The present invention relates to a hydraulic slow an reversible ^' motor, with high specific work.

Rotary hydraulic motors with pistons of significan displacement and rotary hydraulic motors with small rating a high number of revolutions per minute are well known. Th latters are keyed on mechanical reduction units which conver the work supplied by the motor at high speed int correspondent adequate work at low speed-

The drawbacks of these rotary hydraulic motors are wel known and consist mainly in their encumbrance, significan weight and consequent high cost.

Furthermore motors are well known made up by hydrauli cylinders with single or double action. Although they hav the advantage of reduced dimensions, they still suffer fro the drawback of a limited stroke.

Another drawback consists in that , when the stroke i increased considerably, the relevant weight, although lowe than corresponding rotary motors, becomes considerably high

A further drawback consists in tha , when used to driv a rotating machine member, they must be hinged on supportin structures with remarkable sizes to withstand the significan bending loads generated in the system.

On the contrary, the hi-speed rotary motors with lo

rating, which may be coupled to a mechanical reduction unit, have reduced sizes, weight and cost, but need the use of a reduction units of high weight and dimensions.

An aim of the invention is to realize a hydraulic slow and reversible motor which may generate, having very limited dimension, a high work, even with limited power rating.

Another aim of the invention is to realize a hydraulic motor 'of reversible type-

Another aim of the invention is to realize a hydraulic motor without dead centers and which remains constantly engaged with the driven member.

These aims are achieved according to the invention by a slow hydraulic reversible motor with high specific work characterized by comprising -a virtual rack of infinite length generated by a hydraulic actuator with linear reciprocating motion and by at least a couple of teeth engaging alternately with the teeth of a gear to be driven.

The present inven ion is hereinafter described with reference to the enclosed drawings in which: fig- 1 shows schematically the motor according to the invention along the partial section I-I of fig- 2, fig. 2 shows it along the longitudinal section II-II of fig- 3,

fig. 3 shows it along the cross section 111-111 of fig- 2 and" fig. 4 shows schema ically the operating and contro hydraulic circuit of the motor according to th inven ion.

As can be seen from the figures the motor according t the invention comprises an assembly cylinder 1 - piston connected to a hydraulic power unit 3, which shall be furthe described in details- The stem 4 of the piston 2 is connected, outside th cylinder 1 , to a cross pin 5 having its ends engaged with tw plates 6,7 which move parallely alongside said stem 4.

Both plates 6,7 present four horizontal slots 8, crosse by pins 9 fixed to the main machine frame, where als cylinder 1 is mounted.

Two racks 10,11 are mounted near the inner opposit faces of plates 6,7.

Particularly the rack 10 protrudes more than rack 11 an both racks engage with two pinions 12,13 located, as thei corresponding racks, at two different levels and supporte respectively by pins 1 . and 15 integral with the main machin frame -

Because of different protruding of the two racks 10,1

the distance between plates α,7 and the axis of the stem 4 is different .and is obviously larger for plate 6 than for plate 7-

The pins 9, supporting plates 6,7, also support two plates 16,17; with respect to stem 4 the plate 16 is located on the same side as plate 6, but is distant from pins 14,15 as much as plate 7.

On plate 16 is mounted a rack 18 engaging with pinion 13- on the contrary the plate 17 is located, with respect to stem 4, on the same side of plate 7, but is distant from pins 14,15 as much as plate 6, engaging with pinion 12; on the plate 16 is mounted, at the same level of rack 10, a rack 19 engaging with pinion 12- Since the conf guration described above foresees that the stem 4 is flanked on both sides by two couples of plates and each plate is connected by its own rack to the two central pinions, such connections are allowed for racks 10 and 19, mounted on "external" plates 6,17, due to the presence in the internal plates 16, 7 of horizontal slots where the above racks pass through-

Similarly, as the pin 5 is connected to plates 6 and 7, which are respectively internal and ex ernal, the connection

with external plate 6 is made possible by means of anoth horizontal _, slot in the corresponding internal plate 16.

Laterally to the two external plates 6,17 two teet 22,23 are provided, moving inside their respective housin 20,21-

Each tooth 22,23 is substantially formed by a metalli body of roughly prismatic shape with lower outline suitabl to engage with the teeth of a wheel 24 or of a rack, whic are ^" the members to be driven- The plates 6,17 integral with the housings 20,21 of th teeth 22,23 present a slot which allows said teeth to mov transversally through; the teeth are moved along their axi towards corresponding plate 7,16 by respectively hydrauli actuators 28, whose cylinder 25,27 is freely housed in th tooth body 22,23 and whose piston 26,29 is fixed to the sai body by the free end of its stem-

A hydraulic circuit controlling the movements of th pistons 26,29 in either directions is connected to power uni 3- Each plate 16,7, adjacent internally to plate 6,17 supporting the corresponding tooth 22,23 presents an openin 30 with larger sizes to allow as it will be explained after the mutual cross movements of other respective tooth 23,22.

