US2046122A

US2046122A - Buffing and polishing wheel

Info

Publication number: US2046122A
Application number: US726555A
Authority: US
Inventors: Nathan C Hunt
Original assignee: Individual
Current assignee: Individual
Priority date: 1934-05-19
Filing date: 1934-05-19
Publication date: 1936-06-30
Anticipated expiration: 1953-06-30

Description

Jame 3&1936. N c, H 2,046,122

BUFFING AND POLISHING WHEEL Filed May 19, 1934 3 Sheets-Sheet J.

BUFFING AND PCLISHING WHEEL Filed May 19, 1954 3 Sheets-Sheet 2 f Fly 6 2 ,10 1 .64 1 if! 5 June 30,1936. N HUNT. 2,046,122

Filed May 19, 1934 5 Sheets-Sheet 5 Patented June 30, 1936 ilhiiTED STATES PATENT OFFICE 15 Claims.

The invention relates to high-speed rotary buffing and polishing wheels having a flexible abrasive band detachably mounted on the periphery of the wheel.

More particularly, the invention relates to polishing wheels having means for taking up the slack in the detachable abrasive band, and for imposing a tensioning force thereon to keep the band tight on the wheel and to compensate for stretching which may occur in the band.

Certain prior bufling and polishing wheel constructions have included means for tensioning the abrasive band upon the wheel, but in such constructions, when the wheel is rotated at high speeds the centrifugal force acting upon the tensioning means may cause the tensioning pressure on the band to be diminished.

Certain other prior bufling and polishing wheel constructions have provided tensioning means for the abrasive band, which means are adapted to be actuated by the centrifugal force of the wheel when rotated, so that the amount of tension imparted to the abrasive band varies in proportion to the speed of rotation, and with the position or leverage of the tensioning weight. However, in these latter prior constructions, as the rotating band becomes stretched due to various conditions such as wear, heat or centrifugal force, the tensioning means necessarily changes its position radially to compensate for the stretch of the band, with the result that the wheel becomes unbalanced, statically and/or dynamically.

In all prior constructions of which I am aware, it is attempted to statically and possibly, dynamically balance the wheel, but no successful provision has been made for automatically maintainstatic and dynamic wheel balance as the band becomes partially or permanently stretched, and for automatically maintaining static and dynamic wheel balance at varying speeds, within practical operating limits.

Obviously, a wheel which is statically balanced is not necessarily dynamically balanced, because the dynamic balance depends, not only upon the mass of the parts, but also upon their location.

In order to be efficient in continuous operation at high speeds, it is imperative that a polishing wheel be possessed of a high degree of strength for mechanical safety, be delicately and accurate- 1y balanced dynamically and statically, and be adapted for maintaining a smooth uniform bufiing suriace in continuous operation.

It is therefore an object of the present invention to provide a polishing wheel having tensioning means for maintaining an abrasive band tight on the periphery of the wheel at all speeds.

Another object is to provide a polishing wheel having tensioning means for automatically dynamically and statically balancing the wheel when the same is rotated.

A further object is to provide tensioning means mounting the abrasive band on the wheel for quick detachment therefrom.

Another object is to provide tensioning means for automatically taking up stretch occurring in 10 the abrasive band while the wheel is rotating and simultaneously maintaining the dynamic and/or static balance of the wheel.

Another object is to provide improved means for securely anchoring the ends of the abrasive 15 band to the wheel without causing tearing of the band when the same is under tension.

A further object is to provide improved anchoring means for the ends of the band, which means will grip the band with increased force as the tension in the band increases.

A still further object is to provide an improved clip for anchoring the end of an abrasive band, which clip can be easily applied to a range of bands of various thicknesses.

Other objects include the provision of a simply and compactly designed polishing wheel having a high degree of strength, and which is adapted for maintaining a smooth uniform buffing or polishing surface at the most eflicient peripheral speeds 30 in continuous operation.

These and other objects are attained by the improvements comprising the present invention, which may be stated in general terms as including a wheel frame having a drum flange, a cush- 35 ion for the drum flange, the drum flange and cushion being slotted for receiving the ends of a bufiing or abrasive band wrapped around the periphery of the cushion, means for rigidly securing or anchoring one end of the band in the frame, and means for applying a yielding tensioning force to the other end of the band, the component parts of said tensioning means acting radially of the wheel in such manner as to automatically, statically and/ or dynamically balance the same.

