US3362685A - Chain hoist - Google Patents

Description

P. R. NOYE ET AL Jan. 9, 19 8 CHAIN HOIST 6 Sheets-Sheet 1 Filed May 18, 1965 INVENTOR.

PAUL R. NOYE HENRY T JAKUBOWSKI ALLAN E. ELDRIDGE asmfim dmwwvwm ATTORNEYS Jan. 9, 1968 P. R. NOYE A 3,362,635

CHAIN HOIST Filed May 18, 1965 6 Sheets-Sheet. z

INVENTOR.

PAUL R. NOYE HENRY T. JAKUBOWSKI ALLAN E. ELDRIDGE M A TTORNEYS CHAIN SPEED PER MINUTE Jan. 9, 1968 I P. R. NOYE Em 3,362,685

CHAIN HOIST Filed May 18, 1965 i e Sheets-Sheet 5 f/XED CENTERS STANDARD GEAR & P/lV/O/V ONE REVOLUTION or L/FTWHEEL 0 1-5 90 I; 5 :80 235 2,70 315 3&0

DEGREES INVENTOR.

PAUL R. NOYE HENRY T. JAKUBOWSKI ALLAN E. ELDRIDGE ATTORNEYS Jan. 9, 1968 P. R. NOYE T AL 3,362,635

CHAIN HOIST Filed May 18, 1965 6 Sheets-Sheet 4 2-HORSE PO WEI? 32 FEET P6P MINUTE T N 7' 0/ r F 6 0 CAP/{Cl YH s d B d A c/xecump amps NON-CIPCUAAR (CCE/V 7'/?/ C) GEARS-0 OFfSfT Fig.8.

/vo/v- C/RC ULAR (,Eccm 72/0) GEARS 6 DUI-F557 IN VENTOR.

PAUL R. NOYE HENRY 'l'. JAKUBOWSKI ALLAN E. ELDRIDGE ATTORNEYS Jan. 9, 1968 P. R. NOYE L 3,362,585

CHAIN HOIST Filed May 18, 1965 e Sheets Sheet 5 I N VENTORS TOR/Vi'YS PAUL R. NOYE HENRY 7TJAKUBOWSK/ ALLEN E. ELDR/DGE O QQWW BANG E LOAD-5 54 52 LOAD one x313 ukQ wk. kmm Qmmkm k 8 t wag United States Patent 3,362,685 CHAIN HOlST Paul R. Noye, 645 Sheridan Drive, Tonawanda, NY.

14150; Henry T. Jakubowski, 365 Drake Drive, North Tonawanda, N.Y. 14120; and Allan E. Eldridge, 184

Harding Road, Williamsville, N.Y. 14221 Filed May 18, 1965, Ser. No. 456,781 Claims. (Cl. 254-168) ABSTRACT OF THE DISCLOSURE The useful life of the load chain of a hoist is extended by cyclically varying the angular velocity of the chain lift wheel. The lift wheel is driven at cyclically varying speed which is related to, but out of phase with, the in stantaneous positions of the lift wheel pockets.

This invention relates to chain hoist mechanisms and pertains, more particularly, to certain improvements therein for reducing and minimizing variations in the forces acting upon the load chain and hoist mechanism incidental to raising and lowering a load.

