US3363881A - Power sheave - Google Patents

Description

Jan; 16, 1968 r J. R. KOBELT 3,363,881

' POWER SHEAVE Filed June 6, 1966 DRIVER United States Patent Office 3,363,881 Patented Jan. 16, 1368 means]. POWER SI-llEA /E Jack Iiohelt, Iiohelt Mfg, hill Main St, Vancouver,

' British Colurnhia, Qanada Filed .linne 6, 196a, tier. No. 555,358 Claims priority, application ganada, dune 25, M65,

in (Claims. in. 254-190 ABSTRACT OF THE DISCL UEURE Background of the invention My invention relates to a power sheave characterized by particular means to secure a cable thereto.

Preferred embodiments of the invention are directed to marine control installations.

In marine control installations it is often required that rotation of a one shaft by a discrete amount shall cause a particular corresponding rotation of another shaft at a distance from the first shaft aforesaid. Positive drive of this kind may be accomplished by chain and sprocket means. This system has certain advantages but, particularly if the two shafts are at a considerable distance from one another, tends to be costly.

Alternatively, cable and sheave means are commonly employed in such installations.

In order to satisfy the requirement of positive drive, and that rotation of a one shaft through a particular angle shall cause the driven shaft to rotate through a particular angle, not necessarily through the same angle, reliance may not be placed upon friction, but positive connection is required between a power sheave of a driven shaft and the cable engaging a groove of the said sheave, and as well positive connection of the cable to a sheave of the driver shaft, or to a lever of the said shaft.

Since the required rotation is usually restricted to within, say 60 or 80 either side of a central position, it is possible to employ sprockets with a short length of chain around each sprocket, the short chains being connected by cables. Such a configuration is rather difficult to adjust properly and usually requires two turnbuckle means, one on each side of the cable.

Summary the invention According to the invention, I overcome these, and other, difficulties by cutting an opening through a face of the sheave, which opening extends through the groove to an end wall tangent to an inner surface of the groove remote from the face in which the opening is made. The opening is concave, being generally circular, and extends towards the shaft to an opening bottom wall, the opening having such depth that space is provided on the end wall aforesaid sufficient to accommodate bolt and washer securing means. The bolt is spaced from the bottom wall of the opening by an amount suflicient to provide such clearance that the cable may pass from the groove, under the bolt, thence to the groove again.

While the securing bolt is loose, the cable may readily be moved with respect to the groove. This has advantages which will later be explained and, as well, permits accurate setting. In order to provide optimum clearance and long life, I have found that a particular size and shape of opening is required according to the cable diameter. When the bolt is tightened, the cable is secured against motion relative to the grooveso that rotation of the sheave may cause, or be caused by, motion of the cable.

Simple bolt and washer securing means is satisfactory in many installations but, used with the larger cable sizes, may cause intolerable bending stresses in the bolt. Further, the simple bolt and washer securing means may cause setting difliculties due to a tendency for the washer to rotate as the bolt is tightened. According to an alternate embodiment of the invention, I overcome both of these difficulties by providing a lugged circular or curved shoe construction described in detail below.

Description of the drawings Examples of embodiments of my invention are now described in detail with reference to the drawings in which,

FIGURE 1 is an elevation of a power sheave of the subject invention,

FIGURE 2 is a plan view of FIGURE 1,

FIGURE 3 is a large scale section on line 3-3 of FIGURE 2,

FIGURE 3A shows schematically an alternative concave bottom wall shape possibility,

FIGURE 4- is a large scale section on line 44 of FIG- URE 1, with the bolt and the cable removed,

FIGURE 5 shows driver and driven pulleys of the invention connected by cable means,

FIGURE 6 shows an alternative washer, or circular shoe,

FIGURE 7 is a section on line 7-7 of FIGURE 6,

FIGURE 8 is a further alternative washer, or curved shoe,

FIGURE 9 shows a curved washer.

Description of FIGURES 1-4 Referring to FIGURES 1 and 2, the power sheave is indicated generally by the numeral It The sheave has a boss 11, drilled for a shaft 12 to which it is secured, for instance by two or more Allen screw means 13. The periphery of the sheave is grooved at 14 to receive a cable 15, which groove is-as best seen in FIG- URE 4-defined by an outer side wall 14A, an inner side wall 14B, and a bottom wall 14C. Referring to FIG- URE l, the sheave has a flange 16 which is cut to provide a concave opening 17. The flange 16 has a continuing portion 18 adjacent the said opening.

