US2179553A - Concrete laying and placing machine - Google Patents

Description

(W. M, 1939. H. M. HADLEY 2,179,553

CONCRETE LAYING AND PLACING MACHINE Filed July 17, 1935 16 J/m Q. 5

ATTORNEYS Patented Nov. 14, 1939 UNITED STATES TENT OFFiCE 19 Claims.

This invention relates to a method and apparatus for effecting the laying of concrete. Considerable economy may be obtained in laying concrete by using a mixture of low cement and also of low water content. In such a dry mix the percentage of cement is relatively low but the percentage of water also being low, the strength of the resulting concrete is equal to that of mixes of higher cement content, but also having a proportionate higher water content. However, concrete of a dry mix, requires considerable care to insure that the aggregate, cement and sand are properly consolidated.

One of the objects of this invention is to provide an improved method and apparatus, which will enable a relatively dry mix to be employed in laying concrete, and which will insure an effective consolidation of the laid mass of concrete.

I-Ieretofore, concrete laying machines have been employed for laying concrete, involving the use of a hopper for the concrete, with a bottom opening through which the concrete passes when the hopper is advanced. The use of that method for laying concrete has some objections, because it necessitates the constant replenishing of the concrete mix in the hopper, and entails the bringing of the concrete from the mixer to the hopper.

One of the objects of this invention is to provide a method and apparatus which will enable the procedure to involve dumping the concrete in piles, or windrcws, on the base surface or base on which it is placed; at the same time, providing for the effective consolidation and leveling of the dumped concrete to form a consolidated mass of laid concrete of desired thickness and surface on the base surface; and a further object of the invention is to provide concrete lay ing apparatus, which can be employed for relaying, leveling down and consolidating concrete already dumped on the base surface; and which can also be readily employed as a hopper when desired, for laying concrete from the hopper onto a base surface or subgrade, at the same time, insuring a thorough consolidation of the concrete when laid.

In accordance with my invention, I provide for efiectively vibrating the concrete already dumped on the base surface, or as it is being laid on the base surface through the hopper bottom, and the consolidation of the concrete is so efiicient that a mix can be employed that is so densely compacted as to enable the concrete immediately after being laid, to support a vehicle such as an automobile or a tractor running on the immediately laid concrete, so that this automobile or tractor can push forward the concrete machine.

A further object of the invention is to provide apparatus of this kind with effective means for imparting vibratory impulses to the concrete while being laid or leveled down; also to provide a freely vibrating strike-01f plate functioning effectively to level off the concrete to the desired surface, and at the same time, imparting vibratory impulses to the same throughout the transverse length of the machine.

A further object of the invention is to provide a concrete laying machine, which can readily be employed to consolidate and level off concrete already dumped on the subgrade, and which can also be employed with an overhead trolley, or with a tractor pushing the same. The use of the trolley enables the apparatus to be employed as a hopper, transported to the point where the hopper is filled, and then returned and advanced over the subgrade at the point where the concrete is to be laid. In this way the hopper not only operates as means fortransporting the mix to the point where it is to be dumped, but also cooperates to enable the concrete to be laid to a desired depth in a consolidated mass.

A furtherobject of the invention is to improve the general construction of machines of this type.

Further objects of the invention will appear hereinafter.

As regards the method, the invention consists in the novel steps and combination of steps oescribed in the following specification, all of which contribute to produce an efficient method for laying concrete.

As regards the apparatus, the invention consists in the novel parts and combination of parts to be described hereinafter, all of which contribute to produce an efficient concrete laying machine,

In the drawing:

Figure 1 is an end elevation of a concrete laying' apparatus embodying my invention, certain parts being broken away'so as to disclose more fully the details of the construction. This view represents the machine as though being used on concrete already dumped on a base surface or base, and indicates the manner in which an automobile may be employed for shoving the machine forward over the dumped concrete.

