WO2007006527A1 - Bellows, especially for a shaft comprising at least one rigidly connected hub - Google Patents

Abstract

The aim of the invention is to provide a bellows, especially for a rigid shaft/hub connection which after expansion by at least approximately 50 % shows only minor initial damages and can all the same be firmly, safely and sealingly secured to a shaft. For this purpose, the bellows comprises a bellows section and a collar section facing the shaft, the inner diameter of the collar section at the shaft end being by at least approximately 5 % smaller than the outer diameter of the shaft and by at least approximately 25 % smaller than the outer diameter of the hub.

Description

 Bellows, in particular for a shaft with at least one firmly connected hub

The present invention relates to a bellows, in particular for a shaft having at least one hub fixedly connected thereto, comprising a fold region and a collar region facing the shaft, and a method for fastening such a bellows and its use.

When assembling bellows on joint components with a shaft with at least one, usually two, with this firmly connected ball hub another method must be selected as in other conventional known joint components. In known joint components, which do not have a fixed shaft-hub connection, a bellows is usually first mounted on the shaft, and then connected this shaft together with bellows with the ball hub. Subsequently, the joint is filled with grease and attached the outer joint part. However, this simple assembly method is no longer possible with fixed shaft-hub connections. For here known from the prior art bellows have to be significantly expanded, so that their shaft-side collar area can be pushed over the ball hub.

In order to enable such a considerable expansion of the bellows, in particular in the shaft-side collar region, according to the prior art bellows, in particular made of rubber or rubber-like materials, are used for this purpose. The preferred prior art, high performance bellows made of TPE materials (thermoplastic elastomers), however, can not be used. When mounting the known from the prior art Gummifaltenbälge on solid shaft hub connections is a very strong expansion of the shaft-side waistband of the bellows, so that it can often lead to a Vorschädschädigung, especially cracking due to the excessive strain , As a result, the reliability of the bellows is no longer guaranteed because its sealing behavior is significantly affected by such previous damage. Therefore, bellows are often selected according to the prior art, whose shaft-side collar portion already has a relatively large inner diameter, so that here a less strong expansion when mounted on a fixed shaft-hub connection is made possible with correspondingly reduced risk of previous damage. The disadvantage, however, that subsequent to the attachment of the same by means of a conventional clamping means, in particular a tension band, on the shaft leaks can occur through the choice of the larger inner diameter of the shaft-side collar portion of the bellows, as in of all rule then the inner diameter of the shaft-side collar portion of the bellows is not insignificantly larger than the outer diameter of the shaft. This can lead to local accumulation of material when mounting the shaft-side collar area on the shaft by means of a tension band, whereby the risk of leakage is given.

Solid shaft-hub connection in the sense of the present invention means that a shaft is connected to at least one ball hub, for example by welding or the like, so that here a one-piece connection is formed. Of course, it may also be provided to produce the shaft in one piece with at least one ball hub. All sorts of possible connection methods between a shaft and ball hub fall within the meaning of the present invention under the concept of the fixed shaft-hub connection, including mechanical connections, in particular by means arranged in the shaft or hub connection means, especially those, the subsequent maintenance do not need or can not be opened again.

It is an object of the present invention to provide a bellows, by which the known from the prior art disadvantages can be avoided.

This object is achieved according to the invention by a bellows, in particular for a shaft with at least one fixedly connected hub, comprising a fold region and a shaft region facing the shaft, wherein the inner diameter d | of the collar region is at least about 5% smaller than the outer diameter d _{w of} the shaft and at least about 25%, preferably at least about 50% smaller than the outer diameter of the hub d _N. Of course, the aforementioned parameters relate to a bellows prior to expansion and mounting on in particular a fixed shaft-hub connection. Preferably, the inner diameter d | of the waistband region by at least about 8%, more preferably at least about 10% smaller than the outer diameter d _{w of} the shaft. In a further preferred embodiment, the inner diameter d | of the waist region by at least about 70%, more preferably at least about 90% smaller than the outer diameter of the hub d _N.

The inventors of the present invention have recognized that, contrary to the usual assumption of choosing a larger inner diameter of the shaft-side waistband region of the bellows, it is more advantageous if it is chosen smaller than the outer diameter d _{w of} the shaft. This advantageously achieves that below the expansion and assembly of the bellows in particular a solid shaft hub connection by means of a clamping means the shaft-side waistband area can be firmly, securely and sealingly mounted on the shaft.

