DE2844486A1 - Precompression of elastomeric pads of polyester rubber - to suppress permanent compressive deformation at high strains in service - Google Patents

Abstract

Pads of elastomeric polyester material for use as compression springs are conditioned by axial compression to strains above the elastic limit, i.e. >=30%. Compressive preconditioning suppresses development of permanent deformation if subjected to compressive strains of >10%, thus extending the range of applications of such springs.

Description

Method for the production of compression spring bodies

Polyester elastomers and pressure buffers made therefrom. The invention relates to a method for the production of compression spring bodies from a block of a copolymer polyester elastomers of a given axial length. She concerns too a method for producing a pressure buffer from a pressure spring body and a pair of plates 1 each arranged on one side of the compression spring body and a method of producing a multilayer print buffer several such compression spring bodies ind plates at the ends of the pressure buffer and between adjacent compression spring bodies. The invention also relates to a method for the production of a pressure buffer aiis a two-sided compression spring body of the aforementioned type and two plates1 each on one side of one side of the compression spring body concerns are bound by them.

Elastomers are widely used in the manufacture of spring bodies that are subjected to tension or compression. A newer elastomer this one Art is a copolymer polyester.

Such a polymer can be broadly considered to be statistically related flexible and rigid segments are described, compare to For example, U.S. Patents 3,651,014, 3,763,109 and 3,766,146. Such a polymer can be, for example consist of three components, namely dimethyl terephthalate, polyglycols such as polytetramethylene glycol, polyethylene glycol or polypropylene glycol and from short-chain Diols such as butanediol or ethylene glycol. If these are implemented together, so result in high molecular weight polymers, in which from the diols and the terephthalate resulting blocks form crystalline, rigid segments and the resilient amorphous Phase consists of the polyglycol terephthalates. Products of this type are in llandel (E.I. DuPont de Nemot.rs & Co, Wilmington, Delaware, USA) under the type designations 5550, 5555, 5556, 5556 HS, 4056 "nd 6356 available, the first two of which Numbers represent the durometer hardness in values on the D-scale.

Copolymeric polyesters of this type have suitable effects in connection with tensioned spring bodies. However, they have proven to be unsuitable for on Pressure-stressed spring bodies have been proven. This is due to the fact that they are at a compression of more than approx. 10% begin to deform permanently. It is obvious, that a spring that is permanently deformable under load for the respective desired purpose is unsuitable. In addition, there are applications where the spring is less than 10% is compressed (i.e. only a small amount of spring action is required) Rare.

The main object of the invention is to indicate a method can be processed by the copolymer polyester elastomers so that a Product is obtained that as a compression spring body also in such applications can serve, in which the force acting on the spring body is so great that the spring body is compressed by significantly more than 10%. In other words, consists of The task of ErfisdunS is to develop a process for production specify a compression spring body made of copolymer polyester, its permanent deformation It is irrelevant who the compression spring body by far under the operating conditions more than 10% is compressed. The compression spring body produced in this way should accordingly experience no permanent deformation to be taken into account, even if the force acting on it in the axial direction reduces the compression spring body by an amount that is greater than the amount at which a permanent deformation of the compression spring body would occur in the axial longitudinal direction.

According to the invention this object is achieved in that the block in axial direction is compressed with a force that is the predetermined axial Length reduced by more than 30%, and that the block then from that in the axial direction acting force is relieved. Preferably the block is pre-compressed annealed.

Elastomer spring elements are also used in railways, among other things applied. In such applications it is known to make the spring body made of elastomers Binds to metal plates on both sides, creating a much improved work area (see, for example, U.S. Patents 2,713,483 and 3,227,288). Both commonly used elastomers could be a good bond between the Spring body llnd the metal plates using commercially available adhesives.

However, it has not yet been possible to find an adhesive for the aforementioned copolymers polyester.

According to the invention, therefore, to produce a pressure buffer from Proceed with copolymer polyester so that the plates are superficial on one side are provided with irregularities that are oriented at an angle to the plate side Steps form that the plates on both sides of the compression spring body under Training a unit to be arranged, with those with the irregularities provided sides of the plates are each facing the compression spring body that the unit is subjected to a further axially acting force, below which the copolymer polyester elastomer flows around the irregularities and a mechanical connection between the compression spring body and the plates is formed is, and that the unit is then relieved of the further axially acting force will. The unit can under the further axially acting force essentially are compressed to the same strength as the compression spring body before.

