Suspension air spring sleeve compression moulding apparatus

Abstract

Suspension air spring sleeve compression moulding apparatus (10) includes a mould core (16) locatable in a cavity (14) defined by outer mould walls (12). The core is movable between a retracted condit

Description

Technical Field The present invention relates to suspension air spring sleeve compression moulding apparatus. Background Conventionally, suspension air spring sleeves are manufactured in a compression moulding process. Typically, the sleeves are formed of a plurality of layers of rubber compound and embedded strengthening fibres which are subjected to heat and pressure during the moulding process to vulcanise the rubber and bond the layers of rubber compound and fibres together. Conventionally, to form suspension air spring sleeves, the compression moulding process uses a sacrificial airbag or bladder. Initially, the sleeve to be formed is in the form of a carcass which is located over the airbag. The airbag is expanded by a steam or heated nitrogen supply to compress the carcass between a wall of a mould cavity and the airbag, thereby forming the carcass to the shape of the wall. However, air bags have a limited life. An airbag will on average last for around 10-20 inflation / deflation cycles before bursting. The process is inefficient since changing airbags causes high downtime. The product quality produced is variable since the distribution of the material is not controlled by the airbag. A well-known method utilises steam press moulding. The use of steam requires a boiler with associated energy costs and potential downtime. Variation in pressure causes early product failure &diameter differences. Lack of pressure causes thickness and diameter variation and there can be high material concentration in overlapping areas and air traps. The process carries a high health &safety risk and attracts an additional insurance overhead. In this specification, the relative terms inner, outer, inwardly, outwardly and other similar orientation terms are used in relation to a mould core which has a longitudinal axis which is arranged with the longitudinal axis vertically. “Inward” is towards the longitudinal axis and “outward” is away from the longitudinal axis; “upward” is away from the ground and “downward” is down into the ground. In this specification, the word “substantially” is used to include the meaning of “exactly or for practical purposes, as will be understood by a skilled person in the technical field”. This includes some variation from “exactly” because of practical considerations. For example, in the technical field of this invention, “substantially horizontal” might include ±10° from the horizontal. Statements of Invention According to a first aspect of the present invention, there is provided a suspension air spring sleeve compression moulding apparatus, the apparatus including: a mould core locatable in a cavity defined by outer mould walls, the core being movable between a retracted condition and an expanded condition; wherein the core includes a set of first fingers and a set of second fingers which are movable relative to each other; the core includes an outer core surface; in the retracted condition, only the first fingers comprise the outer core surface of the core in the cavity; and in the expanded condition, both the first and the second fingers together comprise the outer core surface of the core in the cavity. Possibly, in use, a carcass for forming into a suspension air spring sleeve is located over the core in the retracted condition. Possibly, in use the core is moved to the expanded condition and the carcass is heated and compressed between the core and the outer mould walls to form the suspension air spring sleeve. Possibly, in use, the outer core surface contacts the carcass. Possibly, in use, in moving from the retracted condition to the expanded condition, the outer core surface causes the carcass to deform, expand, compress and / or stretch. Possibly, in the retracted condition, only the first fingers are located in the cavity. Possibly, in the expanded condition, both the first and the second fingers are located in the cavity. Possibly, the apparatus includes the outer mould walls. The outer mould walls may comprise a base wall, side walls and an end wall. Possibly, the apparatus is movable between an open condition, in which the carcass can be located on the core and removed therefrom, and a closed condition, in which the cavity is closed. Possibly, as the apparatus moves from the open condition to the closed condition, the core moves towards the outer mould walls and / or vice versa. Possibly, the core is elongate, and may extend along a longitudinal axis. Possibly, in the closed condition, the first fingers substantially do not move along the longitudinal axis. Possibly, in moving between the retracted condition and the expanded condition, the first fingers substantially do not move along the longitudinal axis. Possibly, in the retracted condition, the first fingers are in relatively close proximity to one another, and may define first finger gaps therebetween, which may be relatively small clearance gaps. Possibly, in the expanded condition, the first fingers are spaced apart from each other. Possibly, in moving from the retracted to the expanded condition, the first fingers move away from each other and the first finger gaps increase in size. Possibly, in moving from the retracted to the expanded condition, the first fingers move away from each other along a direction which is substantially normal to the longitudinal axis. Possibly, the second fingers move along the longitudinal axis and may also move outwardly normally relative to the longitudinal axis. Possibly, as the core moves from the retracted condition to the expanded condition, each one of the second fingers interposes between a pair of the first fingers. Possibly, in the expanded condition, the second fingers alternate with the first fingers to form the outer core surface of the core. Possibly, the carcass comprises a plurality of layers of rubber compound and embedded strengthening fibres. The strengthening fibres may be formed of a plastics material and may be