Part 1

Chapter 13,537 wordsPublic domain

Transcriber’s Notes:

Underscores “_” before and after a word or phrase indicate _italics_ in the original text. Equal signs “=” before and after a word or phrase indicate =bold= in the original text. Small capitals have been converted to SOLID capitals. Illustrations have been moved so they do not break up paragraphs. Typographical and punctuation errors have been silently corrected.

Hoisting Appliances

By I.C.S. STAFF

HOISTING Parts 3-4

447 Published by INTERNATIONAL TEXTBOOK COMPANY SCRANTON, PA.

Hoisting, Parts 3 and 4:

Entered at Stationers’ Hall, London

Printed in U. S. A.

INTERNATIONAL TEXTBOOK PRESS Scranton, Pa.

CONTENTS

NOTE.--This book is made up of separate parts, or sections, as indicated by their titles, and the page numbers of each usually begin with 1. In this list of contents the titles of the parts are given in the order in which they appear in the book, and under each title is a full synopsis of the subjects treated.

HOISTING, PART 3 _Pages_ Hoisting Appliances 1-43

Hoist Indicators 1-5 Column indicators; Dial indicators; Special indicators.

Drums and Reels 6-20

Cylindrical Drums 7-8

Conical Drums 9-16 Hoisting with cylindrical drums; Hoisting with conical drums; Comparison of cylindrical and conical drums.

Flat Rope Reels 17-20

Rope Wheels 21-26 Koepe system; Whiting system; Modified Whiting system.

Rope Fastenings 27

Clutches 28-31 Jaw clutch; Band friction clutches; Beekman friction clutch.

Brakes 32-43 Block brake; Post brake; Strap brake; Differential brake; Power for brakes; Differential lever; Power brakes; Crank brake.

HOISTING, PART 4

Hoisting Appliances 1-51

Sheaves 1-5 Cast-iron sheave; Wood-lined sheaves; Diameter of sheave; Rollers and carrying sheaves.

Cages for Vertical Shafts 6-11 Construction of cage; Safety catches; Multiple-deck cages.

Automatic Dumping Cages 12-16 Definition; Slope, or inclined shaft hoisting; Slope carriage.

Skips, or Gunboats 17-22 Definition; Method of loading skips; Method of dumping skips; Skip cage.

Buckets 23

Car Locks 23-24

Cage Guides 25

Landing Fans, or Keeps 26-28 Common forms of fans; Hydrostatic fans; Pneumatic fans; Cage chairs.

Head-Frames 29-45 Head-frames in general; Types of head-frames; Examples of various types; Head-frame specification.

Detaching Hooks 46-47

Signaling 48-51 Hammer-and-plate signal; Electric bells; Speaking tubes; Pneumatic gong signal; Telephones.

HOISTING

Serial 851C (PART 3) Edition 1

HOISTING APPLIANCES

HOIST INDICATORS

=1. The hoist indicator= is a mechanism attached to the drum shaft of a hoisting engine to show the hoisting engineer the position of the cage or skip in the shaft throughout the time of hoisting. The use of such indicators is sometimes required by law, but there is a great diversity of opinion as to the advisability of using them. The objections to them are that they are liable to get out of order, and that in general the use of any automatic device that tends to relieve the hoisting engineer of responsibility and constant attention to his engine is not to be commended. A hoisting engineer, however, depends for his stopping point mainly on a mark made on the rope, or on the drum, or on both, and uses an indicator mostly as a guide for the position of the cage during the hoist.

TYPES OF INDICATORS

=2. Column Indicators.=--A very simple indicator, and one that was formerly very commonly used, is made by inserting a pin into the center of the end of the drum shaft and using this as a miniature drum on which to wind and unwind a chain or cord, which corresponds to the hoisting rope as the pin corresponds to the drum. This chain or cord is led over a pulley placed at the top of a pair of guides, representing the shaft, and carries at its end a weight, pointer, or gong, representing the cage or car, as shown in Fig. 1.

The pointer _a_, Fig. 3, is moved by the rotation of the screw shaft _b_, which is revolved by the bevel gears _c_ and _d_. This indicator also registers the number of hoists by means of the dials _e_, for at each hoist the lower end of the pointer a engages a ratchet wheel behind the two dial faces shown and thus registers on the dial.

=4. Dial Indicators.=--Fig. 4 shows a positive-motion indicator that is operated as follows: A worm _a_ on the drum shaft _b_ engages with the worm-wheel _c_ on the small shaft _d_ that is supported by the bearings _e_. The pointer _f_ is rigidly attached to the shaft _d_ and revolves in front of the properly marked dial _g_.

