Tubular saw with torsional vibration damping.

Abstract

The present invention relates to a sawing machine with a saw shaft (2) on which a saw blade (3) is mounted, which provides torsional vibration damping using a vibration damper (7), characterized in that the vibration damper (7) is arranged on the saw shaft (2) beside the saw blade (3) and completely surrounds the saw shaft (2) in cross section, the vibration damper (7) is separated from the saw shaft (2) by a gap (11) and is arranged with clearance on the saw shaft (2), and the gap (11) between the vibration damper (7) and the saw shaft (2) is filled with a fluid.

Description

[Technical field]

[0001] The present invention relates to a sawing machine with a saw shaft on which a saw blade is mounted. [Background technology]

[0002] Sawing machines are known in the prior art. For example, a pipe saw capable of cutting sections of pipes to length is known from DE 102004053732. The pipe saw is often part of an integrated saw plant, which not only cuts the pipes to length but also cleans, bevels and otherwise processes the pipes.

[0003] The high accuracy requirements for cut to length pipe sections and the service life of saw blades remain an issue, for example metal pipes should be cut to length with an accuracy of 0.01 mm and this accuracy should be maintained 99.99% of the time.

[0004] Torsional vibrations have proven to be a particular problem, caused by the fact that the load acting on the saw blade is not constant, but is subject to periodic variations due to the teeth moving in and out of the tube material, which results in undesirable torsional vibrations in the saw shaft and the saw blade. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] German Patent No. 102004053732 Summary of the Invention

[0006] SUMMARY OF THE PRESENT EMBODIMENT It is therefore an object of the present invention to provide a saw which reduces the above mentioned disadvantages.

[0007] The object is met by a sawing machine as mentioned beginning with the features of claim 1. The sawing machine according to the invention has a saw shaft on which a saw blade is mounted. According to the invention, for torsional vibration damping, a vibration damper is provided which is arranged on the saw shaft beside the saw blade and completely surrounds the saw shaft in cross section, the vibration damper being separated from the saw shaft by a gap and having a clearance on the saw shaft, the gap between the vibration damper and the saw shaft being filled with a fluid.

[0008] The damper preferably runs completely around the saw shaft along a section of the saw shaft in each cross section. The damper is preferably mounted on the saw shaft with a clearance in each cross section direction. The clearances preferably have the same numerical size, with the gap preferably having a width of 0.01 mm + / - 0.005 mm. However, other numerical ranges are also contemplated.

[0009] The damper fits over the saw shaft with a clearance, the gap being preferably filled with a viscous fluid, so that the damper creates a damping effect on the saw shaft, i.e., it opposes the change in angular velocity of the saw shaft. If the saw shaft increases its angular velocity slightly, the damper follows that change slightly, braking the saw shaft with the fluid. Conversely, when the angular velocity of the saw shaft slows down, the advancing damper causes the saw shaft to accelerate.

[0010] Preferably, the saw blade is mounted on one end of the saw shaft and a drive gear fixedly rotatably connected to the saw shaft is disposed along the saw shaft between the vibration suppressor and the saw blade.

[0011] The saw shaft and therefore the saw blade are driven via a drive gear. The saw blade is used to cut profiles to length or the like, preferably metal tubes, metal profiles.

[0012] In an advantageous embodiment of the invention, the surface of the saw shaft is cylindrical along the longitudinal section on which the damper is arranged, and the inner wall of the damper's bore is also cylindrical. This means that the outer wall of the saw shaft and the inner wall of the damper are shaped as two cylinders arranged concentrically towards each other. The gap is formed by a circumferential ring that can be filled with a fluid. The damping effect in this case is produced by Newtonian friction forces. The damper is preferably fully rotatable around the saw shaft.

[0013] However, gaps of other cross-sectional shapes are also possible. Preferably, the surface of the saw shaft has a profile in the longitudinal part on which the damper is arranged, and the inner wall of the damper's bore has a corresponding profile. For example, the profile can be a serpentine profile and the corresponding profile can be a corresponding serpentine profile. As a result, the damper is not arranged rotatably on the saw shaft, but still has play in each direction. In this case, the damping effect is less influenced by Newtonian friction forces and more by the fact that the fluid arranged in the gap flows back and forth between the tooth faces of the serpentine profile, creating a suction effect or a pressure effect on the teeth of the saw shaft that acts against the change in the angular speed of the saw shaft.

[0014] Advantageously, the vibration damper has a radial bore for filling the gap with a fluid, the bore being capable of being closed from the outside.

[0015] The invention is illustrated by means of two example embodiments in four figures. [Brief description of the drawings]

[0016] [Figure 1] 1 is a longitudinal section of a portion of a first embodiment of a vibration damper for a saw according to the present invention. [Diagram 2] 1 is a graphical representation of the dependence of angular velocity on time with and without damping. [Diagram 3] 4 is a cross-section of a second embodiment of a vibration damper according to the present invention. [Figure 4] 1 is a cross-section of a second embodiment of a vibration damper in operation. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] FIG. 1 shows a cross section of a saw 1 according to the invention with a saw shaft 2, at one end of which a saw blade 3 of circular cross section with a saw jaw cover 4 is mounted on a saw bearing 5. The saw shaft 2 is driven by a drive gear 6 which is rotatably and fixedly connected to the saw shaft 2. The drive of the drive gear 6 itself is not shown. In addition to the drive gear 6, a vibration damper 7 is provided on the saw shaft 2. The vibration damper 7 completely surrounds the saw shaft 2 along the section in the cross section. The drive gear 6 is arranged between the vibration damper 7 and the saw blade 3. A housing 8 runs between the drive gear 6 and the saw bearing 5. The saw shaft 2 is mounted on a sliding bearing 9 in the housing 8.

