GB1571827A

GB1571827A - Tuning arrangements

Info

Publication number: GB1571827A
Application number: GB948276A
Authority: GB
Original assignee: British United Shoe Machinery Ltd
Current assignee: Noxet UK Ltd
Priority date: 1977-03-09
Filing date: 1977-03-09
Publication date: 1980-07-23

Description

(54) IMPROVEMENTS IN OR RELATING TO H.F. TUNING ARRANGEMENTS (71) We, THE BRITISH UNITED SHOE MACHINERY COMPAN f LIMITED, a British Company of Union Works, Belgrave Road in the City of Leicester, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed; to be particularly described in and by the following statement: This invention is concerned with H.F.

tuning arrangements by which the frequency at which an H.F. machine will operate can be tuned to the output frequency of an H.F. generator connected to said machine. By the phrase "an H.F.

machine" is to be understood any machine which carries out an operation on a workpiece utilising high frequency electrical energy; examples of such machines are H.F. welding presses and H.F. embossing machines.

So-called "inductance tuning" arrangements are already available for use with certain commercially available H.F. generators. Such an inductance tuning arrangement comprises two tuning elements one of which is connected in a circuit including also a generator output and a machine input, and between which elements relative movement can take place so as to vary the amount of overlap between the two elements, whereby the inductance of said circuit, and thus the frequency at which the press will operate, can be varied. In such an arrangement, said one tuning element is usually in the form of a loop having a generally circular configuration while the other of said elements is usually a co-operating circular core, relative movement therebetween being achieved by moving the core along a generally linear path relative to the loop.

For moving the core in the above manner, various proposals have been made.

In one instance, it was proposed to use a piston and cylinder arrangement of the so-called rolling diaphragm type, the desired tuning being achieved by pre-setting the fluid pressure to be exerted on the piston and cylinder arrangement against the influence of spring means, the fluid pressure being correlated to a desired power output to be applied in the machine. In another instance, the position of the moving core was proposed to be determined according to a pre-setting for the anode current of the H.F. generator, which current again was correlated to a desired power output.

Whichever proposal is followed, the occasion may arise when a particular die being used causes the movable core to be positioned in relation to the loop in such a manner that the overlap therebetween is minimal, that is to say the core is just about to leave, or has just left, a condition of overlap. When the core and loop are in an overlapping condition, varying the amount of such overlap is effective to cause the inductance of the circuit to be similarly varied in a predictable manner.

When, however, the core and loop achieve the minimal overlap condition referred to above, the tuning becomes unpredictable.

This situation is exacerbated where the edges of the core and loop are parallel one with another, as indeed is usually the case, in that the transition from a state of some overlap to a state of no overlap is instantaneous.

It is one of the various objects of the present invention to provide an improved H.F. tuning arrangement in which the problems arising from the aforementioned minimal overlap condition are substantially eliminated.

The invention provides an H.F. tuning arrangement by which the frequency at which an H.F. machine will operate can be tuned to the output frequency of an H.F. generator connected to said machine, said arrangement comprising two tuning elements one of which is connected in a circuit including also a generator output and a machine input, and between which elements relative movement can take place in a linear path so as to vary the amount of overlap between the two elements, whereby the inductance of said circuit, and thus the frequency at which the machine will operate, can be varied, wherein the edge of at least one of the said elements, which edge first overlaps an edge of the other of said elements when relative movement takes place along the linear path between the elements to bring them from a non-overlapping to an overlapping condition, is inclined at an angle to a plane which extends normal to said linear path.

If desired, the edges of both of said elements can be so inclined, in which case, however, the situation in which a plane passing through the edge of one of said elements is coincident with a plane passing through the edge of the other of said elements, that is to say the edges are parallel, should be avoided, since this condition represents a minimal overlap condition similar to that achieved by an arrangement where the edges are not inclined.