formed of nylon. Possibly, the carcass comprises between 1 and 5 layers of the embedded strengthening fibres and more desirably could comprise 2 layers of the embedded strengthening fibres, which may be arranged in axial or bias angle as the product requires. Possibly, the carcass is in the form of a sleeve which is open at the top and bottom and may comprise a side wall. Possibly, the apparatus includes an electrical heating arrangement for heating the core and / or the outer mould walls. Possibly, the heating arrangement includes one or more electrical elements and / or temperature sensors, which may be embedded in the core, the core fingers and / or the outer mould walls. Possibly, the apparatus includes a compressive force device, which may produce a compressive force on the carcass during the moulding process. Possibly, the compressive force device comprises a hydraulic cylinder. Possibly, in use, the carcass is subjected to a predetermined temperature and pressure profile, which may include stages of raising the temperature and pressure of the carcass to a holding temperature and holding pressure, and / or holding the carcass at the holding temperature and the holding pressure for a predetermined holding time period and / or then lowering the pressure, possibly to permit release from the mould cavity. Possibly, the holding temperature is in the range of 120° to 280°C; desirably in the range of 150° to 180°C; and optimally around 160°C. Possibly, the holding pressure is in the range of 50 to 220 bar; desirably in the range of 100 to 210 bar; and optimally around 200 bar. Possibly, the predetermined holding time is in the range of 4 to 12 minutes; desirably in the range of 6 to 10 minutes; and optimally around 8 minutes. Possibly, in the expanded condition, each first finger abuts alongside (ie in contact with) one of the second fingers on each side and vice versa. Possibly, in the expanded condition, the outer core surface is without gaps between the first and the second fingers and may be substantially continuous and relatively smooth. The outer core surface may include an surface pattern which may comprise an etching pattern. Possibly, the core is elongate, and may extend along a longitudinal axis. Possibly, the core is rotationally symmetrical about the longitudinal axis. Possibly, the apparatus includes a first finger actuator arrangement for moving the first fingers, which may include one or more first finger actuators, which may move the first fingers laterally, possibly towards and away from the longitudinal axis. Possibly, the apparatus includes a second finger actuator for moving the second fingers. Possibly, the second finger actuator comprises a body and a an actuator member, which may be rod-like and which may extend from the body along a second finger passage which may be defined by the second fingers. Possibly, the second finger actuator and the second finger passage extend along the longitudinal axis. Possibly, the second finger actuator includes a cam arrangement, which may include a plurality of spaced apart cam formations. Each cam formation may include a sloping cam surface and may include an outer flat surface. Possibly, each of the second fingers includes a cam follower arrangement. Possibly, the cam follower arrangement includes a plurality of inwardly projecting bumps. Possibly, the cam arrangement is arranged to engage with the cam follower arrangement to move the second fingers laterally outwardly to the expanded condition. Possibly, in use, the bumps engage the cam surfaces to move the second fingers laterally outwardly to the expanded condition. Possibly, the second finger actuator includes a guide arrangement, Possibly the guide arrangement comprises a plurality of pins which locate in slots defined by the second fingers. Possibly, the slots are angled and / or curved, possibly to accommodate the upward movement of the second finger actuator and the outward movement of the second fingers. Possibly, each first finger comprises a top end face, which in plan is tapered in shape from the outside to the inside, possibly having the shape of a truncated wedge, which may have end sides which are angled inwardly towards each other and may have an internal side and an external side which are arcuate and may be concentric. The apparatus may move from the retracted condition to the expanded condition in a plurality of stages. Possibly, in a first stage of movement, the first fingers move laterally outwardly, possibly to or towards the expanded condition. Possibly, the first finger actuators operate to move the first fingers laterally outwardly. Possibly, in the first stage, the second fingers do not move. Possibly, in a further stage of movement, the second fingers move upwardly but not outwardly, possibly while the first fingers do not move. Possibly, as the second fingers move upwardly, each second finger locates between two first fingers. Possibly, the second fingers are moved by the second finger actuator. Possibly, each first finger includes a pair of guide faces, and the second fingers may locate between the guide faces of neighbouring first fingers. Possibly, in a final stage of movement, the second fingers move outwardly but not upwardly to the expanded condition. Possibly, in the final stage of movement, the second finger actuator operates to move the second fingers outwardly but not upwardly to the expanded condition. Possibly, in the final stage of movement, the cam arrangement engages with the cam follower arrangement to move the second fingers laterally outwardly to the expanded condition. Possibly, the second finger actuator includes a guide arrangement, Possibly, the guide arrangement comprises a plurality of pins which locate in slots defined by the second fingers. Possibly, the slots are angled or curved to accommodate the upward movement of the second finger actuator and the outward movement of the second fingers in the final stage of movement. Possibly, each first finger top end face has a pair of end sides which are angled and may taper inwardly relative to each other, possibly at an end side angle. Possibly, the end side angle is dependent on the number N of first fingers, possibly such that the