Patent Description:
As a drive device forming a syringe pump, there is known a drive device including a feed screw that rotates about a central axis and a guided member that is guided in an axial direction along the central axis, the guided member including a nut member that has a screw portion screwed with the feed screw and a pressing portion that presses a plunger of a syringe. Since the guided member is moved in the axial direction by rotation of the feed screw in a state where the feed screw and the screw portion are screwed together, the plunger is pushed into a syringe body by the pressing portion of the guided member, whereby a liquid is extruded from the syringe body.

As such a drive device, for example, there is known a drive device, configured such that a screw portion is moved in a direction toward a central axis in a transverse section orthogonal to the central axis, as described in Patent Literature <NUM>. According to such a configuration, even when a relative position between a feed screw and the screw portion in the traverse section varies due to thermal expansion of a component, a manufacturing error, or the like, the screw portion can move in the direction toward the central axis in the traverse section so as to narrow a gap between the feed screw and the screw portion caused by the variation, and thus, the misalignment of the screw portion with respect to the feed screw can be reduced. Therefore, it is possible to improve the accuracy of the movement of the guided member, that is, the plunger of the syringe in the axial direction.

However, it is desirable that the guided member be movable with high accuracy by further reducing the misalignment of the screw portion with respect to the feed screw.

In view of such a point, an object of the present invention is to provide a drive device and a medical infusion pump capable of moving a guided member with high accuracy.

A drive device according to a first aspect of the present invention includes a feed screw according to independent claim <NUM>.

As one embodiment of the present invention, the drive device includes a pair of the nut members, and the screw portions of the pair of nut members are arranged so as to sandwich the feed screw.

As one embodiment of the present invention, in the drive device, each of the pair of nut members has a bearing portion that turns the screw portion such that the screw portion moves in the direction toward the central axis in the traverse section orthogonal to the central axis, each of a pair of the bearing portions has a long hole shape that is long in a direction intersecting the direction toward the central axis in the traverse section orthogonal to the central axis, and the guided member has a shaft member received by both of the bearing portions of the pair of nut members.

As one embodiment of the present invention, in the drive device, the guided member includes a housing to which the shaft member is attached and which accommodates the pair of nut members.

As one embodiment of the present invention, the drive device includes a switching member that switches a position of the screw portion between a screwing position where the screw portion is screwed with the feed screw and a non-screwing position where the screw portion is not screwed with the feed screw.

As one embodiment of the present invention, in the drive device, the switching member includes a cam that slides with respect to the nut member.

As one embodiment of the present invention, in the drive device, the cam slides with respect to a portion between the screw portion and the bearing portion in the nut member.

As one embodiment of the present invention, the drive device is arranged such that the cam is sandwiched between the pair of nut members.

As one embodiment of the present invention, the drive device includes a biasing member that biases the screw portion in a direction toward the central axis.

As one embodiment of the present invention, in the drive device, the guided member includes a spring forming the biasing member.

As one embodiment of the present invention, the drive device includes a position detection sensor that detects a position of the screw portion.

As one embodiment of the present invention, in the drive device, the position detection sensor includes a transmission unit that transmits a signal and a reception unit that receives the signal, and the nut member includes a blocking plate that blocks the signal when the nut member is located at one of the screwing position and the non-screwing position.

A medical infusion pump as a second aspect of the present invention includes the drive device.

As one embodiment of the present invention, the medical infusion pump includes a pressing portion in which the guided member presses a plunger of a syringe.

As one embodiment of the present invention, in the medical infusion pump, the switching member includes a cam that slides with respect to the nut member, a rotation shaft connected to the cam, and an operation member connected to the rotation shaft, the guided member includes an end member having the switching member and the pressing portion, and the operation member is rotatably supported by the end member.

According to the present invention, it is possible to provide the drive device and the medical infusion pump capable of moving the guided member with high accuracy.

Hereinafter, a drive device and a medical infusion pump according to an embodiment of the present invention will be illustrated and described in detail with reference to the drawings.

