Golf ball mixing and dispensing apparatus

The present invention provides an improved apparatus and system for mixing castable polyurethanes and polyureas and for prolonging the dispensing time for dispensing them into a golf ball mold for application to a golf ball sub-assembly. A nozzle framework includes support housing heaters and heater adaptors for each dispensing port to delay the onset of drool and improve cut off in the dispensing tubes. The combination of fluorinated dispensing ports, the heating of the polyureas or polyurethanes, and inclusion of a capillary orifice in each dispensing port significantly prolongs the time before the advent of drool is detected.

FIELD OF THE INVENTION

This invention relates generally to an apparatus for mixing of castable polyurethanes and polyureas, and, more particularly, to an improved apparatus for temperature control and prolonged dispensing of the mixture with improved cutoff of material flow.

BACKGROUND OF THE INVENTION

In castable flow molding processes employing a plurality of castable polyurethane components, the homogeneity and the quality of the molded material is mainly determined by the mixing operation which immediately precedes the molding.

For example, after an amount of time in which the reactants come into contact, a polymerization reaction process begins producing the moldable material. Many times, striae form within the moldable material that is visible. The striae are a result of poor mixing which inhibits the quality of the material. Therefore, it is desirable to produce a mixture which is as homogeneous as possible, in the shortest possible time, in order to bring about a uniform reaction to avoid the formation of striae. However, there is an additional difficulty presented in mixing reactive components in the case of polyurethane, in that the two components, i.e., polyol and the isocyanate, have substantially different viscosities.

The use of known mixing processes does not lead to the desired result for producing a high quality polyurethane material. For example, with some processes that employ static mixers that make use of various known mixers for mixing liquids in the laminar flow regime, it is found that a relatively long mixing length is needed to produce sufficient mixing. Often, the mixture requires a relatively long time to pass through this long mixing length, meanwhile, the polymerization process has already begun. Due to the quick setting characteristics of polyurethane, the material will gel or “set up” within the mixer instead of being discharged into the usual succession of molds. The molds are generally moved past the discharge of the mixer in time relation to the discharge. If, for any reason, a slight delay or decrease in the flow rate of the mixture through the mixer occurs, the mixture gels in portions of the mixer and restricts flow, thus further slowing the discharge and resulting in the entire mixer being clogged with hard setting components. An improvement in slowing down the gel time is necessary to allow the mixture to progress through the system.

Generally, static mixers are in the form of a tubular chamber, with a rigid static mixing device disposed therein. Because of the very nature of the static mixer, the mixer cannot be cleaned readily once any appreciable quantity of material has gelled in the various mixing elements which form the static mixing device. Attempts have been made to clean the static mixer, but due to the cementing and interlocking effects of the material this approach has proven impractical. Therefore, available static mixers perform poorly in practice because the mixer may only be used, in some instances, for 15 to 30 minutes before “plugging-up”.

In place of the static mixer, a dynamic mixer may be employed with the aim of reducing the mixing time. While the results generally improve the quality of mixing, the temperature of the reaction mixture may be increased by frictional and shear heating, and local fractions of the mixture which can be generated in an advanced state of polymerization must be eliminated. Consequently, when dynamic mixers are used, significant improvements must be made towards controlling the exothermic temperatures. Additionally, caution must be taken to insure that the dynamic mixer does not introduce pockets of gas in the form of air bubbles into the moldable material, which may lead to poor quality. Moreover, dynamic mixers may require frequent flushing with solvents resulting in a sludge material which has to be disposed of.

In dispensing of a polyurea material a particular problem has been seen in maintaining or prolonging the dispensing time. A major problem exists in the accumulation of cured material in the dispensing tubes wherein the dispensing time is greatly reduced.

The present invention is directed to overcoming one or more of the problems as set forth above, particularly towards prolonging the dispensing time.

SUMMARY OF THE INVENTION

The present invention is directed to an apparatus for mixing and dispensing of urethane and urea components for application upon a golf ball sub-assembly. The apparatus comprises a rear mixing block for receiving at least two components, a system for pumping the urethane components through the mixing block, a mixer body having a middle portion that defines a bore extending axially along its longitudinal axis with a plastic disposable dynamic mixer element disposed in the bore for mixing the components, a temperature control chamber encompassing the mixer body for controlling heat generated by the exothermic reaction that is created when the urethane components combine and mix, and a nozzle assembly for dispensing the mixed urethane and urea components into a mold cavity containing the golf ball sub-assembly.

Employed in the present invention is a dynamic mixer element having a structure of multiple segments at a 90° relationship to each to create a tortuous and effective mixing path.

