US1481741A - Method of manufacturing piston rings - Google Patents

Description

Jan. 22,1924. 148L741 F. RAY

METHOD OF MANUFACTURING PISTON RINGS Filed May 27, 1920 2 Sheets-Sheet 1 F. RAY METHOD OF MANUFACTURING PISTON RINGS .Fian. 22 1924;

Fi1ed-May 27 1920 2 Sheets-Sheet 2 Patented Jan. 22, 32%.

FREDERICK BAY, OF SHQRT HILLS, JERSEY.

METHOD OF UFACTURING PISTON RINGS.

Application filed May 27, 1920. Serial No. 334,604.

To all whom it may concern Be it known that I, Fnanamon RAY. a citizen of the United 'States, residing at Short Hills, Essex County, State of New Jersey, have invented certain new and useful Improvements in Methods of Manufacturing Piston Rings, of which the following is a specification.

This invention relates to a method ofmanufacturing piston rings of concentric form, that is to say, uniform cross-section, which are split and then hammered or otherwise acted upon on their inner circumferences with localized blows or pressure definitely varied at the different sections of the ring so as to cause the same to open and, when compressed again to circular form in a cylinder, to exert approximately equal reaction upon the confining wall at all points, as compared with concentric rings which have had a piece cut out and have not been hammered, which are distinctly non-uniform in their outward pressure under working conditions.

Concentric equal pressure rings can be produced by taking ring blanks of the diameter of the cylinders which they are to enter (plus a slight excess for finishing on the outer circumference,) splitting them at one point without material removal of metal. then clamping them by pressure applied to their side faces in a suitable chuck,

and rotating this chuck'with the ring slowly or in a step-by-step manner relatively to a trip-hammer mechanism with a suitably shaped point, preferably a rounded or a narrow or a wedgershaped point, within the ring, the lift of the hammer and therefore the intensity of the blows being automati cally varied in the hammering of each ring thru the action of a control cam turning with the chuck.

I have demonstrated that a ring to exert truly uniform reaction, when compressed and retained in circular shape, as under working conditions. must contain stress moments in all its sections varying in accord ance with the expression, 1 cos a, where a is variable,being the angle between the split and any section of the ring. Acting upon the theory that the bending moments existing in the completed ring when compressed back to circular form correspond to the stress moments which were set up in the ring blank during the hammering and opening operation. I have provided a control cam which embodies the 1-cos a law, that is to say one wherein the elevation of the hammer corresponding to every point of the cam varies as the expression 1cos a, a be substantially perfect rings, provided the point on the cam which corresponds to the split of the ring. Cos a is the abbreviation for the cosine of said angle.

Theoretically such a cam will produce substantially perfect rings, prowided the hammering or pressing point is absolutely sharp, in which event, evidently, the stress moment is proportionalto the intensity of the blow or pressure. The edge cannot, however, be absolutely sharp, and must become duller with use, and in some instances rounded points are employed. Actually, I have discovered that the real law is that the stress moments set up are in proportion to the intensities of the blows plus a constant, and that the value of this constant depends upon the sharpness or dullness or shape of the point. Thus, in order to hammer a piston ring so as to give uniform radial pressure at all points of the circumference when in use, it is necessary to vary the intensities of the blows in accordance with the expres sion lcos a plus a constant.

If the hammer blow is caused by a falling weight, the intensity of the blow is in proportion to the height of drop of the weight. In such case it follows from the foregoing that the shape of the control cam should be such that the height of fall of theweight would vary in accordance with the law, height varies as 1cos a plus a constant. For such a hammer to operate satisfactorily it would be necessary for the point to be kept always in exactly the same condition of sharpness or it would be necessary to preserve its shape if other than a sharp point were used, which would be exceedingly difficult from a practical standpoint.

Hammers are also in use in which a large portion of the intensit of the' blow is due to the recoil of a spring. In such a case, if

the spring is entirely expanded and exerts no pressure whatever when the hammer strikes the ring, then the intensity of the blow due to the compression of the spring is directly in proportion to the amount of such compression (or tension). If the direction of the compression of the spring has avertical component, then the intensity of the blow, due to the weight of the moving parts, being proportional to the lift, is also in proportion to the amount of coinpression of the spring and consequently the whole intensity of the blow is in proportion to the amount of compression. Therefore to hammer a ring with such a machine, to give uniform radial pressure at all points of the circumference under conditions of use, the cam' would apparently have to be so shaped as to cause the compression of the spring to vary in accordance with the expression, compression varies proportionately to 1cos a plus a constant. Such a cam would only be suitable for a hammer point in but a single condition of sharpness.

