[0001] The invention relates to a machine for the smoothing of freshly poured concrete surfaces,
consisting substantially of a horizontally displaceable frame with fastening and mounting
points for
(a) two sets of trowels, each set being attached perpendicularly to the end of a rotating
shaft, which trowels can be made to work the freshly poured concrete surface in a
rotary motion, the said shaft being capable of a tilt from the vertical, whilst the
effective ranges of the trowels overlap;
(b) an engine drive capable of making the sets of trowels rotate synchronously and
in opposite directions;
(c) means of positioning the rotating shafts with at least one operating lever in
a desired tilt relative to the vertical;
(d) a seat from which the lever(s) and the engine drive can be operated; and
(e) means of vertically adjusting each set of trowels relative to the frame.
[0002] The machine is characterized in that it is self-propelled and that the operator
can occupy a seat thereon and move the machine in a direction which is required for
the smoothing of the concrete surface to be worked.
[0003] A machine of this type is known from U.S. Patent No. 4 046 484. In it, the propulsion
and the concurrent smoothing of a freshly poured concrete surface take place by slightly
tilting the sets of rotating trowels symmetrically and/or systematically relative
to one another round their axis of rotation. Figures 6 - 11 of U.S.P. 4 046 484 show
that in this manner a forward, backward and lateral or rotary movement can be accomplished.
This design permits a large concrete surface to be treated quickly, indeed much faster
than can be done with a manually propelled rotating set of trowels which involves
the necessity of "obliterating" footsteps on the fresh concrete.
[0004] The aforesaid known machine has two disadvantages:
(a) both rotating shafts are linked according to a certain system and are adjustable
in all directions relative to the vertical. Now it has been found that this design
is unduly complex and that it suffices to have the shaft of one set of trowels only
adjustable relative to the vertical according to a plane crosswise to the forward
or backward movements, whereas only the other shaft is adjustable in all positions
relative to the vertical;
(b) between the drive engine and the rotating shafts of the sets of trowels there
is no clutch provided which slides into engagement only at a predetermined torque
to be transmitted. Only the presence of such a clutch precludes the risks of the trowels
stalling and the engine cutting out and ensures a consistently optimum operation of
the smoothing trowels.
[0005] The machine described in the introductory paragraph is therefore characterized in
that
(a) one of the driving shafts of the two sets of trowels is adjustable by means of
a lever relative to the vertical in a plane crosswise to the rectilinear forward movement;
(b) the second driving shaft of the two sets of trowels is adjustable by means of
a second lever in any desired position relative to the vertical; and
(c) between the drive engine and the mechanism of the rotating shafts of the two sets
of trowels a clutch is provided which slides into engagement at a certain predetermined
torque to be transmitted.
[0006] It has been found that the machine instantly works with optimum efficiency as soon
as the clutch engages. The propulsion and the rate thereof (also in reversing) are
controlled by the simultaneous manipulation of the two levers (or control sticks),
and a lateral or rotary movement can be performed by shifting the appropriate lever
to the desired position. The velocity of the movements may, in addition, be influenced
by the position of the other lever.
[0007] The invention will now be elucidated with reference to the drawings which represent
the machine in a simplified form, of which
Figure 1 is a side view, and
Figure 2 is a front view according to arrow A of Figure 1.
[0008] All component parts are attached to a frame 1, supporting a seat 2 for the operator
and a drive engine 3 with fuel tank 4. Each set of trowels 5, 5', 5'' and 6, 6', 6''
is horizontally fitted to vertically adjustable shafts 7 and 8, respectively. These
shafts are driven through transmission gear cases 9 and 10, respectively, whereby
the horizontal rotation of shaft 11 is converted into the vertical rotation. Shaft
11 actuates the gears 9 and 10 through toothed drive belts 12 and 13, respectively,
which are provided with tightening pulleys. This set-up ensures synchronous operation
of the two sets of trowels, whilst leaving scope for some measure of operational mobility.
It is this embodiment which must be considered largely essential for the invention
since a smooth adjustability while preserving the desired synchronization is imperative.
[0009] Shaft 11 is driven by the engine 3 through a belt 14 looped round a pulley 15 and
through an adjustable centrifugal clutch 16.
[0010] The two sets of trowels 5, 5', 5'' and 6, 6', 6'' are vertically adjustable together
with their shafts 7, 8 and transmission gear cases 9, 10 by means of set screws 17
and 18.
