This invention relates to a guide for a metering device and like devices.
Certain types of automated production lines use chuting for the conveyance of articles. Individual articles move along the conveyance path in succession, one after another. Metering devices are utilized with the chuting to perform positioning operations on the articles.
One type of metering device is known as a gate. The gate operates to release articles one at a time.
A typical construction for a gate comprises a pair of fluid-operated cylinders arranged side-by-side adjacent the conveyance path along the chuting. An article-engaging member is connected to the free end of the rod of each cylinder by a thrust block. Each article-engaging member is guided by a guide structure for straight line motion in a direction which is transverse to the direction of motion of the articles along the conveyance path. Typically the transverse motion of each article-engaging member is perpendicular to the direction of travel of the articles along the conveyance path. The article-engaging members are typically spaced apart along the length of the conveyance path approximately one article apart, though this spacing distance may be different in some instances.
The cylinders are operable to extend and retract the respective article-engaging members whereby in the extended position the corresponding article-engaging member is positioned in the conveyance path and in the retracted position it is positioned out of the conveyance path. The cylinders are typically operated at the same time but in opposite directions. In other words when one cylinder rod is extended, the other is retracted and vice versa.
When the downstream cylinder is extended and the upstream one retracted, the downstream cylinder's article-engaging member blocks the flow of articles so that a succession of articles can accumulate behind it. When the gate is then operated to retract the downstream cylinder and extend the upstream one, the first article in the accumulation is released while the remainder of the articles behind it are arrested by the extended upstream cylinder.
A further cycling of the gate causes the upstream cylinder to retract and the downstream cylinder to extend whereby what is now the first article in the accumulation is allowed to advance to the extended downstream cylinder, and the next cycling of the gate will release that article.
Based upon this description, it can be appreciated that the gate is effective to release bhe articles one at a time.
Any given piece of automation equipment may comprise a number of such metering devices at different locations.
Metering devices may perform other than the gating function just described. For example, a shot bolt comprises a single cylinder and article-engaging member for performing an operation on an article which may involve either orienting the article in a particular way on the conveyance path or stopping the article.
From the standpoint of assembly considerations, the use of a thrust block connection between the cylinder rod and the article-engaging member is advantageous. A thrust block is a standard part which can be readily attached to the end of the cylinder rod. A suitable hole and slot can be machined in one end of the article-engaging member to allow the article-engaging member to be slipped onto the thrust block without the use of any other attaching parts. The thrust block connection provides a joint which contains a certain range over which the article-engaging member can move angularly relative to the cylinder rod about an axis which passes through the joint transversely of the length of the cylinder rod. By providing this limited pivotal capability, precise alignment of the cylinder rod is not critical, and the guide structure alone guides the travel of the article-engaging member. The guide structure also preferably encloses the thrust block joint throughout the range of travel of the article-engaging member.
The article-engaging member is typically fabricated from a bar of rectangular transverse cross section because such bar stock is readily available and its ends can be machined to the desired shapes for the thrust block and for engagement with the articles.
Heretofore it has been conventional practice to fabricate the guide structure from multiple metal parts assembled together. For example, a typical construction for such a guide structure comprised a pair of guide blocks spaced apart parallel to each other to form the sides. Base and cover plates sandwiched the guide blocks so that a guideway of rectangular cross section was thereby co-operatively defined by the four pieces. Each guide block contained a pair of spaced apart holes, and the base and cover plates each comprised a rectangular pattern of four holes. Fasteners such as screws passed through the holes in the cover plate, through the holes in the guide blocks and through the holes in the base plate to secure the several parts in assembled relationship. The holes in the guide blocks and in at least one, and usually both, of the base and cover plates were merely clearance holes.
In order to fabricate a metering device it was necessary to handle a number of individual parts and then to assemble them together. In the assembly of the parts the potential existed for the two guide blocks to have too loose a fit and/or some degree of non-parallelism with respect to the article-engaging member between them because they were separate pieces and because they had merely clearance holes. Not only were a number of individual pieces required to be fabricated in order to construct a guide, but these parts required a certain amount of time for their assembly and the assembly was often cumbersome, especially difficult where the gate is arranged vertically and the guides are required to be vertical. The person assembling the various parts had to manipulate them, hold them in place and then tighten the fasteners after the parts had been assembled. Even at that, the potential existed that the completed assembly would have the guide blocks in other than an optimum engagement with the article-engaging member.
While such a guide construction might initially perform satisfactorily, a less than optimum alignment often resulted in accelerated wear, extra noise, and even aggravated the alignment. For example, repeated impacting of an article-engaging member by articles could result in loosening of the assembled parts because of the manner in which the guide structure reacted the effect of impact loads imposed on the article-engaging member by the articles being gated. An example of this is illustrated in a vertical gate for controlling part flow along a declined chute. Where an article-engaging member is disposed in the conveyance path to arrest the flow, it is possible that an article could impact the article-engaging member with a significant amount of momentum. This would be reacted by the guide blocks in such a way that it could tend to spread the guide blocks apart and/or loosen the assembly.
The present invention is directed to an improved guide for a metering device of the type described. The invention possesses a number of significant improvements over the prior multi-piece guide structure.
An especially significant improvement is that the guide of the present invention comprises a one-piece unitary member of a rigid, dimensionally stable non-metallic material. An example of a suitable material is glass, teflon-filled material The guide member can be fabricated from conventional injection molding techniques so that it e1iminates the separate guide blocks and cover and base plates which were required of prior guide structures.
The guide member of the present invention is preferably fabricated in a generally rectangular overall shape to comprise a through-hole of rectangular cross section just slightly larger than the rectangular cross section of the article engaging member which it guides. Because the guide member of the present invention is molded as one piece the through-hole's walls are always accurately related to each other. Hence the possibility for misaligned or poorly fitting guide blocks characteristic of the prior construction is avoided through use of the present invention. Moreover, because the present invention is a one-piece construction, it can be more easily and quickly assembled into a metering device.
The invention is efficient in its use of material forming the guide member, and certain specific details constitute further inventive features. The present invention offers significant savings not only from the standpoint of part cost but also from the standpoint of assembly cost. Moreover, the invention has further functional attributes which when put to use may be fairly said to include improved wear characteristics and lower noise levels.
The foregoing features, advantages, and benefits of the invention, along with additional ones, will be seen in the ensuing description and claims which should be considered in conjunction with the accompanying drawings. The drawings disclose a preferred embodiment of the invention according to the best mode contemplated at the present time for carrying out the invention.