GB2259262A

GB2259262A - Blade control system

Info

Publication number: GB2259262A
Application number: GB9118801A
Authority: GB
Inventors: Rodney David Greenough; Alan G I Jenner; Anthony James Wilkinson
Original assignee: University of Hull
Current assignee: University of Hull
Priority date: 1991-09-03
Filing date: 1991-09-03
Publication date: 1993-03-10
Anticipated expiration: 2011-09-03
Also published as: GB2259262B; GB9118801D0

Abstract

A blade control system includes a number of magnetostrictive rods (9) arranged so as to change the profile of a blade (5). Preferably, each rod is held under a compressive force by a spring (11). Application of a magnetic field on the rods causes their expansion or contraction thus changing the blade profile. <IMAGE>

Description

BLADE CONTROL SYSTEM This invention relates to blade control systems. The invention has particular, although not exclusive relevance, to blade control systems for controlling the profile of coating blades. Such coating blades are used, for example, in the floor coverings industry to produce layers of, for example, linoleum. As it is very important to be able to control the thickness of the liquid linoleum while it is being spread, it is necessary to use a blade control system to adjust the profile of the coating blade.

In known blade control systems the necessary blade control is achieved by connecting thermal bolts between a fixed yoke and various points along the blade. The thermal bolts are heated, or cooled, to produce expansion or contraction of the bolts, thereby altering the transverse forces acting on the blade and thus changing the profile of the blade. This will be necessary, for example to correct a blade having a naturally corrugated form.

It is an object of the present invention to provide an alternative form of blade control system, which does not require the use of heat.

According to the present invention there is provided a blade control system including at least one body of magnetostrictive material effective to change the profile of a blade when a magnetic field is applied to the magnetostrictive body.

Preferably, the blade control system includes means effective to keep the magnetostrictive body under a compressive force. The compressive force means is suitably a spring means.

Preferably, there are a plurality of magnetostrictive bodies each effective to change the profile of the blade at a different point along the length of the blade.

Each magnetostrictive body is suitably made of dysprosium terbium iron alloy. A suitable alloy is Terfenol.

One blade control system, in accordance with an embodiment of the invention, will now be described, by way of example only, with reference to the accompanying drawings in which: Figure 1 is a schematic diagram of a blade control system in accordance with the invention shown with a blade incorporated; Figure 2 is a detail of the blade control system of Figure 1 illustrating schematically the principle of operation of the system; and Figure 3 illustrates the magnetic field against strain characteristics of the magnetostrictive material incorporated in the system of Figure 1.

Referring firstly to Figure 1, the blade control system to be described incorporates a fixed yoke 1 which is rigidly mounted on a machine bed 3. A coating blade 5 is connected to the fixed yoke 1 by means of six actuators 7.

Referring now also to Figure 2, each actuator 7 comprises a magnetostrictive rod of Terfenol 9 of typical composition Dy0 7Tbo 3Fel 95 Across each rod 9 there is connected a respective flat coil spring 11, effective to provide a compressive uniaxial pressure across the bar 9, this compressive pressure being necessary to obtain sufficient expansions of the rods 9 as will be described in more detail hereafter.

In use of the blade control system, suitable magnetic fields are applied to the actuators 7 such that expansion or contraction of the actuators 7 causes forces to be exerted on the blade 5 sufficient to change the profile of the blade to the required form. It will be appreciated that the change of the profile of the blade 5 will generally be achieved by some of the actuators 7 pushing on the blade 5, while others pull on the blade 5, this being illustrated in Figure 2. If the blade profile at a particular point is changed by pulling with an actuator 7, the relevant spring 11 must be sufficiently strong to put the associated Terfenol rod 9 under a compressive force and to pull the blade 5 towards the yoke 1.If, however, the blade profile at any particular point is to be changed by pushing with an actuator 7, the relevant Terfenol rod 9 must be of sufficient diameter such that by application of the necessary magnetic field, a force will be generated which not only acts against the compressive force of the associated spring, but deforms the blade 5. The springs 11 will therefore, be designed to have a very high spring constant so as to enable the blade 5 to be pulled towards the yoke 1 when necessary. The springs 11 will, however, be long enough such that the displacement of any particular spring does not significantly affect the forces acting on adjacent springs. In particular net tensile forces acting on the rods 9 must be avoided, as Terfenol does not exhibit magnetostrictive properties when acting under a tensile stress.

Referring now to Figure 3, this Figure illustrates the variation in strain produced in the magnetostrictive rods 9 with applied field, for different values of pressure applied by the springs 11 to the rods 9. In order to obtain a working strain range of between 250 ppm and 750 ppm for the Terfenol rods, with the necessary applied magnetic field strengths being of up to about 25 kA/m which are readily available, it will be necessary for the springs 11 to apply a compressive force of between 8 and 14 MPa to the rods 9.

It will be appreciated that other materials, other than Terfenol, may be used for the rods 9. Such materials will, however, normally also comprise rare earth iron compounds, or alloys.

It will also be appreciated that whilst the springs 11 are shown connected across the end of the actuator rods 9, other spring configurations which will produce the necessary compressive forces on the rods 9 may also be used.

Claims

1. A blade control system including at least one body of magnetostrictive material effective to change the profile of a blade when a magnetic field is applied to the magnetostrictive body.

2. A blade control system according to claim 1, including means effective to keep the magntostrictive body under a compressive force.

3. A blade control system according to claim 2, in which the compressive force means is a spring means.

4. A blade control system according to claim 3, in which the spring means comprises a compression spring connected across the magnetostrictive body.

5. A blade control system according to any of the preceding claims, in which the magnetostrictive body is made of a rare earth iron alloy.

6. A blade control system according to claim 5, in which the magnetostrictive body is made of dysprosium terbium iron alloy.

7. A blade control system according to claim 6, in which the alloy is Terfenol.

8. A blade control system according to any one of the preceding claims, including a plurality of said magnetostrictive bodies, each effective to change the profile of the blade at a different point along the length of the blade.

9. A blade control system substantially as hereinbefore described with reference to the accompanying drawings.