CN113101675B

CN113101675B - Staggered swing type suspension amusement device for children amusement

Info

Publication number: CN113101675B
Application number: CN202110416069.2A
Authority: CN
Inventors: 赵宏伟; 陈红阳; 孙鹏; 王伟; 邬婧; 黄启红; 张文翔
Original assignee: Yueyang Vocational Technical College
Current assignee: Yueyang Vocational Technical College
Priority date: 2021-04-19
Filing date: 2021-04-19
Publication date: 2022-05-13
Anticipated expiration: 2041-04-19
Also published as: CN113101675A

Abstract

The invention discloses a staggered swing type suspension amusement device for children amusement, which comprises a support column, a planet wheel rotating mechanism, a belt transmission mechanism and a swinging mechanism, wherein the top end of the support column is fixedly provided with a support frame, a driving device is arranged in the support frame and is in transmission connection with the planet wheel rotating mechanism and the belt transmission mechanism, the lower end of the planet wheel rotating mechanism is provided with a plurality of uniformly arranged swinging mechanisms, and the lower end of each swinging mechanism is fixedly provided with a seat. The fun is increased, the facility cost and the operation cost are reduced, and the physical strength and the energy of parents are saved.

Description

Staggered swing type suspension amusement device for children amusement

Technical Field

The invention relates to a suspension amusement device for children, in particular to a staggered swing type suspension amusement device for children amusement, and belongs to the field of amusement facilities.

Background

The traditional child amusement facilities need good safety, meanwhile, the facilities need to be stable in operation, irritation is low, and children are prevented from being frightened, at present, the child amusement facilities are multiple, such as swings swinging back and forth, but the swings need parents to assist in pushing beside, meanwhile, children have the risk of falling off the swings due to unstable grasping, and the physical strength and the energy of the parents are consumed, such as a small revolving train and a revolving trojan which rotate in a circle, however, the revolving trojan and the small revolving train lack irritation, the operation mode is single, amusement experience is insufficient, and driving systems of the revolving and up-and-down rolling motion of the revolving trojan respectively operate, and the cost and the operation cost of the facilities are high.

In summary, a staggered swing type suspension amusement device for children amusement is provided.

Disclosure of Invention

The invention aims to provide a staggered swing type suspension amusement device for children amusement, which is suspended in the air and swings back and forth alternately towards the middle while rotating.

In order to achieve the purpose, the invention provides the following technical scheme: a staggered swing type suspension amusement device for children amusement comprises a support column, a planet wheel rotating mechanism, a belt transmission mechanism, a swinging mechanism, a seat, a driving device and a support, wherein the support column is fixed on the ground, the support is fixedly installed at the top end of the support column, the planet wheel rotating mechanism is rotatably installed on the support, the belt transmission mechanism is arranged at the upper end of the planet wheel rotating mechanism, the driving device is installed in the support and is in transmission connection with the planet wheel rotating mechanism and the belt transmission mechanism, the lower end of the planet wheel rotating mechanism is provided with a plurality of uniformly arranged swinging mechanisms, the swinging mechanisms are connected with the belt transmission mechanism, and the seat is fixedly installed at the lower end of each swinging mechanism;

the driving device comprises a speed reducer and a driving motor, the speed reducer and the driving motor are fixed on the support, the upper end of the speed reducer is in transmission connection with a third transmission shaft, the third transmission shaft extends out of the outer side of the planetary wheel rotating mechanism and is fixedly connected with a belt transmission mechanism, the lower end of the speed reducer is in transmission connection with a second transmission shaft, and the second transmission shaft is fixedly connected with the planetary wheel rotating mechanism.

Preferably, the support column comprises a support column, the top end of the support column is welded with a support disc, and a support is fixedly mounted at the upper end of the support disc.

Preferably, the planet wheel slewing mechanism includes the center disk, the center disk rotates and installs on the support, and the center disk equipartition welding connecting rod all around, connecting rod other end welding planet wheel go up the ring frame, and planet wheel go up ring frame lower extreme passes through branch welding planet wheel lower ring frame, and outer ring gear is welded in the middle of the ring frame under the planet wheel, four planet wheels of outer ring gear inner gearing, the planet wheel rotates respectively and installs on the support, meshing sun gear in the middle of the planet wheel, sun gear fixed connection is on transmission shaft two.

