Device for automatically switching the displacement of a machine with axial pistons

1. Device ( 10 ) for controlling the displacement of a machine ( 20 ) with axial pistons comprising a case ( 23 ) that houses a control unit comprising:

A displacement control spool ( 110 ) adapted to be switched between two positions by a control pressure (Ps) according to an axis of sliding (Δ):

a working position wherein the control spool ( 110 ) provides a connection between at least one inlet ( 103 , 104 ) that receives a supply pressure and an outlet ( 105 , 106 ) connected to a cylinder for adjusting the inclination of said machine ( 31 a , 31 b ), and

an idle position wherein the control spool ( 110 ) interrupts the connection between said inlet ( 102 , 104 ) and said outlet ( 101 , 103 ), and

means for switching adapted to vary the position of the adjusting cylinder ( 31 a , 31 b ),

a spring ( 140 ),

characterised in that:

said means of communication comprise a second switching spool ( 130 ), coaxial to the control spool ( 110 ),

a switching pressure (Pm) exerts an axial force on the second spool ( 130 ) in the direction of the control spool ( 110 ),

the spring ( 140 ) exerts an axial force on the two spools ( 110 , 130 ), which tends to move them apart from each other,

a control pressure (Ps) exerts an axial force on the control spool ( 110 ) in the direction of the second tool ( 130 ), and

wherein a second end ( 110 b ) of the control spool ( 110 ) comprises a recess ( 114 ) wherein the spring ( 140 ) is partially housed.

2. Device according to claim 1 , wherein

The control spool ( 110 ) comprises at least one circular groove ( 111 , 112 ) and the spool having two ends ( 110 a , 110 b ),

The second spool ( 130 ) comprises a head ( 131 ) and a body ( 132 ), with the head sliding in a plug ( 120 ) located on the axis of sliding (Δ),

The axial force of the control pressure (Ps) is exerted via oil by a control pressure line ( 105 ) in a cavity formed by the case ( 23 ) and the first end of the piston ( 110 a ),

The spring ( 140 ) exerts its force on the body ( 132 ) of the second tool ( 130 ) and on the second end of the control spool ( 110 ),

The axial force of the switching pressure (Pm) is exerted via oil by a switching pressure line ( 121 ) in a cavity ( 122 ) formed by said plug ( 120 ) and the head ( 131 ) of the second tool ( 130 ).

3. Device according to claim 1 , wherein the body ( 132 ) of the second tool ( 130 ) is able to come into contact with the second end ( 110 b ) of the control spool ( 110 ) when the spring ( 140 ) is compressed inside said recess ( 114 ) of the control spool ( 110 ).

4. Method for using a device according to claim 1 , wherein:

a. If no control pressure (Ps) is applied, then the control spool ( 110 ) is maintained in idle position by the spring ( 140 ),

b. If a control pressure (Ps) is applied then the change in displacement is automatically carried out according to the load applied to the machine ( 20 )

i. If the force exerted by the control pressure (Ps) is greater than the force exerted by the switching pressure (Pm), then the control spool ( 110 ) is in working position,

ii. If the force exerted by the control pressure (Ps) is less than the force exerted by the switching pressure (Pm), then the control spool ( 110 ) is in idle position.

5. Method for using according to claim 4 , wherein when the control spool ( 110 ) is in idle, respectively working, position, the machine ( 20 ) has a large displacement, respectively small, displacement.

6. Method for using according to claim 4 , wherein the control pressure (Ps) is constant.

7. Method for using according to claim 4 wherein the switching pressure (Pm) is variable.

8. Method for using according to claim 4 , wherein:

the control pressure (Ps) is between 20 and 40 bars.

the switching pressure (Pm) is between 40 and 250 bars and depends on the load of the machine ( 20 ).

9. Device ( 10 ) for controlling the displacement of a machine ( 20 ) with axial pistons comprising a case ( 23 ) that houses a control unit comprising:

A displacement control spool ( 110 ) adapted to be switched between two positions by a control pressure (Ps) according to an axis of sliding (Δ):

a working position wherein the control spool ( 110 ) provides a connection between at least one inlet ( 103 , 104 ) that receives a supply pressure and an outlet ( 105 , 106 ) connected to a cylinder for adjusting the inclination of said machine ( 31 a , 31 b ), and

an idle position wherein the control spool ( 110 ) interrupts the connection between said inlet ( 102 , 104 ) and said outlet ( 101 , 103 ), and

means for switching adapted to vary the position of the adjusting cylinder ( 31 a , 31 b ),

a spring ( 140 ),

characterised in that:

said means of communication comprise a second switching spool ( 130 ), coaxial to the control spool ( 110 ),

a switching pressure (Pm) exerts an axial force on the second spool ( 130 ) in the direction of the control spool ( 110 ),

the spring ( 140 ) exerts an axial force on the two spools ( 110 , 130 ), which tends to move them apart from each other,

a control pressure (Ps) exerts an axial force on the control spool ( 110 ) in the direction of the second tool ( 130 ), and

wherein the case comprises:

a first inlet ( 102 ),

a first outlet ( 101 ),

a second inlet ( 104 ),

a second outlet ( 103 ),

and the control spool ( 110 ) comprises two parallel grooves ( 111 , 112 ), wherein in working position, the control spool ( 110 ) makes it possible to connect the first inlet ( 102 ) to the first outlet ( 101 ) via the first gorge ( 111 ) and the second inlet ( 104 ) to the second outlet ( 103 ) via the second groove ( 112 ).

10. Machine with axial pistons according to claim 9 characterised in that the control pressure line ( 105 ) comprises a restriction, more preferably an orifice of 0.5 mm in diameter.

11. Device ( 10 ) for controlling the displacement of a machine ( 20 ) with axial pistons comprising a case ( 23 ) that houses a control unit comprising:

A displacement control spool ( 110 ) adapted to be switched between two positions by a control pressure (Ps) according to an axis of sliding (Δ):

a working position wherein the control spool ( 110 ) provides a connection between at least one inlet ( 103 , 104 ) that receives a supply pressure and an outlet ( 105 , 106 ) connected to a cylinder for adjusting the inclination of said machine ( 31 a , 31 b ), and

an idle position wherein the control spool ( 110 ) interrupts the connection between said inlet ( 102 , 104 ) and said outlet ( 101 , 103 ), and

means for switching adapted to vary the position of the adjusting cylinder ( 31 a , 31 b ),

a spring ( 140 ),

characterised in that:

said means of communication comprise a second switching spool ( 130 ), coaxial to the control spool ( 110 ),

a switching pressure (Pm) exerts an axial force on the second spool ( 130 ) in the direction of the control spool ( 110 ),

the spring ( 140 ) exerts an axial force on the two spools ( 110 , 130 ), which tends to move them apart from each other,

a control pressure (Ps) exerts an axial force on the control spool ( 110 ) in the direction of the second tool ( 130 ), and

wherein the case comprises:

a first inlet ( 102 ),

a first outlet ( 101 ),

a second inlet ( 104 ),

a second outlet ( 103 ),

and the control spool ( 110 ) comprises two parallel grooves ( 111 , 112 ), wherein in working position, the control spool ( 110 ) makes it possible to connect the first inlet ( 102 ) to the first outlet ( 101 ) via the first gorge ( 111 ) and the second inlet ( 104 ) to the second outlet ( 103 ) via the second groove ( 112 ), and

wherein the switching pressure (Pm) is the supply pressure (P 1 , P 2 ) of the machine.