专利给予你对于一项发明的权利。专利权保护它的所有者，即未经所有者同意，这项发明不能被复制或出售。 而交换的条件是，专利所有人必须公开这项发明的信息。这项发明必须是实用的，并且包含新的特性——前所未有也无人利用过的东西。一项专利通常可持续约二十年。

A parent grants you a right of inventing. The parent protects/preserves its possessor, that is, the invention cannot be copied or sold without his or her agreement. The item for exchange is that the possessor must make the information of this invention known to the public. The invention must be practical and include (be of) new characteristics/features--something that has never been exsited or used before. A patent usually can last around 20 years.  

总体而言，翻译相当不错。个别地方有改进的余地。修改示例如下：

A patent grants the patentee the right to an invention. It protects the patent owner, that is, the invention cannot be copied or sold without his or her permission. The items for exchange are that he or she must make the information on this invention known to the public and that the invention must be practical and include some new features, something that has never  existed or been used before. A patent usually lasts around 20 years.  

1 对于一项发明的权利，the right to an invention. right为特指，与介词to搭配表示对...的权利。发明有名词invention，不用动名词inventing，动名词表示动作、过程。名词可以表示发明的结果（如技术等）。

2 you与后面的his or her矛盾。故改用名词，避免代词使用混乱。

3 使用人称代词it, 避免重复名词。

4 专利保护用protect, 不是preserve（保存，使保持原样）。

5 专利所有人为patentee或patent owner，可交替使用，避免重复。

6 未经同意，此处的同意应该用permission（允许、许可）。

7 terms表示条件通常用复数形式，而且原文的条件也是二个，而不是一个。故用复数，表语从句为并列的that从句。

8 exist为不及物动词，没有被动语态。

9 情态动词can在此不用更好，改为一般现在时态。