Handling Rod Assembly For Investment Casting Mold

Abstract

A handling rod assembly comprises a rod having a connecting lug detachably mounted at its lower end to provide a drive connection between the rod assembly and a wax pattern pre-attached to the lug. The lug is detachably connected to the rod assembly by a bayonet connection and a pair of drive lugs which cooperate to prevent axial and rotational movement of the lug relative to the rod during spinning thereof. A coil spring is mounted on the rod to retain the drive lugs in driving engagement during such spinning.

Description

BACKGROUND OF THE INVENTION

Automated handling apparatus for making ceramic shell molds normally comprise a handling rod assembly, including a connecting lug embedded in a wax cuff having a wax pattern secured thereto. The lug is threadably connected to an elongated rod of the rod assembly during formation of the mold, wherein the wax pattern is repeatedly dipped in a ceramic slurry to form a ceramic shell mold therearound. During such formation, the wax mold is elevated and twirled to evenly distribute a coating of the ceramic slurry therearound and to permit the run-off of excess slurry.

The mold is then rapidly spun in alternate directions for final removal of excess slurry and is thereafter dipped in a fluidized bed for drying purposes. Such spinning and abrupt reversal of the rod assembly tends to unscrew the threaded connection between the rod and the lug. In addition, manual threading of the rod and the lug together is unduly time-consuming, particularly when used in connection with high-speed automated handling apparatus wherein time is of the essence.

SUMMARY OF THE INVENTION

An object of this invention is to overcome the above, briefly described problems by providing an economical and non-complex handling rod assembly, particularly adapted to expeditiously and positively detachably connect a wax pattern thereto during an investment casting process. The rod assembly comprises an elongated rod having attachment means on its upper end, adapted to attach the rod assembly to automated handling apparatus. A connecting lug is detachably connected to a lower end of the rod for embedment in a cast cuff and anti-rotation means are provided to prevent rotation of the lug relative to the rod.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects of this invention will become apparent from the following description and accompanying drawings wherein:

FIG. 1 is a front elevational view of a handling rod assembly, having a cast cuff and pattern attached thereto; and

FIG. 2 is an exploded, isometric view of the handling rod assembly.

DETAILED DESCRIPTION

FIG. 1 illustrates a handling rod assembly 10 operatively connected to a wax pattern 12, simulating the crankshaft of a fuel injection pump, by means of a cast cuff 13. The cuff may be cast from any suitable material, such as wax or aluminum, and suitably secured to the upper end of the wax pattern. When the pattern and the cuff each constitute a wax material, thay may be bonded together at the wax interface therebetween.

A connecting lug 14 has an irregularly shaped head 15 formed thereon for embedment in the cast cuff. The head thus provides a drive connection between the lug and cuff to rotate pattern 12 during formation of a ceramic shell mold thereon. The lug further comprises a bore 16 formed centrally therethrough to intersect a pair of diametrically opposed bayonet-type locking slots 17, each comprising a vertically disposed portion 18 and an intersecting horizontally disposed portion 19, closed at one end thereof. A pair of diametrically opposed driving and locking tabs 20 are formed on the lug to extend upwardly therefrom and in circumferentially spaced relationship relative to locking slots 17.

Referring to FIG. 2, the handling rod assembly further comprises an elongated rod 21 having attachment means 22 formed on its upper end, adapted to attach the rod assembly to clamping fingers (not shown) of standard automated mold handling apparatus. A mold attaching end 23 of the rod comprises a cylindrical portion 24 terminating at its lower end at a reduced extension 25 and at its upper end at an annular flange 26. A hole 27, formed transversely through rod portion 24, has a drive pin 29 press-fitted therein to have its free ends project radially outwardly from the rod.

A hole 30 is formed transversely through extension 25 and has a locking pin 31 press-fitted therein. The free ends of the locking pin project radially outwardly from each side of the extension to engage locking slots 17 to form a bayonet connection or coupling means therewith for connecting lug 14 to a lower end of rod 21 and for preventing axial movement therebetween. A locking sleeve 32 is telescopically mounted on cylindrical portion 23 of the rod and has a pair of diametrically opposed and elongated slots 33 formed longitudinally therethrough.

As shown in FIG. 1, each of the slots receives a free end of pin 29 to form a lost-motion connection therebetween for permitting limited axial movement between the sleeve and rod, but for preventing relative rotation therebetween. A coil spring 34 is normally compressed between flange 26 and the upper end of sleeve 32 to provide releasable retaining means for biasing the sleeve downwardly on the rod to ensure continuous axial engagement of locking tabs 20 in a pair of axially opposed and mating locking slots 36. Such tab and slot arrangement thus comprise anti-rotation means, along with pin 29 and slot 33, for preventing both clockwise and counter-clockwise rotation of lug 14 relative to rod 21.

During an investment casting process, lug 14, having pattern 12 and cuff 13 pre-attached thereto, is selectively connected to rod assembly 10 to facilitate formation of a ceramic mold on the pattern in the manner described above. In particular, sleeve 32 is manually retracted to compress spring 34 to expose extension 25 of rod 21 for telescopic engagement in bore 16 of connecting lug 14. The free ends of lock pin 31 are then inserted into vertical slot portions 18 of locking slots 21 and the rod and lug are rotated relative to each other to seat the ends of the lock pin in the closed ends of slot portions 19.

Sleeve 32 is then released to allow locking slots 36 to engage locking tabs 20 to aid in preventing rotation of rod 21 relative to the connecting lug. The handling rod assembly and attached shell mold core are thus placed in position for engagement by the clamping fingers of automated handling apparatus at attachment means 22. The above procedure is substantially reversed when lug 14 is detached from the rod assembly, upon formation of the ceramic shell mold.

Claims

I claim:

1. An investment casting handling rod assembly adapted for use in making an investment casting mold comprising

a rod having attachment means on its upper end adapted to attach the rod assembly to mold handling apparatus,

a casting connecting lug having an irregularly shaped head,

coupling means detachably connecting said lug to a lower end of said rod assembly and for preventing axial movement of said lug relative to said rod, and

anti-rotation means for preventing both clockwise and counter-clockwise rotation of said lug relative to said rod.

2. The handling rod assembly of claim 1 further comprising releasable retaining means for continuously maintaining said anti-rotation means in a locked position.

3. The handling rod assembly of claim 1 further comprising a sleeve telescopically mounted on said rod, said anti-rotation means comprising at least one mating tab and slot connection formed on axially opposed ends of said lug and said sleeve.

4. The handling rod assembly of claim 3 further comprising an annular flange secured on said rod and a normally compressed coil spring mounted on said rod between said sleeve and said flange.

5. The handling rod assembly of claim 3 wherein said anti-rotation means further comprises a pin secured to said rod to have an end thereof project radially through at least one side of said sleeve.

6. The handling rod assembly of claim 5 further comprising an elongated slot formed longitudinally through said sleeve to receive the end of said pin therein to form a lost-motion connection permitting limited axial movement, but for preventing relative rotation between said rod and said sleeve.

7. The handling rod assembly of claim 1 wherein said coupling means comprises a bayonet connection.