Patent Description:
Nowadays robots of selective compliance assembly robot arm (SCARA) have become more and more popular. A SCARA robot generally includes a ball screw or ball screw spline for performing a movement along and around Z-axis.

For current ball screw spline installation and maintenance in most SCARA robots, the ball screw spline itself has to be disassembled first. For example, a spline nut of the ball screw spline has to be removed from a shaft in order to mount the ball screw spline to a housing. It is inconvenient to disassemble the spline nut from the shaft when installing or maintaining the ball screw spline in the SCARA robots. This also hampers an automatic assembly of a ball screw spline to a housing, and it is hard to achieve an automatic production of a robot arm.

Furthermore, a pulley installed on the spline nut has risks to interfere with bolts mounted on a flange of the spline nut. Generally, the pulley is separated from the bolts for the spline nut by a distance, so as to avoid interaction between the pulley and bolts. This leads to an increased size of a ball screw spline based assembly. Otherwise, the pulley on the spline nut must be customized to prevent interference with the bolts mounted on the flange of the spline nut. Patent application <CIT> discloses a multi-axial industrial robot including a first arm and a second arm pivotally connected to the first arm. The second arm includes a base body, fixed on which is a driving assembly, and a covering body, which is mounted on the base body and is designed to constitute, together with the base body, a casing enclosed within which is the driving assembly. Utility model <CIT> refers to an automation technology of a four-axis manipulator having a rotating linear helical end.

Embodiments of the present disclosure provide a method for installing a ball screw spline and a resulting ball screw spline assembly, and further provide a robot arm and robot comprising such a ball screw spline assembly.

In a first aspect, a ball screw spline assembly, according to claim <NUM>, is provided. The ball screw spline assembly comprises a ball screw spline, a housing and a connecting plate. The ball screw spline includes: a first nut including a first mounting surface adapted to receive a first fastening element for installing the first nut to a housing; a second nut including a second mounting surface adapted to receive a second fastening element for installing the second nut to the housing; and a shaft passing through the first nut and the second nut. The housing includes a first portion and a second portion. The first portion extends in a direction substantially parallel to the shaft, and the second portion extends in a direction substantially perpendicular to the shaft. The connecting plate couples the second nut to the first portion of the housing, and the first nut is installed to the second portion of the housing. The first mounting surface and the second mounting surface are located within a space defined by the first portion, the second portion of the housing and the connecting plate, such that the ball screw spline is integrally installable to the housing.

In some embodiments, the first nut includes a first end adjacent to the second nut and a second end opposite to the first end; and the first mounting surface is provided at or adjacent to the first end.

In some embodiments, the first mounting surface is provided such that the first fastening element is received within the housing without protruding from the second portion of the housing.

In some embodiments, the first nut is partially located in a first opening of the second portion of the housing, and the second nut is partially located in a second opening of the connecting plate.

In some embodiments, the first nut are adapted to receive a first pulley at the second end of the first nut, and the second nut are adapted to receive a second pulley at an end of the second nut remote from the first nut.

In some embodiments, the first mounting surface is provided on a first flange portion of the first nut; and/or the second mounting surface is provided on a second flange portion of the second nut.

In some embodiments, the first nut is one of a ball screw nut and a spline nut, and the second nut is the other one of the ball screw nut and the spline nut.

In a second aspect, there is provided a method for installing a ball screw spline to a housing, according to claim <NUM>. The ball screw spline includes a shaft, a first nut and a second nut, wherein the shaft passes through the first nut and the second nut. The housing includes a first portion and a second portion, wherein the first portion extends in a direction substantially parallel to the shaft, and the second portion extends in a direction substantially perpendicular to the shaft. The method comprises: installing the first nut to the second portion of the housing with a first fastening element, the first fastening element being received by a first mounting surface of the first nut; installing the second nut to a connecting plate with a second fastening element, the second fastening element being received by a second mounting surface of the second nut; and installing the connecting plate to the first portion of the housing; wherein the first mounting surface and the second mounting surface are located within a space defined by the first portion, the second portion of the housing and the connecting plate in the case that the ball screw spline is installed to the housing, such that the ball screw spline is integrally installable to the housing.

