US2191448A - Method of dredge bucket operation - Google Patents

Description

Feb. 27, 1940. M BIRD I METHOD OF DREDGE BUCKET OPERATION V Filed April 5, 1937 2 Sheets-Sheet 1 IN VEN TOR. floaAer- M 5/20 Mp/paw A TTORNEYS.

JAN. fZ-a. MAR. APR. "MAY .Jum: JULY AUG. 55m: 001: Nov. DEC.

Feb. 27, 1940. H, M. BIRD 2,191,448

METHOD OF DREDGE BUGKET OPERATION Filed April 5, 1937. 2 Sheets-Sheet 2 Patented Feb. 27, 1940 UNITED STATES rA E T" OFFICE The present invention, as will readily appear to those skilled in the art, is in general directed to the art of digging, and particularly where this is accomplished by means Eofa series of buckets which are adapted to be connected together to form an endless chain supported on a ladder. Buckets of this kind vary widely in size, and therefore the capacity, or the size of the load carried, as well as the weight of the buckets themselves, have a correspondingly wide range. Regardless of the size and weight variable, the full weight of the buckets plus the force of the driving power applied to the chain is transmitted to the cutting lips of these buckets as they come around the end of the ladder to dig their loads. Because of the constant digging, mostly in gravel and sand, and the nature of the casting material,

the cutting lip or leading edge of the bucket subject to continual wear.

If the digging operations are usual, it is generally said that the wear on the lip is about one f1 inch per month, and this represents: merely a rough average of the amount of wear taking place. However, it is to be understood that many rate of wear, and that the amount here stated is, in any event, an approximation only.

To meet the problem of wear on the bucketlips, it has long been known in the art to provide detachable lips which can be removed from the bucket, and new ones put on in their stead.

The usual or general practice heretofore" is to put new lips on an entire bucket chain at the same time and to operate the chain continuously (except for clean up periods, break downs, etc.) until such time as all the lips are worndown to the point where they can be discarded, and then they are all removed, and a complete set of new lips is put on. Occasionally it is necessary to replace a single lip due to breakage, cracking etc., but when this is done the practice is to cut down the newly inserted lip with a torch-untilit is the same height as the balance of the partly worn bucket lips in the chain. a

Not only are the dredges expensive and complex machines, but their profitable, practicable operation requires, among other things, a practically continuous uninterrupted operation. It

takes skilled workers fromten to sixty hours to chain of from fifty to eighty buckets, with the time usually about twenty to thirty hours. Usually when there is need to replace the entire set of lips because of wear, a special time is set by the operator to accomplish this, and the entire variables have to be considered in evenstating a change at one time all the lips on the usual bucket dredgingoperation is halted until all the new lips are in place. This is an expensive task inasmuch as each lip is. usually secured to the bucket by-means of rivets, from twenty to sixty in number, which have to be trimmed off with a cutting torch. Also,precisely as many new rivets are required in fastening in place the new setoflip's. All of this work must'usually be done on the location, wherever, it may be, and much elaborate,

expensive'equipment must be carried by' each dredge to take care of thesechanges. One of the chief problems in the operation of abucket line has been the loss of time, and large expense entailed, in making the change from' the worn lips to the whole new set.

It is an object of this inventionto provide a novel bucket chain and method of.v operation which will elminate the necessity for costly, spe-' ,cial'periodic shut-"downs for the purpose of changing sets of lips, and one which will, at the same line in place of adozen worn buckets. 'The worn buckets when removed have new lips applied and are placed back in the line; This is repeated until .all the worn buckets are removed. This process cedure to attain the objects of the present in- .vention.

' Another operation problem or defect long known to dredge operators, and which it is a main object of this invention to solve, is that of falling bucket chainfcapacity as the lips begin to wear away.

;As has been stated, the rate of assumed Wear on the lipsv for ordinary digging, chosen merely for purposes of illustration, may roughly be approximated at one inch per month. In the practice heretofore the lips have been made large and heavy, for the reason, among others, of spacing the required periodic shut-downs as far apart as possible.

yet from the standpoint of bucket capacity emciency the less-Irequent the changes, the more the drop in digging recovery.

The lips, however, which have been in use and The more infrequent these periods, "5' u the more is the saving in total operating time, and

which are now in use, are so made as to permit from five to ten inches of wear, depending upon the capacity of the bucket, before the change is made. Nearly all the efforts in the art have been directed to prolonging the life of the cutting lip.