Preferably, the lower end of the central disc is provided with a fixing groove.

Preferably, belt drive includes drive pulley, driven pulley and transmission shaft one, drive pulley fixed mounting is on transmission shaft three, eight a transmission shaft circumference equipartition rotates and installs on planet wheel slewing mechanism, driven pulley of an upper end fixed mounting of every transmission shaft, installs the belt on drive pulley and the eight driven pulley.

Preferably, seven rotating shafts are fixed on the planet wheel upper ring frame at intervals, each rotating shaft is located between two first transmission shafts, the included angle between each rotating shaft and each first transmission shaft is consistent in size, a tensioning wheel is rotatably installed on each rotating shaft, and the tensioning wheels are rotatably attached to the outer side of the belt.

Preferably, the swing mechanism comprises a fixed plate and an inner gear ring, connecting plates are welded on two sides of the fixed plate, the connecting plates are welded at the lower end of the planetary gear rotating mechanism, a through groove is formed in the middle of the fixed plate, the lower end of the inner gear ring is welded with a bottom plate, the lower end face of the bottom plate is flush with the lower end face of the inner gear ring, a second rack is convexly arranged in the middle of the lower end of the bottom plate and is slidably embedded into the through groove, the inner gear ring is slidably attached to the upper end face of the fixed plate, two first racks are symmetrically arranged on the inner side of the inner gear ring, the first racks are meshed with a semicircular gear, the semicircular gear is fixedly connected with a first transmission shaft of a belt transmission mechanism, fixing rings are symmetrically welded on two sides of the lower end of the fixed plate, driven shafts are rotatably installed in the two fixing rings, gears are fixedly installed in the middle of the driven shafts, the gears are meshed with the second racks, fixed blocks are respectively at two ends of the driven shafts, and connecting rods are installed at the lower ends of the two fixed blocks, the lower end of the middle part of the connecting rod is provided with a swing rod, and the fixed block, the connecting rod and the swing rod are welded into a whole.

Preferably, the seat comprises a hanging frame and a safety barrier, the hanging frame is welded at the lower end of the swinging rod, three sides of the hanging frame are closed, and the safety barrier is installed at the opening end of the hanging frame.

Preferably, the support includes solid fixed ring, and solid fixed ring normal running fit is in the fixed slot, four spinal branch vaulting poles of solid fixed ring lower extreme circumference equipartition welding rotate on every bracing piece and install a planet wheel, the bracing piece is fixed on the support column top, and solid fixed ring lower extreme welded fastening motor bracket fixes speed reducer and driving motor on the motor bracket, horizontal welding baffle in the motor bracket, baffle laminating speed reducer and driving motor side, the baffle width is less than the motor bracket.

Preferably, the outer sides of the planet wheel rotating mechanism, the belt transmission mechanism and the swinging mechanism are provided with protective covers.

Compared with the prior art, the invention has the beneficial effects that:

1. according to the invention, the seat can swing back and forth stably through the installed swing mechanism, parents do not need to push the seat in a side-by-side manner, the safety guardrail is arranged to enable children to take the seat safely, the risk of falling from amusement facilities is avoided, the safety is improved, and the parents can rest at the side and other times, so that the physical strength and the energy are saved;

2. according to the invention, the rotation of the amusement facility is realized by the motor drive through the arrangement of the planet wheel rotating mechanism, the planet wheel is labor-saving and speed-reducing, the rotating speed of the whole amusement facility is proper and stable, meanwhile, the other end of the driving motor is directly connected with the belt transmission mechanism, the swinging mechanism is driven to swing through the belt transmission mechanism, the whole structure can be driven by only one motor, and the cost and the operation cost of the facility are reduced;

3. according to the invention, through the arrangement of the planet wheel rotating mechanism and the swinging mechanism, the chair hoisted on the amusement facility can swing back and forth while rotating, the operation modes are rich, certain stimulation is brought, the amusement experience is high, the fun is increased, and the physical strength and energy of parents can be saved.

