Quick coupling system for on-orbit replacement of large payloads

Abstract

This invention relates to a quick-connect system for on-orbit replacement of large loads, belonging to the technical field of on-orbit maintenance systems in aerospace. It solves the problems of existing on-orbit maintenance methods, such as large size, high cost, and poor versatility. The quick-connect system of this invention includes a handheld frame and N quick-connect units, where N≥3; each quick-connect unit includes a lever, a pawl mechanism, a pawl mounting base, a guide block, and a multi-directional slider. The quick-connect system uses a multi-directional slider and pawl mechanism mounted together on the handheld frame, while the guide block and pawl mounting base are mounted on the on-orbit replaceable large load. During operation, the quick-connect system is quickly connected to the on-orbit replaceable large load through the cooperation of the multi-directional slider and the guide block, and the locking and unlocking of the pawl mechanism and pawl mounting base. Afterwards, on-orbit operations can be performed on the large load. The system has a simple and compact structure, is lightweight, and small in size, making it suitable for widespread use in on-orbit integration and on-orbit maintenance of similar functional modules.

Description

Technical Field

[0001] This invention belongs to the field of on-orbit maintenance system technology for aerospace, specifically relating to a quick-connect system for replacing large loads on-orbit. Background Technology

[0002] With the rapid development of aerospace technology, space activities are becoming more frequent, the number of spacecraft in orbit is increasing, and the structure and composition of spacecraft are becoming more complex, while their performance and technological level are constantly improving. However, due to factors such as launch costs and objective environmental conditions, spacecraft rarely undergo the same maintenance, upkeep, and upgrades as ground equipment. Moreover, the space environment is complex and harsh, and spacecraft often experience functional failures during their missions, resulting in significant losses. Therefore, ensuring the long-term and stable operation of spacecraft in the space environment is one of the most pressing problems to be solved. Thus, on-orbit maintenance of spacecraft is particularly important.

[0003] Current technologies for on-orbit maintenance of spacecraft include using robotic arms and extravehicular activity (EVA) by astronauts. These methods have the following problems:

[0004] Using a robotic arm for maintenance requires the installation of a robotic arm adapter, which takes up a certain amount of space and is relatively expensive.

[0005] Using the extravehicular activity (EVA) maintenance method requires the installation of a special maintenance handle, which occupies a certain amount of space and is not compatible with robotic arms.

[0006] Based on the above, there is an urgent need to develop a small-sized, low-cost, and versatile on-orbit maintenance system. Summary of the Invention

[0007] The purpose of this invention is to propose a quick-connect system for replacing large loads on the track, which solves the problems of large size, high cost and poor versatility of existing on-track maintenance methods, and realizes the rapid connection of large loads on track with maintenance tools or other interfaces.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows.

[0009] A quick-connect system for on-orbit load changing, including a handheld frame and N quick-connect units, where N≥3;

[0010] The quick-connect unit includes a lever, a pawl mechanism, a pawl mounting base, a guide block, and a multi-directional slider;

[0011] The pawl mechanism includes an upper pressure cover, a lower pressure cover, a pawl slider, and a pawl spindle. The upper pressure cover is fixedly connected to the handheld frame. One end of the pawl spindle is conical, and the other end has an extension along the outer circumference. The extension is clamped in the cavity formed by the upper and lower pressure covers and is positioned by several spring plungers evenly distributed in the cavity. There are three or more retractable pawl sliders evenly distributed in the middle circumference of the pawl spindle.

[0012] The lever is fixedly connected to the pawl spindle. Rotating the lever can drive the pawl spindle to rotate within the cavity formed by the upper and lower pressure covers.

[0013] One side of the pawl mounting seat is fixed to the guide block, and the other side has a groove that cooperates with the pawl mechanism. More than three locking structures are evenly distributed around the circumference of the groove. Each locking structure can lock a pawl slider, and the pawl slider can move out of the pawl mounting seat along the gap between two adjacent locking structures.

[0014] The multi-directional slider is fixed on the handheld frame, and the guide block can slide along the multi-directional slider.

[0015] Furthermore, the lever consists of a rocker arm and a connecting rod. The rocker arm and the connecting rod are vertically arranged and fixedly connected at one end to form an L-shaped structure. The other end of the connecting rod is coaxially and fixedly connected to the pawl spindle.

