EP1667920B1 - Feeding piston - Google Patents

Abstract

Disclosed is a feeding piston for a single-use dispenser comprising a receptacle (6) that tapers in a slightly conical manner. The inventive feeding piston is provided with a piston element (2) and a holding element (4) which prevents the feeding piston from moving counter to the conveying direction. The holding element (4) is made of plastic and encompasses different holding segments (30) whose contact surfaces (36) can be placed against the interior peripheral surface of the receptacle (6). The holding segments (30) differ from each other insofar as the final points of the contact surfaces (36) are located at different distances from a center (34) of the holding element (4).

Description

The present invention relates to a follower piston for a slightly tapered container of a disposable dispenser with a piston member and a holding member which inhibits the movement of the follower piston against the conveying direction.

The follower piston is primarily used in a slightly tapered container of a disposable dispenser for dispensing pasty masses, e.g. for body care. The disposable dispenser carries at its upper end to the container slidable head piece, which has a communicable with the container output channel for the pasty mass. The follower piston is displaced in the direction of the head piece when the conveyor provided in the head piece, designed as a hand-operated pump, generates a negative pressure in the container.

Such a follower piston is known from US-A-3,768,705.

The follower piston known from the prior art consists of a piston element produced by means of plastic injection molding, a holding plate and a holding element, which is formed as a star-shaped stamped part with a central circular opening and a plurality of circumferentially distributed holding arms. The retaining plate is connected to the piston element, wherein the star-shaped punched part is clamped between the piston element and the retaining plate. For this purpose, the retaining plate has a central fastening pin which penetrates the circular opening of the star-shaped stamped part and over which the retaining plate is longitudinally displaceably connected to the piston element.

During assembly of the dispenser, the follower piston is introduced into the container filled with pasty mass and advanced to the pasty mass in the conveying direction. When the end face of the follower piston rests against the pasty mass, a vent channel, through which air has escaped from the container during assembly, is closed by longitudinal displacement of the retaining plate against the piston element. In this case, the metallic support arms are erected and biased against the inner peripheral surface of the container. The sharp ends of the support arms, which are bent at the ends in the opposite direction to the conveying direction, cling firmly in the inner peripheral surface of the container and thereby inhibit the movement of the follower piston against the conveying direction.

This prior art is disadvantageous in that in the production of such a follower piston several different material-related manufacturing processes must be used. The piston element and the retaining plate are made of plastic, the retaining element made of a metallic material. Furthermore, it requires a lot of effort to add these three components together.

The present invention is based on the problem, the generic follower piston in such a way that the follower piston is cheaper and easier to manufacture.

The technical problem underlying the invention is solved by a follower piston with the features of claim 1, which differs from the prior art in that the retaining segments differ from each other in that the end points of the contact surfaces have different distances from a center of the retaining element.

The follower piston according to the invention is completely made of plastic, so that on the other hand, the same production method is used for the production of the holding element on the one hand and the piston element. Metallic production processes are, in contrast to the prior art, not required for the production of the follower piston according to the invention. Consequently, the production cost for the follower piston according to the invention is reduced and a more cost-effective production is possible. The holding element of the follower piston according to the invention takes over the functions of the known from the prior art metallic support member and the holding plate. Accordingly, the follower piston according to the invention has at least one component less than the previously known follower piston and thereby simplifies the assembly of the components significantly in a follower piston composed of piston element and retaining element. The piston element and the retaining element of the follower piston according to the invention can also be designed as a one-piece Part to be made.

According to a preferred development of the present invention, the retaining element has a plurality of groups of retaining segments, wherein the retaining segments of a group are distributed substantially in the circumferential direction of the retaining element and their end points have the same distance to the center. The retaining segments are preferably distributed alternately in the circumferential direction and lie in a plane extending at right angles to the conveying direction, so that the retaining element is substantially designed as a plate-shaped compact component. The retaining element has a plurality of groups of retaining segments.

When inserting the follower piston into the container, the retaining segments on the inner peripheral surface of the container, which have the greatest distance, first rest against the movement of the follower piston against the conveying direction. The further the trailing piston is moved in the conveying direction, the more these retaining segments are bent due to the taper of the container against the conveying direction. Finally, the group of holding segments with the next greatest distance inhibits the movement of the follower piston against the conveying direction. With progressive movement of the follower piston in the conveying direction, the holding segments of this second group are also bent in the conveying direction until the holding segments of the next group come to rest on the inner peripheral surface of the container and these inhibit the movement of the follower piston against the conveying direction.