A preferred embodiment of the present invention is shown in the accompanying drawings in which Figure 1 is a plan sectional view of the improved polishing wheel, taken substantially on line l-l, Fig. 4, and showing the abrasive band loosely wrapped around the same before tension is applied;

Fig. 2 is a fragmentary view similar to Fig. 1,

showing a predetermined amount of tension applied to the band by the tensioning means Fig. 3 is a similar view showing the position of the component parts of the tensioning means when the wheel is rotated at high speed;

Fig. 4 is a transverse sectional view as on line 4-5, Fig. 1; I

Fig. 5 is a fragmentary sectional view as on line 5--5, Fig. 2; V

Fig. 6 is a transverse sectional view taken suba thrust'washer 21.

.screwed on the outer end of the spindle 2B for stantially on line 5, Fig. 3;

1 Fig. vie" taken on line '!i, Fig. 3;

8 is a fragmentary'transverse sectional as online 88,Fig. 3; V V g. 9 is a fragmentary transverse sectional as on line Q-S, Fig. 3; Fig. 19 is a fragmentary sectional view, as on line iii-59, Fig. 9; 7 11 is an enlarged fragmentary view similar to showing themethod of anchoring the ends of an abrasive band to the wheel frame and to the tensioning means;

Fig. 12 is an enlarged fragmentary perspec tive of one of the improved abrasive band anchoring clips; r 1 a Fig. 13 is an enlarged sectional View of one end of the band secured in one of the clips;

14 is an enlarged sectional view of the clip and band inserted in one of the clip holders;

15'is an enlarged sectional viewof one end of a very much thinner abrasive band secured'in one of the clips; and a Fig. 16 is an enlarged sectional view of the clip and band of Fig. 15 inserted in one of the clip holders. 1 a

Similar numerals refer to similar parts throughout the drawings.

The improved polishing Wheel. is indicated generally atiil, and preferably includes two similar frame members ii and! i, clamped together inabutting relation as by bolts indicated atl2 passing through bosses i3 and [3 provided on the respective frame members. a

The frame members it and H preferably include side disk portions M and Mand periph erai drum flanges i5 and 55 respectively. Thus the abutting frame members H and H form'a closed drum, and the abutting flanges J5 and i5 form the facing surface upon, which the abrasive cushion i6 is mounted.

The cushion I8 may be of rubber, or may comprise a cork base with a rubber or fabric facing,

or with a composite rubber and fabric facing,

or with a leather facing. The cushion or its component partsmay be vulcanized, cemented or otherwise secured to the facing surface provided by the drum flanges i 5 and I5.

As'shown in Figs. 1, 2, 3 and 11, the drum flanges and the cushion are slotted at ll trans- ,versely of and throughout the width of the. drum for receiving the ends of a flexible abrasive loop or band i8 wmch is wrapped around the outer periphery of the cushion I6; 7 7 r The improved polishing wheel illmay be quickly'attach to or detached from any rotatable spindle. Preferably, the frame members i l and Hf are provided with hub portions l9 and 19' respectively for receiving a spindle 20.

'ivieans for securing the-wheel l0 upon spindles having slight variations in diameter pref-V '7 is a fragmentary transverse sectional conical inner surface as shown at .22 in Fig. 4.

An annular clamping collet 23 is locatedrwithin each ring 21, and has a tapered outer surface 24 conforming to and abutting the inner surface 22 of the ring, and an inner cylindrical surface 24a for fitting around the spindle 29. The annular portion of each collet 23 is slottedradially at intervals as shown at 25. The outer face of one of the collets 23 abuts a shoulder 26 on the spin- 20, and the outer face of the other collet abuts 1 Preferably, a nut 28 is abutting the washer 21.

By adjusting the nut 28, the coilets 23 may be wedge-fitted between the rings 24 and the spindle so as to secure the buffing wheel l0 upon spindies having slight variations in diameter. Moreover, .collets 23 with other sized bores may be used for mounting a particular size of wheel on shafts of other diameters from that shown.

The frame members I I and Hi are preferably provided with abutting webs indicated generally at 30 and extending radially from the hub portions l9 and. I9 to the drum flanges l5 and I5. The webs 30 inciude outer Web portions 3| extending radially inward from the drum flanges, and inner web portions 32 extending radially outward from the hub portions.

