GB2234690A - Paper shredder and letter opener - Google Patents

Abstract

The apparatus has the inlet for paper on the front of the machine casing. Between the collecting box and the machine casing, there is a switch, 220, Fig 2B so that if the collecting box is removed the paper shredding machine will stop operating. The machine also comprises a first shredder 208, Fig 2A, and a second shredder with an adjustable mechanism comprising a body, a rotary button 302, a gear, a hollow screw 303, a thread crown post (304, Fig 4), a screw cutter 206, a cardboard cutting knife (308 Fig 4), a hexagon head bolt (309), a hexagon nut (313), two sets of spring rings (313) and a C type snap ring (314). The cardboard cutting knife adjusting mechanism is able to adjust the distance between the cardboard cutting knife and the screw cutter automatically based on the resistance of the paper shreds by means of the action of balance of the supporting of the two sets of springs in the operation of the paper shredding machine to maintain the function of shredding the paper into strips; the driving rod inside the paper shredding machine extends out of the casing and two sets of small gears with round washers are installed on its ends, which can be used to cut the edge of an envelope by means of a scissoring force produced by the mutual close contact rotation of the two round washers 211, 212 in order to open the envelope. <IMAGE>

Description

The present invention relates to improvements in a paper shredding machine, such a machine being smaller than the conventional one and is able to be placed on a desk. The paper inlet is provided on the front of the machine casing and has safety switch. The space between the cardboard cutting knife and screw cutter can be adjusted automatically based on the load of the scraps in order to protect the cutting tool, increase the life expectancy of the shredding machine and to avoid the trouble of a letter receiver looking for a pair of scissors or a knife to open an envelope. By holding the envelope by hand and gently touching it with the related part of the present machine, it will be opened automatically with a straight opening remaining on the envelope.

A defect of conventional paper shredding machines is that1 after being used for a long time, the space between the screw cutter and the cardboard cutting knife of the paper shredding machine becomes enlarged due to falling off of the locking parts resulting from vibrating or the wearing out of the blades, so that they are unable to cut paper entirely. In such cases if the user is not acquainted with the mechanics of the machine, he would have no option but to request help from an expert to adjust it, which is extremely inconvenient. Furthermore, people require to open letters frequently in daily life, in general, envelopes are ripped open with fingers, or cut with scissors or a blade.Ripping an envelope with ones fingers results in an uneven edge to the envelope and in order to cut them with scissors or a blade people usually require to search for the cutting tocl in drawers or boxes, which is considerably annoying.

Accordingly, an objedt of the present invention is to overcome the defects of conventional paper shredding machines such as large size and a heavy body weight, its inconvenience for feeding paper and the danger that could be caused by the continuous operating whilst the collecting box is removed to clear it due to the power source not having a cut off. Not only is the size greatly reduced enabling it to be placed on a desk, the inlet of paper is located in the front of the machine, making feeding of the paper very convenient but also the power supply is cut off once the collecting box is removed.

According to the present invention a paper shredding machine, comprises a paper inlet on the front thereof, a switch being arranged between a collecting box and an inner wall of the machine casing, the switch when pressed, being adapted to cause an electric circuit to open and thereby stopping the machine from functioning automatically.

Preferably an automatic adjusting mechanism for a cardboard cutting knife is arranged in the interior thereof, a screw cutter and the card board cutting knife being screw fixed to a base, the cardboard cutting knife being arranged on horizontal and vertical portions of the machine body bv means of a hexagonal screw rod, matching round nut and spring, threaded crown post and fixing screw, to adjust the space between the cardboard cutting knife and the screw cutter automatically based on the amount of the loading of paper via the action of the deformation of the spring.

The invention will now be described further, by way of example, with reference to the accompanying drawings, in which: Fig. 1 is the perspective view of a device in accordance with the invention; Fig. 2A shows the components of the device; Fig. 2B shows the electric circuit; Fig. 3 is the perspective view of a cardboard cutting knife automatic adjusting mechanism; Fig. 4 shows the components of the cardboard cutting knife automatic adjusting mechanism; Fig. 5 is a sectional view of the device; Fig. 6A is the perspective view of a prior art paper shredding machine; and Fig. 6B is a diagram of the prior art conventiona board knife mechanism.