Another embodiment of the apparatus has for a temperature control chamber, a mixing housing encompassed by a cooling jacket. The mixing housing has a middle portion defining a bore extending axially therein with means disposed in the bore for mixing the components. The mixing housing has a helical groove extending generally about its outer perimeter and along the longitudinal length of the housing, and having a water inlet and a water outlet for permitting the cooling water to circulate about the housing. The cooling jacket surrounds the mixing housing in a relatively tight sealing relationship to the housing, and provides a means for controlling the heat generated by the exothermic reaction of the urethane components combining and mixing.

The present invention provides for a process to mix urethane reactive components into homogenous material. The process comprises pumping bulk materials through the apparatus wherein they are mixed by a plastic disposable mixer element, while the temperature of the mixing components (which emit a relatively large amount of heat due to their exothermic reaction), is controlled. The mixed urethane composition is dispensed into a golf ball mold cavity for forming around a golf ball sub-assembly.

The apparatus is completed by a nozzle assembly which utilizes pneumatic pressure to dispense via dispensing ports the mixed urethane components into mold cavities containing golf ball sub-assemblies. The nozzle assembly employs cartridge heaters and heating adaptors to heat the components such that drool is delayed or eliminated in the dispensing ports such that the dispensing time can be increased up to 5 hours.

DETAILED DESCRIPTION OF THE DISCLOSURE

Referring toFIGS. 1 to 3, an apparatus10of a hybrid urethane mixing system for producing a homogenous material from a mixture of a plurality of reactive components is shown. The apparatus10is comprised of four main portions: a mixing portion comprising of a mixer housing11, having a rear mixing block11a, and a front mixing block11b, and a mixer body12; a temperature control chamber13encompassing the mixer body12; and, a nozzle assembly14. The apparatus10utilizes a disposable plastic mixer element16(rotor). The apparatus10is designed to yield a more consistent product and enhanced temperature control for a urethane molding process for golf balls.

Advantageously, the present invention is directed to producing a flow moldable material from at least two castable urethane materials, such as urethanes, polyureas, and blends thereof. The materials need to be mixed, temperature controlled, and dispensed. In an embodiment of the invention, pumps (not shown) are provided to pump materials in pre-measured amounts into the apparatus through openings17aand17b, in the rear mixing block11awherein they have an initial mixing. The materials are then pumped through to the mixer body12which contains the disposable plastic mixer element (rotor)16that is rotated by attachment to a slotted drive shaft18. It is in the mixer body12where the primary mixing takes place.

The front mixing block11bhas an internal groove15having four apertures15afor quick disconnect to the mixer body12. At the rear end of the mixer body12are four raised ridges19which when inserted into the internal groove15through the apertures15athe connection is completed by merely rotating the mixer body12, within the internal groove15. The front mixing block11balso has four corner sections20that inherently define a large opening for receiving the temperature control chamber13which has four raised lip sections25disposed about its outer perimeter for easy insertion into four internal slots23defined in the four corner sections20for a quick disconnect fitting therein. A drive shaft18has a leading end slotted to allow a relatively easy friction fit coupling to the disposable mixer element16, which is dimensioned to fit within the slot of the drive shaft18without the use of tools. The dynamic mixer element16includes left and right hand helical elements that aggressively mix the material as the material is pumped through the mixer body12. The mixer body12is surrounded by an outer sleeve which forms the temperature control chamber13. Controlling the temperature is extremely necessary in order to control the heat generated by the exothermic reaction from the urethane components combining and mixing. For a cooling medium, water is introduced to the temperature control chamber13by a water inlet28in near proximity to the front mixing block11band is removed via a water outlet29near the other end of the temperature control chamber13. The water temperature control chamber13provides uniform process temperatures in the mixer body12which minimize “plating out” (build-up of cured material) on the dynamic mixer element16. With reduced plate-out, the rotor cycle time is increased and apparatus downtime is reduced.