In a further preferred embodiment of the present invention, the wavy waistband, when radially expanded by at least about 25%, preferably at least about 50% after relaxation, is at most about 20%, more preferably at most about 15%, even more preferably at most about 10%. larger inner diameter di on. The relaxation time should last at least 5 seconds, more preferably at least about 10 seconds. The radial expansion can preferably take place by at least about 70%, more preferably by at least about 90%. As a result, it is advantageously achieved that the shaft-side collar region of the bellows has an inner diameter d | which is at most insignificantly larger than the outer diameter dw of the shaft. Thus, a secure and sufficiently tight attachment of the bellows on the shaft is possible.

In a further preferred embodiment, the bellows is made of a thermoplastic elastomeric material, which is more preferably a copolyester. Even more preferably, the thermoplastic elastomeric material is partially crystalline and / or crystalline Nn, at least in partial regions of the polymer network structure formed. This partial crystallinity or crystallinity of the thermoplastic elastomeric material of the bellows according to the invention advantageously results in at least about 50%, preferably at least about 70%, even more preferably at least about 90% for mounting on, in particular, a fixed one after an expansion of the shaft-side waistband region of the bellows Shaft-hub connection the material still has sufficient elastic properties and has only a small proportion of plastic properties. The plastic strain rate of the thermoplastic elastomeric semi-crystalline or crystalline material is responsible for the fact that the inner diameter d | the wave-side collar area after expansion only slightly larger than the inner diameter di before radial expansion.

In a further preferred embodiment, the thermoplastic elastomeric material is a copolyester prepared by copolymerizing polyethylene terephthalate with a hydroxyl group-substituted organic acid, in particular p-hydroxybenzoic acid or its derivatives and related organic acids, or cocondensation of polybutylene terephthalate and oligomeric and / or polymeric ethers , Further, the present invention relates to a method of attaching a bellows to a shaft having at least one hub fixedly connected thereto, wherein a waistband portion of the bellows facing the shaft is radially expanded by at least about 5% at a temperature equal to or less than about 100 ° C, wherein the elongation time is equal to or less than about 100 seconds, more preferably equal to or less than about 10 seconds, even more preferably equal to or less than about 1 second. The temperature during the radial separation is preferably equal to or less than about 80 ⁰ C, more preferably equal to or less than about 50 ⁰ C, even more preferably equal to or less than about 30 ⁰ C. If the aforementioned temperature and time parameters simultaneously tur- adhered to, by means of the method according to the invention, on the one hand, an at least significant reduction, if not complete avoidance of pre-damage of the bellows avoided, further, the wave-side waistband of the bellows after application to the fixed shaft-hub connection safely with this and above all Things sealingly fixable by means of a clamping means. A radial expansion is achieved, for example, by pulling the bellows over an expanding body, in particular a conical body, in particular a circular cross-section, the diameter of the conical body expanding in the pulling direction. The expansion takes place up to a diameter which is equal to or greater than the outer diameter of the hub d _N. The conical body may be made of any type of material, but is preferably formed of a metallic material, more preferably made of a steel, and further preferably formed solid, and is optionally provided with a cooling.

Advantageously, the bellows and / or the shaft and / or the hub and / or the Aufdehnkörper, which may be formed in particular conical, provided before expansion with a grease. As a grease all known from the prior art and suitable for joint components greases can be used. However, greases are preferably used which are based on a base oil, in particular a mineral or paraphenic oil, mixed with a lithium soap or a urea derivative, in particular a diurea, triurea, tetraurea or polyurea derivative as thickener, which furthermore Advantageously, as auxiliaries molybdenum sulfite or Molybdänorganoverbindungen such Molybdändithiocarbamat and sulfur-nitrogen or sulfur phosphorus compounds, in particular dithiazoles. However, apart from an expanding body, the radial expansion of the wave-side collar area can be based on Ren suitable aids, or be made without aids with sufficient elasticity of the bellows material used.

Furthermore, the present invention relates to the use of a bellows according to the invention for mounting on a shaft with at least one hub fixedly connected thereto, preferably with two hubs fixedly connected thereto, in particular ball hub.

These and other advantages of the present invention will be explained in more detail with reference to the following figures. Show it:

Fig. 1: a view of a fixed shaft-hub connection with bellows and

Outer joint part in assembled or pre-assembled state;

Fig. 2: a shaft with two fixedly connected to this ball hub;

3 shows a sectional view of a bellows according to the invention;

Fig. 4: a plot of an elongation and a tension of a thermoplastic elastomeric material in the form of a longitudinally cut bottle according to

DIN 53504-S 2;

FIG. 5 is a plot of the total strain theoretically obtained from FIG. 4 against the plastic strain fraction in an extrapolation; FIG.