A conventional industrial chain hoist includes a lift wheel over which the load chain is trained, an electric motor, and gear reduction mechanism connecting the motor to the lift wheel. In order to maintain the weight and size of the chain hoist within reasonable limits, the lift wheel is made with a small number of chain wheel pockets so that not only is its size minimized, but so that it may also avoid the necessity for such numerically large gear reduction between the motor and the lift wheel as would require a large number of reduction steps. Since a lift wheel having but a few chain link pockets will be grossly out ofround, the center line of the load bearin g flight of the load chain will shift back and fourth (radially of the lift wheel) as the lift wheel rotates to impart a fundamental vibration to the load chain which is related to the angular .velocity of the lift wheel and the number of chain link pockets therein. The natural frequency of the load suspended by a load chain, on the other hand, is dependent upon the weight of the load and the length of the load chain (i.e. the distance between the load and the lift wheel). Obviously, the natural frequency of the load-load chain combination is constantly changing as the load is lifted or lowered (increasing as the load moves toward the lift wheel and vice versa). Under many circumstances, the natural frequency of the load chain combination will, throughout the range of operation, be much higher than the fundamental frequency imparted by the lift wheel. Other circumstances may, however, be such as to produce a situation in which the fundamental frequency imparted to the load chain by the lift wheel is in resonance with the load-chain combination at some point (critical load chain length) during the normal operation of the hoist, particularly in circumstances wherein the angular velocity of the lift Wheel is increased to obtain more rapid raising or lowering of the load. Thus, the natural frequency of the load chain and load combination may, during raising or lowering, pass through one or more critical values at which time such natural frequency will be in resonance with either the aforesaid fixed fundamental frequency of the force system or a harmonic thereof. Under such conditions, the actual load experienced by the load chain and hoist mechanism may significantly exceed the actual load being handled which, in turn, accelerates load chain fatigue and shortens the service life of the hoist. It is, therefore, of primary concern in connection with this invention to provide improvements in chain hoists so that overloads stemming from vibration effects, as above, may be minimized. More partic- 3,362,685 Patented Jan. 9, 1968 ularly, it is an object of this invention to provide means whereby the angular velocity of a lift wheel is varied cyclically so as to minimize overloads as aforesaid.

More specifically, the present invention concerns the combination, in a chain hoist, of a lift wheel of small or minimum size having a load chain engaged therewith and a drive train, between a suitable motor and such lift wheel, which incorporates means for cyclically varying the angular velocity of the lift wheel in a manner to alleviate vibration-induced overloads as aforesaid.

In accord with the preceding objects, this invention specifically concerns the provision of a gear drive embodying an eccentrically mounted pinion and a driven gear constantly in mesh therewith; in which the driven gear is provided with a member of lobes equal in number to the number of chain link pockets of the associated lift wheel which, in conjunction with a gear ratio between pinion and driven gear which also is equal to the number of pockets as aforesaid, may be used to impart a cyclically varying angular velocity to the lift wheel.

With relation to the preceding object, we have found that for maximally affecting vibration-induced overloads, there are optimum conditions of pinion eccentricity and phase relationship between the pinion and lift wheel which may be employed to substantially eliminate the vibration-induced overloads. Accordingly, it is a further object of this invention to provide an improved chain hoist employing these optimum conditions of eccentricity and phase.

Other objects and advantages of the invention will appear from the description hereinbelow and the accompanying drawing wherein:

FIG. 1 is a bottom plan view, partly broken away illustrating a hoist mechanism constructed in accordance with the present invention and, in particular, illustrating components of the drive train thereof;

FIG. 2 is an enlarged section taken substantially along the plane of section line 22 in FIG. 1 and illustrating the eccentric pinion and multi-lobe driven gear;

FIG. 3 is an enlarged sectional view taken substantially along the plane of section line 33 in FIG. 1 illustrating details of the lift wheel;

FIG. 4 is a diagrammatic view illustrating the operation of the eccentric pinion and the multi-lobe driven gear;

FIG. 5 is a graph illustrating load chain velocity variations during one revolution of the lift wheel in a prior art arrangement;

FIGS. 6-8 are graphs illustrating lift chain overloads at resonant conditions and showing the improvement according to this invention in FIG. 7 in comparison with effects in the prior art (FIG. 5) and effects when using the eccentric drive near multi-lobe driven gear in phase with the lift wheel (FIG. 6);

FIG. 9 is a graph showing the effect of eccentricity for a fixed phase angle; and

FIG. 10 is a graph showing the effect of variation of phase angle.