I have found that as these hammers are run, the hammer point gradually dulls and the value of the constant changes. I have also found that different'hammer points require differentconstants. This would require that the shape of the cam be changed from time to time and would be very objectionable from a commercial standpoint.

I have also found that it is possible to overcome this difficulty by properly adjusting the spring which furnishes a portion or the whole of the energy required to drive the hammer. Thus I can utilize a single cam which is laid out so as to cause the compression of the spring to vary in accordance with the law, compression varies proportionately to 1co s a, and by providing means for adjusting the amount of the initial compression of the spring while the hammer point is in contact with the ring, I can add any desired constant to the intensities of the blows. A perfectly elastic spring if com.- pressed from its free state ofiers a resistance to the compression exactly in proportion to the amount of the compression. If, how ever, this same spring is subjected to an initial compression, which will give any desired reaction, then on further compression from this point of initial compression the total reaction is in proportion to the amount compressed plus the initial compression. Thus in a hammer provided with such a spring and with means for appropriately varying its initial compression and with a cam laid out according to the law of com pression varies proportionately to 1cos a, by giving the spring a proper initial compression when the hammer point is resting upon the ring the intensity of the blows will vary as, lcos a due to the shape of the cam, and plus a constant, due to the initial compression of the spring; but the stress moments set up in the ring, and consequently the bending moments in-the ring when in use, will vary according to the first law (1-cos a) and not according to the second or modified law. By this means I am, therefore, enabled to hammer a ring to give uni form radial pressure at all points of its circumference bv using a single cam and ad usting the initial compression of the spring to suit the shape of the hammer point. Likewise as the hammer point varies, due to wear, I can compensate for this variation by further adjustment of the initial compression of the spring.

In the manufacture of such rings, it is necessary to hammer rings of different diameters and'rings of the same diameter giving different intensities of pressure. This requires that the intensity of every blow dehvered to some rings shall be greater or less than the intensity of the corresponding blows delivered to other rings, without changing the law of the variation of the blows relativeto the ring. In the ase of a weight-loaded hammer this could be accomplished by changing the weight of the hammer. In the case of a spring-loaded hammer, such as shown in the drawing. the same result could be accomplished by changing the size and consequently the stiffness of the sprin This, however, requires more or less time and it is not always possible to have the stiffness of the various springs graduated exactly to the required amount. I overcome this difiiculty by using a single spring of such length and strength or stiffness that when the whole of the spring is permitted to deliver the blow, the intensity of the blow will be as small as normally required. Then by means of a clamp nut, which is provided with an internal thread so that it will screw over the cOilS of the spring, as an ordinary nut screws over the thread on a bolt, I am enabled to shorten up the effective or active part of the spring to any desired amount, and thus increase its resistance to compression, and thus increase the intensity of the blows to any desired extent within the limits of the strength of the spring. This follows from the fact that a spring of a given size compressed a given linear amount exerts a resistance to the compression inversely in proportion to the total original length of the spring. Thus by means of the clamp nut I am enabled to make the intensity of each blow any desired amount Within the limits of the spring by simply screwing the nut to the desired position on the spring and clamping it to the post, the portion of the spring within the nut and above same not acting. After placing the nut in this position I am able to add any desired constant to the intensity of each blow by simply sliding the nut lengthwise and clamping without turning. thus giving any desired initial compression to that portion of the spring in use. I am thus enabled by means of the cam. shaped so as to give a variation to the compression of the spring in accordance with the law. compression varies proportionately to 1cos a and a spring provided with means for varying both its length and its initial compression, to hammer rings with blows varying in intensity according to the law, intensity varies proportionately to 1cos a plus a constant, but producing stress moments accord-v ing to the law 1cos a and rat the same time making the absolute value of'the intensities of the blowsany desired amount. 1 I am thus enabled to produce rings of any size giving a uniform radial pressure at all points of the circumference, the magnitude of this pressure being anything desired within the possible limits.

In the accompanying drawings constitutin part of the specification:

Tig. 1 is a rear elevation of one form of machine for carrying out my process, parts being in section;

Figs. 2, 2, 3, 3, and 4e, 4? are diagrams.

F i 5 is a detail of the hammer and ring chucfi.

