The present invention relates to pallet-making machines in general, and in particular to nail-driving chucks for use in pallet-making machines.
The forerunners of today's wooden pallets were developed during World War II to assist the armed forces in moving large amounts of goods in short time periods with forklift trucks. Wooden pallet usage has increased explosively since that time.
Automated pallet-making machines were developed in response to the high demand for wood pallets and now occupy an important position in the pallet manufacturing industry. The primary function of these pallet-making machines is the automatic nailing of pallet boards which have been positioned either manually or with some assistance from the pallet-making machine.
Automated pallet-making machines often use drive pins or rams to drive nails being held by a chuck into boards located below the chuck. Nails driven into the component boards of a pallet must be countersunk so that the nail heads do not protrude above the top surface of the boards. Countersinking is important because bags or packages containing goods which are placed on pallets can be torn by nail heads protruding above the boards.
Depending upon the pallet buyer's specifications, pallet manufacturers countersink the top of the nails to different depths below the top surface of the pallet boards. This change in countersink depth has traditionally been made by changing the relative distance between the board end of the nailing chuck and the drive end of the nailing chuck so that the pin's final extended position of the nail-driving pin is changed relative to the board end of the nailing chuck.
An example of such a countersink adjustment apparatus is shown in the Wallin U.S. Pat. No. 4,782,989. In the Wallin patent the board end of the nailing chuck and the drive end of the nailing chuck are connected together by threads. The drive end of the nailing chuck contains female threads and the board end of the nailing chuck contains male threads. Where the drive end and the board end connect, a female threaded lock ring selectively locks the board end of the nailing chuck in position. The drive end of the nailing chuck is independently fastened in place so that the drive end cannot rotate about the longitudinal axis of the nailing chuck.
The board end of the chuck can be selectively rotated about the longitudinal axis of the nailing chuck while connected to the drive end of the chuck to change the relative distance from the board end of the chuck to the drive end of the chuck. The nail-driving pin is connected to the drive end of the chuck and extends into the board end of the chuck. When the distance from the board end of the chuck to the drive end of the chuck is changed, the position of the nail-driving pin, relative to the board end of the chuck, is also changed since the position of the nail-driving pin is fixed relative to the drive end of the chuck. Consequently, by changing the position of the board end of the chuck relative to the drive end of the chuck, the final extended position of the nail-driving pin can be adjusted relative to the board end of the chuck, and the nail countersink depth can be selectively changed.
One complication of this nail countersink depth adjustment method is that automatic nail feeding devices are often connected to the board end of the chuck. Since the board end of the chuck must be rotated to adjust the countersink depth, the automatic nail feeding device must be removed from the board end of the chuck prior to its adjustment and must be reattached following adjustment of the countersink depth. Since the automatic pallet-making machinery does not operate when the chuck is not operating, pallet making is suspended during the time required for removing and reattaching the automatic nail feeding equipment to the board end of the chuck and during the relatively short period of time required for actual adjustment of the board end of the chuck relative to the drive end of the chuck.