Patent Application
20200166107
The application claims the benefit of China application serial No. 201811417138.6, filed on Nov. 26, 2018, the subject matter of which is incorporated herein by reference.
The present invention relates to a linear translational mechanism and a machine tool including the linear translational mechanism and, more particularly, to a planetary screw for converting a rotational motion into a linear translational motion or vice versa, and a machine tool including the planetary screw.
With reference to
To maintain smooth rotation of the planetary screw 9, an oil seal 951 is mounted between each of the two fixing boards 95 and an associated one of the shaft rings 94, and lubricating oil is filled into the nut 92 and between the two fixing boards 95. Furthermore, two end caps 96 are threadedly coupled to the main screw 91 to seal two ends of the nut 92, preventing leakage of the lubricating oil.
In the conventional planetary screw 9, to assure stable rotation of the plurality of rollers 93 about the main screw 91 and in the nut 92, the plurality of rollers 93 must be processed to form the outer toothed portion 932, the nut 92 must be processed to form the two non-threaded portions 922 that receive the shaft rings 94, and the shaft rings 94 must be processed to form the inner annular toothed portions 941. As a result, the conventional planetary screw 9 has a complicated structure and results in an increase in the processing costs.
Furthermore, the lubricating oil still tends to gradually leak through portions at the outer threading 911 of the main screw 91 and the outer threadings 931 of the plurality of rollers 93, such that noise occurs when the planetary screw rotates. Thus, the two end caps 96, the two fixing boards 95, the shaft rings 94 and the plurality of rollers 93 must be frequently and troublesomely detached before filling the lubricating oil into the nut 92 and between the two fixing boards 95. As a result, the filling of the lubricating oil is troublesome and difficult.
Thus, improvement to the conventional planetary screw is desired.
When the terms “front”, “rear”, “left”, “right”, “up”, “down”, “top”; “bottom”, “inner”, “outer”, “side”, and similar terms are used herein, it should be understood that these terms have reference only to the structure shown in the drawings as it would appear to a person viewing the drawings and are utilized only to facilitate describing the invention, rather than restricting the invention.
As used herein, the terms “engagement”, “coupling”, “assembly”, or similar terms include two members that can be separated after connection without destructing the members or that cannot be separated after connection, such as welding or threading connection between elements with threadings, which can be appreciated and selected by one having ordinary skill in the art according to the materials or the assembly demands of the elements to be connected.
As used herein, the term “machine tool” refers to a machine capable of processing with various power transmission and output, including converting a rotational motion into a linear translational motion or vice versa. The machine tool can be, but not limited to, a plastic forming machine, a press machine, a linear actuator, or a 3D printer.
To solve the above problem, an objective of the present invention is to provide a planetary screw having a simplified structure to thereby reduce the processing costs.
Another objective of the present invention is to provide a planetary screw having a simple structure while permitting easy filling of the lubricating oil, reducing the noise while the planetary screw rotates.
A further objective of the present invention is to provide a machine tool including the planetary screw, permitting easy maintenance and easy filling of the lubricating oil, thereby reducing the malfunction rate of the machine tool and reducing the noise during rotation of the planetary screw.
A planetary screw according to the present invention includes a main screw having an outer threading and a connecting portion. A nut includes a hole extending through two end faces of the nut. The hole includes an inner periphery having an inner threading. A planetary unit includes a supporting mechanism and a plurality of rollers rotatably supported by the supporting mechanism to rotate in a fixed position. The plurality of rollers is identical to each other. Each of the plurality of rollers has an outer threading meshed with the outer threading of the main screw and the inner threading of the nut.
Thus, in the planetary screw according to the present invention, the supporting mechanism does not contact the main screw and the nut, and only the outer threadings of the plurality of rollers mesh with the outer threading of the main screw and the inner threading of the nut to enable the plurality of rollers to rotate and revolve relative to the main screw and the nut. The overall structure is simple, and the friction is reduced. Thus, the processing costs of the planetary screw can be significantly reduced, and the production efficiency and assembly efficiency can be enhanced. Since the supporting mechanism does not directly contact the main screw and the nut, the noise resulting from rotation of the planetary screw can be reduced.
In an example, wherein the hole of the nut is a stepped hole. The inner periphery of the hole of the nut includes an intermediate section having a first inner diameter and two end sections respectively on two sides of the intermediate section. Each of the two end sections of the stepped hole includes a second inner diameter larger than the first inner diameter and is a sealing portion. The inner threading is at the intermediate section. This assures that the outer threadings of the plurality of rollers can only mesh with the inner threading of the nut, avoiding the outer threadings of the plurality of rollers from impinging the other portions of the inner periphery of the nut.
In an example, the nut includes at least one through-hole extending from the inner periphery of the nut through an outer periphery of the nut, and a plug is removably received in each of the at least one through-hole. Thus, the lubricating oil can be conveniently filled into the nut.
In an example, the nut includes two through-holes configured to connect to two oil guiding pipes, respectively. Thus, the lubricating oil can be circulatingly filled into the nut.
