CN208871006U - A kind of heavy-duty gear speed reducer of high-strength low noise - Google Patents

Abstract

The utility model relates to speed reducer equipment technical fields, and disclose a kind of heavy-duty gear speed reducer of high-strength low noise, including fixing seat, decelerating chassis is fixedly connected in the middle part of the fixing seat top, the side of the decelerating chassis is fixedly connected with fixed case, the middle part fixing sleeve on the decelerating chassis top is connected to oil guide pipe, the bottom end of the oil guide pipe extends to the inside of fixing seat, the top movable of the decelerating chassis inner cavity is set with the worm screw below oil guide pipe, and the internal activity of the decelerating chassis is set with the rotary shaft below worm screw.The heavy-duty gear speed reducer of the high-strength low noise, by bearing in fixing pipe pivot bush unit, the activity of one end of rotation axis and output shaft, to using the elastic force of the elastic force of second spring and the first spring as cushion effect, damping is carried out to output shaft, so that the meshing resistance between second gear and first gear not will increase, and then improve the working efficiency of speed reducer.

Description

A kind of heavy-duty gear speed reducer of high-strength low noise

Technical field

The utility model relates to speed reducer equipment technical field, specially a kind of heavy-duty gear speed reducer of high-strength low noise.

Background technique

Speed reducer is generally used for the drive apparatus of low rotation speed large torque, be related to food light industry, electric machinery, building machinery, The fields such as metallurgical machinery, cement machinery and environmental protection machinery, by the way that motor, internal combustion engine or other power to run at high speed are passed through Gear wheel on the few gear engagement output shaft of the number of teeth on the input shaft of speed reducer achievees the purpose that deceleration.

However, speed reducer is during the work time, the transmission between gear can generate vibration, and existing speed reducer antidetonation passes through Damping is carried out to whole, so that the vibrating effect of output shaft can not be eliminated, is increased so as to cause the gear meshing resistance of output shaft end Greatly, to influence the working efficiency of speed reducer, and after lubricating oil is added in transmission gear in existing speed reducer, lubricating oil is most of Lubricating oil falls into the bottom of speed reducer, cannot make full use of, so that the lubricant effect of lubricating oil is not high, is easy to cause worm and gear Contact site is impaired, reduces the service life of speed reducer.

Utility model content

In view of the deficiencies of the prior art, the utility model provides a kind of heavy-duty gear speed reducer of high-strength low noise, has The advantages of carrying out damping convenient for the output shaft to speed reducer and being convenient for lubricating oil persistently to gear lubrication, solves existing deceleration Machine antidetonation is by carrying out damping to whole, so that the vibrating effect of output shaft can not be eliminated, so as to cause the gear of output shaft end Meshing resistance increases, to influence the working efficiency of speed reducer, and after lubricating oil is added in transmission gear in existing speed reducer, moistens Lubricating oil major part lubricating oil falls into the bottom of speed reducer, cannot make full use of, so that the lubricant effect of lubricating oil is not high, is easy to lead The problem of causing worm and gear contact site impaired, reducing the service life of speed reducer.

The utility model provides the following technical solutions: a kind of heavy-duty gear speed reducer of high-strength low noise, including fixing seat, institute It states and is fixedly connected with decelerating chassis in the middle part of fixing seat top, the side of the decelerating chassis is fixedly connected with fixed case, described The middle part fixing sleeve on decelerating chassis top is connected to oil guide pipe, and the bottom end of the oil guide pipe extends to the inside of fixing seat, described to subtract The top movable of fast cabinet inner cavity is set with the worm screw below oil guide pipe, and the internal activity of the decelerating chassis is set with position The middle part fixing sleeve of rotary shaft below worm screw, the rotary shaft is equipped with worm gear, the outer of the worm gear and the outer of worm screw It engages, fixing sleeve is equipped with the first gear positioned at worm gear side in the rotary shaft, and one end of the rotary shaft extends to fixation Simultaneously fixing sleeve is equipped with turntable for the inside of case, and the outer of the turntable is fixedly connected with fixing axle, the decelerating chassis intracavity bottom Side be fixedly connected with fuel reserve tank, the top movable sleeve inside the fuel reserve tank is connected to rotation axis, fixed in the rotation axis It is set with the second gear being located inside fuel reserve tank, one end fixing sleeve of the fuel reserve tank is connected to the positioning positioned at fuel reserve tank side Plate.