[0011] The set of trowels 6, 6', 6'' can be tilted from the vertical in the plane of the
view according to Figure 1 by means of a control lever 20 to be operated from the
seat 2. This is effected by moving a lever 21 through a tie rod 22 with a fixed hinge
point 21', which movement is transmitted with the aid of a tie rod 23 through a hinge
point to a rocker shaft 24 which can tilt the case 10 with shaft 8 and trowel blades
6, 6', 6'' perpendicularly to the plane of projection of Figure 2. The arrangement
is indicated somewhat schematically, because several embodiments of this mechanism,
other than the one here specified, can be conceived without detracting from the essence
of the invention. One conceivable mode of transmission could utilize a Bowden cable.
[0012] The same mechanism is provided for the other set of trowels 5, 5', 5'', comprising
control lever 25, lever 26, tie rods 27 and 28 and rocker shaft 29, for tilting the
case 9, shaft 7 and the trowel blades 5, 5', 5'' in the aforesaid plane.
[0013] The control lever 25 can, in addition, be shifted in a direction perpendicular to
the one first mentioned. A shift in this direction gives rise to the activation of
a shaft 30, which makes it possible to tilt case 10, shaft 7 and the trowels 5, 5',
5'' in a plane parallel to that of the projection according to Figure 2. To this end,
a rod 31 which is linked to an extension of the control lever 25 acts in concert with
a lever 33 which hinges on shaft 32 and which is connected to case 9. Again, the system
of this shift mechanism is not compulsorily bound up with the embodiment here specified,
as stated hereinbefore.
[0014] An essential feature of the invention is that the means of adjustment of the shift
mechanisms for the trowels to be positioned are not interconnected and are not movable
relative to one another according to a systematic pattern of motions, whilst nonetheless
the trowels rotate synchronously vis-à-vis one another in a smooth and adjustable
mode of operation through the toothed belts 12 and 13 on motive power derived from
the common shaft 11. The design incorporates a simple operating system for a set of
trowels 6, 6',6'' and only a straightforward extension for the more complex range
of movements to be performed by the set of trowels 5, 5', 5''. A further essential
feature of the invention is that the clutch 16, in this embodiment a centrifugal clutoh
, drives the trowels synchronously, but not until a predetermined torque to be transmitted
has been attained.
1. A machine for the smoothing of freshly poured concrete surfaces, consisting substantially
of a horizontally displaceable frame with fastening and mounting points for
(a) two sets of trowels, each set being attached perpendicularly to the end of a rotating
shaft, which trowels can be made to work the freshly poured concrete surface in a
rotary motion, the said shaft being capable of a tilt from the vertical, whilst the
effective ranges of the trowels overlap;
(b) an engine drive capable of making the sets of trowels rotate synchronously and
in opposite directions;
(c) means of positioning the rotating shafts with at least one operating lever in
a desired tilt relative to the vertical;
(d) a seat from which the lever(s) and the engine drive can be operated; and
(e) means of vertically adjusting each set of trowels relative to the frame,
characterized in that
(a) one of the driving shafts (18) of the two sets of trowels (5, 5', 5'' and 6, 6',
6'') is adjustable by means of a lever relative to the vertical in a plane crosswise
to the rectilinear forward movement;
(b) the second driving shaft (17) of the two sets of trowels is adjustable by means
of a second lever (25) in any desired position relative to the vertical; and
(c) between the drive engine (3) and the mechanism of the rotating shafts (7,8) of
the two sets of trowels (5, 5', 5'' and 6, 6', 6'') a clutch (16) is provided which
slides into engagement at a certain predetermined torque to be transmitted.
2. A machine according to claim 1, characterized in that the clutch (16) is a centrifugal
clutch.
3. A machine according to claims 1 and 2, characterized in that the two driving shafts
(7,8) of the sets of trowels (5, 5', 5'' and 6, 6', 6'') are operated synchronously
through a transmission mechanism (9,10) by self-tightening toothed belts (12, 13)
on motive power derived from a common actuation shaft (11) connected after the clutch
(16).
4. A machine according to any one of the preceding claims, characterized in that the
shaft (8) which is movable in one direction can be adjusted by the control lever (20)
and the assembly of rods which are hinge-jointed thereto besides being mutually hingeable
(22, 21, 23) and the rocker shaft (24) through the gear case (10) and that the shaft
(7) which is movable in two directions relative to the vertical position can be adjusted
in one direction by the control lever (25) and the first hinge-jointed assembly of
rods (24, 26, 31) and the shaft (30), whilst it can also be adjusted in a direction
perpendicular thereto through an additionally connected rod (31), the lever (33) and
the gear case (9).
5. A machine according to any one of claim 1-3, characterized in that the gear case
(10) with the shaft (8) can be tilted in a vertical plane by means of a Bowden cable
and that the case (9) with the shaft (7) can be tilted in two planes perpendicular
to one another by means of two Bowden cables.
6. A machine according to any of the preceding claims, as described and elucidated
with reference to a drawing.