GB2084252A

GB2084252A - Improvements in or relating to adjusting drive devices

Info

Publication number: GB2084252A
Application number: GB8030119A
Authority: GB
Original assignee: Elektrowatt AG
Current assignee: Siemens Building Technologies AG
Priority date: 1979-10-02
Filing date: 1980-09-18
Publication date: 1982-04-07
Also published as: SE443844B; CH640610A5; GB2084252B; DE3034294A1; FR2466653B1; FR2466653A1; SE8006335L

Abstract

A hydraulically actuated member (24) for adjustably driving an element (26) which is displaceable against spring-biasing (28) is supplied with operating fluid by a pump 21 driven by an electromagnet (12). In order to maintain the adjusting force, the distance over which the element can be moved, and the adjusting time independent of the force of the electromagnet (12) the latter is energised by pulses. <IMAGE>

Description

SPECIFICATION Improvements in or relating to adjusting drive devices The present invention relates to a device for moving an element against spring-biasing by means of an electromagnet. Such a device will hereinafter be referred to as an adjusting drive.

Known adjusting drives of this type have the disadvantage that their displacement force and regulating distance are modest as the regulating distance and/or the required displacement force are limited by the nature of the magnet. Thus economic and technical limits are quickly reached.

This is all the more so since on increasing size of the adjusting members, it is frequently desirable to extend the adjusting time of the adjusting drive.

Thus known adjusting drives of the above type require additional measures such as damping.

Basically hydraulic adjusting drives are also known in which a constantly driven hydraulic pump supplies a pressure fluid via a restrictor to a hydraulic working member. The flow cross-section of the restrictor, and thus the pressure drop across the restrictor, is varied, for example, electromagnetically, in response to a control signal. Such an adjusting drive has much higher limits with reference to regulating distance and/or displacement force than the previously described solely electromagnetic type. However it has the disadvantages of greater expense as it requires an auxiliary energy source to ensure the operation of the hydraulic pump and supply of pressure fluid.

Accordingly the present invention has for an object to provide an adjusting drive which apart from the control signal does not require an auxiliary energy source but which is however capable of considerably high regulating distances and/or displacement forces than can be achieved with the direct action of an electromagnet.

Accordingly the present invention consists in an adjusting drive comprising a hydraulic pump, an electromagnet operative to drive said hydraulic pump in response to a pulse control signal, and a hydraulic actuation member operative to displace an adjustable element in response to the hydraulic pump.

In order that the present invention may be more readily understood an embodiment thereof will now be described by way of example and with reference to the accompanying drawing, in which: Figure 1 is a schematic section through an adjustable drive constructed in accordance with the present invention, and Figure 2 is a schematic section through a valve unit arranged between the hydraulic pump and the actuating member of the embodiment of Figure 1.

Referring now to the drawings, Figure 1 shows an adjustable drive 10 having a magnet 12 arranged in a housing 1 , the winding 13 of the magnet 12 being supplied with an electric control signal via two lines 14, 1 5. An interrupter 1 6 which is only shown schematically is switched into the conductor 14 and this interrupter is operative to divide the control signal into pulses which are separated time-wise from each other, for example at a frequency of 1-5 hz. The winding 13 is surrounded by a magnetic interference housing 1 7 mounted in the housing 11 and in turn surrounds a plunger-type armature 1 8 which, on energisation of the winding 1 3 is pulled against the effect of spring biasing into the winding 13.Thus the force with which the plunger 1 8 is pulled depends on the voltage of the control signal.

