CHAIN HOISTING DEVICE WITH SAFE DESCENDING STROKE

Abstract

 The present invention provides a chain lifter with safe descending stroke, which comprises: a lifting body, a motor, a driving sprocket group, a linkage mechanism, a first safe switch and a second safe switch. The linkage mechanism is composed of a first rocking rod, a second rocking rod, a first connecting rod, a second connecting rod and an elastic resetting mechanism which are in the same plane. The first end of the first rocking rod is connected with a first adjusting wheel, the first end of a second rocking rod is connected with a second adjusting wheel. In the present invention, the lifting body is provided with a linkage mechanism which can reset automatically by collaborating with the rocking rod, the linkage crank and the adjusting wheel to change the wrap angle of the chain on the wheel and automatically adjust the looseness of the loose edge of the chain, so as to ensure the lifter to be provided with enough descending stroke when the lifter touches the ground, to prevent from operation fault and accidents caused by the over-loosening or over-tightening of the chain, and to increase the operation reliability and safety of the lifter observably.

Description

Field of the invention

[0001] The present invention relates to a lifter, in particular, to a kind of chain lifter with safe descending stroke.

Description of the Prior Art

[0002] The existing lifter achieves the ascending or descending of the bearing body by the usual use of the chain transmission, the belt transmission, the gear transmission or the hydraulic cylinder extension and etc. The chain transmission can work reliably under harsh conditions such as high temperature, oil or acid and accordingly behaves with very high adaptability owing to the ability to transmit movements and forces under the condition that the distance between the center of two shafts is long, which is one of the most widely used movable parts in the mechanical handling and lifting system, for example, the lifting device of stereo garage, the lifter of logistics equipment and the small elevator for serving diner, these devices are all equipped with the chain transmission mechanism.

[0003] In practical applications, a Chinese Patent CN2820819Y titled "Lifting Driving Device" (Patent Number is ZL200520026711.2) is a classic application of the chain transmission in the garage lifting system. The lifting driving device comprises a system box that can move up and down along two lifting guiding rails, a group of main driving engine mounted in the middle of the system box, a first transmission chain group, a second transmission chain group and a pressure tension sprocket device which all driven by the main driving engine; the whole lifting driving device is directly provided on the bottom of a lifting body; the first transmission chain group and the second transmission are respectively engaged on and the main shaft of the main driving engine respectively through a first chain and a second chain; the first chain and the second chain are engaged on the main shaft in reverse direction, which leads to the forming of equal reverse force of the first chain and the second chain on the main shaft, according the main shaft load of the main driving engine can be substantially eliminated, so that the service life of the main driving engine will be prolonged. The chain transmission group in this patent can be directly provided in the system box, it makes the lifting device can be provided on the bottom of the lifting body through the system box, so as to substantially save space and reduce cost, and the use of the chain transmission can reduce the load of the main shaft of the main driving engine, so as to prolong the service life.

[0004] However, during the ascending or descending process of the lifting device in the up stated patent, due to the gravity, the chain fixed on the top side of the stand column keeps in tight all along, especially when the lifting device touches the ground, owing to the lag of brake of the motor, the motor will continue to drive the chain to rotate under the role of inertia. Accordingly, during the period from the receival of stop signal to the complete brake, the motor continues to rotate, and makes the chain originally in loose to turn tight and the chain originally in tight to turn loose. As the motor continues to rotate, the chain turning loose will have increasing looseness, and too large looseness will further lead to poor meshing and vibration of the chain, which will cause unsteady chain transmission and even chain-disengaging. If the motor still rotates, the chain turning tight will be stretched to crack and can not work normally. Therefore, the adjustment of the chain looseness when the motor brakes is failed to be considered in the lifting device in the up stated patent, that is, the lifting device is not provided with enough safe descending stroke, which influences the widespread use of the lifting device to some extent.

[0005] In order to solve the problem of the chain loosening, another Chinese Patent CN201193154Y (Patent Number is ZL200820300554.3) discloses a tensioning and centering device of the driven sprocket of the lifter. In this device, the lower sprocket group is mounted on the lower sprocket group framework, the slip connection is provided between the lower sprocket group and the stand column, a tension adjustment screw is provided between the base on the bottom of the stand column and the frame of the lower sprocket group, the top of the tension adjustment screw is provided with a tension nut; furthermore, the joint between the main transmission shaft and the cantilever sprocket of the lower sprocket group and the frame of the lower sprocket group is provided with a centering device.

