WO2007145511A1

WO2007145511A1 - Detachable device and method for determining the tension in a wire or a stay

Info

Publication number: WO2007145511A1
Application number: PCT/NL2007/050263
Authority: WO
Inventors: Tom Oosterman
Original assignee: Tom Oosterman
Priority date: 2006-06-15
Filing date: 2007-06-05
Publication date: 2007-12-21
Also published as: NL1032010C1

Abstract

There is disclosed a practical device to be used for a number of wires for determining a measure of the tension in a wire, comprising: gripping means for detachably gripping a part of the wire that is to be measured, means for measuring a change in length of the gripped part of the wire, and calculating means connected to said measuring means for determining the aforesaid measure, using elasticity data of the wire.

Description

DETACHABLE DEVICE AND METHOD FOR DETERMINING THE TENSION IN A WIRE OR A STAY

The present invention relates to a device for determining a measure of the tension in a wire, comprising: means for measuring a change in length of the wire, and calculating means connected to said measuring means for determining the aforesaid measure, using elasticity data of the wire.

The present invention further relates to a corresponding method, wherein a measure of tension in a wire is determined.

Such a device and such a method are known from WO 2005/075286. From said document, measuring means to be fastened to the stays or the rigging of a vessel are known, by which measuring means the elongation of at least part of a stay is measured. The measuring means, which are fastened to one or more stays, for example by welding, soldering or glueing, form an integral part of one or more of the stays along their entire length, and the measure of the tension is calculated from the measuring results that relate to the entire stay and from the elasticity data of the stay in question.

A drawback of the device is that when the tension or stress in several different wires or stays is to be monitored, said stays must each be provided with at least the measuring means in question upon production thereof.

The object of the present invention is to provide a less costly alternative for determining the tension or stress in a wire in a simple manner.

In order to accomplish that object, the device according to the invention is characterised in that the device comprises gripping means connected to the measuring means for gripping a part of the wire that is to be measured .

Accordingly, the method according to the invention comprises the features that a measure of the tension in a wire is determined by gripping/clamping a part of the wire and, in case of a change in the tension, measuring the change in length of the gripped part and determining said measure from said measurement and from elasticity data of the wire.

The advantage both of the device and of the method according to the invention is that the gripping means make it possible to make repeated use of the device, which is not necessarily incorporated in each stay and which can now be detached therefrom after use, even without having to adapt the stay in any way during production thereof or during the actual measurement. The term wires is understood to include possibly pre-stressed reinforcing bars, cables, spokes or guys and the like. Measuring the absolute or relative tension with the same device has thus become possible at lower cost and is no longer available only to the higher echelons of, in particular, competitive yachting. The device can be clamped over a small part of the wire, without the accuracy of the tension measurement that is required in practice being affected too much.

One embodiment of the device according to the invention is characterised in that the gripping means are configured for being connected in a manually detachable manner to the wire.

This makes it possible in practice to determine the tension by means of an easy-to-use embodiment. Another embodiment of the device according to the invention is characterised in that the gripping means are provided with means that can be hooked over the wire, which means are preferably provided with rotary knobs to be screwed down on the wire, by means of which the tension measurement can be carried out in a simple and quick manner.

Another embodiment of the device according to the invention is characterised in that the measuring means comprise a contactless electronic, preferably digitally readable, length measuring system or a slide gauge, which preferably comprises an inductive measuring system, so that a readable indication as regards the measured tension is provided, by which, in addition, reliable and reproducible results are obtained also in rainy conditions, because such an inductive measuring system is practically insensitive to moisture or water.

Another preferred embodiment is characterised that measuring, calculating and gripping/clamping means are integrated in the device, thus providing a compact object which is easy to carry along and which is useful in practice.

The device and the method according to the invention will now be explained in more detail with reference to the figures below, in which: Figure 1 shows a preferred embodiment of the device according to the invention; and

Figure 2 shows another preferred embodiment of the device according to the invention.

Figure 1 shows a device 1 by means of which at least a measure of the tension or tensile force or the stress or pre-stress in wires D, such as stays or stay wires, guys, ropes, reinforcing bars, spokes and the like can be measured, adjusted and/or set. Various compositions and designations of the wires D are possible, for example stainless steel wires, Rodriggings, Dyform wire, blank wire or electroplated wire, or wires of plastic material, such as PBO, Vectran, Dyneema, Kevlar and the like. To be suitable, the wire D must elongate elastically upon being subjected to a mechanical stress and shrink elastically when said stress is released. In other words, the wires D must comply with the well-known Hooke ' s law within the applicable range of stress. The wires that are used in practice in the world of sailing generally have a diameter of 3-12 mm; for wires having a larger diameter adapters (to be briefly explained hereinafter) may be used.

