Counterbalance or Lift-Assist
Counterbalance is a force which negates another undesirable force. Often, counterbalance is used to neutralize the weight of a heavy object. Counterbalance can be combined with dampers or a friction component to provide rate control and moderate holding forces respectively.
Counterbalance mechanisms help you lift heavy objects with ease. This increases the safety and ergonomics of your product by counteracting the hazard of massive moving components and reducing the strain of repeated motions. They work by storing energy in a spring which is released when the mechanism is being lifted.
Counterbalance mechanisms must be mounted correctly in order function properly. To illustrate this point, imagine a lid that opens from the top like a piano. The counterbalance mechanism must provide the most force while the lid is just beginning to open. The force continues the decrease until it is zero when the lid is vertical. Compare this to an access door that opens from the side with a hinge at the top. While the door is starting to open, little force is required. As the door continues to open, the force increases until it reaches horizontal when the force is greatest. A counterbalance mechanism which is designed for the top-opening lid will not work for the access door and vise versa. For more help finding the right lid support, check out our design guide:
Soft-close or Damping
Damping is an influence on a mechanism which will resist motion in a manner proportional to velocity. This effect is often produced by fluids flowing through or around an obstacle.
Damping limits the rate at which a mechanism can move. With the appropriate damping, mechanisms will move smoothly, quietly, and safely. Because of this, damping mechanisms are often called soft-close mechanisms. They are often found in glove boxes and modern kitchen drawer slides.
Soft-close mechanisms must not be confused with the position control mechanisms described below (detent, free-stop, and position locking). Position control mechanisms will prevent the device from moving. In contrast, soft-close mechanisms will begin to close slowly as soon as you let go of them.
Position Control Functions
A detent inclines the position of a mechanism to specific locations. Detents may be placed at the limits of a mechanism’s range or may be arranged in increments within the range of motion. These provide tactile feedback that a mechanism is aligned with predefined positions. Detents typically provide much less holding force than position locks but are not required to be disengaged before being adjusted.
Detent positioning allows a mechanism to be lightly held in fixed positions. This allows the mechanism to be reposition quickly and easily. The center position of a stereo balance often has a detent which provides tactile feedback that the stereo is exactly balanced.
A detent mechanism has two parts, a follower and a detent, which move relative to one another. The follower is spring loaded and presses against the detent. The detent is a hole or impression that allows the follower to partially fall into it. Force is required to slide the follower out of the detent which is how the mechanism holds its position. When the follower is not in the detent, there is reduced holding forces. When the follower gets near the detent, the mechanism “clicks” into position. A common design is to use a small ball bearing with a spring as a follower and smaller holes as detents.
Free-stop positioning means a mechanism will allow for continuous adjustment of a given lid, door, arm or other moving component attached to a main body. Common examples include the screen of a laptop or a rear-view mirror both of which will stop in any position and can be freely repositioned.
Free-stop positioning allows a mechanism to be held at any position and repositioned quickly. Laptop screens have free-stop hinges so that the screen can be reoriented to any angle. These mechanisms work by using friction to hold the mechanism where you set it. Free-stop hinges have torque friction which prevents rotation. For this reason, they may also be called friction or torque hinges.
Friction hinges work particularly well when the holding force required is low. If the mechanism must have high holding forces, high friction is required to prevent motion. This high friction could make repositioning the mechanism difficult. To circumvent this, a heavy mechanism may be counterbalanced to reduce the holding force required. Most counterbalance mechanisms already have just enough friction to prevent unwanted motion. Position locks may also be used when high holding forces are required.
A position lock arrests the motion of a mechanism. There may be a discrete number of locking positions or continuous locking through the range of motion. Unlike detents, position locks must be disengaged to allow motion but typically supply much more holding force.
Position locks prevent motion and, unlike detent and free-stop positioning, must be toggled off to allow motion. They are especially effective when high holding forces are required. Some position locks have a finite number of locking positions while others can be locked in any position. Additionally, locks may be toggled electrically or mechanically.
Clutches are a type of position lock which are used to engage and disengage power transmission between two components. Mechanisms Market provides a unique locking technology using residual magnetics. This toggles electrically and will stay in either the locked or unlocked state indefinitely without energy consumption.