DE102016201574B4 - Coordinate measuring machine with a quill, method for operating the coordinate measuring machine and method for manufacturing the coordinate measuring machine - Google Patents

Abstract

Coordinate measuring device (1) with a quill (27; 57) on which a sensor for recording measured values for determining coordinates of a workpiece (12) can be attached and the vertical position of which can be adjusted by moving the quill (27; 57) upwardly facing surface (44) of the quill (27) and / or an upwardly facing surface (65) of a component (64) connected to the quill (57) which moves with a movement of the quill (57), at least one limited gas space which is under negative pressure during operation of the coordinate measuring machine, so that the quill (27; 57) experiences an upward force which corresponds to a difference between a gas pressure in the vicinity of the quill (27; 57) and the negative pressure.

Description

The invention relates to a coordinate measuring device with a quill, to which a sensor for recording measured values for determining coordinates of a workpiece can be attached and the vertical position of which can be adjusted by moving the quill. The invention also relates to a method for operating and a method for producing such a coordinate measuring device.

Coordinate measuring machines with a quill have been known for a long time. The sensor (e.g. a tactile sensor or an optical sensor) is or is usually attached to the lower end of the quill. While the coordinate measuring machine is in operation, the quill is moved, in particular in order to scan the workpiece to be measured from different sensor positions. Quills are e.g. used on coordinate measuring machines in portal design or in gantry design. However, the invention is not restricted to these types of coordinate measuring machines.

The quill is movable relative to a supporting part of the coordinate measuring machine and the vertical position of the quill can be adjusted by moving the quill. There is therefore the problem that the weight of the quill can influence the measurement of the workpiece to be measured by the coordinate measuring machine. In particular, the weight can lead to a deformation of load-bearing parts of the coordinate measuring machine, in particular depending on the position of the quill relative to the base of the coordinate measuring machine. Furthermore, the weight of the quill can interfere with the measurement of the position of the quill. In addition, the weight of the quill can interfere with the movement of the quill. In particular, the weight causes inertia and maximum values can therefore be specified for the acceleration and speed during the movement of the quill.

Arrangements for balancing the weight force have already been proposed. In the past, counterweights were used to balance the weight. Coordinate measuring machines of this type are for example in the DE 26 13 451 and the DE 29 43 431 described. The disadvantage of this, however, is that a counterweight increases the total mass of the parts to be moved, as a result of which the dynamics during the movement of the quill or other parts of the coordinate measuring machine are adversely affected. Mechanisms with spring and cable pull also do not compensate the quill weight (including attached parts such as the sensor) exactly in all vertical positions of the quill.

It has also already been proposed to provide pneumatic cylinders instead of the counterweight. A corresponding coordinate measuring machine is for example in U.S. 4,207,680 described. Such pneumatic cylinders or gas pressure springs have the cylinder, also called a pressure tube, a piston rod with a piston and suitable mechanical connections for introducing the forces onto the piston rod. The pressure pipe is filled or acted upon with a compressed gas. Depending on the application, either one or both sides of the piston are filled with gas in the axial direction of the pressure tube. There are also constructions that also have a separating piston that separates two areas filled with gas and oil.

Previously known compensation devices also have the disadvantage of taking up a lot of space. For example, the coordinate measuring machine (hereinafter abbreviated to KMG) provides evidence U.S. 4,207,680 a deflection device, which consists of two coaxially mounted discs. In this way a conversion of the torque and thus the tensile force between the load and the air pressure cylinder is possible. However, the cylinder extends in the horizontal direction and the deflection device requires a considerable amount of space in order to be able to effect the force conversion. Air pressure cylinders also generally have the disadvantage that they have to be positioned very precisely so that they do not cause any transverse forces during the upward and downward movement of the quill. Frictional forces also occur in any case due to the friction between the piston and cylinder.

DE 38 23 042 A1 describes a CMM with a compression spring (there a helical spring), the longitudinal axis of which runs in the horizontal direction. The pull rope, which transfers the weight to the spring, is deflected twice in order to shorten the spring travel. However, the combination of compression spring and deflection requires a lot of space in the horizontal direction.

DE 86 094 23 U1 describes a compensation device for a coordinate measuring machine with a compression spring whose longitudinal axis is oriented in the vertical direction. A deflection device with two deflection rollers is located above the compression spring. The fastening of the pull rope is also located above the compression spring. Despite the shortened spring travel, the space requirement is relatively high.

Compensation devices with mechanical springs in principle have the disadvantage that they cannot exactly balance the weight of the quill in all vertical positions of the quill.

EP 0 104 972 A1 describes a coordinate measuring machine with a vertically movable sensor which is carried by the lower portion of a sensor arm, the weight of which is balanced by a pneumatic counterweight. Using a source of compressed air, a spherical piston of the counterweight is pushed upwards.

EP 0 072 314 A1 describes a pneumatic counterweight system for a coordinate measuring machine, which has a vertically movable sensor. Air under pressure is used to exert a force on a ball-shaped piston, which piston is connected directly to the sensor arm that supports the sensor.

U.S. 4,835,871 A describes a coordinate measuring machine with a vertically movable part which has an air cylinder. A piston inside the air cylinder is fixed, but connected to a stationary machine element via a flexible element. In the cylindrical space between the piston and an axial opening located at the top of the cylinder, compressed air is passed, which compensates for the weight of the moving part.

U.S. 4,799,316 A describes a coordinate measuring machine with a pneumatic sensor counterweight system.

