CH652071A5 - Process for producing a rubber/metal bond - Google Patents

Description

The invention relates to a method for producing a rubber-metal bond for parts stressed in the plane of the binding layer by interfacial vulcanization of the rubber with the metal surface.

From US Pat. No. 2,351,329 a method for producing rubber-metal parts subject to torsion is known. Three concentric rings, two preformed, ring-shaped rubber bodies and two press punches are arranged in a casting mold. The shape or the press stamp lies / are between two heated plates and is / are pressed together by them. The heated plates make it easier to inject the rubber between the rings. After the injection process has been completed, the vulcanization of the rubber on the rings is completed by the addition of heat.

There are shoulders between the storage space for the prefabricated rubber parts and the workpiece space for the inserted rings, through which the inner and outer ring lie in the “splash shadow”. This means that only the middle ring is coated directly from two sides during the injection process, while the inner and the outer ring come into contact with the rubber little by little, i.e. without any recognizable regularity. This means that only the middle ring is coated on both sides by the direct application of the rubber in its binding plane, but not the other two rings. The inner ring, whose rubber-metal bond is exposed to the greatest loads, has a different specific strength of the rubber-metal bond due to the non-uniform application of the rubber.

After the rings are made of brass, the rubber-metal bond is easy since no previous coating with an adhesive is required. However, if there is another material instead of the brass, e.g. Steel in front, for which an adhesive is required, the adhesive coating is destroyed on both sides by the injection process and there is no adequate rubber-metal bond. It is therefore not possible to learn from this document how a reproducible rubber-metal bond can be achieved on highly stressed metal parts.

The object of the invention is therefore to propose a method for producing a reproducible rubber-metal bond. This object is achieved with the characterizing features of claims 1 and 2. The invention makes it possible to adjust the rubber-metal bond with regard to the shear strength.

If the main direction of stress of rubberized rotating bodies or flat bodies is known, the peel strength of the rubber can be adjusted by the flow direction of the rubber in the manufacturing process according to the invention. If the direction of flow when vulcanizing the rubber is opposite to the direction of stress, the peel strength is five times higher than in the direction of flow. There is no flow direction with respect to the binding level, i.e. If the rubber has been applied to the metal at right angles to the direction of stress, the peel strength is the same in all directions of stress in the binding plane.

In the case of metal parts to be rubberized with - due to the unfavorable shape of the metal part - flow conditions which cannot be produced uniformly, it is possible on the basis of the teaching of the invention to standardize the strength values distributed differently over the metal part by the metal part during the initial phase of vulcanization, i.e. when the rubber already lies on the entire surface,

for rotating parts it is rotated by up to 180 ° and for the more flat bodies, it is moved back and forth.

This ensures that zones of high peel strength are balanced with zones of low peel strength, so that the original zones of low peel strength have an approximately 100% higher peel strength.

The size of the liability depends on the following relationships:

I. Flow direction equal to the direction of stress in the peeling direction = low adhesion

II. Flow direction against the direction of stress = high

liability

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III. Flow direction transverse to the direction of stress = medium, but uniform adhesion.

The flow direction is to be understood to mean that the rubber is moved in a specific or a preferred direction.

Under stress direction to understand the direction of the main stress.

By knowing the main direction of stress and the flow behavior during the vulcanization process, the results can be optimized according to the given relationships I - III by using appropriate preforms made of ready-made rubber and, if necessary, outlet channels on the press mold.

The appropriate choice of the inlet channels to be provided and, if appropriate, the outlet channels of the injection mold applies to the injection process.

It is essential for the reproducible peel strength a) in the compression process that the rubber flows uniformly and specifically in the case of a preheated metal part. The direction of flow depends on the application. If there are several directions of stress in one plane, the rubber blank must be placed centrally on the metal part, so that the press ram displaces the rubber in a radial direction outwards.

b) in the compression process with transfer form that instead of the rubber blank to be inserted and appropriately dimensioned, the rubber is applied to the preheated metal part via injection hoppers arranged in a suitable manner in order to achieve a single flow direction or multiple directions,

c) in the compression process with transfer form and outlet channels that in addition to b) the outlet channels are or are open in accordance with the direction of flow or directions of flow in order to achieve the targeted flow over the entire metal part into the peripheral zones of the metal part,

d) for injection molding that c) is to be followed,

e) in the compression process with twisting a bolt to be vulcanized, that the twisting takes place approximately when the boundary surface vulcanization is completed to approx. 50%.