Fig. 2 is a plan of one end of the machine, with certain parts broken away, and with other parts shown in section.

Fig. 3 is a view upon a reduced scale and illustrating the manner in which the machine may be employed with a trolley and drag line for carrying the concrete in the hopper, and for laying the same on a subgrade.

Fig. 4. is a vertical section'through the machine taken in a front and rear plane, and further illustrating details of the construction. This View particularly illustrates the construction of a vibrating shoe, which is located at the subgrade level, and also illustrates the preferred construction for the strike-01f plate, together with the vibrating means for vibrating the shoe and the strike-off plate during the operation of the machine.

Fig. is a section through one end of the machine in a substantially horizontal plane, particularly illustrating the manner of mounting the adjustable retainer plates for confining the concrete at the ends of the machine as it is being laid, and this View also further illustrates the means for mounting the removable forward plate of the machine, which can be used to transform the apparatus into a hopper capable of carrying the mixed concrete to the point where it is to be laid.

Fig. 6 is a vertical cross section through a preferred form of vibrator shaft, which is employed forimparting vibratory impulses to the shoe and the strike-off plate. This same vibrating means may also be employed on the retainer plates at theends of the machine;

The apparatus of the concrete laying machine of my invention enables two methods of procedure to be used in laying the concrete. In one method the mixed concrete is dumped on the subgrade in piles or windrows. The machine is then pulled or pushed through, and over the dumped concrete. As this occurs the dumped concrete is subjected to vibratory impulses, which consolidates it, and toward the rear of the machine means are provided for striking off the concrete to the desired surface and for simultaneously subjecting it to vibratory impulses. If the concrete mix is relatively'dry, the mass of concrete behind the machine is sufficiently consolidated to enable an automobile or a tractor to run upon it. Hence-it is possible with this machine, to advance it by meansof an automobile or tractor running-on the concrete immediately laid, and pushing the machine ahead.

In extensive concrete laying operations, as in the building of dams, it is the practice to carry the concrete to the place where it is to be laid, by means of buckets handled on overhead supporting lines or drag lines. My invention is adapted for employment in connection with such a method of laying concrete, because the apparatus is provided with a removable plate which, when in place, cooperates witha rear plate of the machine and-an extensible strike-off plate to form a hopper. This enables the machine to be operated by cables to carry it to a filling point, and then return it to the point where the concrete is'to be laid. Then by raising the strikeoif plate, an outlet can be formed at the hopper ttcm through which the concrete will pass as the machine is being advanced, either by pushing it from the rear, or by pulling it forward with a cable. The machine'includes a vibrating shoe that is located at a low level, so that it will advance close to the level of the base upon which the concrete is to be laid. When the machine is being used to consolidate and strike oif concrete already dumped, this shoe is forced under the concrete ly'ng on the base in front of. the ma chine, crowding it up over the top of the shoe,

and as the concrete falls over the rear edge of the shoe, it descends onto the base while being subjected to vibratory impulses, and at the same time, the strike-off plate that is striking off the concrete subjects it from above to vibratory impulses. The machine preferably includes vertically movable retainer plates at both ends, which may be extended down to about the level of the base surface or subgrade, and these plates preferably are employed so as to confine the concrete at the ends of the machine and increase the effect of the vibratory impulses imparted to the concrete. These movable retainer plates at the ends of the machine are themselves vibrated by vibrator means which vibrates them in a general transverse horizontal plane. This vibration of these plates tends to cause the concrete to form a continuous side edge or face to the laid concrete.