Referring now more particularly to FIG. 1, the reference numeral 16 therein indicates generally a housing or body of hollow form and which forms the main frame or mounting component for the chain hoist mechanism according to the present invention. As shown, the body 10 is comprised of several sections such as those indicated by reference characters 12, 14, 16, 18, 20 and 22, disposed in stacked relationship relative to each other and, compositely, forming the main frame or body of the mechanism. Disposed within a portion of the body 10 is a suitable drive source such as the electric motor 24 having a drive shaft 26 extending therefrom. In the specific embodiment shown, the wall portion 28 of the section 16 is provided with a bearing seat receiving a suitable ball bearing 39 supporting the corresponding end of the drive shaft 26 through the intermediary of a coupling sleeve 32. The coupling sleeve 32 is internally splined and serves to connect the splined end portion of the shaft 26 with the splined portion 34 of the pinion shaft 36, the latter shaft being provided with an integrally formed or otherwise suitably provided pinion member 38 and the shaft 36 is provided with an extension finding bearing support in a further portion of the housing assembly 10, as will be readily apparent. Surrounding the shaft 36 is the quill shaft member 40 having a lift wheel 42 formed integrally therewith, such quill shaft being supported by the ball bearings 44 and 46, substantially as is shown. The quill shaft 40 also mounts a driven gear 48 as by splines or the like and this driven gear is in constant mesh with a pinion gear 50 fixed to a shaft 52 as by being formed integrally therewith and a further gear 54 is fixed to the shaft 52 as by splines or the like, which latter gear 54 is in mesh with the aforementioned pinion 38. The shaft 52 is suitably supported by bearings 56 and 58.

As can be readily appreciated from a study of FIG. 1, it is necessary to obtain in order a compact, rigid and lightweight unit, that the dimensions, that is the diameter, of the lift wheel 42 be relatively small. A conventional form of lift Wheel is shown more particularly in FIG. 3 wherein it will be seen that the specific configuration shown incorporates four chain link pockets such as that indicated by the reference character 60 in FIG. 3. As a practical matter, the lift wheel may be constructed to contain as few as three chain link pockets about its periphery. As a consequence of this small diameter construction of the lift wheel 42, taking into consideration the fact that the length of each of the pockets 60 is pro-fixed due to the length of the links of the load chain, it can be appreciated that with a small number of pockets, and a consequently small diameter for the lift wheel 42, the pockets 60 in each case represent a substantial extent of the total circumferential length of the lift wheel. As a result, if the lift wheel is rotated at a constant angular velocity, the load bearing flight of the load chain will cyclically vary in linear velocity during each revolution of the lift wheel. A graph of load chain velocity variations during one revolution of a of a four pocket lift wheel rotated at fixed angular velocity is shown in FIG. 5. From this figure, it will be appreciated that attainment of a fixed load chain velocity would be a formidable, if not impossible, undertaking. Thus, one might reasonably expect to obtain some smoothing out of the load chain velocity but one would, at the same time, except some cyclic variation to remain. In practice, we have found this to be indeed true and although this smoothing out of the load chain velocity variations produces a measurable reduction in overload forces in the load chain, we have found that slight deviation from what would otherwise appear to be the ideal situation with regard to smoothing out load chain velocity variations produces unexpected results and virtually eliminates the most troublesome overload factor.

To appreciate the above, it will be realized that the curve of FIG. 5, since the lift wheel is being rotated at constant angular velocity, also represents variations in the effective diametral pitch of the lift wheel as it acts upon the load chain. Thus, as is shown in FIG. 4, the reference character 62 represents the center line of the load bearing flight of the chain as it issues from the lift wheel 42. The center line 62 will shift relative to the vertical plane 64 passed through the fixed axis of the lift wheel 42 between the minimum position shown in FIG. 4 and various other different positions as the lift wheel is rotated. Thus, even though the linear velocity of the chain may be altered by cyclically varying the angular velocity of the lift wheel, noting the fact that the linear velocity of the chain at any instant is equal to the angular velocity of the lift wheel 42 multiplied by the effective radius (68 in FIG. 4) at that instant, the effective diametral pitch of the lift wheel at any given instant remains unaltered and variations in the diametral pitch bear a relationship such as is shown in FIG. 4. It is important to bear this relationship in mind since the minimums of diametral pitch, occurring at points 68 in FIG. 4, will hereinafter appear to be reference points bearing upon the inventive concepts hereinafter pointed out.