[0006] However, the tensioning device in this patent can only be achieved by manual adjustment, which has the disadvantage that the looseness of the loose edge of the chain can not be accurately obtained, it means that an accurate judgment for the descending limit position of the lifting mechanism is required. Yet, as the running environment and motor performance are usually different, and the triggering time of the limit switch varies, it is hard to know the accurate descending limit position. If the looseness of the chain after adjustment is too small, then the chain scission will occur when the motor continues to rotate; if the looseness of the chain after adjustment is still too large, then the vibration and even chain-disengaging will occur during the running process. Therefore, the tension device of the up stated patent still cannot well solve the problem of unsteady descending caused by the chain loosening, so that the safety of the equipment during the running process still cannot be effectively guaranteed.

Summary of the invention

[0007] It is an object of the present invention to provide a chain lifter which can automatically change the wrap angle of the chain with loose edge on the wheel/sprocket to ensure the looseness of the chain to be kept within a given range; the chain lifter accordingly ensures enough safety stroke during the descending process, so as to improve stability and safety of the work of the lifter.

[0008] For achieving the above stated object, a chain lifter with safe descending stroke comprising:

a lifting body which can move up and down along a pair of vertical guiding grooves;

a motor which is fixed on the middle of the lifting body;

a driving sprocket group, including a first driving wheel and a second driving wheel both mounted on the output shaft of the motor, two first traction wheels respectively disposed at two sides of the output shaft of the motor, a first tension wheel disposed between one of the two first traction wheels and the first driving wheel, a first chain engaged on the two first traction wheels, the first tension wheel and the first driving wheel, two second traction wheels respectively disposed at two sides of the output shaft of the motor, a second tension wheel disposed between one of the two second traction wheels and the second driving wheel and located at the different side of the first tension wheel relatively to the output shaft of the motor, a second chain engaged on the two second traction wheels, the second tension wheel and the second driving wheel;

characterized in that the chain lifter also comprises:

a linkage mechanism disposed between the first tension wheel and the second tension wheel, which includes a first swing rod, a second swing rod, a first connecting rod and a second connecting rod all disposed substantially in a same plane, a first end of the fist swing rod is hinged with a first end of the second swing rod through a first pin which forms a first hinge point, a first end of the second connecting rod is hinged at the middle of the second swing rod, a second end of the first connecting rod is hinged with a second end of the second connecting rod through a second pin which forms a second hinge point, furthermore, the linkage mechanism also includes an elastic resetting mechanism which makes the first hinge point and the second hinge point keep apart with each other all along;

a first rocking rod, the first end of which is hinged on the lifting body, the second end of which is provided with a first fixing shaft on which the first tension wheel surround, and which the second end of the second swing rod is hinged on;

a second rocking rod, the first end of which is hinged on the lifting body, the second end of which is provided with a second fixing shaft on which the second tension wheel surround, and which the second end of the second swing rod is hinged on;

a first safe switch, fixed on the lifting body and located corresponding to the position of the second rocking rod, when the lifting body touches the ground, the second rocking rod can trigger the first safe switch to control the motor to stop;

a second safe switch, fixed on the lifting body and located corresponding to the position of the first rocking rod, when the lifting body touches the ground and the first safe switch fails to work, the first rocking rod can trigger the second safe switch to control the motor to stop;

a first linkage crank; a first pulling rod; a second linkage crank; a second pulling rod;

a first adjusting wheel for adjusting the wrap angle of the loosen edge of the first chain on the first traction wheel, the main shaft of the first adjusting wheel is fixed on the first end of the first linkage crank, the middle of the first linkage crank is hinged on the lifting body, the second end of the first linkage crank is hinged on the first end of the first pulling rod, the second end of the first pulling rod is hinged on the first rocking rod;

a second adjusting wheel for adjusting the wrap angle of the loosen edge of the second chain on the second traction wheel, the main shaft of the second adjusting wheel is fixed on the first end of the second linkage crank, the middle of the second linkage crank is hinged on the lifting body, the second end of the second linkage crank is hinged on the first end of the second pulling rod, the second end of the second pulling rod is hinged on the second rocking rod.

[0009] In order to reduce the volume of the device and ensure the stability of resetting, as a preference, the elastic resetting mechanism includes a spring seat, a frame and a spring, the spring seat is in conversed U-shape, a positioning sleeve is provided on the top of the main body of the spring seat for the spring to surround, a guiding column is inserted in the positioning sleeve which can slide up and down relatively to the positioning sleeve, the upper portion of the guiding column is fixed with the frame, the two side walls of the main body of the spring seat are respectively provided with a lengthways guiding hole, and the bottom ends of the two side walls are respectively provided with a first hinging holes;
the first hinge point and the second hinge point are both disposed on the two side walls of the main body of the spring seat, and journals of the two ends of the first pin are respectively rested in the corresponding first hinging hole, the two ends of the second pin are respectively disposed through the corresponding lengthways guiding hole and the second pin can slide lengthways along the lengthways guiding hole;
the frame is disposed above the main body of the spring seat, the frame can keep linkage with the first connecting rod and the second connecting rod through the second pin, the spring is limited between the frame and the main body of the spring seat to make the frame keep apart with the spring seat all along.

