US2979996A - Troweling machine - Google Patents

Description

April 1951 c. H. SPITLER z-rrm. 2,979,996

TROWELING MACHINE 4 Sheets-Sheet 1 Filed April 24, 1957 INVENTORS 64 {M H. SP/ n 6.2 uo/wv 0. 6/7 r61? By S WM April 18, 1961 c. H. SPITLER ETAL TROWELING MACHINE 4 Sheets-Sheet 3 Filed April 24, 1957 IN VEN TORS a M #1 WWW m ad 4 Sheets-Sheet 4 TROWELING MACHINE wm QM R C. H. SPlTLER ETAL llm m 3 I mm P! .m IVE? I w an \R mm IE? April 18, 1961 Filed April 24, 1957 Ctr- in wwmmage m 5 mm W R Wm M E V/ 2 N2 WW 0 15 T A W M W B V. B

United States Patent TROWELING MACHINE Clem H. Spitler, Dayton, and John D. Gayer, Alliance, Ohio, assignors to Master Vibrator Company, Dayton, Ohio, a corporation of Ohio Filed Apr. 24, 1957, Ser. No. 654,836

8 Claims. (Cl. 9445) This invention relates to power operated concrete troweling machines, and more particularly to a generally new organization in a machine as described offering improved efliciency, greater stability and compactness, and power and safety controls.

In machines of the class described, relatively stationary engine means is supported upon a rotary series of troweling blades, which blades rest upon the work surface of unset concrete, and, in the use of the machine, are ro tatively driven by the engine means to effect floating and finishing operations upon the work surface. A handle is attached to the engine means and is held by the operator in order that the machine may be guided over the work surface and in order that the engine-means may be held from rotating with the troweling blades. Machines of the present class conventionally incorporate means for tilting the troweling blades relatively to the work surface and to the engine means in order that the action of the blades upon the work surface may be varied, as from floating to finishing and vice versa.

The object of the invention is to simplify the construction as well as the means and mode of operation of troweling machines, whereby such machines may not only be economically manufactured, but will be more efficient and satisfactory in use, adaptable to a wide variety of applications, and be unlikely to get out of order.

A further object of the invention is to reduce the center of gravity of the machine by a general lowering of the parts thereof toward the work surface, this being achieved by a structural concept in which the rotary mount for the troweling blades is constructed as a housing for the drive unit in the form of a gear train unit interconnecting the engine and the blade mount. 1

Another object of the invention is to obviate the need for manual blade adjustment, there being introduced into the machine a principle of power operation remotely controlled by the operator from his position at the free end of the handle.

A further object of the invention is to enable the troweling blades to be adjusted in a tilting direction while the machine is continued in operation, revolving the blades over the work surface.

Still another object of the invention is to provide for power tilting of the troweling blades in either direction without interrupting operation of the machine.

A still further object of the invention is to increase the drive efliciency from the engine to the blade mount through the use of helical gears in the transmission and reduction mechanism instead of the belt drive and worm gear combination heretofore known tobe used for this purpose.

Still another object of the invention is to provide a safety control in the machine which will prevent run away operation thereof, there being provided on the ban: dle an engine control means adapted to be received in the grasp of the operator on the handle and which when released enforces an idling of the engine.

A further object of the invention is to provide a troweling machine possessing the advantageous structural features, the inherent meritorious characteristics and the mode of operation herein mentioned.

With the above and other incidental objects in view as will more fully appear in the specification, the invention intended to be protected by Letters Patent consists of the features of construction, the parts and combinations thereof, and the mode of operation as hereinafter described or illustrated in the accompanying drawings, or

their equivalents.

Referring to the accompanying drawing wherein is shown one but obviously not necessarily the only form of embodiment of the invention,

Fig. 1 is a view in perspective of a troweling machine in accordance with an illustrated embodiment of the present invention;

Fig. 2 is a detail view in longitudinal section of the gear train unit of the machine;

Fig. 3 is a plan view of the top of the engine casting or mount, with the engine removed and with a part of the casting broken away to show a pawl and ratchet mechanism provided for tilting the troweling blades in response to a revolving motion thereof;

7 Fig. 4 is a view in cross section, taken substantially along the line 44 of Fig. 3;

Fig. 5 is a view in cross section, taken substantially along the line 5--5 of Fig. 3;

Fig. 6 is a view in cross section, with some parts omitted, showing the engine mount and its mutually supporting relation to the blade mount;

Fig. 7 is a detail view in side elevation of the handle, showing the connections to the blade tilting mechanism from the relatively remote control therefor on the handle;

Fig. 8 is a detail view in side elevation of engine idler control means mounted on the carburetor of the engine; and

Fig. 9 is a view in longitudinal section through the engine control of Fig. 8.

