The present invention relates to an improved heat seal apparatus of the type used for mating a covering material with a product-filled container to seal the container. More particularly, the present invention relates to an improved carrier assembly for the heat seal apparatus which is configured to increase the sealing pressure in a sealing zone of at least the flange on the container to ensure that an acceptable seal is produced between the covering material and the flange of the container.
Conventional heat seal machines used for mating a covering material with the sealing areas of a product-filled container are well-known. Such heat seal machines generally are capable of heat sealing a covering material onto individual product-filled containers while the containers are continuously moving along a path. Such heat seal machines generally include some type of reciprocating carriage which reciprocates over the continuously moving path of containers, with the carriage matching the speed and direction of the moving containers for a period of time. Attached to the carriage is one or more heat seal heads which are moved upwardly and downwardly by some type of actuation device, normally a fluid cylinder. Each heat seal head is configured and oriented to be moved downwardly to come in contact with the covering material which has been routed over the opening in the product-filled containers, and to force the covering material into direct sealing contact with the sealing area on the container. Each heat seal head includes a heating element which, by thermal interaction with the covering material, causes the covering material to adequately seal against the container sealing area.
It has been found in such conventional heat seal machines that a ridge can be placed around the periphery of each heat seal head, with the ridge oriented to come into contact with a sealing area of the container flange. By placing this ridge, or raised portion on the downwardly face of each heat sealing head, the ridge thus comes in contact with the covering material and container sealing area before the remainder of the face of the heat sealing head, with the ridge creating an increased sealing pressure with respect to the sealing pressure created by the remainder of the face of the heat sealing head which comes in contact with the container. It has been found that this increased sealing pressure acts to ensure that an adequate seal is created around the entire sealing area of the container. It will be understood that it is necessary to ensure that adequate seals are provided around the entire sealing area, normally the flange of the container, in order to ensure the quality of the product within the container during storage. Because the flanges of the containers used on such heat seal machines are somewhat deformable, the ridge on the face of the heat sealing head acts to deform the flange to a greater extent in the sealing zone with respect to the deformation of the flange caused by the remaining portions of the heat sealing heads which come in contact with the flange. This increased deformation or increased compression of the flange in the designated sealing zone provides the localized increased sealing pressure necessary to ensure the adequate seal of the covering material with the flange.
One problem associated with conventional heat seal machines having the sealing ridge disposed on the heat seal head is that, because of the increased compression of the container flange caused by the raised ridge, a permanent indentation is formed in the top surface of the container flange after the seal has been completed. This permanent indentation creates a somewhat unattractive product container from a consumer acceptance point of view. Additionally, by creating a permanent indentation in the upper surface of the flange, the covering material is forced to conform to the contours of the indentation. Again, this permanent indentation of the covering material and of the top surface of the container flange presents a somewhat unattractive sealed container.
A more serious problem also presents itself in conventional heat seal machines having a raised ridge on the downwardly facing surface of the heat sealing heads. Because the heat sealing heads only move in unison with the continuously conveyed trays during a brief period of time, the mechanism for aligning the heat sealing heads with the moving trays during this period of time is prone to misalignment. It is possible for the heat seal heads to be misaligned or out of time with the movement of the containers if the timing mechanism of the machine is out of adjustment. The timing mechanism of the heat seal machine can become out of adjustment for several reasons, including chain stretch of the machine, general wear of the machine, and improper machine operator adjustments. In a heat seal machine which includes a raised ridge on a downwardly facing surface of the heat sealing head, any misalignment of the heat sealing head with respect to the containers will cause a misalignment and misplacement of the increased sealing pressure area out of the ideal sealing zone on the container. Again, the primary sealing area on most conventional containers is the container flange portion. This possible misalignment of the increased sealing area outside of the sealing zone is disadvantageous for several reasons.