[0010] As a result, when the second end of the first swing rod and the second end of the second swing rod draw closely to each other under the function of the traction of the chain, the second hinge point will move along the lengthways guiding hole and move close to the first hinge point, and the spring is in compression state; when the external force disappearing, under the action of the elastic resetting force of the spring, the frame will move depart from the spring seat, and the second hinge point will move along the lengthways guiding hole and away from the first hinge point.

[0011] In order to make the spring be assembled firmly and be positioned easily, as a preference, the frame is designed to be conversed U-shaped, the bottom ends of the two side walls of the frame are respectively provided with a second hinging hole, journals of the two ends of the second pin are respectively rested in the corresponding second hinging holes;
the upper portion of the guiding column has threads outside, the top of the frame has a through hole for the upper portion of the guiding column to go through, and the top of the guiding column which is above the top of the frame is threaded connected with a first nut, the portion of the guiding column which is below the top of the frame is threaded connected with a second nut, the first nut and the second nut make the upper portion of the guiding column be limited in the through hole of the frame.

[0012] The first safe switch can be an electro-optical switch, or a reed ripe, or a Hall switch or other existing common used trigger switch. As a preference, the first safe switch is a micro switch, The first safe switch is a micro switch, the second rocking rod includes a main portion which is parallel to the lifting body, a L-shaped bending portion located above the main portion and bending toward the lifting body, and a second fixing shaft which is vertically disposed on the vertical wall of the L-shaped bending portion, the bottom of the main portion is the first end of the second rocking rod which is hinged on the lifting body through a fourth pin, the top of the main portion is provided with a first triggering block which can press the first safe switch.

[0013] The second safe switch can be an electro-optical switch, or a reed ripe, or a Hall switch or other existing common used trigger switch. As a preference, the second safe switch is a micro switch, the top of the first rocking rod is the first end of the first rocking rod which is hinged on the lifting body through a third pin, a first fixing shaft is disposed at the bottom of the first rocking rod, and the bottom of the first rocking rod is provided with a second triggering block which can press the second safe switch.

[0014] Compared with the prior art, in the present invention, the lifting body is provided with a linkage mechanism which can reset automatically, and the looseness of the loose edge of the chain can be automatic adjusted by collaborating with the rocking rod, the linkage crank and the adjusting wheel; as the linkage mechanism in the present invention is a planar four-bar linkage with the double herring bone structure, which is small in size and can be installed in a tiny space accordingly; all hinge points of the linkage mechanism can move freely without fixed points, therefore, the stroke can be amplified with non-constant rate, i.e. the motor inertia can be transmitted to the sprocket, and the rocking rod can be driven to ensure the linkage between the pulling rod and the linkage crank, in the meanwhile, the stroke of the elastic resetting mechanism can be changed through the linkage mechanism, and the wrap angle of the chain on the wheel/sprocket can be changed, so as to prevent from operation fault and accidents caused by the over-loosening or over-tightening of the chain;

[0015] As a result, the present invention can achieve the automatic adjustment to the chain looseness through the various size of the motor inertia force, so as to avoid the defect of improper adjustment caused by inaccurate prediction of manual adjustment, the adjustment mode of the present invention is more flexible, reliable and accurate, and such adjustment mode can achieve better adjustment effect, so as to ensure the lifter to be provided with enough descending stroke when the lifter touches the ground, and the loose edge of the chain to be kept within proper range all along.

[0016] In addition, the present invention is also provided with a double protection switch which has a lower limit and a lower check, so that the motor can stop reliably when the lifter touches the ground, it can increase the operation reliability and safety of the lifter.

Brief Description of the Drawings

[0017] 

FIG.1 is a perspective view of a chain lifter with safe descending stroke in accordance with an exemplary embodiment of the present invention.

FIG2 is a perspective view of the lifting body shown in FIG.1. 1.

FIG.3 is a perspective view of the first rocking rod in accordance with the exemplary embodiment of the present invention.

FIG.4 is a perspective view of the second rocking rod in accordance with the exemplary embodiment of the present invention.

FIG.5 is a perspective view of a part of the linkage mechanism in accordance with the exemplary embodiment of the present invention.