In some embodiments, the first mounting surface is provided such that the first fastening element is received within the housing without protruding from the second portion of the housing in the case that the first nut is installed to the housing.

In some embodiments, the method further comprises installing a first pulley to the first nut at the second end of the first nut; and installing a second pulley to the second nut at an end of the second nut remote from the first nut.

In a third aspect, a robot arm is provided. The robot arm comprises the ball screw spline assembly according to the first aspect.

In a fourth aspect, a robot is provided. The robot comprises the robot arm according to the third aspect.

In some embodiments, the robot is of a type of selective compliance assembly robot arm (SCARA).

The ball screw spline of the present disclosure is integrally installable to the housing, and thus there is no need to remove the spline nut from the shaft when installing and maintaining the ball screw spline. With the bolts adapted to be received within the housing without protruding from the housing, the robot arm comprising the ball screw spline assembly of the present disclosure can be compact since the pulley no longer interferes with the bolts mounted on the spline nut.

It is to be understood that the Summary is not intended to identify key or essential features of implementations of the subject matter described herein, nor is it intended to be used to limit the scope of the subject matter described herein. Other features of the subject matter described herein will become easily comprehensible through the description below.

Drawings described herein are provided to further explain the present disclosure and constitute a part of the present disclosure. The example embodiments of the disclosure and the explanation thereof are used to explain the present disclosure, rather than to limit the present disclosure improperly.

Principles of the present disclosure will now be described with reference to several example embodiments shown in the drawings. Though example embodiments of the present disclosure are illustrated in the drawings, it is to be understood that the embodiments are described only to facilitate those skilled in the art in better understanding and thereby achieving the present disclosure, rather than to limit the scope of the disclosure in any manner.

As used herein, the term "includes" and its variants are to be read as open terms that mean "includes, but is not limited to. " The term "based on" is to be read as "based at least in part on. " The term "one implementation" and "an implementation" are to be read as "at least one implementation. " The term "another implementation" is to be read as "at least one other implementation. " The terms "first," "second," and the like may refer to different or same objects. A definition of a term is consistent throughout the description unless the context clearly indicates otherwise.

A robot of a selective compliance assembly robot arm (SCARA) type or a horizontal multi-joint type has become more and more popular. A SCARA robot generally includes a ball screw spline for performing a movement along and around Z-axis. In particular, it is an arm of a SCARA robot that includes a ball screw spline.

<FIG> illustrates an assembly view of a ball screw spline <NUM> installed to a housing <NUM> in the prior art, and <FIG> illustrates an exploded view of the assembly view shown in <FIG>. The assembly of a ball screw spline <NUM> installed to a housing <NUM> may be used to constitute an arm of a SCARA robot, for example.

As shown in the assembly view of <FIG>, a ball screw spline <NUM> includes a shaft <NUM>, a ball screw nut <NUM> and a spline nut <NUM>. The surface of the shaft <NUM> may have a spiral groove and an axial groove extending along an axis L of the shaft <NUM> (also referred to as Z-axis). A first pulley <NUM> is adapted to be mounted to the spline nut <NUM>, so as to cause the shaft <NUM> to perform a spiral movement; and a second pulley <NUM> is adapted to be mounted to the ball screw nut <NUM>, so as to cause the shaft <NUM> to perform an axially rectilinear translation.

The existed housing <NUM> is adapted to receive the ball screw spline <NUM> and includes an internal wall <NUM> and an external wall <NUM>. In the assembly state as shown in <FIG>, the spline nut <NUM> is mounted to the internal wall <NUM> of the housing <NUM> by bolts <NUM> through a first flange surface <NUM> of the spline nut <NUM>. The ball screw nut <NUM> is also mounted to the internal wall <NUM> by bolts <NUM> through a second flange surface <NUM> of the ball screw nut <NUM>. In the case that the ball screw spline <NUM> is installed to the housing <NUM> in the prior art, the internal wall <NUM> of the housing <NUM> is located between the first flange surface <NUM> and the second flange surface <NUM>.

