CN115091610A

CN115091610A - Concrete mixing equipment capable of preventing materials from being accumulated

Info

Publication number: CN115091610A
Application number: CN202210688317.3A
Authority: CN
Inventors: 程永华; 郑小浩; 曾天宝
Original assignee: Hangzhou Gaoxiang Concrete Co ltd
Current assignee: Hangzhou Gaoxiang Concrete Co ltd
Priority date: 2022-06-16
Filing date: 2022-06-16
Publication date: 2022-09-23

Abstract

The invention relates to the field of building material manufacturing equipment, in particular to concrete stirring equipment. The invention discloses a concrete mixing device capable of preventing materials from being accumulated, which mainly comprises a support frame and a mixing tank, wherein the mixing tank is arranged above the support frame, the top of the mixing tank is provided with a sand and stone inlet pipe, a water inlet pipe and a cement inlet pipe, the bottom of the mixing tank is provided with a speed reducing motor and a discharge hole, the central line inside the mixing tank is provided with a mixing shaft, the surface of the mixing shaft is provided with a mixing blade, the mixing blade is in a hollow shape, a built-in blade is fixed in the mixing blade, the size of the mixing blade is changed from small to large from the top of the mixing tank to small from the bottom of the mixing tank, a filter sieve is arranged between the top of the mixing shaft and the inner wall of the top of the mixing tank, and the bottom of the mixing shaft is connected with the speed reducing motor, and the concrete mixing device has the beneficial effects that: the material conveying is more uniform, and the blockage of a discharge port or overlarge instantaneous flow is avoided; secondly, crushing the sand and stones before stirring to prevent the sand and stones from caking; and hardening caused by material accumulation or splashing is prevented.

Description

Concrete mixing equipment capable of preventing materials from being accumulated

Technical Field

The invention belongs to the field of building material manufacturing equipment, and particularly relates to concrete stirring equipment capable of preventing material accumulation.

Background

With the continuous development of economic construction and the acceleration of urbanization process in China, the infrastructure and real estate development industries in cities in China are rapidly developed, the rapid improvement of the concrete yield is promoted, the commercial concrete production changes the traditional production mode of dispersing and stirring concrete on site, and the important reform of building industrialization is realized. In the case of rapidly increasing concrete production, the production of concrete mixers is also increasing. Present concrete mixing equipment stirs through rotating the agitator mostly, causes the stirring inhomogeneous so easily, and agitated vessel material splashes at the stirring in-process moreover and leads to gluing to harden on the inner wall, or the material is not stirred and is leaded to hardening at the agitated vessel inner wall, causes the waste of material so easily, consequently needs to provide one kind can evenly stir and prevent the accumulational concrete mixing equipment of material.

Chinese patent CN109176872A discloses a concrete mixing device, which comprises a support base, wherein the upper part of the support base is symmetrically provided with support frames; the middle part of the stirring barrel is arranged on the support frame, one end of the stirring barrel is provided with a feeding hole, the other end of the stirring barrel is provided with a discharging hole, and an auxiliary mixing roller is arranged inside the stirring barrel; the feeder hopper, the feeder hopper sets up in the top of agitator. Be equipped with supplementary mixing roller in the agitator, can carry out abundant stirring to the concrete in the agitator and mix, be equipped with rotary driving device on the support frame to be connected with the middle part of agitator, can drive the agitator along the rotation in the vertical plane, simultaneously, supplementary mixing roller rotates in the inside of agitator, is favorable to the stirring of concrete, has practiced thrift the time cost greatly, improves the efficiency of construction. The concrete stirring device can not prevent the materials from being accumulated and hardened in the stirring barrel, thereby causing the waste of the materials and increasing the difficulty of cleaning.

Disclosure of Invention

The invention provides a concrete mixing device for preventing material accumulation in order to overcome the defects of the prior art.

