Shaft brake

Abstract

To provide a shaft brake which can easily secure a large and stable holding force in the axial direction, has a simple structure, has a small number of parts, and can easily be reduced in cost. [Solution] Retaining rings 40a, 40b, through which the shaft 10 passes, are provided within an annular housing 20 that surrounds the shaft 10. The retaining rings 40a, 40b have an inner diameter larger than the outer diameter of the shaft, and are supported by receiving rings 30a, 30b on both ends so that they can tilt. A fulcrum member 60 and an elastic member are disposed between the retaining rings 40a, 40b, and the shaft 10 is restrained by pressing the retaining rings 40a, 40b axially with a piston 50, which serves as an actuator, to tilt the retaining rings 40a, 40b.

Description

[Technical Field]

[0001] The present invention relates to a shaft brake for stopping primarily axial movement of a linear shaft having a cylindrical outer periphery. [Background technology]

[0002] This type of shaft brake, also known as a shaft clamper, is widely used in height adjustment mechanisms for various types of support legs. It is also used as a brake for sliders that move along a shaft. This type of shaft brake has two main structures: a cam type and a wedge type. The cam type uses a cam lever attached to one side of a housing that is movable along a linear shaft to press and hold the linear shaft from the side (Patent Document 1). The wedge type clamps the linear shaft from the periphery by pressing multiple wedge members arranged in the housing so as to surround the linear shaft in the axial direction of the shaft (Patent Document 2).

[0003] Comparing cam-type and wedge-type brakes, cam-type brakes have a simple structure that holds the shaft by pressing on it from one direction around the shaft, which reduces costs. However, the pressing force cannot be offset within the brake, resulting in a larger device. Furthermore, the holding force is not stable. Wedge-type brakes, on the other hand, can press on the shaft from all directions around the shaft, ensuring a large holding force, ensuring stability of that holding force, and making it easy to miniaturize the device. However, they require an increased number of parts, which inevitably increases the cost of the device. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-351331 [Patent Document 2] Utility Model Registration No. 3186759 Summary of the Invention [Problem to be solved by the invention]

[0005] The object of the present invention was developed in view of the above circumstances, and is to provide a shaft brake that can easily ensure a large and stable axial holding force, has a simple structure with a small number of parts, and is easy to reduce costs. [Means for solving the problem]

[0006] In order to achieve the above object, the shaft brake of the present invention is a shaft brake for holding a linear shaft having a cylindrical outer peripheral surface in an axial direction, an annular housing surrounding the shaft; a retaining ring that is accommodated between the housing and the shaft and is tiltable relative to the axis of the shaft, and that allows the shaft to move in the axial direction when in a state perpendicular to the axis; a fulcrum member that fixes a circumferential portion of the retaining ring in an axial direction, and uses this portion as a fulcrum for tilting of the retaining ring; an elastic member that is located on the opposite side of the fulcrum member across the center of the retaining ring and that elastically holds the retaining ring in a state before tilting; The present invention is characterized in that it comprises an actuator that presses the retaining ring in the axial direction.

[0007] In the shaft brake of the present invention, when the retaining ring in the housing is not pressed axially by the actuator, the retaining ring is held in a position perpendicular to the axis by support from the fulcrum member and elastic pressure from the elastic member, allowing the shaft to move freely axially, i.e., the unlocked state.

[0008] When the retaining ring in the housing is pressed axially by the actuator from this state, the pressure from the fulcrum member causes the retaining ring to tilt relative to the axis against the elastic retaining force of the elastic member. As a result, the projected diameter of the inner peripheral surface of the retaining ring in the axial direction becomes smaller in the tilting direction, and the shaft is restrained at two points on either side of the axis. This holds the shaft in the axial direction, i.e., the locked state.

[0009] By applying a greater axial force to the retaining ring, the restraining force against the shaft is increased.

[0010] When the actuator stops pressing the retaining ring, the retaining ring returns to its original position perpendicular to the axis due to the pressure from the elastic member, and the shaft is released from the constraint of the retaining ring, allowing it to move freely in the axial direction, i.e., returning to the unlocked state.

[0011] The retaining rings are preferably configured as a pair, symmetrically arranged with the fulcrum member and elastic member in between. If there is only one retaining ring, a tilting force will be generated in the shaft due to the constraint by the retaining ring, but if there is a pair symmetrically arranged with the fulcrum member and elastic member in between, this tilting force will be canceled out.

