Hydraulic motor control arrangement

Claim 2

A hydraulic servomechanism comprising, in combination, hydraulic motor means having a rotary output member capable of assuming any of a plurality of angular orientations; reversible and adjustable hydraulic pump means connected to said hydraulic motor means and operative for furnishing hydraulic fluid to said motor means for changing the angular orientation of said output member in either rotational direction thereof, said hydraulic pump means including movable adjusting means operative for varying the flow of fluid to said motor means; selecting means for selecting an angular orientation for said rotary output member and including a movable selecting member whose position is indicative of the selected angular orientation; and hydraulic control means operative for moving said adjusting means in a sense reducing substantially to zero any discrepancy between the angular orientation of said output member and said selected orientation, said control means comprising a servo valve including a valve housing and a valve body movable therein for changing the position of said adjusting means by varying the flow of fluid in said hydraulic control means, and mechanical linkage means operative for mechanically coupling said servo valve to said rotary output member and to said movable selecting member in such a manner as to constrain said valve body to assume a position dependent upon the difference between the orientation of said output member and the orientation indicated by the position of said selecting member.

Claim 3

A servomechanism as defined in claim 1, wherein said pump means includes fluid conduits so connected to said motor means as to form a closed hydraulic circuit including said pump means and said motor means.

Claim 4

A servomechanism as defined in claim 2, wherein said selecting means comprises a step motor whose output shaft controls the position of said selecting member.

Claim 5

A servomechanism as defined in claim 1, wherein said hydraulic control means further comprises an hydraulic cylinder and a piston slidable therein and mechanically coupled to said adjusting means and defining a chamber in said cylinder having an inlet, and wherein said servo valve has an outlet for hydraulic fluid connected to said inlet and is so contructed as to deliver fluid into said chamber at a pressure dependent upon the position of said valve body.

Claim 6

A servomechanism as defined in claim 1, wherein said hydraulic control means further comprises an hydraulic cylinder and a piston slidable therein and mechanically coupled to said adjusting means and dividing the interior of said cylinder into two chambers each having a respective inlet for hydraulic fluid, and wherein said servo valve has two outlets for hydraulic fluid each connected to one of said inlets and is so constructed as to deliver fluid into said chambers at unequal pressures to move said piston in dependence upon the position of said valve body.

Claim 7

A servomechanism as defined in claim 5, wherein said hydraulic control means further includes auxiliary pump means supplying fluid under pressure to said servo valve.

Claim 8

A servomechanism as defined in claim 6, wherein each of said chambers furthermore has an outlet and an adjustable outlet valve controlling the outlet, and wherein one of the outlets of said servo valve is connected to one of the inlets of said chambers via a fixed throttle, said control means further including an additional cylinder and piston arrangement including an additional hydraulic cylinder and a piston slidable therein and mechanically coupled to said outlet valves for adjusting the same and dividing the interior of said additional cylinder into two chambers each having an inlet, a fluid conduit connected to one of said two last-mentioned inlets and also to one side of said fixed throttle, and another fluid conduit connected to the other of said two last-mentioned inlets and also to the other side of said fixed throttle, for furnishing fluid at different pressures into the chambers of said additional cylinder.

Claim 9

A servomechanism as defined in claim 5, wherein said servo valve comprises two inlet nozzles and wherein said valve body is pivotably mounted in operative proximity to said nozzles for movement through a range of positions changing the outflow of fluid from one of said nozzles relative to the outflow of fluid from the other of said nozzles, and wherein said control means further includes auxiliary pump means for supplying hydraulic fluid into said servo valve to be discharged from said nozzles.

Claim 10

A servomechanism as defined in claim 8, wherein each of said nozzles is associated with one of said outlets of said servo valve for varying the relative pressures of fluid flowing out from said outlets of said servo valve in dependence upon the position of said valve body.

Claim 11

A hydraulic motor driving arrangement comprising, in combination, pulse generator means for providing a source of input pulses; step-motor means connected to said pulse generator means and positioned as a function of said input pulses; servo valve means having a first input connected to the output of said step motor means; adjustable and reversible hydraulic pump means connected to said servo valve and adjusted by said servo valve means; hydraulic motor means connected to said pump means and supplied with hydraulic fluid in closed circuit by said pump means; means for connecting the output of said hydraulic motor means with a second input of said servo valve means, said servo valve means comparing the output of said step motor means with the output of said hydraulic motor means and adjusting said pump means as a function of the difference between said output of said hydraulic motor means and said output of said step motor means, and further including displacement cylinder means connected between said hydraulic means and said servo valve means for positioning and adjusting said pump means in response to the output of said servo valve means, said output of said servo valve means being the difference between the output of said hydraulic motor means and the output of said step motor means, and further including auxiliary pump means connected to said servo valve means; and two flow control lines connecting said servo valve means to said displacement cylinder means and further including fixed throttle means connected in one of said flow control lines; further displacement cylinder means connected to said fixed throttle means and responding to the pressure difference across said fixed throttle means; two adjustable throttle means adjusted by said further displacement cylinder means in response to said pressure difference; and flow-off line means connected to said adjustable throttle means.