The plates can be provided with irregularities and holes and the irregularities may protrude from the side of the panels. It This creates a mechanical connection between the compression spring body and the plates -manufactured.

The mechanical connection between the plates and the compression spring body and thus the work area of such a print buffer can be added be reinforced so that the sides of the plates facing the compression spring body e.g. be roughened with a sandblasting blower.

Multilayer print buffers can also be created in a corresponding manner alls assemble several compression spring bodies of the aforementioned type, with between adjacent compression spring bodies correspondingly provided with irregularities plates are arranged.

In a combination of the aforementioned methods, according to the invention a pressure buffer made of a compression spring made of copolymer polyester elastomers and these enclosing plates are obtained directly by at the length of the block of polyester elastomer by more than 30 after the pressing process Só is reduced and at the same time the mechanical link is made between the plates and the compression spring body.

Embodiments of the invention are shown in the figures and are explained and described in detail below with reference to the reference symbols. 1 shows a flow chart to illustrate the manufacturing process of the Compression spring body made of copolymer polyester elastomer according to the invention; Fig. 2 shows a section through a casting mold for the copolymer polyester; Fig. 3 is a schematic Representation of the pre-compression of the tempered block of all copolymer polyester, Fig. 4 is a view of a using the compression spring body made of copolymer Polyester-made first embodiment of a pressure buffer; Fig. 5 in Top view of one of the plates for producing a pressure buffer according to the invention using a compression spring body of all copolymer polyester; Fig. 6 a Cross section taken along line 6-6 in Fig. 5; Fig. 7 is a view of another Embodiment of the pressure buffer according to the invention; Fig. 8A shows a partial Broken plan view of another embodiment of the one shown in FIG Plate; Fig. 8B is a cross section taken along line 8B-8B in Fig. 8A; FIG. 9A is a partially broken away plan view of a further embodiment of FIG plate shown in Fig. 5; Figure 9B is a cross section taken along line 9B-9B in Fig. 9A; FIG. 10A is a plan view of a further embodiment of the one shown in FIG Plate; FIG. 10B shows a cross section along the line 10B-10B in FIG. 10A; and Fig. 11 is a view of a further embodiment of the pressure buffer according to the invention using the plates shown in Figures 10A and 10B.

The above-mentioned copolymeric polyesters are generally in the form of grains or balls, the material being cast or extruded is further processed. As shown at the top of FIG. 1, there is the first step is that a block is preformed from the material. This can In the case of small cross-sections, the result is that the obtained from an extruder Strand of this material is divided into individual blocks. For larger cross-sections the dimensions and capacity of the extrusion presses that are necessary for this are unacceptable large, and it is more convenient to cast blocks with such cross-sections.

The grains or balls are used to carry out the casting process melted by heating to 165 to 2320 C (3300 to 4500 F). The melted one Material is placed in a mold 10 and while solidifying with a pressure applied from the outside. In the embodiment shown, the pressure is on brought the middle area of the Gllßblocks to action. Extends accordingly In FIG. 2, a weight li can be seen through a central opening 12 in the lid of the mold 10 and is freely movable in the vertical direction through this central opening 12. To this Way is by the weight il pressure on the central area of the as copolymer Polyester existing material 13 exerted1 while this solidifies in the mold 10. The pressure can also be done by other means, e.g.

Springs, instead of the force of gravity exerted by the weight will. Other areas and not necessarily limited parts can also be used a surface can be pressurized.

The application of pressure to the material during solidification is used mainly to avoid the problems or at least to limit their effect, created by cavities in the block being formed. Such cavities arise quite often when copolymer polyesters are cast into bodies with a high cross-section will. This is because the middle area of the material is in the mold 10 continued to be obtained in molten form after solidification of the outer components remains and on the other hand because the material shrinks when it cools. There so the outer shape of the material is given from the start and that in the middle area material located later solidifies within this given shape the shrinkage upon solidification of the material in the central area to occur of cavities.

These cavities remain in the manufactured compression spring body and are detrimental to this. When applying pressure as described above, the cavities are created only very rarely, if at all.

Another benefit that comes with pressurizing the material is connected from above by the weight 11, consists in that this weight on the end face of the block from the solidified material, a version 15 is determined.

