Abstract: A garbage disposing device 1 comprises a disposing tank 10 of substantially the inverted-conical shape for storing organic substance such as garbage and fermentation accelerator additives in which fermentation microorganism is seeded beforehand in a sealed condition, a rotating shaft 12 which passes vertically through the disposing tank 10 and is driven to rotate by a motor connected to the lower or upper end thereof, a plurality of cutter blades 14 which are fixed in a cantilevered fashion to the rotating shaft 12 at intervals in the vertical direction for grinding and mixing the fermentation accelerator additive and the organic substance, and a plurality of thermo sensors 16 for detecting the temperatures of the disposing tank at a plurality of portions positioned at intervals in the vertical direction.

Abstract: The test mill is a reduced-scale model of an industrial mill used in the mining industry and comprising a rotary shell (10) capable of rotating about its longitudinal and horizontal axis. This shell is capable of containing a certain amount of grinding media and of receiving a certain amount of material to be ground so as to be able to operate under conditions comparable with those of an industrial mill. The shell is divided, in the longitudinal direction, by a perforated transverse partition (24), into a grinding chamber (20) and a measurement chamber (22), the perforations in the partition being sized to hold the grinding charge back and allow the ground matter to pass through, whereas the shell (10) comprises a series of injectors (28) allowing fluid products to be injected into the grinding chamber (20). It is possible to make in-situ and continuous analyses of the pulp in the measurement chamber.

Abstract: An ice shaver machine that includes a hopper for receiving ice, a blade and scraper for drawing the received ice across the blade, thereby producing thin, snow-like ice shavings or flakes, which are scraped to a spout, which, in turn, is provided for delivering the ice shavings to a container. The spout is shaped so as to be used to create a domed-like snow ball shape on the top surface of the shaved ice in the cup container. Also provided is a flavoring delivery system that permits the user to select a flavoring for addition to the ice shavings.

Abstract: The present invention provides a shredder, which has a housing, an entry slot on the housing for inserting a desired medium, a shredding device installed inside the housing for shredding the medium, and a central trigger for sensing the medium and therefore triggering the shredding device. The shredding device has a shredding gap between two shredding knives. The central trigger is installed above the central portion of the shredding gap. The shredder further has a side trigger installed between the central portion and an end of the shredding gap. When a large medium is inserted into the entry slot, the medium will trigger the central trigger device and therefore trigger the shredding device. However, when a sufficiently short medium is inserted into the entry slot, the medium is capable of triggering only the side trigger, and therefore triggers the shredding device.

Abstract: A safety device for a food processor, enables operation of the motor only when a pusher occupies the chute through which food products are introduced, thus preventing injury to the hands. The pusher has a rib, the lower end of which bears against a slider that can have a parallelogram cross section with inclined opposite end faces. When the pusher is advanced so the rib passes the slider, the rib displaces the slider laterally. The displaced slider in turn displaces a lid rod. The lid rod bears against a bowl rod. The lower end of the bowl rod operates a switch.

Abstract: A crushing device which is suitable, in particular, for chips, including a hopper for filling the chips therein, a tearing arm serving as a coarse breaking mechanism, and a fine breaking mechanism. The fine breaking mechanism has a grinding mechanism with at least one centrally arranged, rotating blade head, which operatively interacts with the stationary teeth arranged around the periphery of the grinding mechanism. The stationary teeth are disposed on at least two support segments, and the two segments are movably arranged in such a way that if a coarse piece enters the crushing device, the segments can be separated from the blade head so that the coarse piece can then be discharged.

Abstract: A food disposal system for installation on a drain of a commercial kitchen sink enables segregation of oil/grease from effluent flows from the drain. A housing collects effluent flows containing water, oil/grease, and solids from the drain, and a macerating pump has an inlet connected to an opening of the housing that is other than downwardly directed and an outlet connected to a sanitary drain. A greasy water outlet extends to an oil/grease separator from an outlet on the housing above the macerating pump inlet, and a hot water backflush source enables hot water to flow into the housing.

Abstract: A food ingredient grinding assembly (10) with a removable ingredient hopper (32, 34) made of translucent material to enable viewing the ingredient within the hopper through a window opening (40, 42) and carries a closure assembly (FIGS. 4A and 4B) that automatically closes an outlet opening (112) when the hopper is removed from the housing (12) and when installed is controlled by a solenoid (118) that when energized pushes a plate (116) to align an opening (126) in the plate with the outlet opening (112) of the hopper. When the solenoid is not energized or when the hopper is removed, a spring (118) automatically returns the plate to a closed position. Because the closure assembly (114) is carried by the hopper and the solenoid is not attached to the closure assembly by fasteners the hopper may be removed without the use of any tools simply by lifting it out of the housing.