FIG.6 is an explosive view of the linkage mechanism shown in FIG.5.

FIG.7 is a sketch of the working status of the chain lifter in accordance with the exemplary embodiment when the chain lifter does not touch the ground.

FIG.8 is a sketch of the working status of the chain lifter in accordance with the exemplary embodiment when the chain lifter touches the ground and the first safe switch is triggered.

FIG.9 is a sketch of the working status of the chain lifter in accordance with the exemplary embodiment when the chain lifter touches the ground and the second safe switch is triggered.

Detailed Description of the Preferred Embodiment

[0018] To enable a further understanding of the innovative and technological content of the invention herein refer to the detailed description of the invention and the accompanying drawings below:

[0019] FIG.1 ∼ FIG.9 show a chain lifter in accordance with an exemplary embodiment of the present invention. The chain lifter comprises a lifting body (1) which can move up and down along a pair of vertical guiding grooves (9) locating at the two sides of the lifting body (1), a motor (2) which is fixed on the middle of the lifting body (1), and a driving sprocket group which is disposed in the lifting body (1).

[0020] The driving sprocket group is composed of a first driving sprocket group and a second driving sprocket group both symmetrically disposed, as shown in Fig. 1 and Fig. 7. The detail is as below:

[0021] The first driving sprocket group includes a first driving wheel (31), two first traction wheels (32) and a first tension wheel (33) which are all disposed in a same plane. The first driving wheel (31) is coaxial with the output shaft of the motor, the two first traction wheels (32) are respectively disposed at two sides of the output shaft of the motor. The first tension wheel (33) is disposed between the first traction wheel (32) which is disposed at the left side of the output shaft of the motor and the first driving wheel (31). A first chain (34), the first free end of which is fixed on the vertical guiding groove (9) below the first traction wheel (32) disposed at the left side of the output shaft of the motor, the second free end of which moves round the top edge of the first traction wheel (32) which is disposed at the right side of the output shaft of the motor being engaged and extends to be fixed on the vertical guiding groove (9).

[0022] As a result, the middle part of the first chain (34) is engaged from the first end of the first traction wheel (32) orderly with the top edge of the first traction wheel (32) at the left side, and with the first tension wheel (33) and the first driving wheel (31) in S-shape, and with the bottom of the first traction wheel (32) at the right side, finally reaching out from the bottom of the first traction wheel (32).

[0023] The second driving sprocket group includes a second driving wheel (41), two second traction wheels (42) and a second tension wheel (43) which are all disposed in a same plane. The second driving wheel (41) is mounted on the output shaft of the motor, two second traction wheels (42) are respectively disposed at two sides of the output shaft of the motor and are respectively coaxial with the corresponding first traction wheel (32). The second tension wheel (43) is disposed between the second traction wheel (42) disposed at the right side of the output shaft of the motor and the second driving wheel (41).

[0024] A second chain (44), the first free end of which moves round the top edge of the second traction wheel (42) disposed at the left side of the output shaft of the motor being engaged and extends to be fixed on the vertical guiding groove (9), the second free end of which is fixed on the vertical guiding groove (9) below the second traction wheel (42) disposed at the right side of the output shaft of the motor. Accordingly, the middle part of the second chain (44) comes out from the bottom of the second traction wheel (42) at the left side, and is engaged orderly with the second driving wheel (41) and the second tension wheel (43) in S-shape, and extends from the top edge of the second traction wheel (42) at the right side finally fixed on the vertical guiding groove (9).

[0025] At the front of the lifting body (1), a planar linkage mechanism (5) is disposed between the first tension wheel (33) and the second tension wheel (43) (see Fig.1, Fig.2 and Fig.5), which includes a first swing rod (51), a second swing rod (52), a first connecting rod (53) and a second connecting rod (54) all disposed in a same plane. A first end of the fist swing rod (51) is hinged with a first end of the second swing rod (52) through a first pin (101) which forms a first hinge point (a), a first end of the second connecting rod (54) is hinged at the middle of the second swing rod (52), a second end of the first connecting rod (53) is hinged with a second end of the second connecting rod (54) through a second pin (102) which forms a second hinge point (b).

