EP2227338B1 - Melting systems for bags - Google Patents

Abstract

A piston wiper plate for a pressing unit for melting systems for bags includes a single-piece wiper plate having an axial upper side and an axial bottom side made of elastically resilient material, and a radially outer wiper edge that surrounds the periphery in the relaxed state. The sealing and sliding properties thereof remain within a predetermined range even when the temperatures fluctuate more drastically in that in the wiper plate includes at least one recess that is inserted in the axial upper side and/or in the axial bottom side and/or between the axial upper and bottom sides thereof and that allows for at least a radial compression of the wiper plate. At least one expandable restoring element can be inserted into the recess.

Description

FIELD OF THE INVENTION

The invention relates to a rearwardly nachhadberen bag melts according to the preamble of claim 1.

TECHNOLOGICAL BACKGROUND

In so-called bag smelters, a solid working substance packed in a packaging bag, such as a hot melt adhesive in a cylindrical receiving space of a squeezing device, is transferred from a first solid to a flowable state at a discharge end for molten working substance, while an extrusion piston in the receiving space from the rear end of the bag propelled is pressed so that melted working fluid and the packaging bag on the cylindrical wall of the receiving space axially gradually pushed together. Thus, a rear reloading new filled packaging bag is possible friction and without much previous cleaning effort, the extrusion piston is provided with a stripper plate. This has primarily a sealing function on the inner cylinder wall and serves as a scraper for about adhering to the cylinder inner wall working fluid, which has undesirably inserted between the outer side of the packaging bag and the cylinder wall inside. In order to allow the most precise predetermined discharge amount, ie dosage, when discharging the melted working material, a low coefficient of friction between the stripper plate and the inner cylinder wall is desired. For this and other reasons, the stripper plate is usually made of an elastically yielding material, such as a plastic and in particular of PTFE (such as Teflon®) preferred and also the cylindrical inner wall is coated with a similarly good lubricious material. Different processing temperatures, in particular cold and hot zones in a bag melter, lead to a changing caliber of the stripper plate according to the respective temperature. It is therefore difficult, especially in bag smelters, to ensure uniform force and sealing relationships between the stripper plate and the cylindrical inner wall over the entire extrusion stroke.

The EP 0 031 052 A1 relates to a sealing piston for the chemical industry made of PTFE (Teflon) whose tightness over the entire stroke should be improved even with temperature fluctuations. For this purpose, the piston is provided on one end side with a radially far outer annular groove, so that only a thin cylindrical annular wall remains to the working cylinder and therefore is radially elastic. However, the sealing piston still has an overall rigid end zone without any radial compressibility. This has the consequence that the sealing piston has no radial compressibility or expandability in the region of the wiping edge. In the annular groove, a rubber-elastic ring is inserted with oversize, which presses the thin cylindrical annular wall against the inner surface of the working cylinder to the outside.

The EP 434 617 A shows the features of the preamble of claim 1.

The EP 0 281 755 A1 describes a delivery piston for discharge cartridges, in which a seal located in a radial annular groove (O-ring) is axially compressed during the working stroke, so that the O-ring deflects radially and applies a sealing against the cylinder wall. This is achieved by a deep gap in the circumferential direction on the groove bottom of the sealing ring receiving groove.

The WO 2007/118907 A1 describes a piston for a medical infusion device, in which a piston body is stiffened by an insert which increases the piston friction.

From the EP 0 245 210 A1 an extrusion piston made of a total of elastic material is known, the annular cylindrical edge region with a radially elastic sealing edge on the cylinder to be emptied inside tightly, wherein the extrusion pressure presses the sealing lip radially outward.

PRESENTATION OF THE INVENTION

On this basis, the invention is based on the problem of changing a Kolbenabstreifplatte a bag smelter so that their sealing and sliding properties remain even with more changing temperatures in a given frame. To solve this problem, a bag melter is proposed the features of claim 1. Thereafter, it is provided that in the kolbenabstrelfplatte in its axial top and / or in its axial bottom and / or between its axial top and bottom at least one recess is inserted, the at least a radial compression of the stripper plate allows, and that at least one expandable return element is inserted or used in the at least one recess.

