Back massager

Abstract

The invention relates to a back massager, which comprises a main plate (1), a main shaft (2), a sub-shaft (3), a massaging device, a power and transmission device and a casing (15). Slow massage is comfortable for the person being massaged; the back can be massaged from top to bottom, and the massage ball (6) will not hurt the spine; the design is reasonable, the structure is simple, and the cooperation between the components is good; the safety hazards of electric shock and skin damage caused by multiple gears are eliminated; when massaging, the back massager is like a back bag, which is convenient to use, and the person being massaged can walk in the room, which can eliminate boredom and annoyance; the same back massager can meet the needs of different people; the back massager replaces manual back massage, and for people who can take care of their own lives, they do not need help, and can promote long-term adherence; for people who cannot take care of their own lives, the labor intensity of the operator can be greatly reduced.

Description

Technical Field

[0001] This invention relates to a back massager, and more particularly to a back massager that replaces manual back massage. Background Technology

[0002] People who need back massages hope to use mechanical massage instead of manual massage. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a back massager that can replace manual back massage.

[0004] To solve the above-mentioned technical problems, the technical solution of the present invention is as follows:

[0005] A back massager, which is a mechanical massage device worn on the back, includes a main board, a main shaft, a secondary shaft, a massage device, a power and transmission device, and a housing.

[0006] The motherboard is a vertical rectangular plate with a height equal to or greater than the height difference between the clavicle and sacrum of a standing person. It has a main spindle hole and a secondary spindle hole.

[0007] The spindle hole is located at the center of the motherboard, and its axis is perpendicular to the surface of the motherboard.

[0008] Two auxiliary spindle holes are located directly above and below the main spindle hole, respectively. The distance between their axes and the axis of the main spindle hole is equal to or less than 1 / 4 of the height of the motherboard, and their axes are parallel to the axis of the main spindle hole.

[0009] The spindle is inserted into the spindle hole of the motherboard, and its axis coincides with the axis of the spindle hole. It is fixedly connected to the motherboard, its front end face is flush with the front surface of the motherboard, and its rear end extends backward from the rear surface of the motherboard.

[0010] Two secondary shafts are inserted into two secondary shaft holes on the main board, respectively. Their axes coincide with the axes of the secondary shaft holes into which they are inserted. They can rotate freely around their respective axes, but neither can move axially. Their front ends extend forward from the front surface of the main board, and their rear ends extend backward from the rear surface of the main board.

[0011] The massage device includes a turntable, a ball plate, massage balls, and connecting strips.

[0012] This massage ball is made of non-toxic, lightweight material and has a smooth surface.

[0013] The turntable is a horizontally vertical circular disc, parallel to the main board. Its outer diameter is equal to or less than 1 / 2 of the height of the main board. Two radial ridges protrude forward on its front surface. These two ridges are located on the same straight line, and their outer surfaces are smooth arc surfaces. The height of their protrusion relative to the turntable is 1 / 3 of the outer diameter of the massage ball.

[0014] Two turntables are fixedly mounted on the forward-extending ends of the two secondary shafts, with their axes coinciding with the axes of their respective secondary shafts. Their front surfaces are located on the same vertical plane and are flush with the front end face of their respective secondary shafts.

[0015] The ball plate is a vertical rectangular plate, parallel to the main plate, located directly in front of the two turntables. Its height and width are the same as the main plate, and its thickness is equal to 2 / 3 of the outer diameter of the massage ball. There are n ball holes on each side of its vertical center line. These n ball holes are located on the same vertical line and are evenly distributed. There are a total of 2n ball holes on the ball plate. The n is an even number equal to or greater than 4.

[0016] Any one of the 2n holes on the ball plate has an inner diameter equal to the outer diameter of the massage ball. Its hole wall is smooth, and four thin spring pieces are installed on its hole wall. These four spring pieces are evenly distributed around its axis. The rear ends of these four spring pieces are fixedly connected to its hole wall, and the front ends of these four spring pieces extend toward its front hole opening, but none of them extend forward from its front hole opening.

[0017] 2n massage balls are placed in the 2n holes of the ball plate.

