CN212788619U

CN212788619U - Intracranial arterial blood vessel thrombus removal device and system

Info

Publication number: CN212788619U
Application number: CN202020855529.2U
Authority: CN
Inventors: 黄定国; 夏欢
Original assignee: Shanghai Tendfo Medical Technologies Co Ltd
Current assignee: Shenzhen Tengfu Medical Technology Co ltd
Priority date: 2020-05-21
Filing date: 2020-05-21
Publication date: 2021-03-26
Anticipated expiration: 2030-05-21

Abstract

The utility model relates to the technical field of medical equipment, a intracranial arterial blood vessel thrombectomy device and system is disclosed. This thrombectomy device includes: at least one first thrombus capture net and a second thrombus capture net which can be elastically expanded in the radial direction and are coaxially arranged; the first thrombus capture net has an integrated thrombus capture structure, and the second thrombus capture net includes: the bolt taking units are axially arranged, and each bolt taking unit comprises a plurality of arc bolt taking structures respectively provided with a free end; the free end of each arc-shaped embolectomy structure faces the far end of the embolectomy device, and when the embolectomy device is opened, the free end of each arc-shaped embolectomy structure is attached to the vessel wall. The arc-shaped thrombus taking structure with the free end is arranged, so that the free end of the arc-shaped thrombus taking structure can still be attached to the blood vessel wall of the device in a bending state, the thrombus can be efficiently and quickly taken out in a stable thrombus taking capacity of the device in a tortuous blood vessel, and the success rate of once thrombus taking is improved.

Description

Intracranial arterial blood vessel thrombus removal device and system

Technical Field

The utility model relates to the technical field of medical equipment, in particular to intracranial arterial blood vessel thrombectomy device and system.

Background

The stroke is an acute cerebrovascular disease, has become the first cause of death in China and is also the leading factor of disability of adults in China. The stroke has the characteristics of high morbidity, high mortality and high disability rate. Ischemic stroke is a disease in which the brain tissue is damaged because blood cannot flow into the brain due to the blockage of blood vessels. The incidence of ischemic stroke accounts for 60-70% of the total stroke. The degree of brain tissue damage caused by stroke is directly related to the treatment time, and the longer the treatment time is, the greater the degree of damage is, and the damage is irreversible damage. Therefore, it is very important to shorten the treatment time for the rescue of stroke.

At present, the minimally invasive interventional mechanical thrombus removal in medicine becomes a world-recognized mainstream mode for effectively treating cerebral apoplexy. At present, a plurality of mechanical embolectomy devices are used in actual clinic in the market, such as the widely used domestic Meidunli Solitaire, Scheck Trevo and the like. However, the thrombus removal device still has some structural defects, for example, the thrombus is easy to be broken in a bent blood vessel, so that the capturing capability of the thrombus is reduced, the treatment effect is poor, the thrombus is failed to be removed, and the thrombus can be completely removed by frequently performing multiple thrombus removal.

SUMMERY OF THE UTILITY MODEL

In view of this, the utility model aims at providing an intracranial artery blood vessel thrombectomy device and system gets and tie the structure through the arc that sets up the free end for the device still accessible arc gets the attached vascular wall of the free end of tying the structure under the bending condition, thereby makes the device in the tortuous blood vessel remain stable thrombectomy ability, and the thrombus is taken out fast to the high efficiency, has improved once and has got the thrombectomy success rate, thereby is favorable to shortening treatment time, improves treatment.

In order to solve the technical problem, an embodiment of the present invention provides an intracranial arterial blood vessel thrombectomy device, including:

at least one first thrombus capture net and a second thrombus capture net which can be elastically expanded in the radial direction and are coaxially arranged;

the first thrombus capture net has an integrated thrombus capture structure, the second thrombus capture net includes: the bolt taking device comprises a plurality of bolt taking units which are axially arranged, wherein each bolt taking unit comprises a plurality of arc-shaped bolt taking structures which are respectively provided with a free end; the free end of each arc-shaped embolectomy structure faces to the far end of the embolectomy device, and when the embolectomy device is opened, the free end of each arc-shaped embolectomy structure is attached to the vessel wall.

The utility model also provides an intracranial arterial vessel embolectomy system, which comprises a pushing device and the embolectomy device;

the far end of the pushing device is connected with the thrombus taking device.

