US3580431A - Aerosol valve tip and stem assembly and method of assembling same - Google Patents

Abstract

This application describes and illustrates a method of making an aerosol valve tip and stem assembly and the interlocked assembly. The interlocked assembly is comprised of a tip and stem, one being a hard material defining a recess or notch, and the other being of a soft cold-flowable material that is caused to coldflow into the notch when the two members are telescopically assembled. When the members are assembled, the soft cold-flowable material cold-flows into the notch to interlock the members and to make disassembly thereof difficult.

Description

United States Patent [72] lnventors Clarence 0. Kufier Niles; Thomas McAvoy, Roselle, lll.

[2|] Appl. No. 21,251

[22] Filed Mar. 20, 1970 [45] Patented May 25, 1971 [73] Assignee Valve Corporation of America Continuation of application Ser. No. 703,103, Feb. 5, 1968, now abandoned.

[54] AEROSOL VALVE TIP AND STEM ASSEMBLY AND METHOD OF ASSEMBLING SAME 8 Claims, 8 Drawing Figs.

[52] U.S. Cl ZZZ/402.1 [51] Int. Cl 865d 83/00 [50] Field of Search ..222/402.2l

402.1, 207; 285/238,'2'60; 345, 239 (Inquired); 239/490 [56] References Cited UNYTED STATES PATENTS 3,100,068 8/1963 Kersten 222/207 3,129,893 4/1964 Green 239/490 Primary ExaminerStanley H. Tollberg AttorneyDressler, Goldsmith, Clement and Gordon ABSTRACT: This application describes and illustrates a method of making an aerosol valve tip and stem assembly and the interlocked assembly. The interlocked assembly is comprised of a tip and stem, one being a hard material defining a recess or notch, and the other being of a soft cold-flowable material that is caused to cold-flow into the notch when the two members are telescopically assembled. When the members are assembled, the soft cold-flowable material cold-flows into the notch to interlock the members and to make disassembly thereof difficult.

AEROSOL VALVE TIIP AND STEM ASSEMBLY AND METHOD OF ASSEMBLING SAME This application is a continuation of US. application Ser. No. 703,103, filed on Feb. 5, 1968, now abandoned.

Background of the Invention This invention is directed to a new and improved method for interlocking an aerosol valve stem and tip and to the interlocked assembly of those members.

One of the widely used types of aerosol valves includes, among other things, a stem projecting from the aerosol container and a tip or-actuator button seated on the end of the stem. The stem is usually of hard material, such as metal, thermoplastic acetal resin, nylon and the like, and the tip is of a softer cold-flowable material such as thermoplastic polyethylene, or the like.

The tip, as stated, is seated on the end of the stem, and may be so seated in a variety of ways. In one of these a stem and a tip have cooperable notch and detent means so that one piece snap fits into the other. In another of these, the bore of the tip receiving the stem is of a lesser .diameter than the stern diameter. Therefore, the bore of the tip receives the stem in aninterference fit. However, because the tip is generally of a material softer than the stem, over a period of time the interference fit decreases in strength and the tip becomes easily dislodged from its condition of securance to the stem, either accidentally or by blowout. That is highly undesirable. Further, as the interference fit decreases in strength, the sealing characteristics of the joint between the stem and the tip correspondingly decrease, thereby allowing the pressurized contents of the associated container to blow back and out between the stem and the tip. This also is highly undesirable.

The retention problem has been dealt with in several ways. By one, the magnitude of the interference fit has been increased. However, that results in a high assembly force which makes assembly of the tip to the valve stem difficult. Further, even with the increased strength of the interference fit, after an extended period of time the fit diminishes in strength and the same problems arise as with an interference fit of a lesser initial magnitude.

Another attempt at solving the retention problem has been to form a stem with a projecting annular barb. This requires the use of a mold which has undercuts in it, resulting in molding difficulties. And, when the barbed stem is forced into the tip, the barb digs into the wall of the tip thereby requiring a greater assembly force than is required where the stem is generally cylindrical in shape. If it becomes necessary to remove the tip and then reassemble it with the stern, as is often desirable, upon removal the barb is damaged and the tip bore is partially stripped so that upon reassembly, the retention force of the barbed assembly is substantially diminished. A further drawback of the barbed assembly is that the seal between the stem and tip bore, because of the presence of the barb, is not nearly as good as where the stem has no projection beyond its cylindrical surface. A good seal is necessary to prevent the passage of the pressurized contents of the can between the stem and tip in preference to or in addition to its passage through the dispensing orifice in the tip.

