Patent Application
20180056552
The invention relates to the production of dipped products of elastomeric material. In particular, the invention relates to the means of drying and curing the elastomer to form the glove and other dipped products whilst it is on the former assembly.
The production of elastomeric gloves and other dipped products involves a conveyor or batch system having a plurality of formers attached. The formers passes through various stages including a dipping stage where the glove formers are dipped within a liquid elastomeric resin, an oven stage for drying and curing the elastomeric film and an extended drying stage.
It is the oven stage to which the present invention is directed. The conventional oven comprises a heating source for elevating the space within the oven to a sufficient temperature to both heat the resin so as to cure the gloves, for example, and maintain the oven at a temperature to prevent “cold spots” developing that may affect the curing process. The length of the oven is determined as a function of the speed the conveyor and the time required to cure the resin. Maximizing the rate of production of the gloves requires the conveyor to be travelling at a high speed, and so the length of the oven, to ensure sufficient curing time, needs to be of considerable length, and consequently, requires heating of a considerable volume within the oven. It follows that the energy required to heat this volume is also considerable.
By volume, the gloves and other dipped products, represent an extremely small proportion of the space within an oven. Therefore, the actual energy used to cure the resin, as compared to the energy required to maintain the temperature of the oven is also extremely small. It is estimated that the energy required to heat the oven is in the range of 90 to 95% of the total heat used. That is, the actual energy to cure the resin is only about 5 to 10% of the total energy. The cost of the wasted energy represents a significant cost of the manufacture of the glove, which is ultimately dissipated to the environment.
It follows, therefore, that any reduction or saving in this wasted energy will have a direct effect on the cost of the glove manufacture, and so provide a significant commercial advantage.
In a first aspect, the invention provides a former assembly for the manufacture of dip product, the assembly comprising: a thermally conductive outer layer in the shape of said product, said outer layer arranged to receive a film of elastomer; a mounting for mounting said former assembly to a former holder for engagement with a conveyor chain; a heating medium within said outer layer, said heating medium in communication with an energy source for heating said medium; wherein said heating medium arranged to apply heat through said outer layer so as to cure said resin.
By providing a separate heat source within each former, the ovens can be discarded from the conveyor line leading to two substantial advantages. First and foremost, the energy required to cure the glove using the system according to the present invention is only 5 to 10% of that of a prior art system. Further, the infrastructure cost in removing the ovens may lead to a substantial reduction in the amortized cost of the manufacturing plant.
Further, the length of the conveyor line may also be substantially reduced, as there is no specific length of conveyor required for the oven stage.
Further still, the gloves may be cured at a temperature controlled by the operator at a much higher efficiency than that compared to the prior art. Whereas the prior art systems can waste in a range 90% to 95% of the generated heat to the atmosphere, it is effectively impossible to optimize the amount of energy used to cure each glove. By using a system according to the present invention, the optimal amount of energy to cure each glove may be selected and so in addition to the gross savings from adopting the present invention compared to the prior art, the ability to fine tune the energy output may also be available.
In a second aspect the invention provides a method of manufacturing a former assembly comprising the steps of: forming a thermally conductive outer layer in the shape of a dip product, said outer layer having an inner surface, and an outer surface arranged to receive a film of elastomer; forming an electrically conductive layer on said inner surface; placing a pair of resistive patterned tracks on said electrically conductive layer; connecting said pair of resistive patterned tracks to an electrical power supply; electrically connecting said pair via an intermediate portion of said electrically conducting layer and, generating resistive heat from said intermediate portion for curing said elastomer.
In a third aspect the invention provides a former assembly for the manufacture of dip product, the assembly comprising: a thermally conductive outer layer in the shape of said product and having an inner and outer surface, said outer layer arranged to receive a film of elastomer; an electrically conductive layer on said inner surface; a pair of resistive patterned tracks on said electrically conductive layer and in communication with an electrical power supply; wherein said pair of resistive patterned tracks is arranged to permit selective heat distribution across said former assembly for curing said elastomer.