Referring to the parts, and particularly Figs. 1 and 4, l indicates the frame of the machine, which comprises a pair of end plates 2 connected by a truss 2a toward the rear, said truss compris ing upper and lower web-plates 2b and to, an inclined web-plate 2d, connected up to transverse angle irons 2e and angle clips 2;. This truss also includes a transverse rear bar 29 that may be in the form of a channel back of the pusher bar or bracket 25. At a low level toward the front I mount a transverse vibrator device 3 of my invention. This vibrator device is preferably in the form of a shoe or plow of substantially triangular form in end elevation, (see Figs. 1 and l), with an inclined main plate 4 having a more or less sharp or rounded nose 5 at its forward end to facilitate its passing under the clumped concrete 6 which lies on the base I in advance of the machine. The vibrator device 3 also includes a rear plate 8, which constitutes the vibrating part of this shoe, and this plate is attached by its overhanging flange at its upper edge 9-to the upper edge of the main plate 4, and from this point it extends downwardly and presents a. forwardly projecting bottom plate H which lies near the base 1, and which extends forwardly just above the rear edge of the rounded nose 5. In this way an inner chamber or space I I is formed, in which vibrating means is mounted. This vibrating means preferably consists of a long shaft l2 that extends throughout the length of the shoe, said shaft being mounted in a plurality of bearings l8 disposed equidistant throughout the length of the shoe and at one end a motor M is provided for rotating this shaft at a high rate of speed.

This motor may be provided with operating fluid such as compressed air passing down through an armored cable l5 leading from the air supply, as will be described hereinafter. The Vibrator plate 8 of the shoe is preferably relatively thin and resilient, and the bottom plate if] is preferably unattached to the part 5 of the shoe so as to enable this vibratorplateto vibrate freely from the point 9. The vibrator shaft I2 is preferably constructed so that its center of gravity is eccentric to the geometric axis of the shaft. This is preferably accomplished as illustrated in Fig. 6, by providing the shaft with a relatively deep groove or key it, which extends throughout its length except at the bearings, This form of shaftis preferable to one in which eccentric Weights are employed, distributed at different points along the shaft, because the present shaft, as illustrated in Fig. 6, is of small diameter and distributes the vibratory impulses uniformly throughout its length. By placing the bearings l3 near together, the vibratory impulses generated in the shoe will be very uniformly distributed throughout its length.

Means are provided for supporting the forward end of the frame i, and this means may include wheels but preferably consists of two skids or supporting shoes ii that are adapted to slide along on the base or subgrade I. As illustrated in Fig. 5, the end plates 2 are preferably constructed of inner plates 2k and outer plates 2 between which retainer plates iii are provided, said retainer plates being adjustable up or down; and in the operation of the machine, these retainer plates extend down to a point near the subgrade so as to retain the concrete at each end of the machine. These retainer plates 59 are also preferably vibrated by means of a vibrator shaft l9 mounted in bearings 29 on the outer sides of. these plates, and driven by an air motor 2! supplied with compressed air through a cable 22. The shaft l9 would have substantially the same cross section illustrated in Fig. 6.

In the operation of the machine, when used to level off dumped concrete 6, it may be pushed forward by means of a tractor or an automobile 23 provided with a pusher bracket 24 at its forward end to push against the pusher bracket or beam 25 extending transversely at the rear of the machine. This will push the vibrating shoe 3 as a plow passing through and under the concrete and subject the concrete to vibratory impulses. As the machine advances, the concrete is leveled off so as to form a more or less even top surface 26, and for this purpose I prefer to employ a compacting plate or strike-01f plate 2i with a convex forward and bottom face 28, under which the concrete passes as the machine advances. This strike-oh plate may be made separate from the rear wall of the hopper, but is preferably formed as an extension on the lower end of the rear wall 29 (see Fig. 4). The strike-off plate 211 has an inclined rearward extension 39 on which the vibrating means is mounted, preferably consisting of a shaft 3! similar to the shaft l2, and rotated continuously by means of an air motor 32 supplied with compressed air through a hose 39 (see Fig. l). The shaft 3! is, of course, mounted in suitable bearings 34, which should be located substantially equidistant throughout the length of the strike-off plate. The rear extension 39 of the strike-off plate is preferably unsupported so that it will vibrate quite freely. If this extension, however, tends to develop a whipping movement, this whipping movement can be dampened if desired. I prefer to provide stiifeners in the form of angle irons 39a secured to the under side of the rear extension 3il-to assist in imparting uniform vibration throughout the entire transverse width of the strike-oh" plate 21.