It will be appreciated that, by providing an edge of the element which is inclined at an angle to a plane which extends normal to the linear path, the instantaneous transition from a non-overlapping to an overlapping condition no longer takes place, with the result that the tuning variation can be made smoothly and predictably. Where one element of the arrangement is constituted by a loop having a generally circular configuration which is fixed and movement relative thereto is achieved by moving the other element, which preferably is in the form of a co-operating circular core, for achieving relative movement in a linear path as aforesaid, the core is conveniently supported on a rod or similar support member of insulating material, which rod or similar support member can be moved thus to move the core.

Preferably motor drive means is provided by which relative movement between the two tuning elements can be effected.

Such means may comprise a piston and cylinder arrangement of the so-called rolling diaphragm type, in which the fluid pressure applied thereto is pre-set according to the power requirements for the workpiece to be operated upon. Alternatively, the motor drive means may comprise an electric motor which is driven under the control of sensing means responsive to the current at the anode of the generator oscillator valve, the desired anode current being correlated to the power requirement for the workpiece to be operated upon and being pre-set accordingly. Furthermore, as a safety measure, limit switches may be provided for limiting the amount of relative movement between the two tuning elements.

The tuning element in the circuit, that is to say the loop, is preferably made from a strip of copper, and similarly the other element, that is to say the core, is made from a strip of copper forming a cylinder; the cylinder is mounted on a cylindrical centre made from an insulating material.

Tuning arrangements in accordance with the invention may be produced as separate items for attaching to an H.F.

generator or between an H.F. generator and an H.F. machine. Alternatively. the arrangement may form an integral part of a generator, and thus the invention further provides an H.F. generator which includes an H.F. tuning arrangement as set out hereinbefore.

Alternatively, the tuning arrangement may form part of an H.F. installation which also comprises an H.F. generator and an H.F. machine as an integral unit.

To illustrate the invention, there is hereinafter described in detail, with reference to the drawings accompanying the provisional specification, one H.F. tuning arrangement (hereinafter called "the illustrative arrangement"). It will be appreciated that this illustrative arrangement has been selected for description merely by way of exemplification of the invention and not by way of limitation thereof.

In the drawings accompanying the provisional specification: Figure 1 is a perspective view, with parts broken away, of the illustrative arrangement; and Figure 2 is a fragmentary side view of a loop and core of said arrangement.

The illustrative arrangement shown in the drawings is mounted on the top of a generator 10, a cover 12 being provided for shrouding the arrangement, together with a lid (not shown).

The illustrative arrangement comprises an inductor in the form of a loop 14, made from a strip of copper, which is mounted on two copper strips 16, 18. The strip 16 is secured on two capacitors C1, C2 (which form part of the tuning circuit and are in series with the platens of an H.F. machine to which the illustrative arrangement is coupled), the capacitors being supported on a base plate 20 of the arrangement. The other strip 18 is supported on a block 22 of insulating material, e.g. polypropylene, the block being itself supported also on the base plate 20. Secured to the strip 18 is a connecting strip 24 by which the inductor is operatively connected to the platens (not shown) of the H.F.

machine.

For coupling the generator to the illustrative arrangement, a coil (not shown) is provided which projects into the generator and ends 26, 28 of which project through the top 10 of the generator. A first connection 30, of predetermined length, extends from the end 26 to the plate 18, while a second connection 32 extends from the other end 28 to the plate 16. Thus, a circuit from the coil in the generator is made which includes also the inductor 14 and the lead strap 24 to the platens of the machine.

The base plate 20 carries two posts 34, one at either side of the loop 14. Each post 34 carries a set of rollers 36 between which is mounted for movement in a linear path a rod 38 made of polypropylene.

The rod, which extends outside the cover 12 at one end, carries towards its centre a cylindrical body 39 of "Tufnol" ("Tufnol" is a registered Trade Mark) and this body 39 carries about its periphery a cylindrical strap 40 of copper constituting a core of the illustrative arrangement.