The method and assembly of this invention provide an assemblage, the elements of which are properly sealed and securely retained to each other. They obviate the disadvantages of the barb and of the other means for securing two members and provide a device wherein the assembly force is substantially less than the retention force and wherein, upon disassembly and reassembly, the retention force is very close to that of the original assembly. Further, in assembling and disassembling the interlocked assembly of this invention, substantially no damage is done to the interlocked elements. Also, the assembly force required to assemble the interlocked assembly of this invention is no more than the force required to assemble a straight-walled cylindrical part into the bore of another part. These advantages, described in the context of an aerosol valve stem and tip, are obviously applicable elsewhere, as well.

In accordance with this invention, a pair of members is pro" vided. One of the members is of a hard material and the other of a soft cold-flowable material. One of the members defines a bore for receiving the other member. The hard member defines a notch in its surface, which notch when the parts are assembled, confronts the cold-fiowable material member. The portion of the member received in the bore and the bore are similarly configured, the portion of the member received, however, being of a greater size than the bore so that upon insertion the member received will be in compression, or in other words, will form an interference fit with the bore. The compression fit will, without the application of external radial forces, cause the soft cold-fiowable material adjacent the notch to flow into the notch to interlock the pair of members. Additionally, the assembly will be well sealed along its assembled length, to resist the flow of fluid between the confronting surfaces of the members.

These and other advantages and purposes of this invention will become apparent from the following description and drawings of which:

FIG. 1 shows an exploded view of an aerosol valve assembly incorporating this invention;

FIG. 2 shows the exploded assembly of FIG. 1 in an assembled relationship;

FIG. 3 is a front view of the assembly of FIG. .2;

FIG. 4 is a cross-sectional view taken substantially along line 4-4 of FIG. 2;

FIG. 5 is a cross-sectional view taken substantially along line 5-5 .of FIG. 2;

FIG. 6 is a cross-sectional view taken substantially along line 6-6 of FIG. 2;

FIG. 7 is a cross-sectional view taken substantially along line 7:! of FIG. 2; and

FIG. 8 is a cross-sectional view of a further embodiment of this invention.

Referring first to FIGS. 1 to 3, those FIGS. illustrate a presently preferred embodiment of this invention in which the interlocked members are a valve stem and a valve tip for a pressurized container such as an aerosol container. The valve and stem assembly is adapted to be assembled to an aerosol container, for example in a manner as illustrated in US. Pat. No. 3,2l9,069 which shows other parts of a valve assembly and their overall assembled relationship to an aerosol container.

As seen in FIG. I, a stem and valve body assembly 10 includes a stem 12 and a valve body 14. Stem l2 defines a conventional metering orifice 16 through which aerosol passes into stem bore 18 for discharge through tip 20. Stern and valve body assembly 10 is preferably a unitary molded part as of a relatively hard plastic material such as Delrin, a thermoplastic acetal resin made and sold under the name Delrin by E. I. Du- Pont de Nemours & Company. Other alternative and suitable hard materials are polycarbonates, epoxy resins, metal and the like.

Stem 12, as best seen in FIG. 1, defines an annular notch 22 adjacent its free or outer end 23. Notch 22 is, in the embodiment illustrated, of a wedge shape and is defined by a trans-. verse shoulder 24 and a sloping wall 26. Wall 26 slopes from.

the innermost. edge of shoulder 24 downwardly and outwardly toward the outer surface 28 of stem 12 until it merges into surface 28. Surface 28 is cylindrical throughout its length, except adjacent notch 22 and at its outermost edge 23 whereat it is rounded slightly to facilitate insertion of the stem into the bore of tip 20.

Tip 20 may be a conventional type, and as such includes a thick annular wall 29 at least twice as thick as the depth of notch 22. The tip defines a bore 30 surrounded by wall 29 for receiving stem 12, a flow passage 32 for aerosol to be dispensed and a further flow channel for the aerosol to pass through to the discharge orifice 34. Discharge orifice 34 may be in a suitable insert 36 which is positioned within a cooperably configured generally annular opening 37 in the tip. Tip 20 is a relatively soft material which will cold-flow when assembled with hard stem 12. A suitable material is polyethylene which is a thermoplastic resin which has been found to have clod-flow characteristics within the context of this invention.

It will be noted that bore 30 is cylindrical substantially throughout its length and thus is complementary to stem surface 28. However, the diameter of the bore 30 is less than the diameter of surface 28 of stem I2. It has been found that a highly desirable relationship between the diametric dimensions or peripheral sizes of stem surface 28 and bore 30 is that the bore size should be substantially the same as the diameter of the notch adjacent its innermost edge, i.e., adjacent the intersection of shoulder 24 and wall 26. Also the total length of the inserted portion of the stem is preferably at least twice the length of the notch as measured along the length of the stem.