[0018] The massage ball in any one of the 2n holes on the ball plate, when not subjected to horizontal forward pressure, is obstructed by the four spring pieces inside the hole, is located at the rear of the hole, and extends 1 / 3 of its outer diameter from the rear surface of the ball plate. When subjected to horizontal forward pressure, it extends forward from the front opening of the hole, with a maximum extension of 1 / 3 of its outer diameter, but it cannot leave the hole through the front opening.

[0019] The connecting strip is a vertical square strip, the length of which is equal to the height of the motherboard, and its horizontal width is much smaller than the horizontal width of the motherboard.

[0020] Two connecting strips, the rear surfaces of which are fixedly connected to the front surfaces on both sides of the main board, and the front surfaces of which are fixedly connected to the rear surfaces on both sides of the ball plate, respectively. The two outer surfaces of which are flush with the two side surfaces of the main board or the ball plate, respectively, and the upper surfaces of which are flush with the upper surfaces of the main board or the ball plate, respectively; the rear surface of the ball plate is close to the protrusions on the two turntables.

[0021] The front surface of the ball plate contacts the person's back. When the two rotating discs on the upper disc rotate around the axis, their two protruding strips will press against any of the massage balls on the ball plate opposite to the disc. This will cause the massage ball to overcome the elasticity of the corresponding spring and extend from the corresponding ball hole to the front opening to press against the person's back. The maximum extension is 1 / 3 of the outer diameter of the massage ball. When the two protruding strips leave the massage ball, the massage ball will automatically return to its original position under the action of the corresponding spring.

[0022] The front surface of the ball plate contacts the person's back. When the two rotating discs on the lower disc rotate around the axis, their two protruding strips will press against any of the massage balls below the ball plate opposite to the disc. This will cause the massage ball to overcome the elasticity of the corresponding spring and extend from the corresponding ball hole to the front opening to press against the person's back. The maximum extension is 1 / 3 of the outer diameter of the massage ball. When the two protruding strips leave the massage ball, the massage ball will automatically return to its original position under the action of the corresponding spring.

[0023] The power and transmission device includes an electric motor, a frame, a power gear, an external gear, an internal gear, a turntable gear, a power supply box, and a power source.

[0024] The frame consists of two frame feet and one frame cross plate.

[0025] The crossbar is located directly behind the spindle hole on the main board. It is parallel to the main board, and its width is equal to the width of the main board, while its height is less than the height of the main board.

[0026] Both of these support plates are rectangular plates, parallel to the side surface of the main plate and perpendicular to the cross plate or the main plate. Their heights are equal to the height of the cross plate. Their rear ends are fixedly connected to the front surfaces of the two ends of the cross plate, and their front ends are fixedly connected to the rear surfaces of the main plate on both sides at the corresponding positions.

[0027] The motor is fixedly mounted on the front surface of the right side of the frame cross plate, with its shaft extending horizontally forward, and its rated voltage is a DC safe voltage.

[0028] The power gear is coaxially fixedly mounted on the shaft of the electric motor.

[0029] The external gear and the internal gear are coaxially fixedly connected as one unit, and are coaxially mounted on the rearward extension end of the main shaft. They can rotate freely around the main shaft, but cannot move axially.

[0030] The external gear is located behind the internal gear. Its outer diameter is larger than that of the power gear, and the number of its upper teeth is greater than that of the power gear. Its upper teeth mesh with the teeth of the power gear.

[0031] The inner gear has a smaller outer diameter than the outer gear, and the number of teeth on the inner gear is less than the number of teeth on the outer gear.

[0032] The outer diameter of the turntable gear is larger than that of the external gear, and the number of teeth on the turntable gear is larger than that of the external gear.

[0033] Two turntable gears are coaxially fixedly mounted on the rearward extension ends of the two secondary shafts, and the upper gear teeth mesh with the teeth of the inner gear.

[0034] The power supply is an isolated power supply with an input voltage of 220 volts AC and an output voltage of DC safety voltage. It supplies power to the motor in a controlled manner and is fixedly mounted on the front surface of the left side of the frame cross plate.

[0035] The power supply box covers the power supply.

[0036] After the motor is powered on, it sequentially drives the two turntables to rotate in the same direction by an angle θ per second through the power gear, the external gear, the internal gear and the two turntable gears, thereby changing the gear ratio between the gears. The angle is selected in the range of 90° to 180°.