A bracket assembly26consisting of an upper section26aand a lower section26bis clamped about the temperature control chamber13at the end nearer to a nozzle assembly14, and is coupled together by simple hex screws. This bracket assembly26forms a base that is connected to one end of an extended arm portion31of the nozzle assembly14. After the material passes through the mixer body12, it is then forced out of the nozzle assembly14through at least one dispensing port. For clarity two dispensing ports21aand21bare shown and described, wherein material is dispensed into a ball mold cavity to be applied about a golf ball sub-assembly (not shown). The dispensing ports21aand21bare seated in a fixture32which is connected to the other end of the extended arm portion31. The ports21aand21bare caused to move vertically into and out of the ball mold cavities by pneumatic pressure. This pressure propels a piston rod33, housed within a tube34, to move down into the golf ball mold cavity and gradually be raised out of the cavity as the castable polyurethane or urea material is deposited in the mold cavity. The temperature control chamber13has at one end, near to the nozzle assembly14, an insulating member36which is sandwiched between the temperature control chamber13and a relatively circle mounting member37. The mounting member37has a slotted recess38defined therein, and the insulating member36and mounting member37are coupled to the chamber13by hex screws39. The nozzle assembly14includes a dispensing tube housing35that holds the plastic tubing making up the dispensing tubes21aand21b. This is done by means of a simple hex screw40. The dispensing tube housing35includes a pair of ears41which are inserted into the slotted recess38of the mounting member37by a simple quick disconnect motion by the operator which requires only a manual rotation of the ears41within the slotted recess38.

The design of the mixing system minimizes exposure to urethane and urea raw materials by utilizing tool-free, quick-change components. The turn-to-lock connections and the slotted rotor drive shaft18are design features that make the operator's mixer maintenance tasks quicker and more efficient. The development of the quick-change mixer assembly provides for a reduction in the downtime necessary to service the apparatus10which requires frequent changing of the disposable mixer element16and even more frequent changing of the plastic tubing making up the dispensing ports21aand21bof the nozzle assembly14. The reduction in the mixer block mass allows for enhanced water temperature control along the entire length of the mixer rotor16resulting in better mixer performance and increased mixer life. Utilizing a disposable dynamic mixer element16eliminates the need for relatively expensive machined mixing rotors, which can require significant cleaning and maintenance. When cleaning non-disposable rotors, workers are often exposed to cleaning chemicals and sensitive urethane materials. The present invention, in using the disposable dynamic mixer element16, requires only that the mixer element16be periodically removed and discarded, and this generally eliminates any undesirable chemical exposure to workers. Frequent cleaning and repeated use of a permanent mixing rotor can often change the rotor mixing characteristics resulting in process variations due to rotor wear. The disposable dynamic mixer element16may be removed and replaced without the use of tools. This tool-free feature is very critical to the system, for in addition to the great reduction in downtime, it also eliminates the contamination of tools when such tools are required to service the mixer.

As shown inFIGS. 1 and 1a, the disposable plastic mixer element16generally is longer, smaller in diameter, and is less massive than non-disposable rotors. These features help to achieve improved temperature control. The mixer element16is disposed within a bore22that extends axially along the middle portion of the mixer body12. The mixer element16is constructed of a predetermined number of segments which have right and left-hand helical twists, and extend axially along the bore22. The segments are alternated and oriented such that one segment lies at 90° with respect to an adjacent segment. For example, one segment has an opposite helical twist and is shifted by a (radial) angle of 90° with respect to a preceding segment. Moreover, the mixer body12and the mixing segments define a tortuous mixing path which insure that the components are aggressively mixed The number of mixing segments comprising the dynamic mixer element16is dependent on the length of the bore22. The extra length of the mixer element16provides increased surface area for better mixing, but also provides for greater surface contact for the cooling water flow. The relatively small diameter of the mixer element16and mixer body12improve forward material flow through the mixer (first in/first out). The temperature control of the mixing components results in an improved cure rate (gel) control, and produces improved material processing properties such as smooth flow and excellent shot cut-off. The gel rate time of the material flowing through the present invention is controlled such that the gel time will be at least 60 seconds, and preferably at least 70 seconds. The temperature of the urethane material is maintained at less than 180° F., preferably at less than 150° F. The dynamic mixer element16is available from ConProTec, Inc. of Salem, N.H. under the trade name “STRATOMIX”®.

The apparatus10is completed by a three hole packing gland42inserted into the back of the rear mixing block11aand a lubricating chamber43and bearings44and45disposed within a bearing housing46support of the drive shaft18. The bearing hosing having a two-hole packing gland47insulating it from the lubricating chamber43. The apparatus10is made of parts that are generally stainless steel but it is appreciated that many various metals may be employed without affecting the structural integrity of the apparatus.

FIGS. 4 and 5disclose another embodiment of a temperature control chamber. This embodiment includes a cooled mixer chamber50comprising a mixing housing51encased in a cooling jacket52. A helical cooling channel53is spirally disposed about the mixing housing51, with the mixing housing51having a helical groove contour that extends around the length of its outer perimeter and provides a track for placement of the helical cooling channel53. The cooling jacket52has O-ring seals56disposed at each end to create a water tight seal between the jacket52and mixing housing51. The helical cooling channel53has an inlet opening54for introducing cooling water and an outlet opening55for removal of the heated water after it has passed through the cooling channel53. This provides positive and very efficient coolant flow over the length of the mixing housing51. This embodiment is especially beneficial for use with castable polyurethanes and urea components which are introduced into the mixing housing through receiving ports57aand57b.

