EP2117771A1

EP2117771A1 - System, device and method for levelling floors

Info

Publication number: EP2117771A1
Application number: EP08705390A
Authority: EP
Inventors: Kåre Kilgren; Håkan THYSELL
Original assignee: HTC Sweden AB
Current assignee: HTC Sweden AB
Priority date: 2007-02-15
Filing date: 2008-02-07
Publication date: 2009-11-18
Also published as: CN101657296A; SE530893C2; SE0700394L; WO2008100211A1; US20100022168A1; AU2008216946A1

Abstract

The present invention relates to a system, a device and a method for leveling floor surfaces by means of a floor grinding machine (10), in which the device comprises a lifting device (90) for adjusting the height of the floor grinding machine above the floor surface during leveling thereof. The system for leveling floor surfaces by means of the floor grinding machine comprises a laser transmitter (60) which is operatively connected to at least one laser receiver (61), which is arranged on the sensing device (70), and the method for leveling floor surfaces by means of the floor grinding machine is performed in that the laser transmitter (60) emits a signal which is received by a laser receiver (61), which is arranged on the sensing device (70) and the height of which is thereby detected and converted into a possible deviation in the level of the floor surface, the height of the floor grinding machine and hence the removal of the floor surface being adjusted in relation to this possible deviation in the level during leveling of the floor surface.

Description

SYSTEM, DEVICE AND METHOD FOR LEVELLING FLOORS

Technical field

The present invention relates to a system, a device and a method for leveling floors by grinding.

State of the art

Machines and tools for grinding floors composed of stone, such as natural stone, concrete and wood are currently available. The building industry currently employs techniques in which the building is produced in factories in the form of multiple different modules. The building is merely assembled on a concrete slab on the site where it is to stand. This system requires an extremely level concrete base with ±1 mm difference in height between the highest and the lowest point. No machines currently on the market are capable of achieving this without repeated manual measurements and gradual intermediate grinding.

The building industry also employs building techniques which require even more level concrete bases, especially for high-rise storage in which automatically raising and lowering trucks move and lift pallets etc. up to great heights and down whilst simultaneously transporting them by means of a vehicle moving along the concrete floor. This requires very precise tolerances for the levelness of the floor, in that the pallet may be situated several meters, possibly tens of meters up in the air whilst being moved vertically and laterally, and minor anomalies in the levelness of the floor result in a very large deviation at this height and these fine tolerances cannot be achieved without machining of the concrete, which is both time-consuming and labor-intensive. Current techniques involve, among other things, grinding two tracks in the floor, in and along which the truck moves, the tracks having to be extremely level. These tracks, however, make it harder to use the floor in that any vehicle passing over these tracks is disturbed by jolts and vibrations and can even become stuck in these and become harder to steer.

Summary of the invention

The object of the present invention is to provide a system, a device and a method for leveling floors by grinding, the height of the floor being continuously measured and the rate of removal of a floor grinding device being continuously controlled during leveling of the floor.

The present invention relates to a device for leveling floor surfaces by means of a floor grinding machine, which comprises a lifting device for adjusting the height of the floor grinding machine above the floor surface during leveling thereof. The device comprises a sensing device, which is in contact with the floor surface during leveling of the floor and is connected to the floor grinding machine in such a way that the sensing device is afforded freedom to move basically perpendicular to the floor surface that is to be leveled.

One embodiment according to the invention relates to a device in which the freedom of movement of the sensing device in a vertical direction is achieved by means of at least one slide rail, which basically extends perpendicularly to the floor surface that is to be leveled.

Another embodiment of the invention relates to a device in which the sensing device comprises a stand, which is displaceable along the slide rail and which has a first free, lower end in contact with the floor surface via a contact member during leveling thereof.

Yet another embodiment relates to a device in which the lifting device comprises a support wheel, which is height-adjustably connected to the floor grinding machine via at least one moveable strut suspension.

A further embodiment relates to a device in which the strut is a parallel strut.

Yet another embodiment relates to a device in which the contact member is at least one spherical roller and in a further embodiment the contact member is at least one PCD dome.

