The range of applications for hinges is expanding, and so are the types of positioning technology available. Key to choosing the right hinge for the job is to determine the full usage case for the application.
Todd Schwanger, Global Product Manager, Southco Inc.
The door hinge is one of the most common and widely used devices. What may not be as well known is that hinge technology offers a sophisticated range of functions that can improve the operation of systems.
From fixed-position detent hinges that hold doors open at predetermined angles and eliminate the cost and labor of additional components, to counterbalanced positioning hinges that offer lift and the ability to control user effort to position panels or screens, there’s an array of innovative capabilities engineered into hinge technology.
Whether opening and lowering a tray table on an airline, or slightly adjusting a credit card/debit card reader device at a checkout counter, individuals take actions and draw impressions from experiencing these “touch points” daily. The diversity and sophistication of the latest hinge technology offers new tools to achieve unique touch point experiences in products.
Positioning technology opens new possibilities
The most common hinge is also the simplest: the standard, free-swinging hinge, for opening and closing, with no resistance, and which falls open under gravity and bears the weight of the device being moved.
Beyond this basic device, hinges have evolved into a new offering: positioning technology. With positioning hinge technology, designers can define and adjust the operating effort required to move or position doors, display screens, safety shields, lights – virtually any mounted component that is opened, closed and moved.
Positioning hinge technology represents a set of tools to fulfill ergonomic requirements and user perceptions of quality in applications. These include:
–Hold doors open or closed, and move panels securely into position without secondary supports or additional components
–Create intuitive, zero-drift motion so that, when a door or cover is opened, it holds a user-defined or pre-defined position securely, and with one motion
–Provide specific tactile feedback to enhance the quality perception of the hinged device
–Eliminate additional components (such as gas struts) or routine maintenance (tightening screws to maintain hinge resistance), thereby helping to lower overall costs
–Provide a smoother, more substantial feel to opening and closing action, or to eliminate vibration
You can use positioning hinges to change – or elevate – a user’s perception in different ways. Consider the airplane tray table. Seating designers must use extremely lightweight plastic components in these applications to help airlines reduce fleet weight and conserve fuel.
However, a tray table that just flops down upon opening can lead a passenger to question the quality of the aircraft itself. Using a constant torque hinge with a factory-set level of resistance, the tray can be lowered by the passenger with just the right level of force, making the tray feel more substantial and instill a perception of quality to their environment. In addition, constant torque hinges designed and manufactured with high-quality materials retain the desired resistance after thousands of flights, without requiring maintenance or parts replacements.
Positioning hinge technology can be broken down into four major categories, or “building blocks,” based on the type of controlled motion and positioning they supply:
–Constant torque – enables the device to be held securely at every position along the range of motion
–Detent and bistable – these hinges automatically drive to and hold a specific position, such as to 90 degrees
–Counterbalance – hinges with technology that enables heavier objects to feel lighter when opened, or pop open with a simple touch
–Damping – hinges that control the speed of motion automatically, without holding
Although many applications would need only one type of hinge, these different categories can also be combined into multifunctional hinges that provide multiple positioning functions in a single device.
Constant torque: Hold securely at every position
Constant torque hinges provide smooth operation and infinite positioning. These features allow intuitive movement of a device – opening and closing a laptop, a mounted display screen at a checkout counter, and so on – that holds the hinged device at any point throughout the full range of motion when stopped.
The amount of effort to move it is just enough to respond to deliberate motion while holding in place for more casual or touch interactions. A now-common example of this is the expanding use of touchscreen interaction monitors at checkout counters.
A constant torque hinge attached the monitor to the base allowed the cashier to tilt the monitor up and down for optimum viewing and interaction with ease; at the same time, tapping icons and touch points on the screen can be done without the screen shifting from the cashier’s desired position.
Traditionally, this capability is accomplished with clamping or latching mechanisms, which often do not provide the infinite positioning ability that a constant torque hinge supplies, or the smooth, flowing tactile feedback. In addition, a constant torque hinge delivers one-handed operation, rather than pushing a button or flipping a lever to move the device.