Like parts are indicated by similar characters of reference throughout the several views.

Referring to the drawings, a troweling machine in accordance with the illustrated embodiment of the invention comprises, as shown in Fig. 1, engine means including a casting or mount 15. On top of the casting or mount 15 is a self contained internal combustion engine 16 supported on end upon the mount 15 in suchmanner that the driven rotary shaft 17 thereof (see Figs. 2 and v6) projects axi-ally within the engine mount 15 or more particularly into a longitudinal through opening 18 therein. The engine 16 is suitably bolted or otherwise secured to the mount 15 to comprise therewith a unitary assembly. The mount 15 is formed on the periphery thereof with a radially projecting portion 19 to which is pivotally attached a bracket 20 at one end of a tubular handle 21. At the other end of the handle 21 is a cross bar 22, provided for the grasp of an operator, the handle being used to guide the troweling machine over the work and to be held to inhibit rotary motion of the engine means.

Also projecting radially from the engine mount 15 is a series of spokes 23 terminating in, or secured to, at their outer ends a common ring 24 which acts as a guard and defines the working area as traversedby a rotary series of troweling blades 25. The latter rest upon the work surface and support the machine thereon and are caused to revolve Within the work area by operation of the engine 16, as will hereinafter be seen.

The blades 25 are flat and generally rectangular in construction and are disposed with their axes in respective planes tangential to a circle concentric with the axis of engine shaft 17. Each has a longitudinally extending rib 26 on its supper surface secured as by a Patented Apr. 18, 1961 I web 27 to a longitudinally offset sleeve 28. The latter is rotatably mounted on a shaft 29 and has integrally formed therewith a laterally projecting arm 31. At its outer end, the latter is received in a cam slot 32 formed by segmental ribs on a ring 33 (see Fig. 6) mounted for relative rotary motion in an external track 34 on the side of a bowl shaped housing 35 beneath the engine mount 15. Also on the exterior of the housing 35 is a series of tangential sockets 36, each receiving one end of a respective shaft 29. The housing 35 thus carries the several tro 'eling blades 25 for unison, bodily rotary motion, and the blades are still further arranged for tilting motion about their respective shafts 29 in response to rotary motion of the ring 33 relatively to the housing 35, this motion being resolved through the cam slot 32 and arm 31 into a rocking motion of sleeve 28. As a result of such tilting motion, the leading edge of the blade is raised or lowered relatively to the surface of the work with a corresponding change in the kind of work performed, as is known in the troweling of unset concrete surfaces.

The open upper end of the bowl shaped housing 35 faces the under side of the engine mount 15, and the housing or blade mount is positioned concentrically of opening 18 and engine shaft 17. The upper end of the lade mount is closed by a plate 37 fastened by studs 38 to the upper edge thereof. The closure plate 37 has a central opening therein within which a bearing 39 is located for supporting a gear train unit 41.

The blade mount 35 receives and serves as an enclosure for a drive unit 41 in the form of a gear train unit. The latter includes a housing 42 on the upper end of which is a boss 43 received in the bearing 39 and abutting the underside of a flange 44 which is a part of the engine mount 15 and which defines the smallest diameter portion of the opening 18 therein. A set of screw studs as pass through the flange 44- and into the upper edge of the boss 43 whereby to hold the housing 42 of the gear train unit 41 stationary along with the relatively stationary engine mount. 42 is closed by a plate 46 bolted thereto, the latter having a central opening 47 receiving a bearing 48. Rotatable in the latter is a centrally projecting portion 49 of a gear 51. On the opposite side of the gear 51 is a recess 52 receiving one end of a pinion shaft 53. On the latter is a pinion 54 meshing with a gear 55 on another pinion shaft 56 supported in the housing 4-2 outside the boss 43. Also secured to the pinion shaft 55 is another pinion 57 meshing with the gear 51. Installed in the central projecting portion 49 of the gear 51 is a plurality of bolts 58 which extend out of the gear train unit by way of opening 47 and are secured to the bottom portion of the blade mount or housing 35. The gear train unit thus affords a direct gear drive from the pinion shaft 53 to the gear 51 and thereby to the blade mount 35. The latter is accordingly rotated with the gear train assembly within the gear train unit 41. The connection provided by the bolts 58 is effective also to retain the blade mount in a concentric relatively fixed location with respect to the engine mount and further suspends the blade mount from the engine mount in the event of the machine being lifted and carried about. In use, it is more accurate to describe the engine mount as being supported upon the blade mount, since the blades 25 in effect support the machine upon the work surface. In order to seal the area of contact between the blade mount and the engine mount, the closure plate 37 for the blade mount is provided in the area surrounding bearing 39 with a felt seal ring insert in contact with a machined surface 61 on the underside of the engine mount 15. The described one end of the pinion shaft 53 is rotatable in a bearing 115. The opposite ends of pinion shaft 56, in the housing 42, are rotatable in respective bearings 116 and 117.

