GB2138536A - Applicator piston - Google Patents

Abstract

A piston for use with a fluid dispensing applicator having a fluid reservoir 20 in which the piston 10 conforms to the internal cross section of the fluid reservoir whereby to urge fluid from reservoir, comprises a main body portion adapted at one end to sealingly to engage the interior surface of the reservoir body 20 and at the other end to receive a driving member, the piston having an annular recess 16 within which is located a tiltable member 18 adapted lockingly to engage the interior walls of the reservoir if the piston moves in a reverse direction. <IMAGE>

Description

SPECIFICATION Applicator piston This invention relates to a fluid dispensing applicator for crease setting compositions.

In our UK Patent No. 1603252 there is disclosed a fluid dispensing apparatus for applying a crease setting composition to garments which comprises a reservoir, a nozzle connectable therewith, a rotatable member engageable with the garment surface and means responsive to rotation of the member for urging fluid from the reservoir through the nozzle. Our European Patent Application No. 0067528 discloses an improved form of applicator. However, both forms of applicator rely on a piston within the reservoir body which urges the crease setting composition through the nozzle.

While the piston is designed to expel composition from the reservoir through the nozzle, it can of course move in the opposite direction and should this inadvertently happen air is drawn into the reservoir through the nozzle which can lead to the composition within the reservoir setting and rendering the apparatus unusable.

Accordingly, the invention seeks to provide a form of piston for use with fluid dispensing applicators which is movable only in the direction which causes expulsion of fluid through the nozzle.

According to the present invention there is provided a piston for use with fluid dispensing applicators having a fluid reservoir in which the piston conforms to the internal cross section of the fluid reservoir whereby to urge fluid from the reservoir, which comprises a main body portion adapted at one end to sealingly engage the interior surface of the reservoir body and at the other end to receive a driving member, the piston having an annular recess within which is located a tiltable member adapted to lockingly engage interior walls of the reservoir if the piston moves in the reverse direction.

Preferably, the recess has a greater axial dimension than the tiltable member and means are provided, either in the recess and/or on the tiltable member, to hold one circumferential portion of the tiltable member in an axially rearward position in relation to the recess. This has the effect that should the piston be driven in a rearward direction the tiltable member tilts which aids the locking engagement of the tiltable member with the walls of the reservoir. The mechanisms of the above-mentioned patents are designed to allow a small rearward displacement to piston at the end of each application of adhesive, to draw the adhesive back and prevent oozing from the nozzle.In the preferred construction of the invention, where the recess is axially longer than the tiltable member, there is sufficient lost motion (up to 3 or 4 mm) in the system to accommodate this action without the tiltable member locking. Further rearward movement, of course, causes locking engagement.

The tiltable member may be a ring or part ring of spring steel, preferably slightly conical tapering in the direction of motion of the piston. The annular recess may extend completely about the piston or may extend only partially around, for example half way. In the latter case the tiltable member will be of similar extent and the free end of the tiltable member may be pivotally attached in an axially rearward position in the recess.

The invention will be described further, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a side view of a piston in accordance with the invention; Figure 2 is a similar view to figure 1 of another form of piston; Figure 3 is a similar view to figure 1, of a further form of piston; Figure 4 is a side view on an enlarged scale of the piston of figure 2; Figure 5 is a similar view of figure 4 illustrating the locking action; Figure 6 shows different forms of conical member; Figure 7 (a) and (b) are front and end elevational views of another embodiment; Figure 8 is a sectional view of the embodiment of figure 7 on an enlarged scale; and Figure 9 shows the tiltable member of figure 8 in plan, front and end elevation.

Referring to the drawings, figure 1 illustrates a piston 10 in accordance with the invention. The piston is designed to fit within a tubular reservoir and has a fluid sealing ring 12 at its forward end.

At its rearward end it is adapted to receive a driving plunger in a recess 14, the plunger in use pushing the piston along the reservoir and expelling the fluid contained therein. Figures 2 and 3 illustrate alternative forms of piston 10 which differ from figure 1 in the arrangement of fluid sealing means 12 and drive receiving portion 14.

