US2854264A - Flexible joint for an air drop hammer - Google Patents

Description

' Sept., 30, i958 y Q. w. cosLQw 2,354,254

FLEXIBLE JOINT FOR AN AIR DROP mmm me@ .my 11, 195e v. n gum im.. mi

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Patented Sept. 30, 1958 FLEXIBLE JOINT FOR AN AIR DROP HAMMER Carl W. Coslow, Los Angeles, Calif.

Application July 11, 1956, Serial No. 597,285

l Claim. (Cl. 287-85) This invention relates generally to air and/or steam drop hammers, and more particularly to connecting rods for such drop hammers.

The service conditions under which modern air and steam drop hammers operate, some of which will be described hereinafter, impose severe bending moments on the connecting rods thereof, suicient to over-stress the rod, and cause rapid fatigue and early failure. When the connecting rod fails, the hammer must be taken out of service for replacement, at a cost, considering both the cost of the new rod, installation and lost hammer time, as much as $3,000 to $4,000. The life of the hammer rods in large air or steam hammers is of the order of four hundred hours. It will be seen that hammer rod failure is a serious and costly occurrence.

It may accordingly be stated as the primary object of the present invention to provide an air or steam hammer connecting rod with a means relieving it of bending moment strains in service, to the end that such rods will stand up practically indefinitely under service conditions.

In general, an air drop hammer as now known comprises essentially an anvil or base, two heavy side frames equipped with guides and gibs that can be moved in and out, i. e., towards and away from the center line of the hammer, a heavy hammer head or ram, and a connecting rod which is driven into the head or ram and held by a tapered lit, a piston attached to the upper end of the connecting rod which runs vertically through a stuffing box to prevent the air from escaping around the rod, an air cylinder, and appropriate timing devices for admitting high pressure air under the piston and exhausting that air from under the piston at the upper end of the piston stroke. The air pressure performs only one function, namely, to lift the weight of the ram through the connecting rod. The work done by the hammer is the blow of the guided, free falling head or ram. The ram may weigh thousands of pounds. The connecting rod thus performs nouseful function on the down stroke of the hammer. It comes into play only in the lifting of the head preparatory to its next down stroke.

Steam drop hammers are essentially similar, with the exception that on the down stroke, steam pressure acts on the top of the piston to add to the acceleration of gravity. At or near the bottom of the stroke, however, the steam pressure is relieved by suitable valving arrangements, and the blow struck is owing entirely to the inertia of the accelerated hammer head.

The side frames on such hammers have adjusting arrangements including slots and hold down bolts which permit the moving of these frames toward and away from the center line of the hammer. These frames move independently of one another in guides on the hammer base. The operator is expected to adjust these frames to maintain proper clearance between the guides and the hammer head at all times. However, this is not always done as it should be. For example, in the morning,

whenthe hammer is cold, the side frames should be brought in towards the center line to provide a properly close working clearance between the hammer head and the frame guides. As the hammer grows hot in service, it expands, requiring that the frames be moved out to maintain proper clearance. If this is not done, the hammer head becomes too tight in the guides, resulting in excessive friction, wear, and loss of proper hammer blow.

Hammer men operating on piece rate, in order to avoid shutdown time for adjustment, are found usually to set the clearance' too wide when the hammer is cold, with the result that the head is not adequately guided and is free to move excessively from side to side. Passing over the fact that this condition of excessive play results in poor work owing to mismatch of dies, which under such conditions are not necessarily in good alinement, such excessive play results in serious bending moments being set up in the rod under certain common conditions of service. The dies commonly are provided across their faces with various pairs of impressions for successive forging operations on the work piece, and while one of such pairs of impressions may be on the center line of the rod, impressions on either side thereof are not. When these off-center line impressions are used, a blow struck by the hammer head results in the hammer head cooking in the assumed loose guides. Since the rod is tightly mounted in the head at one of its ends, and constrained to alinement with the center line of the cylinder at its other end by the piston and air cylinder, such cocking sets up severe bending moments in the rod. T he repeated bending moment, and capability of bending under the described conditions, results in undue fatigue of the rod and early failure.

Again, even though proper spacing of the side frames with respect to one another be achieved, it is almost impossible, owing to the crude method of moving the frames, to adjust them at exactly equal distances from the center line of the piston on the air cylinder. The piston and the upper end portion of the connecting rod are constrained to move on the center line of the cylinder. But if the frames, even though properly spaced from one another, are not equally spaced from the center line of the cylinder, they guide the hammer head along an olfset center line, which condition sets up severe bending momentsV in the rod, in addition to causing scoring of the rod as it passes through the stung box, wear on the stung box, leakage, packing troubles, and expensive repair. The described bending of the, rod under these conditions contributes greatly to fatiguev and early failure of the rod.