In order to achieve the above purpose, the present invention provides the following technical solutions: a concrete mixing device capable of preventing material accumulation comprises a support frame, a mixing tank fixedly arranged above the support frame and a filter tank arranged on the right side of the support frame, wherein one end of the mixing tank is fixedly provided with a gravel inlet pipe, an inlet pipe and a cement inlet pipe, one end of the gravel inlet pipe, the inlet pipe and the cement pipe extend into the mixing tank, one end of the mixing tank close to the gravel inlet pipe, the inlet pipe and the cement pipe is fixedly provided with a filter screen, the gravel inlet pipe, the inlet pipe and the cement pipe are not in contact with the filter screen, one end of the mixing tank far away from the gravel inlet pipe, the inlet pipe and the cement pipe is provided with a discharge port, one end of the mixing tank far away from the gravel inlet pipe, the inlet pipe and the cement pipe is provided with a speed reduction motor, one end of the mixing tank is fixedly provided with a motor base, the speed reduction motor is arranged on the motor base, and a motor output shaft of the speed reduction motor is fixedly connected with a mixing shaft, the one end that gear motor was kept away from to the (mixing) shaft stretches into inside the agitator just the (mixing) shaft surface is equipped with a plurality of screw thread recesses. When the stirring raw materials flowed into the agitator through gravel inlet pipe, inlet tube and cement pipe, the filter screen screened out the raw materials of blocking and shaken the bits of broken glass with it, prevented to stir out and had cubic concrete, produced extra work load or influenced the result of use of concrete to the follow-up.

Preferably, the surface of the stirring shaft is provided with a plurality of stirring blades which are in a hollow state, the stirring blades are in threaded connection with the stirring shaft, support columns are arranged inside the stirring blades and are connected with the stirring blades through bolts, built-in blades are arranged on the surfaces of the support columns and are connected with the support columns through bolts, and a certain distance is reserved between the built-in blades and the inner walls of the stirring blades. The (mixing) shaft drives the stirring leaf and carries out rotatory stirring in the agitator, and built-in blade helps the stirring in-process concrete more fine and smooth, reduces the fritter concrete.

Preferably, the diameter of the stirring blades is reduced from the top of the stirring barrel to the bottom of the stirring barrel from small to large, a certain distance is arranged between the stirring blades and the inner wall of the stirring barrel, and a certain distance is kept between the stirring blades. The diameter that the stirring leaf becomes little grow again helps the concrete downstream at the stirring in-process, and can prevent that the too big jam of concrete flow from being in the condition of discharge gate.

Preferably, the positions of the internal blades in the mixing blades are not fixed, the positions of two adjacent internal blades of the internal blades are staggered, namely the position of the internal blade in the next mixing blade is crossed and embedded with the position of the internal blade in the previous mixing blade, and the diameter of the internal blade is a fixed value. The dislocation of the positions of the built-in blades in different stirring blades on the same side helps the concrete to be stirred in all directions in the stirring process, so that the un-stirred concrete is reduced, and more fine concrete is stirred.

Preferably, the support frame comprises a bottom frame, an inclined plane and an inclined column, one end of the inclined column is hinged to the bottom frame, the other end of the inclined column is hinged to the inclined plane, and the inclined plane is hinged to one end of the bottom frame. The tilt post urges the tilt surface upward, and the hinged relationship between the tilt surface and the undercarriage assists in tilting the tilt surface.

As preferred, the filter vat includes water storage bucket and centrifugal bucket, the centrifugal bucket sets up in water storage bucket inside and with water storage bucket inner wall contactless, the fixed rotation axis that is equipped with in centrifugal barrel head portion, rotation axis key-type connection rotating electrical machines, the rotating electrical machines peripheral hardware buckler, the buckler is fixed to be set up in centrifugal barrel head portion, the centrifugal bucket ladle body is the filter screen. The rotating motor drives the centrifugal barrel to rotate, and in the rotating process of the centrifugal barrel, concrete with water in the centrifugal barrel also rotates, water is thrown out and enters the water storage barrel, and the concrete is left in the centrifugal barrel, so that the separation of redundant water and the concrete is realized.

Preferably, a groove is formed in the surface of the gear ring, an electric push rod is arranged in the groove, one end of the electric push rod is fixedly connected with the groove, a scraper is fixedly arranged at the other end of the electric push rod, and the scraper is attached to the wall of the stirring barrel.

Preferably, the tilt column is an electric push rod, and the tilt column pushes the tilt surface to tilt.

Preferably, the filter screen is a vibrating screen

In conclusion, the beneficial effects of the invention are as follows: the material conveying is more uniform, and the blockage of a discharge port or overlarge instantaneous flow is avoided; secondly, crushing the sand and stones before stirring to prevent the sand and stones from caking; and hardening caused by material accumulation or splashing is prevented.

