Patent Description:
There are many prior art bag making machines. Generally, bag making machines seal one or more layers of film to form the bags. Often times the seals are made use a seal bar that receives hot air in the seal bar. The hot air raises the temperature of the seal bar so that it can melt the film to form the seal. One style of bag machine is a rotary drum bag machine, which typically has an input section, a sealing section and an output section. A controller controls the bag machine. Input section, as used herein, refers to the portion of a bag machine where the web is received and/or provided to the sealing section, such as an unwind and a dancer assembly. Sealing section, as used herein, refers to the section of the machine where the seals are formed. Output section, as used herein, includes assemblies that act on a web downstream of the seals being formed, such as perforators, winders, folders, etc. Controller, as used herein, refers to hardware and/or software that controls one or more aspects of a bag machine in response to user inputs and/or feedback, and may be located in one place, or distributed over several locations.

One commercially successful prior art bag machine is the CMD™ <NUM> Global Drawtape System™. Descriptions of that prior art, and similar prior art, may be found in: <CIT>; <CIT>; <CIT>; <CIT>; <CIT>; <CIT>; <CIT>; <CIT>;<CIT>; <CIT>. The disclosure below will be described in the context of this prior art, although the invention may be implemented in other bag making machines, and using other methods.

<FIG> shows a typical prior art bag machine. A detailed description of the operation of rotary bag machines may be found in the patents referenced above, but their general operation may be see with respect to <FIG>. A rotary bag machine <NUM> continuously processes a web or film <NUM> using a dancer assembly <NUM>, a pair of drum- in rolls <NUM> and <NUM> (<NUM>-<NUM> are part of an input section), a sealing section including sealing drum <NUM>, a pair of drum-out rolls <NUM> and <NUM>, a sealing blanket <NUM>, a pair of knife-in rolls <NUM> and <NUM>, a knife <NUM> (which could be any other web processing device such as a perforator, knife, die cutter, punching station, or folding station), a pair of knife-out rolls <NUM> and <NUM> (<NUM>-<NUM> are part of an output section), and a controller <NUM>.

The web is provided through dancer assembly <NUM> to drum <NUM>. Drum <NUM> includes a plurality of seal bars <NUM>. The seals bars are heated and create the seals forming the bags from web <NUM>. Web <NUM> is held against drum <NUM> (and the seals bars) by a Teflon® coated blanket. The distance between seals created by the drum is related to the bag length (for bags formed end to end) or the bag width (for bags formed by making side seals). End to end bags are formed with one seal from the drum, and side to side bags are formed with a pair of seals. The drum diameter may be adjusted and/or less than all of the seal bars turned on to determine the distance between seals, and hence bag size.

The machine of <FIG> provides that after web <NUM> leaves drum <NUM> it is directed to rotary knife <NUM>, which creates a perforation between bags, or could separate adjoining bags. Some bag machines create the perforation when the seal is being created, instead of using rotary knife <NUM>.

Controller <NUM> is connected to the various components to control speed, position, etc..

Bag machines with air heated seal bars typically have a plenum or heater block that provides heated air to a manifold in the seal bar. The heated air either heats the seal bar which heats the film, or the heated air is directed through openings in the seal bar toward the film to directly heat the film. Seals are formed more consistently when the heated air is maintained at a desired temperature. Prior art bag machines typically have a controller that receives feedback of the temperature of the air in the heater. That feedback is used to regulate the heating of the air. However, the temperature of the air that is delivered to the film, rather than in the heater, should be maintained at a desired temperature to consistently form seals.

<FIG> is a diagram of a prior art seal bar and related components. A source of compressed air provides air through a pressure regulator <NUM> to a pair of heater blocks <NUM> and <NUM>. A pair of thermocouples <NUM> and <NUM> in heater blocks <NUM> and <NUM> provide thermal feedback to a controller comprised of modules <NUM> and <NUM>. Controller <NUM>, <NUM> and <NUM> can be considered parts of a single controller, or can be considered individual controllers. The heated air is provided through restrictions to a manifold <NUM>. The placement of thermocouples <NUM> and <NUM> in the heater blocks means that the control is based on heater block air temperature, not manifold air temperature. Thus, any temperature differences between the heater blocks and manifold results in inaccurate control.

The plenum or heater block and manifold/bar in prior art bag machines typically are not insulated. This results in heat loss which reduces efficiency and requires more time to bring the seal bar up to temperature when starting the machine. For example, a start up time of <NUM> minutes is typical. Heat loss also exacerbates the problems caused by sensing heater block air temperature, rather than manifold air temperature.