The plunger 1 8 is connected via a rod 19 with the free end 20 of a bellows pump 21 which is filled with hydraulic fluid. The other end of the bellows pump 21 is anchored to one side of a block 22 clamped in a housing 11, the block 22 housing a valve unit 23 which is shown in greater detail in Figure 2. The end flange 25 of an adjusting element in the form of a spindle 26 is attached to the free end of a working bellows 24, the other end of bellows 24 being anchored to the other side of block 22. The adjusting spindle 26 passes through the housing 11 at 27 and its lower end is coupled to a member to be adjusted which is not shown. A spring 28 is mounted coaxially on the adjusting spindle 26 between the flange 25 and the interior of the housing 11 so as to bias the bellows 24 together.A container 29 is suspended from the block 22 within the bellows 24 and serves as a storage container or sump 29' for the hydraulic fluid. An intake pipe 30 leads to the valve unit 23 from container 29, as does a vent opening 31 which passes through the block 22 into the area outside the bellows 21.

A discharge opening 32 leads from within the bellows 21 to the valve unit 23 and from the latter a discharge opening 33 leads to the interior 34 of the bellows 24 surrounding the container 29.

In Figure 1 a return pipe 35 also leads from the valve unit 23 directly back to the container 29, whereas in Figure 2 this return pipe 35 leads via the intake pipe 30 back to the container 29.

Referring now to Figure 2 for a more detailed description of the valve unit 23, there can be seen in this figure the intake pipe 30 leading off from the container 29, the discharge opening 32 to the interior of the bellows pump 21 and the discharge opening 33 to the interior 34 of the bellows 24 surrounding the container 29.

A spring-loaded intake valve 36 is mounted between the intake pipe 30 and the discharge opening 32 and opens towards the latter. A branch 37 leads from the discharge opening 32 and houses a spring-loaded non-return valve 38 which closes backwards towards the discharge opening 32. The branch 37 leads to one end of a valve chamber 39 from the other end of which the discharge opening 33 proceeds. A piston valve 40 is mounted in the valve chamber 39 and, in its extreme position as shown in Figure 2, closes the return pipe 35, the pipe 35 being opened in the other extreme position of valve 40. This can be seen in Figure 1. A discharge opening 41 is formed in the piston valve 40 and connects the two sides of the piston valve. The opening 41 also houses a spring-loaded non-return valve 42 which opens back towards a discharge opening 43.

The piston valve 40 has a recess constriction 43 in its periphery and its end section 44, which is adjacent the branch 37 and the non-return valve 38 is a loose fit within the valve chamber 39. As will be described hereinafter hydraulic fluid can leak by section 44 when pressure at the discharge opening 33 drops. In either extreme position of the piston valve 40 this leakage fluid flows via the constriction 43 through a drainage pipe 45 and back into the container 29 via the intake pipe 30.

It is thus possible for the piston valve 40, under the action of an over-pressure from the discharge opening 33, to be pushed more or iess quickly in proportion to the amount of leaking hydraulic fluid into its other end position and thus after a delay to free the return pipe 35. if there is no adjusting signal on lines 14, 1 5 or only a signal which does not reach the control resolution of the electromagnet 12, the plunger 1 8 undergoes no lifting movement. The pressure spring 28 may thus be released as far as possible to press the bellows 24 together as far as possible.The overpressure in the interior 34 of the hydraulic fluid presses on the piston valve 40 (the non-return valve 42 is closed, and the piston then slides, due to the space between the end section 44 and the wall of the valve chamber 39 upwardly and frees the return pipe 35 so that fluid displaced from the interior 34 flows back into the container 29.

As soon as a signal occurs on the lines 14 and 15 which exceeds the control resolution of the electromagnet 12, this signal begins the cycle of the pulses generated by the interrupter 1 6 to cause working and return strokes of the plunger 1 8 and the rod 19. On each working stroke the bellows 21 is pressed together and hydraulic fluid is displaced through the discharge opening 32, the non-return valve 38 opens, the piston valve 40 is pushed into the position shown in Figure 2, the non-return valve 42 also opens and the hydraulic fluid is led under pressure into the interior 34 in accordance with the strength of the control pulse.