In some applications, for example in the railroad industry, a plurality layered by compression spring bodies made of elastomers. The neighboring compression spring body has a projection of a corresponding shape which protrudes into the socket 15. This keeps the compression spring bodies in mutual alignment. In the Form 10 in Fig. 2 is a recess 16 at the bottom. This recess is filled by the molten material and this forms on the corresponding Front side of the block has a projection 17.

Of course, this projection has such a shape1 that it is straight in the socket 15 of an adjacent compression spring body fits.

According to the illustration in Fig. 1, the material is after shaping of the block 18 annealed. The temperature used for this changes with the respective material used; for the material with the code number 5550 it is around 1210 C (2500 F). The annealing time is at least 64 hours. It has shown1 that the annealing can also take place over 180 hours, the material gets slightly better properties. The annealing can be done for a shorter time take place, but the properties of the compression spring body are better, if at least is annealed for 50 hours.

It looks like a longer tempering time leads to better Suspension properties leads, i.e. that the compression spring body better after unloading takes on its original shape.

Presumably, the tempering promotes crystal growth. Annealing should be done shortly after the ingots are cast.

In the next stage of the process, the tempered block 18 pre-compressed. This takes place in the manner shown schematically in FIG. 3. A plate 20 is arranged on one side of the tempered blook 18. This record has a projection 21 of a size which is adapted to the socket 15, to keep their shape. Located on the opposite side of block 18 a plate 22 with a recess 23 of such a size that therein the projection 17 of the block 18 is received and held.

A force F is applied to the two plates 20, 22 in such a direction caused the block 18 to be compressed. This force F should sufficient to compress the block 18 in the axial direction to such an extent that that the dimension of the block 18 in the axial direction is reduced by at least 30%. The axis to which the above expression "in the axial direction11 refers, is the perpendicular to the two sides of the block 18 against which the plates 20, 22 abut, running axis. Better torsion springs are obtained when the compression is considerably larger. According to previous attempts is under consideration of all other factors the optimum value for the compression at a value which leads to a length reduction of approx. 50%. With regard to the spring force of the Compression spring body, the properties of the elastomer are even better when the pre-compression leads to a length reduction of 90 to 94%. However this is Length reduction generally not very practical because of the preformed block necessarily has a great axial length and is formed by a column, that is difficult to squeeze. If, on the other hand, the block is not columnar, but a considerable cross section perpendicular to the axis, so will the force for compressing to 90 to 94% over such a cross-section is astronomical great.

The compression force does not take a substantial amount of time to be brought into action. The compression can be carried out in a press which is operated in such a direction that the plates 20, 22 against each other be pressed. When the desired compression is reached, the press stopped and released to relieve the block 18 of the force F and the block refer to. The force F thus only acts over the length of time during which the press is stopped and released. Probably be essentially The same results are obtained if the force F is only applied for a short time in one push however, this has not yet been attempted.

Fig. 4 shows a first embodiment of a print buffer, in which the compression spring bodies 25 and 25 'obtained in this way are used. To the load areas of each compression spring body, plates 26 are bound as a metal, for example by means of a Adhesive, as far as it is available. Each compression spring body 25, 25 'has a socket 15 and a protrusion 17; as shown, the protrusion is 17 the spring 25 is inserted into the socket 15 of the spring 25 '.

The version 15 and the projection 17 are not for the creation of the Compression spring body necessary parts. The shape 10 must therefore not have a recess 16. In this case, and with completely flat plates 20, 22 (without the protrusion 21 and the recess 23) are the load surfaces of the compression spring body (to which the Plates 26 in Fig. 4 are bound) completely flat. While the weight 11 at the top of the preformed block 18 has a recess formed, this is Depression no longer exists after pressing together.

The thus obtained compression spring body made of elastomers can with favorable Results are applied, compare e.g.

LS-PS 3 741 406. Other uses are related with Bumpers on cranes and automobiles, with shock absorbers on conveyors and buffering under machines, which attenuate the transmission of shocks, that are generated in the operation of the machines, and others.