The air in the manifold is directed to the film as indicated by the arrows, and the film is located under the arrows. The smaller center arrows indicate less air flow in the center of the manifold. Prior art bag machines with air heated seal bars typically do not deliver the same air flow to all portions of the seal bar. However, seals could be better formed if the air flow to different portions of the bar was evenly distributed or controlled in a desired manner.

Accordingly, a bag machine that regulates the temperature of air in or near the seal bar and/or manifold is desired. Preferably the bag machine provides a reduced start-up time. Preferably air flow is provided evenly to different portions of the seal bar, or a desired airflow profile is provided.

<CIT> discloses an apparatus for heat sealing the respective layers of film in a pair of hems in a moving web of film in the manufacture of draw tape bags. A pair of hot air hem sealer units is provided, each of the units including a hot air hem sealer heat exchanger having a plurality of nozzles which direct hot air against a continuously moving film. The nozzles are in line with film movement and the film is backed up by a metal plate positioned between the hems. Following the heating phase, cool compressed air is directed against the film in the heated area to cool the film prior to contact with the hem seal on the other side of the bag. The heat exchanger includes a plurality of circumferential grooves that deliver hot air to the nozzles. A thermocouple controls the temperature of the hot air.

<CIT> discloses a machine and method for making bags including a web traveling from an input section to a rotary drum, to an output section. The rotary drum includes at least one seal bar, having a single sealing zone, and a weakening zone disposed within the single sealing zone. The single sealing zone includes a heating wire. The weakening zone creates a line of weakness that is uniform or varies in intensity. The sealing zone may include temperature zones, cartridge heaters, cooling air, or heated air, or a source of ultrasonic, microwave or radiative energy.

<CIT> discloses an automobile structure casing assembling device for use in automobile industry. The device has two segments each including a main bore formed through the segment. A number of exhaust bores extend from the main bore to an upper surface of one of the segments. The upper surface is designed such that the upper surface corresponds to the casings that are to be assembled. The casings are adhered with a glue line in the area of an outlet of the exhaust bores.

<CIT> discloses an apparatus for manufacturing plastic film stock material including a sealing head utilizing heated air for continuous welding of re-closable plastic closure strips of plastic film. The sealing head is an elongated block having tapered walls which form a narrow bottom edge. The edge is curved longitudinally to match the curvature of a cooperating platen to define a small welding gap through which pass plastic webs to be welded. The sealing head includes a plurality of air distribution manifolds interconnected by passageways to provide a tortuous path for air flowing through the head from an inlet to an elongated, narrow exit slot formed at the bottom edge of the head. Multiple sealing heads are mounted on a carrier frame for positioning adjacent the platen to produce elongated welds to secure two-piece closure strips to a plastic web.

A first aspect of the invention is defined by a bag machine for forming bags according to claim <NUM>.

A second aspect of the invention is defined by a method of forming bags according to claim <NUM>.

The sealer is a hem sealer and/or a pocket sealer, and/or a bottom sealer in various alternatives.

The bag machine includes a feedback circuit connected to the temperature sensor and to the controller, and the feedback sensor provides a signal indicative of temperature near the sensor to the controller.

The temperature sensor is located in the manifold in one embodiment.

The temperature sensor is a thermocouple in various embodiments.

The sealing section includes a second temperature sensor located in or near the heater block, and a second feedback circuit is connected to the second temperature sensor and to the controller, and the second feedback sensor provides a signal indicative of temperature near the second sensor to the controller.

The sealing section includes a rotary drum disposed along the film path such that the film travels around a portion of the rotary drum in another alternative.

The sealer includes a seal bar on the rotary drum in one embodiment.

The heater block and/or the manifold are insulated in various embodiments.

The manifold includes a first end portion near a first edge of the film path, a second end portion near a second edge of the film path, and a middle portion between the first end portion and the second end portion, and the manifold include an air flow restriction located in the middle portion in another alternative.

Other principal features and advantages of will become apparent to those skilled in the art upon review of the following drawings, the detailed description and the appended claims.

Before explaining at least one embodiment in detail it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of the components set forth in the following description or illustrated in the drawings. Like reference numerals are used to indicate like components.

While the present disclosure will be illustrated with reference to a rotary drum bag machine, and making bags using a rotary drum, it should be understood at the outset that the seal bar described herein can also be implemented with other types of bag machines.