If the concrete laid by the machine is to be top-surfaced, I prefer to provide for bonding this top surface to the laid concrete 35 by providing a roller 36 to roll on the upper side of the laid concrete as it passes from the rear of the machine, and this roller is provided with spurs 37. on its periphery, that form small pockets 38in the upper face 28 of the laid concrete.

The height of the strike-off plate can be regulated as desired, and in order to accomplish this the rear hopper plate 29, which carries the strike-off plate, is guided to slide up and down in the guide plates or angle irons 39 on the end plates 2 (see Fig. 4), and if it is desired to use power for raising or lowering this plate, this can be accomplished by providing air cylinders 40 located respectively, at each end of the machine, supplied with compressed air through connections 4|. Each of these air cylinders 49 has a piston 42, the forward end of which is provided with a fork pivotally attached by a pivot bolt 43 to the upper edge of the plate 29. The connection 4! includes a hand-controlled valve 44, which can be operated to admit compressed air to the lower end of the cylinder to raise the plate 29.

In some situations it may be desired to hold the strike-oif plate in an inclined position; for example, where a roadway is being formed with a super-elevation, or where for any other reason it is necessary to incline the upper face of the laid concrete. The strike-01f plate can be held in such inclined position by operating the air cylinders 49 so as to have one of them hold the strike-off plate in a more elevated position at one end.

The retainer plates Hi can also be raised or lowered to any desired position by any suitable means; for example, each plate may be provided near its upper end with a threaded adjusting screw 45 pivoted to the plate at 4.5 and passing through a guide 47 on the frame. Above this guide a handwheel 48 is provided, the hub of which is threaded on the screw 45. Evidently, by rotating this hand-wheel 43 the corresponding retainer plate Hi can be raised or lowered.

In order to enable the apparatus to be used as a hopper for carrying concrete and for distributing it onto the subgrade, I prefer to provide the machine with a removable forward plate 49 (see Fig. 4) the ends of said plate being guided in guide channels 59 mounted on the end plates 2. When this plate 49 is in position it cooperates with the vibrator shoe 3 to substantially close the hopper at its forward side, and when the strike oif plate 27 is in its lowest position, this strike-off plate will come in contact with the rounded rear portion of the plate 8 so as to close the hopper. This arrangement enables the machine to be handled like a large bucket or hopper to move it over to a point where it can be filled froma concrete mixer and then returned to the point where the concrete is being laid. After being returned, the air cylinders 49 would be controlled so as to raise the rear hopper plate 29, thereby raising the strike-off plate 2'! to a slightly elevated position as indicated by the dotted lines 21a in Fig. i. This will withdraw the strike-off plate from the vibrator shoe 3, and

enable the concrete to pass through the opening which will then be formed at the point As the concrete passes down through the outlet at 5 l it will be subjected to vibratory impulses from the shoe and from the strike-off plate.

Any suitable means can be employed for attaching the machine to tackle or cables for moving it about. In Fig. 3 I illustrate some such arrangement in which the machine is provided with a hitch 52 above, with a ring 53 attached to a short drag line 54 extending down from a trolley 55 running on an overhead cable 56. The trolley is attached between cables 51 and 58, which enable it to be pulled to and fro on the taut cable 56. When the machine is operating to place concrete already dumped on the subgrade, the vibrator device 3 may be removed if desired. In order to enable this to be done, the ends of the vibrator device are supported on brackets 3a secured to end gusset plates 3b by bolts 36.

In order to enable the vibrator device 3 to be adjusted up or down when it is to be used, the bolts are preferably mounted in inclined slots 3d in the gusset plates 322. These bolts may be loosened if desired, to permit the vibrator 3 to move up and down freely on a rough subsurface.

