Abstract: A wedge mechanism including at least one wedge element and a guide member. The guide member is attached to the second assembly and adapted for receiving the wedge element in a way that and at least an inactive position of the mechanism is defined where the first and second assemblies can be detached from each other, and an active position where at least one of the wedge element and the guide member presses against two different sectors of the first assembly such that the first assembly and the second assembly remain attached to each other.

Abstract: A sensor system is disclosed for detecting positions of two at least partially ferritic components that can move relative to one another, namely a stationary component and a component that can move lengthwise along a longitudinal extension of the stationary component, which are mounted right next to one another. The sensor system can include a Hall sensor and a preloaded magnet, eliminating flux concentrators and shielding sheets. The Hall sensor and the preloaded magnet are arranged along a longitudinal extension of the movable component such that relative movement of the two components is detected by monitoring a free longitudinal end of the stationary component.

Abstract: The invention relates to a rotor and a motor and compressor comprising the rotor. The rotor comprises a rotor core defining an outer periphery, a bore concentric with a center of the rotor core, a plurality of magnet slots positioned on the outer periphery, and a plurality of oil holes located radially outward from the center between the bore and the magnet slots. Each oil hole includes a body portion and at least one projected portion. The projected portions are located radially outward from the body portions and positioned between the body portions and the magnet slots. The projected portions may increase the contact area of the compressor oil with the rotor core to effectively cool down the rotor core. Another advantage of the projected portions may be to further cool down the magnets in the magnet slots. Cooling the magnets may protect against their demagnetization.

Abstract: Apparatus and methods for a magnetic coupling motor drive for a surgical cutting instrument. A magnetic coupling motor drive unit includes a motor housing containing a motor and a magnetic drive hub assembly, the magnetic drive hub assembly having a drive hub and a driven hub, the driven hub rotating about a driven hub spindle, the driven hub spindle attached to a seal cap, the seal cap sealing the drive hub and the motor to the motor housing, wherein the drive hub includes an array of magnets aligned to a respective array of magnets in the driven hub.

Abstract: A DC permanent magnet synchronous motor, including: a motor body including a rotating shaft, a permanent rotor assembly, a stator assembly, and a housing assembly; a motor controller including a first microprocessor for drive control, an inverter circuit, and a detection circuit for detecting operating parameters of the motor; and an external control card including a second microprocessor for application control. The operating parameters of the motor are input into the first microprocessor by the detection circuit. The first microprocessor outputs a PWM signal to control the inverter circuit. An output end of the inverter circuit is connected to a coil winding. The external control card is disposed outside the motor body and is connected to the motor body via an electric wire. The second microprocessor and the first microprocessor are interconnected so that they can communicate.

Abstract: A method for manufacturing a permanent-magnet motor rotor includes manufacturing a rotary shaft, a permanent magnet, a front end cover, a rear end cover, and a magnetic yoke unit, where the magnetic yoke unit contains multiple pole shoe parts and one iron core part, where each pole shoe part and the iron core part are connected therebetween via a connecting strip; manufacturing a rotor spacer; all positioning holes of the magnetic yoke unit correspond to the permanent-magnet through hole of the rotor spacer to form a permanent-magnet passage; inserting the permanent magnet into the permanent-magnet passage; inserting tightening bolts; cutting off the mid-section of each connecting strip, overlapping the pole shoe parts to form a rotor pole shoe, overlapping the iron core parts to form a rotor iron core; and arranging respectively the front end cover and the rear end cover on a front end and a rear end.

Abstract: A rotor for an electric machine has a rotor member extending circumferentially about the axis of rotation of the rotor, and a locking device in an axial end region of a guide to mount permanent magnets in the direction of the axis of rotation of the rotor. The locking device is retained on the rotor member in the radial direction and in the direction of rotation of the rotor by guides. The locking device has a movable movement element and is designed such that when the movement element is moved, the locking device is positively or non-positively connected to the rotor member.

Abstract: A rotary electric machine includes a stator; and a rotor including an iron core, which has a tubular connecting portion surrounding a shaft and 10 magnetic pole portions integrally formed with the connecting portion corresponding to a pole number, and a plurality of permanent magnets arranged between the magnetic pole portions. The iron core includes axially-penetrated magnet accommodating air gaps formed between the magnetic pole portions at the radial outer side of the connecting portion, and the permanent magnets are installed in the respective magnet accommodating air gaps such that a radial outer surface of each of the permanent magnets makes close contact with an inner surface of each of the magnet accommodating air gaps and such that a gap exists between a radial inner surface of each of the permanent magnets and the connecting portion.

