Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C45/00—Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor
  • B29C45/17—Component parts, details or accessories; Auxiliary operations
  • B29C45/46—Means for plasticising or homogenising the moulding material or forcing it into the mould
  • B29C45/47—Means for plasticising or homogenising the moulding material or forcing it into the mould using screws
  • B29C45/50—Axially movable screw
  • B29C45/52—Non-return devices
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C45/00—Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor
  • B29C45/02—Transfer moulding, i.e. transferring the required volume of moulding material by a plunger from a "shot" cavity into a mould cavity

Definitions

• the invention relates to a non-return valve for injection molding machines according to the preamble of patent claim 1.
• Such backflow stops are mounted on an ejection-side end of a plasticizing screw in an injection cylinder and serve as a "valve" to prevent plasticized plastic material from being forced back into the flight during an injection process.
• a non-return valve according to the preamble of claim 1 is known from DE 198 36 871.
• a locking ring is concentric with the center piece of a worm head between an open position in which he tangs with his front page to a stop surface on the back of the tail of the Seh ncke Nes, and a blocking position in which it rests against a thrust ring of the worm head , axially and circumferentially displaceable, ie during rotation of the screw, the locking ring is not necessarily carried by the screw head.
• the distance that the locking ring is displaceable relative to the screw head is to be referred to below as stroke A.
• the locking ring forms an annular gap together with the center piece and has holes for the material passage in the vicinity of the end face. In the open position of the locking ring is located with its front side on the stop surface on the back of the tail and plastic melt can flow through the holes and then past the tail of the screw head in the Schneckenvorraum.
• the locking ring is in the aforementioned open position. Due to the forward movement of the screw, the plastic melt flows in the direction of the locking ring and moves it backwards to the worm. As a result, the locking ring is lifted from the stop surface on the tail. The stroke A is reduced to a smaller degree A '. As a result, the plastic melt can increasingly flow through the annular gap between the inner diameter of the locking ring and the outer diameter of the middle piece. Thus, shortly after the start of injection, an approximate pressure equalization occurs over the backflow barrier. Due to the pressure build-up in the antechamber as a result of the injection process, the plastic melt is pressed through the not yet closed backflow and the stroke of the locking ring is further reduced.
• a backflow lock in which the locking ring has a plurality of melt lines in the form of holes that are not in communication with each other.
• the locking ring is guided on a shoulder of the screw head, which is smaller than the screw head outer diameter, and taken in the tip, i. the locking ring rotates forcibly with a screw rotation with the main body of the backflow lock.
• a disadvantage of this embodiment are the measures that must be taken to minimize the wear effect of the co-rotating Sperringes on the corresponding inner wall of the plasticizing, because this, the gap between these parts must be large enough. This is particularly important for large screw diameters.
• the invention has the object, so to develop a return flow lock of ein ⁇ initially mentioned type that it has an improved closing behavior and low wear on the cylinder inner surface and a low material damage.
• the solution of this object is achieved by a non-return valve with the features of claim 1; the following claims relate to advantageous developments of the invention.
• the end piece has a recess in the region between the center piece and its stop surface, such that the end piece in this area has a slider with a diameter D GL on which the locking ring with its inside axially and circumferentially relative to the tail and slidably rests on the middle piece, wherein the slider has a length L which is greater than the stroke A of the locking ring and the locking ring is not necessarily carried by the main body of the backflow preventer (Seh tease head) in the circumferential direction.
• This solution prevents plastic melt from flowing between the locking ring and the end piece into the annular gap. During the injection process, the pressure in front of the locking ring is thus kept constant or increased.
• Fig. 2 is a longitudinal sectional view of the first variant in an intermediate position shortly after