[0037] The casing is box-shaped with an open front opening. It is fixedly connected to the outer periphery of the main board and the ball plate with screws. Two hanging rings for hanging on the shoulders and a belt for fastening around the waist are fixedly connected to it.

[0038] When massaging the back, wear the back massager on your back like a backpack, with the front surface of the ball plate in contact with your back, and fasten the belt around your waist. After the motor is powered on, it drives the two turntables to rotate slowly. The protrusions on the two turntables push the 2n massage balls on the ball plate forward in sequence, pressing on the back and thus providing a massage effect. The massage stops when the motor is powered off.

[0039] This back massager replaces manual back massage. For people who can take care of themselves, it not only eliminates the need for assistance but also encourages long-term adherence. For people who cannot take care of themselves, it can greatly reduce the labor intensity of the operator.

[0040] In order for the two turntables to rotate in both clockwise and counterclockwise directions, the direction of the current in the motor is controlled by a reversing switch mounted on the housing.

[0041] To protect the skin on the back, the person receiving the massage must wear a tight-fitting top when using this back massager.

[0042] With this structure, the number of teeth on the external gear is greater than that on the power gear, the number of teeth on the internal gear is less than that on the external gear, and the number of teeth on the turntable gear is greater than that on the external gear. This results in the turntable rotating much slower than the motor, creating conditions for slow massage and making the person receiving the massage feel comfortable.

[0043] With this structure, the 2n massage balls are divided into two groups, which are located on the left and right sides of the vertical center line of the ball plate. The n massage balls in each group are located on the same vertical line and are evenly distributed. On the one hand, the massage balls will not injure the spine when massaging the back. On the other hand, the back can be massaged from top to bottom.

[0044] With this structure, the outer surface of the raised strip on the turntable is a smooth arc surface, which allows the raised strip to pass smoothly through the massage ball and reliably press the massage ball forward.

[0045] With this structure, because the rear surface of the ball plate is close to the protrusions on the two turntables, and because the thickness of the ball plate is equal to 2 / 3 of the outer diameter of the massage ball, the massage ball located in the ball hole on the ball plate, when not in contact with the protrusions of the turntables, can protrude 1 / 3 of its outer diameter from the rear surface of the ball plate, thanks to the cooperation of the corresponding springs. When the protrusions contact the massage ball, they press the massage ball so that 1 / 3 of its outer diameter protrudes from the front surface of the ball plate, thus providing pressure on the back. When the protrusions leave the massage ball, the corresponding springs retract the massage ball back into the ball hole, and it automatically protrudes 1 / 3 of its outer diameter from the rear surface of the ball plate again. The design is reasonable, the structure is simple, and the cooperation between the above components is good.

[0046] With this structure, the power supply is an isolated power supply, and the output voltage of the power supply is a safe DC voltage, thus eliminating the safety hazard of electric shock.

[0047] With this structure, the various gears are hidden inside the casing, thus eliminating the safety hazard of skin damage caused by these gears.

[0048] With this structure, the back massager can be carried on the back like a backpack, making it convenient to use. As long as the external power cord is long enough, the person receiving the massage can move around the room, eliminating boredom and annoyance.

[0049] With this structure, the pressure of the massage balls on the back can be adjusted by controlling the tightness of the waist belt, allowing the same back massager to meet the needs of different people.

[0050] With this structure, the direction of the motor current is controlled by a reversing switch, which is mounted on the casing. This not only overcomes the monotony of the back massage sequence but also improves the ease of operation.

[0051] With this structure, the massage ball can prevent damage to the skin on the back from the recipient having to wear a tight-fitting top.

[0052] With this structure, the back massager replaces manual back massage. For people who can take care of themselves, it not only eliminates the need for assistance but also encourages long-term adherence. For people who cannot take care of themselves, it greatly reduces the labor intensity of the operator. Attached Figure Description

[0053] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0054] Figure 1 This is a rear view diagram of the motherboard on the back massager.

[0055] Figure 2 It is along Figure 1 A schematic diagram of the horizontal cross-section of line AA in the middle.