[0012] The retaining ring is preferably tiltably supported by a combination of a concave spherical surface formed on either the retaining ring or a receiving ring disposed adjacent to the retaining ring, and a corresponding convex spherical surface formed on the other ring, from the viewpoints of support stability, mobility, etc. Also, as will be explained in detail later, a tiltably supported configuration using a second fulcrum member is also desirable.

[0013] A particularly desirable configuration is a unit structure in which the fulcrum member and elastic member are disposed between the opposing surfaces of a pair of retaining rings, and a pair of receiving rings are disposed on both ends of the retaining rings. By arranging these in a vertical row in the axial direction, the shaft restraining force in the locked state can be easily increased. In this case, the actuator may be a bidirectional type disposed between the units in the unit row, or a unidirectional type disposed at one end of the unit row. [Effects of the Invention]

[0014] In the shaft brake of the present invention, the shaft passing through the housing is held and restrained in the axial direction by the retaining ring disposed between the shaft and the housing, which is tilted by linear axial pressure applied by the actuator. Therefore, the structure is simple, the number of parts is small, and manufacturing costs can be kept low. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a perspective view of a shaft brake showing an embodiment of the present invention. FIG. [Figure 2] FIG. 2 is an exploded perspective view of the shaft brake. [Figure 3] FIG. 2 is a vertical cross-sectional view of the shaft brake. [Figure 4] FIG. 10 is a vertical cross-sectional side view showing the holding operation of the shaft brake. [Figure 5] FIG. 10 is an exploded perspective view showing another embodiment of the shaft brake. [Figure 6] FIG. 10 is a vertical cross-sectional side view showing still another embodiment of the shaft brake. DETAILED DESCRIPTION OF THE INVENTION

[0016] An embodiment of the present invention will be described below with reference to FIGS.

[0017] As shown in Figures 1 to 3, the shaft brake of this embodiment is a cylindrical assembly with a round bar-shaped shaft 10 inserted inside, and has a cylindrical housing 20 that surrounds the shaft 10 as its main component.

[0018] The housing 20 comprises a cylindrical first housing 20a and a cylindrical second housing 20b connected in the axial direction. The first housing 20a, excluding one end, is a first housing section with a large inner diameter, in which, from one end, a first receiving ring 30a, a first retaining ring 40a, and a second retaining ring 40b are housed. The second housing 20b, excluding the other end, is a second housing section with a similarly large inner diameter, in which, from one end, a second receiving ring 30b and a ring-shaped piston 50 are housed.

[0019] The first retaining ring 40a and the second retaining ring 40b are annular disks of the same structure butted together symmetrically in the axial direction, and a cylindrical fulcrum member 60 and a spring-like elastic member 70 are disposed between them. The inner diameters of the first retaining ring 40a and the second retaining ring 40b are set slightly larger than the outer diameter of the shaft 10 so as not to hinder tilting of these rings.

[0020] One end of the first retaining ring 40a is a protrusion with a small outer diameter, and its outer peripheral surface is a convex spherical surface 41. On the other hand, the inner peripheral surface of the first receiving ring 30a is a concave spherical surface 31 into which this convex spherical surface 41 fits, and this spherical fit allows the first retaining ring 40 to tilt freely in all directions around the periphery. Similarly, the second retaining ring 40b has a convex spherical surface 41 at its other small-diameter end, and this fits into the inner peripheral surface (concave spherical surface 31) of the second receiving ring 30b, allowing it to tilt freely in all directions around the periphery.

[0021] The fulcrum member 60 is a cylindrical roller disposed between the opposing surfaces of the first retaining ring 40a and the second retaining ring 40b, particularly between the outer peripheries, and functions as a fulcrum when the first retaining ring 40a and the second retaining ring 40b tilt. A semi-cylindrical or V-shaped recess 43 is formed on the opposing surfaces of the first retaining ring 40a and the second retaining ring 40b to position the fulcrum member 60.

[0022] The elastic member 70, which is disposed between the opposing surfaces of the first and second retaining rings 40a and 40b together with the fulcrum member 60, is located on the opposite side of the center line of the two rings from the fulcrum member 60 and is composed of a pair of coil springs arranged symmetrically in the tangential direction of the two rings. These elastic members 70 apply a pressing force in the expanding direction between the opposing surfaces of the two rings to maintain the opposing surfaces parallel. Circular recesses 44 are formed on both opposing surfaces to position the support member 70.

