# US 8,770,503 B2 · Staged paper shredder

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- Number: US 8,770,503 B2
- Document ID: US8770503B2
- Status: Granted
- Kind: B2
- Application number: 13/012,202
- Filed: 2011-01-24
- Published: 2012-01-12
- Granted: 2014-07-08
- Earliest claimed: 2010-07-08
- Assignees: Shred-It International ULC
- Applicants: Richard Weidman; Gary Klowak; Ann Bisson
- Inventors: Richard Weidman; Gary Klowak; Douglas Bisson
- Web page: https://patentgrep.com/patent/US8770503B2

## CPC

- B02C 18/0007: {specially adapted for disintegrating documents}
- B02C 18/142: {with two or more inter-engaging rotatable cutter assemblies}
- B02C 2018/147: {of the plural stage type}
- B02C: CRUSHING, PULVERISING, OR DISINTEGRATING IN GENERAL; MILLING GRAIN ({household tools and machines for pulverising foodstuffs, e.g. coffee and spice mills A47J42/00; pharmaceutical mortars A61J3/02; mechanical processing of refuse and garbage B03B9/06; dressing mould materials by grinding B22C5/04}; obtaining metallic powder by crushing, grinding or milling B22F9/04; {recovery of plastics by disintegrating B29B17/00; crushing raw materials in starch making C08B30/02; beaters for papermaking D21D1/02; crushing devices specially for transport in mines E21F13/002; slag crushing devices F23J1/00; fuel milling devices in combustion apparatus F23K1/00; household devices for crushing coal F24B15/02; ice disintegrating devices F25C5/02})

## Abstract

This invention relates to a paper shredder. A first stage shredder accepts paper from a hopper. The first stage shredder includes two knife shaft assemblies with a plurality of sequentially oriented knives and spacers on hexagonal shafts. A second stage shredder accepts the output of the first stage shredder. The second stage shredder has two counter rotating shafts with saw tooth disk knives and separating spacers and cuts the paper finer than that of the first stage shredder. A third stage shredder may be connected to the second stage shredder providing even further paper size reduction.

## Claims

### Claim 1

A paper shredder, said shredder comprising:
a hopper for receiving paper;
a first stage shredder comprising offset blades driven by a first stage power drive and first speed feedback components;
a second stage shredder operatively connected to said first stage shredder, said second stage shredder comprising offset blades driven by a second stage power drive and second speed feedback components;
a third stage shredder operatively connected to said second stage shredder, said third stage shredder comprising offset blades driven by a third stage power drive and third speed feedback components;
wherein the offset blades of the second stage shredder are smaller than the offset blades of the first stage shredder and larger than the offset blades of the third stage shredder; and
a program logic controller adapted to control said paper shredder, wherein the program logic controller is configured to:
automatically detect if at least one of the first, second and third stage shredders is slowing based on the first, second and third speed feedback components and cause the detected stage shredder to operate in reverse for a predetermined time and then return to forward operation;
simultaneously stop any of the first or second stage shredders that precede the detected stage shredder while the detected stage shredder is reversing and then automatically start the stopped stage shredders once the detected shredder commences forward operation such that at least one of the first, second and third stage shredders remain in operation while at least one of the first, second and third stage shredders is stopped, and
wherein the program logic controller is configured to hydraulically slidably remove at least one of said second or third stage shredders when at least one of said second or third stage shredders are not required based on user input.

### Claim 2 (depends on 1)

The paper shredder of claim 1 wherein said program logic controller is operatively connected to optical sensors for each stage, said optical sensors informing said program logic controller if a stage is receiving an overload of paper so that the preceding stages may be shut down until the stage receiving the overload can deal with the flow, wherein once the overload is cleared the program logic controller restarts the preceding shredders.