US2424087A - Chain - Google Patents

Description

July 15, 194 A. E. FO'CKE ET AL CHAIN Filed July 26, 1940 n r "IIIII' INVENTORS. 1 67mm fff'acxs and Patented July 15, 1947 CHAIN Arthur E. Focke and George G. Mize, Indianapolis, Ind., assignors to Diamond Chain and Manufacturing Company, Indianapolis, Ind,

a corporation of Indiana Application July 26, 1940, Serial No. 347,612

25 Claims. 1

Our invention relates to power-transmission chains of the type in which each pair of adjacent links are interconnected through the medium of a transversely extending pin press-fitted into pitch holes in laterally spaced side plates of one link and rotatably received in a transversely eX- tending opening in the other link. Most commonly, such transverse openin is the bore of a bushing the ends of which are press-fitted. into pitch holes in the side plates of the associated link; and the chain is made up of alternating pin-links and bushing-links, each pin-link embodying two longitudinally spaced pins and each bushing-link embodying two longitudinally spaced bushings. Frequently, sprocket-engaging rollers are rotatably mounted on the chain-bushings; and our invention will hereinafter be described as embodied in such a roller chain. It is to be understood, however, that this invention is directed to the mounting of the pins in side plates and, in the case of a chain embodying bushings, to the mounting of the bushings in side plates; and that the invention is applicable to various types of chain having pins or pins and bushings through the medium of which adjacent chainlinks are pivotally interconnected.

When such chains of the general type just referred to fail in fatigue as the result of repeated variations in the load to which they are subjected in use, the failure is almost always a fracture of one or more of the side plates in the vicinity of one of the pitch holes therein. It is the primary object of our invention to improve the fatigue resistance of chains of the type described by increasing materially the maximum load which, when repeatedly applied to the chain, will not result in failure of the side plates.

We have discovered that the resistance of the side plates to fatigue is greatly affected by the character of the fit of the pins and bushings within the pitch holes in the side plates. The smoother and more dense the surfaces of the pitch holes in the side plates and, within limits, the more tightly the pins or bushings fit in those holes, the greater will be the fatigue resistance of the chain against failure by fracture of the side plates.

The accompanying drawing illustrates our invention: Fig. 1 is a plan view, in partial section, of a roller chain; Figs. 2 and 3 are sectional views illustrating two different means by which the surfaces of the holes in each side plate may be improved to enhance fatigue resistance; and Fig, 4 is a section through a side plate finished in the preferred manner.

The chain shown in Fig. 1 is of the conventional roller type. It embodies a plurality of sprocketengaging elements interconnected by a series of pin-links, each of the latter comprising two outer side plates Ill and two pins II which extend through alined holes in the ends of the side plates. Each of the sprocket-engaging elements comprises a pair of spaced inner side plates I5, pinreceiving bushings [6 extending through holes in the ends of such side plates, and rollers ll rotatably mounted respectively on such bushings between the side plates I5.

When chains of the type described fail in fatigue the failure is almost always by fracture of one or more of the side plates [0 and 15, the fracture extending outwardly from one of the pitch holes generally laterally of the side plate. As indicated above, we have found that the resistance of the side plates to such failure as the result of fatigue is dependent to a great extent upon the fit of the pins and bushings Within the pitch holes in the side plates. Specifically, the resistance of the side plates to failure may be increased by increasing the smoothness and density of the surfaces of the pitch holes in the side plates and, within limits, by increasing the tightness of the fit of the pins or bushings within those holes.

It has been customary in chain of the type with which our invention is concerned to make the pins I l of such a diameter that they will have a press fit in the holes in the side plates I 0. The purpose of this was to prevent the pins from turning in the side plates and thereby to insure that any wear resulting from relative angular movement of two adjacent links of the chain would occur on the interengaging surfaces of the pins and bushings, as those surfaces are of considerably larger area, and therefore subject to a materially smaller unit load, than are the interengaging surfaces of the pins H and side plates [0.

Since rotative movement and axial movement of a pin H within the associated side-plate hole both involve friction between the same surfaces, the firmness with which the pin is held against rotation in the side plate, as Well as the firmness with which the pin is held against axial movement, may be measured by the force required to expel the pin from the side plate. To insure prevention of pin movement it has been found that the force required to expel the pin axially from the side plate should vary with the square of the pin-diameter and, in pounds, should be about such as is represented by the expression 10,000 D where D is the diameter of the pin in inches. Tolerances now in common use by manufacturers of chain are such as will provide, irrespective of side-plate thickness, pin-expelling forces in the neighborhood of 10,000 D pounds when the side plates are not heat-treated. When heat-treated side plates are employed, the pinexpelling force found in present day commercial chain may be somewhat higher than 10,000 D pounds.