In a further preferred embodiment of the follower piston according to the invention, all holding segments have a peripheral portion surface having the end point, and the peripheral portion surfaces are formed with the same radius. The peripheral portion surfaces are those surfaces that can be applied against the inner peripheral surface of the container. The radius is the distance between the starting point of the radius and the end point of the respective contact surface. The starting point of the radii of a group of holding segments lies on a circle arranged concentrically to the center of the holding element, wherein the different groups of holding segments have different starting points for the radii. The radii of the group with the smallest distance can have their starting points in the center.

According to a preferred embodiment of the present invention, the holding element has a central fastening pin, via which the holding element is guided longitudinally displaceable with the piston element. This embodiment allows a longitudinal displacement between the holding element and the piston element and thus the release of a vent passage during assembly of the follower piston according to the invention. By the fastening pin, the sliding movement of the holding element is guided relative to the piston element. Moreover, the fastening pin can reduce the flow cross-section of a vent passage to a level that allows the escape of air at normal pressure differences, but prevents passage of the same through the vent passage due to the high viscosity of the pasty mass.

For venting the container interior during assembly of the follower piston is preferably between the mounting pin and the holding element in a first position, in which the holding element is held at a distance from the piston member to this, a vent passage released in a second position in which the holding element is shifted from the first position in the direction of the piston element, is closed. Upon insertion of the follower piston into the container, air can escape from the container through this vent passage. After the follower piston has been inserted so far in the container during assembly that the piston element rests against the pasty mass, the holding member is moved in the direction of the piston member longitudinally in the second position and the vent passage closed.

According to a preferred embodiment of the present invention, the fastening pin is formed with star-shaped cross-section and has at its foot on a sealing collar which is sealingly engageable in the second position to a projecting from the mounting pin in the first position retaining opening. The leading the sliding movement mounting pin thus seals with its sealing collar from the vent passage and thereby prevents the pasty mass from leaking out of the container.

In a further preferred embodiment of the follower piston according to the invention, the holding element has a sealing cylinder and the piston element has a skirt surrounding the sealing cylinder circumferentially, which cooperating with the sealing cylinder and this has locking in the first position locking projections.

Due to these latching projections, the sliding-slidably held against each other and a vent passage between them releasing parts piston member on the one hand and retaining element on the other hand, captively connected to each other for the purpose of assembly.

According to a preferred development of the present invention, an annular stop is provided on the inner circumferential surface of the jacket section and a retaining ring cooperating with the stop in the first position is provided on the outer peripheral surface of the sealing cylinder. During assembly of the retaining element on the piston element, the fastening pin of the retaining element is inserted into the retaining opening of the piston element. In this case, the retaining ring of the sealing cylinder spreads the surrounding skirt portion until the front end face of the retaining ring abuts against the stop. The stop and the associated retaining ring thus secures the first position of the piston element relative to the retaining element. In this position, the latching projections engage behind the rear side of the retaining ring and thereby further secure the connection of the retaining element with the piston element.

In a further preferred embodiment of the follower piston according to the invention, a circumferential ramp is formed on the sealing cylinder, which is spread in a direction of the piston member in the direction of the piston member from the first to the second position of the skirt portion to space the stop radially from the retaining ring , By the movement of the holding element in the direction of the piston element of the positive connection between the stop and the retaining ring is released. The movement causes the second position to be reached. In this second position, the sealing collar of the fastening pin sealingly bears against the inner circumferential surface of the retaining opening.

According to a preferred embodiment of the present invention, the sealing cylinder Functional surfaces with which the holding element can be held for mounting by a handle. These functional surfaces facilitate the mounting of the retaining element with the piston element and the introduction of the follower piston in the container.

Preferably, the functional surfaces are formed by ring segments which are distributed on the inner circumference of the sealing cylinder and arranged at a distance from each other, so that between a introduced in the sealing cylinder mounting mandrel and the follower piston, a rotationally fixed connection can be created.

In a further preferred embodiment of the follower piston according to the invention, the holding element is produced by means of plastic injection molding and the piston element facing edge of the peripheral portion surface lies in the parting plane of an injection mold. As a result of this construction, the edge of the circumferential section surface facing the piston element, which cooperates with the inner circumferential surface of the container to inhibit the movement counter to the conveying direction, can be made relatively sharp-edged.