Abstract: A permanent magnet rotor includes a shaft, a rotor core fixed to the shaft, a bracket fixed to the rotor core, and a plurality of permanent magnets contacting an outer surface of the rotor core. The bracket includes a base at one axial end thereof, a plurality of arms axially extending from the base and spaced in a circumferential direction, and an end ring connecting the arms at the other axial end thereof. The base has an opening for the insertion of the shaft. The rotor core is positioned between the arms. Each magnet is sandwiched between two adjacent arms. An inner diameter of the end ring is greater than an outer diameter of the rotor core.

Abstract: Rotor arrangement for a generator is disclosed. The rotor arrangement includes a rotor including a number of circumferentially adjacently disposed magnetic elements, at least one axially extending spacer element is disposed between at least two circumferentially adjacently disposed magnetic elements.

Abstract: A permanent magnet rotor (3) for a rotary electric machine (1) comprises a rotor body (10) having a rotation axis (A) and a plurality of radial magnets (4), wherein the magnets (4) exhibit a head portion (5) located in proximity to an external surface (30) of the rotor body (10) and a base portion (6) facing towards the rotation axis (A). The base portion (6) of each magnet (4) has a width smaller than a width of the head portion (5).

Abstract: According to one embodiment, there is provided an electric rotating apparatus including a permanent magnet type rotor in which wedge-shaped slots are formed on an outer circumferential portion of a rotor core along an axial direction of a rotor, and permanent magnets are fitted in the wedge-shaped slots, thereby forming a plurality of rotor magnetic poles. Nonmagnetic regions extending in the axial direction of the rotor core are formed between the plurality of rotor magnetic poles.

Abstract: A rotating electric machine includes a stator and a rotor. The rotor includes an iron core and permanent magnets. The iron core includes a cylindrical connection portion and ten magnetic pole portions. The cylindrical connection portion surrounds a rotation shaft. The ten magnetic pole portions, the number of which corresponding to the number of poles, are disposed radially outside the connection portion. The connection portion and the magnetic pole portions are integrated with each other. The permanent magnets are disposed between the magnetic pole portions. The magnetic pole portions include flange portions that cover parts of radially outer surfaces of the permanent magnets while allowing at least parts of the radially outer surfaces to be exposed. Each of the permanent magnets includes a tapered portion in at least a part thereof, and the tapered portion has a length in a direction perpendicular to the radial direction that decreases radially inward.

Abstract: A magnet rotor assembly comprises a magnet sleeve held on a rotor shaft by a rigid adhesive layer that includes at least one axial wedge shape corresponding to an axial irregularity on at least one of the surfaces bonded by the adhesive layer. Improved crush strength in the magnet sleeve and in other bonded metal parts, both initially and after exposure to high temperatures is accomplished by impregnating the parts with a curable resin.

Abstract: A motor includes: a rotor comprising: a rotary shaft; a magnetic body rotatable together with the rotary shaft; and first and second permanent magnets fixed on an outer circumference or an inner circumference of the magnetic body, and a stator comprising: an iron core arranged around the rotor; and a coil for exciting the iron core.

Abstract: A rotor for a motor is provided including: a rotor core including at least one a first coupling portion on an outer circumference thereof, wherein the first coupling portion includes a first coupling groove or a first coupling projection; at least one division core spaced apart from the rotor core and including a second coupling portion on an outer circumference thereof, the second coupling portion including a second coupling groove or a second coupling projection; and a connecting pin including a third coupling portion and a fourth coupling portion, the third coupling portion to be coupled to the first coupling portion and the fourth coupling portion to be coupling to the second coupling portion.

Abstract: Disclosed are a motor rotor and a motor having same, wherein the motor rotor comprises an iron core (10) and permanent magnets (20) provided within the iron core (10), sets of mounting grooves (30) are provided in the peripheral direction of the iron core, with each set of mounting grooves comprising more than two mounting grooves (30) arranged intermittently in the radial direction of the iron core (10). The permanent magnets (20) are correspondingly embedded into the individual mounting grooves (30). The thickness of the permanent magnet (20) at the centre of the cross section thereof and perpendicular to the rotor axis is greater than the thickness at both ends thereof. The rotor optimizes the shape of the permanent magnets (20) and improves the efficiency of the motor.