As illustrated in <FIG>, a drive device <NUM> according to the present embodiment forms a medical infusion pump <NUM>. The medical infusion pump <NUM> is a syringe pump, but is not limited thereto, and may be, for example, an infusion pump, a nutrient pump, a blood pump, or the like.

<FIG> illustrates the drive device <NUM> in a direction in which the up and down and the left and right are reversed with respect to <FIG>. As illustrated in <FIG>, the drive device <NUM> includes a drive source <NUM>, a feed screw <NUM>, and a guided member <NUM>. The drive source <NUM> is configured using, for example, an electric motor, and generates power for rotating the feed screw <NUM>. The drive source <NUM> rotates the feed screw <NUM> about a central axis Z1 via a power transmission device <NUM> configured using a gear train. The power transmission device <NUM> is not limited to the gear train. The feed screw <NUM> has the central axis Z1 and a male threaded portion 4a that spirally circles around the central axis Z1.

The guided member <NUM> is configured to be guided by a guide member <NUM> in an axial direction Dz along the central axis Z1. The guide member <NUM> includes three rod members 7a each extending in the axial direction Dz and a guide tube portion 7b. The guided member <NUM> includes a housing <NUM> that slides with respect to the three rod members 7a, and a hollow shaft <NUM> that slides with respect to the guide tube portion 7b. However, a structure for guiding the guided member <NUM> in the axial direction Dz is not limited thereto.

In addition, the guided member <NUM> includes an end member <NUM> and a switching member <NUM>. One end of the hollow shaft <NUM> is connected to the housing <NUM>, and the other end of the hollow shaft <NUM> is connected to the end member <NUM>. The switching member <NUM> includes an operation member <NUM>. The operation member <NUM> is supported by the end member <NUM> to be rotatable about a rotation axis Z2.

As illustrated in <FIG>, the end member <NUM> includes a pressing portion <NUM> that presses a plunger of a syringe (not illustrated) in the axial direction Dz. In addition, the end member <NUM> is provided with a fixing member <NUM> including two arm members arranged to oppose the pressing portion <NUM> in the axial direction Dz. The fixing member <NUM> is configured to be open in conjunction with the operation member <NUM> to release the fixing of the plunger by rotating in a direction of the hollow arrow in <FIG> as the operation member <NUM> is operated, and to be closed in conjunction with the operation member <NUM> to fix the plunger as the operation member <NUM> is returned as illustrated in <FIG>. An end flange of the plunger is sandwiched between the pressing portion <NUM> and the closed fixing member <NUM>, whereby the plunger is fixed to the end member <NUM>. The configuration of the fixing member <NUM> can be appropriately changed. A configuration in which the fixing member <NUM> is not provided may be also adopted.

The medical infusion pump <NUM> has a case <NUM> including a placement unit <NUM> on which a syringe body into which the plunger is pushed is placed. The syringe includes the syringe body and the plunger. A fixing lever <NUM> is provided in a portion adjacent to the placement unit <NUM>. The fixing lever <NUM> is configured to rotate the fixing lever <NUM> to rotate an overhanging portion 17a of the fixing lever <NUM> to a position opposing the placement unit <NUM> as illustrated in <FIG> so as to fix the syringe body placed on the placement unit <NUM>, and to rotate the fixing lever <NUM> to rotate the overhanging portion 17a of the fixing lever <NUM> to a position not opposing the placement unit <NUM> so as to release the fixing of the syringe body placed on the placement unit <NUM>. The configuration of the fixing lever <NUM> can be changed as appropriate. A configuration in which the fixing lever <NUM> is not provided may be also adopted.

