GB2286227A - Actuator - Google Patents

Abstract

An actuator for moving a wheel up or down comprises an actuating cylinder 100 equipped with a locking mechanism for looking the cylinder rod 400 in its extended state. The looking mechanism comprises a claw 500 which can fall into the hole 420h of the rod 400 for locking, and a locking piston 700 provided with a retaining portion 770 for retaining the claw 500 in place. The cylinder 100 is also provided with two lever members, one of which is a lever 910 for detecting the movement of the locking piston 700 and the other is a crank 920 for detecting the movement of the claw 500, which cooperatively change a mechanical limit switch 460' between an ON-state and an OFF-state alternatively. Preferably, the crank 920 is rotatively mounted on the lever 910 to form a scissor-shaped construction, so that the limit switch 460' is switched by the force from the one end of the crank 920. <IMAGE>

Description

ACTUATOR Field of the invention The invention relates to an actuator for moving a wheel up and down, and more particularly, to means for locking it in a state with the wheel in a lowered position. The invention is applicable to landing gears for magnetic levitation vehicles, other vehicles or aircraft.

Magnetic levitation vehicles levitated, for example, by electromagnetic induction methods, travel at high speeds whilst levitating, but travel on wheels at low speeds because no great levitation force cannot be obtained. The wheels are incorporated in landing gear which includes an actuator to move the wheels up and down. The actuator is a linear actuator in the form of a piston rod and cylinder that moves the wheels down to engage the ground by extension of the piston rod, and moves the wheels up by retraction of the piston rod for levitated travelling. In order to ensure that the vehicle is supported assuredly on its wheels, and as a fail-safe measure, it is preferable to lock and retain the piston rod in its extended state.

Japanese Utility Model Laid-Open Application No. 4-108476 discloses an actuating cylinder having such a locking function.

This locking function involves a locking piston which is hydraulically actuated and presses an annular collet into the recess at the outer periphery of the extended piston rod for locking. Also, the end of a spool member is applied to the cam surface of the locking piston from outside the cylinder body and operates a limit switch located outside the cylinder body through movement of the spool member. This design therefore offers the benefit of a locking mechanism and means to detect whether or not the locking mechanism is in a locked state. However, it has several disadvantages, one of which is that the means for detecting locking is located outside the cylinder body. If the means is outside the cylinder body, it is more vilnerable to damage by a mechanical shock, and it requires extra space around the cylinder.Another disadvantage is that, even if the locking piston performs the correct operation required for locking, the collet does not always enter the recess on the piston side, and therefore an error is likely to occur in detecting locking.

Disclosure of the invention It is an object of the present invention to provide improved means for detecting assuredly whether or not a locking mechanism is in a locked state.

According to the present invention, first detecting means is provided to detect movement of the locking piston, second detecting means is provided to detect the movement of positioning members such as the aforesaid collet and claw, and third detecting means such as a limit switch is provided to be operated by said first and second detecting means. In this way, the third detecting means is operated on the basis of the movements of both the locking piston and the positioning members. Therefore, if, for example, the positioning members were not at the locking positions although the locking piston is located at the position for locking, the third detecting means would not indicate that the wheel is at the lowered position.

Preferably, the first detecting means comprises a lever member, one end of which is rotatively supported, the second detecting means comprises a crank which is rotatively supported at the mid-part of its lever member, and the third means comprises a limit switch disposed at the end of the crank. Such a combination of the lever member - the crank -and the limit switch can be easily housed in the interior of a hollow rod.

Description of the drawinqs The invention will now be described by way of example with reference to the accompanying drawing, in which: Figure 1 is a perspective view showing the general image of a landing gear including an actuating cylinder according to the present invention; Fiaure 2 is a cross-sectional structural view showing an embodiment of an actuating cylinder according to the present invention; Figure 3 is a sectional side elevation view taken on line 33' of Figure 2; and Figure 4 is an essential sectional view showing another state of an actuating cylinder in Figure 2.

Mode of carving out the invention Figure 1 is a perspective view showing the general image of an embodiment of a landing gear including an actuating cylinder according to the present invention, in which X indicates the travelling direction of the vehicle, and Y and Z indicate the vertical and lateral directions which intersect X at right angles respectively. First, with reference to this Figure 1, the location of the actuating cylinder in the landing gear will be described.