The ball screw spline <NUM> is provided in the market as an assembly of a shaft <NUM>, a ball screw nut <NUM> and a spline nut <NUM>. As shown in <FIG>, the shaft <NUM> passes through the ball screw nut <NUM> and the spline nut <NUM>. For current ball screw spline installation and maintenance in most SCARA robots, the ball screw spline <NUM> itself has to be disassembled first. Since the detaching of the ball screw nut <NUM> will cause a failure of the ball screw spline <NUM>, the spline nut <NUM> usually has to be removed from the shaft <NUM> in order to mount the ball screw spline <NUM> to a housing <NUM>.

As shown in <FIG>, the spline nut <NUM> and its first pulley <NUM> have been removed from the shaft <NUM> to facilitate the installation of the ball screw nut <NUM> and the spline nut <NUM> to the housing <NUM>.

It is inconvenient to disassemble the spline nut <NUM> from the shaft <NUM> when installing or maintaining the ball screw spline <NUM> in SCARA robots. Moreover, for example, the first pulley <NUM> installed on the spline nut <NUM> has risks to interfere with bolts <NUM> mounted on the first flange surface <NUM> of the spline nut <NUM>. This is caused by the protruding of bolts <NUM> (e.g., heads of bolts <NUM> in <FIG>) from the first flange surface <NUM> of the spline nut <NUM>. As a result, the first pulley <NUM> on the spline nut <NUM> must be customized to prevent interference with the bolts <NUM> mounted on a flange of the spline nut <NUM>.

<FIG> illustrates an assembly view of a ball screw spline <NUM> installed to a housing according to embodiments of the present disclosure, and <FIG> illustrates an exploded view of the assembly view shown in <FIG>. In some embodiments, the assembly of the ball screw spline <NUM> installed to the housing may be used to constitute an arm of a SCARA robot.

As shown, according to embodiments of the present disclosure, a ball screw spline assembly includes a ball screw spline <NUM>, a housing and connecting plate <NUM>. The ball screw spline <NUM> includes a first nut <NUM>, a second nut <NUM>, and a shaft <NUM>. The shaft <NUM> passes through the first nut <NUM> and the second nut <NUM>. In some embodiments, the first nut <NUM> may be one of a ball screw nut and a spline nut, while the second nut <NUM> may be the other one of the ball screw nut and the spline nut. For example, in some embodiments, the first nut <NUM> is a spline nut and the second nut <NUM> is a ball screw nut. Alternatively, in other embodiments, the first nut <NUM> and the second nut <NUM> may be exchangeable and identical. Of course, the first and/or second nuts may be implemented by any other suitable mechanism as well.

In some embodiments, the surface of the shaft <NUM> may have a spiral groove and an axial groove extending along an axis L of shaft <NUM>. A first pulley <NUM> is adapted to be mounted to an end <NUM> of the spline nut remote from the ball screw nut, so as to cause the shaft <NUM> to perform a spiral movement. Additionally, a second pulley <NUM> is adapted to be mounted to an end <NUM> of the ball screw nut remote from the spline nut, so as to cause the shaft <NUM> to perform an axially rectilinear translation. Advantageously, the first pulley <NUM> and the second pulley <NUM> are adapted not to be provided between the spline nut and the ball screw nut, thereby facilitating the integral and automatic installation of the ball screw spline <NUM>.