We have found that the resistance of the outer side plates H! to failure from fatigue can be materially increased if such nominal diameters for pins and pin-holes, and such permissible tolerances for those dimensions, are maintained as will insure minimum pin-expelling force considerably higher than those found in commercial chain as now generally manufactured. In practicing our invention with side plates which are not heat treated, we establish nominal diameters and tolerances such that the minimum force required to expel any pin from its associated side plate will be at least 15,000 D and preferably at least 20,000 D pounds. When employing heattreated side plates the nominal diameters and tolerances are set so that the minimum force required to expel each pin from its side plate will be at least 20,000 D pounds, and preferably at least 30,000 D pounds.

The above values for the minimum force required to expel a pin from its side plate are those suitable for use in practicing our invention when the thickness of the side plate is approximately 40% of the pin diameter, which is the proportion obtaining in the vast majority of roller chains made today. The best results in increased fatigue resistance are secured when the force required to expel a pin increases with the sideplate thickness. Taking into account the possibility that the relation of side-plate thickness to pin-diameter may vary, the complete expression for the minimum force in pounds required to expel pin from an untreated side plate is 37,500 DT (and preferably 50,000 DT) where D is the nominal pin diameter as before, and T is the side-plate thickness in inches. For heattreated side plates, the expression would be 50,000 DT, and preferably 75,000 DT.

The increased tightness in the fit of the pins, which results from the practice of our invention,

introduces into the outer side plates in the regions surrounding the pitch holes initial unit stresses which are materially higher than those existing in chains as now manufactured. We

believe that it is the enhancement of these initial unit stresses which accounts for the increased fatigue resistance possessed by chain made in accordance with our invention.

In the same way that increased initial unit stress in the region of the pin receiving holes promotes increased fatigue resistance of the outer side plates I0, so will increased initial stress in the region of the bushing-receiving holes promote increased fatigue resistance of the inner side plates I5. Present day practice in respect to the tightnes of fit of the bushings 16 within the side plates results in bushing-expelling forces in the neighborood of 3000 D pounds when the inner side plates are not heat treated, and of 4,000 D pounds, when the inner side plates are heat treated. If the diameter and tolerances of the bushings and of the pitch holes in the inner side plates are established to insure materially higher bushing-expelling forcessay of 4500 D (and preferably 6000 D pounds for untreated side plates and 6000 D (preferably 9000 D pounds for heat-treated side plates-a noticeable increase in fatigue resistance of the inner side plates will be obtained. Here again, these minima presuppose a fixed relationship between the thickness of the side plate and the diameter of the pitch holes therein, such relationship being that existing in the majority of roller chan now being manufactured in which the thickness of the inner side plates is approximately 28% of the diameter of the bushing-receiving holes. Taking into account possible variations in this relationship, the minimum bushing-expelling force with untreated side plates should be at least 16,000 DT and preferably 21,000 DT. With heat-treated side plates, the permissible and preferred forces would be 21,000 DT and 32,000 DT, respectively. In these expressions for minimum bushing-expelling forces, D represents bushing diameter and T side-plate thickness in inches.

The actual force required to expel any pin or bushing from an associated side plate will vary not only with dimensions but also to some extent with the condition of lubrication of the pitch-hole surface and the surface of the pin or bushing therein. The values above set forth for expelling forces, both in the case of pins and in the case of bushings, assume that the parts will be in the condition existing after ordinary manufacturing operations-that the pins, bushings, and side plates will not have been subjected to any processing designed to render their surfaces substantially oil free and, on the other hand, that no lubricant will be employed especially for the purpose of facilitating the entry of the pins or bushings into the side plates.

