GB2113854A

GB2113854A - Measuring force components

Info

Publication number: GB2113854A
Application number: GB08231829A
Authority: GB
Inventors: Hans W Hafner
Original assignee: Pfister GmbH
Current assignee: Pfister GmbH
Priority date: 1981-11-07
Filing date: 1982-11-08
Publication date: 1983-08-10
Also published as: GB2113854B; DE3240713C2; DE3240713A1

Abstract

Apparatus for measuring several force components acting on a body (e.g. in a wind tunnel) comprises a carrier 3 for the body supported by hydrostatic bearings 4 in a housing 2. The housing is connected to a cylindrical guide 1 mounted in hydrostatic bearings 5, 6. Bearing 5 is mounted in hydrostatic bearings 7 for horizontal movement. Forces and moments are measured by force sensors 21, 22, 23, 29, 31, 31. The guide cylinder 1 can be rotated by a gear ring 8 engaging a gear wheel 9 driven by a motor 11, the angle of rotation being measured. <IMAGE>

Description

SPECIFICATION Apparatus for measuring several force components The invention is concerned with apparatus for measuring a plurality of force components, in particular those derived from the forces of a flowing medium, acting on a body. Such apparatus will comprise a carrier for the body, a bearing system in which the carrier is guided so that it can swing and rotate and is horizontally and vertically movable, being held in each such direction by at least one force measuring device.

Apparatus is known from GB-PS 1 587 293 for measuring several force components, which has a bearing system for the object carrier which consists of three guide arrangements. Between these three guide arrangements hydro-static bearings are provided which permit movement of the object carrier in all directions. Since both the object carrier and also the guide arrangements are held by force measuring devices, all desired components of the forces acting on the object can be recorded and investigated.

The object of the invention lies in improving the accuracy of such an apparatus and also in simplifying its construction.

Moreover, it is often required to be able to turn the object in relation to the forces acting upon it.

Accordingly, the invention proposes apparatus for measuring a plurality of force components, acting on a body, comprising a carrier for the body, a bearing system in which the carrier is supported, and a corresponding plurality of force measuring devices, wherein said bearing system includes a rod or cylinder on which is mounted the carrier, said rod or cylinder being supported with minimum friction for rotation about the vertical axis, and the cylinder being connected to a rotary drive.

By means of these inventive measures, it is advantageously achieved that with higher measurement accuracy, more compact construction of the measurement apparatus is achieved, the apparatus being also simpler in construction and more economical then the previously known apparatus. Moreover, the object can be turned about its vertical axis, for example within a wind tunnel.

According to a further advantageous development of the invention, the rotary drive is connected with a force measuring device via a moment arm connected to it. Due to this measure, the forces acting on the moment arm or the moments acting can be measured with iittle difficulty and with particular accuracy.

Further details, characteristics and advantages of the invention will appear from the following description of an exemplary embodiment shown schematically in the drawing. This shows: Fig. 1 shows an apparatus for measuring several force components according to the invention, in longitudinal section; Fig. 2 shows a cross-section on the line A-B in Fig. 1.

The apparatus shown in the drawing for measuring several force components consists of a cylinder 1 formed as a guide, which has a boxshaped housing 2 at its upper end. In this housing, a spherical object carrier 3 is mounted between hydro-static bearings 4 for rotation and swinging movement. The cylinder 1 is itself also mounted hydro-statically in bearings 5 and 6 for rotation and longitudinal movement in the Z-axis. The bearing 5 is also itself mounted in hydrostatic bearings 7 for movement in the two horizontal directions. On the guiding cylinder 1 is a gear ring 8, which is connected by a toothed wheel 9 and gearing 10 to a drive motor 11. This rotary drive consisting of the drive elements 8, 9, 10 and 11 is arranged on a moment arm 13 with the interposition of a bearing 12.As seen in Fig. 2, the arm 1 3 is itself mounted for movement vertically, that is parallel to the Z-axis, in a hydrostatic bearing 14. The bearing 14 is arranged externally on a cylindrical housing 15, which connects together the two hydro-static bearings 5 and 6.