Drawings

FIG. 1 is a schematic view of the main structure of an amusement apparatus according to the present invention;

FIG. 2 is a schematic structural diagram of a planetary gear rotating mechanism and a belt transmission structure of the invention;

FIG. 3 is a schematic cross-sectional structural view of the planetary gear rotating mechanism of the present invention;

fig. 4 is a schematic internal structure diagram of the planetary gear rotating mechanism of the invention;

FIG. 5 is a schematic structural view of a stent of the present invention;

FIG. 6 is a schematic structural diagram of the rocking mechanism of the present invention;

fig. 7 is a schematic sectional structure view of the rocking mechanism of the present invention.

In the figure: 1. support column, 101, support column, 102, support plate, 2, planet wheel rotating mechanism, 201, center plate, 202, connecting rod, 203, planet wheel upper ring frame, 204, planet wheel lower ring frame, 205, outer gear ring, 206, planet wheel, 207, sun wheel, 208, fixing groove, 3, belt transmission mechanism, 301, driving belt pulley, 302, driven belt pulley, 303, transmission shaft I, 304, tensioning wheel, 305, rotating shaft, 306, belt, 4, swing mechanism, 401, fixing plate, 402, through groove, 403, connecting plate, 404, inner gear ring, 405, rack I, 406, bottom plate, 407, rack II, 408, gear, 409, driven shaft, 410, fixing ring, 411, fixing block, 412, connecting rod, 413, swing rod, 414, semi-circular gear, 5, seat, 51, hanging frame, 52, safety guard, 6, driving device, 601, speed reducer, 602, driving motor, 603. a second transmission shaft 604, a third transmission shaft 7, a bracket 701, a fixing ring 702, a support rod 703, a motor bracket 704 and a baffle.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Referring to fig. 1-7, the present invention provides a technical solution: a staggered swing type suspension amusement device for children amusement comprises a support column 1, a planet wheel rotating mechanism 2, a belt transmission mechanism 3, a swinging mechanism 4, a seat 5, a driving device 6 and a support 7, wherein the support column 1 is fixed on the ground, the support 7 is fixedly installed at the top end of the support column 1, the planet wheel rotating mechanism 2 is rotatably installed on the support 7, the belt transmission mechanism 3 is arranged at the upper end of the planet wheel rotating mechanism 2, the driving device 6 is installed in the support 7, the driving device 6 is in transmission connection with the planet wheel rotating mechanism 2 and the belt transmission mechanism 3, the lower end of the planet wheel rotating mechanism 2 is provided with a plurality of uniformly arranged swinging mechanisms 4, the swinging mechanisms 4 are connected with the belt transmission mechanism 3, and the seat 5 is fixedly installed at the lower ends of the swinging mechanisms 4; the driving device 6 comprises a speed reducer 601 and a driving motor 602, the speed reducer 601 and the driving motor 602 are fixed on the support 7, the upper end of the speed reducer 601 is in transmission connection with a third transmission shaft 604, the third transmission shaft 604 extends out of the planetary wheel rotating mechanism 2 and is fixedly connected with the belt transmission mechanism 3, the lower end of the speed reducer 601 is in transmission connection with a second transmission shaft 603, and the second transmission shaft 603 is fixedly connected with the planetary wheel rotating mechanism 2.

