在专利侵权诉讼中，企业作为被告时，可以采取以下有效应诉策略：
1. 及时组建专业团队
仔细研究专利文件： In the face of patent infringement allegations, a professional team composed of patent lawyers and technical personnel should be immediately formed. This team will be responsible for a comprehensive evaluation of the case, including the validity of the patent, the reasonableness of the infringement allegations, and possible defense strategies. Carefully study the plaintiff’s patent documents, clarify the scope of patent protection and technical solutions, and determine the points of dispute.
分析侵权判定标准，全面覆盖原则： According to Article 7 of the Interpretation of the Supreme People’s Court on Several Issues Concerning the Application of Law in the Trial of Patent Infringement Dispute Cases, if the technical features of the accused infringing technical solution are missing one or more technical features recorded in the claims, or if one or more technical features are different or not equivalent, the people’s court shall determine that it does not fall within the scope of protection of the patent right.
2. 收集不侵权证据
技术特征对比： Collect evidence that does not constitute infringement of one’s own product or behavior, such as product design, production process, usage instructions, etc., to prove that there are differences between one’s product and patented technology.
现有技术抗辩： 如果被告能够证明其使用的技术或设计在专利申请日之前已经公开，可以提出现有技术抗辩。
3. 提起专利无效宣告请求
Destroy the plaintiff’s patent foundation: submit a request to the China National Intellectual Property Administration for invalidation of the patent, requesting invalidation of the patent involved. If the patent is declared invalid, the patent infringement lawsuit will lose its basis, and the court may reject the plaintiff’s claim.
争取更多应诉时间： 请求中止诉讼，争取更多时间来准备应诉材料和证据。
4. 积极参与庭审
充分阐述观点： During the trial, the defendant should fully articulate their viewpoints and evidence, refute the plaintiff’s claims, and safeguard their legitimate rights and interests.
5. 考虑和解或调解
避免诉讼成本： 如果诉讼过程中发现双方存在和解的可能，可积极与原告协商，寻求和解或调解的方式解决纠纷，避免诉讼的时间和成本。
6. 其他抗辩方式
科研实验使用 抗辩： 专为科学研究和实验而使用有关专利的，不视为侵犯专利权。
权利用尽抗辩： 如果被告能够证明其使用的产品是通过合法渠道购买的，且该产品已经经过专利权人的许可首次投放市场，可以提出权利用尽抗辩。
先用权抗辩： 如果被告在专利申请日之前已经使用了相同的技术或设计，并且在专利申请日之后继续使用，可以提出先用权抗辩。
合法来源抗辩： 如果被告能够证明其使用的产品有合法来源，且不知道该产品侵犯了专利权，可以提出合法来源抗辩。

通过以上策略，被告可以更有效地应对专利侵权诉讼，维护自身的合法权益。