GB1601560A

GB1601560A - Throttle arrangement for flowing media

Info

Publication number: GB1601560A
Application number: GB1546278A
Authority: GB
Original assignee: Carl Schenck AG
Current assignee: Carl Schenck AG
Priority date: 1977-07-25
Filing date: 1978-04-19
Publication date: 1981-10-28
Also published as: DE2733446A1; JPS5424318A

Description

(54) A THROTTLE ARRANGEMENT FOR FLOWING MEDIA (71) We, CARL SCHENCK AG of Landwehrstrasse 55, Darmstadt 61, Federal Republic of Germany, a German body corporate, 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:- The invention relates to a throttle device for flowing media having a throttle channel (throttle bore, throttle groove) of a small cross-section in relation to its length.

In hydraulics, throttle devices are known in many embodiments and for many purposes, i.e. needle valves, needle hole diaphragms, sliding aperture, threaded throttles, jet dividers etc. With the aid of throttles, the throughflow of hydraulic media can be easily controlled. Thus the piston motion of operating pistons can be controlled for example. This is particularly true for pistons which perform relatively slow movements and in which the forces acting do not change very much nor very jerkily.

Throttles can be used, for example, for stepless control of the speed of movement of an operating piston. The larger the drop in pressure provided at the throttle in relation to the pressure required for movement of the operating piston, the more precisely can the piston speed be maintained under loading fluctuations at the piston.

Furthermore, throttles are suited to synchronous control of two or more pistons in operating cylinders. The accuracy of synchronization which can be achieved also depends on the ratio of the drop in pressure at the throttle and the pressure required for piston movement. If the drop in pressure in the throttle is large as compared to the pressure required for operation at the piston then relatively good synchronization can be achieved in the pistons.acted upon.

In the known throttles the change in the throughflow quantity is generally caused by changing the throttle cross-sections.

However, these throttles are sensitive to temperature and/or dirt. In sliding valves disruptive leakage flows occur.

Apertured diaphragms are susceptible to dirt because of thc small ratio of the throughflow surface to the surface of the periphery. Threaded throttles in fact permit a large cross-section but also have a leakage flow so that the reproducibility of the values to be set is not guaranteed.

The present invention seeks to create a throttle device which has little sensitivity to temperature and dirt which is simple and cheap to manufacture, has a small constructional volume and permits simple setting of the throttling effect moreover.

Furthermore the throttle device is, in specific embodiments thereof suitable for synchronized control of pistons in operating cylinders, for example the clamping pistons of hydraulic clamping devices on testing machines and permits accurage dosage of quantities of liquid as far as possible.

According to the invention, there is provided a throttle device for fluids comprising a channel of small cross-section compared to its length, a supply opening into the channel, two outlets leading from the channel each of which lies on opposite sides of the supply and means for varying the relative positions of the supply and outlets so as to vary the length of channel therebetween.

A throttle device in accordance with the invention with a substantially constant throttle cross-section is not sensitive to changes in temperature or to dirt. It can be easily manufactured and can be kept small in its dimensions. A very simple and refined adjusting facility of the throttle device is given by displacing or shifting the supply and/or outlet opening at the throttle channel.

The portions of the throttle channel between the supply and the outlets (throttle distances) may be approximately the same length in a median setting of the device. By means of this arrangement, a very simple synchronized control of two pistons can be achieved. A particularly simple construction of the throttle device may be produced if it has a base member with an at least partially open throttle channel therein and at least two outlets therein and a sealing member arranged on the base member having a supply opening to the throttle channel and if the sealing member is arranged displaceably on the base member.

Thus it is seen as particularly advantageous if the throttle channel is of part circular form in the base member and a sealing member is rotatable on the base member approximately about the centre of the circle on which the throttle channel lies. The throttle effect can be set in this embodiment by rotating the sealing member on the base member very simply and very precisely within a wide range.

Further advantageous refinements of the throttle device may be given by its use as a correction throttle and by use of the throttle for synchronized control of hydraulically actuated clamping pistons of clamping devices on testing machines.