Compressed air for operating the mechanism of the machine may be supplied from a compressed air reservoir 59 mounted on one end of the machine and provided with a pipe system 60 including suitable valves ill for enabling the flow of the compressed air to be controlled through the different motors or air cylinders.

In the operation of the machine as illustrated in Fig. 1, the machine is advanced over dumped concrete 6 already dumped on the base or subgrade. As the machine advances the vibrating shoe 3 passes through the laid concrete and subjects it to vibratory impulses. The retainer plates [8 at the ends of the machine also retain the concrete at these points and subject it to vibratory impulses due to the rotation of the shafts IS.

The machine can be advanced by a cable or by an automobile or tractor pushing it from the rear, as illustrated in Fig. 1. In any case the skids l1 assist in supporting the forward end of the machine and keep the machine upright.

When the plate 49 is in place, as illustrated in Fig. 4, the machine is transformed into a hopper. It can then be handled by cables, as illustrated in Fig. 3, to run it to a filling point and then return it. When using the machine as a hopper in this way, the rear plate 29 (see Fig. 4) is moved down to its most depressed position where the strike-off plate will cooperate with the vibrator shoe to close the space between the lower ends of the plates 29 and 49.

After the machine is returned to the point where the concrete is to be laid, the air cylinders 40 will be operated to raise the strike-01f plate to an elevated position to determinethe level of the upper face of the laid concrete. This is illustrated by the dotted lines 21a in Fig. 4.

The application of vibration to the laid concrete at the strike-off plate through a convex face instead of a fiat plate lying on top of the concrete, is most advantageous for several reasons, one of which is that the vibration is applied to the laid concrete along a relatively narrow strip or zone, which gives an increased condensing effect in the mass of concrete just below the strike-01f plate; and, furthermore, by applying the Vibrations on a relatively narrow strip, I reduce the tendency to form a smooth surface on the upper face of the concrete, the concrete rising more or less irregularly behind the strikeoff plate. This is very advantageous because it facilitates forming a good bond with an upper layer of top surfacing or concrete laid on later.

It is understood that the embodiment of the invention described herein is only one of the many embodiments this invention may take, and I do not wish to be limited in the practice of the invention, nor in the claims, to the particular embodiment set forth.

What I claim is:

1. In a concrete laying machine for laying concrete already dumped on a subgrade, the combination of a frame adapted to be advanced over the subgrade, substantially vertical end plates at the ends of the frame, a transverse shoe supported on the frame between the end plates and located at the subgrade on which the concrete is being laid, means for advancing the machine to cause the shoe to pass under and through the concrete, so that the previously dumped concrete flows down past the rear of the transverse shoe, means for imparting vibratory impulses to the said shoe, a rear plate extending between the end plates, a strike-off plate located adjacent the lower end of the rear plate having means for leveling off the laid concrete, means for imparting vibratory impulses to the strike-off plate, and a removable forward plate mounted between the end plates and cooperating with the rear plate to form a hopper for concrete.

2. In a concrete laying machine for laying concrete on a subgrade, the combination of a frame adapted to be advanced over the subgrade, substantially vertical end plates at the ends of the frame, a transverse shoe supported between the end plates and located at the subgrade on which the concrete is being laid, means for imparting vibratory impulses to the said shoe, a rear plate extending between the end plates, a strike-oil plate located adjacent the lower end of the rear plate having means for leveling off the laid concrete, means for imparting vibratory impulses to the strike-off plate, a removable forward plate mounted between the end plates and cooperating with the rear plate to form a hopper for concrete, and means for mounting the strike-01f plate so that it is capable of adjustment downwardly to close the bottom of the hopper formed for the concrete between the forward plate and the rear plate.