Abstract: A solid medicine crushing apparatus comprises: a solenoid mounted within an enclosure wherein the solenoid engages a crushing ram in an attitude for moving vertically downward when the solenoid is energized. A return spring engaged with the ram moves the ram to a starting position when the solenoid is deenergized. A cup assembly is used for holding a medicine to be crushed. The cup assembly includes an outer cup and an inner cup, where the outer and the inner cups are joined with a living hinge such that the inner cup is able to be rotated from a side-by-side position with the outer cup, to a position within the outer cup. A medicine is placed in the outer cup, the inner cup is then rotated into the outer cup to sandwich the medicine between the outer cup and the inner cup. The cups with the medicine are placed into the enclosure which is sealed by closing an interlocked door of the enclosure. The solenoid is then energized to bring the crushing ram into contact with the inner cup to crush the medicine.

Abstract: An impacting body is mounted rotatably to a spindle provided on a principal plane of a rotor. The impacting body is mounted so that a predetermined fitting gap is provided between the impacting body and the spindle and a part of periphery of the impacting body can be positioned beyond a periphery of the rotor. The rotor is rotated at a high speed to allow the impacting body to impact on an object to be processed at least at its critical impact velocity. This enables only the top layer of the object to be processed at the part on which the impacting body has impacted to be broken instantaneously. When the rotor is moved while being rotated, the object to be processed can be cut. According to this cutting device, an object formed of a single member such as glass, ceramics, resin, metal, or the like, or a composite member thereof can be cut continuously with one kind of cutting tool.

Abstract: The data destruction machine is a desk-top, portable unit with a short (under 10 second) cycle time, pluggable into a wall outlet. Upon insertion of a disk (such as a CD or split DVD) into the machine, which is fully automatic, data is removed. The machine converts the data-storage layer into residue consistent with security destruction standards from which no data is retrievable. A single machine may be used for declassifying CDs and split DVDs. Splitting DVDs in preparation for inserting them into the data destruction machine may be accomplished quickly and simply.

Abstract: A coffee grinder with a removable storage and dispensing element that has a housing and rotatable assembly in the housing. The rotatable assembly includes a distributor allows a single one of multiple open sectors to be filled in any given position. A dispensing component has an open sector angularly offset from the open sector of the distributor. When the dispensing component open sector aligns with a filled sector, the beans drop into a hopper for grinding. A grinder operates until all the beans in the hopper are ground.

Abstract: A shredder for shredding metal shavings, chips and the like includes a housing (10) containing a shredder assembly having first and second roller motor-operated shafts (40,42) carrying spaced knives (50) for shredding metal. A sensor (66,68) on at least one shaft (40,42) senses a change in rotation of the shaft, indicative of a jammed condition. A microprocessor (70) responds to the sensor to open an ejection door (20) normally closing an ejection outlet (16) and to reverse rotation of the shaft (42) to dislodge the jamming object. When the jamming object is dislodged, the microprocessor halts rotation of one shaft (40) to permit the knives on the reverse rotating shaft (42) to carry the jamming object toward the open ejection outlet (16). After the object has been ejected, the microprocessor (70) returns the shafts (40,42) to their normal operation to continue shredding metal.

Abstract: An apparatus for comminuting, grinding and dispersing flowable grinding stock has a grinding receptacle with an inner, first grinding surface, which is rotationally symmetrical relative to an axis of rotation, and is drivable to rotate about the axis of rotation. Also provided is a grinding roller, which has a second grinding surface that is rotationally symmetrical relative to a central longitudinal axis, and is drivable to rotate about the axis. A grinding gap is defined between the first grinding surface and the second grinding surface.

Abstract: A driving and controlling system for driving a shredding mechanism by a motor to shred paper sheets increases shredding capacity represented by the number of paper sheets that can be simultaneously shredded while limiting input current in an allowable range and reduces time necessary for shredding a predetermined number of paper sheets. The driving and controlling system comprises a motor (4) for driving a shredding mechanism (5) for shredding paper sheets (10), and a controller (1) interposed between the motor and a commercial power supply system (13) to control power to be supplied to the motor. The motor has a characteristic to reduce motor torque substantially linearly with the increase of operating speed for voltage applied thereto as a parameter.

