RTM Tool with Sealing System

Abstract

The subject matter of the present invention pertains to a RTM tool having a sealing system. This sealing system comprises an elastic sealing strip which is disposed in an undercut manner in one of at least two tool parts to be sealed. It is characterized in that the sealing strip is essentially stressed perpendicular to the sealing strip surface when the tool parts are closed by means of the part of the tool pressing on the sealing strip and deforming it into the sealing gap which is present, in the direction of the mould cavity. The sealing strip comes into contact with the moulding compound without forming a mechanical connection therewith.

Claims

1. A RTM tool having a sealing system, comprising an elastic sealing strip which is disposed in an undercut manner in one of at least two tool parts to be sealed, characterized in that a. the pressing tool part comprises a mould piece which is configured so as to be convex in the direction of the sealing strip, which contacts the sealing strip first during the closing movement of the tool parts and enables the sealing strip to be deformed essentially without stressing the sealing strip with shear forces b. when the tool parts are being closed, the sealing strip is loaded by means of the tool part pressing the sealing strip essentially perpendicularly to the sealing strip surface and is deformed into the sealing gap which is formed in the direction of the moulding cavity, and c. the sealing strip comes into contact with the moulding compound without producing a mechanical connection therewith.

2. The RTM tool having a sealing system as claimed in claim 1, characterized in that the central plane of the sealing gap (25) is primarily at an angle of between 89 and 89, preferably between 45 and 45 and particularly preferably between 15 and 15 to the vector of action of the pressing tool part.

3. The RTM tool having a sealing system as claimed in claim 1, characterized in that the central plane of the sealing gap (25) is primarily at an angle of between 1 and 179, preferably between 45 and 135 and particularly preferably between 75 and 105 to the vector of action of the pressing tool part.

4. The RTM tool having a sealing system as claimed in claim 1, characterized in that the pressing tool part comprises a mould piece which is configured so as to be convex in the direction of the sealing strip, which contacts the sealing strip first during the closing movement of the tool parts and enables the sealing strip to be deformed essentially without sliding friction at the contact surfaces of the sealing strip.

5. The RTM tool having a sealing system as claimed in claim 1, characterized in that the angle between the line formed by the contact point and the centroid of the area and the vector for the travel direction of the pressing tool part has a value of between 44 and 44, preferably between 20 and 20 and particularly preferably between 10 and 10.

6. The RTM tool having a sealing system as claimed in claim 1, characterized in that the pressing tool part comprises concave regions which form a sealing strip accommodation cavity for sealing strip material which is displaced during the deformation of the sealing strip.

7. The RTM tool having a sealing system as claimed in claim 6, characterized in that the shape of the sealing strip accommodation cavity corresponds exactly to that of the deformed seal when the tool has been closed.

8. The RTM tool having a sealing system as claimed in claim 6, characterized in that the filled sealing strip accommodation cavity has an area of at least 1%, preferably 2% and particularly preferably 3% of the cross-sectional area of the unstressed sealing strip.

9. The RTM tool having a sealing system as claimed in claim 1, characterized in that the excrescence depth into the sealing gap is at least 1%, preferably 3% and particularly preferably 6% of the characteristic length of the sealing strip.

10. The RTM tool having a sealing system as claimed in claim 1, characterized in that the sealing strip is produced from silicone.

11. The RTM tool having a sealing system as claimed in claim 1, characterized in that the pressing tool part deforms the sealing strip in the seal in a manner such that in the cross-section of the sealing strip, the absolute values for the principal strains are less than 150%, preferably less than 100% and particularly preferably less than 75%.

12. The RTM tool having a sealing system as claimed in claim 1, characterized in that the static pressure in the ungelled moulding compound is less than 250 bar, preferably less than 175 bar and particularly preferably less than 100 bar.

13. The RTM tool having a sealing system as claimed in claim 1, characterized in that the RTM tool in the region of the seal is operated in a temperature range of 40 C. to +250 C.

14. The RTM tool having a sealing system as claimed in claim 1, characterized in that when the tool is opened, the seal loosens itself in an elastic manner from the solidified moulding compound in a peeling movement and reverts to its initial shape.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0033] FIG. 1a to FIG. 1d diagrammatically show the relationships upon closing (FIG. 1a and FIG. 1b) and upon opening following the injection procedure (FIG. 1c and 1d) for the RTM tool having a sealing system in accordance with the invention.

[0034] FIG. 2, FIG. 3 and FIG. 4 diagrammatically show the RTM tool having a sealing system in accordance with the invention with a central plane of the sealing gap angled at 90 to the vector of action in the closed state after injection is complete.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0035] In the following exemplary embodiments, the sealing strip consists of silicon rubber with an operating temperature range of 60 C. to 250 C. Other possible materials are suitable elastomers (for example: natural rubber (NR), perbunan (NBR), silicone (VMQ), EPDM, fluorinated rubber (Viton, FPM)).