Abstract: A permanent magnet rotor comprising a rotor rim and a plurality of permanent magnet modules arranged on the outer or inner circumference of the rotor rim. The permanent magnet modules comprise a base adapted to be fixed to the rotor rim, one or more permanent magnets, and a central magnet support structure. The base and the central magnet support structure comprise a plurality of radial holes. The permanent magnet modules are adapted so that, when bolts are inserted in the radial holes to fix the central magnet support structure to the base, at least a portion of a first and a second surface of each permanent magnet remain substantially in conforming contact with a surface of the base and a surface of the central magnet support structure, respectively.

Abstract: An arrangement for attaching a permanent magnet to the rotor of an electrical machine and such a rotor are provided. The rotor is assembled of sheets and includes at least two magnetic poles and a magnetic core. Permanent magnets are installable on a surface of the magnetic core, and a pole piece assembled of sheets is installable on a side of the permanent magnet that faces an air gap. At least one channel passing through the pole piece is built in the pole piece and magnetic core. A tightening strip is installable in the channel. The tightening strip is attachable to the pole piece using locking parts, and an end of the tightening strip facing the magnetic core includes fixing parts for attaching the tightening strip to the magnetic core.

Abstract: A permanent magnet type rotating electric machine includes: a rotor including a rotor core having a polygonal shape and a plurality of permanent magnets; and a stator including a stator core and armature windings, in which, when the number of poles is M, the number of slots is N, M permanent magnets are sequentially numbered from first to M-th in a circumferential direction, and a positional shift amount in the circumferential direction from a corresponding one of equiangularly arranged reference positions, each being at the same radial distance from a center of a rotating shaft, for an i-th (i=1, 2, . . . , M) permanent magnet is hi, M unit vectors in total, each being in an angular direction of 2?N(i?1)/M (rad), are defined, and a sum of M vectors obtained by multiplying the unit vectors respectively by the positional shift amount hi is smaller than a maximum value of an absolute value of the positional shift amount hi.

Abstract: A permanent magnet rotor arrangement is provided. The arrangement includes a rotor, a plurality of nonmagnetic profiled tubes defining a closed channel and affixed circumferentially along the outer rim of the rotor, and a plurality of permanent magnet pole pieces arranged in the channels. In a preferred embodiment, the tubes are monolithic and one pole piece is arranged in every channel.

Abstract: A rotor for an electric machine has a rotor member extending circumferentially about the axis of rotation of the rotor, and a locking device in an axial end region of a guide to mount permanent magnets in the direction of the axis of rotation of the rotor. The locking device is retained on the rotor member in the radial direction and in the direction of rotation of the rotor by guides. The locking device has a movable movement element and is designed such that when the movement element is moved, the locking device is positively or non-positively connected to the rotor member.

Abstract: A permanent magnet type rotating electric machine includes: a rotor including a rotor core having a polygonal shape and a plurality of permanent magnets; and a stator including a stator core and armature windings, in which, when the number of poles is M, the number of slots is N, M permanent magnets are sequentially numbered from first to M-th in a circumferential direction, and a positional shift amount in the circumferential direction from a corresponding one of equiangularly arranged reference positions, each being at the same radial distance from a center of a rotating shaft, for an i-th (i=1, 2, . . . , M) permanent magnet is hi, M unit vectors in total, each being in an angular direction of 2?N(i?1)/M (rad), are defined, and a sum of M vectors obtained by multiplying the unit vectors respectively by the positional shift amount hi is smaller than a maximum value of an absolute value of the positional shift amount hi.

Abstract: A permanent magnet rotor for a brushless electric motor of the kind with an internal stator, has a carrier structure of molded plastic that includes a disc portion fixed to a shaft. The disc portion has a periphery joined to a substantially cylindrical cage portion coaxial with the shaft. The cage portion accommodates a magnetic flux conducting structure forming an wall which is coaxial with the shaft, and a plurality of permanent magnets shaped as ring segments, disposed at angular intervals within and adjacent to the flux conducting structure. Each magnet has its circumferentially terminal faces parallel with each other or converging in the outward direction. The cage portion is overmolded onto the flux conducting structure and has a plurality of angularly spaced struts which are essentially parallel to the axis of the rotor and which protrude radially inwards.