Drawings

FIG. 1 is an external view of the present invention.

Fig. 2 is a schematic view of the inside of a mixing tank according to the present invention.

FIG. 3 is a schematic view of a stirring assembly of the present invention.

Fig. 4 is a schematic structural view of a mixing tank according to the present invention.

FIG. 5 is a schematic view of a gear tooth ring structure of the present invention.

Fig. 6 is a schematic structural view of a filter vat according to the present invention.

FIG. 7 is an enlarged view of the position I of the present invention.

In the figure, 1 sand feeding pipe, 2 water inlet pipe, 3 cement feeding pipe, 4 mixing tank, 401 toothed ring, 402 gear, 404 scraper, 405 electric push rod, 5 speed reducing motor, 6 mixing shaft, 601 filter screen, 602 mixing blade, 603 support column, 604 built-in blade, 7 discharge port, 8 support frame, 801 inclined column, 802 underframe, 803 inclined plane, 9 filter tank, 901 water storage tank, 902 centrifugal barrel.

Detailed Description

In order to make the technical solutions of the present invention better understood, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention.

Referring to fig. 1-7, a prevent accumulational concrete mixing equipment of material, including support frame 8, the fixed agitator 4 that sets up in support frame 8 top with set up in the filter vat 9 on support frame 8 right side, the fixed gravel and sand inlet pipe 1 that is equipped with of 4 one ends of agitator, inlet tube 2, cement inlet pipe 3, gravel and sand inlet pipe 1, inlet tube 2, cement pipe 3 runs through 4 one ends of agitator and extends to inside the agitator 4, gravel and sand inlet pipe 1, inlet tube 2, cement pipe 3 directly stretches into the loss that the agitator can reduce raw and other materials, massive raw and other materials appear when gravel and sand inlet pipe 1 and filter screen 601 cooperation use can reduce the stirring simultaneously. The fixed filter screen 601 that is equipped with of one end that is close to gravel and sand inlet pipe 1, inlet tube 2 and cement pipe 3 inside of agitator 4, gravel and sand inlet pipe 1, inlet tube 2 and cement pipe 3 and filter screen 601 contactless, the garrulous bold raw and other materials can be shaken to filter screen 601, alleviates agitating unit's burden, also makes the concrete that the stirring came out more fine and smooth simultaneously. Gravel and sand inlet pipe 1 is kept away from to agitator 4, discharge gate 7 has been seted up to the one end of inlet tube 2 and cement pipe 3, gravel and sand inlet pipe 1 is kept away from to agitator 4, the one end of inlet tube 2 and cement pipe 3 is equipped with gear motor 5, gear motor 5 sets up in agitator 4 center, be equipped with a bit distance between discharge gate 7 and the gear motor 5, the fixed motor base that is equipped with of 4 one end of agitator, gear motor 5 places on motor base, gear motor 5's motor output shaft fixedly connected with (mixing) shaft 6, gear motor 5 drives (mixing) shaft 6 and rotates, realize the stirring. The one end that gear motor 5 was kept away from to (mixing) shaft 6 stretches into inside and (mixing) shaft 6 surface of agitator 6 and is equipped with a plurality of screw grooves, and the screw groove on (mixing) shaft 6 surface realizes connecting stirring subassemblies such as stirring leaf 602, realizes dismantling and conveniently changing of stirring subassembly.

The surface of the stirring shaft 6 is provided with a plurality of stirring blades 602, the stirring blades 602 are in a hollow state, and the hollow state of the stirring blades 602 helps to leave raw materials and incompletely-formed concrete on the surface of the stirring blades 602 in a large area in the stirring process. Stirring leaf 602 and (mixing) shaft 6 threaded connection, threaded connection realizes that stirring leaf 602 is convenient to be changed. The inside support column 603 that is equipped with of stirring leaf 602, support column 603 passes through bolted connection with stirring leaf 602, and threaded connection realizes that support column 603 conveniently changes. The surface of the supporting column 603 is provided with a built-in blade 604, the built-in blade 604 is connected with the supporting column 603 through a bolt, and the built-in blade 604 is conveniently replaced through threaded connection. The built-in blades 604 and the inner walls of the stirring blades 602 are arranged at a certain distance, and the distance between the built-in blades 604 and the stirring blades 602 ensures that the built-in blades 604 and the stirring blades 602 do not rub in the stirring process, so that the loss of the built-in blades 604 and the stirring blades 602 is reduced.

