CA1082003A - Belt pulley - Google Patents

Abstract

SLIPPING BELT CLUTCH

ABSTRACT OF THE DISCLOSURE

A belt drive system in a washing machine for bidirectional operation in selection of agitation and spin cycles and having a belt and pulley arrangement adapted to transmit full motor torque in the agitation direction and substantially limited torque through belt slippage in the spin direction whereby final spin speed is reduced in proportion to out-of-balance conditions existing in the spin tub. A motor drive pulley having heat barrier means is pro-vided to isolate friction heat generated by belt slippage on the pulley rim from the motor shaft and to prevent damage to elements in engagement with the shaft. A method of calibrating a belt tensioning spring is also disclosed.

Description

The invention relates to a pulley of the type for use in mechanical power transmission.
This is a division of co-pending Canadian Patent Application Serial No. 255,328 r filed June 21, 1976.
Numerous belt drive applications require that the torque transmitted to a driven member be limited to less than :~
the torque capacity of a driving member. In the specific application of domestic washing machines, it has been the ~.
custom in many product designs to limit the torque which is ~ :
applied in at least the initial period of a spin cycle to allow the motor to reach full speed as soon as possible, while permitting the spin tub to accelerate somewhat more slowly to its final speed. Typically, the starting-winding of the appliance motor would overheat if it remained energized during the time required to accelerate the spin tub to its final -:
speed, owing to its rotational inertia and the damping forces developed by water in and surrounding the spin tub. Besides .
:l motor protection, slow acceleration of the spin tub through drive slippage allows the clothes or other articles to distribute themselves evenly within the spin tub. Add.itionally, slow spin tub acceleration avoids polka dot spotting of the articles, which may : ' ,:

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occur ~her~ soiled water is no~ removed from the spin tub before articles are -tightly held against the perforations of the tub by centrifugal force and water being cen~rifuged is forced through I ~he articles at the spin tub perforations The differential ¦ r~tes of start-up between the motor and spin tub ha~e generally ¦ been accommodated by either a slip clutch such as ~hat disclosed ¦ in U.S. patent 3,783,652 to Archbold, or slipping belts such as l disclosed, for exampler in U.S. pa~cen~s 2,653,483 to Smi'ch;
¦ 3,029,624 to Fog~; 3,057,218 to Knerr; 3,525,241 to Morton; and ¦ Swiss patent ~84,878, published December ~ 1952.
¦ Prior machines, for instance those em~odying the slipping ¦ disc drive disclosed in the a~orementioned patent 3,783,652 to ¦ Archbold, have been arranged to limit the final spin speed in ¦ proportion ~o the magnitude of the out-of-balance condition of ¦ articles dis~ribut~d within the spin tub. Without ~uch speed ¦ protection, there is a risk that unbalanced loads will result in ¦ excessive ~ibration, noise, movement of the machine on the floor, ¦ and striking of the cabinet by the gyrating inner tub. Generally, ¦ the torque level necessary for final speed limitation in out-of-¦ balance situations is substantially less than that which produces ¦ acceptably slow acceleration of the spin ~ub so that final speed ¦ limitation is not usually achieved by simple resort to limitation of torque satisfactory for 810w acceleration.
Many current domestic washing machine designs depend upon ~¦ selec on of agitation snd cpin operational modes by seleotion of ¦

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the direction of rotation of a reversible drive motor.
Generally, it is desirable that full motor torque be available throughout the agitation cycle for full washin~
effectiveness, since this cycle is the highest power con-suming mode and, generally, rotational inertia is readily overcome by the s-tarting-winding of the drive motor upon initiation of this mode~ In the past, limitation of the delivered torque during rotation in the spin direction and positive drive in the agitation direction have been achieved, as for example in the aforementioned patent 3,7~3,652, b~
using, in addition to a slip clutch, a one-way spring clutch on the transmission input shaft to lock the transmission pulley to the input shaft in the agitation direction. A
problem associated with slipping disc arrangements is an inherent sensitivity which makes initial adjustment difficult, and which leads to wide variation in performance with normal wear or contamination by oil or other foreign material.
It is an object of the present invention to provide a belt pulley which effectively reduces heat transfer be- ;
tween its rim and hub and which is advantageously employed to isolate frictional heat generated in the slippin~ belt drive of a washing machine~ for example, from conduction to the drive motor shaft.
According to one aspect of the present invention ~ -there is provided a shaft mountable pulley for cooperation with the drive belt, the pulley including an outer peripheral ; rim portion including a circumferential surface engageable by the belt, a hub portion having an axial bore for re-ception therein of the shaft, and a web portion intermediate the rim and hub portions. The web portion defines the minimum heat conduction path-substantially longer than the distance between the rim and hub portions and being solely ~, ~ 3 kh/~