Abstract: This invention is related to a dual-functional medium shredding machine structure, specifically designed for shredding or destroying paper printed with data to be destroyed, optical discs containing data to be destroyed, or expired credit cards.

Abstract: A paper shredder enables to control power consumption and achieve energy saving by realizing a torque characteristic of low torque at high speed or high torque at low speed keeping an output of a motor within a steady level. This circuit adopts a paper shredder structured with a driving motor for a rotary cutter having an inverted linear flow characteristic between rotation speed and torque and a control circuit composed of a detecting block for said rotation speed of said motor, a voltage control block for restricting a voltage output of said motor within a certain range in accordance with said rotation speed, and a current and voltage detecting block for monitoring a current flow of said motor.

Abstract: A shredder for shredding material is provided that includes a housing. having a cutting device to shred material. A receptacle is also included and is positioned to receive the shredded material. A detecting device is positioned between the cutting device and the receptacle and emits and detects a beam so that when shredded material occupies a first position within the receptacle the beam is interrupted. Advantageously, the detecting device may be used as a bin full detection device to provide indication that a bin is filled or substantially filled with shredded material.

Abstract: The present invention provides a shredder, which has a housing, an entry slot on the housing for inserting a desired medium, a shredding device installed inside the housing for shredding the medium, and a central trigger for sensing the medium and therefore triggering the shredding device. The shredding device has a shredding gap between two shredding knives. The central trigger is installed above the central portion of the shredding gap. The shredder further has a side trigger installed between the central portion and an end of the shredding gap. When a large medium is inserted into the entry slot, the medium will trigger the central trigger device and therefore trigger the shredding device. However, when a sufficiently short medium is inserted into the entry slot, the medium is capable of triggering only the side trigger, and therefore triggers the shredding device.

Abstract: An automatic start mechanism for a shredding apparatus is disclosed. The shredding apparatus includes a shredding mechanism for cutting the paper when the paper passes through a channel, a power source for outputting a motive power for the shredding mechanism, a trigger disposed at an entrance of the channel for arising a move when the paper passing through the channel to be against thereto, a delay unit for producing an against force driven by the power source, a lever connected between the trigger and the delay unit for moving in response to the trigger and the delay unit against, and a switch electrically connected to the power source and contacted to a first portion of the lever. The distance between the first portion of the lever and the trigger is smaller than a distance between the delay unit and the trigger.

Abstract: The invention relates to a food processor (1) with a motor (M) to drive at least one tool and with input means (13 to 18) to switch on at least one operating process, with a microcomputer (43) to control the operating processes and realize a detection stage (44) for the detection of the interruption of an operating process, which microcomputer contains a memory (50) for storing operating values present immediately before the interruption of an operating process, the microcomputer (43) being designed to start the continuation of an interrupted operating process following an activation of a reactivation switch (13 to 18) provided for the reactivation purpose, the reactivation switch (13 to 18) preferably being formed by the operating-mode switch (13 to 18) concerned.

Abstract: The invention relates to a feed sensor mechanism for a mill cylinder. The purpose of the invention is to provide a structurally simple sensor to detect the product in the entry port of the feed regulator. To this end, a sensor is located in the feed cylinder of the cylinder mill. The sensor is able to detect the force of the incoming product so that a control signal can then be sent to the feed device via a signal converter.

Abstract: Apparatus for treating waste, particularly all types of medical waste, to facilitate its disposition includes a treatment vessel having an open top pivotal within a housing to a waste-loading position with its open top aligned with the housing inlet for receiving the waste, a waste-treating position for shredding the waste by a shredder unit disposed within the treatment vessel, and a waste-removing position with its open top aligned with the housing outlet for removing the shredded waste. The apparatus further include a compactor head for compacting the waste within the treatment vessel, a water feed line, and a disinfectant feed line, for feeding water and a disinfectant into the treatment vessel, for mixing with the waste while it is being compacted and shredded.