As best seen in FIGURES 3 and 4, the opening extends axially from the flange continuing portion 18 to the inner sidewall 14-13 of the groove 14 and is defined by a flat end wall 19, and concave bottom wall 20'. The said bottom wall suitably is a portion of the surface of a cylinder having an axis parallel to the axis of the shaft 12 so as to define, as seen in FIGURE 3, the concave bottom wall aforesaid. The flat end wall 19 is a plane surface normal to the axis of the shaft 12, being a continuation of the inner groove sidewall ltd-B remote from the flange portion 18. The greatest depth of the opening, measured from the sheave periphery as indicated at A FIGURE 3, is about five times the diameter of the cable 15. For example, in a sheave designed for a /8 cable, the dimension A would be about of an inch. As stated, the bottom wall 213 is a portion of the surface of a cylinder, suitably the diameter of this cylinder is about half the diameter of the pulley It A hole 21 is drilled and tapped centrally in the end wall 19 to receive a bolt 22 (FIG- URE l). The position of the hole 21 is such that there 3 shall be a clearance, designated C in FIGURE 3, to the bottom wall 20. C may be equal to, and should not be less than, about 1.5 X the diameter of the cable 15, that is to say with a one-eighth inch cable, C would be about three-sixteenths of an inch.

Referring now to FIGURE 1, the bolt 22 is provided with a plain washer 23. The depth of the bottom wall measured parallel to the shaft axis is, desirably, not less than the cable diameter plus the washer thickness. The outside diameter of the washer is such that, when the bolt is inserted in the hole 21 as shown in FIGURE 1, the said washer shall just clear the bottom wall 2d of the concave opening 17. The bolt 22 is provided with a locknut 24- seen in FIGURE 2 only.

Referring to FIGURE 3, junctions of the bottom wall 20 with the groove bottom wall 14C are rounded as shown at 25. The radius of curvature of the rounded portion 25, as seen in FIGURE 3, desirably is not less than twice the diameter of the cable 15.

The cable 15 is bent around the sheave 10 by loosening the bolt 22 and pushing the cable beneath the said bolt through the clearance C, FIGURE 3. When the cable is in the required position, the bolt 22 is tightened to compress the cable between the end Wall 19, FIGURE 4, of the opening 17 and the washer 23, after which the locknut 24 is tightened.

Power sheaves are generally used for throttle shafts, gear box shafts, single lever control units, jack shafts, and the like.

Description of FIGURE 5, with further reference to structure of FIGS. 1-4

FIGURE is a diagram showing two sheaves Iii-A and Ill-B according to the invention, which sheaves are to be connected by the cable 15 so that rotation of the driver, here shown as B, shall cause the driven sheave 10A to rotate. Sheaves Iii-A and 10B should first be placed on, but not yet secured to, their respective shafts, and the cable bent around both as above described. At this time, the cable is not secure-d in the sheaves by means of the bolts 22. The two sheaves MlA, 1043, FIGURE 10 need not be of the same diameter, and in fact usually are not. In the best common practise, the driver is the smaller of the two. These diameters are chosen to give the required ratio of travel of the driver shaft to travel of the driven shaft.

Referring to FIGURES 1 and 5, it is seen that rotation beyond a particular maximum either side of a central position will result in the cable losing contact with the rounded junction 25, FIGURE 3. For the sheave of FIGURE 1 used in a FIGURE 5 configuration, this maximum is about 70 and, while the sheaves could rotate further, it is desirable to confine the motion within these limits to avoid undue bending stresses at the rounded junction, which matter is later referred to.

It is usually required that there be a fixed relationship between one position, say a central or neutral position, of the driver and a corresponding position of the driven sheave. To set up the FIGURE 5 arrangement, both shafts are turned to an index position-cg. the central position aforesaid. In this position the bolts 22 of each sheave are required to be opposite to one another, as shown in FIGURE 5. The sheaves are rotated to this position, when the Allen screws are tightened to secure the sheaves to their respective shafts. If it is desired, a first Allen screw may be tightened and a hole drilled in the position of the second Allen screw which, when the said hole has been drilled, the second Allen screw may be inserted and tightened, positively to secure the sheave to the shaft. This procedure may of course be repeated with the first Allen screw. At this time, the cable 115 is not secured to the sheaves (other than by friction). It is common practise that the two free ends of the cable be brought together and joined by means of a turnbuckle 26, which turnbuckle may be adjusted for the proper tension. When this has been done, and a check has been made to ensure that the turnbuckle 26 is sufficiently distant from both the sheaves so that it may accomplish the required travel, the bolt 22 of each sheave may be tightened, and secured by means of the lockout, as above described. It is clear that a rotation of the driver will now rotate the driven sheave, and that the required phase relationship between the two has been achieved.

