GB2062243A

GB2062243A - Electric manual control apparatus

Info

Publication number: GB2062243A
Application number: GB8033476A
Authority: GB
Original assignee: Danfoss AS
Current assignee: Danfoss AS
Priority date: 1979-10-17
Filing date: 1980-10-16
Publication date: 1981-05-20
Also published as: DK410480A; SE8006623L; DE2942003A1; IT1130535B; JPS5665415A; DK148221B; FR2468154A1; ES495970A0; DE2942003C2; DK148221C; ES8106613A1; IT8068585A0; JPS6016051B2; SE443052B; FR2468154B1; GB2062243B

Abstract

An electric control apparatus for fluid-flow valves comprises a control lever 3 with a head 6 attached to one end of it, which is pivotable about an axis 5 transverse to the lever axis and which is displaceable through limited angles in opposite directions from a neutral position against returning forces provided by leaf springs 8 and 9. A device 21 provides a magnetic field and produces an electric signal in response to changes in that field, the device comprising a part which is fixed to the lever and is axially spaced from the head and another part 20 which is movable in dependence on movement of the head, relative movement between the parts changing the magnetic field. A leaf spring 14 has one end 13 operatively connected to the head, and its other end is secured near the fixed part and has a blade carrying the movable part 20. <IMAGE>

Description

SPECIFICATION Electric control apparatus The invention relates to an electric control apparatus comprising a control lever, a head which is attached to the end thereof, pivotable about an axis transverse to the lever axis and is displaceable through limited angles in both directions from a neutral position against returning forces, and a signal transmitter which is actuated by the head and emits a direction responsive electric control signal, particularly for controlling electrically controlled valves.

In a known control apparatus of this kind, the control lever can be pivoted to both sides from a neutral vertical position into a first plane to actuate a respective control potentiometer and into a second plane likewise in both directions to actuate a respective further control potentiometer.

The head which is pivoted with the thumb carries two springs which are each adapted to actuate a respective microswitch fixed in the control lever.

In this manner six different valves can be controlled which, for example, bring about the leftright movement, forward-backward movement and up and down movement in a hydraulic appliance. However, the microswitches can emit only-constant control signals whereas it is often desired that all control functions be changed continuously.

The present invention, therefore, seeks to provide a control apparatus of the aforementioned kind with which the signal transmitter actuated by the pivotable head is also adapted to emit continuously variable control signals.

According to the invention the signal transmitter is a magnetic field responsive differential sensor comprising two sensing elements which are fixed in the control lever and are mutually offset in the pivoting direction of the head and an exciter element which influences the magnetic field thereof and is movable with the aid of the head, and that at least one limb of a leaf spring is secured to the control lever near the field plates, has its opposite end mounted at the head and carries the exciter element on a lug extending alongside the limb.

With the aid of the differential sensor mounted in this manner, it is possible despite the limited space available in the handle of a control lever to provide a control signal which can vary depending on the pivotal angle of the head, i.e. continuously.

The leaf spring here serves as a transmission element which adapts the deflection of the exciter element necessary for producing a certain signal size to the actual pivotal motion of the head. The exciter element can for example be a permanent magnet or, if the magnetic potential is produced at a different position, a simple soft iron member.

Desirably, the leaf spring has two limbs and the lug is disposed between these limbs. This produces a symmetric construction which operates very accurately.

Preferably, the lug is shorter than the limb(s).

This leads to a step-down transmission of the pivotal motion of the head so that comparatively large pivotal angles of the head are possible which facilitate a fine control but the motion of the exciter element nevertheless corresponds to the usual sizes of a differential sensor used for this purpose.

Further, the length of the limb(s) should be no more than 75%, preferably about 60%, of the length of the leaf spring. Between the root of the limb(s) or the lug and the opposite terminal edge of the spring there therefore remains a comparatively long length of spring which exhibits no interruptions and is therefore comparatively stiff. This is a particularly easy way of setting the transmission ratio.

Preferably, the sensing elements of the magnetic field responsive differential sensor are field plates. This provides a very compact construction.

Preferably, the exciter element is in this case a soft iron member and the field plates are unified with a permanent magnet. The soft iron member can be comparatively small so that it will not be difficult to secure it to the lug. The relatively larger permanent magnet is fixed in the control lever and thus there are no accommodation problems.

In a very economical solution, the sensing elements of the magnetic field responsive differential sensor are Hall generators.

In a further alternative, the sensing elements of the magnetic field responsive differential sensor are induction coils.

The present invention also provides an electric control apparatus for fluid-flow valves comprising a control lever; a head which is attached to one end of the lever, which is pivotable about an axis transverse to the lever axis and which is displaceable through limited angles in opposite directions from a neutral position against returning forces; a device which provides a magnetic field and which produces an electric signal in response to changes in that field, the device comprising a part which is fixed to the lever and is axially spaced from the head and another part which is movable in dependence on movement of the head, relative movement between the parts changing the field; and a leaf spring which has one end operatively connected to the head, which has at least one limb the end of which is secured near the fixed part and which has a blade extending alongside the limb and carrying the movable part.

An electric control apparatus constructed in accordance with the invention will now be described, by way of example, with reference to the accompanying drawing, wherein: Fig. 1 is a side elevation of the electric control apparatus; Fig. 2 is a vertical section through the handle of the control lever in Fig. 1; Fig. 3 is a side elevation of a leaf spring used in Fig. 2; Fig. 4 is a side elevation of the lower portion of a differential sensor used in Fig. 2, and Fig. 5 is a plan view of Fig. 4.

