Cylinder locking device

Description

[0001] The invention relates to a cylinder locking device for locking the piston rod of a fluid pressure cylinder at an arbitrary position, and more specifically to a cylinder locking device which can lock the piston rod automatically and securely in the event of a fault in a fluid pressure source.

[0002] The present inventors have already proposed in JP-A-59-83 810 a cylinder locking device of a simple mechanical type which enables the piston rod of a fluid pressure cylinder to be securely locked at an arbitrary position.

[0003] In the latter cylinder locking device, a thick-walled cylinder, having outer and inner circumferential surfaces in eccentric relation, is divided in two in the region of maximum thickness and the region of minimum thickness in the axial direction to form two thick semi-cylindrical brake members, and the piston rod of a fluid pressure cylinder is slidably fitted within the inner circumferential portion of the two semi-cylindrical brake members, these brake members, these brake members being rotatably fitted in a housing, and the two brake members being rotatable in opposite directions to each other whereby to lock the piston rod therebetween.

[0004] The cylinder locking device as described above can lock the piston rod using a relatively small force and without producing shearing or rotational forces on the piston rod. In order for the device to be useful widely in practice, however, a mechanism to operate the semi-cylindrical brake members automatically is required and so far no such mechanism has been available.

[0005] In order to increase the utility of the above-described cylinder locking device, it is desirable to provide a cylinder locking device which can lock the piston rod of a fluid pressure cylinder automatically and which will reliably and safely lock the piston rod in the event that a fluid pressure source or a power source is turned off for any reason.

[0006] It is already known from DE-A-2 850 561 to provide a spring which is arranged to bias the two brake members in a direction to lock the piston rod, and an actuator for selectively rotating the brake members against the biassing force of the spring in a direction to release the locking action of the brake members on the piston rod.

[0007] It is an object of the present invention to provide an improved structure, developing the latter basic arrangement.

[0008] In accordance with the present invention, the coil spring is arranged between two brackets fixed respectively to the two brake members at one side thereof and is arranged to angularly bias the two brackets, and hence the two brake members, in opposite directions such as to lock the piston rod, and the actuator is arranged between two arms fixed respectively to the two brake members at the opposite sides thereof to said two brackets for selectively rotating the brake members against the biasing force of the coil spring in a direction to release the locking action of the brake members on the piston rod.

[0009] Advantageously, bushes made of fluororesin material are disposed at support portions of the support members for rotatably supporting the brake members.

[0010] The invention is described further hereinafter, by way of example only, with reference to the accompanying drawings, wherein:

Fig. 1 is a sectional side view of one embodiment of a cylinder locking device in accordance with the present invention installed to a fluid pressure cylinder; and

Fig. 2 is a sectional end view taken on the line II-II in Fig. 1.

[0011] The fluid pressure cylinder of Fig. 1 comprises a cylinder tube or wall 1, a cylinder head 2 and a cylinder cover 3, tightened and fixed at both ends of the cylinder tube 1 by one or more tie rods (not shown), a piston 4 fitted within the cylinder tube 1, and a piston rod 5 passing through the centre of the cylinder cover 3 and fixed at its base end to the piston 4. A cylinder locking device is installed on the cylinder cover 3 and surrounds the outer circumference of the piston rod 5. Numerals 6 and 7 designate nearly semi-cylindrical brake members arranged to embrace an outer circumferential portion of the piston rod 5.

[0012] The brake members 6, 7 are formed by taking a thick-walled cylinder which is arranged to have outer and inner circumferences which are in eccentric relation and dividing this cylinder into two about an axial plane which passes through the maximum thickness portion and the minimum thickness portion of the cylinder. The two axial ends of both outer circumferential portions of the brake members 6, 7 are rotatably supported by support members 8, 9; respectively. The support member 8 serves also as a housing on one end of the cylinder cover 3. The piston rod 5 passes through the centre of the support member 8, a bearing metal being positioned at the support region. The support member 9 includes a bearing metal fitted to the inside of a housing 10, an end portion of the housing 10 slidably supporting the piston rod 5. Bushes 11 made of fluororesin as its starting material are interposed at the positions where the support members 8, 9 rotatably support the brake members 6, 7, whereby to decrease the sliding friction. As shown in Fig. 2, the nearly semi-cylindrical brake members 6, 7 have a respective circumferential space between each pair of opposing regions so that both members 6, 7 can be mutually rotated to some extent. In the course of such rotation the centre of the circle including the outer circumference of the brake members 6, 7 is shifted slightly downwards relative to thecentre of the inner circumference thereof, i.e. relative to the central axis of the piston rod 5. Consequently, when the brake members 6, 7 are rotated in a direction to open the lower portion thereof as directed by the arrows in Fig. 2, the brake members 6, 7 are rotated in the support members 8, 9 for the outer circumference thereof and the piston rod 5 within the members 8, 9 is gripped from both sides and locked.

