LEVELLING BAR

Abstract: Levelling bar, in the form of a simple bar (11) or several into each other displaceable bars (11a, 11b), to determine the elevation difference between different points and which is provided with a slide (14) which is displaceable along said bar and lockable in different positions said slide being provided with a level indicator (16). The slide (14) is provided with a counter apparatus (20), which in cooperation with the bar/bars (11a, 11b) or a reference means (12) attached to said bar/bars is provided to indicate the relative distance from one of the outer ends of the bar/bars to said level indicator (16).

Description: LEVELLING BAR The present invention concerns a levelling bar, in the form of a simple bar or several telescopically into each other displaceable bars, to determine the elevation difference between different points and which is provided with a dis¬ placeable slide which can be locked in different positions, on which is arranged a level indicator. Background of the invention Differences in elevation between different points are deter¬ mined by means of a levelling instrument, by which is pro¬ vided an optically horizontal line of sight, from which is measured the distance to the ground by means of a levelling bar. Until now this has consisted of a wooden bar normally foldable to lengths easy to handle and said bar is provided with a painted scale on one side, with e.g. 1 cm as the smallest unit. At index point levelling the elevation is determined for a number of marked points, whereby one starts from an index point with known or assumed elevation. When determining elevations of a larger area, a number of moving points are often also required, this involves a large number of cal¬ culations to be carried out, in order to obtain the required elevations. Object of the invention and the most essential features The object of the invention is to provide a levelling bar, which considerably simplifies the calculation of the eleva¬ tions, especially when the elevation variations are large. This problem has been solved by providing the slide with a counter, which in cooperation with the bar/bars or a refe¬ rence means fixed to said bar/bars is arranged to indicate the relative distance from one of the outer ends of the bar/bars to said level indicator. Description of the drawings The invention will be described below in a number of em¬ bodiments with reference to the appended drawings. Fig. 1 shows a lateral view of a first embodiment of the levelling bar according to the invention. Fig. 2 a section along the line II-II in fig. 1. Fig. 3 shows a longitudinal section through a second embodi- ment of the levelling bar according to the invention. Fig. 4 is a section along the line IV - IV in fig. 3. Fig. 5 shows a longitudinal section through a third embodi- ment of the levelling bar according to the invention. Fig. 6 shows a longitudinal section through a fourth em¬ bodiment of the levelling bar according to the invention. Fig. 7 is a section along the line VII-VII in fig. 6. Description of embodiments In its simplest design the levelling bar contains of a profile bar with mainly U-shaped cross section. On the inside of the profile bar in the mid section 19 of the U between the shanks is provided a reference means 12 which in the embodiment shown is constituted by a rack 13. Along the profile bar 11 a displacable slide 14 is provided, which by means of a clamping screw 15 is lockable in different dis¬ placement positions. In the slide 14 a level indicator 16 is provided which contains a window 17 provided with an index mark (not shown) and on the outside of the mid section 19 of the profile bar a scale (not shown) is provided, the divi¬ sion of which can be brought into relation with the index mark. In the slide 14 is provided a counter 20, which contains a pinion 21 which is meshed into the rack 13 and which trans¬ mits its rotational movement by a suitable gear ratio to a number of digit wheels 22 which can be preset and also reset by a button 23. When the slide is displaced along the profile bar 11 the counter thus will indicate the relative elevation of the slide 14, whereby the index point can either be a given elevation, which is fed into the counter as a presetting of the digit wheels 22 or one can start from a zero position. In a conventional manner the levelling instrument is level¬ led towards the levelling bar, the slide of which is dis¬ placed such that the index of the level indicator coincides with the line of sight of the levelling instrument. In this position the slide is locked to the profile bar and the obtained digit value is read. If the profile bar should be too short (a suitable length may be 2 meters), it can be lengthened by an extension bar in its upper end, which extension bar is provided with an insertion end, which trough a snap-on lock or the like can be joined to the profile bar. Likewise the extension bar 24 is provided with a rack 13, so that the rack without inter- ruption also can be displaced along the extension bar 24. In the embodiment shown in fig. 3 and fig. 4 the levelling bar 10 consists of two telescopically into each other dis¬ placeable bar sections 11a and lib. The outer bar section 11a in its upper end is provided with a first pulley 26 mounted in bearings in this end for an endless chain 27, which at the lower part of the outer bar section is conveyed around a second pulley 28. This is mounted in bearings in a bracket 29, which is inserted through a slot in the in¬ terior of the outer bar section 11a. The bracket is also provided with a clamping means 31, for clamping the two bar sections 11a and lib to each other. In this embodiment the chain 27 constitutes the reference means 12, which coopera¬ tes with a pinion 21 mounted in bearings in the slide 14. Similarly to the embodiment according to figures 1 and 2 a counter 20 is provided in the slide 14. In order to compensate the change in length at the counter when the inner bar section lib in withdrawn from the outer bar section 11a, a third and a fourth pulley 32 and 33 are arranged on the shafts of the pulleys 26 and 28 for a second endless chain 34. In the folded up position of the bar sections 11a and lib, shown in fig. 3 the upper end portion of the inner bar section lib by means of a carrier 35 is connected to the second chain 34 so that when the inner bar section is pulled out, it drags along the chain 34 and accordingly also the chain 27 which activates the gear-wheels of the counter 21. Modern levelling instruments operate with a laser light beam as a line of sight and in such cases the level indicator 16 consists of a receiver 36, which emits an acoustic signal, when the level indicator and accordingly the slide 14 comes into position of sight with the levelling instrument. A somewhat simplified version of the embodiment shown in fig. 3 and 4 is illustrated in fig. 5. In this embodiment a pulley 26 is provided at the upper end part of the outer bar section 11a for a chain 27, the ends which are secured to lower end part of the inner bar section lib. To the inner chain portion an expansion device 18 is connected, which in the displayed embodiment consists of a tension spring 37, which is attached by an end plug 38 inserted in the outer end of the bar section lib. In order to prevent that the position of the chain 27 is altered when the slide 14 is displaced because of the spring elastic mounting, in the upper end part of outer bar section 11a, a blocking means 39 is provided, which in active posi¬ tion blocks the pulley 26 and accordingly the chain 27, while in the withdrawn passive position the chain can run over the pulley 26, so that a relative displacement between the bar sections 11a and lib can be carried out. In the same way as in the previous embodiments the slide 14 is provided with a counter 20 with gear-wheel 21 which cooperates with the chain 27. In the embodiment shown in fig. 6 and 7 the detection of the reference means 12 is carried out non- contact by means of a photo electric interrupter 40 connected to the slide 14. In this case the reference means 12 consists of a windable steel strip 41, which is preferably provided with a longi¬ tudinal perforation through which the light beam can pass. The steel strip is connected to an expansion device 18 which in the embodiment shown consists a spring loaded wind up mechanism 42 which is arranged at the upper end part of the outer bar section, respectively one to the upper end part connectable end cover 43. The wind up mechanism 42 is pro¬ vided with a blocking means which can be activated by a control button not shown, which blocking means blocks up the winding mechanism in activated position. The steel strip 41 with its free end firmly joined to the lower end part of the inner bar section lib, so that when this is withdrawn and the blocking device 39 released the both bar sections can be displaced with respect to each other. The non-contact detection of the steel strip 41 is prefe¬ rably carried out by means of a light-emitting diode as a transmitter and the output signal is fed if necessary after amplification to an electric counter, for example an elec¬ tromagnetic impulse counter of known design. Instead of a steel strip also a nonmagnetic strip can be used which is provided with magnetic scale divisions, which can be non- contact detected by means of a magnetic slot switch.

