DE3039868C2 - - Google Patents

Description

The invention relates to a shock absorber of three rotationally symmetrical parts that are concentric are ordered and the outer annular and that inner sleeve-shaped part made of relatively hard material, and the middle part connected to the inner and outer part made of a thermoplastic, organic elastomer material consists.

Such a shock absorber is for example from DE-OS 26 07 341 known. Here are the three concentric parts made separately and glued together. This construct tion enables the production of shock absorbers in different ways sizes for different load ranges. The production is extremely time consuming and therefore expensive. It is also known to make a shock absorber from outer metal parts and an inner elastomeric part, but what is also very expensive because the elastomeric component in vulcanized into a mold using heat and pressure must become.

The invention is therefore based on the object, a genus modern shock absorbers cheaper and easier to manufacture than this was previously possible.

The task is solved by the in the labeling part of claim 1 specified features.  

The invention is accordingly based on the finding that a subsequent gluing can be omitted if the Workpieces for the three concentric parts can be selected that the material for the middle part in the sprayable Condition so far in the material already placed from the outside and inner part can penetrate that permanent connection remains intact.

According to the method, the task is solved by Features specified in the characterizing part of claim 3. Appropriate configurations of the method result from claims 4 to 6.

The invention also relates to a device for Production of a shock absorber according to claim 1. Die Device solves the task by labeling Features of claim 7.

The following are exemplary embodiments of the invention hand described in the drawing. In the drawing shows

Fig. 1 shows an axial section of a plate-like impact or vibration damper in accordance with a preferred exporting approximately of the invention,

Figs. 2A to 2C are sectional view showing the different positions of len an injection mold assembly depicting that finds application 1 for the preparation of the shock absorber according to FIG.

FIGS. 3 and 4 of Fig. 1 corresponding axial sections of two further embodiments of to the invention OF INVENTION vibration dampers.

The plate-like shock absorber shown in Fig. 1 consists of an inner part 2 and an outer part 4 and an intermediate piece 6th Inner and outer part are made of relatively rigid thermoplastic material, while the intermediate piece consists of a thermoplastic elastomer. The term "substantially rigid thermoplastic material" means that it is a solid, substantially rigid material which is melted (ie, becomes softer and softer until it becomes liquid) when heated to an appropriate temperature, and it is hardened and becomes solid and substantially rigid when cooled to room temperature of, for example, 21 ° C. The term "thermoplastic elastomer" refers to a solid material which has the properties that it melts when heated to an appropriate temperature, and that it hardens and becomes firm and elastic and has the behavior of an elastomer when it is on Room temperature is cooled. These thermoplastic materials can consist of a single thermoplastic polymer substance or a mixture of such substances, and additives such as colorants, plasticizers, antioxidants, stabilizers and other components can be added which modify one or more physical properties of the thermoplastic substance.

Another requirement of the invention is that parts 2, 4 and 6 are made by injection molding. Accordingly, the substantially rigid ther moplastic material and the thermoplastic elastomeric material must consist of injection molding materials that can be processed by injection molding. The materials can mainly consist of one or more polymerization products and / or one or more copolymers. In addition, the material used for the production of parts 2 and 4 and the material used for producing the middle part 6 and intermediate part 6 or intermediate piece 6 lying between inner part 2 and outer part 4 should be compatible in the sense that the materials can be joined together by fusion, ie by touching the materials while at least one of the materials is in a liquid state, after which the liquid material is cooled until solidification and connection to the other material is complete. The parts 2 and 4 can consist of different compatible len materials that melt and solidify at about the same tem peratures, but it is advisable to manufacture the two parts from the same material. Preferably, the parts 2 and 4 have a flexural modulus of over 27,600 bar (400,000 psi), while the intermediate piece 6 consists of a soft thermoplastic ela stomer with a low modulus, which has a hardness value between 35 and 85 according to a hardness meter with a Shore A. Scale. For example, parts 2 and 4 are made of polystyrene with a flexural modulus of about 32 085 bar (465,000 psi) and the intermediate piece consists of butadiene styrene compounds with a hardness value of 55, measured with a hardness meter with a Shore A scale.

