This invention involves a kind of improved structure of a key cylinder

Through applying force to damage a key cylinder on one side of a common door lock, burglars can unlock a door lock through the lock's unlocking cam. In this respect then, the lock's performance is not ideal. To solve this problem, cylinder locks with blocking pins are known, they block the movement of the unlocking cam when the first cylinder body is broken off. European Patent application, EP 2 679 749 A1, discloses such a lock. Furthermore, patent applications CN 203 271 290 and CN 103 615 154 disclose locks with two cylinder bodies and a connection member having two seperate connecting blocks and two cylinder bodies with a sliding stop pin in the locking cam and an additional lock shotpin being able to constrain the sliding stop pin in a second position.

To solve the problem that, in the current technology, the performance of the common door lock under the resistance to force applied by a burglar is not ideal, this invention provides an alternative structure of a key cylinder. It is designed to be compact and more solid and can positively limit the rotating opening of the unlocking cam under certain damage by force, which improves its burglar resistance and has a high reliability.

According to the present invention, there is provided A key cylinder as defined by claim 1.

It has advantages including simple and compact design, strong burglar resistance, wide range of application and high reliability.

The detailed contents of the invention can be illustrated through the drawings and living examples below.

• Figure 1 is an exploded diagram of an embodiment of the lock structure;
• Figure 2 is a side elevation with partial cutaway showing the assembly structure of the lock structure.
• Figure 3 is a side elevation with partial cutaway showing when one side of the cylinder body has been broken by force
• Figure 4 is the A-A section view of Figure 2.
• Figure 5 is the B-B section view of Figure 2.
• Figure 6 is the C-C section view of Figure 3.

Referring to figure 1, this invention includes a left cylinder body 1 and right cylinder body 2, connected by connection member 3.

A left barrel of key cylinder 1 and a right barrel 5 of key cylinder 2 are inserted into a left cylinder body or housing 1 and the right cylinder body or housing 2 respectively. Between the left cylinder body 1 and the right cylinder body 2, an unlocking cam 6 is set. An extension from the side of the connection member 3 forms a fixed block 7.

The fixed block can be set between the left barrel of key cylinder 1 and the unlocking cam 6, or between the right barrel 5 of key cylinder 2 and the unlocking cam 6, depending on the specific requirement. The indication here of right or left, is not to prescribe a limit to the range. The left cylinder barrel 4 and the unlocking cam 6 are connected and driven by the left driving shaft 8 which extends through a bore in the fixed block 7. The unlocking cam 6 and the right barrel 5 of key cylinder 2 are connected and driven by the right driving shaft 9. The connection member 3 is initially positioned in the left key cylinder 1 by a circlip 26 which engages in a slot 27 on the left key cylinder 1 and secured with bolt 25 which extends through bore 24 before engaging with a threaded bore in the left key cylinder 1. The connection member 3 is secured to the right key cylinder 2 in a similar manner.

The specific structure of the driving shaft described above, is that on the proximal end

(i.e. the ends nearest the unlocking cam 6) of both the left driving shaft 8 and the right driving shaft 9, there is formed a convex cam surface 19, and the other distal end forms the connection joint having convex profiles as shown, which engages with key cylinder; the end of the convex joint driving shaft 9 can by axially inserted into the barrel of the key cylinder, and is rotationally driven by the barrel of the key cylinder; the end of the convex joint of cam 19 can be axially inserted into the into the unlocking cam 6 (and held in position by spring 22,23 which fits behind the cam 19) to drive the unlocking cam 6 to rotate it. Compressed spring 10 and lifting pin 11 are set in the right barrel 5 of key cylinder 2. A restraining plug 12 is set inside the fixed block 7.

A sliding stop pin 13 is set at an eccentric position from the axis of rotation of the unlocking cam 6 sets. Referring also to figure 2, one end of sliding stop pin 13 abuts a lifting pin 11, the other end cooperates with the restraining plug 12. Around the sliding stop pin 13, two circumferential grooves 14 are symmetrically formed. Two lock-stopping channels 15 are formed in a radial direction in the unlocking cam 6, the lock-stopping channels 15 each being equipped with a lock-stopping spring 16 and a lock shotpin 17, packed by the sealing covers 21, and the lock shotpin 17 is corresponds with the circular grooves 14. The effect of the cooperation between the lock shotpin 17 and the circular grooves 14 is to prevent burglars from removing the sliding stop pin 13 in order to rotate the unlocking cam 6. When one side of the lock body and the restraining plug 12 are taken away or fall apart under force, the lock shotpin 17 maintains an engagement with the sliding stop pin 13 through the circumferential groove 14.

Limit lugs 18 are set on the two sides of walls of the fixed block 7, which prevents the whole key cylinder being knocked into the lock body by force while the key cylinder as a whole is installed in the lock body.

Referring also to figure 3, when the left cylinder body 1 is damaged by force, the right compressing spring 10 will no longer be resisted, and it will push (through the lifting pin 11) the sliding stop pin 13 leftwards. One left end of the sliding top pin 13 will knock the restraining pin 12 to enter the fixed block 7, making the unlocking cam 6 and the fixed block 7 locked, so that the unlocking cam 6 can no longer rotate. In this way, the lock structure prevents unlocking through force. Referring to figure 4, when the sliding stop pin 13 is moved to this position, the lock shotpin 17 under the urging of the lock-stopping spring 16 enters the circumferential groove 14 of the sliding stop pin 13 through the zigzag profile of the sliding stop pin 13, which prevents further movement of the sliding stop pin 13. With the stop pin constrained in this way, the burglars cannot rotate the unlocking cam through taking the sliding stop pin out, further enhancing the lock's ability to guard against burglary.

The embodiment above is just to describe the optimized mode of execution of an improved structure of key cylinder of this invention, not a conception of this invention nor to limit the range of it. Provided the principles of the invention are not departed from, all the changes of the appearance and improvement of the technical proposals of this invention made by the technicians in this field should belong to the scope of protection of the improved structure of the key cylinder of this invention. In particular, the mechanism could be adapted using the same principles so that rotation of the unlocking is prevented when either key cylinder is removed by force. It will also be realised that though both cylinders shown here are key operated barrel locks, the principles may be extended to other barrel types, such as electronic operated locks, or one side may have a thumb turn, and other variations as is known in the art.

Many variations are possible without departing from the scope of the present invention as defined in the appended claims.