[0023] The first retaining ring 40a and the second retaining ring 40b have portions cut out on the elastic member 70 side to prevent mutual interference when the two rings are tilted in the direction in which the elastic member 70 is compressed.

[0024] Piston 50, housed in the large-diameter housing portion of second housing 20b, is a unidirectional actuator that advances toward one end by fluid pressure applied from joint 51, and presses second receiving ring 30b, which is located on one end side, toward said one end. When piston 50 is at its retract limit, the pressing force of elastic member 70 keeps the opposing surfaces of first retaining ring 40a and second retaining ring 40b parallel.

[0025] Next, the operation and function of each part of the shaft brake of this embodiment will be described with reference to FIGS.

[0026] 3 shows an unlocked state in which the shaft 10 is not constrained. In this state, the piston 50 is at its most retracted position (the stroke end on the other end side), and the first retaining ring 40a and the second retaining ring 40b held between the first receiving ring 30a and the second receiving ring 30b are supported from the inside by the fulcrum member 60 and the elastic member 70, so that the first retaining ring 40a and the second retaining ring 40b are perpendicular to the axis and their opposing surfaces are parallel.

[0027] The inner diameters of both the first retaining ring 40a and the second retaining ring 40b are set to be larger than the outer diameter of the shaft 10, so the shaft 10 is free to move in the axial direction, that is, in an unlocked, unconstrained state.

[0028] From this state, the piston 50 is forcibly driven (i.e., moved forward) toward one end by fluid pressure. Then, as shown in FIG. 4, due to pressure applied to one end via the second receiving ring 30, the second retaining ring 40b on the other end side receives a repulsive force from the fulcrum member 60 and tilts with the fulcrum member 60 as a fulcrum. Specifically, the fulcrum member 60 side tilts toward the other end side, and the elastic member 70 side tilts toward the one end side. At the same time, the first retaining ring 40a on the one end side tilts in the opposite direction with the fulcrum member 60 as a fulcrum due to the pressure from the fulcrum member 60 and the support from the first receiving ring 30a. That is, the fulcrum member 60 side tilts toward the one end side, and the elastic member 70 side tilts toward the other end side.

[0029] As a result, the pair of first and second retaining rings 40a, 40b are tilted in an inverted V-shape when viewed from the side. At this time, the fulcrum member 60 functions as both a fulcrum and a force point. As a result, the first retaining ring 40a grips the shaft 10 with end A on the fulcrum member 60 side of its inner circumferential surface at one end and end B on the elastic member 70 side of its inner circumferential surface at the other end. Similarly, the second retaining ring 40b grips the shaft 10 with end C on the fulcrum member 60 side of its inner circumferential surface at the other end and end D on the elastic member 70 side of its inner circumferential surface at one end. In other words, parts A to D are points of application.

[0030] As a result, the shaft 10 is restrained and held in the axial direction. The greater the driving force of the piston 50, the greater the shaft holding force. The shaft holding force due to the tilt of the first retaining ring 40a and the second retaining ring 40b applies a tilting force to the shaft 10, but because both rings tilt in opposite directions, the tilting forces of the two rings cancel each other out and do not actually tilt the shaft 10.

[0031] Furthermore, the shaft 10 is also held in the circumferential direction by the gripping between parts A and B and parts C and D due to the inclination of the first and second retaining rings 40a and 40b. However, because each ring is only partially held in two circumferential locations, the holding force is weaker than the axial holding force of a conventional wedge-type brake (Patent Document 2). However, the structure is very simple, and the number of parts is small. Furthermore, the structure is simpler and the number of parts is smaller than that of a clamp-type brake (Patent Document 1).

[0032] As described above, in the shaft brake of the first embodiment, a pair of retaining rings 40a and 40b, each having an inner diameter larger than the outer diameter of the shaft 10, are tiltably supported from both ends by a pair of receiving rings 30a and 30b, and with the fulcrum member 60 and elastic member 70 interposed between the two rings, the two rings are pressed in the axial direction and tilted symmetrically about the axis, thereby restraining and holding the shaft 10. This generates a large holding force in the axial direction, and the structure is simple, the number of parts is small, and it is highly economical.