Relative to known methods, the present invention provides means for manufacturing a former assembly which is capable of generating resistive heat with minimal electrical conducting material mass. The significant reduction in material mass simplifies design and methods of manufacturing former assemblies. It follows that capital investment and long term operating cost may therefore be reduced.
In one embodiment, the placing step further includes the steps of varying one or more dimensions of said pair of resistive patterned tracks at pre-determined areas of said outer layer, and so varying a distribution of heat about said electrically conductive layer.
In alternative embodiments, said resistive patterned tracks are formed using electro-deposition.
The present invention provides a means for varying and fine tuning the distribution of heat about the electrically conductive layer for drying and curing the elastomeric film. It may be appreciated that the heat provided, as a result of electrical connection between the pair of resistive patterned tracks and the electrically conductive layer, may be transferred to the elastomer formed on the outer layer or outer shell so as to dry and cure the elastomer. Further, heat distributed within a former assembly may be varied by changing or varying the dimensions, such as thickness, width and length, of the resistive patterned tracks at pre-determined or targeted areas of the outer layer. For instance, a thin layer of the resistive patterned track may be placed at pre-determined area of the electrically conducting layer if lesser heat distribution is desired. Alternatively, a resistive patterned track will not be placed within a pre-determined area of the electrically conductive layer if no heat is desired. Further, additional pairs of resistive patterned tracks may be deposited at areas where a greater heat intensity and distribution are desired. It will be appreciated that the arrangement of resistive patterned tracks on electrically conductive layers may be customized according to requirements of an intended application.
The present invention is thus advantageous relative to the prior art because of the ability to fine tune the energy output provided for the manufacturing dip products. This may in turn translate to one or a combination of the following benefits:
It will be convenient to further describe the present invention with respect to the accompanying drawings that illustrate possible arrangements of the invention. Other arrangements of the invention are possible and consequently, the particularity of the accompanying drawings is not to be understood as superseding the generality of the preceding description of the invention.
In describing the preferred embodiments of the invention, specific terminology will be resorted to for the sake of clarity. However, it is not intended that the invention be limited to the specific terms so selected and it is to be understood that each specific term includes all technical equivalents that operate in a similar manner to accomplish a similar purpose. Combination of the various embodiments of the present invention as described herein may also be used depending on specific facility requirements.
The following description will refer to the invention applied to the manufacture of gloves, for convenience. It will be recognised that the invention may be applied to any dip product, including condoms, probe sheaths and other such objects formed by moulds dipping into an elastomer bath. Accordingly, the reference to glove manufacture is not to be read as limiting the application of the invention.
The core invention involves providing a heating medium within a glove former assembly so as to transfer heat from the heating medium within the assembly to the elastomer formed on the outer layer, which may be an outer shell, of the former so as to dry and cure the glove. This is contrast to passing the glove former assembly through an oven heated to a temperature to not only cure the elastomeric glove film but also to maintain heat within the oven to a degree beyond that required for the resin curing.
In achieving the invention, one embodiment may include applying an electrically conductive coating to an injection molded thermo-plastic former, then forming patterned tracks in a cavity of the former in a 3 dimensional configuration so as to have an internally positioned electrically resistive heater.
Such heating sources will depend upon the heating medium, and may include a convective heat source such as a flowing hot liquid medium, for instance water, or a conductive heat source such as heating a gel resident within the outer shell. In this case, there may be a thermally conductive member intermediate the heating source and the gel to transfer heat directly. In either case, access to the inner portion of the outer layer/shell may be through the cuff 20. This may require a modification of the holder (not shown), such as by providing an annular rotatable ring, and passing the heating conduit through said ring. Other means of heating the glove former assembly may include various forms of electrical heating as will be described with reference to further embodiments.