3. In a concrete laying machine for laying concrete on a subgrade, the combination of a frame adapted to be advanced over the subgrade, a strike-off late supported on the frame at one edge only with its other end bent rearwardly and upwardly and unsupported, means mounted on the said rear end for imparting vibratory impulses to the same, said strike-01f plate having a convex lower portion connecting the same with its rear end and forming a vibrating plate presenting a convex face for engaging and for leveling off and consolidating the laid concrete.

4. In a concrete laying machine for laying concrete on a subgrade, the combination of a frame adapted to be advanced over the subgrade, substantially vertical end plates at the ends of the frame, a transverse plate mounted between the end plates with its lower end bent upwardly and rearwardly and unsupported, means mounted on the said rear end for imparting vibratory impulses to the same, said transverse plate having a convex lower portion connecting the same with its rear end and forming a vibrating strikeoff plate presenting a convex strike-off face to the concrete for leveling off and consolidating the laid concrete, and means for raising and lowering the transverse plate, enabling the same to be raised toward either end while depressed at the other end to form a laterally inclined upper face for the laid concrete.

5. In a concrete laying machine for laying concrete on a subgrade, the combination of a frame adapted to be advanced over the subgrade, substantially vertical end plates at the ends of the frame, a transverse plate separate from the end plates and mounted between the end plates with its lower end bent upwardly and rearwardly and unsupported, means mounted on the rear end of the same for imparting vibratory impulses to the said transverse plate having a convex uner portion connecting the same with its rear end and forming a vibrating strike-ofi plate presenting a convex under face for leveling off and consolidating the laid concrete.

6. In a concrete laying machine, the combination of a frame having substantially vertical end plates, retainer plates movably. mounted at the end plates to extend down from the lower edge of the end plates to a point adjacent the level of the subgrade, and means for imparting vibratory impulses to the retainer plates.

7. In a concrete laying machine, the combination of a frame having substantially vertical end plates, retainer plates movably mounted at the end plates to extend down from the lower edge of the end plates to a point adjacent the level of the subgrade, means for imparting vibratory impulses to the retainer plates, skids attached respectively at each end of the machine to run on the subgrade and support the forward end of the machine, a strike-on" plate for leveling off the concrete, and a transverse roller to the rear of the strikaoif plate having means on its periphery for penetrating the upper face of the laid concrete to form pockets therein.

8. In a concrete laying machine, the combination of a frame having substantially vertical end plates, a transverse shoe supported between the end plates and located at the subgrade on which the concrete is being laid, and hitching means connected with the frame above for supporting the same from an overhead cable, and for enabling a drag cable to be attached to the frame to pull the same along the overhead cable, a rear plate between the end plates with a strikeofi plate at its other end, and a removable front plate to cooperate with the rear plate to form a hopper for supporting concrete.

9. In a machine for placing concrete on a base surface, the combination of a frame to be advanced over the base surface and having end plates extending in a front and rear direction with respect to the direction of advance, end retainer plates adjacent the end plates to come into contact with the concrete between the end plates, and means for vibrating the end retainer plates.

10. In a concrete laying machine, for operating on concrete dumped in advance of the ma chine, the combination of a frame, a transverse shoe located at the subgrade on which the concrete has been dumped, means for advancing the machine so that the shoe penetrates, and plows forward under the laid concrete and so that the concrete flows first upwardly and then downwardly behind the rear end of the shoe as the shoe advances, means for imparting rapid vibratory impulses to the said shoe to condense the concrete, and a strike-off plate located to the rear of the shoe for leveling oif the laid concrete.

11. In a concrete laying machine for leveling off concrete already dumped on a subgrade, the combination of a frame adapted to be advanced over the subgrade, a transverse shoe connected with the frame and located at the subgrade on which the concrete is being laid, means for advancing the machine to cause the shoe to penetrate and pass through and under the dumped concrete so that the concrete flows down behind the rear end of the shoe as the shoe advances, means for imparting rapid vibratory impulses to the said shoe to condense the concrete, a transverse plate, a strike-off plate located adjacent the lower end of the transverse plate having means for leveling off the laid concrete back of the transverse shoe, and means for imparting vibratory impulses to the strike-01f plate.

