Pulley-Mounted Screw Nut With End-Face Recirculation Layout
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Solution Overview
Problem
Existing ball screw spline designs for SCARA robots face challenges in reducing size and weight, leading to increased outside diameter due to flange-shaped protrusions and ring-shaped outside-diameter portions, which can cause pulley looseness due to gaps between components.
Innovation Solution
A screw nut or spline nut design featuring a recirculation component at the end portion of the nut body in the axial direction, with a pulley mounted on the outer surface and fastened to the end surface using a fastening member, eliminating the need for ring-shaped protrusions and reducing the outside diameter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a flange-shaped protrusion is provided integrally with the outer surface of the nut body to mount the pulley, then the pulley position can be determined in radial and axial directions, but the outside diameter of the nut is increased by the length required to provide the flange-shaped protrusion
Solution Approach 1:
The invention moves the pulley mounting interface from the radial direction (flange-shaped protrusion) to the axial direction (end surface of the nut body). By providing a mounting surface on the end surface in the axial direction, the pulley can be mounted without requiring radial protrusions, thus reducing the outside diameter while maintaining secure mounting capability.
2Reliability
If a return pipe is provided on the outer surface of the nut body as a recirculation component, then the screw balls can be recirculated, but the outside diameter of the nut is increased by the length required to provide the return pipe
Solution Approach 1:
The invention nests the recirculation components (return pipe and turn-around path) inside the nut body rather than placing them on the outer surface. The return pipe is positioned within the internal space of the nut body, and the turn-around path is formed inside the nut, allowing ball recirculation without increasing the outside diameter.
3Ease of operation
If an outside-diameter portion protruding in the axial direction is provided to surround the recirculation component, then the pulley position can be determined in radial and axial directions, but the outside diameter of the nut is increased and a gap is created between the pulley and recirculation component
Solution Approach 1:
The invention relocates the pulley mounting interface from the radial direction (outside-diameter portion) to the axial direction (end surface). This dimensional change eliminates the need for radial protrusions that increase outside diameter, while the pulley is securely mounted on the end surface without creating gaps between the pulley and recirculation components.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design reduces the outside diameter of the nut, eliminates pulley looseness by eliminating gaps, and allows for a more compact and secure pulley mounting, enhancing the mechanical stability and efficiency of the ball screw spline.
Implementation Method 1
a nut (23, 33) rotatably assembled to the outer ring (21, 31) via a first rolling element (22a, 22b, 32a, 32b)
Implementation Method 2
a screw groove (24b, 34b) or a spline groove (34b) in an inner surface of the nut body (24, 34); and a recirculation component (25a, 25b, 35a, 35b) having a turn-around path for recirculating a second rolling element (27, 37) rolling along the screw groove (1a, 24b) or the spline groove (1b, 34b)
Data Source
AI summary
A screw nut on which a pulley is mounted is capable of promoting reductions in the size and weight thereof. The screw nut includes: an outer ring; and a nut rotatably assembled to the outer ring via a first rolling element. The nut includes: a nut body having a screw groove in an inner surface thereof; and a recirculation component provided at an end portion of the nut body in an axial direction, the recirculation component having a turn-around path for recirculating a second rolling element rolling along a screw groove. A pulley to be mounted on the nut is fitted on an outer surface of the nut body, and is brought into contact with an end surface of the nut in the axial direction. The pulley is mounted on the end surface of the nut with a fastening member.