Abstract
An under sleeper pad (1) for fastening to an outer surface (2) facing a ballast bed (16), in particular an underside, of a railroad sleeper (3). The under sleeper pad (1) includes an elastomer layer (5), the elastomer layer (5) having a density in the range of 250 kg/m.sup.3 to 350 kg/m.sup.3, preferably 250 kg/m.sup.3 to 330 kg/m.sup.3.
Claims
1. An under sleeper pad for fastening to an outer surface facing a ballast bed of a railroad sleeper, the under sleeper pad comprising: an elastomer layer having a density in a range of 250 kg/m.sup.3 to 350 kg/m.sup.3.
2. The under sleeper pad as claimed in claim 1, wherein the elastomer layer comprises a polyurethane.
3. The under sleeper pad as claimed in claim 1, further comprising a fastening layer for fastening to the railroad sleeper.
4. The under sleeper pad as claimed in claim 1, wherein the elastomer layer has a tear resistance of 2.2 N/mm.sup.2 to 4.0 N/mm.sup.2.
5. The under sleeper pad as claimed in claim 1, wherein the elastomer layer has an elongation at break of 50% to 200%.
6. The under sleeper pad as claimed in claim 1, wherein the elastomer layer has a compression set of 15% to 24%.
7. The under sleeper pad as claimed claim 1, wherein the elastomer layer has a Shore A hardness of 50 to 80.
8. The under sleeper pad as claimed in claim 1, wherein the under sleeper pad has a relative residual deformation rv in the range of 50% to 80%, for a residual deformation test performed on the under sleeper pad which is fastened on an outside of a test specimen carrier of concrete and includes the following test steps: a) inserting the test specimen carrier of concrete with the under sleeper pad fastened thereto in a test apparatus, the test apparatus comprising a geometric test plate fastened to a pressure punch of a press, the geometric test plate comprising a pressing surface with elevations and depressions and the pressing surface of the geometric test plate being brought into contact with a surface of the under sleeper pad that faces away from the test specimen carrier, b) measuring a starting thickness d0 of the under sleeper pad at a measurement location in a region of a maximum one of the elevations of the geometric test plate, c) pressing the pressing surface of the test plate into the under sleeper pad by the pressure punch for five hundred thousand pressing cycles following one another directly in succession, the test plate being pressed into the under sleeper pad with a pressure exhibiting a sinusoidal curve between 0.01 N/mm.sup.2 and 0.15 N/mm.sup.2 and at a cycle frequency of 15 Hz in each of said pressing cycles, d) measuring a first modified thickness d1 of the under sleeper pad at the measurement location upon the five hundred thousandth pressing cycle, the under sleeper pad being in a maximally compressed state, which results during the five hundred thousandth pressing cycle, when the first modified thickness d1 is being measured, e) lifting the test plate completely off of the under sleeper pad with a constant lifting-off speed of 1 mm/s starting directly after the first modified thickness d1 has been measured, f) measuring a second modified thickness d2 of the under sleeper pad at the measurement location directly after a period of time of 60 s has elapsed, the period of time starting directly at an end of the measurement of the first modified thickness d1, and g) calculating the relative residual deformation rv according to the formula rv=(d0?d2)/(d0?d1).
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0028] Further features and characteristics of preferred embodiments of the invention are explained by way of example below in the description of the figures, in which:
[0029] FIG. 1 shows a longitudinal view of a railroad sleeper according to the invention having an under sleeper pad mounted on a ballast bed;
[0030] FIG. 2 shows a face-side view of the structure from FIG. 1;
[0031] FIG. 3 shows an enlarged view of the detail in the region A from FIG. 2;
[0032] FIG. 4 shows an illustration of a test apparatus suitable for performing the residual deformation test, and
[0033] FIG. 5 to 12 show further illustrations for explaining the individual test steps of the residual deformation test.
DETAILED DESCRIPTION
[0034] FIG. 1 schematically shows a longitudinal view of a railroad sleeper 3 which rests on a ballast bed 16, formed from the ballast 22, with an interposed under sleeper pad 1 according to the invention. The under sleeper pad 1 is on the outer surface 2 facing the ballast bed 16, that is to say here the underside, of the railroad sleeper 3, and by means of its fastening layer 4 is fastened to the railroad sleeper 3. In addition to the fastening layer 4, the under sleeper pad 1 comprises the elastomer layer 5. Furthermore, the under sleeper pad 1 may also comprise further layers in a manner known per se, which do not need to be explained in more detail here.
[0035] FIG. 2 shows a face-side view of the arrangement from FIG. 1. In the region A from FIG. 2, which is illustrated in an enlarged view in FIG. 3, it can be seen particularly clearly how the ballast 22 of the ballast bed 16 penetrates certain regions of the elastomer layer 5 and thus the under sleeper pad 1, in order as a result to increase the transverse displacement resistance, that is to say prevent to the greatest possible extent the railroad sleeper 3 from being displaced in its longitudinal direction with respect to the ballast bed 16 by corresponding stresses in the track system.
