Toggle clamps are also named quick clamp, quick release clamp,over-center clamp, etc. A toggle clamp is a fastening device that usually consists of a handle to control the device, a holding bar to grip the workpiece, and a linkage system of pivot pins and levers to boost the applied force(see structure picture below). Once engaged, the toggle clamp essentially becomes locked. A toggle clamp typically serves to secure an object tightly in order to prevent it from moving or separating when inward pressure is applied.
Toggle mechanism is used widely in the mechanical industry for various applications ranging from injection molding machines to tools & fixtures. Toggle clamps are available for different types to suit the desired application.
Toggle action clamps operate through a linkage system of levers and pivots. The fixed-length levers, connected by pivot pins supply the action and clamping force. Toggle action has an over-center lock point which is a fixed stop and linkage. Once in the over-center position, the clamp cannot move or unlock unless the linkage is moved. All types of toggle clamps have the same action, just oriented differently.
Functions of Toggle Mechanism :
1.) To multiply a hand force at the handle into a high clamping force to hold work.
2.) To create an over-center lock to prevent the clamp from opening and releasing the work until opened by the operator.
3.) To rapidly open and close the clamp giving a wide clearance in which to load and unload the workpiece.
Toggle Clamp Diagram:
Toggle Clamp Parts :
- Handle – Handle is operated by operator or Worker. Handle oscillate about fulcrum or pivot.
- Clamping arm – Clamping arm applies force on the workpiece . when the handle gets operated then the clamping arm comes in contact with the workpiece’s surface and holds it against the holding Force.
- Linkages – Linkages are used to get maximum mechanical advantages. Linkages also ensure quick clamping action and release without delay in time.
- Spindle for pressure adjustment
- Base – Base is a metal body on which all assembly mounted. The base has holes at the bottom for mounting on the worktable.
Toggle Clamping Mechanism :
The toggle clamping mechanism is widely used in the manufacturing industry in areas like bending, grinding, welding, fitting, etc. Tools & fixtures industry are the major user of the toggle clamp mechanism, metalworking and assembly are the areas where this mechanism is seen often. Toggle mechanisms are commonly used within linkages in order to lock their position. These mechanisms do this by passing through a “toggle” point where any force into the linkage would cause the linkage to maintain its position. While passing through the “toggle” point, there is a great deal of stress applied to the links.
A generic toggle mechanism can be considered as a good mix of a couple of traditional linkages, a four-bar linkage, and a slider-crank mechanism.
Fig. 1 shows the toggle clamping mechanism.
Ground link is represented by link C and other details are;
- A – Clamping member (output link)
- P – Input link (Hydraulic cylinder)
- C – Ground link
- m – Coupler (Output link)
- n – Crank (Support link)
Clamping member, A is an output link which holds the clamping jaw. Output link velocity and the force available at the output link which holds or clamp the workpiece is a function of the mechanism configuration, link position, link lengths, joint friction, and actuator parameters.
Force amplification ratio is the key design parameter toggle clamping mechanism. Performance of the toggle clamp mechanism is based upon the force available at the clamping location which is output link. The clamping force available at the output link is the function of the input cylinder force, the geometric position of all the links, the coefficient of friction between moving and turning parts.
The main objective of the toggle clamping mechanism design is to generate a maximum mechanical advantage and kept the cost low. Design parameters of the toggle clamp mechanism mentioned below are crucial in formulating the optimization function of the mechanism. This optimization function can be solved using different optimization techniques such as genetic algorithms or artificial neural networks.
Following parameters are important for toggle clamping mechanism design:
- The velocity of the clamping/sliding member
- Stroke and velocity of hydraulic cylinder
- Force magnification factor
- Pin reaction at joints
- Initial position of the links
- Structural strength
Types of Toggle Clamps :
There are many different types of adjustable toggle clamps.
- Horizontal toggle clamps are in the locked position when the handle is in the horizontal position. These clamps have a low profile.
- Vertical toggle clamps are in the locked position when the handle is positioned vertically.
- Diagonal hold-down clamps are similar to horizontal toggle clamps, but diagonal handle hold-down clamps are in the locked position when the handle is in a diagonal position. These clamps also have a low profile.
- Push pull clamps to have a plunger that travels in and out. These clamps provide push and pull forces. The clamp may lock in either the push or pull position. They may also be referred to as plunger-style or straight-line clamps.
- Toggle edge clamps apply force both forward and downward at the same time.
- The action of hook clamps in pulling two parts together makes them suitable for applications such as closing and holding closed doors, lids, molds, etc. Hook clamps may require a separate fixed catch.
- Latch type clamps are clamps that use a pull action to tighten. Latch type clamps may also be referred to as pull clamps. They are ideal for latching, locking, or fastening doors or fixtures. Latch clamps may be provided in horizontal or vertical configurations. Latch toggle clamps may require a separate fixed catch.
- Plier toggle clamps are handheld clamps that are configured similar to a set of pliers. A squeeze action is used to close, or toggle, the clamp. Plier toggle clamps may be referred to as squeeze clamps.
- The pullback clamp has an action similar to a plier clamp but has a method of mounting the body.
- Cam clamps are similar to vertical clamps but the clamping force is generated by the action of a roller on a cam. The cam action allows components of different thicknesses to be clamped without readjustment of the clamping spindle.
Advantages of Toggle Clamps :
- Quick Operation and Time-Saving: The clamping and releases are achieved in seconds, this gives tremendous time saving per cycle.
- Easy to Setup: No additional accurate machining, slotting, etc. is needed while using these clamps in any tooling.
- Lots of variety: Available in push, pull, hold down, latch type, plier type.
- Durability: All vital components are hard and zinc plated giving adequate wear and corrosion resistance ensuring longer working life.
- Very low maintenance: These clamps are virtually maintenance-free. Occasionally few drops of lubricating oil are all that is needed to keep them in good working conditions.
- Cost Saving: Tooling costs are reduced as tool design and tool making become simpler. Reduced cycle time reduced with low maintenance. Reduced production cost by increasing productivity
Applications of Toggle Clamps :
- Toggle clamps are used in a welding fixture.
- Electronic Test Fixtures
- Toggle clamps also serve as machine tool positioners
- Toggle clamps are also used for Inspection and Gaging Fixtures
- Toggle clamp is also used in a door closure, assembly, and woodworking jigs, and latches for container lids.
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