end side angle is 360° / N. Possibly, the number N of first fingers is four and the end side angle is 90°. Possibly, each first finger top end face has an external side and an internal side, which may be arcuate and may be concentric. Each of the second fingers has a top end face. Possibly, each of the second finger top end faces has a pair of end sides which may be substantially parallel to each other. Possibly, each of the second finger top end faces has an internal side and an external side which may be arcuate and may be concentric. Possibly, each of the first and second finger top end face external sides has a radius of curvature. Possibly, the radius of curvature of each first finger top end face external side is substantially the same as the radius of curvature of each second finger top end face external side. Possibly, in the expanded condition, in plan, the core has a circular cross-sectional ring shape which may comprise an internal side having an internal radius R1 centred on the longitudinal axis and an external side having an external radius R2 centred on the longitudinal axis, so that the internal and external sides may form concentric circles. Possibly, the first finger top end faces and the second finger top end faces comprise the ring shape. Possibly, in the expanded condition, the second fingers completely fill the expanded first finger gaps, so that the outer core surface is substantially smooth and continuous, without gaps. Possibly, the apparatus includes a spreader, which may be movable, and which may hold or spread the first fingers in / to their expanded condition. Possibly, the spreader is mounted above the core and may be aligned along the longitudinal axis of the core. Possibly, in use, the spreader engages the first fingers and may move downwardly to engage the first fingers. Possibly, the spreader comprises one or more spreading surfaces which may be angled relative to the core longitudinal axis. Possibly, in use, the spreader surfaces contact internal faces of the first fingers. Possibly the spreader defines a spreader hole, which may take the form of a passage, bore or recess and which, may, in the expanded condition, receive a tip of the actuator member. Possibly, the spreader includes a plurality of spreader projections. Possibly each spreader projection is arranged to engage one of the first fingers. Possibly, each spreader projection includes one of the spreading surfaces. Possibly, the spreader projections define gaps therebetween in which the second fingers are receivable. Possibly, in the expanded condition, the apparatus defines an annular space between the ends of the first and second fingers and the actuator member tip. Possibly, in the expanded condition, the tip is located in the spreader hole and the spreader projections are located in the annular space, providing an interlock arrangement. Possibly, each first finger has a bottom end face which is wedge-shaped and may taper (ie narrow in width) inwardly, possibly to a point and may comprise two straight sides and a curved side, which may comprise all of the sides of the bottom end face. Possibly, the two straight sides subtend an internal angle, which may be greater than 95° and may be less than 110°, and desirably may be more than 100° and may be less than 105°, and more desirably may be around 102.5°. Possibly, each first finger includes a pair of angled guide faces, the lower edges of which may comprise two of the sides of the first finger bottom end face. Possibly, each of the guide faces tapers (narrows) in width upwardly, possibly to a point which lies at between 40% to 60% of the length of the first fingers from the lower edges. According to a second aspect of the present invention, there is provided a method of compression moulding suspension air spring sleeves, the method including the step of providing suspension air spring sleeve compression moulding apparatus, the apparatus including: a mould core locatable in a cavity defined by outer mould walls, the core being movable between a retracted condition and an expanded condition; wherein the core includes a set of first fingers and a set of second fingers which are movable relative to each other; the core includes an outer core surface; in the retracted condition, only the first fingers comprise the outer core surface of the core in the cavity; and in the expanded condition, both the first and the second fingers together comprise the outer core surface of the core in the cavity. Possibly, the apparatus includes any of the features described in any of the preceding statements or following description. Possibly, the method includes any of the steps described in any of the preceding statements or following description. Figures Embodiments of the present invention will now be described, by way of example only, and with reference to the accompanying drawings, in which: Fig. 1A is a schematic side sectional view of suspension air spring sleeve compression moulding apparatus in an open condition, the apparatus comprising outer mould walls and a core, with a carcass located over the core, the core being in a retracted condition; Fig. 1B is a schematic side sectional view of the apparatus of Fig. 1A in a closed condition; Fig. 2A, 3A, 4A, 5A and 6A are side cross-sectional views of the core of the compression moulding apparatus, showing the core moving from a retracted condition in Fig. 2Ato an expanded condition shown in Fig. 6A, with Figs. 3A, 4A and 5A showing the core in first, second and third intermediate conditions; Figs. 2B, 3B, 4B, 5B and 6B are perspective views of the core corresponding with the respective views Figs. 2A, 3A, 4A, 5A and 6A; Fig. 3C is a cross-sectional view at the level indicated by Ill-Ill in Fig. 3A of first finger bottom end faces and second finger top end faces in the first intermediate condition; Figs. 7 A, 7B and 7C are schematic plan views from above of the top end faces of first and second fingers of the core, showing, in Fig. 7A, the top end faces of the first fingers in the retracted condition; in Fig. 7B, the top end faces of the first and the second fingers in the second intermediate condition shown in Figs. 4A and 4B; and in Fig. 7C, the top end faces