By Derek Clark at the Bet Butler Stadium
Mark Warburton made it 11 wins in a row since taking over the Ibrox reins with a battling if not unspectacular performance.
The Light Blues could consider themselves lucky to go in at the break level.
Garry Fleming struck the post with a header while Willie Gibson and Darren Barr came close with efforts.
It took Rangers until the 40th minute to fully test Mark Brown in the Sons goal when James Tavernier fired a fizzing shot that was tipped over.
Tavernier struck the woodwork himself on the stroke of half-time with a curling free-kick.
The second half started in similar fashion for the visitors until Martyn Waghorn broke the deadlock on the 64th minute.
The Englishman unleashed a blistering strike from all of 30 yards that nestled into the back of the net.
Nine minutes later Rangers doubled their advantage from the penalty spot.
Mark Docherty sold the jerseys with a short back pass which allowed Kenny Miller to nip in, he was taken out by Gregor Buchanan who was shown a straight red.
Waghorn then stepped up to convert the resultant penalty.
Dumbarton won a penalty of their own in injury time when Frazer Wright was upended in the box and Fleming fired home the spot-kick.
Gers boss Warburton was pleased to come away with maximum points despite a far from scintillating display.
“It’s a tough place to come, Dumbarton were well organised but we were patient and I’m glad to get the three points.”
Sons manager Stevie Aitken couldn’t fault his players for effort.
“The fact we can compete with a team we all know will probably have the league wrapped up by February is pleasing, I can be really proud of the players”