WO2017002870A1 - Screw structure, feeding device, medical apparatus, and infusion pump - Google Patents

Abstract

The cross sections of a thread (22) of a screw shaft (20) and a thread (32) of a half nut (30) include substantially trapezoidal bases (60, 65) and tops (70, 75). Each of the tops (70, 75) has an apex (71, 76) and slopes (72, 77) sloping from the apex (71, 76) toward the base (60, 65).

Description

Screw structure, feeding device, medical device, and infusion pump

The present invention relates to a screw structure, a feeding device, a medical device, and an infusion pump.

In recent years, a feeding device having a screw structure including a screw shaft and a nut has been used as a device for feeding the liquid of an infusion pump. For example, in Patent Document 1, the cross section of the thread of the male screw portion and the female screw portion has a parallel portion whose top portion is parallel to the axial direction of the screw, and extends from one end of the parallel portion and is orthogonal to the axial direction of the screw. A configuration having an orthogonal part and an inclined part extending from the other end of the parallel part and extending in a direction inclined with respect to the axial direction of the screw is disclosed.

However, in the screw structure disclosed in Patent Document 1, since the screw thread has an orthogonal portion, when the screw structure is used as a feeding device, the nut can be fed only in one direction, and after feeding, the nut is reversed. I couldn't get it back. In addition, when contact occurs at the orthogonal portion in the female screw portion and the male screw portion, a play for preventing biting is required in the inclined portion, and there is a problem that this play becomes a backlash. Furthermore, in order to form the orthogonal part as described above at the time of manufacturing, rolling processing cannot be used, and processing such as cutting is required, resulting in an increase in cost.

Therefore, Patent Document 2 discloses a configuration in which a thread cross section of a male screw portion and a female screw portion is formed in a trapezoidal shape in a screw structure including a screw shaft and a nut. In this configuration, the nut can be returned in the opposite direction after being sent in one direction. In addition, backlash can be reduced, and molding can be performed by rolling.

Special table 2013-534601 gazette JP 2003-56667 A

By the way, in the above-described screw structure, a split nut is used as a nut, and the split nut is brought into close proximity to the screw shaft from the side of the screw shaft (perpendicular to the axis of the screw shaft). In some cases, the nut may be detachable from the screw shaft. At this time, in the screw structure having a trapezoidal screw thread as described in Patent Document 2, when the split nut is brought close to the screw shaft from the side surface, the upper bases of the trapezoid contact each other, and the screw shaft screw The thread and the thread of the split nut may not engage and may not screw together. As described above, when the split nut is brought close to the screw shaft, it is difficult to accurately feed the screw unless the threads are screwed together.

The present invention has been made in view of the above, and a screw structure and a feeding device capable of reliably screwing the split nut and the screw shaft when the split nut is brought close to the side surface side of the screw shaft. An object is to provide a medical device and an infusion pump.

In order to solve the above-described problems and achieve the object, a screw structure according to one aspect of the present invention includes a screw shaft having a male screw portion, and a female screw portion provided so as to be screwable with the male screw portion. A screw structure comprising a split nut having a cross section of a thread of the male screw part and a screw thread of the female screw part, a skirt formed in a substantially trapezoidal shape, a vertex and the skirt from the vertex And a top portion having an inclined portion that is inclined toward the side portion. In other words, the screw structure includes a screw shaft and a split nut that is screwed onto the screw shaft, and a screw thread of the screw shaft and a cross section of the thread of the split nut are formed in a substantially trapezoidal shape. And a top portion, the top portion having a vertex and an inclined portion inclined from the vertex toward the skirt portion.

Further, in the screw structure according to one aspect of the present invention, a cross section of the thread of the male screw portion and the screw thread of the female screw portion is a line with respect to a line that includes the apex and is orthogonal to the axis of the screw shaft. It is symmetric. In other words, in the screw structure, the screw shaft threads and the split nut thread cross-sections are line symmetric with respect to a line passing through the apex and perpendicular to the axis of the screw shaft. .