In a landing gear 10 for a magnetic levitation vehicle, including an actuating cylinder 100 according to the present invention, its connecting portions are concentrated on one surface of a bogie (not shown) to improve the workability in mounting the landing gear 10 and the like, and to reduce the weight of the bogie. This is the same with a case where a bogie is independently located for each vehicle, and with a case where a bogie is located between vehicles, so-called "articulated truck" is used.

The landing gear 10 is equipped with a wheel 20, and a supporting mechanism 30 for supporting the wheel 20 and moving it up or down. The wheel 20 consists of a wheel (without pneumatic tyre) (not shown), and a pneumatic tyre 24 supported at its outer periphery, and the wheel (without pneumatic tyre) can be freely rotated around a cylindrical central shaft 26.

The central shaft 26 supporting the wheel 20 is naturally along the Z direction, and a supporting mechanism 30 is located outside the wheel 20. In this respect, Figure 1 shows a state in which the rod 110 of the actuating cylinder 100 extends and the wheel 20 is at a lowered position.

The central portion of the trailing arm 40 extending along the X direction is mounted and fixed to the central shaft 26. The trailing arm 40 supports the wheel 20 to control its position, and functions to support the force of the brake in the X direction. The trailing arm 40 has a length enough to extend substantially across the wheel 20 over the entire surface thereof, and one end 42 thereof is rotatively mounted to one surface of the bogie. A portion 40a, a half of the trailing arm 40 from the one end 42 to the central shaft 26, and a portion 40b, the other half including the other end 44 on the opposite side are not in a straight line, but the latter is slightly inclined. This inclination enables a force from the trailing arm 40 side to be transmitted to a shock absorber 50 coupled to the other end 44 more smoothly.

A vertical link 60 extends substantially vertically in the Y direction to intersect the horizontal trailing arm 40, and substantially across the wheel 20 over the entire surface thereof. The central portion of the vertical link 60 is supported around the central shaft 26 so that the vertical link 60 and the trailing arm 40 can be rotated with each other. A guide wheel 61 is rotatively supported at the lower portion of the vertical link 60, and used to guide the vehicle in cooperation with the side wall on the road surface side when the vehicle is turning a curve in a carriage shed or the like.

On the other hand, the upper end 62 of the vertical link 60 is rotatively mounted to the leaf spring 70 by means of a pin member 63. Also, the vertical link 60 supports a pin 80 serving as a brake reaction receptacle on the midway to the end 62.

The vertical link 60 has a function of connecting the trailing arm 40 and the leaf spring 70 in addition to the functions of receiving the brake reaction from the brake device within the wheel 20, and supporting the guide wheel 61. The leaf spring 70 is located above the trailing arm 40 to extend in the X direction like the trailing arm 40. For the leaf spring 70, a one-piece leaf spring may be used, but the illustrated one is constructed so that two leaf spring members 76 and 78 are provided in the upper and lower sides to be connected with each other at the central portion to obtain a greater force of spring. The central portions of these two leaf spring members 76 and 78 are supported by a bolt member in such a state that the concave and convex portions are fitted with each other.

Further, the central portion of the leaf spring 70 is rotatively supported at the upper end 62 of the vertical link 60 by means of a pin member 63. The support of this pin member 63 allows the leaf spring 70 to form a parallel motion mechanism in cooperation with trailing arm 40 and the vertical link 60.

To obtain more excellent ride comfort, the leaf spring 70 has such a length as to extend across the wheel 20, and one end 72 thereof is rotatively mounted to one surface of the bogie.

Also, to the other end 74 of the leaf spring, the cylinder bottom side of the shock absorber 50, and the end of a rod 110 of the actuating cylinder 100 according to the present invention are rotatively mounted respectively. The actuating cylinder 100 has at least a function of moving the wheel 20 up or down by inserting or drawing the rod 110 into or out of the cylinder body 120, and a function (this locking function will be described in detail later) of locking the wheel 20 in a state of having been moved down as shown in Figure 1. The end 122 of the actuating cylinder 100 on the bottom side is rotatively mounted to one surface of the bogie in the same manner as the end 72 of the leaf spring 70 and the end 42 of the trailing arm 40.The leaf spring 70, the vertical link 60 and the trailing arm 40 constitute the parallel motion mechanism even if the actuating cylinder 100 extends or contracts the rod 110, and therefore, the movements of those members, the shock absorber 50 and the actuating cylinder 100 can be housed in the limited space including the projected area portion of the wheel 20.