We have also found that the resistance of the side plates to failure in fatigue is dependent upon the character of the surfaces of the pitch holes. The smoother these surfaces, and the more dense they are, the greater will be the resistance to fatigue. Most chain made today, or at least most chain made in high-quantity production, employs side plates in which the pitch holes have been formed by punching and shaving. In the punching operation, the punch employed is appreciably smaller than the mating die, to provide the necessary break out; and, as a result, a hole produced by a single punching operation is frusto-conical. To remove or reduce the taper from punched holes in side plates, they are usually subjected to a shaving operation, in which a punch slightly larger than the maximum diameter of the original punched hole is forced through the hole to remove a relatively small quantity of metal. The surface left by such operations is, for the most part, a fracture surface, or a surface resulting from a multiplicity of relatively small fractures; and, as a result, it is relatively rough. Other common methods of holesizing, such as reaming and broaching, also involve the removal of metal and produce surfaces which are relatively rough.

If the irregularities left by the usual methods of finishing the pitch holes are removed and the holes in the side plates given their final size by an operation which will produce a smooth, dens-e surface, 'an improved fatigue resistance will result. In order to produce a pitch-hole surface of the desired characteristics, we enlarge the pitch holes to their final size by a coldwvorking operation, preferably by drifting either with a hardened ball 25 as shown in Fig. 2 or with a hardened and tapered drift-pin 26 as shown in Fig. 3. The diameter of the ball 25, or the maxi mum diameter of the drift-pin 126, should be a few thousandths of an inch larger than the lar est diameter of the hole through which the ball or pin is forced.

We find that with the pitch holes drifted to their final diameter, either with a hardened ball or with a hardened drift-pin, the fatigue resistance of the side plates is materially increased even though fit of the pins or bushings within those holes is such as will result in expelling forces approximating those found in standard chain; but in order to obtain the optimum result from our invention, it is necessary that the tightness of the fit of the pins and bushings within the side plates be increased to produce the higher expelling forces above set forth.

Cold-working of the surfaces of the pitch holes, as by drifting, has several eifects which contribute to increasing the fatigue resistance of the side plates. In the first place, drifting tends to smooth the hole surface and to eliminate minute cracks which, under repeatedly imposed loads, might develop into fractures. In the second place, drifting eliminates high. spots or projections which, by yielding when the pin or bushing is pressed into the hole, would lessen the stress created in the side plate in the region surrounding the hole. In the third place, cold-working of the metal adjacent the surface of the pitch hole tends to make that metal more dense, so that when the pin or bushing is pressed into the hole higher unit stresses will result not only in the metal of increased density but also outwardly therebeyond.

We find it desirable to chamfer the edges of the pitch holes at least at that side of the side plate from which the pin or bushing enters during assembly of the link. The chamfering of the holeedge is preferably effected by cold working, conveniently in the manner indicated in Fig. 2. There the drifting ball 25 is shown as being forced through the pitch hole by a punch 3d having above its lower end a shoulder 3 l. The lower portion of the punch is cylindrical, and, at the point where it joins the shoulder 3!, a fillet 32 is provided. At least for a short distance below the fillet 32 the punch has a diameter equal to, or 0.001 or 0.002 inch larger than, the final, diameter of the pitch hole. In the operation. of forcing the ball 25 through the pitch hole, downward movement of the punch is continued until the fillet 32 engages the edge of the hole and chamfers it, as shown somewhat exaggeratedly at 3? in Fig. 4. Such chamfering not only facilitates entry of the pin or bushing into the pitch hole during subsequent assembly, but also tends to prevent the pin or bushing from tearing the side plate metal and thus destroying the desirable surface conditions produced by the drifting operation.

When the surfaces of the pitch holes are smoothed and made more dense as by drifting, and when nominal diameters and tolerances are established to insure minimum expelling forces such as previously set forth, we find that fatigue resistance of the side plates will be increased by as much as 50 We claim as our invention:

1. In a power-transmission chain, a series of pin links each comprising a pair of side plates provided with alined holes and pin-s received in such holes, the fit 0f the pins within the sideplate holes being materially tighter than necessary to prevent movement of the pins in the side plates during operation of the chain, the holes 6 in the side plates being enlarged to final size by drifting prior to assembly.

2. In a, power-transmission chain, a series of pin links each comprising a pair of side plates provided with alined holes and pins received in such holes, the fit of the pins within the sideplate holes being such that the force in pounds required to expel each pin from a side plate is at least 37,500 DT if the side plates are not heattreated and at least 50,000 DT if the side plates are heat-treated, where D and T are, respectively, the diameter of the pins and the thickness of the side plates in inches.

3. In a power-transmission chain, a series of pin links each comprising a pair of side plates provided with alined holes and pins received in such holes, the fit of the pins within. the sideplate holes being such that the force in pounds required to expel each pin from a side plate is at least 50,000 DT if the side plates are not heattreated and at least 75,000 DT if the side plates are heat-treated, where D and T are, respectively, the diameter of the pins and the thickness of the side plates in inches.

