GB1563694A - Shredding machines - Google Patents

Description

(54) IMPROVEMENTS IN OR RELATING TO SHREDDING MACHINES (71) We, W. & S. ENGINEERING (MILDENHALL) LIMITED, a British Company, of 9 Chiswick Avenue, The Industrial Estate, Mildenhall, Suffolk, IP28 7AY, do hereby declare the invention for which we ray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to shredding machines.

Shredding machines are generally used to destroy confidential papers or to create packaging material from paper, cellulose, polypropylene, foam and similar material.

Shredding machines generally comprise a housing supporting a cutting head, a tray for feeding material to be shredded to the cutting head, and an output station at which the shredded material is discharged. The cutting head comprises two juxtaposed rotatable cutting elements each of which has a rotatable shaft, a plurality of circular cutter blades mounted for rotation with the shaft, and a plurality of non-rotatable separator members disposed intermediate successive blades or groups of blades. In all known shredding machines the cutter blades protrude radially beyond the separator members in the vicinity of the output station. A problem which occurs in conventional shredding machines, particularly when shredding cellulose or polythene, is clogging due to the shredded material being trapped between the cutter blades and the separators.

We have found that if each separator is made with a part circular portion which protrudes radially a small distance beyond the periphery of the cutter blades in the vicinity of the output station of the machine, the problem of clogging is greatly reduced.

According to one aspect of the present invention there is provided a cutting element for a shredding machine comprising a rotatable shaft, a plurality of circular cutting blades mounted for rotation with the shaft, and a plurality of non-rotatable separator members disposed intermediate successive cutter blades or groups of cutter blades, each separator member having a part circular portion which is disposed coaxially with the blades, the diameter of each part circular portion being slightly greater than the diameter of each blade, the arrangement being such that in use the cutting element is disposed in juxtaposition with a similar cutting element with the part circular portions of each separator member being disposed adjacent the position at which shredded material is fed from between the two cutting elements.

Each cutter blade may be made from steel, e.g. material 080 M 40.

Each separator may be made from mild steel.

A spacer ring may be mounted coaxially and concentrically with each separator, each spacer ring having a thickness slightly greater than the thickness of each separator, and each cutter blade may be annular and a loose fit on the shaft, the cutter blades being locked for rotation with the shaft by means of lock nuts which engage opposite ends of the shaft and urge the cutter blades into contact with the spacer rings leaving the separator members free therebetween.

The amount by which each part circular portion of each separator member protrudes beyond the periphery of each cutter blade depends upon the material which is to be shredded. We have found that this amount is typically in the range l/32 in to l/l6in.

According to another aspect of the present invention there is provided a shredding machine comprising a housing, a pair of cutting elements according to the one aspect of the invention, the two cutting elements being so disposed that a peripheral portion of each blade or group of blades of one element is interleaved between a peripheral portion of two blades or groups of blades of the other element, and drive means for rotating the shafts of the cutter elements.

The drive means may comprise two motors, one for each shaft. The motors may be electric motors each provided with its own reduction gear, the motors being arranged to operate in synchronism.

The invention will be described now by way of example only with particular reference to the accompanying drawings. In the drawings: Figure 1 is a side elevation of a shredding mchine in accordance with the present invention; Figure 2 is a front elevation of the shredding machine.

Figure 3 is an end elevation of the shredding machine; Figure 4 is a top plan view of the shredding machine; Figure 5 is an end elevation of the cutting head of the shredding machine; Figure 6 is a section on the line 6-6 of Figure 5; Figure 7 is a top plan view of the cutting head, and Figure 8 shows the drive motors for the cutting head.

Referring to the drawings the shredding machine has a housing which comprises two spaced rectangular side frames 10, 11 between which extend a front wall 12, a rear wall 13 and a top 14. The front wall 12 has a laterally extending slot 16 which defines an inlet through which material to be shredded can be fed into the machine. The two side frames 10, 11 carry two forwardly extending support members 18, 19 which suppoert a horizontally disposed tray 22. The tray 22 is arranged with its rear edge adjacent the lower will of the slot 16. The upper surface of the tray 22 provides a surface along which material to be shredded is fed into the machine.

The upper edge of the rear wall 13 of the housing is spaced from the top 14 of the housing to define an outlet opening 24 through which shredded material is discharged from the machine. The outlet opening 24 accommodates an inclined chute 25 along which the shredded material is passed.