The support column 1 comprises a support column 101, a support disc 102 is welded to the top end of the support column 101, a support bracket 7 is fixedly mounted at the upper end of the support disc 102, and the support disc 102 increases the support area and is used for fixing the support bracket 7. The planet wheel rotating mechanism 2 comprises a center plate 201, the center plate 201 is rotatably installed on a support 7, connecting rods 202 are uniformly welded around the center plate 201, a planet wheel upper ring frame 203 is welded at the other end of each connecting rod 202, a planet wheel lower ring frame 204 is welded at the lower end of the planet wheel upper ring frame 203 through a support rod, an outer ring gear 205 is welded in the middle of the planet wheel lower ring frame 204, four planet wheels 206 are meshed in the outer ring gear 205, the planet wheels 206 are respectively rotatably installed on support rods 702 of the support 7, a sun wheel 207 is meshed in the middle of the planet wheel 206, and the sun wheel 207 is fixedly connected to a second transmission shaft 603. The lower end of the central disk 201 is provided with a fixing groove 208, and the fixing groove 208 is used for connecting and positioning the planet wheel rotating mechanism 2 and the bracket 7. The belt transmission mechanism 3 comprises a driving belt pulley 301, a driven belt pulley 302 and a transmission shaft 303, the driving belt pulley 301 is fixedly installed on three 604 transmission shafts, eight transmission shafts 303 are circumferentially and uniformly distributed and rotatably installed on the planetary wheel rotating mechanism 2, the transmission shafts 303 penetrate through the planetary wheel upper ring frame 203 and the planetary wheel lower ring frame 204, the driven belt pulley 302 is fixedly installed at the upper end of each transmission shaft 303, the driven belt pulley 302 drives the transmission shafts 303 to rotate together when rotating, belts 306 are installed on the driving belt pulley 301 and the eight driven belt pulleys 302, the belts 306 are located on the outer sides of the driven belt pulleys 302, and the driving belt pulley 301 plays a tensioning role. Seven rotating shafts 305 are fixed on the planet wheel upper ring frame 203 at intervals, each rotating shaft 305 is positioned between two first transmission shafts 303, the included angle between each rotating shaft 305 and each first transmission shaft 303 is consistent, a tensioning wheel 304 is rotatably arranged on each rotating shaft 305, and the tensioning wheels 304 are rotatably attached to the outer side of the belt 306. The swing mechanism 4 comprises a fixed plate 401 and an inner gear ring 404, connecting plates 403 are welded on two sides of the fixed plate 401, the connecting plates 403 are welded at the lower end of the planet wheel rotating mechanism 2, a through groove 402 is arranged in the middle of the fixed plate 401, the lower end of the inner gear ring 404 is welded with a bottom plate 406, the lower end surface of the bottom plate 406 is flush with the lower end surface of the inner gear ring 404, a rack II 407 is convexly arranged in the middle of the lower end of the bottom plate 406, the rack II 407 is slidably embedded into the through groove 402, the inner gear ring 404 is slidably attached to the upper end surface of the fixed plate 401, two rack I405 are symmetrically arranged on the inner side of the inner gear ring 404, the rack I405 is meshed with a semi-circular gear 414, the semi-circular gear 414 is fixedly connected with a transmission shaft I303 of the belt transmission mechanism 3, the belt 306 drives the transmission shaft I303 to rotate together when driving the driven pulley 302 to rotate, the transmission shaft I303 drives the semi-circular gear 414 to rotate, the semi-circular gear 414 rotates to drive the inner gear ring 404 to slide back and forth, fixing rings 410 are symmetrically welded on two sides of the lower end of the fixed plate 401, the driven shaft 409 is rotatably installed in the two fixing rings 410, the gear 408 is fixedly installed in the middle of the driven shaft 409, the gear 408 is meshed with the second rack 407, the second rack 407 moves forwards and backwards to drive the gear 408 to rotate forwards and backwards, the two ends of the driven shaft 409 are fixedly installed with the fixing blocks 411 respectively, the driven shaft 409 rotates along with the gear 408 to drive the fixing blocks 411 to rotate together, the connecting rods 412 are installed at the lower ends of the two fixing blocks 411, the swing rods 413 are installed at the lower ends of the middle portions of the connecting rods 412, and the fixing blocks 411, the connecting rods 412 and the swing rods 413 are welded into a whole. The seat 5 comprises a hanging frame 51 and a safety guard rail 52, wherein the hanging frame 51 is welded at the lower end of the swinging rod 413, the hanging frame 51 is closed on three sides, and the safety guard rail 52 is arranged at the opening end of the hanging frame 51. The support 7 comprises a fixing ring 701, the fixing ring 701 is rotatably matched in a fixing groove 208, four support rods 702 are uniformly welded on the circumference of the lower end of the fixing ring 701, a planet wheel 206 is rotatably mounted on each support rod 702, the support rods 702 are fixed at the top end of a support column 1, a motor bracket 703 is fixedly welded at the lower end of the fixing ring 701, a speed reducer 601 and a driving motor 602 are fixed on the motor bracket 703, a baffle 704 is transversely welded in the motor bracket 703, the baffle 704 is attached to the side faces of the speed reducer 601 and the driving motor 602, and the width of the baffle 704 is smaller than that of the motor bracket 703. The outer sides of the planet wheel rotating mechanism 2, the belt transmission mechanism 3 and the swing mechanism 4 are provided with protective covers to protect the stability of the transmission mechanism.

