Easily Upgrade D-Sub Connectors with a Tool-Free Push-Pull Mechanism

For decades, D-subminiature (D-sub) connectors have served as a standard interface for industrial applications. However, traditional D-sub connectors require time-consuming screw connections, which significantly slow down installation and maintenance. This is particularly problematic in applications requiring frequent connection changes, such as test equipment, production lines, and control panels. Designers need a solution that maintains the reliability and widespread compatibility of D-sub interfaces while reducing connection time and ensuring electromagnetic compatibility (EMC).

This article provides a brief explanation of why D-sub remains relevant in a world of modern connector options. It then introduces a D-sub connection mechanism from HARTING and shows how it transforms the traditional D-sub architecture into a tool-free, click-to-connect process that reduces mating/de-mating time while maintaining compatibility and reliability.

Why D-sub connectors still matter

D-sub connectors are practically ubiquitous in automation and control, robotics, and machine tools. They can also be found throughout transportation infrastructure, test equipment, and communications, including railways, semiconductor tools, and control networks.

This is not just a matter of legacy infrastructure. D-sub remains attractive because of the wide variety of options available from numerous vendors. In addition to standard signal connectors, designers can access mixed layouts that combine signal, power, and coax in a single housing, making them a practical go-to choice for many designs. The connectors are also backed by decades of standardization and compliance testing, which adds assurance in regulated industries such as transportation and rail.

Despite these advantages, D-subs are not as straightforward to deploy and maintain as modern push-pull alternatives. Yet replacing them outright is rarely practical, as the technology is deeply embedded in existing infrastructure. Introducing new connectors alongside existing D-sub infrastructure is also problematic, as it complicates inventories, tooling, and training.

Upgrading D-sub connectors with true push-pull capabilities

The HARTING D-sub push-pull mechanism (Figure 1) offers a compelling solution to this dilemma. At the heart of the mechanism is a push-pull hood that replaces the traditional D-sub backshell. This hood engages with locking bolts that can be installed into existing jack posts.

Figure 1: The D-sub push-pull locking mechanism includes a push-pull hood (1) that surrounds the backshell and locking bolts (2) that can be retrofitted into existing jack posts (3). (Image source: HARTING, modified by Kenton Williston)

By replacing fixing screws with a click-to-connect locking mechanism, designers get the convenience of modern connectors while maintaining compatibility with decades-old D-sub technology. Critically, it can be retrofitted into existing installations without any changes to the equipment; only the cable assembly needs to be upgraded.

Engagement and release are simple. To connect, the hood is pushed straight into the device-side bolts until it locks with a clearly audible and tactile click, confirming a secure fit. To disconnect, the user simply pulls on the hood cover, which disengages the locking mechanism and releases the connector in a single smooth motion. The locking force is consistent and repeatable, even after hundreds of mating cycles, ensuring dependable performance during frequent equipment servicing.

The push-pull mechanism is versatile, with hoods available in both plastic and metalized plastic versions. These are offered in shell sizes 1, 2, and 3 to accommodate standard 9-, 15-, and 25-position connectors. The hoods support cable diameters as wide as 14 millimeters (mm) and come with one to three entries to serve different cable orientations.

The locking bolt options are similarly flexible. Versions are available for both 4-40 UNC and M3 threads, with front- and rear-mount solutions to fit common panel designs.

Key features of the D-sub push-pull hoods

The 09670090200 hood (Figure 2) illustrates the standard features of a plastic push-pull design. This size E hood supports 9-position connectors and includes two cable entries, one at the top and one at a 45° angle on the side. A blind plate is provided to seal off the unused entry.

Figure 2: The 09670090200 is a typical plastic D-sub push-pull hood. It comes with a blind plate to fill the unused cable entry. (Image source: HARTING)

An internal cable clamp with screws is also included, ensuring secure retention of cables up to 7.5 mm in diameter. By anchoring the cable inside the hood, the clamp reduces mechanical stress on solder joints and crimp contacts, supporting long-term reliability.

The hood body is made from durable thermoplastic, providing a rugged enclosure that is vibration and shock tested to IEC 61373, Category 1, Class B. The material meets the UL 94 V-0 rating for flammability and withstands temperatures from -55°C to +125°C.