The lower end of the engine shaft 17 has a hearing The bottom of the housing 4 62 installed therein receiving an upper end of the pinion shaft 53. A sleeve 63 is mounted on the shaft 53 between the bearing 62 and the pinion 54. The sleeve 63 is keyed to the shaft 53 and at its upper end is secured to a clutch shell 64. The shell 64 is a part of a centrifugal clutch assembly engageable to effect a driving connection between'the shaft 17 and the pinion shaft 53. When the clutch is engaged, operation of the engine is accompanied by rotation of the blade mount 35 and thereby by a sweeping action of the blades 25 over the work surface. The speed of motion of the blades is a function of the speed of operation of the engine (reduced by the gearing in said gear train unit 41) which in turn is regulated by a throttle control lever 60 mounted on the handle 21 convenient to the hand of the operator and suitably connected, as by flexible cable, to the engine carbureter. When the clutch is disengaged the engine may idle or otherwise operate without effect upon the blade mount. In this regard, the use of a centrifugal clutch provides automatic actuation of the blade mount in response to the speed of rotation of the engine shaft and may be constructed to disconnect the blade mount from the engine drive when the engine is at an idling speed. In the illustrated instance, the clutch mechanism shown in a part of a specific form of clutch wherein a centrifugally operated mechanism is received within the shell 64 and rotatively driven by the shaft 17 in such manner that a predetermined speed of rotation of the shaft causes the centrifugal mechanism to establish a frictional driving engagement with the shell 64, and, through the sleeve 63, to rotate the pinion shaft 53.

The ring 33, utilized to adjust the degree of inclination of the blades 25 relatively to the work surface, is mounted in a track or groove 34 as described, the track or groove being defined by an integral flange on the side of the blade mount 35 and by an overhanging lip on the closure plate 37. The ring 33 is frictionally held in its mounting to rotate with the blade mount 35 by means of a rubber 0 ring 33'. On the upper surface of the ring 33 is an arcuate segment of a rack 65 projecting laterally in overlying relation to a pant of the periphery of the closure plate 37. Also in overlying relation to the closure plate 37, and vertically spaced therefrom is a bracket or mounting plate 66 made secure against rotary motion relatively to the closure plate by interconnecting studs or bolts 67, 68, and 69 (Fig. 5). The spaced apart Walls defined by the plates 37 and 66 provide a mounting for laterally spaced apart stub shafts 71 and 72 suitably journaled at their ends in the respective plates. On the stub shaft 71, in superposed relation to one another and effectively interconnected for unison rotation, are a ratchet 73 and a pinion 74, the latter being in meshing engagement with the upper part of a relatively elongated gear 75 the lower part of which is in meshing engagement with the rack 65. The gear 75 is rotatably mounted on a stud 76 set in the plate 37. On the stub shaft 72, in superposed, relation to one another and effectively interconnected like elements 73 and '74, are a ratchet '77 and a gear 78, the latter in meshing engagement with the rack 65. According to the construction and arrangement of parts, therefore, the ratchets 73 and 77 are in rotary driving engagement with the rack 65 so that rotary movement imparted to either of the ratchets is effective rotatively to adjust the ring 33 and thereby to tilt the blades 25 relatively to the work surface. The ratchets 73 and 77 are in vertically spaced apart or different horizontal planes.