In the screw structure according to one aspect of the present invention, at least a part of the inclined portion is linear in a cross section of at least one of the thread of the male screw portion and the screw thread of the female screw portion. It is formed. In other words, in the screw structure, in the cross section of at least one of the thread of the screw shaft and the thread of the split nut, the inclined portion of the top portion has a straight portion.

Further, in the screw structure according to one aspect of the present invention, in the cross section of at least one of the thread of the male thread part and the thread of the female thread part, at least a part of the inclined part of the top part has a curvature. It is characterized by having. In other words, in the screw structure, in the cross section of at least one of the thread of the screw shaft and the thread of the split nut, the inclined portion of the top is curved.

Further, in the screw structure according to one aspect of the present invention, in the cross section of at least one of the thread of the male thread part and the thread of the female thread part, at least a part of the side part of the skirt part is It has a straight part. In other words, in the screw structure, in the cross section of at least one of the thread of the screw shaft and the thread of the split nut, the side portion of the skirt has a straight portion.

Further, in the screw structure according to one aspect of the present invention, in the cross section of at least one of the thread of the male thread part and the thread of the female thread part, at least a part of the side part of the skirt part is It has a curvature. In other words, in the screw structure, in the cross section of at least one of the thread of the screw shaft and the thread of the split nut, the side portion of the skirt is curved.

Further, the screw structure according to one aspect of the present invention is characterized in that at least one of the male screw part and the valley bottom of the female screw part is flat. In other words, in the screw structure, at least one of the screw shaft and the valley bottom of the split nut is flat.

The feeding device according to one aspect of the present invention is characterized by applying the above-described screw structure.

In the feeding device according to one aspect of the present invention, the split nut is movable in a direction perpendicular to the axis of the screw shaft with respect to the screw shaft, and reciprocates in a direction parallel to the axis of the screw shaft. It is provided to be movable.

An infusion pump according to an aspect of the present invention includes the above-described feeding device.

A medical device according to one aspect of the present invention includes the above-described feeding device.

According to the present invention, when the split nut is approached from the side of the screw shaft, the split nut and the screw shaft can be reliably screwed together.

FIG. 1 is a schematic explanatory diagram of an infusion pump according to an embodiment of the present invention. FIG. 2 is a cross-sectional view taken along the line AA in FIG. FIG. 3 is a schematic view showing a cross section of the screw structure according to the embodiment of the present invention. FIG. 4 is an enlarged view of a cross section of the screw structure shown in FIG. FIG. 5 is a schematic view showing a state where the screw shaft and the split nut are separated from each other in the screw structure shown in FIG. 3. FIG. 6 is a schematic view showing a state when the screw shaft and the split nut are brought close to each other in the screw structure shown in FIG. 3. FIG. 7 is a schematic explanatory view of a conventional screw structure. FIG. 8 is a schematic view of a screw structure showing Modification Example 1 of the screw structure according to the first embodiment of the present invention. FIG. 9 is a schematic view of a screw structure showing Modification Example 2 of the screw structure according to the first embodiment of the present invention. FIG. 10 is a schematic view of a screw structure showing a third modification of the screw structure according to the first embodiment of the present invention. FIG. 11A is a diagram illustrating a modified example of a screw thread in the screw structure according to the first embodiment of the present invention. FIG. 11B is a diagram showing a modified example of the screw thread in the screw structure according to the first embodiment of the present invention.

Embodiments of a screw structure, a feeding device, a medical device, and an infusion pump according to the present invention will be described in detail below with reference to the accompanying drawings. In addition, this invention is not limited by the following embodiment. In the drawings, the same or corresponding elements are denoted by the same reference numerals as appropriate, and repeated descriptions are omitted as appropriate.

