US 3275200 A
Description (OCR text may contain errors)
p 7, 1966 A. LIVINGSTONE PRESSURIZED DISPENSING CONTAINER Original Filed Nov. 16, 1962 INVENTOR a 0 4)? um asmvi United States Patent 3 275,200 PRESSURIZED DFSPENSING CONTAINER Alexander Livingstone, Washington, N.J., assignor to American Can Company, New York, N.Y., a corporation of New Jersey Original application Nov. 16, 1962, Ser. No. 238,208. Divided and this application Dec. 14, 1964, Ser. No.
4 Claims. (Cl. 222389) thereof an imperforate cup-shaped piston mounted in an inverted position and so sized with respect to the inner diameter of the container that product in the upper chamber forms a thin film between the piston skirt and container side wall for purposes of providing a lubricant to facilitate piston movement and also a sealant to prevent escape of propellant in the lower chamber around the piston and into the product chamber. While a pressure can of the foregoing character functions most effectively with many products, difliculties have been encountered from a transmigration standpoint with certain other products.
To explain, :a product having a low viscosity or a consistency which resembles that of water gravitationally bypasses the piston and at least a portion thereof mixes with the propellant in the lower chamber, producing unsatisfactory results. Then too, the reverse situation occurs with some substances having particular lubricity, viscosity and penetrating properties. Exemplary thereof are certain petrolatum-base materials typified by hair grooming waxes, and in the case of this type product the propellant often by-passes the piston, expands within the product and destroys the clear or translucent appearance thereof with the result that product identification is lost.
It is accordingly an important aim of the present invention to provide a pressurized dispensing container featuring therein means preventing admixture of product and propellant.
Another object of this invention lies in the provision of a pressure can of the character which employs interiorly thereof a freely movable piston and which has associated therewith an annular seal member preventing prodnot and propellant from leaking between the piston and can side walls.
Still another object of the instant invention is to provide a pressurized container for dispensing applications having a free moving piston therein which features barrier means separably or integrally associated therewith to prevent propellant and product by-pass.
A further object of this invention lies in the provision of a dispensing container including a tubular body sealed at opposite ends and mounting valve means at one of said ends, an imperforate generally cup-shaped piston mounted in an inverted position Within said body and movable therein, said piston dividing the interior of said body into a product chamber and a propellant chamber, and barrier means between said piston and said body preventing product and propellant admixture.
Other objects and advantages of the invention will become more apparent as the description proceeds, particularly when taken in connection with the accompanying drawings.
In the drawings, wherein like numerals are employed to designate like parts throughout the same:
FIGURE 1 is .a side elevational view, with parts there of taken in section, showing :a pressure can constructed in accordance with the principles of this invention; and
FIGURES 2 and 3 are fragmentary elevational views with portions there-of in section illustrating further exemplary embodiments of the invention.
Designated generally in FIGURE 1 by the numeral 10 is a pressurized dispensing container, shown as comprised of a tubular metal body 11 to which is attached by conventional seaming techniques upper and lower end closures 12 and 13, respectively. Mounted in the center of the upper closure is valve means 14 which is of conventional construction and accordingly is not shown in detail. The opposite end closure, on the other hand, has a central opening 15 which is closed after pressurization of the container by a plug member 16, again in a manner known to the art.
Interiorly of the can body 11 there is freely or floatingly mounted a piston member 18, which divides the space therewithin into chamber 21 for containing product 22 and a chamber 23 housing propellant 24. The piston 18 is constructed of a relatively flexible material which is essentially inert to chemical substances, and one of the polyolefins such as polyethylene may be used. The piston is desirably cup-shaped or essentially dome-like in configuration and has an end wall 25 which may be centrally recessed as at 19 for receiving valve part 17, thereby assuring that maximum upward piston travel can take place and essentially all of the contained product is dispensed.
The piston 18 is further characterized as to shape by a smoothly curved or rounded shoulder portion 26 and a slightly outwardly flaring depending skirt portion 27 normally dimensioned slightly smaller than the inner diameter of the can body 11 so as to provide an annular space 28 between the maximum diameter portion of the skirt and the can body inner diameter. Thereby, in accordance with the prior art teachings, a thin film of product would extend at least part way down between the piston skirt 27 and adjacent portion of the can body side wall so as to lubricate the piston as it moves upwardly after valve 14 is opened, and to also provide a seal against propellant transmigration into the product chamber 21.
However, as was earlier noted, low viscosity products may actually leak past the piston skirt into the propellant chamber, and conversely, propellant may by-pass the skirt portion and infuse the product in chamber 21. In
either situation, a package of little, if any, commercial appeal results.
Each of these problems which has plagued the prior art is herein effectively overcome by barrier means, designated at 30 in FIGURE 1, 40 in FIGURE 2 and 50 in FIGURE 3. The barrier means or annular seal may be either separable from or integral with the piston 18, but in either case preferably is located along the radius of the arcuate piston shoulder portion 26, 26a or 26b, as appears respectively in the three views presented.