JP S60-152 910 A describes in a coordinate measuring machine a slider that is movable in the vertical direction and has a measuring sensor at its lower end. A piston is coupled to the lower end of a piston rod which is arranged in a cylinder of the slider. A pressure that can be controlled acts on the piston. This enables a weight compensation to be made.

US 2006/0 242 959 A1 describes a pneumatic balancing device for a machine tool for weight balancing. The balancing device has a pneumatic cylinder which contains compressed air during operation and thus leads to a weight balance.

It is an object of the present invention to provide a coordinate measuring machine with a quill whose weight can be compensated without generating additional forces which interfere with the movement of the quill. In particular, the weight force compensation should be adjustable in order to also be able to compensate for different weights of joints, measuring heads and / or measuring sensors for scanning the workpiece to be measured, which are optionally and exchangeably attached to the quill. Further objects of the invention are to specify a corresponding method for operating a coordinate measuring machine and a method for producing a corresponding coordinate measuring machine.

According to a basic idea of the present invention, the weight of the quill is at least partially compensated for by a negative pressure in at least one gas space which is above a material area. The material area is part of the quill and / or an additional component firmly connected to the quill and delimits the at least one gas space. Since the pressure in the gas space is lower than in the vicinity of the quill, it can be referred to as negative pressure and the state of the gas space can be referred to as vacuum. To get the weight, i.e. the weight force to be able to at least partially compensate the quill, the gas space lies above the part of the quill and / or the additional component connected to the quill. The invention is not limited to a single gas space with negative pressure. Rather, the quill and / or at least one additional component firmly connected to the quill can delimit more than one gas space under negative pressure on its underside.

The invention has the advantage that a negative pressure can be generated in the at least one gas space in a simple manner and at low production costs. Furthermore, the gas, which is under low pressure in the gas space and its supply line, does not cause any significant friction when the quill moves and therefore no frictional and transverse forces which adversely affect the dynamics of the quill movement. In particular, when the quill moves in a straight line, this enables very high dynamics of movement with an equally high level of accuracy in setting the vertical position of the quill. In other words, the vacuum-based weight compensation does not adversely affect the precise motion control of the quill.

Another advantage of using a vacuum to compensate for weight is that no heat is generated in the gas space even when the quill moves, as is the case with friction between movable ones Share known compensation devices is the case. Heat leads to changes in the dimensions of the affected parts of the coordinate measuring machine and can in particular lead to measurement errors when reading the scales of axes of movement.

In particular, the movement mechanism and the movement drive of the quill can be designed as known from the prior art. E.g. an air bearing can be provided which supports the movement of the quill relative to a supporting part. E.g. the movement of the quill can be driven by a friction wheel drive. However, other drives can also be used (e.g. via a gear wheel and / or spindle).

A quill of a coordinate measuring machine is understood to be a moving part whose vertical position (i.e. position in the vertical direction) can be adjusted. A sensor for recording measured values for the purpose of determining coordinates of a workpiece is attached or can be attached to the quill. To keep the weight of the quill low, the quill can be hollow on the inside. However, this is not a mandatory feature for a quill. In particular, the quill can be linearly movable in the vertical direction, so that the vertical position is adjusted directly by moving the quill in the vertical direction. However, it is also possible that the quill is not or not exactly linearly movable in the vertical direction, but the coordinate measuring machine has a movement mechanism that moves the quill from top to bottom in a different way (and vice versa). E.g. the quill can be attached to a parallelogram movement mechanism. The movement in the vertical direction can therefore be superimposed on a movement in another direction and / or about an axis of rotation. In any case, the coordinate measuring machine has a supporting part, relative to which the quill is movable from top to bottom and vice versa. The vertical position of the quill is e.g. measured relative to this supporting part. The supporting part can in turn be movable relative to another part of the coordinate measuring machine. The load-bearing part can e.g. be a cross slide of the coordinate measuring machine, which is linearly movable in the horizontal direction. All moving parts of the coordinate measuring machine can be driven manually and / or by machine in order to move them. In particular, the measuring sensor can be attached to the bottom of the quill. However, this is not absolutely necessary. Usually the sensor is attached to the quill in an exchangeable manner via a mechanical interface, e.g. via an adapter plate. It is also known to attach the sensor (e.g. tactile or optical sensor) to the quill using a measuring head. Furthermore, the sensor can optionally be attached to the quill via at least one movement mechanism (e.g. a swivel joint or swivel / swivel joint).

As already mentioned, the term coordinate measuring machine is not limited to coordinate measuring machines in portal design, but includes z. B. in particular also devices with a gantry design. The term optionally also includes machines that are not primarily designed as coordinate measuring machines, but that are set up to work like a coordinate measuring machine. This includes, for example, machine tools on which, instead of a machining tool, a sensor for detecting the workpiece surface (for example a tactile sensor) is attached to a quill. With regard to the movement mechanics, in addition to portal mechanics with linear movement axes cascaded to one another, for example hexapod mechanics with a quill are possible.

In particular, a coordinate measuring device with a quill is proposed, on which a sensor for recording measured values for determining coordinates of a workpiece can be attached and whose vertical position can be adjusted by moving the quill. An upward-facing surface of the quill and / or an upward-facing surface of a component connected to the quill, which moves along with a movement of the quill, delimits at least one gas space that is under negative pressure during operation of the coordinate measuring machine, so that the quill Upward force is experienced, which corresponds to a difference between a gas pressure in a vicinity of the quill and the negative pressure.

Furthermore, a method is proposed for operating a coordinate measuring machine with a quill, on which a sensor for recording measured values for determining coordinates of a workpiece is attached and the vertical position of which is set by moving the quill, wherein on an upward-facing surface of the quill and / or a negative pressure is generated on an upwardly facing surface of a component connected to the quill and which moves with a movement of the quill, so that the quill experiences an upward force that is a difference between a gas pressure in an area surrounding the Quill and the negative pressure. Refinements of the operating method result from the description of the refinements of the coordinate measuring machine.