• Wenn die eine oder die mehreren Aussparungen strahlenförmig in die Abstreifplatte eingearbeitet sind, kann dadurch ein besonders hohes Maß an radialer Ausdehnung oder radialer Kompression erreicht werden. Die von den radial erstreckten Aussparungen voneinander getrennten Segmente der Arbeitsplatte bleiben am radialen Außenrand vorzugsweise zusammenhängend. Eine radiale Unterbrechung der Abstreifkante, wie sie bei Kolbenringen von Verbrennungsmotoren üblich ist, ist also entbehrlich.

According to the invention, thermally induced expansions of the stripper plate are no longer exclusively directed radially outwards. Rather, the recesses according to the invention, which are generally perforations of the stripper plate between the axial upper and lower sides, allow in such a way that the reaction forces of thermal expansion lead to a reduction in volume of the recesses. Nevertheless, a sufficient radial expansion capability of the stripper plate is maintained, so that any temperature-induced radial expansion of the cylinder inner wall is still compensated. A "memory effect" is not present in the usual materials for stripper plates in the rule. In order to prevent a scraper plate clamped in the cylinder after thermal deformation of the at least one recess of the stripper plate misses its target size on re-cooling, ie not re-achieved, in the at least one recess, an expandable return element is inserted or visible. The combination of elastically resilient recesses of the worktop with expandable restoring elements means that a stripper plate according to the invention can reliably perform its intended function even after a large number of cycles of thermal cycling. It is now possible to use a stripping plate according to the invention in various ways, and in particular to shape the recesses in very different ways and to use a variety of expandable return elements:

• If the one or more recesses are incorporated radially into the stripper plate, a particularly high degree of radial expansion or radial compression can be achieved. The segments of the worktop which are separated from each other by the radially extended recesses preferably remain connected at the radial outer edge. A radial interruption of the wiping edge, as is customary in piston rings of internal combustion engines, is therefore unnecessary.

For the restoring elements in particular rubber-elastic materials come into consideration, they are designed according to a preferred embodiment of the invention approximately the same shape with the associated recesses and preferably have a certain excess in relation to the recess in the stripper on. As a result, not only a secure hold of the expandable restoring element in the recess is ensured in a simple manner, but the stripper plate is radially radially outwardly clamped radially to a certain extent.

In order to be able to use stripper plates with a certain radial oversize, the insertion opening of the cylindrical receiving space for the piston carrying the stripper plate has a substantially conical insertion region.

When compression springs are provided between a squeezing piston and a scraper or stripping plate, the scraper or scraper plate is extended to a non-pressurized rest condition so as to avoid injury to the piston when the piston is inserted into the cylinder. In the Auspressstadium these springs are compressed.

The above-mentioned and the claimed components to be used according to the invention described in the exemplary embodiments are not subject to special conditions of size, shape, material selection and technical design, so that the selection criteria known in the field of application can be used without restriction

Further details, features and advantages of various embodiments of the invention will become apparent from the dependent claims, as well as from the following description of the accompanying drawings and table, in which - by way of example - an embodiment of a Kolbenabstreifplatte is shown.

BRIEF DESCRIPTION

Fig. 1

einen Beutelschmelzer im halbseitigen Axialschnitt bei frisch eingesetztem und gefüllten Verpackungsbeutel;

Fig. 2

dieselbe Vorrichtung nach völligem Auspressen abgeschmolzenem Arbeitsstoffes aus dem Aufnahmebeutel;

Fig. 3A/B

von dem Beutelschmelzer nach Fig. 1 und 2 eine Abstreifplatte in Draufsicht sowie

Fig. 4A/B

eine alternative Ausführungsform mit federn abgestützter Schabe- oder Abstreifplatte im drucklosen bzw. komprimierten Zustand.

In the drawing show

Fig. 1

a bag melter in half-sided axial section with freshly inserted and filled packaging bag;

Fig. 2

the same device after complete squeezing melted working material from the receiving bag;

Fig. 3A / B

from the bag smelter Fig. 1 and 2 a stripper plate in plan view as well

Fig. 4A / B

an alternative embodiment with feather-supported scraper or stripper plate in the pressureless or compressed state.

