Miniature measuring head zero returning mechanism capable of being modularized

Abstract

The invention relates to the technical field of precision measuring instruments, mainly relates to the field of three-dimensional scanning measuring heads, and specifically relates to a modularized small measuring head zero returning mechanism. The mechanism comprises a U-shaped support, blocking covers, a force measuring tube, a tension spring and a thin rope, the force measuring tube is cylindrical, the tension spring is arranged on the central axis in the force measuring tube, and the two ends of the force measuring tube are provided with a pair of blocking covers; the two ends of the tension spring are connected with thin ropes respectively, the thin ropes penetrate through the blocking covers on the two sides respectively and are fixedly connected with the two blocking covers, and the two blocking covers abut against the two ends of the force measuring pipe under the action of the tension spring. And the string is connected with the U-shaped bracket in a tensioning manner. According to the invention, an ideal return-to-zero mechanical characteristic curve can be completely reproduced, damping lag is avoided, and the measuring force is approximately constant; the structure is simple, the size is small, independent modules can be manufactured, and installation and adjustment are convenient; the method provided by the invention is easy to implement, and is particularly suitable for a compact three-storey building structure with a narrow space as a miniaturized mechanism.

Description

Technical Field

[0001] The invention relates to the technical field of precision measuring instruments, mainly to the field of three-dimensional scanning probes, and in particular to a modular small probe zero return mechanism. Background Art

[0002] The 3D scanning probe is a key component of precision measuring instruments such as CMMs and CNC gear measuring machines. The interior of the 3D scanning probe is similar to a small CMM. During the measurement process, the probe needle moves horizontally in three directions and accurately transmits the displacement of the front end of the probe to the sensors in three directions. After the measurement, in order to prevent the probe from repeatedly oscillating near the zero position, a damping device or a zero return mechanism is generally set inside the probe to ensure the normal operation of the measurement process.

[0003] Existing mechanical return-to-zero mechanisms, for example, the document with patent number "CN201420764759.2" proposes "a precise mechanical return-to-zero device for a digital scanning probe". The lever is supported on the lever seat by a flexible hinge. Regardless of whether the movable plate of the parallel spring mechanism drives the support to move upward or downward, the lever always rotates counterclockwise and returns the movable plate to zero position under the action of the tension spring.

[0004] Patent CN200710018316.3 mentions a zero return device. When the movable plate of the parallel spring mechanism moves to the right, the top plate pushes the right baffle to move to the right, while the left baffle remains stationary. The internal tension of the tension spring resets the movable plate. Conversely, when it moves to the left, the left baffle moves, while the right baffle remains stationary. The tension spring still resets the movable plate. The problem with this mechanism is that the spatial positions of the two baffles and the tension spring are floating. When working for a long time, under the interference of factors such as gravity vibration, the baffle and the tension spring will move downward over time, deviate from the designed position, and cause the mechanism to fail.

[0005] The common problem of the above two mechanisms is that they are bulky and occupy a large space inside the probe. If the guide mechanism is a nested compact type, the space is smaller and the assembly and adjustment are difficult, so it only stays in the theoretical principle stage and cannot be actually applied to the 3D scanning probe.

[0006] Based on the above problems of mechanical zero return mechanism, the existing 3D scanning probe generally uses damper to achieve zero return. For leaf spring guide rails, a damping device is set between the two active guide rails (in pairs), see Figure 1 The damping device is composed of two leaf springs, one of which is fixed on the upper plate and the other on the lower plate, forming a capillary gap between the two leaves, in which viscous silicone oil is placed, so that the two-layer guide rail generates damping when moving.

[0007] Figure 2It is a magnetic induction damper structure used in the inertial type rotation unevenness inspection instrument. The damping plate is fixed on the rotor, and the permanent magnets are fixed on the stator. When the stator and the rotor produce relative motion, the damping plate moves in the magnetic field, thereby inducing eddy currents on the damping plate. According to Lenz's law, the induced eddy currents will hinder the relative motion between the damping plate and the magnetic field, thus forming a damping effect.