The present invention contemplates the provision of means for cyclically varying the angular velocity of the lift wheel 42 during each revolution thereof in such fashion as to be timed in a particular manner with the cyclic shifting of the load bearing flight center line 62 relative to the axis of rotation of the lift wheel 42, that is, with the instantaneous diametral pitch of the lift wheel.

The specific manner in which the above is accomplished in connection with the present invention will be seen more clearly from a study of FIG. 4. In this figure, the driven gear 48 of FIG. 1 will be seen to be provided with four lobe portions 70, 72, 74 and 76 which are equidistantly spaced around the periphery of the gear and which have maximum radii which diifer from the radii at the intermediate points by an amount equal to the eccentricity 78 with which the pinion 50 is formed with respect to its fixed axis of rotation at 80. It will be noted that there are a number of lobes on the driven gear 48 equal in number to the number of pockets on the lift wheel 42 and it is also to be noted that the gear ratio between the pinion 50 and the driven gear 48 is also equal to the number of pockets on the lift wheel 42. With this arrangement prevailing, and with the additional arrange ment prevailing, that the effective radius 67 of the pin= ion 50 is at a maximum when the lift wheel radius 68 is at a minimum as shown in FIG. 4, the angular velocity of the lift wheel 42 will be varied in such ways as to minimize cyclic variations in the linear velocity of the chain during each revolution of the lift wheel. However, this ostensibly ideal situation does not, we have found, produce the minimum condition of load chain overload. Instead, we have found that if the eccentric pinion and lobed gear are so related to the lift wheel that the minimum radius 68 of the lift wheel is effective close to but not at the attainment of maximum radius 67 of the pinion, overload conditions in the load chain are drastically reduced.

To appreciate the above, reference is had to FIGS. 6-8. In FIG. 6, overload conditions in the load chain of a hoist employing a circular pinion 50 and a circular gear 48 are shown, the particular hoist used being loaded at its maximum capacity of 2000 pounds. From FIG. 6, it will be clear that the load chain undergoes loading which exceeds the actual load by approximately 1500' pounds, see point A. In FIG. 7, the conditions are the same as in FIG. 6 except that an eccentric pinion 50 and lobed gear 48 are used, with the maximum radius of the pinion being timed to be effective at the minimum diametral pitch points of the lift wheel. That is to say, the drive gears are in phase with the left wheel as it acts upon the load chain. As a result, the load chain in FIG. 7 is subjected to an overload of only approximately 900 pounds at point A. In contrast to the effects shown in FIGS. 6 and '7, FIG. 8 shows identical conditions as FIG. 7 except that the pinion 50 and gear 48 are related to the lift wheel 42 so that, in the hoisting direction, the maximum radius 67 of pinion 50 is effective 6 /2 prior to occurrence of the attainment of the minimum radius 68 of the lift Wheel, the angular measure being relative to the lift wheel. As can be seen from FIG. 8, there is a practical absence of any overloading such as occurs at the points A and A respectively in FIGS. 6 and 7. The overloading at regions B, B and B" is due to forces arising from acceleration of the load from rest to the indicated speed of 32 feet per minute, whereas overloads in regions such as C in FIG. 6 and C in FIG. 7 appear to be related harmonically to the overloads occurring at points A and A. That is to say, it will be appreciated that as the load is moved, the length of the load chain flight supporting the load changes so that the natural frequency of the load chain-load combination varies accordingly. At points of resonance (A and A) where the natural frequency of the load chain-load combination coincides with the fixed frequency of the force variations occasioned by the unavoidable cyclic variation in the linear velocity of the load chain, maximum overloading will occur, whereas at other natural frequencies, harmonically related to the resonant frequency, other overloadings (regions C and C) will occur.