Generally, the operation of rotary bag machines may be consistent with the prior art, except for the design of and operation of the seal bar and related components. Thus, this disclosure will be made with reference to the prior art bag machine of <FIG>. However, seals bars <NUM> (and related components), along with controller <NUM>, <NUM> are replaced as described below.

The temperature of air from the manifold (or shoe) is more directly a function of the manifold temperature, rather than the temperature of the heater block. Yet, prior art systems only use feedback of heater block temperature in their control loop. This disclosure provides for using the temperature of or near the manifold (or of air in or near the manifold). Also, in the prior art heat loss from the manifold is significant and effects the temperature of the air in the manifold. This increases heat up time, wastes energy, and results in a more difficult control. This disclosure provides, in an alternative, for reducing heat loss by insulating components, which reduces heat up time, reduces energy waste, and results in an easier control.

The preferred embodiment provides that the sealing section includes a sealer having a heater block and a manifold. An air flow path is provided so that air may be provided to the manifold by the heater block. The air is heated in the heater block. The heating of the air in the heater block is controlled by a controller. A temperature sensor is disposed in the air path and/or the manifold. A feedback circuit preferably is connected to the temperature sensor and to the controller, and the feedback sensor provides a signal indicative of temperature near the sensor to the controller so that the controller can control the air temperature. This allows the temperature of the manifold or of air in or near the manifold to be controlled to the desired temperature.

The temperature sensor is a thermocouple in the preferred embodiment, but is a different type of sensor in other embodiments. A second temperature sensor is located in the heater block, and provides a signal indicative of the temperature near the second sensor to the controller. The second sensor is used as a fail safe or runaway sensor. Thus, if for some reason the block overheats (for example a bad sensor in the manifold or a leak before the manifold), the failsafe sensor prevents overheating of the block.

In the preferred embodiment the sealing section includes rotary drum <NUM> which is disposed along the film path such that the film travels around a portion of the rotary drum. The seal bars on drum <NUM> each include a temperature sensor, and each is fed by a separate heater block in the preferred embodiment. The heater blocks and/or manifolds are insulated in the preferred embodiment, and not insulated in alternative embodiments. The sealer is a hem sealer, and/or a pocket sealer and/or a bottom sealer in various embodiment.

The preferred embodiment restricts air flow in the center of the manifold, so that relatively more air is directed to either end of the manifold in the preferred embodiment. The preferred embodiment provides that greater air flow at the ends than in the middle of the seal bars results in more consistent seals.

In operation bags are formed by directing the film to the input section and then directing the film from the input section to the sealing section. Air is heated in the heating block (or blocks) for each seal bar. The heated air is directed to the manifold of each seal bar. The temperature of the manifold, or heated air in the manifold, or the heated air as it is being directed to the manifold, is measured. The heating of air in the heating blocks is controlled in response to the measured temperature. Seals are formed using the seal bar manifolds. Alternatives provide for one or more of the seal bars to be those of the prior art, rather than as described herein. The film is provided to the output section after the sealer.

Referring to <FIG>, a seal bar that is a hem sealer, related components and a controller is shown. Alternatives provide that the sealer is a pocket sealer or a bottom sealer. A source of compressed air provides air through a pressure regulator <NUM> and an air flow restriction <NUM> to a heater block <NUM>. A controller <NUM>, <NUM> controls the heating of air in heater <NUM> in response to a set point and feedback. The setpoint is preferably user set, but can be fixed. Heater block <NUM> is a Cool Touch™ Flow Torch™ in the preferred embodiment.

Heated air is provided by heater block <NUM> to a distribution plenum <NUM>. Air flows from plenum <NUM> to manifold <NUM>. A thermocouple <NUM> in manifold <NUM> provides feedback on line <NUM> to controller <NUM>, <NUM>. Because thermocouple <NUM> is located in manifold <NUM> controller <NUM>, <NUM> can more accurately control the temperature of manifold <NUM>. Thermocouple <NUM> can be embedded in manifold <NUM> where it senses the temperature of manifold <NUM>, or it can be in an open area of manifold <NUM> where it senses the temperature of the air in manifold <NUM>. Alternatives provide for thermocouple <NUM> to be located in plenum <NUM>, or in the air flow path from plenum <NUM> to manifold <NUM>.