of the first and second fingers in the expanded condition; Fig. 8 is a perspective view from one side of a spreader for spreading the first fingers to the expanded condition; and Fig. 9 is a side part sectional view showing the spreader in proximity to the first fingers of the core. In the drawings, where multiple instances of the same or similar features exist, only a representative one or some of the instances of the features have been provided with numeric references for clarity. Description Figs. 1A and 1B show, in simplified form, a suspension air spring sleeve compression moulding apparatus 10. The apparatus 10 includes outer mould walls 12 defining a mould cavity 14 and a mould core 16 which is locatable in the cavity 14. The core 16 is movable between a retracted condition and an expanded condition. In use, a carcass 18 for forming into a suspension air spring sleeve is located over the core 16 in the retracted condition as shown in Fig. 1 A. The carcass 18 comprises a plurality of layers of rubber compound and embedded strengthening fibres, which could be formed, for example of a plastics material and could be formed of nylon. In one example, the carcass 18 could comprise between 1 and 5 layers of strengthening fibres and more desirably could comprise 2 layers of strengthening fibres. The fibres could be arranged in axial or bias angle as the product requires. The carcass 18 is in the form of a sleeve which is open at the top and bottom and comprises a side wall 120. The apparatus 10 is movable between an open condition, in which the carcass 18 can be located on the core 16 and removed therefrom, and a closed condition, in which the cavity 14 is closed. As the apparatus 10 moves from the open condition to the closed condition, the core 16 moves towards the outer mould walls 12 and / or vice versa. In use, the core 16 with the carcass 18 is located in the mould cavity 14 and the apparatus 10 moved to the closed condition. The apparatus 10 includes an electrical heating arrangement (not shown) for heating the core 16 (including the core fingers 101, 102) and / or the outer mould walls 12. The heating arrangement could include one or more electrical elements and / or temperature sensors, which could be embedded in the core 16, the core fingers 101, 102 and / or the outer mould walls 12. The apparatus 10 includes a compressive force device (not shown), which produces a compressive force on the carcass 18 during the moulding process. The compressive force device comprises an hydraulic cylinder (not shown). The core 16 is moved to the expanded condition as shown in Fig. 1B, compressing the carcass 18 between the core 16 and the outer mould walls 12 to form the suspension air spring sleeve. To achieve satisfactory vulcanisation, bonding and forming of a formed sleeve, the carcass 18 must be subjected to a predetermined temperature and pressure profile, which includes stages of raising the temperature and pressure of the carcass to a holding temperature and holding pressure, holding the carcass at the holding temperature and the holding pressure for a predetermined holding time period and then lowering the pressure to permit release from the mould cavity. In one example, the holding temperature could be in the range of 120 to 280°C; desirably in the range of 150 to 180°C; and optimally around 160°C. In one example, the holding pressure could be in the range of 50 to 220 bar; desirably in the range of 100 to 210 bar; and optimally around 200 bar. In one example, the predetermined holding time could be in the range of 4 to 12 minutes; desirably in the range of 6 to 10 minutes; and optimally around 8 minutes. The core 16 includes a set of first fingers 101 and a set of second fingers 102. The first and second fingers 101, 102 are movable relative to each other. The core 16 comprises an outer core surface 20. In the retracted condition, only the first fingers 101 comprise a retracted outer core surface 20A of the core 16 in the cavity 14. In the expanded condition, both the first and the second fingers 101, 102 comprise an expanded outer core surface 20B of the core 16 in the cavity 14. The outer mould walls 12 comprise a base wall 22, side walls 24 and an end wall 26. The core 16 is elongate, extending along a longitudinal axis 28. In the example shown, the core 16 is rotationally symmetrical about the longitudinal axis 28. In the retracted condition, the first fingers 101 are in relatively close proximity to one another. As shown in Fig. 7A, the first fingers 101 define gaps 98 therebetween, which, in the retracted condition comprise relatively small retracted first finger gaps 98A. The retracted first finger gaps 98A provide clearance between neighbouring first fingers 101 to ensure free movement of the first fingers 101. In the expanded condition, the first fingers 101 are spaced apart from each other. In moving between the retracted and expanded conditions, the first fingers 101 substantially do not move along the longitudinal axis 28, but move laterally, along a direction which is substantially normal to the longitudinal axis 28. As the core 16 moves from the retracted condition to the expanded condition, each one of the second fingers 102 interposes between a pair of the first fingers 101. The second fingers 102 move along the longitudinal axis 28 and also move outwardly normally relative to the longitudinal axis 28. In the expanded condition, the second fingers 102 alternate with the first fingers 101 to form the expanded outer core surface 20B of the core 16, with each first finger 101 abutting alongside (ie in contact with) one of the second fingers 102 on each side and vice versa. The expanded outer core surface 20B is continuous and relatively smooth, without gaps between the first fingers 101 and the second fingers 102. Figs. 2Ato 6B show the arrangement of the mould core 16 in more detail and show progressive stages in the movement from the retracted condition shown in Figs. 2A and 2B to the expanded condition shown in Figs. 6A and 6B. The apparatus 10 includes a first finger actuator arrangement 30 which could include one or more first finger actuators 32, which move the first fingers 101 laterally towards and away from