• • Anordnen einer Pinole an einer tragenden Konstruktion des Koordinatenmessgeräts, sodass eine vertikale Position der Pinole durch Bewegung der Pinole einstellbar ist, wobei an der Pinole ein Sensor zum Aufnehmen von Messwerten zur Bestimmung von Koordinaten eines Werkstücks anbringbar ist,
• • Ausbilden zumindest eines Gasraumes oberhalb einer nach oben weisenden Oberfläche der Pinole und/oder oberhalb einer nach oben weisende Oberfläche eines mit der Pinole verbundenen Bauteils, das sich bei einer Bewegung der Pinole mitbewegt, wobei der Gasraum während eines Betriebes des Koordinatenmessgerätes unter Unterdruck steht, so dass die Pinole während des Betriebes eine nach oben gerichtete Kraft erfährt, die einer Differenz zwischen einem Gasdruck in einer Umgebung der Pinole und dem Unterdruck entspricht.

In addition, a method is proposed for producing a coordinate measuring machine, in particular the coordinate measuring machine according to one of the embodiments described, with the following steps:

• • Arranging a quill on a supporting structure of the coordinate measuring machine so that a vertical position of the quill can be adjusted by moving the quill, with a sensor for recording measured values for determining the coordinates of a workpiece being attachable to the quill,
• • Forming at least one gas space above an upward-facing surface of the quill and / or above an upward-facing surface of a component connected to the quill, which moves with a movement of the quill, wherein the gas space is under negative pressure during operation of the coordinate measuring machine, so that the quill experiences an upward force during operation, which corresponds to a difference between a gas pressure in the vicinity of the quill and the negative pressure.

The at least one gas space can be connected to a negative pressure generating device via a connecting line. Preferably, the vacuum generating device is / is arranged separately and remotely from the coordinate measuring machine. The connecting line therefore connects the gas space, which is / is delimited by the upwardly facing surface, with the negative pressure generating device when the coordinate measuring machine is operated. However, the vacuum generating device is not part of the coordinate measuring machine. E.g. For example, the negative pressure generating device can have at least one vacuum pump which partially evacuates at least the interior of the connecting line and optionally also a gas container, which is / is preferably also arranged separately and remotely from the coordinate measuring machine. Such a gas container provides a buffer volume in order to keep the gas pressure constant within the connecting line and thus also in the gas space in the upwardly facing surface.

In particular, the coordinate measuring machine has a connecting line which, together with the upward-facing surface, delimits the gas space and enables the gas space to be connected to a vacuum generating device. The connecting line, which is part of the coordinate measuring machine, can be the entire connecting line or a section of the entire connecting line that leads to the negative pressure generating device while the coordinate measuring machine is being operated. A course, shape and / or size of the connecting line of the CMM is variable and adapts itself to a vertical position of the quill when the quill is moved, so that the upward-facing surface of the gas space under negative pressure is in different vertical positions of the quill limited and the quill therefore experiences an upward force in each of the various vertical positions.

In the operating method, this corresponds to the use of a connecting line of this type which is at least part of a connection between the gas space and a vacuum generating device.

With regard to the production method, this corresponds to leading such a connecting line to the upward-facing surface, so that the connecting line, together with the upward-facing surface, delimits the gas space and enables the gas space to be connected to a vacuum generating device.

Since the course, the shape and / or the size of the connecting line of the CMM is / are variable, the quill can be moved and there is negative pressure on the upward-facing surface during operation of the CMM. With regard to a connecting line with a variable course, this means that the course of the connecting line or at least a section of the connecting line changes from the upwardly facing surface to the vacuum generating device when the quill is moved and therefore the vertical position of the quill changes . If only the course of the connecting line changes due to the movement of the quill, this has the advantage that the volume within the connecting line does not change and therefore the negative pressure is not changed either by the movement of the quill.

However, it can be relatively expensive to avoid the generation of constraining forces on the quill if only the course of the connecting line changes when the quill moves.

It is therefore preferred that the shape and / or size of the connecting line of the CMM change when the vertical position of the quill is changed. In this case, a change in length of the connecting line of the CMM is particularly preferred. E.g. In this case, vacuum hoses can be used as connecting lines, which are known from handling technology for lifting and carrying objects. When using this handling technique, heavy objects are mostly lifted and transported in the lifted state, a gas space with negative pressure being present on an upwardly facing surface of the lifted object.

With regard to the connecting line of the CMM, it is therefore preferred that the connecting line extends upwards from the surface pointing upwards. When changing the vertical position of the quill, this enables the length of the connecting line in the vertical direction to adapt to the changed or changing vertical position of the quill. In particular, the end of the connecting line on the upwardly facing surface remains permanently in contact with the part that forms the upwardly facing surface during the movement of the quill. As a result, the gas space, which the upwardly facing surface together with the connecting line delimits, is permanently closed off at least in the area of the quill during the movement to the outside. Very slight gas leaks in the area of the quill can easily be compensated for by operating the vacuum generating device (eg the at least one vacuum pump) so that the vacuum remains constant, for example, permanently while the quill is moving.

