EP0077837A1

EP0077837A1 - Double cylinder unit

Info

Publication number: EP0077837A1
Application number: EP82901367A
Authority: EP
Inventors: Hajimu Inaba; Seiichiro Nakajima
Original assignee: Fanuc Corp
Current assignee: Fanuc Corp
Priority date: 1981-05-06
Filing date: 1982-05-06
Publication date: 1983-05-04
Also published as: KR830010321A; JPS57184708A; EP0077837A4; WO1982003896A1

Abstract

Double cylinder unit in which a rod-shaped piston rod (22) having first and second pressure bearing surfaces is laterally slidably provided in a single cylinder box (10) to impart an actuation to a driven unit, and a rod-shaped piston rod (34) having a third pressure bearing surface substantially equal to and opposing the second pressure bearing surface of the piston rod (22) and a fourth pressure bearing surface smaller than the area of the third pressure bearing surface is mounted on the piston rod of the second pressure bearing surface side of the piston rod (22), thereby controlling the hydraulic pressure acting on the first to fourth pressure bearing surfaces to provide a double action with the rods (22) and (34).

Description

The present invention relates to a cylinder unit which is used as an actuator for actuating various kinds of operative matters and more particularly to a duplex cylinder unit capable of applying two actuating actions or double operating forces to an operative matter through the sequential sliding motion of two rod pistons which are received practically concentrically within a single cylinder casing.

BACKGROUND ART

Cylinder units using fluid pressure such as air pressure and oil pressure and including various kinds of cylinders, which are classified by the operating mode into single-acting cylinders, duplex cylinders and multistage cylinders, have been widely used. Even the multistage cylinder among those conventional cylinders, however, merely applies a single operating force to an operative matter in a two-stage mode or in a multistage mode through the two-stage or multistage linear motion of a single rod piston, that is, since a single operating force is applied to one part of an operative matter merely in, at the utmost, a two-stage mode or multistage mode, the application of individual actuating actions or operating forces to two parts of an operative matter is impossible.

DISCLOSURE OF THE INVENTION

An object of the present invention is to provide a duplex cylinder unit of a new structure, capable of applying two actuating actions or double operating forces to an operative matter.
According to the present invention, duplex cylinder unit is provided characterized in that a double-rod piston having a first pressure-receiving surface and a second pressure-receiving surface which is smaller than the first pressure-receiving surface is provided within a-single cylinder casing so as to be slidable from side to side, a single-rod piston having a third pressure-receiving surface of a pressure-receiving area which is practically the same as that of the second pressure-receiving surface, and a fourth pressure-receiving surface of a pressure-receiving area which is smaller than that of the third pressure-

-receiving surface is fitted on the piston rod of the double-rod piston on the side of the second pressure-
-receiving surface with the third pressure-receiving surface disposed opposite the second pressure-receiving surface, and a duplex action by means of the double-rod piston and the single-rod piston is provided by selectively applying a fluid pressure to the first to the fourth pressure-receiving surfaces.

BRIEF DESCRIPTION OF THE DRAWING

Figure 1 is a longitudinal sectional view of a duplex cylinder unit in accordance with the present invention, showing the constitution thereof and the initial state of first and second rod pistons within the cylinder unit;
Fig. 2 is a longitudinal sectional view of the same cylinder unit showing a state in which the first rod piston has moved through the full stroke; and
Fig. 3 is a longitudinal sectional view of the same cylinder unit, showing a state in which the second rod piston has moved through the full stroke.