A further embodiment relates to a device in which at least one laser receiver is arranged on the sensing device and yet another embodiment relates to a device in which a laser receiver is arranged at a second free, upper end of the stand.

The present invention also relates to a system for leveling floor surfaces by means of a floor grinding machine, in which a laser transmitter is operatively connected to at least one laser receiver, which is arranged on the sensing device.

The present invention further relates to a method for leveling floor surfaces by means of the floor grinding machine, in which a laser transmitter emits a signal which is received by a laser receiver, which is arranged on the sensing device according to any of the preceding claims and the height of which is thereby detected and converted into a possible deviation in the level of the floor surface, the height of the floor grinding machine being adjusted in relation to this possible deviation in the level during leveling of the floor surface.

According to the invention the height is measured by a rotational laser and a laser receiver on the grinding machine, the receiver being seated on a sensing device in contact with the surface that is to be ground and the sensing device being connected to the grinding machine via a slide attachment, which affords the sensing device a substantially vertical freedom of movement in relation to the grinding machine and also the support wheel. The height deviation is registered and the machining of the concrete surface is regulated by a system which controls the lifting device. At the front edge of the grinding machine the lifting device is connected to the wheel, which supports the grinding machine, said lifting device in turn regulating the removal cut of the grinding machine by raising, lowering or maintaining the height of the grinding machine in relation to the surface that is to be ground and the support wheel.

By means of the invention, which continuously measures the height and controls the machine accordingly, the floor leveling process is rendered considerably more efficient and greater levelness is achieved in floor grinding, the grinding process also being rationalized. The invention provides a well-functioning floor leveling system, which affords great levelness in grinding. The invention reduces the number of personnel required and much of the time-consuming measurements, especially the manual measurements, and reduces the costs of floor leveling and the time spent doing this. The object of the invention was to provide a new measuring system which was lacking on the market. The ambitions were to develop an already existing floor grinding machine to also encompass a measuring system. The results of the grinding tests show that the measuring system according to the invention works. The points which were raised too high in the measurement prior to grinding were machined and the points that were too low were not machined. Since measurement is performed at the front edge of the grinding head, certain low points are machined by the rear edge of the grinding head where large differences in level occur within a short space. There are several advantages with the system according to the invention in that it is easy to move and assemble, and it saves time as a result of the smaller number of measurements and also improves the accuracy, that is to say the levelness after grinding. The design construction and the method according to the invention are of great benefit to the operator when high-precision grinding is required, and also afford economic advantages due to the low material costs. This means that the use of rotational lasers in producing a level grinding result is a good solution to the problem and gives a more even result. The use of rotational lasers and at least one laser receiver provides a solution which fulfills the accuracy requirement, which is robust and which is reasonably priced.

Brief description of the drawings

The invention will now be described in detail below with reference to the drawings attached, in which

Fig. 1 shows an example of a grinding machine,

Fig. 2 shows an example of a grinding tool holder of the grinding machine in Fig. 1,

Fig. 3 shows an example of a measuring device which can be used on the grinding machine according to the invention,

Fig. 4 shows how an angular adjustment produces a vertical adjustment according to the invention,

Fig. 5 shows the height adjustment according to Fig. 4 in more detail,

Fig. 6 shows the range and sensitivity for a receiver which can be used in the measuring device according to the invention,

Fig. 7 shows an example of a receiver which can be used according the invention,

Fig. 8 shows a side view of an embodiment of a lifting/measuring device according to the invention, Figs. 9 and 10 show perspective views of the lifting/measuring device in Fig. 8 from different angles,

Fig. 11 shows a side view of another embodiment of the lifting/measuring device,

Fig. 12 shows another part of the lifting/measuring device in Fig. 11,

Fig. 13 shows a part of Fig. 12 in greater detail,

Fig. 14 shows a part of the method for controlling the grinding machine according to the invention,

Fig. 15 shows another part of the method for controlling the grinding machine according to the invention,

Fig. 16 shows yet another part of the method for controlling the grinding machine according to the invention,

Fig. 17 shows a further part of the method for controlling the grinding machine according to the invention,

Fig. 18 shows a floor measurement prior to grinding,

Fig. 19 shows a floor measurement after grinding,

Fig. 20 shows a flow chart for the method of controlling the grinding machine according to the invention,

Fig. 21 shows a circuit diagram of the electrical design according to the invention, and

Fig. 22 shows the measuring result from a test of the invention (surveying of concrete slab Strandgatan; difference from theoretical; + = raised slab; unit mm and scale 1:75) .