FIG. 1 is a schematic explanatory view of an infusion pump 1 according to a first embodiment of the present invention, and FIG. 2 is a cross-sectional view taken along the line AA of FIG. The infusion pump 1 includes a feeding device 10, a plunger 2, a syringe 3, and a gantry 4 for disposing these at predetermined positions. The feeding device 10 includes a motor 11, a speed reducer 12, a screw shaft 20, a split nut 30, a movable arm 40, and a connecting rod 41. The infusion pump 1 according to the present embodiment is used as a pump device for artificial dialysis, for example.

The motor 11 serves as a drive source for the infusion pump 1 and the feeding device 10, and the output shaft of the motor 11 is connected to one of the gears 12 a to 12 d of the speed reducer 12. The motor 11 is driven by power or a control signal input from the external input terminal 11a, for example. The speed reducer 12 is configured by meshing four gears 12a to 12d. When the gear 12a is rotated by the rotation of the output shaft of the motor 11, the adjacent gears 12b to 12d are sequentially rotated. ing. The gear 12d is connected to the screw shaft 20, and the reduced power is transmitted to the screw shaft 20 as the gear 12d rotates.

The screw shaft 20 extends in one direction and has a male screw portion 21 on the outer peripheral surface. Both ends of the screw shaft 20 are installed on the gantry 4 and are arranged so as to be capable of rotating about the axis. A split nut 30 is disposed on the outer peripheral surface of the screw shaft 20.

The split nut 30 is a nut having an internal thread portion 31 on the inner peripheral surface. In this embodiment, the split nut 30 is a half nut (half nut), but is not limited to this. The female screw portion 31 of the split nut 30 and the male screw portion 21 of the screw shaft 20 are screwed together, and the split nut 30 can be moved in the axial direction of the screw shaft 20 in accordance with the rotation of the screw shaft 20. Has been. The screw structure 50 constituted by the screw shaft 20 and the split nut 30 will be described in detail later.

Further, the split nut 30 is connected to a movable arm 40, and this movable arm 40 is further connected to a connecting rod 41. The movable arm 40 moves the split nut 30 in a direction orthogonal to the axial direction of the screw shaft 20 by operating the lever 42, for example. That is, the movable arm 40 moves the split nut 30 toward and away from the screw shaft 20. The lever 42 is configured to be interlocked with the plunger holder 43 and the connection member 44. The connecting rod 41 is connected to the plunger 2 via a connecting member 44 having a plunger holder 43. The movable arm 40, the connecting rod 41, the connection member 44, the plunger holder 43, and the plunger 2 move together according to the amount of movement of the split nut 30 due to the rotation of the screw shaft 20.

The syringe 3 has a cylindrical shape with an open base end side, and a part of the plunger 2 is inserted inside. A pusher 2 a is provided at the distal end of the plunger 2, and the liquid filled in the syringe 3 is discharged from the distal end of the syringe 3 through the tube 45 as the plunger 2 advances in the cylinder of the syringe 3. It is like that. The amount of movement of the plunger 2 (the pusher 2a) is determined according to the amount of movement of the split nut 30.

Further, the feeding device 10 includes various sensors. For example, in the present embodiment, the feeding device 10 includes a pressure sensor 13, a rotation detection sensor 14, and a position detection sensor 15. The pressure sensor 13 is provided at one end of the screw shaft 20 and detects whether or not the split nut 30 is moving normally by detecting the pressure applied to the screw shaft 20.

The rotation detection sensor 14 is attached to the outer peripheral surface of the split nut 30 and detects the rotation of the screw shaft 20. The position detection sensor 15 is for detecting the position of the split nut 30, and by detecting the position of the split nut 30, the position of the pusher 2 a of the plunger 2 is grasped, and the solution in the syringe 3 is detected. You can check the remaining amount.