Abstract: A method and two apparatuses for comminuting chips are presented. Chip breakers without a coarse-part ejecting element are often used for comminuting chips. Blocking constituents therefore have to be removed with great effort, for example by hand. If a coarse-part ejecting element is present, there is no differentiation between blocking hard parts and blocking clumps of chips, but instead both types are ejected. It is now envisaged to subdivide blocking constituents in horizontal chip breakers into categories, depending on the negative acceleration of the shaft (3, 17, 18) caused by the blocking, and to assign to each category a defined reversing operation for loosening the blocking constituents and, if appropriate, discharge from the comminuting space (1, 15) by means of a coarse-part ejecting element (12, 32).

Abstract: The present invention provides a self-propelled crushing machine in which a crushed material having a widely desired grain size can be obtained, a degree of freedom for automatically controlling a rotary tub and a rotary crusher can be preferably improved, and a crushing having a high efficiency can be performed.

Abstract: A coffee grinder with a removable storage and dispensing element that has a housing and rotatable assembly in the housing. The rotatable assembly includes a distributor allows a single one of multiple open sectors to be filled in any given position. A dispensing component has an open sector angularly offset from the open sector of the distributor. When the dispensing component open sector aligns with a filled sector, the beans drop into a hopper for grinding. A grinder operates until all the beans in the hopper are ground.

Abstract: Apparatus for treating waste, particularly all types of medical waste, to facilitate its disposition includes a treatment vessel having an open top pivotal within a housing to a waste-loading position with its open top aligned with the housing inlet for receiving the waste, a waste-treating position for shredding the waste by a shredder unit disposed within the treatment vessel, and a waste-removing position with its open top aligned with the housing outlet for removing the shredded waste. The apparatus further include a compactor head for compacting the waste within the treatment vessel, a water feed line, and a disinfectant feed line, for feeding water and a disinfectant into the treatment vessel, for mixing with the waste while it is being compacted and shredded.

Abstract: An improved wet and dry food grinder having a base assembly and a grinder assembly receivable on the base. The base contains an electric motor with associated electrical circuitry and drive means attached thereto. The grinder assembly has a cylindrical cover and a cylindrical grinder bowl received within the cover. Grinder blades are mounted in the grinder bowl and are driven by the drive means. The motor is actuated by placing the grinder assembly in position on the base and pressing down.

Abstract: An improved brush cutter having an upper feed control member with stop, forward, neutral, and reverse positions also has a lower feed stop member with selectable sensitivity. Another aspect of the invention is to predict the feed roller shutoff point according to the rate of engine deceleration. According to another aspect, when the feed rollers stop feeding material into the cutters, to overcome drag on the cutters, a controller stops the feed rollers and then reverses them for a short time, and then reverses the rollers again if the problem is still present. To prevent jamming, a pressure switch senses when oil in a hydraulic motor system for rotating the feed rollers is too high and the controller momentarily reverses the feed rollers and then causes them to go forward, a cycle which can occur several times until the feed rollers are no longer stalled.

Abstract: A method for shredding a document which renders the information unintelligible and prevents or minimizes reassembly of the shredded document reconstruction of the information contained in the document. The ability to reassembly a shredded document is greatly reduced by shredding each page of the document into segments formed by cuts made in the blank space between characters or images on the page. A cut pattern in which all cuts are made in the blank spaces between characters or images produces pieces or shreds of the document which have no partial or portions of characters or marks which can be matched across adjacent pieces. A document is first scanned to provide an image which can be analyzed by a processor to determine a desired cut pattern for the document. The processor then generates a set of instructions to control and adjust the cutting blades in a shredding device to cut the document in the desired cut pattern.

Abstract: A blender for home food preparation is improved by the incorporation of electronic motor control circuitry responsive to a microcontroller. The microcontroller includes memory for storage of data and programmed instructions. The programmed instructions permit a user to select from a plurality of blending speeds and define a pre-determined end time. Use of a pre-determined end time produces a two-speed blending cycle. The programmed instructions determine the length and energy level associated with each portion of the two-speed blending cycle. A user can stop the blending cycle at any time, with or without a pre-determined end time. Safety features include a pre-determined maximum motor run time, top jar load detector and auto shut down after a period of inactivity. The pre-determined end time from a previous blending cycle is stored in memory, allowing the microcontroller to reproduce the duration of the previous blending cycle.

Abstract: An apparatus for crushing waste metal products includes a rotor having crushing means on a periphery thereof and a casing enclosing the rotor. The casing has an inlet and an outlet for products to be crushed. An exhaust gas from the casing is partly returned to the inlet of the casing by a circulator. The rest of the exhaust gas is ventilated and processed by an exhaust processor. An oxygen concentration is monitored in a gas pathway of the circulator to control the gas concentration in the casing. If the oxygen concentration is high, a water shower sprays into the casing.