Detailed description of the drawings

The present invention relates to a system, a control system, a device and a method for leveling floors by means of grinding. The control and measuring system according to the invention is designed for a grinding machine 10 (Fig. 1), which is radio-controlled in order to make the work easier for the operator and is controlled via two brushless DC servomotors, each fitted to a wheel 20. The machine rests on these two wheels 20 and on one or more grinding disks 30 (Fig. 4) . The dynamic friction is considerably lower than the static friction, which means that m operation the machine becomes relatively easy to maneuver, despite its weight of 600 kg.

The motor that drives the grinding disks 30 is a three- phase asynchronous motor 31 having a power output of 15 kW. The motor is controlled via a frequency converter, which feeds with a frequency of 30 - 90 Hz, a belt drive system with gearing delivering a speed of 450 to 1350 rpm. The grinding is performed by diamond tools, which are fixed to four tool holders 40 mounted on the larger rotary grinding disk 30. Fig. 2 shows one of the tool holders 40 with six tools 50. The tools are easy to change and the operator has the facility for choosing whether to use one, two, three or six tools, depending on the type of floor and the desired rate of removal. The grinding machine 10 is also equipped with a "mist cooler system", which means that a fine water mist is sprayed onto the floor, which then cools the diamond tools 50. This results m more efficient grinding and a longer tool service life.

The rotational laser 60 (Fig. 3) is a rotating laser leveling instrument, which together with at least one or more laser receivers 61, for example two or three, measures the difference in height. One function which most rotational lasers have is self-leveling and this permits automatic self-leveling when it is activated. This function allows an inclination of the laser of up to ± 10 degrees without affecting the accuracy. Another function is automatic level monitoring, which gives an alarm if the stand 70 should begin to drop or if the instrument is dislodged from its original position. The rotational laser has a robust design and the rotor head is protected by a laser housing enclosure, which can withstand a fall from a height of 1 meter onto a concrete surface. It is also dust- and watertight, which permits use out of doors. The rotational lasers 60 used are of laser class 1, 2, 3A or 3R, class 3A and 3R allowing a power output or pulse energy five times greater than class 2, although, when the beam is propagated by means of an optical system, it becomes equivalent to class 2 from the risk standpoint.

The laser receiver 61 (Fig. 7) is the unit which receives the signal emitted by the rotational laser 60 and accordingly indicates at what height the receiver is situated. The accuracy of the receiver 61 is taken into account, since it may vary from ±0.05 mm to ±12 mm, depending on which unit is selected. Something else which should be considered is the reception angle of the unit, which can also vary greatly from ±45 degrees to 360 degrees. The receiver 61 is described in more detail below.

In order to create the measuring system, the rotational laser 60 is arranged on a stand on the fringes of the surface that is to be machined, due to the fact that the rotational laser must not be affected so that it is shifted out of its position. The receiver 61 that is used to receive the laser signal is placed on the grinding machine 10 on top of the stand 70 as shown in Figs. 8-10 and 11.

The placing of the laser receiver 61 has a great bearing on the accuracy of the measurement. Since the machine 10 is constantly in motion and the conditions change during the course of the machining, certain factors need to be considered when placing the receiver 61.

• Tool wear - Tool wear affects the height of the machine in relation to the floor. The difference between a brand new tool and a worn-out tool may be up to 15 mm. • Same distance from the underlying surface - One requirement for accuracy in the measurements is that the receiver 61 should always be at a specific distance from the floor. This is in order to afford the facility for assessing the levelness of the floor through measurements of the difference in height in relation to a reference point.

• Thermal interference from the underlying surface - According to Gunilla Blomkvist of NCC Construction Sverige AB, who was measurements engineer on the construction of a concrete slab, the measuring point relative to the floor plays a significant role. The measuring point should be located half a meter above the ground surface in order to avoid the effects of heat radiated from the underlying surface. This is especially true of laser measurement and the influence is most pronounced in warm environments and especially on asphalt, although concrete also gives off heat which could cause interference.

