US 3211377 A
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Oct. 12, 1965 M. BRENNER 3,211,377
METHOD OF PREVENTION OF NOZZLE FOULING Filed June 28, 1963 United States Patent 3,211,377 METHOD OF PREVENTION OF NOZZLE FOULING Mannie Brenner, Cambridge, Mass., assignor to W. R. Grace & (30., Cambridge, Mass, a corporation of Connecticut Filed June 28, 1963, Ser. No. 291,417 4 Claims. (Cl. 2391) This invention relates to the application of container sealing compositions to closures, and more particularly to a method and means of preventing the build-up of compositions on an applicator nozzle.
The gasket which forms the hermetic seal between the body and the end of a can is applied to the end in liquid form. The sealing composition is ejected through a small nozzle which is placed directly above the sealing periphery of the can end. At the moment of lining as the operation is known in the container sealing industry, the end, supported on a continuously rotating chuck, turns beneath the nozzle. As a result, a peripheral strip of composition is placed on the sealing area.
Nozzle build-up is a difficulty which most usually occurs in the lining of can ends with sealing compositions which contain a solvated or partially solvated elastomer. It is particularly severe when ends are lined on the shoulder, i.e., the inner wall of the channel, rather than on the floor of the channel or against the cur i.e., the incurved margin. This is a placement which is preferred by certain can manufacturers and is often used for cans which must withstand internal pressure such as beer and soft drink cans. Since the can end at the moment it receives the lining is spinning at 2000 to 2500 rpm. the sealing composition would be thrown oh the shoulder and packed under the curl were it not a sticky and comparatively stiff plastic mass. This sticky adhesiveness, necessary to prevent displacement, is a main cause of build-up, for the composition sticks to the nozzle as well as to the end.
In contrast to many compositions which may be run for hours without fouling the machine, these compositions require frequent shut-down for clean-up. On one type of lining machine where a turret of nozzles fixed on radial spokes as well as the can ends beneath the nozzles travel in a circular path, the trouble is compounded. The large centrifugal force and turbulent air patterns set up by a large revolving assembly causes so much build-up that down time is excessive and approaches running time.
Since most solvent-based sealing compositions contain elastomeric high polymers which in the liquid sealing composition are solvated to some degree, none are Newtonian fluids. A few where solvation is negligible can be Elassed as Bingham Plastics. Others exhibit much more complex flow characterstics.
The most troublesome class of compounds may, for the descriptive purpose of setting forth their troublesome behavior, be called elastic. As the flow from the nozzle to the can end ceases, one end of the stream of composition is anchored on the revolving can end, the other extends to the nozzle. As the radial distance increases, the strand stretches, then breaks. The ends of the strand fly back violently as if one had snipped a stretched rubber band. The strand attached to the can end usually snaps back into the can end channel and does no harm, but the strand attached to the nozzle snaps back and sticks to it.
3,211,377 Patented Oct. 12, 1965 Shortly, so big a deposit builds up on the nozzle that shut-down of the machine is imperative. The nozzle must be cleaned.
I have discovered that if the exterior surface of the tip is continuously covered with some fluid which wets the metal surface, the head of fluid which otherwise would collect at the tip will be dragged from it by the emerging jet of sealing compound. Presumably it is dragged away as a sheath of fluid on the surface of the emerging stream, for the performance of the strand which forms after the nozzle shuts off is greatly modified. The strand will drop away from the tip rather than fly back on to it. In consequence, much longer periods of noninterrupted machine production result.
It is the purpose of this invention to reduce to a material degree the amount of build-up of such compositions on the nozzles of the lining machinery and by reducing the amount of build-up to permit the machines to run for much longer times without the necessity of shut-down and clean-up.
The fluid may be led on to the tip directly through a capillary tube maintained in contact with the tip surface, or preferably the tube may be led into a small bore in the tip-holding nut. In this instance, either the thread space or a channel especially cut at the root of the thread forms a header from which the liquid may flow down the exterior surface of the tip.