First, because the ridge creates a permanent indentation in the top surface of the container flange, any misalignment or misplacement of the ridge results in a misaligned and obvious misplacement of the permanent indentation in the container flange. Such misalignment of the permanent indentation in the top surface of the container flange presents an obvious warning to the consumer that the seal of the container may be less than perfect. Second, any misalignment or misplacement of the increased sealing area can have adverse effects on the actual seal created between the covering material and the container. Thus, quality control of the seal containers can be adversely affected, which increases the cost because of inadequately sealed containers which must be removed from the assembly line after the sealing process.
It is therefore one object of the present invention to provide a heat seal apparatus that is capable of creating an increased sealing pressure in the sealing zone of a container to produce an acceptable, consistent seal without creating a permanent indentation in the upper surface of the container.
Another object of the present invention is to provide a heat seal apparatus that is capable of creating an area of increased sealing pressure in the sealing zone of the container and in which the orientation and alignment of the increased pressure area is consistent, and does not depend upon the position and alignment of the heat seal head.
According to the present invention, an apparatus for mating a covering material with at least deformable outwardly extending flange portion of a product-filled container to seal the container is provided. The apparatus includes means for providing a covering material over the container opening and over the container flange. The apparatus also includes means for applying a downwardly directed force of a specified magnitude to the covering material and to at least the container flange to mate the covering material to the flange. A support member or carrier plate is provided that is oriented to oppose the force exerted by the applying means, with the support member and applying means cooperating to compress the container flange in response to the force exerted by the applying means. The support member includes first and second portions for compressing the container flange, with the first portion having a first cross-sectional area and the second portion having a second cross-sectional area. The second portion is elevated above the first portion a specified distance such that the second portion compresses the flange a greater amount relative to the compression of the flange by the first portion. By providing an increased compression area on the underneath side of the container flange, the sealing pressure exerted on the covering material by the second portion is greater than the sealing pressure exerted on the covering material by the first portion.
One feature of the foregoing structure is that the lower support member includes a raised second portion having a second cross-sectional area. One advantage of this feature is that the raised second portion acts as a ridge to increase the sealing pressure in the area of the ridge to provide an adequate seal of the covering material on the upper surface of the flange.
In preferred embodiments of the present invention, the support member includes an upstanding wall which has an upwardly facing top section, with the top section formed to include both the first portion and the raised second portion. Also in preferred embodiments of the present invention, the first portion of the top section of the upstanding wall includes two generally planar ledges, with the second elevated portion interposed between these two ledges. One feature of the foregoing structure is that the raised second portion is interposed between two lower ledge-like first portions. One advantage of this feature is that, when the applying means forces the deformable container flange against the upstanding wall, the compression of the container flange is greater in the area of the second portion with respect to the compression of the container flange in the area with respect to the two first portions. Thus, an increased pressure sealing area is created in the vicinity of the second portion of the upstanding wall.
Also in preferred embodiments of the present invention, the applying means includes a multi-stage fluid cylinder assembly that is capable of imposing a preselected, adjustable, downwardly directed force on to the covering material and to the container flange. One feature of the foregoing structure is that the multi-stage fluid cylinder is adjustable, and is capable of providing a preselected, downwardly directed force on the heat seal head, and thus on the covering material and container flange. One advantage of this feature is that the applying means can be adjusted, depending upon the characteristics of the material forming the container flange.
Thus, the present invention provides a heat seal apparatus which is capable of producing an increased sealing pressure in a selected sealing zone of the container. Unlike conventional heat seal machines with a ridge on the heat seal head to provide an increased sealing pressure, the present invention incorporates the ridge on a lower support member of the apparatus so that any permanent indentation of the container is located on the underneath side of the container sealing zone. Thus, the top surface of the container flange and the covering material cooperate with the ridge positioned beneath the container to affect an adequate seal around the entire sealing area, without the disadvantages associated with any type of permanent indentation in the top surface of the container.
Additional objects, features, and advantages of the invention become apparent to those skilled in the art upon consideration of the following detailed description of a preferred embodiment exemplifying the best mode of carrying out the invention as presently perceived.