• Vibrations - During grinding, vibrations occur in the machine 10. The vibrations vary depending on factors such as the type of tool 50, the grinding speed and material to be machined. Observing the machine during the ongoing grinding process, relatively small vibrations will be noted, which are assumed not to cause problems with the measurements.

For these reasons, placing the sensor on existing parts of the machine 10 is excluded without compensating for tool wear. This is because the machine rests with most of its weight on the grinding head and the rest of the construction follows as the tool is worn, so that the grinding head is always pressed against the floor. The result is that the machine with grinding head and motor subsides as the tool wear progresses and varies by 15 ram in a vertical direction depending on the state of the tool.

A separate sensing device 70 in the form of a receiver stand with a reference wheel/ball or wearing surface against the floor, fixed to the front edge of the grinding machine 10, results in an accurate measurement of the surface to be ground. The difference between new and worn tools results in a change in the angle, which leads to a variation in the distance between the surface and the receiver 61. This angular variation can be calculated, making it possible to also calculate the vertical error. The receiver stand 70 is located in front of the machine 10 (Fig. 8-10) . The tool wear is 15 mm after half the length and is equal to 30 mm after the full length, as can be seen in Fig. 4.

The angular variation to which the tool wear gives rise affects the front part of the machine 10 with the same angle as the change in the wheel axis. This angle gives rise to a variation in the vertical direction, as shown in Fig. 5. The height of the measuring stand 70 is 500 mm in this embodiment, but it may be shorter or longer in other embodiments, in order to avoid the problem of heat radiation as described earlier. The designation X in Fig. 5 is the new height relative to the ground/the floor.

Through calculations with various trigonometric correlations, it is possible to calculate x and the variation in the vertical direction can be written as

Xi = 500 - X = 500* (1-cos (a) )

which gives the result

X₁ = 500 * ( 1- cos ( 1 . 342 9 ) ) = 0 . 138 6 mm The vertical error that occurs from new tools to completely worn-out tools is relatively small and is assumed not to cause major errors in the accuracy of the system. Bearing in mind the problems described here, the measuring stand 70 which is located at the front edge of the machine is a good solution.

No receiver with signal pickup on the market meets the accuracy requirements sought. The receivers which afford the facility for deriving useable signals are machine receivers designed to sit on excavators, road graders or similar machines having a lesser accuracy requirement. These receivers have an accuracy of about 10 mm and are not acceptable for this application. Receivers affording sufficiently high accuracy are so- called handheld receivers 61. These have no facility for delivering a useable electrical signal since the measuring result is only displayed on an LCD screen and light-emitting diodes on the receiver, giving an indication of the position of the receiver in relation to the laser.

The handheld receivers 61 have an inclined surface with photodiodes where the laser strikes. The receiver 61 then has various ranges within which the laser is deemed to lie. These ranges are illustrated in Fig. 6. Since the receiver 61 has a sensitive range for zero level and the next area is large, it will only be possible to use indications of how the receiver lies in relation to the laser 60. This comes down to three signals: High, Normal and Low. None of the manufacturers is willing to divulge information on how their product is designed or will come up with proposals as to how signals can easily be coupled out. With essentially only three signals it was decided to use the existing light-emitting diodes 62 on the receiver 61, as can be seen from Fig. 7. The receiver 61 causes both of the diodes 62 to light if the receiver is situated on a level with the laser 60 and only one of the diodes if it is too high or too low. The solution that was chosen for handling the existing signals from the light-emitting diodes was phototransistors . The advantage to this is that the signals can be utilized without the need to intervene in the receiver 61. With the measuring system according to the invention, the machine 10 is controlled according to the signals emitted by the receiver.

In order to produce a control system according to the invention, in which the result of the measurements is interpreted and the information is then used to decide whether the floor needs to be machined, it is necessary to control the rate of removal of the grinding machine 10. The grinding machine is equipped with a system in which the operator has the facility for varying the rate of removal by adjusting the grinding speed, the rate of advance or a change in the grinding pressure, which is done manually by means of adjustable weights on the side of the machine.