After such an installation has been in use for some time, the cable may stretch and it may become necessary further to tighten the turnbuckle 26. This will alter the phase relationship above and, if the stretch is significant, it will be necessary to readjust. This is readily accomplished by loosening one bolt 22 when the correction can readily be made.

After further use, the portion of the cable in the vicinity of the rounded portions, as 25, FIGURE 3, the smaller sheave, may commence to show signs of wear. Eventually, the cable could fail here through fatigue stress, particularly in an installation where the maximum angle aforesaid might be exceeded. The worn portions may readily be made to occupy straight portions of the run by loosening the securing bolts and the turnbuckle, and by moving the cable with respect to the sheaves.

It is well understood in the art that there is a desirable relationship between. the diameter of the driver and the diameter of the cable used. When the diameter of the driver is too small, excessive wear will take place. In the foregoing description I have related the clearance C FIGURE 3 directly to the diameter of the cable. Apart entirely from the considerations just stated, if this were not done the cable could not be inserted in the manner described. I have however related the diameter of the sheave opening 17 and the depth A thereof to the diameter of the sheave rather than to the diameter of the cable. In a variety of situations it could arise that the diameter of the cable 15 actually used in an installation such as FIGURE 5 may be materially smaller than the maximum size which could be accomodated by the driver iii-B. The sheaves will of course operate equally well in these circumsta ces. In any proper installation the opposite situation should never arise, that is to say, a cable of too large diameter in relation to the diameter of the driver should never be used; therefore that situation is not discussed. Having further reference to FIGURE 5, it is established in the art that the diameter of the driven sheave should 'be larger than the diameter of the driver, or in the limit equal to it. Thus, in most installations, considering tie diameter of the driven sheave the cable 15 is usually of smaller diameter than could be accommodated. As before stated, such an installation will operate well.

The Allen screw means to secure a power sheave to its shaft is preferred because of the ease of adjustment as above described. Obviously, other well known means may be used to secure a sheave to its shaft. If the clearance C is smaller than the diameter of the cable, then of course the cable could not be inserted in the manner described, and could not be inserted at all without flattening-which is not desirable; thus C has a critical lower limit. The curvature at 25 FIGURE 3 is of importance. If a sharp corner is left at thi point, it is clear that there could be a cutting action, and that wear or breakage could occur. I have found that in installations Where there is a substantial amount of power to be transmitted, and where accordingly the stress in the cable 15 might approach its working strength, that the figure given above is satisfactorynamely, that the radius here shall be 1.5 times the diameter of the cable. It is satisfactory to have a curvature less than this, but the curvature should not exceed the figure given. it is seen too that the fiexture at this point, namely in the vicinity of. 25, is a function of the curvature of the bottom wall 2%. This curvature could be made less, that is to say of greater diameter, in which case we could somewhat reduce the curvature at 25. However, an increase in diameter of the opening will decrease the possible are of rotation of a sheave. The depth A in FIGURE 3 may be increased or reduced without changing the curvature of the bottom wall 2%. If A is increased, the permissible angle will again be re duced-which may or may not be a serious disadvantage according to circumstances. If A is reduced, the possible arc of rotation will increase and the centre of the whole 21 will move upwards; provided that 21 is not noved sufficiently far upwards to weaken the structure from a mechanical point of view, and provided that the washer 23 does not then extend beyond the periphery of the drum, no harm is done. The limits that l have given have been found in the practise to give satisfactory results in critical installations. Subject to the qualifications given above, the limits are capable of substantial variation.

The bottom wall of the opening, see FIGURE 3, is shown and described as being circular, and this is preferred because of ease of manufacturing. FIGURE 3A shows schematically an alternate shape of bottom wall ZilA, having straight portions 2GB and 28C, with the curved juncture 25 as before. The FIGURE 3A configuration, and other configurations, not shown, having a noncircular bottom wall would act in an equivalent manner to attain the objects of the invention. It is seen that the essential characteristics of the opening structure, best to attain the objects of the invention, are that it shall have suflicient depth A so that the fastening means shall not extend outwards beyond the sheave periphery to cause possible interference, and for the other reasons given, and that the junction 25 be rounded to avoid sharp bending of the cable at this point.