For moving the rod in a linear path, a motor 42 is provided mounted on a bracket 44 on the outside of the cover 12 and the motor has a drive spindle 46 which is connected to the rod 38, rotation of the drive spindle 46 being effective to move the rod linearly. For limiting the movement of the rod, two microswitches MS1 and MS2 are mounted also on the bracket 44 and the rod is provided with a camming face 48 by which the switches can be operated.

The edge 50 (see Figure 2) of the core 40 of the illustrative arrangement lies in a plane which is inclined at an angle of 5" to the plane which extends normal to the axis of the rod 38 (and thus to the direction of movement of the core 40).

Similarly, the edge 52 of the loop 14 lies in a plane which is inclined, in an opposite direction, also at an angle of 5 to the plane which extends normal to the axis of the rod 38. Thus, as the core moves, together with the rod 38, from a position in which it does not overlap the loop 14 to a position in which it does overlap it, the overlapping relationship begins over a relatively small area and progressively extends along the length of each edge 50, 52. In this way, the inductance of the circuit of which the loop forms part is progressively but smoothly varied, and thus also the frequency at which the H.F.

machine will operate is varied.

The body 39 on which the core 40 is mounted is secured on the rod 38 by means of a clamp screw 54, so that the core is capable of being rotated about the axis of the rod 38 and relative thereto. In this way, the overlap condition between the core 40 and the loop 14 can also be varied, thus also to vary the inductance of the circuit and therewith the frequency at which the H.F. machine will operate. In using the illustrative arrangement, the intention is that the position of the core radially in relation to the loop 14 will be a factory setting as opposed to an operator setting, and the operator will rely on axial movement of the core relative to the loop in order to tune the circuit according to the workpiece to be operated upon.

For controlling the operation of the motor by which the rod 38 is driven, the illustrative arrangement utilises sensing means (not shown) sensitive to the anode current of the oscillator valve of the generator, the arrangement being such that the operator selects a desired power output to be applied to the workpiece to be operated upon, and this power output is correlated to a given anode current which is achieved, in the operation of the illustrative arrangement, by the positioning of the core 40 relative to the loop 14, the motor serving to maintain the anode current at the desired level, and thus maintain the desired power output, during the whole of the application of the H.F.

energy to the workpiece.

The illustrative arrangement may be made available as an independent unit for attachment to an H.F. generator, or alternatively it may be supplied as an integral part of an H.F. generator.

WHAT WE CLAIM IS:- 1. An H.F. tuning arrangement by which the frequency at which an H.F.

machine will operate can be tuned to the output frequency of an H.F. generator connected to said machine, said arrangement comprising two tuning elements one of which is connected in a circuit including also a generator output and a machine input, and between which elements relative movement can take place in a linear path so as to vary the amount of overlap between the two elements, whereby the inductance of said circuit, and thus the frequency at which the machine will operate, can be varied, wherein the edge of at least one of said elements, which edge first overlaps an edge of the other of said elements when relative movement takes place along the linear path between the elements to bring them from a nonoverlapping to an overlapping condition, is inclined at an angle to a plane which extends normal to said linear path.