The outer web portions 3| are slotted transversely throughout the width of the wheel as shown at 33 and the slot 33 registers with the slot l'lin the drum flanges and the cushion, and extends radially inward from slot H to the inner end" portions of the outer web portions 3|. At

their abutting surfaces and preferably axial with the slot-33, the webs 3| are provided witha cylindrical bore 34 extending radially inward from the slot ll to the hub portions i9 and 19.

7 scribed, and one of said clips is inserted endwise in the clip holding member 36, as best shown in Fig. 11, the webs 35 being slotted at 38 to receive the adjacent end portion of the abrasive band l8.

Thus one end of the abrasive band is securely held in the'band-ho-lding webs .35 of the frame members.

The other clip end of the band is inserted endwise' in a clip holding member 36' similar to member 36, and the member 36 is substantially coextensive with the width of the band I8 and is 10- cated in the slot 33. i 1 As best shown in Figs. 11 to 16 inclusive, improved means are provided for anchoring one end of the abrasive band to the wheel frame and for securing the other end'to the tensioning means. Theband' I8 is preferably made of paper, fibre, fabric or cloth and the like, and has abrasive grains imbedded in one surface. Prior means for gripping or anchoring the ends of the band have been found to puncture or cut the fabric, etc., and/or crush the abrasive grains thereon so as to cause the band to rupture or tear under tension. The improved clip 31 is substantially U-shaped in cross section, and the legs 37:; have rounded ends; and as shownin Fig. 12, the legs of the clip when formed are spaced apart slightly more than 7 the maximum thickness of the abrasive band to be gripped.

The clip is made of relatively strong and soft metal such as aluminum, or of strong and soft other material. The inner surfaces of the legs 31a are preferably provided with a series of serrations indicated at 31b.

7 One end of the band is is inserted into the clip 31 and the legs 31a are then squeezed together sufiiciently to grip the band tightly, as shown in Fig. 13. The soft metal serrations are adapted to press into the surface of the fabric of the band without puncturing the same. On the abrasive surface of the band, the serrations force themselves against and in between the grains and the grains become imbedded in the clip material so as to prevent withdrawal of the band unless the legs of the clip are spread apart.

When the ends of the band 18 with the clips 3'! squeezed thereon are inserted endwise in the clip holding members 36 and and tension is applied to the band, the rounded ends of the legs 31a abut the plane surfaces of the angular flange portions 39 of the holder, and the band extends through a slot 35a provided between the flange portions 39. This slot is slightly wider than the maximum thickness of band to be used.

The flange portions 39 are disposed to the sides of the holding

members

35 and 36 at an angle so calculated as to abut and tend to compress the ends of the legs S'ia together when tension is applied to the band, and increasingly grip the band more tightly as the tension is increased.

The improved clip and clip holding member are adapted to anchor the ends of bands of varying thicknesses less than the relative thickness of the band shown in Figs. 13 and 14.

As shown in Figs. 15 and 16 the improved clip may be applied to a very thin band indicated at H8.

The legs l3'la of the clip are squeezed together sufficiently to tightly grip the band I I8, and the clip i3? assumes the shape shown in Figs. 15 and 16. The overall thickness of the clip and band is greater than the width of the slot 135a in the holder !36, so that the rounded ends of the legs are abutted and compressed together by the plane surfaces of the angular flange portions 139, when the band is under tension.

A tension link 46 is slidably mounted in the bore 34, and its upper or outer end is bifurcated to form ears 4| which are pivotally secured to the sides of the clip holding member 36 at its longitudinally central portion by pins 42, as best shown in 11. Thus the end of the abrasive band 18 is pivotally connected at its laterally central portion to tension link Gil, so that tension applied to said link will be equally distributed over the width of the band and the direction of the pull of the band on the link is coaxial with the link.

Preferably, the upper or outer portion of the bore as is enlarged as shown at 34a to accommodate the heads of pins 42. A Washer 342) of cork and the like, is preferably located in the web portions 3i below the enlarged portion 34a of the bore, for closely fitting around link and 'sealing the portion 34a from bore 34.

A cross bar 34 extends transversely through the lower or inner end of link 45 preferably in the plane of the abutting surfaces of the frame members. The inner web portions 32 are slotted as at 45 in the plane of their abutting surfaces for slidably receiving the oross bar 44, and the slot 45 extends radially from the hub portions 19 and I 9' to the outer web portions 3|.

