US3564778A - Apparatus for finishing forming dies - Google Patents

Abstract

A POWER TOOL FOR GRASPING HIGH MASS RECTANGULAR ABRASIVE STONES AND FOR OSCILLATING THE HIGH MASS ABRASIVE STONES IN STRAIGHT LINE INERTIA-BALANCED OPPOSITION.

Description

Feb. 23, 1971 c; H. HAAS APPARATUS FOR FINISHING FORMING DIES Filed NOV. 21, 1968 l N VENTOR.

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CHARLES HAAS IAJVQM ATTORNEY United States Patent 3,564,778 APPARATUS FOR FINISHING FORMING DIES Charles H. Haas, Philadelphia, Pa., assignor to The Budd Company, Philadelphia, Pa., a corporation of Pennsylvania Filed Nov. 21, 1968, Ser. No. 777,758 Int. Cl. B24b 23/00 U.S. Cl. 51-170 1 Claim ABSTRACT OF THE DISCLOSURE A power tool for grasping high mass rectangular abrasive stones and for oscillating the high mass abrasive stones in straight line inertia-balanced opposition.

BACKGROUND OF THE INVENTION It has been the general practice in the die making art to contour machine a rough casting and then finish the die by hand tools and hand operations. Only one of the several hand operations was performed with the aid of a power tool. After the die surface is rough machined, the raised ridges or cusps are usually removed with a hand-held rotary grinder fitted with abrasive wheels and/ or abrasive cones. Rotary grinders are heavy and require that they be held and guided in a precise position relative to the die surface or else they cut below the desired finished surface of the die. Rotary grinding operations are performed intermittently because of the need to visually check the progress of the operation and the need for the operator to rest.

Other types of power tools have been suggested for finishing dies, such as rotary and oscillating abrasive carrier tools commonly employed in automobile body sheet metal repair shops. In addition to requiring physical exertion and skill of the operator, the abrasive carriers wear out rapidly. Abrasive carriers tend to clog and to lose grit which causes scratches on the Work piece. Abrasive carrier tools, such as sanders, employ resilient pads as backing for the abrasive carrier which concentrates forces on isolated spots causing rapid wear to the abrasive carrier as well as the workpiece, thus, limiting the usefulness of sanders for accurate die finishing.

SUMMARY OF THE INVENTION Accordingly it is the principal object of the present invention to provide a novel power operated tool for finishing the surfaces of metallic dies.

It is a primary object of the present invention to provide a power operated tool for finishing die surfaces which is supportable by the die surface.

It is a further object of the present invention to provide a power operated tool with a pair of large mass abrasive stones oscillated in direction opposite to each other to neutralize inertia forces.

It is another object of the present invention to provide a novel clamping plate adapted to securely grasp and hold abrasive stones and to rapidly and easily release them.

It is a general object of the present invention to provide a power operated die finishing tool which is operable by personnel of average skill to perform grinding, rough stoning, finish stoning and polishing operations having equal or superior quality results to those obtained by highly skilled personnel performing the same operations by hand.

The above and other objects of the invention as well as its many features and advantages will be apparent from the following description of the prefered embodiment, reference being made to the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a perspective view of the preferred embodiment of the invention.

3,564,778 Patented Feb. 23, 1971 DESCRIPTION OF THE PREFERRED EMBODIMENT Power tool 10 comprises a pneumatic head 12 having an air supply hose 14 which feeds two opposed pistons (not shown) in the head which reciprocate in opposed straight line action. Such heads are commercially available and have been employed to drive sanders and buffers. A slide 16 or 18 is guided by and bears upon the bearing plate 20 is connected to each piston. Actuation of the control valve (not shown) causes the air supply to move the pistons and their attached slides back and forth While the head 12 remains stationary. It is preferred that the pistons always move in opposite direction to each other to neutralize inertia forces.

Shoe plates 22, 24 are connected to the slides 16, 18 by bolts 26 which are accessible through apertures 28 in the clamping plate assemblies 30, 32. Shoe plates 22, 24 are connected to the clamping plates assemblies 30, 32 preferably by welding at 34.

Each clamping plate assembly 30, 32 comprise a bed plate 36 and a pair of fixed clamp bars 38, 40* attached along the edges of the bed plate. One fixed clamp bar 38 is undercut as at 42 to provide a firm grip on the stone 44. On the side opposite the undercut fixed clamp bar is provided an undercut movable clamp bar 46 slidably supported on the bed plate 36 by Allen head screws 48.