A distinction is therefore made between two types of preferred interface vulcanization.

1. The way of applying rubber to metal and then fixing the flow direction by vulcanization.

2. The way of applying rubber to metal and then correcting the flow direction at about 50% interface vulcanization by reversing the flow direction by reversing the flow direction via valves or moving or rotating the metal part relative to the rubber. The time of interface vulcanization of approx. 50% is different. It depends, among other things, on the preheating temperature of the metal part, the pressing pressure and the vulcanization temperature. The time is therefore to be determined by experiments.

A reproducible isotropic or specifically anisotropic rubber-metal bond can be achieved with the invention. If the main direction of stress is known, to increase the peel strength, it is possible to successfully counter the detachment of rubber parts by already working with the rubber-metal part in accordance with the indicated relationships I-III in order to achieve the best possible effect and cost.

On the other hand, a reproducible peeling of the rubber from metal is possible, for example: Ener652 071

Casting bumpers for vehicles with the function that the rubber is deformed in the event of a shock and the rubber is peeled off after a certain impact energy has been exceeded. The work that has to be done to peel the rubber from the metal removes part of the impact energy.

An example of high peel strength is a flat bearing element for processing machines with a single main direction of stress. The boundary layer between upholstery and metal is mainly subject to shear stress in one direction. Contrary to the direction of action of the shear force, the rubber-metal bond is to be produced according to relationship II and the bearing element is to be installed in accordance with the main direction of stress.

As a further example, a bearing bolt to be rubberized for processing machines is given, in which the main direction of stress extends in the circumferential direction of the bolt. In the compression method to be used, a suitably dimensioned rubber plate is placed on the bolts arranged in a suitable press, which, after the press has closed, fills the cavities provided in the press mold by pressure and temperature. The rubber flows around the bolt according to the pressure. To avoid an anisotropic rubber-metal bond, the bolt must be moved mechanically, by ultrasound or electrically induced vibrations during the vulcanization process.

An axial movement of the bolt fulfills the relationship III, a medium but uniform adhesion is achieved. Rotation of the bolt in the circumferential direction in the main direction of stress fulfills the relationship II, i.e. high adhesion is achieved.

For flat rubber-metal bindings to be produced in the pressing process, the following applies: The rubber body inserted into the mold in a well-fitting manner results in a medium but uniform adhesion due to the lack of flow on the inserted metal plate in accordance with relationship III, and that an extremely eccentrically inserted rubber body in accordance with the relationship II achieved high liability.

For a stamp press with transfer form, the application of the inventive teaching for the relationship according to II with the most isotropic bond results in the fact that the press-in funnel (s) for the rubber is or are to be arranged on the side to which the main direction of stress points. In order to achieve a completely clear flow direction, one or more outlet channels must be provided in the lower part of the mold opposite to the press-fit funnel.

For rubber-metal parts produced in the injection molding process, according to the relationship according to II, it applies that in the mold, the injection channel or channels open laterally and somewhat above the metal surface to be coated and, if appropriate, outlet channels are provided opposite one another.

For cold vulcanization, the devices and process steps described above or mentioned in the drawing description can be used in the same way, with the exception of the influence of temperature.

Exemplary embodiments according to the invention are evident from the following description of the drawings.

They show in a simplified representation

Figures 1, la, 2, 2a and 2b stamp presses for flat rubber-metal body in different steps and views,

FIG. 3 shows a stamp press with transfer form for flat rubber-metal bodies,

3a shows a partial section from FIG. 3 according to IHa-IIIa,

FIG. 4 a press for cylindrical rubber-metal bodies,

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4a shows a rubber-metal body produced with the press according to FIG. 4,

FIG. 5 shows an injection molding machine with a mold,

Figure 6 shows a casting mold in a spatial representation.

The presses according to Figures 1 and 2 are identical in construction. It means 1 stamp, 2 base body, 3 ejector, 4 metal plate with adhesive 4 ', 5 rubber blank, 9 heating channels.

According to FIGS. 1 and 1 a, the rubber blank 5 with a good pre-assembly is inserted into the cavity 6 of the base body 2 on the metal plate 4 with adhesive 4 '.

When the plunger 1 is lowered in the direction of arrow A, there is no flow on the metal plate when the rubber blank 5 is pressed. The result is an isotropic rubber-metal bond. The ejector 3 transports the finished object from the press in the opposite direction to A.

2, in contrast to FIG. 1, the rubber blank 5 'is inserted into the mold cavity 6 in such a way that it fits snugly against the side walls T-2' "of the mold cavity according to FIG. 2b, but is at a relatively large distance 10 from the side wall 8 .