According to an advantageous embodiment, the connecting line has a vacuum hose, the length of which can be changed, the length of the vacuum hose increasing with a downward movement of the quill and vice versa (i.e. with an upward movement of the quill, the length is reduced). A connecting line (in particular a vacuum hose), the length of which can be changed, has the advantage that the connecting line can at least partially and preferably completely compensate for the change in position of its end on the quill. There is therefore no need for a complex additional mechanical construction that adapts the position of the end of the connecting line to the changed vertical position of the quill and / or reduces constraining forces by deflecting line sections of the connecting line.

It is true that forces can also be exerted on the quill due to a change in length of the connecting line. With a suitable choice of the connecting line, however, these forces can have a very low strength. E.g. The connecting line can have a telescopically adjustable body, the length of which increases with a downward movement of the quill and vice versa. The frictional forces acting between the individual elements of the telescopically variable-length body can be minimized by a suitable choice of the material or materials, in particular on the surfaces of the segments that are adjacent to one another. As an alternative or in addition, the connecting line can have a vacuum hose, the length of which can be changed, as already mentioned. Suitable vacuum hoses are known from the handling technology already mentioned, the length of which can also be changed.

At least one elastically deformable stabilizing element, which stabilizes the wall against forces that act on the wall due to the negative pressure, preferably runs along a wall of the vacuum hose. Areas of the wall between sections of the stabilizing element can e.g. be formed from a sheet material, e.g. a fabric or fleece with an airtight coating or impregnation, or one or more layers of plastic (in which case a fabric can be dispensed with). The elastically deformable stabilization element is designed and combined with other components of the wall of the vacuum hose that a restoring force is generated when the vacuum hose changes in length, which in the absence of other forces would lead to the change in length being reversed. Conversely, at the beginning of a movement of the quill, the vacuum hose can be in a state in which the at least one elastically deformable stabilizing element is pretensioned, i.e. the pretensioning forces support the change in length that takes place when the quill moves.

The negative pressure in the connecting line is preferably matched to the forces generated by the at least one elastically deformable stabilizing element and compensate for the differential pressure forces caused by the pressure differences between the area around the quill and the gas space and the elastic deformation forces of the stabilizing element or elements together, the weight or the weight force the quill (and optionally the parts attached to it, such as the measuring sensor and swivel joint).

If the elastic deformation forces of the stabilizing element (s) change with the change in length of the vacuum hose, it is preferred that a controller of the negative pressure generating device controls this in such a way that the negative pressure and thus the differential pressure forces are adapted to the changed elastic forces so that the sum of the both forces remains constant despite the change in length. It is at least preferred that part of the change in the elastic forces with a change in length of the vacuum hose is compensated for by changing the negative pressure.

Regardless of the question of whether the elastically deformable stabilizing element generates a force acting in the longitudinal direction of the vacuum hose or not, a vacuum hose with a stabilizing element has the advantage that it changes its outer diameter only slightly or not significantly when changing length. The construction of the vacuum hose with an elastically deformable stabilizing element and cloth-shaped wall areas also has the advantage that it can be produced in a simple and inexpensive manner. In contrast to connecting lines with sub-elements that move relative to one another when the length changes and are in contact with one another (such as the telescopically length-adjustable body), only negligibly small frictional forces occur with such a vacuum hose when the length changes. For example, the at least one elastically deformable stabilizing element can have the shape of a helical spring.

The invention has the advantage, particularly when the movement of the quill is driven by a motor, that the drive only requires a very low drive power, since the weight of the quill is at least partially and preferably completely compensated. Since lateral forces are also avoided due to the weight compensation, the drive can in particular generate a linear movement of the quill in a straight direction (in particular in a vertical direction) which runs very precisely and exclusively in the straight direction. Since counterweights can also be dispensed with, the total moving mass when the quill moves is small. The connecting line can have a very low mass.

• 1 ein Koordinatenmessgerät in Portalbauweise, das eine in vertikaler Richtung (z-Richtung) bewegliche Pinole aufweist,
• 2 einen Längsschnitt durch eine Pinole mit einer ersten Ausführungsform einer in Längsrichtung längenveränderlichen Verbindungsleitung, wobei sich die Pinole in einer oberen vertikalen Position befindet,
• 3 die Pinole aus 2, wobei sich die Pinole in einer unteren vertikalen Position befindet,
• 4 eine Teildarstellung der in 2 und 3 dargestellten Pinole mit einer Andeutung der am unteren Ende auf die Pinole wirkenden Kräfte, die durch Unterdruck erzeugt werden,
• 5 zwei verschiedene Längenzustände eines Vakuumschlauchs mit einem helixförmigen elastisch verformbaren Stabilisierungselement,
• 6 einen Längsschnitt durch eine Pinole mit einer zweiten Ausführungsform von Verbindungsleitungen, wobei sich die Pinole in einer oberen vertikalen Position befindet,
• 7 die Pinole aus 6, die sich in einer unteren vertikalen Position befindet,
• 8 eine Teildarstellung der in 6 und 7 dargestellten Pinole in einem Bereich, wo die Enden der Verbindungsleitungen an einem mit der Pinole verbundenen zusätzlichen Bauteil enden, und
• 9 zwei verschiedene Zustände einer Verbindungsleitung mit verschiedenen Längen, wobei es sich bei dem dargestellten Abschnitt der Verbindungsleitung um einen teleskopartig längenveränderbaren Körper handelt.