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within an axial zone between the planes of the faces of the pulley and the hub portion. The heat conducting path of the web includes at least one cylindrical tubular wall concentric with the pulley axis, the tubular wall being supported by first means at one end by the hub portion and a second means at an opposite end by the rim portion.
Another aspect of the invention resides in a belt drive system including a shaft, a pulley having a hub, web, and V-groove web por-tions with the hub por-tion fixed to the shaft, a second pulley, an endless V-belt carried on the pulleys, and a resiliently biased idler limitiny the tension of the V-belt on the pulleys by allowing the V-belt to slip on the V-groove pulley. The V-groove pulley has a web portion configuration forming a heat barrier to reduce transmission of heat, generated by slipping of the belt on the V-groove pulley, from the rim portion to the hub portion to thereby protect the shaft from excessive temperatures. The web por-tion, in axial cross section, defines a sinuous heat path which extends axially substan-tially fully across spaced planes defined by the oppositefaces of the rim portion so that the total length of the heat path is substantially greater than the radial distance between the hub and rim portions.

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l ~RIEF DESCR~PrION OF THE DRAWINGS
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¦ Fig. 1 is a plan view of a slipping belt and pulley drive system in a washing machine;
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¦ . Fig. la is a somewha~ simplified view of a portion of ~Ihe area of Fig. l, illustra~ing use of a device for cali~rating ¦ a ten~ion spring which con~rols bel~ tension;
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l Fig~ 2 is an elevational view of the belt and pulley : ¦ drive of Fig. 1, including further details of associated com-l ponents; . .
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¦ Fig. 3 is a graph depicting the relationship between idl~r load versus belt tension ~or different angles of belt ¦ ~rap over an idle~. and delineating a critical range of belt ¦ wrap for reliable torque limiting action in one direction and . ¦ .nonslip action in the opposite direction; .
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Fig. 4 is a face view of a pulley constructed in . I accordance with the invention;
' I . '. ' '' ' ., . ,",' . I ~Ig. 5 ~s a cross sectional view of the pulley taken ¦ along the line 5-5 in Fig. 4; and .
I .' ' ' "''- '' '. '' ~ ¦ Fig. 6 is a graph illustrating a typical relationship.
; ¦ of f al spin speed to eccentrio load in a~spin tub. ¦

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DESC:R~PTION OF THE P ~EFE~RED EMBODIMENT

Referring particularly ~o ~igs. 1 and 2, there is ~ho~*n a power drive system lO for a clothes washing machine ~hichJ with the ~xception of the belt and pulley drive system to be described, is generally conventional in construction.
A ~uitable m~chine in which ~he present invention may be employed is shown in the aforementioned UOS. patent 3,783,652 to Archbold, ~he disclos~re of which is incorporated herein by xeference. This patent describes the physical association and~
~orking rela~ionship of an imperforate, nonrotating, water-holdin inner tub or drum, a perforate spin tub, an agitator, and a ~uitable tra~smission for selectively driving either the spin _ tub or agitator, depending upon the direction of rotation of the input shaft of the transmi6sion~ In the present disclosure, the direction of rotat.ion o~ the various elements o the power drive sy~tem is indicated by the legends "AGITATE" and "SPIN" in Fig. 1.
A reversible electric motor ll has a vertical output shaft 12 on which a drive pulley 13 is keyed by a setscrew or other suitable means. The motor ll is supported by studs 14 on a generally horizontally disposed mounting plate within a cabinet ~not shown) of the washing machine. The motor ll is laterally spaced from a transmission 18, the lower end of which is r~siliently supported in a cavity l9 infegrally formed in the mounting plate 16. ~

