UNIT FOR TRANSMITTING ROTARY MOTION TO THE OPERATING ELEMENTS OF TROWELING MACHINES

Technical Field

The present invention relates to a unit for transmitting rotary motion to the operating elements of troweling machines. Background Art

Units for transmitting rotary motion to the operating elements of troweling machines are known which have a driving shaft that can be connected to motor means, for example of the type of a conventional electric motor or internal combustion engine.

The driving shaft is connected, by way of interconnection means, for example of the type with gears, belts mounted on pulleys or chains that mesh with sprockets, to at least one driven shaft that can be associated with the operating elements of a troweling machine. The operating elements are constituted generally by a rotating disk provided with blades arranged radially to lay the concrete and therefore to provide floorings and the like.

In these transmission units it is further known to use clutch devices, and particularly expansion clutches, which are adapted to activate/deactivate at a preset rotation rate of at least one between an input portion or an output portion of the driving shaft that is imparted by the motor means.

The rotation imposed on the driving shaft is converted, by way of the interconnection means, into the rotation of the driven shaft, which in turn produces the rotation, for example conveniently reduced by a reduction unit, to the operating elements of the troweling machine.

However, these known types of transmission unit are not free from drawbacks, which include the fact that the torque delivered by the motor is always constant and does not consider the different operations required by such machine. In particular, the machine is generally used for two different

operations: the first one, known as troweling, which requires a high torque delivered by the motor means to push the operating elements on the material to be troweled; the second one, so-called polishing/smoothing, seeks to finish the previously troweled material and therefore requires a lower torque delivered by the motor means.

In known types of troweling machine, the fact that the torque delivered by the motor means is constant determines a power of such motor means that must be overestimated in order to perform the troweling step; this fact therefore leads to low efficiencies of such machine, which accordingly has high consumptions as well as a high environmental impact. Disclosure of the Invention

The aim of the present invention is to eliminate the above-mentioned drawbacks of the background art, by providing a unit for transmitting rotary motion to the operating elements of troweling machines that allows to optimize the use of such machine on the basis of the processing operations required, with particular reference to the operations described above of troweling and polishing/smoothing.

Within this aim, an object of the present invention is to provide a troweling machine that delivers a high torque upon use for troweling operations and a reduced torque for polishing/smoothing operations.

Another object of the invention is to reduce the consumption of such troweling machines and at the same time reduce the environmental impact, decreasing the pollution caused by the motor means of such machines.

Another object of the present invention is to provide a device that is simple, relatively easy to provide in practice, safe in use, effective in operation, and of relatively low costs.

This aim and these and other objects, which will become better apparent hereinafter, are achieved by the present unit for transmitting rotary motion to the operating elements of troweling machines, which comprises at least one driving shaft that can be associated with motor means, at least one

driven shaft that can be associated with operating elements of a troweling machine, interconnection means which are interposed between said driving shaft and said driven shaft to transmit the rotary motion between them, characterized in that it comprises means for varying the rotation rate of said driven shaft which cooperate with said interconnection means. Brief description of the drawings

Further characteristics and advantages of the present invention will become better apparent from the following detailed description of a preferred but not exclusive embodiment of a unit for transmitting rotary motion to the operating elements of a troweling machine, illustrated by way of non-limiting example in the accompanying drawings, wherein:

Figure 1 is a front sectional view of a transmission unit according to the invention;

Figure 2 is a side view of the unit of Figure 1 ; Figure 3 is a sectional view, taken along the line H-II, of a detail of

Figure 2. Ways of carrying out the Invention

With reference to the figures, the reference numeral 1 generally designates a unit for transmitting rotary motion to the operating elements of troweling machines.

The unit 1 comprises at least one driving shaft 2, which can be associated with motor means, such as for example an internal combustion engine or an electric motor or the like, which is not shown in the figure since it is of a known type. The unit 1 comprises at least one driven shaft 3, which can be associated with operating elements of a troweling machine, for example, a rotating disk provided with blades for troweling, polishing/smoothing floorings and the like.

The driving shaft 2 and the driven shaft 3 are, in a preferred embodiment, arranged with substantially parallel longitudinal axes;

however, different spatial arrangements of such driving shaft and driven shaft are not excluded.

The unit 1 further comprises interconnection means which are interposed between the driving shaft 2 and the driven shaft 3 to transmit rotary motion between them.

Particularly, for the purposes of the present invention, the unit 1 comprises means 4 for varying the rotation rate of the driven shaft 3, which cooperate with the interconnection means.