A variation in the grinding speed by adjusting the rotational speed of the tools is a complex operation. The highest speed does not always give the fastest removal, there being many other factors that come into play such as the tool used, what material is being ground and the moisture content of the material. The fact that the rate of removal is not proportional to the grinding speed is not the only problem to which an adjustment of the grind speed gives rise. Problems occur since the design of the machine is based on the fact that the dynamic friction is lower than the static friction and adjusting the grinding speed gives rise to different prerequisites for the rate of advance.

The normal rate of advance during grinding is 0.2 m/s. This speed can be adjusted in order to increase the floor machining time and in this way to increase the removal by a relatively simple intervention.

The signals that control the drive motors are 0-5 V, where 2,500 V is stationary. The signal could easily be connected to a PLC and damped if removal is to take place and could bypass the PLC without manipulation for more rapid advance when removal is not to take place. One problem with this is that it interferes with the operator' s scope to drive the floor grinding machine as he or she sees fit.

Another method for regulating the rate of removal is to adjust the grinding pressure. This method is currently used partly by changing the adjustable weights and by placing external weights on the machine 10 in order to increase the grinding pressure. This method can be applied in that a lifting/elevating device lifts/elevates the machine 10 and in this way removes large proportions of the weight of the machine and redistributes the weight to a support wheel 80, which is located at the front edge of the machine. This would mean a reduced contact pressure against the floor and lead to slower removal.

The preferred method for regulating the rate of removal is a variation in the grinding pressure, involving a normal grinding pressure when removing material, which can then be reduced if an area does not need to be machined. This affords a very simple facility for varying the rate of removal.

The grinding machine 10 (in this embodiment an HTC 950 RX model) has an accessory in the form of a support/transport wheel 80, similar to the support wheels fitted to trailers. The floor grinding machine 10 then rests on the two drive wheels 20 and the support wheel 80 fitted to the front edge. This allows it to be moved, driven by the DC motors which normally steer the machine 10, or allows the machine to be rolled manually, which would not be possible when the stationary tools are in contact with the floor.

The transport wheel 80 is the starting point for two embodiments according to the invention. These can be seen from Figs. 8 to 11. The development of the transport wheel construction means that the system according to the invention can easily be shifted to another machine 10. Parts of the existing support wheel construction are used to reduce costs and also to improve the compatibility with existing grinding machines. In order not to create any problems in turning or in grinding, when the machine swivels in a sideways direction, the wheel 80 from the old construction is used. The major difference is that the manual elevation has been replaced by a lifting device 90 comprising an adjusting fixture 91. The function of the adjusting fixture is to elevate or lower the machine 10 and in this way to adjust the force with which the grinding head presses against the floor. The maximum capacity of the adjusting fixture 91 is 6800 N, which is sufficient for lifting the entire weight of the machine.

The wheel 80 that is used requires that the suspension should always be vertical to the floor so that the height will not be affected by the modified wheel angle. This problem is solved in that the lifting device 90 also comprises a load cell 92 for sensing what load the wheel 80 is being subjected to. Figs. 11 and 12 show the fitted load cell 92 in a first embodiment. Knowing the load on the wheel 80 via the load cell 92, it is possible to estimate the grinding pressure. The adjusting fixture 91 adjusts the machine 10 to the given levels of grinding pressure, depending on the level of the surface. This results in a constant height from the floor irrespective of the position of the wheel 80. The system according to the invention is based on the fact that measurements which give the level of the floor are performed continuously. In order to achieve this, the measuring stand 70 must have contact with the underlying surface, that is to say the floor, and must be able to slide freely when attached to the grinding machine 10. The measuring stand 70 is designed with a contact member 73 in the form of at least one spherical roller on the end/bottom or at least one polycrystalline or compact diamond (PCD) dome (one embodiment in Fig. 11 and 12 has a PCD dome whilst a second embodiment in Figs. 8-10 has two PCD domes as contact members and is arranged on a parallel strut 100 in order to ensure that the wheel 80 is perpendicular to the floor) , which touches the floor surface and allows movement in all directions. Since the measuring stand 70 only needs to carry its own weight, the spherical roller/PCD dome successfully copes with the load by a large margin.

