There are devices for continuous manufacture of endless tubular articles from reinforced polymers and other materials (eg. fibreglass pipes etc.).

They all employ different means of pulling the pipe off the mandrel while the pipe is being manufactured. For example, one previous device [USSR patent No. 234650] proposes mounted into a rotating single-piece mandrel push rods fitted with self-gripping eccentrics on their ends. This proposal has the limitation that the pipe being manufactured must meet certain minimum axial and radial strength requirements to ensure its integrity while in the process of pulling it off the mandrel. The reason for this requirement lies in the fact that, in order to pull the pipe off the mandrel the self-gripping eccentrics which are in tangential contact with the inner surface of the pipe push against the inner surface of the pipe while moving forward. This imposes restrictions on the minimum permissible pipe wall thickness and the structure of the pipe wall. Furthermore, the device being described has inherent limitations of the production speed of the manufacturing process as an increase in the length of the mandrel causes a corresponding increase in the forces needed to be applied by the self-gripping eccentrics in order to pull the pipe off the mandrel. This results in the fact that, when some critical maximum mandrel length is reached it is impossible to ensure the integrity of the pipe being pulled by eccentrics off the mandrel.

Another previous device [USSR patent No. 106359] proposes a mandrel consisting of individual longitudinal elements (segments) concurrently reciprocally moving along the longitudinal axis thereof in such a way that each of the segments makes a cycle of movement comprising of a slow working stroke forward and an alternate quick return to the point of departure. This proposal has the disadvantage that, since the production speed of such processes is proportional to the length of the mandrel the technical difficulties of manufacturing long mandrels with a large number of segments result in a dramatic rise in the price of the mandrel. On the other hand, decreasing the number of segments leads to an increase in the surface area of each of the segments. This results in irregular feed and hence a decrease in quality of the pipe as a quickly moving back segment jerks the pipe backwards causing distortion of non-hardened (under-cured) areas of the pipe being manufactured.

These problems are overcome by the present invention, which provides a device (mandrel) for continuous manufacture of an endless hollow cylinder and tubular articles of other convex cross sections comprising a pipe- forming body manufactured with a possibility of concurrent reciprocating movement of its individual longitudinal components and an additional bearing element not being any part of the pipe-forming body, each of the individual longitudinal components of the pipe-forming body and the additional bearing element making a cycle of concurrent reciprocating movement consisting of a slow working stroke forward and an alternate quick return to the point of departure.

In one form of the invention, the device (mandrel) consists of several (eg. two) longitudinal components (segments) connected with the groove of a

cylindrical cam of the driving gear via tie rods with rollers and an additional bearing element. The additional bearing element comprises a slit bush with the inner conical surface spring-loaded to a cone at the end of a push rod.

The other end of the push rod is connected with the groove of the cylindrical cam of the driving gear via a tie rod with a roller.

To assist with understanding the invention, reference will now be made to the accompanying drawings which show one example of the invention.

In the drawings: FIG. 1 shows the proposed device (mandrel) with two segments connected to a driving gear, and an additional bearing element.

FIG. 2 shows the pipe-forming part of the mandrel with tie rods and the additional bearing element.

Referring to FIG. 1 it can be seen that the device for continuous manufacture of an endless hollow cylinder and tubular articles of other convex cross sections comprises a pipe-forming body 9 with an additional bearing element 19. The devise is connected to driving gear comprising a console driving shaft 1 which is secured in supports 2 and has a gear wheel 3 on one end. On the other end of the driving shaft there are a cylindrical cam 4 and a crown bush 5 in the slots of which the tie rods 6 of the segments 7 and the push rod 8 are moving. Rotation from a drive is transferred to the pipe-forming body 9 via the shank 10 of the driving shaft 1.

Segments 7 represent the two halves of a cut-along-the-axis cylinder with a full length groove on their inside surfaces and tie rods 6 attached to one of

their ends. The shank 10 of the driving shaft 1 comes into the internal cavity 11 formed by the two grooves of the segments 7. Components 12 are press- fitted into the groove of one of the segments 7. The groove of the other segment is slightly wider than that of the first one so that the segment moves over the side surfaces of the components 12 with guaranteed clearance. A push rod 8 moves freely inside the apertures of the components 12. The tail end of the push rod comes out through the slot in the shank 10 of the driving shaft 1 and connects with its tie rod. On the other end of the push rod there is a cone 13 to which a slit bush 15 with inner conical surface is spring-loaded with a spring 14.

FIG. 2 shows a close-up of the pipe-forming body with its tie rods with rollers and the additional bearing element with its push rod, tie rod, and the roller. The rollers 16 of the tie rods 6 of the segments 7 are situated in the feeding side of the groove of the cylindrical cam 4, and the roller 17 of the tie rod 18 of the push rod 8 is in the return side of the groove. The outer surface of the slit bush 15 is in slight contact with the inner surface of the pipe being manufactured.

The rollers 16 of the tie rods 6 of the segments 7 are moving in the feeding side of the groove of the cylindrical cam 4 and the segments 7 are moving forward in the direction towards the additional bearing element 19. At the same time, the roller 17 of the push rod 8 is moving in the return side of the groove of the cylindrical cam 4 causing the cone 13 and hence the slit bush 15 to move in the direction opposite to the travel of the segments 7. As the consequence of this, the load applied by the cone 13 to the inner surface of the slit bush 15 reduces which results in the decrease in the outer diameter of the bush 15. This, in turn, results in the bush 15 disengaging from the

contact with the inner surface of the pipe. The pipe is now being carried forward and off the pipe-forming body 9 by the segments 7 on their working stroke forward.

When the roller 16 of one of the segments 7 comes into the return side of the groove of the cylindrical cam 4 it causes its corresponding segment to start quickly moving back to its point of departure. At this time the roller 17 of the tie rod 18 of the push rod 8 enters the feeding side of the groove of the cam, causing the push rod move forward in the direction of the additional bearing element 19. The cone 13 applies a load to the inner conical surface of the slit bush 15 resulting in a quick increase in its outer diameter. As the consequence of this the bush 15 engages in firm contact with the inner surface of the pipe being manufactured. The pipe is now being carried forward and off the pipe-forming body 9 by both the additional bearing element 19 and one of the segments 7 on their working stroke forward. Any attempt of the pipe to move back with the moving back segment causes further increase in the pressure applied by the outer surface of the slit bush 15 of the additional bearing element 19 to the inner surface of the pipe supporting the pipe and enhancing its movement forward.

It will be realised that the device for continuous manufacture of an endless hollow cylinder and tubular articles of other convex cross sections according to this invention is not restricted to the form of pipe-forming body with additional bearing element shown in the example, but may use any other suitable arrangement which does not require the additional bearing element to be any part of the pipe-forming body of the device.