4. The invention set forth in claim 2 with the addition that the holes in the side plates are enlarged to final size by drifting prior to assembly.

5. The invention set forth in claim 2 with the addition that the holes in the side plates are enlarged to final size by drifting prior to assembly, that edge of each hole adjacent the longitudinal center line of the chain being chamfered by cold compression.

6. In a power-transmission chain, a. series of pin links each comprising a pair of side plates provided with alined holes and pins having a press fit in such holes, the holes in the side plates are enlarged to final size by drifting prior to assembly, that edge of each hole adjacent the longitudinal center line of the chain being chamfered by cold compression.

7. In a power-transmission chain, a series of pin links each comprising a pair of side plates provided with alined holes and pins having a press fit in such hole, the holes in the side plates being enlarged to final size by drifting prior to assembly.

8. In a, power-transmission chain, a series of sprocket-engaging links each comprising a pair of side plates provided with alined holes and bushings received in such holes, the fit of the bushing within the side-plate holes being materially tighter than necessary to prevent movement of the bushings in the side plates during operation of the chain, the holes in the side plates being enlarged to final size by drifting prior to assembly.

9. In a power-transmission chain, a series of sprocket-engaging links each comprising a pair of side plates provided with alined holes and bushings received in such holes, the fit of the bushings within the side-plate holes being such that the forcein pounds required to expel each bushing from a side plate is at least 16,000 DT if the side plates are not heat-treated and at least 21,000 DT if the side plates are heat-treated, where D and T are, respectively, the diameter of the bushings and the thickness of the side plates in inches.

10. In a power-transmission chain, a series of sprocket-engaging links each comprising a pair of side plates provided with alined holes and bushings received in such holes, the fit of the bushings within the side-plate holes being such that the force in pounds required to expel each bushing from a side plate is at least 21,000 DT if the side plates are not heat-treated and at least 32,000 DT if the side plates are heat-treated, wher D and T are, respectively, the diameter of the bushings and the thickness of the side plates in inches.

11. The invention set forth in claim 9 with the addition that the holes in the side plates are enlarged to final size by drifting prior to assembly.

12. The invention set forth in claim 9 with the addition that the holes in the side plates are enlarged to final size by drifting prior to assembly, that edge of each hole adjacent the longitudinal center line of the chain being chamfered by cold compression.

13. In a power-transmission chain, a series of sprocket-engaging links each comprising a pair of side plates provided with alined holes and bushings having press-fit in such holes, the holes in the side plates are enlarged to final size by drifting prior to assembly, that edge of each hole adjacent the longitudinal center line of the chain being chamfered by cOld compression.

14. In a power-transmission chain, a series of sprocket-engaging links each comprising a pair of side plates provided with alined holes and bushings having a press-fit in such holes, the holes in the side plates being enlarged to final size by drifting prior to assembly.

15. In a power-transmission chain, a plurality of sprocket-engaging links connected in series by pin links, each of said sprocket-engaging links comprising a pair of inner side plates provided with alined holes and bushings received in such holes, each of said pin links comprising outer side plates provided with alined holes and pins received in said holes and respectively extending through bushings in adjacent sprocket-engaging links, the fit of the bushings within the inner side-plate holes being such that the force in pounds required to expel each bushing from a side plate is at least 16,000 U1 if the side plates are not heat-treated and at least 21,000 DT if the side plates are heat-treated, where D and T are, respectively, the diameter of the bushings and the thickness of the side plates in inches, and the fit of. the pins within the outer side-plate holes being such that the force in pounds required to expel each pin from a side plate is at least 37,500 DT if the side plates are not heat-treated and at least 50,000 D'T' if the side plates are heattreated, where D and T are, respectively, the diameter of the pins and the thickness of the side plates in inches.

16. In the process of manufacturing powertransmission chain embodying pin links each comprising side plates and a pair of pins, the steps of punching holes in the side plates, enlarging such holes to final size by drifting, pressing the pins in the holes, and controlling the diameters of the respectively interfitting pins and holes so that the force in pounds required to expel any pin from a side plate is at least 37,500 DT if the side plates are not heat-treated and at least 50,000 DT if the side plates are heat-treated, where D and T are, respectively, the diameter of the pins and the thickness of the side plates in inches.