The outer shell/layer 5 may be of thermally conductive materials, such as modified Polyphenylene Sulfide (PPS), modified Glass Reinforced Plastic (GRP) or a ceramic material sufficient to efficiently conduct heat from the heat source to the elastomeric coating the outer layer
As can be seen, a busbar configuration 55, 60 is distributed throughout the inner core 35 with an isolating strip 50 for isolating the busbar arrays. In this embodiment, the busbars are arranged as elongate filaments positioned in parallel with alternating positive and negative strips. The busbars are connected at an extreme point (not shown) of the former. By applying a current from an electrical power supply (not shown) to the busbars 55, 60, resistive heat is generated, with the greater the concentration of filaments, the higher the heat generated. The resistive heat is then communicated to the outer layer (not shown) so as to heat the glove. An advantage of this arrangement is the ability to place busbars 60 at the extremities through the fingers of the glove, because of the fine arrangement of the filaments, so as to ensure uniform curing of the glove. The busbars may be placed and adhered to the surface of the core. Alternatively, they may be added as a composite within an injected moulded section. A still further alternative may include a damascene construction, whereby the busbars are placed within corresponding recesses within the internal core surface.
In one embodiment, the electrical power supply may operate in the range 5 to 50 volts, and possibly in the narrower range 10 to 30 volts. In so doing, the design system may operate at a low voltage high current. Accordingly, the electrical output is arranged to be at a safe level for human interaction.
In a still further embodiment, the heating medium may be integral with the outer layer/outer shell. For convenience, in this arrangement, the busbars may be placed on an inside face of the former. In this case, the medium may include a substantial portion of the thickness of the former. In certain circumstances, the outer shell and medium may be visually indistinguishable, with the external directed heat transfer from the busbars to the elastomer on an outer surface of the outer shell indicating the notional position of the medium.
Whereas
Whilst
It will be appreciated that whilst the embodiment of
The busbars 70, 80 are connected to polarity rings 75, 85, for instance with a negative polarity ring 75 connected to the negative busbars 70 which are returned through the electrically conductive layer 130 to the positive polarity ring 85 via the positive busbars 80.
Between halves of the inner core is provided a positive polarity common ring main plate 55 being a plate of conductive metal such as aluminium, copper, steel etc. The electrically conductive plate 55 is to connect the positive polarities.
Here the internal core (not shown) receives a power supply through the polarity rings 145, 150 through electrically conductive tracks 155, 160 specifically a negative track 170 and a positive track 165. The polarity rings remain in contact with the tracks, and so act to rotate the glove formers in the same way the former holder at different stages within the conveyor system engage a separate track in order to rotate the holders. Thus, the means of providing a power supply to the inner core is seamlessly introduced into the conventional design for a glove system to rotate the gloves as required.
It will be appreciated that the first and/or second busbar layers may be filament arranged layers sufficient to be electrically or thermally conductive. Alternatively, and as shown in
Further, it will be appreciated that the heat generating layer may be continuous, in that it substantial coats the former. Alternatively, the heat generating layer may be a discontinuous layer, such as an array of discrete “patches” placed about the former.
Disposed immediately underneath the first busbar layer 604 is the heat generating layer 606, which is a mixture of carbon nanotube graphite and ceramic power that exhibits Positive Temperature Coefficient (PTC) properties. An example of the ceramic powder, but not limited only to the described, is Barium Titanate, which is mixed in a ratio of approximately between 2% to 40%, preferably 3% to 35% and most preferably 5% to 20% (calculated by weight to weight basis of fine Barium Titanate powder) with the carbon nanotube graphite, and the resulting mixture is then bended and heat cured to form the heat generating layer 606. It is to be appreciated that the heat generating layer 606 is a solid integral layer and is about 1-2 mm thick. In addition, the heat generating layer 606 is arranged intermediate between the first and second busbar layers 604, 608, as will be appreciated from
Further, immediately underneath the heat generating layer 606 is the second busbar layer 608, which is materially and structurally similar to the first bus bar layer 604, except that the second busbar layer 608 is electrically arranged with a negative polarity (i.e. “−VE”). The first and second busbar layers 604, 608 are collectively electrically connected to an electrical power source (not shown) in order to provide the necessary electrically energy to energise the heat generating layer 606 for generating heat. In other words, the heating generating layer 606 is thus a heat generating medium. Finally, at the bottom most layer of the internal layer arrangements 602-610 of
Further, it is to be appreciated that the heat insulting layer 610 may alternatively be in the form of a coating, rather than being formed as an integral layer.