Next, the screw structure 50 according to the embodiment of the present invention will be described. FIG. 3 is a schematic view showing a cross section of the screw structure 50 according to the embodiment of the present invention, and FIG. 4 is an enlarged view of the cross section of the screw structure 50 shown in FIG. The screw structure 50 includes the above-described screw shaft 20 having the male screw portion 21 and the split nut 30 having the female screw portion 31 provided so as to be screwable to the male screw portion 21. That is, the screw structure 50 includes a screw shaft 20 and a split nut 30 that is screwed into the screw shaft 20. The cross section of the screw structure 50 shown in FIG. 3 (a cross section parallel to the direction of the axis of the screw shaft 20) is a state in which the male screw portion 21 of the screw shaft 20 and the female screw portion 31 of the split nut 30 are screwed together. Show.

In the screw structure 50, the cross section of the screw thread 22 of the male screw part 21 and the screw thread 32 of the female screw part 31 has skirt parts 60 and 65 formed in a substantially trapezoidal shape, apexes 71 and 76, and skirt part 60, And top portions 70 and 75 having inclined portions 72 and 77 inclined toward 65. That is, in the screw structure 50, the cross section of the screw thread 22 of the screw shaft 20 and the screw thread 32 of the split nut 30 includes skirt parts 60 and 65 formed in a substantially trapezoidal shape and top parts 70 and 75. , 75 have vertices 71, 76 and inclined portions 72, 77 inclined from the vertices 71, 76 toward the skirt portions 60, 65. In FIG. 4, the boundaries between the top portions 71 and 76 and the bottom portions 72 and 77 are indicated by broken lines. In FIGS. 5, 6, and 8 to 11 described later, the boundary between the top and the bottom is indicated by a broken line. Here, in the screw shaft 20, the skirt 60 is arranged on the outer peripheral side of the screw shaft 20 with respect to the top 71. Further, in the split nut 30, the skirt portion 65 is arranged on the outer peripheral side surface side of the split nut 30 with respect to the top portion 76. Further, the cross sections of the thread 22 of the male thread portion 21 and the thread 32 of the female thread portion 31 include lines L1 and L2 including apexes 71 and 76 and perpendicular to the axis of the screw shaft 20 (indicated by a one-dot chain line in FIG. 4). Line symmetry). That is, in the screw structure 50, the cross sections of the thread 22 of the screw shaft 20 and the thread 32 of the split nut 30 pass through the vertices 71 and 76, and are lines L 1 and L 2 that are orthogonal to the axis of the screw shaft 20. On the other hand, it is line symmetric.

Here, in the cross section of at least one of the thread 22 of the screw shaft 20 and the thread 32 of the split nut 30, the inclined portions 72 and 77 of the top portions 70 and 75 have straight portions. In the present embodiment, the inclined portions 72 and 77 have straight portions in the cross section of the screw thread 22 of the male screw portion 21 and the screw thread 32 of the female screw portion 31. Further, in the cross section of the thread 22 of the male thread portion 21 and the thread 32 of the female thread portion 31, fillets are formed (chamfered) at the apexes 71 and 76 and the intersections of the inclined portions 72 and 77 and the skirt portions 60 and 65. Has been.

Further, in the cross section of at least one of the thread 22 of the screw shaft 20 and the thread 32 of the split nut 30, the side portions (legs 61, 66) of the skirt portions 60, 65 have straight portions. In the present embodiment, the leg 61 (side part) of the skirt 60 of the screw thread 22 in the male screw part 21 and the leg 66 (side part) of the skirt 65 of the screw thread 32 in the female screw part 31 form a straight line part. The leg 61 and the leg 66 are in contact with each other. Thereby, the external thread part 21 and the internal thread part 31 are easy to closely_contact | adhere, and generation | occurrence | production of a backlash can be suppressed. Furthermore, since the bottom portions 60 and 65 are substantially trapezoidal in the thread 22 of the male thread 21 and the thread 32 of the female thread 31, the split nut 30 is set in a direction parallel to the axis of the screw shaft 20. It can be moved back and forth.

Further, a gap is provided between the top portion 60 of the screw thread 22 in the male screw portion 21 and the valley bottom 85 of the female screw portion 31. Similarly, a gap is provided between the top portion 60 of the screw thread 32 in the female screw portion 31 and the valley bottom 80 of the male screw portion 21.

