Measuring Tool for Frameworks

The present invention relates to measuring tools for checking frameworks, preferably chassis frames on vehicles, the measuring tool according to the invention comprising an adjustable measuring bar, with the help of which the position and straightness of the frame centreline can be reproduced outside the frame itself, and accurately studied. The centreline is thus conceived to be subjected to a parallel displacement from its true position, and this is done in an extremely simple way by means of the measuring tool according to the invention.

It is previously known to provide such a conceived parallel displacement of a chassis frame centreline with the help of a so-called frame gauge consisting of two mutually displaceable bars made as racks, which engage with at least one common intermediate pinion. In the relation to the latter the bars can each be extended the same distance in opposite directions, and if their ends are fitted between a pair of longitudinal beams, a sighting pin fixedly oriented in relation to the pinion can be arranged always to be located in the middle of the two beams. If a number of such gauges are mounted along a chassis frame and the same number of equally long rods are arranged commonly parallel and extending one each sighting pin so that they project outside the frame on one side of it, the free ends will thus lie along a line extending parallel with the true centreline of the chassis frame. With the aid of suitable sighting means it can be established, for example, whether the centreline is straight or not.

Known frame gauges with associated details as above are rather costly and difficult to use and the system is very prone to backlash, which reduces accuracy. The object of the invention is thus to accomplish an improved measuring tool of the kind in question, in which the above-mentioned drawbacks in similar earlier measuring devices have been obviated. The object is attained and a simple, reliable and cheap measuring tool for frames is provided by the tool according to the invention having been given the distinguishing features disclosed in the accompanying claims.

An embodiment of the invention will now be described for the purpose of exemplification, while referring to the attached drawing, wherein

FIG. 1 schematically illustrates a measuring tool according to the invention, and how it is suspended and adjusted between the beams in a framework,

FIGS. 1a and 1b show some important sections of FIG. 1 on a larger scale, and

FIG. 2 is an enlarged detail view of a second embodiment of the invention.

As is apparent from FIG. 1, the embodiment of the measuring tool according to the invention shown there comprises a fixed part and a movable part, the former constituting a suspended part 15, which comprises a bar portion 12 and two holders or suspending means 16 and 18, by which the bar portion can be suspended between two opposing beams 20 and 21 incorporated in a framework. The movable part of the measuring tool constitutes an indicator part 17 and comprises a sliding portion 14 which is telescopically accommodated in the bar portion 12 of the suspended part 15, and is freely displaceable in it. Of the two holders, the holder 16 is fixedly arranged at one end of the bar portion 12, whereas the holder 18 is connected to a sleeve or slide 22 which is displaceable along the bar portion 12. Both holders 16 and 18 can have an arbitrary form and have suitably adjustable lengths so that the measuring tool can be suspeded as a unit in a horizontal position between the beams 20 and 21, approximately as shown in FIG. 1. The movable parts of the measuring tool are provided with conventional fixing or locking means not more closely shown, e.g. thumbscrews or the like, by which the tool is locked in is operative position to form a rigid unit.

The bar portion 12 is provided with a longitudinal scale 24 on its exterior, whereas the sliding portion 14 is provided with a longitudinal scale 26. The sleeve or slide 22 is provided with a window 28 through which the scale 24 can be read against an index 30, see FIG. 1a. In a corresponding manner the bar portion 12 in its turn is provided with a window 32 close to its free end, i.e. the end opposite the holder 16, and through this window the scale 26 on the sliding portion 14 is read against an index 34, see FIG. 1b.

The indicator part 17 also comprises a sighting pin 36 mounted on the free end of the sliding portion 14, where there is also arranged a scale 38 intended for optical measurements, as is schematically shown in FIG. 1.

