The invention refers to the field of speed reducers. More specifically, it refers to a worm and helical wheel gear reducer which, in operation, tends to achieve a basically zero backlash in speed reduction.

Speed reducers are mechanical devices forming part of mechanical power transmission. Generally, they consist of a series of gears housed inside a shell (bearing body), the gears reducing rotational speed from an input shaft (or high speed shaft) to an output shaft (or low speed shaft) and forming a gearmotor if coupled with an engine.

Such devices, mostly consisting, as previously mentioned, of gears which transform the rotational speed of motors to which they are associated, are used everywhere in the modern technique and in some cases it is necessary for the hysteresis or backlash between motion input and output to be minimal or preferably equal to zero.

According to the prior art a worm gearmotor generally comprising:

A. a bearing body;

B. a gear reducer drive motor;

C. a mechanical part (named as kinematic chain) consisting of a worm screw and a helical wheel. Worm screws

Gearmotors with such type of configuration are employed in every field of the modern technique and electronic control systems handle all kinds of mechanical equipment, resulting in what is called "Mechatronics". There are fields wherein highest precision in transformation (reduction or amplification) of the angular velocity of motors is required, such as:

1. Robotics 2. Computer Numerical Control (CNC) Machines

3. Scientific Laboratory Equipment

4. Optical Systems, Pointing Systems

5. Stabilization Systems

6. Astronomical Systems, etc. The list is very long and includes every area of the technique.

Therefore, having gearmotors in which there is a two-way relationship with zero hysteresis between the high speed shaft (drive shaft) and the low speed shaft (driven shaft) is of paramount importance. GENERAL DESCRIPTION OF THE INVENTION

The object of the present invention is to provide motion transmissions with motion reduction or multiplication, characterized by a total absence of backlash between input shafts (drive shaft) and output shafts (driven shaft). This and other objects, which will be clear throughout this description, are achieved through the herein described invention composed by a combination of gears and in particular by worms (the term "worm" is hereinafter used to designate the transmission components formed by a single shaft in the central section of which are obtained the actual worm screws), helical wheels and toothed wheels, arranged in such a way as to obtain the backlash elimination by means of a mechanism capable of changing its operating conditions by adapting to cogent requirements in real-time and capable of adapting to changing needs during gear reducer operation.

This is achieved by introducing a gearmotor electronically controlled having the function of regulating preload which eliminates backlash between transmission gears; in addition, two load cells having a dual function were used: The first function is to measure the zeroing load or preload,

·/ The second function is to monitor the load status or torque transmitted by the transmission assembly during normal operation.

By so doing, electronic control/monitoring systems can detect abnormal operating conditions and proceed with reporting such abnormal conditions or stopping the system. This takes into account temperatures, loads, performance optimization, etc.

The "screw adjustment" gearmotor varies the loop closing load (continuous cycle) based on an electronic control unit command. The control unit collects information from a series of sensors arranged in the kinematic chain and optimizes their operation in real-time, by monitoring working conditions and communicating the gear reducer status to the "exterior" so as to perform monitoring from a higher level and operate in order to change operating conditions to prevent faults in advance. This control unit, hereinafter also referred to as "MECHATRONIC GEARMOTOR", is in principle composed by the following elements (Fig. 1):

1. motor quadrature encoder with a low speed shaft encoder (an encoder is a digital electronic component, the simplest version thereof consists of a "i" number of inputs and a "n" number of outputs with i < 2 ⁿ ). The Electronic Control Unit compares the Motor Encoder with the Low Speed Shaft Encoder, measures the actual backlash between the two last ones, and regulates the preload on the kinematic chain by acting on the operating gearmotor.

2. Load cells for measuring the instantaneous operating torque and the preload for backlash zeroing.

3. Internal Temperature Sensor

4. External Temperature Sensor

5. Vibration Sensor

6. Oil level Sensor

7. LAN/WiFi Connection

The above described elements organization results in an absolute precision gearmotor, a real Mechatronic device, which provides a bidirectional and constant electronic control of the instantaneous torque, an electronic preload optimization and a backlash zeroing, as well as all parameters with reference to the gearmotor internal/external temperature.

The previously mentioned objectives are achieved by means of a controlled-backlash gear reducer as claimed in claims 1 to 1 1. To provide a detailed description of the embodiments of the invention, the accompanying drawings will be now considered, in which:

Fig. 1 shows the present invention with all its essential elements. Fig 2 shows the gear reducer according to the present invention with the electronic control unit 31 and the encoder 32 clearly visible.

Fig 3 is the same gear reducer shown in Fig. 2, but sectioned in its height according to a median plane so that it is possible to clearly see the placement of its constituent parts. Figure 4 is an enlarged view of the "G" area, allowing to see how the

(operating gearmotor 4) shaft 20 engages the right preload screw 13 by mean of a pin 21.