The embodiment of the utility model provides an intracranial arterial vessel thrombus removal device and a system, the second thrombus capture net is provided with a plurality of thrombus removal units arranged along the axial direction, each thrombus removal unit comprises a plurality of arc thrombus removal structures respectively provided with a free end, the free end of the arc-shaped embolectomy structure faces to the far end of the embolectomy device, when the embolectomy device is released and opened, the free end of each arc-shaped embolectomy structure is attached to the vessel wall, because the free end of the arc-shaped embolectomy structure in the embolectomy device can not be separated from the vessel wall along with the bending of the vessel, but can be stably and reliably attached to and supported by the blood vessel wall in a tortuous blood vessel, and therefore, when the embolectomy device is withdrawn, the thrombus between the blood vessel wall and the thrombus taking device can be taken out of the body by the pressing action of the free end of the arc thrombus taking structure on the blood vessel wall, meanwhile, the second thrombus capture net can capture thrombus into the thrombus taking device during the withdrawing process so as to withdraw the thrombus out of the body. Therefore, the embodiment of the utility model provides a catch the net through increase the second thrombus on the basis of net is caught to first thrombus, overcome current thrombectomy device because self rigidity is big and take place to buckle in tortuous blood vessel easily, form the space after buckling between thrombectomy device and vascular wall, the thrombus of space department easily escapes and leads to the condition of thrombectomy failure, the crooked thrombectomy performance of thrombectomy device has been improved, it can follow the crooked form of tortuous blood vessel better to make it, the free end that still can get the structure through the arc in tortuous blood vessel is reliable and stable attached vascular wall, and then keep stable thrombectomy ability, the thrombus is taken out to the high efficiency fast, once has improved and has got the bolt success rate, and then be favorable to shortening treatment time, improve treatment.

In one embodiment, the curved embolectomy structure has two spaced apart first connecting ends, and the second thrombus capture net further comprises: a plurality of connecting structures each having a connecting rod; the connecting structure has two spaced apart second connecting ends; the two first connecting ends of each arc-shaped bolt taking structure are connected with the two second connecting ends of one connecting structure; the connecting rod is connected with the adjacent arc-shaped bolt taking structure.

As an embodiment, a plurality of arc-shaped bolt taking structures in each bolt taking unit are arranged in parallel, and arc-shaped bolt taking structures in adjacent bolt taking units are arranged in a staggered mode.

In one embodiment, the first thrombus capture net extends with a plurality of connecting arms, and each connecting arm is respectively connected with the first connecting end of the adjacent arc-shaped thrombus taking structure.

In one embodiment, the number of the first thrombus capture net is one, and the number of the second thrombus capture nets is two or more; a plurality of the second thrombus capture nets are connected and then connected with the first thrombus capture net; or

The intracranial arterial blood vessel thrombus removal device comprises a plurality of first thrombus capture nets and second thrombus capture nets, and the first thrombus capture nets and the second thrombus capture nets are alternately arranged along the axial direction.

In one embodiment, the first and second thrombus capture meshes are each cut from a metal tube.

In one embodiment, a developing member is disposed at an inner end of the thrombus removal device and/or a connection portion of the first thrombus capture net and the second thrombus capture net.

As an embodiment, the arc-shaped bolt structure is in a petal shape.

As an embodiment, the pushing device includes: the developing device comprises a reducing push rod with a thin far end and a thick near end and a developing connecting piece;

the pushing device is connected with the bolt taking device through the developing connecting piece.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required to be used in the description of the embodiments or the prior art will be briefly introduced below, it should be understood that the drawings in the following description are only embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the provided drawings without creative efforts.

FIG. 1 is a schematic structural diagram of an intracranial arterial vessel thrombectomy device provided in one embodiment;

FIG. 2 is a schematic plan view of an embodiment of an intracranial arterial vessel embolectomy device;

FIG. 3 is a schematic plan view of an intracranial arterial vessel embolectomy device according to yet another embodiment;

FIG. 4 is a schematic perspective view of a second thrombus-capturing net according to an embodiment;

FIG. 5 is a schematic perspective view illustrating a structure of a first thrombus-capturing net connected to a second thrombus-capturing net according to an embodiment;

FIG. 6 is a schematic perspective view of a first thrombus-capturing net according to an embodiment;

FIG. 7 is a schematic structural diagram of a first developing unit of a thrombus removal device according to an embodiment;

FIG. 8 is a schematic structural diagram of a second developing element of the embolectomy device according to an embodiment;

fig. 9 is a schematic structural diagram of a thrombus removal system according to an embodiment.