The parts 2, 4 and 6 are Darge in the drawing as if they have sharp boundaries, but, as mentioned in detail below, transition areas are provided between those parts in which mixtures or diffusion phenomena of the thermoplastic material are present .

As seen from Fig. 1, the inner part 2 has a flat annular upper surface 8 and a unte re annular surface 10, an inner cylindrical surface 12 defining an axial bore 17 and an outer boundary, which is designed as a rotary body surface, and cylindrical end portions 16 and 18 and a double-curved intermediate portion 20 has. The outer part 4 serves as a flange for the vibration damper structure and has a cylindrical outer surface 22 and an inner boundary 24 , which is formed as a cylindrical surface, as well as an upper ring surface 26 and a surface 28 running parallel thereto, and these surfaces are parallel to the corresponding surfaces of the inner ring 2 and extend perpendicular to the axis of the inner part. The outer part 4 has a plurality of mounting holes 5 . The intermediate piece 6 has an inner portion 30 and an outer portion 32 , which are each attached to the inner part 2 at the transition section 18 and part 4 on the inner transition part 24 , and also the inter mediate piece has a curved transition portion 34 which is between the inner Part 2 and the outer part 4 runs. The transition section 34 is fixed to the inner part 2 in the transition section 20 . The transition section 34 acts as a spring to elastically support the inner part 2 with respect to the outer part 4 .

If the shock absorber shown in Fig. 1 is made by the molding process described below, then there is little diffusion or mixing of one material with the other at the interfaces instead. In addition, there is only a slight distortion of one material by the other along the border areas. Reviewing the cross sections of the shock absorber according to FIG. 1, which were provided in accordance with the invention, has shown that when viewed with an electrode microscope with a magnifying rod of 1: 20,000, the boundary regions between the butadiene styrene thermoplastic elastomer and the polystyrene share one Have intermediate area (the Diffusionsbe rich or the mixing of one material with the other) that has a thickness of the order of only 25.4 × 10 ^-6 mm. Nevertheless, the connection between the elastomeric and the non-elastomeric parts is sufficiently firm to act as a vibration damper in a satisfactory manner.

In the following, reference is made to FIGS. 2A to 2C. The shock absorber according to FIG. 1 was produced according to the invention with a preferred method of manufacture by means of an injection mold, which consists of three relatively movable mold parts 36, 38 and 40 and a core 42 is comprised, which is fixed on the molding 36. As shown in FIG. 2A, has the shape of body 36 a contouring te inner end face with four discrete Stufenabschnit th 44, 46, 48 and 50 while the mold body 38 having a flat inner end surface 52 and a cylindrical inner surface 54. The molded body 40 has a profiled inner end face with sections 56 and 58 and a cylindrical outer surface 60 which is in a tight sliding fit to the surface 54 . The moldings are arranged so that, when the moldings are in a closed position, the surfaces 50 and 52 fit one another, while the surfaces 44 and 58 and the pin 42 form a first cavity 62 , while the surfaces 48 and 52 and the upper portion of the Surface 60 form a second cavity 64 . The Formkör by 40 has a central hole 66 in which the center pin 42 fits with a tight press fit. A plurality of pins 68 of the inner molded body 36 protrude into holes 70 of the molded body 38 in a sliding fit. The pins 68 serve as cores for producing the mounting holes 5 . The shaped bodies 36, 38 and 40 are arranged (by conventional means, which are not shown in the drawing, but which are clear to the person skilled in the art), that they can move relative to one another along the axis of the pin 42 , so that the Shaped bodies 38 and 40 are movable separately and can be fixed in different positions along the axis relative to the shaped body 36 .

