KR890000853B1 - Overthrust rotecting device of lead screw - Google Patents

Abstract

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Description

Lead Screw Overload Protection Device

FIG. 1 is a partial elevation view showing a part of a cross section taken along line 1-1 of FIG. 2, showing a lead screw driven by a servo motor and a mechanical member moved by it.

FIG. 2 is a partial elevation view in section taken along line 2-2 of FIG. 1. FIG.

3 is an elevation view showing a modified form of any part of FIG.

* Explanation of symbols for main parts of the drawings

14: mechanical member 16: lead nut

18: lead screw 20, 22, 24: bearing

28,42: sleeve 50,60: spring

74,126: Original 82,84,86,88: Block

120: piston 122: seal

160: limit switch

BACKGROUND OF THE INVENTION Field of the Invention [0001] The present invention generally relates to a device for preventing damage to a machine due to an overload. In particular, in a lead screw drive machine, the device is protected from overload caused when the movement of the machine is interrupted. Related to the automatic device.

There are a number of possible causes that sometimes cause mechanical destruction, but the following causes, especially in N Servo-driven machines.

1. Foreign substance present on the movement path of the machine member.

2. Electrical defects in the servomotor drive circuit, causing the servomotor to dislodge.

3. Improper programming of electronically controlled servomotors.

4. A deficiency in any mechanical function that determines the position of a machine member.

The rapid movement of these machines is achieved by high inertia energy in mechanical drive. In a potential failure situation, this energy must be dissipated quickly before breaking force is generated. The essence of servo drive lies in the servo following the command of the controller. As resistance to movement occurs, the servomotor increases its output torque to overcome the resistance. Since the servo torque tries to comply with the servo command, it may be increased to 400% or more of the destructive force amplified from the normal state. Members of servomotor drives sometimes run at speeds of 400 ipm (ich per min) or higher. In order to be protected against destructive forces, this speed of motion must sometimes stop from its high speed until it detects an overload and travels a distance of 0.01 inch or less. This time interval is sometimes as short as 1 to 2 msec.

The rotation speed of the servomotor and drive line is usually 160rpm or higher. This rotational energy must sometimes be rapidly dissipated between one revolution or within 30 to 40 msec.

Preferably, the protection against these conditions should be independent of each other and all electronic control parts which may inherently cause a potential breakage and become inoperable in an emergency.

Depending on the operation of the protective device, the machine may be in a state of great stress, which creates a danger for the operator to remove it. In this case, the protective mechanism must be able to release the force of the machine to a safe state before the operator intervenes to remove the obstruction.

According to the present invention, a lead screw overload prevention device includes a rotary shaft support device for supporting the rotary shaft with respect to an axial movement, the rotary shaft being positioned in an axially operable position and axial movement in both directions of the shaft from this position. And a brake device that stops rotation of the shaft when the shaft is moved axially in either direction from an operating position of the shaft, wherein the shaft is in rotation when the movement of the movable member is disturbed. In response to the force of, the shaft is moved from the operating position of the shaft in the axial direction.

It is an object of the present invention to provide an apparatus that meets the above requirements. Other objects will become more apparent with reference to the following description, particularly with reference to the accompanying drawings.

1 and 2, the machine base 12 is equipped with a machine member 14 which reciprocates. The lead nut 16 is attached to the member 14, and the ball lead screw 18 is shown in a state where the lead nut 16 and the screw thread are engaged with each other, so that the lead nut and the mechanical member are rotated according to the rotation direction of the lead screw. 14 moves in either direction or vice versa.

The middle section of the lead screw 18 shows that the bearings 20 and 22 are mounted for rotation. The lead screw is mounted on the bearing 24 near the opposite end of the end thread and the belt pulley 26 is fixedly mounted on the lead screw by the tapered sleeve 28, which is attached to the lead screw of the pulley. To form a wedge bite that inhibits rotation to about.

