Question

A plant pruner (cutter) with two studs P and Q are shown on the left in open and closed positions. Which options(s) will allow the pruner to return to its open position?

• A. Fig A
• B. Fig B
• C. Fig C
• D. Fig D

Hint:

Differentiate between compression springs (visible gaps between coils or scroll layers) and tension springs (coils touching tightly). Mechanisms requiring separation always rely on compression or torsion elements.

Answer 1

The Correct Option is A

Step 1: Understanding the Question:
We are examining the mechanical handle assembly of a garden pruner equipped with two mounting studs, P and Q. When a user squeezes the handles closed, studs P and Q move closer together. We must identify which spring designs can be mounted on these studs to automatically push the handles apart upon release.

Step 2: Key Formula or Approach:
To serve as an automatic opening return mechanism:

• The spring must possess end geometry compatible with sliding over or hooking onto studs P and Q.

• The decrease in distance between P and Q during handle closure must store mechanical energy by compressing or winding the spring element.

• The stored energy must generate a repulsive outward force along the axis connecting P and Q.


Step 3: Detailed Explanation:

• Let us evaluate

Option A:
- Depicts a traditional volute spring formed from a spirally rolled strip of flat spring steel.
- The open circular openings at the top and bottom of the scroll fit directly onto studs P and Q.
- As the handles close, the steel coils slide inside one another, resisting compression and generating a smooth outward force. This is the industry-standard spring for heavy-duty secateurs. Therefore, Option A is fully correct.

• Let us evaluate

Option B:
- Depicts a wire-formed double-torsion spring terminating in two circular mounting eyes.
- The eyes hook securely over studs P and Q.
- Squeezing the pruner forces the two wire legs inward, which winds the central coils tighter. Releasing the grip allows the coils to unwind, pushing the legs outward. Therefore, Option B is fully correct.

• Let us evaluate

Option C:
- Depicts a standard open-coil helical compression spring.
- The internal diameter of the wire cylinder slips over the mounting studs.
- It compresses axially as the handles close and exerts an outward pushing force to return the tool to its open state. Therefore, Option C is fully correct.

• Let us evaluate

Option D:
- Depicts a tightly wound helical extension (tension) spring.
- Extension springs are engineered with tightly touching coils that resist being pulled apart.
- When studs P and Q move closer together, an extension spring simply buckles or becomes loose. It stores zero energy during compression and cannot push the handles apart. Therefore, Option D is incorrect.


Step 4: Final Answer:
Options (A), (B), and (C) provide the correct mechanical return action.