[0056] Figure 3 It is along Figure 1 A schematic diagram of the vertical cross-section of the BB line.

[0057] Figure 4 This is a rear view diagram of the ball plate on the back massager, with n=8.

[0058] Figure 5 It is along Figure 4 A schematic diagram of the vertical cross-section of the CC line.

[0059] Figure 6 This is a rear view diagram of the casing. Detailed Implementation

[0060] like Figures 1 to 6 As shown in the figures, a back massager is a mechanical massage device worn on the back, comprising a main board 1, a main shaft 2, a secondary shaft 3, a massage device, a power and transmission device, and a housing 15.

[0061] like Figure 1 , Figure 2 , Figure 3 As shown, the main board 1 is a vertical rectangular plate with a height equal to or greater than the height difference between the clavicle and sacrum of a standing person. It has a main shaft hole 1a and a secondary shaft hole 1b.

[0062] like Figure 2 , Figure 3 As shown, the spindle hole 1a is located at the center of the main board 1, and its axis is perpendicular to the surface of the main board 1.

[0063] like Figure 2 , Figure 3 As shown, there are two secondary shaft holes 1b, which are located directly above and directly below the main shaft hole 1a, respectively. The distance between their axes and the axis of the main shaft hole 1a is equal to or less than 1 / 4 of the height of the main board 1, and their axes are parallel to the axis of the main shaft hole 1a.

[0064] like Figure 2 , Figure 3 As shown, the spindle 2 is inserted into the spindle hole 1a of the motherboard 1, and its axis coincides with the axis of the spindle hole 1a. It is fixedly connected to the motherboard 1, its front end face is flush with the front surface of the motherboard 1, and its rear end extends backward from the rear surface of the motherboard 1.

[0065] like Figure 1 , Figure 3 As shown, there are two secondary shafts 3, which are respectively inserted into the two secondary shaft holes 1b of the main board 1. Their axes coincide with the axes of the secondary shaft holes 1b into which they are inserted. They can rotate freely around their respective axes, but neither can move axially. Their front ends extend forward from the front surface of the main board 1, and their rear ends extend backward from the rear surface of the main board 1.

[0066] like Figure 3 , Figure 4 , Figure 5 As shown, the massage device includes a turntable 4, a ball plate 5, a massage ball 6, and a connecting strip 7.

[0067] like Figure 4 , Figure 5 As shown, the massage ball 6 is made of non-toxic, lightweight material and has a smooth surface.

[0068] like Figure 1 , Figure 3 As shown, the turntable 4 is a horizontally vertical disc, parallel to the main board 1. Its outer diameter is equal to or less than 1 / 2 of the height of the main board 1. Two radial protrusions 4a protrude forward on its front surface. These two protrusions 4a are located on the same straight line, and their outer surfaces are smooth arc surfaces. The height of their protrusion relative to the turntable 4 is 1 / 3 of the outer diameter of the massage ball 6.

[0069] like Figure 3 As shown, two turntables 4 are fixedly mounted on the forward-extending ends of the two secondary shafts 3, and their axes coincide with the axes of their respective secondary shafts 3. Their front surfaces are located on the same vertical plane and are flush with the front end face of their respective secondary shafts 3.

[0070] like Figure 3 , Figure 4 , Figure 5 As shown, the ball plate 5 is a vertical rectangular plate, parallel to the main plate 1, located directly in front of the two turntables 4. Its height and width are the same as the main plate 1, and its thickness is equal to 2 / 3 of the outer diameter of the massage ball 6. There are n ball holes 5a on each side of its vertical center line. These n ball holes 5a are located on the same vertical line and are evenly distributed. There are a total of 2n ball holes 5a on the ball plate 5. The n is an even number equal to or greater than 4.

[0071] like Figure 4 , Figure 5 As shown, any one of the 2n ball holes 5a on the ball plate 5 has an inner diameter equal to the outer diameter of the massage ball 6. Its hole wall is smooth, and four thin spring pieces 5b are installed on its hole wall. These four spring pieces 5b are evenly distributed around its axis. The rear ends of these four spring pieces 5b are all fixedly connected to its hole wall, and the front ends of these four spring pieces 5b all extend toward its front hole opening, but none of them extend forward from its front hole opening.