The improved tensioning means preferably includes cylinders mounted one on each side of the webs 3D, and preferably secured to side disk I4 by means of screws 5| screwed in bosses 52 provided on the side disk M (Fig. 9).

The axes of the cylinders 50 are preferably in the plane of the abutting surfaces of the frame members II and II, that is, in the median plane laterally of the wheel. The axes of the cylinders 58 are located at a particular acute angle with the axis of bore 34 and link 40, for a purpose to be hereinafter described.

Each cylinder 50 is provided at its inner end with an inturned spring retaining flange 53. A spring abutting disk 54 is slidably mounted in each cylinder, and a coil compression spring 55 is interposed between the flange 53 and the disk 54.

An airplane strand cable 55a of substantially nonexpansible material connects one of the disks 54 with one end of the cross bar 44, and a similar cable 56b connects the other disk 54 with the other end of the cross bar 44 for transmitting the compressive force of springs 55 to the link 40 to cause an inward pull on the end of the abrasive band 58 to which the link 48 is conhected.

Each of the cables 5%, and 56b is preferably double and is looped over one end of the cross bar 44 to fit in a groove provided therein, as shown.

The two strands of each of the cables 56a and 55b are led inward from cross bar 44 in a direction parallel to the bore 34 and link 40, and pass successively around a pair of

pulleys

51 and 58, mounted on

pins

59 and 60 which are journalled in

bosses

61 and 52 respectively, provided on the side disks I4 and 14' (Fig. 6).

From the pulleys 58, the two strands of each of the

cables

56a and 56b pass into one of the respective cylinders 50, and the ends of the strands are connected with the respective disk 54 of the cylinder. Between the pulleys 58 and the disks 54, the strands of the cable are preferably parallel with the axis of the respective cylinder 50.

As shown in Fig. 10, the ends of each cable 56a or 5612 are secured to one of the disks 54 by passing the cable strands through diametrically opposite portions of a boss 63 provided on the central portion of disk 54, and thence led into grooves provided on the underside of a clamping plate 64 which is secured to the disk 54 by means of a screw 65 screwed into the disk 54.

Thus the pull or tensioning force imparted to the abrasive band l8 by the compression of springs 55, through

cables

56a and 56b, cross bar 44 and link 40, is transmitted in directions substantially radially of the wheel; that is, the force components of the tensioning means act radially of the wheel.

Means for manually moving the link 49 radially outward against the compression of springs 55, and for holding said link in its outermost position to permit connection of the clip end of band l8 in the clip holding member 36, preferably includes a lever member 68 pivotally mounted on the side disks l4 and 14 of the frame members H and H by means of a pin 69 journalled in bosses 10 provided on said frame members adjacent the drum flanges l5 and I5.

A longitudinally slotted plate H is pivotally connected at its upper end to the end of arm 38a of lever member 58, as at 12, and the strands of the cable 56a pass through the slot 13 (Fig. 6) of the plate H.

The lower end of plate H is .provided with a transverse portion 74, which is located between the cable 560. and the web 30. By rotating the lever member 68 in a counter-clockwise direction about its pivot 69, the transverse portion 14 may be engagedin a notch 15 provided in the bar M, for movingthe link 4i] radially outward. 'Means for manually rotating the lever member 68 may include a shaft 16 journalled' in bosses 11 provided on the side disk members 14 and I4. As best shown in Fig. 5, the shaftlfi extends throughout the width of the wheel l0 and is provided at its ends with squared sockets 18 for receiving a suitable wrench.

At its central portion, the shaft 16 is provided with a slot 15a adapted to receive arm 68a'of lever and crank arms 19 extend angularly from shaft 16 adjacent slot 15a for journalling a roller 89 on pivot pin 8!. The roller 88 is adapted to engage a spring steel plate 58b secured to the underside of the arm 53a. Rotation of the shaft 16 in a counter-clockwise direction will move the lever member 68 from the position shown in Figs. 2 and 3 to the position shown in Fig. l, with the transverse portion 14 of the plate 1! engaging the notch 15 in cross bar 45, to move the link to its outermost position, as shown in Fig. 1.

