The present invention is a machine for manufacturing thermoplastic tubes from thermoplastic sleeves.
The machinery commonly used today for making finished, headed thermoplastic tubes from 2 to 10 inches in length and from xc2xd inch to 3 inches in diameter comprises a series of machines arranged linearly and having a total process line length of about 80 to 100 feet and a total height of about 20 to 30 feet. Process lines of such dimensions are housed in factories often having several acres of floor space.
A conventional process line for producing a single type of thermoplastic tube in today""s manufacturing plants includes machines for heating raw polymer material into molten plastic; extruding the molten plastic through a die to form an extruded, stretched hollow body; cooling and then cutting the hollow body into sleeves of equal lengths; transporting the sleeves to a machine for molding a head on one end of the sleeves to form headed tubes; transporting the headed tubes to another machine for decorating or applying a graphic to the headed tubes; transporting the printed tubes to yet another machine for applying a coating; transporting the printed tubes to a different machine for applying a cap to the headed end of the tubes and transporting the capped tubes to a final machine for unloading the tubes from the process line. The removed tubes are then packed for inventory or shipment. Such a process line requires at least four workers during operation, with one worker at the extrusion machine, at least two workers along the line to monitor the tube conveyors and other various machines and a final worker to pack the finished tubes at the end of the line.
Increasing size has dominated production equipment design in an effort to take advantage of economies associated with large size. A conventional process line can simultaneously handle several hundred tubes in different stages of production. While some production advantages can be achieved by large size, many limitations exist, even in view of the giant size of the machinery.
Conventional process lines have inherent manufacturing inefficiencies dictated by several factors such as those associated with the line machinery itself namely: large scale, mechanical operation, and process limitations as well as other inefficiencies like unit cost limitations. Manufacturing inefficiencies, like those described below, are serious barriers which ultimately can limit the varieties of tubes available in the market.
Large scale processing machines have land, capital, and labor requirements, the costs of which are high. Additionally, large scale equipment is complex and as a result it requires more labor and higher skilled labor to operate and maintain. Most importantly, large scale design does not necessarily improve total efficiency. While production capacity may be increased, it may be done at the cost of efficiency. Complex machines require a significant amount of capital, time and labor input which can mean low overall efficiency when compared to the output.
The mechanical operation of conventional line machinery can add inefficiency to the manufacturing process. Process line down-time is inevitable because of the mechanical constraints of current machinery. For example, about 70% to 80% of line down-time is attributable to the tube and sleeve conveyor systems. One process line will have several transport systems, each system typically being a long chain with tube holding mandrels spaced every couple of inches, wrapped around many drive gears. These chain systems easily become jammed, frequently deliver improperly positioned articles to the process machinery and often need to be stopped for adjustment and resetting. As a result of stopping one transport system, the entire manufacturing line must be shut down.
Line down-time results in production loss. If one of the processing machines on the line malfunctions on the night shift, for example, when an engineer is not available to correct the problem, the entire line will be stopped and it will remain idle until morning. This loss is inefficient and costly to a manufacturer.
The inflexibility of the production equipment creates inherent constraints on the manufacturing process. Line equipment cannot easily be rearranged to effectuate different manufacturing processes because the individual machines weigh several thousands of pounds and are not readily mobile. Furthermore, large scale machines are built for a single purpose and are limited to that purpose. For example, offset printing machines are limited to printing articles by the offset printing method. Thus the arrangement of production equipment limits the number of processing methods available to a manufacturer.
Process control for monitoring and controlling the quality of each individual tube product is not commercially available for adaption to current machinery. For example, there is no known practical way to identify, monitor and track defective products during the manufacturing process. Defective products are removed only at the end of the line. When a defect occurs on a tube at the beginning of the line, continued processing of that tube is inefficient since the tube will eventually be discarded.
Because an 80 to 100 foot tube production line requires at least four laborers per shift, has a predictable defect rate, requires time to retool for each job and costs money even to remain idle, it creates a high manufacturing cost that can only be lowered by large production jobs. It is a waste of resources to manufacture small numbers of tubes on such large machinery because the manufacturing cost per tube is too high. Conventional process lines can be limited to certain size manufacturing jobs in order to recapture manufacturing costs.
While the output of a single machine of the present invention does not compare to the production capacity achieved by one conventional 80 to 100 foot processing line, if the output of one simple efficient machine is multiplied by the use of a series of such machines, then the total output of the series of machines can rival the conventional process lines. Thus, where efficiency is maximized and multiplied, a great number of thermoplastic tubes may be produced.
It is the principle object of the invention to provide a machine for manufacturing thermoplastic tubes that more efficiently uses land, labor and capital, as compared to conventional manufacturing machines.
It is an object of the present invention to provide a flexible machine for manufacturing thermoplastic tubes to accommodate different manufacturing process methods.
It is a another object of the present invention to provide a machine for manufacturing thermoplastic tubes which can mark, identify, index and track every thermoplastic article being handled.
It is still another object of the present invention to provide a machine for manufacturing thermoplastic tubes which can be associated with other similar machines of the present invention.
It is yet another object of the present invention to provide a machine that provides an operating environment substantially free of contaminants, such as dirt and dust, for manufacturing thermoplastic tubes suitable for the pharmaceutical industry.
It is a further object of the present invention to provide a machine for manufacturing thermoplastic tubes of improved quality.
It is yet a further object of the present invention to provide a machine for manufacturing thermoplastic tubes which can manufacture large numbers of tubes as well as small numbers of tubes at similar operational costs.
It is still a further object of the present invention to provide a machine for manufacturing thermoplastic tubes which can be operably associated with a programmable logic controller.
It is a specific object of the present invention to provide a machine for manufacturing thermoplastic tubes which can monitor and confirm the integrity of each manufacturing process step.
It is another specific object of the invention to provide a single machine for the production of thermoplastic tubes which can fit into a 4xc3x974 foot area.
Other objects, features and advantages of the present invention will become apparent from the following detailed description taken in conjunction with the accompanying drawings.
The machine of the present invention manufactures thermoplastic tubes from thermoplastic sleeves by a variety of different process methods. The machine has an indexing device with a plurality of mandrels for holding thermoplastic sleeves for the purpose of transporting the same around a closed manufacturing path. The manufacturing path of the machine of the present invention comprises a series of manufacturing stations which have mechanical devices for carrying out the manufacturing steps necessary to produce tubes from blank sleeves.
The manufacturing stations of the manufacturing path are modular so that they may be removed, added or rearranged; the stations may be optionally connected to a programmable logic controller (PLC) and may optionally have sensors for information feedback to the PLC device. The flexibility to add, remove or rearrange manufacturing stations gives the machine of the present invention the capacity to carry out a variety of different manufacturing process methods for making thermoplastic tubes. Further, with the addition of at least one PLC device, the machine can be operated by feedback control and can be associated with other similar machines.
The machine of the present invention overcomes the aforementioned disadvantages of the conventional process lines for manufacturing thermoplastic tubes. The machine is itself more mechanically efficient than a conventional process line. For example, it utilizes a single indexing device, a few feet in diameter at its maximum, which serves the same purpose as the 100 foot or longer transportation system of conventional process lines. The machine has modular manufacturing stations which can be added, removed or rearranged to create a variety of different manufacturing processes and the stations are simplistic in design which lowers the necessary capital and labor inputs. Furthermore, accurate process control may be added to the machines which creates labor savings, improves efficiency and reduces product waste.