GB1581938A

GB1581938A - Ejection piston

Info

Publication number: GB1581938A
Application number: GB2760977A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1976-07-01
Filing date: 1977-07-01
Publication date: 1980-12-31
Also published as: DE2629682C3; DK143693B; DE2629682A1; CH617251A5; BE856268A; ES460344A1; DK143693C; DE2629682B2; FR2356576B3; DK288177A; FR2356576A1

Abstract

The piston (12) has an annular piston part (16), on the container side of which a convexly curved sealing plate (15) is secured by means of a bendable or foldable connecting part (17). When the piston is pressed into the container (11) in direction (20), the sealing plate (15) is deformed in such a way that its rim is pressed against the inner wall of the container (11). The seal between the inner wall and the piston is thereby improved. <IMAGE>

Description

(54) EJECTION PISTON (71) 1, NIELS BAY-SCHMITH, a citizen of Denmark, of Svanholm, DK-4050 Skibby, Denmark, do hereby declare the invention for which I pray that a patent may be granted to me and the method by which it is to be performed, to be particularly described in and by the following statement: The present invention relates to an ejection piston for a hollow cylindrical extrusion container. The piston has an annular piston component including a cylindrical outer piston wall and a sealing disc which is arranged at one end of the annular piston component and provides the base of the piston. The face of the sealing disc directed away from the annular piston component is convexly curved.An ejection piston of this kind may be used, for example, in a cylindrical or partly cylindrical container or in a cartridge for plastic substances and for insertion in a manually or pneumatically operated ejection pistol. The cylindrical cartridge wall or container wall, which may be made for example of plastics or cardboard, is often so flexible that the desired seal between the piston and the internal wall of the container is not obtained as a result of the contents being ejected so that a leak may be formed on the piston.

In a known piston of the kind referred to the concave side of the curved sealing disc has an annular lip catch which can lie against the ejection plunger. This lip catch is formed in such a way that the pressure .exerted on it during ejection may lead to a reduction in the curvature of the sealing disc and, therefore, to an improvement in the contact and seal between the wall of the sealing disc and the internal surface of the container. With this known piston, in which the annular piston component is rigidly connected to the sealing disc on its edge, the desired reduction in the curvature or flattening of the sealing disc is counter acted to a disadvantageously high degree.

An object of the present invention is to provide an ejection piston of the kind referred to, which has an improved seal between the piston and the internal wall of the container which co-operates with the piston.

According to the invention, this object is achieved by an ejection piston for a hollow cylindrical extrusion container, the said piston having an annular piston component with a cylindrical outer piston wall and a sealing disc-arranged at one end of the annular piston component so as to form the base of the piston, the sealing disc having a flexible peripheral edge part and a convex face directed away from the annular piston component and the annular piston component and the sealing disc being axially moVable with respect to each other so that the peripheral edge part of the sealing disc may rest under pressure on the outer edge of the end face of the annular piston component and the annular piston component and the sealing disc being permanently connected together by one or more flexible or folding connecting pieces.The annular piston component may be pressed inwards in the container during an ejection operation, for example, by an ejection pistol activated mannually or by compressed air, and the annular piston component thus engages the flexible edge part of the disc. The pressure exerted on the sealing disc by the substance in the container and the pressure exerted by an annular piston component on the edge part of the disc tend to 'reduce the curvature of the disc so that the edge of the disc always comes to press against the internal wall of the container as a seal during an ejection operation.

The external diameter of the sealing disc may be such that the disc may easily be inserted in the associated cylindrical container without tension or substantially without tension and without sealing completely, and any air enclosed in the cylindrical container may escape past the edge of the sealing disc when the piston is inserted. Subsequently, and before the ejection operation begins, the annular piston component and the sealing disc may be pressed against each other axially so that the desired seal is obtained between the edge of the disc and the internal wall of the container, and when the catches lock, the annular piston components and the sealing disc may be fixed in this position reciprocally pressed axially against each other.The catches are advantageously formed in such a way that they allow the annular piston component and the sealing disc to be further compressed axially.

In the accompanying drawings, which illustrate two different embodiments of the invention, Figure 1 is a side view partly in section of an extrusion container, Figures 2 to 4 are enlarged detail views illustarting a piston co-operating with an extrusion container in a first embodiment, and Figures 5 and 6 are detail views of a second embodiment of the piston.