The nature of the liquid is primarily governed by the nature of the sealing composition, and consequently will vary widely. The compounder, having this disclosure in hand, can readily select fluids which will wet the nozzle tip yet which are compatible with his composition. His choice may run from petroleum solvents such as hexane, oils such as palm, cyclic hydrocarbons such and toluol and xylol, glycols such as ethylene and propylene glycols, aliphatic esters such as ethyl acetate, ketones, e.g., methyl ethyl ketone, alcohols, e.g., octyl alcohol, and, particularly when the sealing composition is a water base dispersion, water in which a wetting agent is dissolved.
As a general statement, the liquid which is the base of the sealing composition will be suitable as the fluid for the sheath, e.g., if the polymeric constituent of the sealing composition is a solvated suspension in hexane, hexane will be found a suitable fluid and will reduce build-up if it is fed through the capillary.
The nozzles used on container closure lining machinery usually comprise a nozzle tip made of some abrasion resistant alloy. The tips are provided with axial bores through which the compound which is under considerable pressure is ejected, and near the lower end of the bore a conical valve seat is formed which is closed by a needle which is raised and lowered by an actuator mounted directly above and in line with the tip. A number of bore diameters are required to adapt the tip to the lining requirements of the particular closure. Hence, the tips are interchangeable and are held to the nozzle body by a shouldered nut which engages a base flange formed on the tip.
In the drawings,
FIG. 1 is an elevation of one form of nozzle equipped with the liquid feed device.
FIG. 2 shows a tip and a conical wind shield.
FIG. 3 shows a tip modified with an external liquidconducting groove leading toward the orifice.
FIG. 4 shows a modified tip having a. radial, flat external face.
FIG. 5 shows a tip assembly in which liquid is fed to a header space, and
FIGS. 6 and 7 show vertical sections of tips which sometimes will be found to improve the effectiveness of this invention either on machines of varying type or with compounds having differing flow characteristics.
Referring to FIG. 1, the nozzle 10 is one of several types of nozzles used. All, however, bear a general similarity. The mechanism which raises and lowers the needle, whether mechanical or electro-pneumatic, is housed in the casing 11. Sealing composition enters the chest section 12 of the nozzle through a conduit, not shown. The valve seat is always formed in the interchangeable tip 13 (the bore size and often its particular shape must meet the demands of various closures). Tip 13 is held in place by the engagement of its base flange 20 with the shouldered nut 15 screwed on to the threaded extension 14 which is formed on chest 12.
The fluid is supplied to the external surface of the tip 13 by the capillary tube 16 which fits through a small hole 17 bored in nut 15. The end of capillary 16 lies directly against the surface of the tip 13.
Fluid is contained in the reservoir 18 here shown in section. Instead of small individual reservoirs, the fluid may be conducted through tubing and several nozzles may be fed from one source. Reservoirs such as 18 should, however, extend horizontally rather than vertically to minimize the variation in head. Reservoir 18 is supported on the nozzle by the bracket 19.
Should the machine be of the revolving turret rather than the linear feed type, the liquid will travel around the tip rather than flow down its surface. Much will be thrown off before it reaches the margin of the orifice. To prevent this, a groove, 21, may be cut in the conical face of the tip 130: as shown in FIG. 3, or a flat, radiused face 22 may be formed on the modified tip 13b (FIG. 4). However, when the nozzles themselves move in a rotary path, if fluid is to be prevented from running around the tip, the channel 21 or flat face 22 must face the center of the rotation, but the line of flow on the surface of the tip must be directed outwardly towards the periphery. If the nozzle is tilted or so shaped as to point the line of flow of fluid on the tip surface towards the center of rotation, fluid will move around the tip rather than flow towards the orifice.
Small grooves or nick-s as shown at 23, FIGS. 4 and 5, may also be ground in the flange portion of the tips. One or a multiple of nicks 23 will then lead fluid from the header space 24 (FIG. 5) to the exposed tip surface. In this case, the nut 15 has the lead hole bore 17 in a position where the capillary 16 is led directly into header 24 (the space between the base flange and the nut 15).
In the rotary turret type of machine windage may be a problem. If turbulent air flow upsets the surface flow of liquid, it may be shielded by the tip shield 25. This is a thin metal spinning slightly larger than the tip 13 and is held in spaced relation to the tip 13 by the nut 15. Capillary 16 enters the shielded space 26 through a small hole in the shield.