Advantages of the internal layer arrangements 602-610 of
In a further embodiment, the methods of manufacturing 900, 940 may include the step of trimming and disposing 925 of the electrically conductive layer or areas formed in excess on the outer layer. In this embodiment, a multi-axis machining equipment may be provided for this purpose. The multi-axis machining equipment may be a standard device such as a multi-axis CNC (Computer Numerical Cutting) router or a laser engraving head, for instance, a device used for fibre laser marking. Such a laser engraving head may be programme to form the pre-determined shapes required for the specific patterns parallel to the required resistive track patterns within the thermally conductive shell. This step 925 may take place prior to placing 930 the pair of resistive patterned tracks on the electrical conductive layer.
According to one embodiment of the present invention, the thermally conducting layer may be an electrically conductive polymer. In this embodiment, the thermally conducting materials may include any one or a combination of thermal conducting materials such as modified nylon.
In an alternative embodiment, the thickness of the thermally conductive outer layer may be within the range of 1.5 to 4 mm. It may be appreciated that the thickness of the outer layer may vary according to the structural and strength requirements of an intended application.
In other embodiments, the thermal conductivity range of the thermally conductive outer layer or shell is within the range 2 to 15 W·m−1·K−1.
In any of the various embodiments, the pair of resistive patterned tracks may be electrically conductive busbar layers.
In a further embodiment, the pair of resistive patterned tracks may be formed using electro-deposition.
According to one embodiment, the electrically conductive layer may include any one or a combination of the following electrically conductive materials: silver, nickel, copper, aluminium, zinc and graphite. In addition, it may be appreciated that the thickness of the electrically conductive layer applied or formed on the outer layer may vary according to the type of material employed and further, the electrical conductivity requirements of an intended application.
In a further embodiment, the electrically conductive layer may be a mixture in paste form. Alternatively, the electrically conductive layer may be in solution form which makes it suitable for spray techniques commonly employed in the manufacture of former assemblies.
In an alternative embodiment, the thermally conductive outer layer is formed using injection molding.
In another embodiment, the electrically conductive layer may be formed using spraying techniques. In the case of an electrically conductive layer, this may be formed using a thermal spraying method, for instance, an arc wire spray method, and so a controlled electrical conductivity and resistivity balance may be required. For example, this may be achieved using a Nichrome (such as in the alloy 80% nickel, 20% chromium) based material, to act as the heater element layer and patterned accordingly to form the resistive tracks later.
Similar to the embodiments discussed in the preceding paragraphs, the outer layer may comprise an outer shell in two halves 990, 997. Further, the two halves may be permanently sealed, such as through heat sealing or vibrational welding or releasably engaged to provide maintenance to the internal heating medium.
The pair of resistive patterned tracks 1005 placed on the electrically conductive layer 1000 of a glove former shell assembly 970 may be more clearly seen in
The dipping form of the present invention finds ready industrial application in the glove making industry. With suitable modifications it is also suitable for the condom and balloon making industries and other industries where thin elastic material are made that require heating for drying and curing.
Those skilled in the art will appreciate that various modifications may be made to the present invention without departing from the inventive concept behind the invention. The embodiments of the invention described herein are only meant to facilitate understanding of the invention and should not be construed as limiting the invention to those embodiments only. Those skilled in the art will appreciate that the embodiments of the invention described herein are susceptible to variations and modifications other than those specifically described. It is to be understood that the invention includes all such variations and modifications that fall within the scope of the inventive concept behind the invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| PI2015000677 | Mar 2015 | MY | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/MY2016/000010 | 3/9/2016 | WO | 00 |