Then the inner structure of the actuating cylinder 100 will be described mainly with reference to Figure 2. The actuating cylinder 100 is a hydraulic actuator, including the cylinder body 120, the end 122 on the bottom side of which is closed, and the end 123 on the head side, opposite thereto, of which is opened. The cylinder body 120 is hollow, in which a threaded portion 120f is formed at the inner peripheral surface of the end 123 on the head side which is opened, a projection 120s having slightly smaller diameter is formed adjacent thereto and the interior is a cylinder hole 120h having a uniform diameter. In the cylinder hole 120h, there is provided a cup-shaped first piston 210 for moving up or down.

The first piston 210 with a seal ring 212 at the outer periphery is capable of moving in the actual line direction of the cylinder body 120 within the cylinder hole 120h. A first chamber 310 is partitioned on the cylinder bottom side by the first piston 210 and a second chamber 320 is partitioned between the seal ring 212 around the first piston 210 and the seal ring 222 in a portion of the projection 120s respectively.

Therefore, the first piston 210 is moved in either direction of the bottom side or the head side by supplying hydraulic pressure into the first chamber 310 or the second chamber 320.

The hollow rod 400 is incorporated with the first piston 210 through screw junction. The rod 400 extends from the first piston 210 to the outside through the opening of the cylinder body 120 on the head side. The diameter of the rod 400 is smaller than the diameters of the cylinder body 120 and the piston 210, and there is a ring-shaped sufficient space between the rod 400 and the latter. The rod 400 comprises a threaded portion 400m at the distal end on the first piston 210 side, a seal ring retaining portion 410 for retaining a similar seal ring 402 at a portion of the seal ring 212 on the inner periphery side in the piston 210, a through-hole 420h passing through from the inside to the outside of the rod 400 at a portion adjacent thereto, a cam portion 430 at a portion adjacent to the through-hole, and rod head 442 for connecting to an external end.The cam portions 430 of the rod 400 are disposed at a plurality of places (for example, 2 to 4 places) in the circumferential direction of the rod. Each of the cam portions 430 includes convex portions 430a and 420b at both ends and a concave groove 430c midway for smoothly communicating between these convex portions. In this respect, there is located a dog 450 near the rod head 442 of the rod 400. The dog 450 is used to detect the raised position (e.g.

raised state) of the wheel 20 in which the rod 400 is contracted by a pin 452 supported by the dog 450 and a limit switch 460 fitted to the outer periphery of the head portion of the cylinder body 120. When the rod 400 is contracted to raise the leg, a head 452a of the pin 452 comes into contact with an end of a detecting rod 460a of the limit switch 460 to press the detecting rod 460a in against the force of a spring (not shown) incorporated for switching operation.

Between the outer periphery of the rod 400 and the inner periphery of the cylinder body 120, there is provided the second piston 520 including a claw 500. The second piston 520 comprises a cylindrical body portion 530 having a threaded portion 520m suitable for the threaded portion 120f on the cylinder body 120 side at the outer periphery, and an arm portion 550 for extending from the body portion 530 and supporting the claw 500 at the distal end. The threaded portion 520m of the body portion 530 engages with the threaded portion 120f of the opening of the cylinder body 120 in such a form that the second piston 520 has, at its inner periphery, a seal ring 522 for sealing between the rod 400 and the second piston 520 to thereby fix the second piston 520 to the cylinder body 120. The second piston 520 is provided with a stepped portion 530d on the inner periphery side of the body portion 530 which is located at the root of the arm portion 550. This stepped portion 530d fulfils a function as a stopper against the convex portion 430b of the cam portion 430 on the rod 400 side, namely a function to control the useful length of the actuating cylinder 100 in the extended state (state shown in Figure 2) of the rod 400. Since the useful length is to determine the lowered position (leg-lowered state) of the wheel 20, it is important to set the length accurately. For this reason, a screw junction between the second piston 520 and the cylinder body 120 is locked by a lock nut 600 with a fastening spring 610 attached thereto not to cause any change in the length.Of course, it is possible to adjust the fixing position by utilizing the screw junction between the second piston 520 and the cylinder body 120 to move the second piston 520 in the axial line direction of the cylinder body 120. One end of the fastening spring 610 enters a groove 660 provided at the outer periphery of the lock nut 600 to stop the rotation, and an adjusting tool also fits in the groove 660.