[0072] like Figure 4 As shown, 2n massage balls 6 are placed in 2n ball holes 5a on the ball plate 5.

[0073] like Figure 4 , Figure 5 As shown, the massage ball 6 in any one of the 2n ball holes 5a on the ball plate 5, when not subjected to horizontal forward pressure, is obstructed by the four spring pieces 5b inside the ball hole 5a. It is located at the rear of the ball hole 5a and extends 1 / 3 of its outer diameter from the rear surface of the ball plate 5. When subjected to horizontal forward pressure, it extends forward from the front opening of the ball hole 5a, and the maximum extension is 1 / 3 of its outer diameter, but it cannot leave the ball hole 5a through the front opening.

[0074] like Figure 2 As shown, the connecting strip 7 is a vertical square strip, the length of which is equal to the height of the motherboard 1, and its horizontal width is much smaller than the horizontal width of the motherboard 1.

[0075] like Figure 2 As shown, the rear surfaces of the two connecting strips 7 are fixedly connected to the front surfaces of both sides of the main board 1, and their front surfaces are fixedly connected to the rear surfaces of both sides of the ball plate 5. Their two outer surfaces are flush with the two side surfaces of the main board 1 or the ball plate 5, and their upper surfaces are flush with the upper surfaces of the main board 1 or the ball plate 5. The rear surface of the ball plate 5 is close to the protrusions 4a on the two turntables 4.

[0076] like Figure 3 , Figure 4 , Figure 5 As shown, the front surface of the ball plate 5 contacts the back of the person. When the two upper turntables 4 rotate around the axis, the two protrusions 4a on the upper turntable 4 will press the massage ball 6 against any of the massage balls 6 on the ball plate 5 opposite to the turntable 4. This will cause the massage ball 6 to overcome the elastic force of the corresponding spring plate 5b and extend out of the corresponding ball hole 5a to press the back of the person. The maximum extension is 1 / 3 of the outer diameter of the massage ball 6. When the two protrusions 4a leave the massage ball 6, the massage ball 6 will automatically return to its original position under the action of the elastic force of the corresponding spring plate 5b.

[0077] like Figure 3 , Figure 4, Figure 5 As shown, the front surface of the ball plate 5 contacts the back of the person. When the two convex strips 4 on the lower of the two turntables 4 rotate around the axis, they will press the massage ball 6 against any of the massage balls 6 below the ball plate 5 opposite to the turntable 4. This will cause the massage ball 6 to overcome the elastic force of the corresponding spring piece 5b and extend out of the corresponding ball hole 5a to press the back of the person. The maximum extension is 1 / 3 of the outer diameter of the massage ball 6. When the two convex strips 4a leave the massage ball 6, the massage ball 6 will automatically return to its original position under the action of the elastic force of the corresponding spring piece 5b.

[0078] like Figure 1 , Figure 2 As shown, the power and transmission device includes an electric motor 8, a frame 9, a power gear 10, an external gear 11, an internal gear 12, a turntable gear 13, a power supply box 14, and a power source.

[0079] like Figure 2 As shown, the frame 9 consists of two frame legs 9a and one frame cross plate 9b.

[0080] like Figure 2 As shown, the cross plate 9b is located directly behind the spindle hole 1a on the main board 1. It is parallel to the main board 1, its width is equal to the width of the main board 1, and its height is less than the height of the main board 1.

[0081] like Figure 2 As shown, both of the two bracket plates 9a are rectangular plates, parallel to the side surface of the main plate 1, and perpendicular to the cross plate 9b or the main plate 1. Their heights are equal to the height of the cross plate 9b. Their rear ends are fixedly connected to the front surfaces of the two ends of the cross plate 9b, and their front ends are fixedly connected to the rear surfaces of the main plate 1 on both sides at the corresponding positions.

[0082] like Figure 2 As shown, the motor 8 is fixedly mounted on the front surface of the right side of the frame cross plate 9b of the frame 9, with its shaft 8a extending horizontally forward, and its rated voltage is a DC safe voltage.

[0083] like Figure 1 , Figure 2 As shown, the power gear 10 is coaxially fixedly mounted on the shaft 8a of the electric motor 8.