The form of barrier member or sealing annulus designated at 30 in FIGURE 1 may be provided by a ring of a substance having the properties of non-adherency to the piston and container side wall, sufiicient strength so as to avoid fracture or disintegration during use, and a relatively low coeflicient of friction in order that it may slide relatively easily along the container side wall and thereby not impede piston movement. Desirably the ring barrier 30 should be capable of formation in situ, and this and the other mentioned characteristics are adequately fulfilled by a petroleum wax. Many petroleum waxes may be found suitable, but preferably the Wax is of the microcrystalline type and in work conan eflicient sealing action.
ducted to date the microcrystalline wax should be modified by a paraflin wax, zinc or aluminum stearate, or a silicone in order to impart the desired lubricity.
As a specific example, good results are obtained when the microcrystalline wax such as polyisobutene has a capillary melting point between 186l94 F., a congeal point of about 186 F., a density of 0.789 gr./cm. at 200 F., a melt viscosity of 0.19 to 0.26 poises at 200 F. and a flexibility of 45 to 60 as measured against a standard of 100 for a very flexible wax and for a very brittle wax. An illustrative modifier for microc-rystalline wax having the named properties is a paraflin wax having a capillary melting point of about 138 to 140 F., a congeal point of about 136 F., a density of 0.765, a melt viscosity of 0.05, and a flexibility of about 50, the density, viscosity and flexibility of the paraflin wax being determined against the same standards as for the microcrystalline wax. An exemplary amount of paraffin wax modifier is about 5% by weight based on the total weight of microcrystalline wax.
After formulation in the approximate amounts indicated the wax in molten condition is poured through the upper open end of the can body 11 prior to filling of the product and propellant therein and with the end closure 12 removed. The molten wax is directed toward the gap between the can side wall and radius of the arcuate shoulder portion 26 of the piston 18, and shortly thereafter hardens to a relatively firm state free of bonded contact with the container side wall and freely slidable thereon. The wax ring 30 forms a cross-section which is substantially round, and after the container is filled and charged, actuation of the valve 14 causes upward piston movement and corresponding travel of the barrier member in scalable relation between product and propellant so that no transmigration in either direction can occur, and yet there is no noticeable interference with free piston movement. Further, in common with the other forms of the invention, the barrier member performs a gentle wiping action on the container side wall and thereby assures that little product residue remains in the container upon completion of piston travel.
In substitution for the formed-in-place barrier means 30 of FIGURE 1, the separable type of sealing annulus of this invention may be of the character indicated at 40 in FIGURE 2. As shown therein, the ring is constructed of a suitable plastic material, and a thermoplastic such as polyethylene is presently preferred. Desirably, the polyethylene of the ring member 40 is of lesser density than that of the piston 18a. The barrier means 40 may be semi-circular in cross-section, or semiround as shown, and may have other shapes appropriate to If a semi-circular cross-section is selected, its radius when inserted may be less than as illustrated so that when the container is pressurized the sealing ring will flare outwardly and provide the desired constant sealing action.
It is also within the contemplation of this invention that the barrier member be integral with the freely movable piston, and in some situations this may be the preferred construction. An illustrative embodiment thereof appears in FIGURE 3, wherein the sealing annulus is designated by the numeral 50. It is to be observed that' the barrier 50 is disposed at the radius of the arcuate shoulder portion 26b of the piston 18b and is generally normal thereto, extending upwardly and outwardly from said radius. Desirably, the barrier member is tapered in cross-section so as to provide a relatively thin wiping edge 51 while at the same time effectively blocking any by-pass of product into the propellant chamber, or the reverse. The wiper-seal member 50 is formed integral with the piston body during the molding thereof, and the edge portion 51 exerts a gentle force on the container side wall by reason of being slightly over-sized with respect to the inner diameter thereof. No substantial product residue thus remains upon completion of piston travel, and an impervious bridge further spans the gap between the piston and container side wall to prevent bypass of product and propellant.
Various forms of barrier means have been disclosed herein, and these and other modifications may of course be effected without departing from the novel concepts of the instant invention.
1. A dispensing container, comprising a tubular body sealed at opposite ends and mounting valve means at one of said ends, an imperforate generally cup-shaped piston mounted in an inverted position within said body and movable therein, said piston dividing the interior of said body into a product chamber and a propellant chamber, and a relatively flexible annular wax seal member freely received between said piston and said body and not connected to said piston or said body preventing product and propellant admixture.
2. A pressurized dispensing container, comprising a tubular metal body, closure means at opposite ends of said body, dispensing means mounted by one of said closure means, an imperforate generally dome-shaped flexible piston received in said body and having an end wall and a downwardly extending skirt wall, said skirt wall being out of engagement over a major portion of its surface with said body and having an annular portion extending inwardly to create an annular recess between said body and said piston, said piston dividing the interior of said body into a product chamber and a propellant chamber, and a relatively flexible annular seal member disposed within said recess and in contact with but not adhered to or formed integral with said skirt wall, said annular seal member being in sliding contact with said tubular body along an annular line of contact for preventing product and propellant admixture.
3. A pressurized dispensing container as defined in claim 2 wherein said annular seal member has a semi-circular cross-section.
4. A pressurized dispensing container as defined in claim 2 wherein said seal member has a circular crosssection.
References Cited by the Examiner UNITED STATES PATENTS 2,459,743 l/ 1949 Trainer et al 2223 89 X 2,826,339 3/1958 Maillard 222387 X 2,925,937 2/1960 Schmidt 222389 X 3,066,836 12/1962 Trumbull 222327 3,179,309 4/1965 Cope 222389 ROBERT B. REEVES, Primary Examiner.
STANLEY H. TOLLBERG, Examiner.