BEST MODE OF CARRYING OUT THE INVENTION

Figures 1 to 3 are longitudinal sectional views showing the constitution and the operating mode of a duplex cylinder unit in accordance with the present invention. The constitution of the duplex cylinder unit in accordance with the present invention will be described first with reference to Fig. 1. The unit has a single cylinder casing 10, which usually has the shape of a hollow cylinder. The opposite ends of the cylinder casing 10 are perfectly sealed with cylinder end plates 12 and 14. Three fluid pressure ports 16, 18, and 20 are formed in the cylinder casing 10. The fluid pressure ports 16 and 20 are provided at positions close to both ends of the cylinder casing, while the fluid pressure port 18 is provided at an intermediate position of the cylinder casing 10. Those positions of the fluid pressure ports will be described in detail afterward. A double-rod piston 22 is received in the cylinder casing 10. A piston 24 is formed in the double-rod piston 22 at the intermediate portion thereof. The respective diameters dl and d2 (dl < d2) of the left-hand rod and the right-hand rod with respect to the piston 24 of the double-rod piston 22 are different from each other, hence the left-hand pressure--receiving surface 24a is greater than the right-hand pressure-receiving surface 24b. A tubular second rod piston 34 is fitted on the right-hand rod of the double-rod piston 22 on the right-hand side with respect to the piston 24. The second rod-piston 34 is formed in a single rod piston having a piston 36 at the left-end thereof. In the embodiment shown in the drawing, the diameter of the rod of the single rod piston 34 is d3 (dl < d2 < d3). Accordingly, also in the piston 36, the pressure-receiving area of the left-hand pressure-receiving surface 36a is greater than that of the right-hand pressure-receiving surface 36b. Since the second single-rod piston 34 slides along the first double-rod piston 22, the second single-rod piston 34 is provided with slide bearings 38 on the opposite ends thereof. The right--hand end 26 of the double-rod piston 22 and the right-hand end 40 of the single-rod piston 34 are projecting outward through the cylinder end plate 14 each forming a cylinder action part. Operating forces are applied to an operative matter through those ends 26 and 40. On the other hand, the left-hand end 28 of the rod extending on the left-hand side of the piston 24 of the first double-rod piston 22 extends outward through the cylinder end plate 12 and is provided with a stopper 30. Accordingly, the rod piston 22 is allowed to move to the right until the stopper abuts against the outside surface of the cylinder end plate 12 and to move to the left until the piston 24 abuts against the inside surface of the cylinder end plate 12. The second rod piston 34 is allowed to move to the left until the piston 36 thereof abuts against the right-hand surface of the piston 24 of the first rod piston 22 and to move to the right until the piston 36 abuts against the inside surface 14 of the cylinder end plate 14. Sealing packings 42 are put on the respective circumferences of the pistons 24 and 36 which slide along the inside circumference of the cylinder casing 10, for isolating the pressure-receiving surfaces 24a and 24b of the piston 24 and the pressure-receiving surfaces 36a and 36b of the piston 36 from each other. Now, the positions of the fluid pressure ports 16, 18, and 20 will be described in detail. The first fluid pressure port 16 is formed for supplying to and for discharging from a cylindrical space, formed between the cylinder end plate 12 and the left-hand pressure-receiving surface 24a of the piston 24, fluid pressure and more particularly, the fluid pressure port 16 is formed at a position on the right of the cylinder end plate 12 adjoining the inside surface of the cylinder end plate 12 for applying a fluid pressure to the left-hand pressure-receiving surface 24a of the piston 24 in order to move the first double-rod piston 22 from the left end position to the right. The fluid pressure port 18 is formed at a position allowing the application of fluid pressure to the interface of the right-hand pressure-receiving surface 24b of the piston 24 and the left-hand pressure-receiving surface 36a of the piston 36 of the second single-rod piston 34 when the first double-rod piston 22 is moved to the right until the stopper 30 of the piston 24 abuts against the cylinder end plate 12. The fluid pressure port 20 is formed at a position adjoining the cylinder end plate 14 on the left side in order to supply into and to discharge from a cylindrical space, formed between the right-hand pressure-receiving surface 36b of the piston 36 and the inside surface of the cylinder end plate 14, fluid pressure.
The action of the duplex cylinder unit of the present invention of the constitution described above will be described hereunder with reference to Figs. 1 to 3. Figure 1 shows a state in which the first and the second rod pistons 22 and 34 are located at their respective initial positions where they are retracted to their respective extremities. Figure 2 shows a state in which the first rod piston 22 has moved together with the second rod piston 34 to the maximum stroke allowed by the stopper 30, and the stopper 30 abuts against the left-hand outside surface of the cylinder end plate 12. Figure 3 shows a state in which the second rod piston 34 has moved further to the right from the position shown in Fig. 2 and the piston 36 abuts against the cylinder end plate 14. When a fluid pressure of the same level is applied through all the fluid pressure ports 16, 18, and 20 with the first and the second rod pistons in the state shown in Fig. 1, both rod pistons 22 and 34 move integrally to the right under the action of a pressure differential between the respective pressures acting on the left-hand pressure-receiving surface 24a and the right-hand pressure--receiving surface 36b, since the pressure-receiving area of the left-hand pressure-receiving surface 24a of the piston 24 is greater than that of the right-hand pressure--receiving