[0008] Figure 3 It is the damper of the lever torsion spring micrometer produced by Harbin Measuring Tool and Cutting Tool Factory. The torsion spring and the pointer form a torsion vibration system, and the torsion spring passes through the hole of the damping frame. The assembled torsion spring instrument drips damping oil into the hole of the damping frame to generate damping.

[0009] The above mechanism can realize the rapid reset of the probe and prevent the probe from oscillating near the zero position. However, the damping mechanism is still relatively complex, and still occupies a large space inside the probe. The problem of difficult installation and adjustment also exists. More seriously, the addition of damping will cause the dynamic response of the probe to lag, causing distortion when the probe measures dynamic signals, thereby affecting the measurement accuracy of the probe. Summary of the invention

[0010] The present invention designs a modular small probe zero return mechanism to solve the problems in the prior art that the damping mechanism is still relatively complex, occupies a large space inside the probe, is difficult to install and adjust, and the addition of damping will cause the dynamic response of the probe to lag, and the probe will be distorted when measuring dynamic signals, affecting the measurement accuracy of the probe.

[0011] In order to achieve the above object, the specific content of the present invention is as follows:

[0012] A modular small probe zero return mechanism includes a U-shaped bracket, a baffle, a force measuring tube, a tension spring and a thin rope. The force measuring tube is cylindrical, a tension spring is arranged on the inner central axis of the force measuring tube, and a pair of baffles are arranged at both ends of the force measuring tube; the two ends of the tension spring are respectively connected to thin ropes, which pass through the baffles on both sides and are fixedly connected to the two baffles. Under the action of the tension spring, the two baffles are tightly pressed against the two ends of the force measuring tube; and they are tightly connected to the U-shaped bracket.

[0013] Furthermore, the thin rope is composed of multiple strands of carbon fiber ropes.

[0014] Furthermore, the thin rope is firmly connected to the blocking cover and the U-shaped bracket by adhesive.

[0015] Furthermore, the U-shaped bracket is provided with a pair of threaded through holes; the U-shaped bracket is connected to the threaded through holes on the mounting seat body by screws, and the mounting seat body is fixedly connected to the fixed plate of the probe guide mechanism.

[0016] Furthermore, a pair of screw holes are provided on the outer wall of the force measuring tube, which are connected to the moving plate of the measuring head guide mechanism by screws.

[0017] Furthermore, the working method of the above-mentioned modular small probe zero return mechanism is: the U-shaped bracket of the zero return mechanism is fixedly connected to the fixed plate of the probe guide mechanism via the mounting base, and the force measuring tube is fixedly connected to the movable plate of the probe guide mechanism; the movable plate of the probe guide mechanism drives the force measuring tube to move to one side, and the end of the force measuring tube pushes the baffle cover on the same side to move, at this time, the thin rope between the baffle cover and the U-shaped bracket on the moving side is bent, and the thin rope between the baffle cover and the U-shaped bracket on the other side is straightened, and the baffle cover does not move, so that a gap is generated between the force measuring tube and the baffle cover on this side, and the tension spring is deformed by force to generate a restoring force F; when the probe is out of contact with the workpiece being measured, the elastic restoring force F of the tension spring will pull the force measuring tube back to its original equilibrium position, and the probe returns to zero.

[0018] Compared with the prior art, the advantages of the present invention are:

[0019] (1) The zero return mechanical characteristic curve proposed by the present invention has excellent zero return characteristics. When the probe is in a balanced position, the spring has an original preset force F0. Only when the measuring force is greater than F0, the probe starts measuring when it leaves the zero position. Since the moving parts of the present invention have a small mass and are not restricted in their spatial installation orientation, the overall performance of the probe is slightly affected, and the ideal zero return mechanical characteristic curve can be fully reproduced without damping hysteresis, and the measuring force is close to constant.

[0020] (2) The present invention has a simple structure and a small size. It can be made into an independent module and is easy to install and adjust. No additional adjustment steps are required when installing with other components, and the assembly and use are simple. It can quickly return to zero position without a damper, and will not generate oscillation, thereby avoiding the hysteresis of dynamic signals.