Also, an adjusting tool fits in a plurality of grooves 560 provided at the end of the second piston 520, and the other end of the fastening spring 610 enters a slot 570 which extends along the outer periphery of the body portion 530 in the axial line direction to prevent the rotation.

When a hydraulic pressure is supplied to the first chamber 310 to raise the leg, the first piston 210 and the rod 400 move to extend the rod 400. At this juncture, the claw 500 on the side of the second piston 520 fixed to the cylinder body 120 is guided by the cam portion 430 to be finally fallen into the through-hole 420h on the rod 400 side. It is a locking piston 700 that presses such a claw 500 from the outside to retain it in the fallen state. The locking piston 700 is cylindrical and disposed between the inner periphery of the first piston 210 and the outer periphery of the vicinity of the seal ring retaining portion 410 of the rod 400. The locking piston 700 retains the seal ring 702 at the outer periphery of the side which is fitted in the inner periphery of the first piston 210, and has an inward flange 710 at its inner periphery.This flange 710 functions as one spring bearing for a spring 730 for biasing the locking piston 700 toward the head side of the cylinder body 120, and as a stopper which controls the moving range of the locking piston 700. A chamber in which a spring 730 is provided is an air chamber, communicating with a chamber within the rod 400 through a hole 750 serving as a passage. On the other hand, an end 770 opposite to the locking piston 700 presses the outer periphery of the claw 500 to fulfil the locking function. In such a locking state, the locking piston 700 maintains a state in which the flange 710 is in contact with a portion 410 on the rod 400 side by the force of the spring 730.

However, when the hydraulic pressure in the first chamber 310 is released and a hydraulic pressure is supplied to the second chamber 320 (namely, when the leg is raised), the locking piston 700 falls into the first piston 210 while deforming the spring 730 by the hydraulic pressure received by the end 770.

At this juncture, the first piston 210 is pressed to the bottom wall on the bottom side of the cylinder body 120 by the hydraulic pressure in the second chamber 320. Figure 4 shows the state when the leg is thus raised. In association with the movements of the locking piston 700, the first piston 210 and the rod 400 incorporated therein, the claw 500 is released from the locking piston 700 to be moved by the convex portion 430b along the cam portion 430 while elastically deforming itself.

On the basis of the movement of the locking piston 700, the actuating cylinder 100 according to the present invention does not only detect (the first detection) whether or not the locking piston is locked, but also detect (the second detection) whether or not the claw 500 has entered the through hole 420h on the rod 400 side. Then, on the basis of these first and second detected results, the actuating cylinder switches the mechanical switch, which is not affected by the magnetism.

As a mechanical switch, a limit switch 460' similar to the aforesaid switch 460 is preferably used. Thus, a switch holder 800 supporting the limit switch 460' is disposed within the hollow rod 400, and yet the detecting means for performing the aforesaid first and second detections are provided in the switch holder 800. The first detecting means for the first detection is a rectilinear lever member 910. In the lever member 910, one end thereof is rotatively supported on the switch holder 800 by a pin 915 while the other end 913 is located outside the rod 400 through the lower through-hole 420h to come into contact with the end of the locking piston 700.

The second detecting means for the second detection is a Lshaped crank 920. In the crank 920, the central portion thereof is rotatively supported on the lever member 910 by a pin 925, and one end 921 thereof falls into the upper throughhole 420h to come into contact with the end of the claw 500 while the other end 923 is in contact with the head 950a of the plunger 950. Since the plunger 950 is biased by a spring 930, the head 950a thereof is always in contact with the end 923 of the crank 920. The plunger 950 is arranged so that its axial center is aligned with the axial centre of the detecting rod 460'a of the limit switch 460'.

The plunger 950 is capable of switching the limit switch 460' by the force from the crank 920. While the leg is raised as shown in Figure 4, the lever member 910 is rocked in the clockwise direction, and yet the crank 920 is also rocked in the clockwise direction. Therefore, the plunger 950 moves toward the bottom of the cylinder body 120, and no force is applied to the detecting rod 460'a of the limit switch 460'.