The diameter of stirring leaf 602 diminishes again from little grow to the direction of agitator 4 bottom from agitator 4 top, and the diameter that the stirring leaf diminishes again helps the concrete downstream at the stirring in-process by little grow, and can prevent the too big jam of concrete flow in the condition of discharge gate. The stirring blade 602 is arranged at a certain distance from the inner wall of the stirring barrel 4, and the distance between the stirring blade 602 and the inner wall of the stirring barrel 4 reduces friction between the stirring blade 602 and the inner wall of the stirring barrel 4, and reduces abrasion between the stirring blade 602 and the stirring barrel 4. The blades 602 are spaced apart from one another, and the distance between the blades 602 helps the incompletely formed concrete to move downward.

The positions of the built-in blades 604 in the mixing blades 602 are not fixed, the positions of two adjacent built-in blades 604 of the built-in blades 604 are staggered, namely the position of the built-in blade 604 in the next mixing blade 602 is crossed and embedded with the position of the built-in blade 604 in the previous mixing blade 602, and the dislocation of the positions of the built-in blades in different mixing blades on the same side helps the concrete to be mixed in all directions in the mixing process, so that the un-mixed concrete is reduced, and more fine concrete is mixed. The diameter of the built-in blade 604 is a fixed value, and the built-in blades 604 are the same in diameter, so that the installation and purchase are convenient.

The support frame 8 comprises a bottom frame 802, an inclined surface 803 and an inclined column 801, one end of the inclined column 801 is hinged to the bottom frame 802, the other end of the inclined column 801 is hinged to the inclined surface 803, and the inclined surface 803 is hinged to one end of the bottom frame 802. The tilt post urges the tilt surface upward, and the hinged relationship between the tilt surface and the chassis assists in tilting the tilt surface.

The inclined column 801 is an electric push rod. The inclined column 801 realizes pushing the inclined surface 803 to incline upward, and finally realizes that the inclined surface 803 is formed into a vertical state, i.e., helps the agitating barrel 4 to assume the vertical state.

The filter barrel 9 comprises a water storage barrel 901 and a centrifugal barrel 902, the centrifugal barrel 902 is arranged inside the water storage barrel 901 and is not in contact with the inner wall of the water storage barrel 901, a rotating shaft is fixedly arranged at the bottom of the centrifugal barrel 902 and is in key connection with a rotating motor, the rotating motor drives the rotating shaft to rotate, the rotating shaft drives the centrifugal barrel to rotate, and the high-speed rotation of the centrifugal barrel can throw away excessive water in the completely-formed concrete to keep the concentration of the concrete. The rotation axis sets up to the mode of can dismantling, makes things convenient for the staff to take out centrifuge bowl 902 after centrifuge bowl 902 work, takes out the concrete in the centrifuge bowl 902. The waterproof shell is arranged outside the rotating motor and protects the rotating motor from contacting water and the rotating motor. The waterproof case is fixed to be set up in the centrifuging barrel bottom, and the centrifuging barrel 902 ladle body is the filter screen, and the filter screen can help water to be thrown away and get into water storage bucket 901. The bottom of the water storage barrel 901 is provided with a water flowing port, so that water thrown out from the centrifugal barrel 902 is guided to the ground without accumulation.

The surface of the toothed ring 401 is provided with a groove, an electric push rod 405 is arranged in the groove, the electric push rod 405 pushes the scraper 404 forwards, so that the scraper 404 extends out of the 4 barrel walls of the stirring barrel, one end of the electric push rod 405 is fixedly connected with the groove, the other end of the electric push rod 405 is fixedly provided with the scraper 404, and the scraper 404 is attached to the 4 barrel walls of the stirring barrel.

The filter screen 601 is a vibrating screen which can shatter the bulk raw materials.