[0021] (3) The method proposed in the present invention is easy to implement. As a miniaturized mechanism, it is particularly suitable for compact three-dimensional probe structures with limited space. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic diagram of the common damping device structure;

[0023] Figure 2 This is a schematic diagram of a common magnetic induction damper structure;

[0024] Figure 3 It is a schematic diagram of the damper structure of a common lever torsion spring micrometer;

[0025] Figure 4 It is a schematic diagram of the mechanism of the present invention;

[0026] Figure 5 for Figure 4 sectional view of

[0027] Figure 6 for Figure 4 The left side view and left side section view;

[0028] Figure 7 Installation diagram;

[0029] Figure 8 Schematic diagram of the mechanism principle for different movement directions;

[0030] Fig. 9 It is the return to zero characteristic curve.

[0031] The reference numerals are as follows:

[0032] 1-U-shaped bracket, 2-blocking cover, 3-force measuring tube, 4-tension spring, 5-thin rope, 6-mounting base, 7-moving plate of the measuring head guide mechanism, 8-fixed plate of the measuring head guide mechanism DETAILED DESCRIPTION

[0033] In order to make the purpose, technical solution and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention and are only used to illustrate the present invention, but not to limit the scope of the present invention.

[0034] See also Figure 4-6 A modular small probe zero return mechanism includes a U-shaped bracket 1, a cover 2, a force measuring tube 3, a tension spring 4 and a thin rope 5. The force measuring tube 3 is hollow inside, and a tension spring 4 is arranged on the inner central axis of the force measuring tube 3. A pair of cover 2 is arranged on the end surface of the force measuring tube 3; the two ends of the tension spring 4 are respectively connected with a thin rope 5, and the thin rope 5 in this embodiment is composed of a plurality of carbon fiber ropes. The two thin ropes 5 pass through the cover 2 on both sides and are fixedly connected to the two cover 2. Under the action of the tension spring 4, the preset force F0 of the tension spring 4 is set in advance according to the measurement requirements, and the two cover 2 are close to the two ends of the force measuring tube 3; the two thin ropes 5 are tightly connected to the U-shaped bracket so that the force measuring tube 3 is located in the middle of the U-shaped bracket. In this embodiment, the thin rope 5 is firmly connected to the tension spring 4, the cover 2 and the U-shaped bracket 1 by adhesive.

[0035] The U-shaped bracket 1 is provided with a pair of threaded holes, through which the U-shaped bracket 1 is connected to the mounting base 6, and the mounting base 6 is fixedly connected to the fixed plate 8 of the probe guide mechanism. The mounting base 6 is used to connect the U-shaped bracket 1 and the fixed plate 8 of the probe guide mechanism, and various shapes can be used, but the internal space of the probe is minimized as much as possible.

[0036] A pair of screw holes are provided on the upper outer wall of the force measuring tube 3 , which is connected to the moving plate 7 of the measuring head guide mechanism by screws.

[0037] The material characteristics of the rope are: high rigidity and small elastic deformation when under tension; easy to bend when under pressure. A multi-strand carbon fiber rope or a material with similar characteristics can be selected. The thin rope 5 can be two or four, and the connection method with the tension spring 4, the blocking cover 2 and the U-shaped bracket 1 can be either adhesive or mechanically fastened, as long as it is firm.

[0038] The assembly steps of a modular small probe zero return mechanism provided by the present invention are as follows:

[0039] First, place the entire return-to-zero mechanism vertically, with the thin rope 5 at the upper end of the tension spring 4 connected to the U-shaped bracket 1 and the upper baffle 2, and the tension spring 4, the force measuring tube 3 and the lower baffle 2 installed in the middle. After the thin rope 5 at the lower end of the tension spring 4 passes through the baffle 2 and the support arm of the U-shaped bracket 1, hang a weight of corresponding weight according to the requirement of the preset force F0 to stretch the tension spring 4, then, close the two baffles 2 and the force measuring tube 3, and firmly connect the thin rope 5 at the lower end to the lower baffle 2 and the U-shaped bracket 1.