17. In the process of manufacturing powertransmission chain embodying sprocket-engaging links each comprising side plates and a pair of bushings, the steps of punching holes in the side plates, enlarging such holes to final size by drifting, pressing the bushings in the holes, and controlling the diameters of the respectively interfi-tting bushings and holes so that the force in pounds required to expel any bushing from a side plate is at least 16,000 DT if the side plates are not heat-treated and at least 21,000 DT if the side plates are heat-treated, where D and T are, respectively, the diameter of the bushings and the thickness of the side plates in inches.

18. In the process of manufacturing powertransmission chain embodying pin links each comprising side plates and a pair of pins, the steps of punching holes in the side plates, pressing the pins in the holes, and controlling the diameters of the respectively interfitting pins and holes so that, the force in pounds required to expel any pin from a side plate is at least 37,500 DT if the side plates are not heat-treated and at least 50,000 DT if the side plates are heat-treated, where D and T are, respectively, the diameter of the pins and the thickness of the side plates in inches.

19. In the process of manufacturing powertransmission chain embodying sprocket-engaging links'each comprising side plates and a pair'of bushings, the steps of punching holes in the side plates, pressing the bushings in the holes, and controlling the diameters of the respectively interiitting bushings and holes so that the force in pounds required to expel any bushing from a side plate is at least 16,000 DT if the side plates are not heat-treated and at least 21,000 DT if the side plates are heat-treated, where D and T are, respectively, the diameter of the bushings and the thickness of the side plates in inches.

20. Li a power-transmission chain, a series of links, each of said links comprising a pair of spaced side-plates overlapping the side plates of an adjacent link, and means for interconnecting adjacent links, each said means comprising a bushing and a pin extending through and projecting beyond the ends of said bushing, the side plates of one of the associated links being provided with alined holes for receiving the ends of said bushing and the side plates of the other of the associated links being provided with alined holes for the reception pf the ends of said pin, the fit of the pins within the pin-receiving sideplate holes being such that .the force in pounds required to expel each pin from a side plate is at least 37,500 DT if the side plates are not heattreated and at least 50,000 U1 if the side plates are heat-treated, Where D and T are, respectively, the diameter of the pins and the thickness of the side plates in inches.

21. In a power-transmission chain, a series of links, each of said links comprising a pair of spaced side-plates overlapping the side plates of an adjacent link, and means for interconnecting adjacent links, each said means comprising a bushing and a. pin extending through and projecting beyond the ends of said bushing, the side plates of one of the associated links being provided with alined holes for receiving the ends of said bushing and the side plates of the other of the associated links being provided with alined holes for the reception of the ends of said pin, the fit of the bushings within the bushing-receiving side-plate holes being such that the force in pounds required to expel each bushing from a side plate is at least 16,000 D'I if the side plates are not heat-treated and at least 21,000 DT if the side plates are heat-treated, where D and T are, respectively, the diameter of the bushings and the thickness of the side plates in inches.

22. In a power-transmission chain, a series of links, each of said links comprising a pair of spaced side-plates overlapping the side plates of an adjacent link, and means for interconnecting adjacent links, each said means comprising a bushing and a pin extending through and projecting beyond the ends of said bushing, the side plates of one of the associated links being provided with alined holes for receiving the ends of said bushing and the side plates of the other of the associated links [being provided with alined holes for the reception of the ends of said pin, each of said pins having a press-fit in the pinreceiving holes of the side plates, said pin-receiving holes lbeing enlarged to final size by drifting.

23. In a, power-transmission chain, a series of links, each of said links comprising a. pair of spaced side-plates overlapping the side plates of an adjacent link, and means for interconnecting adjacent links, each said means comprising a bushing and a pin extending through and projecting beyond the ends of said bushing, the side plates of one of the associated links being provided with alined holes for receiving the ends of said bushing and the side plates of the other of the associated links being provided with alined holes for th reception of the ends of said pin, each of said bushings having a press-fit in the bushing-receiving holes of the side plates, said bushing-receiving holes being enlarged to final size by drifting.

24. The invention set forth in claim 1 with the addition that that edge of each hole adjacent the longitudinal center-line of the chain is chamfered by cold compression.

25. The invention set forth in claim 8 with the addition that that edge of each hole adjacent the longitudinal center-line of the chain is chamfered by cold compression.

ARTHUR EL FOCKE. GEORGE G. MIZE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS

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