The decelerating chassis is fixedly connected with damping device, the bottom of the damping device far from the bottom of fixed case side It is fixedly connected with support base, is fixedly connected at the top of the bottom of the support base and fixing seat, the middle part of the damping device is living Dynamic to be socketed with output shaft, one end of the output shaft extends to the inside of decelerating chassis and fixing sleeve is equipped with limiting plate, and described turn One end of moving axis extends to the inside of output shaft and is fixedly connected with restriction axis, and the quantity for limiting axis is two, and two The front and back that axis is located at rotation axis one end is limited, two restriction axis all extend to defeated far from one end of rotation axis The outside of shaft, is fixedly connected with the first spring between the limiting plate and positioning plate, first spring be located at output shaft and The outside of rotation axis, the side fixing sleeve of the fuel reserve tank bottom are connected to flowline, and one end of the flowline extends to fixation Simultaneously fixing sleeve is connected to oil storage box for the inside of case, and the oil storage box is fixedly connected on the bottom of fixed box cavity, the oil storage box top The side fixing sleeve in portion is connected to petroleum pipeline, and the top fixing sleeve of the petroleum pipeline is connected to sealing device, and fixing sleeve on flowline Equipped with another sealing device being located inside fixed case, the top of sealing device and the bottom end fixing sleeve of oil guide pipe It connects, the side fixing sleeve of the petroleum pipeline is connected to the fuel delivery device between sealing device and petroleum pipeline, the fuel delivery device The back side be fixedly connected with the inner wall of fixed case.

Preferably, the damping device includes fixing pipe, and the side movable sleeve inside the fixing pipe is connected to bearing, described The middle part of bearing and one end of output shaft are fixedly attached, and the internal activity of the fixing pipe is socketed with the gear positioned at bearing side Plate, the side of the baffle are fixedly connected with second spring, and the second spring movable set is on output shaft, and second spring One end far from baffle is fixedly connected with the side wall of fixed tube cavity.

Preferably, the sealing device includes oil transportation box, and the bottom of oil transportation box inner cavity is fixedly connected with positioned at oil transportation First fixing axle of pipe two sides, the top of two first fixing axles are fixedly connected at the top of oil transportation box inner cavity respectively, and two Pivot bush unit has limited block respectively in a first fixing axle, and one end of two limited blocks is fixedly connected with sealing valve Body, the bottom of the sealed valve body and the top pivot bush unit of petroleum pipeline are fixedly connected with third bullet at the top of the limited block Spring, the third spring movable set is in the first fixing axle, and the top of third spring and the top of oil transportation box inner cavity are fixed Connection.

Preferably, the fuel delivery device includes tube body, and the internal activity of the tube body is socketed with sealing-plug, the sealing-plug Side be fixedly connected with wire, the wire far from one end of sealing-plug extend to tube body outside and with fixing axle One end is fixedly connected, and the side of the sealing-plug is fixedly connected with the 4th spring, and the 4th spring movable set is in wire On, and the one end of the 4th spring far from sealing-plug is fixedly connected with the side wall of the inner cavity of tube body.

Preferably, the side wall of the decelerating chassis inner cavity is fixedly connected with the oil guide plate between worm gear and positioning plate, And one end of decelerating chassis inner wall oil guide plate is located at the top of fuel reserve tank.

Preferably, the front and back of described output shaft one end offers sliding slot, and the sliding slot and limit of output shaft one end Dead axle is adapted.

Be compared with the prior art, the utility model have it is following the utility model has the advantages that

1, the heavy-duty gear speed reducer of the high-strength low noise, pivot bush unit, rotation axis and output in fixing pipe by bearing One end activity of axis, to subtract using the elastic force of the elastic force of second spring and the first spring as cushion effect to output shaft Shake so that the meshing resistance between second gear and first gear not will increase, and then improves the work effect of speed reducer Rate.

2, the heavy-duty gear speed reducer of the high-strength low noise, is rotated by driven by rotary disc fixing axle, so that wire drive is close Blocking moves up, so that the lubricating oil inside fuel reserve tank enters in oil storage box, and is acted on using the elastic force of the 4th spring, so that sealing Plug moves down, using air pressure by lubricating oil be pressed into oil guide pipe in so that lubricating oil fallen on worm screw through oil guide pipe, to be continuously Worm and worm wheel are lubricated, and avoid worm and gear contact site impaired, to improve the service life of speed reducer.