[0040] When in use, this mechanism is used as a functional module and is installed in the X, Y, and Z directions of the 3D scanning probe. Figure 7 Two parallel springs, the movable plate 7 of the probe guide mechanism and the fixed plate 8 of the probe guide mechanism constitute a probe relative motion assembly. The U-shaped bracket 1 of the zero return mechanism is fixedly connected to the fixed plate 8 of the probe guide mechanism through the mounting base 6, and the force measuring tube 3 is fixedly connected to the movable plate 7 of the probe guide mechanism.

[0041] When the probe contacts the workpiece for measurement, Figure 8 As shown. When the probe motion assembly drives the force measuring tube 3 to move to the left, the force measuring tube 3 pushes the left baffle 2 to move and creates a gap with the right baffle 2. At this time, the left thin rope 5 is bent, the right rope is straightened, and the tension spring 4 is deformed by force to generate a rightward restoring force F; when the probe is out of contact with the workpiece, the elastic restoring force F of the tension spring 4 will pull the force measuring tube 3 back to the original equilibrium position, and the probe returns to zero. The situation where the probe motion component drives the force measuring tube 3 to move to the right is similar to the left side.

[0042] The zero return mechanism of the present invention has Fig. 9 The zero return characteristics shown in the figure can be completely reproduced because the moving parts of the present invention have a small mass, the spatial installation orientation is not restricted, and the overall performance of the probe is slightly affected. Fig. 9 Ideal return-to-zero mechanical characteristic curve, no damping hysteresis, and the measuring force is nearly constant.

[0043] The above is an explanation of the specific implementation of the present invention, rather than a limitation of the present invention. Those skilled in the relevant technical field can also make various equivalent technical solutions without departing from the scope of the present invention, so all equivalent technical solutions should be included in the patent protection scope of the present invention.

Claims

1. A modular small probe zero return mechanism, characterized by: The invention comprises a U-shaped bracket (1), a stop cover (2), a force measuring tube (3), a tension spring (4) and a thin rope (5); the force measuring tube (3) is cylindrical, a tension spring (4) is arranged on the inner central axis of the force measuring tube (3), and a pair of stop covers (2) are arranged at both ends of the force measuring tube (3); the two ends of the tension spring (4) are respectively connected to the thin rope (5), the thin rope (5) passes through the stop covers (2) at both sides, and is fixedly connected to the two stop covers (2); under the action of the tension spring (4), the two stop covers (2) are closely attached to the two ends of the force measuring tube (3); the thin rope (5) is tightly connected to the U-shaped bracket (1).

2. The modular small probe zero return mechanism according to claim 1, characterized in that: The thin rope (5) is formed by combining multiple strands of carbon fiber ropes.

3. The modular small probe zero return mechanism according to claim 2, characterized in that: The thin rope (5) is firmly connected to the tension spring (4), the blocking cover (2) and the U-shaped bracket (1) by means of an adhesive.

4. The modular small probe zero return mechanism according to claim 3, characterized in that: The U-shaped bracket (1) is provided with a pair of threaded through holes.

5. The small modular probe zero return mechanism according to claim 4, characterized in that: A pair of screw holes is provided on the outer wall of the force measuring tube (3).

6. The modular small probe zero return mechanism according to claim 1, characterized in that: The modular small probe zero return mechanism works as follows: the U-shaped bracket (1) of the zero return mechanism is fixedly connected to the fixed plate (8) of the probe guide mechanism via the mounting base (6), and the force measuring tube (3) is fixedly connected to the movable plate (7) of the probe guide mechanism; the movable plate (7) of the probe guide mechanism drives the force measuring tube (3) to move to one side, and the end of the force measuring tube (3) pushes the same side cover (2) to move, at this time, the thin rope (5) located between the cover (2) and the U-shaped bracket (1) on the moving side is bent, and the thin rope (5) located between the cover (2) and the U-shaped bracket (1) on the other side is straightened, and the cover (2) does not move, so that a gap is generated between the force measuring tube (3) and the side cover (2), and the tension spring (4) is deformed by force to generate a restoring force F; when the probe is out of contact with the workpiece to be measured, the elastic restoring force F of the tension spring (4) pulls the force measuring tube (3) back to the original equilibrium position, and the probe returns to zero.

Images