A prior art paper shredding machine is shown in Fig. 6A, the size of the machine is big and it is heavy and the paper inlet 600 is at the top of the machine casing when the collecting box 610 is removed to clear it, the paper shredding machine will still operate continuously, unless the power source is cut off, which might cause danger. .Nleanwhile, in the internal structure, the cardboard cutting knife and the screw cutter are both fixed to the body of the machine stand, the practical example is shown as in Fig. 6B; both the cardboard cutting knife 601 and the screw cutter 500 are fixed on the machine stand and the cardboard cutting knife 601 is fixed on the body 6 W of the machine stand by screws 602, 603.Generally, the amount of adjustment of the space is obtained via a thin paper film 60D but after long use, the film would certainly rot. Besides, the vibration of the machine will change th space between the screw cutter and the cardboard cutting knife1 its readjustment being timeconsuming an difficult. Because the spacing is unable to be adjusted or changed, when too much paper has to be shredded, the excessive load is borne by the cardboard cutting knife and screw cutter, the cutting blades bear fairly large bumping forces, which is extremely damaging to the cutting blades which are made of hard and fragile material and it is easy to arrive at remediless defects of cracking or knocked-off opening of the blade.

Referring to Fig. 1, the rectangular opening 101 on the front of the casing is a paper inlet, being smaller than the size of a finger so there are no safety problems. There are operating buttons 104 and 105 on each side of the paper inlet 101 respectively, a slot 102 on the side of the casing, at right angles to the inlet 101, comprises a letter opening mechanism behind it. In operation, it is only necessary to insert the edge of an envelope into the slot, then it will be rolled over and cut by two circular blades so that the envelope is opened automatically.

There is a collecting box 103 at the bottom of the casing in the form of a drawer which can be made of transparent acrylic material in order to observe the amount of the shredded material therein so that it can be removed for the purpose of clearing the box 103 whereby the internal parts do not become clogged.

Fig. 2A shows the components of the sturcture of the present invention, including the power transmission and gear driving mechanism. The drive is supplied by a motor 201, a capacitor 207 providing the large amount of current required for starting it.

The drive is transmitted in sequence by gears 202, 203, 204, 205 to a first shredding paper mechanism 208 and part of the drive is transmitted from the gear 204, to a screw cutter 206 which operates the second shredding. Although the gears 203 and 204 are coaxial, they are not mutually connected. The gear 203 is an independent moving gear so it does not interfere with the rotation of the gear 204 in operation. This device is able to reduce the moving space of the gear operation greatly. On one side of the shelf of the machine 217, there is a letter opening mechanism, comprisir,g two small gears 209 and 210 and circular blades 211 and 212 mounted on driving shafts extending out of the machine casing each blade being separated from its respective gear by small circular washers 213 and 214 to reduce friction. The letter opening is fixed in position by screws 215 and 216. The scissoring and cutting force required to open the envelope is provided by the close contact rotation of the circular blades 211 and 212. As shown in Fig. 2B, a switch 220 is installed on the inner wall of the casing outside the collecting box 103, when the switch 220 is depressed, i.e. the collecting box is pushed, it will not affect the action of the electric circuit; when the switch 220 is released to contact the inner wall of the casing it causes the circuit to open, the motor 201 will then stop immediatley.

This safety precaution prevents a- child being hurt if his fingers are inserted into the collecting box because of his curiosity.

Fig. 3 is the perspective view of ;he cardboard cutting knife 206 automatic adjusting mechanism, it shows that there is a convex edge 315 on the peripheries of the two ends of the casing of the base of the mechanism, to suit the grooves of the machine shelf 217 exactly. Further, by adding the screw 316a, 316b it will form an excellent supporting force for the mechanism.

Fig. 4 shows the components of the automatic adjusting mechnism of the card board cutting knife shown in Fig. 3. Driving of the gear of a hollow screw 303 is effected by a gear on a rotary button 302.

