Portable Weighing-Scale (John W. Hunter, No. 570,553)
The patent by John W. Hunter of Tabor, Iowa, describes a Portable Weighing-Scale intended for retail dealers. The objective is to provide a simple, cheap, and reliable hand-held scale and scoop combined for measuring articles like flour, sugar, lard, and butter.
Invention and Mechanism
The scale is a spring-balance assembly housed within a handle, featuring an integrated lock for scooping and friction-reducing components for accuracy.
1. Frame and Weighing System
- Handle (1): A hollow cylindrical outer casing that the user grips. It has a viewing slot (19) and a reading pointer (22).
- Sliding Tube (5): A tube of slightly smaller diameter that slides vertically inside the handle (1). The graduated scale (18) is marked on the outside of this tube, visible through the handle’s slot (19).
- Spring Balance:
- A rigid central shaft (9) is fixed to the handle’s lower end.
- A spiral spring (14) encircles the shaft (9).
- The bottom of the sliding tube (5) is connected to a socket (16), to which the lower end of the spring (14) is secured.
- Function: When weight is applied to the scoop, the sliding tube (5) and its socket (16) are pulled down, stretching the spring (14). The weight is read where the graduated scale (18) aligns with the pointer (22).
2. Friction Reduction (Accuracy)
- Antifriction Rollers (7): A series of rollers are journaled in recesses (6) at the upper end of the handle (1), forming a bearing for the tube (5).
- Radial Rollers (): A series of rollers is mounted in the socket (16), allowing the socket to slide freely up and down on the central shaft (9) with “little or no friction.”
3. Scoop/Scale-Pan and Accessories
- Removable Scoop (24): The scoop is provided with a cylindrical handle (25) that inserts into the open upper end of the sliding tube (5).
- Locking Scoop: Longitudinal slits (28) in the scoop handle allow the solid portion to spring inward for insertion, and then spring outwardly once inserted to hold the scoop in place within the tube (5).
- Zero Adjustment: An adjustable circular nut (12) is mounted on the screw-threaded upper end of the central shaft (9). The upper end of the spring (14) is secured to this nut, allowing the operator to adjust the zero-point of the scale.
4. Scooping Lock (Clutch)
- Spring-Lever (3): A lever secured near the top of the handle (1), positioned for the user’s thumb.
- Toe (23): An inwardly projecting toe on the lever (3).
- Flange (17): A circumferential projecting flange on the tube socket (16).
- Operation: When the scale is used as a scoop, the user presses the thumb-lever (3). The toe (23) engages the flange (17), locking the sliding tube (5) in place (preventing it from moving downward). This allows the scale to be used like a rigid scoop to gather material. Releasing the lever (3) frees the tube (5) for weighing.
Historical Significance and the Inventor
John W. Hunter’s 1896 patent is a great example of an inventor merging two common tasks—scooping and weighing—into a single, specialized retail tool, focusing on convenience and accuracy.
- Retail Efficiency: In the late 19th century, many general stores and grocers sold bulk goods (sugar, flour, tea, coffee) by weight. Hunter’s invention offered a tool that sped up the retail process by allowing the merchant to scoop and weigh with the same implement in one continuous motion, improving efficiency and customer service.
- Friction Reduction: The detailed inclusion of multiple sets of antifriction rollers (7 and ) shows a dedicated effort to overcome the limitations of common spring scales, where internal friction often compromised the accuracy of the reading.
- The Inventor (John W. Hunter): Hunter, residing in Tabor, Iowa, contributed to the wave of specialized tools designed for retail and commerce in a time of growing domestic consumption.
Core Concepts Utilized Today
Hunter’s portable scale employs principles that are still foundational in precision measurement and convertible tools.
- Combined Scoop-Weighing Tools: The concept of a single device performing both material handling (scooping) and measurement (weighing) is seen in modern digital kitchen scales with integrated bowls and specialized measuring scoops that have digital readouts built into the handle .
- Mechanical Friction Reduction: The use of antifriction rollers on key sliding contacts is a core design principle in high-precision mechanical instruments, such as dial calipers, indicators, and medical scales, where minimizing internal friction is essential for accurate measurement and repeatability.
- Locking/Clutch Mechanisms: The thumb-lever lock (3) that rigidizes the tool for handling and releases it for measurement is a common clutch mechanism found in convertible tools and measuring devices, such as:
- Hand brake/lock levers on utility carts.
- Plunger locks on certain types of adjustable measuring rods.
- Telescoping/Spring-Retention Fastening: The scoop’s handle using longitudinal slits (28) to hold it in the tube (5) through outward spring pressure is the principle of snap-fit or spring-retention used widely in consumer electronics, automotive trim, and quick-change tool handles.