[0026] Furthermore, the linkage mechanism (5) also includes an elastic resetting mechanism which makes the first hinge point (a) and the second hinge point (b) keep apart with each other all along. The linkage mechanism (5) is composed of a spring seat (55), a frame (56) and a helical compression spring (57). The main part of the spring seat (55) is in conversed U-shape, a positioning sleeve (551) is provided on the top of the main body of the spring seat (55) for the spring (57) to surround, a guiding column (554) is inserted in the positioning sleeve (551) which can slide up and down relatively to the positioning sleeve (551), the upper portion of the guiding column (554) is fixed with the frame (56), the two side walls of the main body of the spring seat (55) are respectively provided with a lengthways guiding hole (552), and the bottom ends of the two side walls are respectively provided with a first hinging holes (553); the first hinge point (a) and the second hinge point (b) are both disposed on the two side walls of the main body of the spring seat (55), and journals of the two ends of the first pin (101) are respectively rested in the corresponding first hinging hole (553), the two ends of the second pin (102) are respectively disposed through the corresponding lengthways guiding hole (552) and the second pin (102) can slide lengthways along the lengthways guiding hole (552).

[0027] The frame (56) is disposed above the main body of the spring seat (55) and designed to be conversed U-shaped, the bottom ends of the two side walls of the frame (56) are respectively provided with a second hinging holes (561), the frame (56) can keep linkage with the first connecting rod (53) and the second connecting rod (54) through the second pin (102), the spring (57) is limited between the frame (56) and the main body of the spring seat (55). The top of the frame (56) has a through hole (562) for the upper portion of the guiding column (554) to go through, and the top of the guiding column (554) which is above the top of the frame (56) is threaded connected with a first nut (563), the portion of the guiding column (554) which is below the top of the frame (56) is threaded connected with a second nut (564), the first nut (563) and the second nut (564) make the upper portion of the guiding column (554) be limited in the through hole (562) of the frame (56), so that the guiding column (554) can connect with the frame(56).

[0028] A rocking rod crank mechanism is provided at the two sides of a linkage mechanism (5), which can deliver the expansion of the linkage mechanism (5) to the adjusting wheel which can change the size of wrap angle of the chain. The rocking rod crank mechanism includes a first rocking rod (61), a second rocking rod (62), the first pulling rod (71), the second pulling rod (72), the first linkage crank (81) and the second linkage crank (82), as shown in Fig.1, Fig.2, Fig.3 and Fig.4.

[0029] The first rocking rod (61) is hinged on a second end (511) of the first swing rod (51) through a pin (613) fixed at the bottom of the first rocking rod (61), the upper portion of the first rocking rod (61) as the first end of the first rocking rod is hinged on the lifting body (1) through a third pin (103), the bottom of the first rocking rod (61) as the second end of the first rocking rod is provided with a first fixing shaft (611) and disposed at the bottom of the first rocking rod (61), the first tension wheel (33) surrounds the first fixing shaft (611).

[0030] A first adjusting wheel (91) is fixed on the first linkage crank (81), which is for adjusting the wrap angle of the loose edge of the first chain (34) on the first traction wheel (32). The middle of the first linkage crank (81) is hinged on the lifting body (1), the second end of the first linkage crank (81) is hinged on the first end of the first pulling rod (71), the second end of the first pulling rod (71) is hinged on the first rocking rod (61) through the pin (614) at the bottom of the first rocking rod (61).

[0031] The second rocking rod (62) includes a main portion (621) which is parallel to the lifting body (1), a L-shaped bending portion (622) located above the main portion (621) and bending toward the lifting body (1), and a second fixing shaft (623) which is vertically disposed on the vertical wall of the L-shaped bending portion (622), on which the second tension wheel (43) surrounds, and the second end (521) of the second swing rod (52) is hinged on the second rocking rod (62) through the pin (625) fixed above the second rocking rod (62).

[0032] A second adjusting wheel (92) is fixed on the second linkage crank (82), which is for adjusting the wrap angle of the loose edge of the second chain (44) on the second traction wheel (42). The middle of the second linkage crank (82) is hinged on the lifting body (1), the second end of the second linkage crank (82) is hinged on the first end of the second pulling rod (72), the second end of the second pulling rod (72) is hinged on the second rocking rod (62).

[0033] In order to meet the double stroke protection requirement, the lifting body (1) is fixed with two micro switches, i.e. a first safe switch (105) as a limit switch and a second safe switch (106) as a check switch (the position of these two safe switches can be replaceable).

[0034] The first safe switch (105) is located corresponding to the position of the second rocking rod (62). When the lifting body (1) touches the ground, the second rocking rod (62) can trigger the first safe switch (105) to control the motor (2) to stop, the top of the main portion of the second rocking rod (62) is provided with a first triggering block (624) which can press the first safe switch (105).

[0035] While, the second safe switch (106) is located corresponding to the position of the first rocking rod (61), when the lifting body (1) touches the ground and the first safe switch (105) fails to work, the first rocking rod (61) can trigger the second safe switch (106) to control the motor (2) to stop, and the bottom of the first rocking rod (61) is provided with a second triggering block (612) which can press the second safe switch (106).