FIGS. 6-8 show the load being lowered since in all cases this represents the most aggravated condition of overloading; the load while being raised exhibiting overload patterns in all cases similar to the respective FIGS. 6-8 but at slightly less overload maximums, inclusive of the overloads occurring in the regions B, B and B. In addition to the vastly reduced maximum overload which occurs in FIG. 8, it is of particular significance that overloading as a function of time is significantly less in FIG. 8 than for either FIG. 6 or FIG. 7 and that substantially greater reduction is experienced in this respect as between FIG. 7 and FIG. 8 than is experienced between FIG. 6 and FIG. 7. In regard to this, it will be noted that the abscissas of FIGS. 6-8 may be considered as time axes as well as load chain lengths.

From the above, it will be appreciated that two factors are involved in minimizing overloads due to vibrationinduced forces, the eccentricity of the non-circular gear and the phase angle between the lift wheel and the noncircular gear. FIG. 9 shows the maximum dynamic load variation with respect to eccentricity at a fixed phase angle (6.9 clockwise). The graph shows that for the phase angle of 6.9, the eccentricity would ideally be 0.02-625, that is, the intercept at the static load line. The fact that the curve crosses the static load line merely indicates transition between conditions in which the dynamic overload is in leading or lagging relation. That is, the point identified as 0.025" offset indicates an undercorrected condition while the point identified as 0.041 offset indicates an overcorrected condition.

FIG. 10 shows the envelope of dynamic load fluctuations above and below the static load for a fixed eccentricity with variable phase angle, and also shows the maximum dynamic load with standard circular gears. As can be seen, substantial improvement over the standard gears is achieved even at zero phase angle, but minimum overloading occurs at about 6.95 clockwise phase angle.

As used herein, clockwise phase an le between the eccentric lift wheel and the pocket wheel means an outof-phase angle between these entities which causes the lift wheel to lag the pocket wheel when the load is being lowered and vice versa as the load is hoisted. It will be understood that the specific data herein refers to a four pocket wheel whereas it is of course possible to use other and diiferent members of pockets, in which case the specific data given would not apply.

It will be understood that increase in fatigue life stems from reduction of the overload range. That is to say, with the standard circular gears as indicated in FIG. 10, the range of overload amounts to approximately 3000 pounds whereas with the accentric gears indicated, the maximum overload range is only about 1500 pounds, occurring at zero index angle, and decreases to the minimum of about 250 pounds at about 7 index angle, as shown.

It is to be understood that certain changes and modifications as illustrated and described may be made without departing from the spirit of the invention or the scope of the following claims.

What is claimed is:

1. In a chain hoist mechanism, a lift wheel journalled for rotation about a fixed axis and having 11 number of chain link-receiving pockets for alternate links of a load chain, a motor having a drive shaft driven at a constant angular velocity, and drive means connecting said drive shaft to said lift wheel, the improvement consisting of:

a pinion and a driven gear forming part of said drive means, said driven gear having its teeth disposed along a closed, non-circular path symmetrical about the axis of the driven gear and defining n lobes, said pinion being eccentrically mounted for constant mesh with said driven gear, and said driven gear having n y teeth in which y is the number of teeth on said pinion, whereby said driven gear is rotated at cyclically varying angular velocity, the varying angular velocity of said driven gear being timed with respect to rotation of said lift wheel to minimize vibration-induced overload of said load chain.