In the figure: the thrombus taking device comprises a thrombus taking device 1, a first thrombus capturing net 10, a connecting arm 100, a second thrombus capturing net 11, an arc-shaped thrombus taking structure 110, a free end 1100 of the arc-shaped thrombus taking structure, a connecting structure 111, a connecting rod 112, a pushing device 2, a reducing pushing rod 20, a developing connecting piece 21, a first developing piece 30 and a second developing piece 31.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention clearer, the following will explain in detail each embodiment of the present invention with reference to the accompanying drawings. However, it will be appreciated by those of ordinary skill in the art that in various embodiments of the invention, numerous technical details are set forth in order to provide a better understanding of the present application. However, the technical solutions claimed in the claims of the present application can be implemented without these technical details and with various changes and modifications based on the following embodiments.

The embodiment of the application provides an intracranial arterial vessel thrombus removal device which can be matched with a pushing device for use and is used for opening intracranial arterial vessel embolism, such as middle cerebral artery, anterior artery, basilar artery, vertebral artery and the like. As shown in fig. 1 to 8, the embolectomy device 1 includes: at least one first thrombus capture net 10 and a second thrombus capture net 11 which are elastically expandable in the radial direction and coaxially arranged. Alternatively, as shown in fig. 1 and 2, the embolectomy device 1 may include one first thrombus capture net 10 and two second thrombus capture nets 11. As another implementation manner, as shown in FIG. 3, the thrombectomy device 1 may further include two first thrombus capture nets 10 and two second thrombus capture nets 11. In this embodiment, the number of the first thrombus capture net and the second thrombus capture net is not particularly limited, and for example, the thrombectomy device 1 may further include two first thrombus capture nets 10 and three second thrombus capture nets. In this embodiment, the first thrombus-capturing net 10 has an integrated thrombus-capturing structure, and the thrombus-taking structure of the first thrombus-capturing net 10 is the same as or similar to that of a conventional thrombus-taking device, and does not have a free end. The second thrombus capture net 11 includes: a plurality of axially arranged bolt-removing units, each bolt-removing unit comprising a plurality of arc-shaped bolt-removing structures 110 respectively having a free end; wherein the free end 1100 of each arc-shaped embolectomy structure 110 faces the distal end of the embolectomy device, and when the embolectomy device 1 is unfolded, the free end 1100 of each arc-shaped embolectomy structure 110 is attached to the vessel wall. Since the free end 1100 of the arc-shaped embolectomy structure 110 in the embolectomy device 1 is not separated from the blood vessel wall along with the bending of the blood vessel, but can be stably and reliably attached to and supported by the blood vessel wall in a tortuous blood vessel, when the embolectomy device is withdrawn, the thrombus between the blood vessel wall and the embolectomy device can be taken out of the body by the squeezing action of the free end 1100 of the arc-shaped embolectomy structure 110 on the blood vessel wall, and the second thrombus capture net can capture the thrombus into the embolectomy device and withdraw the thrombus out of the body during the withdrawing process. Therefore, the embodiment of the utility model provides a thrombus is caught effectively to the net not only accessible first thrombus, and overcome current thrombectomy device in addition because self rigidity is big and take place to buckle easily in tortuous blood vessel, and form the space after buckling between thrombectomy device and the vascular wall, thrombus in the space easily escapes and leads to thrombectomy failure's the condition, thereby the crooked thrombectomy performance of thrombectomy device has been improved, it can comply with the crooked form of tortuous blood vessel better to make it, still can get the attached vascular wall of free end reliable and stable of embolus structure through the arc in tortuous blood vessel, the thrombectomy ability that remains stable, the thrombus is taken out fast to the high efficiency, one-time thrombectomy success rate has been improved, and then be favorable to shortening treatment time, and treatment effect is improved.

Alternatively, as shown in fig. 1, 2, 3 and 6, the first thrombus capture net 10 may be cut from a metal tube, and may be specifically prepared from a nickel-titanium metal tube by a laser engraving process. It is understood that the first thrombus capture net can also be made of other suitable materials, and can also be made by other suitable processes, such as a metal wire weaving process, 3D printing and other technical means, which are not limited in this respect. In this embodiment, three or four meshes may be distributed in the circumferential direction of the first thrombus capture net 10, the meshes may be hexagonal, elliptical, nearly elliptical or rhombic, and the meshes of the first thrombus capture net 10 may be uniformly distributed, or may be distributed in different sizes.

Alternatively, in this embodiment, the number of the first thrombus capture net 10 is one, and the number of the second thrombus capture nets 11 is greater than or equal to two. The plurality of second thrombus capture meshes 11 are connected to the first thrombus capture mesh 10. As shown in FIGS. 1 to 2, since the number of the second thrombus capture meshes 11 is two, the two second thrombus capture meshes 11 are connected to the first thrombus capture mesh 10, that is, in the thrombus removal device 1 of the present embodiment, the first thrombus capture mesh 10 and the second thrombus capture mesh 11 having an integrated thrombus capture capability have a spliced structure.