[0013] Brackets 12, 13 having an L-shaped cross-section are fixed to lower portions of the two brake members 6, 7 and a coil spring 14 for biasing the brackets 12, 13 apart is hooked in a compressed state between the brackets 12, 13. The brake members 6, 7 are normally biased by the coil spring 14 into their position in which they lock the piston rod 5.

[0014] Further L-shaped arms 15, 16 are fixed in opposition to each other on upper portions of the brake members 6, 7. A fluid pressure actuator 20 is arranged between the two arms 15, 16 and is fixed to a mounting plate 17 mounted on an upper portion of the housing 10. The fluid pressure actuator 20 comprises a cylinder 21, two pistons 22, 23 spaced from each other and fitted inside the cylinder 21, and pressure projections 24, 25 located on the outside of the two pistons 22, 23 for pushing the two arms 15, 16 apart. When fluid pressure is applied between the pistons 22 and 23, they are moved outwards, thereby urging the upper portions of the arms 15, 16 apart, which in turn rotate the brake members 6, 7 in a direction counter to the arrows in Fig. 2 to release the piston rod 5.

[0015] Operation of the above-described cylinder locking device is as follows.

[0016] In normal operation, the piston 4 of the fluid pressure cylinder, and with it the piston rod 5, can be moved to the left in Fig. 1 by fluid pressure supplied via a port 18. Movement of the piston and piston rod 5 to the right is obtained by fluid pressure supplied via a port 19.

[0017] In the operating state of the piston rod 5 shown in Fig. 2, the fluid pressure actuator 20 is energised to hold the upper portions of the arms 15, 16 apart whereby the brake members 6, 7 are in the non-braking state. In other words, when fluid pressure is applied to a port 26 of the fluid pressure actuator 20, both pistons 22, 23 are moved outwards so as to urge the portions of the arms 15, 16 apart by way of the projections 24, 25. The two brake members 6, 7, whose outer circumferential portion is supported in the support members 8, 9, and thus rotated against the biasing force of the coil springs 14 so as to open the circumferential gap between the upper portions of the brake members and to close the circumferential gap between the lower portions of those members.

[0018] Since the centre of the circle which includes the outer circumference of the brake members 6, 7 is shifted downwards relative to the centre of the inner circumference, i.e. from the centre of the circular section of the piston rod 5, a small gap is produced between the brake members 6, 7 and the piston rod 5 and the brake is thereby released.

[0019] On the other hand, if the fluid pressure applied to the fluid pressure actuator 20 is decreased, either delibrately in order to effect locking of the piston rod 5 or as a result of a fault, the brake members 6, 7 are caused to be rotated in the direction of the arrows in Fig. 2 and lock the piston rod 5 automatically. In other words, if fluid pressure within the fluid pressure actuator 20 is removed for any reason, the force necessary to push the pistons 22, 23 apart disappears whereby the biasing force of the coil spring 14 acting on the brake members 6, 7 causes them to rotate within the inner circumference of the support members 8, 9 so that the circumferential gap between the upper portions of the brake members 6, 7 is opened. Since the centre of the inner circumference of the support members 8, 9, i.e., the centre of the circle including the outer circumference of the brake members 6, 7, is shifted from the centre of the inner circumference of the brake members 6, 7, i.e., the centre of the circular section of the piston rod 5, the piston rod 5 is grasped by the brake members 6, 7 from both sides and thereby locked. The piston rod 5 can thus be locked without being subjected to shearing or rotational forces.

[0020] As an alternative, an electromagnetic actuator may be used in place of the fluid pressure actuator 20.

[0021] According to the cylinder locking device of the invention described above, since the piston rod is grasped by the two nearly semi-cylindrical brake members, it can be locked by a mechanical brake of simple structure without producing shearing or rotational forces, whereby the piston rod or the bearing parts therefor is prevented from deformation or abrasion and the piston rod can be stopped securely and reliably. Furthermore, since the brake members are normally biased in the locking direction by the spring, even if the fluid pressure source or the power source of the actuator is suddenly turned off as a result of a fault, the piston rod is immediately locked by the biasing force of the spring and safety is secured.

Claims

1. A locking device for the piston (4) of a fluid pressure cylinder (1-5) comprising two nearly semi-cylindrical brake members (6, 7) formed in effect from a thick-walled cylinder, whose outer and inner circumferential surfaces are in eccentric relation, and which is divided in two in the axial direction in the regions of maximum and minimum thickness of the cylinder, and support members (8, 9) for rotatably supporting outer peripheral portions of the two brake members (6, 7) with a piston rod (5) of the fluid pressure cylinder (1-5) slidably fitted within the inner circumferential portions of the brake members '(6, 7) such that said piston rod (5) can be locked by relative angular displacement of the two brake members (6, 7) in opposite directions, characterized by a coil spring (14) arranged between two brackets (12, 14) fixed respectively to the two brake members (6, 7) at one side thereof and which is arranged to angularly bias the two brackets (12, 14), and hence the two brake members (6, 7), in opposite directions such as to lock the piston rod (5), and an actuator (20) arranged between two arms (15, 16) fixed respectively to the two brake members (6, 7) at the opposite sides thereof to said two brackets (12, 14) for selectively rotating the brake members (6, 7) against the biasing force of the coil spring (14) in a direction to release the locking action of the brake members (6, 7) on the piston rod.