However, while the leg is lowered as shown in Figure 2, the lever member 910 is rocked in the counterclockwise direction, and yet the crank 920 is also rocked in the counterclockwise direction. Therefore, the plunger 950 moves toward the head of the cylinder body 120 to press the detecting rod 460'a of the limit switch 460' for switching operation. It is possible to know that it is in a leg-lowered state in response to the switching operation by the limit switch 460'. Also, in this case, if the claw 500 should not be located within the throughhole 420h resulting from any damage to the claw 500 or any inconvenience occurred in its movement dlthough the locking piston 700 has moved for locking, the lever member 910 is located at a correct swung position for lowering the leg while the end 921 of the crank 920 comes into contact with the side wall of the convex portion 430a of the cam portion 430 to move the plunger 950 that much toward the bottom of the cylinder body 120. As a result, the limit switch 460' does not transmit any signal indicating the leg-lowered state, and therefore, it is possible to prevent the vehicle from starting travelling on wheels without locking the claw 500.

According to the embodiment shown in the figure, the lever member 910 and the crank 920 are constructed to form a scissors-shaped construction so that the limit switch 460' is operated by joining their movements, thus enabling the switching operating assuredly even if the respective amounts of rocking are set to be small.

According to the present invention, the second detecting means for detecting the movement of the positioning member such as the claw 500 is provided in addition to the first detecting means for detecting the movement of the locking piston 700 to thereby cause the mechanical switch such as the limit switch 460' to perform the switching operation. Therefore, it is possible to detect assuredly and safely the leg-lowered state in which the wheel 20 has lowered. And yet, since the first and second detecting means and the mechanical switch are located within the rod 400 or the cylinder body 120, an actuating cylinder 100 which are advantageous to save the space and to prevent any damage can be obtained.

Claims (6)

1. An actuator for moving a wheel up and down, comprising a first piston which is capable of moving in the axial line direction within a cylinder body and which partitions the interior of the cylinder body into first and second chambers; a rod which is incorporated with the first piston and extends from the first piston to the outside of the cylinder body in said axial line direction; a second piston which is located at the outer periphery of this rod and includes a positioning member for retaining the first piston and the rod in place with respect to said cylinder body by mechanically coupling with the first piston or the rod when extending in said axial line direction to an extended state; a locking piston capable of either the first piston or the rod and locking the mechanical coupling of said positioning member with the first piston or rod; a first detecting means for detecting a locked or unlocked state of the locking piston; a second detecting means for detecting whether or not the positioning member of said second piston is in a position-retaining state; and a third detecting means that detects when said first detecting means detects the locked state, and said second detecting means detects the position-retaining state and indicates that said fist piston and said rod are in the extended state and said wheel is at a lowered position.

2. An actuator for moving a wheel up and down, comprising a first piston which is capable of moving in the axial line direction within a cylinder body and partitions the interior of a cylinder body into first and second chambers; a hollow rod which is incorporated in the first piston and extends from the first piston to the outside of the cylinder body in said axial line direction; a second piston which is located at the outer periphery of this rod, and includes a claw for retaining the rod in an extended state with respect to said cylinder body by fitting into a recess in the rod when it extends in said axial line direction; a locking piston capable of locking the claw in the recess in the rod by engaging the outer periphery of said claw; a lever member one end of which is rotatively supported with respect to the rod, and the other end of which is in contact with the end of the locking piston to detect the movement of the locking piston and thereby detect a lockedstate or unlocked-state of this locking piston; a crank which is rotatively supported at the mid-part portion of said lever member, and one end of which is located within the recess of said rod to detect whether or not said claw is within the recess; and a mechanical switch for switching between ON and OFF by the force from the other end of the crank.

3. The actuator according to claim 2, wherein said lever member, said crank and said mechanical switch are disposed within said hollow rod.

4. The actuator according to claim 2, wherein said second piston is screw-coupled with said cylinder body and the position of said second piston is adjustable in said axial line direction.

5. The actuator according to claim 4, wherein there is provided a locking member for locking the screw junction between said second piston and said cylinder body.

6. An actuator for moving a wheel up or down substantially as herein described with reference to the accompanying drawings.