With such an extremely eccentrically inserted rubber blank 5 ', there is a flow to the right during the pressing process, as can be seen from FIG. 2a by "X", which already shows the process during the pressing.

To ensure that in the finished rubber-metal body the rubber flow to the right is present until the pressing process is complete, outlet channels 12 (only one visible) must be provided in the base body approximately at the interface 11.

After completing the vulcanization process following the pressing process, the following results are achieved:

High resistance to peeling of the rubber from right to left. Low peel strength of the rubber from left to right. Average peel strength of the rubber perpendicular to the paper plane.

3 and 3a, in contrast to FIGS. 1 and 2, a stamp 15 is divided into two stamps 16, 17, 17 funnels 18-20 being arranged in the stamp.

Left and right outlet channels 25, 26 are provided in the base body 2 at the level of the metal plate surface 11. On the ejector 3, the metal plate 4 is coated with adhesive 4 '.

The rubber blank 27, which is arranged in the cavity between the stamps 16 and 17, is pressed by the stamp 16 through the funnels 18 to 20 into the mold cavity 28. After the mold cavity 28 is filled, the stamp 17 moves from the position shown in the direction of arrow A to the predetermined completion of the pressing process. Excess rubber can escape through the outlet channels 25, 26. This is followed by the final vulcanization process. The ejector 3 then conveys the finished object from the base body 2.

The following conditions apply to the rubber-metal bond:

If the right and middle funnels 19, 20 are closed, during the injection process the stamp 16 on the metal plate causes a strong flow to the right, which can still be supported by the outlet channels 26.

Result:

High resistance to peeling of the rubber from right to left.

If, however, instead of the outlet channels 26 arranged on the right, only outlet channels 25 arranged on the left are provided, the initial flow direction of the transfer process is compensated for by the stamp 17 when compressed.

The result is an undirected, uniform binding strength.

4, a press consists of an upper part 30, a lower part 31 and the usual heating connections, not shown here, for the above-mentioned molded parts. In the parts 30, 31, half-shell-shaped recesses 34, 35 for the bolt and recesses 36 for the rubber rings are formed for the bolts 32, 33 to be rubberized.

Plate-shaped rubber blanks 37, 38 are placed on the inserted bolts 32, 33. Then the upper part is moved in the direction of arrow A towards the lower part 31. The upper part 30 places the plates 37, 38 on one side around the bolts 32, 33. The rubber then flows through pressure and temperature from top to bottom into the recesses 36 provided in the lower part and wraps around the bolts therein. The vulcanization process then takes place under pressure and an increase in temperature. According to FIG. 4a, the fully vulcanized bolt has so-called film strips 38 ', which are pressed out of the recesses 36 by the necessary, excess rubber.

The invention begins with the above-described process after the mold has been closed and during the pressing process, either by rotating the bolts in the direction of arrow B or axially, that is to say back and forth, in the directions of arrow C, D.

With a bolt with a diameter of 30 mm, the vulcanization time is about 40 minutes.

A uniform peel strength on the bolt 32 is achieved if, after the bolt 32 has flowed around it and after an interface vulcanization of approximately 50% (approximately 3 minutes after the mold has closed), the bolt 32 is rotated by 180 °. The zones of high strength are thus averaged with the zones of low strength.

In FIG. 5:

40 an injection molding machine,

41 whose input opening,

42 the screw conveyor,

43 a locking unit,

44 a flow controller,

44 'some inflow valves,

45.45 ', 46 valve-controlled injection channels,

47 a casting mold,

48.48 ', 48 ", 48'" (opposite 48 ") exit channels in the mold,

49 a metal plate, 50 adhesive on the metal plate 49,

51 the rubber, and

52 an ejector.

For a medium, isotropic bond of the rubber 51, which is flowable through the screw 42 and compressed in front of the closing unit 43, the rubber is injected through the injection channels 46 when the outlet channels 48, 48 'are closed by opening the closing unit 43.

A high bond of the rubber to the metal plate 49 is achieved by injecting via the injection channel or channels 45 with the controller 44 switched and the outlet channels 48 open. Here, the injection channels 45 ', 46 are to be closed by the valves 44'. The flow directions can be set or reversed by appropriate selection of the injection channels 45, 45 ', 46 and the outlet channels 48-48' "to be opened. Instead of the injection molding machine, a piston injection machine can also be used movable ejector 53 removable from the mold 47.