In this position, the roller 88 has been moved over center with respect to the shaft 18 so that the link 30 will be held in its outermost position until shaft 16 is initially rotated in a clockwise direction by means of a wrench.

Also, in this position the roller 86 engages the curved'portion 82 of the spring steel plate 68b, which curved portion acts as a stop to limit movement of theroller 80 in a counter-clockwise direction.

Preferably, the lever member 68 is provided with an arm 83, which may be weighted as indi- :ated at 83a, so that when the wheel is in operation the moment of the arm'due to centrifugal force will holdit' out against the drum flange l5 and i5, as shown in dot-dash lines in Fig. 1, and maintain the means for moving link iii radially outward in the positions shown in Figs. 2 and 3.

Weighted bosses

34 and 85 are provided on frame members i l and i B respectively at locations substantially opposite the webs 35, for partially maintaining the static balance of the wheel, or in other words for bringing the center of gravity of the wheel at its geometric center.

In applying an abrasive band 48 to the improved wheel 1%, the link is first moved radially outward to its outermost position by inserting a wrench in one of the sockets 18 of the shaft 16 and rotating the same counter-clockwise to the position shown in Fig. l, in a manner previously described. 7

One clip end 31 of the abrasive band I8 is then inserted endwise into the clip holding member 36 and the band wrapped around the outer periphery of the cushion it to bring the other end of said band into the slot Ailradially inward to the position shown in Fig.

2 and impose a tensioning force or pull upon the band 18, bringing it tightly into contact with the cushion I6 throughout its length. At the same time the lever member 68 moves toward the position shown in Fig. 2. i V

As viewed in Figs. 1 and'Z, the radial inward movement of link 49 and the inward movement of members 68 and H causes the center of gravity of the wheel to be shifted slightly downwardly. The acute angles between the axes of cylinders 50' and the link 48 are so calculated that as the disks 54 are moved radially outward by the springs to anced regardless of variations in the length of the abrasive band 18 between limitsdetermined by the radial length of slot "45, such as may result from permanent stretch in the band due to continued wear, because as the band becomes longer, the springs move the link!!!) inward which causes the center of gravity of the wheel to shift accordingly, but this shift is compensated for by the corresponding radially outward movement of the disks 5 and springs 55, so that the parts may assume the positions indicated in dot-dash lines in Fig. 3. 7

Assuming the parts to be in the 2, when the wheel is rotated at high speeds, the centrifugal force acting on the abrasive loop or band i8 is compensated for or balanced by the centrifugal force acting on the springs and disks 54 so that the band is kept tightly against 15 the cushion H6. The centrifugal force overcomes the force tending to extend the compression springs 55 and moves them away from the flanges 53, further compressing the springs, as shown in Fig. 3, so that at high speeds the tensioning pull on the band is entirely provided by the centrifugal force on the springs 55 and disks 54 acting radially of the wheel. 7

By means of this construction, the band is maintained tight on the, cushion i 6 so as to maintain a smooth, uniform bufiing or polishing surface, and the wheel is automatically maintained in dynamic and/or static balance at high speeds.

I claim: V 1. A polishing wheel having a drum face, a cushion secured on the drum face, .an abrasive band surrounding said cushion, and means on'the wheel for always imposing a tension on the abrasive band and for automatically statically balancing the wheel for varying amounts of tension. 2. A polishing wheel having a drum face, a cushion secured on the drum face, an abrasive band surrounding said cushion, and means on the wheel for always imposing a tension on the abra-" sive band as the length thereof is varied between predetermined limits and for automatically statpositions of Fig. I

ically balancing the wheel for varying lengths of the band.

3. A polishing wheel having a drum face, a cushion secured on the drum face; an abrasive band surrounding said cushion, means on the wheel for always imposing a tensioning pull on the abrasive band for maintaining the band tight on the cushion and for maintaining the dynamic balance of the wheel as thewheel is rotated at high speed. a r

A polishing'wheel having a drum face, a

cushion secured on the drum face, an abrasive.

band surrounding said cushion, means on the wheel for imposing a tensioning pull on the abrasive band, said tensioning means being acted upon by centrifugal force to increase the tensioning pull on the band and to maintain the dynamic balance of the wheel as the wheel is rotated at high speed.

