Stable adjusting device for explosive ordnance disposal mechanical arm

Abstract

The utility model provides a stable adjusting device for an explosive ordnance disposal mechanical arm. Comprising a supporting frame, a cantilever shaft, a stabilizing frame, a rotating assembly, an assembling shaft and a connecting pipe. The cantilever shafts are assembled on two mounting holes of the supporting frame respectively, the stabilizing frame is assembled between the two cantilever shafts through a rotating assembly, the assembling shaft is arranged on the stabilizing frame through the rotating assembly, the direction of the assembling shaft is perpendicular to the direction of the cantilever shafts in space, and the connecting pipe is assembled in the center of the assembling shaft. Through rotation of the rotating assembly, the stabilizing frame and the cantilever shaft are kept dynamically stable on the XY plane, the stabilizing frame and the assembling shaft are kept dynamically stable on the YZ plane, and therefore the mechanical arm assembled on the connecting pipe is always kept in a stable state in the space. Compared with an existing explosive ordnance disposal mechanical arm, dynamic balance of the gravity center of the explosive ordnance disposal mechanical arm is always kept when the explosive ordnance disposal mechanical arm moves explosives, the shaking influence of external factors on the explosives is reduced, and the safety of explosive ordnance disposal personnel when the explosive ordnance disposal personnel transfer the explosives is improved.

Description

Technical Field

[0001] The utility model relates to a mechanical arm in the field of explosive disposal equipment, in particular to a stabilizing and regulating device for the explosive disposal mechanical arm. Background Art

[0002] At present, in the case of handling explosives, some explosives need to be transferred. Usually, the bomb disposal personnel use the bomb disposal rod equipped with a mechanical arm to transfer the explosives into the bomb disposal tank, or transfer them to a place convenient for destruction.

[0003] The Chinese patent with the announcement number CN208992693U discloses a telescopic electric bomb disposal robot arm, which includes a robot claw 1, a video collector 2, a three-section telescopic robot arm 3, a display 4, a shoulder strap 5, a control button box 6, a battery box 7 and a counterweight 8. The thin end of the three-section telescopic robot arm 3 can be rotatably mounted with the robot claw 1, and the thick end is equipped with a battery box 7. The three-section telescopic robot arm 3 is equipped with a display 4, a shoulder strap 5 and a control button box 6, the video collector 2 is installed on the robot claw 1, and the counterweight 8 is installed at the end of the battery box 7. Two motors are installed in the shell of the robot claw 1, the three-section telescopic robot arm 3 is wired, and the line plug is inserted into the interface of the control button box 6. The battery box 7 uses a rechargeable lithium battery, the display 4 uses a 7-inch LCD display, and the video collector 2 uses an infrared camera with infrared night vision function. When the bomb disposal robot arm is in use, the three-section telescopic robot arm 3 is manually stretched and each section of the lock is manually locked to make the robot arm extend to its longest length. The bomb disposal personnel carry the shoulder strap 5 on their shoulders and manually press the four buttons on the control button box 6 to control the opening and closing and rotation of the robot claw 1 through different motors. The locating pin at the claw joint can be manually adjusted to change the swing angle of the robot claw 1, which is convenient for actual use needs, and the explosive materials can be safely transferred or transferred to the bomb disposal tank for blasting, thereby ensuring the life safety of the bomb disposal personnel.

[0004] However, in the process of implementing the above technical solution, the inventors of this application found that the above technology has at least the following technical problems:

[0005] In the process of grabbing and moving explosives at a long distance, the mechanical gripper 1 changes the swing angle of the mechanical gripper 1 by manually adjusting the positioning pin at the gripper joint, thereby adjusting the center of gravity of the explosives to be stable. However, in the process of moving explosives, due to the unevenness of the road surface and the shaking caused by the walking of the bomb disposal personnel, the bomb disposal personnel will inevitably change the tilt angle of the three-section telescopic mechanical arm 3, causing the tilt angle of the mechanical gripper 1 locked with the three-section telescopic mechanical arm 3 to change, thereby changing the center of gravity of the explosives, and being unable to maintain its center of gravity dynamic balance, which brings safety hazards to the bomb disposal personnel, threatens personal safety, and has no safety guarantee. Utility Model Content

[0006] In order to solve the problem of insufficient safety caused by the shortcomings of the existing technology, the embodiment of the present application provides a stabilization adjustment device for an explosive disposal robot arm. The device uses multiple stepped shafts, bearings and a frame to construct a simple stabilizer structure to solve the technical problem that the explosive disposal robot arm cannot maintain the dynamic balance of its center of gravity when moving explosive objects.