The first nut <NUM> includes a first mounting surface <NUM> adapted to receive a first fastening element <NUM> for installing the first nut <NUM> to a housing. The second nut <NUM> includes a second mounting surface <NUM> adapted to receive a second fastening element <NUM> for installing the second nut <NUM> to the housing. The housing includes a first portion <NUM> and a second portion <NUM>. The first portion <NUM> extends in a direction substantially parallel to the shaft <NUM>. The second portion <NUM> extends in a direction substantially perpendicular to the shaft <NUM>. The first nut <NUM> is installed to the second portion <NUM> of the housing. For example, the first mounting surface <NUM> of the first nut <NUM> is above the second portion <NUM> of the housing as shown in <FIG>. The connecting plate <NUM> may couple the second nut <NUM> to the first portion <NUM> of the housing.

The first mounting surface <NUM> and the second mounting surface <NUM> are located within a space defined by the first portion <NUM>, the second portion <NUM> of the housing and the connecting plate <NUM>, such that the ball screw spline <NUM> is integrally installable to the housing. Alternatively, in some embodiments, the ball screw spline <NUM> is replaceable and integrally detachable from the housing. In some embodiments, the first mounting surface <NUM> and the second mounting surface <NUM> face to each other, and both are adapted to be received between the connecting plate <NUM> and the second portion <NUM> of the housing. In this way, by changing the orientation of a mounting surface relative to an associated housing portion (i.e., changing from the first flange surface <NUM> and the second flange surface <NUM> in <FIG> to the first mounting surface <NUM> and/or the second mounting surface <NUM> in <FIG>), the ball screw spline <NUM> can be easily installed to the housing without the first nut <NUM> or the second nut <NUM> being removed from the shaft <NUM>. In other words, the first nut <NUM> and the second nut <NUM> now can be mounted to the housing along the same direction. This enables an automatic assembly of the ball screw spline <NUM> to the housing, and thus an automatic production of a robot arm.

As an example and without limitation, the first fastening element <NUM> and the second fastening element <NUM> are bolts, such that it is easy to install and detach the ball screw spline <NUM> to and from the housing. Alternatively, the first and/or second fastening elements may be viscous elements. Of course, the first and/or second fastening elements may be implemented by any other suitable securing mechanism as well. In some embodiments, the first mounting surface <NUM> is provided on a first flange portion <NUM> of the first nut <NUM>, thereby facilitating receiving the first fastening element <NUM>. Alternatively, or in addition, the second mounting surface <NUM> is provided on a second flange portion <NUM> of the second nut <NUM>, thereby facilitating receiving the second fastening element <NUM>. Alternatively, the first and/or second mounting surfaces may be any surfaces for fixing the first and/or second nuts.

In some embodiments, the first nut <NUM> includes a first end <NUM> adjacent to the second nut <NUM> and a second end <NUM> opposite to the first end <NUM>. The first mounting surface <NUM> is provided at or adjacent to the first end <NUM>. In this way, the first fastening element <NUM> such as a bolt will be located adjacent to the first end <NUM> after being received on the first mounting surface <NUM>. In other words, the first fastening element <NUM> will be received within the housing as much as possible. This makes room for mounting a first pulley <NUM> at the second end <NUM>. Thereby, the length of the assembly of the ball screw spline <NUM> and the housing in the axis L can be reduced.

In some embodiments, the first mounting surface <NUM> is provided in such a way that in the case that the first nut <NUM> is installed to the housing, the first fastening element <NUM> is adapted to be received within the housing without protruding from the housing. For example, the threaded portion of a bolt provided as the first fastening element <NUM> may not protrude from the second portion <NUM> of the housing. In this way, the first pulley <NUM> no longer interferes with the bolts mounted on the first nut <NUM> such as a spline nut. As a result, the assembly of the ball screw spline <NUM> and the housing may be made compact. Moreover, the first pulley <NUM> can be located close to the first nut <NUM>, which can reduce the bending moment on the bearings of the ball screw spline <NUM> and increase the lifetime of the ball screw spline <NUM>. Of course, it is possible that the first fastening element <NUM> protrudes from the second portion <NUM> of the housing. In some embodiments, the protruded portion of the first fastening element <NUM> is shorter than the case shown in <FIG>.