During operation, concrete raw materials are added according to a certain proportion from cement inlet pipe 3, inlet tube 2, gravel and sand inlet pipe 1, through cement inlet pipe 3, inlet tube 2, gravel and sand inlet pipe 1, inside the raw and other materials that constitute concrete got into agitator 4, at first raw and other materials fell into filter screen 601 surface, and filter screen 601 shakes garrulous with great blocking material, and raw and other materials through filter screen 601 get into agitator 4 stirring department. Stirring equipment begins to work, gear motor 5 rotates, gear motor 5 takes (mixing) shaft 6 to rotate, stirring leaf 602 along with (mixing) shaft 6 begins the stirring, along with most material entering stirring, the fretwork design of stirring leaf 602 for the material can flow through from stirring leaf 602, and built-in blade 604 among stirring leaf 602 realizes stirring more finely, and the stirring thoroughness can be guaranteed to the staggered arrangement of built-in blade 604 among the preceding stirring leaf 602. During the stirring process, the stirred concrete is conveyed to the discharge port 7 through the stirring blades 602 with the diameters changing from small to large and then becoming small, and the discharge port 7 cannot be blocked due to overlarge flow.

After the stirring, the inclined column 801 pushes against the inclined plane 803 to start extending upwards, the inclined plane 803 drives the stirring barrel 4 to be vertical gradually, meanwhile, a motor inside the stirring barrel 4 starts rotating, then the gear 402 starts driving, the gear 402 rotates to drive the toothed ring 401 to rotate, the electric push rod 405 in the groove on the surface of the toothed ring 401 starts working at the moment, the electric push rod 405 pushes forwards, then the scraper blade 404 is driven forwards, the scraper blade 404 extends out of the wall of the stirring barrel 4, the toothed ring 401 rotates to drive the electric push rod 405 to rotate, namely, the toothed ring 401 drives the scraper blade 404 to rotate, the scraper blade 404 scrapes off residual concrete on the wall of the stirring barrel 4, and meanwhile, the water inlet pipe starts adding water.

When the inclined surface 803 is completely inclined to 90 degrees, the residual concrete scraped by the scraper plate mixes with water and flows out from the discharge port 7 to enter the filter barrel 9, the centrifugal barrel 902 is covered with a cover, the centrifugal barrel 902 starts to rotate, the rotating centrifugal force throws the water out of the centrifugal barrel, the water flowing port of the water storage barrel 901 discharges the water, the concrete is remained in the centrifugal barrel 902, and after the rotation of the centrifugal barrel 902 is finished, a worker takes out the centrifugal barrel 902 and pours out the concrete after the water is dewatered.

As some terms are used throughout the description and claims to refer to particular components. As one skilled in the art will appreciate, manufacturers may refer to a component by different names. This specification and claims do not intend to distinguish between components that differ in name but not function. In the following description and in the claims, the terms "include" and "comprise" are used in an open-ended fashion, and thus should be interpreted to mean "include, but not limited to. "substantially" means within an acceptable error range, and a person skilled in the art can solve the technical problem within a certain error range to substantially achieve the technical effect.

It should be noted that the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a good or system that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such good or system. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other like elements in a commodity or system that includes the element.

The foregoing description shows and describes several preferred embodiments of the present application, but as aforementioned, it is to be understood that the application is not limited to the forms disclosed herein, and is not to be construed as excluding other embodiments, but rather is capable of use in various other combinations, modifications, and environments and is capable of changes within the scope of the application as expressed herein, commensurate with the above teachings, or the skill or knowledge of the relevant art. And that modifications and variations may be effected by those skilled in the art without departing from the spirit and scope of the application, which is to be protected by the claims appended hereto.

Claims

1. The utility model provides a prevent accumulational concrete mixing equipment of material, includes support frame (8), fixes agitator (4) that sets up in support frame (8) top and sets up in filter vat (9) on support frame (8) right side, a serial communication port, the fixed feeding subassembly that is equipped with of agitator (4) one end, agitator (4) inside one end that is close to the feeding subassembly is fixed and is equipped with filter screen (601), agitator (4) keep away from the one end of feeding subassembly and seted up discharge gate (7), the one end that the feeding subassembly was kept away from in agitator (4) is equipped with gear motor (5), the fixed motor base that is equipped with of agitator (4) one end, gear motor (5) are placed on the motor base, the motor output shaft fixedly connected with (mixing) shaft (6) of gear motor (5), the one end that gear motor (5) were kept away from in (mixing) shaft (6) stretches into agitator (6) inside just (mixing) surface is equipped with a plurality of screw thread recess (6) .