A cutting head 30, which extends between the two side frames 10, 11 is disposed adjacent the slot 16. Referring to Figures 5-7 the cutting head 30 comprises two cutting elements 32, 33. Each cutting element comprises a rotatable shaft 35, 36 the opposite ends of which are mounted in bearings carried by the inner walls 38, 39 of the side frames 10, 11. One end 41 of the shaft 35 protrudes outwardly beyond the wall 38, the protruding portion of the shaft 35 carrying a pulley 42. The opposite end 43 of the shaft 36 protrudes outwardly beyond the wall 39, the protruding portion of the shaft 36 carrying a pulley 45.

Each shaft 35, 36 carries a plurality of annular cutting blades 48 which are a loose fit on the respective shaft. Each cutting blade is made from steel, e.g. material 080 M 40.

A plurality of separator members 50 are arranged on each shaft 35, 36 each separator member being disposed intermediate two successive cutter blades. Each separator member 50 has a part circular portion 52 which is disposed coaxially with the shaft and which has a flat portion at 54, and a forwarding extending trapezoidal portion 53. The trapezoidal portion 53 of each separator member 50 has a pair of apertures 55, 56. The apertures of the separators 50 of the upper cutting element form two sets of aligned apertures which accommodate two laterally extending rods 58, 59, which are fixed at their ends to the walls 38, 39.

Similarly the apertures of the separator members of the lower cutting element are aligned and accommodate two laterally extending rods which are fixed at their ends to the walls 38, 39. The part circular portion of each separator member 50 has a circular aperture 62, the diameter of which is greater than the diameter of the shafts 35, 36. A spacer ring 63 is disposed concentrically within each aperture 62 around the respective shaft 35, 36. The thickness of each spacer ring 63 is slightly greater than the thickness of each separator member 50.

Each shaft 35, 36 carries locking nuts 65 which threadably engage each end of the respective shafts. The locking nuts 65 lock up the cutting blades with the spacer rings 63 leaving the separator members free between the blades since the spacer rings 63 are thicker than the separator members 50.

The two cutting elements 32, 33 are so mounted that a peripheral portion of each cutting blade 48 of one element is interleaved between a peripheral portion of two successive blades of the other element. The separator members of one cutting element are arranged in mirror image manner relative to those of the other element so that the trapezoidal portions 53 of the separator members 50 define a space which converges from the tray 22 towards the juxtaposed portions of the cutting blades 48. The flat portion 54 on the separator members of the cutting elements are contained in two horizontal planes, one above and one below the juxtaposed portions of the cutting elements 32. 33.

Drive for rotating the shafts 35, 36 is provided by two synchronised motors 67, 68 which are located at the bottom of the housing. The motor 67 is arranged to drive the shaft 35 via a belt 69 which extends around the pulley 42, and the motor 68 is arranged to drive the shaft 36 via a belt 70 which extends around the pulley 45. Each motor has its own reduction gear.

It will be noted that the part circular portions of the separate members are located on the outlet side of the cutting elements 32, 33. The circular portions protrude radially slightly beyond the periphery of the cutting blades 48.

In use material to be shredded is fed along the tray 22 to the cutting head 30. As the material passes between the cutting elements of the cutting head 30 it is cut intq elongate shredded portions and is then discharged through the outlet opening 24 along the inclined chute 25. We have found that by making the separators protrude radially beyond the cutting blades in the vicinity 66 of the outlet side of the cutting head reduces the likelihood of the material becoming clogged between the cutting blades.

The amount by which each part circular portion of each separator member protrudes beyond the peripheral of each cutter blade depends upon the material which is to be shredded. Generally this amount is in the range l/32in to l/16in.

The machine can be used to shred material such as paper, cellulose, foam or polythene, and is particularly suitable for the last three materials as these are prone to clogging in conventional shredding machmes.

It will be noted that a separate motor is provided for driving each shaft of the cutting elements. This arrangement reduces the complexity of the gearing required for the machine.

WHAT WE CLAIM IS: 1. A cutting element for a shredding machine comprising a rotatable shaft, a plurality of circular cutting blades mounted for rotation with the shaft, and a plurality of non-rotatable separator members disposed intermediate successive cutter blades or groups of cutter blades, each separator member having a part circular portion which is disposed coaxially with the blades, the diameter of each part circular portion being slightly greater than the diameter of each blade, the arrangement being such that in use the cutting element is disposed in juxtaposition with a similar cutting element with the part circular portions of each separator member being disposed adjacent the position at which shredded material is fed from between the cutting elements.