However, it is often difficult to establish a good connection between the compression spring bodies 25 and the panels 26 with adhesives, as the available adhesives do not bind with the copolymer polyester elastomers. As a secure connection between the plates and the compression spring bodies are essential for the use of the pressure buffers is a relatively simple method of making a mechanical connection has been developed between the compression spring bodies and the plates. To do this, the Plates superficially provided with irregularities on the side, which on the compression spring body with the irregularities aligned at an angle to the plate side Form steps or stops. These irregularities can result from holes in the Plates, protrusions protruding from the plate side, or both. A unit made from the plates and the pre-compressed compression spring body is then compressed again so far that the copolymer polyester flowing around the irregularities and against the stops or steps.

An embodiment is shown in FIGS. A plate 26 'made of metal is superficially provided with irregularities, generally denoted by 27 are and have been punched out of the plate 26 'or cast together with it are.

The plate 26 'is also hemispherical, rather than cylindrical Projection 29 instead of projection 17 in FIG. 4, but which has the same function Fulfills.

The irregularities 27 each contain an annular projection 30 extending outward and one through the protrusion and the plate 26 'extending breakthrough 28. The projections 30 can be continuous one Pieces formed with the plate 26 'as shown; You can also consist of a plurality of pieces that are welded or otherwise are connected to the plate 26 '.

The projections 30 are preferably beveled at their outer ends 32, to tighten the mechanical connection z1.

The outer ends 32 can also be cut and bent apart to form a jagged edge similar to the edge shown.

In Fig. 5 there are nine irregularities causing the mechanical connection 27 shown, which at equal angular intervals in the radial direction equidistant from the projection 29 are removed. The number and the spacing of the irregularities 27 necessarily depends on the size of the plate 26 'and its actual purpose addicted.

Around each opening 28 around the metal of the plate 26 'and of the projections 30 have a stop or a step which is at an angle to the plate side 26'a of the plate is aligned, which is in contact with the compression spring body the elastomer. Similarly, the periphery of the protrusions 30 form one such angled face or step.

To produce a pressure buffer 31, a cylinder block is first used Cast from the copolymer polyester without the socket 15 and the projection 17 cylindrical block is tempered and pre-compressed, as schematically in Fig. 3 is shown between an opposing pair of flat surfaces (i.e. without the protrusion Z1 and the recess 23). The compression takes place by more than 30% of the lungs of the cast block. After squeezing it will the block is placed between a pair of plates. The upper one shown in FIG Plate is plate 26 'shown in Figures 5 and 6. The lower plate 50 is identical formed therewith except that the projections 30 from their opposite Face, i.e. in the direction of the pre-compressed block. Another Compression with a force F 'occurs in the axial direction to that of the plates and the block formed unit, the force being sufficient to cause the copolymer polyester elastomer around the projections 30, into the openings 28 flows into and onto the angled surfaces. In practice it is enough also this second compression out to the unity in strength just as far as with the pre-compression. After the relief of the force F 'decreases the strength of the unit again. In general, the required force F 'must be greater than the force initially applied to compress the block 18 F.

For example, it is an untreated block of copolymer polyester with a diameter of 86.36 mm (3.4 inches) compressed so much that its length reduced to 2514 mm (1 inch), so there is a total force for it Approximately 890,000 to 980,000 N (200,000 to 220,000 lb) required. With relief from this force the length of the block increases again to 50.8 mm (2 inches). After placing the panels on opposite sides of the block, the thus obtained unit compressed one more time to such an extent that that the length of the unit is again 25.4 mm (i inch). To do this is a force of approximately 1.07 to 1.11 MN (240,000 to 250,000 lb) in total.

During this second compression, the plates are attached to the Compression spring body firmly connected. After releasing this force, the length increases the unit back to 50Z8 mm (2 inches).

With the devices usually available, the print buffers 31 prepared in the manner described above in a two-step process will; the compression spring body is first produced in a pre-compression and in a further compression step the connection between the compression spring body and the plates.

With an appropriately designed device, both process stages can be used can also be carried out in one step. It then becomes the tempered and still uncompressed block of copolymer polyester between two panels like 26 'and 50 and a compressive force to act on this arrangement brought sufficient to the block by more than 30% of its original length to squeeze. This means that the block is all copolymerized in one step Elastomers receive a product suitable as a compression spring body, as well as causing that the copolymer polyester around the projections such as 30 and into the openings how 28 flows in and thus a mechanical connection between the compression spring body and manufactures the plates.