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I . ~ -. ' The i_ransmis5ion 18 includes a verticall~ depending ¦ input shaE~ 21 whi~h, i~ wi71 be understood, is adapted to '~
¦ oscillate a ~er~ical 2gi~a~0r when dr.iven in a clockwise ¦ ~irection as vie~.7ed in ~ig. 1 and to spin a perforate tub . ¦ surrounfling the agitator w~en driven in a counterclockwise or : I opposite direction. .
A driv2n pulley 2~ is keyea by suitable means, such ,~ ~ a~tscr~w, to 'che ~ower end o~ the input sha~t 21~ The ¦ shaf~ ro~atabl~ supported in a bearing 24 on a tubular ~ ..
. ¦ ext~nsion ~5 o th~ transmission.l8~, The pulley 23 is somewhat large~ than the motor drive pulley 13 to effect a speed reduc-¦ tion at the input shaft 21 from motor speed. A V-~elt 27, ! ~ ¦ ' ideally of the type known in the trade'to which the invention ¦ pertains as a l'dry belt" fo,r.intentional slipping.operation, is a~sembled around the pulleys 13 and 23j and is constantly ':' , ¦ t2nsioned at one side or reach by an idler pulley 29. The idler ,., I pulley 29 i8 rotatably mounted on a shoulder bolt 30 at an oute~
end of a pivotal lever 31., The pivotal lever 31 swings'in a ¦ horizontal plane on.a vertical pin 3~. At an end opposite the ., ; ¦ idler pulley 29, the lever 31 i8 provided with a series of re,gularly spaced adjustment notches 36. A tension spring 37 is .~
hooked between one of the notches 36a and a rigid post 38 . :
depending ~rom the mounting plate 16. As iliustrated, the variou~
~ I elements are arranged such that the idler pulley 29 is supported ., .,, for movement generally perpendicular to the adjacent belt reach ' :
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and t e Lorce ~f Lhe spring 37 op~rates on a line generally perpendicular to the longitudinal direction of the lever during normal operation.
A pump 41.such as that disclosed in my U.S. patent 3,851,9g3, for discharging water from the inner tub while the perforate ~ub ~herein is in the spin mode, is mounted below the motor 11~ The pl~mp 41 includes a housing 42 supported on a plurality of posts 38. Within the housing 42 is an impeller .
having an integral hub 43 which may be formed o. a suitable thermo plastic material. The impeller hub 43, as shown, is fixed dir~ctly to the motor shaft 12.
Ideall~, the belt and.pulley system is arranged to transmit sufficient ~orque to the transmission input pulley 23 without ~el~ slippage on either pulley 13 or 23 ~ox ade~uate power during agitation operation and a lower level of torque, ~.
limited by ~elt slippage on the motor pulley, in the manner of a clutch, during spin operation. The lower torque level in spin provides slow acceleration of the spin tub during the initial part of each spin cycle, and, as explained hereinbelow, in cases where an eccentric o~ out-of-balance condition persists during .
a spin cycle, the lower torque limits the final spin speed to avoid excessive vibrationr noise bearing loads, and other harmful e~fe s -.7 - . .
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. 1 1082003 . ..... -~ n the agi~ation d.ir~e~ion~ the bel~ 27 operates in constentional manner in transmi~ting torque fxom the motox ¦ pulley 13 to ~he transmission pulley 23 by tension in the .
. I reach designated 46 opposite an idler pulley 29~ During ¦ agitation, because of high fric~ional engagement between the ¦ b21t 27 and ~he pulleys 1~ and 23~ tension in the reach 46 is s~bstantially higher than that in the reach, designa'ced 47 r a~60ciatea with t~e idler pulle~ 29, and is only slightly ¦ affected ~y ~ension in.~his idler reach~ With ~he belt 27.and ¦ pulleys.13 and 23 properly sized, under such circumstances, and ¦ with a relatively low tension in the idler reach 47, the belt ¦ i6 capa~le of transmi~ing substantially all of the motor torque t~ th~ transmi~sion in agi.tation. ~ ..
¦ On the other hand, te~sion in the idler reach 47 is . ¦ directl.y limi~ed by the force applied by the idler spring 37, ¦ si~ce the idler 29 is forced to withdraw inwardly toward the.
¦ pulleys 13 and .23 when the force components of the belt tension :. .:
. I exceed the biasing force of the spring at the idler. Such with-. ¦ drawal of the idler 29 immediately allows the belt to slip on the drive pulley 13 to thereby limit torque transmission to the driven pul~ey 2~. :~
~ t has been found that a substantial difference or ratio of torque transmission between spin and agitation must 1 1 be provided to achieve satisfactory speed iimitation during out-i ~ of-~alance conditions in the spin tub. The measure of this .
torque. ratio is given empirically by the difference in motor ' 1082003 . 1. .