=5.= Fig. 5 shows a =dial indicator= attached to drum hoists where the speed of rope is constant for each revolution. The wheel _a_ of this indicator may be a worm-wheel working in a worm on the drum shaft, as described in connection with the indicator shown in Fig. 4, or it may be a sprocket wheel driven by a link belt from a sprocket wheel on a drum, or it may be a gear-wheel driven directly from another gear-wheel on the drum. The gear-wheels _b_ revolve a vertical shaft _c_ fitted at the upper end with a worm _d_ that drives the worm-wheel _e_ placed on the end of the pointer spindle. The different levels from which hoisting is to be done may be painted on the dial, or better, they may be placed on movable targets that are clamped to the dial and can thus be moved as occasion requires.

EXAMPLE.--An indicator is desired for a shaft 800 feet deep at which the drum of the hoisting engine to be used is 10 feet in diameter; what ratio of gearing must be used so that the pointer will make one revolution during the hoist?

SOLUTION.--The circumference of the drum is 31.42 ft. (π_D_ = 10 × 3.1416 = 31.416 ft.); hence, the revolutions per hoist are 800 ÷ 31.42 = 25.46 revolutions. Then, if the pointer is to make one revolution per hoist, the ratio of the gearing will be 25.46 to 1. Ans.

=6. Special Indicators.=--One fault of nearly all indicators is that they give a regular movement throughout the winding, and the space over which the pointer travels is too small to enable the engineer to land the cage accurately. Indicators have been made with a differential motion to the pointer, the motion being greater at the time of landing and less during the middle of the hoist. They are also made with two pointers, one operating like the dial indicator above described and the other remaining stationary during all the hoist but the last few feet, when it moves around its circle.

=7.= Where flat ropes are used or where round ropes wind on a conical drum, the length of rope wound or unwound is different for each turn of the drum. With all the indicators thus far described, while the speed with which the indicator moves is proportional to the speed at which the drum and the drum shaft revolve, it is not proportional to the speed of the rope when winding and unwinding on a conical drum or on a flat rope reel. Fig. 6 (_a_) and (_b_) shows two views of a compensating dial indicator. By means of the spiral form of sheave _c_, the hand _d_ is made to move equal distances around the disk _e_ for equal distances of cage movement in the shaft. The rope _f_ passes about the spiral sheave and one end is attached at the small end _g_ of the spiral, while the other end is fastened to the periphery of the sheave _h_, which takes its motion from the drum shaft or crank-shaft of the hoisting engine by means of the bevel gear _i_. Consequently, while the sheave _h_ has a regular motion dependent directly on the revolution of the hoisting drum, the pointer _d_ moves irregularly, depending on the position of the spiral sheave _c_; that is, whether a small or large diameter of the spiral is presented to the rope. The rope _j_ carrying the counterweight _k_ is attached to a small circular drum _l_ that is on the same shaft as the spiral sheave. The purpose of this cord and counterweight is to keep the indicator line _f_ taut and to bring the indicator back to position as the cord _f_ unwinds from the sheave _h_.

=8.= In order that the pointer may not stand at exactly the same point on the dial when the cage is at the top and at the bottom, and so that the engineer may be able to distinguish between the top and the bottom positions of the cage by the pointer, the ratio of the gearing is usually increased by allowing one or two extra teeth on the worm-wheel. In the example in Art. =5=, assume a ratio of 27: 1; that is, if a worm-gear is used, the worm-wheel will have 27 teeth.

If the pitch of the teeth is ¾ inch, the circumference of the pitch circle will be ¾ × 27 = 20.25 inches and the diameter 6.44 inches.

The pitch of the worm will, of course, be the same as that of the wheel, and its diameter will be whatever is necessary to give sufficient strength outside of the shaft, since it bears no relation to the ratio of the gearing.

DRUMS AND REELS

=9.= The =drum=, or =reel=, of a hoisting engine is the part on which the rope winds. It is either keyed fast to the engine shaft or is connected to the shaft by means of a clutch, the shaft being made extra heavy to carry the strain due to the weight of the drum and the pull of the rope.

CYLINDRICAL DRUMS

=10.= The outer part, or =shell=, of a drum _a_, Fig. 7, is supported on rims _b_, and these rims are connected by arms or spiders _c_ with the hubs _d_. The brake rings _e_ are for the band brakes, of which there may be one or two. The part _a_ may be lagged with strips of wood bolted to the rims _b_, the heads of the bolts being countersunk. Fig. 8 shows the detailed dimensions of a drum 8 feet in diameter having a 4-foot face designed to carry heavy loads and a large amount of rope. The shell is of boiler plate and the spiders of cast-steel.