Embodiments of the invention will now be described with reference to the accompanying drawings. The individual figures of the drawing show schematically:

• 1 a coordinate measuring machine in portal design, which has a quill movable in vertical direction (z-direction),
• 2 a longitudinal section through a quill with a first embodiment of a connecting line variable in length in the longitudinal direction, wherein the quill is in an upper vertical position,
• 3 the quill off 2 with the quill in a lower vertical position,
• 4th a partial representation of the in 2 and 3 shown quill with an indication of the forces acting on the quill at the lower end, which are generated by negative pressure,
• 5 two different lengths of a vacuum hose with a helical, elastically deformable stabilizing element,
• 6th a longitudinal section through a quill with a second embodiment of connecting lines, wherein the quill is in an upper vertical position,
• 7th the quill off 6th which is in a lower vertical position,
• 8th a partial representation of the in 6th and 7th quill shown in an area where the ends of the connecting lines end at an additional component connected to the quill, and
• 9 two different states of a connecting line with different lengths, wherein the section of the connecting line shown is a telescopically variable length body.

1 schematically shows a coordinate measuring machine (short: KMG) 1 in portal design. Along two parallel guides in the area of a measuring table 2 (e.g. a granite slab) is a first sled 3 movably guided in the form of a portal. A first scale is used to measure the position of the portal in accordance with a first linear movement axis y 4th . The position is read off with a corresponding reading sensor (not shown), as is the case with other scales that are described below. In addition, a first drive (not shown) is provided through which a movement of the first carriage 3 can be driven in y-direction.

Along the the measuring table 2 horizontally spanning traverse of the portal-shaped first slide 3 , is a second sled 5 movably guided, with a second scale for measuring its position relative to the portal corresponding to a second linear movement axis x 6th and a corresponding second reading sensor (not shown) are provided. A movement of the second slide 5 in the x-direction can be driven by a second drive (not shown).

On the second sled 5 is in turn is a third slide, namely a quill 7th , movably guided, for measuring the position of the quill relative to the second slide 5 a third scale corresponding to a third linear movement axis z 8th and a corresponding third reading sensor (not shown) are provided. A movement of the quill 7th in the z-direction, a third drive (see e.g. 2 , 3 , 6th , 7th ) are driven. Below the lower end of the quill 7th is a Measuring sensor 10 arranged, in the present case in the form of a stylus with stylus ball 11 (ie as a tactile sensor), which has a measuring head and an interchangeable interface 9 at the lower end of the quill 7th is attached.

On the measuring table 2 is a workpiece 12th arranged by moving the three carriages 3 , 5 , 7th from the measuring sensor 10 can be scanned from the signals of the measuring sensor 10 and / or the measuring head as well as from the scale positions of the scales 4th , 6th , 8th Measured values on the surface of the workpiece to be measured 12th be determined. One control 13th controls and / or regulates the drives of the slide 3 , 5 , 7th . In addition, the controller 13th the benchmark values of the benchmarks 4th , 6th , 8th read out, as well as the signals of the measuring sensor 10 and / or the measuring head. With the controller 13th a measuring computer can be connected (not shown).

Via a connecting cable 16 is the upper end of the quill 7th with a gas container 17th connected, which has a buffer volume to keep the gas pressure constant in the connection line 16 and the z. B. forms in the interior (not shown) connecting line. The gas container 17th turn is via a gas pipe 18th with a vacuum generating device 19th connected.

2 and 3 show a longitudinal section through a quill 27 and by a load-bearing part, which can in particular be formed by a slide which, as in FIG 1 shown is movable in the x-direction along the traverse of a portal. The supporting part forms the motion guide for the movement of the quill 27 in the vertical direction. In the case of the 1 this is the z-direction. While 2 the quill 27 in an upper vertical position is in 3 the quill 27 shown in a lower vertical position.

In relation to the quill of a CMM, the term load-bearing part means that the load-bearing part bears the weight of the quill if there is no weight compensation of the quill. In conventional weight compensation devices, the load-bearing part would also bear at least part of the weight of the quill, even if the weight compensation device is present, depending on the embodiment of the weight compensation device. In the weight force compensation according to the invention, however, the load-bearing part does not carry that part of the weight of the quill which is compensated for by the negative pressure in the gas space or spaces. Preferably, the weight and thus also the weight is completely compensated for by negative pressure.

Based on 2 and 3 and later also on the basis of 6th and 7th two exemplary embodiments for weight compensation by means of negative pressure are explained on schematically represented constructions.

The main part of the in 2 and 3 construction shown has a cover 21st , Movement camp 22nd , a drive motor 24 and a friction wheel 25th on. The movement camp 22nd store the movement of the quill 27 For example, at two axial positions in the z-direction (the vertical direction in the figure plane of 2 and 3 ). The movement camp 22nd can be designed as known per se from the prior art. Air bearings in particular are possible. Camps 22nd guide the movement of the quill 27 in the vertical direction, in which case the movement guide can also have additional guide components in practice.

Also the representation of the drive motor 24 and the friction wheel 25th from the drive motor 24 is driven are to be understood schematically. For example, in contrast to what is shown, a friction wheel for driving the movement of the quill can be located on opposite sides of the quill 27 are located. By turning the at least one friction wheel 25th A rotational movement arises around its axis of rotation, which is due to the rolling of the outer circumferential surface of the friction wheel 25th a linear movement of the quill 27 causes in the vertical direction (in particular the z-direction). Depending on the direction of rotation of the friction wheel 25th the quill is moved down to a lower vertical position or up to a higher vertical position. In the illustrated embodiment, the at the lower end of the quill 27 arranged change interface 9 and the measuring sensor 10 moved so that the probe ball 11 of the measuring sensor 10 is brought into a desired vertical position, in particular by the control 13th of the KMG 1 is specified.

The in 2 and 3 illustrated embodiment of the quill 27 there is a connecting line inside 23 whose outer wall is gas-tight and in particular airtight, so that the interior of the connecting line 23 to a desired negative pressure compared to the gas pressure outside the connecting line 23 and thus outside the quill 27 can be evacuated. By three upward arrows in 2 and four upward arrows in 3 inside the connection line 23 it is indicated that gas and in particular air from the interior of the connecting line 23 can be evacuated.