Figur 1

eine Draufsicht auf ein Ausführungsbeispiel eines in einem Behälter montierten Nachlaufkolben;

Figur 2

eine Schnittansicht entlang der Linie II-II in Figur 1;

Figur 3

eine Ausschnittsvergrößerung des Bereiches Z in Figur 2;

Figur 4

eine Unteransicht des in der Figur 1 bis 3 gesehenen Nachlaufkolbens;

Figur 5

eine Draufsicht auf das Halteelement des in Figur 1 bis 4 gezeigten Ausführungsbeispiels; und

Figur 6

eine Schnittansicht entlang der Linie VI-VI in Figur 5.

Further details, advantages and features of the present invention will become apparent from the following description of an embodiment in conjunction with the drawings. In this show:

FIG. 1

a plan view of an embodiment of a container mounted in a follower piston;

FIG. 2

a sectional view taken along the line II-II in Figure 1;

FIG. 3

an enlarged detail of the area Z in Figure 2;

FIG. 4

a bottom view of the seen in the figure 1 to 3 follower piston;

FIG. 5

a plan view of the holding element of the embodiment shown in Figures 1 to 4; and

FIG. 6

a sectional view taken along the line VI-VI in Figure 5.

Figures 1 and 2 show a plan view and a sectional view of an embodiment of the follower piston according to the invention with a piston element 2 and a holding element 4. In Figures 1 and 2, the follower piston is inserted into a slightly tapered container 6 of a donor, not shown. Here, a pasty mass, not shown, facing front sealing lips 8a and rear sealing lips 8b of the piston element 2 are on the inner wall of the container 6 at.

The piston element 2 is designed as an injection molded component. The end face of the piston element 2, which can be applied to the pasty mass, rises from the outside inwards and merges in the middle region into a venting passage 10 extending essentially in the axial direction. Approximately in the axial height between the front sealing lip 8a and the rear sealing lip 8b, the vent passage 10 has a radially inwardly extending holding web 12 with a central holding opening 14. On the pasty mass facing away from the vent passage 10, a jacket portion 14 is formed. The vent passage 10, the holding opening 14 and the shell portion 16 are arranged concentrically to the central longitudinal axis of the container 6.

The jacket section 16 is designed as a cylindrical area which is substantially circumferentially perforated by axial slots and has circumferential latching projections 18 on its inner peripheral surface at its front-side ends. Between the latching projections 18 and the holding web 12 is also a circular circumferential Ansch lay 20 on the inner peripheral surface of the shell portion 16 is provided.

As can be seen from the plan view shown in FIG. 1, the end face of the piston element 2 facing the pasty mass has a plurality of slots 22 extending in the radial direction, which penetrate the dome-shaped end face of the piston element 2. The bottom of the slots 22 is at the level of an annular channel 24 formed between the dome-shaped end face and the front sealing lip 8a.

The holding element 4 is likewise designed as an injection-molded component and formed essentially in the form of a plate-shaped disk, in the center of which rises a sealing cylinder 26, on which a fastening pin 28 reduced in diameter relative to the sealing cylinder rests (see FIG. The attachment pin 28 has a star-shaped cross section, i. has a plurality of extending in the axial direction vent grooves. At the foot of the fastening pin 28, this has a closed cylindrical shape, through which a sealing collar 29 is formed. As can be seen from the plan view of the retaining element according to FIG. 5, this has a plurality of retaining segments 30 arranged distributed in the circumferential direction, which are formed as sectors and are separated from one another by radial slots 32 extending in the radial direction. The radial slots 32 extend from the outer peripheral surface of the holding element 4 in the direction of the center 34 of the holding element 4 and have a length corresponding to approximately half the radius of the holding element. Between the inner end of the radial slots 32 and the outer peripheral surface of the sealing cylinder 26 remains an annular base portion 33rd

In the exemplary embodiment shown, the holding element 4 has three groups a, b, c of holding segments 30. The holding segments 30 of a group a; b; c each have identical distances between the center 34 and an end point of the respective holding segments 30. The end point is that point of the retaining segments which lies on the outer peripheral surface of the retaining segment 30, which cooperates with the inner peripheral surface of the container 6 and has the greatest distance from the center 34. The retaining segments 30 may have multiple endpoints. In the design principle realized in this embodiment, however, the holding segments 30 of the first group a and second group b have only a single end point, which will be explained in more detail below.