[0018] Between the damper 7 and the saw shaft 2 there is a circumferential gap 11, so that the damper 7 is placed on the saw shaft 2 with a clearance of 0.01 mm + / - 0.005 mm. The gap 11 is filled with a fluid. The fluid may be oil. To fill the gap 11, a channel may be provided through the damper 7, which allows the gap 11 to be filled from the outside.

[0019] The gap 11 is annular in cross section in the first embodiment shown in Fig. 1 perpendicular to the longitudinal direction L when the saw shaft 2 and the damper 7 are positioned concentrically with respect to one another. The gap 11 is shaped along the entire extension in the longitudinal direction L of the damper 7 surrounding the saw shaft 2. The damper 7 has a hollow cylindrical shape.

[0020] FIG. 1 shows a saw blade 3 cutting a workpiece 12, for example a tube, to be cut to length.

[0021] 2 shows undamped oscillations with angular velocity 13 and damped oscillations with angular velocity 14 about a constant operating angular velocity ω0. The saw blade 2 has an operating angular velocity ω0 during operation. Torsional oscillations of the saw blade 3 are superimposed on the operating angular velocity ω0. The torsional oscillations are caused by the fact that the saw blade periodically decelerates and slightly accelerates due to the alternating tooth meshes and tooth outlets.

[0022] The damped vibration with angular velocity 14 in FIG. 2 shows the effect of the damper 7, which significantly reduces the amplitude of the torsional vibration compared to the undamped vibration with angular velocity 13. The damper 7 is arranged on the saw shaft 2 so that it can move in the circumferential direction. In FIG. 1, the Newtonian friction force between the damper 7 and the saw shaft 2 is given by: Fr = Aη(dv:dy) It occurs when the angular velocity of the saw shaft 2 increases or decreases. Here, A means the gap area, η means the viscosity of the fluid, in this case the oil, and (dv:dy) means the change in speed in the direction of rotation.

[0023] The inertia of the damper 7 results in the fact that when the angular velocity ω of the saw shaft 2 decreases, the damper 7 moves forward and generates an additional force opposing the decreasing angular velocity ω, while the opposite effect occurs if the angular velocity ω of the saw shaft 2 increases.

[0024] Figure 3 shows in cross section a second embodiment of a gap 11 according to the invention between the damper 7 and the saw shaft 2. The gap 11 has a serpentine-shaped cross section. Whereas in the first embodiment there is a Newtonian friction between the damper 7 and the saw shaft 2, in the second embodiment the damper 7 lags behind the change in angular velocity due to its inertia and thus displaces or sucks fluid out of the gap 11 section due to torsional vibration. The cross-sectional shape of figure 3 is referred to here as a serpentine shape. Other cross-sectional shapes are also conceivable.

[0025] Figure 4 shows in detail the effect of the gap 11 in a serpentine configuration. The angular velocity ω of the saw shaft 2 is variable. As the teeth enter the workpiece 12 the angular velocity ω decreases and as the teeth leave the workpiece 12 it increases. The change in angular velocity ω of the saw shaft 2 is Δω.

[0026] A slight change in angular velocity Δω occurs, in which the saw blade 3 and thus the saw shaft 2 slows down slightly due to tooth entry, and the vibration damper 7 advances in the direction of rotation, counterclockwise in FIG. 4, and shifts clockwise relative to the saw shaft 2. A gap widening 16 and a gap narrowing 17 result. The gap widening 16 has a suction effect on the fluid, and the gap narrowing 17 displaces the fluid. This creates a small additional thrust on the saw shaft 2 and the torsional vibrations are damped. [Explanation of symbols]

[0027] 1 saw 2 Saw shaft 3 Saw blade 4 Saw clamp cover 5 Saw bearing 6 Drive gear wheel 7 Vibration damper 8. Housing 9 Plain Bearing 12 Processed products 13 Undamped Oscillations of Angular Velocity 14 Damped oscillation of angular velocity 16 Widening Gap 17. Narrowing the gap L Vertical ω angular velocity ω0 Operating angular velocity Δω Change in angular velocity

Claims

1. 1. A sawing machine with a saw shaft (2) on which a saw blade (3) is mounted, characterized in that the torsional vibration damping using a vibration damper (7), the vibration damper (7) is arranged on the saw shaft (2) beside the saw blade (3) and completely surrounds the saw shaft (2) in cross section, the vibration damper (7) is separated from the saw shaft (2) by a gap (11) and is arranged with a clearance on the saw shaft (2), and the gap (11) between the vibration damper (7) and the saw shaft (2) is filled with a fluid.

2. 2. A saw according to claim 1, characterized in that the vibration damper (7) is arranged on the saw shaft (2) with a clearance of 0.01 mm ± 0.005 mm in each cross-sectional direction.

3. 3. A sawing machine according to claim 1 or 2, characterized in that the saw blade (3) is mounted on one end of the saw shaft (2) and a drive gear (6) rotatably and fixedly connected to the saw shaft (2) is arranged between the vibration damper (7) and the saw blade (3).

4. 4. A saw according to claim 1, 2 or 3, characterized in that the surface of the saw shaft (2) in the longitudinal section on which the vibration damper (7) is arranged is cylindrical and the inner wall of the bore of the vibration damper (7) is also cylindrical.

5. 4. A saw according to claim 1, 2 or 3, characterized in that the surface of the saw shaft (2) has a profile in the longitudinal section in which the vibration damper (7) is arranged and the inner wall of the bore of the vibration damper (7) has a corresponding profile.

6. 6. The saw of claim 5, wherein the profile is a serpentine profile and the corresponding profile is a corresponding serpentine profile.

7. A saw according to any one of the preceding claims, characterized in that the vibration damper (7) has a radial bore for filling the gap (11) with the fluid.

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