5. A polishing wheel having a drum face, a cushion secured on the drum face, an abrasive band surrounding said cushion, means on the wheel for imposing a tensioning pull on the abrasive band, said tensioning pull being automatically increased in exact proportion to the increase in tension in the band as the speed of rotation of the wheel is increased.

6. A polishing wheel having a drum face, a cushion secured on the drum face, an abrasive loop surrounding said cushion, means for detachably securing one end of the loop to the wheel, link means movable radially of the wheel, means for detachably connecting said link means to the other end of the loop, and yielding means movable radially of the wheel for imparting a tensioning pull to said link means in a direction parallel to its path of movement.

'7. A polishing wheel having a drum face, a cushion secured on the drum face, an abrasive loop surrounding said cushion, means for detachably securing one end of the loop to the wheel, link means movable radially of the Wheel, means for detachably connecting said link means to the other end of the loop, yielding means movable radially of the wheel for imparting a tensioning pull to said link means in a direction parallel to its path of movement, and manually operable means for moving said link means outward and for maintaining said link means at its outermost position.

8. A polishing Wheel having a drum face, a cushion secured on the drum face, an abrasive loop surrounding said cushion, means for detachably securing one end of the loop to the Wheel, link means movable radially of the wheel, means for detachably and pivctally connecting said link means to the other end of the loop at its laterally central portion, and yielding means movable radially of the wheel for imparting a tensioning pull to said link means.

9. A polishing wheel having a drum face, a cushion secured on the drum face, an abrasive loop surrounding said cushion, means for detachably securing one end of the loop to the wheel, link means movable radially of the wheel, means for detachably connecting said link means to the other end of the loop, and yielding means acting radially of the wheel at an acute angle with the path of movement of the link means for imparting a tensioning pull to said link means.

10. A polishing wheel having a drum face, a cushion secured on the drum face, an abrasive loop surrounding said cushion, means for detachably securing one end of the loop to the wheel, link means movable radially of the wheel, means for detachably connecting said link means to the other end of the loop, yielding means movable radially of the wheel at an acute angle with the path of movement of the link means, and flexible substantially non-stretchable means connecting the link means to the yielding means, component parts of said flexible means moving substantially radially of the wheel.

11. A polishing wheel having a drum face, a cushion secured on the driun face, an abrasive loop surrounding said cushion, means for detachably securing one end of the loop to the wheel, and means for applying a yielding tensioning pull to the other end of the loop, component parts of said tensioning means acting radially of the wheel in angular relation to each other so as to automatically statically balance the wheel.

12. A polishing wheel having a drum face, a cushion secured on the drum face, an abrasive loop surrounding said cushion, means for detachably securing one end of the loop to the wheel, and means for applying a yielding tensioning pull to the other end of the loop, component parts of said tensioning means acting radially of the wheel in angular relation to each other so as to automatically dynamically balance the wheel.

13. A polishing wheel having a drum face, a cushion secured on the drum face, an abrasive loop surrounding said cushion, means for detachably securing one end of the loop to the wheel, clip means secured on the other end of said loop, link means movable radially of the Wheel, and yielding means for imparting a tensioning pull to said link means, said clip means being pivctally connected at the central portion laterally of the loop to said link means for exerting a pull on the link means in a direction coaxial therewith.

14. In a polishing wheel having an abrasive band, means for anchoring an end of the band to the wheel including a substantially U-shaped clip having serrated inner surfaces for gripping the band, the free ends of the legs of the clip being rounded, and means surrounding the clip provided with a slot through which the end of the band extends having plane surfaces engaged by said rounded clipends extending from each side of the slot and angularly converging toward said band end, whereby when tension is applied to the band, the plane surfaces react against said rounded clip ends to automatically compress and wedge the free ends of the clip toward each other and increasingly grip the band end more tightly as the band tension is increased.

15. In a polishing wheel having an abrasive band, means for anchoring an end of the band to the wheel including a substantially U-shaped clip having serrated inner surfaces for gripping the band, the free ends of the legs of the clip being rounded, and a clip holder surrounding said clip provided with a slot through which the end of the band extends and having angular flange portions provided with plane surfaces engaged by said rounded clip ends extending from each side of the slot and angularly converging toward said band end, whereby when tension is applied to the band, the plane surfaces of the holder react against said rounded clip ends to automatically compress and wedge the free ends of the clip toward each other and increasingly grip the band end more tightly as the band tension is increased.

NATHAN C. HUNT.