[0007] The solution adopted by the utility model to solve the technical problem is:

[0008] A device for stabilizing and adjusting an explosive disposal robot arm, one end of which is fixedly connected to the robot arm, and the other end of which is fixedly connected to the robot hand; the device for stabilizing and adjusting an explosive disposal robot arm comprises: a support frame, which is mounted on the front end of the robot arm, and is used for installation and support, and has two mutually symmetrical mounting holes along the X-axis on one side of the positive direction of the Y-axis; a cantilever shaft, wherein the two cantilever shafts are respectively mounted in the two mounting holes of the support frame, and extend in opposite directions along the X-axis; a stabilizing frame, which is rotatably mounted on the cantilever shaft, and has through holes of the same size on its four end faces; rotating components, which are symmetrically mounted on the stabilizing frame in pairs. The through holes on the four end faces of the frame are used to provide dynamic stability conditions for the device; the assembly shaft is rotatably assembled on the stabilizing frame and is perpendicular to the cantilever shaft in space; the connecting tube has a through hole on the upper part axially along the Y axis that is adapted to the size of the assembly shaft, and is assembled at the center position of the assembly shaft, and its lower end is assembled and connected with the upper end of the manipulator; wherein, the stabilizing frame and the cantilever shaft maintain dynamic stability in the XY plane through the rotating component, and the connecting tube and the assembly shaft maintain dynamic stability in the YZ plane through the rotating component, so that the manipulator always maintains a stable state in space.

[0009] The embodiment disclosed herein comprises a rotating assembly including a bearing seat, which is assembled in a through hole on the end face of the stabilizing frame; a bearing, which is assembled in the bearing seat, so that the rotating assembly drives the stabilizing frame to rotate on the cantilever shaft and drives the assembly shaft to rotate on the stabilizing frame, thereby maintaining the stable state of the manipulator in space.

[0010] According to the embodiment disclosed, a mounting plate is provided between the support frame and the robotic arm to improve the connection stability between the support frame and the robotic arm, and a reinforcing beam is provided inside the support frame to improve the supporting strength of the support frame.

[0011] The cantilever shaft disclosed in this embodiment is a two-section stepped shaft, and its two shaft diameters are respectively matched with the inner diameter and outer diameter of the bearing, so that the bearing is clamped on its shaft shoulder and locked on the other side by a nut.

[0012] The present embodiment discloses that the assembly shaft is a five-section symmetrical stepped shaft, wherein the shaft diameters of the first and second sections are respectively matched with the inner diameter and outer diameter of the bearing, so that the bearing is clamped on its shaft shoulder and locked on the other side by a nut; the shaft diameter of the third section is larger and is a smooth axis, which is used to assemble the connecting tube, and the two sides of the connecting tube are locked by nuts to fix its position at the center of the assembly shaft; the fourth section has the same structure as the second section and is symmetrically arranged, and the fifth section has the same structure as the first section and is symmetrically arranged.

[0013] The present embodiment discloses that the connecting tube is designed to be bendable at the bottom end, and has an I-shaped connecting tube and an L-shaped connecting tube, which are used to adapt to different usage scenarios.

[0014] According to the embodiment disclosed, the through hole on the connecting pipe can also be arranged at multiple angles in the XY plane, so as to adjust the rotation angle of the robot in the Z-axis direction when necessary.