Constant torque hinges can also be engineered to provide asymmetric torque: Different amounts of effort are required to move the hinge in one direction – open or close, up or down. This feature has been used in certain types of headrests in airplane seats. The passenger can pull the headrest wings forward in the low torque direction easily, while still having the high torque direction resist the force of their head leaning on the rest in the opposite direction.
Detent hinges: drive and hold to pre-sets
Detent hinges are engineered to provide specific motion and tactile feedback: The door or device is opened and locks into place at a pre-set angle, usually with a distinctive “click” that can be felt. These types of hinges are often useful for lightweight cabinet doors or other devices that must be consistently opened, out of the user’s way. Detent hinges require the user to keep moving the device until it reaches the right position for the working environment, for instance, a pre-set angle of 90 degrees.
A variation on detent hinges is called bi-stable, which contains a built-in spring mechanism that automatically drives the door or device to the pre-set angle once the door is open. This functionality is useful for doors, access panels or covers that must be opened to a minimum angle for easy entry, or to avoid collisions with surrounding equipment. The bi-stable mechanism automatically rotates the panel to one of two preferred positions, either fully open or fully closed, with simple touch operation.
For applications requiring this type of automatic full open and close, some designers may include gas struts or gas springs in addition to a basic hinge to achieve the desired function, adding component cost to the system. With the bi-stable detent hinge, essentially the hinge does all the driving.
Counterbalance: move heavy objects with minimal effort
Counterbalanced hinges help users easily open and move heavy doors and other fixtures. These hinges use heavy-duty counterbalance springs that store energy when the door or fixture is closed; upon opening, the energy is released and the effort to move the door to a fully open position is minimal – the hinge does most of the work.
Counterbalance positioning technology suits applications where the element being lifted has significant weight, thus making operation safer and easier for the end user. Medical equipment such as blood analyzers or centrifuges is one example; large capacity deep freezers are another.
For applications where operators routinely open and close heavy doors – industrial copiers are one example – counterbalance technology can help reduce fatigue and improve operator efficiency. For instance, a door with a symmetric torque hinge may require 2.3 kilograms (kg) of effort to open from fully closed to 90 degrees open. Using a counterbalance hinge instead, the energy required to open the door can be reduced to 0.9 kg.
In the past, to help open heavier doors designers would incorporate gas struts or other devices to provide the added lift; counterbalanced hinges offer a more economical, single device solution. And the newest counterbalanced hinges can incorporate a latch to support pop-up opening: When first opened, the heavy door lifts a few degrees, and then the user pushes gently to fully open it to the desired position.
Damping hinges: Controlled opening
Damping hinges provide designers with a unique option: Rather than control the position of the device, they control the speed with which it moves. With a door, compartment or other device using a damping hinge, when force is exerted, it moves steadily to the open or closed position, rather than popping open or requiring the user to push it all the way closed.
This kind of smooth, steady motion is becoming widely preferred in a number of high-end applications, such as car interiors. For items such as eyeglass storage compartments, USB port carriers and other compartments that are opened and closed, damping hinges add to the impression of a high-tech, finely engineered interior that is a crucial element many designers seek to achieve.
Adding tactile value to “open and close”
Leading suppliers of hinge technology have recognized that every time an end user opens, closes or moves a hinged device, the individual is both exerting force and experiencing a distinctive tactile experience. Positioning hinge technology gives designers a new set of tools to enhance the user experience and thus, the impression they have of the devices.
The range of applications is expanding, and so are types of positioning technology available. The four types of hinging technology described can actually be combined to satisfy multiple requirements – for example, detent and damping functionality can be combined in a single hinge, so that a door easily opens to a fixed position and clicks in place, and then moves on its own in a controlled fashion to the closed position when it is pushed shut.
The key is to determine the full usage case for each application – what ergonomic effort should be expended to open, position and close a device, what user feedback is needed or desired to accomplish this motion effectively and repeatedly. The industry’s leading hinge suppliers have extensive experience working through these usage cases to help define the optimum solution, and can provide in-depth expertise to cost-effectively configure the right positioning technology for each application.
Filed Under: Design World articles, Fastening + joining • locks • latches • pins