the longitudinal axis 28. The first finger actuators 32 are located at or just below the surface of the base wall 22. Each first finger actuator 32 includes a first finger actuator body 34 and a first finger actuator member 36. Each of the first finger actuator members 36 extends from the respective first finger actuator body 34 to actuate a different one of the first fingers 101. The movement of the first finger actuator members 36 is in a direction normal to the longitudinal axis 28. In the example shown, the first finger actuators 32 constrain the outward movement of the first fingers 101. In another possible first finger actuator arrangement 30, the arrangement 30 could include one first finger actuator 32 which actuates the all of the first fingers 101 via a mechanism (not shown). The base wall 22 defines a hole 38. The mould core 16 locates in the base wall hole 38. The apparatus 10 includes a second finger actuator 40 for moving the second fingers 102. The second finger actuator 40 comprises a body 42 and a rod-like member 44 which extends from the body 42 along a second finger passage 46 defined by the second fingers 102. The second finger actuator 40 and the second finger passage 46 extend along the longitudinal axis 28. The rod-like member 44 includes a cam arrangement 124. In the example shown, the cam arrangement 124 includes two spaced apart cam formations 48, each of which extends circumferentially around rod-like member 44. Each cam formation 48 includes a sloping cam surface 50 and an outer flat surface 52. Each of the second fingers 102 includes a cam follower arrangement 126. The cam follower arrangement 126 includes a pair of spaced inwardly projecting bumps 54 which project inwardly into the second finger passage 46 and are arranged to engage with the cam formations 48, as will be described below. The second finger actuator 40 includes a guide arrangement 138 which in the example shown comprises a plurality of pins 62 which locate in slots 64 defined by the second fingers 102. The slots 64 are angled or curved to accommodate the upward movement of the second finger actuator 40 and the outward movement of the second fingers 102. In use With the apparatus 10 in the open condition and the core 16 in the retracted condition, the carcass 18 is located onto the core 16 and the apparatus 10 moved to the closed condition. In an initial phase of the moulding process, the core 16 is moved from the retracted condition to the expanded condition. During this phase, the apparatus 10 is heated and pressure applied to compress the carcass between the core 16 and the outer mould walls 12. Figs. 2A and 2B show the core 16 in the retracted condition. Referring to Fig. 7A, which shows a plan view of the top end faces 76 of the first fingers 101 in the retracted condition. Each first finger 101 is tapered in shape from the outside to the inside, having the shape of a truncated wedge. Each first finger top end face 76 has end sides 84 which are angled inwardly towards each other. Each first finger top end face 76 has an internal side 82 and an external side 80 which are arcuate and concentric. The first finger top end face has an inside circumferential dimension 70 and an outside circumferential dimension 72. In the retracted condition, the first finger actuators 32 are in an extended condition and hold the first fingers 101 in the retracted condition. The first fingers 101 define a first finger passage 56. In the retracted condition, the second fingers 102 are located below and outside of the first finger passage 56 and below the mould cavity 14; the bumps 54 are located just in front of the sloping cam surfaces 50; and the pins 62 are in a lower part of the slots 64. In Figs. 2A and 2B, the carcass 18 is shown as transparent for illustrative purposes. The apparatus 10 moves from the retracted condition to the expanded condition in a plurality of stages. Figs. 3A and 3B show the core 16 in a first intermediate condition after a first stage of movement, in which the first finger actuators 32 operate to move the first fingers 101 laterally outwardly away from each other to or towards the expanded condition, indicated by arrows A in Fig. 7A, increasing the size of the first finger gaps 98. After the first stage, the second fingers 102 have not moved and are in a first position; the bumps 54 are located just in front of (ie, above) the sloping cam surfaces 50; and the pins 62 are in a lower part of the slots 64. In moving from the retracted to the expanded condition, the first fingers move and the first finger gaps 98 increase in size. When the first fingers 101 are in the expanded condition, the first finger gaps 98 comprise expanded first finger gaps 98B as shown in Figs. 3B and Fig. 3C. As shown in Fig. 3A and 3C, each first finger 101 has a bottom end face 68 which is wedge-shaped and tapers (ie narrows in width) inwardly to a wedge point 68P. The bottom end face 68 comprises two straight sides 68S and a curved outer side 68C, and these sides 68S, 68C comprise all of the sides of the bottom end face 68. The two straight sides 68S subtend an internal angle 130, which in the example shown is around 102.5°. In other examples the internal angle 130 could be greater than 95° and could be less than 110°, and desirably could be more than 100° and could be less than 105°. Each first finger 101 includes a pair of angled guide faces 128, the lower edges 68S of which comprise the straight sides 68S of the first finger bottom end face 68. Each of the guide faces 128 is flat and tapers (narrows) in width upwardly, to an intermediate point 128P which lies at between 40% to 60% of the axial length of the first fingers from the lower edges 68S. Each first finger 101 has a curved internal face 134 which extends downwardly from an inside edge 136 (which is also the internal side 82) of the top end face 76. The curved internal face 134 is substantially constant in width downwardly to the intermediate points 128P of the adjacent guide faces 128 and then extends downwardly between the adjacent guide faces 128, tapering (narrowing) downwardly to the wedge point 68P. Figs. 4A and 4B show the core 16 in a second intermediate condition after a second stage