Claims: CLAIMS 1. Levelling bar, in the form of a simple bar (11) or seve¬ ral into each other displaceable bars (11a, lib), to deter¬ mine the elevation difference between different points and which is provided with a slide (14) which is displaceable along said bar and lockable in different positions said slide being provided with a level indicator (16) c h a r a c t e r i z e d t h e r e i n, that the slide (14) is provided with a counter apparatus (20), which in cooperation with the bar/bars (11a, lib) or a reference means (12) attached to said bar/bars is provided to indicate the relative distance from one of the outer ends of the bar/bars to said level indicator (16). 2. Levelling bar according to claim 1 c h a r a c t e r i z e d t h e r e i n, that the counter apparatus (20) is a counter provided with a digit indicator (11), preferably with preset and zero set¬ ting facilities, said counter being arranged to be activated by a transducer (21, 40) which is engaged to or provided to detect said reference means (12). 3. Levelling bar according to claim 2 c h a r a c t e r i z e d t h e r e i n, that the bar (11) contains of at least two telescopic into each other displaceable and in different displacement posi¬ tions lockable bar sections (11a,lib) that the reference means (12), which consists of a chain (27), a flexible strip (41) or the like is provided to extend between the end portions of the both bar sections (11a, lib), that the reference means is in cooperation with an expansion device (18) formed to allow an extension re¬ spectively a shortening of the reference means (12) at the relative displacement of the bar sections (11a, lib) and that blocking means is provided to block respectively to release the displacement movement of the reference means (12). 4. Levelling bar according to claim 3, c h a r a c t e r i z e d t h e r e i n, that the reference means consists of an endless chain (27), strip or the like, that in the first bar section (11a) in its both end portions pulleys (26,28) are mounted on be¬ arings for the reference means (12) and that in the inner end of the second bar section (lib) is by way of a carrier (35) firmly connected to the chain or strip part (27) or with a second doubled chain/strip cooperating with the gear- wheel (21) of the counter. 5. Levelling bar according to claim 3, c h a r a c t e r i z e d t h e r e i n, that the reference means (12) is placed around a pulley (26) provided at the end portion of the first bar section (11a) and that the both free ends of the reference means (12), one of said ends through an expansion device (18) eg. in the form of a tension spring (37), are mounted to the outer end portion of the other bar section (lib). 6. Levelling bar according to claim 3, c h a r a c t e r i z e d t h e r e i n, that the reference means (12) is connected to an expansion device (18) which consists of a spring loaded winding mecha- nism (42) placed at the end portion of the first bar section (11a), while the opposite end of the reference means is attached to the outer end portion of the second bar section (lib). 7. Levelling bar according to claim 2, c h a r a c t e r i z e d t h e r e i n, that the transducer (21) consists of a gear-wheel or the like, which is meshed into the reference means (12) consis¬ ting of a chain (27) or a strip (41), and that the gear- wheel (21) is arranged to transfer its rotation to a number of digit wheels (22) of a digit display. 8. Levelling bar according to claim 2, c h a r a c t e r i z e d t h e r e i n, that the transducer (40) consists of a photo electric inter¬ rupter, a magnetic slot switch or the like and that the reference means (12) consists of a strip provided with perforations, magnetizable markings or the like.

Inventors: MARTINSSON JONAS, MARTINSSON, JONAS
Applicants: MARTINSSON JONAS, MARTINSSON, JONAS
Application year: 1990
Main classification: G01D5
IPC codes: G01C15