A second thermocouple <NUM> is located in heater block <NUM> and provides a signal on feedback line <NUM> to controller <NUM>, <NUM>. Thermocouple <NUM> and is used to prevent runaway heating (overheating) of heater block <NUM>. Thus, controller <NUM>, <NUM> has two feedback loops, each with a set point - one for manifold <NUM> and one for heater block <NUM>. Controller <NUM>, <NUM> "ANDS" the control, so that heating is provided when both feedback loops indicate heating is needed. The heater block control loop prevents runaway temperatures. Thermocouple <NUM> can be embedded in heater block <NUM> where it senses the temperature of heater block <NUM>, or it can be in an open area of heater block <NUM> where it senses the temperature of the air in heater block <NUM>. Alternatives provide for thermocouple <NUM> to be located in an air flow path between heater block <NUM> and plenum <NUM>, in plenum <NUM>, or for it to be omitted.

Heater block <NUM>, distribution plenum <NUM> and manifold <NUM> are insulated in the embodiment of <FIG>. The insulation can be a simple insulation jacket or some other wrap, or can be internal to the components. Various alternatives omit the insulation from one or more of heater block <NUM>, distribution plenum <NUM> and manifold <NUM>.

The embodiment of <FIG> provides uneven heating of the film. Specifically, less air flow is provided in the middle portion of the seal bar (relative to the end portions), as indicated by smaller air flow arrows <NUM>. Alternatives provide for other air flow patterns.

The typical start up time of prior art systems is about <NUM> minutes. It takes this long to heat the system to the desired temperature because of heat loss. Also, because the prior art systems control using heater block temperature, the heater reaches the set point before the manifold temperature is at the desired level. Thus, prior art systems turn the heater off even though the temperature at the manifold is not as hot as desired.

Using the embodiment of <FIG> provides a much faster start-up time. <FIG> is a graph of measured temperatures of the air delivered to the film at start up using the embodiment of <FIG> (line <NUM>) and the prior art (line <NUM>). It can be seen that the embodiment of <FIG> reaches almost <NUM>% of the desired temperature in <NUM> seconds, and reaches the desired temperature in <NUM> seconds, while the prior art takes about <NUM> seconds to almost reach the desired temperature, and takes <NUM> seconds to reach the desired temperature. This means that the prior art is not able to consistently produce seals for the first <NUM> minute of operation, while the embodiment of <FIG> will be able to consistently produce seals in just <NUM> minutes.

Referring to <FIG> another embodiment of the seal bar and related components and the controller is shown. The sealer of <FIG> is a pocket sealer in the preferred embodiment, and is a hem sealer or bottom sealer in alternative embodiments. Some of the components of <FIG> may be the same as the embodiment of <FIG>. The source of compressed air provides air through an air supply path that includes a controllable pressure valve <NUM>, an air flow or pressure sensor <NUM>, and air flow restriction <NUM> to heater block <NUM>. A controller <NUM> controls pressure valve <NUM> in response to feedback from air flow sensor <NUM> to provide air flow at a set point. Controller <NUM> preferably uses a PID control loop. When air flow sensed by air flow sensor <NUM> is less than a set point, valve <NUM> is controlled to allow greater air flow, and when the sensed flow is greater than the set point valve <NUM> is controlled to allow less air flow. The desired flow is set by the user, factory, or process control in various embodiments. When set by the process, temperature feedback can be used to set the air flow set point. Any embodiment can be used with pressure sensor <NUM> and controllable valve <NUM>, and/or with pressure regulator <NUM>. In one alternative the source of compressed air provides air through pressure regulator <NUM> and air flow restriction <NUM> to heater block <NUM>. In the embodiment of <FIG> heater block <NUM> is disposed in a different orientation relative to a distribution plenum <NUM>. The layout of components and design of plenum <NUM> provides for improved air distribution which reduces heat loss. Controller <NUM>, <NUM> controls the heating of air in heater <NUM>.

Heated air is provided by heater block <NUM> to distribution plenum <NUM>. Air flows from plenum <NUM> to a manifold <NUM>. Thermocouple <NUM> is in manifold <NUM> and provides feedback on line <NUM> to controller <NUM>, <NUM>. Because thermocouple <NUM> is located in manifold <NUM> controller <NUM>, <NUM> can more accurately control the temperature in manifold <NUM>. Thermocouple <NUM> can be embedded in manifold <NUM> where it senses the temperature of manifold <NUM>, or it can be in an open area of manifold <NUM> where it senses the temperature of the air in manifold <NUM>. Alternatives provide for thermocouple <NUM> to be located in plenum <NUM>, or in the air flow path from plenum <NUM> to manifold <NUM>.