[0033] The inner diameter of the retaining rings 40a and 40b is preferably 1.002 to 1.020 times the outer diameter of the shaft 10. If this is too small, the inclination angle of the retaining rings 40a and 40b will be small, and there is a concern that the durability will be reduced due to wear caused by continuous or intermittent contact between the two rings. On the other hand, if this is too large, the inclination angle of the retaining rings 40a and 40b will increase, and the tilting movement will become larger, which may reduce the operational stability of the two rings. There is also a concern that the product will become larger due to the increased movement of the piston 50. In Figure 4, the inclination of the first retaining ring 40a and the second retaining ring 40b is exaggerated for the sake of explanation, but the actual inclination angle is approximately 1°.

[0034] In this embodiment, a fluid pressure piston 50 is used as an actuator for applying axial pressure to the retaining rings 40a and 40b, but a screw-in type may also be used. Also, to tiltably support the retaining rings 40a and 40b, the receiving rings 30a and 30b are used, which utilize spherical seats on both ends. However, as shown in Figure 5, a configuration in which second fulcrum members 80, 80 are sandwiched between the retaining rings 40a and 40b and the receiving rings 30a and 30b may also be used.

[0035] Here, the second fulcrum members 80, 80 are cylindrical rollers arranged symmetrically about the axis and are arranged perpendicular to the relative positions of the fulcrum member 60 and the elastic members 70, 70, and recesses 45 for positioning are formed on the opposing surfaces of the retaining rings 40a, 40b. The other configuration is the same as in the previous embodiment, and the same parts are designated by the same numbers and will not be described again. Furthermore, by supporting the retaining rings 40a, 40b with pins, it is possible to support the retaining rings 40a, 40b tiltably without using the receiving rings 30a, 30b.

[0036] 6 shows yet another embodiment. In this embodiment, a connecting structure is employed in which a pair of retaining rings 40a and 40b are tiltably supported by receiving rings 30a and 30b, and the retaining units U are arranged on both ends of the third housing 20c for the actuator. The actuator is a bidirectional type that combines a first piston 52 for the retaining unit on one end and a second piston 53 for the retaining unit on the other end.

[0037] Although not shown, the holding unit U may be directly connected in the axial direction, and a one-way type piston may be disposed on the actuator side.

[0038] In any of the embodiments, the holding force can be significantly increased by simply connecting the holding units U.

[0039] In all embodiments, no anti-rotation members are used for the retaining rings 40a, 40b. That is, while the circumferential positional relationship between the retaining rings 40a, 40b is important, the fulcrum member 60 and elastic member 70 disposed between them, and in particular the fulcrum member 60, are fitted into the positioning recess 43 formed on the opposing surface, preventing relative circumferential movement. Therefore, no anti-rotation measures are taken. However, this does not preclude the use of anti-rotation measures if necessary. [Explanation of symbols]

[0040] 10 shaft 20a, 20b, 20c Housing 30a, 30b Receiving ring 31 Concave spherical surface 40a, 40b Retaining ring 41 Convex sphere 50, 52, 53 Pistons 60 Support member 70 Elastic member 80 Second support member

Claims

1. A shaft brake for axially holding a linear shaft having a cylindrical outer peripheral surface, an annular housing surrounding the shaft; a retaining ring that is accommodated between the housing and the shaft and is tiltable with respect to the axis of the shaft, and that allows the inner shaft to move in the axial direction when perpendicular to the axis; a fulcrum member that fixes a circumferential portion of the retaining ring in an axial direction, and uses this portion as a fulcrum for tilting of the retaining ring; an elastic member that is located on the opposite side of the fulcrum member across the center of the retaining ring and that elastically holds the retaining ring in a state before tilting; an actuator for urging the retaining ring in the axial direction.

2. 2. The shaft brake of claim 1, The shaft brake is configured so that the retaining rings are a pair of rings arranged symmetrically with the fulcrum member and elastic member in between.

3. 3. The shaft brake according to claim 1 or 2, A shaft brake in which the retaining ring is tiltably supported by a combination of a concave spherical surface formed on one of the retaining ring or a receiving ring arranged adjacent to the retaining ring, and a corresponding convex spherical surface formed on the other.

4. In the shaft brake according to claim 1 or 2, The retaining ring is a shaft brake having a unit structure in which the fulcrum member and elastic member are arranged between the opposing surfaces of a pair of retaining rings, and a pair of receiving rings are arranged on both ends of the retaining rings, and this is one unit and is arranged one or more times in the axial direction.

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