In an example, the supporting mechanism includes two fixing boards and a plurality of fixing rods. Each of the two fixing boards includes a central hole at a central portion thereof and a plurality of fixing holes surrounding the central hole. The plurality of fixing holes is located on a circumference having the same radius about a central axis of the central hole. Each of the plurality of fixing rods has two ends respectively mounted in the plurality of fixing holes. Thus, the supporting mechanism reliably supports the plurality of rollers to rotate at a fixed position.
In an example, each of two ends of each of the plurality of fixing rods includes an engaging portion protruding beyond an associated one of the two fixing boards. Each engaging portion includes an outer threading configured to be in threading connection with an engaging member. Thus, the plurality of fixing rods can be conveniently detached and assembled, such that the supporting mechanism and the plurality of rollers can be conveniently maintained and replaced.
In an example, each of the plurality of fixing rods has an outer threading. The plurality of fixing rods is identical. The outer threading of each of the plurality of fixing rods meshes with the outer threading of the main screw and the inner threading of the nut. A gap exists between each engaging member and an associated one of the two fixing boards. Each gap is slightly larger than a backlash between the outer threading of each of the plurality of fixing rods and the outer threading of the main screw and another backlash between the outer threading of each of the plurality of fixing rods and the inner threading of the nut. Thus, the plurality of fixing rods can rotate and revolve relative to the main screw and the nut.
In an example, each engaging member is received in an associated one of the plurality of fixing holes. Thus, the engaging members will not protrude beyond the faces of the two fixing boards.
In an example, each engaging member protrudes beyond an outer face of an associated one of the two fixing boards and does not contact the nut. Thus, the engaging members are prevented from impinging the nut, and the plurality of fixing rods can be conveniently detached.
In an example, each of two ends of the plurality of rollers includes a mounting portion rotatably extending through the fixing hole of an associated one of the two fixing boards. Thus, the plurality of rollers can rotate smoothly between the two fixing boards.
In an example, wherein any two adjacent fixing rods of the plurality of fixing rods has the same quantity of rollers therebetween. Thus, the plurality of fixing rods can uniformly withstand the friction resulting from the revolution of the plurality of rollers relative to the main screw and the nut, achieving excellent, balanced load.
In an example, each of the sealing portions at the two end sections of the nut has a sealing member detachably engaged with the nut. The sealing members seal the lubricating oil in the nut to avoid leakage, improving the tidiness of the working environment and preventing ambient dust or alien objects from entering the rotational space, thereby avoiding the rotational smoothness of the nut and the main screw from being adversely affected.
In an example, each sealing member is made of an elastic material. Thus, the sealing members provide a better sealing effect to avoid leakage of the lubricating oil.
In an example, each sealing member is in threading connection with the main screw. Each sealing member includes a threading having a pitch and a shape. The pitch or the shape of each sealing member is different from a pitch or a shape of the outer threading of the main screw. This assures the sealing members to seal the lubricating oil in the hole of the nut, avoiding the lubricating oil from leaking through the threading connection portions between the sealing members and the main screw.
Furthermore, the planetary screw according to the present invention can be used in a machine tool for converting a rotational motion into a linear translational motion or vice versa. Furthermore, maintenance and filling of the lubricating oil can be easily carried out with the planetary screw.
The present invention will become clearer in light of the following detailed description of illustrative embodiments of this invention described in connection with the drawings.
With reference to
The main screw 1 includes an outer threading 11. The outer threading 11 can be disposed on an end of the main screw 1. The main screw 1 further includes a connecting portion 12 that can be located on the other end of the main screw 1. The connecting portion 12 can be connected to a power device (not shown) for driving the main screw 1 to rotate.
The nut 2 includes a hole extending through two end faces of the nut 2. The hole includes an inner periphery that has a uniform diameter. Alternatively, the inner periphery of the hole can have different diameters to form a stepped hole. In this embodiment, the hole is a stepped hole, and the inner periphery of the stepped hole includes an intermediate section having a first inner diameter 2a and two end sections respectively on two sides of the intermediate section. Each of the two end sections of the stepped hole includes a second inner diameter 2b larger than the first inner diameter 2a. Preferably, a third inner diameter portion is provided between each of the two end sections and the intermediate section and has an third inner diameter 2c larger than the first inner diameter 2a but smaller than the second inner diameter 2b. The intermediate section of the inner periphery of the nut 2 having the first inner diameter 2a has an inner threading 21. Each of the two end sections of the nut 2 having the second inner diameter 2b can be a sealing portion 22. Furthermore, each third inner diameter portion having the third inner diameter 2c can be a recessed portion 23. The nut 2 preferably includes at least one through-hole 24 extending from the inner periphery of the nut 2 through an outer periphery of the nut 2. A plug 25 is removably received in each of the at least one through-hole 24. Thus, lubricating oil can be filled into the nut 2 via the at least one through-hole 24. In a case that the nut 2 is positioned and does not rotate, the nut 2 can include two through-holes 24 configured to connect to two oil guiding pipes (not shown), respectively. Thus, the lubricating oil can circulate through the two through-holes 24, providing a better lubricating effect.
