GB2346416A - Bayonet-type connection between a cap and a body of a drum pump - Google Patents

Abstract

A drum pump of a kind comprising an open-ended cylindrical pump body (10) having an upper open end closed by a cap (60). The body (10) has outwardly extending locking pins (30) received within cranked slots (63) of the cap (60). The outer wall of the cap containing the cranked slots (63) is of substantially uniform thickness throughout its circumference and the lower cap edge has long ramped surfaces (61) and short flattened surfaces (64) between successive slots (63). The cap has features of shape and construction which, when compared with conventional pumps of this kind, enable the pump parts to be of polypropylene, a material suitable for receiving a wide variety of potentially hazardous liquid substances.

Description

PUYS THIS INVENTION relates to pumps. i The invention is concerne with improvements in pumps, for example, the type known as a drum pump used predominantly for the discharge from drums of hazardous chemicals including solvents, and petroleum products including lubricants from drums either to a ! hose or to a free-standing vessel.

A known pump of ttlis kind is described in patent specification GB 2290352 and comprises, predominantly, a cylindrical pump body the lower end of which is adapted to be located in an aperture in the top of a drum, a telescopic suction tube extending from the bottom of the body down into the drum, a removable cap on the upper end of the body with a discharge pipe communicating therewith and a piston operable within the body by means of a handle thus to draw liquid from the drum into the pump body and outwardly through the discharge pipe.

The engagement of the cap on the body is by way of radial pins extending from the upper wall region of the body and engageable within cranked or s-called bayonet fit slots in a cylindrical wall of the cap which fit$ over the top of the body. i In GB 2290352, at least the cap is made from nylon and its cylindrical wall, in the region of the cranked slots, is of increased thickness to provide adequate strength for the connection between the cap and the body.

An O-ring seal is disposed between the cap and the body when assembled.

For ease of location of the cap on the body, the lower edge of the cylindrical wall of the cap has a short ramped region in the thickened portion adjacent each slot. Thus, an operator may locate the cap on the body and rotate it until the pins on the body rise up the ramp and then naturally enter the cranked slots.

It has been found that engineering nylon, which in any case is of increasing cost, is unsuitable for pumping certain liquids and it is therefore proposed to produce a pump of this kind wherein the components are made from polypropylene or some other more appropriate material, and yet may still be of nylon, or a combination of materials, for appropriate liquids.

With polypropylene, in order to provide adequate strength it has been found advantageous to increase the thickness of the cylindrical wall of the cap to be the same as the increased thickness previously provided in a localised region adjacent each slot. Thus, the cylindrical wall of the cap in accordance with the present invention is of uniform thickness and the ramp surface adjacent each slot is extended.

Thus, according to the present invention, there is provided, a drum pump comprising an open-ended cylindrical pump body with locking pins extending outwardly from the upper wall region of the body, a closure cap mounted on the body to close the open end thereof, and cranked slots in a cylindrical wall of the cap to receive the locking pins; characterised in that the cap wall is of substantially uniform thickness around its circumference and in that the cranked slots are joined by a lower cap edge a substantial extent of which between the slots comprises a ramp surface disposed generally at an acute angle with respect to a circumferential line between the slots.

An embodiment of the. invention will now be described by way of example only, with reference to the accompanying drawings, in which: Fig. I illustrates a drum pump of the known kind to which this invention relates; Fig. 2 is an enlarged localise view of a cylindrical wall of a cap forming part of the pump of Fig. 1; Fig. 3 is a view similar to Fig. 2 illustrating the cap of a pump produced in accordance with the invention; and Fig. 4 illustrates a drpm pump incorporating features in accordance with the invention.

Referring now to the drawings, a cylindrical pump body 10 defines an inner chamber 10a with a base 11 and is closed by a cap 12. The base of the body has two threaded portions 13 for insertion into an aperture in the top of a drum containing liquid to be pumped, and a telescopic friction fit suction tube 14 extending down to the liquid.

In the upper region of the cap 12 is a discharge pipe 21 with spout 22. A handle 23 operates a piston 24 within the body to draw liquid upwardly through the suction pipe 14 and out of the discharge pipe 21. A clack valve (not shown) associated with the piston 24 enables the liquid to pass the piston in one direction.

The cap 12 is engaged upon the body 10 by means of a number of radial pins 30 extending outwardly from the body and engaged within right-angled cranked slots 31 in the cylindrical wall of the cap.

Referring now to Fig. 2, in a conventional pump, and particularly as described in GB 2290352, the cylindrical wall 50 of the pump is thickened locally at 51 in the region of each cranked slot 31.

For ease of assembly when locating the cap on the body there is a short ramped surface 52 on the bottom edge of the cap 12 so that the pin may ride up the respective ramp and drop into the cranked slot.

An O-ring seal 8 is located in a channel defined by an inner cap wall 9 of a depth greater than the seal.

Referring now to Fis. 3 and 4 and in accordance with the invention, the cap is made frpm polypropylene and its cylindrical wall 60 is of uniform thickness typically in the region of 3.5mm which is substantially equal in thickness to the thickened portion illustrated in Fig. 2.

Again, in accordance with the invention, the ramped surface 61 is gradually curved and has been extended substantially throughout the entire lower edge 62 extending between adjacent cranked slots 63, there being a very short flattened portion 64 forward of each slot.