The circular body 1 of the ring chuck is mounted rotatably in a suitable frame 2 mounted on a base 3. The ring a to be operated u on is held in this chuck by removable an interchangeable ring seat and laterally clamping members i and 5. The hammer 6 is mounted slidably on a vertical post guide 7 rising from the base and is prevented from turning laterally by a rear guide-pin 8 depending from a top bracket 9.

he hammer, as usual, has a forward projection extending within the ring chuck and carrying a removable striker 10 having preferably a wedge-shaped point, which is usually either sharp, slightly rounded or slightly flattened.

The ring holder is rotated sowly in a step-by-step manner by a pawl 11 pivoted at 12 on a vertical rod 13 which is mounted slidably in the frame of the machine. The point of this pawl engagesratchet teeth 14, which are formed all the way around the circumference of the chuck. and is pressed into engagement with these teeth by a spring 15 which is interposed between a collar 16 fixed to the rod 13 and another collar 17 which is slidable thereon to press against thebase of the pawl. The rod 13 is repeatedly raised by an eccentric 18 on the main drivin shaft 19 of the machine, this eccentric actlng upon the lower end of the rod thru the interposition of a lever 20. A spring 21 is compressed by the raising of the rod and restores the same to its lower position after each elevation.

The hammer is raised and permitted to fall by a tapered tripping cam 22, which is splined on the shaft 19 so as to be mova le lengthwise but not rotatably with reference thereto. This cam co-operates with the lower end of a reciprocatory rod 23, which is guided in the interior of the post 7 and united with the hammer 6 by a crosspin 24 working inslots 25' in the sides of the hollow post. The position of the cam 22 on the shaft, and therefore the degree to which it lifts the hammer, is automatically varied. during the: hammering of each.- ring" by the action of a control cam'26 whichtis:

secured to the chuck 1 bymeans of screws 27.

The shifting of the cam 22 is effected thru the intermediate agency of a downwardly extending lever 28, which is piv'- tulcrumed at 29 at its upper end on ping cam in one direction while the control cam acts to move them in the opposite direction. Slots 36 in the control cam, beneath the heads of the screws 27, enable this cam to be adjusted rotatably with respect to the ring holder.

The cam 26, it will be understood, is to be made in accordance with the expression, compression varies as 1cos a, a being a variable and representing the angle between any point on the periphery of the cam and the low point I), which corresponds to the split in the ring. The exact shape of the cam itself depends upon the levers, etc. This does not mean that the point I) is adjacent the split in the ring. This may or may not be so, according to the particular arrangement of the mechanism. lln the illustrated construction the point I) should be at one side, in contact with the roller 34 when the split in the ring is at the lowest position immediately below the hammer point. The proper positioning of the ring relatively to the control cam may be left to the judgment of the operator, or suitable means may be provided for insuring accurate positioning when the ring is inserted in the chuck. The region 5 of the cam may be notched or flattened, and any suitable power throw-oil arrangement may be provided as in Wesson Patent 1,016,380. so that the machine is stopped automatically when the point I) returns opposite the roller 34 after having completed the circuit.

Coming now to the step of my process for adding a constant to the hammer blow. it will be observed that a helical spring 37 is interposed between the top of the hammer 6 and a fixed upper abutment 38. As heretofore explained. this spring should be of sufi cient length to enable the hammer to deliver the lightest blows with which the machine is designed to operate.

In accordance with the process, I vary the efi'ective length of the spring. thereby changing its stitl'ness. I also hold it, or not, under initial compression, and vary the degree of such initial compression. The means may be varied, but preferably com-- .halves of the collar 39 are formed with a der the action of the control cam.

spiral groove, like a screw-thread, to receive the convolutions of thespring. In order to vary the effective length of the spring the locking screw 41 and the screws 40 are loosened and the collar is turned so as to be screwed up or down the desired distance on the spring, after which the screws 40 and 41 are again tightened. It will be understood that all that portion of the spring within and above the nut collar is inactive. Consequently the further down 'on this spring the nut is screwed, the

shorter will be the efiective spring length and the greater the resistance to compression when the hammer is lifted. Conversely. the further upward thecollar is screwed on the spring, the greater will be the efiective length and the lighter will be the blows. At any spring length the active portion of the spring beneath the collar may be placed under any desired degree of initial compression by moving the collar 39 downward without turning it and then locking it by clamping the collar upon the post, by the screws 40. in the new position.

