US2101080A - Raking mechanism for sedimentation tanks - Google Patents

Description

Dec. 7, 1937. N B UN 2,101,080

' RAKING'MECHANISMFOR SEDIMENTATION TANKS- Filed Jan. 4, 1955 4' Sheets-Sheet 1 T6 f I F as INVENTOR NELS B. L UND,

ATTORNEY.

Dec 7, 1937. N B LUND 2,101,080

RAKING'MECHANISM FOR SEDIMENTATION TANKS Filed Jan. 4, 1935 4 Sheets-Sheet 5' FIG.5.

IX'VENTOR' NELS B.LUND,

j ATTORNEY.

Dec. 7, 1937. N LUND I 2,101,080

BAKING MECHANISM FOR SEDIMENTATION TANKS Filed Jan. 4, 1955 4 Sheets-Sheet 4 v Q\ g- R 1 I f I p8 N v o 3 N w 3, Q ts 0 g g] w '1;

v m m (D Q g 4, v u. 0 L? INVENTOR J NELS B.I UND,

ATTORNEY.

Patented Dec. 7, 1937 UNITED STATES BAKING MECHANISM FOR SEDIMENTATION TANKS Nels B. Lund, Seaford, N. Y., assignor to The Dorr Company, Inc., New York, N. Y., a corporation of Delaware Application January 4, 1935, Serial No. 356

10 Claims.

This invention relates to reciprocating sludge collecting or removal mechanism for sedimentation tanks. More specifically it relates to improvements in the driving mechanism for the travelling reciprocating sludge conveyors in such tanks.

Mechanism of this class usually includes a carriage which extends over or spans the width of a longitudinal or rectangular tank and is operatively supported on tracks along the sides of the tank for reciprocating movement between the ends of the tank. Especially in arrangements where the track gauge is relatively wide and the carriage wheel base consequently relatively short,

this involves that the carriage spanning the tank may not find sufiicient directive guidance upon the track to positively prevent sideslipping or slewing of the carriage relative to a prescribed path or tracks. Therefore it is one of the requirements in the operation of these machines that a preferably power-driven carriage should be propelled along a predetermined path in a manner which affords uniform bodily progress or locomotion irrespective of any influences which may tend .to hamper or interfere with such uniformity or regularity of movement.

7 Therefore, one of the objects of the invention is to provide a sludge conveying mechanism in which the carriage progresses in a manner which 39 is positive in character, and which avoids slewing, sidewinding, wheel spinning, or otherwise unsatisfactory progress of the carriage. In other words, this invention aimsat the design of a parallel guiding or marginal drive arrangement for the carriage, which is instrumental in producing dependably uniform progress thereof.

Another object is the realization of a power drive for the carriage, including means to effeet and insure at all times a bodily uniform and positively progressive movement of the carriage, and which will protect the driving machinery from undesired stoppage, undue strain, excessive wear or power consumption, and from other emergencies.

In order to attain these ends, the invention provides carriage operating means including flexible elements arranged substantially marginally of the tank to be instrumental in providing an identical rate of progress for each side of the carriage. More specifically, the arrangement has a pair of symmetrically acting and identically efiective rope branches, sections, or loop elements, each of which serves a respective side of the tank in a way which makes it impossible for the one or the other side of the carriage to be urged into and left in an undesirably crooked position as through irregular influences of load or otherwise. Hereinafter an arrangement of this character providing flexible elements at the margin of the tank may be called a parallel rope 5 guide, or else a parallel or marginal rope driving device.

In principle a rope guiding system as hereby proposed functions according to what may be called a complementary operation. Thatis to 10 say, identical lengths of guiding rope are paying out at each side of the carriage at a rate which is identical to the rate of carriage progress, while simultaneously identical lengths are absorbed in the very progress of the carriage, so 15 that the efiective total length of the rope system remains essentially constant. In still other Words, a symmetrically acting rope system is operatively associated with the carriage to effect positive guidance along its path by preventing 20 a bodily or differential slippage relative to the path and preventing relative displacement of the carriage or of portions thereof.

, The carriage operating arrangement or guide system according to this invention has associated 25 therewith a prime mover when automatic propulsion or reciprocation of the carriage is tobe eifected along the prescribed linear path. More specifically 'the'prime mover includes a driven rotary member or power driven winch the very 30 rotation of which correlates and synchronizes the operation of the two symmetrical operating sections or loops of the rope system in causing them to function identically with regard to propelling both sides of the carriage. 5.

In an organization of elements such as proposed by'this invention there will be essent ally no'uncontrolled slippage of cooperatively associated elements. That is to say, the operative coordination of the power driven winch, the pul- 40 ley guided rope system, the carriage, and the tank is such that the carriage must necessarily progress inthe manner desired, its operation being substantially insusceptible to any possible extraneous tendencies adverse to such uniformity. 45

According to one feature a carriage-guiding rope system comprises two substantially symmetrical rope branches, or loops, suitably maintained marginally of the tank, both branches being cooperatively interrelated or interconnected as by 50 g the powered winch in a manner to insure identically controlled or synchronized movement and progress of each side of the carriage. More specifically this rope arrangement is characterized by a certain crosswise or compensatory ar- 55 rangement of the guiding branches, making it effective to absorb or distribute unevenness of load or the like in a compensatory manner. A characteristic section of the rope system operates marginally of the tank by paying out rope length at one side of the carriage and taking up or shortening the equivalent amount at the opposite side as the carriage progresses. Through the crosswise arrangementof such symmetrical rope sections a positive and parallel guidance of the carriage movement is effected.

According to another feature a marginally operating rope drive after the principle of this invention is adapted to operate simultaneously the two carriages of a twin tank arrangement. A

single endless driving element forms a series of carriage driving loops, each loop surrounding one tank of the twin arrangement. A stationary power winch may be charged with a suitable number of non-slipping windings of this endless rope to impart translator-y or cyclic movement thereto.

Other features relate to self-adjusting and safety means for the rope drive. A driving rope may constitute an excellent and Valuable element in the way of positive driving means,- yet its life has a natural limit in that rope may wear out through constant bending and unbending or winding and unwinding in the course of itsjservice, ifnot otherwise through deteriorative effects of corrosion. As a rule a cosiderable amount of stretching will precede an otherwise unexpected breakage of a rope. I

Consequently a feature provides suitable warning or safety means to indicate the weakening or stretching of the rope, so that breakage and damage of machinery and apparatus may be avoided.

Another feature provides permanently responsive compensating means for constantly and instantaneously equalizing undesired relative discrepancies of stress and tension which may occur in the respective driving sections of the rope system. To this end resilient tensioning means are arranged to interconnect the respective driving loops or flexible elements.

. More specifically, a bodily movable guide pulleyor auxiliary device is provided to interconnect the two operating branches of the rope system resiliently in such a mannerthat any slack of the rope is taken up since tension in the one branch is thus at all times spring balanced against tension in the other. The relative amount of spring expansion being an indicator of the amount of rope stretch, a safety switch arrangement may be caused to respond when a predetermined maximum of total rope stretch has been reached.

Further aspects of advantage will be evident by comparison of the present rope driven mechanism with sludge collector or conveyor carriages of the automatically moving or self-propelling type. The latter type usually depends on the track friction of its carriage wheels for locomotion and thus may be subject to slippage of the Wheels upon the tracks, whereas the type of mechanism herein preferred may be said to belong to the positively driven class being controlled from stationary points outside the track surface.

Moreover the self-propelling type of carriage,

in order to execute various phases of its opera-' tion, requires driving and auxiliary motors respectively, for propelling the carriage or for hoisting the rake, as the case may be. These motors are mounted on the self-propelling type of carriage and in turn require movable connections in that they must draw their electric current from an overhead live wire, or from some suitable kind of a live rail, or else from an automatic reel or the like to take care of the varying length of electric cable for feeding the travelling motors. Such arrangements are in needof special attention inasmuch as exposed, moving, or non-stationary motor connections constitute potential sources of disturbance. So it is an advantage of the present class of positively driven mechanisms to avoid such connections by the use of stationary motors.

Still another aspect of advantage lies in the fact that in a positively or rope driven mechanism the sludge collector carriage and operating tracks may be submerged where lack of sufiicient headroom makes such arrangement desirable. A stationary rope driving motor may then be located accessibly at any suitable place above the liquid. A self-propelling motor driven carriage cannot readily operate in submergence and to submerge such a mechanism in sewage is repulsive.

V In a preferred embodiment of the invention the guide rope system is actuated by a stationary motor-driven winch. The winch controls linear, translatory, or cycling movement of a single endless driving'rope fashioned into certain kinds of symmetrical driving sections or loops operating marginally or around the tank, and effective to impart the desiredtype of carriage movement. Since the motor winch is stationary it is clear that the driving rope must move or travel in a linear path relative to the tank and that the sides of the carriage must be fixed at suitable points to corresponding sections of the rope system; so that linear progress of the travelling rope will be identical with the rate of carriage movement. 7

A resiliently mounted guide pulley device or compensatory tension means interconnects the aforementioned operating sections of the rope system. This device mechanically coordinates and couples certain guide pulleys of the respective rope sections in a manner Which makes the pulleys movable relative to eachother as Well as movable together in relation to a stationary base or mounting. Consequently a floating pair of pulleys is at once capable of equalizing the rope tension, taking .up the rope stretch, and also capable of preventing unexpected or impending breakage of the rope when a maximum of stretch is reached. The rope stretch expresses itself in a combination of relative bodily pulley movements and can be utilized to actuate a limit switch or the like. Stationary conduits from this compensating and safety device may carry the impulse to stop the stationary driving motor so that no moving electric conduits are required.

Nor is it necessary, in this preferred embodiment, for the sludge collector mounted from the movable carriage to be approached by any electric conduits for its operation, inasmuch as it may be actuated in some suitable mechanical way to convey sludge in the desired one Way fashion. For instance suitable abutment means at each end of the tank may set up the change mechanically. between the respective operative and inoperative positions of the sludge collector member;

'If the collector member be of the type which is pivotaily suspended from the carriage, then the marginal or circumferential arrangement of the driving rope makes possible the unobstructed manipulation for removal or withdrawal of the sludge collector from the tank to a point above the liquid level, as by swinging the collector upwardly through the free space which intervenes between the marginal sections of the driving rope.

Power consumption and wear moreover can be reduced in a preferred twin arrangement of tanks, in which a rope driving system according to the principle of the present invention may serve to operate two carriages, one for each tank, in alternating fashion, so that power consumption and wear is equalized, and that idle travelling movements of the carriageare eliminated. Loops of a travelling driving rope may then surround each tank, with the loops formed in current series from a single endless element, and a stationary power winch may be charged with a suitable number of nonslipping windings of this endless rope to impart translatory or cycling movement thereto.

The invention possesses other objects and features of advantage, some of which with the foregoing will be set forth in the following description. In the following description and in the claims, parts will be identified by specific names for convenience, but they are intended to be as generic in their application to similar parts as the art will permit. In theaccompanying drawings there has been illustrated the best embodiment of the invention known to'me, but such embodiment is to be regarded as typical only of many possible embodiments, and the invention is not to be limited thereto. More in'particular it is to be noted that the scope of this invention is not confined to the specific arrangement of the drive rope shown, but that respective rope portions which constitute driving loops may be arranged in various ways without departing from the spirit of this invention and so that one loop drives one respective end portion of the carriage, and both loops or rope portions are driven simultaneously by rotatable winding means or a common rope winding unit.

The novel features that I consider characteristic of my invention are set forth with particularity in the appended claims. The invention itself, however, both as to its organization and its method of operation, together with additional objects and advantages thereof, will best be understood from the following description of a specific embodiment when read in connection with the accompanying drawings in which Fig. 1 is a plan view of a marginal rope drive having a stationary rope engaging motor, for a reciprocating carriage spanning the width of the tank.

Fig. 2 is a cross-sectional view taken upon Fig. 1 along the line aa.

Fig. 3 is a longitudinal sectional view taken upon Fig. 1 along the line bb.

Fig. 4 is a perspective skeleton view of the marginal rope drive disclosed in Fig. 1, having a stationary motor winch and travelling rope.

Fig. 5 is a plan view of a marginal rope drive, having stationary ropes and a rope engaging motor winch mounted to travel with the carriage.

Fig. 6 is a skeleton perspective view of the essential part of the marginal rope'drive disclosed in Fig. 5.

Fig. '7 is a plan view upon a twin tank arrangement with a marginal rope drive adapted thereto, with a stationary rope tension compensating and safety device.

Fig. 8 is a detail side view taken from Fig. 'l

of the rope tension compensating and safety device.

carriage or sediment collecting element operable on tracks l9 and 20 respectively on top of the' side walls l3 and M .of the tank. Propelling means for the sediment collecting element are described as follows: A marginal rope drive symmetrically engages each side of the carriage. The rope drive includes a rotary member or winch 2! powered with an electric motor unit 22. The winch or winding drum has two winding sections 23 and 24. A flexible element is indicated by the numeral 25 and it is here preferably shown in the wayof an endless rope which is wound in two groups of windings 26 and 21 upon the winch 2|. (See perspective Fig. 4.) The driving rope forms two symmetrically operating rope portions or loops indicated as 28 and 29 respectively, one loop extending marginally along each side of the tank.

The one loop 28 runs over pulleys 30, 3| and 32, the other loop 29 over pulleys 33, 34 and 35. The pulleys 3i and 34 are mounted or anchored upon the rear end of the tank as indicated by corresponding numerals 35 and 31. Arrows along the rope indicate the direction of linear translatory movement of the respective sections thereof. It is noted that a pair of codirected sections of the rope such as indicated at 38 and 39 are fixedly attached to the corresponding sides of the carriage l8 at 4B and 4| respectively. Complementary rope sections 42 and 43 are substantially free and travel in the opposite direction. For reasons later on to be explained however these latter sections are shown to form subsidiary loops 44 and 45 which travel with the carriage H3. The loop M is maintained by a pulley 46 having its rotary bearing 45a upon the carriage frame, and by a floating pulley 41. In the same manner and as a symmetrical counter part the loop 45 is maintained by a pulley 48 suitably mounted upon the carriage frame as at 48a, and by a floating pulley 49. The floating pulleys 41 and 49 are resiliently interconnected as indicated by the pulley shackles 50 and 5| and a spring 52 interconnecting the same. The pulleys 41 and 49 and the spring 52 form a floating 'pulley system or tension compensating device to travel with the carriageand to maintain a desired steady and equal operating tension in the rope sections or loops 28 and 29.

Fig. 2 is a cross section through the tank of Fig. 1 and shows more clearly the mounting of rope sections and pulleys upon the lower side of a carriage frame 53. The carriage frame is here also shown to be operatively supported by track rollers 55. Fig. 3 is a longitudinal section of the tank of Fig. 1 and illustrates the operation of a movable sludge collector member 55 which is pivotally supported from the carriage frame as at 56, having a raking blade 51. A positioning mechanism for the sludge collector member 55 comprises a horizontal thrust or contact rod 58 which is guided for longitudinal sliding movement in horizontal bearing members 59'extendlng from the carriage frame. The thrust rod 58 is formed to provide a toothedrack having teeth 60. A gear wheel or toothed rotary member 6| is rotatably mounted upon frame work or bracing 62 or the like shown to extend from the carriage frame, by means of a transverse shaft 63, and so arranged as to operatively engage upon the teeth of the thrust rod 59. The shaft 63 also carries a rigid crank arm 64. A link connects the free end of the crank arm 64 with the lower portion of the sludge collector member 55. It is clear that longitudinal sliding movement of the thrust rod 58 will act through the gear connection 60, BI, the crank arm 64 and the'link :65 to position the sludge collector member in its respective raised and lowered operating positions as indicated in full and dotted lines respectively. The thrust rod 58 carries a front and a rear limit stop. 58a and 58b respectively.

Fig. 4 is a perspective skeleton view of the major part of the drive rope arrangement of Figs. 1, 2, and 3, and it shows more clearly the two "winding sections 23 and 24 of the motorpowered winch 2| and the manner in'which the respective strands of the driving rope are run onto and off the winch, and also the two groups of rope windings 2'6 and 21. Arrows along the rope indicate the' directions of rope movement corresponding to an assumed rotation of the winch in the direction of arrow 65.

Fig. 5 together with the perspective skeleton view of Fig. 6 shows another example of the marginal type of rope drive for a longitudinal or rectangular tank. It reverses the kinematic relationship of stationary and driven parts, having sides 6'! and 69 and end walls 69 and 69a. Marginal guide rope sections 19 and .H respectively are substantially stationary, while a motor driven winch or motor-winch unit 12 is mounted upon a carriage l3 and operatively associated with the rope sections 70 and 7! through a winding drum M to propel the carriage through frictional contact of rope windings. A positive parallel guidance or bodily uniform progress of the carriage is effected by a peculiar crosswise or complementary arrangement of the rope sections 19 and 'II. The winch or winding drum 14 also has two winding sections '26 and l! which serve the respective rope sections I9 and 'II as seen more clearly in the fractional perspective view of Fig. 6. In a practical instance the two rope sections 19 and "I! form a continuous strand of rope the ends of which have stationary anchorings as at 78 and 79 respectively at the end wall 59 of the tank. Starting from the anchoring point 18 the rope runs over a pulley 80 mounted upon the carriage, thence crossing the tank it passes over the carriage and in a suitable number of windings over 7 the winding section 16 of the winch, and over a pulley 8i 7 also mounted on the carriagen After thus crossing the tank via the carriage or travelling bridge 13 the rope continues along the side a 68 of the tank and reaches the end of the tank as it passes over a stationary corner pulley 82. Thence back along the endwall of the tank and over a stationary but bodily adjustable tensioning and take up device 83, the rope passes over another stationary corner pulley 84 to lead back towards the starting end of the tank. From here on, the path of the rope to the anchoring point 19 is substantially symmetrical to the section first described, in that the ropeleads over a pulley 95 mounted on the carriage, on over the second winding section 11 of the winch in a ment.

Another example of a marginal guide rope or carriage driving arrangement is shown'in Fig. '7.

In this case a peculiar arrangement of driving loops is adapted to reciprocate the two carriages of a twin tank unit in alternating fashion. Two longitudinal tanks and 9! are disposed alongside each other to form a tank unit; Each tank has its sludge collecting carriage 92 and93 travel lingin opposite directions. An endless driving rope 94 receives its linear cycling motion from a winch 95 driven by an electric motor 96, The rope leads in a series of partly overlapping loops around each of the tanks 99 and 9| and in such a manner that codirected travelling sections of the rope can be fastened'to the respective sides of the carriages 92 and 93. To this end the .rope forms a suitable number of windings 9'! around the winch and leads consecutively over stationary pulleys 93 and 99 over a movably or resiliently mounted pulley I99 and over the stationary pulley IGI where it substantially completes the first operating loop- I92. It then continues over sta 'tionary pulley J93 to form the second operating loop 104 substantially symmetrical and. partly overlapping the first one. That is to say the rope continues over another movably or resiliently mounted pulley I95 leading to stationary pulleys I96 and I01, whence it finally leads back onto the winch 95. One branch of the loop I92 is fixed to the carriage 92 as at 92a and 9212, the other branch of that same loop being fixed to the other carriage 93 as at 93a and 93b. correspondingly and in complementary fashion the other loop I04 is found to be fixed to carriage 93 as at 93c and 93d and to carriage 92 as at 82c and 92d.

The resilient pulleys I99 and I95 substantially constitute a safety or monitor device I98. They are coupled through a link or double armed lever I080; which is shown to be. fulcrumed upon the end of a link I 98 the other end of which has pivotal mounting upon another double-armed or main lever I09 rotatable upon a stationary bearing I I0. The main lever I99 has a short arm II I and a long arm II2. A compression spring H3 is shown to bear upon the free end of the long arm H2 and confined between that free end and a stationary base member H4. A bolt or rod H5 is indicated as determining the potential expansion of the spring H3 as the latter through the lever and link connections III8a to H2 takes up or compensates for slack or stretching of the rope. The tilting of the lever 18w tends to equalize the tension in the two operating loops I 92 and H34. A.

maximum predetermined amount of expansion of the spring H3 through rod H5 causes an electric switch or contact H9 to function so as to effect stoppage of the driving motor 96 through electric conduits II 5a. Such safety measure will take effect as a warning when an undue stretching of the driving rope indicates a case of weakening thereof or of impending breakage. This stationary safety switch device is also shown in part in an enlarged detail side view in Fig. 8.

From the foregoing it should be understood that this invention aims to cover a marginal guide rope orits equivalent arrangement for the carriage of sedimentation tanks or the like, ir-

respective of whether aprime mover is directly the rope.

Operation The carriage driving arrangement according to Figs. 1, 2, 3 and 4 operates as follows:- Assuming the winch member or drum 2I to rotate in the direction of the arrow 66, the rope runs oif the top of drum section 23 and over the stationary corner pulley 33 along the side I4 of the tank to the point 4| where it is fixed to the one side of the carriage frame. Continuing over the return pulley 34 at the end I2 of the tank it returns upon itself to form the driving loop 29. It then passes onto the pulley 48 which has a fixed pivot 48a. upon the carriage, to form the auxiliary or compensating loop 45 as it swings around the spring held floating pulley 49, back onto pulley 48 and over stationarypulley 35, closing the first loop as it reaches the lower side of the second winding section 24 of the winding drum 2I.

The otherdriving loop 28 begins where the rope having made a suitable number of windings 21 leaves the winding drum, to lead over the stationary pulley 39 along the side I 30f the tank to the point 49 where it is attached to the carriage' frame. It then reaches the return pulley 3| at the end I2 of the tank and thus doubling upon itself it forms the loop 28 which consists of the rope branches 38 and .42. The branch 42 forms the second auxiliary or compensatory loop 44 as it swings. around the pulley 46 upon the carriage and the floating pulley 41 which is remembered to be resiliently interconnected through the spring 52 with the other floating pulley 49. From pulley 46 the rope leads on its last lap over the stationary pulley 32 onto the top of the winding section 23 of the drum 2| to form a suitable number of windings 26 thereon before it closes the cycle by merging into the beginning of the first driving loop 29.

Assuming the winding drum to rotate in the direction of arrow66 (see Fig. 4) the respective driving branches of the rope will move in the direction of arrows indicated therealong and will effect movement of the .carriage I8 in the direction of arrows II 1 towards the end I2 of the tank. where suitable automatic electric switch means (not shown) may be provided to reverse the driving motor 22 fora return of the carriage. Suitably timed with the phase of carriage return is the actuation of the sludge collecting element 55. It will be clear from Fig. 3 that this element is automatically set and reset between its operative (full line) and inoperative (dotted line) position at the respective end phases of the carriage movement when the thrust rod 58 is caused to abut against the end wall II or I2 respectively of the tank I9.

The carriage driving arrangement of Figs. 5 and 6 operates as follows: Since in this case the motor driven winch I4 is unitary with the travelling carriage I3, it is clear that the circumferential guide rope must be stationary if relative movement of the carriageis to take place. If rotation of the rope windingdrum is assumed in the direction of arrow 1 I8 (see Fig. 6) it will move the carriage in the direction of the arrows 89-. That is to say the branch 19 of the rope pays out along the side 61 of the tank'from the top of the drum section 16 while a complementary portion of branch 19 is absorbed from the opposite side 68 of thetank as it winds up on the top of the drum section 16. The-pathof the rope branch I9 across the carriage I3 is guided-by the pulleys 89 and SI. The rope branch I9 of itself would, in tending to drive the carriage, have a horizontal twisting effect upon the carriage tending to derail the same. Such tendency howeveris counteracted and completely compensated for by the crosswise arrangement of the rope branch II which sets up a tendency in horizontal direction exactly opposite to that of rope branch 19, producing at all times a fully determined bodily uniform rectilinear movement of the carriage as long as there is no appreciable relative slippage of the rope-windings or of the rope as a whole. More specifically then the rope branch II pays out (see Fig. 6) from the lower side of the drum section I? along the side 98 of the tank running over the pulley 86 which is stationary upon the carriage I3. At the same time an identical length of branch II, winds onto'the same drum'section IT at the lower side thereof. The effect of such symmetrical crosswise operation of the rope branches I9- and II is that all portions of the carriage must progress bodily at the same rate insuring bodily uniform rectilinear carriage movement.

The automatic reciprocation of the carriage as well as synchronized actuating of a sludge collecting member may be effected as described in connection with Figures 1 to 4..

The operation of a marginal carriage drive ap-' plied to a twin tank arrangement (see Fig. 7) is as follows: The winch 95 driven by motor 96 is stationary and carries on its winding drum a constant number of windings of the rope element 94 frictionally or otherwise engaging upon the drum and by its rotation imparts cycling travelling movement to the endless rope element. The endless rope runs off the top of the winding drum over the stationary pulley 98, to reach anchoring points 920. and 92b upon the carriage 92, and. then swing around the end of tank 99 over the pulleys 99 and I99 to reach its anchoring points 93a and 93b upon the other carriage 93. In this way the loop I92 ties up the two corresponding halves of the carriages 92 and 93'. The second loop I94 follows in series and coordinates the movements of the other halves of the carriages 92 and 93. That is to say the rope continues over pulleys I9I and I93 to be attached again at 92c and 92d to the carriage 92. Continuing over pulleys I95 and I96 the rope then reaches corresponding anchoring points 930 and 93d upon carriage 93, finishing the rope cycle over the pulley I91 as it reaches the winding drum 95.

In this embodiment, anystretch or unequal tension in the loops I92 and I94 will be taken upby'the resilient or movable pulleys I99 and I95 and manifest itself in a corresponding'expansion of the spring II3 of the safety device I99. Therefore if an excessive or objectionable stretch of the rope occurs it will cause the rod H5 or other suitable member to actuate, the switch II6 to shut off the driving motor 96 through the stationary electric conduits 5a.

The automatic reciprocation of the carriage and actuation of its sludge raking parts may be assumedto be the same as described in connection with the embodiment in Figs. 1 to 4. In this twin arrangement of Fig. '7 the load upon the prime mover is evenly balanced since the load is distributed at all times between the alternating carriages 92 and 93. No moving or travelling electric connections appear to be necessary in this embodiment in view of the fact that the driving motor as well as the safety switch device have stationary power connections.

'Iclaimi 1. Ina reciprocating sludge removal apparatus for rectangular sedimentation tanks or the like, having a sludge collecting carriage extending across the tank and movable therealong in a linear path, a carriage operating system associated with both sides of the carriage to effect positive guidance thereof along said path, which system comprises flexible linear guided elements extending marginally along the tank and operatively connected with respective sides of the carriage, means for operating said elements in a manner to provide the identical rate of movement for each side of the carriage, and a 'tensioning and tension equalizing device which interconnects said flexible linear elements.

2. In a reciprocating sludge removal apparatus for rectangular sedimentation tanks or the like, having a sludge collecting carriage extending across the tank and movable therealong in a linear path, a carriage operating system associated with both sides of the carriage to efiect positive guidance thereof along said path, which system comprises flexible linear elements adapted to travel in translatory fashion, and forming a pair of operating loops operatively connected to control the respective sides of the carriage, means for operating said elements in a manner to provide the identical rate of movement for each side of the carriage, a tensioning and tension equalizing device which interconnects the two loops and which comprises a guide pulley for each loop, means for movably and operatively coupling. said pulleys to'form a pulley system which'in turn is bodily movable, a mounting to support said movable pulley system, and means for resiliently tensioning said pulley system against the pull of said operating loops.

3. In a reciprocating sludge removal apparatus for longitudinal sedimentation tanks or the like, having a sludge collecting carriage extending across the tank and movable therealong: in a linear path,.a carriage driving system which comprises 'a flexible linear element extending along the tank, motor means for propelling said carriage through said flexible element, a resiliently movable anchoring mechanism to operatively support said flexible element and adapted to absorb slack and stretch therefrom by reason of its resiliency, and means associated with said anchoring mechanism, which means are responsive to a predetermined amount of stretching of said flexible element to eifect stoppage of said motor means. 7 r 1 4. In a reciprocating sludge removal apparatus for longitudinal sedimentation tanks or the like, having a sludge collecting carriage extending across the tank and movable therealong in a linear path, a carriage driving system which com prises a flexible linear element extending along the tank, an electric prime mover for propelling said carriage through said flexible element, a resiliently movable stationary anchoring mechanism to operatively support said flexible element and adapted to absorb slack and stretch therefrom by reason of its resiliency, and switch means associated with said anchoring mechanism and responsive to a predetermined amount of stretching of said flexible element, and thereby effective to cause stoppage of said motor means, said switch means having substantially stationary electric conduit connections with said electric prime mover.

-5. A sludge-removal apparatus for longitudinally-extending type of sedimentation tanks, which comprises a sludge-collecting carriage extending transversely-of the tank andmovable therealong in a rectilinear path, a carriageoperating drive rope device associated with the tank and with the carriage, and effectiveto enable the desired positively-guided bodily-uniform reciprocatory movement of the carriage along said path, which drive rope device includes a pair transversely of the tank into mutually co-operative relationship, a rope-winding device mounted upon said carriage anda driving motor therefor, which rope-winding device is 'co-operatively. associated with, said rope' sections through non-slipping rope windings constituting part of said transverse rope portions, in such a manner that the winding operation of the device in one or the other rotary direction through said motor will produce the desired bodily-uniform reciprocating movement of the carriage-due to the non-slipping and symmetrically-operative engagement thereof by said rope sections.

6. A sludge-removal apparatus according to claim 5, in which each rope section leads from a fixed point at one end on one side of the tank over one of said pulleys mounted at one side by Way of said carriage transversely across to the opposite side of the tank and over another one of said pulleys mounted at the other side of the carriage, the section in thus traversing the tank having a series of windings upon said rope-winding device so as'to be operated thereby, said rope sections then continuing along said opposite side to the opposite end of the tank, both rope sections thus being arranged in substantially symmetrical crosswisefashion by way of said car-' riage and more specifically by way of said ropewinding device.

7.'In combination with a rectangular settling tank having a sediment collecting element movable along a path parallel to two opposite Walls of the tank and extending substantially transversely with respect to said path; propelling means for said sediment collecting element,'ineluding a rope portion operatively supported for driving one end of the sediment collecting element, a plurality of guide means for said rope portion'and arranged with respect to the ends of the tank so that the rope portion is in the form of a loop, a part of which extends parallel to and along the length of the pathiof the sediment collecting element, said rope portion being attached toione end of said sediment collecting element and extending from that element along the path thereof togone of saidfguide means, thence back over at least another one of said guide means, thence, torotatable rope winding means and back to one end of said sediment collecting element by way of at least one of said guide means; and a second in effect substantially similar rope portion and a similarguide means for the other end of said-sediment collecting element; and rotatablerope winding means having stationary mountings, so constructed and arranged as to drive both rope portions 8. Propel ling means according to claim '7, in which the one rope portion constitutes a loop which extends as such substantially along one side of the tank, and the other rope portion constitutes a loop which extends as such substantially along the other side of the tank.

9. Propelling means according to claim 7, so arranged that rope portions of substantially equal length are provided to pull at the respective end portions of the sediment collecting element.

10. Propelling means according to claim 7, in

which both rope portions constitute in efl'ect one 5 endless rope element.

NELS B. LUND.

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