On each return stroke of the plunger 1 8 the nonreturn valves 38 and 42 close immediately whereas the piston valve 40 oniy moves in proportion to the amount of leakage flowing past the end section 44. The inlet valve 36 also opens immediately whereby the pump bellows 21 sucks back hydraulic fluid from the container 29. The work and return strokes of the plunger 1 8 and rod 19 continue as long as hydraulic fluid is pumped into the bellows 24, that is, until the latter is so far expanded and the adjusting spindle 26 has moved so far that the counter-pressure from the spring 28 can no longer be overcome by the electromagnetic force of the plunger 1 8.

If the control signal becomes stronger the plunger 18 again starts to carry out the work and return strokes until pressure equalisation is again produced between the interior of the pump bellows 21 and the interior 34. If, on the other hand, the control signal becomes weaker the pressure in the interior 34 begins to go out of balance, the piston valve 40 is gradually pressed into its other position, as is already described, until the return pipe 35 is free. When return pipe 35 is freed liquid is forced back into the container 29 from the interior 34 until equality of pressure is again produced.

The adjusting force available can be considerably increased by suitably selecting the effective cross-section areas of the pump bellows 21 and the bellows 24. The maximum regulating distance does not depend on the stroke length of the plunger 1 8 but on the formation of the working bellows 24 and the pressure spring 28.

Furthermore the adjusting time is increased which is particularly desirable in larger adjusting members.

Claims

1. An adjusting drive comprising a hydraulic pump, an electromagnet operative to drive said hydraulic pump in response to a pulse control signal, and a hydraulic actuation member operative to displace an adjustable element in response to the hydraulic pump.

2. An adjusting drive according to claim 1, and including an interrupter connected to the winding of said electromagnet and operative to divide a control signal into control pulses.

3. An adjusting drive according to either claim 1 or claim 2, wherein the hydraulic pump is a diaphragm or bellows pump.

4. An adjusting drive according to any one of the preceding claims wherein a valve unit is arranged between the hydraulic pump and the hydraulic actuation member, which valve unit on a fall in pressure in the actuation member connects an outlet of the hydraulic pump with the actuation member, and which on a fall in pressure in the hydraulic pump closes this outlet.

5. An adjusting drive according to any one of the preceding claims wherein the hydraulic pump has a sump.

6. An adjusting drive according to any one of the preceding claims wherein the hydraulic actuation member is a working bellows.

7. An adjusting drive according to claim 6, wherein the sump comprises a container mounted inside said working bellows.

8. An adjusting drive according to claim 7, wherein the working bellows and the container are attached to a block in which said valve unit is mounted.

9. An adjusting drive according to claim 8, wherein the hydraulic pump is mounted on the side of the block away from the working bellows and the container.

10. An adjusting drive according to claim 4, and claim 5 wherein the valve unit comprises a springloaded inlet valve opening against the outlet of the hydraulic pump and connecting this with a pipe leading to said sump, and a spring-loaded nonreturn valve closing against the outlet which is formed in a pipe leading from the latter to the inlet of the hydraulic actuation member.

11. An adjusting drive according to claim 10, wherein the pipe leading to the inlet of the actuation member is formed in a valve chamber in which is displaceable mounted a piston valve, which piston valve on an over-pressure occurring in the hydraulic actuation member releases a return pipe leading back to the sump.

12. An adjusting drive according to claim 10, wherein the areas of the valve chamber lying on both sides of the piston valve are connected together with a spring-loaded non-return valve opening in the direction of the inlet of the hydraulic actuation member.

13. An adjusting drive according to claim 12, wherein the last-mentioned non-return valve is mounted in the piston valve.

14. An adjusting drive according to claim 2 or any one of claims 3 to 14 when dependent on claim 2, wherein the operative frequency of the interrupter is less than 10 hz.

1 5. An adjusting drive substantially as hereinbefore described with reference to the accompanying drawings.

14. An adjusting drive according to any one of the preceding claims wherein the effective crosssection area of the hydraulic actuation member is larger than that of the hydraulic pump.