Claim 12

A hydraulic motor driving arrangement comprising, in combination, pulse generator means for providing a source of input pulses; step-motor means connected to said pulse generator means and positioned as a function of said input pulses; servo valve means having a first input connected to the output of said step motor means; adjustable and reversible hydraulic pump means connected to said servo valve and adjusted by said servo valve means; hydraulic motor means connected to said pump means and supplied with hydraulic fluid in closed circuit by said pump means; means for connecting the output of said hydraulic motor means with a second input of said servo valve means, said servo valve means comparing the output of said step motor means with the output of said hydraulic motor means and adjusting said pump means as a function of the difference between said output of said hydraulic motor means and said output of said step motor means, and further including displacement cylinder means connected between said hydraulic means and said servo valve means for positioning and adjusting said pump means in response to the output of said servo valve means, said output of said servo valve means being the difference between the output of said hydraulic motor means and the output of said step motor means, and further including auxiliary pump means connected to said servo valve means; and two flow control lines connecting said servo valve means to said displacement cylinder means and further including fixed throttle means connected in one of said flow control lines; further displacement cylinder means connected to said fixed throttle means and responding to the pressure difference across said fixed throttle means; two adjustable throttle means adjusted by said further displacement cylinder means in response to said pressure difference; and flow-off line means connected to said adjustable throttle means.

Claim 13

A hydraulic motor driving arrangement comprising, in combination, pulse generator means for providing a source of input pulses; step-motor means connected to said pulse generator means and positioned as a function of said input pulses; servo valve means having a first input connected to the output of said step motor means; adjustable and reversible hydraulic pump means connected to said servo valve and adjusted by said servo valve means; hydraulic motor means connected to said pump means and supplied with hydraulic fluid in closed circuit by said pump means; means for connecting the output of said hydraulic motor means with a second input of said servo valve means, said servo valve means comparing the output of said step motor means with the output of said hydraulic motor means and adjusting said pump means as a function of the difference between said output of said hydraulic motor means and said output of said step motor means, and further incluDing displacement cylinder means connected between said hydraulic means and said servo valve means for positioning and adjusting said pump means in response to the output of said servo valve means, said output of said servo valve means being the difference between the output of said hydraulic motor means and the output of said step motor means, and further including axuiliary pump means connected to said servo valve means; and two flow control lines connecting said servo valve means to said displacement cylinder means and wherein said servo valve means comprises a swivellable lever pivoted about a fixed axis; means for positioning said lever as a function of the positions of said step motor means and said hydraulic motor means; and two nozzles controlled by said lever so that fluid from said auxiliary pump passes through said nozzles in a predetermined manner.

Claim 14

A hydraulic motor driving arrangement comprising, in combination, pulse generator means for providing a source of input pulses; step-motor means connected to said pulse generator means and positioned as a function of said input pulses; servo valve means having a first input connected to the output of said step motor means; adjustable and reversible hydraulic pump means connected to said servo valve and adjusted by said servo valve means; hydraulic motor means connected to said pump means and supplied with hydraulic fluid in closed circuit by said pump means; means for connecting the output of said hydraulic motor means with a second input of said servo valve means, said servo valve means comparing the output of said step motor means with the output of said hydraulic motor means and adjusting said pump means as a function of the difference between said output of said hydraulic motor means and said output of said step motor means, and further incluDing displacement cylinder means connected between said hydraulic means and said servo valve means for positioning and adjusting said pump means in response to the output of said servo valve means, said output of said servo valve means being the difference between the output of said hydraulic motor means and the output of said step motor means, and further including axuiliary pump means connected to said servo valve means; and two flow control lines connecting said servo valve means to said displacement cylinder means and wherein said servo valve means comprises a swivellable lever pivoted about a fixed axis; means for positioning said lever as a function of the positions of said step motor means and said hydraulic motor means; and two nozzles controlled by said lever so that fluid from said auxiliary pump passes through said nozzles in a predetermined manner.

Claim 15

An arrangement as defined in claim 11, including pressure lines controlled by said nozzles and communicating with said first-mentioned displacement cylinder.