[0015] Positive effects:

[0016] The utility model assembles cantilever shafts on two mounting holes of the support frame respectively, assembles a stabilizing frame between the two cantilever shafts through a rotating assembly, sets an assembly axis on the stabilizing frame through a rotating assembly, and its direction is perpendicular to the direction of the cantilever shaft in space, and assembles a connecting pipe at the center of the assembly axis. By rotating the rotating assembly, the stabilizing frame and the cantilever shaft maintain dynamic stability in the XY plane, and maintain dynamic stability with the assembly axis in the YZ plane, so that the manipulator assembled on the connecting pipe always maintains a stable state in space. Compared with the existing bomb disposal robot arm, this device always maintains the dynamic balance of its center of gravity when moving explosive items, reduces the shaking effect of external factors on explosive items, and improves the safety of bomb disposal personnel when transferring explosive items. It is suitable for use as a stabilizing and adjusting device for a bomb disposal robot arm. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a schematic diagram of the installation of the embodiment of the present application;

[0018] Figure 2 This is the main view of the embodiment of the present application;

[0019] Figure 3 A top view of an embodiment of the present application;

[0020] Figure 4 This is a rear view of an embodiment of the present application;

[0021] Figure 5 A side view of an embodiment of the present application;

[0022] Figure 6 This is the AA cross-sectional view of the embodiment of the present application;

[0023] Figure 7 This is the BB cross-sectional view of the embodiment of the present application;

[0024] Figure 8 This is a cross-sectional view of a type I connecting pipe according to an embodiment of the present application;

[0025] Fig. 9 This is a cross-sectional view of the L-shaped connecting pipe according to an embodiment of the present application.

[0026] In the figure:

[0027] 10. A stabilization and adjustment device for an explosive disposal robot arm.

[0028] 20. Robotic arm,

[0029] 30. Robotic arm,

[0030] 40. Support frame, 41. Mounting plate, 42. Reinforcement beam,

[0031] 50. Cantilever shaft,

[0032] 60. Stabilizer,

[0033] 70. Rotating assembly, 71. Bearing seat, 72. Bearing,

[0034] 80. Assembly shaft, 81. First section, 82. Second section, 83. Third section, 84. Fourth section, 85. Fifth section,

[0035] 90. Connecting pipe, 91. I-type connecting pipe, 92. L-type connecting pipe. DETAILED DESCRIPTION

[0036] The following will be combined with the drawings in the embodiments of the utility model to clearly and completely describe the technical solutions in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, not all of the embodiments. Although the embodiments of the utility model have been shown and described, it can be understood by those of ordinary skill in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the utility model, and the scope of the utility model is defined by the attached claims and their equivalents. Based on the embodiments in the utility model, all other embodiments obtained by those of ordinary skill in the art without making creative work are within the scope of protection of the utility model.

[0037] As shown in the figure, a bomb disposal robot arm stabilization adjustment device 10, one end of which is fixedly connected to a robot arm 20, and the other end of which is fixedly connected to a robot hand 30; comprises:

[0038] The support frame 40 is mounted on the front end of the robot arm 20 for installation and support, and has two symmetrical installation holes on one side of the positive direction of the Y axis along the X axis;

[0039] Cantilever shafts 50, two of the cantilever shafts 50 are respectively mounted in two mounting holes of the support frame 40, and extend axially opposite to each other along the X-axis;

[0040] The stabilizing frame 60 is rotatably mounted on the cantilever shaft 50, and through holes of the same size are respectively opened on the four end faces thereof;

[0041] The rotating components 70 are symmetrically assembled in pairs in the through holes on the four end surfaces of the stabilizing frame 60 to provide dynamic stability conditions for the device;

[0042] An assembly shaft 80 is rotatably assembled on the stabilizing frame 60 and is perpendicular to the cantilever shaft 50 in space;

[0043] The connecting tube 90 has a through hole axially opened along the Y axis on the upper part thereof and matched with the size of the assembly shaft 80, and is assembled at the center position of the assembly shaft 80, and the lower end thereof is assembled and connected with the upper end of the manipulator 30;

[0044] The stabilizing frame 60 and the cantilever shaft 50 are dynamically stable on the XY plane through the rotating assembly 70, and the connecting tube 90 and the assembly shaft 80 are dynamically stable on the YZ plane through the rotating assembly 70, so that the manipulator 30 always maintains a stable state in space.