Fig. 6: a plot of the output inner diameter of the shaft side

Collar area of a bellows against the inner diameter after expansion (theoretically);

Fig. 7: an expansion body, conically shaped, for expanding the bellows according to the invention.

First, it should be noted that the features shown in the figures are not limited to the individual embodiments. On the contrary, the features given in the description, including the description of the figures and the drawings, are the Continuing education can be combined with each other. Incidentally, the same reference numerals are used for the same features.

Fig. 1 shows for better understanding of the subject matter of the present invention in a view a shaft 16 with arranged at both ends of ball hubs 18.1 and 18.2. The ball bosses 18.1 and 18.2 are firmly connected to the shaft 16 by welding and subsequent hardening. At the left end of the shaft 16, an outer joint part 20 is also already arranged, which is in communication with a bellows 10 via the joint-side collar region. A wave-side collar region 14 of a bellows 10 stands with the shaft 16 in connection. This connection can be done in particular by a not shown here in detail clamping means, in particular clamping band. For simplicity, these are also not shown on the outer joint part 20 and the shaft 16 binder for fixing the bellows 10 in Fig. 1.

To further clarify the outer joint part 20 is shown in the unmounted state at the right end of the shaft 16 as shown in FIG. 1 of the bellows 10. The shaft 16 has an outer diameter d _w , whereas the hubs 18.1 and 18.2 have an outer diameter d _N.

Fig. 2 shows to further illustrate the reproduced in Fig. 1 shaft 16 with the fixed thereto by welding and hardening ball hubs 18.1 and 18.2.

3 now shows the bellows 10 according to the invention with the wave-side waistband region 14, an immediately adjoining fold region 12 with pleats 24.1 to 24.5 and a subsequent waist region 22, which is arranged on the hinge part side. The collar region 14 has an inner diameter d | on. This inner diameter d | is in the context of the present invention, about 10% smaller than the outer diameter d _{w of} the shaft 16 and about 95% smaller than the outer diameter d _{N of} the hub 18.1 or 18.2.

Figure 4 now shows a stress-strain curve obtained from measurements of a thermoplastic elastomeric, semi-crystalline copolyester (Arnitel EB463, DSM Engineering Plastics, Sittard, The Netherlands). Measurements were made in accordance with DIN 53504-S 2, but with stretching not to break but to 6 cycles of elongation and release with a respective increase in maximum elongation in each cycle of 10%. The measurements were carried out on bottle-shaped test specimens produced from said thermoplastic elastomeric material, which were cut longitudinally. Expansions were from 0% to 5%, 0% to 10%, 0% to 15%, 0% to 20%, 0% to 30%, 0% to 40%, 0% to 50% and 0% to 60 % Elongation, wherein the expansion time was 5 mm / min. FIG. 4 shows a hysteresis-like course of the recorded measurement curves, from which, inter alia, a plastic strain fraction can be extracted.

This plastic strain component calculated from FIG. 4 is plotted against the total strain in FIG. 5 and was further extrapolated with a linear regression R ² = 0.9998 and y = 0.0013 × ² + 0.1739 × -0, 9th The circularly reproduced measuring points in FIG. 5 have been taken from FIG. 4, the solid line of FIG. 5 represents the extrapolation obtained therefrom. FIG. 5 can be seen that with an expansion of approximately 77%. a plastic elongation of 20% is present. This would mean that after a total expansion of about 77%, a bellows having an original inside diameter of the wave-side waistband area of about 34 mm after elongation has a width of about 40.8 mm. This can be seen, for example, in FIG. 6, which is shown in FIG. 5 on the basis of different initial internal diameters d | the Weil side waistband of a bellows was determined theoretically. It can be seen from FIG. 6 that the smallest inner diameter d 1 obtained after expansion has been about 77% of the wave-side collar area is about 37 mm as the lowest limit for a starting inner diameter d | from about 22 to 23 mm. According to the theoretical prerequisites which can be taken from FIG. 6, with an expansion of approximately 77% of the shaft-side collar region, inner diameter d | receive the same, which may be too large to ensure a secure attachment and fixation of the bellows on the shaft after installation.