Modification of the usual tip improves performance. Considering the tip as a cone, the best results are achieved when the orifice occupies almost the entire area of its upper base. In other words, the tip should be ground so as to make the margin surrounding the orifice sharp and narrow (see FIGS. 6 and 7). Thus, the external dimensions of the tip are related to the diameter of its bore to provide a sufficiently small surface area to permit fluid on the extremity of the tip to come into direct contact with each emerging jet of sealing composition.
FIGS. 6 and 7 illustrate two of the orifice configurations which may be used. Bore size (which determines the width of the lining) and flow characteristics of the composition dictate the choice. FIG. 7 shows an angle delivery tip. It is useful in shoulder lining.
4 Example I Tests using five different tips with five different sealing compositions were run on one machine under conditions tabulated below:
Tip Type 1 2 3 4 5 Composition A B C D E Percent total solids in composition 47. 5 44. 5 43. 5 54. 0 39. 0 Viscosity, centipoises (Brookfield Viscosimetcr) 6, 2,050 2, 600 9, 000 1, 750 Production speed (ends per min.) 350 210 150 350 300 Chuck Speed (r.p.m.) 2, 200 1, G59 1, 710 2, 212 1, 900 Flow through capillary (seconds per drop) 7. 5 7. 5 7. 5 7. 5 Varied Diameter of orifice (inches) .028 .028 .028 O28 028 Can end size 307 401 307 307 211 Dry weight of lining (mg 77 99 80 84 75 Specific gravity (dry film) 1. 38 1. 33 1.38 1. 25 1. 23
RESULTS No. of Amount of Temp. 0! Ends Build-up Composition,
A 100 B 106 C 115 115 D-. 115
E 115 Skelly 100 drop/5 sec.
1 Several thousand.
The amount of fluid supplied to the nozzle was determined by stopping the machine following flow adjustments which had been found to give satisfactory lining performance, and then measuring the volume of liquid which dropped from the nozzle. The flow rate was found to lie between one drop every 4 to one drop every 10 seconds-the most effective rate being one drop every 7% seconds. Assuming 10 mg. of hexane to be the weight of one drop, 60150 mgs. of hexane per minute is an effective flow from the nozzle tip. At such rates, can end sizes varying from 211-401 may be lined at from -350 ends per minute. Other fluids may be found to require different drop rates to achieve maximum effectiveness.
1. The method of reducing build-up of container sealing compositions on the tips of lining machine nozzles which tips are of generally conical configuration and possess a lower and upper base which includes Wetting the surface of the emerging jet of container sealing composition with a compatible liquid, application of the liquid to the jet being made by conducting the liquid to the exterior surface of the tip through a capillary passage, and relating the external dimensions of the tip to the diameter of its bore by reducing the surface area of the upper base suificiently to permit fluid on the extremity of said tip to come into direct contact with each emerging jet of the sealing composition.
2. The process of claim 1 wherein the liquid in its descent to the extremity of the tip is shielded from air currents by a surrounding shield maintained in spaced relation to the exterior surface of the tip.
3. The process of claim 1 wherein liquid is conducted to the extremity of a nozzle tip despite the centrifugal force of a revolving nozzle assembly by forming a notch 0n the exterior surface of the nozzle tip leading from the base to the margin at the tip orifice and positioning the notch in the plane of a radius of the nozzle rotation in the lining machine, facing the center of rotation.
4. The process of claim 1 wherein liquid is conducted to the extremity of a nozzle tip despite the centrifugal force of a revolving nozzle assembly by forming a flat radial face on the tip and directing said face towards the center of rotation of the nozzles and in a plane normal to a rotational radius of the machine, and said radial face being positioned vertically so as to direct the flow of fluid outwardly from the center of rotation of the nozzles and simultaneously downwardly toward the tip of the nozzle.
References Cited by the Examiner UNITED STATES PATENTS 4/ 16 Englemann 2393 14 1/34 Weiss 239--1 9/ 34 Collasure 239-434 1/ 46 Radonich 239-l 7/61 Hjulian 239-424 3/62 Gascoigne et al 239424 FOREIGN PATENTS 3/58 Australia.
1/ 62 Great Britain.
2./ 34 Switzerland.
EVERETT W. KIRBY, Primary Examiner.
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