of movement, in which the second finger actuator 40 operates to move the second fingers 102 along the longitudinal axis 28 to a second position in which the second fingers 102 have entered the first finger passage 56. In the second stage of movement, the second fingers 102 enter the first finger passage 56 and locate between the angled guide faces 128 of neighbouring first fingers 101. The angled guide faces 128 provide an increased gap size between the first fingers 101 at the entrance to the first finger passage 56 to ease location of the second fingers 102 between the first fingers 101. After the second stage of movement, the bumps 54 are still located just in front of (ie, above) the sloping cam surfaces 50; and the pins 62 are still in a lower part of the slots 64. Figs. 5A and 5B show the core 16 in a third intermediate condition after a third stage of movement. The apparatus 10 includes a second finger axial movement limit 118 comprising a limit surface 66 which is located below the surface of the base wall 22. Each of the second fingers 102 includes a laterally and outwardly extending second finger axial movement stop projection 74. As shown in Fig. 5A, the second fingers 102 move until the second finger axial movement stop projection 74 engages the second finger axial movement limit surface 66, which prevents further upward axial movement of the second fingers 102. Each of the first fingers 101 has a top end face 76 and each of the second fingers 102 has a top end face 78. After the third stage of movement, as shown in Fig. 5B, the top end faces 78 of the second fingers 102 are now level with the top end faces 76 of the first fingers 101. However, the second fingers 102 are located partially laterally inwardly of the first fingers 101, as shown in plan view in Fig. 7B. At this stage, the bumps 54 are still located just in front of (ie, above) the sloping cam surfaces 50; and the pins 62 are still in a lower part of the slots 64. Figs. 6A and 6B show the core 16 in the expanded condition after a fourth and final stage of movement. With the second fingers 102 locked against further upward axial movement by the limit surface 66, the second finger actuator 40 continues to move upwardly along the longitudinal axis 28, pushing the second finger actuator member 44 with the sloping cam surfaces 50 upwardly along the longitudinal axis 28. The sloping cam surfaces 50 engage the bumps 54, causing the second fingers 102 to move laterally outwardly (as indicated by arrows B in Fig. 7B) between the first fingers 101 to the expanded condition. In the expanded condition, the bumps 54 are located on the flat surfaces 52 of the cam formations 48. The second finger actuator 40 includes a second finger actuator stop surface 140. The second fingers 102 include a second finger actuator movement limit 58. As shown in Fig. 5A, the second finger actuator 40 moves until the second finger actuator stop surface 140 engages the second finger actuator movement limit 58, which prevents further upward axial movement of the second finger actuator 40. It will also be noted that in this stage the pins 62 have moved along to an upper end of the slots 64. The engagement of the pins 62 in the slots 64 thus provides a limit to further upward axial movement of the second finger actuator 40. The slots 64 are angled inwardly upwardly to accommodate the upward movement of the second finger actuator 40 and the outward movement of the second fingers 102. In the expanded condition, the top surface of the second finger actuator member 44 is substantially level with the top end faces 76, 78 of the first fingers 101 and the second fingers 102. Figs. 7A, 7B and 7C show in more detail the shape of the first fingers 101 and the second fingers 102 and the way in which the first fingers 101 and the second fingers 102 fit together. Each of the first finger top end faces 76 has an external side 80, an internal side 82, and two end sides 84. The end sides 84 subtend an end side angle 86 with each other. The end side angle 86 is dependent on the number N of first fingers 101, such that the end side angle 86 is 3607N. Thus, when N is four, as in this example shown, the end side angle is 90°. The external side 80 subtends an outer corner angle 88 with the end sides 84. The outer corner angle 88 could be an acute angle (ie less than 90°). Each of the second finger top end faces 78 has an external side 90, an internal side 92, and two end sides 94. The end sides 94 are substantially parallel to each other. The external side 90 subtends an outer comer angle 96 with the end sides 94. The outer corner angle 96 is an obtuse angle (ie greater than 90°). Each second finger top end face external side 90 and internal side 92 is arcuate and the sides 90, 92 are concentric. Each of the first and second finger top end face external sides 80, 90 has a radius of curvature. The radius of curvature of each first finger top end face external side 80 is substantially the same as the radius of curvature of each second finger top end face external side 90. It is an advantage that the end sides 94 are mutually parallel as this reduces the risk of the second fingers 102 becoming jammed while moving. Referring to Fig. 7C, in the expanded condition, in plan, the core 16 has a circular cross-sectional ring shape, comprising an internal side 82 having an internal radius R1 centred on the longitudinal axis 28 and an external side 80 having an external radius R2 centred on the longitudinal axis 28, so that the sides 80, 82 form concentric circles. Each of the first finger top end faces 76 and the second finger top end faces 78 comprises a part of the ring shape and all have the same internal radius R1 and external radius R2. In the expanded condition, the second fingers 102 completely fill the expanded first finger gaps 98B, so that the expanded outer core surface 20B is substantially smooth and continuous, without gaps. With the core 16 in the expanded condition, the apparatus 10 continues to apply heat and pressure to the carcass 18 to bring the carcass 18 up to the holding temperature and pressure, and then hold the carcass at the holding temperature and the holding pressure for a predetermined holding time