Advantageously, the variation means 4 comprise at least one mechanical speed shift, which is associated with at least one between the driven shaft 3 and the driving shaft 2.

In the particular embodiment shown in the figures, the mechanical speed shift is associated directly with the driven shaft 3.

The interconnection means comprise at least one first driving transmission element 5 and one first driven transmission element 6, which are mutually connected rotationally to provide a first gear ratio between the driving shaft 2 and the driven shaft 3.

The first driving transmission element 5 is advantageously keyed onto the driving shaft 2, for example by connection with a first key 7 or tab. The first driven transmission element 6 is instead freely associated on the driven shaft 3.

In particular, the first driven transmission element 6 is jointly associated, for example by way of first threaded elements 8, with a first hub 9, which is coupled with play to the driven shaft 3 and is coaxial thereto; a first bearing 10 is interposed between the driven shaft 3 and the first hub 9 and is locked axially by first axial retention means 1 1 , for example of the type of a snap ring or the like, for free rotary and joint translational association of such first driven transmission element with the driven shaft 3.

For the purposes of the present invention, the interconnection means further comprise at least one second driving transmission element 12 and

one second driven transmission element 13, which are mutually connected rotationally to provide a second gear ratio, which is different from the first gear ratio between such driven shaft and driving shaft.

The second driving transmission element 12 is keyed onto the driving shaft 2, for example by connection with a second key 14 or tab.

The second driven transmission element 13 in turn is associated freely on the driven shaft 3.

In particular, the second driven transmission element 13 is jointly associated, for example, by way of second threaded elements 15, with a second hub 16, which is coupled with play to the driven shaft 3 and is coaxial thereto; a second bearing 17 is arranged so that it is interposed between the driven shaft 3 and the second hub 16 and is locked axially by second axial retention means 18 for free rotary and joint translational association of such second driven transmission element with the driven shaft 3.

The driven shaft 3, in the embodiment shown in the figures, comprises an actuation shaft 19, which is axially hollow and is jointly associated with a transfer shaft 20, which is formed coaxially and internally thereto, for the transfer of the rotary motion to the operating elements of the troweling machine.

The actuation shaft 19, in the embodiment shown, is keyed by means of a third key 21 to the transfer shaft 20.

The first and second driven transmission elements, respectively 6 and 13, are freely associated externally with respect to the actuation shaft 19. The variation means 4 comprise at least one engagement element that is jointly rotationally connected to the driven shaft 3 and can be activated for the transfer of the rotary motion selectively of at least one between the first or second driven transmission elements, respectively 6 or 13, to such driven shaft. The engagement element comprises at least one sleeve 22, which is

associated for joint rotation and free translational motion with the driven shaft 3, particularly with the actuation shaft 19, which is interposed directly between the first and second driven transmission elements, respectively 6 and 13. In particular, the actuation shaft 19 comprises means for the sliding along an axial direction of the driven shaft 3, of the type of sets of teeth 23 with a longitudinal axis that is substantially parallel to the longitudinal axis of the driven shaft 3, which are associated with the outer surface of such driven shaft, therefore, of the actuation shaft 19, for example, provided monolithically with such actuation shaft.

The sleeve 22 in turn comprises first slots 24 for accommodating the sets of teeth 23 arranged in an axial direction on the internal surface of the sleeve 22 for contact with the actuation shaft 19 for the axial sliding of such sleeve with respect to the driven shaft 3. The sleeve 22 comprises advantageously at least two rings of front teeth, respectively 25a and 25b, which are mutually axially opposite and can be associated selectively with respective accommodation seats 26a and 26b, which are formed respectively in the first and second driven transmission elements, respectively 6 and 13, for the rotary actuation of the driven shaft 3, respectively according to the first or second gear ratio.

The rings of front teeth 25a and 25b, in the preferred embodiment, are of the type with straight teeth; however, different embodiments in which the rings of front teeth, respectively 25a and 25b, are of the type with inclined teeth or other technical equivalents are not excluded. The unit 1 comprises at least one clutch device 27, which is interposed between at least one input portion 28 of the driving shaft 2, which can be associated with such motor means, and an output portion 29 of such driving shaft, which is coaxial to such input portion.

The output portion 29 is associated with the driven shaft 3, as described above, by way of the interconnection means.

The clutch device 27 is suitable for the mutual disengagement/engagement of the input portion 28 and the output portion 29.