[0036] FIG. 4 schematically shows a test apparatus 7 for performing the residual deformation test for determining the relative residual deformation rv of the under sleeper pad 1. The test apparatus 7 has a correspondingly stable and fixed base 18 and a pressure punch 8. The test plate 9 is fastened to the pressure punch 8. The test plate has a pressing surface 10 with elevations 11 and depressions 12. The pressure punch 8 is fastened to a press 17, which is illustrated only highly schematically here but is known per se and makes it possible to press the pressure punch 8 together with the test plate 9 into the under sleeper pad 1 and lift it out again. The press 17 may be for example a hydraulic press but may also be other presses that are known per se and are suitable for this application. In FIG. 4, a test specimen carrier 6 of concrete with the under sleeper pad 1 fastened thereto has already been inserted into this test apparatus 7, it being possible for the pressing surface 10 of the test plate 9 to be brought into contact with a surface of the under sleeper pad 1 that faces away from the test specimen carrier 6.
[0037] In FIGS. 5 to 10, which are described below, the pressure punch 8 and the press 17 are no longer illustrated but of course are present nevertheless.
[0038] FIG. 5 shows the situation in which the pressing surface 10, with the elevations 11 and the depressions 12, of the test plate 9 is brought into contact with that surface of the under sleeper pad 1 that faces away from the test specimen carrier 6. In FIG. 5, and in particular in the detail B from FIG. 5 that is shown in FIG. 6, it can be seen that the under sleeper pad 1 here still has its starting thickness d0, which is measured at the measurement location 13 in the region of a maximum elevation 11 of the geometric plate 9. After this starting thickness d0 has been measured according to FIGS. 5 and 6, when the residual deformation test is performed, the pressing surface 10 of the test plate 9 is then pressed into the under sleeper pad 1 by means of the pressure punch 8 in five hundred thousand pressing cycles 14 following one another directly in succession, the test plate 9 being pressed into the under sleeper pad 1 with a pressure 15 exhibiting a sinusoidal curve between 0.01 N/mm.sup.2 and 0.15 N/mm.sup.2 and at a cycle frequency of 15 Hz in each of these pressing cycles 14. FIG. 11 shows such a pressing cycle 14. This illustrates the curve of the pressure 15 in this pressing cycle 14 in a diagram, which plots the pressure D against the time t. The cycle frequency of 15 Hz means that the duration of the cycle is one fifteenth of a second. In FIG. 11, the sinusoidal curve of the pressure 15 between 0.01 N/mm.sup.2 and 0.15 N/mm.sup.2 can be clearly seen. During the residual deformation test, five hundred thousand such pressing cycles 14 following one another directly in succession are performed.
[0039] In a diagram which plots the travel 20 of the pressure punch 8 or of the test plate 9 that occurs along the axis W against the time t, FIG. 12 shows how the pressing surface 10 of the test plate 9 increasingly penetrates the under sleeper pad 1 at the measurement location 13 while the pressing cycles 14 are being performed. Here, of course not all five hundred thousand pressing cycles 14 are illustrated in FIG. 12, this being symbolized by the cycles illustrated in dashed line in the center. At the end of these five hundred thousand pressing cycles, the state 21 illustrated symbolically in FIG. 12 is reached in any case, and in this state the modified thickness d1 of the under sleeper pad 1 is determined at the measurement location 13. The measurement of the first modified thickness d1 is thus determined in the maximally compressed state 21 produced during the five hundred thousandth pressing cycle 14. FIG. 7 shows this state 21, in the case of which the pressing surface 10, by means of the elevation 11 of the test plate 9, has been pressed into the under sleeper pad 1 far enough that the latter retains only the thickness d1 at the measurement location 13. FIG. 8 shows an enlarged view of the region C from FIG. 7 and thus also the thickness d1 of the under sleeper pad 1 at the measurement location 13 at this point in time.
[0040] Directly after the measurement of the first modified thickness d1, the test plate 9 is completely lifted off of the under sleeper pad 1 with a constant lifting-off speed of 1 mm/s. The arrow 19 in FIG. 7 depicts the direction in which the test plate 9 is lifted off by means of the pressure punch 8 and the press 17 during this load-relieving operation, with the result that the state illustrated in FIG. 9 can be reached. FIG. 9 schematically illustrates that, after the five hundred thousand pressing cycles 14, the under sleeper pad 1 has a corresponding residual deformation which gradually resets over time. Directly a period of time of 60 seconds has expired, the second modified thickness d2, illustrated in FIG. 10 in an enlarged view of the detail D from FIG. 9, of the under sleeper pad 1 is measured at the measurement location 13. This period of time of 60 seconds starts directly at the end of the measurement of the first modified thickness d1.
[0041] The relative residual deformation rv can then be calculated from the thicknesses d0, d1 and d2 measured during the residual deformation test in the manner presented by means of the formula specified in test step g).
LIST OF REFERENCE SIGNS
[0042] 1 Under sleeper pad [0043] 2 Outer surface [0044] 3 Railroad sleeper [0045] 4 Fastening layer [0046] 5 Elastomer layer [0047] 6 Test specimen carrier [0048] 7 Test apparatus [0049] 8 Pressure punch [0050] 9 Test plate [0051] 10 Pressing surface [0052] 11 Elevation [0053] 12 Depression [0054] 13 Measurement location [0055] 14 Pressing cycle [0056] 15 Pressure [0057] 16 Ballast bed [0058] 17 Press [0059] 18 Base [0060] 19 Direction [0061] 20 Travel [0062] 21 State [0063] 22 Ballast