Referring to the accompanying drawings, the electric control apparatus 1 in Fig. 1 comprises a control lever 3 provided with a handle 2. The latter is pivotable about an axis 4 perpendicular to the plane of the drawing as well as about an axis perpendicular to that plane. During the first mentioned pivotal motion, one can for example actuate two potentiometers for the forwards and backwards motion of a hydraulic appliance (not shown). During the second mentioned pivotal motion, one can for example actuate two potentiometers for the left-hand and right-hand motion of this appliance. At the end of the control lever, there is a head 6 pivotable about an axis 5, during the pivotal motion of which further continuously variable control signals can be produced, for example for the up and down motion of the appliance.The head 6 comprises an extension 7 which projects inwardly beyond the pivotal axis 5 and to the outside of which two return leaf springs 8 and 9 are applied. These are supported against abutments 10 and 11 which are mounted at a fixed location in the control lever 3. This secures the neutral position of the head 6.

The extension also comprises a knife bearing 12 in which one terminal edge 13 of a leaf spring 14 engages. It comprises two limbs 15 and 16 of which the lower ends 17 and 18 are tightly secured in the control lever 3. The lower end of a lug 19 located therebetween carries a soft iron exciter element (or pole-piece) 20 at both sides.

This exciter element is part of a field plate differential sensor 21 of which the lower portion 22 is fixed in the control !ever 3. For assembly, there is a carrier element 23 which receives the lower portion 22, carries the abutments 10 and 11 and also comprises clamping means for the limbs 15 and 16 of the leaf spring 14.

Figs. 4 and 5 show the lower portion 22 of a known magnetic field differential sensor that can be used for the present purpose. Two sensing elements 24, and 25 in the form of field plates are juxtaposed and offset in the pivotal direction of the head 6. They each consist of a semi-conductor element which changes its ohmic resistance under the influence of a magnetic field. Normally, these field plates are traversed by equally large magnetic fluxes produced with the aid of a permanent magnet 26. This magnetic flux is reversed when the exciter element 20 moves out of the central position between the sensing elements. If these sensing elements are disposed in two branches of an ohmic bridge, one can, depending on the motion of the exciter element 20, derive a sinusoidal control voltage which is almost proportional to the pivotal angle to both sides of the neutral position.Lugs 27, 28 and 29 serve to connect the required conductors. The top of the sensing elements is covered by a protective layer.

During operation, if the head 6 is swung clockwise (as seen in Fig. 2) the knife edge 12 is displaced to the left in Fig. 2 whereby the leaf spring 14 is bent. The predominant part of this bending takes place in the limbs 1 5 and 16. Since the lug 1 9 does not participate in this bending, it projects from the leaf spring 14 at the right-hand side. With the illustrated spring configuration, therefore, the exciter element 20 moves to the right. For example, displacement of the knife edge bearing 12 by 4 mm results in opposite displacement of the exciter element 20 of about 0.6 mm. This control is very accurate because the exciter element 20 is fixed to the lug and there is no detrimental play at any position of the system.

The transmission ratio can be simply changed in that the slots between the limbs 15, 1 6 and the lug 19 are altered.

The sensing elements 24 and 25 need not be field plates but can be Hall generators (Hall-effect devices) or induction coils.

Claims

1. An electric control apparatus for fluid-flow valves comprising a control lever; a head which attached to one end of the lever, which is pivotable about an axis transverse to the lever axis and which is displaceable through limited angles in opposite directions from a neutral position against returning forces; a device which provides a magnetic field and which produces an electric signal in response to changes in that field, the device comprising a part which is fixed to the lever and is axially spaced from the head and another part which is movable in dependence on movement of the head, relative movement between the parts changing the field; and a leaf spring which has one end operatively connected to the head, which has at least one limb the end of which is secured near the fixed part and which has a blade extending alongside the limb and carrying the movable part.

2. A control apparatus as claimed in claim 1, in which the fixed part comprises two elements which are equispaced from, and lie on opposite sides of a plane containing the said axes.

3. A control apparatus as claimed in claim 1 or claim 2, wherein the leaf spring comprises two limbs and the blade is disposed between those limbs.

4. A control apparatus as claimed in any one of claims 1 to 3, wherein the blade is shorter than the limb(s).

5. A control apparatus as claimed in any one of claims 1 to 4, wherein the length of the limb(s) is no more than 75%, of the total length of the leaf spring.

6. A control apparatus as claimed in any one of claims 1 to 5, in which the length of the limb(s) is about 60% of the total length of the leaf spring.

7. A control apparatus as claimed in any one of claims 1 to 6, wherein the fixed part comprises field plate(s).

8. A control apparatus as claimed in any one of claims 1 to 6, wherein the fixed part comprises Hall-effect device(s).

9. A control apparatus as claimed in any one of claims 1 to 6, wherein the fixed part comprises induction coil(s).

10. A control apparatus as claimed in any one of claims 7 to 9, wherein the movable part is a soft iron member and the fixed part is secured to a permanent magnet.

11. An electric control apparatus comprising a control lever, a head which is attached to the end thereof, pivotable about an axis transverse to the lever axis and is displaceable through limited angles in both directions from a neutral position against returning forces, and a signal transmitter which is actuated by the head and emits a direction responsive electric control signal, particularly for controlling electrically controlled valves, characterised in that the signal transmitter is a magnetic field responsive differential sensor comprising two sensing elements which are fixed in the control lever and are mutually offset in the pivoting direction of the head and an exciter element which influences the magnetic field thereof and is movable with the aid of the head, and that at least one limb of a leaf spring is secured to the control lever near the field plates, has its opposite end mounted at the head and carries the exciter element on a lug extending alongside the limb.

12. A control apparatus substantially as hereinbefore described with reference to, and as illustrated by the accompanying drawings.