At the top of the connecting line 23 is this to a connection line 28 connected via which the connection line 23 can be connected to a vacuum generating device (not shown) and is also connected during operation of the CMM.

In the embodiment of 2 and 3 the connecting line extends 23 inside the quill 27 to the lower end of the quill 27 . Like the enlarged partial representation in 4th shows an upward-facing surface 44 made from material of the quill 27 is / is being formed. In the partial representation of the 4th is below the lower end of the quill 27 the measuring sensor is omitted. It's just the interface 9 shown, via which a measuring sensor optionally via a measuring head on the quill 27 can be attached. Of course, the gas space must be directly on the surface facing upwards (here surface 44 ) the quill cannot be variable in length, but the variable length section of the connecting line can only begin above it.

When the interior of the connecting line 23 is evacuated and there is therefore a negative pressure in the interior (ie the gas in the interior has a lower pressure than gas in the vicinity of the quill), acts as indicated by six upward arrows in FIG 4th is indicated, an upward force on the quill according to the pressure difference. In other words, the gas pressure is inside the connecting line 23 pointing to the upward-facing surface 44 acts less than the gas pressure from below via the changeover interface 9 acts on the material that makes up the surface 44 forms, and this difference in gas pressure causes the upward force, which the weight or the weight of the quill 27 at least partially compensated.

The upward-facing surface does not have to be, as in 2 to 4th is shown, located at the lower end of the quill. Rather, the connecting line in the interior of the quill could, for example, only extend as far as an upwardly facing surface of the quill, which is at a higher position than the lower end of the quill. In this case too, the difference in the gas pressure inside the connecting line and thus inside the quill to the gas pressure outside the quill would lead to the upwardly directed compensation force.

In all cases, however, there is an upward-facing surface of the quill, above which there is a gas space with a lower pressure than below the quill when the weight force compensation is active during operation of the CMM.

The upward facing surface need not be a flat surface. E.g. the surface can be curved. The surface facing upward can also be a distributed surface. The upwardly facing surface is generally formed by all partial surfaces of the quill and the at least one connecting line, above or above which there is a gas space with a lower pressure than outside the connecting line. In this case, the upward-facing surface effective for weight compensation by pressure difference or negative pressure is formed by the sum of all areas that limit a gas space under negative pressure downwards. Each such partial area makes a contribution to the effective total area, the contribution being able to be calculated by vertical projection onto a plane projection area running perpendicular to the vertical direction, that is to say in the horizontal direction.

In the case of the embodiment of 2 to 4th is the surface facing up 44 the only upward-facing surface that delimits a gas space with negative pressure downwards, and is also a flat surface that runs in the horizontal direction. By projecting the surface facing upwards vertically 44 this is projected onto itself. Instead, it would be at the bottom of the connecting line in 4th are a curved upwardly facing surface, wherein the horizontal cross-sectional area of the connecting line is the same as in the embodiment of FIG 4th then this curved upward-facing surface would point to the in 4th upward facing surface shown 44 projected and the compensation effect would be the same with the same gas pressure conditions as in the embodiment of FIG 4th .

5 shows in the left part of the figure a longitudinal section of a connecting line which is designed as a vacuum hose. It has a helical shape around the longitudinal axis of the connecting line 23 wound around elastically deformable reinforcing element, so that the wall of the connecting line 23 the pressure differences outside and inside the connection line 23 withstands. The wall areas between the respective sections of the helical reinforcement element 57 are in 5 with the reference number 56 designated. They are made of a cloth-shaped material. 5 shows left and on the right the same section of the vacuum hose, three turns of the helical reinforcing element being in this longitudinal section in the schematically illustrated external view 57 are located. The middle gear is with the reference number 57 designated.

Due to the helical reinforcement element 57 can be the section of the connecting line 23 change its length and can therefore adapt the connecting line to a changed vertical position of the quill. In other words, the end of the connecting line attached to the quill follows the movement of the quill and the length of the connecting line changes accordingly. Depending on the type of wall areas of the connecting line made of cloth-like material, the cloth-like material can differ from that in FIG 5 shown fold or bulge in the shortened state of the connecting line.

The above considerations on the effective, upwardly facing surface of the quill are based on a connecting line with a constant cross section, which extends in the vertical direction. However, cases are also conceivable in which the cross section of the connecting line tapers or widens in its course from bottom to top. Since the connecting line is attached to the quill, the forces acting on the connecting line also have an at least partial effect on the quill and thus on the weight compensation. If the connecting line tapers from bottom to top, the horizontal area effective for weight compensation is reduced to the smallest horizontal cross-section of the connecting line, since the pressure outside the connecting line exerts a downward force on the wall of the connecting line. If the cross-section of the connecting line increases in its course from bottom to top, the same applies. In this case, the ambient pressure exerts an additional upward force on the wall of the connecting line.

In contrast, the connection lines running horizontally (such as the in 2 and 3 connection cable shown 28 ) acting forces, which are caused by the pressure difference inside the connection line compared to the outside space of the connection line, do not contribute to the weight force compensation of the quill. The from below on the lower wall of the connection line 28 The forces acting are equal to those from above on the upper wall of the connection line 28 acting forces. Sections of the connection line running from bottom to top 28 on the other hand are to be regarded as the connecting line attached to the quill if the connecting line is also attached to the quill. In the embodiment of 2 and 3 is the connecting cable 28 however, it is attached to the supporting part and there are therefore no forces directly between the connection line 28 and transferred to the quill. When the connecting line 23 with its upper end is also attached to the load-bearing part of the CMM, the weight of the connecting line only partially contributes to the total weight of the sleeve and any vertical forces acting on the wall of the connecting line due to the pressure difference between the interior of the connecting line and the The outer space of the connecting line only partially affects the quill. For this reason, a connecting line with a constant horizontal cross-section is preferred. In this case, the compensation force caused by the pressure difference results in a simple manner from the upward-facing surface of the quill arranged at the lower end of the connecting line.