2. The concrete mixing equipment for preventing material accumulation according to claim 1, wherein a plurality of mixing blades (602) are arranged on the surface of the mixing shaft (6), the mixing blades (602) are in a hollow state, the mixing blades (602) are in threaded connection with the mixing shaft (6), a support column (603) is arranged inside the mixing blades (602), the support column (603) is in bolted connection with the mixing blades (602), a built-in blade (604) is arranged on the surface of the support column (603), the built-in blade (604) is in bolted connection with the support column (603), and a certain distance is reserved between the built-in blade (604) and the inner wall of the mixing blades (602).

3. The concrete mixing equipment for preventing the material accumulation according to claim 2, wherein the diameter of the mixing blade (602) is gradually reduced from the top of the mixing barrel (4) to the bottom of the mixing barrel (4), a certain distance is arranged between the mixing blade (602) and the inner wall of the mixing barrel (4), and a certain distance is kept between the mixing blades (602).

4. The concrete mixer for preventing the accumulation of materials as claimed in claim 2, wherein the positions of the internal blades (604) are not fixed in the mixing blades (602), and the positions of two adjacent internal blades (604) of the internal blades (604) are staggered, that is, the position of the internal blade (604) in the next mixing blade (602) is cross-embedded with the position of the internal blade (604) in the previous mixing blade (602), and the diameter of the internal blade (604) is a fixed value.

5. The concrete mixer for preventing the accumulation of the materials as claimed in claim 1, wherein said support frame (8) comprises a bottom frame (802), an inclined plane (803) and an inclined column (801), one end of said inclined column (801) is hinged to said bottom frame (802) and the other end of said inclined column (801) is hinged to said inclined plane (803), said inclined plane (803) is hinged to one end of said bottom frame (802).

6. The concrete mixing equipment for preventing material accumulation according to claim 1, wherein the filter barrel (9) comprises a water storage barrel (901) and a centrifugal barrel (902), the centrifugal barrel (902) is arranged inside the water storage barrel (901) and is not in contact with the inner wall of the water storage barrel (901), a rotating shaft is fixedly arranged at the bottom of the centrifugal barrel (902), the rotating shaft is in key connection with a rotating motor, a waterproof shell is arranged outside the rotating motor, the waterproof shell is fixedly arranged at the bottom of the centrifugal barrel, and the barrel body of the centrifugal barrel (902) is a filter screen.

7. The concrete mixing equipment for preventing materials from being stacked according to claim 1, wherein an interlayer is formed in the mixing tank (4), a toothed ring (401) is arranged in the interlayer, the toothed ring (401) is in rotating fit with the interlayer, a gear (402) is arranged on the inner wall of the toothed ring (401), the gear (402) is meshed with the toothed ring (401), a rotating shaft is fixedly arranged in the gear (402), a key connection motor is arranged at one end, away from the gear (402), of the rotating shaft, and the motor is fixedly arranged on the inner wall of the interlayer.

8. The concrete mixing equipment for preventing the accumulation of the materials as claimed in claim 7, wherein the surface of the toothed ring (401) is provided with a groove, the groove is internally provided with an electric push rod (405), one end of the electric push rod (405) is fixedly connected with the groove, the other end of the electric push rod (405) is fixedly provided with a scraper (404), and the scraper (404) is attached to the wall of the mixing tank (4).

9. The concrete mixing equipment for preventing material accumulation according to claim 5, wherein the feeding component comprises a sand and stone feeding pipe (1), a water inlet pipe (2) and a cement feeding pipe (3), the sand and stone feeding pipe (1), the water inlet pipe (2) and the cement feeding pipe (3) penetrate through one end of the mixing tank (4) and extend into the mixing tank (4), and one end of the sand and stone feeding pipe (1), the water inlet pipe (2) and the cement feeding pipe (3) in the mixing tank (4) is not in contact with the filter screen (601).

10. The concrete mixing equipment for preventing the material from being accumulated according to claim 1, wherein the filter screen (601) is a vibrating screen, and the inclined column (801) is an electric push rod.