The vibration damper according to FIG. 1, with reference of a mold assembly shown in FIG. 2A to 2C according to the following the procedures made. First, the molded parts 36, 38 and 40 are moved into the closed position according to FIG. 2A (this is the first injection position) and a suitable liquid thermoplastic injection molding material is injected, which is capable of being solidified into a rigid, solid body ( for example polystyrene), and this material is injected into the hollow cavities 62 and 64 through the injection openings 74 and 76 , so that the parts 2 and 4 are made in this way. The molded body 40 is then retracted until the outer edge of its surface 56 is flush with the surface 52 , thereby forming a third cavity 78 as shown in FIG. 2B (this forms the second injection position). A suitable liquid thermoplastic injection molding material is then injected, which is solidified into a solid body with properties of an elastomer, for example butadiene styrene, and this material is injected into the cavity 78 via one or more injection openings 80 , so that the intermediate piece (middle part) 6 is formed. This injection step is carried out after the material injected into the cavities 62 and 64 has solidified or at least become so viscous that it will no longer be displaced or distorted when the material is injected through the opening 80 . However, it must be soft enough to ensure a connection with the elastomeric material. Accordingly, the second injection stage is performed while the material in cavities 62 and 64 is still hot, but after it has solidified. By properly selecting the materials, it is possible for the cavity 78 to be filled in as little as 3 seconds after the cavities 62 and 64 are filled, and still a satisfactory bond can be ensured between the elastomeric and the non-elastomeric parts . After the intermediate piece 6 has settled in the cavity 78 and forms a solid body, the molded parts 38 and 40 are finally separated from the molded part 36 , as can be seen in FIG. 2C, whereupon the finished vibration damper is removed from the mold and for Cooling can be set aside. Since after the molded parts are returned to the position shown in FIG. 2A, so that the next molding process can be initiated.

According to the preferred method according to the invention, parts 2 and 4 of the vibration damper are molded from polystyrene, which solidifies in such a way that a flexural modulus of approximately 32 085 bar (465,000 psi) is obtained, and the vibration damper intermediate piece 6 consists of a butadiene styrene copolymer, which solidifies in such a way that a hardness is obtained which lies on the Shore A scale between 35 and 85 (depending on the required spring rate), the polystyrene preferably being the material which Shell company sells under the trade name Shell DP -203, and butadiene styrene is a material sold by Shell under the name Kraton 3000 Series thermo plastic rubber. Appropriate temperatures and pressures are determined by the properties of the material used, ie the polystyrene material mentioned is injected under a pressure of about 345 bar (5000 psi) at a temperature of about 200 ° C (390 ° F) and the butadiene styrene material is injected into the cavity 78 is injected under a pressure of about 414 bar (6000 psi) and a temperature of about 200 ° C (390 ° F). The last-mentioned injection should expediently take place 1 to 3 s after the injection of the polystyrene molding material into the cavities 62 and 64 . The spray materials are kept at a temperature of approximately 200 ° C (390 ° F) during the two injection processes, but the mold should be kept at a temperature between approximately 38 ° C and 66 ° C during the molding process. Then the mold is opened and the finished part is removed about 1 min after the completion of the second injection process. Then the molded part is set aside and allowed to cool to room temperature before being labeled, checked and packaged. The finished products show a shear bond strength between parts 6 and 2 or 6 and 4 of at least 27.6 to 34.5 bar and usually between 41.4 and 55.2 bar. As a comparison, there is a connection strength of about 34.5 bar between metal and elastomer in conventional vibrating metal connections.

In this context it should be noted that the injection of the elastomeric material after the injection of the rigid material is critical. It has been found that if the elastomer is injected simultaneously or in front of the rigid material, a satisfactory end product cannot be obtained because the elastomer is unable to deform in cavity 78 under the required and applied pressures Resist injection of the plastic material into the cavities 62 and 64 . This is true even if the elastomeric material is fully cured before the non-elastomeric material is injected. Only when the injection of the elastomeric material is delayed until the rigid plastic material has settled sufficiently to withstand a deformation under a given pressure required to inject the elastomeric material will it be possible to establish a connection between the elastomeric material and to create the non-elastomeric material that is strong enough, and also to create a vibration damper that exactly matches the shape of the three mold cavities.

Another important advantage of the invention is that the spring rate of the vibration damper can be changed by changing the composition, and thereby the hardness of the material used for the intermediate piece 6 is changed. For example, Shell offers a Kraton molding material which, under the name Kraton 3226, has a hardness of 35 on the A scale, while a Kraton 3202 material has a hardness of 55 on the A scale. A Kraton 3204 material has a hardness of 85 on the A scale. Other hardness values can be achieved by appropriately mixing the three materials or adding other thermoplastic elastomers. The rigidity of parts 2 and 4 can be changed by mixing some elastomeric molding material with the polystyrene molding material. Parts 2 and 4 do not have to be absolutely rigid and in certain applications of the vibration damper it may be sufficient or even desirable to make these parts only stiff, ie semi-hard.