Abstract: A permanent magnet motor, generator or the like that uses ceramic magnets in the rotor to concentrate the magnetic flux in the airgap. Magnet poles are formed by pole plates with tabs forming north and south poles with magnetic separators therebetween. Magnet sections are stacked axially. Connection to the shaft is made by means of a collet or other attachment method.

Abstract: A rotor magnet engagement assembly includes a rotor base plate, a first magnetic interpole element, and a second magnetic interpole element. The first magnetic interpole element and the second magnetic interpole element are attached to the rotor base plate in such a manner that a gap is provided between the first magnetic interpole element and the second magnetic interpole element. The first magnetic interpole element, the second magnetic interpole element, and the rotor base plate form a recess, wherein the recess is adapted to receive a magnet in such a manner that the magnet is fixed to the rotor base plate. It is further described a method for manufacturing a rotor magnet engagement assembly, a rotor magnet arrangement, a rotor for an electromechanical transducer, and an electromechanical transducer.

Abstract: Electrical machine rotors and electrical machines are disclosed. The electrical machine rotors may include a shaft, a pair of permanent magnets arranged to form a magnetic pole on the rotor, a pole iron, and a pair of opposed inter-pole irons. The pole iron may retain the pair of magnets against the inter-pole irons and relative to the shaft. The electrical machine rotors may be assembled into electrical machines that include the rotor and a stator that includes a stator iron and at least one coil. In some examples, the shaft may be hollow, nonmagnetic, fiber-reinforced, and/or fabricated at least partially from a composite material.

Abstract: A retention system in which rotor pole pieces are retained within complementarily shaped channels in a rotor hub, permanent magnets are secured between the pole pieces and within clamp members, and wedge-shaped pieces are used to apply positive locking forces along the axial length of each clamp member and of adjacent pole pieces. A curable resin preferably in disposed within gaps between the permanent magnets and the clamp members.

Abstract: A permanent magnet rotor includes: a rotor core of a laminated structure about a rotation shaft; a plurality of permanent magnet embedment slots provided to the rotor core at equally spaced positions from the rotation shaft; and permanent magnets inserted into the respective permanent magnet embedment slots. The permanent magnet embedment slots each have a magnet storing portion and a buffer and other members storing portion continuing to the magnet storing portion. One permanent magnet is stored in the magnet storing portion and a buffer member and a pushing member used to fix the permanent magnet are stored in the buffer and other members storing portion. It thus becomes possible to provide a permanent magnet rotor capable of not only preventing damage on a permanent magnet by reducing resonance even when the magnet resonates under a vibration condition, but also enhancing mass-productivity.

Abstract: A permanent magnet rotating electrical machine includes a stator and a rotatable, approximately cylindrical rotor. The rotor includes a shaft, rotor cores, radial permanent magnets, and side plates. The shaft includes projected and depressed engagement portions. The rotor cores are separated from each other on a magnetic pole basis. The rotor cores constitute circumferentially arranged pole shoes. The radial permanent magnets are each on a circumferential side of a pole shoe among the pole shoes. Each of the radial permanent magnets is engaged with an engagement portion among the engagement portions of the shaft. The side plates are on axial ends of the rotor. The side plates support the rotor cores and the permanent magnets in a radial direction of the rotor.

Abstract: A radial flux permanent magnet AC motor/generator employs a flat circular stator plate having a plurality of separately-formed electromagnets mounted in a ring pattern on a top surface thereof. A circular flux ring fabricated of powdered metal is mounted to the stator plate outside the ring of electromagnets. A plurality of permanent magnets are mounted in a ring pattern on the outer cylindrical surface of a steel rotor. The stator plate and rotor are axially and diametrically aligned such that the ring of permanent magnets rotates in close proximity to and inside the ring of electromagnets. The electromagnets utilize powder metal cores shaped to have rounded corners and flat sides that permit the use of heavier gauge windings and eliminate the air gaps that exist between the core and windings of prior art electromagnets.