[0084] like Figure 1 , Figure 2 As shown, the external gear 11 and the internal gear 12 are coaxially fixedly connected as one unit, and are coaxially mounted on the rearward extension end of the main shaft 2. They can rotate freely around the main shaft 2, but they cannot move axially.

[0085] like Figure 1 , Figure 2As shown, the external gear 11 is located behind the internal gear 12. Its outer diameter is larger than that of the power gear 10, and the number of its upper teeth is larger than that of the power gear 10. Its upper teeth mesh with the teeth of the power gear 10.

[0086] like Figure 1 , Figure 2 As shown, the outer diameter of the inner gear 12 is smaller than that of the outer gear 11, and the number of teeth on the inner gear 12 is smaller than that of the outer gear 11.

[0087] like Figure 1 , Figure 3 As shown, the outer diameter of the turntable gear 13 is larger than that of the outer diameter of the external gear 11, and the number of teeth on it is greater than that of the external gear 11.

[0088] like Figure 1 , Figure 3 As shown, two turntable gears 13 are coaxially fixedly mounted on the rearward extension ends of the two secondary shafts 3, and their upper gear teeth mesh with the gear teeth of the inner gear 12.

[0089] like Figure 2 As shown, the power supply is an isolated power supply with an input voltage of 220 volts AC and an output voltage of DC safety voltage. It supplies power to the motor 8 under control and is fixedly installed on the front surface of the left side of the frame cross plate 9b of the frame 9.

[0090] like Figure 2 As shown, the power supply box 14 covers the power supply.

[0091] like Figure 1 , Figure 2 , Figure 3 As shown, after the motor 8 is powered on, it sequentially drives the two turntables 4 to rotate in the same direction by an angle θ per second through the power gear 10, the external gear 11, the internal gear 12 and the two turntable gears 13, thereby changing the gear ratio between the gears. The angle is selected in the range of 90° to 180°.

[0092] like Figure 2 , Figure 3 , Figure 6 As shown, the housing 15 is a square box with an open front opening. It is fixedly connected to the outer periphery of the main board 1 and the ball plate 5 with screws. Two hanging rings 16 for hanging on the shoulders and a belt 17 for fastening around the waist are fixedly connected to it.

[0093] like Figure 3 , Figure 4 , Figure 5 , Figure 6As shown, when massaging the back, the back massager is worn on the back like a backpack, with the front surface of the ball plate 5 in contact with the back, and the waist belt 17 is fastened around the waist. After the motor 8 is powered on, it drives the two turntables 4 to rotate slowly. The protrusions 4a on the two turntables 4 push the 2n massage balls 6 on the ball plate 5 forward in sequence, so that they press on the back, thereby achieving a massage effect. When the motor 8 is powered off, the massage ends.

[0094] This back massager replaces manual back massage. For people who can take care of themselves, it not only eliminates the need for assistance but also encourages long-term adherence. For people who cannot take care of themselves, it can greatly reduce the labor intensity of the operator.

[0095] like Figure 1 , Figure 2 , Figure 3 As shown, in order for the two turntables 4 to rotate both clockwise and counterclockwise, the current direction of the motor 8 is controlled by a reversing switch, which is mounted on the housing 15.

[0096] To protect the skin on the back, the person receiving the massage must wear a tight-fitting top when using this back massager.

[0097] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. The present invention is not limited to the above embodiments, and various changes can be made within the scope of knowledge possessed by those skilled in the art without departing from the spirit of the present invention. Such changes, without departing from the spirit of the present invention, still fall within the scope of the present invention.