The ratchet 73 is formed with a series of peripheral teeth '79 and a planar or blank surface 81. Similarly, the ratchet 77 is formed with teeth 82 and a blank surface 33. The ratchets 73 and 77 are constructed identically to one another and are mounted on their respective stub shafts in a like manner. The-machined peripheries thereof are adapted to make selective cooperative engagement with respective pawls 84 and 85 which are received in a recess 36 in the engine casting 15 and pivotally mounted therein on respective vertical studs 87 and 88. The pawls 84 and 85 lie in. spaced apart horizontal planes corresponding to the planes of respective ratchets 73 and 77. An end 89 of the pawl 84 may be interposed into the path of a tooth on the ratchet 73, as the ratchet is carried or revolved about the axis of the casting 15 in response to rotation of the blade mount 35. Similarly a corresponding end 91 on the pawl 85 may be interposed in the path of a tooth on the ratchet 77.

The end 89 of the pawl 84 is formed with a slot 92 and overlaps the adjoining end of the pawl 85 which is the end opposite to the described end 91 thereof. The said opposite end of the pawl 85 is formed with an opening 93. The pawls 84 and 85 are interconnected by the turned over end 94 of a rod 95, such turned over end passing through the slot 92 and the opening 93 so that a pu1ling or pushing motion exerted upon the rod 95 is eifective to rock the pawls 84 and 85 about their respective studs 87 and 88 and in respectively different directions. A spring pressed plunger 96 engages the pawl 84 and tends normally to hold the pawls in the position illustrated wherein the resepctive ends 89 and 91 thereof are out of the paths of movement of the ratchets 73 and 77.

The opposite end of the rod 95 is connected to a lever 97 pivotally mounted at 98 to projection 19 of casting 15. Also connected to the lever 97 :is one end of a rod 102 which extends upward through the tubular handle 21 and is connected adjacent to'its opposite end to an anchor block 103 within the handle. A knob 104 is slidably mounted on the handle exteriorly thereof and is con nected to the block 103 by a screw fastener 105. Longitudinal sliding motion of the knob 104, relatively to the handle 21, accordingly effects an axial movement of the rod 102 and a rocking motion of the lever 97 with a resulting longitudinal motion of the rod 95. Movement of the knob 104 forwardly or downwardly of the handle 21 rocks the lever 97 in a counterclockwise direction (Fig. 7) and eifects a relatively extending motion of the rod 95. The results or effect upon the pawls 84 and 85 is to rock pawl 84 in a counterclockwise direction about'its stud 87 and to rock the pawl 85 in a clockwise direction about its stud 88. A predetermined extent of movement of the mechanism in this direction serves to place the end 89 of pawl 84 in the path of movement of the teeth 79 on ratchet '73. The end 91 of pawl 85 is in this operation rocked a farther distance out of cooperative relation with its ratchet 7 7 Return of the knob 104 to a normal or neutral position as illustrated restores the pawls 84 and 85 to the normal position shown in Fig. 3 wherein both pawls are inelfective with respect to their associated ratchets. Continued movement of the knob beyond the neutral positon in an upward or rearward direction along the handle 21 effects a reverse movement of the parts with the result that the nose or end 91 on the pawl 85 is interposed in the path of the teeth 82 on ratchet 77 while the pawl 84 continues to be ineifective with respect to the ratchet 73.

The knob 104 is located adjacent adjacent to the grip or cros bar portion 22 of the handle and so is readily accessible for manipulation by the operator. It serves as a remote control for the adjustment of the pawls 84 and 85 and thereby for selective adjustment of the blades 25 in either direction.

The changing of the angle of adjustment of the troweling blades is accordingly a power operation initiated and controlled by the operator but effected by power supplied from the engine. Thus, the ratchets 73 and 77 are caused bodily to revolve with the blade mount 35 as the troweling blades sweep over the work. The selective interpositioning of one or another of the pawls '84 and 85 into the path of movement of an associated ratchet results in engagement of the teeth of the ratchet with an end of the pawl and a consequent imparting of a rotary impulse to the ratchet as it passes by the pawl. This increment of motion is transmitted through gearing to the rack 65 and results in a corresponding tilting adjustment of the troweling blades through a corresponding increment of movement and in a direction determined by the direction of adjustment of the control knob 104. It may be seen, moreover, that the mechanism operates to adjust the blades in a series of steps, one for each revolution of the blade mount 35 as the ratchet teeth successively engage the pawl. The maximum permitted movement of the troweling blades in either direction is determined by the number of teeth on the respective ratchets since the rotary movement of the ratchets are discontinued as the planar surfaces 81 or 83 thereof reach cooperative relation with continue to be held in an actuated position. The work of adjusting the blades is carried out without interruption in the operation of the machine and may bediscontinued at any desired point by action of the operator in restoring the knob 104 to a neutral position.