The fixing to the grinding machine 10 comprises two slide rails 71 fitted to the stand 70 and attachments 72 to the modified support wheel construction and the parallel strut construction 100. The reason for using two rails is that it lends greater stability in response to movement in all horizontal directions. The construction according to the invention allows the stand to move freely in a vertical direction and means that each spherical roller/PCD dome is at all times pressed against the underlying surface under the stand's own weight.

For the control system, a separate electrical switch box is used with a function relay as central unit. A circuit diagram of the electrical design is shown in Fig. 21. Zelio Logic is a digital function relay manufactured by Telemecanique, which is used in the control system. The function relay is supplied with 24 V DC and is fitted on a 35 mm DIN rail, which affords good prerequisites for fitting in the electrical switch box. Zelio Logic has eight digital inputs for 24 V DC, of which four can be used for analog signals in the range 0-10 V. The internal A/D converter uses 8 bits, which gives an acceptable resolution. The outputs provided are four relay outputs which can cope with 8 A.

The load cell 92 (Figs. 11-13) used in the invention is a TB model. A bending beam is used to measure pressure and is capable of measuring 0-500 kg with a safe overload of 750 kg, which means that it can handle the full weight of the machine 10. The maximum supply is 15 V DC and the output signal is 2 mV/V, which means a maximum output signal of 20 mV at full load when the feed voltage is 10 V. Strain gauges are fitted inside a cavity in the load cell 92. Two gauges measure the longitudinal extension and two measure the transverse extension. The four strain gauges are coupled to a Wheatstone bridge. The bridge connection to four gauges means that the load cell 92 does not become sensitive to changes in resistance due to changes in temperature.

In the first embodiment as shown in Figs 8-10, the load cell 92 is located so that it senses the force to which the adjusting fixture 90 is subjected. In the second embodiment according to Figs. 11-13 the load cell measures the pressure to which the wheel 80 is subjected, from which the contact pressure of the grinding head can be calculated. These embodiments mean that through the load cell 92 it is possible to detect the force which the grinding head of the grinding machine 10 is applying to the underlying surface, that is to say the floor, allowing the surface removal of the grinding machine to be automatically controlled.

In order to amplify the signal from the load cell 92, a load cell amplifier is used to convert signals from the load cell into an analog voltage or current signal. The amplifier permits a connection from the load cell 92 to a PLC without the use of a separate balancing instrument. The amplifier is adjusted by panel potentiometers mounted on the front of the grinding machine 10.

The program used according to the invention has three signals. Two of these are discrete signals emanating from the phototransistors, which are high when the light-emitting diodes 62 on the receiver 61 light up. The third input signal emanates from the load cell amplifier and is an analog signal, which is converted by an 8-bit A/D converter. The two discrete input signals also go to timer circuits, which convert the signals into pulses. This step makes it possible, by simple means, to handle the signals generated by light- emitting diodes. This is followed by a processor step, in order to prevent the system reacting to just one measurement without availing itself of a mean value in assessing whether or not the surface is to be ground. This step has four processors, which count pulses from each input, when both of the inputs are active simultaneously, and the total number of pulses. Fig. 14 shows the timer circuits to which the inputs go and how the signals are relayed to the processor step.

After the processor step comes a comparator step (Fig. 15) , which by means of ensuing gate logic interprets the information in the processors and determines whether the surface is to be machined. The output signal from this step consists of a discrete signal, where high signifies that the surface is higher than the reference and is to be machined.

In order to provide a memory, which retains the information on whether the surface is to be machined, a processor is used. The memory functions so that, if grinding is to be performed, the processor contains the digit 0 and, if the surface is not to be machined, the processor contains the digit zero. Fig. 16 shows the processor and the rest of the circuits for memory processing. The information from the memory is used to select what pressure the load cell 92 must bear. The signal from the load cell is compared with preprogrammed values for the various levels. The preprogrammed levels also contain tolerance limits so that vibrations and other interference will have less influence. Depending on the signal from the memory, the pressure on the load cell is adjusted, which means that machining of the surface is always performed with the same pressure and the grinding head is always elevated by the same height when grinding is not to be performed. Fig. 17 shows the comparators, which determine whether the pressure on the load cell 92 is within the correct levels. According to the comparators, the memory determines what signals are to be used and relayed to the outputs that control the adjusting fixture 91.