The base 12 has a drive motor 30 attached to its upper end. The pulley 32 is installed on the output shaft of the motor and the belt 34 extending between the pulleys 23, 32 transfers the motor output to the lead screw 18, according to the rotation direction of the motor Allow the direction of rotation to be determined.

The bearings 20 and 22 are mounted in a cylindrical bearing cage 36 having a square flange curved inwardly at one end. The bearings 20 and 22 are sandwiched in the cylindrical body of the bearing cage 36 and are firmly fixed to the flange 38 by bearing nuts 40 which are threaded in the cylindrical body. The bearing cage 36 is axially slidably mounted in the cylindrical sleeve 42, and the lengths of the bearing cage and the sleeve are exactly the same as shown in FIG. The sleeve 42 fits into an opening 43 formed concentric with the shaft 18 in the base 12. The sleeve 42 is fixed by a retainer 44 fitted in the cylindrical opening 43 of the base to prevent axial movement therein. The retainer 44 forms a cylindrical body 46, the end of which is supported at one end in the sleeve 42. Retainer 44 is fixed on the base by bolts 48.

A cylindrical Belleville spring 50 is inserted into the cylindrical body 46 of the retainer 44, and the spring 50 has a disc-shaped washer 52 fitted at one end to the cylindrical body 46. The other end thereof is compressed and supported by the shoulder 54 of the ring-shaped expansion portion 56 of the retainer 44. The washer 52 is in contact with the adjacent end of the cage 36 and the sleeve 42.

The base 12 forms another cylindrical opening 57 smaller in diameter than the opening 43 but arranged concentrically. The openings 43 and 57 are separated by the shoulders 58 and another end supported by the disc washer 62 and the ends 64 by the shoulders 64 of the base 12 into the openings 57. Belleville spring 60 is inserted. The washer 62 is in contact with the adjacent end of the cage 36 and the sleeve 42.

Washers 52 and 62 are supported by opposite ends of the sleeve 42 and opposite ends of the cage 36 of the same length as the sleeve 42, so that the spring 50 60, elastically compressed. As a result, the bearing cage 36 is suppressed with respect to the axial movement as long as the axial force does not exceed the compression force of the Belleville springs 50 and 60 previously dropped. In this restrained position the ends of the cage are coplanar with the ends of the sleeve 42 by washers 52 and 62.

The inner race and pulley 26 of the bearings 20, 22 and 24 are attached to the lead screw and screwed at one end of the shaft with a nut 66, tapered sleeve member 28 and bearing 24 By spacer sleeves 68 and 70 fitted between the inner races of the crankshaft and between the inner races of the control rings 24 and 20, the axial movement is fixed. Here, it should be noted that the bearing 20 is in contact with the bearing 22 and the bearing 22 is in contact with the shoulder 72 formed on the shaft.

The washer-shaped disc 74 on the inner side of the pulley 26 is slidably fitted in the cylindrical space or opening 76 formed in the extension 56 of the retainer 44. Since the cylindrical outer wall of the space 76 in which the disk 74 slides is located concentric with the shaft 18, the disk 74 is also concentric with the shaft 18. The disc 74 is provided with a space for attaching the disc brake member 80.

The four blocks 82, 84, 86 and 88 are attached and secured to the extension 56 of the retainer 44 by bolts 90 so as to be arranged circumferentially at 90 ° to each other. These blocks have the same size and shape and surround the pulley 26. The thickness, which is the distance between the inner surface 92 and the outer surface 94 thereof, is formed slightly larger than the thickness of the pulley 26. Blocks 82-88 have coplanar inner surfaces 92 slightly inward of the inner surface of the pulley 26, and coplanar outer surfaces 94 are slightly outside of the outer surface of the pulley 26. It is located on the side.