As seen in FIGS. 2 and 4, when the hard stem 12 is inserted into and assembled with the soft cold-flowable tip in a compression or interference fit, the notch becomes filled with the cold-flowable material as shown at 40. That material is caused to flow into notch 22 by the forces exerted by the tip and wall 29 without the application of external compressive forces and serves to interlock with notch 22. If one seeks to withdraw the stem from the tip, material 40 cooperating with notch 22 and shoulder 24 thereof resists withdrawal.

In accordance with this invention, upon insertion of the stem into the bore of the tip, the wall 29 of the tip forces wall material to flow into notch 22 without the application of external compressive forces. It is thought that the stresses in the immediate vicinity of the notch are so great that the elastic limit of the softer plastic material is there exceeded resulting in its inelastic deformation or cold-flow. Remote from the area of the notch, the stresses are not as great in the softer member so that the elastic limit is not there exceeded. In the remote portions the material being only elastically deformed compressively acts to cause the portions stressed beyond their elastic limit to cold-flow into the notch substantially immediately. However, that theory is mentioned here as a theory and without any intention to so limit the invention, It has been found that the force required to insert the stem into the tip is substantially less than the retention force, i.e'., the force required to disassemble the parts, clearly demonstrating that the assembled system has itself acted to enhance the retentiveness of the tip for the stem.

Indeed it was determined that the retentive force of the assembled stern and tip is as much as 50 percent greater than the force required to assemble them. It has also been found that this increased retentive force is obtained without any increase in the assembly force required to assemble a straight-walled nonnotched stem to a tip wherein the tip bore and stem diameter are of the same size, dimensions and materials. It has also been found that significantly increased retention is obtained with a partial notch, rather than a complete annular notch as illustrated in the figures hereof.

It has been further observed that the retentive force increases with the depth of the notch and that increased retentiveness can be obtained by varying the shape and dimensions of the notch. A particularly advantageous construction is one in which the shoulder depth is approximately one-tenth of the stem length of the notch as measured along the length of the stem surface, although it has been found that significant improvements over other stem-tip retention methods are provided by other notch dimensions and configurations. Y

The improvements in retention made possible by this invention may be readily observed from the following data. Considering a polyethylene tip of the general configuration and proportions illustrated and defining a bore 30 of about 0.120 inch, and a Delrin stem absent a notch and having a diameter of about 0.l30 inch and a wall thickness of from about 0.030 to 0.035 inch, the tip bore and stem having a mating length of about 0.145 inch, the arithmetic average retention force of a number of samples tested shortly after assembly was found to be about 90 ounces. The assembly force was approximately 8 pounds.

With the dimensions and assembly force remaining the same except for the provision of an annular notch as illustrated herein, the following arithmetic averages of retention forces of a number of specimens were determined: with a notch depth of 0.008 inch-and notch length of 0.032, the average retentive force was about 167 ounces; with a notch depth of 0.006 inch and a notch length of 0.020 inch, the average retentive force was about ll8 ounces; with a notch depth of 0.006 inch and a notch length of 0.040 inch, the average retentive force was about 126 ounces; and with a notch depth of 0.006 inch and a notch length of 0.060 inch, the average retentive force was about 186 ounces. In each of these instances the notch was of the shape illustrated in FIG. I and the depth was measured along shoulder 24 and the length along the surface of the stem. These retention forces are those which develop substantially immediately after assembly. It was also determined that annular notches of rectangular cross section also developed an increased retentive force in the assembly and that notches partially circumscribing the stem surface also displayed in an assembly increased retentiveness.

In addition to the interlocked aspect of the joint which gives significantly improved retentiveness, it has also been found that the joint between the tip bore and the stem surface provides a good tight fluid seal. This is important because prior art assembled tip-stem systems frequently permitted blow back or, in other words, pressurized fluid to pass downwardly between the assembled tip and stem in preference to or in addition to passage through the discharge orifice. Finally, it has been found that the dimensions and shape of the interlocked members, except for the bore size adjacent the stem remain substantially the same as they were prior to assembly and that the bore size returns substantially to its original dimensions upon withdrawal of the stem therefrom.

In addition to polyethylene, other exemplary materials which are adapted to cold-flow in a manner similar to that described here are polypropylene, polyvinyl-acetate and polyvinyl chloride.

Another environment in which this invention has been found to be highly desirable is in connection with securing an insert to a tip and that is illustrated in the drawing hereof. Inserts are frequently used to regulate closely and to permit the selection of a desired spray pattern from an aerosol container. Such inserts frequently comprise a cylindrical portion which fits into the tip with an end wall having a discharge orifice.