The embodiment of 6th to 8th shows a comparison with the embodiment of FIG 2 to 4th modified arrangement. The same reference numerals designate the same elements of the supporting part, the cover 21st is slightly changed in the upper area of the load-bearing part, since in the embodiment of the 6th to 8th There is no central connection line at the top, but two connection lines at the side 68a , 68b .

In the second embodiment, the quill is inside 57 no connecting line whose interior is evacuated. Rather, it is with the quill 57 an additional component 64 connected, in the exemplary embodiment at the upper end of the quill 57 . Alternatively, the additional component could be at a different height position relative to the quill 57 be attached to this.

The cover 21st in the embodiment of 6th to 8th is recessed on the side. The additional component 64 is designed in the embodiment in the manner of a yoke, ie extends in the horizontal direction on two opposite sides of the quill 57 through the recesses in the cover 21st through. The additional component 64 forms on the two opposite sides of the quill 57 outside the cover 21st each has an upward-facing surface 65a , 65b that each share with one of two connecting lines 67a , 67b form one of the gas spaces that are connected to the connecting lines 68a , 68b can be evacuated and cause the weight force compensation.

As from the difference of 6th and 7th can be seen, the lengths of the two connecting lines can vary 67a , 67b change. The lower ends of the connecting lines 67a , 67b can therefore move the quill 57 and thus also the additional one on the quill 57 attached component 64 consequences.

Like the enlarged partial view of the 8th shows, acts due to the negative pressure in the connecting lines 67a , 67b each on the upward facing surfaces 65a , 65b an upward force on the additional component 64 and thus to those with the component 64 firmly connected quill 57 .

The attachment of at least one connecting line to an additional component that is connected to the quill has the advantage that the effective area of the upward-facing surface, which delimits the gas space downward, is not restricted by the space available within the quill . Rather, for example, the two upward-facing surfaces 65a and 65b the 6th to 8th Be dimensioned larger than the maximum available horizontal cross-sectional area in the interior of the quill. It is also possible to provide more than two upwardly facing surfaces on an additional component, each of which delimits the gas space under negative pressure with a connecting line. However, a construction which is symmetrical with respect to the central longitudinal axis of the quill is preferred in order to avoid transverse forces due to the weight force acting transversely to the direction of movement of the quill.

The z. B. in 2 to 4th The embodiment shown with a connecting line running inside the sleeve has the advantage that the installation space is used optimally. In addition, the connecting line can extend within the quill over a great length in the vertical direction (or in the longitudinal direction of the quill). Depending on the overall design of the CMM, a greater length can therefore be available within the quill than in the exemplary embodiment in FIG 6th to 8th for the connecting lines above the additional component. The relative change in length of the connecting line (s), which is caused to a maximum due to the range of motion of the quill in the vertical direction, can therefore in the embodiment of 2 to 4th be less than in the embodiment of 6th to 8th .

9 shows similar to 5 , however, for another embodiment of a connecting line, two different states of a section of a connecting line 67 , for example one of the connecting lines 67a , 67b out 6th to 8th . It is the section of the connecting line 67 around a telescopically adjustable line with three segments in the illustrated embodiment 91 , 92 , 93 running in the longitudinal direction of the connecting line 67 are mounted displaceably relative to each other. Hence the inside diameter of the segment shown above 91 larger than the inner diameter of the middle segment shown 92 and the inside diameter of the middle segment shown 92 is again larger than the inner diameter of the segment shown below 93 . The outer diameters of the segments 92 and 93 are in accordance with the inner diameter of the segment above 91 or. 92 adapted that the interior of the connecting line 67 Can be evacuated and in particular the transition between two adjacent segments is sufficiently gas-tight to handle the negative pressure within the connecting line 67 to be able to maintain. Optionally, additional seals can be used at the transitions between adjacent segments 91 , 92 or. 92 , 93 be provided.

While 9 in its left part the connecting line 67 represents in its shorter longitudinal state, is in the right part of the 9 the elongated longitudinal state shown. Such telescopically variable-length lines are not limited to the number of three segments. There can be only two segments or there can be more than three segments. A connecting line can also not only have one section in which the inner diameter of the segments that can be telescopically displaced against one another become larger from bottom to top, but alternatively or additionally have at least one section in which the inner diameter (and also the outer diameter) is from bottom to top successive segments become smaller. Furthermore, stops can be provided so that the segments do not inadvertently separate from one another when the length of the connecting line is increased or decreased and thus form a gas leak.