The working principle of the invention is as follows: before the facility is started, a child sits in the hanging frame 51, fixes the safety guardrail 52, starts the driving motor 602 to drive the second transmission shaft 603 to rotate, synchronously rotates the sun gear 207 fixed on the second transmission shaft 603, the sun gear 207 drives the planet gear 206 engaged with the planet gear 206 and the outer gear ring 205 engaged with the planet gear 206 to rotate, the outer gear ring 205 drives the whole planet carrier to rotate, the swinging mechanism 4 fixed on the planet carrier rotates along with the rotation, simultaneously, the driving motor 602 drives the third transmission shaft 604 to rotate, the driving pulley 301 fixedly arranged on the third transmission shaft 604 rotates along with the rotation, the driving pulley 301 drives the belt 306 to rotate, the belt 306 drives the driven pulley 302 fixed on the planet carrier to rotate, the tension pulley 304 outside the belt 306 rotates along with the rotation and tensions the belt 306, the driven pulley 302 drives the first transmission shaft 303 to rotate, and the semicircular gear 414 fixedly arranged on the first transmission shaft 303 rotates along with the rotation, the semi-circular gear 414 drives the inner gear ring 404 provided with the first rack 405 to move back and forth, the second rack 407 at the lower end of the inner gear ring 404 moves back and forth simultaneously to drive the gear 408 meshed at the lower end to rotate forward and backward, the driven shaft 409 fixedly connected with the gear 408 rotates along with the driven shaft 409 to drive the fixed block 411, the connecting rod 412 and the swinging rod 413 which are fixed at two sides and welded into a whole to swing back and forth, the seat 5 fixed at the lower end of the swinging rod 413 swings back and forth along with the driven shaft, when the playing time is over, the driving motor 602 is turned off, the whole mechanism stops rotating, and the swinging rod 413 and the seat 5 stop perpendicular to the ground.

Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.

Claims

1. The utility model provides a crisscross oscillating formula of children's amusement hangs amusement device, includes support column (1), support column (1) are fixed subaerial, support column (1) top fixed mounting support (7), its characterized in that: the device is characterized by further comprising a planet wheel rotating mechanism (2), a belt transmission mechanism (3), a swinging mechanism (4), a seat (5) and a driving device (6), wherein the planet wheel rotating mechanism (2) is rotatably mounted on the support (7), the belt transmission mechanism (3) is arranged at the upper end of the planet wheel rotating mechanism (2), the driving device (6) is mounted in the support (7), the driving device (6) is in transmission connection with the planet wheel rotating mechanism (2) and the belt transmission mechanism (3), the lower end of the planet wheel rotating mechanism (2) is provided with a plurality of uniformly arranged swinging mechanisms (4), the swinging mechanisms (4) are connected with the belt transmission mechanism (3), and the lower end of each swinging mechanism (4) is fixedly mounted on the seat (5);

the driving device (6) comprises a speed reducer (601) and a driving motor (602), the speed reducer (601) and the driving motor (602) are fixed on the support (7), the upper end of the speed reducer (601) is in transmission connection with a third transmission shaft (604), the third transmission shaft (604) extends out of the planetary wheel rotating mechanism (2) and is fixedly connected with the belt transmission mechanism (3), the lower end of the speed reducer (601) is in transmission connection with a second transmission shaft (603), and the second transmission shaft (603) is fixedly connected with the planetary wheel rotating mechanism (2);

the belt transmission mechanism (3) comprises a driving belt pulley (301), driven belt pulleys (302) and transmission shafts I (303), the driving belt pulley (301) is fixedly installed on a transmission shaft III (604), eight transmission shafts I (303) are circumferentially uniformly distributed and rotatably installed on the planet wheel rotating mechanism (2), the driven belt pulley (302) is fixedly installed at the upper end of each transmission shaft I (303), and belts (306) are installed on the driving belt pulley (301) and the eight driven belt pulleys (302);