[0036] The working principle of the embodiment of the present invention is as below:

(1) At the status of the chain lifter in normal ascending and descending

[0037] When the lifter ascends, the motor (2) respectively drives the first driving wheel (31) and the second driving wheel (41) to rotate clockwise; when the lifter descends, the motor (2) respectively drives the first driving wheel (31) and the second driving wheel (41) to rotate anticlockwise. Furthermore, during the normal ascending and descending of the lifter, the chains on the first driving sprocket group and the second driving sprocket group are respectively engaged to be N-shaped.

[0038] The first end of the first chain (34) moves round the bottom of the first traction wheel (32) and is fixed on the top of the vertical guiding grooves (9). Due to the gravity, whether the lifter ascends or descends, the chain at this side is in tight state. The second end of the first chain (34) moves round the top edge of the first traction wheel (32) and is fixed on the bottom of the vertical guiding grooves (9), hanging on the first tension wheel (33) and the first driving wheel (31), whether the lifter ascends or descends, the chain at this side is in loose state.

[0039] Likewise, the second chain (44) moves round the bottom of the second traction wheel (42) and is fixed on the top of the vertical guiding grooves (9) with the chain at this side in tight state, and the second chain (44) moves round the top edge of the second traction wheel (42) and is fixed on the bottom of the vertical guiding grooves (9) with the chain at this side in loose state.

[0040] Accordingly, under the pre-tightening force of the spring (57) of the linkage mechanism (5), the first rocking rod (61) and the second rocking rod (62) keep partial to right, as shown in Fig. 7, the first tension wheel (33) surrounding the first rocking rod (61) is for tensioning the first chain (34), and the second tension wheel (43) surrounding the second rocking rod (62) is for tensioning the second chain (44).

(2) At the status of the chain lifter in touching the ground

[0041] After the lifter descends and touches the ground, the motor (2) continues to drive the first chain (34) and the second chain (44) to rotate anticlockwise owing to inertia, the loose edge side of the originally first and second chain rotates to be in tight state, the tight edge side of the originally first and second chain rotates to be in loose state, i.e. the chain fixed on a first side of the vertical guiding grooves (9) is in loose state.

[0042] As the motor keeps rotating, the first rocking rod (61) and the second rocking rod (62) rotate anticlockwise under the pulling force of the first chain (34) and the second chain (44), wherein the first triggering block (624) fixed on the second rocking rod (61) conflicts with the first safe switch (105) first, and the first safe switch (105) sends brake instructions to the brake module of the motor (2) through PLC after the contact closes to control the motor to stop.

[0043] As the motor brake lags, the second chain (44) continues to pull the second rocking rod (62) to rotate anticlockwise before the motor stops, as shown in Fig. 8, when the second rocking rod (62) rotates anticlockwise, the second linkage crank (82) rotates the same way under the action of the second pulling rod (72), and drives the second adjusting wheel (92) to swing up, and then changes the wrap angle on the second traction wheel (42) at the right side of the second chain (44), so as to reduce the looseness of the loose edge side of the second chain (44).

[0044] Likewise, when the motor (2) continues to rotate, the first chain (34) forces the first rocking rod (61) to rotate anticlockwise, pass the first pulling rod (71) and cause the first linkage crank (81) to rotate clockwise, thus driving the first adjusting wheel (91) to swing up, and then changing the wrap angle on the first traction wheel (32) at the left side of the first chain (34), so as to reduce the looseness of the loose edge side of the first chain (34).

[0045] In order to improve the safe operation of the equipment, the lifter is usually provided with a double switch protection device, i.e. if the first safe switch (105) fails to send the brake signal owing to some reason, the first rocking rod (61) and the second rocking rod (62) continue to rotate anticlockwise under the traction force of the chain, as shown in Fig. 9, the loose edge on the first chain (34) and the second chain (44) is provided with more looseness; after the second triggering block (612) fixed on the first rocking rod (61) touches the second safe switch (106), the contact of the second safe switch (106) closes, and the second safe switch (106) sends fault signal to the motor through PLC to control the motor to stop, before the motor completely stops running, the first adjusting wheel (91) and the second adjusting wheel (92) continue to swing up, which further reduces the wrap angle of the first traction wheel (32) at the left side of the first chain (34) and the wrap angle of the second traction wheel (42) at the right side of the second chain (44), and ensures the loose edge of the first chain (34) and the second chain (44) to be kept at 20∼25mm (the chain pitch in the embodiment is 31.75mm).