It will be understood that the stone 44 varies in width and is fitted into the clamping plate assemblies when the movable clamp bar 46 is open. After the stone is inserted, screws 50 treaded in the fixed clamp bar 40 are first tightened to hold the stone, then screws 48, threaded in the movable clamp bar 46, are tightened to lock the movable bar in place. Stepped-face-slots 52 are provided in bed plate 36 to guide screws 48.

Finger shields 54, 56 are mounted on the head 12 to prevent the operator from inserting his fingers in the opening between the plates and the stones. An air cleaning tube 58 may be provided which directs an air stream between the two stones, thus keeping the workpiece clean.

A comparison between the former and the new methods of making dies will best explain the advantages of the present invention. Heretofore, after the rough casting was machined the high marks left by the cutting tools were completely removed by rotary hand grinders employing abrasive wheels and/ or abrasive cones having a number 43 grit size. Care had to be taken to avoid grinding any of the low areas or troughs left by the cutting tool. In the prior art method of hand finishing the forming die, a typical operation required successive hand stoning with three ditferent stones, such as numbers 46H, 461 and 601. In the typical prior art method, hand finishing was followed by hand polishing employing at least two polishing stones having a grit or grain size approximately numbers and 120. If a very high polish was required, another hand polishing step with a stone having a grit number was employed.

The new method permits the rotary hand grinding operation to be effected with broad abrasive wheels and/ or cones and does not require that the complete cusps or raised area be removed. The grinding operation is completed and the finishing operation started by employing the novel apparatus fitted with open or porous hard stones, such as number 43K. Grinding stones of this coarseness are not employed in typical hand finishing operations.

It is possible to complete the finishing operation with one or two stones, such as 46H and 461, dispensing with formerly used 601 stone. If both 46H and 461 stones are used, the resulting finish on the die is comparable to a light or low polish. If a higher polish is desired, hand polishing With number '80 grit stone is recommended. A very high polish can be obtained by subsequent hand polishing with number 120 and/or 150 grit stone. Plastic molding dies are further polished with oil and 200 to 400 grit compound and/ or jewelers rouge usually applied with a rotary rag or buffing wheel.

It is conservatively estimated that the time required to finish a forming die after it has been contour machined is reduced by two-thirds on the average. The two pairs of stones on the powered apparatus cover one-third square foot; the largest practical hand stone covers only onetwelfth square foot or one fourth as much area as the powered apparatus. The two pairs of stones on the powered apparatus are moved approximately fifteen thousand feet per hour, Whereas a hand opeartor is doing well to move the hand stone three hundred feet per hour.

The operator of the powered apparatus does not exert any force on the stones since the force is applied by the weight of the stones and the apparatus. The rapid inertiabalanced oscillating stones tend to float on the workpiece or die.

Careful selection of the stones used for self-cleaning characteristics has the additional adavntage that the stones tend to wear to the shape or contour of the die, thus insuring uniform wear and more accurate finishing operations.

Having explained the invention and its method of use it is apparent that the novel apparatus is capable of performing a grinding operation and a finishing operation with the same stone because the apparatus cuts smoother. Further, the apparatus is capable of performing a finishing opeartion and a polishing operation with the same stone because the apparatus cuts smoother and more accurate. The ability to cut smoother and more accurate with coarser stones has effetcively eliminated one or more steps formerly required when the dies were hand stoned. It is apparent that many types and grades of stones may be attached to the novel apparatus to better accomplish finishing operations as previously performed in the prior art, but in addition thereto stones employed to perform 5 finishing opeartions have now been etxended in usefulness to perform grinding operations or polishing operations.

I claim: 1. An oscillating abrasive-stone apparatus comprising, a head having a fixed bearing plate and at least one horizontally movable slide,

a recessed plate connected to the slide for mounting abrasive stones thereto, rectangularly shaped abrasive stones mounted on said plate,

a pair of fixed clamp bars connected to said plate, a movable clamp bar mounted on said plate, one of said fixed clamp bars having a plurality of bolts threaded therein and engageable with the movable clamp bar to clamp the abrasive stones between a fixed clamp bar and the movable clamp bar, and a plurality of bolts slidably guided in slots in the plate and threadably mounted in said movable clamp bar for lockingthe movable clamp bar to the plate. References Cited UNITED STATES PATENTS 175,566 4/1876 Kepler 51170.3 871,143 11/1907 Prugh 51175 928,154 7/1909 Prugh 51-175 1,840,108 1/1932 Kincaid 51-1703 1,873,011 8/1932 Modglin 51170.3 2,328,613 9/1943 Burleigh 51---175 FOREIGNPATENTS 173,155 12/1921 Great Britain 51-173 WILLIAM R. ARMSTRONG, Primary Examiner

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