Figure 5 is a sectional view of the G-area, taken along the line H-H, which allows to see how the shaft 20 and the pin 21 engage together a slotted hole in the right preload screw 13 in order to transmit (by acting as a screwdriver on a screw) their rotating motion to mentioned preload screw; the figure shows the shaped hole of the preload screw. (See Figure 5bis)

Fig. 6 is an exploded axonometric view of the invention, clearly showing all the essential elements the numbering of which is provided hereinafter (said numbering also applies to Figures 1, 2, 3, 4, 5, 6 and 5bis).

DESCRIPTION OF THE OPERATING MODE

The shaft/worm screw 9 rotates on bearings 16 and 17, where it is free to rotate and slide axially according to the arrows 27 direction, similarly the worm screw 11 rotates on bearings 18 and 19 and is also free to rotate and slide axially according to the arrows 27.

Moreover, at the assembly, worm screws' midlines 28 and 29 coincide with the rotational axis 30 of the helical wheel 12.

Finally, with the elements arranged in such a manner, the (left) preload screw 24 is adjusted to be in contact with the (left) load cell 25 and the (left) thrust bearing 26 and the latter one is in contact with the worm screw 11.

Under these conditions, if the operating gearmotor 4 is activated to cause, through a drive pin 21, a screwing rotation of the preload screw 13 it will be achieved that both load cell 14 and (right) thrust bearing 15 will press together on worm screw 9 forcing it to move forward and thus press on the helical wheel 12 teeth sides (helical wheel which is mounted on the shaft 30 guided on bearings 22 and 23) and said helical wheel will in turn be rotated.

Preload screw 13 advancement will stop when the teeth of all gears forming the circuit will come into contact with each other as a result of the helical wheel 12 rotation by mean of worm screw 9 and the rotation of worm screws 9 and 11 themselves, said rotation being determined by the worm screws' reversibility that will close the path which connect gears 8-9-12-1 1-10-6-7 and still 8.

By continuing operating gearmotor 4 rotation, having all parts in contact with each other, load cells 14 and 25 will start to measure the induced preload.

At this point, when a prescribed preload value for a specific working condition will be reached, electronic control unit 32 (Fig. 1) will stop the operating gearmotor 4 and will be able to change the preload value by rotating in an appropriate direction to increase or decrease said preload value based on the achieved working temperature or changed working conditions.

The encoder 32 associated with helical wheel 12, as well as the Temperature Sensor and any other sensors, not indicated herein, are connected to the electronic control unit.

In particular, the Encoder 32 allows control unit 31 to compare a motor 3 and helical wheel 12 rotation, especially when the system is switched on, to check and, if necessary, correct the system preload status. (Test - Preset function).

Further, in a preferred embodiment, there is an operating gearmotor 4 which is connected to one of the two irreversible adjusting screws, said operating gearmotor works by increasing or decreasing the load on the associated screw and consequently on the entire gear train due to gear train reversibility which is previously set as a condition.

Actually, it was indicated with the number 4 an operating gearmotor on one of the two irreversible adjusting screws since this is the basis of the invention and the minimum condition for the kinematics to be functional.

It is equally evident that, due to particular operating needs, it will be possible to insert two gearmotors, each of which acts on one of the two adjusting screws, as well as an operating gearmotor which acts on both the adjusting or preload screws, by using an element for transmitting and synchronizing the operating gearmotor motion simultaneously on both the adjusting screws. ADVANTAGES AND INDUSTRIAL VALIDITY OF THE INVENTION.

Electronic control unit 31 is capable of controlling a variety of sensors and functions adapted to monitor instantaneous operating conditions, such as:

- Kinematic backlash (Main and Secondary Encoder Monitoring)

- static and dynamic charges exerted on the kinematics teeth (load cells monitoring)

- temperature

- oil level

- etc.

Electronic control unit 31 includes the circuits for bidirectionally communication with the outside by a LAN and WiFi network connection, in order to allow for gearmotor remote monitoring, all functional parameters reception by a control room as well as the control room capability to change and vary gearmotor functional modes adapting them to current requirements.

Reference numbers:

** 1 Gearmotor bearing body

**2 Closing cover of the bearing body

**3 Main motor (of the gear reducer)

**4 Operating gearmotor (preload regulating gearmotor)

**5 Main motor joint

**6 Gear (smaller toothed wheel) **7 Gear (smaller toothed wheel)

**8 Gear (greater toothed wheel)

**9 Shaft/worm screw

** 10 Gear (greater toothed wheel)

** 11 Shaft/worm screw

** 12 Helical wheel

** 13 Right preload screw

** 14 Right load cell

** 15 Thrust bearing

** 16 Bearing of the worm screw 9

** 17 Bearing of the worm screw 9

** 18 Bearing of the worm screw 1 1

** 19 Bearing of the worm screw 1 1

**20 Shaft of the operating gearmotor 4

**21 Drive pin on the shaft 20

** 22 Bearing of the helical wheel 12

**23 Bearing of the helical wheel 12

**24 Left preload screw

**25 Left load cell

**26 Left thrust bearing IT2017/000167

** 27 Arrows of the worm screw sliding direction

** 28 Midline of the worm screw 9

** 29 Midline of the worm screw 1 1

** 30 Rotational axis of the helical wheel 12

**31 Electronic control unit

** 32 Encoder