In each case an annular recess 16 is formed in the piston 10 within which is carried a tiltable member 18, in this case a conical spring. The recess is axially longer than the axial dimension of the conical member 18. As can be seen more clearly from figures 4 and 5, the piston 10 is located within a tubular reservoir 20 and the front portion of the piston 1 2 - is in fluid sealing relationship with the interior walls of the reservoir 20. The conical member 1 8 fits within the recess 1 6 and is held towards the axially rearward face of the recess 1 6 by means of a spacing member 22, which may be integrally formed with the piston 10.

In use, the piston is driven in the direction illustrated by arrow A in figure 4 when it will move smoothly along the interior of the reservoir 20 expelling the fluid therefrom. However, should a reverse force, as illustrated by the arrow B in figure 5, be applied to the piston 10 the conical member 1 8 will tilt as illustrated in figure 5 and at the point 24 its leading edge will, after a small rearward displacement, bite into a lock against the wall of the reservoir 20. Since the reservoir 20 will normally be made of a plastics material whereas the conical member may be made of a metal such as spring steel, the leading edge 24 will actually cut into the wall of the reservoir 20 and lock very tightly therewith preventing further motion in the direction of arrow B.

Figure 6 illustrates different forms of conical member. Figure 6a illustrates the form shown in figures 4 and 5 with which a separate spacing member 22 is necessary. With the embodiment shown in figure 6b lugs 26 are provided on the conical member 18 itself and so no spacer portion 22 is required, the function of this being taken over by the lugs 26. Figure 6c illustrates a further alternative embodiment.

Referring now to figures 7 to 9, in which like numbers denote like parts, it can be seen that the recess 1 6 extends approximately half way round the piston 1 0. Likewise the tiltable member 1 8 is approximately semi-circular in plan (figure 9). The free end 1 8a of the member 18 locate within pockets 30 formed in the piston 10 adjacent the ends of the semi annular recess 16. The half round shape of the ends 1 8a and their respective pockets 30 allow the member 18 to pivot. The pockets 30 are located at the most axially rearward position in relation to the recess 1 6.

Thus, in operation, during forward motion of the piston 10 the configuration shown in figure 7a is taken up by the member 18 and an unimpeded sliding of the piston can occur within the reservoir body. However, on rearward displacement of the piston, greater than a few millimetres, the member 18 pivots about its ends 1 8a and the pockets 30 and tilts to the left as viewed in figure 7a causing its rearward edge to extend beyond the recess 16 (figure 8) and bite into the wall of the reservoir as discussed with previous embodiments.

Should crease setting composition find its way past the sealing means 12 into the recess 1 6 it may set, and tend to prevent proper operation of the tiltable member 18. The provision of a projection or barb on the wall contacting edge 24 will help ensure proper operation in these circumstances.

The piston of the invention provides a simple and effective solution to the problem of the piston being driven rearwardly allowing air to be drawn into the reservoir resulting in the curing of air sensitive compositions.

Claims (9)

1. A piston for use with fluid dispensing applicators having a fluid reservoir in which the piston conforms to the internal cross section of the fluid reservoir whereby to urge fluid from the -reservoir, which comprises a main body portion adapted at one end sealingly to engage the interior surface of the reservoir body and at the other end to receive a driving member, the piston having an annular recess within which is located a tiltable member adapted lockingly to engage the interior walls of the reservoir if the piston moves in the reverse direction.

2. A piston as claimed in claim 1 in which the recess has greater axial dimension than the tiltable member.

3. A piston as claimed in claim 2 in which means are provided either in the recess and/or on the tiltable member to hold one circumferential portion of the tiltable member in an axial'y rearward position in relation to the recess.

4. A piston as claimed in any one of claims 1 to 3 in which there is sufficient lost motion in the system to accommodate a small reverse movement.

5. A piston as claimed in any one of claims 1 to 4 in which the tiltabie member is a ring or part ring of spring steel.

6. A piston as claimed in any one of claims 1 to 5 in which the annular recess extends compietely about the piston.

7. A piston as claimed in anyone of claims 1 to 5 in which the annular recess extends only partially around the piston.

8. A piston as claimed in claim 7 in which the tiltable member is of similar extent to the annular recess and the free end of the tiltable member is pivotally attached in an axially rearward position in the recess.

9. A piston substantially as heretobefore described with reference to and as illustrated in the accompanying drawings.