<FIG> illustrates a part of the guided member <NUM> of the drive device <NUM> in an exploded manner in a direction in which the left and right are reversed with respect to <FIG>. As illustrated in <FIG>, the switching member <NUM> includes the operation member <NUM>, a cam shaft <NUM>, a cam <NUM>, and a ring member <NUM>. The cam shaft <NUM> is a shaft member having the rotation axis Z2 as a central axis, and penetrates a hollow portion of the hollow shaft <NUM>. One end of the cam shaft <NUM> is connected to the operation member <NUM> to be integrally rotatable. The cam <NUM> is connected to a portion protruding from the hollow shaft <NUM> on the other end side of the cam shaft <NUM> to be integrally rotatable. The ring member <NUM> is fixed to the other end of the cam shaft <NUM> by, for example, a fastener that is screwed into two screw holes 20a penetrating the ring member <NUM> in the radial direction and abuts on an outer peripheral surface of the cam shaft <NUM>.

As illustrated in <FIG>, the guided member <NUM> includes two nut members <NUM>. Each of the nut members <NUM> has a screw portion <NUM> screwed with the male threaded portion 4a of the feed screw <NUM>. <FIG> is an exploded perspective view of the two nut members <NUM> and the cam <NUM> illustrated in <FIG>.

<FIG> is a transverse sectional view illustrating a part of the drive device <NUM> illustrated in <FIG> in a state where the screw portion <NUM> is at a non-screwing position. <FIG> is a transverse sectional view illustrating a part of the drive device <NUM> illustrated in <FIG> in a state where the screw portion <NUM> is at a screwing position. The non-screwing position is a position where the screw portion <NUM> is not screwed with the feed screw <NUM>. The screwing position is a position where the screw portion <NUM> is screwed with the feed screw <NUM>. The transverse section is a cross section orthogonal to the central axis Z1.

As illustrated in <FIG>, the screw portions <NUM> of the two nut members <NUM> are arranged so as to sandwich the central axis Z1 of the feed screw <NUM>. In addition, each of the nut members <NUM> has a bearing portion <NUM> that turns the screw portion <NUM> such that the screw portion <NUM> moves in a direction toward the central axis Z1 in the traverse section. The guided member <NUM> has a shaft member <NUM> that is received by both of the bearing portions <NUM> of the two nut members <NUM>.

The cam <NUM> is arranged to be sandwiched between the two nut members <NUM> so as to slide with respect to each of portions between the screw portion <NUM> and the bearing portion <NUM> in the two nut members <NUM>.

As illustrated in <FIG>, the housing <NUM> has a box shape having an open portion 8a, formed by an opening into which the two nut members <NUM> sandwiching the cam <NUM> can be inserted, on an upper surface in <FIG>, and accommodates the two nut members <NUM>. However, the housing <NUM> may be changed to a member having a shape that does not accommodate the two nut members <NUM>. Each of two surfaces of the housing <NUM> opposing each other in the axial direction Dz has a shaft member through-hole <NUM> through which the shaft member <NUM> passes. The shaft member <NUM> is configured using a headed pin. In a state where the cam <NUM> is sandwiched between the two nut members <NUM> and accommodated in the housing <NUM>, the shaft member <NUM> is passed through the two shaft member through-holes <NUM> of the housing <NUM> and the bearing portions <NUM> of the two nut members <NUM>, and a C-ring-shaped fastener is fitted to a distal end of the shaft member <NUM>, whereby the shaft member <NUM> is attached to the housing <NUM>. An attachment structure for attaching the shaft member <NUM> to the housing <NUM> can be appropriately changed.

Each of the two surfaces of the housing <NUM> opposing each other in the axial direction Dz has a cam shaft through-hole <NUM> through which the cam shaft <NUM> passes. A region on the other end side including the other end of the cam shaft <NUM> has a non-circular cross-sectional shape fitted with a cam hole 19a penetrating the cam <NUM>. In the state where the cam <NUM> is sandwiched between the two nut members <NUM> and accommodated in the housing <NUM>, the region on the other end side of the cam shaft <NUM> passes through the two cam shaft through-holes <NUM> of the housing <NUM> and the cam hole 19a of the cam <NUM>, and the ring member <NUM> is fixed to the other end of the cam shaft <NUM>, whereby the cam shaft <NUM> is attached to the housing <NUM>. An attachment structure for attaching the cam shaft <NUM> to the housing <NUM> can be appropriately changed.