[0016] Furthermore, the upper pressure cover is a cylindrical shape with an open bottom and an opening on the top surface. The lower pressure cover is a circular structure. The upper and lower pressure covers are respectively fitted onto the upper and lower sides of the outer extension of the pawl mandrel and are fixedly connected by a second screw. The side of the upper pressure cover is provided with several spring plunger holes evenly distributed around its circumference. Each spring plunger extends into the cavity formed by the upper and lower pressure covers through a spring plunger hole and contacts the outer surface of the outer extension.

[0017] Furthermore, the pawl mechanism also includes a spring and a slider cover. The pawl spindle has a sliding cavity, and the spring and pawl slider are installed in the sliding cavity. One end of the spring is fixedly connected to the end of the sliding cavity, and the other end is fixedly connected to the pawl slider. The slider cover includes a pressure plate and two limiting plates. The pressure plate has a limiting hole in the middle. The two limiting plates are fixed on the pressure plate and located on both sides of the limiting hole. The limiting hole of the pressure plate fits over the pawl slider. The two sides of the pressure plate are fixed to the side wall of the pawl spindle by first screws. The two limiting plates are inserted into the sliding cavity. The two sides of the pawl slider have protrusions that cooperate with the pressure plate outside the limiting hole to limit the movement of the pawl slider in the sliding cavity.

[0018] Furthermore, the pawl mounting base is a cylindrical structure, with one circular surface fixed to the surface of the guide block, and another circular surface having a groove that mates with the pawl mechanism. Three or more locking structures are evenly distributed around the circumference of the groove, each locking structure mates with a pawl slider, and there is a gap between adjacent locking structures.

[0019] Furthermore, the bottom of the pawl mount is provided with a flange, and the pawl mount is fixed to the guide block by the flange.

[0020] Furthermore, the outer end face of the locking structure is provided with an inward and upward inclined surface, and the pawl slider is provided with an outward and downward inclined surface. After the inclined surface of the pawl slider contacts the inclined surface of the locking structure, the spring gradually contracts. After the inclined surface is completely separated, the spring pops out, and the pawl slider is locked by the locking structure. The rotating lever drives the pawl spindle to rotate, and the pawl slider rotates axially, disengaging from the locking structure and being removed from the gap between adjacent locking structures.

[0021] Furthermore, the guide block has at least two sides that are mutually perpendicular planes, and the multi-directional slider is an L-shaped right-angle plate with one end fixed to the handheld frame. Several rollers are provided on the inner wall. The multi-directional slider cooperates with the two right-angle sides of the guide block, and the guide block slides along the rollers inside the multi-directional slider.

[0022] Furthermore, the guide blocks of the N quick-connect units are symmetrically distributed about the center of the on-orbit load.

[0023] Furthermore, the quick-connect unit also includes a fixing frame, which is fixed to the handheld holder via a connecting column, and the upper pressure cover and multi-directional slider are fixed to the fixing frame.

[0024] The principle of this invention is as follows:

[0025] The present invention provides a quick-connect system for on-orbit replacement of large loads. A multi-directional slider and a guide block together constitute the guide mechanism of a ratchet mechanism. The multi-directional slider and the ratchet mechanism are mounted together on a handheld frame. The guide block and the ratchet mounting base are mounted on the on-orbit replaceable large load. When an astronaut (or robotic arm) operates the quick-connect system of the present invention, the quick-connect system is quickly connected to the on-orbit replaceable large load through the cooperation of the multi-directional slider and the guide block, as well as the locking and unlocking of the ratchet mechanism and the ratchet mounting base. After that, the large load can be operated on-orbit.

[0026] Compared with the prior art, the beneficial effects of the present invention are:

[0027] The quick-connect system for replacing large payloads in orbit of the present invention adopts a pawl mechanism supplemented by a multi-directional rolling guide mechanism (including guide block and multi-directional slider), which facilitates guidance and alignment and rapid on-orbit installation. It can achieve the rapid installation and disassembly of maintenance tools or other interfaces with large payloads with low operational precision. Astronauts only need simple operations to complete the task conveniently and quickly.

[0028] The quick-connect system for replacing large payloads in orbit of the present invention has good versatility. It can quickly install the adapter in orbit and replace the payload using a robotic arm, or quickly install astronaut operating tools in orbit and replace the payload manually.