In particular, the output portion 29 advantageously is hollow internally and the input portion 28 is associated for joint translational motion and free rotation, by way of third bearings 30, which are locked axially by third axial retention means 31, inside such output portion.

The first and second driving transmission elements, respectively 5 and 12, are keyed respectively, by means of the keys 7 and 14, externally with respect to such output portion.

The clutch device 27 comprises at least one clutch element 32, which is interposed directly between the input portion 28 and the output portion 29 and is jointly associated either with such input portion or with such output portion. In particular, the clutch device 27 comprises a supporting body 33 of friction masses 34, for example made of sintered material. The supporting body 33 is, for example, hollow internally and is jointly associated externally with respect to the input portion 28, by way of third threaded elements 35 which cooperate with the axial retention means 31, for mutual axial retention; such supporting body is arranged inside the output portion 29.

The clutch device 27 is of the type of a centrifugal or expansion clutch and is adapted to mutually engage/disengage the input portion 28 and the output portion 29 at a preset minimum rotation rate of at least one between such input portion or output portion and, in the embodiment shown in the figures, of such input portion.

In particular, the friction masses 34, arranged on pivots 36, are connected to the supporting body 33 by way of elastic preloading means 37 to determine the minimum rotation rate, as is known to the person skilled in the art.

During the rotary motion of the input portion 28 with a rotation rate that is higher than the minimum rotation rate, due to centrifugal force, the friction masses 34 are moved radially by the centrifugal force produced by the rotation of such input portion, in contrast with the elastic preloading means 37, until they make contact with a contact region 38 of the internal surface of the output portion 29 that faces such friction masses for the rotary actuation, by friction, of such output portion.

The clutch device 27 advantageously is provided at a region of the output portion 29 that forms a box-like enclosure 39, which is adapted to enclose the clutch element 32 in the intermediate region between such input portion and output portion and axially between the first and second driving transmission elements, respectively 5 and 12, ensuring that the unit 1 has good compactness and functionality.

In the preferred embodiment, in order to improve the operations for installing the unit 1, the output portion 29 has a first portion 29a on which the first driving transmission element 5 is keyed which is adapted to mate as described above with the input portion 28; a second portion 29b, which is coaxial to the first portion 29a and of which it is an axial extension, on which the second driving transmission element 12 is keyed as described above; a third portion 29c, which is intermediate between the first and second portion 29a and 29b and is jointly associated with them by way of threaded means 40 and/or welds.

In particular, the third portion 29c is shaped like a cover of the box- like enclosure 39 that is formed by the output portion 29 and accommodates the clutch device 27.

The unit 1 comprises means for activating with translational motion the sleeve 22 intended to transfer such sleeve from at least one first configuration for engagement with the first driven transmission element 6 and a second configuration for engagement with the second driven transmission element 13, at the mutual disengagement between the input

portion 28 and the output portion 29.

The activation means comprise at least one fork-like element 41 , which is associated rotatably with the sleeve 22 by way of threaded means

42 which are fixed to the ends of the fork-like element 41 and are provided with sliding means 43, for example of the type of bearings or others, which are guided along a guide 44 that is formed perimetrically with respect to the sleeve 22.

The activation means further comprise maneuvering means, for example of the type of levers 45 that can be actuated manually or other technical equivalents, which are associated with such fork-like element for the translational motion of the sleeve 22 from the configuration for engagement with the first driven transmission element 6 to the configuration for engagement with the second driven transmission element 13 and vice versa. In particular, the threaded means 42 are such as to transmit the motion of the levers 45 to the walls of the guide 44 for the translational motion of the sleeve 22.

In the preferred embodiment shown in the figures, the first and second driving transmission element, respectively 5 and 12, and the first and second driven transmission element, respectively 6 and 13, are of the type with ring gears.

The interconnection means comprise at least one pair of chains 46 and

47 for mutual rotary connection of the first and second driving ring gears, respectively 5 and 12, to the respective first and second driven ring gears, respectively 6 and 13.

However, different types of embodiment of the interconnection means not shown in the figures are not excluded in which for example the first and second driving transmission elements, respectively 5 and 12, and the first and second driven transmission elements, respectively 6 and 13, are of the type of sprockets or pulleys, and accordingly in the case of pulleys the

interconnection means comprise at least one pair of belts for mutual rotary connection of the first and second driving pulleys respectively to the first and second driven pulleys.

