To allow a single kind of a lorry tap to support all oil feed port taps by providing an engaging means for coupling with the oil feed port tap and the lorry tap on an adapter.

An engaging part on a side of an oil feed port tap 17 is fitted into a notch of an oil feed adapter 1. Then the adapter 1 is rotated by a predetermined angle, a hook 6 is engaged with the engaging part, and the oil feed adapter 1 is fixed to the oil feed port tap 17. A gap between them is completely sealed with a sealing packing 16. Then a tip 10 of a lorry tap 7 is fitted toward an opening of the adapter 1. Then an engaging claw 13b of a locking lever 13 first comes over a protrusion 2 while it is in contact with a slope of the protrusion 2 of the adapter 1. Then the tip 10 of the lorry tap 7 comes into contact with an upper face of an elastic receive 15. Then by further pushing the lorry tap 1, the elastic receive 15 elastically deforms, and the engaging claw 13b is completely engaged with the protrusion 2 by a function of a spring 12.