[0029] The quick-connect system for replacing large loads in orbit according to the present invention has a simple and compact structure, is lightweight and small in size, and is suitable for widespread use in the field of on-orbit integration and on-orbit maintenance of similar functional modules. Attached Figure Description

[0030] To more clearly illustrate the technical solutions in the specific embodiments of the present invention, the accompanying drawings used in the specific embodiments will be briefly introduced below. Obviously, the drawings described below are only some specific embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0031] Figure 1 This is a schematic diagram of the quick-connect system for on-orbit replacement of large loads according to the present invention;

[0032] Figure 2 This is a schematic diagram of the ratchet mechanism of the quick-connect system for on-orbit replacement of large loads according to the present invention.

[0033] Figure 3 This is a schematic diagram of the guide block and pawl mounting base of the quick-connect system for on-orbit replacement of large loads according to the present invention.

[0034] Figure 4 This is a cross-sectional view of the pawl mechanism and pawl mounting base of the quick-connect system for on-orbit replacement of large loads of the present invention in the locked state.

[0035] Figure 5 This is a schematic diagram of the pawl mechanism and pawl mounting base in the locked state of the quick-connect system for on-orbit replacement of large loads according to the present invention.

[0036] In the diagram, 1. Handheld bracket, 2. Lever, 3. Pawl mechanism, 3-1. Upper pressure cover, 3-2. Lower pressure cover, 3-3. First screw, 3-4. Pawl slider, 3-5. Spring, 3-6. Slider pressure cover, 3-7. Pawl spindle, 3-8. Spring plunger, 3-9. Second screw, 4. Pawl mounting base, 4-1. Locking structure, 5. Guide block, 6. Multi-directional slider, 7. Fixing bracket. Detailed Implementation

[0037] The following is in conjunction with the appendix Figure 1-5 The embodiments of the present invention will be further described.

[0038] like Figure 1-5As shown, the quick-connect system for on-orbit replacement of large loads of the present invention includes a handheld frame 1 and N quick-connect units, where N≥3;

[0039] The quick-connect unit includes a lever 2, a pawl mechanism 3, a pawl mounting base 4, a guide block 5, and a multi-directional slider 6;

[0040] The pawl mechanism 3 includes an upper pressure cover 3-1, a lower pressure cover 3-2, a pawl slider 3-4, and a pawl spindle 3-7. The upper pressure cover 3-1 is fixedly connected to the handheld frame 1. One end of the pawl spindle 3-7 is conical, and the other end has an extension along the outer circumference. The extension is clamped in the cavity formed by the upper pressure cover 3-1 and the lower pressure cover 3-2, and is positioned by several spring plungers 3-8 evenly distributed in the cavity. Three or more retractable pawl sliders 3-4 are evenly distributed on the circumference of the middle part of the pawl spindle 3-7.

[0041] The lever 2 is fixedly connected to the pawl spindle 3-7. Rotating the lever 2 causes the pawl spindle 3-7 to rotate within the cavity formed by the upper pressure cover 3-1 and the lower pressure cover 3-2.

[0042] One side of the pawl mounting base 4 is fixed to the surface of the guide block 5, and the other side has a groove that cooperates with the pawl mechanism 3. Three or more locking structures 4-1 are evenly distributed around the circumference of the groove. Each locking structure 4-1 can lock a pawl slider 3-4, and the pawl slider 3-4 can move out of the pawl mounting base 4 along the gap between two adjacent locking structures 4-1.

[0043] The multi-directional slider 6 is fixed on the handheld bracket 1, and the guide block 5 can slide along the multi-directional slider 6.

[0044] In this invention, the structure of the handheld frame 1 is not particularly limited; any frame structure that facilitates handheld use is acceptable. Preferably, the structure of the handheld frame 1 is adapted to accommodate the installation of a robotic arm.

[0045] In this invention, the lever 2 consists of a rocker arm and a connecting rod. The rocker arm and the connecting rod are arranged vertically and fixedly connected at one end to form an L-shaped structure. The other end of the connecting rod is coaxially fixedly connected to the pawl spindle 3-7. By rocking the rocker arm, the connecting rod is rotated, which in turn drives the pawl spindle 3-7 to rotate.