ttage re~uirea ~or agi~a~ion al~d spin r which may range, by way l of ex~mple, be~ween 700 and ~750 wa~ts for agitation, depending ¦ on the particu1ar machine in ~uestion~.and corresponding wattages l or spin in the order of 600 to 650 watts. This ratio of I agitation-to-Spin power, which is approximately in the order of between ~:6, in accordance with the invention, is I ~hieved by arranging ~he geometry o the belt and pulleys such . tha~ the anyle of ~rap on ~he ldler pulley 29 falls in a critical range approximately between 20 and 40 degrees as indicated in the shaded area of ~ig. 3. .
It has been determined that an angle of belt wrap ~. .
a~out the idler pulley 29 in this range yields the most easily adjusted cvnEigllration ~nd khe most consistent performance. At angles substantially greater than this range, it is difficult to obtain a substantial ratio of spin-to-agitate torque because fo a given slip torque in spin, there appears to be a fall-off of agi~ation torque capacity wherein the belt tends also to slip in the agitation mode.' At an~les substantially less than this range, i~ is'difficult to initially adjust the idler spring tension to give sa~isfactory results., . , Fig. 6 illustrates the relationship of ~inal spin tub .
speed after initial acceleration and eccentric load as produced by the belt and pulley arrangement of Fig. l. , Inspec~ion of the curve of Fig. 6 reveals that a maximum spin speed is achieved , with little or no eccentric load, i.e., when articles of clothing .,,~ or the like in the spin tub are distributed.evenly about the 3 . . ' .
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periphery sf -the ~ub. The final spin speed falls o~f gra~ually s~ith lncreasing eccentric load~ as where the articles in the ~pin tub are yathered at one side of the ~ub, to a final speed of l40 rpm with lO pounds of e¢centric load idealized at a ~inyle poin~ on the periphery of the spin tub. The reduction in final spe~d i3 ~he result o~ the dissipation of energy, equal ~ -~ the l~mited power transferred by ~he slipping belt during ~he ~pLn mode, ~n d~nping ~c~ion o ~he suspension on which ~he Lnnzr tub, khe spin ~ub, transmission, and ~arious other ~lements are supported. A suitable suspension is illustrate in the aforementioned Archbold patent 3,783,652 and U.S. patent 3,493t118 to Brucken~
. The setting of the tension spring 37 in a particular notch 36a o~ the lever 31 depends on the final combination o~
toler~nce~ hetween the variou~ elements o~ the washing machine, These tolerclnces include variation in the actual belt length from a nominal d~mension and positional variations of the centers of the motor and transmission pulleys 13 and 23. In accordance with an important aspect of the invention, there i8 provided a method of calibrating the tension spring 37 and notched lever 31 to a . .
particular machine and it~ set of manufac~uring tolerances. The method, il1ustrated in Fig. la, comprises the use of a tool or ~aug~ 51 which provides a series of indicating holes 52 spaced in equal increments along a straight line at an angle of about 45 degrees from the longitudinal direction of the gauge. The ~'1 ' . .
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h~les 52 of th~ gauge 51 are calibrated to indicale an appropriate ~ -notch 35a on ~h~ idler l~ver 31 for a particular machine and its specific dimensional characteris~ics. The gauge indicating holes -57, equal in number ~o ~he n~mber of no~ches 36, are arranged to cooperate with a reference point 55 on ~he lever 31, in the illus-trated embodiment, taken a~ the upper lef~ corner of the lever.
~lith the idler ~ eV2r 31 provisionally ~ensioned by ~he spring 37 in the centr;ll no~5h ~notch number 4 in Fig. la) and a yoke or base point 53 o~ the lever embracing the spring anchor post 38 the gauge 31 is pivo~ed about the post until a hole 52 which most c~osely registers wi~h the reference point 55 is found. ~his closel~ registering hole 52 indicates in a reverse order the proper notch 36a in whlch ~he spring should be hooked, In the illustration of Fig~ la, the number 5 hole, count-;ng from the le~t, is in close registration with the reference poin t SS and there~ore the spring 37 is hooked in the fifth notch count-ing from the right ~Fig. 1~. The spacing of the holes 52 from the yoke or base point S3 is derived empirically for belts varying from a nominal dimension and other machine dimensional variations to yield ~or all of the notch settings, a single slip torque in the spin mode.
As will b~ understood with referenc to Figs~ 1 and 3, where the belt length is relatively long from a nominal dimension, the belt angle of wrap will be relatively high and therefore will require a high idler load for a given tension or torque. In thi's situation, the notched idler lever 31 swings close to the fixed ~i . ' . ' ' . .~
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., ,, ~ , , post 38 and a high numbered hole will be indicated so that the spring 37 is hooked at a notch remo-te from both the lever pivot 34 and the anchor poin-t 38 and a high idler force will be developed by the spring. Conversely, where the belt is relatively short, the wrap angle will be relatively low, a low hole number will be indicated, and a relatively light force will be applied by the spring in a low numbered notch.
When properly adjusted, the idler pulley 29 vibrates during ~ ~
belt slipping action to permit the belt to rapidly slip and -grab on the drive pulley 13. The idler pulley 29 and spring -37, moreover, are self-adjusting for normal belt wear during the life of the machine.
The above-described belt drive is also described and is claimed in above-identified Canadian Application Serial No. 255,328.
Referring to Figs. 4 and 5, there are illustrated details of a pulley which is particularly suited for use as the motor drive pulley 13 to isolate the motor shaft 12 from heat generated by the belt 27 during extended slipping action in the spinning of an unbalanced load. The pulley 13 is conveniently fabricated by turning it from free machining, round steel bar stock having a diameter approximately equal to or slightly greater than the finished outside diameter of the pulley. The pulley 13 includes sb~
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1` ~082003 ., I , , . , an O~l~er periph~ral rim portion ~6 in which ar~ formed surfaces o~ a ~onventional ~-groove 5~ ~n inner hu~ portion 58 of the ley 13 includes a bore 59 ~or recep~ion therein of the motor shaft 12. A threaded radlal bore ~l in the hub 58 is adapted to receive a ~ets.cr2w for locking the pulley 13 ~n ~he shaft 12.
As shown, th~ sur~aces o ~he rim, hub, and intermedi.ate web portions at each ~ac~ of the pulley are coplanarO
The p~lley 13 is p~rt.ially tr0panned or ~rooved at opposite ~aces, ~lith the groove 66 of one face being spaced radiall~ ol~tside of the groove 67 formed at the opposite face.
The grooves ~6 and 67 are concentric with the bore 59 and each extend substanti~lly through the length or axial thickness of ~:
the pulley 13, terminating at relatively thin radial end wall 6ections 68 and 6g at opposite faces of the pulley. The grooves 66 and 67 are of substantial radial thickness i.n comparison to the total radial extent of the we~ portion 64, so that a remain-ing cylindrical land section 71 o~ the web is also relatively thin. Stated in other words, the web portion 64 is that material remaining after the provision of the axially extending, radially spaced grooves 66 and 67. The cylindrical land section 71 is ~upported a~ its respective ends -by the radial wall sections ~8 and ~9. By way of comparison, the radial and axial wall ~ections 68, 69, and 71 o~ the web 64 are substantially thinner than e h~o and rim . , ,' . '~' ,1 . ,' ' ' .