• FIG. 6 shows a longitudinal section of a fourth variant in the blocking position
• FIG. 7 Top view of the non-return valve of FIG. 5 from the direction of the arrow in FIG. 5.
• the remindströmsperre shown in Figures 1 to 3 comprises a screw head 10 with an ejection-side end piece 12, a cylindrical centerpiece 14 and a Montage ⁇ end 20 for mounting at one end of an injection screw, wherein the screw head 10 between its mounting end 20 and the center piece 14 a Pressure ring 16 carries.
• Concentric to the center piece 14, a locking ring 18 is arranged and forms together with the center piece 14 an annular gap 22.
• the outer diameter of the locking ring 18 is dimensioned so that the locking ring is just axially displaceable in a plasticizing cylinder, not shown here, on the one hand an open position (Figure 1) and a locking position ( Figure 3) to take, but on the other hand to allow almost no relative movement in the circumferential direction.
• the locking ring 18 is axially displaceable with respect to the Seh tease head, in an open position (Fig. 1), in which a stop surface 30 of the end piece 12 with a head-bearing surface 28 of the locking ring 18 comes into contact, and in a locking position (Fig 3), in which a stop surface 24 of the pressure ring 16 comes into contact with a locking bearing surface 26 of the locking ring 18.
• a flow of material passes the gap between the surfaces 24 and 26, the annular gap 22 and the bores 32.
• the locking ring In the blocking position, the locking ring is in its right end position, and the gap between the surfaces 24, 26 is closed, so that no Material can be pressed in the direction of the screw.
• the end piece 12 has on its back - so the locking ring side facing - a recess 40, such that a slider 42 is formed with a diameter D GL .
• This slider 42 forms an over the entire circumference extending and continuous support surface on which the locking ring 18 is displaceable with its front end 46 both in the axial direction and in the circumferential direction.
• the locking ring 18 is not taken by the worm head during its rotation.
• the length L of the slider 42 is greater than or equal to the stroke A of the locking ring 18 between the open and the locked position. This ensures that plastic melt can only penetrate through the openings 32 into the annular gap 22 during injection (see FIGS. 2 and 3).
• a part of the stop surface 28 can already be made available in the open position as an inflatable cross-sectional area.
• Various embodiments of this are shown in Figures 4 to 6. It remains up to the expert to design further embodiments with an inflatable cross-sectional area.
• the outer diameter D AE of the end piece 12 may be smaller than the outer diameter D AS of the locking ring 18 at its front end 46, so that a leading edge 54 is formed.
• the end piece 12 may, for example, have at least one axial or angled channel 50, wherein the diameter D K of the end piece 12 in the region of the channel 50 at the channel bottom is the same (as shown in FIG. not shown here), or smaller (as shown in Figure 6) than the diameter D GL of the slider 42 may be.
• the length U of the channel 50 is to be designed so that it ends in the region of the length L of the slider 42, so that a shoulder 52 remains, in which the locking ring 18 still rests tightly on the slider 42 and no plastic melt from the annular gap 22 in the channel 50 and vice versa can pass, but the plastic melt continues to flow exclusively through the openings 32.
• FIG. 7 shows the top view of the embodiment according to FIG. 5 from the direction of the arrow in FIG. 5.
• four channels 50 distributed over the circumference are provided in the end piece 12 and four openings 32 are distributed over the circumference in the locking ring 18.
• the mounting end may also be integrally formed together with the pressure ring and the middle piece, in which case the tail is attached to the center piece, for example by screwing.

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• Engineering & Computer Science (AREA)
• Manufacturing & Machinery (AREA)
• Mechanical Engineering (AREA)
• Injection Moulding Of Plastics Or The Like (AREA)

Applications Claiming Priority (2)

Publications (1)

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ID=35116149

Family Applications (1)

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Citations (4)

Family Cites Families (3)

• 2004
  • 2004-09-01 DE DE102004042615.5A patent/DE102004042615B4/de not_active Expired - Fee Related
• 2005
  • 2005-08-18 WO PCT/EP2005/054067 patent/WO2006024607A1/de active Application Filing
  • 2005-08-18 CN CNA2005800291203A patent/CN101022934A/zh active Pending
  • 2005-08-18 KR KR1020077004041A patent/KR20070048198A/ko not_active Application Discontinuation

Patent Citations (4)

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