[0046] In this invention, the upper pressure cover 3-1 is preferably a cylindrical shape with an open bottom and an opening on the top surface, while the lower pressure cover 3-2 is an annular structure. The upper pressure cover 3-1 and the lower pressure cover 3-2 are respectively fitted onto the upper and lower sides of the outer extension of the pawl mandrel 3-7 and are fixedly connected by a second screw 3-9. The side of the upper pressure cover 3-1 has a spring plunger hole, through which the spring plunger 3-8 extends into the cavity formed by the upper pressure cover 3-1 and the lower pressure cover 3-2, contacting the outer surface of the outer extension. By operating the lever 2, the pawl mandrel 3-7 can rotate and lock around its axis inside the upper pressure cover 3-1 and the lower pressure cover 3-2, thereby locking and unlocking the pawl slider 3-4 and the locking structure 4-1 of the pawl mounting seat 4.

[0047] In this invention, the pawl mechanism 3 further includes a spring 3-5 and a slider cover 3-6. A sliding cavity is provided on the pawl spindle 3-7. The spring 3-5 and the pawl slider 3-4 are installed inside the sliding cavity. One end of the spring 3-5 is fixedly connected to the end of the sliding cavity, and the other end is fixedly connected to the pawl slider 3-4. The slider cover 3-6 includes a pressure plate and two limiting plates. A limiting hole is provided in the middle of the pressure plate. The two limiting plates are respectively fixed on the pressure plate and located on both sides of the limiting hole. The limiting hole of the pressure plate fits over the pawl slider 3-4. The two sides of the pressure plate are fixed to the sidewalls of the pawl spindle 3-7 by first screws 3-3. The two limiting plates are inserted into the sliding cavity. The two sides of the pawl slider 3-4 have protrusions that cooperate with the pressure plate outside the limiting hole to limit the movement of the pawl slider 3-4 within the sliding cavity. The pawl slider 3-4 slides within the sliding cavity under the elastic force of the spring 3-5 and is limited by the slider cover 3-6. Preferably, the spring 3-5 is a cylindrical helical spring.

[0048] In this invention, the pawl mounting base 4 has a cylindrical structure. One circular surface is fixed to the surface of the guide block 5, and the other circular surface has a groove that mates with the pawl mechanism 3. Three or more locking structures 4-1 are evenly distributed around the circumference of the groove. Each locking structure 4-1 mates with a pawl slider 3-4, and there is a gap between adjacent locking structures 4-1. Preferably, the bottom of the pawl mounting base 4 is provided with a flange, and the pawl mounting base 4 is fixed to the guide block 5 through the flange. The outer end face of the preferred locking structure 4-1 is provided with an inward and upward inclined surface (with the pawl spindle 3-7 as the inner side), and the pawl slider 3-4 is provided with an outward and downward inclined surface. After the inclined surface of the pawl slider 3-4 contacts the inclined surface of the locking structure 4-1, the spring 3-5 gradually contracts. After the inclined surface is completely separated, the spring 3-5 pops out, and the pawl slider 3-4 is locked by the locking structure 4-1. The rotating lever 2 drives the pawl spindle 3-7 to rotate, and the pawl slider 3-4 rotates axially, disengaging from the locking structure 4-1 and being removed from the gap between adjacent locking structures 4-1.

[0049] In this invention, the quick-connect and unlocking of the pawl spindle 3-7 and the pawl mounting base 4 are preferred, and the force required to be applied meets the ergonomic requirements of aerospace personnel.

[0050] In this invention, guide blocks 5 are fixed to the surface of the on-rail load. Depending on the layout of different on-rail loads, 3 to 4 guide blocks 5 may be installed on the surface of each on-rail load, i.e., N is 3 to 4. To ensure smooth guidance and balanced force distribution, the guide blocks 5 of the N quick-connect units should be symmetrically distributed about the center of the on-rail load. Preferably, the guide blocks 5 have at least two sides that are mutually perpendicular planes.

[0051] In this invention, the multi-directional slider 6 can complete guidance in more than two directions, such as the transverse and longitudinal directions (xy directions) within the mating surface, ensuring good guiding and positioning effects in both directions. Preferably, the multi-directional slider 6 is an L-shaped right-angled plate, with one end fixed to the handheld frame 1. Several rollers are provided on the inner wall. The multi-directional slider 6 cooperates with the two right-angled sides of the guide block 5, and the guide block 5 slides along the rollers within the multi-directional slider 6.