Figure 1 illustrates a hollow cylindrical extrusion container 11 which may be made, for example, from plastics or another elastically flexible material. The container 11 is filled with a plastic substance 10, for example, sealing compound, adhesive or the like. The container 11 is closed at one end by a movable piston 12 and at the other end by a transverse wall 13 which is provided with an ejection nozzle 14. The piston 12 has a sealing disc 15, the convex face of which is directed towards the interior of the container 11 and away from the piston.

The disc 15 forms the base of the piston.

An annular piston component or skirt 16 projects from the sealing disc outwards of the container.

In the embodiment shown in Figures 2 to 4, the sealing disc 15 and piston skirt 16 are connected to each other by a ringshaped connecting piece 17 formed as a thin folding wall section. The piston 12 may be produced from a plastics material for example by injection moulding. As indicated in Figures 2 and 3, the connecting piece allows moulding cores 18, only one of which is shown in Figures 2 and 3, to be extracted after the moulding operation.

When the substance 10 is to be ejected from the container 11 through the ejection nozzle 14, the container 11 may be placed in an ejection pistol (not shown) which is activated manually or by compressed air or in a similar activating device. A force directed inwards as indicated with an arrow 20 in Figure 4, is subsequently exerted on the annular section of the piston 16 by a plunger 19 of the ejection pistol. This force (indicated by arrow 20) is transferred to a free, flexible peripheral edge part 24 of the sealing disc 15 and in combination with the reaction force (indicated by arrow 21) exerted by the substance 10, causes a reduction in the curvature of the sealing disc 15 so that the peripheral edge of the sealing disc, which may be formed as a sealing lip (not shown), is pressed firmly and tightly against the internal wall of the container 11.When the forces 20 and 21 increase, the sealing disc 15 is flattened even more so that an even better seal is obtained between the edge of the disc 15 and the internal wall of the container 11.

In the embodiment illustrated in Figures 5 and 6, several flexible or folding stripshaped connecting pieces 17 are provided.

A catch 22 provided with ratchet teeth and projecting axially outwards is provided on the sealing disc 15 between each successive pair of connecting pieces 17. Each catch component 22 has two ratchet teeth each of which may co-operate with a locking projection 23 projecting radially inwards. When there is no tension (as shown in Figure 5); the sealing disc 15 of the piston preferably has an external diameter such that the piston 12 may be easily inserted in the open end of the container after the container 11 has been filled with the substance 10. The air enclosed between the disc 15 and the substance 10 may simultaneously escape from the container chamber.The sealing disc 15 and the annular section of the piston 16 may subsequently be pressed against each other axially until the locking projections 23 can each lock behind one of the ratchet teeth on the catch components 22 (Figure 6). The curvature of the sealing disc 15 is reduced by the piston components pressing against each other axially in this way so that the edge of the disc is pressed firmly and tightly against the internal wall of the container and the interlocking parts 22 and 23 secure the sealing disc 15 and the annular section of the piston 16 in this opposed axial position. When the sealing disc 15 and the section of the piston 16 press against each other, the connecting pieces 17 are bent or compressed together (see Fig. 6).

The catches 22 may be replaced by a single circular catch which is provided with continuous circular ratchet teeth. In this case, the flexible or folding connecting pieces 17 may for example project from the free edge of the catch 22.

The piston of the invention may be formed from plastics material in one piece.

WHAT I CLAIM IS: 1. An ejection piston for a hollow cylindrical extrusion container, the said piston having an annular piston component with a cylindrical outer piston wall and a sealing disc arranged at one end of the annular

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **.

any air enclosed in the cylindrical container may escape past the edge of the sealing disc when the piston is inserted. Subsequently, and before the ejection operation begins, the annular piston component and the sealing disc may be pressed against each other axially so that the desired seal is obtained between the edge of the disc and the internal wall of the container, and when the catches lock, the annular piston components and the sealing disc may be fixed in this position reciprocally pressed axially against each other. The catches are advantageously formed in such a way that they allow the annular piston component and the sealing disc to be further compressed axially.

In the accompanying drawings, which illustrate two different embodiments of the invention, Figure 1 is a side view partly in section of an extrusion container, Figures 2 to 4 are enlarged detail views illustarting a piston co-operating with an extrusion container in a first embodiment, and Figures 5 and 6 are detail views of a second embodiment of the piston.