The wear on the lip occurs mainly at the front half, as there is very little wear back of the center line, and practically none four or five inches back of the center line along the side. The bucket is shaped with sloping sides so that when tipped over, the contents will drop out readily. Thus,

the area of the horizontal section, in general, be-

comes progressively smaller from rim to bottom, which means that the sectional area of each bucket in the chain is greater at the top where the wear occurs. If five to ten inches of lip wear takes place at the point of greatest sectional area, before renewing the lips, there must in consequence be a great falling off in the capacity of each bucket. When this is multiplied by the number of buckets in the chain, and the number of trips each bucket takes in operation, the enormity of the operating loss is revealed. In operation, it is not infrequent to have twenty to thirty per cent drop in bucket capacity between the periodic changes. One proposed effort at solving this problem was attempted by speeding upthe bucket chain as the capacity dropped, but this proved too involved to be practical.

This problem of maintaining substantially con-' tinuous capacity in the bucket chain has long been the objective of investigators, and it is an important object of this invention to solve this problem by the provision of an apparatus and a method of operation which will maintain a substantially constant bucket capacity.

A third desirable feature sought by dredge operators is to have a minimum of scrap left in the lip when it is removed .at the end of its life.

Both buckets and lips are rough steel castings usually, and are purchased on the basis of poundage or weight. From the viewpoint of the practice heretofore, it is not practicable to change the sets of lips frequently because of the large amount of scrap involved. As this specification proceeds it will be seen how the present invention assists in achieving a saving in the amount of steel scrap.

Essentially, the practice heretofore required that the entire'set of lips be changed practically at one and the same shut-down, and that these shut-downs be spaced as far apart as possibl being determined by the rate of wear.

Nothing less than a full set of new lips could or can be put on a worn bucket chain digging in gravel deposits because a few new protruding lips would catch in the bank, wreck the bucket line, impose an undue strain on the chain, stop the dredge, tear off the lip, or eifect some other serious and costly damage. Operators avoid such recklessness. When tried, trouble from this cause has been so great that it is practically axiomatic that all lips in the line should show approximately the same degree of wear. In fact, when a single lip anywhere in the line becomes broken, or cracked, and needs replacement prior to the time set for the customary shut-down, it is necessary to cut down the new lip with a cutting torch to equal the approximate stage of wear of the other lips. It is an object of the invention to provide an apparatus and a method of operation in which it is practical to have any number of lips, less than the whole number,

changed at any convenient time, without danger of damage.

This invention, involving as it does a wholly new and novel concept of dredge bucket chain construction and operation, contemplates such other and further objects as will appear as the description of the invention proceeds.

Broadly, the present invention comprises a new method of operating a dredge bucket chain as'well as a new conception of a dredge bucket chain in which a substantially constant capacity for the whole chain is attained by purposely having in the chain buckets with lips in varying stages of wear and maintaining a predetermined average lip height for the chain by replacing frequently (usually at the time of clean-ups) a portion of the most worn lips with new lipsthe maximum difierence in lip heights on the bucketsat any one time being calculated according to the kind of digging encountered.

The variation in capacity for the whole chain Of buckets is a function of the rate of lip wear, thereforethe capacity need only vary as much as the lip wear occurring between renewing a portion of the lips and the next renewal of a portion of the lips.

In attaining the foregoing objects, together with such further benefits, advantages and capabilities as may hereafter appear, and as are inherently. possessed thereby, there is illustrated in the accompanying drawings schematic or diagrammatic charts suggestive of the operation of the method and apparatus of this invention.

Referring now to the drawings:

Fig. 1. is a diagrammatic view of a segment of, a bucket chain withvarious levels of wear indicated for the front of the bucket lip only, and also showing the lower tumbler and a portion of the bank.

Fig. 2 is a diagrammatic chart showing the relative lip wear and capacity variance under the old practice, and the corresponding lip wear and capacity variance of the method and apparatus of this invention.

Fig, 3 is a vertical section of one of the buckets of the chain equipped with asmall lip.

Fig. 4 is a fragmentary transverse section taken on. the line 4-4 and looking in the direction of the arrows, s

Fig. 5 is a View similar to Fig. l by showing at least two complete consecutive groups of buckets with the lips thereof graduated in height between the optimum limits of wear as indicated .bythe lines A and B.

In Fig. 1 there is shown a fragment of an endless bucket chain composed of buckets l0 suitably hingedtogether and passing around the lower tumbler 2t journaled in the lower end of the dredge ladder H. The ladder is suspended downwardly from the front of the dredge boat (not shown). The line of the bank being cut is indicated by the numeral 22.