The interior of the hollow screw 303 contains a threaded crown post 304. The internal threads of the hollow screw and the threads of the crown post are right-handed with a pitch of 1.25mm, the external thread of the hollow screw are right-handed with a pitch of about 1.5mm; while the hollow screw rotates one turn, the threaded crown post 304 requires to move up and down 0.25mm only. Due to the amplification of the gear driving ratio of the rotary button 302 and the hollow screw 303, the small adjusting distance is acurate to 0.01mm. This compares favourablv with the requirement of the precision of 0.03mm of the space between the card board cutting knife and the screw cutter in conventional paper shredding machines.The above is only practical example of the thread specification and the figures of the minute adjustment, it is able to be enlarged to attain a more precise amount of minute adjustment. Under such circumstances, if a blade is worn out or the space is changed, the problem is easily resolved by adjusting only the rotary button 302.

The cardboard cutting knife 308 is locked in the horizontal direction on the machine body 301 by a hexagonal screw rod 309 with a spring 312 and a screw nut 313. There is a trapezoidal groove 308A on the two ends of the cardbaord cutting knife 308 to be snared by the trapezoidal end of the threaded crown post 304; furthermore, with the supporting of the spring 310 onto the bottom of the cardboard cutting knife, this will be fixed in the vertical direction of the machine body 301. Because the shape of the spring is changed if a force is applied thereto, the space between the cardboard cutting knife and the screw cutter is adjusted automatically based on the force applied on the spring, consequently, it prevents the two blades from being damaged due to overloading of shredded paper.In order to control the force of the springs 310, 312 and avoid possible spring fatigue, adjusting the hexagonal screw rod 309 and the fixing bot 311 is effected. The screw cutter is installed inside the machine body 301 and cushioned with a round washer 306 and C type check ring 314.

Fig. 5 is a sectional view of the present invention and shows that the combination of the components of the machine is extremely solid due to the use of a set of movable gear 203, i.e., it takes no original space but presents the effect to transmit driving force. The conventional paper shredding machine is driven by three sets of gears in series, such that it is a narrow long arrangement.

In conclusion, the machine of the present invention is superior, in that firstly, it is protected and has a longer useful life secondly, the internal mechanism can easily be adjusted during operation which saves time and labour, moreover front feeding of paper is also very convenient; thirdly, it has a safety installation to guarantee security. Furthermore, the letter opening mechanism brings the effect of double use with one machine.

Claims (6)

1. A paper shredding machine, in which a paper inlet is provided on the front thereof1 a switch being arranged between the collecting box and an inner wall of the machine casing, the switch when pressed, being adapted to cause an electric circuit to open and thereby stopping the machine from functioning automatically.

2. A paper shredding machine as claimed in claim 1, in which an automatic adjusting mechanism if provided for a cardboard cutting knife in the interior thereof, a screw cutter and the cardboard cutting knife being fixed to a base, the cardboard cutting knife being arranged on horizonta and vertical portions of the machine body by means of the hexagonal screw rod, matching round nut and spring, threaded crown post and fixing screw, to adjust the space between the cardboard cutting knife and the screw cutter automatically based on the amount of the loading of paper via the action of the deformation of the spring.

3. A paper shredding machine as claimed in claim 2, in which the hollow screw and the threaded crown post of the automatic adjusting mechanism screwed inside it have the same right-handed threads but their pitches are different, to cause a differential motion during rotation effecting the device of minute adjustment of distance via the action of amplification of the gear ration between a rotary button and the hollow screw to attain the required degree of precision of the space between the cardboard cutting knife and the screw cutter.

4. A paper shredding machine as claimed in any preceding claim in which a gear driving mechanism comprises two coaxial but un-connected gears, one of which is movable, so that it has larger gear speed change ratio and reduces the space to be occupied by the gear mechanism.

5. A paper shredding machine as claimed in claim 4, in which a gear driving rod protrudes out of the casing of the machine to snare a set of gears and a set of round blades cushioned with a small washer, it utilizing the action of scissoring and cutting to be produced by the close contact rotation of the round blades to open an envelope.

6. A paper shredding machine constructed and arranged to operate substantially as herein described with reference to and as illustrated in figs. 1 to 4 of the accompanying drawings.