Figure 1 illustrates a hollow cylindrical extrusion container 11 which may be made, for example, from plastics or another elastically flexible material. The container 11 is filled with a plastic substance 10, for example, sealing compound, adhesive or the like. The container 11 is closed at one end by a movable piston 12 and at the other end by a transverse wall 13 which is provided with an ejection nozzle 14. The piston 12 has a sealing disc 15, the convex face of which is directed towards the interior of the container 11 and away from the piston.

The disc 15 forms the base of the piston.

An annular piston component or skirt 16 projects from the sealing disc outwards of the container.

In the embodiment shown in Figures 2 to 4, the sealing disc 15 and piston skirt 16 are connected to each other by a ringshaped connecting piece 17 formed as a thin folding wall section. The piston 12 may be produced from a plastics material for example by injection moulding. As indicated in Figures 2 and 3, the connecting piece allows moulding cores 18, only one of which is shown in Figures 2 and 3, to be extracted after the moulding operation.

When the substance 10 is to be ejected from the container 11 through the ejection nozzle 14, the container 11 may be placed in an ejection pistol (not shown) which is activated manually or by compressed air or in a similar activating device. A force directed inwards as indicated with an arrow 20 in Figure 4, is subsequently exerted on the annular section of the piston 16 by a plunger 19 of the ejection pistol. This force (indicated by arrow 20) is transferred to a free, flexible peripheral edge part 24 of the sealing disc 15 and in combination with the reaction force (indicated by arrow 21) exerted by the substance 10, causes a reduction in the curvature of the sealing disc 15 so that the peripheral edge of the sealing disc, which may be formed as a sealing lip (not shown), is pressed firmly and tightly against the internal wall of the container 11.When the forces 20 and 21 increase, the sealing disc 15 is flattened even more so that an even better seal is obtained between the edge of the disc 15 and the internal wall of the container 11.

In the embodiment illustrated in Figures 5 and 6, several flexible or folding stripshaped connecting pieces 17 are provided.

A catch 22 provided with ratchet teeth and projecting axially outwards is provided on the sealing disc 15 between each successive pair of connecting pieces 17. Each catch component 22 has two ratchet teeth each of which may co-operate with a locking projection 23 projecting radially inwards. When there is no tension (as shown in Figure 5); the sealing disc 15 of the piston preferably has an external diameter such that the piston

12 may be easily inserted in the open end of the container after the container 11 has been filled with the substance 10. The air enclosed between the disc 15 and the substance 10 may simultaneously escape from the container chamber.The sealing disc 15 and the annular section of the piston 16 may subsequently be pressed against each other axially until the locking projections 23 can each lock behind one of the ratchet teeth on the catch components 22 (Figure 6). The curvature of the sealing disc 15 is reduced by the piston components pressing against each other axially in this way so that the edge of the disc is pressed firmly and tightly against the internal wall of the container and the interlocking parts 22 and 23 secure the sealing disc 15 and the annular section of the piston 16 in this opposed axial position. When the sealing disc 15 and the section of the piston 16 press against each other, the connecting pieces 17 are bent or compressed together (see Fig. 6).

The catches 22 may be replaced by a single circular catch which is provided with continuous circular ratchet teeth. In this case, the flexible or folding connecting pieces 17 may for example project from the free edge of the catch 22.

The piston of the invention may be formed from plastics material in one piece.

WHAT I CLAIM IS: 1. An ejection piston for a hollow cylindrical extrusion container, the said piston having an annular piston component with a cylindrical outer piston wall and a sealing disc arranged at one end of the annular

piston component so as to form the base of the piston, the sealing disc having a flexible peripheral edge part and a convex face directed away from the annular piston component and the annular component and the sealing disc being axially movable with respect to each other so that the peripheral edge part of the sealing disc may rest under pressure on the outer edge of the end face of the annular piston component and the annular piston component and the sealing disc being permanently connected together by one or more flexible or folding connecting pieces.
2. A piston according to Claim 1 wherein locking catches are provided on the annular piston component or the sealing disc and are arranged to lock in one or more different axial positions of the annular piston component and the sealing disc when the annular piston component and the sealing disc are axially pressed against each other.
3. A piston according to Claim 2, wherein the flexible or folding connecting pieces are flexible strips which are arranged alternately in a circle with the locking catches.
4. An ejection piston for an extrusion container substantially as described with reference to the accompanying drawings.