2. A cutting element as claimed in claim 1 wherein each cutter blade is made from steel.

3. A cutting element as claimed in claim 1 or claim 2 wherein each separator is made from mild steel.

4. A cutting element as claimed in any preceding claim wherein a spacer ring is mounted coaxially and concentrically with each separator, and each cutter blade is annular and a loose fit on the shaft, the cutter blades being locked for rotation with the shaft by means of lock nuts which engage opposite ends of the shaft and urge the cutter blades into contact with the spacer rings leaving the separator members free therebetween.

5. A cutting element as claimed in any preceding claim wherein each separator member has a tapering portion diametrically opposite to said part circular portion.

6. A shredding machine comprising a housing, a pair of cutting elements as claimed in any one of claims 1 to 5, the two cutting elements being so disposed that a peripheral portion of each blade or group of blades of one element is interleaved between a peripheral portion of two blades or groups of blades of the other element, and drive means for rotating the shafts of the cutter elements.

7. A shredding machine as claimed in claim 6 wherein the drive means comprises two motors, one for each shaft.

8. A shredding machine as claimed in claim 7 wherein the motors are electric motors each provided with its own reduction gear, the motors being arranged to operate in synchronism.

9. A cutting element as claimed in claim 1 and substantially as hereinbefore described with reference to and as shown in the accompanying drawings.

10. A shredding machine as claimed in claim 6 and substantially as hereinbefore described with reference to and as shown in the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (10)

**WARNING** start of CLMS field may overlap end of DESC **. around the pulley 42, and the motor 68 is arranged to drive the shaft 36 via a belt 70 which extends around the pulley 45. Each motor has its own reduction gear. It will be noted that the part circular portions of the separate members are located on the outlet side of the cutting elements 32, 33. The circular portions protrude radially slightly beyond the periphery of the cutting blades 48. In use material to be shredded is fed along the tray 22 to the cutting head 30. As the material passes between the cutting elements of the cutting head 30 it is cut intq elongate shredded portions and is then discharged through the outlet opening 24 along the inclined chute 25. We have found that by making the separators protrude radially beyond the cutting blades in the vicinity 66 of the outlet side of the cutting head reduces the likelihood of the material becoming clogged between the cutting blades. The amount by which each part circular portion of each separator member protrudes beyond the peripheral of each cutter blade depends upon the material which is to be shredded. Generally this amount is in the range l/32in to l/16in. The machine can be used to shred material such as paper, cellulose, foam or polythene, and is particularly suitable for the last three materials as these are prone to clogging in conventional shredding machmes. It will be noted that a separate motor is provided for driving each shaft of the cutting elements. This arrangement reduces the complexity of the gearing required for the machine. WHAT WE CLAIM IS:

1. A cutting element for a shredding machine comprising a rotatable shaft, a plurality of circular cutting blades mounted for rotation with the shaft, and a plurality of non-rotatable separator members disposed intermediate successive cutter blades or groups of cutter blades, each separator member having a part circular portion which is disposed coaxially with the blades, the diameter of each part circular portion being slightly greater than the diameter of each blade, the arrangement being such that in use the cutting element is disposed in juxtaposition with a similar cutting element with the part circular portions of each separator member being disposed adjacent the position at which shredded material is fed from between the cutting elements.

2. A cutting element as claimed in claim 1 wherein each cutter blade is made from steel.

3. A cutting element as claimed in claim 1 or claim 2 wherein each separator is made from mild steel.

4. A cutting element as claimed in any preceding claim wherein a spacer ring is mounted coaxially and concentrically with each separator, and each cutter blade is annular and a loose fit on the shaft, the cutter blades being locked for rotation with the shaft by means of lock nuts which engage opposite ends of the shaft and urge the cutter blades into contact with the spacer rings leaving the separator members free therebetween.

5. A cutting element as claimed in any preceding claim wherein each separator member has a tapering portion diametrically opposite to said part circular portion.

6. A shredding machine comprising a housing, a pair of cutting elements as claimed in any one of claims 1 to 5, the two cutting elements being so disposed that a peripheral portion of each blade or group of blades of one element is interleaved between a peripheral portion of two blades or groups of blades of the other element, and drive means for rotating the shafts of the cutter elements.

7. A shredding machine as claimed in claim 6 wherein the drive means comprises two motors, one for each shaft.

8. A shredding machine as claimed in claim 7 wherein the motors are electric motors each provided with its own reduction gear, the motors being arranged to operate in synchronism.

9. A cutting element as claimed in claim 1 and substantially as hereinbefore described with reference to and as shown in the accompanying drawings.

10. A shredding machine as claimed in claim 6 and substantially as hereinbefore described with reference to and as shown in the accompanying drawings.