The machine incorporates a safety control designed to prevent a'run-away operation should the operator lose his grasp upon' the handle. This control includes a lever 106 positioned to be received within the grasp of the operator upon the cross bar 22. A cable 107 is connected at its one end to the lever 106 and extends into and downwardly through the tubular handle 21. Near the lower end of the handle, the cable 107 emerges therefrom and is extended for attachment at its opposite end to a stud 108 (Figs. 8-9) in one end of a lever 109 pivotally mounted intermediate its ends on a bracket 111. The latter is secured to the carbureter assembly. The opposite end of the lever 109 is formed with a turned over ear 112 cugageable with a screw 113 attached to the butterfly gate of the carbureter. A compression spring 114 is interposed between the pin 108 and a turned over portion of the bracket 111 in such manner as to cause the ear 112 on lever 109 to engage and hold the screw 113 in a position in which the butterfly gate is closed or substantially closed in such a way that the engine cannot operate at anything higher than an idling speed. A retracting or pulling force exerted upon the cable 107 serves to rock the lever 109 in a clockwise direction from the full line position shown in Fig. 8 to the dotted line position thereof, in the course of which motion the car 112 thereon releases the screw 113 and permits free adjustment of the butterfly gate under control of the throttle. Under the influence of the spring 114 the hand lever 10'6 normally occupies a position as shown in Fig. 1 wherein it is in divergent relation to the cross bar 22 of the handle. When received in the grasp of the operator, the lever 106 may be retracted and brought back to a position substantially parallel to the cross bar. In so moving, the lever pulls upon the cable 107 and rocks the lever 109 in a clockwise direction with the result above described. Should the operator release his grip upon the handle, while the machine is running, the control of the described mechanism is restored immediately to the spring 114'which rocks the lever 109 in a counterclockwise direction and, through its action upon the screw 113, reduce the speed of engine operation to idling.

If found necessary or desirable, the ring '33 may be manually adjusted by grasping rods 115 and rotating the ring about the housing 35.

From the above description it will be apparent that there is thus provided a device of the character described possessing the particular features of advantage before enumerated as desirable, but which obviously is susceptible of modification in its form, proportions, detail construction and arrangement of parts without departing from the principle involved or sacrificing any of its advantages.

While in order to comply with the statute the invention has been described in lauguage more or less specific as to structural features, it is to be understood that the invention is not limited to the specific features shown, but that the means: and construction herein disclosed 7 comprise but one of several modes of putting the invention into, effect, and the invention is therefore claimed in any of its forms or modifications within the legitimate and valid scope of the appended claims.

It will be seen from the structure heretofore described that the gear train, its housing, the working blades and the blade mount are not in the same plane but are in substantially the same plane since the gear train and blade mount are substantially symmetrical about a horiontal plane and the blade assembly structure is just below said horizontal plane thereby producing a compact assembly in the vertical direction resulting in a substantial lowering of the center of gravity of the machine as compared to the prior art and in producing stability in operation.

What is claimed is:

l. A power operated troweling machine, including drive means having a relatively stationary mount which in use occupies a position in vertically spaced approximately parallel relation to a work surface, a housing secured in immediately dependent relation to said mount, a gear train unit within said housing operatively connected for drive by said drive means, a blade mount surrounding the periphery of said housing and operatively connected to said gear train unit means for rotation thereby, troweling blades, means tiltably mounting said blades to peripheral portions of said blade mount in a substantially co-planar relationship therewith for rotational movement therewith and tilting movement thereon and a ring frictionally engaging said blade mount and a cam surface on said ring, means on said blades engaging said cam surface and means for retarding the rotation of said ring on said blade mount to cause tilting of said blades.

2. A troweling machine including a relatively stationary mount for drive means which in use occupies a position in vertically spaced approximately parallel relation to a work surface, a gear train unit supported in immediately dependent relation to said stationary mount, blade mount means surrounding the periphery of said gear train unit and positioned substantially co-planar with said gear train unit and operatively connected thereto for rotation thereby, troweling blades connected to said blade mount for rotation therewith, said troweling blades being adapted to rest on the work surface and provide support for said troweling machine, said troweling blades being substantially co-planar with said blade mount and gear train unit whereby to effect a low center of gravity for said trowel ing machine.

