# US 5,939,646 A · Sheet media weight detector

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- Number: US 5,939,646 A
- Document ID: US5939646A
- Status: Granted
- Kind: A
- Application number: 08/806,993
- Filed: 1997-02-26
- Granted: 1999-08-17
- Earliest claimed: 1997-02-26
- Assignees: Hewlett-Packard Company
- Inventors: Pat Fowler
- Web page: https://patentgrep.com/patent/US5939646A

## CPC

- G03G 15/5029: {by measuring the copy material characteristics, e.g. weight, thickness}
- G03G 2215/00742: of sheet weight
- G03G: ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY

## Abstract

A method and device that automatically measures and monitors the pick/feed motor torque as an indicator of paper weight, and controlling pertinent printer operations according to the measured torque. The method of the invention includes the steps of measuring the torque output of the motor during a pick/feed operation and controlling at least one printer operation according to the torque measurement. Preferably, the torque is measured by measuring the electrical current drawn by the pick/feed motor during the pick/feed operation.

## Claims

### Claim 1

A method for detecting the weight of sheet media in printers, copiers and other image forming machines, comprising:
driving a pick/feed mechanism with an electric motor;
measuring torque output of the motor during a pick/feed operation;
establishing a relationship between the torque output of the motor during the pick/feed operation and the weight of the sheet media; and
controlling at least one printer operation according to the measured torque and the corresponding weight of the sheet media.

### Claim 2 (depends on 1)

A method according to claim 1, wherein the step of measuring torque comprises measuring electrical current drawn by the motor during the pick/feed operation and further comprising establishing a relationship between the electrical current drawn by the motor during the pick/feed operation and the weight of the sheet media.

### Claim 3 (depends on 1)

A method according to claim 1, further comprising transmitting the torque measurement to a print controller.

### Claim 4 (depends on 2)

A method according to claim 2, further comprising transmitting the current measurement to a print controller.

### Claim 5 (depends on 1)

A method according to claim 1, wherein the image forming machine is an electrophotographic image forming machine and further comprising controlling fusing temperature according to the torque measurement and the corresponding weight of the sheet media.

### Claim 6 (depends on 1)

A method according to claim 1, wherein the image forming machine is an electrophotographic image forming machine and further comprising controlling fusing pressure according to the torque measurement and the corresponding weight of the sheet media.

### Claim 7 (depends on 1)

A method according to claim 1, wherein the image forming machine is an electrophotographic image forming machine and further comprising controlling transfer current according to the torque measurement and the corresponding weight of the sheet media.

### Claim 8 (depends on 1)

A method according to claim 1, wherein the image forming machine is an electrophotographic image forming machine and further comprising controlling a rate at which the sheet media is advanced through the machine according to the torque measurement and the corresponding weight of the sheet media.

### Claim 9

A method for detecting the weight of sheet media in printers, copiers and other image forming machines, comprising:
driving a feed roller with an electric motor;
causing the feed roller to apply a separation force to a top sheet in a stack of sheet media;
defining a relationship between the weight of each sheet of sheet media and the separation force applied to the top sheet;
measuring the separation force; and
controlling at least one printer operation according to the measured separation force and the corresponding weight of the sheet media.

### Claim 10 (depends on 9)

A method according to claim 9, wherein:
the step of causing the feed roller to apply a separation force comprises causing the motor to apply a torque to the feed roller;
the step of measuring the separation force comprises measuring the torque applied to the feed roller; and
the method further comprises defining a relationship between the torque applied to the feed roller and the weight of the sheet media.

### Claim 11 (depends on 10)

A method according to claim 10, wherein the step of measuring the torque applied to the feed roller comprises measuring electrical current drawn by the motor during the application of the torque to the feed roller and the method further comprises defining a relationship between the electrical current drawn by the motor during the application of the torque to the feed roller and the weight of the sheet media.