A second thermocouple <NUM> is located in heater block <NUM> and provides a signal on feedback line <NUM> to controller <NUM>, <NUM>. Thermocouple <NUM> and is used to prevent runaway heating (overheating) of heater block <NUM>. Thus, controller <NUM>, <NUM> has two feedback loops, each with a set point - one for manifold <NUM> and one for heater block <NUM>. Controller <NUM>, <NUM> "ANDS" the control, so that heating is provided when both feedback loops indicate heating is needed. The heater block control loop prevents runaway temperatures. Alternatives provide for thermocouple <NUM> to be located in an air flow path between heater block <NUM> and plenum <NUM>, in plenum <NUM>, or for it to be omitted.

The embodiment of <FIG> provides even heating of the film. Specifically, substantially the same air flow is provided in the middle portion of the seal bar (relative to the end portions), as indicated by air flow arrows <NUM>. Substantially the same air flow, as used herein, refers to air flow that forms seals in an even manner. This even air flow provides better flow from manifold <NUM> and is accomplished using plenum <NUM> and removing restrictions in the center of manifold <NUM>, or providing restrictions away from the center of manifold <NUM> as needed. Alternatives provide for other air flow patterns.

Referring to <FIG> another embodiment of the seal bar and related components and the controller is shown. The sealer of <FIG> is a bottom sealer in the preferred embodiment, and is a hem sealer or pocket sealer in alternative embodiments. Some of the components of <FIG> may be the same as the embodiment of <FIG>. The source of compressed air provides air through pressure regulator <NUM> and air flow restriction <NUM> to an integrated heater and air distributor <NUM>. Heater and air distributor <NUM> is controlled by a controller <NUM> via lines <NUM>-<NUM>.

Heated air is provided by integrated heater and air distributor <NUM> to a plenum <NUM>, which serves the purpose of the manifold in other embodiments. Using the arrangement of <FIG> provides for improved air flow. Air flows from plenum <NUM> to the film, as indicated by arrows <NUM>. Thermocouple <NUM> in plenum <NUM> provides feedback on line <NUM> to controller <NUM>, <NUM>. Because thermocouple <NUM> is located in plenum <NUM> controller <NUM> can more accurately control the temperature of air delivered to the film. Thermocouple <NUM> can be embedded in plenum <NUM> where it senses the temperature of plenum <NUM>, or it can be in an open area of plenum <NUM> where it senses the temperature of the air in plenum <NUM>. Alternatives provide for thermocouple <NUM> to be located elsewhere in plenum <NUM>, or in the air flow path to plenum <NUM>.

A second thermocouple is used as in other embodiments to prevent runaway heating (overheating) of integrated heater and air distributor <NUM>. The embodiment of <FIG> provides even heating of the film. Specifically, the same air flow is provided in the middle portion of the seal bar (relative to the end portions), as indicated by air flow arrows <NUM>. This even air flow is accomplished using plenum <NUM> without air flow restriction, or by providing restrictions away from the center as needed. Alternatives provide for other air flow patterns.

Claim 1:
A bag machine for forming bags from a film that follows a film path through the machine, comprising:
an input section located on the film path;
a sealing section, located on the film path down stream of the input section;
an output section, located on the film path downstream of the sealing section; and,
a controller (<NUM>), connected to control the sealing section,
wherein the sealing section includes a sealer that includes a heater block (<NUM>) and a manifold (<NUM>) with an air flow path from the heater block (<NUM>) to the manifold (<NUM>), wherein air is heated in the heater block (<NUM>) in response to a control signal provided by the controller (<NUM>) to the heater block (<NUM>), and wherein the heated air is provided through the air flow path to the manifold (<NUM>), and wherein the sealer includes a temperature sensor (<NUM>) disposed in at least one of the air flow path and the manifold (<NUM>),
wherein the bag machine further comprises a feedback circuit (<NUM>) connected to the temperature sensor (<NUM>) and to the controller (<NUM>), wherein the feedback sensor provides a signal indicative of temperature near the sensor to the controller (<NUM>),
and characterized in that the sealing section includes a second temperature sensor (<NUM>) located in the heater block (<NUM>), and further comprising a second feedback circuit (<NUM>) connected to the second temperature sensor (<NUM>) and to the controller (<NUM>), wherein the second feedback sensor provides a signal indicative of temperature near the second sensor to the controller (<NUM>).