The cylinder 100 is located concentrically with the closed end 120 and the screw 18, and the closed end to form the skirt members 106, 108, 110, 114, 116, and the like. It consists of a cylinder wall or skirt 104 having a longitudinally long hole at the end away from 120. These skirt members are located on both sides of the blocks 80 and 88, and as shown in FIG. 2, the skirt members 106 and 108 are provided on both sides of the block 82, with a skirt member ( 110 and 112 span both sides of 84, skirt members 112 and 114 on both sides of 86, and skirt members 114 and 116 across both sides of 88, respectively. Will be. In this way, the rotational movement of the cylinder is suppressed. These skirt members are secured to the disc 74 by bolts 118, whereby the disc 74 is supported coaxially with the cylinder.

The piston 120 is capable of reciprocating in the cylinder 100 on the outer side of the pulley 26, the seal (sea1) 122 is formed to prevent the leakage of the fluid. The piston 120 has an inner end 124 having a space formed therein so as not to contact the end of the shaft 18. Another disc-shaped brake member 126 is slidably fitted in the cylinder 107 and attached to the skirt surface of the piston surrounding the space 124. Blocks 82-88 extend into the space between the skirt members and are inserted into the cylinder 100. The brake members 80 and 126 oppose each other with the radially outer wall ends of the pulleys 26 and the radially inner wall ends of the blocks 82-88.

The pin 130 is attached to the head of the cylinder 100 and is slidably inserted into the hole 132 in the piston to prevent the piston from rotating in the cylinder.

The air hole 140 formed in the head of the cylinder 100 is from a suitable source through a three way valve 142 when the solenoid 144 is excited to overcome the force of the spring 146. Compressed air is supplied. The air cannot escape the cylinder by the check valve 148.

When solenoid 144 loses force, spring 146 moves valve 142 to the position of FIG. 1 to block the inlet of compressed air entering cylinder 100 and to restrict the inlet air in the cylinder. Discharge through the outlet 150.

When compressed air is supplied into the cylinder 100, the piston 120 contacts the brake member 126 with the face 94 of blocks 82-88, and the cylinder 100 has a disc 74. And its brake disc 80 in contact with the face of the block 92. In the normal position of the members, the brake members 80 and 126 are slightly spaced apart on both sides of the pulley. When the servo drive is operated, the solenoid 144 is excited to supply compressed air into the cylinder 100 through the valve 142.

The limit clutch 160 is attached in the opening 162 of the base 12, and the limit switch operating rod 164 is inserted into the hole in the sleeve 42. The end of the limit switch operating rod 164 is fitted in the annular elongated groove 166 formed on the outer surface of the cage 36. Any axial movement of the cage 36 will move the groove 166 and the operating rod will disengage from the designated position so that the closing circuit is opened.

In operation, the servomotor 30, although not shown, is electrically driven by the controller according to the method described above. By the pulleys 32 and 26, and the belt 34, the lead screw 18 is rotated. The movable mechanical member 14 together with the lead nut 16 can thereby be moved left and right, depending on the direction of rotation of the lead screw 18. When the mechanical member 14 is subjected to the movement force, the servomotor automatically increases the output torque by its servo command. The axial thrust on the lead nut 16 is also increased to overcome the movement resistance of the machine member 14. If the axial resistance to the movement is abnormally large and the force previously loaded on either of the springs 50 and 60 exceeds, the cage 36 slides in the sleeve 42 and the mechanical member 14 stops, and the lead screw 18 moves axially as it is rotated. Since the inertial force of the relatively slow moving mechanical member 14 is small compared with the rotational inertia force of the high-rotational drive system, the mechanical force generated by the sudden increase in axial thrust will only counter a small portion of the inertia force of the entire drive system, Power can be avoided.

Since the spacing in which the lead screw 18 is formed to be movable in the axial direction is limited by the springs 50 and 60 and other mechanical limitations, the rotation of the drive system must be stopped quickly, and its relatively high inertia force is also possible. If so, it should be lost quickly in one round. If the excess resistance to movement occurs when it is counterclockwise (see FIG. 2), the axial movement of the lead screw 18 begins, and the release surface 96 is in contact brake with the brake disc 126. The time interval required for this is very short, for example, in the case of rotation of 1600rpm is less than 1msec. Since this is a purely mechanical system, no electrical faults or delays have been taken into account, and the braking contact is instantaneously and reliably.