Thus the device may be connected in front of and/or after at least one fixedly set throttle and may have a substantially lower throttling effect than the fixedly adjusted throttle(s).

The invention will now be described in greater detail, by way of example, with reference to the drawings, in which: Fig. 1 shows a section through a throttle device having a supply channel and two outlet channels; Fig. 2 shows a throttle device having a circular throttling channel (Fig. 2a axial section, Fig. 2b radial section); Fig. 3 shows a circuit diagram of a throttle arrangement with a throttle device in accordance with the invention, connected in front of (Fig. 3a) or after (Fig.

3b) a further fixedly adjusted throttle(s), and Fig. 4 shows the synchronized control of hydraulically actuated clamping pistons of a tensioning device for testing machines.

The essential parts of a throttle device in accordance with the invention are shown schematically in Fig. 1. A throttle channel 2 with any desired cross-section, for example square, round, or triangular is located in a base member i. The throttle channel can be constructed as a groove, bore or the like.

The cross-section of the channel is small in relation to its length. The channel crosssection and the channel length can be fixed by the expert according to the desired throttling effect and according to any other requirements (manufacture, size of the device to be controlled, surface composition of the throttle channel). Thus many embodiments are conceivable for shaping and arranging the throttle channel which the expert can select. The throttle channel can comprise bores arranged in the base member or a combination of grooves and bores for example.

A sealing member 3 is arranged on the base member 1 and covers the throttle channel 2, open towards the sealing member. The sealing member 3 is displaceably arranged on the base member 1 as indicated by arrows. Base member and sealing member can be connected in a suitable manner by screws 4 for example and can be sealed with respect to each other by sealing elements 5. The sealing elements can be omitted in the case of appropriate preparation of the surfaces to be sealed.

The sealing member 3 has a supply opening 6 through which pressure medium is supplied into the throttle channel 2 in the direction of the arrow at a pressure P and of a quantity Q. In the base member 1 are provided outflow openings 7 and 8 at the ends of the throttle channel. The pressure medium is conducted by the outflow openings to the loads.

Pressure medium supply, pipes, connections etc. are now shown for the sake of simplicity since they are not necessary for understanding the invention. The quantity Q of the pressure medium supplied at the pressure P through the supply ow opening 6 is divided up in the throttle channel into two part-flows Ql and Q The part-pressures åPI and AP2 drop across the throttle paths 11 and 12. The quantities of pressure medium Ql and Q2 are available at the outflow openings 7 and 8 at pressures (P-BP,) and (P-A P2).

The quantity of pressure medium flowing through the throttle channel is inversely proportional to the drop in pressure in the channel. The proportionality factor depends on the flow ratios in the throttle channel (laminar, turbulent or mixed flow).

By changing the length of the throttle path, the throughflow quantity can be set by the throttle device.

If the base member 1 and the sealing member 3 are connected together so that the supply opening 6 is located exactly above the centre of the throttle channel 2 then with the same channel cross-section, the supplied quantity Q of pressure medium through the two partial paths 11 and 12 of the throttle channel are divided up evenly into the two outflow openings 7 and 8. Therefore the same quantities Ql and Q2 are available at the outflow openings. If the sealing member 3 on the base member 1 is displaced as indicated in the direction of the arrow than the length of the throttle paths 11 and 12 changes and thus the throttling effect or the throughflow quantities Ql and Q2 change at the outflow openings 7 and 8.By displacing the sealing member on the base member the throttling effect and thus the throughflow quantity can be finely adjusted.

This type of adjustment is required for example if, during synchronized control of two operating pistons, slightly varying piston diameters or piston frictions are to be balanced out.

The throttle device according to the invention can be implemented so that the supply opening is fixed in the base member with the throttle channel and so that the outflow openings in the sealing member are displaceable along the throttle channel.

Nothing is changed in the effect and mode of operation of the device by this.

Fig. 2 shows an embodiment of the throttle device with a circular throttle channel. The base member 1 and the sealing member 3 are constructed as circular discs.