Abstract: An appliance includes a housing (1) containing a motor (2) whose output shaft (8) passes through the housing base (4) and drives in rotation a tool (16) housed in a bowl (9) locked on the housing and closed by a lid (12); and a safety device (25) having a vertical thruster (27) mounted sliding in the bowl (9) peripheral wall (30) and actuated by a cam (43) borne by the lid (12) so as to penetrate in an opening (39) provided in the base to be urged to actuate a switch controlling the motor. A rigid cover (49) is mounted on the base movable between an inoperative position wherein it conceals the base opening (39), when the bowl is not on the base (4), and an operative position wherein it clears the opening (39) by the action of an actuating member (51) borne by the bowl (9) when the latter is locked on the base (4).

Abstract: A programmable drink blender (20) includes a blender motor (25), a user interface and display (24) having a plurality of buttons (30) for entry of various user selections, a base memory (70) storing a blend program, a key card (50) having a memory storing a blend program, a socket (68) receiving the key card (50), and a processor (62) for controlling blender motor (25) in accordance with the blend program. The blend program has a plurality of operating segments with variable blend program operating characteristics. The user presses selected buttons (30) to cause processor (62) to modify and save any desired characteristic of the blend program. The user also presses selected buttons (30) to cause processor (62) to copy the blend program from memory in key card (50) to base memory (70), and vice versa.

Abstract: There is provided a food processor having a motor, an impeller rotatably driven by the motor, a controller for rotating the motor in a first direction or a second direction, and a switch for controlling the controller to change the direction of the rotation of the motor.

Abstract: An apparatus is provided for comminuting solid waste material. The apparatus includes a frame, a set of overlapping scissor rolls, a separator screen and a recycle manifold section. The frame has an enclosure with an entrance for receiving solid waste material. The set of overlapping scissor rolls are rotatably mounted within the enclosure for shearing the waste material into subdivided pieces when the material passes between the scissor rolls. Each scissor roll has a substantially horizontal axis of rotation, with a first scissor roll elevated relative to a second adjacent scissor roll. The separator screen is carried by the frame beneath at least one of the scissor rolls. The separator screen has a plurality of apertures for separating pieces having a size less than a predetermined size which pass through a shear outtake manifold for separation while preventing large subdivided pieces having a size greater than the predetermined size from passing therethrough.

Abstract: A comminuting apparatus includes a frame, a set of overlapping scissor rolls, a first drive motor, and a second drive motor. The frame has an enclosure with an entrance opening for receiving waste material. The set of overlapping scissor rolls is carried within the enclosure for rotation, including a first scissor roll and a second scissor roll. The first drive motor is coupled to the first scissor roll, and the second drive motor is coupled to the second scissor roll. The first drive motor is operative to drive the first scissor roll at a substantially variable operating speed. The second drive motor is operative to drive the second scissor roll in co-rotation at a substantially constant operating speed.

Abstract: The present invention provides a self-propelled crushing machine in which a crushed material having a widely desired grain size can be obtained, a degree of freedom for automatically controlling a rotary tab and a rotary crusher can be preferably improved, and a crushing having a high efficiency can be performed.

Abstract: A coffee blending and dispensing apparatus whereby coffee purchasers can automatically customize a desired blend of two or more different types of coffee beans that weighs and packages the blended coffee in containers either as ground coffee blend or as a whole coffee bean blend. The blending and dispensing apparatus includes a plurality of coffee bins, each containing a predetermined type of coffee bean supported over a scale. Each coffee bin includes a controlled discharge for directing selected predetermined amount of coffee beans contained therein to the scale for weighing. Upon weighing, the selected blend of coffee beans are conveyed to a bagging station, where blended coffee beans may be finally packaged either in a ground form or a whole bean form.

Abstract: The data destruction machine is a desk-top, portable unit with a short (under 10 second) cycle time, pluggable into a wall outlet. Upon insertion of a disk (such as a CD or split DVD) into the machine, which is fully automatic, data is removed. The machine converts the data-storage layer into residue consistent with security destruction standards from which no data is retrievable. A single machine may be used for declassifying CDs and split DVDs. Splitting DVDs in preparation for inserting them into the data destruction machine may be accomplished quickly and simply.