The contact of the brake disc instantaneously generates high braking torque due to the influence of the piston thrust in the cylinder 100. Rotation of the cylinder 100 and the disc 74 attached thereto is prevented because the blocks 82-88 are fitted in the holes of the cylinder skirt 104. The rotation of the piston 120 is limited by the pin 130. As the axial movement of the lead screw 18 continues, the brake disc 126 is brought out of contact with the face 94 of the members 82-88 by the release face 96.

Since the air suppressed between the piston 120 and the cylinder 100 cannot escape past the check valve 148, it is compressed by the relative movement of the piston and the cylinder. As the air pressure rises rapidly, the reactivation effect of the disc 126 also increases rapidly.

For example, an initial air pressure of 60 psi can be increased to 180 psi when the gap in the piston head is sufficiently reduced. This high braking torque can quickly dissipate the inertial energy and stop the servomotor even if it is still in operation.

Note that the clockwise rotation shown in FIG. 2 causes the lead screw to move axially to the right (FIG. 1). The braking contact with the brake disc 80 of the release face 98 causes the cylinder 100 to move to the right, while the piston contacts the brake disc 126 on the face 94 of the members 82-88. It stops and is stopped. The braking effect in this case is caused by the disc 80. The air is again compressed in the cylinder 100 for rapid braking. In this way, the mechanical member 14 can avoid destructive forces in both directions of movement.

When the cage 36 moves along the axis in either direction, one side of the groove 166 is engaged with the operating rod 164 of the limit switch 160, which opens the closed circuit. This electrical fault signal, although not shown, is connected such that solenoid 144 of valve 142 loses force. The valve 142 is resiliently retracted to withdraw air from the space of the cylinder 100. The discharge rate of air is limited by the restriction hole 150. Thus, very little air is discharged in a short time of the braking effect. Limit switch 160 is also used to electrically stop all mechanical drive that may be placed in a potential failure state, including servomotor 30.

In view of this closing cycle, it is understood that either of the springs 50 and 60 is significantly compressed so that the pressure is a mechanical disturbance. The mechanical member 14 is rapidly moved forward by the pressure of the spring bundle may cause damage. However, since air is continuously discharged through the restriction hole 150, the air pressure in the cylinder 100 is reduced. That is, the braking effect is continuously reduced until the pressure of the spring 50 or 60 may move the lead screw and the servomotor backward. The cage 36 is thus returned to its normal position, and the safety risks of the pressure present on the mechanical disturbance are automatically eliminated. Elimination of the braking effect also makes it possible to use the servomotor 30 so that the mechanical member is further retracted to a position away from the obstacle.

3 is a washer or ring in a portion similar to that of FIG. 1, in which the air cylinder piston, air circuit, etc. consist essentially of a cylindrical wall or skirt 204 with longitudinal long holes at the ends to form skirt members. Only one replaced with 200 represents another variant, an example. The cylindrical wall 240 and members of FIG. 3 are similar to the cylindrical members 104 and members 106-116 of FIGS. 1 and 2. Only member 208 is shown in FIG. The skirt members are spread over both sides of the block members in the same manner as in FIG. The bolt 290 is fixed to the disc 74 and the ring 200 is slidable on this bolt. The bolt 290 is parallel to the screw 18, so that the ring 200 remains concentric with the screw. The ring 200 forms a space to which the brake member or the disc 126 is attached. The brake discs 126 and 80 have a relationship with the pulley 26 and the block members, as in the embodiment of FIGS. 1 and 2. The spring 210 on the bolt 290 is compressed between the bolt head 212 and the ring 200 such that the ring 200 and the disc 74 move toward each other, such that the brake members 126 and 80 are moved. Are brought into contact with both sides of the block members, respectively. Thus, when the force loaded on the springs 50 and 60 is exceeded, the braking force provided by the cylinder 100 and the piston 120 in FIGS. 1 and 2 is caused by the spring 210 in FIG. Is provided.