surface 36b of the piston 36 and the rightward movement of the first rod piston 22 is interrupted when the stopper 30 of the first rod piston 22 abuts against the cylinder end plate 12, which is shown in Fig. 2. When the fluid pressure is applied continuously through the fluid pressure ports 16, 18, and 20 in this state, the second rod piston 34 moves rightward under a pressure differential between a total pressure working on the left-hand pressure--receiving surface 36a through the fluid pressure port 18 and a total pressure working on the right-hand pressure--receiving surface 36b through the fluid pressure port 20, since the left-hand pressure-receiving surface 36a of the piston 36 of the second rod piston 34 is greater than the right-hand pressure-receiving surface 36b of the same, during which the first rod piston 22 remains stopped, since the fluid pressure is applied to the left-hand pressure-receiving surface 24a of the piston 24 of the rod piston 22 through the fluid pressure port 16. The second rod piston 34 stops when the right-hand pressure-receiving surface 36 abuts against the inside surface of the cylinder end plate 14, as shown in Fig. 3. As described hereinbefore, a duplex cylinder action can be applied to an operative matter with the respective outer ends 26 and 40 of the rod pistons 22 and 34 through the sequential cylinder action of the first rod piston 22 and the second rod piston 34.
Referring now to Fig. 3, the first and the second rod pistons 22 and 34 can be returned easily to the respective initial positions shown in Fig. 1 after the first and the second rod pistons 22 and 34 have moved to the respective maximum stroke by changing the fluid pressure supply. In the state shown in Fig. 3, the fluid pressure ports 16 and 18 among the fluid pressure ports 16 and 18 are changed to the discharge side and the fluid pressure is supplied only through the fluid pressure port 20, then the rod pistons 22 and 34 move integrally leftward until the initial state shown in Fig. 1 is attained, since the fluid pressure is applied only to the right-hand pressure-receiving surface 36b of the piston 36 in the first and the second rod pistons 22 and 34.
Furthermore, in the state shown in Fig. 3, only the second double-rod rod piston 34 can temporarily be retracted to the state shown in Fig. 2, when the fluid pressure ports 16 and 20 are kept in a fluid pressure supplying mode while the fluid pressure port 18 is changed to the fluid pressure discharging side. When the fluid pressure port 16 also is changed to the fluid pressure discharging side after the rod piston 34 has been retracted to the state shown in _Fig. 2, the first and the second rod pistons 22 and 34 are allowed to return integrally to their respective positions in the initial state shown in Fig. 1.
Still further, when the fluid pressure ports 16 and 20 are changed to the fluid pressure discharging side and only the fluid pressure port 18 is kept in the fluid pressure supplying mode in the state shown in Fig. 3, first only the first rod piston 22 moves leftward to return to the initial position. When the fluid pressure port 18 is changed to the fluid pressure discharging mode and the fluid pressure port 20 from the fluid discharging mode into the fluid supplying mode after the first rod piston 22 has returned to the initial position, the fluid pressure works only on the right-hand pressure-receiving surface 36b of the piston 36 of the second rod piston 34, therefore, the second rod piston 34 moves leftward and finally returns to the state' shown in Fig. 1.
It is apparent from what has been described hereinbefore that according to the present invention, a double-rod piston having a first pressure-receiving surface and a second pressure-receiving surface which is smaller than the first pressure-receiving surface is provided within a single cylinder casing so as to be slidable from side to side, a single-rod piston having a third pressure-receiving surface of a pressure-receiving area which is practically the same with that of the second pressure-receiving surface and a fourth pressure-receiving surface of a pressure-receiving area which is smaller than that of the third pressure--receiving surface is fitted on the piston rod of the double-rod piston on the side of the second pressure--receiving surface with the third pressure-receiving surface disposed opposite to the second pressure-receiving surface, and a duplex action which is effected by means of the double-rod piston and the single-rod piston is provided by selectively applying a fluid pressure from the first to the fourth pressure-receiving surfaces, thus an operative matter can be made to perform various works through the application of the duplex action to the operative matter.
For example, in some cases it is necessary to incorporate a two part element concentrically into a one part element by press fitting during the processes for machining and assembling various mechanical, electronic, and electrical devices. In such cases, the use of the duplex cylinder unit of the present invention makes extremely simple and accurate assembling possible; one of the two part elements is press fit into one part element by means of the first rod piston of a duplex cylinder unit, then the other one of the two part elements may be press fit by means of the second rod piston while the previously press fit part element is held in its place. In a DC motor assembling process, which is a practical example of such a press fit assembling process, when the rotor part of the motor is first press fit to the flange part, then the stator outer frame part having permanent magnets is press fit concentrically on the outer circumference of the rotor part while the misalignment is prevented by holding the rotor part with the first rod piston of the duplex cylinder unit, the stator outer frame part can be accurately press fit into the flange part for assembly while the misalignment resulting from the magnetic attraction is prevented if the magnetic attraction is exerted between the rotor part and the stator outer frame part by the permanent magnets.