FIGS. 6-14depict an embodiment wherein the dispensing tube housing35, the nozzle assembly14, and primarily the fixture32of the nozzle assembly14are substituted with a dispensing housing135that couples a nozzle framework114to the temperature control chamber13. The nozzle framework includes a heated support housing132that houses at least one dispensing port and may house multiple dispensing ports, while only a pair121a,121bare shown herein, and a capillary orifice148affixed to a distal end of each dispensing port121a,121b. The tubing forming the dispensing ports121aand121bare substantially disposed within channels138aand138bdefined in the metal body136of the heated support housing132(FIGS. 7 and 9). The dispensing housing135that connects the nozzle framework114to the temperature control chamber13includes a pair of ears141at the entrance to the manifold139. These ears141are similar to ears41described above, which are inserted into the slotted recess38of mounting member37by a simple quick disconnect motion by the operator which requires only a manual rotation of the ears41within the slotted recess38. The quick disconnect is essential towards achieving maximum production time efficiency.

As best shown inFIG. 7, the support housing132comprises a body136, a pair of side sections133aand133b, a pair of channels138aand138bwhich are defined by the body136and the side sections133a,133b, and wherein the dispensing ports121aand121bare disposed. The support housing132has a top portion134that is connected to the base136. The top portion has means for connecting to the extended arm potion31(FIG. 6). The support housing132may have an optional pair of support housing heaters142aand142bdisposed therein which are typically about 250W, 240V and about 0.25 inch in diameter (as best seen inFIG. 9). Although there is heating of the material in the temperature control chamber13, there is a significant advantage achieved by heating the dispensing ports121aand121bdirectly. The main reason for this is that the material resides in the temperature control chamber13for about 18 to 22 seconds, but it only resides in the heated support housing132for about 1 second. Therefore the bulk of the material is left unaffected and only that material actually being dispensed need be heated.

Prolonging the dispensing time for castable ball molding processes, especially materials such as light stable polyurea, is a production necessity. These dispensing times are inherently shortened by the onset of what is termed “drooling” after a certain amount of production time. Light stable ureas are especially prone to drooling. Drooling is a term used to describe a reaction which causes an inevitable build-up of material on the lid of the dispensing tube. As the material continues to build-up, it causes the diameter to inherently reduce in size. When the material is dispensed, it thus is forced through a smaller opening, and as it exits the dispensing ports121aand121b, there is a rapid decrease in pressure that results in an expansion of the material at the orifice. This is commonly referred to as die swell, which is defined as a percentage of the extrudate diameter. The casting material eventually adheres to the outer wall of the dispensing ports121aand121bresulting in a drool initiation site. When the pressure is removed at the decompression stage of the process, some of the material is sucked back into the dispensing ports, however, the drool initiation site remains. Over time, more of the material accumulates in this area resulting in a long, thick agglomeration. During the molding process the drool can be deposited on the parting line of the mold causing excessive clean-up issues, as well as potentially interfering with the mold closing. Another feature that the capillary provides is a clean cutoff of material when applied to a golf ball mold.

When polyethylene was used as the dispensing tubing material, it generally took a period of about 5 minutes before the mixed castable material started to drool out of the tubing ports. It is a key inventive concept that if heat of sufficient temperature is applied, then this 5 minute period can be extended by a significant amount of time. However, because of the high temperatures necessary to heat the material, the use of polyethylene as a material for the tubing was eliminated. The necessary physical characteristics needed for tubing include: a reduced coefficient of friction; an increase in thermal conductivity; and the ability to conduct heat to the material. It was determined that the dispensing time could be extended from 5 to 12 minutes by just changing the tubing material from polyethylene to fluorinated thermoplastics. By heating the fluorinated thermoplastic dispensing ports121aand121bwithin the heated support housing132to an elevated temperature range of 150° F. to about 350° F., a significant improvement was obtained towards prolonging the dispensing time before the onset of drooling. This use of fluorinated thermoplastic material in conjunction with the application of heat prolonged the dispensing time to about 1-2 hours. The choice of material is crucial in improving dispensing properties, and although fluorinated thermoplastics are preferred, such materials as seamless aluminum, copper, titanium, nickel, brass and silica-coated stainless steel are all improvements over the prior art.