=11.= The shell may be cast in one piece for small drums or built up in sections for large drums, as in Figs. 7 and 8. The shell may have a smooth surface, Fig. 8, or it may have grooves, Fig. 7, for the rope to lie in as it is wound on the drum. On an iron drum without grooves, the rope will chafe sidewise; and furthermore if the rope winds on a hard flat surface it bears here and there on a single wire and tends to flatten, causing internal wear between the wires; while, in the case of a rope winding in a groove, it is supported on about one-quarter of its circumference, bringing many more wires to bear on the drum and dividing the pressure between them. A wooden-lagged drum causes less wear on a rope than an ungrooved iron-shell drum, as grooves are gradually worn in the lagging, but is not so good as a grooved iron drum. It is not good practice to allow a rope to wind on itself, and the drum should be long enough to take the full length of the rope required for the hoist. At least two turns of the rope should be on the drum when the load is at the bottom, as the friction between the rope and drum thus greatly lessens the strain coming on the rope at the point where it is fastened to the drum. Allowance for two or three additional turns of the rope should also be made so that the cage may be hoisted above the landing.

The shell usually has a flange at each end, as shown in Figs. 7 and 8, but it may have a flange at one end only, or may be without flanges entirely. If, however, the flanges are not used, the drum must be extra long to prevent the rope running off the end. If the drum is very long, a third spider is added midway between the other two to stiffen it against collapse.

EXAMPLE.--Find the length of a drum 6 feet 3 inches in diameter necessary to hold 1,000 feet of 1¼-inch wire-rope.

SOLUTION.--The diameter from center to center of the rope when wound on the drum is 6 ft. 3 in. plus 1¼ in., or 6 ft. 4¼ in., which is equal to 19.96 ft. (approximately 20 ft.) of circumference. Then, to wind 1,000 ft. will require ¹,⁰⁰⁰/₂₀ = 50 turns on the drum. Allowing two turns of the rope to protect the fastening and three turns in case of overwinding, gives fifty-five turns to be allowed for on the drum. If the drum is of iron with grooves turned in it, ¼ in. must be left between adjacent parts of the rope, or 1½ in. from the center of one turn to the center of the next. Then, 55 × 1½ = 82½ in. plus ¾ in. at each end = 84 in., or 7 ft. for the length of the drum between the flanges. Ans.

If the drum has wooden lagging, clearance need not be allowed between two adjacent coils of rope, as in this case the rope winds against itself and so takes up only 1¼ in. It will then be 55 × 1¼ in. = 68¾ in., or 5 ft. 8¾ in. long (say 5 ft. 9 in.). Ans.

CONICAL DRUMS

=12.= In hoisting in balance from deep shafts with cylindrical drums, if no tail-rope is used, or in hoisting from a single shaft with an unbalanced cage, the hoisting engine is not loaded equally at different points of the hoist owing to the gradually changing weight of the unbalanced rope. The following illustrations will further explain this.

=13. Hoisting With a Cylindrical Drum.=--Suppose that, from a single-compartment vertical shaft 1,000 feet deep, it is required to hoist each trip a load, including friction, of 11,000 pounds made up as follows:

POUNDS Weight of material 4,000 Weight of car 3,000 Weight of cage 3,000 Friction, 10 per cent. 1,000 ------ Total 11,000

If a 1⅜-inch cast-steel rope weighing 3 pounds per foot is used, winding about a drum 7 feet in diameter, the weight of rope is then 3 × 1,000 = 3,000 pounds and the load on the rope, when the cage is at the bottom, is 11,000 + 3,000 = 14,000 pounds, while at the top the load on the rope is only 11,000 pounds. The moment of the load at the bottom is then the load 14,000 multiplied by the radius 3½, or 14,000 × 3½ = 49,000 foot-pounds; and at the top, 11,000 × 3½ = 38,500 foot-pounds. This shows that the load against the engine is much greater at the beginning than at the end of the hoist.

=14.= Take now a double-compartment vertical shaft of the same depth as in Art. _13_ and assume the same amount of material hoisted at a trip, in the same mine car and on the same cage; but that an empty car and cage are lowered in one compartment while the loaded car and cage are hoisted in the other. The two cars and the two cages will balance each other, and the loads will be as follows: At the beginning of the hoist, when the loaded car and cage are at the bottom, the gross load is 14,000 pounds, made up as follows:

POUNDS Weight of material 4,000 Weight of mine car 3,000 Weight of cage 3,000 Friction, 10 per cent. of above 1,000 Weight of rope 3,000 ------ Total 14,000

Multiplying this by the radius of the drum, the gross turning moment is 14,000 pounds × 3½ feet = 49,000 foot-pounds, as before, but there is a counterbalancing load of 6,000 pounds, made up as follows:

POUNDS Weight of mine car 3,000 Weight of cage 3,000 ----- Total 6,000 Less friction, 10 per cent. 600 ----- 5,400

This means a counterbalancing load moment of 5,400 pounds × 3½ feet = 18,900 foot-pounds. The net load moment to be overcome by the engine at the beginning of the hoist is, therefore, 49,000-18,900 = 30,100 foot-pounds.

