초록 ▼

A seal assembly for packaging machines facilitates the heat sealing of layers of material at the mouth of loaded bags. An operator may insert the layers of material between a pressure pad and a seal member positioned in a spaced position. Upon activation of a switch by the operator, an oscillating s

A seal assembly for packaging machines facilitates the heat sealing of layers of material at the mouth of loaded bags. An operator may insert the layers of material between a pressure pad and a seal member positioned in a spaced position. Upon activation of a switch by the operator, an oscillating signal is applied to a solenoid to actuate movement of the pressure pad toward the seal member with a relatively soft force. An optical sensor senses when the pressure pad moves within a predetermined distance from the seal member and generates a sensor signal. In response to the sensor signal, a relatively constant voltage signal is applied to the solenoid to actuate movement of the pressure pad with a relatively high seal or clamping force to secure the layers of material against the seal member. The sensor signal also triggers energization of a heating element carried by the seal member to effectuate the heat seal between the layers of material. In this manner, damage to an object that becomes situated or jammed between the pressure pad and the seal member is minimized or avoided as such jammed objects prevent application of the clamping force and energization of the heating element. Such objects may be also be removed in a relatively easy manner because of the relatively soft force with which the pressure member exerts upon such objects.

대표청구항 ▼

[ What is claimed is:] [1.] A method for forming a seal between at least two layers of material, the method comprising the steps of:(a) actuating a seal assembly to move with a relatively low force from a spaced position toward a seal position to seal the at least two layers of material, wherein the

[ What is claimed is:] [1.] A method for forming a seal between at least two layers of material, the method comprising the steps of:(a) actuating a seal assembly to move with a relatively low force from a spaced position toward a seal position to seal the at least two layers of material, wherein the actuating step (a) includes the step of applying a first electrical signal to a solenoid operatively coupled to the seal assembly;(b) sensing when the seal assembly has reached a seal-ready position;(c) actuating, in response to the sensing step (b), the seal assembly to move to the seal position with a seal force greater than the low force, wherein the actuating step (c) includes the step of applying to the solenoid a second electrical signal different from the first electrical signal; and(d) sealing the at least two layers of material when the seal assembly is in the seal position. [7.] An apparatus for moving a seal assembly from a spaced position to a seal position, the seal assembly including relatively moveable components, the apparatus comprising:(a) a solenoid operatively interposed between the components for relatively moving the components from the spaced position to the seal position;(b) a sensor for generating a sensor signal when the components have reached a seal-ready position; and(c) circuitry coupled to the solenoid and to the sensor, the circuitry responsive to a switch for applying a first electrical signal to the solenoid to move the components with a relatively low force toward the seal position, the circuitry being responsive to the sensor signal for applying to the solenoid a second electrical signal different from the first electrical signal to move the components, when in the seal-ready position, with a seal force greater than the low force to the seal position.