Detailed description of the invention

FIG. 1 is a schematic structural view of the utility model；

Fig. 2 is the side sectional view of the utility model structure fixed case；

Fig. 3 is the utility model structural damping schematic device；

Fig. 4 is the utility model configuration seals schematic diagram；

Fig. 5 is the utility model structure fuel delivery device schematic diagram.

In figure: 1, fixing seat；2, decelerating chassis；3, fixed case；4, oil guide pipe；5, worm screw；6, rotary shaft；7, worm gear；8, First gear；9, turntable；10, fixing axle；11, fuel reserve tank；12, rotation axis；13, second gear；14, positioning plate；15, damping Device；151, fixing pipe；152, bearing；153, baffle；154, second spring；16, support base；17, output shaft；18, limiting plate； 19, axis is limited；20, the first spring；21, flowline；22, oil storage box；23, petroleum pipeline；24, sealing device；241, oil transportation box； 242, the first fixing axle；243, limited block；244, sealed valve body；245, third spring；25, fuel delivery device；251, tube body； 252, sealing-plug；253, wire；254, the 4th spring.

Specific embodiment

The following will be combined with the drawings in the embodiments of the present invention, carries out the technical scheme in the embodiment of the utility model Clearly and completely describe, it is clear that the described embodiments are only a part of the embodiments of the utility model, rather than whole Embodiment.Based on the embodiments of the present invention, those of ordinary skill in the art are without making creative work Every other embodiment obtained, fall within the protection scope of the utility model.

Fig. 1-5, a kind of heavy-duty gear speed reducer of high-strength low noise, including fixing seat 1 are please referred to, in 1 top of fixing seat Portion is fixedly connected with decelerating chassis 2, and the side wall of 2 inner cavity of decelerating chassis is fixedly connected between worm gear 7 and positioning plate 14 Oil guide plate, and one end of 2 inner wall oil guide plate of decelerating chassis is located at the top of fuel reserve tank 11, will be fallen on worm gear 7 using oil guide plate Lubricating oil import fuel reserve tank 11 in, convenient for lubricating oil circulation continuous utilize, the side of decelerating chassis 2 is fixedly connected with fixation Case 3, the middle part fixing sleeve on 2 top of decelerating chassis are connected to oil guide pipe 4, and the bottom end of oil guide pipe 4 extends to the inside of fixing seat 1, subtracts The top movable of fast 2 inner cavity of cabinet is set with the worm screw 5 positioned at 4 lower section of oil guide pipe, and the internal activity of decelerating chassis 2 is set with position The middle part fixing sleeve of rotary shaft 6 in 5 lower section of worm screw, rotary shaft 6 is equipped with worm gear 7, and the outer of worm gear 7 and the outer of worm screw 5 are nibbled It closes, fixing sleeve is equipped with the first gear 8 positioned at 7 side of worm gear in rotary shaft 6, and one end of rotary shaft 6 extends to the interior of fixed case 3 Portion and fixing sleeve are equipped with turntable 9, and the outer of turntable 9 is fixedly connected with fixing axle 10, and the side of 2 intracavity bottom of decelerating chassis is solid Surely it is connected with fuel reserve tank 11, the top movable sleeve inside fuel reserve tank 11 is connected to rotation axis 12, and fixing sleeve is equipped with position in rotation axis 12 Second gear 13 inside fuel reserve tank 11, one end fixing sleeve of fuel reserve tank 11 are connected to the positioning plate positioned at 11 side of fuel reserve tank 14。