Preferably used in practice for the manufacture of the print buffer 31, the surfaces of the plates 20, 22, 26 ', 50 which abut the block 18 are roughened zii prevent the block from flowing along the plates. This can be done through treatment the plate surfaces with a sandblasting blower.

By roughening the rich, the sensitivity of the resulting pressure buffer against the acting force, because the roughened Plates hold the block between them, so that a pressure buffer of larger Compressive strength arises.

The copolymer polyester elastomer of block 18 is also "shock sensitive", i.e., a momentary compression of the compression spring body (as it is with the spring function occurs) does not cause any permanent deformation.

In view of this, all of the factors to be considered are the plates shown in Figs. 5 and 6 are preferable. There are also practical aspects to this such as cost, manufacturing technique, etc., as well as the best possible superficial Irregularities to achieve a solid mechanical connection between the plates and the compression spring body.

However, the mechanical connection can also be obtained in other ways will. Thus, in Figs. 8A and 8B, a different design of the plate is shown. The surface irregularities of the plate, generally designated 27 ' 26 "each consist of an opening 28 'and an outwardly extending one Protrusion 30 '* The protrusions 30' define steps or stops that are at an angle are aligned with the plate side. There are two or more through bores in the protrusion 30 34 trained. When building a print buffer 31 as in Fig. 7 with this plate 26 "causes the force F 'to compress the copolymer polyester-elastomer flows around and into the projections 30 'and into the through bores 34. Through the elastomer material in the through holes 34 is the final from the Plates and the compression spring body formed pressure buffer 31 additionally held together. A similar effect is further achieved in that the broken lines 28 ' limiting walls converge.

Another formation of the superficial irregularities is shown in Figures 9A and 9B. At the point of the generally designated 27 " superficial irregularity is a generally square one Opening 35 in the plate 26 "'. On opposite sides of the opening 35 there are triangular depressions defined by protrusions 36 and 37 in of the plate 26 "'. The plate 26"' has a plurality of such spaced apart superficial irregularities 27 ″ arranged thereon. During assembly a pressure buffer 31 according to FIG. 7 with the aid of the plate 26 '' 'the copolymer flows Polyester elastomers in the openings 35 and in those of the projections 36 and 37 formed depressions, whereby a mechanical connection is formed. The sides of the openings 35 and the projections 36 determine steps or stops, which are at an angle to the side of the plate that rests against the compression spring body.

In a modified version, which is also shown here, the openings 35 are omitted and the projections 36 llnd 37 each through Projections 38 and 39 have been replaced.

In each projection 38 and 39, piercings 40 are arranged to the mechanical connection between the plate 26 '' 'and the pressure spring body 25 to reinforce when assembling the pressure buffer 31 according to FIG. In the performance the projections 38 and 39 are arranged at an angular distance from one another, but can like the projections 36 and 37, they can also be aligned radially to one another. Naturally A large number of these superficial irregularities are also used.

In addition, there are other, similar irregularities on the surface of the plates possible, which can be formed in the plate or connected to the plate can be and serve to engage in the compression spring body 25 so that a secure mechanical connection to the plates in the pressure buffer 31 is created. Therefore only examples are shown in FIGS. 5 to 9B.

Should compression spring bodies be connected one behind the other in a row like in FiS. 4 and are intended to make the panels used in assembly superficial be provided with irregularities, so in some application examples preferably only simple plates between adjacent compression spring bodies 25 instead of the pair of plates 26 shown in Fig. 4 is used. The compression spring bodies are then bound to one plate on opposite sides. This one record is then provided with irregularities that are mechanically in both compression spring bodies engage from copolymer polyester elastomers, between which it is located. Such a plate is shown in FIGS. 10A and 10B. The plate 52 has a Series of superficial irregularities, angularly spaced from one another 54, each consisting of an opening 56 and either an upward or downward one directed projection 58 and 60 exist. Since the plate 52 is set up for this is, be arranged between two adjacent compression spring bodies is the number of projections 58 and 60, which, as shown in FIGS. 10A and 10B, are radial and angularly spaced at such a distance that through the plate on the adjacent compression spring bodies are each exerted the same holding forces. Although this is not shown, the projections 58 and 60 with the through bores can also 40 in FIGS. 9A and 9B corresponding through bores may be provided to the mechanical Reinforce connection.

