Abstract: A heating unit includes a bridge having an arm in which there is located a heating element, and a circuit for directing a sensing current through the heating element. The circuit of the present invention reduces the duty cycle of the sensing current, thus reducing the average sensing current and allowing the use of higher peak sensing currents. In one embodiment, a set of zener diodes determines the start and stop points of the sensing current pulses. In another embodiment, the start and stop points are determined by electronic logic performed by a quad comparator. In another embodiment, one of the zener diodes is replaced by a SIDAC. The invention allows sensing of heating elements having very small temperature coefficients. The circuits of the invention produce a sensing current which is relatively unaffected by variations in supply voltage.

Abstract: A heating unit includes a bridge having an arm in which there is located a heating element, and a circuit for directing a sensing current through the heating element. The circuit of the present invention reduces the duty cycle of the sensing current, thus reducing the average sensing current and allowing the use of higher peak sensing currents. In one embodiment, a set of zener diodes determines the start and stop points of the sensing current pulses. In another embodiment, the start and stop points are determined by electronic logic performed by a quad comparator. In another embodiment, one of the zener diodes is replaced by a SIDAC. The invention allows sensing of heating elements having very small temperature coefficients. The circuits of the invention produce a sensing current which is relatively unaffected by variations in supply voltage.

Abstract: A control device includes both a heating element and a temperature sensor. The control device has the form of a Wheatstone bridge which applies sensing current to the heating element. When the bridge is unbalanced, the control device may apply heating current to the heating element. In one embodiment, the sensing current is switched, so that it flows only for a relatively small part of the electrical cycle. The circuit also includes a provision for reduction or elimination of electrical spikes. The circuit further includes a calibration arrangement, which enables the user to adjust the bridge without passing heating current through the heating element. Another feature of the invention enables the set point of the bridge to be remotely controlled, by adjusting a level of analog current applied to the bridge. The circuit also includes an arrangement for compensating for temperature-induced changes in its components.

Abstract: The present invention is used to heat seal seams, and the like, of item holding means such as plastic bags holding loose fill product like beans, hard candy, pretzels, potato chips, etc. The heating station of the present invention has at least two independently controlled heating positions in each half of a pair of jaws and each heating position is heat insulated from the other and each respectively can provide different amounts of heat to material coming in contact therewith. Accordingly, the bonded areas of item holding means can be manipulated to control local package characteristics, i.e., sealed to have a stronger bond strength at one location that at another location, adjust tear properties to suit marketing methods (such as hole punched top seals) and to control seal integrity.

Abstract: The present invention includes at least one low mass flexible heat transfer member to which there is secured a plurality of electrical resistance paths, for each area of the material to be sealed during an excursion through the heat station. The electrical resistance paths are respectively connected to a power source, or power sources, to generate different quantities of heat respectively at different positions along the heat transfer member. The heat transfer member is flexible and is formed and disposed to push against sealable material to transfer heat thereto and cause said sealable material to be sealed.

Abstract: A cascaded fluid heating for electrically heating to fluid, such as a gaseous fluid in a flameless torch, to a high temperature includes a pump to pump a relative constant stream of fluid through a pair of heating chambers arranged in series. A first electric heating element formed of a nickel-iron alloy having a substantially linear positive temperature coefficient of resistance up to 1100.degree. F. is disposed in the first chamber and heats the fluid stream to a first temperature. A second heating chamber receives the heated fluid from the first chamber and contains a second electric heating element of a material, such as Kanthal A, which does not oxide at temperature up to 2000.degree. F. for heating the fluid to a higher temperature. The first electric heating element acts as a sensor for a temperature controller for the first heating element whereby the current supplied by the controller to the first heating element responsive to the changes in resistance of thereof.

Abstract: The present invention provides a low mass, flexible heat transfer member which is made of a suitable material to transfer heat, as well as a plurality of independent heat generating members to provide zoned heat along a portion of the length of said heat transfer member. The heat generating members are encased in an electrical insulation material which is secured to the heat transfer member. The consolidated structure, i.e. the heat transfer member and heat generating members constitute a flexible strip. The ends of said flexible strip are actually sections of the heat transfer member and these ends are respectively looped around two pins, or studs, and over the respective loops there is positioned an associated slotted hollow tube. The slotted hollow tube is formed to be located in a base of a machine with which the flexible heating means is used.

Abstract: The present invention includes a heating element which is secured to a rigid member and which is located so that when a plastic like material is being formed into a package or bag, by effecting a seam along the side of the package, the inside of said side seam will be heated, in addition to said outside of said side seam to help provide a better sealed seam.

Abstract: Method and apparatus for controlling static charges on dielectric material by producing an ionized field and controlling the balance and magnitude of the directional conductivity of the ionized field. The directional conductivity characteristics are typically controlled by applying a DC bias of selected polarity and magnitude to a high voltage AC output which is applied to an ionizing member to produce the ionized field.

Abstract: A method and apparatus for controlling static charges on film formed into packages and filled with particulate material to prevent the particulate material from attaching to the film and degrading the seal area of the package.