The yoke is a part of a swing check valve that is used to support the valve flap and to rotate the valve disc about a pin mounted on the valve body to open and close the industial valve.

The yoke is an elongated rod with a rectangular cross section and is less rigid and belongs to the shank type. There is a pin hole at one end and a valve disc hole at the other end, and the two holes are perpendicular to each other.

The yoke is generally made of carbon steel or stainless steel, and the blank is mainly forgings and castings. The small size yoke is generally a die forging, and the large size is a casting.

The main technical requirements of the yoke are: the pin hole and the cylindrical hole on which the valve flap is mounted have an accuracy of 6 and a surface finish of ▽5. The non-perpendicularity of the axis of the two holes shall not exceed 0.03 mm over a length of 100 mm.

yoke machining process

The main machining surface of the yoke is the pin hole, the valve hole and several end faces perpendicular thereto. The yoke is less rigid and should be installed so that it does not deform under the action of the clamping force and the cutting force. Usually, the cylindrical boss of the pin end is used as a rough reference. First, the pin hole and the one end face are driven well, and the subsequent steps are all based on the pin hole and the end face.

When turning the pin hole, because the cylindrical boss is short, it should be leveled according to the symmetrical center line of the yoke during installation, so as to avoid the skew of the pin hole of the car. Therefore, a scribing process should be arranged in the hole of the pin shaft. In order to ensure the vertical requirements of the two cylindrical holes, special clamps can be used when machining the valve disc holes.

The large-sized yoke is inconvenient to machine on the lathe due to its large diameter of rotation. Therefore, the valve disc hole and the pin hole are generally processed on the boring machine, and the end face is milled or planed. The clamping positioning method is basically the same as that of the medium and small size yokes.

Machining of swing check valve disc hole

The valve disc hole and its end face are generally turned. In order to ensure the non-perpendicularity of the valve disc hole and the pin hole, the part is positioned with the pin hole and the end face, and the clamp shown in the following figure is used. The fixture is mounted directly on the spindle of the lathe. When machining the yoke of different lathes, the positioning shaft can be replaced and the distance from the positioning shaft to the center of the fixture can be adjusted. In order to facilitate the control of the thickness of the yoke, the tool holder is provided with a tool setting device.

The above-mentioned jig is also used when turning the other end face of the valve disc hole. At this time, the part must be turned over and adjusted to support the height of the stud and the platen.