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It m~.y be ppreciated tha~ ~he minimum heat ~low path ¦ betw2erl the r~n 56 and hu~ 58; defined in series by the radial wall se~-~ion 63, ~he axial ex~ending section or cylindrical land 71, and the radial wall seotion 69, is substantially longer than tha ra-lial distance between ~he hub and web.. In the illustrated I conigllra~ion~ ~he increased length of the heat conduction path - oS~r the radi~l distance between the rim ~ and the hub 58 is that i correspondiny ~ ~he ~eng~l~ of the cylindrical weh ~ection 71.
.~ ~eat conduc~ion between the rim and hub is additionally lessened ¦ ~ the reduced ~ross sectional area of the heat.path a~forded ¦ by.the relatively thin walls of these sections. In addition to ¦ ~he restristion of heat transfer between the rim and hùb by the I ~elati~tely long heat path of limited cross sectional ~rea, the ¦ grooves 66 and 6~ provide air circulation for convection heat transer away from the pulley surfaces, as well a~ radiation ¦ h~at transer. A plurality of angularly ~paced radial holes 73 ¦ may be provided through the rim and web sections 56 and 58 to ..
increase air flow.through the pulley grooves 66 and 67. .
The pulley 13 thereby protects the motor shaft 12 from excess heat, which, in.certain instances, might cause harm to the ¦ ~:
I a~sbciated motor shaf~ bearing (not shown) and the pump impeller ~ -I hub 43. In actual tests, it has been found that the pulley ~;
I structure is capable at room temperatures of maintalning the hub ¦ ~8 at. a temperature of no more than 250 F. while the rim is ¦ heated to a temperature of 700 F. , I . ' , ' ' .
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iIt is c~nt~mplat2d tha~ the pulley 13 may be formed by other procPsses, such as casting or molding, or o~her suitable . :
fa~ricatiny ~echni~ues, and ~hat it may be advantageously employe in Yarious other belt drive systems in which it is either a driving or dri~en pulley ~nd in which it is desired, ~or example, l to isolate hea~ emanating from the shaft on which it is mounted ¦ to ~he rim to protec~ a bel~ mounted thereon. Furthe~, where ¦ necessary or de~iredr more than two axial grooves may be pro~ided in the faces of the pulley.
¦ Figs~ 1 and 2 ~re drawn substantially to scale, and, by wa~ o example, the motor drive pulley has a nominal outside ¦ diameter o ~-~/16 inch, while the transmission pulley 23 has ¦ ~n outside diameter o 6-13/16 inch, with each pulley having a Y-groove of 38 degrees and being spaced on a center-to-center ¦ distance relative to each other of 8-7/32 inch.
While the invention has been described in connection with .
peciic embodiments thereof, it is to be clearly understood that ¦ this is done only by way of example, and not as a limitation to I the scope of the invention as set forth in the objects thereof anc :. :
I s I in the appended Cl~Lm5. ~:

