The invention relates to an apparatus for conducting component and material tests on samples, in particular, compression and tensile tests on springs and elastic components, assemblies, and material samples, comprising two spaced sample holders between which a force can be generated so as to apply a load to the sample therebetween, the one sample holder being fixed to a base frame while the other sample holder is carried on a movable positioner, furthermore comprising a motion detector that uses a probe to record the travel distance of the sample holder, and comprising a force sensor that records the force applied to the sample.
Various embodiments of these types of apparatuses are well-known from practice in which, however, first-order measurement errors according to Abbe are observed depending on the constructive design whenever the path to be measured and the measurement standard are not aligned.
In addition, tilt errors and elastic deformations occur due to the fact that the application of force is typically effected outside the test axis, with the result that measurement precision is also degraded.
The object of this invention is to improve an apparatus of the above-described type so as to largely minimize the measurement errors due to tilt motions caused by the application of force outside the test axis, and additionally to design the apparatus so as to enable a continuous force-displacement graph to be recorded instead of recording individual measurement points.
This object is achieved according to the invention by an approach wherein the positioner includes a tubular force application element that surrounds the probe with a small clearance and is connected to the sample holder, the force application element being in the form of a spindle, gear rack, hydraulic unit, or pneumatic cylinder, or the like, through which the manual or motorized application of force is effected coaxially or at least nearly coaxially relative to the test axis.
The advantage achieved by the invention consists essentially in the fact that tilting moments by forces that engage the positioner eccentrically and act to deform the sample are largely prevented, with the result that measurement errors also caused thereby are considerably minimized.
To this end, a preferred embodiment of the invention is provides an additional design aspect whereby in the case of the force application element in the form of a spindle this spindle is attached by a spindle nut to the positioner.
In addition, it is recommended within the scope of the invention that the positioner be connected through a backlash-free guide on the base frame. This allows any lateral forces occurring to be absorbed by this additional guide.
In order to implement the application of force in a force application element in the form of gear rack, the invention proposes that the gear rack be provided with a radially extending row of teeth to which the application of force is effected by a pinion.
It is recommended here that the positioner be provided with a cut-out in the region of the rack through which engages the pinion.
In a first embodiment of the invention, the rack is formed in the cylindrical peripheral surface of the gear rack. The pinion here can have an outer shape that is matched to the peripheral surface of the gear rack.
In a second, metrologically even more advantageous embodiment of the invention, the gear rack is provided with an axially extending cut-out at least in the region of the rack, by which a U-section is created that half surrounds the probe, wherein both edges are provided with a rack, and one pinion each on a common shaft engages each rack. As a result, the application of force is effected uniformly on both sides of the actual measurement axis, where, given an appropriate design of the spindle, the actual application of force can be effected directly in the plane of the measurement axis. This embodiment thus does not produce any tilt errors, or at worst only the most minimal tilt errors.
The following discussion describes the invention in more detail based on the embodiments illustrated in the drawing; therein:
The apparatus showed in the drawing functions to conduct component tests and material tests on samples 1, in particular, compression and tensile tests of springs and elastic components, assemblies, and material samples.
Specifically, the apparatus has two spaced sample holders 2.1 and 2.2 between which a force can be generated so as to apply a load to the sample 1 between these sample holders 2.1 and 2.2.
The lower sample holder 2.1, is fixed to a base frame 3, while the upper sample holder 2.2 is on a movable positioner 4.
A probe 5 is connected to a motion detector 6 so the is travel distance of upper sample holder 2.2 can be determined.
In addition, the upper sample holder 2.2 is connected to a force sensor 7 that records the force applied to the sample 1.
In the embodiment of
The spindle 8 itself is attached as shown in
As
As is evident in
As showed in
In contrast to this, the spindle 8 in the embodiment of
Two respective pinions on a common shaft engage the two racks, thereby causing the resulting force to fall in the test axis. Similarly, it is also possible instead to employ a single pinion having a radial recess.
Number | Date | Country | Kind |
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10 2009 036 247.9 | Aug 2009 | DE | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/DE2010/000681 | 6/17/2010 | WO | 00 | 2/8/2012 |