[0045] Specifically, the support frame 40 is assembled at the front end of the robot arm 20 by means of a snap-fitting method, and has a gate-shaped structure. Two end faces on one side of the positive direction of the Y-axis are provided with two mutually symmetrical mounting holes along the axial direction of the X-axis, and the two mounting holes are coaxially arranged to provide mounting space for the cantilever shaft 50; the two cantilever shafts 50 respectively pass through the two mounting holes of the support frame 40 and are coaxially assembled, and the two extend in opposite directions along the axial direction of the X-axis, and nuts are used on both sides of the mounting holes to lock the cantilever shaft 50 on the support frame 40; The four end faces of the stabilizing frame 60 are respectively provided with through holes of the same size, and the apertures thereof are adapted to the rotating components 70. The rotating components 70 are symmetrically assembled in the through holes in pairs, so as to provide dynamic stability conditions for the device; the stabilizing frame 60 is assembled on the cantilever shaft 50 through the rotating components 70, and the stabilizing frame 60 is driven by the rotating components 70 to rotate axially around the X-axis on the cantilever shaft 50, so that when the support frame 40 has an angular deviation in the Z-axis direction, the stabilizing frame 60 is in the XY plane. The assembly shaft 80 is assembled on the stabilizing frame 60 through the rotating assembly 70, and is perpendicular to the cantilever shaft 50 in space. The assembly shaft 80 is positioned and locked by a nut on the outside of the rotating assembly 70, so that it can rotate around the Y-axis through the rotating assembly 70; a through hole matching the size of the assembly shaft 80 is opened on the upper part of the connecting pipe 90 along the Y-axis, and the assembly shaft 80 passes through the through hole. The connecting pipe 90 is assembled and locked at the center of the assembly shaft 80 using nuts on both sides of the outside of the connecting pipe 90. The connecting pipe 90 is driven by the assembly shaft 80 to rotate at the center of the stabilizing frame 60, so that when the support frame 40 has an angular deviation in the X-axis direction, the connecting pipe 90 always maintains dynamic stability in the YZ plane, thereby making the manipulator 30 assembled at the lower end of the connecting pipe 90 always maintain a stable state in space, reducing the influence of external factors on the center of gravity of the manipulator 30, and improving the safety of bomb disposal personnel when using the device to transfer explosives.

[0046] The rotating assembly 70 includes a bearing seat 71, which is assembled in the through hole on the end face of the stabilizing frame 60; a bearing 72, which is assembled in the bearing seat 71, so that the rotating assembly 70 drives the stabilizing frame 60 to rotate on the cantilever shaft 50 and drives the assembly shaft 80 to rotate on the stabilizing frame 60, thereby maintaining the stable state of the manipulator 30 in space.

[0047] Specifically, the size of the bearing seat 71 is adapted to the size of the through hole opened on the stabilizing frame 60, so that it can be positioned by snap-fitting, and is fastened to the end surface of the stabilizing frame 60 using a combination of bolts and nuts on both sides of the bearing seat 71; the bearing 72 is adapted to be assembled in the bearing seat 71, so that the rotating assembly 70 drives the stabilizing frame 60 to rotate axially around the X-axis on the cantilever shaft 50, and drives the assembly shaft 80 to rotate axially around the Y-axis on the stabilizing frame 60, thereby maintaining the stability of the manipulator 30 in space.

[0048] A mounting plate 41 is provided between the support frame 40 and the robotic arm 20 to improve the connection stability between the support frame 40 and the robotic arm 20 . A reinforcing beam 42 is provided inside the support frame 40 to improve the supporting strength of the support frame 40 .

[0049] Specifically, the mounting plate 41 is disposed between the support frame 40 and the robotic arm 20, and the connection stability between the support frame 40 and the robotic arm 20 is improved by increasing the clamping assembly area between the support frame 40 and the robotic arm 20; the support frame 40 is provided with a reinforcing beam 42 inclined at 45° inside, and the supporting strength of the support frame 40 is improved by constructing a triangular structure.

[0050] The cantilever shaft 50 is a two-section stepped shaft, and its two shaft diameters are respectively matched with the inner diameter and outer diameter of the bearing 72, so that the bearing 72 is clamped on its shaft shoulder and locked on the other side by a nut.

