Wrench with a fixed maximum operational torque

A wrench comprising:

• a rod comprising a driving portion on an end thereof for engaging with a fastener;
• a control member securely mounted to the rod to turn therewith;
• a casing for rotatably accommodating the control member, wherein the casing includes a first compartment for rotatably receiving the control member, a second compartment communicated with the first compartment, and a third compartment communicated with the second compartment, wherein the casing comprises a recessed portion surrounding the first compartment, the second compartment, and the third compartment;
• retaining means mounted in the casing and including an end operably connected to the control member, wherein the retaining means includes a pressing member and an elastic element for biasing the pressing member to press against the control member, with the pressing member being slidably received in the second compartment, and with the elastic element being received in the third compartment;
• and
• a lid mounted in the recessed portion for closing the first compartment, the second compartment, and the third compartment;
• wherein when a rotational force applied to the casing is smaller than an engaging force between the control member and the end of the retaining means, the control member and the rod are turned to thereby turn the fastener;
• and
• wherein when a rotational force applied to the casing is greater than the engaging force between the control member and the end of the retaining means, the casing slides while the control member and the rod are not turned.

A wrench comprising:

• a rod comprising a driving portion on an end thereof for engaging with a fastener;
• a control member securely mounted to the rod to turn therewith;
• a casing for rotatably accommodating the control member, wherein the casing includes a first compartment for rotatably receiving the control member, a second compartment communicated with the first compartment, and a third compartment communicated with the second compartment;
• retaining means mounted in the casing and including an end operably connected to the control member, wherein the retaining means includes a pressing member and an elastic element for biasing the pressing member to press against the control member, with the pressing member being slidably received in the second compartment, and with the elastic element being received in the third compartment;
• a lid for enclosing the first compartment, the second compartment, and the third compartment of the casing;
• wherein the lid comprises a hole through which the rod extends;
• wherein when a rotational force applied to the casing is smaller than an engaging force between the control member and the end of the retaining means, the control member and the rod are turned to thereby turn the fastener;
• and
• wherein when a rotational force applied to the casing is greater than the engaging force between the control member and the end of the retaining means, the casing slides while the control member and the rod are not turned.