Lift truck rotator with pressure-relieved valving

In a rotator attachment for a lift truck of the type including an inner gear means with external teeth and surrounding outer gear means with a greater number of internal teeth engaging said external teeth, the teeth of both gear means being in surrounding relationship to an axis of rotation, one of the gear means being mounted by rotational mounting means for rotation about said axis for rotating a connected load, the other gear means being mounted by eccentric mounting means to a frame for movement in a gyratory eccentric path about said axis to rotate said one gear means about said axis;

• a drive means for moving said other gear means in said gyratory eccentric path comprising:
• multiple hydraulic cylinders connected at one set of ends to said frame and at their opposite set of ends to said other gear means at an angular relationship to one another,
• position-responsive control valve means responsive to the position of said other gear means in its said gyratory eccentric path for controlling sequentially the flow of hydraulic fluid under operating pressure to said multiple cylinders,
• and fluid pressure-responsive relief valve means in association with said control valve means and operable in response to a predetermined excessive fluid pressure in any of said hydraulic cylinders to relieve said excessive pressure and prevent pressure-locking therein,
• said control valve means including a control valve for each said cylinder, said control valve including a valve body defining a valve cavity and cylinder passage means for connecting said cavity to said associated cylinder, a valve spool within said cavity movable relative to said body between an operating position connecting a source of fluid under operating pressure to said associated cylinder and a neutral position blocking communication between said source and said associated cylinder, one of said body and spool being operatively connected to said associated cylinder such that positional changes of said cylinder effects positional changes of said control valve between neutral and operating positions, said relief valve means comprising a movable relief valve member housed within said body.

A combination control valve and relief valve for controlling the operation of a hydraulic cylinder and protecting such cylinder against excessive internal pressures due to pressure-locking therein when said cylinder is operated in sequence with other hydraulic cylinders to move a common connected member in a rotary path, said combination valve comprising:

• a valve body,
• a valve spool having at least two axially separable spool sections,
• means defining a spool cavity within said body for receiving said spool, cylinder passage means within said body for communication between said cavity and said cylinder, and relief passage means within said body in communication with said spool cavity,
• biasing means urging said spool sections into abutment with one another so that said sections normally act together as a unit in functioning as a control valve,
• said spool having an operating position relative to said body for connecting a source of fluid under operating pressure to said cylinder, said spool also having a neutral position relative to said body for blocking said source from said cylinder with said spool sections acting as a unit,
• said spool including a circumferential groove with opposing side walls, one said opposing side wall being defined at least in part by a first said spool section and the other said opposing side wall being defined at least in part by a second said spool section next adjacent to said first spool section,
• said groove being in communication with said cylinder passage means but not with said relief passage means when said spool is in said neutral position and when said first and second spool sections are in abutment,
• said groove being in communication with both said cylinder passage means and said relief passage means when said spool is in its neutral position and said first and second spool sections are axially separated from one another,
• whereby with said spool in its neutral position and an excessive fluid pressure in said cylinder, said excessive pressure is transmitted to said groove to overcome the force of said biasing means and separate said first and second spool sections to relieve said excessive cylinder pressure.

A combination control valve and relief valve means for controlling the operation of a hydraulic cylinder and protecting such cylinder against excessive internal fluid pressures due to pressure-locking therein when said cylinder is operated in sequence with at least one other hydraulic cylinder to move a common connected member in a rotary path, said combination valve means comprising:

• a valve body,
• a valve spool,
• means defining a spool cavity within said body for receiving said spool, cylinder passage means within said body for communication between said cylinder and said cavity, and relief passage means within said body in communication with said cavity,
• said spool including an operating position relative to said body for connecting a source of fluid under operating pressure to said cylinder, said spool also having a neutral position relative to said body for blocking communication between said source and said cylinder,
• one of said valve spool and said valve body including a fluid pressure-responsive movable relief valve member in fluid communication with said cylinder passage means and normally blocking communication between said cylinder passage means and said relief passage means in said neutral position
• said relief valve member being operable in response to an excessive fluid pressure in said cylinder with said spool in its neutral position to connect said cylinder passage means and said relief passage means to relieve said excessive pressure.

A combination control and relief valve means for controlling the operation of a hydraulic cylinder and protecting such cylinder against excessive internal pressures due to pressure-locking therein when said cylinder is operated in sequence with other hydraulic cylinders to move a common connected member in a rotary path, said combination valve means comprising:

• a valve body,
• a valve member,
• said body including a cavity for receiving said valve member and enabling relative movement between said valve member and said valve body,
• cylinder fluid passage means within said body connecting said cavity with said cylinder,
• relief fluid passage means within said body and in communication with said cavity,
• said valve body and member being relatively movable between an operating position connecting said cylinder to a source of fluid under operating pressure and a neutral position normally blocking communication between said source and said cylinder,
• and a movable relief valve means in one of said valve body and valve member, said relief valve means being sensitive to fluid pressure in said cylinder passage means in said neutral position,
• said relief valve means being operable in said neutral position under normal fluid pressures in said cylinder passage means to block communication between said cylinder passage means and said relief passage means,
• said relief valve means being operable in said neutral position in response to excessive fluid pressure in said cylinder passage means to connect said cylinder passage means to said relief passage means and thereby relieve said excessive pressure in said cylinder passage means and in said cylinder.

In a drive apparatus for driving a rotatably mounted element in a rotary path with respect to an axis of rotation, said drive apparatus comprising:

• at least two double-acting hydraulic cylinders angularly disposed to one another and pivotally mounted at one set of ends for oscillatory movement about relatively fixed axes,
• said cylinders being pivotally and operably connected at their opposite set of ends to said element at positions offset radially from said axis, with the angular disposition of said cylinders with respect to one another being such that said cylinders can be extended and retracted in sequence to rotate said element continuously about said axis,
• control valve means operable to control the supply and exhaust of fluid from the opposite sides of said cylinders in a sequence required to rotate said element in said path,
• said control valve means having with respect to each said cylinder (1) a first operating position in which pressure fluid is supplied to one side and exhausted from the opposite side of said cylinder, (2) a second operating position in which pressure fluid is supplied to said opposite side and exhausted from said one side of said cylinder, and (3) a third neutral position blocking the flow of pressure fluid to and from said cylinder, said valve moving through said neutral position in moving between said first and second positions and when said cylinder is changing its directional mode,
• relief valve means associated with said control valve means, said relief valve means being sensitive to fluid pressure at both sides of a cylinder when said valve means is in said neutral position with respect to said cylinder and being operable in said neutral position in response to excessive pressure in either side of said cylinder to relieve said excessive pressure.