The full line A represents the height of the lips when the buckets are at their maximum capacity and before any wear. The dotted line B represents the height of the lip"(preferred for the method and apparatus of the present invention). at the lowest point of wear. In past practice all the lips have been changed at once when worn to thelowest point selected by the operator as practical. In the present invention this line represents the point of wear which a portion only of the buckets reachesat one time, and which portionis renewed. The dash line C represents the average or mean lip height-on constant. average digging, a three inch tolerance or varialine, in the example, three inches.

fclean-up days. frequently, and depending upon the place of dig- 2,191,448 a bucket line maintained by the new method of operation, disclosed herein. The dot-dash line 'D (Figs, 1 and 2) represents the minimum capacity of the usual large lips (the practice heretofore) at the point at which all the lips must be changed.

The manner in which the apparatus and method of the invention is used in the accomplishment of the objects stated, among others, brings about the new concept of employing lips in various stages of wear in the bucket chain in order to keep the bucket capacity substantially It has been found, that in ordinary,

tion between lips in the bucket line is practical if the variously worn lips are staggered regularly or irregularly throughout the bucket line. .If too great a variation were attempted in ordinary digging, for instance, having one lip in the bucket line protruding unduly above the lips on either side of it, then the protruding lip would catch in the digging, wreck the bucket line, or cause serious damage to the machinery. On the other hand. a three inch over all range or variance between lips is possible with lips in various stages of wear if they are either regularly or irregularly staggered throughout the bucket line.

The practice of replacing the lips on a portion of the buckets only as that portion has its lips wear down to the point B,lends itself very readily to the use of short replaceable lips, .as these can --be made to have a minimum of scrap steel in them when removed.

- In the accomplishment of the apparatus and method of the invention there is preferably employed what is now termed a little lip. The small lip H (see Fig. 3) is made with a possible wearing capacity which is approximately the maximum tolerance or variation of lip wear in the bucket The rate of wear being normally the same in the small lip I I as in the large lip of the prior art, it is readily seen that instead of trying to prolong the life of the lip by increasing its height, there has been a very definite shorteningof the lip and its life.

This means that there must be a correspondingly more frequent change. Heretofore, as noted, there have been special set days for the complete replacement of the entire set of'lips. There are also periods of shutdown in dredge operation which are termed The clean-up days occur rather ging, are usually every ten to fifteen days. During the four to eight hours duration of these frequent clean;-up periods, the entire operation of dredging is shut down to take care of the prod- The amount of time during this ofv the entire bucket line, and therefore, it has always been necessary, heretofore, to provide the special shut down for accomplishing this job. The present invention enables the dredge operator to eliminate entirely these special shutdowns as there is time enough during the periodic clean-ups to accomplish the change of the lips on a selected number of buckets less than the whole. Thus, by using the apparatus and method of operation taught by this invention, the cleanup time is utilized for changing the lips on a portion of the bucket line, thereby eliminating entirely any necessity for a special and extended time for the complete change of all bucket lips.

The rapidity and speed of change ofthe lips tent of about three inches.

may be further facilitated by the manner and means of attaching the little lip II to the bucket l (Figs. 3 and 4). Instead of employing a number of rivets as used by the prior art, the little lip is preferably fastened in place on the bucket rim by inside-outside flanges l3, and secured thereto by a minimum number of' bolts l4, usually three to six, which are readily removed or tightened. Thus, no expensive equipment is necessaryin changing the bucket lips I I. Even though rivets are used as a fastening means, by employing the method of this invention, there is ample time at the clean-up day to change whatever bucket lips may be necessary or desirable.

The method of the invention is practiced to most advantage from the standpoint of scrap steel when each bucket making up the chain is provided with a little lip H, which, for example, on the medium or large buckets, has a wear conbe practiced by an apparatus in which a predetermined number of complete buckets instead of lips were changed.

It is to be understood that the illustration to follow of a typical chain bucket operation accordi ing to the present invention is not intended to The invention could stages of wear or height and attempts tokeep the various lip heights with an average maximum and. minimum bucket capacity (gauged by the lip height) which average capacity is never as great as itwould be with all new lips, or as small as it would be with all the lips worn to the minimum, and needing renewal all at once.

The preferred method is practiced when the dredge operator selects the average bucket capacity to be maintained, selects the maximum and minimum lip height possible to use in the particular gravel being dug (i. e., the variance between new'and most worn lips), determines the average lip wear on the buckets in the chain, and computs a schedule of lip changes so that as a predetermined number of the lips approach the minimum lip size they are replaced with new lips of maximum height, thereby maintaining within close'limitsa substantially constant capacity for the whole bucket chain.