DETAILED DESCRIPTION OF AN EMBODIMENT

The in Figures 1 and 2 Bag melter 10 shown in two working positions comprises a receiving space 12 surrounded by a cylindrical inner wall 12A. Surrounding receiving space 12, wall 12B forms opposite mouth ends 12C and 12D at their upper and lower working positions, respectively. The lower mouth end 12D is closed with an end plate 14 having a plurality of outlet openings 14A. Within the receiving space 12 is ( Fig. 1 A packaging bag 18 tightly filled with a hot melt adhesive 16. The packaging bag is tightly closed at its rearward end 18A in the drawing and fully opened at its front end 18B lying down in the drawing to form a discharge opening 18C. This opening is usually done immediately before the onset of solid working substance tightly filled packaging bag 18 into the receiving space 12 from top to bottom, ie from the upper mouth end 12C ago. For this purpose, the squeezing device 20 for the packaging bag 18 can be removed in a suitable manner.

The ejection device 20 comprises an extrusion piston 22, which is axially advanceable within the receiving space 12. The extrusion piston 22 has a scraping or stripping plate 24 (e.g., PTFE, e.g., Teflon®) and has a sharp-edged circumferential scraping edge 24A. In conjunction with a PTFE inner coating 12E of the wall 12B of the receiving space 12, a low-loss sliding of the extrusion piston 22 on the cylinder wall and thus a reasonably well-defined pressure on melted working substance 16A in the region of the lower heating zone can be realized.

The receiving space 12 has in the region of its lower mouth end 12D via an annular constriction 40. This is executed in the illustrated preferred embodiment as at the lower mouth end of the receiving space 12 on the wall 12B releasably attachable and / or placed on the end plate 14 or attached ring , This has on its the receiving space 12 side facing a conical, serving as a sealing surface 40A wall. This acts self-centering on the packaging bag 18 when it is inserted into the receiving space 12. Once the z. B. annular shaped heating element 30 leads to a melting in the region 16A of the working substance 16, the mouth edge zone 18D of the packaging bag 18 automatically applies itself to the conical sealing surface 40A. As a rule, the lateral pressure which the expanding working substance exerts on the edge zone 18D under the pressure of pressure is generally sufficient for this purpose.

The extrusion piston 22 is further equipped with a head plate 26 which are connected via pressure springs 28 which are passed through the cocking plate 24, with the extrusion piston 22. This cross-sectional area of the top plate is less than that of the scraping plate 24, such that an edge gap 26A between the outer edge the top plate and the cylinder wall 12A of the receiving space 12 remains. This edge gap 26A is dimensioned so that the top plate 26 can penetrate into the zone constricted with respect to its cross section at the lower mouth end of the receiving space 12 by a predeterminable distance. In the in FIG. 1 shown working position, the compression springs 24 are compressed under the pressure of the extrusion piston. If, on the other hand, the packaging bag 18 is almost empty and the remaining working fluid in it is liquefied, the pressure of the springs 28 is sufficient to advance the head plate into the constriction area and thereby squeeze out the last remains of working substance from the packaging bag, although the cocking plate 24 does not lower further, but stops before the beginning of the constriction 40.

Out FIG. 3A is a cocking or Abstreifplatte 24 seen in plan view, which has four arranged on a circumferential circle openings 24B for the compression springs 28 can be seen. In addition, a central opening 24C can be seen, from which radiate eight recesses 24D emanate. As a result, the scraping or stripping plate 24 becomes slightly deformable radially, ie, it is compressible by radial pressure directed towards the center and / or expandable radially outwards. When such a scraper or scraping plate is pressed into the receiving space 12 at the upper mouth end 12C by means of an insertion cone 12C ', the scraping edge 24A subsequently abuts tightly against the cylindrical inner wall 12A of the receiving space 12. If the cross-section of the receiving space 12 in the region of the heating element 30 increases due to heating, the cross-section of the scraping or stripping plate 24 can follow this cross-sectional enlargement.