At the end of the hoist there is a gross load on the loaded side of 11,000 pounds, made up as follows:

POUNDS Weight of material 4,000 Weight of mine car 3,000 Weight of cage 3,000 Friction, 10 per cent. 1,000 ------ Total 11,000

This is equal to a gross load moment of 11,000 pounds × 3½ feet = 38,500 foot-pounds, but there is a counterbalancing load of 8,100 pounds, made up as follows:

POUNDS Weight of mine car 3,000 Weight of cage 3,000 Weight of rope 3,000 ----- Total 9,000 Less friction, 10 per cent. of 6,000 600 ----- 8,400

This is equal to a counterbalancing load moment of 8,400 pounds × 3½ feet = 29,400 foot-pounds, and leaves a net load moment against the engine of 38,500-29,400 = 9,100 foot-pounds. In other words, the load moment that the engine has to overcome varies from 30,100 foot-pounds at the beginning of the hoist to 9,100 foot-pounds at the end of the hoist.

=15. Hoisting With Conical Drums.--Conical drums= are designed to make the work of the engine as nearly uniform as possible throughout the hoist. To accomplish this, when the cage is at the bottom of the shaft, and the load is therefore heaviest, the rope winds on that part of the drum having the smallest diameter. As hoisting continues, the rope winds on a gradually increasing diameter of drum, and when the cage is at the top of the hoist, and the load therefore least, the rope is winding on that part of the drum having the greatest diameter; in this way, the moment of the load at every point of the hoist is approximately the same. The great difference in the loads at different parts of the hoist is due mainly to the variation in the weight of the rope hanging from the drum; hence, the less the weight of the rope in proportion to the total load on the engine, the more nearly uniform is the load on the engine.

=16.= Fig. 9 (_a_) shows the condition at the beginning of the hoist when conical drums are used. Cage _a_ is at the bottom and carries a loaded car; cage _b_ is at the top and carries an empty car. The net moment that the engine must overcome is the sum of the weight of the material to be hoisted, weight of the cage and car at _a_, and the weight of the rope attached to _a_, multiplied by the small radius _r_ of the drum, minus the weight of the car and cage at _b_, multiplied by the large radius _R_ of the drum.

Fig. 9 (_b_) shows the condition of things at the end of the hoist, when the cage _a_ is at the top and cage _b_ at the bottom. The loaded car and cage _a_, whose rope in Fig. 9 (_a_) was winding on the smallest diameter of the drum, is now at the top and the rope is winding on the largest diameter of the drum. The cage _b_ with the empty car is now at the bottom and the rope is unwinding from the smallest diameter of the drum. The net moment that the engine must overcome in this position is equal to the sum of the weight of the material hoisted, the weight of the cage _a_ and the car, multiplied by the larger radius _R_ of the drum, minus the sum of the weights of the cage _b_, the car, and the rope, multiplied by the small radius _r_ of the drum.

=17.= If the moment of the load against the engine at the beginning of the hoist is to equal that at the end of the hoist, it is possible to determine what relative diameters of drum will produce such an effect, as follows:

Let _Wₘ_ = weight of material hoisted; _Wₖ_ = weight of cage and car; _Wᵣ_ = weight of rope; _R_ = large radius of drum; _r_ = small radius of drum.

The load moment may be calculated by including friction as ⅒ of the total weight hoisted, except the weight of the rope, as shown in Art. =14=; or the friction may be disregarded without serious error. Then, under the conditions shown in Fig. 9 (_a_), and disregarding friction,

Load moment = (_Wₘ_+_Wₖ_+_Wᵣ_)_r_ - _Wₖ__R_ (=1=)

and under the conditions shown in Fig. 9(_b_),

Load moment = (_Wₘ_ + _Wₖ_)_R_ - (_Wₖ_ + _Wᵣ_)_r_ (=2=)

Placing formula =1= = formula =2=,

(_Wₘ_+_Wₖ_)_R_ - (_Wₖ_+_Wᵣ_)_r_ = (_Wₘ_+_Wₖ_+_Wᵣ_)_r_ - _Wₖ__R_,

and (_Wₘ_+ 2_Wₖ_+ 2_Wᵣ_) _R_ = _r_ ------------------- (=3=) (_Wₘ_ + _2Wₖ_)

Since the diameter of a drum is generally given instead of the radius, it follows that if _D_ = larger diameter, _d_ = smaller diameter, and then, since _D_ = 2_R_ and _d_ = 2_r_, formula =3= may be written

(_Wₘ_ + 2_Wₖ_ + 2_Wᵣ_) _D_ = _d_ ---------------------- (=4=) (_Wₘ_ + 2_Wₖ_)

Formula =4= gives only approximate results, which are, however, sufficiently accurate for the mine superintendent’s use, and for this reason friction has been omitted, as it would make the formula much more complex. It may be expressed as a rule as follows: