US 3920363 A
A drag trowel device having a plurality of leaves which contact the interior surfaces of a pipe coated with a lining substance to effect the trowelling of same. The leaves are mounted on one end of a longitudinal lever arm and a counterweight is mounted at its other end. The lever arm is pivotally connected at an intermediate location thereon to a pulling means. The counterweight serves to cancel the net weight of the trowel itself so that the trowelling pressure exerted by the leaves will be the same along the top and bottom of the pipe.
Claims available in
Description (OCR text may contain errors)
United States Patent [191 Nelson Holland DRAG TROWEL WITH COUNTERWEIGHT MEANS  Inventor: Henry A. Nelson Holland, Houston,
 Assignee: Raymond International, Inc.,
 Filed: Mar. 11, 1974  App]. No.: 450,161
52 us. Cl. 425/95; 425/262; 425/460  Int. Cl. B28B 21/94  Field of Search 425/59, 95, 262, 457, 460, 425/469 56] References Cited UNITED STATES PATENTS.
2,261,928 11/1941 Perkins et a1. 425/262 2,484,018 10/1949 Crom 264/270 3,108,348 10/1963 Schultz 425/262 3,167,837 2/1965 Matheny 425/460 Nov. 18, 1975 3,263,296 8/1966 Barton 425/460 3,334,389 8/1967 Matheny.... 3,384,940 5/1968 Barton 425/262 Primary Examiner-Francis S. Husar Assistant Examiner-John MCQuade Attorney, Agent, or Firm-Fritzpatrick, Cella, Harper & Scinto  ABSTRACT A drag trowel device having a plurality of leaves which contact the interior surfaces of a pipe coated with a lining substance to effect the trowelling of same. The leaves are mounted on one end of a longitudinal lever arm and a counterweight is mounted at its other end. The lever arm is pivotally connected at an intermediate location thereon to a pulling means. The counterweight serves to cancel the net weight of the trowel itself so that the trowelling pressure exerted by the leaves will be the same along the top and bottom of the pipe.
28 Claims, 3 Drawing Figures US. .Patent Nov. 18, 1975 Sheet 2 of 3 3,920,363
I I I H DRAG TROWEL WITH COUNTERWEIGHT MEANS This invention relates to an improved drag trowel device and, more specifically, to such a device which employs a novel means of positioning and mounting trowel leaves so as to effect more uniform trowelling of the interior walls of pipes, tubes and other conduits.
The present invention is suited foruse with lining machines which coat the intcrior walls of pipes and the like with plastic or mortar-like substances. These lining machines have a spray or distributor head which rotates at speeds approaching two thousand revolutions per minute while the lining machine is pulled through the pipe or conduit. This high speed rotation causes the lining substance to be flung outwardly by centrifugal action so that it becomes deposited on the conduit wall. A trowelling device is moved along behind the distributor head; and various leaf-like trowelling elements mounted on the trowelling device wipe along the conduit walls to smooth out the deposited material. The trowelling elements are spring biased radially against the interior walls to ensure full trowelling of the deposited material.
In the past, certain problems have been encountered in the use of these trowelling devices. More particularly, it has been difficult to maintain even trowelling pressure around the conduit being lined. In most prior art arrangements, the trowelling device was coupled to .thedepositing device by means of a flexible connection. However, this was disadvantageous because, the weight of the trowelling device would add to the downward leaf pressure so that the bottom of the conduit was trowelled more severely than the other regions. On the other hand, it would not be practical to mount the trowelling device to extend out cantilever fashion behind the material depositing device because in such case the conduit irregularities, i.e. turns or dips, encountered by the material depositing device would cause it to swing the trowelling device quite severely and in a manner unrelated to the particular conduit irregularities in the vicinity of the trowelling device.
The present invention overcomes the above described problems and permits the trowelling of conduit interiors in a smooth and uniform manner. The trowelling obtained through the present invention is not effected by the weight of the trowelling device nor is it subject to the'movements of the material depositing mechanism to which it is coupled.
According to the present invention there is provided a novel drag trowelling arrangement wherein a drag trowelling assembly is mounted toward one end of .a longitudinally disposed lever arm. A counterweight is mounted on the lever arm toward its other end and a swivel connection to a material depositing device or are applied around the interior of the conduit. Also,'
any movements of the swivel connection away from the axis of the conduit will be accomodated automatically by a swinging of the lever arm about the swivelconnection and a corresponding countermovement of the trowelling assembly so that: it will remain centered and continue to exert even trowelling pressure around the conduit interior.
As will be described more fully hereinafter, the present invention, in certain aspects, involves arrangements in which a plurality of tandemly disposed trowelling assemblies are mounted as above described to obtain rough and finish trowelling. Also, according to one embodiment the two trowelling assemblies are mounted on a common arm which itself is pivoted to the lever arm so as toimprove the balancing of trowelling forces and to maintain proper orientation of the trowelling device. i
There has thus been outlined rather broadly the more important features of the invention in order that the detailed description thereof that follows may be better understood, and in order that the present contribution to the art may be better appreciated. There are, of course, additional features of the invention thatwill be described more fully, hereinafter. Those skilled in the art will appreciate that the conception onwhich this disclosure is based may readily be utilized as the basis of the designing of other structures for carryingout the purposes of this invention. It is important, therefore, that this disclosure be regarded as including such equivalent constructions as to not depart from the spirit and scope of the invention. I
Cetain specific embodiments of this invention have been chosen for purpose of illustration and description, and are shown in theaccompanying drawings, forming a partof the specification, wherein:
FIG. 1 is an elevation view,'partially in section, showing a drag trowel device in which the present invention is embodied:
FIG. 2 is aview similar to FIG. 1 but showing a modified form of the drag'trowel device of the present invention; and v 2 FIG. 3 is a view similar to FIG. 2, but showing a still further modified form of the drag trowel device of the present invention. 1
As shown in FIG. 1 a conduit 10, such as a pipe, is provided with a lining 12 of a castable material, such as cement or mortar, which reconditions the pipe by sealing any leaks and allowing smooth and free fluid flow therethrough without further corrosion.
The lining 12 is applied by'a combination depositing and trowelling machine 14 which is pulled lengthwise through the pipe 10. The depositing and trowelling machine 14 comprises a material depositing mechanism 16 and a trowellingdevice 18 which is attached to and follows the materialdepositing mechanismthrough the pipe. The material depositing mechanism 16 includes a housing 20 which contains material feed arrangements and drive motors for depositing the lining material. Wheels 22, or equivalent support elements, extend from the pipe 10 to hold the material depositing mechanism 16 centered in the pipe as it ispulled through the pipe by any suitable means (not shown).
The material depositing mechanism 16 also includes a rotary distribution head 24 extending from behind the mechanism. This head rotates at high velocity, e.g. at 2000 revolutions per minute and thereby causes a wet fluent lining material 26, such as cement or cementmortar, to be thrown centrifugally outward so that it becomes deposited on the inner surface of the pipe 10 in the form of a rough lining 12a. This rough lining 12a is then acted upon by the trowelling device 18 as it moves along behind the material depositingmechanism 3 l6; and the trowelling device 18 smooths out the rough lining 120 before it hardens so that there is formed the smooth lining 12.
The trowelling device 18 comprises a frame 28 made up of a conical ring 30 somewhat smaller in diameter than the pipe 10, a hollow central axial shaft 32 and a plurality of spokes 34 and 36 extending, respectively, from the front and rear of the shaft 32 to the conical ring 30. A plurality of sheet metal trowelling leaves 28 are mounted in overlapping array about the conical ring 30; and each leaf is secured to the ring 30 by means of a pivot 40. The trowelling leaves 38 extend out behind the ring 30 and their pivots 40 are so oriented that as the leaves swing about them their rearward edges flare outwardly more or less to accommodate different pipe diameters.
' A bias spring 42 is provided to urge the trowelling leaves outwardly against the interior surface of the pipe 10. This bias spring 42 is a coil spring bent around to form a torus which fits inside the overlapped trowelling leaves; and it is secured to the ring 30 by means of wires 44 which extend forwardly from the spring to the pivots The trowelling device 18 is connected to the material distributing mechanism 16 by means of a coupling device 46. This coupling device comprises a bracket in the form of cup shaped housing 48 having its open end flanged and secured, by means of screws 50, to a plate 52 mounted at the rear of the distributor head 24. The base of the cup shaped housing 48 is formed with a ball socket 54. This socket accommodates a ball formation 56 located along the length of a rod-like mounting lever 58. The mounting lever passes through the base of the cup shaped housing 48 and terminates near the plate 50. The'housing 48 thus serves as a bracket to connect the mounting lever pivotally near its central region to the distributor head 24. A cylindrical counterweight 60 is fitted onto the mounting lever 58 within the housing 48; and the distance of the counterweight from the ball and socket joint, formed by the socket 54 and the ball formation 56, can be adjusted simply by moving the counterweight along the length of the mounting lever and securing it in place with a setscrew (not shown). It will be seen that the counterweight 60 is free to move inside the cup shaped housing 48 as the mounting lever 58 pivots at the ball and socket connection 54, 56. The counterweight may also be threaded onto the lever 58 and adjusted simply by rotating it on the lever.
The portion of the mounting lever 58 which projects beyond the base of the cup shaped housing 48 extends into and through the central axial shaft 32 of the troweling device 18. The rearward tip of the lever 58 is threaded; and a washer 62 and a nut 64 are provided on it to hold the shaft 32 onto the lever. This allows free rotation of the shaft 32 and the trowelling device 18 on the lever 58.
It will be appreciated that the ball and socket joint formed by the socket 54 and the ball formation 56, serves both as a swivel and as a lever fulcrum for the lever 58. The lever 58 is weighted on one side of this fulcrum by the trowelling device 18; and it is weighted on the opposite side of the fulcrum by the counterweight 60. By proper adjustment of the location of the counterweight 60 along the lever arm 58, as above described, the weight of the trowelling device 18 can be precisely balanced. As a result, the weight of the trowelling device 18 is not supported by the trowelling leaves 38 but instead it is supported by the material depositing mechanism 16 acting through the lever arm fulcrum. Because of this the only outward forces exerted by the troweling leaves on the interior of the pipe 10 are those which are produced by the bias spring 42; and these forces are equally distributed in all radial directions. At the same time the troweling device is free to move up or down or sideways as the combination depositing and trowelling machine 14 passes over inclines, dips or curves in the pipe 10.
In operation of the above described combination depositing and trowelling machine 14, the material depositing mechanism 16 is pulled through the interior of the pipe 10 by any known means, while the wheels 22, which ride along the inner surfaces of the pipe, serve to maintain the rotary distributor head 24 centered in alignment with the pipe axis. Thus, as the distributor head rotates while moving along through the pipe 10, it throws lining material 26 out against the inner walls of the pipe to form the uniformly distributed, though rough, lining 12a.
As the trowelling device 18 is pulled along behind the material depositing mechanism 16, the leaves 38 of the trowelling device press outwardly against the rought lining 12a and smooth it to form the finished lining 12. Because of the above described counterbalancing provided by the coupling device 46, the weight of the trowelling device 18 is not transmitted through the trowelling leaves 38; and accordingly an even trowelling pressure is exerted in all radial directions so that the thickness of the finished lining 12 is uniform all about the pipe interior. At the same time should the depositing and trowelling machine 14 pass through inclines, dips or curves in the pipe 10, the pivoting characteristic of the coupling device will allow the leaves of the trowelling device to remain centered in the pipe even though the fulcrum point of the lever arm 58 may temporarily be shifted away from the pipe axis.
-In certain instances, the material depositing mechanism 16 does not have a separate plate such as the plate 52 extending beyond the rotary distributor head 24. Accordingly, it becomes necessary in such instances to mount the drag trowel directly to the rear face of the rotary distributor head 24. Since these distributor heads rotate typically at about two thousand revolutions per minute, it becomes necessary to provide special rotary bearing arrangements which allow the drag trowel to move through the pipe 10 without rotation. Such an arrangement is illustrated in FIG. 2. As can be seen in FIG. 2, there is provided a mounting plate on the rear face of the rotary distributor head 24. A tapered conically shaped housing 72 is affixed to the mounting plate 70 to rotate with it and with the rotary distributor head 24. The housing 72, as shown, tapers rearwardly toward the axis of the device. The outer race of a ball bearing assembly 74 is mounted toward the rearward end of the housing 72. The inner race of the ball bearing assembly 74, as shown, is formed with a ball socket 76 which accommodates a ball formation 78 of a mounting lever 80. The mounting lever 80 is similar in structure and operation to the lever arm 58 of the preceding embodiment. Also, the remainder of the elements forming the coupling device are the same as in the embodiment of FIG. 1. Thus the housing 72 serves as a bracket to connect the mounting lever pivotally near its central region to the distributor head 24.
The arrangment of FIG. 2, however, allows very rapid rotation of the conically shaped housing 72 while the mounting lever 80 remains free from such rotation; al-
5 though, it is free to swivel .in the ball and socket formationdefined by the socket .76 and the ball formation 78.
The embodiment of FIG. 2 provides an additional refinement whereby both rough and finish trowelling can be accomplished Simultaneously. According to this refinement, there is provided a second or rearward trowelling frame assembly 81 made up of a rearward conical ring 82 and spokes 84, which extend from the ring 82 to the rearward end of the shaft 32. This assembly is rigidly mounted by means of struts-86 secured to spokes 88 which in turn extend between the forward conical ring 30 and the hollow a-xial shaft 32. As can be seen in FIG. 2, the mounting lever 80 extends completely through the axial shaft 32, as in the preceding embodiment, and it is secured there by means of a nut and washer assembly 62, 64 as described above.
The rearward trowelling assembly 81 is of substantially the same construction as the forward trowelling assembly 18. As shown, the rearward trowelling assembly 81 comprises trowelling leaves 86, which are connected to the conical ring 82 by means of pivots 88. These leaves are biased radially in an outward direction by means of a circumferential bias spring 90. The spring 90 is also secured to the rearward conical ring 82 by means of wires 92 extending between the pivots 88 and the spring.
It will be noted from FIG. 2 that the trowelling leaves 86 are in staggered relationship withrespect to the leaves 38 of the forward trowelling assembly. Thus, any irregularities which may be left by the forward trowelling assembly are smoothed out by the subsequent passage of the rearward. trowelling assembly 81. In addition, the bias spring 90 may be more lightly stressed than the bias spring 42 of the forward trowelling assembly so that a lighter finishing trowelling action can be obtained.
The two trowelling assemblies are rigidly mounted with respect to each other; however, they are free to pivot as a unit about the fulcrum point of the mounting lever 80 defined by the ball and socket assemblys76, 78. The counterweight 60 may be adjusted, as in the preceding embodiment, to counterbalance the net weight of the two sets of trowelling leaves.
The embodiment of FIG. 3 provides a further refinement which allows two sets of trowelling leaves tobe mounted rigidly with respect to each other and yet permits a more flexible pivoting acting so that the device may follow a sharper curvature in the pipe 10. As can 'be seen in FIG. 3, the overall structure of the two trowelling assemblies is substantially the same as that described above in connection with FIG. 2. However, in
the arrangement of FIG. 3, there is provided a large diameter hollow axial shaft 100 which replaces the axial shaft 32 of the preceding. embodiments. The large diameter hollow axial shaft 100 is rigidly connected to, and forms a portion of, the frame and strut assemblies of the forward and rearward trowelling assemblies. The
mounting lever 80 extends back through the center of 6 mechanism moves around a curvature or a dip in a pipe can be visualized by considering the rotary, distributor head 24 to have moved upwardly from its normal position along the pipe centerline as shown in FIG. 3. This movement occurs, for example, when the distributing mechanism moves into a dip .in the pipe 10. This upward movement causes the ball and socket pivot 74, 76 to moveupwardly. However, the trowelling assemblies 18 and 81 remain in position while the mounting lever 80 pivots to move the counterweight 60 to its phantom line position. It will also be seen, that the orientation of the trowelling assemblies 18 and 81 is not affected. by this movement. Instead they remain aligned along the centerline of the pipe 10 in the region they happen to be trowelling. This is due to the fact that the pivot 104 allows the orientation of the trowelling assemblies 18 and 81 to remain independent of the angular position assumed by the mounting lever 80. Instead, the align- In order to ensure thatthe two trowelling assemblies I exert balanced forces against) the pipe. being trowelled they should be maintained balanced with respect tothe pivot 104. This balancing may be precisely controlled and maintained, as shown in FIG. 3, by means of a balance ring 106 which fits over and is slideable along the hollow axial shaft 100. The balance ring 106 is moved back and forth until the overall weight distribution of the two trowellingassemblies 18 and 81 and the hollow axial shaft with the ring 106 is balanced with respect to the pivot 104. The ring 106 may then be secured in place with a setscrew 108.
Although particular. embodiments of the invention are herein disclosed for purposes of explanation, various modifications thereof, after study of this specification, will be apparent to those skilled in the art to which the invention pertains.
.What is claimed and desired to be secured by Letters Patent is:
1. A drag trowelling device comprising a frame, trowelling leaves supported from said frame, an elongated lever arm, said frame being mounted at a first location on said lever arm, counterweight means to neutralize the net weight of the frame and trowelling leaves, said counterweight means being mounted at a second location on said arm and support means including a pivot supporting said arm for swinging movement about a third location intermediate said first and second locations.
2. A drag trowelling device according to claim l wherein said counterweight means is adjustably positionable along said lever arm.
3. A drag trowelling device according to claim 2 wherein said counterweight means. is provided with locking means for securing it to said lever arm at different locations along its length.
4. A drag trowelling device according to claim 1 wherein said trowelling leaves are resiliently biased in radial outward directions.
5. A drag trowelling device according to claim 1 wherein said frame is mounted for free rotation about said lever arm about its longitudinal axis.
6. A drag trowelling device according to claim 1 wherein said pivot is constructed to allow swinging movement of said lever arm in all directions radial of its axis.
7. A drag trowelling device according to claim 1 wherein said pivot comprises a ball and socket construction.
8. A drag trowelling device according to claim 1 wherein said pivot includes a bearing permitting free rotational movement of said lever arm about its axis.
9. A drag trowelling device according to claim 1 wherein said frame supports plural sets of trowelling leaves.
10. A drag trowelling device according to claim 9 wherein said frame is pivotally connected to said lever arm at a location intermediate said sets of trowelling leaves.
11. A drag trowelling device comprising a support member, centering means for maintaining said support member generally centered within a tubular conduit as it is pulled through the conduit, an elongated lever arm, connector means pivotally connecting said lever arm, at a location thereon intermediate its ends, to said support member, trowel means mounted on the elongated lever arm on one side of the said location and counterweight means to neutralize the net weight of the trowel means, said counterweight means being mounted on the elongated lever arm on the other side of said location. i
12. A drag trowelling device according to claim 11 wherein said support member includes means for contacting the interior of a conduit for maintaining said support member substantially centered therein.
13. A drag trowelling device according to claim 11 wherein said connector means comprises a swivel allowing both swinging and rotary movement of said lever arm.
14. A drag trowelling device according to claim 11 wherein said connector means includes a ball and socket construction.
15. A drag trowelling device according to claim 14 wherein said connector means further includes rotary bearing means allowing free rotation of said support member with respect to said lever arm.
16. A drag trowelling device according to claim 11 wherein said connector means includes a generally cup shaped housing having its open end secured to said support member and its base pivotally connected to said lever arm.
17. A drag trowelling device according to claim 16 wherein said lever arm extends through the base of said housing and wherein said counterweight means is positioned between the walls of said housing.
18. A drag trowelling device according to claim 17 wherein the base of said housing is connected to the outer race of a rotary bearing having a rotational axis extending along .the longitudinal axis established by said centering means and a ball and socket structure connected to the inner race of said bearing.
19. A drag trowelling device according to claim 11 wherein said support member is a portion of a lining depositing device.
20. A conduit lining mechanism comprising a lining material depositing mechanism operable, when dragged through a conduit, to impel hardenable liner material onto the interior walls of the conduit, trowelling means having a plurality of trowel elements biased radially outwardly to press upon and smooth out the deposited liner material when the trowelling means is pulled along through the conduit behind the material depositing mechanism and coupling means connecting said trowelling means to said material depositing mechanism to be pulled along behind it, said connecting means comprising a support bracket secured to and extending out behind the depositing mechanism, an elongated lever arm extending generally axially of said trowelling mechanism, means pivotally connecting said lever arm, at a location thereon intermediate its ends, to said support bracket, said trowelling means being attached to the elongated lever arm on one side of said location and counterweight means to neutralize the net weight of the trowelling means, said counterweight means being mounted on said elongated lever arm on the other side of said location.
21. A conduit lining mechanism according to claim 20 wherein said support bracket is in the form of a cup shaped housing having its open end mounted on the material depositing mechanism and having secured to its opposite end said means pivotally connecting said lever arm.
22. A conduit lining mechanism according to claim 20 wherein said trowelling means comprises a frame supporting two sets of trowelling leaves tandemly thereon.
23. A conduit lining mechanism according to claim 22 wherein said trowelling means includes a central axially extending member from which radial elements extend to support said trowel elements.
, 24. A conduit lining mechanism according to claim 23 wherein said trowelling means is attached to said lever arm at said central axially extending member.
25. A conduit lining mechanism according to claim 24 wherein said trowelling means is attached to said central axially extending member at a location thereon intermediate said two sets of trowelling leaves.
26. A conduit lining mechanism according to claim 25 wherein said lever arm is pivotally attached to said central axially extending member.
27. A conduit lining mechanism according to claim 26 wherein said central axially extending member is tubular and of substantially larger diameter than said lever arm, said lever arm extending inside said member and pivotally secured to an inner flange in said member.
28. A conduit lining mechanism according to claim 27 wherein said central axially extending member includes a balance weight longitudinally adjustable there-