Decelerating chassis 2 is fixedly connected with damping device 15 far from the bottom of 3 side of fixed case, and damping device 15 includes fixing Pipe 151, the side movable sleeve inside fixing pipe 151 are connected to bearing 152, and the middle part of bearing 152 and one end of output shaft 17 are fixed Socket, the internal activity of fixing pipe 151 are socketed with the baffle 153 positioned at 152 side of bearing, and the side of baffle 153 is fixedly connected There is second spring 154,154 movable set of second spring is on output shaft 17, and the one end of second spring 154 far from baffle 153 It is fixedly connected with the side wall of 151 inner cavity of fixing pipe, it is mobile in the inside of fixing pipe 151 by bearing 152, utilize second spring 154 elastic force effect, the vibration generated to output shaft 17 shift, are buffered, to avoid first gear 8 and the second tooth The meshing resistance of wheel 13 increases, and influences the working efficiency of speed reducer, and the bottom of damping device 15 is fixedly connected with support base 16, branch The bottom of support seat 16 is fixedly connected with the top of fixing seat 1, and the middle part movable sleeve of damping device 15 is connected to output shaft 17, output shaft The front and back of 17 one end offers sliding slot, and the sliding slot of 17 one end of output shaft is adapted with axis 19 is limited, in output shaft 17 because of vibration when shifting, and is buffered using the first spring 20 and the effect of the elastic force of second spring 154, it is ensured that the first tooth Transmission between wheel 8 and second gear 13 is unaffected, and one end of output shaft 17 extends to the inside of decelerating chassis 2 and fixing sleeve Equipped with limiting plate 18, one end of rotation axis 12, which extends to the inside of output shaft 17 and is fixedly connected with, limits axis 19, limits axis 19 Quantity be two, and two limit axis 19 and are located at the front and back of 12 one end of rotation axis, and two restriction axis 19 are separate One end of rotation axis 12 all extends to the outside of output shaft 17, and the first spring is fixedly connected between limiting plate 18 and positioning plate 14 20, the first spring 20 is located at the outside of output shaft 17 and rotation axis 12, and the side fixing sleeve of 11 bottom of fuel reserve tank is connected to flowline 21, one end of flowline 21 extends to the inside of fixed case 3 and fixing sleeve is connected to oil storage box 22, and oil storage box 22 is fixedly connected on Determine the bottom of 3 inner cavity of case, the side fixing sleeve at 22 top of oil storage box is connected to petroleum pipeline 23, and the top of petroleum pipeline 23 is fixedly attached There is sealing device 24, and fixing sleeve is equipped with another 24 sealing device being located inside fixed case 3, sealing device on flowline 21 24 include oil transportation box 241, and the bottom of 241 inner cavity of oil transportation box is fixedly connected with the first fixing axle 242 positioned at 23 two sides of petroleum pipeline, The top of two the first fixing axles 242 is fixedly connected at the top of 241 inner cavity of oil transportation box respectively, in two the first fixing axles 242 Pivot bush unit has limited block 243 respectively, and one end of two limited blocks 243 is fixedly connected with sealed valve body 244, sealed valve body 244 Bottom and petroleum pipeline 23 top pivot bush unit, the top of limited block 243 is fixedly connected with third spring 245, third spring 245 movable sets are in the first fixing axle 242, and the fixed company in the top of the top of third spring 245 and 241 inner cavity of oil transportation box It connects, during sealing-plug 252 moves up, so that the sealed valve body between petroleum pipeline 23 and oil guide pipe 4 inside oil transportation box 241 closes It closes, the sealed valve body inside oil transportation box 241 on flowline 21 is opened, so that the lubricating oil inside fuel reserve tank 11 enters oil storage The inside of box 22, in 252 folding process of sealing-plug, so that between petroleum pipeline 23 and oil guide pipe 4 inside oil transportation box 241 Sealed valve body is opened, the closing of sealed valve body positioned at oil transportation box 241 on flowline 21 inside, the lubricating oil inside oil storage box 22 according to It is secondary to be fallen on worm screw 5 by oil transportation box 241 and oil guide pipe 4, oil transportation is carried out convenient for being continuously worm screw 5, sealing device 24 Top and the bottom end of oil guide pipe 4 are fixedly attached, and the side fixing sleeve of petroleum pipeline 23 is connected to positioned at sealing device 24 and petroleum pipeline 23 Between fuel delivery device 25, fuel delivery device 25 includes tube body 251, and the internal activity of tube body 251 is socketed with sealing-plug 252, is sealed The side of plug 252 is fixedly connected with wire 253, and wire 253 extends to the outer of tube body 251 far from one end of sealing-plug 252 Portion is simultaneously fixedly connected with one end of fixing axle 10, and the side of sealing-plug 252 is fixedly connected with the 4th spring 254, the 4th spring 254 Movable set is on wire 253, and the side wall of the one end of the 4th spring 254 far from sealing-plug 252 and the inner cavity of tube body 251 is solid Fixed connection, during driving fixing axle 10 to move up by turntable 9, wire 253 drives sealing-plug 252 to move up, so that fuel reserve tank Lubricating oil inside 11 is drawn into oil storage box 22, is driven in 10 folding process of fixing axle in turntable 9, is utilized the 4th spring 254 Elastic force effect fallen on worm screw 5 so that lubricating oil oil storage box 22 inside passes through oil transportation box 241 and oil guide pipe 4, oil transportation fills 25 back side is set to be fixedly connected with the inner wall of fixed case 3.

