This invention relates to rolling mills and in particular, but not exclusively, to tube or profile rolling mills. Typically in tube and profile rolling mills there are a number of rolls and pairs of rolls spaced longitudinally along a forming path, the rolls being shaped to form a tube or profile from an initially flat strip, as the strip passes along the mill. Each roll has its own gearbox set to a carefully calculated ratio and is driven from that gearbox by a driven shaft. Although at manufacture, the gear ratios and roll dimensions are precisely defined, in practice these calculations are frequently invalidated by variations in material thickness and wear on the rolls. The result is that very often only one pair of rolls is travelling at the material speed and other rolls are either being pushed or. pulled along by the material. This action not only causes further wear but also leads to a substantial recirculation of energy within the unit making it inefficient and expensive to run. To date no economic solution to this problem has been discovered and indeed in many mills the drive from a number of rolls is simply disconnected because of this problem.

The lack of an adequate solution is particularly surprising in view of the fact that on a typical tube forming mill the refurbishing of worn rolls costs many

thousands of pounds per annum quite apart from the expensive down-time which occurs during the replacement of the rollers.

It is an object of the Applicant's invention to mitigate many of these difficulties.

The present invention consists in a roll forming mill having a plurality of rolls longitudinally spaced along a forming path, means for driving the rolls and free wheel means between the forming surface of a roll and the drive means.

Not all rolls in the mill need necessarily be provided with free wheels to obtain at least some of the advantage of the invention. However it is considered generally advantageous that if a free wheel is provided for one roll in a co-operating pair, there should also be a free wheel provided for the other roll of that pair.

A co-operating pair may be formed by adjacent rolls in the direction of travel of the material or by rolls which are aligned laterally to that direction. The rolls may be driven from a common shaft by respective gearboxes and the free wheel means is disposed between the forming surface of a roll and the common shaft.

• Preferably all the rolls are provided with a free wheel means which may be disposed within the gearbox, at either end of its respective drive shaft or between its ends or, alternatively; within the hub of the roll itself.

The provision of free wheel means, such as a free wheel or uni-directional clutch in any roll drive allows the roll

to free wheel as soon as the material tries to drive the roll faster than the drive shaft, thereby preventing the recirculation of energy and reducing wear. Where all the rolls are provided with free wheels the free wheels will effectively act together to achieve an even distribution of lead throughout the machine, not only reducing roll wear, but also wear on other transmission elements.

In addition to these advantages the system can easily be retrofitted to existing machines and achieves control within the introduction of expensive and unreliable electronic control feedback circuits or the like.

Although the invention has been defined above, it is to be understood that it includes any combination of the features set out above or in the following description. The invention may be performed in various ways and specific embodiments will now be described, by way of example, with reference to the accompanying drawing which i'llustrates part of a device system of a roll forming mill.

Thus a power source 10 drives a common drive shaft 11 which in turn drives respective gearboxes 12 to 15. Each of these gearboxes 12 to 15 drives a respective shaft 16 to 19 which in turn drives a respective roll 20 to 23. In each transmission link between the gear and its respective roll there is provided a free wheel or unidirectional clutch 24. The position of the free wheel or clutch 24 is not critical and it can for example be located in any one of the positions marked A,B,C or D. Any appropriate free wheel or unidirectional clutch may be used and the type employed will

depend on the power being transmitted and the roll speed for any particular roll.

Alternatively the single motor and common drive shaft, illustrated in Figure 1 of the earlier Application, may be replaced by individual motors for each roll or pairs of rolls or associated groups of rolls. Additionally or alternatively the free wheels may be in the gearboxes associated with the rolls.