| 摘要 |
An injector (10) having a needle (14) which is exposed by a retractable shroud ( 13). Mounted within the body (11) of the injector (10), is a first interacting piston (30) and cylinder (31) which cooperate to enclose a first space (33) which receives the l iquid to be injected. A second interacting piston (26) and cylinder (27) cooperate to enclos e a second space (28). A gas under pressure is delivered to the second space (28) to cause movement of the second piston (26). The second piston (26) is attached to the first pisto n (30) and therefore moves with it. The shroud (13) is operatively associated with a valve (35) to regulate the delivery of the gas under pressure to the space (28) to cause opera tion of the injector (10). A user of the injector (10) grips the body (11) by means of a han dle portion (12) and presses the injector (10) against the skin of the animal. This causes r etraction of the shroud (13) as the needle (14) penetrates. That retraction of the shroud (13 ) then causes actuation of the valve (35) to cause operation of the injector (10).
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