[0051] Specifically, the cantilever shaft 50 is a two-section stepped shaft, the thicker section of which is a threaded shaft, the shaft diameter of which is matched with the outer diameter of the bearing 72 and slightly larger than the inner diameter of the bearing 72, so that the bearing 72 is clamped on its shaft shoulder; the thinner section of the cantilever shaft 50 is a combination of an optical axis and a threaded shaft, the optical axis portion is arranged close to the thicker section, and its shaft diameter is matched with the inner diameter of the bearing 72, and the threaded shaft portion cooperates with a nut to lock the bearing 72 on the inner side of the stabilizing frame 60.

[0052] The assembly shaft 80 is a five-section symmetrical stepped shaft, wherein the shaft diameters of the first section 81 and the second section 82 are respectively matched with the inner diameter and the outer diameter of the bearing 72, so that the bearing 72 is clamped on its shaft shoulder and locked on the other side by a nut; the shaft diameter of the third section 83 is larger and is a smooth axis, which is used to assemble the connecting tube 90, and the two sides of the connecting tube 90 are locked by nuts to fix its position at the center of the assembly shaft 80; the fourth section 84 has the same structure as the second section 82 and is symmetrically arranged, and the fifth section 85 has the same structure as the first section 81 and is symmetrically arranged.

[0053] Specifically, the first section 81 is a combination of an optical axis and a threaded shaft, the optical axis portion is arranged close to the second section 82, and its shaft diameter is adapted to the inner diameter of the bearing 72, and the threaded shaft portion cooperates with a nut to lock the bearing 72 on the outer side of the stabilizing frame 60; the second section 82 is a threaded shaft, and its shaft diameter is adapted to the outer diameter of the bearing 72 and is slightly larger than the inner diameter of the bearing 72, so that the bearing 72 is clamped on its shaft shoulder; the fourth section 84 has the same structure as the second section 82 and is symmetrically arranged, and the fifth section 85 has the same structure as the first section 81 and is symmetrically arranged; the third section 83 is an optical axis, and its shaft diameter is slightly larger than the second section 82 and the fourth section 84, and is adapted to the size of the through hole opened in the connecting tube 90, and its section length is slightly smaller than the outer diameter of the cross-section of the connecting tube 90, so that the two sides of the connecting tube 90 can be locked by nuts to fix the position of the connecting tube 90 at the center of the assembly shaft 80.

[0054] The connecting tube 90 is designed to be bendable at the bottom, and has an I-shaped connecting tube 91 and an L-shaped connecting tube 92 for adapting to different usage scenarios.

[0055] Specifically, the connecting tube 90 is designed to be bendable at the bottom, and has an I-type connecting tube 91 and an L-type connecting tube 92. When there is sufficient space above the explosive items to be transferred, the I-type connecting tube 91 can be used to enable the manipulator 30 installed at its lower end to perform a grasping action in the XZ plane; when there is insufficient space above the explosive items to be transferred, the L-type connecting tube 92 can be used to enable the manipulator 30 installed at its lower end to perform a grasping action in the XY plane.

[0056] The through holes on the connecting tube 90 can also be arranged at multiple angles in the XY plane, so as to adjust the rotation angle of the robot arm 30 in the Z-axis direction when necessary.

[0057] Specifically, the through hole on the connecting tube 90 can be set at multiple angles in the XY plane as needed. When the bomb disposal personnel cannot adjust the gripping angle by moving themselves, the through hole through which the assembly shaft 80 passes can be switched to adjust the rotation angle of the manipulator 30 in the Z-axis direction.

[0058] Features of this utility model:

[0059] The utility model assembles cantilever shafts 50 on the two mounting holes of the support frame 40 respectively, assembles a stabilizing frame 60 between the two cantilever shafts 50 through a rotating assembly 70, and sets an assembly shaft 80 on the stabilizing frame 60 through the rotating assembly 70, whose direction is perpendicular to the direction of the cantilever shaft 50 in space, and assembles a connecting pipe 90 at the center of the assembly shaft 80.

[0060] In actual use, the bearing 72 rotates to keep the stabilizing frame 60 and the cantilever shaft 50 dynamically stable in the XY plane and the assembly shaft 80 dynamically stable in the YZ plane, so that the manipulator 30 assembled on the connecting pipe 90 always keeps a stable state in space. Through this technical solution, the explosive disposal personnel can always keep the center of gravity of the explosives in dynamic balance when moving the explosives, reduce the shaking effect of external factors on the explosives, and improve the safety of the explosive disposal personnel when transferring the explosives.