The peripheral surfaces of the individual retaining segments 30 each form peripheral portion surfaces 36 with a radius. All peripheral portion surfaces 36 of all groups a, b, c each have an identical radius. The starting point of the radii to the Umfangsabschnittsftächen 36 a of those holding segments 30 a, which have the largest distance to the center, lies on a first circular path around the center 34. The radius for the holding segments 30b with the next smaller distance to the center lies on a second circular path around the center 34 and between this and the first circular path. The holding segments 30 of a group a; b; c are each distributed on the circumference of the holding element 4. In the circumferential direction, therefore, the retaining segments 30 are alternately in the order a, b, c; a, b, c provided. In the embodiment shown, therefore, for each group a, b, c of the retaining segments 30 four peripheral portion surfaces 36, which are each arranged um.90 ° offset from one another. A tangent to the peripheral portion surfaces 36 of a group a; b; Accordingly, c enclosing retaining segments 30 and containing the respective end points describes a circular path and the three envelopes are concentric with each other but with slightly different radius around the midpoint 34. The peripheral portion surfaces 36 of the group of retaining segments 30c with the smallest spacing are on the associated envelope , The radius of this envelope corresponds to the radius of all peripheral portion surfaces 36.

As can be seen in the illustration in Figure 6, the sealing cylinder 26 at its front, the mounting pin 28 end facing a circumferential retaining ring 38 and at the transition to the circular base portion 33 in diameter relative to the mounting pin enlarged base 40 which has a Ramp 42 merges into the outer surface of the sealing cylinder.

As can be seen in FIG. 4, two ring segments 44 are arranged on the inner peripheral surface of the sealing cylinder 26, which are arranged in the circumferential direction at a distance from each other and which form functional surfaces for the assembly of the follower piston. An assembly mandrel, not shown here, cooperates with these functional surfaces, which is connected to a handle, for example a robot, and is inserted into the sealing cylinder 26 for installation.

The retaining element 4 thus held is removed from the injection mold and initially connected to the piston element 2. For this purpose, the fastening pin 28 is inserted into the holding opening 14. In this case, the retaining ring 38 of the sealing cylinder 26 spreads the surrounding shell portion 16 against the advancing movement of the holding element 4 in the piston member 2, the front end face of the retaining ring 38 against the stopper 20 abuts. In this position, the holding element 4 and the piston element 2 are thereby captively connected to each other, that the spring-back locking projections 18 engage behind the back of the retaining ring 38.

The thus pre-assembled follower piston is now inserted in this first position of piston element 2 and retaining element 4 relative to each other in the container 6. The case between the pasty mass and the piston member 4 trapped air escapes with progressive insertion movement through the vent passage 10 and through the holding hole 14 and radially formed by between each locking projections 18 of the skirt portion 16 axial slots to the outside. As the insertion movement continues, the end face of the piston element 2 is placed against the pasty mass, which, with continuous displacement of the remaining air, penetrates all clearances in the annular channel 24, from there into the slots 22 and finally into the ventilation passage 10 until all trapped air has been displaced is.

Due to the higher viscosity of the pasty mass compared to air results in an increased resistance to the insertion movement which causes the ramp 42 of the sealing cylinder 26, the locking projections 18 radially spread and thereby the positive connection between the stopper 20 and the retaining ring 38 is repealed. The applied by the mounting mandrel contact force causes the holding member 4 shifts relative to the piston member 2 from the first position to a second position in which the sealing collar 29 of the mounting pin 28 sealingly abuts the inner peripheral surface of the retaining hole 14.

During operation of the disposable dispenser mounted in this way, pasty mass is discharged at the upper end of the container by a conveying device, not shown here, in that a pump piston compresses the paste-like mass received in the container, which is dispensed by the conveyor due to the resulting pressure. When returning the pump piston in the starting position this takes the liquid column of the pasty mass with, which also follows the follower piston in the direction of the pumping device due to the given incompressibility of the pasty mass and the sealing of the vent passage.

The holding element 4 inhibits in this use of the disposable dispenser movement of the follower piston against the conveying direction. At the conclusion of the assembly and at the beginning of the use of the disposable dispenser, the peripheral portion surfaces 36a at the greatest distance first cooperate with the inner circumferential surface of the container 6. The retaining segments 30a assigned to the circumferential section surfaces 36a are in this case bent by approximately 7 ° to 10 ° relative to the conveying direction with respect to a plane extending at right angles to the central longitudinal axis of the container 6. The piston element 2 facing edges 46 of the peripheral portion surfaces 36a are pressed with relatively high surface pressure against the inner peripheral surface of the container 6 and thus secure the follower piston against undesired movement thereof opposite to the conveying direction. The sharp edge of the edges 46 desired for this purpose can be increased by designing the injection molding tool to produce the retaining element in such a way that the edges 46 of the circumferential section surfaces 36 lie in the parting plane of the tool. Due to the angular position of the holding segments 30, these are bent in the desired trailing movement of the trailing piston counter to the conveying direction and thus allow the necessary trailing of the trailing piston in the conveying direction.