As an example, the connecting plate <NUM> may include a flange (not shown). The width of the flange in a radial direction lateral to the axis L is larger than that of the second nut <NUM>, thereby facilitating the integral installation of the ball screw spline <NUM>. In some embodiments, the first nut <NUM> is partially located in a first opening <NUM> of the second portion <NUM> of the housing. The second nut <NUM> is partially located in a second opening <NUM> of the connecting plate <NUM>. The shaft <NUM> may also pass through the connecting plate <NUM> and the second portion <NUM> of the housing.

In some embodiments, the first portion <NUM> of the housing has a cylindrical shape. The cylindrical space defined by the first portion <NUM>, the second portion <NUM> of the housing and the connecting plate <NUM> is adapted to partially accommodate the ball screw spline <NUM>. Compared with the existed housing <NUM> as shown in <FIG>, the housing of <FIG> includes no portion between the first mounting surface <NUM> and the second mounting surface <NUM> along the shaft.

<FIG> is a diagram illustrating the size of a robot arm according to embodiments of the present disclosure compared with the size of the traditional robot ann. The robot arm according to embodiments of the present disclosure (shown on the right hand) includes the ball screw spline <NUM> and the housing, and the conventional robot arm (shown on the left hand) includes the ball screw spline <NUM> and the housing <NUM>.

In the traditional robot arm, there is a large gap between the internal wall <NUM> and the external wall <NUM> of the housing <NUM> due to a casting process of the housing <NUM>. On the contrary, in the improved assembly for ball screw spline <NUM>, there is no housing wall such as the internal wall <NUM> between the first nut <NUM> and the second nut <NUM>. As a result, the diameter of the housing can be reduced. In this example, as shown in <FIG>, the diameter of the proposed housing is <NUM> smaller than that of the existed housing <NUM> of <NUM>. It is to be understood that the specific numeral values are given only for illustration, without suggesting any limitations as to the scope of the present disclosure.

In addition, as discussed above, due to the changed orientation of the first mounting surface <NUM> relative to an associated housing portion, the first pulley <NUM> installed on the first nut <NUM> has no risks to interfere with bolts mounted on the first mounting surface <NUM>. Thus, as shown in <FIG>, the length of the assembly of the ball screw spline <NUM> and the housing in the axis L can be reduced by <NUM> compared with the traditional robot arm. As a result, the robot arm according to embodiments of the present disclosure may be compact. It is to be understood that the specific numeral values are given only for illustration, without suggesting any limitations as to the scope of the present disclosure.

<FIG> is a flowchart illustrating a method <NUM> for installing a ball screw spline <NUM> to a housing according to embodiments of the present disclosure. In some embodiments, the method <NUM> may be at least in part automatically performed, for example, by a manipulator or a robot arm. The method <NUM> may be described in conjunction with <FIG>. As discussed above, the ball screw spline <NUM> includes a first nut <NUM>, a second nut <NUM> and a shaft <NUM> passing through the first nut <NUM> and the second nut <NUM>. The housing including a first portion <NUM> and a second portion <NUM>. The first portion <NUM> extends in a direction substantially parallel to the shaft <NUM>. The second portion <NUM> extends in a direction substantially perpendicular to the shaft <NUM>.

In block <NUM>, for installing the ball screw spline <NUM>, the first nut <NUM> is first installed to the second portion <NUM> of the housing with a first fastening element <NUM>, and the first fastening element <NUM> is received by a first mounting surface <NUM> of the first nut <NUM>. For example, the first mounting surface <NUM> of the first nut <NUM> is above the second portion <NUM> of the housing as shown in <FIG>.

In block <NUM>, the second nut <NUM> is installed to a connecting plate <NUM> with a second fastening element <NUM>. The second fastening element <NUM> is received by a second mounting surface <NUM> of the second nut <NUM>. The second mounting surface <NUM> of the second nut <NUM> may be located under the connecting plate <NUM>.