Claims

1. A duplex cylinder unit comprising: a single cylinder casing which is closed at opposite ends with end plates,

a first rod piston received in said cylinder casing for sliding movement from side to side and including a piston having a first pressure-receiving surface on one side thereof and a second pressure-receiving surface which is smaller than said first pressure-receiving surface on the other side thereof, and two rods extending on the respective sides of said piston,

a second rod piston slidably fitted on the rod part of said first rod piston on the side of said second pressure-receiving surface and including a piston received within said cylinder casing and having a third pressure--receiving surface disposed opposite to said second pressure--receiving surface and a fourth pressure-receiving surface which is smaller than said third pressure-receiving surface and is formed opposite said third pressure-receiving surface, and a rod extending on the side of said fourth pressure--receiving surface, and

a fluid pressure port means provided in said cylinder casing for supplying and discharging a pressurized fluid which acts on said first, second, third, and fourth pressure-receiving surfaces, wherein

a double actuation action performed by said first and second rod pistons can be obtained by selectively changing the fluid pressure which acts on the respective pressure-receiving surfaces.

2. A duplex cylinder unit according to claim 1, wherein both rod parts of said first rod piston are formed so as to extend through the end plates attached to the respective ends of said cylinder casing, and the rod part of said second rod piston is formed also so as to extend through one of the end plates of said cylinder casing.

3. A duplex cylinder unit according to claim 2, wherein the rod part of said first rod piston on the side of said first pressure-receiving surface is provided with a stopper which is adapted to abut against the end plate of said cylinder casing on the outside end thereof.

4. A duplex cylinder unit according to claim 2 or 3, wherein the rod part of said first rod piston on the side of said second pressure-receiving surface is longer than the rod part of said second rod piston.

5. A duplex cylinder unit according to claim 1, wherein said fluid pressure ports include a first fluid pressure port for supplying and discharging a pressurized fluid which acts on said first pressure-receiving surface, a second fluid pressure port for supplying and discharging a pressurized-fluid which acts simultaneously on said second and third pressure-receiving surfaces, and a third fluid pressure port for supplying and discharging a pressurized fluid which acts on said fourth pressure-receiving surface.