period. After the predetermined holding time has elapsed, the pressure is lowered to permit release of the formed sleeve from the mould cavity. The apparatus of the invention has been found to achieve a compression ratio of 30% ie the wall thickness of the formed sleeve is 30% of the wall thickness of the carcass. It is advantageous that the outer core surface 20 is without gaps, being substantially smooth and continuous in the expanded condition. Otherwise, when temperature and pressure is applied by the core 16 to the carcass 18, material of the carcass 18 could be squeezed into any gaps, spoiling the formed sleeve and fouling the core 16. Advantageously, the compression moulding apparatus 10 of the invention does not require a sacrificial bladder or airbag. Compared to conventional methods, the process of the present invention is more reliable, requires less maintenance and produces more consistently sized formed sleeve of better quality. Advantageously, the use of a mechanical core enables electrical heating to be utilised rather than steam, improving safety and efficiency and reducing costs. The electricity can be generated by renewable sources so that greenhouse gases and global warming are reduced. The electrical heating better retains heat during demoulding and loading so that cycle times are reduced. Electrical heating means the apparatus is easier to insulate. Pressurised steam is not used so that the process is safer and insurance costs are reduced. Other Embodiments Fig. 8 shows another embodiment of the invention, many features of which are similar to those already described in relation to the embodiment of Figs 1 to 7. Therefore, for the sake of brevity, the following embodiment will only be described in so far as it differs from the embodiment already described. Where features are the same or similar, the same reference numerals have been used and the features will not be described again. Fig. 8 shows a second embodiment apparatus 210 which includes a movable spreader 104, and which holds or spreads the first fingers 101 in / to their expanded condition. The spreader 104 is mounted above the core 16 and is aligned along the longitudinal axis 28 of the core 16. The spreader 104 comprises one or more spreading surfaces 106 which are angled relative to the core longitudinal axis 28. The spreader 104 defines a spreader hole 108 which could take the form of a passage, bore or recess and which, in the expanded condition, receives a tip 44A of the actuator member 44. In use, the spreader 104 moves downwardly to engage the first fingers 101 when the core 16 is in the first intermediate condition shown in Figs. 3A and 3B. As the spreader 104 moves downwardly, the angled spreading surfaces 106 engage uppermost parts of the internal faces 134 of the first fingers 101 to ensure that the first fingers 101 have moved fully to a correct fully expanded position and are maintained in that position throughout the moulding operation. The spreader 104 is also helps reduce or prevent any flexing or movement of the upper parts of the first fingers 101 particularly when the first fingers 101 are relatively long. Otherwise, if the first fingers 101 have not fully moved to the fully expanded position, or if they move during the moulding operation, the upper parts of the first fingers 101 might slow or jam the movement of the second fingers 102. In the example shown, the spreader 104 includes a plurality of spreader projections 110 which are arranged in pairs, with each pair arranged to engage one of the first fingers 101. In another example (not shown), the number of projections arranged to engage one of the first fingers 101 could vary. Each spreader projection 110 includes one of the spreading surfaces 106. Neighbouring pairs of spreader projections 110 define gaps 112 therebetween in which the second fingers 102 are receivable in the third intermediate condition shown in Figs. 5A and 5B. In the expanded condition, the apparatus 210 defines an annular space 116 between the ends of the first and second fingers 101, 102 and the actuator member tip 44A, shown in Figs. 6A and 6B. In the expanded condition, the tip 44A is located in the spreader hole 108 and the spreader projections 110 are located in the annular space 116, providing an interlock arrangement between the upper parts of the first fingers 101, the second fingers 102, the actuator member tip 44A and the spreader 104. This helps to minimise movement of the mould parts during the heating and compression part of the process and results in an improvement in product quality. Other Modifications Various other modifications could be made without departing from the scope of the invention. The apparatus could be of any suitable size and shape, and could be formed of any suitable material (within the scope of the specific definitions herein). The various components including the mould core and the components thereof could be of any suitable size and formed of any suitable material (within the scope of the specific definitions herein). In one example, the second finger actuator 40 could include one or more additional cam formations 48 (not shown) located between the two cam formations 48 described above and each of the second fingers 102 could include additional projecting bumps 54 corresponding thereto, to provide increased stiffening of the core 16 during the heating and compression parts of the moulding process, which prevents or reduces movement and flexing of the mould parts which can result in thickness variation of the side wall of the formed sleeve. Any of the features or steps of any of the embodiments shown or described could be combined in any suitable way, within the scope of the overall disclosure of this document. Final Remarks There is thus provided suspension air spring sleeve compression moulding apparatus with a number of advantages over conventional arrangements. In particular, the apparatus is electrically heated rather than steam heated, and the core mechanism mechanically expands so that a bladder or airbag is not required. These improvements reduce power consumption, greenhouse gases, global warming effects, costs and cycle time and increase product quality and efficiency.

