why doesn't my child object react to the Y to the constraint?

after spending two days tripping over myself, i’ve attached this C# script onto my child obj.
parent is a rigidbody, and this child moves with the parent. i do have a need to constrain the Y axis to “10”;
but the script does not seem to respond to the yMax.
does anyone have any ideas on how to ensure that the constraint is being complied with by the child?

using UnityEngine;
using System.Collections;

public class mover: MonoBehaviour {
public float movementSpeed = 5;
public float xMin, xMax, yMin, yMax, zMin, zMax;
public Rigidbody rb;

// Use this for initialization
void Start() {
//rb = GetComponent.Find<“Parent”>();
}

// Update is called once per frame
void Update () {
if(Input.GetKey(“t”))
transform.Translate (Vector3.up * movementSpeed * Time.deltaTime);
//max
transform.position = new Vector3 (
rb.position.x, Mathf.Clamp (transform.position.y, yMin, yMax), rb.position.z);

}
}

Please use code tags!