With reference to
Two ends of each of the plurality of fixing rods 32 are respectively engaged in the two fixing boards 31, such that the plurality of fixing rods 32 and the two fixing boards 31 together form a stable supporting mechanism. The plurality of fixing rods 32 surrounds the main screw 1 without contacting the main screw 1 and the nut 2. In this embodiment, each of the two ends of each of the plurality of fixing rods 32 includes an engaging portion 321 protruding beyond an associated one of the two fixing boards 31. Each engaging portion 321 is securely coupled with an engaging member 322. In this embodiment, each engaging portion 321 has an outer threading, and each engaging member 322 is a nut. Each engaging member 322 can be disposed in an associated one of the plurality of the fixing holes 312. Alternatively, each engaging member 322 protrudes beyond an outer face of an associated one of the two fixing boards 31. The two fixing boards 31 and the engaging members 322 correspond to the third inner diameter portions having the third inner diameter 2c of the nut 2 and do not contact with the third inner diameter portions.
Each of two ends of each of the plurality of rollers 33 includes a mounting portion 331 rotatably extending through the fixing hole 312 of an associated one of the two fixing boards 31. The plurality of rollers 33 is identical to each other. Each of the plurality of rollers 33 has an outer threading 332 meshed with the outer threading 11 of the main screw 1 and the inner threading 21 of the nut 2. Thus, the two fixing boards 31 and the plurality of fixing rods 32 of the supporting mechanism do not contact the main screw 1 and the nut 2 while permitting each of the plurality of rollers 33 to revolve and rotate relative to the main screw 1 and the nut 2.
The outer threading 332 of each of the plurality of rollers 33, the outer threading 11 of the main screw 1, and the inner threading 21 of the nut 2 can include a single thread or plural threads. Furthermore, the shape of the outer threading 11 of the main screw 1 is preferably identical to the shape of the inner threading 21 of the nut 2, and the shape of the outer threading 332 of each of the plurality of rollers 33 is preferably different from the shapes of the outer threading 11 of the main screw 1 and the inner threading 21 of the nut 2. As shown in
The central axes of the plurality of rollers 33 and the plurality of fixing rods 32 are on the circumference of the same radius, are disposed around the main screw 1, and are spaced from each other by regular angular intervals. Preferably, a ratio of the number of the plurality of rollers 33 to the number of the plurality of fixing rods 32 is an integer, such that the number of the plurality of rollers 33 between any two adjacent fixing rods 32 is the same. For example, the total number of the plurality of rollers 33 and the plurality of fixing rods 32 is nine, and the ratio of the number of the plurality of rollers 33 to the number of the plurality of fixing rods 32 is 2:1. Thus, the plurality of fixing rods 32 can uniformly withstand the friction resulting from the revolution of the plurality of rollers 33 relative to the main screw 1 and the nut 2, achieving excellent, balanced load.
With reference to
With reference to
By the above structure, when the planetary screw according to the present invention operates, the main screw 1 can be driven to rotate, such that the plurality of rollers 33 meshed with the outer threading 11 of the main screw 1 and the inner threading 21 of the nut 2 can rotate and can revolve about the main screw 1. Thus, when the nut 2 rotates at a fixed position, the main screw 1 can proceed with relative linear motion. Furthermore, when the main screw 1 rotates in the forward direction and the reverse direction, the main screw 1 can proceed with reciprocating linear motion. Alternatively, when the main screw 1 rotates at a fixed position, the sealing members 4 and the nut 2 proceed with relative axial motion, and the sealing members 4 and the nut 2 can proceed with recirpocating linear motion through forward and reverse rotations of the main screw 1.
In view of the foregoing, in the planetary screw according to the present invention, the supporting mechanism does not contact the main screw 1 and the nut 2, and only the outer threadings 332 of the plurality of rollers 33 mesh with the outer threading 11 of the main screw 1 and the inner threading 21 of the nut 2 to enable the plurality of rollers 33 to rotate and revolve relative to the main screw 1 and the nut 2. The overall structure is simple, and the friction is reduced. Thus, the processing costs of the planetary screw can be significantly reduced, and the production efficiency and assembly efficiency can be enhanced. Since the supporting mechanism does not directly contact the main screw 1 and the nut 2, the noise resulting from rotation of the planetary screw can be reduced. Furthermore, the planetary screw according to the present invention can be used in a machine tool to permit convenient maintenance and easy filling of the lubricating oil.
Thus since the invention disclosed herein may be embodied in other specific forms without departing from the spirit or general characteristics thereof, some of which forms have been indicated, the embodiments described herein are to be considered in all respects illustrative and not restrictive. The scope of the invention is to be indicated by the appended claims, rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are intended to be embraced therein.
| Number | Date | Country | Kind |
|---|---|---|---|
| 201811417138.6 | Nov 2018 | CN | national |
