Common Questions about Jaw Crushers
If you are a veteran of the rock, sand, gravel, or mineral processing industry or an avid reader of our blog, you know that there are many types and styles of crushing equipment. The exact crushers you need (jaw, cone, impact, or rotary) will depend on your site, the product you are making, and how much you need to produce.
The construction and capabilities of a personal shredder also determine where it will fit into your processing duties. That is, you can have different types of crushers located at primary, secondary, and tertiary stations in loop format to do the required material reduction work. Each type of shredder brings unique strengths and advantages to the process.
Today’s article focuses on compression jaw crushers, which are often used in the primary stage of crushing circuits. It’s important to know that cone crushers are sometimes used instead, and we’ll also talk a bit about when cone crushers may be preferred over jaw crushers.
What is a Jaw Crusher?
As we introduced in a recent blog post about all the different types of crushing equipment available, jaw crushers are sometimes also referred to as “rock breakers,” which speaks to their brute force. They are used almost exclusively as primary crushers because they excel at breaking down some of the largest and toughest materials into more manageable pieces for further reduction by various crushing equipment. Jaw crusher has a multitude of advantages, including:
- Can handle many different types of materials – from hard granite to reclaimed asphalt pavement (RAP) and more – without exhibiting as much wear and tear as primary impact-style crushers.
- Typically, a minimum of fine material and dust is produced.
- More efficient than primary gyratory crushers.
Due to their small physical size, jaw crushers are also ideal for tight spaces, such as underground mining and mobile crushing applications, where some other primary crushing solutions simply do not fit.
types of jaw crushers
Jaw crushers have been around for 200 years at this point and are one of the most “historic” crusher types. Because of this, jaw crushers have advanced technologically over the years to make them more durable and improve their movement to reduce choking and increase operating speed. Over time these designs have proven a machine that is simple enough in its working principle that it may not actually become obsolete.
Today, there are two main jaw crusher configurations you’ll see from major equipment manufacturers. They differ based on how the swing jaw moves, although their output is similar.
Double Toggle – Black Type or Overhead Pivot Movement
Double toggle movement jaw crushers such as the Blake Style (named for the inventor of the first successful mechanical jaw crusher, Eli Whitney Blake), have long been the standard used for crushing hard and abrasive rocks, as well as for viscous feed. These jaw crushers have high energy efficiency. The overhead pivot design further minimizes wear on the black stile versus crusher faces.
Single Toggle – Overhead Eccentric Movement
More compact than the double toggle design, the single toggle movement jaw crusher was unable to accept such large feed sizes at a time, although it could generally move faster. Technological innovations solved the issue of feed size, and now these machines are quite popular due to how quickly they work. However, they do experience a bit more wear and tear than double toggle style crushers. Of course, wear parts are widely available and affordable, so that fact hasn’t stopped the single toggle design from catching on.
How does Jaw Crusher work?
As we mentioned above, different jaw crusher designs will work slightly differently, but how they work is the same across the board. All jaw crushers reduce large-sized rocks, ore, or other material by a compressive action. A fixed jaw, mounted in a V-shaped alignment, has a stable breaking surface, while a movable, “swing” jaw exerts a force on the feed material by pushing against the stationary plate.
The space below the “V”-aligned jaw plates is the output gap that determines the size of the product being crushed with the jaw crusher. The rock remains in the jaw until it is small enough to move into space.