Padlock

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a padlock and, more particularly, to a padlock in which the correct key is not allowed to be pulled out after the padlock is opened, so as to prevent the door of a building, especially of a warehouse, from being locked up while the key is left in the building.

[0003] 2. Description of Related Art

[0004] As shown in FIG. 7, a conventional padlock used for a warehouse includes a casing <b>90</b> receiving a cylinder assemble <b>91</b> that has a rotary cylinder capable of being turned by a correct key. The rotary cylinder has an upper paw <b>92</b> contoured as half a round. Received in the casing <b>90</b> above the rotary cylinder is a cylindrical tumbler <b>93</b> that has a lower butt <b>94</b> contoured as a quarter of a round engagable with the upper paw <b>92</b>.

[0005] When the rotary cylinder is turned away from its original position by the correct key, the paw <b>92</b> will press the butt <b>94</b> and hence turn the cylindrical tumbler <b>93</b> until a pair of curved grooves <b>95</b> defined in the periphery of the tumbler <b>93</b> are aligned with a pair of movable balls <b>96</b>. The two balls <b>96</b> are then moved into the grooves <b>95</b> from curved notches <b>98</b> of a shackle <b>97</b>. Consequently, the released shackle <b>97</b> can be raised relative to the casing <b>90</b> and the padlock is opened.

[0006] In the conventional padlock, however, the butt <b>94</b> contoured as a quarter of a round allows the rotary cylinder to be turned by the correct key in an opposite direction even after the padlock has been opened. Once the rotary cylinder returns to its original position, the key can be pulled out. Yet the opened padlock without the key can be closed again simply by depressing the shackle <b>97</b>. The separation of the key from the opened padlock results in a possibility that the door of a building, especially of a warehouse, may be locked up while the key is left in the building.

SUMMARY OF THE INVENTION

[0007] The object of the present invention is to overcome the aforementioned problem and to provide a padlock in which the correct key is not allowed to be pulled out after the padlock is opened.

[0008] Other objects, advantages and novel features of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009]FIG. 1 is an exploded perspective view of a first preferred embodiment of a padlock in accordance with the present invention;

[0010]FIG. 2 is a transverse cross-sectional view showing the padlock of FIG. 1 in its closed position;

[0011]FIG. 3 is a cross-sectional view taken along lines <b>3</b>-<b>3</b> in FIG. 2;

[0012]FIG. 4 is a transverse cross-sectional view showing the padlock of FIG. 1 in its open position;

[0013]FIG. 5 is a cross-sectional view taken along lines <b>5</b>-<b>5</b> in FIG. 4;

[0014]FIG. 6 is an exploded perspective view of a second preferred embodiment of the padlock in accordance with the present invention; and

[0015]FIG. 7 is a transverse cross-sectional view of a conventional padlock used for a warehouse.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0016]FIG. 1 shows a first embodiment of a padlock in accordance with the present invention for locking the door of a building, especially a warehouse. The padlock includes a casing <b>1</b>, a cylindrical tumbler <b>2</b> and a cylinder assembly <b>3</b>.

[0017] The casing <b>1</b> has an opening <b>11</b> defined therein for receiving both the cylindrical tumbler <b>2</b> and the cylinder assembly <b>3</b>, with the assembly <b>3</b> retained in the opening <b>11</b> by means of a fastening <b>12</b>, such as in the form of a screw. The casing <b>1</b> is further formed with a movable shackle <b>13</b> that defines a pair of curved notches <b>14</b> for partially receiving a pair of opposed balls <b>15</b>, which is movable laterally in the opening The cylindrical tumbler <b>2</b>, rotatably received in the opening <b>11</b> of the casing <b>1</b>, has a periphery that defines a pair of curved grooves <b>21</b> (only one is shown) to receive the balls <b>15</b>. The tumbler <b>2</b> is further formed with a neck <b>22</b> terminating in a butt <b>23</b>, with a torsion spring <b>24</b> and a retainer ring <b>25</b> mounted around the neck <b>22</b>. The torsion spring <b>24</b> is provided for urging the tumbler <b>2</b> to turn back to its original angular position within the opening <b>11</b>, and the butt <b>23</b> is contoured as a sector less than half a round, preferably as a sector about a quart of a round which has an arched edge projecting from the periphery of the neck <b>22</b>.

[0018] Furthermore, the cylindrical tumbler <b>2</b> is provided with a detent <b>26</b> extending outward axially from a bottom end of the tumbler <b>2</b>, for the purpose which is to be described hereinafter. In the illustrated embodiment, the detent <b>26</b> is configured as a pin partially fitted in a hole <b>27</b> defined in the bottom end of the tumbler <b>2</b>.