Further, at least one of the bottoms 80 and 85 of the screw shaft 20 and the split nut 30 may be flat. That is, at least one of the valley bottoms 80 and 85 of the male screw portion 21 and the female screw portion 31 may be flat. In the present embodiment, the bottom 85 of the female thread portion 31 of the split nut 30 is flat. On the other hand, the valley bottom 80 of the male screw portion 21 is formed in a shape symmetrical to the screw thread 32 of the female screw portion 31.

Here, in this embodiment, the split nut 30 is connected to the movable arm 40 and is movable in a direction orthogonal to the axial direction of the screw shaft 20. FIG. 5 is a schematic view showing a state in which the screw shaft 20 and the split nut 30 are separated from each other in the screw structure 50 shown in FIG. 3. In the screw structure 50 configured as described above, the split nut 30 is brought close to the screw shaft 20 and the male screw portion 21 of the screw shaft 20 and the female screw portion 31 of the split nut 30 are screwed together. Further, since the cross section of the thread 32 of the male screw portion 21 and the female screw portion 31 includes the above-described skirt portions 60 and 65 and the top portions 70 and 75, the screw thread 32 and the male screw portion 21 of the female screw portion 31 are provided. As shown in FIG. 4, the female screw portion 31 and the male screw portion 21 can be reliably screwed together (see FIG. 6).

For example, in a screw structure 50a using trapezoidal screws 51a and 56a, which is a conventional screw structure, the split nut 30a is brought close to the screw shaft 20a from a direction perpendicular to the axial direction of the screw shaft 20a, and the female of the split nut 30a is connected. When the screw portion 31a and the male screw portion 21a of the screw shaft 20a are screwed together, the trapezoidal upper bases 73a and 78a may contact each other and cannot be screwed (see FIG. 7). In this case, when trying to send the split nut 30a by rotating the screw shaft 20a, the split screw 30a cannot be precisely fed because the female screw portion 31a is not screwed into the male screw portion 21a. On the other hand, in the screw structure 50 according to the present embodiment, when the split nut 30 is brought close to the screw shaft 20, the male screw portion 21 and the female screw portion 31 can be reliably screwed together. Compared with the screws 51a and 56a, the split nut 30 can be sent more precisely.

In the present embodiment, the cross sections of both the thread 22 of the male thread portion 21 and the thread 32 of the female thread portion 31 are on lines L1 and L2 that include the vertices 71 and 76 and are orthogonal to the axis of the screw shaft 20. Since it is made symmetrical with respect to the line, the leg 61 of the skirt 60 of the male screw portion 21 and the leg 66 of the skirt 65 of the female screw portion 31 can be reliably brought into contact with each other. Can be suppressed.

Further, the male threaded portion 21 of the screw shaft 20 described above has a thread 22 having a skirt 60 and a top 70 and a valley bottom 80 formed symmetrically, and such a shape can be formed by rolling. Therefore, it is not necessary to perform cutting or the like, and the manufacturing cost can be suppressed. Moreover, since the trough part of the split nut 30 is formed flat, it is easy to produce by sintering metal powder, for example.

(Modification 1)
Next, the modification 1 of the screw structure 50 which concerns on embodiment of this invention is demonstrated. FIG. 8 is a schematic view of a screw structure 150 showing a first modification of the screw structure 50 according to the first embodiment of the present invention. The screw structure 150 includes a male screw portion 121 and a female screw portion 131. The screw threads 122 and 132 of the male screw portion 121 and the female screw portion 131 are substantially trapezoidal skirt portions 160 and 165, and apexes 171 and 176, respectively. And top portions 170 and 175 having inclined portions 172 and 177 inclined from the apexes 171 and 176 toward the side portions 161 and 166 of the skirt portions 160 and 165, respectively. In the screw structure 150, the inclined portions 172 and 177 of the top portions 170 and 175 have curvature in the cross section of at least one of the screw threads 122 of the male screw portion 121 and the screw threads 132 of the female screw portion 131. That is, in the cross section of at least one of the thread 122 of the screw shaft 20 and the thread 132 of the split nut 30, the inclined portions 172 and 177 of the top portions 170 and 175 are curved. In other words, the inclined portion 172 of the top portion 170 of the thread 122 of the screw shaft 20 is curved from the vertex 171 to the skirt portion 160. Further, the inclined portion 177 of the top portion 175 in the thread 132 of the split nut 30 is curved from the apex 176 to the skirt portion 165. This screw structure 150 also has the same effect as the screw structure 50 of the above-described embodiment.