Another advantage of the method according to the invention is that the molding materials are inserted coaxially can be injected instead of using a biaxial process use as described in US Pat. No. 3,950,483 is. It has been shown that the formation by coaxial Injection is easier to do and to be failsafe product leads.

Another advantage of the invention is that vibration dampers of various shapes, sizes and vibration damping characteristics can be produced. For example, the shape and / or size of the intermediate piece 6 can only be changed by modifying the various molded parts. In addition, the mold assembly is by appropriate design created Mög friendliness, a flat insulator 90 (Fig. 3) to create the group consisting of a cylindrical inner part 2 A, a cylindrical outer part 4 A with a flat annular flange 92 and a cylindrical intermediate piece 6 A is that has flat end faces. It is also possible to provide an axially elongated vibration damper 96 ( Fig. 4) in which the three parts 2 B , 4 B and 6 B are all cylindrical and the length of the part 6 B significantly exceeds the inner radius and the outer radius . The two alternative forms of vibration dampers have vibration isolation characteristics that are different from that of the embodiment of FIG. 1, even if the same materials as in this embodiment were used.

Another advantage of the invention is that it can be realized in connection with a wide variety of thermoplastic injection molding materials. The thermoplastic elastomer material which forms the intermediate piece 6 can also consist of materials other than butadiene styrene. The term "thermoplastic elastomer" is a term that is unique to those skilled in the art and is described, for example, in the book by Tobolsky et al "Polymer Science and Materials", p. 277 (Wiley-Interscience) (1971). As described in AA Walker's "Handbook of Thermoplastic Elastomers" (1979), there are a large number of such materials.

In addition, for example, the "rigid" thermoplastic parts 2 and 4 made of acrylonitrile butadiene styrene (ABS), polymethyl methacrylate (plexiglass) or a polypropylene polymerisation product or other products such as those described in US Pat. Nos. 39 41 859, 39 62 154 and 40 06 116 are described. The exact choice of the materials used depends on the desired characteristic and the compatibility of the elastomeric material with the non-elastomeric materials with regard to a mutual connection.

Claims (7)

1. Shock absorber, consisting of three rotationally symmetrical parts, which are arranged concentrically and in which the outer annular and the inner sleeve-shaped part made of relatively hard material and the middle part connected to the inner and outer part made of a thermoplastic, organic, elastomer material, characterized that the middle part (6) is formed on the inner and on the outer part (2, 4) consisting of a rigid thermoplastic polymer material in its final configuration. 2. Shock absorber according to claim 1, characterized in that the parts ( 6, 2, 4 ) are fused together at their connecting surfaces at a depth of about 25.4 µm. 3. A method for producing a shock absorber according to claim 1, characterized in that the outer part ( 4 ) and the inner part ( 2 ) are simultaneously injected in concentric, radially spaced mold cavities, and that thereafter the middle part ( 6 ) is injected into an intermediate cavity ( 78 ) which is delimited radially on the outside and radially on the inside by the previously formed parts ( 2, 4 ). 4. The method according to claim 3, characterized in that the central part in its shape cavity is injected after the thermoplastic Polymer material from the outer and inner part has settled, however, before it is cured.   5. The method according to claims 3 and 4, characterized in that the inner and outer parts are made of Polystyrene can be injected. 6. The method according to claims 3 and 4, characterized in that the central part from a Copolymers of styrene and butadiene is injected. 7. Device for performing the method according to claims 3 to 6, characterized in that a first molded body ( 36 ) together with a second molded body ( 38 ) limits the outer mold cavity ( 64 ), that the first molded body ( 36 ) together with a third molded body ( 40 ) delimits the inner mold cavity ( 62 ), and that the central mold cavity ( 78 ) from the first molded body ( 36 ), the third molded body ( 40 ) offset axially by the axial extent of the central part ( 6 ), and the already sprayed outer and inner parts is limited.