Because of the potentially large coefficient of thermal expansion of the scraping or stripping plate 24 compared to the coefficient of thermal expansion of the wall 12B of the receiving space 12, it may be advantageous to provide the scraper or stripping plate 24 with a nominal diameter reasonably close to the nominal diameter of the cylindrical inner wall at room temperature 12A of the receiving space 12 corresponds. In order to achieve a good wiping result even if the cockroach or stripping plate 24 is increasingly heated by the heating element 30, it is advantageous if in the recess 24C, 24D an expandable return element 25 is inserted. Such is in FIG. 3B represented and manufactured for example from a rubber-elastic material. This will cause the scraper or stripper plate 24 to expand more easily after any initial radial compression upon release of the radially inwardly directed forces, and / or the scraper or stripper plate 24 to expand radially after initial expansion Return element 25 can reversibly deform due to externally applied radial compression forces on the original cross-sectional dimension. Overall, such a designed scraper or stripper plate 24, which is of inventive inventive importance to keep the inner cylinder wall 12A of the receiving space 12 clean and to achieve a particularly high sealing effect, without the sliding coating 12E of the receiving space 12 is injured.

It is understood that such a stripper plate can be successfully used with a variety of squeezing devices and for a variety of different working materials. Thus, the working materials need not necessarily be in solid form and must be meltable and / or packaged in a packaging bag. Rather, a pasty at room temperature agent can be processed with a device according to the invention. Likewise, the recesses for compression absorption and the Rückstelielemente in the context of the invention can be varied in many ways.

In the alternative embodiment according to FIG. 4 A / B are provided between the extrusion piston 22 and the scraper or stripping plate 24 compression springs 42 so that they are in the pressureless state ( Fig. 4A ) hold the scraping and stripping plate 24 in the extended state with axial distance from the extrusion piston. In the in FIG. 4B shown compression state of the piston pressure of the squeezing piston 22 is transferred by contact with the scraper or stripper plate 24 on this.

LIST OF REFERENCE NUMBERS

10

bag melter

12

accommodation space

12A

cylindrical inner wall

12B

wall

12C

upper mouth end

12C '

introduction cone

12D

lower mouth end

12E

internal coating

14

endplate

14A

outlet openings

16

Hot melt adhesive

16A

melted hot melt adhesive

18

packing bags

18A

rear end

18B

front end

18C

discharge opening

18D

border zone

20

ejection device

22

extrusion piston

24

Cockroach or stripper plate

24A

scraping

24B

perforations

24C

central openings

24D

radial recesses

25

expandable return element

26

headstock

26A

marginal gap

28

compression spring

30

heating element

40

constriction

40A

conical sealing surface

42

Kompressionsfedem

Claims (6)

1. Rearwardly reloadable bag melting system (10) comprising a cylindrical receiving space, a discharge device, which can be moved axially within the receiving space, and a discharge-side heating zone for melting off the solid working material, characterized by a discharge device in the form of a discharge piston (22) with a piston stripping plate (24) of elastically compliant material with an axial upper side (24') and an axial underside (24"), and with a radially outer stripper edge (24A), which in the relaxed state runs continuously around the piston stripping plate, wherein at least one clearance (24C, 24D) is provided in the piston stripping plate (24), introduced into the axial upper side thereof and/or into the axial underside thereof and/or between the axial upper side and underside thereof and allowing at least radial compression of the piston stripping plate, and wherein at least one expandable restoring element (25) is inserted or can be inserted into the clearance (24C, 24D).
2. Bag melting system according to Claim 1, characterized in that the at least one clearance (24C, 24D) is of a radially extending form.
3. Bag melting system according to Claim 1 or 2, characterized by radially extended segments of a circle which are separated from one another by spacing gaps and are joined together at least at their radial outer edge.
4. Bag melting system according to one of Claims 1 to 3, characterized in that the restoring element comprises rubber-elastic material.
5. Bag melting system according to one of Claims 1 to 4, characterized in that the restoring element is shaped in substantially the same form as the at least one clearance.
6. Bag melting system according to one of Claims 1 to 5, characterized by a flared feed (12C') at a feed orifice of a cylindrical receiving space (12) for a working material (16) that can be discharged from the receiving space.

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