The device 1 is a separate, practical device that is easy to transport and to store, which device can be used in practice for measuring or setting or adjusting the tension, expressed in Newton, or the stress, expressed in Newton per unit area of the wire, in an absolute or relative sense, the latter without measuring. The device 1 comprises the following means to be explained hereinafter: means 2 for measuring changes in length of a part of the wire that is to be gripped, gripping means 3 connected to the length measuring means 2 for gripping/clamping the part of the wire that is to be measured, and calculating means 4 connected to the measuring means 2 for determining the aforesaid measure, using elasticity data of the wire. This embodiment of the device 1, which can be detached from the wire, is so configured that the respective measuring, clamping and calculating means 2, 3 and 4 are integrated in one housing. The gripping means 3 are provided at two ends 6 and 7, which project from the housing 5 in this embodiment . The clamping means 3 are each provided with means 8 to be hooked round the wire. One of the ends 6 is fixedly connected to the housing 5 accommodating the means 2, 3 and 4, whilst the other end 7 is movably connected thereto .

In figure 1 an embodiment of the gripping means 3 provided with the hook means 8 is shown by way of illustration. In this embodiment the hook means 8 comprise screw means 9 provided with knobs 10 to be manually tightened for clamping down the means 8 hooked onto the wire therein. Thus the starting length of the gripped part of the wire is determined. On a vernier forming the mechanical measuring means 2, which may be provided on the movable end 7, the vernier starting value constitutes the reference value. If the device 1 is an electronic device 1 as shown, the zero position is displayed on an LCD screen 11 by pressing a button thereon. In a first case, the wire D may already be prestressed when the gripping means 3 are clamped down on the wire, but in a second case the stress on the wire D may be negligible. In the first case the elastic change in length, being an increase or a decrease of the length to be measured with the measuring means 2, can be read from the vernier or from the screen 11 and provide a measure of the increase or decrease of the tension based on the elasticity modulus of the wire - which may have been input in advance or be read from a table - possibly in combination with the diameter of the wire D, so as to be able to provide information regarding the increase or decrease of the mechanical stress in the wire. In the second case the elastic length increase now provides information - absolute information in this case - about the current tension or stress as set. In the electronic version of the slide gauge or, more generally, of the length measuring system, the measuring means 2 are preferably contactless means that can be read, preferably digitally, on the screen 11. The electronic measuring system or the slide gauge may comprise a capacitive or an inductive measuring system, the latter being preferred because of the insensitiveness of the contactless inductive measurement of the change in length to moisture and water. In one operating mode of the calculating means 4 in the device 1, the current tension or the tension change can be read directly from the screen 11. When the required data, such as the elasticity modulus and the diameter of the wire D in question, have been input into a memory of the electronic device 1 in advance, the value of the stress change in the wire D can be read directly, if desired. After the tension or the stress has been set or adjusted, the device 1 can be detached from one wire by loosening the knobs 10 and be hooked onto a next wire, after which the method described herein can be carried out again on the next wire, using the same device 1. As already said before, adapters 8, 9, 10 having different dimensions may be combined with the device 1 so as to enable the device 1 to set and measure the mechanical stress in different types of wires D having different thicknesses. Said adapters may be suitably configured to be detachably connectable to the device 1, and several adapters may be supplied with one and the same device 1, if desired, or be sold separately.

The gripping means 3 may also comprise so-called measuring cams A as shown in figure 2, which are (to be) provided on the wire D and which may for example be integrated in the clamping means, defining between them the part B of the wire D that is to be measured. The two measuring cams A are mounted a known distance apart on the unstressed wire D. Said distance equals the selected measuring length of the device 1 and amounts to 200 mm, for example. Upon tensioning of the wire D, the change, in particular the increase, in the stress in the wire D can be determined in the above-explained manner by means of the device 1 from the change in length of the gripped wire portion B to be measured. If the device 1 is detached at a specific value of the stress in the wire and the stress in the wire is checked after some time, during which time the ship may or may not have been sailed, measurement of the length of the gripped part B shows the stress associated with said length of the wire portion at that point in time. It is not necessary in that case to slacken the wire before the current stress can be determined.

Claims

1. A device for determining a measure of the tension in a wire, comprising: - means for measuring a change in length of the wire, and

- calculating means connected to said measuring means for determining the aforesaid measure, using elasticity data of the wire, characterized in that the device comprises gripping means connected to the measuring means for gripping a part of the wire that is to be measured.

2. A device according to claim 1, characterized in that the calculating means are arranged for determining the tension on the basis of the change in length of the gripped part .

3. A device according to claim 1 or 2 , characterized in that the gripping means are configured for being connected in a manually detachable manner to the wire.

4. A device according to any one of the claims 1-3, characterized in that the gripping means are provided with means that can be hooked over the wire.

5. A device according to any one of the claims 1-4, characterized in that the gripping means are provided with screw means .

6. A device according to any one of the claims 1-5, characterized in that the gripping means are provided with rotary knobs to be manually screwed down on the wire.

7. A device according to any one of the claims 1-6, characterized in that the measuring means comprise a contactless electronic, preferably digitally readable, length measuring system or a slide gauge.

8. A device according to claim 7, characterized in that the electronic slide gauge comprises a capacitive, but preferably an inductive measuring system.

9. A device according to any one of the claims 1-8, characterized in that said device is a device which can be detached from the wire and in which the measuring, calculating and gripping means are integrated.

10. A method wherein a measure of the tension in a wire is determined by gripping a part of the wire and, in case of a change in the tension, measuring the change in length of the gripped part and determining said measure from said measurement and from elasticity data of the wire.