Such change of claim in OA allowed?

Question

There is a basic device existing (simple mechanic) as prior art and I made two innovations on it, part C and part D. I want to patent it in such a way that if somebody is using either one of these innovations, or both together, on the basic device, will infringe my patent.

I would like to write claims in the following way:

1. A device comprising:
   a. part A
   b. part B
   c. part C
   

2. The device of claim 1 further comprising a part D.

3. A device comprising:
   a. part A
   b. part B
   c. part D
   

4. The device of claim 3 further comprising a part C.

The problem is that when I initially filled my application, due to lack of experience, I wrote my both main claims actually the same, just different wording, namely A, B, C, further comprising D, as in claim 1 above. Due to OA received (obviousness rejection-objection which I should be able to overcome) I have now the chance to change claims. Is such a change in the second main claim, as presented above, now allowed? What will be Examiner's reaction to such a change? Will he need/want to make further patent search?

Any help would be appreciated.

Answer 1

The Examiner might tell you there are two separate inventions, in which case you would have to file a divisional application to capture both the ABC and ABD claims. You may also have to file a terminal disclaimer due to the overlap of the dependent claims. In either case the Examiner will let you know.

Please do ensure that the claims you are making are supported by the specification, i.e. you have disclosed that C and D can be used independently and not necessarily together.

Answer 2

You can certainly amend and there is no reason it should be taken particularly unfavorably by the examiner. Almost any amendment can be cited as a reason for a new search and in this case you would be presenting a particular combination of limitations for the first time. Amending in this way will allow the next OA to be final. (Final doesn't mean final, just final until you send more money.)