The present invention relates to a device for smoothing and flattening newly laid concrete or a similar plastics mass, comprising a beam structure having connect¬ ed thereto a rotary type oscillator which is intended to impart an oscillatory movement to the beam structure when said structure is passed over a concrete surface or the sur- face of a like mass.

Devices of this kind, in which the beam structure normally comprises a double-beam, are used when laying con¬ crete floors or other horizontal surfaces, to smooth and flatten the concrete, subsequent to having optionally vi- brated the concrete internally with the aid of tube vibra¬ tors. The beam is vibrated while drawing it over the sur¬ face of the concrete, while resting on the edges of the mould or on specially constructed tracks.

The beam structure, which acts to vibrate the sur- face of the concrete, is given a vibratory movement in the vertical plane. Among other things, this tends to force the cc-.crete up behind the beam structure, especially when a large amount of concrete is pushed in front of the beam. Further, such a beam structure must be advanced at a con- stant, well adapted speed, since if the beam should, for example, be stopped there is obtained a pumping action which causes fine material in the concrete to migrate to¬ wards the surface thereof.

It has also been proposed to arrange the vibraor so that its rotary axis is vertical. In this case, the os¬ cillations are in the horizontal plane, which reduced the tendency of the concrete to press up behind the beam struc¬ ture. One disadvantage with this embodiment, however, is that the beam structure is subjected to an obliquely di- rected advancing force which makes the work difficult to carry out and has a negative effect on the final result.

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The aforementioned problems are eliminated when the beam structure is vibrated solely in the direction of its longitudinal axis, i.e. with no vibration components acting in either the vertical plane or the forward direction of movement of the beam structure. Such vibratory movement has a minimum negative effect on the concrete, and produces a very smooth and flat surface. Moreover, when vibrating the beam in the direction of its long axis, it is not necessary to advance the beam at a constant speed; the beam can even be stopped, without creating any pumping wffect or result¬ ing in any negative effect.

In the Swedish Patent Specification No. 7216244-9 there is described a device which is said to cause vibra¬ tory beams to oscillate in a substantially horizontal direc- tion. This device, however, requires two beams mutually joined together by means of spring elements. The use of a crank element illustrated in the Figures of said Patent Specification causes the shaft of the motor to be eccentri¬ cally loaded, causing the beam structure, to which the motor is rigidly connected, to be subjected to a vibratory component in the vertical plane as well. As a result of the angle of attack of the crank relative to thp second beam, said second beam will also probably be imparted a vibra¬ tion component in the vertical plane. It is stated in the Patent Specification that the crank element can be changed for a rotary-type vibrator. This would result in the same problems as those encountered with the previously known devices.

In the known devices, the oscillator is arranged centrally of the beams, which gives rise to undesirable punctiloading of the beam, -rendering it difficult to align the beams and also affecting the vibratory pattern of the beams.

The prime object of the present invention is to produce a device of the kind mentioned in the introduction, with which all the aforementioned problems are eliminated

by enabling the beam to be oscillated or vibrated by means of a rotary-type vibrator substantially solely in the longi tudinally direction of the beam, without imparting to the beam any appreciable vibration component acting in the vertical plane.

The aforementioned object is achieved in accordance with the invention by arranging the vibrator at one end of the beam structure, with the axis of rotation substantially horizontal and substantially at right angles to the longi- tudinal axis of the beam structure; and by resiliently mounting the vibrator in a manner such that substantially only those vibrations acting in the longitudinal direction of the beam structure are transmitted thereto, while vibra¬ tions in the vertical plane are substantially absorbed by the spring mounting.

In order to achieve the best effect, the vibrator is preferably located externally of one end of the beam structure and substantially on a ^' level with said structure. In this respect, the axis of rotation of -.the vibrator is preferably located substantially on a level with a horizon¬ tal plane passing through the centre of the beam structure. This eliminates all vibrational components in the vertical plane.

In accordance with a preferred embodiment, the vi- brator is mounted on the end of at least one leaf spring, the other end of which is connected to the beam structure, said spring being arranged so that it is resilient in the vertical plane but substantially stiff in the direction of the longitudinal axis of the beam structure. Thus, the spring transmits vibrations in the long direction of the beam structure, while vibrations acting in the vertical plane are absorbed as spring movement. The aforementioned leaf spring or springs is or are suitably connected sub¬ stantially in the horizontal centre plane of the beam structure.

