Injection devices
First Claim
1. An injection device with an elongate barrel-ilke body for giving a sequence of injections of liquid from a capsule, the capsule being carried therein in a manner allowing longitudinal movement between limiting positions, and having a needle at one, forward end and a piston actuable through the other, rear end to cause emission of doses through the needle, the device comprising a plunger to act on the piston, spring drive means with a limited travel and with a pawl and ratchet engagement with the plunger to drive the plunger in the forward direction, manually operable priming means to energise the drive means to withdraw the capsule to its rear limit, and means for releasably holding the spring drive means energised after priming, wherein the energised spring means engages the plunger at a first position thereon and when released drives the plunger and thus the piston forwardly, the drive in a first phase carrying the capsule from a rear to a forward limit by virtue of the contents of the capsule, with escape only through the needle, forming a substantial hydraulic lock, the needle then projecting from the body, and in a second phase forcing the piston alone on to eject a dose, and wherein the priming means when operated carries the plunger rearwardly with the capsule until the spring drive means re-engages the plunger at a second position more rearward thereon than the first position.
1 Assignment
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Accused Products
Abstract
An injection device is adapted to eject a sequence of doses from the needle of a capsule carried within its barrel-like body. A plunger extending rearwardly from the capsule has ratchet teeth along its length engaged by pawls at the forward end of a drive tube biased forwardly by a spring. The capsule is in a sleeve-like carrier having limited longitudinal travel, a lost motion connection to the drive tube and an engagement with the ratchet teeth by pawls. The drive tube can be releasibly retained in a rearward position by a trigger mechanism. When released, the drive tube urges the plunger, capsule and carrier forwards to project the needle. The liquid acts effectively as a solid. With the carrier stopped, the plunger carries on to eject a dose, clicking past the carrier pawls. The re-prime, the knob is pulled to retract the drive tube and the carrier, the lost motion connection allowing the drive tube to move further and have its pawls click back along the plunger until the trigger mechanism re-engages.
200 Citations
9 Claims
- 1. An injection device with an elongate barrel-ilke body for giving a sequence of injections of liquid from a capsule, the capsule being carried therein in a manner allowing longitudinal movement between limiting positions, and having a needle at one, forward end and a piston actuable through the other, rear end to cause emission of doses through the needle, the device comprising a plunger to act on the piston, spring drive means with a limited travel and with a pawl and ratchet engagement with the plunger to drive the plunger in the forward direction, manually operable priming means to energise the drive means to withdraw the capsule to its rear limit, and means for releasably holding the spring drive means energised after priming, wherein the energised spring means engages the plunger at a first position thereon and when released drives the plunger and thus the piston forwardly, the drive in a first phase carrying the capsule from a rear to a forward limit by virtue of the contents of the capsule, with escape only through the needle, forming a substantial hydraulic lock, the needle then projecting from the body, and in a second phase forcing the piston alone on to eject a dose, and wherein the priming means when operated carries the plunger rearwardly with the capsule until the spring drive means re-engages the plunger at a second position more rearward thereon than the first position.
Specification