2012年9月13日星期四

Hydraulic And Pneumatic Actuators Types And Descriptions

In this article I want to discuss the different actuators that are used in both hydraulics and pneumatics.

Linear actuators, are most common such as hydraulic and pneumatic cylinders. The advantage of hydraulic cylinders over pneumatic cylinders is that you get so much more power due to higher pressures. While pneumatic linear actuators (cylinders) give very inexpensive and functionality in certain industrial application that do not require high forces such as the food industry, pharmaceutical industry and a lot of others. Remember Pneumatic is limited to approximately 120 psi. and this times the area equals the power.

Rotary actuators, are hydraulic and pneumatic motors, fixed rotary actuators that give a set motion of 90 deg. to 180 deg. rotation in back and forth motions. Another version of the rotary actuators is the Rack and Pinion type where there are opposing cylinders moving back and forth across a rack and pinion which in turn produces a rotating motion output at a preset rotational movement. The motors continue to turn in either a uni-directional fashion or a bi-directional fashion providing torque for rotary movement. Based on the requirement of the equipment and design this determines whether you use hydraulic or pneumatic.

The critical part of applying any actuator is understanding first what you want it to do, how much power you will need to accomplish the task and how to functionally create the circuit needed to control it. This applies whether it is hydraulic or pneumatic.

Example 1; I have a tilting arm on top of a conveyor belt that I want to raise and lower a cleaning brush during running of the conveyor to clean it. Can I do it with a linear or rotary actor? The answer is BOTH, but this depends on how much space, how Rhinestone Watches far the brush has to move and it is all relative to the application. Say you need 16" of travel for the actuator to lower the brush to the belt, providing the distance will allow for clearance of a 16" stroke cylinder this would be a good application. However if the quarters are tight and there is not enough clearance then a rotary actuator may be the best application to use and apply during pivot arms for the torque.

I think you see, Oval Watches Fluid Power is an applied product not just something you call up and get without knowing something about. Having a better understanding of fluid power (hydraulics and pneumatics) is so important to the person marketing this type of applied product. One cannot expect to get any technical or design help from some of Wholesale Antique Watches the large companies that only sell from a page in a book and an item number. This is most important to the end user, and should be taken into consideration when looking at fluid power components and selecting vendors. I will be discussing this in detail in future articles.

If you continue to follow my articles I will attempt to explain the Oval Watches components and details used in fluid power and will give you access to join my monthly eBooks and videos for the most inexpensive and comprehensive Fluid Oval Watches Power Training on the planet.

2012年9月4日星期二

Introduction to PHP

What Is PHP?

PHP is a language that has outgrown its name. It was originally conceived as a set of macros to help coders maintain personal home pages, and its name grew from Solar Gadgets its purpose. Since then, PHP's capabilities have been extended, taking it beyond a set of utilities to a full-featured programming language, capable of managing huge database-driven online environments.

As PHP's capabilities have grown, so too has its popularity. Solar Gadgets According to NetCraft (http://www.netcraft.com), PHP was running on more than 1 million hosts in November 1999. As of September 2001, that figure had already risen to Spy Gadgets over 6 million hosts, and by October 2003 PHP was reportedly installed on almost 14 million hosts. According to SecuritySpace.com, PHP is the most popular Apache module available, beating mod_ssl, Perl, and FrontPage.

PHP is officially known as PHP: Hypertext Preprocessor. It is a server-side scripting language often written in an Solar Gadgets HTML context. Unlike an ordinary HTML page, a PHP script is not sent directly to a client by the server; instead, it is parsed by the PHP engine. HTML elements in the script are left alone, but PHP code is interpreted and executed. PHP code in a script can query databases, create images, read and write files, talk to remote servers—the possibilities are endless. The output from PHP code is combined with the HTML in the script and Xbox 360 Adapter the result sent Solar Gadgets to the user.

PHP is also installed as a command-line application, making it an excellent tool for scripting on a server. Many system administrators now use PHP for the sort of automation that has been traditionally handled by Perl or shell scripting.

Ali

Writer, Web Designer, Graphics