Abstract: A rotating machine has a stator and a permanent magnet rotor that is more easily made, lower cost, and lighter by virtue of a plurality of permanent magnet assemblies mounted on a rotor body. Each magnet assembly includes two facing core plate stacks supporting a permanent magnet between them. Each core plate stack is made from a plurality of core plates of substantially identical size and shape and with on or more holes in substantially the same location to form respective bores in the stack. A tie rod is formed in each bore and retains the plates in a stack via bevels in the holes of the end plates. Preferably, the tie rods also apply compressive force as a result of placing the stacked plates in an injection mold, injecting plastic into the mold to fill each bore with plastic, and allowing the plastic to cure. As the plastic cures, it shrinks so that the tie rods pull the end plates together. To enhance the pressure, the stacked plates can be compressed before and during the injection process.

Abstract: A rotor structure of a permanent magnet electrical machine and a method for manufacture of the rotor structure. The rotor structure has a shaft. An outer surface of the shaft is provided with a permanent magnet. A support collar encircles the permanent magnet. A protective piece is located between the outer surface of the shaft and an inner surface of the support collar and is arranged as an axial mechanical extension for the permanent magnet. The protective piece reduces local maximum values of forces forming between the support collar and the permanent magnet during rotation of the rotor.

Abstract: A motor rotor has: a rotor yoke; a plurality of magnet fixing sections formed on the lateral surface of the rotor yoke; segment magnets respectively fixed to the magnet fixing sections and extending in the axial direction of the rotor yoke; and a plurality of projections which are provided, on the rotor yoke, at each boundary section located between each of the adjacent magnet mounting sections, and which protrude outward from the rotor yoke; and a pair of end claws are formed by bifurcating the end of each projection into two prongs, and each of the end claws is locked to the outer surface of each of the segment magnets.

Abstract: Disclosed is a rotor assembly for an electric machine includes a rotor core. The rotor core has at least one magnet slot with an increasing slot width as radial distance from a rotor shaft increases, and at least one slot lip extending at least partially across the slot width. The rotor assembly also includes at least one permanent magnet located in at least one magnet slot, the magnet having an increasing magnet width as radial distance from a rotor shaft increases. The rotor assembly further includes a retainer disposed in the magnet slot radially between the magnet and the at least one slot lip. Also disclosed is a method of securing at least one permanent magnet in a rotor assembly of an electric machine.

Abstract: A motor rotor has a rotor yoke having a polygonal column structure, a plurality of magnet fixing sections formed on the lateral surface of the rotor yoke, segment magnets respectively fixed to the magnet fixing sections and extending in the axial direction of the rotor yoke, and projections provided on the rotor yoke and protruding outward from the rotor yoke, the projections being provided at each boundary section located between each of the adjacent magnet fixing sections and being provided in pairs in the axial direction of the rotor yoke.

Abstract: A retention system in which rotor pole pieces are retained within complementarily shaped channels in a rotor hub, permanent magnets are secured between the pole pieces and within clamp members, and wedge-shaped pieces are used to apply positive locking forces along the axial length of each clamp member and of adjacent pole pieces. A curable resin preferably in disposed within gaps between the permanent magnets and the clamp members.

Abstract: A buried-magnet internal rotor (1) for an electric rotating machine, the rotor comprising: a shaft (2), a plurality of polar parts (30) made of a magnetic material and surrounding the shaft, the polar parts delimiting magnet housings (40) between them, a plurality of permanent magnets (4) placed in the magnet housings (40), a lateral shroud (5, 5?) axially on each side of the polar parts along the shaft (2), the shaft passing through each lateral shroud, in which the housings are closed radially by wedges (51) interacting with longitudinal splines (31) of the polar parts, the said rotor being characterized in that the wedges have a T-shaped profile, the radial bearing faces (54) of the wedges in the polar parts being perpendicular to the central radius (41) of the housings (40), and in that, since the wedges (51) extend axially beyond the polar parts, their ends (511) are thinned and folded into a peripheral groove (52) of each lateral shroud (5, 5?).

Abstract: A rotating machine with a permanent magnet rotor that is easier, lower cost, and lighter includes a plurality of permanent magnet assemblies (20) mounted on a rotor body (1). The magnet assemblies (20) are mounted via magnet holders that each include a pair of claws (2, 3) connected by a bridge (5) and forming a seat for a respective magnet assembly (20). The claws have terminal expansions (11) that extend beyond the bridge (5) and form a second seat in which a tightening section (9) is received. The claws (2, 3) can elastically pivot about the bridge (5) when the terminal expansions (11) are squeezed together or forced apart, allowing insertion of and securing the magnet assembly, respectively.