In block <NUM>, the connecting plate <NUM> is installed to the first portion <NUM> of the housing, such that the connecting plate <NUM> may be located on the top of the first portion <NUM>. The first mounting surface <NUM> and the second mounting surface <NUM> are located within a space defined by the first portion <NUM>, the second portion <NUM> of the housing and the connecting plate <NUM> in the case that the ball screw spline <NUM> is installed to the housing, such that the ball screw spline <NUM> is integrally installable to the housing.

In some embodiments, the first nut <NUM> includes a first end <NUM> adjacent to the second nut <NUM> and a second end <NUM> opposite to the first end <NUM>. The first mounting surface <NUM> is provided at or adjacent to the first end <NUM>.

In some embodiments, the first mounting surface <NUM> is provided such that the first fastening element <NUM> is received within the housing without protruding from the second portion <NUM> of the housing in the case that the first nut <NUM> is installed to the housing.

In some embodiments, the first nut <NUM> is partially located in a first opening <NUM> of the second portion <NUM> of the housing, and the second nut <NUM> is partially located in a second opening <NUM> of the connecting plate <NUM>, in the case that the ball screw spline <NUM> is installed to the housing.

In an optional block <NUM>, finally, a first pulley <NUM> is installed to the first nut <NUM> at the second end <NUM> of the first nut <NUM>, and a second pulley <NUM> is installed to the second nut <NUM> at an end <NUM> of the second nut <NUM> remote from the first nut <NUM>.

In some embodiments, the first mounting surface <NUM> is provided on a first flange portion <NUM> of the first nut <NUM>. Alternatively, or in addition, the second mounting surface <NUM> is provided on a second flange portion <NUM> of the second nut <NUM>.

In some embodiments, the first nut <NUM> is one of a ball screw nut and a spline nut, and the second nut <NUM> is the other one of the ball screw nut and the spline nut.

It is understood that although the method <NUM> is described as a sequential process, some of the actions may be performed in parallel or concurrently. In addition, the order of the actions may be re-arranged, and additional actions not shown in the flowchart may also be included.

When installing and maintaining the ball screw spline <NUM> according to embodiments of the present disclosure, there is no need to remove a nut such as the spline nut from the shaft <NUM>. The assembly of the ball screw spline <NUM> and the housing may be compact since the first pulley <NUM> no longer interferes with the bolts mounted on the first nut <NUM> such as a spline nut. The first pulley <NUM> can be close to the first nut <NUM>, which can reduce the bending moment on the bearings of the ball screw spline <NUM> and increase the lifetime of the ball screw spline <NUM>.

Claim 1:
A ball screw spline assembly, comprising:
a ball screw spline (<NUM>) including
a first nut (<NUM>) including a first mounting surface (<NUM>) adapted to receive a first fastening element (<NUM>) for installing the first nut (<NUM>) to a housing, the first fastening element (<NUM>) being received by the first mounting surface (<NUM>) of the first nut (<NUM>);
a second nut (<NUM>) including a second mounting surface (<NUM>) adapted to receive a second fastening element (<NUM>) for installing the second nut (<NUM>) to the housing, the second fastening element (<NUM>) being received by the second mounting surface (<NUM>) of the second nut (<NUM>); and
a shaft (<NUM>) passing through the first nut (<NUM>) and the second nut (<NUM>);
the housing including a first portion (<NUM>) and a second portion (<NUM>), wherein the first portion (<NUM>) extends in a direction substantially parallel to the shaft (<NUM>), and the second portion (<NUM>) extends in a direction substantially perpendicular to the shaft (<NUM>);
a connecting plate (<NUM>) coupling the second nut (<NUM>) to the first portion (<NUM>), wherein the first nut (<NUM>) is installed to the second portion (<NUM>) with the first fastening element (<NUM>);
wherein the first mounting surface (<NUM>) and the second mounting surface (<NUM>) are located within a space defined by the first portion (<NUM>), the second portion (<NUM>) and the connecting plate (<NUM>), such that the ball screw spline (<NUM>) is integrally installable to the housing.