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Claims (6)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A shaft mountable pulley for cooperation with a drive belt, comprising an outer peripheral rim portion including a circumferential surface engageable by the belt, a hub portion having an axial bore for reception therein of the shaft, a web portion intermediate said rim and hub portions, said web portion defining a minimum heat conduction path substantially longer than the distance between said rim and hub portions, and being solely within an axial zone between the planes of the faces of said pulley at said hub portion, said heat conducting path of said web including at least one cylindrical tubular wall concentric with the pulley axis, said tubular wall being supported by first means at one end by said hub portion and by second means at an opposite end by said rim portion, whereby conduction heat transfer between said rim and said hub is maintained at a low level.

2. A pulley as set forth in claim 1, wherein said hub and rim portions have face planes which are substantially identical.

3. A pulley as set forth in claim 1, wherein said first support means is formed by a relatively thin, radially extending end wall between said hub and said cylindrical tubular wall and said second support means is formed by a relatively thin, radial end wall between said cylindrical tubular wall and said rim.

4. A pulley as set forth in claim 3, wherein said rim, intermediate, and hub portions are integral.

5. A shaft mountable pulley for cooperation with a drive belt, comprising an outer peripheral rim portion including a circumferential V-groove engageable by a V-belt, a hub portion having an axial cylindrical bore for reception therein of a shaft, means on said hub portion for fixing said pulley on a shaft positioned in said bore, a web portion intermediate said rim and hub portions, said rim, intermediate web, and hub portions being integral and said web portion being within an axial zone between planes of faces of said pulley of said hub portions, said web portion including at least one axially extending cylindrical tubular land portion formed by at least two axial grooves concentric with said bore and each other, each of said grooves extending axially inward from an associated pulley end face towards the opposite pulley end face of the other groove, said grooves being radially relatively close to one another such that said land portion is relatively thin in comparison to the rim and hub portions, said grooves having sufficient axial length relative to the length of the pulley that relatively thin end walls are formed at their respective opposite pulley faces.

6. A pulley as set forth in claim 5, including a plurality of radial holes extending through said rim portion and at least a section of said web portion to improve air circulation in said grooves.