Furthermore, in correspondence to said opening 30 there is a recess 31 where the end of tooth 22,23 constrained to the correspondent plate engages-

The power unit 3, operating the two actuators 28 of the teeth 22.23 and the assembly cylinder 1 - piston 2 comprises:

- one twelve-ways flow deviation device 32 and a double distributor 33,

- a first couple of sequence valves 34,35, the one 34 being located between the distributor 33 and the inlet side of the cylinder 27 (inlet side denominates the portion of cylindrical room which includes the piston stem); the other 35 is placed between distibutor 33 and inlet side of the other cylinder 25,

- a second couple of sequence valves 36,37 located between the delivery duct 38, return duct 39 and distributor 33,

- a couple of pressure relief valves 40,41 located in the circuit controlling the spool of distributor 33,

- a first couple of interception valves 42,43 actuated by th main piston 2, near the two stroke-end positions, suitabl to intercept the duct controlling the spool o distibutor 33,

- four piloted block valves 45,46,4-7,48 controlling th assembly cylinder 1 - piston 2,

- a quantity of ducts properly interconnecting the vario components to ensure the correct sequence of the operati cycle of the machine: reference to them shall be made i

. the following description of the operation. To fix a reference point it is useful to consider th configura ion shown in the figures as the initial one- In this start configuration:

- the* tooth 22 actuated by the piston 26 protrudes from plat 6 and engages its end with the corresponding plate 7 passing through the plate 16,

- the tooth 23 actuated by the piston 29 is completely lodge in the housing 21,

- the piston 2 is at mid-strok in its cylinder 1,

- the hydraulic fluid is pushed by the pump, through duct 38 flow deviation device 32, distributor 33, duct 49 and henc it is split in two branches and through one of the two duct 50 and 51 , it acts on pistons 26 and 29 o corresponding cylinders 25 and 27. As these pistons ar both at stroke-end the fluid shall not affect them an because of its high pressure shall maintain the sequenc valve 37 open, through which the fluid crosses distributo 33 and hence splits into the two branches in ducts 52 an 53.

In the duct 52 the fluid is stopped by interception valve 43, - which is now close, whereas in duct 53 it crosses block valve 48, actuated by the pressure at the outlet of sequence valve 34, and valve 45 and enters the inlet side of cylinder 1, keeping piston 2 moving.

The axial movement of piston 2 causes, by means of connecting pin 5, the axial translation of plates 6,7 as shown-- y the arrow 54 in fig- 1-

The displacement of the two plates 6 and 7 and of racks 10,11 integral with them causes the two pinions 12 and 13 to rotate in different directions and thus the displacement in opposite direction of plates 16,17 because of the interconnection with the two racks 18 and 19.

Practically the stroke of piston 2 as shown by arrow 54 causes the two plates 6,7 to move consistently and plates 16,17 to move oppositely to said piston.

As tooth 22 associated with plates 6,7 is during this phase protruding and engaged with the tooth-wheel 24, the displacement of the two plates 6,7 causes said wheel to rotate of a certain angle.

Contemporarly the two plates 16, 17 translating in opposite direction, do not cause any interference with the movement of wheel 24, as the tooth 23 associated with them is

fully lodged in its housing 21.

When _' the piston 2 reaches its stroke-end it releases t interception valve 43, which opens the fluid flow through t duct 44. The fluid may then crosses the interception val 43, the flow deviation device 32 and opens the pressu relief valve 41 to operate the spool of distributor 33.

Following this operation the fluid coming from the du 38 may enter directly the distributor 33 through the duct 55 without passing through the sequence valve 37, and goes ou from duct 56 to split in two branches, one entering directl through the duct 57, the outlet side of the cylinder 27, thu causing relevant piston 29 to protrude, the other enterin the inlet side of cylinder 25, after having passed throug the sequence valve 35, which function is to allow the flow o the fluid only after that the piston 29 has reached it stroke-end-

Practically the fluid coming from the duct 56 firstl causes the operation of the piston 29, then the protruding o relevant tooth 23 and subsequently the operation of th piston 26 with consequent lodging of relevant tooth 22-

During the above movement the two block valves 47 and 4 prevent any flow of the fluid, which otherwise could untimel act the piston 2-

When the tooth 23 is fully engaged, the block valves 47 and 48 ar,e open and consent the fluid to act the piston 2 in the cylinder 1 performing its return stroke- With a sequence opposite to that described before, the two plates 6,7 translate in opposite direction than before, while the two plates 16,17, which the tooth 23, now engaged with the wheel 24, is associated to, translate as shown by arrow 54 in fig- 1, i.-e. in such direction as to cause a further rotation of wheel 24. Practically, due to alternate engaging of the teeth 22 and 23 with the wheel 24, to reciprocating strokes of the piston 2, unidirectional strokes of the tooth being engaged with the wheel correspond-

The above described operation continues as long as the motor driving the fluid circulation pump is fed. If it is whished to rotate the wheel 24 in the opposite direction, the two ducts 38,39 in the power unit 3 must be exchanged eaσhother; in such a way first the flow deviation device 32 is operated, as to invert the feeding cycle of the cylinder 1, without however modifying the feeding cycle of the two cylinders 25,27 actuating the teeth 22,23- This exchange of the fluid feeding ducts 38,39 shall cause the sequence valve 36 to operate instead of the 37, all other considerations made insofar remaining unchanged-

Practically the hydraulic motor according to th invention . is based on the principle of creating, wit reciproca ing movement of teeth 22,23, a virtual rack to b engaged with a wheel 24 or with a rack in order to actuate b means of this a machine member whatsoever.

It clearly results from what is explained above that th motor according to the invention presents a number o advantages with respect to both the traditional rotar hydraulic motors and to the traditional hydraulic cylinde with single or double action.

With respect to the former the motor according to th invention has sizes significantly smaller, for the sam quantity or work supplied, and therefore implies much lowe weight and cost- Furthermore it may be considered as "self-locking" i the case of damage of the hydraulic feeding, as one of tw teeth is always engaged and allows at the most it displacement un il it reaches the position corresponding t the stroke-end position of the piston 2. With respect to the latter it offers the advantage of practically unlimited stroke and of the exclusion of whateve articulated linking to the supporting structure, with all th pratical advantages resulting from this exclusion.