[0061] Finally, it should be noted that the above is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Although the present utility model has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments, or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present utility model shall be included in the protection scope of the present utility model.

Claims

1. A stabilization and adjustment device (10) for an explosive disposal robot arm, one end of which is fixedly connected to the robot arm (20) and the other end of which is fixedly connected to the robot hand (30); Features: include: A support frame (40) is mounted on the front end of the mechanical arm (20) and is used for installation and support. Two mutually symmetrical installation holes are provided on one side of the positive direction of the Y axis along the axial direction of the X axis. Cantilever shafts (50), two of the cantilever shafts (50) being respectively mounted in two mounting holes of the support frame (40) and extending axially in opposite directions along the X-axis; A stabilizing frame (60) is rotatably mounted on the cantilever shaft (50), and through holes of the same size are respectively opened on four end surfaces thereof; Rotating components (70) are symmetrically assembled in pairs in the through holes on the four end surfaces of the stabilizing frame (60) to provide dynamic stability conditions for the device; An assembly shaft (80) is rotatably mounted on the stabilizing frame (60) and is perpendicular to the cantilever shaft (50) in space; A connecting pipe (90) having an upper portion provided with a through hole axially opened along the Y-axis and having a size matching that of the assembly shaft (80), and being assembled at the center of the assembly shaft (80), and having a lower end assembled and connected to the upper end of the manipulator (30); The stabilizing frame (60) and the cantilever shaft (50) are dynamically stable on the XY plane through the rotating assembly (70), and the connecting tube (90) and the assembly shaft (80) are dynamically stable on the YZ plane through the rotating assembly (70), so that the manipulator (30) always maintains a stable state in space.

2. According to claim 1, a stabilization and adjustment device for an explosive disposal robot arm, Features: The rotating assembly (70) comprises: A bearing seat (71) is assembled in a through hole on an end surface of the stabilizing frame (60); The bearing (72) is assembled in the bearing seat (71), so that the rotating assembly (70) drives the stabilizing frame (60) to rotate on the cantilever shaft (50) and drives the assembly shaft (80) to rotate on the stabilizing frame (60), thereby maintaining the stable state of the manipulator (30) in space.

3. According to claim 1, a stabilization and adjustment device for an explosive disposal robot arm, Features: A mounting plate (41) is provided between the support frame (40) and the mechanical arm (20) for improving the connection stability between the support frame (40) and the mechanical arm (20), and a reinforcing beam (42) is provided inside the support frame (40) for improving the supporting strength of the support frame (40).

4. According to claim 2, a stabilization and adjustment device for an explosive disposal robot arm, Features: The cantilever shaft (50) is a two-section stepped shaft, the two shaft diameters of which are respectively matched to the inner diameter and outer diameter of the bearing (72), so that the bearing (72) is clamped on its shaft shoulder and locked on the other side by a nut.

5. According to claim 2, a stabilization and adjustment device for an explosive disposal robot arm, Features: The assembly shaft (80) is a five-section symmetrical stepped shaft, wherein the shaft diameters of the first section (81) and the second section (82) are respectively matched to the inner diameter and the outer diameter of the bearing (72), so that the bearing (72) is clamped on its shaft shoulder and is locked on the other side by a nut; the third section (83) has a larger shaft diameter and is a smooth axis, and is used to assemble the connecting tube (90), and the two sides of the connecting tube (90) are locked by nuts so that its position is fixed at the center of the assembly shaft (80); the fourth section (84) has the same structure as the second section (82) and is symmetrically arranged, and the fifth section (85) has the same structure as the first section (81) and is symmetrically arranged.

6. According to claim 1, a stabilization and adjustment device for an explosive disposal robot arm, Features: The connecting tube (90) is designed with a bendable bottom end and comprises an I-shaped connecting tube (91) and an L-shaped connecting tube (92) for adapting to different usage scenarios.

7. According to claim 6, a stabilization and adjustment device for an explosive disposal robot arm, Features: The through holes opened on the connecting tube (90) can also be arranged at multiple angles in the XY plane, so as to adjust the rotation angle of the robot arm (30) in the Z-axis direction when necessary.

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