Patent Application
20070059093
This invention concerns guide pins and bushings used in such construction of forming dies. Forming dies are comprised of two die parts respectively mounted to an upper and lower press platen. A guide pin or post is mounted to one die part and a guide bushing mounted to the other die part in alignment with the pin. The pin and bushing mate with each other when the press is actuated to guide the die parts into accurate registry. Such pins and posts may be press fit into holes in the respective die parts, but this makes disassembly for repairs difficult so that so called “demountable” pins and bushings have been developed, in which the pin and bushing are slidably fit in the die bases, and are held with clamps engaging a flange on the pin or bushing pressing the same against the adjacent die part surface which is ground so that the pin and bushing are thereby precisely aligned with each other.
The flange has hereto been formed by machining down large diameter stock to form the pin or bushing thus producing much wasted material but also greatly adding to the time necessary to produce the pin or bushing. It thus has been necessary to manufacture and stock these items so as to achieve reasonably rapid delivery times. These requirements substantially increases costs as many configurations and sizes of pins and bushings must be available for delivery on short notice.
It is an object of the present invention to provide a method of manufacturing flanged guide pins and bushings to a customer order, allowing them to be made rapidly to order while eliminating the need for wasting time and material in machining the pins to form an integral flange, and to stock a large number of different configuration pins and bushings.
The above object and other objects which will become apparent upon a reading of the following specification and claims are achieved by stocking lengths of standard diameter shafts and tubes which have been heat treated and precision ground to a finished inside or outside diameter. When an order is received, the shafts and/or tubes of the desired diameters are cut to length. A ring is assembled onto the pin or bushing at a specified location in such a way as to be the functional equivalent of the integral flange, i.e., a flange which is accurately controlled size, location and orientation which is sufficiently rigid to perform the retention function of an integral flange.
In a first method, a groove at the desired location of the flange is machined into the outside diameter of the pin or bushing. The pieces of a split ring having a tapered outside diameter is assembled onto the pin or bushing fit within the groove. A second ring having an inside taper which locks to the outside diameter taper of the split ring is pressed onto the split ring, creating the flange.
In a second method, the pin or bushing is machined with a double stepped diameter forming an intermediate land between large and small diameter sections thereof. A solid ring is press or shrunk fit onto a first step in abutment with a shoulder formed by a second step on the pin or bushing section.
In a third method, a solid ring is precisely located and oriented on the outside diameter of the pin or bushing by use of suitably fixturing and secured by a shrink fit to the pin or bushing outside diameter. While less strong, this method is the least expensive as no additional machining is required.
In the following detailed description, certain specific terminology will be employed for the sake of clarity and a particular embodiment described in accordance with the requirements of 35 USC 112, but it is to be understood that the same is not intended to be limiting and should not be so construed inasmuch as the invention is capable of taking many forms and variations within the scope of the appended claims.
Referring to
A land 24 on a pin segment 26 received in the hole 14 may mate with a precision ground outer section of the hole 14 for achieving precisely accurate location thereof. The flange 16 being held in abutment against the ground die surface 18 accurately aligns the pin axis normal to the surface 18 to insure proper mating engagement with a bushing on another die plate (not shown) in the well known manner. The remaining section of the pin segment 26 may be machined to be a clearance fit with the hole 14. The flange 16 must thus be accurately oriented to be normal to the pin axis.
According to the present invention, the flange 16 is not made by machining a larger diameter section of stock material to form an integral flange on a pin (or bushing), but rather the flange 16 is created by securing a separate piece or pieces onto a premachined pin to form the flange.
This allows stocking of standard diameter shafts and tubes which have been mostly machined. When an order is received, appropriate lengths are cut and certain details, i.e. grooves, etc. are machined into the shafts or tubes. The separate flange piece or pieces are then installed at the appropriate location.
Thus, stocking of finished pins or bushings is not necessary while allowing prompt delivery schedules for made to order pins or bushings.
A pin 36 has a pre-finished diameter 40 which is the same diameter as 36, to be inserted in a hole, with a slightly smaller diameter land 38 optionally precision machined adjacent to diameter 40.
In
Three or more clamps 68 and screws 69 force one face of the flange formed by the installed ring 54 against the ground die face 70 to secure the demountable bushing 60 and align the axis thereof.
This results in less strength than the above described flanges, but is adequate for the purposes described.