With progressive emptying of the disposable dispenser, the follower piston moves in the direction of the pumping device slightly tapered in the injection molding for technical reasons. The holding segments 30a of the first group a are thereby increasingly arcuate until finally reach the holding segments 30b of the next group b to bear against the inner peripheral surface of the container 6 and finally progressing movement in the conveying direction take over the function of the first group a of the retaining segments 30a, due to increasing bend to lose effect.

LIST OF REFERENCE NUMBERS

2

piston element

4

retaining element

6

container

8a

front sealing lip

8b

rear sealing lip

10

Vent passage

12

holding web

14

holding opening

16

shell section

18

catch projection

20

attack

22

slot

24

annular channel

26

sealing cylinder

28

fastening pins

29

sealing collar

30

holding segment

32

radial slot

33

base section

34

Focus

36

Peripheral portion surface

38

retaining ring

40

base

42

ramp

44

ring segment

46

edge

Claims (12)

1. Follower piston for a disposable dispenser having a slightly conically tapering container (6), a piston element (2), and a retaining element (4) for restraining the movement of the follower piston in an anti-feeding direction, said retaining element (4) being formed of a synthetic material and comprising different retaining segments (30) having contact surfaces (36) partly adapted to abut the inner peripheral surface of the container (6), characterized in that said retaining segments (30) differ from each other in that the end points of the contact surfaces (36) are at different distances from a central point (34) of the retaining element (4).
2. Follower piston according to claim 1, characterized in that said retaining element (4) comprises several groups (a, b, c) of retaining segments (30), in which the retaining segments (30) of a group (a, b, c) being distributed essentially in the peripheral direction of the retaining element (4) and the end points thereof being spaced at a same distance from the central point (34).
3. Follower piston according to claim 1 or 2, characterized in that each retaining segment (30) has a peripheral surface section (36) having the end point, and in that the peripheral surface sections (36) of thel retaining segments are formed with the same radius.
4. Follower piston according to any of the preceding claims, characterized in that the retaining element (4) comprises a central fixing spigot (28) by means of which the retaining element (4) is guided in longitudinally displaceable manner in the piston element (2).
5. Follower piston according to any of the preceding claims, characterized in that a ventilating passage (10) between the fixing spigot (28) and the retaining element (4) is exposed in a first position in which the retaining element (4) is held on the piston element (2) and is spaced therefrom, said ventilating passage (10) being closed in a second position to which the retaining element (4) is displaced with respect to the first position in the direction towards the piston element (2).
6. Follower piston according to claim 5, characterized in that the fixing spigot (28) has a star shaped cross section and at the foot thereof it comprises a sealing collar (29) which, in the second position, is adapted to be placed in sealing manner on a retaining opening (14) through which the fixing spigot (28) projects in the first position.
7. Follower piston according to claim 5 or 6, characterized in that the retaining element (4) comprises a sealing cylinder (26) and in that the piston element (2) comprises a casing section (16) peripherally surrounding the sealing cylinder (26), said casing section having latching projections (18) cooperating with the sealing cylinder (26) and securing the latter in the first position.
8. Follower piston according to claim 7, characterized in that a ring-like stop member (20) is provided on the inner peripheral surface of the casing section (16) and a retaining ring (38) cooperating with the stop member (20) in the first position is provided on the outer peripheral surface of the sealing cylinder (26).
9. Follower piston according to claim 7, characterized in that a peripheral ramp (42) is formed on the sealing cylinder (26) said ramp being expanded by a movement of the retaining element (4) in the direction of the piston element (2) from the first into the second position for radially spacing the stop member (20) from the retaining ring (38).
10. Follower piston according to any of the preceding claims, characterized in that functional surfaces cooperating with a manipulating means for installing the retaining element (4) are provided on the inner surface of the sealing cylinder (26).
11. Follower piston according to claim 10, characterized in that the functional surfaces are formed by ring segments (44) which are distributed around the inner periphery of the sealing cylinder (26) and are mutually spaced.
12. Follower piston according to any of the preceding claims, characterized in that the retaining element (4) is manufactured by means of a synthetic material injection moulding process and in that the edge of the peripheral surface section (36) facing the piston element (2) is located in the dividing plane of an injection moulding tool.

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