In addition, each of the two surfaces of the housing <NUM> opposing each other in the axial direction Dz has a feed screw through-hole <NUM> through which the feed screw <NUM> passes and a rod member through-hole <NUM> through which one of the three rod members 7a passes. A sliding-contact portion 8b is provided on each of outer surfaces of two corner portions of the housing <NUM> located at the lower right and the lower left in <FIG>. The two sliding-contact portions 8b are in sliding contact with the remaining two of the three rod members 7a, respectively.

The drive device <NUM> includes two coiled springs <NUM> as biasing members that bias the two screw portions <NUM> in the direction toward the central axis Z1. Each of two surfaces of the housing <NUM> opposing each other in the left-right direction in <FIG> has a spring through-hole <NUM> through which the spring <NUM> passes. Each of the two springs <NUM> biases the screw portion <NUM> in the direction toward the central axis Z1. In the state where the cam <NUM> is sandwiched between the two nut members <NUM> and accommodated in the housing <NUM>, each of the two springs <NUM> passes through the spring through-hole <NUM>, and the cover <NUM> is fitted to the housing <NUM>, whereby the two springs <NUM> are arranged. A structure for arranging the two springs <NUM> can be appropriately changed. The two springs <NUM> are not limited to the coil shape. The biasing member is not limited to the two springs <NUM>. A configuration in which the drive device <NUM> has no biasing member may be adopted.

The switching member <NUM> slides with respect to the two nut members <NUM> as the cam <NUM> rotates about the rotation axis Z2, thereby switching the positions of the two screw portions <NUM> between the screwing position illustrated in <FIG> and the non-screwing position illustrated in <FIG>. In <FIG>, the positions of the two screw portions <NUM> are switched from the screwing position to the non-screwing position as the cam <NUM> rotates counterclockwise.

When each of the screw portions <NUM> is at the screwing position, the guided member <NUM> can be moved in the axial direction Dz by rotating the feed screw <NUM> using the drive source <NUM>, and thus, the plunger can be pushed into the syringe body by the pressing portion <NUM>, and a liquid can be extruded from the syringe body. When each of the screw portions <NUM> is at the non-screwing position, a user can grip the guided member <NUM> and freely move the guided member <NUM> in the axial direction Dz, and thus, the plunger can be easily attached to the pressing portion <NUM> of the guided member <NUM> when the syringe having a desired dimension is attached to the medical infusion pump <NUM>.

In addition, each of the screw portions <NUM> moves in the direction toward the central axis Z1 when moving from the non-screwing position toward the screwing position. Therefore, even when a relative position between the feed screw <NUM> and each of the screw portions <NUM> in the traverse section varies due to thermal expansion of a component, a manufacturing error, or the like, each of the screw portions <NUM> can move in the direction toward the central axis Z1 in the traverse section so as to narrow a gap between the feed screw <NUM> and each of the screw portions <NUM> caused by the variation, and thus, the misalignment of each of the screw portions <NUM> with respect to the feed screw <NUM> can be reduced. Therefore, it is possible to improve the accuracy of movement of the guided member <NUM>, that is, the plunger of the syringe in the axial direction Dz.

Further, the drive device <NUM> of the present embodiment is configured such that each of the screw portions <NUM> also moves in a direction intersecting the direction toward the central axis Z1 in order to further reduce the misalignment of each of the screw portions <NUM> with respect to the feed screw <NUM> to move the guided member <NUM> with high accuracy. More specifically, the bearing portion <NUM> of each of the nut members <NUM> has a long hole shape that is long in a direction substantially orthogonal to the direction in which the screw portion <NUM> is directed toward the central axis Z1 in the traverse section. That is, each of the bearing portions <NUM> has a short axis O1 and a long axis O2 orthogonal to each other, and the long axis O2 extends in the direction (vertical direction in <FIG>) substantially orthogonal to the direction in which the screw portion <NUM> is directed toward the central axis Z1.