Abstract: A retention system in which rotor pole pieces are retained within complementarily shaped channels in a rotor hub, permanent magnets are secured between the pole pieces and within clamp members, and wedge-shaped pieces are used to apply positive locking forces along the axial length of each clamp member and of adjacent pole pieces. A curable resin preferably in disposed within gaps between the permanent magnets and the clamp members.

Abstract: An illustrative embodiment of the present invention is concerned with a permanent magnet rotor for an electric machine provided with an internal stator and a coaxial external rotor. To overcome the drawbacks associated with the use of an adhesive to mount the permanent magnets to the rotor body, permanent magnet spacing and retaining elements are mounted to the inner surface of the rotor, between adjacent magnets.

Abstract: A rotating shaft disclosed by the present invention includes a plurality of bumps spacedly formed along an outer circumferential surface thereof. The bumps are each formed with two engagement portions extending outwardly and bilaterally and a deformation space therebetween. The engagement portions undergo resilient deformation toward the deformation space when subjected to a force, thus providing stable engagement with a magnetic body, protecting the magnetic body from cracks and damages during assembling, and enhancing yield. The present invention further discloses a motor rotor having the above-described rotating shaft.

Abstract: A synchronous motor having a rotor, a magnet positioned on the rotor and a clamping element that fixes the magnet on the rotor, wherein the clamping element includes a strip arranged between the magnet and the rotor.

Abstract: The invention is directed to an arrangement for fastening permanent magnets to rapidly rotating rotors of electric machines. It is the object of the invention to find a novel possibility for fastening permanent magnets to the rotor of rapidly rotating electric machines which allows the magnets to be fixed so as to be secure against centrifugal forces for high rotating speeds and under confined spatial conditions without a frictionally engaging connection of magnet holders to the rotor.

Abstract: Holder anchoring grooves are arranged on the outer periphery of a rotor core so as to extend axially. A holder arm having a substantially T-shaped cross section is fitted to each of the holder anchoring grooves. The holder arm has a main body section, an engaging projection and magnet holding pieces. The engaging projection is engaged with the corresponding one of the holder anchoring grooves. Each of the magnet holding pieces includes a first contact section, a second contact section and a non-contact area. A magnet containing section is defined by the magnet holding pieces that are located vis-à-vis relative to each other of any two adjacently located holder arms and the outer peripheral surface of the rotor core. In the magnet containing sections, a rotor magnet is press fitted and anchored from the shaft direction. Thus, there is provided a magnet fixing structure that can accurately anchor magnets to a rotor core or the like at low cost.

Abstract: An integrated blower and motor is provided. The integrated blower and motor can include a rotor and a stator, wherein the rotor is disposed with a central bore of the stator. The integrated blower and motor includes a fan, wherein the fan can be attached to the rotor. According to the embodiments described herein, an integrated blower and motor is provided that is compact and uses less space.

Abstract: A device to hold at least one magnetic flux producing permanent magnet onto a surface of an electrical machine comprising at least one slot recessed from the surface and extending from one end of the surface; and at least one gripping bar inserted into an associated at least one slot having a protrusion extending past the surface to engage at least one magnet where at least one slot and at least one gripping bar are shaped to retain the at least one gripping bar within the associated at least one slot to hold the at least one engaged magnet onto the surface.

Abstract: A pole assembly for a rotor, the pole assembly includes a permanent magnet pole including at least one permanent magnet block, a plurality of laminations including a pole cap mechanically coupled to the pole, and a plurality of laminations including a base plate mechanically coupled to the pole.

Abstract: A permanent magnet rotor for a brushless electrical machine has a rotor shaft and a cylindrical plastic cage. Permanent magnets are inserted in this plastic cage. The plastic cage has dovetailed retainers. The permanent magnets are trapezoidal in shape and are inserted so as to fit tightly in the dovetailed retainers.

Abstract: An integrated blower and motor is provided. The integrated blower and motor can include a rotor and a stator, wherein the rotor is disposed with a central bore of the stator. The integrated blower and motor includes a fan, wherein the fan can be attached to the rotor. According to the embodiments described herein, an integrated blower and motor is provided that is compact and uses less space.