In the diagrams, Figs. 2, 2* illustrate the condition which exists with maximum spring length and without the initial compression. The inner shaded area an on the control cam 26 indicates the lift ofthe hammer by the tripping cam 22 as shifted un- The height to which the hammer is raised varies thruout the hammering of each ring, but it is the same in amount at corresponding points in the hammering of all the rings and under all adjustments of the spring. Thus the shaded area a: is the same in Figs. 2 3. and. 4*. The outer shaded area 3 in Fig. 2 represents the intensity of the blows, due to the force of gravity plus the recoil of the spring. In Fig. 3 the efi'ective length of the spring has been shortened but it has not been placed under initial compression. Consequently the shaded area y representing intensity of blows, is wider in Fig. 3 than in 2, because of the greater stifiness of the spring. If Fig. 4 the effective length of the spring has been shortened and in addition the active part of the spring has been placed under initial compression by sliding the collar 39 straight downward, as heretofore described. Consequently in Fig. 4* there is a supplementary shaded area 11 of uniform width thruout the circle, which represents the constant. added by the initial compression.

amet l'he procedure of hammering these rings consists in placing a blank in the chuck of the hammer provided with a cam made in accordance with the above law for the cam, then adjusting the length of the spring by means of the nut to some length which the operator considers to be approximately correct for the desired intensity of pressure, then giving the spring a slight initial compression, the amount also being a matter of judgment. The ring is then hammered and tested by means of the gaging device of my copending application Serial No. 93,904, filed April 25, 1916. The scale reading of the gaging device, divided by the radius of the ring, gives the pressure per inch of circumference and if this pressure is too great the nut is screwed up on the spring, so that a longer section of the spring becomes operative. If the intensity is too small the spring is correspondingly shortened. The circularity of the ring is then tested. If the diameter of the ring passing across the points is found to be shorter than the diameter perpendicular thereto, slightly more additional initial compression is given to the spring by sliding the nut down slightly without turning and then clamping. If the points are long then the initial compression is reduced. If one point is longer than the other then the cam is rotated slightly relative to the ring so that the intensity of the hammer blows on that side of the ring will be slightly decreased, and the intensity of the hammer blows on the other side will be slightly increased. After these adjustments are made as well as possible from the indications of the gauge, a second ring is hammered and again is tested on the gauging device. Ordinarily it requires but a few trials of this sort to set the hammer so that a substantially perfect ring is produced.

The hammer is then placed in operation and from time to time a ring is tested on the gaging device, and if necessary the initial compression of the spring is changed slightly to allow for any dulling' or change of shape of the hammer point. By this method of operation of the hammers it is possible to continuously produce substantially perfect rings with slight adjustments to the spring and occasional replacement of the dull hammer point with/a sharp hammer point.

My invention may be carried out either by the machine illustrated in the drawings, of which additional illustration is provided in my copending allowed case Serial No. 257 .843 or by means of my rolling machine of Patent Number 1,304,371 or in other ways.

W hat I claim as new is:

1. The method of condensing the metal of the inner circumference of a piston rin so as to give substantially uniform radia pressure at all points of the circumference when in use, which consists in so varying the intensities of the condensing forces that the intensity of the condensing force at any point is proportional to unity minus the cosine of the angle between the split of the ring and the point which is being condensed, plus a constant.

2. The method of hammering a piston ring so as to give substantially uniform radial pressure at all points of the circum ference when in use, which consists in so varying the intensities of the hammer blows that the intensity of the blow at any point is proportional to unity minus the cosine of the angle between the split of the ring and the point which is being hammered, plus a constant.

3. The method of hammering a series of piston rings so that they give substantiall the same uniform radial pressure at a 1 points of the circumference when in use, irrespective of the dulling of the hammer point, which consists in so varying the intensities of the hammer blows while hammering one group of the series that the intensity of the blow at any point is proportional to unity minus the cosine of the angle between the split of the ring and the polnt which is being hammered p us a constant, choosing a new constant in accordance with the condition of the hammer point, and re-hammering another group of said series of rings in accordance with the law that the intensity of the blows at any point is proportional to unity minus the cosine of the angle between the split of the ring and the point which is being hammered plus the new constant, all of the rings of the said series being thereby hammered so as to give substantially the-same uniform pressure at all points.

In testimony whereof, I have signed my name to this specification, in the presence of two subscribing witnesses. N

FREDERICK RAY.--'

Witnesses:

A. M. WILSON, FRANCIS RAINES.

Images