[0019] The cylinder assembly <b>3</b> is also received in the opening <b>11</b> of the casing <b>1</b> and is retained therein by the fastening <b>12</b>, as mentioned above. This assembly <b>3</b> has a rotary cylinder <b>31</b> adapted to be turned by a correct key <b>35</b>, and the cylinder <b>31</b> is formed with a paw <b>34</b>, contoured as half a round, that extends more deeply into the casing <b>11</b> to abut the butt <b>23</b> of the cylindrical tumbler <b>2</b>.

[0020] Preferably, the rotary cylinder <b>31</b> is covered with a hard guard <b>33</b> which is in turn covered with a protective cover <b>32</b>. The guard <b>33</b> may be made of any heat-treated metal having a hardness sufficient to protect the rotary cylinder <b>31</b> from illegal destruction with a drilling tool. The guard <b>33</b> should be rotatable synchronously with the rotary cylinder <b>31</b> and be formed with a slot <b>331</b> allowing the correct key <b>35</b> to be inserted into the cylinder <b>3</b>.

[0021] It is more preferable that the guard <b>33</b> has a recess <b>332</b> defined in a lower face thereof in a location adjacent to the slot <b>331</b> to lead to an easy insertion of the key <b>35</b>. In the preferred embodiment, accompanying the formation of the off-centered recess <b>332</b> in the lower face, the guard <b>33</b> may be formed in its upper face with a protrusion <b>333</b> shaped to mate with a pit <b>331</b> of the cylinder <b>31</b>, thereby ensuring the synchronous rotation of the guard <b>33</b> with the rotary cylinder <b>31</b>.

[0022]FIG. 2 shows the first embodiment of the padlock being in a closed position. Now the cylindrical tumbler <b>2</b> and the cylinder assembly <b>3</b> are retained sequentially in the opening <b>11</b> of the casing <b>1</b> by the fastening <b>12</b>. And the balls <b>15</b> are laterally moved into the curved notches <b>14</b>, thus remaining the shackle <b>13</b> in its depressed position. At this time, the paw <b>34</b> of the rotary cylinder <b>31</b> abuts the butt <b>23</b> of the cylindrical tumbler <b>2</b> in a manner as shown in FIG. 3, and the detent <b>26</b> formed on the tumbler is positioned in an angular space between the paw <b>34</b> and the butt <b>23</b>.

[0023]FIG. 4 shows the first embodiment of the padlock being in a open position after the rotary cylinder <b>31</b> is turned away from its original position by the key <b>35</b>. During the turning process of the cylinder <b>31</b>, the paw <b>34</b> pushes the butter end <b>23</b> and hence turns the tumbler <b>2</b> to such a position that the curved grooves <b>21</b> of the tumbler <b>2</b> are aligned with the respective balls <b>15</b>, which are then immediately moved from the curved notches <b>14</b> into the grooves <b>21</b>. As a result, the released shackle <b>13</b> is raised by a compressed spring (not numbered), and so the padlock is opened.

[0024] The key <b>35</b> can never be pull out directly from the cylinder <b>31</b> which has been turned away from its original position, due to the mechanism involving the rollers in the cylinder <b>31</b> as well known in the art. The key <b>35</b> can be pull out only when the cylinder <b>31</b> is turned back to its original position. If the cylinder <b>31</b> is intended to be turned back with the key <b>35</b>, the paw <b>34</b> would be turned, for example, in a counterclockwise direction as view in FIG. 5. The paw <b>34</b> then tends to push the detent <b>26</b> and hence to turn the tumbler <b>2</b>, which, however, is motionless now because the balls <b>15</b> in its curved grooves <b>21</b> is not allowed to return to the notches <b>14</b> in the raised shackle <b>13</b>. In one word, the arrangement of the detent <b>26</b> prevents the key <b>35</b> from being turned and pulled out until the padlock is closed again, i.e., the shackle <b>13</b> is depressed.

[0025]FIG. 6 shows a second embodiment of the padlock in accordance with the present invention. In this embodiment, the cylindrical tumbler <b>2</b> is provided with a detent <b>26</b> extending outward radially from the butt <b>23</b>. This detent <b>26</b> is positioned in the angular space between the paw <b>34</b> and the butt <b>23</b>, thus preventing the key <b>35</b> from being pulled out after the padlock is opened.

[0026] From the foregoing, it is clear that the invention has an advantage of preventing the correct key from being pulled out as soon as the padlock is opened. With the inventive padlock, the door of the warehouse will not be locked up while the key is left in the room or the building. Furthermore, the protective cover and the hard guard may effectively protect the inventive padlock from illegal destruction.

[0027] It is to be understood that the present invention can be implemented in many other form without departing the spirit and principle thereof and that the disclosure in the preferred embodiments is illustrative only, but not a limitation thereto. The prevent invention is intended to cover all the modifications and verifications which falls into the scope of the invention defined in the appending claims.