2. A cylinder locking device as claimed in claim 1, wherein bushes (11) made of fluororesin material are disposed at support portions of the support members (8, 9) for rotatably supporting the brake members (6, 7).

Ansprüche

1. Verriegelungseinrichtung für den Kolben (4) eines Flüssigkeitsdruckzylinders (1-5) mit zwei annähernd halbzylindrischen Bremselementen (6, 7), die effektiv aus einem dickwandigen Zylinder hergestellt sind, dessen äußere und innere Umfangsoberflächen in exzentrischer Beziehung stehen, und der in axialer Richtung in den Bereichen der maximalen und minimalen Dicke des Zylinders zweigeteilt ist, und mit Stützelementen (8, 9) für die drehbare Lagerung äußerer Umfangbereiche der zwei Bremselemente (6, 7), wobei eine Kolbenstange (5) des Flüssigkeitsdruckzylinders (1-5) drehbar in den inneren Umfangsbereichen der Bremselemente (6, 7) eingepaßt ist, so daß die Kolbenstange (5) durch eine relative Winkelverschiebung der zwei Bremselemente (6, 7) in entgegengesetzte Richtungen festgeklemmt werden kann, gekennzeichnet durch eine Spiralfeder (14), die zwischen zwei Klammern (12, 14) angeordnet ist, die jeweils an den zwei Bremselementen (6, 7) an einer Seite davon angebracht sind, und die angeordnet ist, um die zwei Klammern (12, 14) und so die zwei Bremselemente (6,7) in entgegengesetzten Richtungen winklig vorzuspannen, so daßdie Kolbenstange (5) festgeklemmt wird, und ein Betätigungsorgan (20), das zwischen zwei Armen (15, 16) angeordnet ist, die jeweils an den zwei Bremselementen (6,7) an den gegenüberliegenden Seiten zu den zwei Klammern (12, 14) befestigt sind, um selektiv die Bremselemente (6, 7) gegen die vorspannende Kraft der Spiralfeder (14) in einer Richtung zu drehen, um die festklemmende Wirkung der Bremselemente (6,.7) auf die Kolbenstange zu lösen.

2. Zylinderverriegelungseinrichtung nach Anspruch 1, dadurch gekennzeichnet, daß Büchsen (11) aus Fluorkunststoffmaterial an den Stützbereichen der Stützelemente (8, 9) vorgesehen sind, um drehbar die Bremselemente (6, 7) zu stützen.

Revendications

1. Dispositif de blocage pour le piston (4) d'un cylindre à pression fluidique (1-5) comprenant deux éléments de frein (6, 7) approximativement semi- cylindriques et formés en fait à partir d'un cylindre à paroi épaisse, dont les surfaces circonférentielles extérieure et intérieure sont en relation excentrique, et qui est divisé en deux en direction axiale dans les zones d'épaisseur maximale et d'épaisseur minimale du cylindre, et des éléments porteurs (8, 9) pour supporter tournantes des parties périphériques extérieures des deux éléments de frein (6, 7), une tige de piston (5) du cylindre à pression fluidique (1-5) étant montée coulissante à l'intérieur des parties circonférentielles intérieures des éléments de frein (6, 7) de telle sorte que ladite tige de piston (5) puisse être bloquée par un déplacement angulaire relatif des deux éléments de frein (6, 7) en directions opposées, caractérisé par un ressort hélicoïdal (14) disposé entre deux consoles (12,14) fixées respectivement sur les deux éléments de frein (6, 7) sur un côté de ceux-ci et qui est agencé pour rappeler angulairement les deux consoles (12, 14), et par conséquent les deux éléments de frein (6, 7), en directions opposées de façon à bloquer la tige de piston (5), et un dispositif d'actionnement (20) placé entre deux bras (15, 16) fixés respectivement sur les deux éléments de frein (6, 7) sur leurs côtés opposés aux deux consoles précitées (12, 14) afin de faire tourner sélectivement les éléments de frein (6, 7) à rencontre de la force de rappel du ressort hélicoïdal (14) dans une direction de cessation réduction de l'action de blocage des éléments de frein (6, 7) sur la tige de piston.

2. Dispositif de blocage de cylindre tel que revendiqué dans la revendication 1, dans lequel des bagues (11) formés d'une matière en fluororésine sont disposés sur des parties de support des éléments porteurs (8, 9) afin de supporter en rotation les éléments de frein (6, 7).

Drawing