In order to obtain the best psosible pattern of vibrations, it is also preferred that the beam stucture

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comprises a highly stiff single beam, and that the leaf spring projects into a central cavity in the beam and is connected to the walls thereof. A single beam is highly advantageous, both with respect to aligning the beam and to cleaning the same. To obtain the best smoothing and flattening effect, the bottom, active surface of the beam is suitably provided with steps and intermediate inclined surfaces. A vibrator according to the invention is very silient in operation relative to known devices, firstly because the device has the form of a single unit and se¬ condly because the vertically acting vibrations have been eliminated.

The invention will now be described in more detail with reference to the accompanying drawings. Figure 1 is a side view, partly in section, of one end of a smoothing beam according to the invention with associated vibrator.

Figure 2 is a horizontal view of the device shown in Figure 1. Figure 3 is a cross-sectional view of a preferred embodiment of a single-beam structure.

In Figures 1 and 2 the reference 1 identifies one end of a smoothing beam, used to smooth and flatten a con¬ crete layer 2. Mounted on one end of the beam is a slide shoe 3, which in the illustrated embodiment co-acts with a mould edge _. 4. Corresponding devices are located on the other end (not shown) of the beam. The slide shoes 3, or like devices, may be vertially adjustable, enabling, for example, the surface of the concrete to be higher than the mould edges. In addition to the mould edges, the beam may be guided by air tracks or the like.

The reference 5 identifies a motor vibrator having an eccentric weight 6 arranged to rotate about a horizontal axis, thereby to impart circular oscillatory movement to the vibrator. The vibrator 5 is mounted on the outer ends of two leaf springs 7 and 8, the other ends of which are inserted into the beam and fixedly connected to the walls

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thereof by means of bolts 9. The inner ends of the leaf springs 7 and 8 are held at a constant mutual distance apart, by means of bolts 10 and intermediate distance sleeves 11. As will be seen from Figures 1 and 2, the leaf springs 7 and 8 are so oriented that they spring in the vertical direction but are substantially rigid in the lon¬ gitudinal direction of the beam. This means that when the eccentric weight 6 rotates, vibrations generated by the vibrator 5 in the vertical plane will be absorbed as a spring movement of the leaf springs 7 and 8, while vibra¬ tions generated by the vibrator in the horizontal plane will be transmitted to the beam 1, causing said beam to vibrate in the longitudinal direction. Since no appreciable vertically acting vibration is imparted to the beam 1, the beam will execute a substan¬ tially pure sawing movement. Since, in this way, no cement is forced up behind the beam, the result is an extremely smooth surface. Further, the work entailed can be carried out more, easily, since it is not necessary to advance the beam at a constant rate. For example, when it is necessary to roughly smooth the concrete surfac or remove excess concrete from in front of the beam, or v/hen needing to clean the tracks along which the device slides, the device can be stopped completely without negative effect.

Because the vibrator is mounted on one end of the beam structure, there is no troublesome spot loading on the centre of the beam, which, among other things, facili¬ tates alignment of the beam and enables a cleaner vibra- tion pattern to be obtained. When the vibrator is arranged externally of the end of the beam, the vibrator can be mounted at such a level that its rotary axis is located substantially on a level with a horizontal plane passing through the centre of the beam, which eliminates the risk of the beam being subjected to vertical oscillations, as a result of the forces generating the longitudinal vibra¬ tion of the beam being transmitted thereto at a certain angle.

In accordance with the invention, there is suitably used a relatively wide unitary beam structure 14 having the cross-section shown in Figure 3. Such a beam structure is extremely stiff and enables beams to be produced in long lengths. Further, alignment of a unitary beam structure can be effected far more readily than previously used double- beam structures, and the pattern of vibrations obtained with the single-beam structure is cleaner than those obtain ed with the double-beam structure. The single-beam structur also affords important advantages with respect to cleaning. The bottom, active smoothing surface of a single- beam structure 14 shown in Figure 3 is suitably provided with sharp steps 12 and intermediate inclined surfaces 13, as shown in the Figure. This provides a better smoothing result than one single, flat working surface. If so desired, the beam can be slightly inclined, or constructed so that its leading edge is somewhat higher than the trailing edge, the concrete surface being worked successively by the different steps, to obtain a given final height and smoothness.

The described embodiment is not limitive, but can be modified in several respects within the scope of the claims. For example, the number of leaf springs used in the embodiment according to Figures 1 and 2 can be varied as desired. The leaf springs may also be replaced by other spring elements able to absorb vertical vibrations generat¬ ed by the vibrator 5 and permitting horizontal vibrations to be transmitted to the beam structure.