Measuring and testing – Liquid level or depth gauge – Float
Reexamination Certificate
1999-08-27
2001-07-03
Williams, Hezron (Department: 2856)
Measuring and testing
Liquid level or depth gauge
Float
C073S308000, C073S313000, C200S08400B
Reexamination Certificate
active
06253608
ABSTRACT:
BACKGROUND OF THE INVENTION
I. Field of the Invention
The present invention relates to liquid level sensors such as are mounted though the side wall of a liquid container, referred to as side mount liquid level sensor assemblies.
II. Description of Prior Art
To monitor liquid level in a liquid container, Such as an automobile coolant overflow reservoir or windshield washer tank, it has been the practice to provide a liquid level sensor mounted to the container. The sensor includes a rod-like member or stem about which a float moves depending upon the liquid level in the container. A reed switch is held to the sensor with a magnet attached to the float moving towards and away from the switch to activate and deactivate the switch. Gaining in popularity arc so-called side mount liquid level sensor assemblies which are mounted through the sidewall of the container such that the stem is held in a horizontal disposition. The reed switch is mounted inside the stem and the float moves vertically relative to the stem to bring a magnet held by the float vertically towards or away from the reed switch.
One side mount liquid level sensor assembly which has met with good success is shown in U.S. Pat. Nos. 5,581,062 and 5,742,999, assigned to the assignee hereof, and the disclosures of both of which are incorporated herein by reference in their entireties. In the liquid level sensor assembly there-shown, a switch housing is provided having a rod-like member extending between a mount end and an enlarged disk end, with the mount end adapted to be secured through the sidewall of a liquid container to hold the rod-like member in a generally horizontally disposition in the container. A float, referred to as a buoyant member, has a slot extending vertically therethrough between an open end and an oppositely disposed closed end. The rod-like member is received in the slot of the buoyant member such that the buoyant member can move vertically as the liquid level in the container varies. The open end of the slot is sized to normally receive the rod-like member therethrough and limit structure comprising arms on the buoyant member adjacent the open end and wings formed on the adjacent sidewalls of the rod-like member cooperate to normally prevent the float from falling away from the rod-like member.
In order to mount the float to the housing, the float is oriented at a ninety degree angle relative to the rod-like member such that the slot may pass over the wings and rod from the side. Thereafter, the float is rotated ninety degrees to bring the arms into confronting relationship with the wings to thereby prevent the float from coming away from the housing. This method of assembly has provided great advantages in the manufacture of the liquid level sensor assembly.
The foregoing notwithstanding, some situations have been encountered in which the switch does not work properly. In particular, the float is free to move vertically over a range of travel between two positions, one where the closed end of the slot is against the rod-like member (with the limit structures spaced apart) and one where confronting surfaces of the limit structures engage. The float moves to and between these positions as the fluid level in the container changes, thereby causing the magnet to move towards and away from the reed switch. The range of travel in the above-described device is about ¼ inch (or 6 mm). In some instances, it has been found that the switch does not reliably change state over that range of float travel.
SUMMARY OF THE INVENTION
In commercial devices based on the aforementioned patents, the vertical depth of the slot has been about 13 mm. Thus, the ¼ inch or 6 mm range of travel available for the float is less than fifty percent (50%) of the vertical depth of the slot. Hence, more of the slot depth is available for range of travel than is currently being utilized in the above-described devices. It is therefore one objective of the present invention to increase the amount of the slot depth which is traversed over range of travel of the float relative to the rod-like member, to thereby improve reliability of the device. It is a further objective of the present invention to increase that range of travel in a manner that does not interfere with the ability to assemble the float to the stem from the side as above-described.
The present invention provides a side mount liquid level sensor that satisfies the above objectives. To this end, and in accordance with one feature of the present invention, the limit structure previously associated with the rod-like member is moved such that its contact surface is spaced vertically away from the stem whereby the arms on the float engage the wings after the float has traversed a greater vertical distance relative to the rod-like member. In this wax, the limit structure of the float and the switch housing are configured such that the float distance travel, i.e., the distance the float can traverse, is more than 50% of the slot depth, and is advantageously more than 75% thereof. Most advantageously, the range of travel is more than 90% of slot depth so as to allow the float to traverse a distance substantially equal to the slot depth. In a particular embodiment, the range of travel is about 12 mm for a 13 mm vertical depth slot, which is thus double the range of travel previously achieved as above-described. With the float distance travel thus increased, the magnet associated with the float can move towards and away from the reed switch over a greater distance to thereby obtain more reliable performance.
In accordance with another feature of the present invention, the vertical spacing between the contact surface of the wings and the rod-like member is selected to accomplish the limit function without interfering with assembly of the float to the housing. To this end, the thickness of the float arms is advantageously larger than that vertical spacing so that in the normal angular orientation of the float relative to the stem, the buoyant member will not come away from the housing and/or the rod-like member cannot pass completely out of the slot. By the same token, however, the transverse width of the arms is not more than, and is advantageously less than, the spacing between the wing contact surfaces and the rod-like members so that rotation of the float to a second, different angular orientation, such as ninety degrees from the normal angular orientation, will allow the arms to pass through the space between the contact surfaces of the wings and the rod-like member to facilitate assembly from the side as was achieved with the previous device. The spacing is further advantageously selected in relation to the diameter of the float so that in the normal angular orientation of the float, it will not pass into or become lodged in that space.
By virtue of the foregoing, there is thus provided a side mount liquid level sensor that has the advantages of the sensor shown in the aforementioned patents, but which has a substantially enhanced float travel distance and yet can be assembled from side in the same manner as shown in the aforementioned patents. These and other objects and advantages of the present invention shall be made apparent from the accompanying drawings and the description thereof.
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Loo Dennis
Standex International Corporation
Williams Hezron
Wood Herron & Evans LLP
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