On construction sites, measurements are at present performed manually at intervals of approximately one meter and measurements are repeated many times with intervening grinding in order to meet the accuracy requirements, which are often of ±1 mm. The measuring result from a building project is shown in Fig. 19. In order to simulate the measurements performed outside on the building project, height measurements were undertaken on the concrete slab within a rectangular area measuring 3.5 x 1 m. On this area 24 measurements of the height relative to a reference point were undertaken, so that the measurements were performed at intervals of half a meter. The DNA 03 instrument from Leica was used for the measurements. This instrument is made for industrial measurements and has a high accuracy with a standard deviation of 0.3 mm per kilometer. Fig. 18 shows the levels measured before grinding with all measurements given in tenths of a millimeter. All results from the measurements presented in this description are in tenths of a millimeter and all measurements have the same fixed reference point, in order to provide an easy way of comparing the results .

In order to get the surface level, an area larger than the actual measured area was machined. The measuring points on the short sides led to complications as the grinding machine 10 could not get to machine these points. This problem was due to the placing of the measured surface and where the grinding was performed the concrete base was poured using two grades of concrete, one harder and one softer. In order to locate the entire measuring surface on the same type of concrete, it had to be applied in such a way that grinding of the outer points became impossible. For this reason the measuring result from the outer measuring points on the upper short side should not be evaluated when interpreting the result.

The zero level for the measuring system, the level which the machine 10 is intended to achieve, is set to 0.3 mm, which corresponds to the value 3 in the drawings showing the result for the various measurements. The result measured after grinding is shown in Fig. 19. As the measurements show, an accuracy of ±2.2 mm was obtained. An error in the grinding meant that the machine was stationary and machining the same point for a longer period of time, which is reflected in the result from the point having the value -1. No great significance need be attached to this point.

Other embodiments of the invention with other equipment, such as a better laser 60 or receiver 61, and the capacity to extract better signals with an indication of how much the level differs from the reference are conceivable. A laser 60 affording better accuracy together with a receiver 61 with greater sensitivity affect the overall accuracy, giving a better result. With signals which more precisely describe the deviation from the reference, it should be possible to achieve an improved adjustment of the grinding pressure. In another embodiment the construction can be modified so that the lifting device 90 is more stably fixed to the top in the second embodiment and not attached to the load cell 92, which is in turn anchored to the machine 10. In the first embodiment with parallel strut 100, which anchors the wheel 80 more stably and with less dependence on the degree of inclination, the adjusting fixture 90 is arranged inside the strut 100.

Conceivable future embodiments may involve the use of a laser and receiver affording better accuracy, which should give the system as a whole an improved accuracy. A receiver with good accuracy in which the difference in level is expressed as an analog output signal should afford significantly better scope for more precise selection of a suitable grinding pressure. It would also be desirable for the receiver to be capable of receiving laser signals from all directions. A specially manufactured load cell 92 for detecting the grinding pressure combined with a more stable construction of the lifting device 90 is expected to afford a facility for more precise control of the grinding head elevation in the second embodiment. The first embodiment is more stable. The measuring stand 70 can have a more stable attachment to the construction, in order to avoid changes in position and to counteract the effects of vibrations, which occur during the grinding process. The receiver 61 can be fixed to the measuring stand 70 so that it cannot be dislodged from its position. In continued use of the embodiment with a spherical roller 73, a system should be designed which automatically cleans the surface before the spherical roller passes over it. One variant for implementing this system is compressed air. The use of embodiments with one, two or more PCD domes 73, however, eliminates the need for cleaning, since there are then no moving parts to become fouled with dirt. Some form of display should also be implemented in order to provide the operator with information on the height compared to the reference point. This function would mean that the operator can steer the machine 10 more towards the points in need of machining and can avoid going over the points that have attained the correct level, since machining does not occur at these points anyway.