[0052] In this invention, the preferred quick-connect unit further includes a fixing frame 7, which is fixed to the handheld frame 1 by a connecting post, and the upper pressure cover 3-1 and the multi-directional slider 6 are fixed to the fixing frame 7.

[0053] Method of using the quick-connect system for on-orbit replacement of large loads of the present invention:

[0054] 1) Install the guide block 5 of each quick-connect unit on the surface of the on-rail load, and ensure that the guide blocks 5 of N quick-connect units are symmetrically distributed about the center of the on-rail load. Fix the pawl mounting seat 4 on the surface of the guide block 5. The guide block 5 and the pawl mounting seat 4 run on the rail with the on-rail load. The handheld frame 1 with pawl mechanism 3, multi-directional slider 6 and lever 2 is ready for use as a tool part.

[0055] 2) Unlock the electromechanical interface connection between the original on-orbit replaceable unit and the platform;

[0056] 3) Connect the multi-directional slider 6 of the tool part to the on-rail load along the guide block 5, and drive the pawl spindle 3-7 to rotate through the lever 2. The pawl slider 3-4 is locked with the locking structure 4-1 to realize the integration of the tool part and the on-rail load.

[0057] 4) Move the replaceable on-rail unit to be replaced along the guide rail (the guide rail refers to the guide rail where the replaceable on-rail unit is located in its original position), and rotate the pawl spindle 3-7 by lever 2 to unlock the pawl slider 3-4 and locking structure 4-1, thereby separating the tool part from the on-rail load. The guide block 5 and the pawl mounting base 4 are not separated and remain fixed on the surface of the replaceable on-rail unit. Store the old replaceable on-rail unit properly.

[0058] 5) Take out the new on-rail replaceable unit. The new on-rail replaceable unit has a guide block 5 with a pawl mounting seat 4 pre-installed and fixed. The pawl spindle 3-7 is rotated by the lever 2, and the pawl slider 3-4 is locked with the locking structure 4-1 and integrated with the tool part.

[0059] 6) Install the new on-orbit replaceable unit according to the guide rail of the on-orbit replaceable unit (the guide rail refers to the guide rail in the original position of the on-orbit replaceable unit to be replaced);

[0060] 7) The pawl spindle 3-7 is rotated by lever 2, and the pawl slider 3-4 is unlocked from the locking structure 4-1, thus separating the tool part from the on-rail load part;

[0061] 8) Complete the electromechanical interface connection between the on-orbit replaceable unit and the platform.

[0062] Obviously, the above specific embodiments are merely examples for clear illustration and are not intended to limit the specific embodiments. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively list all specific embodiments here. However, obvious variations or modifications derived therefrom are still within the protection scope of this invention.