(Modification 2)
Next, Modification Example 2 of the screw structure 50 according to the embodiment of the present invention will be described. FIG. 9 is a schematic view of a screw structure 250 showing a second modification of the screw structure 50 according to the first embodiment of the present invention. The screw structure 250 includes a male screw portion 221 and a female screw portion 231, and the screw threads 222 and 232 of the male screw portion 221 and the female screw portion 231 are substantially trapezoidal skirt portions 260 and 265 and apexes 271 and 276. And top portions 270 and 275 having inclined portions 272 and 277 inclined from the apexes 271 and 276 toward the side portions 261 and 266 of the skirt portions 260 and 265, respectively. In the screw structure 250 of the second modified example, the side portions 261 and 266 of the skirt portions 260 and 265 are curved in the cross section of at least one of the screw thread 222 of the male screw portion 221 and the screw thread 232 of the female screw portion 231. Have That is, the side portions 261 and 266 of the skirt portions 260 and 265 are curved in the cross section of at least one of the thread 222 of the screw shaft 20 and the thread 232 of the split nut 30. In other words, the side part 261 of the skirt 260 in the thread 222 of the screw shaft 20 is curved from the top part 270 to the valley bottom 280. Further, the side portion 266 of the bottom portion 265 of the thread 232 of the split nut 30 is curved from the top portion 275 to the valley bottom. In the screw structure 250, the inclined portions 272 and 277 of the top portions 270 and 275 also have a curvature, and the screw threads 222 and 232 have a round shape as a whole. Moreover, in the external thread part 221, the valley bottom 280 also has a curvature. Here, as for the screw shaft 20 and the split nut 30, the inclination angle of the side part of a skirt part differs from the inclination angle of the inclination part of a top part. For example, in the screw shaft 20, the inclination angle of the side portion 261 of the skirt portion 260 and the inclination angle of the inclined portion 272 of the top portion 270 are different. Further, in the split nut 30, the inclination angle of the side portion 266 of the skirt portion 265 and the inclination angle of the inclined portion 277 of the top portion 275 are different. It should be noted that the screw structure 50 and the screw structure 150 described above similarly have the difference in the inclination angle. This screw structure 250 also has the same effect as the screw structure 50 of the above-described embodiment.

(Modification 3)
Next, Modification 3 of the screw structure 50 according to the embodiment of the present invention will be described. FIG. 10 is a schematic view of a screw structure 350 showing a third modification of the screw structure 50 according to the first embodiment of the present invention. The screw structure 350 includes a male screw portion 21 of the screw structure 50 and a female screw portion 231 of the screw structure 250. In this way, even if the thread shapes of the male screw portion and the female screw portion are different, the same effects as those of the screw structure 50 described in the above-described embodiment can be obtained.

Note that the present invention is not limited to the above embodiment. What was comprised combining each component mentioned above suitably is also contained in this invention. Further effects and modifications can be easily derived by those skilled in the art. Therefore, the broader aspect of the present invention is not limited to the above-described embodiment, and various modifications can be made.

In the above embodiment, the case where the top inclined portion has a straight portion or a case where the top inclined portion has a curvature has been described, but the top inclined portion may have a straight portion and a curved portion having a curvature. Moreover, although the case where the side part of a skirt part has a linear part or the case where it has a curvature was demonstrated in the said embodiment, the side part of a skirt part may have a linear part and the curved part which has a curvature. . In such a case, it is preferable that the side part of the hem part of the male screw part is in contact with the side part of the hem part of the female screw part at at least two points. The occurrence of backlash can be further suppressed by contacting the side part of the hem part of the male screw part and the side part of the hem part of the female screw part at at least two points.