[0036] The sealing strip has a circular cross-section with a diameter of 10 mm. However, sealing strips of this type with larger or smaller diameters, preferably in the range 4 mm to 20 mm, may also be employed.

[0037] The sealing strip is designed for compressive forces of up to a maximum pressure of 50 bar in the exemplary embodiment. In principle, applications of up to the maximum pressure for HP-RTM technology may be envisaged.

[0038] The moulding compound material which may be used may be a multi-component heat-cured epoxy resin system (typically in the temperature range of 40 C. to 160 C.); snap-cure systems with activation after a specific period or when a temperature threshold is exceeded may also be considered, as well as PUR resins or simple vinyl ester resins or polyester resins.

Exemplary Embodiment 1

[0039] FIG. 1a shows the sealing strip (1) in the sealing groove (24). Because of the shape of the sealing groove (24) and sealing strip (1), a free sealing strip portion (12) is formed which protrudes out of the sealing groove (24) along with a trapped sealing strip portion (11). The two sealing strip portions (11, 12) meet at the smallest cross-sectional extent (13) of the sealing groove (24). Because the smallest cross-sectional extent (13) of the sealing groove (24) is shorter than the diameter of the sealing strip and the sealing groove (24) in the tool half (22) has a larger cross-section than the smallest cross-sectional extent (13), the sealing strip (1) is retained in the sealing groove (24) in an undercut manner.

[0040] When the upper tool half (21) is closed, the sealing strip (1) is deformed and thus rolls onto the bead (26) of the upper tool surface (21). It is thus specifically forced into the cavity (27) and the sealing gap (25). In the closed state (see FIG. 1b) the sealing strip (1a) is deformed in a manner such that it is stretched homogeneously around the bead (26) and forms an excrescence in the sealing gap (25) in the form of a semi-circular bead therein which seals it. A specifically defined fraction of the sealing strip is accommodated in the cavity (27a).

[0041] If the injection pressure is now applied (FIG. 1c), the moulding compound (3), in this case plastic, penetrates into the sealing gap (25). Because of the pressure, the seal (1b) in the sealing gap (25) is placed under more pressure, flattening the semicircle protruding into the sealing gap (25) and compressing the material against the walls of the tool.

[0042] Following curing (FIG. 1d) of the moulding compound (3), the tool (21, 22, 23) is opened. During the opening movement of the tool halves, the sealing strip (1) reverts to its original shape and now no longer lies against the plastic component (3). During the release movement of the sealing strip (1), it is peeled off the moulded part (3), in a manner that preserves the material. After unmoulding the plastic component (3), the latter is no longer in contact with the seal (1).

[0043] The exemplary embodiments corresponding to FIGS. 2, 3 and 4 show different shapes for the closing (upper) tool portion (21) and a sealing gap which is primarily disposed perpendicular to the vector of action.

[0044] FIG. 2 depicts a closing tool (21, 22) with a bead (26) which compresses the sealing strip (1) into its sealing groove and thus places the sealing strip (1) under a great deal of mechanical stress, obtaining a strong sealing action.

[0045] In the exemplary embodiment of FIG. 3, the closing tool part (21) has a depression in which the sealing strip (1) is fixed in its position while the closing process is being carried out.

[0046] The closing tool (21) in the exemplary embodiment of FIG. 4 has a very pronounced bead (26) which forces the sealing strip (1) in the direction of the mould cavity into the sealing gap (25), while the remaining displaced sealing strip (1) is specifically accommodated in the sealing strip cavity (27).

LIST OF REFERENCE NUMERALS

[0047] 1 sealing strip [0048] 1a deformed sealing strip with closed tool parts [0049] 1b deformed sealing strip with closed tool parts and moulding compound counter-pressure [0050] 11 trapped sealing strip portion [0051] 12 free sealing strip portion [0052] 13 smallest extent of the sealing groove [0053] 14 line from centroid of the area to first contact point of tool bead and sealing strip [0054] 15 first contact point of tool bead and sealing strip [0055] 16 angle at which the tool bead meets the sealing strip during the closing movement of the tool [0056] 17 angle between line (14) and the direction of closing movement of tool [0057] 18 centroid of the area of the sealing strip (in cross-section) [0058] 19 rounded transition between the sealing groove and the sealing surface of the tool [0059] 21 upper tool part [0060] 22 lower tool part [0061] 23 third tool part [0062] 24 sealing groove [0063] 25 sealing gap in direction of mould cavity [0064] 26 bead on upper tool part [0065] 27 cavity for accommodating a portion of the displaced sealing strip [0066] 27a filled cavity for accommodating sealing strip [0067] 28 vector of action [0068] 29 central plane of sealing gap [0069] 3 moulding compound [0070] 31 ring of maximum deformation of sealing strip in the sealing gap [0071] 32 excrescence depth of sealing strip into the sealing gap