Claims

1. A back massager; characterized in that: The back massager is a mechanical massage device worn on the back, which includes a main board (1), a main shaft (2), a secondary shaft (3), a massage device, a power and transmission device, and a housing (15). The main board (1) is a vertical rectangular plate with a height equal to or greater than the height difference between the clavicle and sacrum of a standing person. It has a main shaft hole (1a) and a secondary shaft hole (1b). The spindle hole (1a) is located at the center of the main board (1), and its axis is perpendicular to the surface of the main board (1). Two secondary shaft holes (1b) are located directly above and directly below the main shaft hole (1a), respectively. The distance between their axes and the axis of the main shaft hole (1a) is equal to or less than 1 / 4 of the height of the main board (1), and their axes are parallel to the axis of the main shaft hole (1a). The spindle (2) is inserted into the spindle hole (1a) of the motherboard (1), its axis coincides with the axis of the spindle hole (1a), it is fixedly connected to the motherboard (1), its front end face is flush with the front surface of the motherboard (1), and its rear end extends backward from the rear surface of the motherboard (1). Two secondary shafts (3) are respectively inserted into two secondary shaft holes (1b) of the main board (1). Their axes coincide with the axes of the secondary shaft holes (1b) into which they are inserted. They can rotate freely around their respective axes, but they cannot move along the axial direction. Their front ends extend forward from the front surface of the main board (1), and their rear ends extend backward from the rear surface of the main board (1). The massage device includes a turntable (4), a ball plate (5), a massage ball (6), and a connecting strip (7); The massage ball (6) is made of non-toxic, lightweight material and has a smooth surface; The turntable (4) is a horizontal vertical disc, which is parallel to the main board (1). Its outer diameter is equal to or less than 1 / 2 of the height of the main board (1). Two radial ridges (4a) protrude forward on its front surface. These two ridges (4a) are located on the same straight line. Their outer surfaces are smooth arc surfaces. The height of their protrusion relative to the turntable (4) is 1 / 3 of the outer diameter of the massage ball (6). Two turntables (4) are fixedly mounted on the forward-extending ends of the two secondary shafts (3), and their axes coincide with the axes of their respective secondary shafts (3). Their front surfaces are located on the same vertical plane and are flush with the front end face of their respective secondary shafts (3). The ball plate (5) is a vertical rectangular plate, parallel to the main plate (1), located directly in front of the two turntables (4). Its height and width are the same as the main plate (1), and its thickness is equal to 2 / 3 of the outer diameter of the massage ball (6). There are n ball holes (5a) on each side of its vertical center line. These n ball holes (5a) are located on the same vertical line and are evenly distributed. There are a total of 2n ball holes (5a) on the ball plate (5). The n is an even number equal to or greater than 4. Any one of the 2n ball holes (5a) on the ball plate (5) has an inner diameter equal to the outer diameter of the massage ball (6), and its hole wall is smooth. Four thin spring pieces (5b) are installed on its hole wall. These four spring pieces (5b) are evenly distributed around its axis. The rear ends of these four spring pieces (5b) are fixedly connected to its hole wall. The front ends of these four spring pieces (5b) extend toward its front hole opening, but none of them extend forward from its front hole opening. 2n massage balls (6) are respectively placed in 2n ball holes (5a) on the ball plate (5); The massage ball (6) in any one of the 2n ball holes (5a) on the ball plate (5) is obstructed by the four spring pieces (5b) inside the ball hole (5a) when it is not subjected to horizontal forward pressure. It is located at the rear of the ball hole (5a) and extends 1 / 3 of its outer diameter from the rear surface of the ball plate (5). When it is subjected to horizontal forward pressure, it extends forward from the front opening of the ball hole (5a) and the maximum extension is 1 / 3 of its outer diameter, but it cannot leave the ball hole (5a) through the front opening. The connecting strip (7) is a vertical square strip with a length equal to the height of the main board (1) and a lateral width much smaller than the lateral width of the main board (1). Two connecting strips (7) have their rear surfaces fixedly connected to the front surfaces on both sides of the main board (1), their front surfaces fixedly connected to the rear surfaces on both sides of the ball plate (5), their two outer surfaces flush with the two side surfaces of the main board (1) or the ball plate (5), and their upper surfaces flush with the upper surfaces of the main board (1) or the ball plate (5); the rear surface of the ball plate (5) is close to the protrusions (4a) on the two turntables (4); The front surface of the ball plate (5) contacts the back of the person. When the two convex strips (4) on the upper turntable (4) rotate around the axis, they will press the massage ball (6) forward to overcome the elastic force of the corresponding spring plate (5b) and