2. A chain hoist mechanism comprising, in combination,

a hollow body assembly providing a frame,

a motor mounted within said body and having a drive shaft,

a lift wheel journalled within said body and having a plurality of chain link pockets for receiving alternate links of a load chain whereby the pitch diameter of the lift wheel varies about the circumference thereof,

a load chain having parallel flights projecting into said body and joined by a bight portion trained over said lift wheel whereby the load chain is cyclically acted upon at the minimum pitch diameter of the lift wheel,

and drive means connecting said drive shaft to said lift wheel for imparting angular velocity to the latter which varies between maximum and minimum limits and in which the maximum limit of lift wheel angular velocity is imparted out of phase with the interaction between the load chain and the lift wheel at the minimum pitch diameter of the latter,

said drive means including an eccentrically mounted pinion and a driven gear meshing with said pinion, said driven gear having equally spaced lobes thereon of a number corresponding to the number of pockets in said lift wheel, and the gear ratio from said pinion to said driven gear also being equal to the number of pockets in said lift wheel.

3. In a chain hoist mechanism, in combination,

a lift wheel having a small number of chain link pockets arranged circumferentially therearound and defining flats thereon,

a chain trained over said lift wheel,

a drive gear for rotating said lift wheel in unison therewith, said drive gear being non-circular and having a number of lobes equal to the number of said flats, said lobes being joined by flattened sectors,

a circular pinion meshing with said drive gear and eccentrically journalled by an amount equal to the difference between the minimum and maximum radii of said drive gear,

said flats on the left wheel and said flattened sectors of the drive gear being substantially in rotational alignment, and the difference between the minimum and maximum radii of said drive gear being of an amount suflicient to minimize vibration-induced dynamic overloads in said chain incidental to raising and lowering of a load which may be supported thereby.

4. In a chain hoist mechanism, in combination,

a lift wheel having a small number of chain link pockets arranged circumferentially therearound and defining flats thereon,

a chain trained over said lift wheel,

a drive gear for rotating said lift wheel in unison therewith, said drive gear being non-circular and having a number of lobes equal to the number of said flats, said lobes being joined by flattened sectors,

a circular pinion meshing with said drive gear and eccentrically journalled by an amount equal to the difference between the minimum and maximum radii of said drive gear,

said flats on the lift wheel and said flattened sectors on the drive gear being out of phase rotationally in an amount sufiicient, and the eccentricity of said pinion being of an amount sufiicient, to minimize vibrationinduced dynamic overloads in said chain incidental to raising and lowering of a load which may be supported thereby.

5. A chain hoist mechanism comprising, in combination,

a body assembly providing a frame,

a motor mounted on said body assembly and having a drive shaft,

a lift wheel journalled in said body assembly and positioned in a vertical plane and having a plurality of elongate chain link pockets for receiving alternate links of a load chain,

a load chain having a load-bearing flight suspended from said body assembly and a portion trained over said lift Wheel,

and drive means connecting said drive shaft to said lift wheel, said drive means including an eccentrically mounted pinion and a driven gear meshing with said 20 pinion, said driven gear having equally spaced lobes thereon of the number corresponding to the number of pockets in said lift wheel, and the gear ratio from said pinion to said driven gear also being equal to 8 the number of pockets in said lift wheel, whereby the angular velocity of said lift wheel varies cyclically between maximum and minimum limits a number of times equal to the number of said pockets during each revolution of the lift wheel, the meshing point between said pinion and said driven gear being related to said lift wheel such that maximum angular velocity is imparted to said lift wheel out of phase with disposition of each pocket in such position as its axis in the direction of elongation is vertically disposed.

References Cited UNITED STATES PATENTS 2,243,358 5/1941 Robins 254-168 2,477,441 7/ 1949 Cole 74437 2,585,971 2/1952 Sloane 74437 2,700,285 1/1955 Bellini 74437 2,861,635 11/1958 Orr 74-437 EVON C. BLUNK, Primary Examiner.

ANDRES H. NIELSEN, Examiner.

H. C. HORNSBY, Assistant Examiner.

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