When building a Druckpffers using the plate 52 flows the copolymer polyester elastomer of each compression spring element into the openings 56 inside and around the projections 58 and 60, creating the mechanical connection is trained. The sides of the openings 56 and the projections 58 and 60 are Steps or stops that rest against the compression spring bodies.

Fig. 11 shows a multilayer pressure buffer, which consists of compression spring bodies 62, 64, 66, 68 exists. The upper compression spring body 62 and the lower compression spring body 68 are connected to a respective associated metal plate 70 or 72. This outer Metal plates 70, 72 are only on one side with superficial irregularities 54 designed to establish a mechanical connection to the Dltlckfederkkörper on this side made of elastomers.

There are plates between the adjacent compression spring bodies 62, 64, 66, 68 52 arranged from metal and bound to it. Each metal plate 52 is like has been explained above in connection with FIGS. 10A and 10B, with a number of Irregularities 54 are provided to reinforce the mechanical connection engage in the adjacent compression spring body.

The metal plate 52 shown in Figures 10 and 11 is not open the superficial irregularities are limited in the manner shown. Instead of of the irregularities 54 can at any time also kick those as shown in Figs.

Here, too, the illustration in FIGS. 10 and 11 is only an example.

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Claims (14)

Claims 1. A method for the production of compression spring bodies from a block of a copolymer polyester elastomer of predetermined axial length, characterized in that the block is compressed in the axial direction with a force which reduces the predetermined axial length by more than 30%, and that the Block is then relieved of the force acting in the axial direction. 2. The method according to claim 1, characterized in that the in the axial Direction effective force respectively on the entire area of two perpendicular to the Axis running surfaces of the block is brought into action. 3. The method according to claim 1 or 2, characterized in that the Block is annealed prior to compression. 4. The method according to claim 3, characterized in that the block is tempered for more than 50 hours before pressing. 5. The method according to any one of claims 1 to 4, characterized in that that the block made of the copolymer polyester elastomer against and during the solidification is subjected to an external pressure on part of its outside. 6. The method according to claim 5, characterized in that the external pressure is only brought into action in the central area of a surface on the outside. 7. The method according to claim 5, characterized in that the external pressure is brought into action on an entire surface of the outside. 8. Method of making a print buffer from one after Method according to one of the preceding claims produced compression spring body and a pair of plates, each arranged on one side of the compression spring body are, characterized in that the plates are superficial on one side with irregularities which form steps oriented at an angle to the side of the plate, that the plates on both sides of the compression spring body to form a unit are arranged, with the sides of the plates provided with the irregularities each facing the compression spring body that the unit with a further axially acting force is applied under which the copolymer polyester-Elastos mere flowing around the irregularities and a mechanical connection between the compression spring body and the plates is formed, and that the unit is then is relieved of the further axially acting force. 9. The method according to claim 8, characterized in that the unit under the further axially acting force essentially up to the same strength The compression spring body is compressed as before. 10. The method according to claim 8 or 9, characterized in that the panels are provided with irregularities and openings. 11. The method according to any one of claims 8 to 10, characterized in that that the plates are provided with irregularities protruding from their side. 12. The method according to any one of claims 8 to 11, characterized in that that the plates before forming the unit with the compression spring body on this facing side are roughened. 13. The method according to any one of claims 8 to 12 for producing a multilayer printing buffer of several according to the method according to one of the claims 1 to 7 produced compression spring bodies and plates at the ends of the pressure buffer and between adjacent compression spring bodies, characterized in that the plates Superficially with irregularities on the sides facing the compression spring bodies which form steps oriented at an angle to the side of the plate, and that the plates provided with the irregularities and the compression spring bodies can be arranged to form a multilayer unit. 14. Method of making a print buffer from a two-sided Compression spring body and two plates, each on one side of one side of the compression spring body abut and are bound to this, characterized in that a block of predetermined Length between the two sides molded from a copolymer polyester elastomer will, that the plates are superficial on one side are provided with irregularities that are oriented at an angle to the plate side Steps form that the plates to form a unit with said one side to be placed on the respective side of the block1 that each plate is acted upon by a force acting in the direction of the other plate, below that the block is compressed by more than 30% of its specified length and the copolymer polyester-elastomer with the formation of a mechanical connection flows around the irregularities between the block and the plates, and that the plates are then relieved of the forces.