The guide cylinder 1 is closed at the bottom by a cover 16, which is supported via a hydro-static bearing 17 with an extension 1 8 on a cross member 19. This at its right-hand end is hinged for downward movement on a projection 20.

In order to be able to record and measure, without feedback, the torques MX, MY, MZ, acting on an object (not shown), which is, in operation of the measuring apparatus according to the invention fixed on the object carrier 3, there are arranged on the housing 2 measured value generators 21,22, and 23. These are connected to the object carrier 3 via transmission elements 24, 25 and 26 and moment arms 27, 28. The measured value generators can for this purpose be known electro-mechanical load cells.

In order to be able to record and measure accurately the force vector acting also in the vertical direction on the object and thus on the object carrier 3, a measured value generator 29 is provided according to the invention at the lower left end of the measuring apparatus shown in the drawing. This generator 29 is connected via a connection member 30 with the cross member 19, extension 18, bearing 1 7 and cover 16 to the guide cylinder 1. The moment arm 13 connected via the rotary drive with the guide cylinder 1 is mounted without friction in hydro-static bearings 14 parallel to the Z-axis. Therefore, using the measured value generator, the forces acting on the object in the vertical direction, can be very accurately measured and investigated.

The measured value generator 29 can alternatively if necessary be provided directly beneath the extension 18, so that the cross member, connection element etc, can be omitted.

For measuring the force vectors acting on the object in the two horizontal directions, at least two measured value generators 31 (only one shown) are provided which engage the bearing 5 via connecting elements 32, preferably lying mutually at an angle of 90 degrees. Further, the guide cylinder 1 with the object carrier 3 and the object attached to it can be rotated as desired about the Z-axis with the aid of the rotary drive formed by the elements 8, 9, 10 and 11.

In order to record and measure the forces operating on the object, which are transmitted to the guide cylinder 1 and act in the direction of rotation about the Z-axis, the rotary drive may advantageously include an angular measuring device, which is not shown in greater detail in the drawing. In addition, for measurement of the forces which are transmitted via the guide cylinder 1 and the rotary drive to the moment arm 13, a force measuring device 33 is provided which, as shown in Fig. 2, is integrated in the arm 13. Alternatively, the device may actually be formed by the arm.

The measuring apparatus according to the invention serves primarily to determine aerodynamic forces which act on an object under test, for example in a wind tunnel. This object may for example be a flying model, a part of air or space travei, a model of a vehicle or a tall building, and/or parts thereof.

The measuring apparatus according to the invention, particularly as shown in the drawing, thus makes possible on the one hand advantageously a very accurate, in particular feedback-free measurement of all forces operating on an object, and is characterised particularly by its compact and space saving construction.

Claims

1. Apparatus for measuring a plurality of force components, acting on a body, comprising a carrier for the body, a bearing system in which the carrier is supported, and a corresponding plurality of force measuring devices, wherein said bearing system includes a rod or cylinder on which is mounted the carrier, said rod or cylinder being supported with minimum friction for rotation about the vertical axis, and the cylinder being connected to a rotary drive.

2 Apparatus as claimed in claim 1, comprising a device for measuring the angle of rotation produced by the rotary drive.

3. Apparatus as claimed in claim 1 or 2, wherein the rod or cylinder can be moved along the vertical axis without said rotary drive being disengaged.

4. Apparatus as claimed in any preceding claim, wherein force measuring devices for torques acting about the three major axes mounted with the carrier on the bearing system, and force measuring devices for forces acting in the three major axes measure forces transmitted by the rod or cylinder.

5. Apparatus according to any preceding claim, wherein the rotary drive is connected via a moment arm to a force measuring device.

6. Apparatus according to claim 5, wherein the moment arm is guided in at least one hydro-static bearing parallel to the vertical axis.

7. Apparatus according to any preceding claim, wherein the rod or cylinder has at its upper end, a box-shaped housing in which a spherical object carrier is mounted in hydrostatic bearings for rotation and swinging, and is held by moment arms connected to measured value generators.

8. Apparatus for measuring a plurality of force components substantially as herein described with reference to the accompanying drawings.