Bending strains on the rod also occur from still another cause. The upper and lower die in the hammer must be lined up, one above the other, to prevent crosswise mismatch. The dies fit in dovetails in the hammer head and anvil, and are held solidly in place by tapered keys driven in by a heavy ram. They must be very tightly locked in place to withstand the jar of the hammer. It is a very diicult matter to exactly line up these dies, one above the other, using wedges, shims, Sledge hammers, rams, etc., for the purpose. Commonly, the operator first achieves a fairly close die alinement by such methods, and then moves the side frames to obtain nal die alinement. This, however, throws the hammer head out of alinement with the cylinder and piston, and again subjects the rod to bending moments, fatigue, and ultimate failure.

Finally, it is commonplace for the faces of the dies to be out of parallel, one with the other. The pounding of the hammer, the effect of the hot metal, the shims, wedges, and the tits in the dovetail, all operate to make it practically impossible to maintain perfect parallelism between the operating faces of the upper and lower dies. When dies that are out of parallel strike die to die, a bending momentrisV set up, the head tends to cock in the guides, which are usually' set fairly loose, and the resultant periodic bending contributes to fatigue and failure.4

The present invention, which provides relief for all of the conditions mentioned hereinabove, comprises a flexible rubber coupling between'the connecting rodv and hammer head. Such coupling permits cooking of the hammer head under the various misalinement conditions mentioned in the foregoing passages without setting up material bending moments in the rod. That is to say, as the hammer head cocks upon striking a blow under the-,several conditions described,-the exible rubber coupling readily deforms to accommodate such action, leaving the rod itself in substantially undisturbed alinement with its piston and cylinder. The flexible coupling also furnishes accommodation for the condition brought about by side frame guides adjusted to proper spacing from one another, but unequally spaced from the true center line of the rod, piston and cylinder. Under such conditions, the coupling may compress suiiiciently in a lateral plane to permit the hammer head to workV up and down easily in the side frame guides, while the rod itself retains its alinement with the piston and cylinder, so that, here again, bending strains are alleviated.

The invention will be further understood from the following detailed description of a present illustrative embodiment thereof, reference being had to the accompanying drawings, in which:

Fig. l is a perspective view of a conventional air drop hammer;

Fig. 2 is an illustrative diagrammatic view of an air drop hammer, parts in section and broken away;

Fig. 3 is a longitudinal sectional view of a connecting rod, flexible coupling and partially illustrated hammer head in accordance with the invention; and

Fig. 4 is a plan view taken on line 4 4 of Fig. 3.

In the drawings, which show an air drop hammer for illustrative purposes, and with particular reference first to Figs. l and 2, numeral designates a conventional air drop'hammer, having base or anvil 11, side frames 12` adjustable toward and from one another along guideways 13, air cylinder 14, piston 15, piston rod 16, stung box 14a, hammer head or ram 17, vertically guided by suitable guides 18 on side frames 12, hammer-carried die 19, and anvil mounted die 20.

The side frames will be understood to be arranged for adjustment of the distance therebetween to follow expansion of the hammer head as a consequence of heating during operation, and it will be further understood that elort is made by the operator to adjust these to be equally spaced from the center line or axis A-A of the air cylinder and piston.

It can be readily appreciated from an inspection of Fig. 2 how unequal spacing of these side frames With respect to piston and cylinder center line A--A' imposes severe bending lmoments on the rod. It can further be readily appreciated how, in event of striking of the hammer against a work piece w in an oli-center position such as indicated will result in cooking of the hammer head, with resulting bending strains in the rod, particularly when the side frames are adjusted With a certain looseness or play between the hammer head and .the guides. And it can further -be readily appreciated how non-parallelism of the striking faces ofthe dies can impose severe bending moments on the rod. Still further, it can readily be appreciated that, even with proper spacing of the side'frames from one another, unequal spacing thereof from the center line of the piston and cylinder results not only in bending 'of the rod, but scoring of the rod at the stuiiing box, wear on the stuing box, etc.

With reference now to Fig. 3, my improved connecting rodv is designated generally a-t 25, and it will be understood that this rod is for use in a conventional drop hammer such as shown in Fig. l, and diagrammed in Fig. 2. Y

The upper end portion of this rod (not shown) will accordingly be understood to run up through the usual stu'ing box and to be conventionally fitted to the piston within the air cylinder.