Base member and sealing member can be rotated with respect to each other about the central point of the circle M whereby the sealing member can be guided for example by a pin or a centre device 9 in the centre of the base member. Sealing member and base member can be connected together by a preferably central screw connection or tensioning connection 10.

The circular throttle channel 2 in the base member 1 is open to the sealing member.

The supply opening 6 in the sealing member is arranged above the open throttle channel 2. By rotating the sealing member or sealing member and base member with respect to each other, the supply opening is displaced along the throttle channel so that the throttling effect or the throughflow quantity changes accordingly at the partial-paths of the throttle channel. The throttled and appropriately dosed quantity of pressure medium is passed on to the loads by the outflow openings 7 and 8.

As is shown in Fig. 3 in a circuit diagram, the throttle device according to the invention can be connected in front of (Fig.

3a) or after (Fig. 3b) further throttles 21, 22 as a correction throttle 20. The throttles connected before or after can be set to fixed values. The throttle device can be particularly accurately set if the correction throttle has a substantially smaller throttle effect than the remaining throttles.

If, for example, only 10% of the total pressure difference of the throttle device drops across the settable correction throttle but 90n e at the fixed throttles, then obviously a very accurate setting of the throttling effect of the entire device can be carried out at the correction throttle.

The use of the throttle device in accordance with the invention in an hydraulic tensioning device for material testing is shown in Fig. 4. Pressure medium is supplied to the correction throttle 20 from a pressure medium source not shown, for example an oil pump. Instead of the correction throttle 20, a throttle arrangement is according to Fig. 3a or 3b can be used. The pressure medium is initially passed by the correction throttle in equal quantities into the cylinder chambers 30, 31 of clamping cylinders 32, 33. The clamping cylinders are a component part of the tensioning device 25 of a testing machine not shown. Clamping pistons 34, 35 are arranged so as to be longitudinally movable in the clamping cylinders. The clamping pistons are brought into the starting position by resetting devices not shown, for example return springs.The clamping pistons 34, 35 are moved against the body 36 to be tested by the pressure medium in the cylinder chambers 30, 31 and clamp the body 36 firmly in the tensioning device of the testing, machine. After the tensioning process, testing forces can be exercised, for example as indicated in the direction of the arrow in the testing machine on the body 36 to be tested.

Unequal movement speeds or unequal advance of the clamping pistons can be caused for example by bore tolerances or diameter tolerances at the pistons and cylinders. These irregularities can be overcome by matching to the pressure medium quantities fed into the clamping cylinders. The pressure medium flow can be controlled with the aid of the correction throttle as described in Fig. 1 so that the desired uniform movement of the clamping piston is achieved. In this way very simple, precise and easily reproducible synchronized control of the clamping pistons is possible. When using the throttle device for synchronized control of pistons the throttle device can also be assembled together with the tensioning device.

WHAT WE CLAIM IS: 1. A throttle device for fluids comprising a channel of small cross-section compared to its length, a supply opening into the channel two outlets leading from the channel each of which lies on opposite sides of the supply and means for varying the relative positions of the supply and outlets so as to vary the length of channel therebetween.

2. A throttle device according to claim 1 wherein, in a median setting of the device, the portions of the throttle channel between the supply and the outlets are approximately of equal length.

3. A throttle device according to claim 1 or 2 wherein the device comprises a base member with an at least partially open throttle channel therein and two outlets therein and a sealing member which is