By way of illustration, the invention perhaps can best be explained by means of a preferred or idealized operation (idealized because in actual, practical operation the results will approximate these conditions). Let us assume a bucket chain of sixty buckets, each with a three inch wear zone on the removable lip. Then let us consider the maximum change of capacity for each bucket to be ten units. This is shown in Fig. 2 by the sloping line SS1;'S2-S3; S4S5 etc. Then let us assume that in the particular material being dug such a lipwill last threemonths, and the clean-up days are fifteen days apart.

If this invention merely involved the changing of the lip wear capacity, in other words, merely line S--S1. But this still would give a wide capacity variance between changes of lips and would not achieve the substantially constant bucket chain capacity of this invention.

Going back to the example, it would be preferred if from the start of operation the bucket chain could be fitted with six'groups of lips in six different stages of wear between S and Sr, so that on the first clean-up the ten most worn lips would have worn to the line. B, or point S1 (see Figs. 2 and 5), and would be replaced by ten new lips of maximum height bringing them up to the line A or point S. The normal operating range would be obtained from the very start of operations, and at each clean-up the ten new lips would restore the average bucket capacity to the 5.5 point on Fig. 2, from the 4.5 point where it would be just before changing ten of the lips.

Where it is not possible to start with this preferred set of graduated lips, (as shown in Fig. 5) and the operator at the startinstalls an entire new set, the bucket capacity of the chain is at its maximum and may be represented by the line A. And in practicing this invention the maximum capacity will never again be attained, and must gradually be reduced by the dredge operator by lipchanges at intervals and in the numbers which will bring the bucket chain into the capacity'range selected by the operator as the best suited to the particular conditions; and then once the bucket chain capacity is in this range the dredge operatorwill select the number of buckets and time of. changing lips which will enable the capacity to be maintained substantially constant, preferably in the narrow range N-N on each side of line C (Fig. 2).

For example, when the chain with all new lips is halted at the first clean-up period, at the end of approximately fifteen days operation, all the lips would show in the neighborhood of onehalf inch of wear. At this time ten of the lips would be taken off in staggered relation, i. e., the lip on every sixth bucket in the chain, and a new lip put on, thus making a lip wear variation of one-half inch in the line. At the second clean-up period, at the end of thirty days, fifty of the lips in the sixty bucket chain would have worn one inch, and ten would have worn one-=half inch. At this time, ten of the fifty showing one inch of wear would be removed, again in staggered relation as explained above, and new lips put on, making the lip wear variation one inch in the line. Similar procedure is repeated at each clean-up until the bucket chain has buckets with lips in varying degrees of wear from new ones having no wear to those worn down two. and one-half inches, if regarded at a time immediately after change; or having from one-half inch to three inches of wear if regarded at a time just prior to the change.

When this point is reached, the dredge, or bucket chain has attained its normal operating range, wherein the bucket capacity crosses back and forth as shown by the line N-N of Fig. 2,

over the average bucket capacity as represented by the dash line C, with a slightly'greater bucket capacity after the change than before. the change. The incompletely worn lips, removed in order to bring the bucket chain capacity down quickly to the preferred operating range, may be used by the operator from time to time as his skill in practicing themethod increases.

The above is given simply as one example of .how the bucket chain capacity canbe brought into. the preferred. operating range, asv itisconceivable each dredge operator may wishto vary the procedure suggested. Whetherxor not a particular operator achieves the greatest efficiency possible will depend to a certain extent upon his skill, but the method will be practiced if employing an apparatus in which a portion of the buckets or bucketlips are changed from time to time to level out the capacity curve for the chain as a whole.

The preferred manner of practicing the method of this invention, when compared with the old practice, taking as an example an eight inch wear on the bucket lips before all are changed at once, shows the following distinct gains and advantages. On Fig. 2 the three inch lip was divided into ten capacity units. The eight (8) inch lip therefore would have approximately twenty six and two-thirds (26 /3) capacity units. According to the preferred method of this invention the capacity operating range is between 5.5 units just after the change, and 4.5 units just prior to the change. This gives an average bucket capacity variant of only one unit between changes as shown by the line N-N of Fig. 2,

as opposed to a 26% unit variance in the use of an eight inch lip bucket chain according to the practice heretofore. This is shown by the line OO1.