Operation of the apparatus of FIG. 3 is similar to that of FIGS. 1 and 2, but the ability to automatically release the braking torque is not available in the case of FIG. Therefore, the lead screw 18 extends the wrench hole 220 so that it can be retracted manually when an operation stop state occurs. Alternatively, the bolt 290 may be retracted to release the compressive force of the spring 210.

Claims (13)

A device having a movable member including a movable member and a rotating shaft operative to move the movable member when it is screwed to the movable member, the apparatus being protected, wherein the apparatus is protected from damage due to overload when the movable member movement is disturbed. The lead screw overload prevention device is a rotary shaft support device for supporting the rotary shaft with respect to the axial movement, and an elasticity for placing the rotary shaft in an axially operable position and suppressing axial movement in both directions of the shaft from this position. And a brake device that stops rotation of the shaft when it moves axially in either direction from an operating position of the shaft, the shaft being rotated against the force of the elastic device when movement of the movable member is disturbed. Characterized in that it is moved in the axial direction from the operating position of the shaft Lead screw overload protection device. 18. The method of claim 17, wherein the resilient device has a first spring acting in either axial direction with respect to the axis and in the same direction with respect to the first fixed adjacency, and in opposite directions with respect to the axis and with a second fixed adjacency And a second spring acting in the opposite direction with respect to the part, wherein the axis during rotation is caused to move axially from the operating position against the force of the one spring when the movement of the member is disturbed and causes an overload. 2. The lead screw overload protection device of claim 2, wherein the force is not assisted by the other screw, whose force is blocked by the fixed adjacent portion. 19. The brake device according to claim 17 or 18, wherein the brake device is composed of brake members axially spaced about the axis on both sides of one component on any axis, the one or the other brake member stopping the shaft from rotation. Lead overload prevention device, characterized in that the shaft is abutted by the component on the shaft when the shaft is moved axially from the operating position. 20. The lead screw overload protection device of claim 19, wherein the brake member includes a flexible brake support member that suppresses the yield pressure against movement of the brake members when brought into contact with the component of the shaft. . 21. The apparatus of claim 20, further comprising an adjacent member that secures the brake member axially spaced from the component of the shaft to provide a small gap when the shaft is in the operating position, the brake members being coupled to the component of the shaft. Lead screw overload prevention device, characterized in that the movement away from the adjacent member when the contact. 22. The lead screw overload protection device according to claim 21, wherein the flexible brake support member increases its resistance according to the movement of one of the brake members falling from the adjacent member. 23. The method of claim 22, wherein the flexible brake support member has a piston connected to any one of the brake members and the hydraulic chamber is reduced in volume as the brake member moves away from the adjacent member. A piston-cylinder assembly formed by a cylinder connected to one, and a lead screw overload protection device, characterized in that consisting of a fluid which is kept compressed in the hydraulic chamber. 24. The method of claim 23, wherein the pressure in the hydraulic chamber is automatically released immediately according to the axial movement of the shaft, and the pressure in the hydraulic chamber is automatically released, thereby sufficiently stopping the rotation of the shaft by either of the brake members. Lead screw overload protection device comprising a pressure release device. 25. The apparatus of claim 24, wherein the pressure relief device in the hydraulic chamber is comprised of a solenoid operated valve and a limit switch for the solenoid operated by the axial movement of the shaft. 27. The lead screw overload protection device according to claim 25, wherein the limit switch in operation deactivates the power unit. 23. The lead screw overload protection device according to claim 22, wherein the flexible brake support member is composed of a spring member. 28. The lead screw overload protection device of claim 27, wherein the shaft includes a device capable of being manually returned to an operating position in accordance with axial movement. 18. The lead screw overload protection device according to claim 17, wherein the shaft includes a device capable of being manually returned to an operating position according to the axial movement.

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