How Constant Force Springs Power Innovation in Medical Devices

Medical devices must deliver exceptional reliability, consistent performance, and user confidence. These standards become even more critical as devices continue to shrink in size, incorporate advanced automation, and rely on components that must perform smoothly and repeatedly under strict regulatory oversight.

ISO 13485 outlines the requirements organizations must meet to ensure their devices meet customer and regulatory demands for safety, consistency, and performance. John Evans’ constant force springs meet these demands by delivering smooth, uniform force output throughout their range of motion. Below, learn how constant force springs benefit medical applications and how John Evans’ Sons supports medical OEMs with certified, high-performance solutions.

Functional Advantages of Constant Force Springs in Medical Devices

Constant force springs provide several mechanical advantages that make them ideal for medical environments where performance, predictability, and reliability are essential:

• Smooth, controlled motion. These springs deliver a uniform force shortly after the moment they begin to actuate, unlike traditional springs, which require a longer ramp-up. This smoothness is valuable in patient-facing devices and precision equipment.
• Steady actuation without lag. Because the force remains constant, devices benefit from immediate responsiveness. Surgeons, clinicians, and technicians experience predictable, repeatable motion every time.
• High force output in compact spaces. Constant force springs deliver strong output despite their small size. This is especially important as devices continue to be miniaturized, including handheld tools and portable or wearable medical technologies.
• Reduced mechanical complexity. In some designs, constant force springs can replace motors, gas springs, or locking mechanisms. This simplification can reduce maintenance needs, lower manufacturing costs, and improve long-term reliability.
• Calibration consistency. With predictable force throughout their lifespans, constant force springs support medical devices that must maintain tight tolerances. This reliability is invaluable during regulatory evaluation.
• Durability under high-duty cycles. These springs are engineered for repeated use, making them well-suited for clinical environments where devices operate continuously or are frequently repositioned.

How Constant Force Springs Power Modern Devices

Imaging Equipment (MRI, CT, X-ray)

In imaging systems, constant force springs can be used to support heavy components, such as imaging heads, articulating arms, and gantries. Technicians must be able to reposition these parts smoothly and accurately to promote clear image quality and safe operation. Springs for MRI systems are often manufactured from non-magnetic materials such as Inconel or Elgiloy.

Surgical Robotic Systems

Robotic systems depend on precise, fluid movement. Constant force springs counterbalance arm segments, reducing motor load and helping the system maintain consistent tool orientation. This improves the responsiveness of robotic joints and supports the surgeon’s need for high-stability, low-resistance movement during delicate procedures.

Handheld Surgical Tools

From retractors to handheld cutters, many surgical tools rely on uniform actuation. Constant force springs provide that consistency, which gives surgeons predictable tactile feedback with every use. This helps improve accuracy, reduces user fatigue, and supports reliable operation in time-sensitive procedures.

Infusion and Drug Delivery Pumps

In drug delivery systems such as auto-injectors, insulin pumps, and infusion devices, constant force springs apply steady pressure to plungers or reservoirs. This allows for regulated, accurate dosing, which is critical for drug efficacy and patient safety.

Patient Support and Rehabilitation Equipment

Constant force springs assist in positioning hospital beds, monitor arms, surgical lights, and rehabilitation machines. They help caregivers adjust equipment with minimal effort, enhancing workflow efficiency and supporting ergonomic safety. The springs also prevent sudden drops or unsteady motion, improving patient protection during repositioning.

Wearables and Portable Devices

In exoskeletons, orthotic braces, prosthetics, and compact wearable pumps, constant force springs provide continuous support that remains consistent throughout the entire motion range. By offsetting device or limb weight, they improve comfort and reduce fatigue for long-term users.

John Evans’ Sons – Experts in Medical Device Springs

As the first spring manufacturer in the United States, John Evans’ Sons brings deep expertise to medical spring engineering. We support a wide range of applications, including imaging equipment, surgical tools, drug-delivery systems, wearables, and patient-care devices, through precision manufacturing and collaborative engineering.

At John Evans’ Sons, we continuously uphold the standards of ISO 13485: 2016. We ensure that every spring is produced under strict quality and traceability requirements. Our in-house tooling, prototyping capabilities, and custom design support help medical OEMs accelerate development and bring safe, reliable products to market.

Contact John Evans’ Sons today for an engineering consultation or to request a quote for your medical-grade constant force springs.