Dumbbell with adjustable weight

1. A dumbbell comprising:

a grip rod having two connection segments formed respectively on two ends of the grip rod, and each of the two connection segments having multiple baffles formed on the respective connection segment at spaced intervals to define multiple connection recesses between the multiple baffles; and

multiple counterweight blocks engaged respectively with the multiple connection recesses in the two connection segments, and each of the multiple counterweight blocks comprising a body having an engaging channel extending from a center of the body to an edge of the body, the engaging channel of the body of each of the multiple counterweight blocks being expandable, and having an opening and two protrusions formed respectively on two inner sides of the body at a position adjacent to the center of the body to form an engaging space at an inner end of the engaging channel for being mounted around one of the two connection segments at a position corresponding to a corresponding one of the multiple connection recesses, and a buckle having a first end connected pivotally to the body and at a position on one of two sides of the engaging channel, and a second end connected detachably with the body at a position on the other one of the two sides of the engaging channel.

2. The dumbbell as claimed in claim 1 , wherein the engaging channel of the body of each of the multiple counterweight blocks is selectively expandable.

3. The dumbbell as claimed in claim 2 , wherein the body of each of the multiple counterweight blocks comprises two halves, each half having a specific weight, and a connection section connected between the two halves; the opening of the engaging channel of each of the multiple counterweight blocks is opposite the connection section of the respective counterweight block to enable the engaging channel to be expandable from the connection section; and the first end of the buckle of each of the multiple counterweight blocks is connected pivotally to one of the halves of the body of the respective counterweight block at a position adjacent to the opening of the engaging channel of the respective counterweight block, and the second end of the buckle of the respective counterweight block is connected detachably with the other half of the body of the respective counterweight block at a position adjacent to the opening of the engaging channel of the respective counterweight block.

4. The dumbbell as claimed in claim 3 , wherein the body of each of the multiple counterweight blocks further has a pivotal portion and a hook portion formed respectively on the two halves of the body and respectively at the two sides of the engaging channel; and the first end of the buckle of each of the multiple counterweight blocks is connected pivotally to the pivotal portion of the body of the respective counterweight block with a pivotal pin, and the second end of the buckle of the respective counterweight block has an engaging portion selectively engaged with the hook portion on the body of the respective counterweight block to keep the engaging channel from expanding.

5. The dumbbell as claimed in claim 3 , wherein each half of the body of each of the multiple counterweight blocks is hollow and has an inlet formed in a side of the respective half to allow filling objects to be filled within the respective half via the inlet and to make the respective half have a specific weight, a cap is attached to the inlet to close the inlet of each of the two halves.

6. The dumbbell as claimed in claim 1 , wherein the body of each of the multiple counterweight blocks comprises two halves, each half having a specific weight, and a connection section connected between the two halves; the opening of the engaging channel of each of the multiple counterweight blocks is opposite the connection section of the respective counterweight block to enable the engaging channel to be expandable from the connection section; and the first end of the buckle of each of the multiple counterweight blocks is connected pivotally to one of the halves of the body of the respective counterweight block at a position adjacent to the opening of the engaging channel of the respective counterweight block, and the second end of the buckle of the respective counterweight block is connected detachably with the other half of the body of the respective counterweight block at a position adjacent to the opening of the engaging channel of the respective counterweight block.

7. The dumbbell as claimed in claim 6 , wherein the body of each of the multiple counterweight blocks further has a pivotal portion and a hook portion formed respectively on the two halves of the body and respectively at the two sides of the engaging channel; and the first end of the buckle of each of the multiple counterweight blocks is connected pivotally to the pivotal portion of the body of the respective counterweight block with a pivotal pin, and the second end of the buckle of the respective counterweight block has an engaging portion selectively engaged with the hook portion on the body of the respective counterweight block to keep the engaging channel from expanding.

8. The dumbbell as claimed in claim 6 , wherein each half of the body of each of the multiple counterweight blocks is hollow and has an inlet formed in a side of the respective half to allow filling objects to be filled within the respective half via the inlet and to make the respective half have a specific weight, a cap is attached to the inlet to close the inlet of each of the two halves.

9. The dumbbell as claimed in claim 1 , wherein the two connection segments are cuboid rods.

10. The dumbbell as claimed in claim 1 , wherein the body of each of the multiple counterweight blocks is made of blow molding.