For example, like the screw thread 310 shown in FIG. 11A, the inclined part 321 of the top part 320 including the apex 325 may have a straight part 322 and a curved part 323 having a curvature. Moreover, the side part 331 of the skirt part 330 may have the linear part 332 and the curved part 333 which has a curvature. FIG. 11B is a schematic explanatory diagram of the screw thread 310, and in the screw thread 310, the range indicated by A indicates the range of the inclined portion 321, and the range indicated by B indicates the range of the side portion 331. Further, the range indicated by A1 indicates the range of the curved portion 323, and the range indicated by A2 indicates the range of the straight line portion 322. The range indicated by B1 indicates the range of the curved portion 333, and the range indicated by B2 indicates the range of the straight line portion 332.

In the above embodiment, the infusion pump including the feeding device has been described. However, the present invention is not limited to this, and other medical devices that require the feeding device may be used.

DESCRIPTION OF SYMBOLS 1 Infusion pump 2 Plunger 2a Pusher 3 Syringe 4 Base 10 Feeder 11 Motor 12 Reducer 12a, 12b, 12c, 12d Gear 13 Pressure sensor 14 Rotation detection sensor 15 Position detection sensor 20, 20a Screw shaft 21, 21a, 121, 221 Male thread part 22, 122, 222 Thread 30, 30a Split nut 31, 31a, 131, 231 Female thread part 32, 132, 232 Thread 40 Movable arm 41 Connecting rod 42 Lever 43 Plunger holder 44 Connection member 45 Tube 50 , 50a, 150, 250, 350 Screw structure 51a, 56a Trapezoidal screw 60, 65, 160, 165, 260, 265 Hem 61, 66 Leg (side)
70, 75, 170, 175, 270, 275 Top 71, 76, 171, 176, 271, 276 Apex 72, 77, 172, 177, 272, 277 Inclined part 73a, 78a Top bottom 80, 85, 280 Valley bottom 161, 166, 261, 266 Side portion 310 Thread 320 Top 321 Inclined portion 322 Straight portion 323 Curve portion 330 Bottom portion 331 Side portion 332 Straight portion 333 Curve portion

Claims (11)

A screw shaft, and a split nut screwed onto the screw shaft,
The cross section of the thread of the screw shaft and the thread of the split nut comprises a skirt formed in a substantially trapezoidal shape, and a top.
The top portion is a screw structure having an apex and an inclined portion inclined from the apex toward the skirt. The cross section of the screw shaft thread and the split nut thread crosses the vertex and is axisymmetric with respect to a line orthogonal to the axis of the screw shaft. Screw structure. 3. The screw structure according to claim 2, wherein in the cross section of at least one of the thread of the screw shaft and the thread of the split nut, the inclined portion of the top portion has a straight portion. The screw structure according to claim 3, wherein an inclined portion of the top portion is curved in a cross section of at least one of the screw shaft thread and the split nut thread. 5. The screw structure according to claim 4, wherein a side portion of the skirt portion has a straight portion in a cross section of at least one of the screw shaft thread and the split nut thread. The screw structure according to claim 5, wherein a side portion of the skirt portion is curved in a cross section of at least one of the screw shaft thread and the split nut thread. The screw structure according to claim 6, wherein at least one of the screw shaft and the valley bottom of the split nut is flat. A feeding device to which the screw structure according to claim 7 is applied. The split nut is provided so as to be movable with respect to the screw shaft in a direction perpendicular to the axis of the screw shaft and reciprocally movable in a direction parallel to the axis of the screw shaft. The feeding device described in 1. An infusion pump comprising the feeding device according to claim 8 or 9. A medical device comprising the feeding device according to claim 8 or 9.

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