<FIG> illustrates contour shapes of the bearing portions <NUM> of the two nut members <NUM> illustrated in <FIG> and the shaft member <NUM> in the traverse section. As illustrated in <FIG>, a contour of the shaft member <NUM> is substantially a perfect circular shape, and the contour of the bearing portion <NUM> is a substantially oval shape having the short axis O1 and the long axis O2, that is, a shape in which half arcs are connected by a straight line.

However, the contour shapes of the shaft member <NUM> and the bearing portion <NUM> are not limited thereto. In addition, an extending direction of the long axis O2 is not limited to the direction substantially orthogonal to the direction in which the screw portion <NUM> is directed toward the central axis Z1, and it is sufficient that the extending direction of the long axis O2 intersects with the direction in which the screw portion <NUM> is directed toward the central axis Z1. With such a configuration, each of the screw portions <NUM> can be moved not only in a direction toward the central axis Z1 but also in a direction intersecting the direction, and the misalignment of each of the screw portions <NUM> with respect to the feed screw <NUM> can be further reduced.

In addition, the bearing portions <NUM> of the two nut members <NUM> can be individually moved with respect to the shaft member <NUM> by, for example, raising one bearing portion <NUM> and lowering the other bearing portion <NUM>, and thus it is possible to further reduce the misalignment of each screw portion <NUM> with respect to the feed screw <NUM>.

The short axis O1 has a length corresponding to "gap fitting" (for example, light fitting or fitting in JIS B <NUM>-<NUM>, <NUM>-<NUM> (<NUM>)) which is general fitting that allows a component to be relatively movable with respect to the shaft member <NUM>, and the long axis O2 preferably has a length exceeding this length. For example, a gap of several tens of microns can be set in a direction along the short axis O1, and a gap of several hundreds of microns can be set in a direction along the long axis O2. With such a setting, each of the screw portions <NUM> can be moved not only in the direction toward the central axis Z1 but also in the direction intersecting the direction, so that the misalignment of each of the screw portions <NUM> with respect to the feed screw <NUM> can be further reduced. In addition, when the position of each of the screw portions <NUM> is switched to the non-screwing position by the cam <NUM>, the movement of each of the bearing portions <NUM> is made difficult, so that each of the screw portions <NUM> can be smoothly moved in the direction away from the central axis Z1.

The cam <NUM> has two cam surfaces 19b opposing each other across the rotation axis Z2. Each of the cam surfaces 19b slides with respect to a portion between the screw portion <NUM> and the bearing portion <NUM> in each of the nut members <NUM>. As illustrated in <FIG>, one nut member <NUM> in sliding contact with one cam surface 19b closer to the central axis Z1 has a shorter overall length than the other nut member <NUM>. That is, the bearing portion <NUM> of the one nut member <NUM> is arranged on a side where the screw portion <NUM> of the one nut member <NUM> is located with respect to a straight line L passing through the central axis Z1 and the rotation axis Z2 in the traverse section. That is, the bearing portions <NUM> of the two nut members <NUM> and the shaft member <NUM> are arranged on the left side of the straight line L in <FIG>. With such a setting, the balance of a force when the two nut members <NUM> are pushed and opened by the cam <NUM> is improved, and the positions of the two screw portions <NUM> can be smoothly switched. However, the arrangement of the bearing portion <NUM> and the shaft member <NUM> is not limited thereto.

