The use of automated machinery to perform machining functions on workpiece has become an essential part of modern manufacturing technology. In such automated equipment, it is typical that one or more forming stations are provided. A workpiece is advanced into engagement with the forming station by means of a positioning mechanism. Upon retraction of the positioning mechanism, the workpiece is ejected from the forming station so that the metal forming cycle can be repeated. Ejection of the formed workpiece is accomplished by gravity or, in some instances, by an ejector rod that may, for example, be mechanically actuated to apply a jarring force to the workpiece to eject the workpiece from the forming station.
A specific example of such a machine adapted to perform a machining function, and a type of machine to which the present invention is particularly directed, is a lid seamer which is used in the food and beverage industry. Here, an open container having an open mount and an upper rim is filled with a product, and a lid is registered with the upper rim so that the combination lid and rim are seated on a chuck assembly as a workpiece. The open container has a can flange, and the lid has an end flange which are placed in registration adjacent to an outer forming surface of a chuck element. One or more forming rollers then revolve around the chuck element to roll the flanges together thus seaming the lid onto the container to produce a sealed, lidded container that is then ejected for packaging. As described more fully below, and as shown in the prior art FIG. 1, such lid seamers are commonly used in the beverage industry. Here, however, the standard ejector mechanism is in the form of a knock-out rod that is cam actuated so as to be mechanically timed to tap the center of the lidded beverage can thereby to eject it from the chuck assembly in the forming station. One such machine of this type in common usage is the Angelus sanitary seaming machine made by Angelus of Los Angeles, Calif.
Use of a knock-out rod of a type typically employed in the industry is not without its problems, however. Even though only a slight force of approximately twenty pounds is necessary to eject a lidded beverage can, the impact of the knock-out rod on the center of the joined lid may rupture the pull opener seal (score) or rivet. This may create several problems. On one hand, rupturing the seal can allow contamination of the food product by bacteria or other microbial organisms, which can endanger the consumer of the food product. On another hand, where a carbonated beverage is packaged in the lidded container, rupture of the pull tab seal or rivet allows the escape of the carbonating gas so that the contained beverage may go "flat" and thus be an undesirable consumer product. It can further lead to the loss of product since the occurrence of any of these events is undesirable to the manufacturer, most manufacturers are quite concerned about quality control of the pull tab integrity.
Even where the pull tab is not ruptured, several other disadvantages arise from use of a knock-out rod. One such disadvantage is the fact that the knock-out rod along with its associated mechanical structure including cam followers, cam grooves and the like greatly increase the complexity of most lid seamers. thus, such machines are expensive and are costly to maintain. Moreover, since the knock-out rod reciprocates a spindle assembly which mounts the forming chuck, it is necessary to lubricate the knock-out rod and its associated bushings, bearings, etc. The presence of lubrication always prevents the problem of leakage which, in rare instances, might contaminate the food product as the open container moved into position under the chuck assembly or, more often, can result in contamination of the surface of the lid after it is seamed onto the container by the leaked lubricating medium. Again, where a beverage can is concerned, a problem arises since consumers often drink the beverage directly from the beverage can so that a user might place his/her mouth on the lid contaminated with the lubricating medium. Further, the inertial mass of the reciprocating knock-out rod and its associated mechanical linkages acts limit on the speed at which such machines can operate.
Accordingly, there has been a long felt need for an improved ejector apparatus and method for machines in general and especially for lid seamers. There has been a need for ejector apparatus and methods which reduce the complexity of such machines by eliminating tradition complex mechanical knock-out rod assemblies. Further, a need has existed for ejector apparatus and methods for lid seamers which reduce the possibility of contamination of the food product where such lid seamers are used in the food and beverage industry.