2. An arrangement according to Claim 1 wherein the edges of both of said ele

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. strip 18 is a connecting strip 24 by which the inductor is operatively connected to the platens (not shown) of the H.F. machine. For coupling the generator to the illustrative arrangement, a coil (not shown) is provided which projects into the generator and ends 26, 28 of which project through the top 10 of the generator. A first connection 30, of predetermined length, extends from the end 26 to the plate 18, while a second connection 32 extends from the other end 28 to the plate 16. Thus, a circuit from the coil in the generator is made which includes also the inductor 14 and the lead strap 24 to the platens of the machine. The base plate 20 carries two posts 34, one at either side of the loop 14. Each post 34 carries a set of rollers 36 between which is mounted for movement in a linear path a rod 38 made of polypropylene. The rod, which extends outside the cover 12 at one end, carries towards its centre a cylindrical body 39 of "Tufnol" ("Tufnol" is a registered Trade Mark) and this body 39 carries about its periphery a cylindrical strap 40 of copper constituting a core of the illustrative arrangement. For moving the rod in a linear path, a motor 42 is provided mounted on a bracket 44 on the outside of the cover 12 and the motor has a drive spindle 46 which is connected to the rod 38, rotation of the drive spindle 46 being effective to move the rod linearly. For limiting the movement of the rod, two microswitches MS1 and MS2 are mounted also on the bracket 44 and the rod is provided with a camming face 48 by which the switches can be operated. The edge 50 (see Figure 2) of the core 40 of the illustrative arrangement lies in a plane which is inclined at an angle of 5" to the plane which extends normal to the axis of the rod 38 (and thus to the direction of movement of the core 40). Similarly, the edge 52 of the loop 14 lies in a plane which is inclined, in an opposite direction, also at an angle of 5 to the plane which extends normal to the axis of the rod 38. Thus, as the core moves, together with the rod 38, from a position in which it does not overlap the loop 14 to a position in which it does overlap it, the overlapping relationship begins over a relatively small area and progressively extends along the length of each edge 50, 52. In this way, the inductance of the circuit of which the loop forms part is progressively but smoothly varied, and thus also the frequency at which the H.F. machine will operate is varied. The body 39 on which the core 40 is mounted is secured on the rod 38 by means of a clamp screw 54, so that the core is capable of being rotated about the axis of the rod 38 and relative thereto. In this way, the overlap condition between the core 40 and the loop 14 can also be varied, thus also to vary the inductance of the circuit and therewith the frequency at which the H.F. machine will operate. In using the illustrative arrangement, the intention is that the position of the core radially in relation to the loop 14 will be a factory setting as opposed to an operator setting, and the operator will rely on axial movement of the core relative to the loop in order to tune the circuit according to the workpiece to be operated upon. For controlling the operation of the motor by which the rod 38 is driven, the illustrative arrangement utilises sensing means (not shown) sensitive to the anode current of the oscillator valve of the generator, the arrangement being such that the operator selects a desired power output to be applied to the workpiece to be operated upon, and this power output is correlated to a given anode current which is achieved, in the operation of the illustrative arrangement, by the positioning of the core 40 relative to the loop 14, the motor serving to maintain the anode current at the desired level, and thus maintain the desired power output, during the whole of the application of the H.F. energy to the workpiece. The illustrative arrangement may be made available as an independent unit for attachment to an H.F. generator, or alternatively it may be supplied as an integral part of an H.F. generator. WHAT WE CLAIM IS:-

1. An H.F. tuning arrangement by which the frequency at which an H.F.

2. An arrangement according to Claim 1 wherein the edges of both of said ele

ments are inclined at an angle to a plane which extends normal to said linear path, but wherein said edges are other than parallel one with the other.

3. An arrangement according to either one of the preceding Claims where the two tuning elements are constituted by a loopand-core arrangement.

4. An arrangement according to any one of the preceding Claims wherein one of the elements is fixed and the other movable relative thereto, the movable element being supported on a support member of insulating material.

5. An arrangement according to Claim 3 wherein the loop is fixed and the core is movable relative thereto, said core being supported on a support member of insulating material.

6. An arrangement according to any one of the preceding Claims comprising motor drive means by which relative movement between the two tuning elements can be caused to take place.

7. An arrangement according to Claim 6 wherein said drive means comprises a piston and cylinder arrangement of the socalled rolling diaphragm type.

8. An arrangement according to Claim 6 wherein the drive means comprises an electric motor which is driven under the control of sensing means responsive to the current at the anode of the oscillator valve of the generator.

9. An arrangement according to any one of the preceding Claims wherein limit switches are provided for limiting the amount of relative movement between the two tuning elements.

10. An H.F. tuning arrangement constructed, arranged and adapted to operate substantially as hereinbefore described with reference to the drawings accompanying the provisional specifications.

11. An H.F. generator which includes an H.F. tuning arrangement according to any one of the preceding claims.