[0046] As the first rocking rod (61) and the second rocking rod (62) rotate anticlockwise before the motor (2) stops, the first rocking rod (51) and the second rocking rod (52) get closer, the second hinge point (b) slides along the lengthways guiding hole (552) to approach the first hinge point (a), the spring (57) is in compression state, the spring (57) in the embodiment is provided with the working stroke of around 30.4mm from the initial pre-tightening state to the completely compressed state, 78mm of descending stroke can be gained through the conversion of the chain operation length.

(3) At the status of the lifter upon touching the ground before ascending

[0047] When the lifter prepares to ascend, the motor drives the first chain and the second chain to rotate clockwise, the chain at the loose side of the first chain and the second chain gradually tightens, and the chain at the tight side of the first chain and the second chain gradually loosens.

[0048] Accordingly, the first rocking rod (61) and the second rocking rod (62) rotate clockwise under the restoring force of the spring (57), and drive the first linkage crank (81) and the second linkage crank (82) to rotate clockwise, the first adjusting wheel (91) and the second adjusting wheel (92) to swing down; as the chain is still provided with certain looseness, the lifting body (1) of the lifter is still in touching the ground state, when the first chain (34) and the second chain (44) fixed on the top side of the vertical guiding grooves (9) is completely tightened, the lifting body (1) begins to ascend away from the ground, at which moment the linkage mechanism is recovered to the original state (i.e. the spring is in pre-tightening state, as shown in Fig. 7), the traction force acted by the chain on the first rocking rod (61) and the second rocking rod (62) is balanced with the pre-tightening force acted by the spring (57) of the linkage mechanism (5) on the first rocking rod (61) and the second rocking rod (62).

[0049] The chain lifer of the present invention automatically changes the wrap angle size for the loose edge of the chain on the chain wheel through the linkage mechanism and the rocking rod crank linkage mechanism, and further changes the looseness of the loose edge of the chain and makes the looseness to be kept within a certain range, it can prevent the chain from being too loose to lead to chain-disengaging or chain-sliding, which makes the lifting body on the lifter have enough descending stroke during running to the bottom of the vertical guiding grooves, and overcomes the defect of inability to be adjusted appropriately for the tight and loose edge of the chain caused by the lag of the motor brake, so as to ensure the work stability and reliability of the lifter, the service life can be increased accordingly and the work efficiency of the lifter being improved, in the same time, the chain wear and the maintenance cost being reduced.

Claims

1. A chain lifer with safe descending stroke comprising:

a lifting body (1) which can move up and down along a pair of vertical guiding grooves (9);

a motor (2) which is fixed on the middle of the lifting body (1);

a driving sprocket group, including a first driving wheel (31) and a second driving wheel (41) both mounted on the output shaft of the motor (2), two first traction wheels (32) respectively disposed at two sides of the output shaft of the motor (2), a first tension wheel (33) disposed between one of the two first traction wheels (32) and the first driving wheel (31), a first chain (34) engaged on the two first traction wheels (32), the first tension wheel (33) and the first driving wheel (31), two second traction wheels (42) respectively disposed at two sides of the output shaft of the motor (2), a second tension wheel (43) disposed between one of the two second traction wheels (42) and the second driving wheel (41) and located at the different side of the first tension wheel (33) relatively to the output shaft of the motor (2), a second chain (44) engaged on the two second traction wheels (42), the second tension wheel (43) and the second driving wheel (41);

characterized in that the chain lifter also comprises:

a linkage mechanism (5) disposed between the first tension wheel (33) and the second tension wheel (43), which includes a first swing rod (51), a second swing rod (52), a first connecting rod (53) and a second connecting rod (54) all disposed substantially in a same plane, a first end of the fist swing rod (51) is hinged with a first end of the second swing rod (52) through a first pin (101) which forms a first hinge point (a), a first end of the second connecting rod (54) is hinged at the middle of the second swing rod (52), a second end of the first connecting rod (53) is hinged with a second end of the second connecting rod (54) through a second pin (102) which forms a second hinge point (b), furthermore, the linkage mechanism (5) also includes an elastic resetting mechanism which makes the first hinge point (a) and the second hinge point (b) keep apart with each other all along;

a first rocking rod (61), the first end of which is hinged on the lifting body (1), the second end of which is provided with a first fixing shaft (611) on which the first tension wheel (33) surround, and which the second end of the second swing rod (52) is hinged on;

a second rocking rod (62), the first end of which is hinged on the lifting body (1), the second end of which is provided with a second fixing shaft (623) on which the second tension wheel (43) surround, and which the second end of the second swing rod (52) is hinged on;