The partiially illustrated ram and hammer heady is again designated by the numeral 17, and the exible coupling between the rod and head is designated generally at 26. Rod 25 has near its lower extremity a tapered section 27, and its lower extremity is screw threaded to receive nut 28. Mounted on tapered section 27 is a steell coupling disk or plate 29, and this disk is secured in posi-V tion by a washer 29a against which the aforementioned nut is tightly set. As shown, the nut is slotted, and a locking pin 30 engaged with a selected slot secures the nut in tightened position.

Enveloping and bonded' tothe peripheral face 29b and upper and lower faces 29e and 29d, respectively, of disk 29, outside the yarea of the rod and nut, is a flexible rubber coupling member 3-1, having Hat upper and lower faces, and a cylindrical periphery, as shown.

This coupling member 31 includes inside cylindrical surface 31a contacting disk surface 29h, downwardly facing inside surface 3111 contacting face 29c of disk 29, and upwardly facing inside surface 31e contacting `face 29d of disk 29. n

The lower face 31d of this coupling member rests on an annular face 32a on the top of an annular upper portion 32 of a ram adaptor 33, there being a central recess 34 in the upper end of the adaptor for reception of nut 28 and the lower extremity of rod 25. Adaptor k33 has a central, downwardly projecting-tapered shank 35 driven into a correspondingly tapered lbushing 36 set tightly into head 17. A coupling housing 37, in the general form of an inverted cup, iits down over rubbercoupling member 31, its inside surface 37a snugly engaging the periphery 31e kof the latter, and slidably fitting over annular adaptor portion 32, with the under face 38a of its top Wall 38 engaging the upper face 31f of coupling member 31. The lower rim of the cylindrical side Wall 39 of this housing cup, upon approximately 1,41" compression of coupling member 31, engages an outwardly n extending annular flange 40 at the base of adaptor 33; The cup side wall is drilled, as at 41,for a plurality of draw bolts 42, and these are adapted to engage in tapped drill holes 43 in base ange 40. Tightening of the draw bolts to seat housing wall 39 on adaptor ange 40 compresses, and thus pre-loads, the exible rubber coupling member 31. When the draw bolts are in position, a pair of key rods 45 are inserted in alined bores 46 and V47 in the housing and adaptor, respectively, to secure the parts The flexible coupling as thus described relieves the rod of the described misalinement and misadjustrnent bending and wear strains. Any cooking of the hammer head upon striking a blow is accommodated by deformation of the Viiexible rubber coupling member 31, any bending forces transmitted `to the rod being entirely insignicant. In the event ofk the side frame guides being positioned to space the hammer head off-center from the center line of the cylinder and piston, the flexible coupling deforrns laterally to permit the head to conform to the position of the guides, while'the rod remains in alinement with the cylinder and piston, and is under no material strain as a consequence of the misalinement. l'naddition, the rod remaining in alinementV with the'cylinder and piston, Wear on the rod, stuing box, etc., as a consequence of this type of misalinement, is relieved. Summarizing briefly, it will be seen that the invention contemplates a ilexible, deformable rubber coupling member between the rod and hammer head or ram, in such arrangement as permits cooking of the head with respect to the rod, withoutbending of the rod, as well as limited lateral displacement ofI the head with respect to the rod, again without imposition of material bending strain on the rod.

I have now disclosed one present preferred embodiment of my invention. It will be understood, however, that various changes in design, structure and arrangement may be made without departing from the spirit and scope of the appended claim.

I claim:

A coupling for the connecting rod and ram of a drop hammer, comprising: a rod coupling means rigidly vconnected to an end of said rod, a ram coupling means rigidly connected to said ram, said rod and ram coupling means having a range of lateral and angular movement relative to one another, and resiliently deformable rubber coupling means interposed between said rod and ram coupling means and having a surface held fast to said rod coupling means and another surface held fast to said ram coupling means, with the portion of said rubber coupling means between said surfaces acting by resilient deformation to accommodate limited lateral and angular displacements of said ram relative to said rod from a normal centered and aligned position relative to the rod, and acting by vresilient restoration to return the displaced ram to `said normal position.

References Cited in the file of this patent UNITED STATES PATENTS 1,641,091 Minck Aug. 30, 1927 1,670,493 Clark May 22, 1928 1,720,592 Fitzgerald July 9, 1929 1,812,464 Billings June 30, 1931 1,864,080 Madge June 21, 1932 1,957,021 Schneider May 1, 1934 2,079,460 Marty May 4, 1937 2,098,703 Geyer Nov. 9, 1937 2,195,644 Fitzgerald Apr. 2, 1940 2,220,036 Fitzgerald Oct. 29, 1940 2,661,969 Thiry Dec. 8, 1953 2,794,661 Sears June 4, 1957 FOREIGN PATENTS 342,996 Great Britain Feb. 12, 1931 828,471 Germany Jan. 17, 1952

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