Not only does the present method and apparatus give a substantially constant capacity to,==

the bucket chain, but from the standpoint of motor strain, overload on parts, etc., it permits a dredge designer to lay out the parts for a fairly constant load instead of the fluctuating load where the bucket capacity drops, as shown by the line 0-01, in Fig. 2. The parts must be designed to take the heaviest load. The relative efficiency of the new and old methods and apparatus, assuming the same size dredge and buckets, is gauged by the dash line C and the line of Fig. 2.

How much variation in volume capacity an operator will put up with is not within the power of this invention to control, however, it is to be understood that there is here disclosed an apparatus and method of minimizing the volume of bucket capacity fluctuation.

In the operation of a dredge bucket chain in accordance with the method of this invention it is to be understood that clean-up days do not usually occur with the precise regularity indicated in the above illustrations, but that the periods differ from location to location and time to time although they are in any event frequent. Also, that operations may not have the mathematical regularity of change as illustrated in the. preferred example. However, it is a part of the method invention to change any number of lips or buckets less than the whole and replace them with new uncut lips or buckets, stag ered regularly or irregularly in the chain, preferably at the clean-up days whenever they occur.

For convenience, in this description the terms lip heights or, lengths, and bucket capacities have been used interchangeably when referring to the apparatus and method. However, it is realized that a ten per cent or one unit of wear in. the lip when first in place will effect a different and greater drop in the bucket capacity than a similar percentage of lip wear when the lip is practically worn out. This is due to the inwardly sloping walls of the bucket from the rim toward the. bottom. The drooping capacity variance curves N-N andO--O1 reflect this actual condition.

- end, it washes; third, it screens;

veys waste ofi by the stacker; fifth, it pumps vast.

The wordsv variance or tolerance as used.

herein refer to the difference in lip heights be-i tween the most worn and least worn lips. For:

different kinds of digging this difference will vary and can be determined by the dredge operator'froxn the nature of the sampling.-

' The method of this invention can be practiced when using buckets without removablelips in which case the whole bucket would be replaced, or it can be practiced with large. lips replaced before they are worn. out, resulting in a large amount of scrap, but neither of these operations would be economical. Theiadvantages achieved by this method will be made clearer perhaps by pointing out that a dredge requires six things: First, it digs; sec.- fourth, it-conquantities of water; sixth, it is manned by a crew of men. standpoint that stant. Heretofore, all were constant except the dredge capacity to dig, which, as seen, will drop off asthe bucket lips wear down. The conse-.

quence of this wear .or drop in digging capacity is that all five other factors have to operate at less than full efiiciency when they are other wise able to achieve full efiiciency. Translated into operating costs, these five things go on costing just the same when the bucket chain is digging litle or much.

, To-take full advantage of the present inven- I tion, the dredge should be designed originally so that all five constant factors above are calculated to bear the proper relationshipto a bucket chain capacity varying only slightly on each side of line C (Fig. 2), rather than'designing them to go with a bucket capacity starting at the lineA. Thiswould mean a slight overload on the ma- I chinery at the start, when new, if the operator started the bucket line with all new lips, but

the operation could soon bemade to asume a condition where all sixfactors above were practically constant.

' -It is to be understood that theforegoing description is made in an efiort to teach the method 7 and disclose an apparatus so that practical dredge operators will be able to grasp its fea- It is preferable from an operators all six of these things-be contures; and apply them.

It is not intended by the foregoing to limit the invention to the particular measurements or, percentages given, be- I yond what is required by the appended claims.

. I. claim:

1. The methodoi maintaining a substantially constant, capacity in a dredge bucketv chain,

which comprises equipping the buckets of the the lips, and replacing the. lips of staggered buckets having lipsoi minimum height withjlips'of maximum height at the termination of each of said periods; v 2. k The method of operating a continuous chain of dredge buckets having, removable lips, which comprises distributing the chain bucket lips which vary in height from throughout the length of a predetermined maximum to a predetermined minimum with corresponding variation in individual bucket, capacity, operating the chain for substantially regular periods of time, notingwear on said lips after each of said periods of-operation, and, replacing in staggered relation to the other bucketsof the chain'those of said bucket by the capacity of the chain of buckets is main-v tained constant within a de'sirednarrow range during substantially continuous operation of the chain.

- lips approaching saiddetermined minima, where-p 3. The method of operating a chain of dredgebucketshaving removable cutting lips, which comprises arranging maximum and minimum heights of bucket lips instaggered relation.

throughout the length of the chain to maintain a desired overall capacity for the chain within a predetermined narrow range and over a series of periods of operations, and changing individual bucket lips which are of minimum height range.

c HOBART M. BIRD.

only on the termination of each ofsaid periods to progressivelydistribute wear and maintain the overall bucket chain capacity within said

Images