a first safe switch (105), fixed on the lifting body (1) and located corresponding to the position of the second rocking rod (62), when the lifting body (1) touches the ground, the second rocking rod (62) can trigger the first safe switch (105) to control the motor (2) to stop;

a second safe switch (106), fixed on the lifting body (1) and located corresponding to the position of the first rocking rod (61), when the lifting body (1) touches the ground and the first safe switch (105) fails to work, the first rocking rod (61) can trigger the second safe switch (106) to control the motor (2) to stop;

a first linkage crank (81); a first pulling rod (71); a second linkage crank (82); a second pulling rod (72);

a first adjusting wheel (91) for adjusting the wrap angle of the loose edge of the first chain (34) on the first traction wheel (32), the main shaft of the first adjusting wheel (91) is fixed on the first end of the first linkage crank (81), the middle of the first linkage crank (81) is hinged on the lifting body (1), the second end of the first linkage crank (81) is hinged on the first end of the first pulling rod (71), the second end of the first pulling rod (71) is hinged on the first rocking rod (61);

a second adjusting wheel (92) for adjusting the wrap angle of the loosen edge of the second chain (44) on the second traction wheel (42), the main shaft of the second adjusting wheel (92) is fixed on the first end of the second linkage crank (82), the middle of the second linkage crank (82) is hinged on the lifting body (1), the second end of the second linkage crank (82) is hinged on the first end of the second pulling rod (72), the second end of the second pulling rod (72) is hinged on the second rocking rod (62).

2. The chain lifter of claim 1, wherein the elastic resetting mechanism includes a spring seat (55), a frame (56) and a spring (57), the spring seat (55) is in conversed U-shape, a positioning sleeve (551) is provided on the top of the main body of the spring seat (55) for the spring (57) to surround, a guiding column (554) is inserted in the positioning sleeve (551) which can slide up and down relatively to the positioning sleeve (551), the upper portion of the guiding column (554) is fixed with the frame(56), the two side walls of the main body of the spring seat (55) are respectively provided with a lengthways guiding hole (552), and the bottom ends of the two side walls are respectively provided with a first hinging holes (553);
the first hinge point (a) and the second hinge point (b) are both disposed on the two side walls of the main body of the spring seat (55), and journals of the two ends of the first pin (101) are respectively rested in the corresponding first hinging hole (553), the two ends of the second pin (102) are respectively disposed through the corresponding lengthways guiding hole (552) and the second pin (102) can slide lengthways along the lengthways guiding hole (552);
the frame (56) is disposed above the main body of the spring seat (55), the frame (56) can keep linkage with the first connecting rod (53) and the second connecting rod (54) through the second pin (102), the spring (57) is limited between the frame (56) and the main body of the spring seat (55) to make the frame (56) keep apart with the spring seat (55) all along.

3. The chain lifter of claim 2, wherein the frame (56) is designed to be conversed U-shaped, the bottom ends of the two side walls of the frame (56) are respectively provided with a second hinging holes (561), journals of the two ends of the second pin (102) are respectively rested in the corresponding second hinging holes (561);
the upper portion of the guiding column (554) has threads outside, the top of the frame (56) has a through hole (562) for the upper portion of the guiding column (554) to go through, and the top of the guiding column (554) which is above the top of the frame (56) is threaded connected with a first nut (563), the portion of the guiding column (554) which is below the top of the frame (56) is threaded connected with a second nut (564), the first nut (563) and the second nut (564) make the upper portion of the guiding column (554) be limited in the through hole (562) of the frame (56).

4. The chain lifter of claim 1 or claim 2 or claim 3, wherein the first safe switch (105) is a micro switch, the second rocking rod (62) includes a main portion (621) which is parallel to the lifting body (1), a L-shaped bending portion (622) located above the main portion (621) and bending toward the lifting body (1), and a second fixing shaft (623) which is vertically disposed on the vertical wall of the L-shaped bending portion (622), the bottom of the main portion (621) is the first end of the second rocking rod (62) which is hinged on the lifting body (1) through a fourth pin (104), the top of the main portion (621) is provided with a first triggering block (624) which can press the first safe switch (105).

5. The chain lifter of claim 1 or claim 2 or claim 3, wherein the second safe switch (106) is a micro switch, the top of the first rocking rod (61) is the first end of the first rocking rod (61) which is hinged on the lifting body (1) through a third pin (103), a first fixing shaft (611) is disposed at the bottom of the first rocking rod (61), and the bottom of the first rocking rod (61) is provided with a second triggering block (612) which can press the second safe switch (106).

Drawing