Referring first to FIG. I, an insert 36 is shown to include a generally cylindrical portion 42, a front wall portion 44 and a discharge orifice 34. The cylindrical-portion is received within cylindrical opening 37 in the tip. Without some means other than an interference fit for securing the insert to the tip, it often occurs that after a period of time, the pressure of the aerosol during dispensing against wall 44 will blow the insert out of the tip. This occurs where, as is usually the case, an interference fit between the cylindrical portion of the insert and the recess in the tip is relied upon to retain the insert within the tip.

To prevent similar problems, other manufacturers have had to resort to matching projecting rings in the insert and recesses in the tip, or vice versa, or the like to firmly interlock the two pieces. Such techniques even so are still unsatisfactory because the rear interface of front wall 44 must be intimate contact with the front face 82 of the tip post 70 to insure proper performance. This condition with multiple-cavity premolded matching components is not always satisfactorily achieved, however, because tolerances of the mass-produced parts will not provide the desired alignment. In contrast the method and device provided by this invention insures the locking feature at the desired position in which the part is assembled.

In accordance with this invention, an insert is provided with a notch 46 in portion 42-which, when inserted into the tip recess, serves as an interlocking means with adjacent coldflowable tip material to prevent blowout of the insert in much the same manner as has been described with the stem tip assembly. When the insert is axially pushed into the tip recess, without the application of external radial force the tip material adjacent the hard insert notch cold-flows into the notch to resist withdrawal or blowout of the insert.

FIGS. 4 to 6 will facilitate an understanding of the flow path of the aerosol material is a typical tip as it passes from metering orifice 16 to discharge orifice 34. The particulars of the flow path configuration are not here intended to be limiting upon the invention in that other known flow channel arrangements may be used as well.

As stated when the tip is depressed or tilted the container contents are admitted to metering orifice l6 and then pass through stem bore 18 and tip flow passage 32. The aerosol then enters channel 60, enters channel 62, flows circumferentially to longitudinal channels 64 and to swirl chamber 66 (configured as best seen in FIG. 6) defined by recess 68 in the face of post 70 and the rear face of front wall 44 of insert 36. The aerosol then passes forwardly through discharge orifice 34 in a pattern determined by the proportioning of the inner tip configuration and the cooperating insert configuration and discharge orifice shape and size.

In connection with the embodiments illustrated and described so far, the hard member has been shown as being the part inserted into the recess or bore of a soft cold-flowable member. It is within the spirit and contemplation of this invention thatthe position of the members may be reversed, i.e., a soft member may be inserted into a hard member defining a notch. That is illustrated in FIG. 8. In FIG. 8 two tubular parts are shown. Tube 50 is illustrated as being of steel and defines a notch 52. A soft cold-flowable tube 54, such as of polyethylene, is shown to have a shape complementary to the shape of the hard member and to have an initial diameter 56 greater than that of the bore 58 defined by the hard member. When the soft member is inserted into the recess of the hard member, the material 59 of the soft member adjacent the notch of the hard member cold-flows into that notch to interlock the members Although several embodiments of this invention have been described in considerable detail, it will be understood that the description of those is intended to be illustrative, rather than restrictive, as many details of construction may be modified or changed without departing from the spirit and scope of this invention.

We claim:

1. An aerosol dispenser valve assembly mounted on an aerosol container comprising an elongate smooth-walled hard stem and a soft plastic actuator button defining a discharge passage and axially receiving one end of said stern in a smoothwalled bore therein, said actuator button receiving said stern in an interference fit and said actuator button bore and said stem being complementarily configured; said stem defining a recess in its outer surface in confronting relation to the wall of the bore of said actuator button, said interference fit autoflowing button material adjacent said recess into said recess to physically interlock said stem and said actuator button and to resist removal of said actuator button from said stem whereby the force to remove said button is greater than the force to assemble same and the autoflowed material assumes substantially the shape of the recess.

2. The aerosol dispenser valve assembly of claim 1 herein the recess is a wedge-shaped transverse annular notch and has a transverse shoulder and a sidewall sloping downwardly and outwardly of said hard stem from the interior edge of said transverse shoulder toward said button.