An example of the dimensioning of an upward-facing surface and the corresponding horizontal cross-sectional area of a connecting line is described below. The compensation force F _K to be achieved through weight compensation results from the effective area A of the upward-facing surface multiplied by the pressure difference Δp of the outer space or the area around the quill and the gas space inside the connecting line: $${\text{F.}}_{\text{K}}=\text{A.}\times \mathrm{\Delta }\text{p}$$

The mass of the quill is, for example, m = 20 kg. Taking into account the acceleration due to gravity g ≈ 9.8 m / s ² , an effective area A results with a pressure difference Δp = 0.4 bar: $$\text{A.}=\left(\text{m}\times \text{G}\right)\mathrm{/}\left(\mathrm{\Delta }\text{p}\right)=\left(\mathrm{20th}\text{kg}\times \text{9}\text{, 81 m}\mathrm{/}{\text{s}}^2\right)\mathrm{/}\left(0.4\text{bar}\right)\approx \mathrm{5,000}{\text{<figure-callout id="2" label="mm" filenames="DE102016201574B4\_0003.png" state="{{state}}">mm</figure-callout>}}^2$$

In the case of the embodiment of 6th to 8th With two upward-facing surfaces and a circular internal cross-section of the connecting lines, the effective area contributed by each of the two upward-facing surfaces is 2,500 mm ² . This corresponds to a diameter of each of the two connecting lines of approximately 57 mm.

Claims (12)

Coordinate measuring device (1) with a quill (27; 57) on which a sensor for recording measured values for determining coordinates of a workpiece (12) can be attached and the vertical position of which can be adjusted by moving the quill (27; 57) upwardly facing surface (44) of the quill (27) and / or an upwardly facing surface (65) of a component (64) connected to the quill (57) which moves with a movement of the quill (57), at least one limited gas space which is under negative pressure during operation of the coordinate measuring machine, so that the quill (27; 57) experiences an upward force which corresponds to a difference between a gas pressure in the vicinity of the quill (27; 57) and the negative pressure. Coordinate measuring machine according to Claim 1 , wherein the coordinate measuring machine has a connecting line (23; 67) which, together with the upwardly facing surface, delimits the gas space and enables the gas space to be connected to a vacuum generating device (19), and wherein a course, a shape and / or a The size of the connecting line (23; 67) is variable and adapts to a vertical position of the quill (27; 57) when the quill (27; 57) is moved, so that the upwardly facing surface (44; 65) is under negative pressure Gas space limited in different vertical positions of the quill (27; 57) and the quill (27; 57) therefore experiences an upward force in each of the various vertical positions. Coordinate measuring machine according to Claim 2 wherein the connecting line (23; 67) extends upwards from the upwardly facing surface. Coordinate measuring machine according to Claim 2 or 3 , wherein the connecting line (23) has a vacuum hose, the length of which can be changed, the length of the vacuum hose increasing with a movement of the quill (27; 57) downwards and vice versa. Coordinate measuring machine according to Claim 4 , wherein at least one elastically deformable stabilizing element runs along a wall of the vacuum hose, which stabilizes the wall against forces which act on the wall due to the negative pressure. Coordinate measuring machine according to Claim 5 wherein regions of the wall which run between sections of the stabilizing element are formed from a cloth-shaped material. Coordinate measuring machine according to one of the Claims 2 to 6th , wherein the connecting line (67) has a telescopically variable length body, the length of which increases with a movement of the quill (27; 57) downwards and vice versa. Method for operating a coordinate measuring machine with a quill (27; 57) on which a sensor (10) for recording measured values for determining coordinates of a workpiece (12) is attached and the vertical position of which is set by moving the quill (27; 57) a negative pressure is generated on an upwardly facing surface of the quill (27) and / or on an upwardly facing surface of a component connected to the quill (57) which moves with a movement of the quill (57), so that the quill (27; 57) experiences an upward force which corresponds to a difference between a gas pressure in the vicinity of the quill (27; 57) and the negative pressure. Procedure according to Claim 8 , a connecting line (23; 67) being used which, together with the upwardly facing surface, delimits the gas space and is at least part of a connection between the gas space and a vacuum generating device (19), with a course, a shape and / or a The size of the connecting line (23; 67) is variable and adapts to a vertical position of the quill (27; 57) when the quill (27; 57) is moved, so that the upwardly facing surface (44; 65) is under negative pressure Gas space limited in different vertical positions of the quill (27; 57) and the quill (27; 57) therefore experiences an upward force in each of the various vertical positions. Procedure according to Claim 9 wherein the connecting line (23; 67) is arranged such that it extends upwards from the upwardly facing surface, and wherein a length of the connecting line (23; 67) follows with movement of the quill (27; 57) enlarged below and vice versa. Method for manufacturing a coordinate measuring machine, in particular the coordinate measuring machine according to one of the Claims 1 to 7th , with the following steps: Arranging a quill (27; 57) on a supporting structure of the coordinate measuring machine, so that a vertical position of the quill (27; 57) can be adjusted by moving the quill (27; 57), with the quill ( 27; 57) a sensor (10) for recording measured values for determining coordinates of a workpiece (12) can be attached, • Forming at least one gas space above an upwardly facing surface (44) of the quill (27) and / or above a Upward-facing surface (65) of a component (64) connected to the quill (57), which component moves with a movement of the quill (57), the gas space being under negative pressure during operation of the coordinate measuring machine, so that the quill (27; 57) experiences an upward force during operation which corresponds to a difference between a gas pressure in the vicinity of the quill (27; 57) and the negative pressure. Procedure according to Claim 11 , wherein a connecting line (23; 67) is led to the upwardly facing surface, the connecting line (23; 67) together with the upwardly facing surface delimiting the gas space and enabling the gas space to be connected to a vacuum generating device (19) , and wherein the connecting line (23; 67) is designed so that a course, a shape and / or a size of the connecting line (23; 67) is variable and when the quill (27; 57) is moved to a vertical position of the Quill (27; 57) adapts so that the upwardly facing surface (44; 65) delimits the gas space under vacuum in various vertical positions of the quill (27; 57) and the quill (27; 57) therefore in the various vertical Positions each experience an upward force.

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