Claims

1. A quick-connect system for on-orbit load changing, characterized in that, Includes a handheld bracket (1) and N quick-connect units, where N≥3; The quick-connect unit includes a lever (2), a pawl mechanism (3), a pawl mounting base (4), a guide block (5), and a multi-directional slider (6); The lever (2) consists of a rocker arm and a connecting rod. The rocker arm and the connecting rod are vertically arranged and fixedly connected at one end to form an L-shaped structure. The other end of the connecting rod is coaxially fixedly connected to the pawl spindle (3-7). The pawl mechanism (3) includes an upper pressure cover (3-1), a lower pressure cover (3-2), a pawl slider (3-4), and a pawl spindle (3-7). The upper pressure cover (3-1) is fixedly connected to the handheld frame (1). One end of the pawl spindle (3-7) is conical, and the other end has an extension along the outer circumference. The extension is clamped in the cavity formed by the upper pressure cover (3-1) and the lower pressure cover (3-2), and is positioned by several spring plungers (3-8) evenly distributed in the cavity. There are three or more retractable pawl sliders (3-4) evenly distributed in the middle circumference of the pawl spindle (3-7). The lever (2) is fixedly connected to the pawl spindle (3-7). Rotating the lever (2) can drive the pawl spindle (3-7) to rotate in the cavity formed by the upper cover (3-1) and the lower cover (3-2). The pawl mounting base (4) is fixed on one side of the guide block (5), and the other side has a groove that cooperates with the pawl mechanism (3). There are three or more locking structures (4-1) evenly distributed in the inner circumference of the groove. Each locking structure (4-1) can lock a pawl slider (3-4), and the pawl slider (3-4) can move out of the pawl mounting base (4) along the gap between two adjacent locking structures (4-1). The pawl mounting base (4) is a cylindrical structure. One circular surface is fixed on the surface of the guide block (5), and the other circular surface has a groove that cooperates with the pawl mechanism (3). There are three or more locking structures (4-1) evenly distributed in the circumference of the groove. Each locking structure (4-1) cooperates with a pawl slider (3-4), and there is a gap between adjacent locking structures (4-1). The guide block (5) has at least two sides that are mutually perpendicular planes. The multi-directional slider (6) is an L-shaped right-angle plate with one end fixed to the handheld frame (1). Several rollers are provided on the inner wall. The multi-directional slider (6) cooperates with the two right-angle sides of the guide block (5). The guide block (5) slides along the rollers in the multi-directional slider (6). The guide blocks (5) of the N quick-connect units are symmetrically distributed about the center of the on-rail load. The multi-directional slider (6) is fixed on the handheld frame (1), and the guide block (5) can slide along the multi-directional slider (6); The quick-connect unit also includes a fixing frame (7), which is fixed to the handheld frame (1) by a connecting column. The upper pressure cover (3-1) and the multi-directional slider (6) are fixed to the fixing frame (7).

2. The quick-connect system for on-orbit load replacement according to claim 1, characterized in that, The upper pressure cover (3-1) is a cylindrical shape with an open bottom and an opening on the top surface. The lower pressure cover (3-2) is a circular structure. The upper pressure cover (3-1) and the lower pressure cover (3-2) are respectively fitted on the upper and lower sides of the outer extension of the pawl mandrel (3-7) and fixedly connected by the second screw (3-9). The side of the upper pressure cover (3-1) is provided with several spring plunger holes evenly distributed around its circumference. Each spring plunger (3-8) extends into the cavity formed by the upper pressure cover (3-1) and the lower pressure cover (3-2) through a spring plunger hole and contacts the outer surface of the outer extension.

3. The quick-connect system for on-orbit load replacement according to claim 1, characterized in that, The pawl mechanism (3) further includes a spring (3-5) and a slider cover (3-6). The pawl spindle (3-7) is provided with a sliding cavity. The spring (3-5) and the pawl slider (3-4) are installed in the sliding cavity. One end of the spring (3-5) is fixedly connected to the end of the sliding cavity, and the other end is fixedly connected to the pawl slider (3-4). The slider cover (3-6) includes a pressure plate and two limiting plates. The pressure plate is provided with a limiting hole in the middle. The two limiting plates are fixed on the pressure plate and located on both sides of the limiting hole. The limiting hole of the pressure plate is sleeved on the outside of the pawl slider (3-4). The two sides of the pressure plate are fixed to the side wall of the pawl spindle (3-7) by the first screw (3-3). The two limiting plates are inserted into the sliding cavity. The two sides of the pawl slider (3-4) are provided with protrusions, which cooperate with the pressure plate outside the limiting hole to limit the pawl slider (3-4) in the sliding cavity.

4. The quick-connect system for on-orbit load replacement according to claim 1, characterized in that, The bottom of the pawl mount (4) is provided with a flange, and the pawl mount (4) is fixed to the guide block (5) by the flange.

5. The quick-connect system for on-orbit load replacement according to claim 3, characterized in that, The outer end face of the locking structure (4-1) is provided with an inward and upward inclined surface, and the pawl slider (3-4) is provided with an outward and downward inclined surface. After the inclined surface of the pawl slider (3-4) contacts the inclined surface of the locking structure (4-1), the spring (3-5) gradually contracts. After the inclined surface is completely separated, the spring (3-5) pops out, and the pawl slider (3-4) is locked by the locking structure (4-1). The rotating lever (2) drives the pawl spindle (3-7) to rotate, and the pawl slider (3-4) rotates along the axial direction, disengaging from the locking structure (4-1) and being removed from the gap between adjacent locking structures (4-1).

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