 4, consists of a pneumatic cylinder 42 having an actuator in the form a piston-rod 44 connected to a lever or drive arm 46, which in turn is connected to the paddle 14A. As the pneumatic cylinder 42 moves the piston-rod 44 in and out, the drive arm 46 causes the paddle 14A to pivot between a retracted position in which it follows the contours of the annular housing 12, and an extended position in which it tends towards the central axis of the housing 12, as shown in dotted lines. As the paddle 1 4A is pivoted by the drive mechanism 16, it causes the ring gear 40 to rotate in the channel 18 which in turn causes the remaining paddles 14 to be pivoted in the same fashion as the paddle 14A.

In this way, the pivoting of the paddles 14 is synchronized. The arms 28 are curved so that the paddles nest into one another in the retracted position.

Although gears 20 and a ring gear 40 are used in the present case to pivot the paddles 14, other appropriate mechanisms may be used. Thus, for example, the paddles 14 may be pivoted by timing pulleys and a timing belt, by sprockets and a chain, by an inner ring gear and planetary gears, or by a similar toothed belt and pulley system. Likewise, although a pneumatic cylinder is used as the drive mechanism in this case, any other appropriate mechanism such as, for example, a hydraulic cylinder or electrical/electronic drive unit can be used In the extended position, shown in dotted lines in Figure 4, the paddles 14 are able to move in an arc 48 between set inner and outer limits corresponding to inoperative and operative positions, respectively. The inner limit 50 is of a diameter sufficiently small to allow a tyre of a given diameter to be positioned around the feet 32. The outer limit 52 is large enough in diameter for the feet 32 to engage the beading 54 of a tyre 56, as illustrated in Figure 5.

Referring to Figure 6, the drive arm 46 includes a number of settings 58 for adjusting the inner and outer limits of the feet 32 in the extended position.

The settings are adjusted by removing a pin 60 and re-inserting it in the desired setting 58. In this way the paddles 14 may be adjusted to accommodate tyres having beadings of varying diameters, typically ranging from 10 to 16 inches (25.4 to 40.6 cm), preferably 10 to 19 inches (25.4 to 48.3 cm) without having to manually measure the desired diameter.

Additionally, as mentioned earlier, the paddles 14 themselves can be adjusted via the cap screws 38 on the shaft 36, to change the movement limits.

However, the paddles 14 are typically only adjusted to set the arms 28 for concentricity. An adjusting screw 62 is also provided for fine adjustments of the paddles 14.

Referring to Figure 7, there is shown an alternative paddle 70 in which the horizontal bar or arm 72, vertical leg 74 and foot 76 are formed as a single die-cast unit. Included is a sensor lever or arm 78 which senses the presence of an uncured tyre to be loaded. When the sensor arm 78 presses against the bead of an uncured tyre it pivots, causing a pin 79 to move down against the bias of a spring 80 to form an electrical contact. This safety feature is arranged to prevent the paddles from moving if the electrical contact is not made. An end clamp 82 is arranged to bolt onto the end 84 of the arm 72 via bolts 83 to capture the undercut portion 86 of the shaft 36 within the bore 88 to secure the arm 72 to the shaft 36.

Once again, it can be seen from Figure 8, that the paddle arm 72 is curved such that successive paddles 70 are able to nest into one another in the retracted position. In addition, the foot 76 is curved to ensure maximum concentricity when it engages the bead of a tyre to be cured.

Because the paddles 14 or 70 of the invention as the case may be, are arranged for pivotal movement analogous to the shutter of a camera, a larger number of paddles 14 or 70 is possible than with the conventional loader assemblies. It has been found that twelve paddles 14 or 70 provide sufficient support for an uncured tyre. However, if greater concentricity is required, additional paddles may be included. Further, because the loader assembly 10 of the invention uses a planetary gear system, as opposed to a conventional linkage system using levers and slides, for moving the paddles 14 or 70, there is less wear on the various parts. As a result, the feet 32 or 76 are moved to substantially the same point every time enhancing the concentricity of the tyre to be cured as well as repeatability of concentricity.

In addition, since the important moving parts such as the gears and ring gear are enclosed in the housing 12, debris and other foreign objects are prevented from being lodged in the gears, reducing the risk of damage.

Furthermore, there is less chance of parts of the loader assembly being dislodged and falling into a mould which could cause a great deal of damage. Exceptions are the paddle assembly 14 (or 70) and its various parts. In order to reduce the risk of these parts being dislodged and damaging the mould, a plastics retaining clip 90, as shown in Figure 9, is provided to grip these parts. The retaining clip 90 includes an attachment ring 92 arranged to clip onto the shoulder 81 of the sensor pin 80, which is undercut (not shown) to prevent the retaining clip 90 from coming loose, and a number of ring-like connectors 94, attached to ring 92 via arms 96 for engaging the end clamp 82, bolts 83 and paddle 70, respectively. This is shown more clearly in Figure 10. If one or more of these parts were to come loose, they would be prevented from falling into the mould by the retaining clip 90.

A further advantage of the tyre loader assembly of the invention is that due to the planetary arrangement of the gears 20, the outer diameter 98 of the housing 12 may be reduced with a corresponding increase in the inner diameter 100 of the housing 12. This allows the tyre loader assembly 10 to be mounted on existing loader arms on most conventional tyre presses, and also accommodates a wider range of tyre diameters.

Another advantage of the invention is that a single drive mechanism is required to pivot all the paddles through the interlinked gear arrangement.