Patent Application
20120204695
The invention relates to an apparatus for punching openings in multi-layer materials. In particular, the invention relates to punches for use in the manufacture of electrochemical test strips.
Designs for test strips suitable for measuring the concentration of an analyte, such as glucose, in a body fluid sample are well known. Typically, these strips have multiple material layers and are manufactured using a continuous web-manufacturing process. In the manufacture of the test strips, it is necessary to punch openings into the multilayer strip in order to produce one or more openings within the strip. For example, one known strip configuration provides a spacer, having an adhesive on one or both surfaces, sandwiched between two layers of metal-coated polyester. When this multi-layer material is processed through a punch tool to create the needed openings within the materials, heat is generated by the punch tool, which heat increases as the process run-time increases. The heat reaches a temperature at which it melts some of the adhesive, which is then transferred to the punch tool resulting in restriction of the punch movement through the guide plate, material and die. As the adhesive continues to accumulate, the tool may become damaged. To avoid this, the manufacturing process must be stopped periodically to enable the punch tool to be stripped down and cleaned interrupting production of a full batch of test strips. This production line down-time results in a significant yield loss.
a is an exploded view of the punch tool of
The invention provides a punch tool apparatus, and process for manufacturing using the punch tool, in which accumulation of adhesive from the material being cut is minimized. The punch tool of the invention may find its greatest utility in the manufacture of multi-layer materials, such as electrochemical-based test strips, in which an opening must be cut into the material.
It is a discovery of the invention that, by reducing the production of heat during the running of the punch tool, the accumulation of adhesive on the punch tool may be minimized providing higher process yields and extending the life of the tool. In the tool of the invention, heat reduction is achieved by cooling the tool using a water cooling system. Additionally, and preferably, the punch tool incorporates a spring-loaded top plate to minimize vertical movement of the material passing through the tool during the punching process and reducing friction and heat within the tool. Still additionally and preferably, the punches used in the tool are coated. Finally and more preferably, the tool of the invention additionally includes a device for monitoring the punching force providing a method for detecting increases in friction before the tool or web material is damaged.
In
Top plate 11, guide plate 12, die 13 and bottom plate 14 are mounted on pillars 28. Except for the bottom plate and die, each of these parts moves upwardly and downwardly along the pillars as the punching process takes place. Preferably, there are four pillars provided to maintain the alignment of the guide plate and punches to the die plate. The tool may be driven upwardly and downwardly on the pillars by any suitable drive mechanism including, without limitation, an eccentric cam and a precision servo mechanism. Typically, the drive mechanism must be suitable to generate a force in excess of 6400 N.
A plurality of punches 35, as shown in
As top plate 11 reciprocates upwardly and downwardly, each of the plurality of punches passes through one of a plurality of openings 27, as shown in
Top plate 11 is spring-loaded onto guide plate 12. Preferably and as shown in
The springs act to hold the web stable during the punch process reducing friction and heat generation. Guide plate 12 is pushed downwardly by the springs during the punch cycle onto a fixed stop, the thickness of which stop may be altered to reduce the clearance between the web and guide plate. In this way, guide plate 12 serves as a ceiling to prevent excessive distortion in the material. That is, the guide plate moves downwardly, preferably to within about 20 mu of the top surface of the web material. This acts to reduce the punch force needed and reduces hear build-up in the tool.
As shown in
The web of material 25 passes over the top surface of die plate 13, which plate sits atop of bottom plate 14. Bottom plate r 14 supports the assembly of the die plate, guide plate and top plate during punching of the web material. Top surface of die plate 13 has a plurality of recesses 36 therein, the position of each of which openings corresponds to an opening within guide plate 12 so that, as a punch penetrates through the web material, the recess accepts the punches. Preferably, these waste slugs are removed from the tool by any convenient method such as by vacuum. Cut-out 37 in the bottom plate permits waste slugs to be extracted after the punches have passed through the web.
With reference to
During operation of the punch tool, cooling water at a temperature of about 5 to about 18° C. flowing at a rate of up to about 60 liters per minute and at a maximum pressure of about 3.8 bar flows into channels within the interior of each of the top plate, guide plate, die plate and bottom plate. A direction that the flow of water may take is shown by the arrows in
The punch tool of the invention may be used in any suitable manufacturing process including a process for manufacturing a test strip or measuring one or more analytes in blood. Using the enzyme ink of the invention may be manufactured using any convenient, known method including, without limitation, web printing, screen printing and combinations thereof. For example, the strip may be manufactured by sequential, aligned formation of three layers, or films; two outer layers each coated on one side with a metal and forming the electrodes and a middle layer, spacer layer coated with adhesive on one or both sides.
An exemplary manufacturing process is as follows. The substrate used for each of the layers may be nylon, polycarbonate, polyimide, polyvinyl chloride, polyethylene, polypropylene, glycolated polyester, polyester and combinations thereof. Preferably, the substrate is a polyester, more preferably MELINEX™, manufactured by DuPont Teijin Films. One or more of the two substrates forming the outer layers may be coated to improves stability as for example by application of a sodium 2-mercapto-ethane-sulphonate coating as well as being preconditioned to reduce the amount of expansion and stretch that can occur in the strip manufacturing process.
Metals, such as gold or palladium or any combination thereof, may be sputtered onto the substrate surface. Additionally, reagents that react with the analyte to be measured and that help to generate a current signal are dispensed onto, for example, the palladium surface. The two outer layers are then laminated to the middle layer.
This processing takes place using continuous rolls, or webs, of the various materials and results in a roll of the laminated materials. This laminated roll is then sent through the punch tool as well as a through a cutting machine for formation of the individual test strips.