The dispensing time is further prolonged by the use of heater adaptors143aand143bas part of the support housing132to further control the viscosity. Each adaptor143a,143b, consist of two hemispherical portions144aand144bwhich form a split sleeve which is mated over the outside diameter of one of the dispensing ports121aand121bas best shown inFIGS. 7 and 12. The adaptors143aand143bare held in place by heater bands145aand145band each adaptor is retained by a pair of screws146to facilitate the ease of handling. The outside diameter of each adaptor143a,143bis machined to the inside diameter of each heater band145a,145b. Each inside diameter of an adaptor is of a size to accommodate the outside diameter of one of the dispensing ports121a,121b. The outside diameter at one end of each adaptor143aor143bis slightly larger than the inside diameter of the heater band145. This diameter extends partially down the adaptor143a,143bto provide a ridge151that prevents an assembled adaptor143a,143b, from sliding completely through a heater band145a,145b. The outside diameter of the two hemispherical portions144aand144b, form a substantially circular cross section when mated over the outside diameter of one of the dispensing ports121a,121b, subsequently defining a circular split147which is typically symmetrical about the center line of the adaptor143aor143b. This allows for positive compression on the outside diameter of the dispensing port121a,121b, which is provided by the clamping action by one of the heater bands144a,144b. The adaptors143a,143bas described herein are best used for either metal dispensing ports.

When the capillary orifice148accommodates the dispensing tube121abeing made out of metal, one end (threaded portion149) of the dispensing tube is machined to accept a tapped thread in the dispensing tube121a. For the present application the opening at the distal end of the dispensing tube121ais machined to accept a 10-32 UNF thread, which would therein match the outside diameter of the capillary orifice148. The machined hole falls short of penetrating completely through the outer size to control the capillary length, L. The metal dispensing tube is threaded with a 10-32 UNF. The capillary orifice148is threaded on to the metal dispensing tube until it stops to complete the assembly. When the nozzles become fouled, they can easily be unscrewed and replaced with a new nozzle.

FIGS. 11-12show a capillary orifice148typically consisting of a metal body having a threaded portion149on one end to attach to the distal end of dispensing ports121a,121b, and a machined capillary portion150at the other end which is designed to penetrate into the pressure drop area. The diameter of the capillary portion150can be sized as desired but is typically smaller than the dispensing port121a, or121b. However, it must be sized to provide free flowing of material and the stated benefits without creating excessive back pressure that can cause mixer seal failure. The capillary orifice148helps minimize material build-up, resulting drool, and improves cut-off of the material after it has been deposited in the mold casing.

While the dispensing ports121a,121b, may be made from metal as described above, the dispensing ports121a,121bare preferably made of a fluorinated thermoplastic having a continuous use temperature of about 450° F. to 500° F. At these temperatures fluorinated thermoplastic may soften slightly but will not melt. By adding heat to the tip of the dispensing ports121a,121b, urea and urethane drooling is significantly reduced or eliminated for greater than 2 hours of production time. Typically the dispensing ports121a,121b, are small in diameter; typically about 0.187 inch.

FIGS. 13 and 14describe an embodiment that utilizes a split adaptor155that comprises a base portion156and a clamping portion157. The capillary section159is defined into a bottom section of the base portion156. Semi-circular recesses158are defined each portion156and157, and when the two portions are combined, they form a groove158for housing the distal end of a fluorinated thermoplastic dispensing port121a. It is to be appreciated that the groove158and dispensing ports121aand121bmay take other shapes than the circular shown herein, and still be effective.

The use of a capillary orifice helps to reduce the area wherein cured material stagnates to produce a drool initiation site. It also increases the pressure at the orifice to help push out any cured material and makes the decompression more effective by limiting the amount of material to be “sucked back” into the pressure reduction area. In addition to reducing die swell due to a small diameter of extrudate, capillary orifices also increase the shear rate at the dispensing port orifice, which reduces the viscosity of polyurethane and polyurea. In addition, the use of capillary orifices provide better control of the viscosity and improve cut-off.

The combination of using support housing heaters142aand142b, heater adaptors143a,143b, capillary orifices148, and fluorinated thermoplastic material for forming the dispensing ports121aand121b, can prolong the dispensing time before the onset of drool of the dispensing ports121a,121bfrom about 5 minutes to about 5 hours.

While it is apparent that the illustrative embodiments of the invention herein disclosed fulfill the objective stated above, it will be appreciated that numerous modifications and other embodiments may be devised by those skilled in the art. Therefore, it will be understood that the appended claims are intended to cover all such modifications and embodiments which come within the spirit and scope of the present invention.