Another feasible but currently too expensive embodiment of the measuring system involves the use of a laser tracker as used primarily for determining the coordinates of large objects in the aviation, shipbuilding and automotive industries, since this technique combines both laser interferometry and goniometry. This measuring system has an accuracy of 0.1 mm at a distance of 100 meters, where measurement is performed at a speed of up to 1000 points per second.

One method of controlling the leveling of the floor surface by means of the grinding machine 10 is shown in Fig. 20. This method is performed in stages in that the rotational laser 60 emits a light signal, which is received by the receiver 61, the height of which is read off/detected and converted in that the rotational laser (the laser receiver 61 always being at a distance of x mm from the floor, see Fig. 5 and the distance x being set via adjustment of the receiver or raising/lowering of the laser) lays out a plane in the space and the receiver 61 senses its position for any deviation relative to the floor plane by means of signals, which are processed by the control system according to the invention (which forms a mean value from a number of points over a short distance) and, if the floor surface is too low in relation to the reference, the grinding pressure is reduced and, if the floor surface is too raised, the grinding pressure is increased. The reference is the height of the laser plane minus the length of the measuring stand 70 to the zero position of the laser receiver 61. Calibration of the reference point for the laser transmitter 60 and the laser receiver 61, however, is not necessary. This means that the grinding pressure adjustment is performed by imposing elements of the pressure from the grinding head on the wheel 80 at the front edge of the machine. This gives a reduced grinding pressure, so that the grinding pressure can be increased by withdrawing the pressure from the front wheel 80, so that the weight of the entire machine again rests on/presses the grinding head down with the grinding disk 30 and the grinding tools 50.

Claims

Patent claims

1. A device for leveling floor surfaces by means of a floor grinding machine (10), which comprises a lifting device (90) for adjusting the height of the floor grinding machine above the floor surface during leveling thereof, wherein a sensing device (70), which is in contact with the floor surface during leveling of the floor surface, is connected to the floor grinding machine (10) in such a way that the sensing device is afforded freedom to move basically perpendicular to the floor surface that is to be leveled and senses the levelness of the floor for interaction with the lifting device (90) when adjusting the height of the floor grinding machine above the floor surface according to the sensing.

2. The device as claimed in claim 1, wherein the freedom of movement of the sensing device (70) in a vertical direction is achieved by means of at least one slide rail (71), which basically extends perpendicularly to the floor surface that is to be leveled .

3. The device as claimed in claim 1, wherein the sensing device (70) comprises a stand, which is displaceable along the slide rail (71) and which has a first free, lower end (70a) in contact with the floor surface via a contact member (73) during leveling thereof .

4. The device as claimed in any of the preceding claims, wherein the lifting device (90) comprises a support wheel (80), which is height-adjustably connected to the floor grinding machine (10) via at least one moveable strut suspension (100) .

5. The device as claimed in claim 4, wherein the strut (100) is a parallel strut.

6. The device as claimed in claim 3, wherein the contact member is at least one spherical roller (73) .

7. The device as claimed in claim 3, wherein the contact member is at least one PCD dome (73) .

8. The device as claimed in claim 1, wherein at least one laser receiver (61) is arranged on the sensing device (70) in such a way that the laser receiver is always at a specific distance from the floor .

9. The device as claimed in claim 3, wherein a laser receiver (61) is arranged at a second, free upper end (70b) of the stand.

10. A system for leveling floor surfaces by means of a floor grinding machine (10), wherein a laser transmitter (60) is operatively connected to at least one laser receiver (61), which is arranged on the sensing device (70) according to any one of the preceding claims.

11. A method for leveling floor surfaces by means of a floor grinding machine (10), wherein a laser transmitter (60) emits a signal which is received by a laser receiver (61), which is arranged on the sensing device (70) according to any of the preceding claims and the specific height of which above the floor is thereby detected and converted into a possible deviation in the level of the floor surface, the height of the floor grinding machine (10) being adjusted in relation to this possible deviation in the level during leveling of the floor surface by means of the lifting device (90) according to any one of the preceding claims .