The hood is rated to IP30 for basic protection against accidental contact and debris. In keeping with D-sub standards, the locking mechanism is specified for 500 or more mating cycles.

These characteristics make the 09670090200 hood well-suited for widely used 9-position interfaces. Typical use cases include RS-232 serial ports and control signal connections, where compact size and reliable operation are essential.

Options for EMC and cable strain relief

The D-sub push-pull hoods are available with various options beyond the baseline configuration, including solutions for electrically noisy environments and setups that call for enhanced cable strain relief. One example is the 09670250210 (Figure 3), which is metalized to improve EMC. These shielded versions are valuable in applications such as factory automation with large motors, RF test setups, or railway signaling equipment.

Figure 3: The 09670250210 is a metalized D-sub push-pull hood designed for use in electrically noisy environments. It comes with two metalized blind plates. (Image source: HARTING)

This size B hood supports 25-position connectors and includes three cable entries and two metalized blind plates. Like the plastic models, it incorporates an internal cable clamp for secure cable retention.

The metalized housing achieves the same mechanical robustness as the standard thermoplastic hoods, including IEC 61373 vibration and shock resistance. However, its operating range is narrower, at -20°C to +90°C, and the flammability rating is UL 94 HB.

For applications that require more space in the housing or need external strain relief, designers can use an InduCom external cable clamp. The 61030000141 (Figure 4) is a representative option. It is compatible with the 09670250210 metalized hood and can handle wires with diameters ranging from 5 mm to 7 mm, accommodating 9 to 37 wires.

Figure 4: The 61030000141 cable clamp can provide external strain relief for push-pull hoods. (Image source: HARTING)

Clamp sizes reach 14 mm, providing flexibility for various cable bundles. By moving the strain relief outside of the hood, these accessories also free up internal space for wiring, which can be helpful when working with multiple cable entries or shielded cables.

D-sub push-pull locking bolt options

A key benefit of the D-sub push-pull mechanism is its ability to be retrofitted into existing installations. For example, the 97000002050 locking bolt (Figure 5, top) is a 4-40 UNC threaded bolt that can be screwed into the jack posts of an existing connector using a standard flathead screwdriver. The bolt incorporates a flange to ensure it is inserted to the proper depth. Once the bolts are installed, the appropriate push-pull hood (Figure 5, bottom) can attach to the legacy D-sub connector.

Figure 5: The 97000002050 locking bolt can be screwed into existing jack posts (top) to perform a retrofit; the push-pull hood can then attach (bottom). (Image source: HARTING, modified by Kenton Williston)

HARTING also offers a variety of locking bolts for greenfield installations, including solutions for front and rear mounting. The 97000002053 (Figure 6) is a typical example designed for rear-mount applications. This M3 threaded assembly can accommodate panel thicknesses of 0.8 to 1.3 mm and includes a bolt with an integrated locking post, washers, and a nut.

Figure 6: The 97000002053 is a locking bolt assembly for rear-mount applications. (Image source: HARTING)

Another example is the 97000002039 (Figure 7). Similar to the 97000002053, this bolt has an M3 thread and is designed for panels ranging in thickness from 0.8 to 1.3 mm. However, this model is intended for front-mount applications.

Figure 7: The 97000002039 locking bolt is designed for front-mount applications and is compatible with the HARTING coding system. (Image source: HARTING)

A notable feature of the 97000002039 is its compatibility with the HARTING coding system. This system adds keyed plastic inserts to the connector assembly to ensure that only matching connectors can be mated. The associated jack posts for this system have a circular cross-section rather than the traditional hexagonal pattern, and the locking bolts also adopt the same circular shape for compatibility.

Together, these bolt options allow the same D-sub push-pull hood design to be used in both retrofit and new installations across a wide variety of panel configurations. This is the key benefit of the push-pull mechanism: like the traditional D-sub connector, it is highly adaptable to fit the needs of many applications.

Conclusion

D-sub connectors continue to play a valuable role in industrial systems, but their traditional screw connections can slow down installation and maintenance. The HARTING D-sub push-pull mechanism enables designers to retain the proven advantages of these connectors without the drawback of slow mating and de-mating. With a broad range of options and an easy retrofit capability, the mechanism can be deployed in a wide variety of new and existing applications.