Working principle, firstly, then being rotated by worm screw 5 lubricating oil is injected into oil storage box 22, so that worm gear 7 drives Rotary shaft 6 rotates, and carries out primary speed-down, is rotated using first gear 8, so that rotation axis 12 drives output shaft 17 to rotate, into Row double reduction, finally, the lubricating oil on worm gear 7 and worm screw 5 enters the inside of fuel reserve tank 11 through oil guide plate, so that second gear 13 and first gear 8 lubricated, using rotary shaft 6 drive turntable 9 rotate so that fixing axle 10 drive wire 253 move up, To move up using sealing-plug 252, the lubricating oil inside fuel reserve tank 11 is extracted, turntable 9 persistently rotates, so that fixing axle 10 rotates To the lower section of turntable 9, acted on using the elastic force of the 4th spring 254, so that the lubricating oil inside oil storage box 22 enters oil transportation box 241 It is interior, and continue to move up and down in the inside of tube body 251 by sealing-plug 252, so that lubricating oil is fallen again from the top of oil guide pipe 4 Enter and is lubricated on worm screw 5.

It should be noted that, in this document, relational terms such as first and second and the like are used merely to a reality Body or operation are distinguished with another entity or operation, are deposited without necessarily requiring or implying between these entities or operation In any actual relationship or order or sequence.Moreover, the terms "include", "comprise" or its any other variant are intended to Non-exclusive inclusion, so that the process, method, article or equipment including a series of elements is not only wanted including those Element, but also including other elements that are not explicitly listed, or further include for this process, method, article or equipment Intrinsic element.

The embodiments of the present invention have been shown and described, it for the ordinary skill in the art, can be with Understand do not depart from the principles of the present invention and spirit in the case where can to these embodiments carry out it is a variety of variation, modification, Replacement and variant, the scope of the utility model are defined by the appended claims and the equivalents thereof.

Claims (6)

1. a kind of heavy-duty gear speed reducer of high-strength low noise, including fixing seat (1), it is characterised in that: fixing seat (1) top Middle part be fixedly connected with decelerating chassis (2), the side of the decelerating chassis (2) is fixedly connected with fixed case (3), the deceleration The middle part fixing sleeve on cabinet (2) top is connected to oil guide pipe (4), and the bottom end of the oil guide pipe (4) extends to the interior of fixing seat (1) The top movable in portion, decelerating chassis (2) inner cavity is set with the worm screw (5) below oil guide pipe (4), the decelerating chassis (2) internal activity is set with the rotary shaft (6) below worm screw (5), and the middle part fixing sleeve of the rotary shaft (6) is equipped with snail It takes turns (7), the outer of the worm gear (7) is engaged with the outer of worm screw (5), and fixing sleeve, which is equipped with, on the rotary shaft (6) is located at worm gear (7) first gear (8) of side, one end of the rotary shaft (6) extends to the inside of fixed case (3) and fixing sleeve is equipped with turntable (9), the outer of the turntable (9) is fixedly connected with fixing axle (10), and the side of decelerating chassis (2) intracavity bottom is fixed to be connected It is connected to fuel reserve tank (11), the internal top movable sleeve of the fuel reserve tank (11) is connected to rotation axis (12), on the rotation axis (12) Fixing sleeve, which is equipped with, is located at fuel reserve tank (11) internal second gear (13), and one end fixing sleeve of the fuel reserve tank (11), which is connected to, to be located at The positioning plate (14) of fuel reserve tank (11) side；