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. displacing the sealing member on the base member the throttling effect and thus the throughflow quantity can be finely adjusted. This type of adjustment is required for example if, during synchronized control of two operating pistons, slightly varying piston diameters or piston frictions are to be balanced out. The throttle device according to the invention can be implemented so that the supply opening is fixed in the base member with the throttle channel and so that the outflow openings in the sealing member are displaceable along the throttle channel. Nothing is changed in the effect and mode of operation of the device by this. Fig. 2 shows an embodiment of the throttle device with a circular throttle channel. The base member 1 and the sealing member 3 are constructed as circular discs. Base member and sealing member can be rotated with respect to each other about the central point of the circle M whereby the sealing member can be guided for example by a pin or a centre device 9 in the centre of the base member. Sealing member and base member can be connected together by a preferably central screw connection or tensioning connection 10. The circular throttle channel 2 in the base member 1 is open to the sealing member. The supply opening 6 in the sealing member is arranged above the open throttle channel 2. By rotating the sealing member or sealing member and base member with respect to each other, the supply opening is displaced along the throttle channel so that the throttling effect or the throughflow quantity changes accordingly at the partial-paths of the throttle channel. The throttled and appropriately dosed quantity of pressure medium is passed on to the loads by the outflow openings 7 and 8. As is shown in Fig. 3 in a circuit diagram, the throttle device according to the invention can be connected in front of (Fig. 3a) or after (Fig. 3b) further throttles 21, 22 as a correction throttle 20. The throttles connected before or after can be set to fixed values. The throttle device can be particularly accurately set if the correction throttle has a substantially smaller throttle effect than the remaining throttles. If, for example, only 10% of the total pressure difference of the throttle device drops across the settable correction throttle but 90n e at the fixed throttles, then obviously a very accurate setting of the throttling effect of the entire device can be carried out at the correction throttle. The use of the throttle device in accordance with the invention in an hydraulic tensioning device for material testing is shown in Fig. 4. Pressure medium is supplied to the correction throttle 20 from a pressure medium source not shown, for example an oil pump. Instead of the correction throttle 20, a throttle arrangement is according to Fig. 3a or 3b can be used. The pressure medium is initially passed by the correction throttle in equal quantities into the cylinder chambers 30, 31 of clamping cylinders 32, 33. The clamping cylinders are a component part of the tensioning device 25 of a testing machine not shown. Clamping pistons 34, 35 are arranged so as to be longitudinally movable in the clamping cylinders. The clamping pistons are brought into the starting position by resetting devices not shown, for example return springs.The clamping pistons 34, 35 are moved against the body 36 to be tested by the pressure medium in the cylinder chambers 30, 31 and clamp the body 36 firmly in the tensioning device of the testing, machine. After the tensioning process, testing forces can be exercised, for example as indicated in the direction of the arrow in the testing machine on the body 36 to be tested. Unequal movement speeds or unequal advance of the clamping pistons can be caused for example by bore tolerances or diameter tolerances at the pistons and cylinders. These irregularities can be overcome by matching to the pressure medium quantities fed into the clamping cylinders. The pressure medium flow can be controlled with the aid of the correction throttle as described in Fig. 1 so that the desired uniform movement of the clamping piston is achieved. In this way very simple, precise and easily reproducible synchronized control of the clamping pistons is possible. When using the throttle device for synchronized control of pistons the throttle device can also be assembled together with the tensioning device. WHAT WE CLAIM IS:

1. A throttle device for fluids comprising a channel of small cross-section compared to its length, a supply opening into the channel two outlets leading from the channel each of which lies on opposite sides of the supply and means for varying the relative positions of the supply and outlets so as to vary the length of channel therebetween.

arranged on the base member and has a supply opening to the throttle channel.

4. A throttle device according to claim 3, wherein that the sealing member is arranged displaceably on the base member.

5. A throttle device according to claim 3 wherein the throttle channel is of part circular form in a base and a sealing member is rotatable on the base member approximately about the centre of the circle on which the throttle channel lies.

6. A throttle device according to any one of claims 1 to 5 wherein it comprises a correction throttle.

7. A throttle device according to claim 6, wherein at least one fixedly adjusted throttle is connected either before and/or after the device.

8. A throttle device according to claim 7, wherein the correction throttle has a substantially lower throttling effect than the fixedly adjusted throttle(s).

9. A throttle device according to any one of the Claims 1 to 8 wherein it comprises a synchronising device for the control of hydraulically actuated clamping pistons of clamping devices on testing machines.

10. A throttle device for fluids substantially as described herein with reference to the drawings.