This device (FIG. 5) is not only in relation to the rubber flow that takes place only through the injection channels 45

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Suitable for metal plates with adhesive, but also for rubber-metal bonds without adhesive, such as rubber and brass.

According to FIG. 6, injection channels 61, 61 ', 62, 62' are provided in the casting mold 60. The injection channels 61, 61 'are at right angles to the metal plate 49 with the adhesive 50. The injection channels 62, 62' form an angle with the metal plate 49 of approximately 45 °. In addition to the injection channels 61, 62 mentioned, the outlet channels 48, 48 'and the ejector 53 according to FIG. 5 are present.

A high peel strength in the arrow directions 54, 55 can be achieved both through the injection channels 62 or 62 '. The rubber front produced by the injection channels 62 and penetrating in the direction of arrow X (see FIG. 5) results in a directed flow front of the rubber by means of the outlet channels 48 '. For this purpose, the rubber is to be kept in motion in the flow direction mentioned, in that after filling the injection mold 60, rubber is continuously fed in via the injection channels 62 or 61 or 62 and discharged through the outlet channels 48 '. The amounts added can be very small. It is also sufficient to increase the pressing pressure without tracking rubber, since the aim is only to ensure that the rubber molecules are aligned on the metal plate 49 or the adhesive 50. Then vulcanization is finished. The ejectors 53 can serve to increase the pressing pressure. For this purpose, the channels 45, 46, 48, 61, 62 are to be closed by known devices.

Furthermore, the injection channels 61, 62 mentioned ensure that the adhesive 50 is not pushed away by the rubber flow from the metal plate made of steel, but remains adherent.

It is important for the rubber-metal bond that in all of the devices according to FIGS. 1 to 6 the rubber is introduced into a preheated mold at a temperature of approximately 373 ° K-423 ° K.

The facilities and process steps described above can be used in the same way for cold vulcanization.

The following applies to the vulcanization process:

1. after a very short contact rubber / metal:

no molecular bond;

2. After 50% of the vulcanization time there is ~ 50% oriented adhesion of the rubber on the interface. Those parts of the rubber that are not yet fixed are still available in their orientation;

3. In the remaining vulcanization time that is still available, the rubber molecules that have not yet been fixed can be brought into the desired orientation by a corresponding movement of the rubber or metal.

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2 sheets of drawings

Claims (9)

652071 1. A method for producing a rubber-metal bond for parts stressed in the plane of the binding layer by interfacial vulcanization of the rubber with the metal surface, characterized in that a compression molding (5, 5 ') made of rubber with a smaller base than that to be vulcanized Metal surface is placed on it in such a way that the rubber (1) of a compression device spreads the rubber against or at right angles to the direction of stress on the metal surface. 2. A process for producing a rubber-metal bond for parts stressed in the plane of the binding layer by interfacial vulcanization of the rubber with the metal surface, characterized in that rubber is applied at an angle to the plane of the binding layer (4 ') by an injection process. 2nd PATENT CLAIMS 3. The method according to claim 2, characterized in that the angle is 90 degrees. 4. The method according to claim 2, characterized in that the angle is between zero degrees and 90 degrees, preferably 45 degrees. 5. The method according to claims 1 or 2, characterized in that after about 50% of the interface vulcanization, the metal surface is moved relative to the rubber or the direction of flow of the rubber by reversing injection channels (18-20, 45,45 ', 46, 61st , 61 ', 62, 62') and outlet channels (12, 25, 26, 48-48 '") is reversed. 6. The method according to claim 1 or 2, characterized in that in the injection method or in the compression method with a transfer mold (16, 17) rubber (27) evenly distributed over channels (45, 45 ', 46) or funnel 18-20) or is pressed into the mold (2, 47, 60) on one side to produce a single flow front (X). 7. The method according to any one of the preceding claims, characterized in that rubber is pressed into the mold in a front that continuously fills the mold (X; FIG. 5). 8. The method according to claims 1 or 2, characterized in that the rubber application takes place uniformly in the hobbing process, in that the application takes place analogously to the rolling motion of a wheel on one level on the metal surface, with simultaneous, only partially occurring vulcanization of approx. 50% of the applied material in order to enable a subsequent correction of the vulcanization direction and that the vulcanization is then finished when the application is stationary. 9. Device for carrying out the method according to the preceding claims, characterized in that in the molds in or almost in the plane of the metal surface to be vulcanized, outlet channels (26, 25, 48-48 '") are provided for producing a single flow front or more Flow fronts in one level.