Dispensing – Nozzles – spouts and pouring devices – Antidrip
Reexamination Certificate
2001-06-04
2002-07-23
Doerrler, William C. (Department: 3754)
Dispensing
Nozzles, spouts and pouring devices
Antidrip
C222S375000, C222S383100, C417S569000
Reexamination Certificate
active
06422434
ABSTRACT:
FIELD OF THE INVENTION
This disclosure relates to dispenser pumps, and particularly but not exclusively to dispenser pumps suitable for mass manufacture predominantly in plastics material.
BACKGROUND
Dispenser pumps of the general kind to which the disclosure relates have a pump chamber alterable in volume by the action of a reciprocable plunger. A pump chamber inlet which receives material from a supply container includes an inlet valve. The outlet through which the dispensed material leaves the pump chamber may have an outlet valve. There may be a projecting discharge spout or nozzle. Some of these options are requirements in certain aspects of this disclosure, as explained below.
Preferably—and in some of the present proposals essentially—volume alteration of the pump chamber is by a piston operating slidably in a cylinder, e.g. a plunger piston operating in a fixed cylinder formed by the pump body, typically with an outward seal on the piston wiping the cylinder wall in use.
The present proposals are preferably embodied in pumps having the outlet (and spout
ozzle, where provided) fixed relative to the pump body but they may also be implemented in movable-nozzle pumps i.e. in which an outlet passage extends through the plunger.
In a first aspect our proposals have to do with the difficulty associated with product which remains in the discharge nozzle of the dispenser after the dispensing stroke. Particular difficulties, depending on the nature of the product, include dripping from the nozzle and nozzle blockage by dried product residues.
These difficulties are known and have been addressed in the prior art by what can generally be called suck-back arrangements whereby product residue is drawn back from the nozzle at the end of the dispensing stroke. See e.g. EP-A-779106 and our own WO-A-95/25600. These earlier proposals delay or compromise the closure of an outlet valve after dispensing so that the negative pressure in the pump chamber during priming can act to suck the residue in the nozzle back through the valve.
SUMMARY OF THE INVENTION
In a first aspect of our new proposals a dispenser pump of the kind described has a discharge passage extending along a discharge nozzle downstream of an outlet valve arrangement, the outlet valve arrangement including a blocking element movable along the discharge passage between a closed valve condition at an upstream position and an open valve condition at a downstream position. The blocking element is biased towards the upstream, closed position e.g by spring means and/or gravity. The valve arrangement defines a draw path in the discharge passage between the mentioned downstream and upstream positions, dimensioned to be substantially blocked by the blocking element. During the dispensing stroke the initial flow of pressurized product from the pump chamber carries the blocking element downstream against the mentioned bias to the open condition at the downstream position where the product can flow out past it. At the end of the dispensing stroke the blocking element is biased back from the open condition and along the draw path which it substantially blocks so that, as it travels back, product residue in the discharge passage region downstream of the outlet valve arrangement is drawn-back away from the nozzle tip.
This arrangement may reduce or prevent dripping at a downwardly-directed nozzle end opening, without relying on generating negative pressure in the pump chamber since material need not pass the valve's blocking element. The arrangement is therefore specially useful for pumps having no means for biasing the plunger back to its extended position after the dispensing stroke, and/or in which the supply is disposed relative to the pump so as to give a prevailing positive pressure in through the inlet valve.
Preferably the nozzle is a fixed nozzle projecting sideways from the pump body. The preferred form has a portion extending upwardly from the outlet valve arrangement—enabling gravity biasing—leading to a downwardly-directed end opening.
The blocking element is preferably a single valve body movable along a valve body housing which provides a sealing seat for the body at the upstream end, an enclosed tubular conduit for the draw path in which the valve body is a relatively close fit (having regard however to the viscosity and other properties of the product so as to avoid sticking), preferably parallel-sided, and one or more flow openings providing for relatively free product flow around the valve body at the downstream end. The downstream end may also provide a retaining stop to limit movement of the valve body. Biasing means such as a spring may also be provided to act on the valve body, e.g. a compression spring disposed between the valve body and a downstream reaction abutment of the valve arrangement.
For products which are viscous and/or contain particulates the valve body preferably makes a sharp edge engagement with the sealing seat.
The valve body may be a simple rigid ball or other form of sliding solid plug. It may have a flexible peripheral sealing lip on a central body if closer sealing in the draw path is required; e.g. for lower viscosity liquids. One special novel form of sealing lip is a radial elastomeric flange e.g. provided by trapping an elastomer disc onto the end of a rigid valve body of smaller diameter. This may seal fluid while allowing particulates to pass.
The valve body may make an axial guide sliding engagement with adjacent fixed structure of the valve arrangement to maintain its axial orientation in the draw path.
The withdrawn residue volume depends on the cross-section and length of the draw path, and is determined with reference to the practical requirements e.g. the shape-and size of the nozzle. Preferably the length of travel of the blocking element while blocking the draw path is at least half and more preferably at least the same as the maximum transverse cross-sectional dimension of the blocking element.
A simple valve body is not the only possibility. For example the blocking element may be itself a sub-assembly comprising a valve body retained in a sleeve, the body being movable along the sleeve between a sealing seat and one or more flow openings for the above-described behaviours, and the sleeve itself being mobile along the discharge passage between upstream and downstream positions, blocking the passage whenever the valve body is against its sealing seat.
The suck-back mechanism proposed above moves product back into the pump chamber. This volume may be accommodated in various ways according to the nature of the pump. Where there is a plunger return spring, the suck-back volume joins the volume priming the pump chamber. If there is compliance or delay in the inlet valve and no back-pressure behind the inlet valve, material drawn back can escape that way. Or, it may be accommodated by a slight movement of the plunger.
However, for the particular case in which the above modes of accommodation are not available, unreliable or not desired we propose that the pump chamber may be provided with a yielding wall element to accommodate the drawn-back volume without requiring back-flow at the inlet or bodily movement of the plunger. It is also preferred that this accommodation is free, i.e. not against a resilience which would tend to urge the extra volume gradually out again past the outlet valve. To this end, the yielding wall element is preferably provided in accordance with the second set of proposals which follow.
In our second set of proposals, a dispenser pump of the kind described has a plunger which is a piston plunger making a sliding primary seal against a cylinder wall comprised in a body of the pump, and reciprocable in this pump body cylinder to alter the pump chamber volume. The piston plunger has a head, and a shaft which has an outer annular shaft element (e.g. a ring, sleeve or tube piston) to which the sliding primary seal is made and an end face directed inwardly onto the pump chamber. The end face has a central portion which by pressing on the plunger head is axially
Lammond Wass Anthony Charles
Law Brian Robert
Smith Richard
Spencer Jeffrey William
Cartagena Melvin A.
Doerrler William C.
Fay Sharpe Fagan Minnich & McKee LLP
Rieke Packaging Systems Limited
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