FIG. 7 shows an expansion means 30 (expanding body) suitable for achieving a radial expansion, which has a conical body whose diameter widens in the direction of the arrow 32. The expanding agent 30 was used in the following example for expanding the bellows 10 according to the invention, produced from a thermoplastic, partially crystalline material. The diameter in the head region 34 of the expansion means 30 was about 26 mm, whereas the diameter in the foot region 36 of the expansion means 30 was about 60 mm. example

It was an inventive bellows with an inner diameter d | of the shaft-side collar area of 30.5 mm by means of the expansion means 30 to an inner diameter d | expanded by 60 mm. This corresponds to a total expansion of about 97%. For radial expansion in the direction of the indicated in Fig. 1 arrows 26.1 and 26.2 while the bellows 10 was pulled in the direction of the arrow 32 on the provided with a grease expander 30. The expansion time was about 1 second or alternatively about 100 seconds. The temperature was about 23 ⁰ C or alternatively about 80 ⁰ C. If the expanding agent 30, for example, made of a metal, especially steel, this can be preheated or tempered to the above temperatures.

Assuming the values theoretically derivable from FIGS. 5 and 6, an overall plastic strain of approximately 29% would exist with an overall expansion of approximately 97% according to the present example, so that with an inner diameter d | of the wave-side waistband area would have to be expected after the expansion of about 39 mm.

Surprisingly, however, it was found that when using a thermoplastic elastomeric, partially crystalline material as Faltenbalgmaterial (Arnitel EB463) at a Aufsehnungszeit of 100 seconds and a relaxation time of 10 seconds, the inner diameter d | 35.5 mm, at a Aufsehnzeit of 1 second was only 33.3 mm, measured at a temperature of 23 ° C, respectively. In a Aufdehnzeit of 1 second and a relaxation time of 10 seconds at a temperature of 80 ⁰ C, the inner diameter was d | 36.6 mm. Thus, it has surprisingly been found that contrary to the theoretical predictions, in particular according to FIG. 6, inner diameter d | of the wave-side collar region were obtained after expansion at expansion times of about 100 seconds or about one second, which are well below the theoretically determined diameter of about 35 mm. It has proven to be particularly advantageous when the temperatures are chosen to be relatively low, at which the expansion takes place, and when the expansion time is a maximum of about 100 seconds, preferably equal to or less than 1 second. Relaxation time in the sense of the present invention refers to the period after completion of the expansion by means of, for example, the expansion agent 30. Surprisingly, according to the method of the invention, values for the inner diameter d | of the wave-side waistband area, which were well below the theoretically achievable levels. As a result, an inventive bellows 10 could be provided, which has an inner diameter d | the shaft-side collar portion 14 which is at least about 5%, preferably at least about 8%, and more preferably at least about 10% smaller than the outer diameter d _{w of} the shaft on which it is mounted.

Claims

claims 1. bellows (10), in particular for a shaft (16) with at least one fixedly connected hub (18.1, 18.2), comprising a pleat region (12) and a collar region (14) facing the shaft (16), characterized that the inner diameter d | the collar portion (14) is smaller than the outer diameter d _{w of} the shaft (16) by at least about 5% and smaller than the outer diameter d _{N of} the hub (18.1, 18.2) by at least about 25%. 2. A bellows according to claim 1, characterized in that the inner diameter d | of the collar portion (14) is at least about 70% smaller than the outer diameter d _{N of} the hub (18.1, 18.2). 3. bellows according to one of the preceding claims, characterized in that the collar region (14) at a radial expansion by at least 25% after relaxation by a maximum of about 20% larger inner diameter d | having. 4. Bellows according to one of the preceding claims, characterized in that it is made of a thermoplastic elastomeric material. 5. Bellows according to one of the preceding claims, characterized in that the thermoplastic elastic material is a copolyester. 6. bellows according to one of the preceding claims, characterized in that the thermoplastic elastic material is partially crystalline. 7. A bellows according to any one of the preceding claims, characterized in that the thermoplastic elastic material is a copolyester, prepared by copolymerization of polyethylene terephthalate with a hydroxyl group-substituted organic see acid or cocondensation of polybutylene terephthalate and oligomeric and / or polymeric ethers. 8. A method for fastening a bellows (10) on a shaft (14) with at least one firmly connected to this hub (18.1, 18.2), one of the shaft (16) facing ter waistband (14) of the bellows (10) to at least about 50% is radially distended at a temperature of equal to or less than about 100 ⁰ C, the Aufdehnungszeit equal to or less than about 100 seconds. 9. The method according to claim 8, characterized in that the bellows (10) and / or the shaft (16) and / or the hub (18.1, 18.2) is provided before expansion with a grease. 10. Use of a bellows according to one of claims 1 to 7 for mounting on a shaft with at least one firmly connected to this hub.