The decelerating chassis (2) is fixedly connected with damping device (15), the damping device far from the bottom of fixed case (3) side (15) bottom is fixedly connected with support base (16), is fixedly connected at the top of the bottom and fixing seat (1) of the support base (16), The middle part movable sleeve of the damping device (15) is connected to output shaft (17), and one end of the output shaft (17) extends to decelerating chassis (2) inside and fixing sleeve is equipped with limiting plate (18), and one end of the rotation axis (12) extends to the inside of output shaft (17) simultaneously It is fixedly connected with and limits axis (19), the quantity for limiting axis (19) is two, and two restriction axis (19) are located at rotation The front and back of axis (12) one end, two described one end for limiting axis (19) separate rotation axis (12) all extend to output shaft (17) outside is fixedly connected with the first spring (20), first spring between the limiting plate (18) and positioning plate (14) (20) it is located at the outside of output shaft (17) and rotation axis (12), the side fixing sleeve of fuel reserve tank (11) bottom is connected to flowline (21), one end of the flowline (21) extends to the inside of fixed case (3) and fixing sleeve is connected to oil storage box (22), the oil storage Box (22) is fixedly connected on the bottom of fixed case (3) inner cavity, and the side fixing sleeve at the top of the oil storage box (22) is connected to petroleum pipeline (23), the top fixing sleeve of the petroleum pipeline (23) is connected to sealing device (24), and on flowline (21) fixing sleeve equipped with being located at Another internal sealing device (24) of fixed case (3), the top of a sealing device (24) and the bottom end of oil guide pipe (4) It is fixedly attached, the side fixing sleeve of the petroleum pipeline (23) is connected to the oil transportation between sealing device (24) and petroleum pipeline (23) The back side of device (25), the fuel delivery device (25) is fixedly connected with the inner wall of fixed case (3).

2. a kind of heavy-duty gear speed reducer of high-strength low noise according to claim 1, it is characterised in that: the damping device It (15) include fixing pipe (151), the internal side movable sleeve of the fixing pipe (151) is connected to bearing (152), the bearing (152) one end at middle part and output shaft (17) is fixedly attached, and the internal activity of the fixing pipe (151) is socketed with positioned at bearing (152) side of the baffle (153) of side, the baffle (153) is fixedly connected with second spring (154), the second spring (154) movable set is on output shaft (17), and one end and fixing pipe (151) far from baffle (153) of second spring (154) are interior The side wall of chamber is fixedly connected.

3. a kind of heavy-duty gear speed reducer of high-strength low noise according to claim 1, it is characterised in that: the sealing device It (24) include oil transportation box (241), the bottom of oil transportation box (241) inner cavity is fixedly connected with positioned at petroleum pipeline (23) two sides One fixing axle (242), the top of two first fixing axles (242) is fixed with the top of oil transportation box (241) inner cavity respectively to be connected It connecing, pivot bush unit has limited block (243) respectively on two first fixing axles (242), and the one of two limited blocks (243) End is fixedly connected with sealed valve body (244), the bottom of the sealed valve body (244) and the top pivot bush unit of petroleum pipeline (23), It is fixedly connected with third spring (245) at the top of the limited block (243), third spring (245) movable set is first In fixing axle (242), and it is fixedly connected at the top of the top of third spring (245) and oil transportation box (241) inner cavity.

4. a kind of heavy-duty gear speed reducer of high-strength low noise according to claim 1, it is characterised in that: the fuel delivery device It (25) include tube body (251), the internal activity of the tube body (251) is socketed with sealing-plug (252), the sealing-plug (252) Side is fixedly connected with wire (253), and the wire (253) extends to tube body (251) far from the one end of sealing-plug (252) Outside and be fixedly connected with one end of fixing axle (10), the side of the sealing-plug (252) is fixedly connected with the 4th spring (254), the 4th spring (254) movable set is on wire (253), and the 4th spring (254) is far from sealing-plug (252) One end be fixedly connected with the side wall of the inner cavity of tube body (251).

5. a kind of heavy-duty gear speed reducer of high-strength low noise according to claim 1, it is characterised in that: the decelerating chassis (2) side wall of inner cavity is fixedly connected with the oil guide plate between worm gear (7) and positioning plate (14), and decelerating chassis (2) inner wall One end of oil guide plate is located at the top of fuel reserve tank (11).

6. a kind of heavy-duty gear speed reducer of high-strength low noise according to claim 1, it is characterised in that: the output shaft (17) front and back of one end offers sliding slot, and the sliding slot of output shaft (17) one end is adapted with axis (19) are limited.