12. In apparatus for laying concrete already dumped on a subgrade, the combination of an elongated shoe to be advanced through the concrete, said member extending transversely with respect to the direction of advance of said shoe, said shoe located at the subgrade and having an inclined forward face elevated toward its rear end so that when advanced, the forward edge of the shoe plows through the dumped concrete, causing the same to move relatively up the said inclined face of the shoe and fall to the rear of the shoe; and means for imparting vibratory impulses to the said shoe.

13. In apparatus for laying concrete already dumped on a subgrade, the combination of a frame, an elongated member carried thereby to be advanced through the concrete, said member extending transversely with respect to the direction of advance, located at the subgrade, and having an inclined forward face elevated toward the rear so that when advanced, the forward edge of said member plows through the dumped concrete, causing the same to move relatively up the said inclined face and fall to the rear of said transverse member, a strike-off plate rigidly attached to the frame and located to the rear of the member, having a convex form on its under side for striking oi the concrete to a level while contacting a relatively narrow zone of the concrete at the strike-off level, and means for imparting vibratory impulses to the said strikeoif plate.

lei. In apparatus for laying concrete, the combination of strike-off means to be advanced over the concrete to strike off its upper surface, retainer plates located toward the sides of the apparatus for confining the concrete, and means for applying rapid vibratory movement to the said retainer plates.

15. In apparatus for placing concrete on a base surface, the combination of a compacting plate having an upwardly inclined forward extension to ride upon and crush down the concrete under the same, the bottom portion of said plate being curved, and its rear portion unsupported and extending away from the concrete so that the bottom of the compacting plate presents a curved relatively narrow zone of contact to the concrete on a relatively narrow transverse zone, and a vibration device for imparting rapid vibratory impulses to the strike-off plate at said narrow zone.

16. In concreting apparatus to be advanced over and upon concrete deposited upon a base surface, the combination of a plate member substantially free to bend and spring, having an upwardly inclined forward extension with respect to its direction of advance to press upon and crush down the concrete, and having a relatively narrow bottom zone for applying a concentrated pressure downward upon the concrete, said plate member also having an upwardly inclined rearward extension, means for supporting and advancing said plate member, and means connected with the upwardly inclined rearward extension of the plate member, for imparting rapid vibratory impulses to the said bottom zone of said plate member.

17. In a concrete laying machine for laying concrete upon a subgrade, the combination of a frame adapted to be advanced over the subgrade, a strike-off plate supported on the frame at one edge only with its other end bent upwardly and unsupported, means mounted on the said upwardly bent end for imparting vibratory impulses to the same, said strike-off plate having a convex lower portion connecting the same with said upwardly bent end and forming a convex vibrating face for striking off, for leveling ofi, and for consolidating the laid concrete, and means for raising or lowering said strike-off plate to hold the same at difierent levels.

18. In a concrete placing machine, the combination of a strike-off plate consisting of a smoothly curved plate having a curved portion at its extreme lower end with an upwardly projecting extension therebeyond, said curved portion being in contact with the concrete along a line substantially coinciding with an element of the curved portion of the plate, means for supporting the plate along one side only, means for applying vibratory impulses to the curved plate at the opposite unsupported side, and means for holding the strike-off plate at a fixed level as it passes over the concrete.

19. In a concrete laying machine for laying concrete already dumped on a subgrade, the combination of a transverse shoe located at the subgrade under the concrete lying on the subgrade and extending transversely to the direction of advance of the machine, said shoe being of wedgeshape cross-section and having a chamber within the same, means for forcing the shoe through the concrete with its small end disposed forwardly with respect to the direction of its advance through the concrete, and a vibrator shaft extending longitudinally of said shoe within the same, with means for rotating the shaft to impart vibratory impulses to the shoe.

HOMER M. HADLEY.

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