Tension Force Meter

Following invention describes a device to measure tension force in pretensioned web alt. pretensioned wire without having any remaining affect on the measured object ( The lashing ).

The device that is primarily expected to find its use in the transport sector is a portable easy handled control instrument for authorities, transporters and senders.

Background of the invention

Background of the invention is the need in the transport sector for the possibility to easily and quickly check tension force in lashing bands to secure wished pretension forces in order to increase traffic safty and decrease transport damages.

Technical problem

The ability to control the so called pretension force in webs ( alt. wires ) is of outermost importance in transport to achieve safe securing of cargo to carrier. This control should also be possible to be carried out in such a way that it doesn ^' t permanently affect the lashing.

Today there are no such equipment that meet the above demand.

State of developement

Measuring tension force in wire or similar objects by bending it over three points and meausure the force across the object for actual bending (approx. a linear function of the tension force), recalculate it to tension force (alt. calibrate it against actual force) and present it as the wanted force is since long known technique. This was described already 1929 in the patent US 1,722,036 and later in among others US 1,871,776, US 3,653,258, US 3,698,244 US 4,860,597 and now latest in US 4,860,597 and FR 2 71 1 425.

The technique, that mostly has been used for wires, has had its main use for lifting devices ( cranes, traverses etc.) where it has been used as so called overload protection.

Because of that, the existing equipment is designed for wire and mainly planned to be used in fixed installations.

The technique is not used in the transport sector, as well as on the type of lashing bands that are so common. For that reason no portable easy handled instrument has been developed for meausering tension force in webs alt. wires.

Purpose of the invention and its most significant identification

The purpose of the invention is to supply a device that makes it easy to check the force momentarily in a lashing from the time it is tightend until it is untightened.

Consequently the tension force meter ways only approx. 3 kg and has the dimension approx. 20 10x30 cm. To achieve bending of the measured object the device hosts rolls / axles. Beside that there is a measure unit ( mechanical or electronic ) that registrates the needed force to produce actual bending and by recalculation / calibration displays the searched tension force.

A significant advantage with a device according to the invention is that it easily can be moved across the object, perform the measuring and as easily be removed without having any remaining affect on the lashing. This calls of course for geometries chosen so that the measured object permanently is in its elastic state.

Description of the invention

With support of fig. 1-4 in view from right above a device called tension force meter according to the invention will be described

Figure 1 shows a chosen design for the desribed device together with a peace of the measured object ( in this case a web ). Figure 2 shows the chassis.

Figure 3 shows the most important parts of the mechanical measuring device. Figure 4 shows measure electronics.

Figure 1 shows a preferable chosen technical solution that corresponds to the invention. It shows among other things the chassis 1 that work both as "holder" of important geometric points for the device as well as force collector and protector shell for the more important parts in the invention. To the chassis (1) is screwed the front gable 2 resp. rear gable 3 which completes the instrument case. The gables (2,3) have longitudanal grooves that give room for the measured object. Pos.4 shows the handle by witch the instrument is manouvered. No.5 is the activating lever that when pulled to a vertical position rotates in the measure unit 6 (fig. 3) towards the measured object 7 and bends it. The guiding list 8 simplifices the introdution of the measured object into the instrument. The knobs for front and rear widthsetters is shown by 9 and 9 ". Also the knob for the lengthsetter 10 and the both battery boxes 11 ' and 11 " can be seen.

Figure 2 shows the chassis (1) with it's four sides 12 (upper side), 13 (handle side), 14 (bottom) and front side 1 . The front side is by a longitudunal opening 16 along its full length devided in an upper part 15' and a lower part 15".

Figure 3 shows the mechanical parts inside the chassis and a measured object (7). The measure unit (6), that through a rotational movement bends the measured object (7) between the support rolls 17 and 18, consist of among other things a roll 19 mounted in bearings, a measure wagon 20, a load cell 21 and a carrier axle (22) which is carried in bearings in the chassis (1). 23 and 24 are widthsetters with the stopplates 25,26 that act as stops for the measured object and which correct set centers the object (7) sidewise under the measure unit (6).

Figure 4 shows the electronic unit 27 which is protectedly placed inside the chassis. The tension force meter is additionally equipped with a switch (not shown in figure) for power supply. This can be arranged in such a way that it is controlled by the activating lever (5). When the activating lever is in rest position (down) all power is shut off but opens automatically when the lever is pulled.

Above is described a technical solution where the measure unit (6) bends the measured object (7) by being rotated into the object. This movement can be replaced by a translation vertical towards the measured object.

The technic is useable on all webtypes and wires as long as the geometry is chosen so it is possible to neglect bending stiffness for the measured object. That means the suffer the web /wire is the larger geometries (distances, rollradies etc.) must be chosen.

Important for the measure accuracy is also that no friction force is lost in support rolls or measure roll why in these contacts there should only exist normal forces towards axle centers. Because of that these components preferably should be mounted in bearings. Of the same reason the widthsetters are important. Correct set friction forces are minimised in the measure unit at the same time as mislined forces are avoided.

Preferably measure geometrie for normal lashing bands with recommended pretension force 5 kN is for example 200 mm between the support rolls and 5-20 mm bending perpendicular to the web. The diameters for the measure roll and the support rolls can at the same time be approx. 20 mm.