Further, in the preferred embodiment of the unit 1 , the ratio between at least one of the diameters and/or the number of teeth of the first driving pulley and/or ring 5 and of the first driven pulley and/or ring 6 is greater than the ratio between at least one of the diameters and/or the number of teeth of the second driving pulley and/or ring 12 and the second driven pulley and/or ring 13. In the preferred embodiment shown by way of example in the figures, the number of teeth of the first driving ring 5 is in fact "twenty-four", the number of teeth of the first driven ring 6 is "forty-five", and therefore the first gear ratio is 0.53; the number of teeth of the second driving ring 12 is "fourteen", the number of teeth of the second driven ring 13 is "forty", and therefore the first gear ratio is 0.35.

Finally, the unit 1 comprises spacers 48 and 49, respectively associated with the driving shaft 2 and with the driven shaft 3 ; such spacers are, in particular, associated freely for rotation and jointly for translational motion, by way of fourth bearings 50 and 51, with at least one between the input portion 28 or the output portion 29 of the driving shaft 2 and the actuation shaft 19 or the transfer shaft 20 of the driven shaft 3 in order to keep constant the center distance between the driving shaft 2 and the driven shaft 3 in any condition of use of the unit 1.

In particular, the spacers 48 and 49 are jointly connected by way of fixing and adjustment means, which comprise fastening screws 52 that are accommodated in second slots 53 provided in such spacers.

The operation of the unit according to the present invention is as follows.

Once the input portion 28 has been actuated rotationally, by way of the motor means, when it reaches the minimum rotation rate that activates

the clutch device 27 and therefore turns the output portion 29, the first and second driving transmission element, respectively 5 and 12, are turned by such output portion. When the sleeve 22 is engaged with the first driven transmission element 6, the driven shaft 3 has a rotation rate that matches the first gear ratio; when instead the sleeve 22 is engaged with the second driven transmission element 13, the driven shaft 3 has a rotation rate that matches the second gear ratio.

In particular, the rotation rate of the driven shaft 3 and therefore of the operating elements of the troweling machine, for an equal rotation rate of the driving shaft 2, provided that it is higher than the minimum rotation rate, when the sleeve 22 is engaged with the first driven transmission element 6, is higher than the rotation rate of such driven shaft when the sleeve 22 is engaged with the second driven transmission element 13.

In particular, the low gear of the driven shaft 3 and therefore of the operating elements of the troweling machine is such as to ensure that such operating elements have a high torque for performing the actual troweling operations.

The engagement of the high gear of the driven shaft 3 instead is such as to facilitate, for the operating elements, the operations for smoothing/polishing the product previously subjected to troweling operations.

In order to pass from the high gear to the low gear and vice versa it is sufficient to bring the driving shaft 2, particularly the input portion 28, to a rotation rate that is lower than the minimum rotation rate, so as to disengage the clutch device 27 and thus disengage rotationally the output portion 29 from the input portion 28, which can continue to rotate freely without requiring the shutdown of the motor means.

Once the output portion 29 has been disengaged from the input portion 28 and stopped, therefore, the rotary motion of the output portion 29 and of the driven shaft 3 jointly rotationally connected thereto is sufficient

to actuate the translational motion of the sleeve 22, by means of the levers 45, from the configuration for engagement with the second driven transmission element 13 to the configuration for engagement with the first driven transmission element 6 or vice versa. In practice it has been found that the invention achieves the proposed aim and objects, and in particular the fact is stressed that the unit for transmitting rotary motion allows to optimize the use of such machine according to the required processing operations, with particular reference to the operations described above of troweling and polishing/smoothing. Further, the transmission unit according to the invention ensures that the troweling machine delivers a high torque to the operating elements upon use for troweling operations and a reduced torque for polishing/smoothing operations.

The unit according to the present invention further allows to reduce the consumption of such troweling machines and at the same time reduce the environmental impact by reducing the pollution produced by the motor means of such machines and, at the same time, to have a simple structure that is relatively easy to provide in practice, safe in use, effective in operation, and of relatively low costs. The invention thus conceived is susceptible of numerous modifications and variations, all of which are within the scope of the appended claims.

All the details may further be replaced with other technically equivalent elements. In practice, the materials used, as well as the contingent shapes and dimensions, may be any according to requirements without thereby abandoning the scope of the protection of the appended claims.

The disclosures in Italian Patent Application No. MO2008A000066 from which this application claims priority are incorporated herein by reference.

Where technical features mentioned in any claim are followed by reference signs, those reference signs have been included for the sole purpose of increasing the intelligibility of the claims and accordingly, such reference signs do not have any limiting effect on the interpretation of each element identified by way of example by such reference signs.