Abstract: In the mechanical refining of wood chips to produce wood pulp, wood pulp quality is improved by employing low refining intensity at least in a final refining stage; the refining is carried out in a double disc refiner or a single disc refiner at rotational speeds that are lower than those conventionally employed, specifically at less than 1200 RPM in a double disc refiner and at less than 1500 RPM in a single disc refiner.

Abstract: The present invention provides a self-propelled crushing machine in which a crushed material having a widely desired grain size can be obtained, a degree of freedom for automatically controlling a rotary tab and a rotary crusher can be preferably improved, and a crushing having a high efficiency can be performed.

Abstract: This invention is related to a delay drive-hanging device of a paper shredder. The paper shredder is provided with a linked delay device that maintains continuous driving force within the duration from insertion of paper between blade wheel shafts to termination of shredding operation so as to effectively grip and then strip the paper. The device is provided on the blade wheel shafts; the device drives and connects to a link dial by means of a belt. The link dial has an end that couples to a control cylinder by means of minute friction. A delay trigger for a paper entry dial is provided between a side of a paper entrance and the control cylinder. A micro-switch is connected to a primary circuit. The control cylinder has an end face having a notch that corresponds to and controls a retaining dial of the delay trigger. The control cylinder is provided on another side with a resilient press plate that corresponds to and controls a recovering dial.

Abstract: A device is intended to monitor the paper shredding action of a paper shredder and composed of two paper guiding grid plates, a microswitch, and a detecting rod. A paper guiding passage is formed between the two grid plates. A first paper guiding grid plate is provided with a fastening seat. The detecting rod is fastened pivotally with the fastening seat such that the detecting rod extends between the two paper guiding grid plates. The microswitch is mounted on the fastening seat such that the microswitch is contiguous to the detecting rod. As the front end of a paper sheet has passed the paper guiding passage, the detecting rod is pushed by the front end of the paper sheet to swivel to trigger the microswitch to activate the shredding tools of the paper shredder.

Abstract: A device for the delayed disconnection or switching-off of the drive of cutting mechanisms of paper shredders, wherein the switching-on process of the cutting mechanisms is automatically triggered predominantly by the insertion of the materials to be shredded into the feed shaft. At least one of the gear stages between the drive motor and the pair of cutting rollers is provided with a spiral or helical gear unit, wherein at least one of the gear wheels of the gear unit is mounted so as to be axially movable in the direction of its axis, and wherein a switching element or limit switch connected to the motor control is arranged in the range of the axial distance of movement of the at least one gear wheel.

Abstract: Method and apparatus for preventing or releasing a blockage occurring in a flow of tree trunks supplied to a wood chipper via a feed hopper and for securing an uninterrupted flow of timber to the chipper. At least one lifting arm is insertable to project through an opening defined in a hopper. The lifting arm is inserted to raise tree trunks wedged in the hopper and release blockages. The duration of the lifting arm insertion is controlled momentarily for limiting the amount of tree trunks supplied to the chipper.

Abstract: An apparatus for removing ice from an electric cable is disclosed. This apparatus comprises an impact actuator, an impact member in the from of a rod, and a fastener to hang the apparatus from the electric cable. The apparatus can be remotely activated and can be activated many times before reloading. Triggering of the impact actuator produces an impact between the rod and the electric cable suitable to produce a shock wave that propagates along the electric cable to cause the accumulated ice to break and fall on the ground.

Abstract: A control circuit of a transportable crusher supplies, by the same pump, a required flow rate to hydraulic motors and actuators for a plurality of operating devices having different loads and improves simultaneous operability, fine adjustment, and reproducibility.

Abstract: In a safety switch for paper shredders, the housing (1) for the cutting mechanism is set on the container (2) for the paper to be cut. The switch element (3), including its pin (3a) and the corresponding switching cam, is arranged on the paper collecting container in a working line (W) inclined relative to the vertical (V) of the apparatus.

Abstract: A paper shredder includes a casing, an impelling roller, and a clutch mechanism. The casing has a pair of shredding rollers mounted rotatably therein. The impelling roller is disposed rotatably below and is adjacent to the shredding rollers. The clutch mechanism is provided for connection of the shredding rollers and the impelling roller to transmit rotation of the shredding rollers to the impelling roller, and for disconnection of the shredding rollers and the impelling roller when an external force is exerted on the impelling roller to slow down the impelling roller with respect to the shredding rollers.