For example, the two nut members <NUM>, the cam <NUM>, and the housing <NUM> may be made of a synthetic resin, and the feed screw <NUM>, the shaft member <NUM>, the cam shaft <NUM>, and the ring member <NUM> may be made of metal. Since the synthetic resin is used instead of metal, the manufacturing cost of a member can be reduced, and weight reduction or the like can be achieved. Examples of the synthetic resin forming the two nut members <NUM>, the cam <NUM>, and the housing <NUM> include polyether ether ketone (PEEK) and polyphenylene sulfide (PPS). In the case where the two nut members <NUM>, the cam <NUM>, and the housing <NUM> are made of the synthetic resin as described above, however, the relative position between the feed screw <NUM> and the screw portion <NUM> in the traverse section easily varies due to a difference in linear thermal expansion coefficient between components accompanying a change in ambient temperature as compared with a case where these are made of metal. In addition, in a case where the two nut members <NUM> and the like are formed by injection molding using a synthetic resin, variations in dimensions of individual members are large as compared with a case of formation by cutting using metal. Therefore, the configuration in which the screw portions <NUM> are moved in both the direction toward the central axis z1 and the direction intersecting the direction in the traverse section as in the present embodiment is particularly suitable in a case of adopting the above material configuration.

As illustrated in <FIG>, <FIG>, and <FIG>, the drive device <NUM> includes two position detection sensors <NUM> that detect the positions of the screw portions <NUM>. Each of the position detection sensors <NUM> includes, for example, a transmission unit 32a that transmits a signal such as light and a reception unit 32b that receives the signal. Each of the nut members <NUM> has a blocking plate 21a that blocks the signal when the nut member <NUM> is located at one of the screwing position and the non-screwing position. According to such a configuration, a screwing state of the screw portion <NUM> can be monitored, and thus, safety can be improved.

The two position detection sensors <NUM> are mounted on a substrate <NUM>. As illustrated in <FIG>, the substrate <NUM> is attached to the housing <NUM> such that the two position detection sensors <NUM> are located inside the housing <NUM> and the substrate <NUM> is arranged to cover the open portion 8a of the housing <NUM>. The number of the position detection sensors <NUM> and the blocking plates 21a is not limited to two, and may be one. A configuration in which the position detection sensor <NUM> and the blocking plate 21a are not provided may be adopted.

The above-described embodiment is merely an example of embodiments of the present invention, and it is a matter of course that various modifications can be made without departing from the scope of the invention as defined in the accompanying claims.

The two nut members <NUM> are configured to be rotatably supported by the common shaft member <NUM> in the above-described embodiment, but may be configured to be rotatably supported by individual shafts without being limited thereto. Although the two nut members <NUM> are provided in the above-described embodiment, the number of the nut members <NUM> is not limited thereto, and may be, for example, one.

Although the nut member <NUM> has the bearing portion <NUM> supported by the shaft member <NUM> in the above-described embodiment, the present invention is not limited thereto, and may be configured such that the nut member <NUM> has a shaft supported by a bearing portion. Although the nut member <NUM> is configured to rotate such that the screw portion <NUM> moves in the direction toward the central axis Z1 in the traverse section in the above-described embodiment, the present invention is not limited thereto, and for example, the nut member <NUM> may be configured to move in parallel such that the screw portion <NUM> moves in the direction toward the central axis Z1 in the traverse section. In this case, the nut member <NUM> can be configured to move also in a direction intersecting the direction of the above-described parallel movement such that the screw portion <NUM> also moves in the direction intersecting the direction toward the central axis Z1 in the traverse section.

Claim 1:
A drive device (<NUM>) comprising:
a feed screw (<NUM>) that is rotatable about a central axis (Z1); and
a guided member (<NUM>) guidable in an axial direction (Dz) along the central axis (Z1),
wherein the guided member (<NUM>) includes a nut member (<NUM>) having a screw portion (<NUM>) configured to be screwed with the feed screw (<NUM>),
the screw portion (<NUM>) is configured to move in both a direction toward the central axis (Z1) and a direction intersecting the direction in a transverse section orthogonal to the central axis (Z1),
characterized in that
the nut member (<NUM>) has a bearing portion (<NUM>) that is configured to turn the screw portion (<NUM>) such that the screw portion (<NUM>) moves in the direction toward the central axis (Z1) in the transverse section orthogonal to the central axis (Z1), and
the bearing portion (<NUM>) has a long hole shape that is long in a direction intersecting the direction in which the screw portion (<NUM>) is directed toward the central axis (Z1) in the transverse section orthogonal to the central axis (Z1).