In addition, the depth of the inner cap wall 9 containing the O-ring seal 8 between the cap and the body has been increased from 2.25mm nominal tolerance (conventionally) to 2.5mm, and the seal 8 is of a softer material especially constructed for the purpose.

The increased depth of the O-ring section provides additional stiffness to the inner cap dome and prevents the O-ring seal from becoming distorted, and the extension of the ramped surfaces 61 provides the !. cap with additional strength and tp minimise or avoid"creep"which tends to take place when moulding in polypropylene.

As will be seen in Fig. 3, the part-circumferentially extending parts 65 of the cranked slots 63 are inclined at a shallow angle such that any tendency for the O-ring seal to become compressed, may be taken up by the ramp effect of the slots.

Indeed, Fig. 3 illustrates the radial pins 30 as being positioned partway along the ramped surfaces. The cap can be tightened further if and when the seal becomes compressed in order to maintain the sealed condition.

Also as can be seen from Fig. 3, in assembly of the product small inserts 66 may be inserted and glued or otherwise fixed selectively in place once the cap has been initially tightened to avoid any risk of the cap becoming dislodged in use.

At the base of the body 10 a dual-threaded portion 67 is provided, which, together with a suitably dimensioned suction pipe similar to that shown at 14 in Fig. 1, enables the pump to be adapted to a variety of sizes of plastics or metal drum, e. g. from 20 litres to 210 litres capacity.

While, conventionally, the piston 24 has been connected to its piston rod by a self-tapping screw fixing, the use of polypropylene material allows the provision of a thread both on the piston and the rod whereby the pump can be assembled and dismantled without the use of metal parts.

Most, if not all, of the parts of the pump, particularly the cylindrical body 10, cap 12 and piston 24, can be produced selectively from a variety of materials for example polypropylene with a 15% by volume chalk-fill or stiffness and additional strength, or alternatively from nylon with a 25% by volume glass-fill, particularly in those areas subject to stresses in operation.

Also, while the pump has been described as having a body for attachment to a fluid containing drum, nevertheless it may be available with flexible suction pipes and discharge pipes and thus operate as an entirely hand-held pump with high vacuum lift with up to 95% efficiency per stroke, and because of its construction and the materials used for its manufacture, all chemicals and other fluids may be handled by the pump, different materials, as may be appropriate, being capable of being moulded to produce the pump using a single universal mould. Thus, for example, for use with certain liquids, particularly strong acids and alkalis, nylon is not suitable, whereas polypropylene is compatible with such liquids.

A drum pump made iq accordance with the invention is predominantly of plastics materials and is readily and rapidly selfassembled and, if required, may be dismantled with similar ease. The modifications of construction when compared with the pump described in GB 2290352 enable the pump to e manufactured from a number of different materials such as those given in the above examples.

All of the components are capable of being manufactured and packaged individually, resulting in a drum pump which can readily be assembled from knock-down par4 by unskilled personnel. the parts can therefore be shipped for production in so-called"third world" countries without the need for any pre-assembly at source

Claims (11)

1. CLAIMS 1. A drum pump comprising an open-ended cylindrical pump body with locking pins extending outwardly from the upper wall region of the body, a closure cap mounted on the body to close the open end thereof, and cranked slots in a cylindrical outer wall of the cap to receive the locking pins; characterised in that the cap wall is of substantially uniform thickness around its circumference and in that the cranked slots are joined by a lower cap edge a substantial extent of which between the slots comprises a ramp surface disposed generally at an acute angle with respect to a circumferential line between the slots.
2. 2. A drum pump according to Claim 1, wherein the cap has a uniform thickness in the region of 3.5mm.
3. 3. A drum pump according to Claim 1 or Claim 2, wherein the ramped surface is gradually curved and extends substantially throughout the entire lower edge of the cap between adjacent cranked slots, there being a short flattened portion forward of each slot.
4. 4. A drum pump according to any preceding claim, wherein the cap includes an inner wall defining with the outer wall, a slot containing an O-ring seal, the inner wall having a depth of 2.5mm.
5. 5. A drum pump according to any preceding claim, wherein the cranked slots include part-circumferentially extending parts which are inclined at a shallow angle to provide, in relation to the locking pins, a ramp effect for tightening the cap onto the body.
6. 6. A drum pump according to any preceding claim, including inserts fixed into the cranked slots adjacent the locking pins, to prevent the cap from becoming dislodged from the body.
7. 7. A drum pump according to any preceding claim, including, at the base of the body, a dual-threaded portion enabling the pump to be attached to a variety of sizes of drum.
8. 8. A drum pump according to any preceding claim, made at least predominantly of polypropylene and including a piston rod and piston removably and threadedly att, ached together without the use of metal parts.
9. 9. A drum pump according to any one of Claims 1 to 7, wherein the cylindrical body and cap are produced from polypropylene including a proportion of chalk-fill for stiffness and additional strength.
10. 10. A drum pump according to any one of Claims 1 to 7, wherein the cylindrical body and cap are produced from nylon with a proportion of glass-fill for additional strength.
11. 11. A drum pump substantially as hereinbefore described, with reference to, and as illustrated in, Figs. 3 and 4 of the accompanying drawings.