Pipe coupling

1. A pipe union comprising:

a first pipe,

a second pipe, and

a pipe coupling, wherein the first pipe is connected to the second pipe by the pipe coupling, said pipe coupling including:

at least one injection outlet for injecting a lubricant for reducing friction with soil during jacking of the pipe coupling through a tunnel,

wherein the at least one injection outlet protrudes into an inner circumferential area of the pipe coupling, and the at least one injection outlet is configured to receive lubricant from within the pipe coupling and expel the received lubricant to an outer side wall of at least one of the pipe coupling, the first pipe or the second pipe, and

wherein the pipe coupling comprises an insert ring, disposed inside the pipe coupling between end faces of the first and second pipes, the first and second pipes connecting to the insert ring at the end faces from both sides, and the at least one injection outlet being at least partially disposed in the insert ring.

2. The pipe union according to claim 1 , wherein the at least one injection outlet is disposed in the wall of the pipe coupling, centrally in relation to a longitudinal axis of the pipe coupling.

3. The pipe union according to claim 1 , wherein the at least one injection outlet is sealingly introduced into an opening in the wall of the pipe coupling.

4. The pipe union according to claim 3 , wherein the at least one injection outlet is sealingly welded and/or sealingly laminated into the opening in the wall of the pipe coupling.

5. The pipe union according to claim 1 , wherein the at least one injection outlet ends flush with an outer side of the wall of the pipe coupling.

6. The pipe union according to claim 1 , wherein the at least one injection outlet comprises a closure piece for closing the opening of the at least one injection outlet, which is removable for injecting the lubricant so as to expose the opening of the at least one injection outlet.

7. The pipe union according to claim 1 , wherein a longitudinal axis of the at least one injection outlet extends perpendicularly to an adjacent region of the wall of the pipe coupling.

8. The pipe union according to claim 1 , wherein the at least one injection outlet comprises at least one sealing means for sealing the interior of the at least one injection outlet from an interior of the pipe coupling.

9. The pipe union according to claim 1 , wherein the pipe coupling has two or more of said injection outlets, which are distributed across a circumference of the pipe coupling spaced equidistantly apart from each another.

10. The pipe union according to claim 1 , wherein the pipe coupling is made of steel.

11. The pipe union according to claim 10 , wherein the pipe coupling is made of stainless steel.

12. The pipe union according to claim 1 , wherein the insert ring is disposed in the center of the pipe coupling.