Alternative fastening structure, FIGS. 69

The simple bolt and Washer securing means in the embodiment above is satisfactory in many installations. However, using the larger cable sizes it is found that the bolt tends to bend. This I am able to overcome by providing a logged washer, or circular shoe, as seen in FIGURES 6 and 7. As here shown the circular shoe 27 has a lug 28 on the face thereto. The thickness of the lug 28 measured axially is about the diameter of the cable used. The cable 15 is indicated in FIGURE 7 by the broken outline 15. Using this alternative, it is seen that the load on the bolt is now almost entirely tensile, with little or no bending stress.

In some circumstances there is a tendency for the Washer to turn as the bolt is tightened, so to tend to move the cable with respect to the sheave. This may impede the setting up procedure described above. While that effect seldom occurs using the circular shoe of FIG- URES 6 and 7, the alternative construction illustrated in FIGURE 8 positively restrains rotation. I refer to the FIGURE 8 construction as a curved shoe. The curved shoe 29 has an upper convex side wall 30 and a lower convex side wall 31. The side wall 30 should not protrude beyond the sheave for reasons which have been explained, and it may thus have a curvature equal to that of the sheave, i.e. the diameter of the convex sidewall 30 may be equal to the outside diameter of the sheave, and be ccaxial therewith. The curvature of the lower sidewall 31 is that of the opening bottom wall 20, to cooperate therewith. A lug 32 is provided, generally similar to the lug 28 of the circular shoe aforesaid. Thus, the curved shoe of FIGURE 8 will not rotate as the bolt is tightened.

A still further alternative, a curved washer, is shown in FIGURE 9. The FIGURE 9 alternative is the curved shoe of FIGURE 8 without the lug 32. Accordingly, upper and lower sidewalls 34 and 35 have the same curvature as the sidewalls 30, 31, of the curved shoe of FIG- URE 8. This curved washer too will not rotate, but it is not suitable for use Where bending stresses in the bolt are likely to develop.

I prefer to use bolt and washer means as described and illustrated as being simple and eflective. It is not however essential that the securing means he as so described. For instance, staple or other well known securing means could be substituted to secure the cable to the end wall of the opening so that the cable shall lie as substantially described, namely adjacent the opening bottom wall at the greatest distance thereof from the sheave periphery.

I claim:

1. A power sheave adapted for rotation about an axis, the sheave having a flange, a peripheral groove to receive a cable, the groove being defined by side walls including an inner side wall remote from the flange and a bottom wall, the foregoing structure characterized by:

(a) an opening in the flange, which opening extends axially of the sheave to the groove inner side wall, (i) the said opening being defined. by an end wall, the said end wall being a continuation of the groove inner side wall and being normal to the pulley axis, (ii) and by a concave bottom wall, and (b) means securing the cable to the end wall of the opening so that the cable lies adjacent the concave bottom wall.

2. Structure as defined in claim 1, wherein the concave bottom wall is a part of the surface of a cylinder coaxial with the sheave, the diameter of the cylinder being about one-half of the outside diameter of the sheave.

3. Structure as defined in claim 2, wherein the concave bottom wall is rounded at a junction thereof with the groove bottom wall.

4. Structure as defined in claim 3, wherein the rounded junction aforesaid has a. radius of curvature not less than twice the diameter of the cable.

5. Structure as defined in claim 4, wherein the opening has a greatest depth, measured from the sheave periphery to the bottom wall of the opening, is about 5 times the diameter of the cable.

6. Structure as defined in claim 5 wherein there is a clearance C between the securing means and the concave bottom wall to accommodate the cable, which clearance C is equal to or greater than about 1.5 times the diameter of the cable.

7. Structure as defined in claim 6, wherein the cable securing means includes a bolt in the end wall aforesaid, and a washer, adapted so that tightening of the bolt compresses the cable between a surface of the washer and the opening end wall.

8. Structure as defined in claim 7, further characterized by a washer having a lug to comprise a circular shoe so that stress developed in the bolt by tightening thereof shall be substantially tension only.

9. Structure as defined in claim 8, further characterized by a washer having a side wall adapted to cooperate with the bottom wall of the opening to prevent rotation of the washer as the bolt is tightened.

References Cited UNITED STATES PATENTS 7/1944 Roby 74-506 4/1947 Wohler 2413'5.1

EVON C. BLUNK, Primary Examiner.

H. C. HORNSBY, Assistant Examiner.

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