According to FIG. 1 the measuring tool is thus hung up in its suspended part 15 by means of the two suspending means 16 and 18 between two beams 20 and 21 incorporated in a framework, of which the central plane between the beams is denoted by C, while the inside distance between the beams is denoted by B. Consequent on the tool being hung up between the beams, the index 30 of the slide 22 will indicate a definite numerical value on the scale 24 of the bar portion 12, see FIG. 1a. According to the invention, the sliding portion 14 shall now be displaced to a position in which it shows, on the index 34 integral with the bar portion 12, the same numerically representative scale division as the value on scale 26, see FIG. 1b. The distance between the central plane C of the frame and the sighting pin 36 has then a definite value x, see FIG. 1. When the measuring tool in its entirety is moved along the beams 20 and 21, the distance x must be the same the whole time, if the sighting pin 36 is continuously to represent a point on the "offset" centre line between the beams, even if the distance B between the beams varies. It will easily be appreciated hereby that if the distance B varies by a certain amount, e.g. .delta., resulting in the slide 22 being displaced the same distance .delta. along the bar portion 12, the slide portion 14 must be displaced in relation to the bar portion by a distance which is only half as great, i.e. .delta./2, for the distance x to be unaltered. As a consequence the distance between two scale marks on the scale 24 must be twice as large as the distance between two corresponding similarly denoted scale marks on scale 26. The absolute value of the scale magnitudes, i.e. where the scales have their zeros, has no importance, but for practical reasons the scale 24 can be suitably graduated such that the true value read off therefrom against the index 30 gives half the frame width B/2, for example, in centimeters, i.e. generally speaking the distance from the index to the central plane C.

A simple numerical example illustrates the relationships. If the distance B between the beams 20 and 21 is such that index 30 is against the figure 40 on the scale 24, which from the above means that the distance B is 80 cm, the sliding portion 14 is set in relation to the bar portion 12 so that the index 34 on the latter points against the same figure 40 on the scale 26. The sighting pin 36 is thus at a definite distance x from the central plane C. If the measuring tool is now moved along the beams to a point where the distance between these has increased by 2 cm, for instance, the slide 22 must be extended outwards 2 cm to retain suspension but, on the other hand, the sliding portion 14 has to be withdrawn 1 cm only from the bar portion 12 to keep distance x constant, as this is the distance from the sighting pin to the central plane C, which has thus only been moved 1 cm in relation to the frame beams. In order that the indexes 30 and 34 shall still point to similarly denoted scale markings, in this case 41, the distance between the scale markings on 24 must thus be twice as large as the distance between those on the scale 16.

In the embodiment according to FIG. 1 there are two separate reading windows with indexes, and it is further necessary to make the one scale, namely 24, with a rising number series, while the scale 26 must be made with a falling number series. A simplified, more practical embodiment of the invention, retaining its basic principles, is shown in FIG. 2 illustrating the essential parts of this second embodiment, while the rest of the measuring tool is made generally as the measuring tool according to FIG. 1.

In the embodiment according to FIG. 2, the bar portion 112 is, as before, incorporated in the suspended part 115 of the measuring tool and provided with a scale 124, the latter appearing in a window 128 arranged in the slide or sleeve 122 of the movable holder 118 accommodating the bar portion 112, reading being carried out against an index 130. In this case, however, a very elongated window 132, corresponding to the window 32 according to FIG. 1, is taken up in the bar portion 112, and through this window, which in actual fact consists of a long slot in the bar portion, the scale 126 appears, which is arranged on the telescopically accommodated sliding portion 114 of the measuring tool. This scale will always appear through the window 128 in the sleeve 122 because of the great length of the slot 132, for reading against an index 134 located exactly opposite the index 130. Both scales extend adjacent each other, and as both indexes 130 and 134 are arranged directly opposite each other, the scales can actually be read directly against each other as well.

It is readily appreciated that the measuring tool according to FIG. 2 functions according to the same principle as the tool according to FIG. 1, i.e. when it is suspended between a pair of beams in a framework, the scale 124 gives against the index 130 a measurement corresponding to half the frame width, and if the sliding portion 114 is set, as before, so that the same measurement numeral on its scale 126 is located against the index 134 (or directly against the corresponding scale marking on the scale 124 of the bar portion 112), the sighting pin (not shown), arranged on the free end of the sliding portion 114, will also in this case be at a distance, which is always the same, from the central plane of the frame, independent of whether the frame is found to have different widths at the measuring locations. In other words, the movable sliding portion 114 keeps still the whole time in relation to the central plane.

With regard to the practical structural embodiment of the measuring tool according to the invention, both the bar portion and the sliding portion as well as the movable holder slide can be made from suitable light metal sections, e.g. square tubes. In the embodiment according to FIG. 2, both the bar portion 112 and the sleeve 122 can be produced from an extruded U-profile with turned-in edges, the opening or slot between these edges forming the necessary window for the scales, as indicated at 128' and 132' in FIG. 2. In this case the windows will be continuous along the whole of the sleeve 122 and the bar portion 112.