the swing mechanism (4) comprises a fixing plate (401) and an inner gear ring (404), connecting plates (403) are welded on two sides of the fixing plate (401), the connecting plates (403) are welded at the lower end of the planetary gear rotating mechanism (2), a through groove (402) is formed in the middle of the fixing plate (401), a bottom plate (406) is welded at the lower end of the inner gear ring (404), the lower end face of the bottom plate (406) is flush with the lower end face of the inner gear ring (404), a second rack (407) is convexly arranged in the middle of the lower end of the bottom plate (406), the second rack (407) is slidably embedded into the through groove (402), the inner gear ring (404) is slidably attached to the upper end face of the fixing plate (401), two first racks (405) are symmetrically arranged on the inner side of the inner gear ring (404), the first racks (405) are meshed with a semicircular gear (414), the semicircular gear (414) is fixedly connected with a first transmission shaft (303) of the belt transmission mechanism (3), and fixing rings (410) are symmetrically welded on two sides of the lower end of the fixing plate (401), two solid fixed ring (410) internal rotation installation driven shafts (409), fixed mounting gear (408) in the middle of driven shaft (409), gear (408) and rack two (407) meshing, driven shaft (409) both ends fixed mounting fixed block (411) respectively, two fixed block (411) lower extreme installation connecting rod (412), connecting rod (412) middle part lower extreme installation swinging arms (413), fixed block (411), connecting rod (412) and swinging arms (413) weld an organic whole.

2. The staggered swing type suspension amusement device for children amusement according to claim 1, wherein: the support column (1) comprises a support column (101), a support disc (102) is welded at the top end of the support column (101), and a support frame (7) is fixedly installed at the upper end of the support disc (102).

3. The staggered swing type suspension play set for children's play of claim 2, wherein: planet wheel slewing mechanism (2) are including spider (201), spider (201) rotate and install on support (7), spider (201) equipartition welded connection pole (202) all around, ring holder (203) on connecting rod (202) other end welding planet wheel, ring holder (204) under the planet wheel upper ring holder (203) lower extreme passes through branch welding planet wheel, outer ring gear (205) of welding in the middle of ring holder (204) under the planet wheel, four planet wheels (206) of outer ring gear (205) inner gearing, planet wheel (206) rotate respectively and install on support (7), meshing sun gear (207) in the middle of planet wheel (206), sun gear (207) fixed connection is on transmission shaft two (603).

4. The staggered swing type suspension amusement device for children amusement according to claim 3, wherein: the lower end of the central disc (201) is provided with a fixing groove (208).

5. The staggered swing type suspension amusement device for children amusement according to claim 4, wherein: seven rotating shafts (305) are fixed on the planet wheel upper ring frame (203) at intervals, each rotating shaft (305) is located between two first transmission shafts (303), the included angle between each rotating shaft (305) and each first transmission shaft (303) is consistent in size, a tensioning wheel (304) is rotatably mounted on each rotating shaft (305), and the tensioning wheel (304) is rotatably attached to the outer side of a belt (306).

6. The staggered swing type suspension amusement device for children amusement according to claim 5, wherein: the seat (5) comprises a hanging frame (51) and a safety guardrail (52), the hanging frame (51) is welded at the lower end of the swinging rod (413), three sides of the hanging frame (51) are closed, and the safety guardrail (52) is installed at the opening end of the hanging frame (51).

7. The staggered swing type suspension amusement device for children amusement according to claim 6, wherein: support (7) are including solid fixed ring (701), gu fixed ring (701) normal running fit is in fixed slot (208), gu fixed ring (701) lower extreme circumference equipartition welding four spinal branch vaulting poles (702), rotate on every spinal branch vaulting pole (702) and install a planet wheel (206), bracing piece (702) are fixed on support column (1) top, gu fixed ring (701) lower extreme welded fastening motor bracket (703), fixed speed reducer (601) and driving motor (602) are gone up in motor bracket (703), horizontal welding baffle (704) in motor bracket (703), baffle (704) laminating speed reducer (601) and driving motor (602) side, baffle (704) width is less than motor bracket (703).

8. The staggered swing type suspension amusement device for children amusement according to claim 7, wherein: and the outer sides of the planet wheel rotating mechanism (2), the belt transmission mechanism (3) and the swinging mechanism (4) are provided with protective covers.