Spline-Locked Support Arm Assembly for Torque Screwdrivers

Solution Overview

Problem

Existing support arm arrangements for screwdrivers rely on clamping or frictional forces for attachment, which can lead to unreliable fastening and increased material wear due to the risk of slipping and abrasion during torque transmission.

Innovation Solution

A support arm arrangement that uses a locking element with a groove on the gear housing and an internal spline on the mounting flange, where the locking element can assume a locked or released position, providing secure and low-wear attachment by engaging with the groove to lock the support arm in a defined longitudinal position.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a support arm is attached to a screwdriver using clamping or frictional forces (as in prior art DE 10 2009 005 997 A1 and EP 2 210 709 A2), then the support arm can be easily attached and detached, but the attachment becomes unreliable under compressive or tensile loads and causes increased material wear due to abrasion

Engineering Contradiction:

Improveattachment reliabilityVSAvoidmaterial wear

Core Design Contradiction:

ReliabilityVSLoss of substance

Solution Approach 1:

The attachment connection is divided into two independent functional segments: the spline connection handles rotational fixation and torque transmission, while the locking element (ball in groove) handles longitudinal positioning and load-bearing. This segmentation allows each segment to be optimized for its specific function, preventing the failure modes of the previous unified friction-based connection.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The friction-based mechanical attachment is replaced with a form-fit (geometric) attachment system. The spline teeth and groove provide positive mechanical engagement that eliminates reliance on friction forces, thereby preventing material wear from abrasion while maintaining attachment reliability under various loads.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Ease of operation

If a support arm is attached using a ball and spring-loaded actuating pin mechanism (as in prior art DE 10 2009 005 997 A1), then the support arm can be fixed in position, but the attachment relies solely on clamping forces that can release under load and cause the support arm to slip off

Engineering Contradiction:

Improvesupport arm positioningVSAvoidfastening security

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The attachment connection is divided into two independent functional segments: the spline connection handles rotational fixation and torque transmission, while the locking element (ball in groove) handles longitudinal positioning and load-bearing. This segmentation allows each segment to be optimized for its specific function, preventing the failure modes of the previous unified friction-based connection.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The friction-based mechanical attachment is replaced with a form-fit (geometric) attachment system. The spline teeth and groove provide positive mechanical engagement that eliminates reliance on friction forces, thereby preventing material wear from abrasion while maintaining attachment reliability under various loads.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Data Source

PatentEP3372343B1Assembly consisting of a torque-discharging support arm and a screwdriver

Publication Date: 2022.05.04 HOHMANN FRANK

Figure 1~2
Figure 3~4
Figure 5

AI summary

A proposed arrangement consists of a support arm (1) for dissipating reaction torques and a rotary screwdriver (2). The rotary screwdriver (2) has a drive section (3) and a gearbox housing (4) with an output shaft (7) extending forward from the gearbox housing (4). An external splined shaft (8) is arranged around the gearbox housing (4), the teeth (9) of which extend rearward to a groove (10) surrounding the gearbox housing (4) over its entire circumference. The base (11) of the groove lies on a diameter (D1) that is smaller than the diameter (D2) defined by the tips (13) of the teeth (9). The support arm (1) has a mounting section (15) with an annular mounting flange (16) and an internal splined shaft, as well as a support section (19) that can be pressed against an external abutment and is arranged laterally offset from the output shaft (7).The splined connection of the mounting flange (16) interacts with the splined connection (8) of the gearbox housing (4) such that the support arm (1) is rotationally fixed to the gearbox housing (4). A locking element (20) is arranged on the mounting flange (16) and is movably mounted transversely to the longitudinal direction of the output shaft (7). This locking element can assume a locked or unlocked position, and in the locked position, the support arm (1) is fixed longitudinally to the gearbox housing (4). To enable a more reliable, secure, and less-wearing attachment of the support arm to the screwdriver, the invention proposes that, in the locked position of the fixing device (25), the locking element (20) extends at least partially into the groove (10), thus locking the support arm (1) longitudinally to the gearbox housing (4).