extend from the corresponding ball hole (5a) to press the back of the person. The maximum extension is 1 / 3 of the outer diameter of the massage ball (6). When the two convex strips (4a) leave the massage ball (6), the massage ball (6) will automatically return to its original position under the action of the elastic force of the corresponding spring plate (5b). The front surface of the ball plate (5) contacts the back of the person. When the two convex strips (4) on the lower of the two turntables (4) rotate around the axis, they will press the massage ball (6) forward when they encounter any massage ball (6) below the ball plate (5) opposite to the turntable (4), so that it overcomes the elastic force of the corresponding spring (5b) and extends out from the corresponding ball hole (5a) to press the back of the person. The maximum extension is 1 / 3 of the outer diameter of the massage ball (6). When the two convex strips (4a) leave the massage ball (6), the massage ball (6) will automatically return to its original position under the action of the elastic force of the corresponding spring (5b). The power and transmission device includes an electric motor (8), a frame (9), a power gear (10), an external gear (11), an internal gear (12), a turntable gear (13), a power box (14), and a power source; The frame (9) consists of two frame legs (9a) and one frame cross plate (9b); The cross plate (9b) is located directly behind the spindle hole (1a) on the main board (1), is parallel to the main board (1), has a width equal to the width of the main board (1), and a height less than the height of the main board (1). Both of these support plates (9a) are rectangular plates, both are parallel to the side surface of the main plate (1), both are perpendicular to the cross plate (9b) or the main plate (1), and both are equal in height to the cross plate (9b). Their rear ends are fixedly connected to the front surfaces of the two ends of the cross plate (9b) in the lateral direction, and their front ends are fixedly connected to the rear surfaces of the main plate (1) on both sides at the corresponding positions. The motor (8) is fixedly mounted on the front surface of the right side of the frame cross plate (9b) of the frame (9), with its shaft (8a) extending horizontally forward and its rated voltage being a DC safe voltage; The power gear (10) is coaxially fixedly mounted on the shaft (8a) of the electric motor (8); The external gear (11) and the internal gear (12) are coaxially fixedly connected as one unit, and are coaxially mounted on the rearward extension end of the main shaft (2). They can rotate freely around the main shaft (2), but they cannot move along the axial direction. The external gear (11) is located behind the internal gear (12), its outer diameter is larger than that of the power gear (10), its number of upper teeth is larger than that of the power gear (10), and its upper teeth mesh with the teeth of the power gear (10). The inner gear (12) has an outer diameter smaller than that of the outer gear (11), and the number of teeth on it is smaller than that of the outer gear (11). The outer diameter of the turntable gear (13) is larger than that of the outer diameter of the external gear (11), and the number of teeth on it is greater than that of the external gear (11). Two turntable gears (13) are coaxially fixedly mounted on the rearward extension ends of the two secondary shafts (3), and their upper gear teeth mesh with the gear teeth of the inner gear (12); The power supply is an isolated power supply with an input voltage of 220 volts AC and an output voltage of DC safety voltage. It supplies power to the motor (8) under control and is fixedly installed on the front surface of the left side of the frame cross plate (9b) of the frame (9). The power supply box (14) covers the power supply; After the motor (8) is powered on and starts working, it sequentially drives the two turntables (4) to rotate in the same direction by an angle θ per second through the power gear (10), the external gear (11), the internal gear (12) and the two turntable gears (13), thereby changing the gear ratio between the gears. The angle is selected in the range of 90° to 180°. The casing (15) is a square box with an open front opening. It is fixedly connected to the outer periphery of the main board (1) and the ball plate (5) with screws. Two hanging rings (16) for hanging on the shoulders and a belt (17) for fastening around the waist are fixedly connected to it. When massaging the back, the back massager is carried on the back like a backpack, with the front surface of the ball plate (5) in contact with the back, and the waist belt (17) is fastened around the waist. After the motor (8) is powered on, it drives the two turntables (4) to rotate slowly. The protrusions (4a) on the two turntables (4) push the 2n massage balls (6) on the ball plate (5) forward in sequence, so that they press on the back, thereby achieving a massage effect. After the motor (8) is powered off, the massage ends.

2. The back massager according to claim 1, characterized in that: The current direction of the motor (8) is controlled by a reversing switch, which is mounted on the housing (15).

3. The back massager according to claim 1, characterized in that: When using the back massager to massage the back, the person receiving the massage must wear a tight-fitting top.

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