Pull-type pneumatic booster

In a pull-type pneumatic booster comprising:

• (a) a body includes a major hollow portion and a first tubular portion of a smaller diameter extending said major portion, said body having an axis extending through said major portion and said first tubular portion;
• (b) a movable member including a wall portion received in said major portion to divide an interior of said major portion into a low pressure chamber and a high pressure chamber, and a second tubular portion extending from said wall portion and received in said first tubular portion, said movable member being movable along the axis of said body, and said lower pressure chamber being in communication with a low pressure source;
• (c) an elongated plunger received in said second tubular portion for sliding movement therealong;
• (d) an input member connected to one end of said plunger;
• (e) first and second air passage means;
• (f) valve means mounted in said second tubular portion, said valve means comprising a first valve seat formed on said plunger, a second valve seat formed on an inner surface of said second tubular portion, and a valve element engageable with said first and second valve seats in accordance with the movement of said plunger along the axis of said body, said high pressure chamber being communicable with said low pressure chamber via said first air passage means when said valve element is disposed in engagement with said first valve seat, said high pressure chamber being communicable with a high pressure source via said second air passage means when said valve element is disposed in engagement with said second valve seat;
• and
• (g) an output member connected to the other end of said plunger;
• (h) the improvement wherein one end portion of said plunger remote from the other end thereof extends beyond said wall portion of said movable member into said low pressure chamber, said plunger has the other end portion of a tubular configuration remote from said one end thereof, said one and other end portions of said plunger being snugly fitted in and disposed in sliding contact with an inner surface of said second tubular portion for guiding the movement of said plunger along the axis of said body, there being provided a load-transmitting means received in said other end portion of said plunger for transmitting a reaction force applied to said output member to said input member via said plunger.