3. An aerosol valve assembly mounted on an aerosol container, said assembly having a stern and a separate tip secured thereto and defining a continuous flow path therebetween, said stem comprising a hard elongate cylindrical portion defining a peripheral notch intermediate the ends of the cylindrical portion, said notch tapering inwardly and upwardly of said stem in said cylindrical portion and terminating in a generally transverse shoulder, said tip being of a soft cold-flowable material and defining an elongate cylindrical socket of generally uniform cross section for receiving said one end of said stem and said peripheral notch, the diameter of said cylindrical socket being slightly less than the peripheral diameter of the cylindrical portion of said stern prior to assembly of said stem and tip, and whereby when said stem is inserted into said socket, the material of said socket cold-flows into said notch thereby to provide a sealingly interlocked stem and tip assembly and to resist disassembly, the disassembly force being greater than the assembly force.

4. 7 The aerosol valve assembly of claim 3 in which the notch is a continuous annular notch.

5. The aerosol valve assembly of claim 3 in which the diameter of said socket is substantially equal to the diameter of said notch at its innermost dimension prior to assembly of the said stem and tip.

6. The aerosol valve assembly of claim 3 in which said tip is polyethylene.

7. A method of sealingly interlocking an aerosol valve stem and tip, the steps comprising, providing a tip of a soft coldflowable material defining an elongate smooth-walled stem receiving bore and a fluid flow passage therethrough, providing an elongate hollow stem of a hard material, said stem having a smooth-walled external peripheral shape complementary to but slightly greater in size than the internal shape of said bore, said stem having a transverse notch in the external wall of said stem adjacent one end thereof, forcing said stem axially into said bore to position said notch within said tip to provide a tight sealing fit between said stem and said tip, and, without external force, inelastically cold-flowing tip material confronting said notch into said notch to interlock said stem and said tip whereby the force required to disassemble said interlocked members is greater than the force required to assemble them, and whereby the cold-flowed material assumes substantially the shape of said notch.

8. The method of claim 7 in which said transverse notch is a wedge-shaped annular notch.

Claims (8)

1. An aerosol dispenser valve assembly mounted on an aerosol container comprising an elongate smooth-walled hard stem and a soft plastic actuator button defining a discharge passage and axially receiving one end of said stem in a smooth-walled bore therein, said actuator button receiving said stem in an interference fit and said actuator button bore and said stem being complementarily configured; said stem defining a recess in its outer surface in confronting relation to the wall of the bore of said actuator button, said interference fit autoflowing button material adjacent said recess into said recess to physically interlock said stem and said actuator button and to resist removal of said actuator button from said stem whereby the force to remove said button is greater than the force to assemble same and the autoflowed material assumes substantially the shape of the recess.

2. The aerosol dispenser valve assembly of claim 1 herein the recess is a wedge-shaped transverse annular notch and has a transverse shoulder and a sidewall sloping downwardly and outwardly of said hard stem from the interior edge of said transverse shoulder toward said button.

3. An aerosol valve assembly mounted on an aerosol container, said assembly having a stem and a separate tip secured thereto and defining a continuous flow path therebetween, said stem comprising a hard elongate cylindrical portion defining a peripheral notch intermediate the ends of the cylindrical portion, said notch tapering inwardly and upwardly of said stem in said cylindrical portion and terminating in a generally transverse shoulder, said tip being of a soft cold-flowable material and defining an elongate cylindrical socket of generally uniform cross section for receiving said one end of said stem and said peripheral notch, the diameter of said cylindrical socket being slightly less than the peripheral diameter of the cylindrical portion of said stem prior to assembly of said stem and tip, and whereby when said stem is inserted into said socket, the material of said socket cold-flows into said notch thereby to provide a sealingly interlocked stem and tip assembly and to resist disassembly, the disassembly force being greater than the assembly force.

4. 7 The aerosol valve assembly of claim 3 in which the notch is a continuous annular notch.

5. The aerosol valve assembly of claim 3 in which the diameter of said socket is substantially equal to the diameter of said notch at its innermost dimension prior to assembly of the said stem and tip.

6. The aerosol valve assembly of claim 3 in which said tip is polyethylene.

7. A method of sealingly interlocking an aerosol valve stem and tip, the steps comprising, providing a tip of a soft cold-flowable material defining an elongate smooth-walled stem receiving bore and a fluid flow passage therethrough, providing an elongate hollow stem of a hard material, said stem having a smooth-walled external peripheral shape complementary to but slightly greater in size than the internal shape of said bore, said stem having a transverse notch in the external wall of said stem adjacent one end thereof, forcing said stem axially into said bore to position said notch within said tip to provide a tight sealing fit between said stem and said tip, and, without external force, inelastically cold-flowing tip material confronting said notch into said notch to interlock said stem and said tip whereby the force required to disassemble said interlocked members is greater than the force required to assemble them, and whereby the cold-flowed material assumes substantially the shape of said notch.

8. The method of claim 7 in which said transverse notch is a wedge-shaped annular notch.

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