3. A power operated troweling machine including a relatively stationary mount which in use occupies a position in vertically spaced substantially parallel relation to a work surface, a gear train unit secured to and beneath said stationary mount, means housing said gear train unit situated immediately below said stationary mount, a blade mount surrounding said housing, means connecting said blade mount to said gear train unit for rotation thereby about said housing, blade means pivotally connected to peripheral portions of said blade mount for rotation there with in a substantially common plane and tilting movement thereon, said blade means being adapted to rest on the work surface and support the troweling machine thereby, a ring type element frictionally engaging the periphery of said blade mount and adjustably mounted on said blade mount substantially co-planar therewith, said ring type element having a cam surface operatively connected to said blade means for effecting tilt thereof on said blade mount corresponding to adjustment of said ring type element on said blade mount, means selectively arresting rotation of the ring element in increments to cause relative movement between said ring type element and said blade mount to change blade tilt adjustment.

4. A power operated troweling machine according to claim 3, characterized in that said means for adjusting said ring includes a gear rack on said ring, relatively rotatable pinions on said blade mount in mesh with said rack and for rotation therewith and rotatably adjustable relative thereto, said ring having a cam surface, means interconnecting said cam surface and said blades for selective tilt of said blades in response to rotary adjustment of said ring relative said blade mount, and means selectively arresting rotation of the ring in increments to cause rel-ative rotational movement between said ring and said blade mount to change blade tilt adjustment.

6. A power operated troweling machine, including a relatively stationary mount which in use occupies a position in vertically spaced approximately parallel relation to a Work surface, said mount including a central opening, a housing fixed to and depending from said mount surrounding said opening having a gear train unit disposed therein including means for. coupling'thereof to a drive means on said stationary mount, a cup shaped blade mount surrounding said housing for rotation relative thereto, means on said gear train unit fixedly securing said blade mount to cause rotation, troweling blades pivotally mounted on the periphery of said blade mount adapted to rest on the work surface to support the machine thereby, means defining a track about said blade mount, a ring engaging said track and frictionally engaging a peripheral portion of said blade mount for rotation with said blade mount and means for rotatably adjusting said ring relative to said blade mount, cam means on said ring, means connected to said blades and operatively engaged with said oam means for tilting of the blades in response to relative adjustment of said ring on said blade mount.

7. A power operated troweling machine including a relatively stationary engine mount, an engine in generally superposed relation to said mount having its drive shaft dependent therethrough, a blade mount positioned in immediately adjacent relation to the underside of said engine mount, a gear train housing disposed within the confines of said blade mount and secured to said engine mount against rotation and a gear train in said housing operatively connecting said shaft and blade mount for rotation of said blade mount, troweling blades connected to said blade mount for rotation therewith, said blades, blade mount and gear train unit being substantially coplanar whereby to effect a lower center of gravity for said machine.

8. A troweling machine including a relatively stationary engine mount for drive means which in use occupies a position in vertically spaced approximately parallel relation to a work surface, a gear train housing supported in immediately dependent relation to said stationary mount and secured to said stationary mount against rotation and a gear train in said housing, blade mount means positioned substantially co-planar with and surrounding said gear train unit and operatively connected thereto for rotation thereby, troweling blades connected for rotation with said blade mount and tiltably mounted thereon, said troweling blades being adapted to rest on the Work surface and provide support for said troweling machine, said troweling blades being substantially co-p-lanar with said blade mount and said gear train unit whereby to efiect a lower center of gravity for said troweling machine and blade tilting means supported on and substantially coplanar with said blade mount operatively connected to said blades.

(Refer nces on following pag 10 References Cited in the file of this patent FOREIGN PATENTS UNITED STATES PATENTS 698,767 France July 9, 1930 2,198,929 Whiteman Apr. 20, 1940 1131320 Austral! June 13, 1941 2,277,389 Conway Mar. 24, 1942 5 1,092,463 France 10, 1954 2,351,278 Mathews June 13, 1944 OTHER REFERENCES 2'826971 Stevens 1958 Engineering News Record, May 19, 1955, p. 52.

2,826,972 Stevens Mar. 18, 1958

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