Claims

1. Suspension air spring sleeve compression moulding apparatus, the apparatus including:10• a mould core locatable in a cavity defined by outer mould walls,• the core being movable between a retracted condition and an expanded condition;• wherein the core includes a set of first fingers and a set of second fingers which are movable relative to each other;• the core includes an outer core surface;• in the retracted condition, only the first fingers comprise the outer core surface of the core in the cavity;• and in the expanded condition, both the first and the second fingers together comprise the outer core surface of the core in the cavity.

2. Apparatus according to claim 1, in which, in the retracted condition, only the first fingers are 5 located in the cavity; in the expanded condition, both the first and the second fingers are C\j located in the cavity.CM3. Apparatus according to claims 1 or 2, in which the core is elongate, and extends along a longitudinal axis; in moving between the retracted condition and the expanded condition, the first fingers substantially do not move along the longitudinal axis but move away from each other along a direction which is substantially normal to the longitudinal axis; the second fingers move along the longitudinal axis and also move outwardly normally relative to the longitudinal axis.25 4. Apparatus according to any of claims 1 to 3, in which, in the retracted condition, the first fingersare in relatively close proximity to one another, and define first finger gaps therebetween, and, in which, in moving from the retracted to the expanded condition, the first fingers move away from each other and the first finger gaps increase in size.30 5. Apparatus according to any of the preceding claims, in which as the core moves from theretracted condition to the expanded condition, each one of the second fingers interposes between a pair of the first fingers, so that, in the expanded condition, the second fingers alternate with the first fingers to form the outer core surface of the core.

6. Apparatus according to any of the preceding claims, in which, in the expanded condition, each first finger abuts alongside (ie in contact with) one of the second fingers on each side and vice versa so that the outer core surface is without gaps between the first and the second fingers.5 7. Apparatus according to any of the preceding claims, in which the apparatus includes a firstfinger actuator arrangement for moving the first fingers.

8. Apparatus according to any of the preceding claims, in which the apparatus includes a second finger actuator for moving the second fingers.

09. Apparatus according to claim 8, in which the second finger actuator comprises a body and an actuator member which extends from the body along a second finger passage defined by the second fingers.

10. Apparatus according to claims 8 or 9, in which the second finger actuator includes a cam arrangement; each of the second fingers includes a cam follower arrangement; in use, the cam arrangement is arranged to engage with the cam follower arrangement to move the second fingers laterally outwardly to the expanded condition.

11. Apparatus according to claim 10, in which the cam arrangement includes a plurality of spaced apart cam formations; each cam formation includes a sloping cam surface; the cam followerarrangement includes a plurality of inwardly projecting bumps; in use, the bumps engage the cam surfaces to move the second fingers laterally outwardly to the expanded condition.25 12. Apparatus according to any of claims 8 to 11, in which the second finger actuator includes aguide arrangement; the guide arrangement comprises a plurality of pins which locate in slots defined by the second fingers.

13. Apparatus according to any of the preceding claims, in which the apparatus moves from the30 retracted condition to the expanded condition in a plurality of stages; in a first stage of movement, the first fingers move laterally outwardly and the second fingers do not move; in a further stage of movement, the second fingers move upwardly but not outwardly while the first fingers do not move and as the second fingers move upwardly, each second finger locates between two first fingers; in a final stage of movement, the second fingers move outwardly35 but not upwardly to the expanded condition.2912 2514. Apparatus according to any of the preceding claims, in which each first finger comprises a top end face, which in plan is tapered in shape from the outside to the inside.

15. Apparatus according to any of the preceding claims, in which each second finger has a top 5 end face and each single finger top end face has two end sides which are substantially parallel to each other.

16. Apparatus according to any of the preceding claims, in which the apparatus includes a spreader, which is movable, and which holds or spreads the first fingers in or to their expanded 10 condition.

17. Apparatus according to claim 16, in which the spreader comprises one or more spreading surfaces; in use, the spreader surfaces contact internal faces of the first fingers.15 18. Apparatus according to claims 16 or 17 when dependent on claim 9 or any claim dependentthereon, in which the spreader defines a spreader hole which, in the expanded condition, receives a tip of the actuator member.

19. Apparatus according to claim 18, in which the spreader includes a plurality of spreader 0 projections; in the expanded condition, the apparatus defines an annular space between the ends of the first and second fingers and the actuator member tip; in the expanded condition, the tip is located in the spreader hole and the spreader projections are located in the annular space, providing an interlock arrangement.25 20. Apparatus according to any of the preceding claims, in which each first finger has a bottomend face which is wedge-shaped and tapers (ie narrows in width) inwardly.

21. Apparatus according to any of the preceding claims, in which the apparatus includes an electrical heating arrangement for heating the core and the outer mould walls.3022. Apparatus according to any of the preceding claims, in which, in use, a carcass for forming into a suspension air spring sleeve is located over the core in the retracted condition; the core is moved to the expanded condition and the carcass is heated and compressed between the core and the outer mould walls to form the suspension air spring sleeve.2Q 1 9 9^23. Apparatus according to claim 22, in which, in use, the outer core surface contacts the carcass; in use, in moving from the retracted condition to the expanded condition, the outer core surface causes the carcass to deform.5 24. Apparatus according to claims 22 or 23, in which the carcass comprises a plurality of layersof rubber compound and embedded strengthening fibres and is in the form of a sleeve which is open at the top and bottom.

25. Apparatus according to any of claims 22 to 24, in which, in use, the carcass is subjected to a 10 predetermined temperature and pressure profile, which includes stages of raising the temperature and pressure of the carcass to a holding temperature and holding pressure, and holding the carcass at the holding temperature and the holding pressure for a predetermined holding time period and then lowering the pressure.5

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