In another embodiment, the thrombectomy device 1 may further include a plurality of first thrombus capture meshes 10 and a plurality of second thrombus capture meshes 11, and the first thrombus capture meshes 10 and the second thrombus capture meshes 11 are alternately arranged in the axial direction. As shown in FIG. 3, in the thrombectomy device 1, two first thrombus trapping meshes 10 and two second thrombus trapping meshes 11 are provided, and the first thrombus trapping meshes 10 and the second thrombus trapping meshes 11 are alternately provided in the axial direction. It should be noted that when the embolectomy device 1 has two or more second thrombus capture meshes 11, the number of the arc-shaped embolectomy structures 110 in each second thrombus capture mesh 11 may be different, and as shown in fig. 3, the number of the arc-shaped embolectomy structures 110 in the second thrombus capture mesh 11 near the distal end of the embolectomy device 1 is 6, and the number of the arc-shaped embolectomy structures 110 in the second thrombus capture mesh 11 near the pusher is 4. The present embodiment does not specifically limit this.

Optionally, as shown in fig. 2 and 3, the curved embolectomy structure 110 has two spaced apart first connection ends 1101, and the second thrombus capture net 11 further comprises: a plurality of connecting structures 111 each having a connecting rod 112, the connecting structure 111 having two spaced apart second connecting ends 1110, the two first connecting ends 1101 of each curved latch structure 110 being connected to the two second connecting ends 1110 of a connecting structure 111, each connecting rod 112 being connected to an adjacent curved latch structure 110. The arc-shaped embolectomy structures 110, the connecting structures 111 and the connecting rods 112 are connected to form a basic composition structure in the embolectomy unit, and the basic composition structure is arranged in parallel along the circumferential direction and alternately arranged in the axial direction to form the second thrombus capture net 11. In some examples, as shown in FIG. 3, the curved embolectomy structure 110 may also be directly connected to the first thrombus capture net 10, so that the first thrombus capture net 10 and the second thrombus capture net 11 are alternately arranged to maintain a good and stable embolectomy capability at the connection therebetween. Optionally, in the present embodiment, the arc-shaped latch structure 110 has a petal shape, but is not limited thereto, and the arc-shaped latch structure 110 may have other suitable shapes. The shape of the connecting structure 111 may be the same as or similar to the shape of the arcuate latch structure 110. The connecting rod 112 may be a linear connecting rod parallel to the axial direction. Alternatively, the free end 1100 of the curved embolectomy structure 110 can extend parallel to the axial direction of the embolectomy device, or be slightly curved inward, thereby facilitating intraoperative retrieval of the embolectomy device and preventing the end of the free end 1100 of the curved embolectomy structure 110 from damaging the vessel wall. In this embodiment, the second thrombus capture net 11 may be fabricated in the same manner or in a similar manner as the first thrombus capture net 10, and preferably, the first thrombus capture net 10 and the second thrombus capture net 11 are both made of cut metal tubes, which will not be described herein again. In this embodiment, the second thrombus capture net 11 has a significantly smaller contact area with the blood vessel wall than the first thrombus capture net 10, and the dense mesh arrangement thereof enables the thrombus to be captured better, so that the thrombus-capturing device has better thrombus-capturing efficiency in tortuous blood vessels.

In this embodiment, the second thrombus capture net 11 includes two axially arranged embolectomy units, each of which includes two arc-shaped embolectomy structures 110 arranged in parallel in the circumferential direction, that is, the second thrombus capture net 11 includes four arc-shaped embolectomy structures. It is understood that the second thrombus capture net 11 may contain other suitable number of the arc-shaped embolectomy structures 110, and the present embodiment is not particularly limited to the number of the arc-shaped embolectomy structures 110 in the second thrombus capture net 11.

Alternatively, as shown in fig. 2, 3 and 5, a plurality of connecting arms 100 extend from the first thrombus capture net 10, and each connecting arm 100 is connected to the first connecting end 1101 of the adjacent arc-shaped embolectomy structure 110, so that the first thrombus capture net 10 is connected to the second thrombus capture net 11 through the connecting arm 100. Optionally, in this embodiment, the first thrombus capture net 10 extends out of two connecting arms 100, and each connecting arm 100 is respectively connected with the first connecting end 1101 of the adjacent arc-shaped embolectomy structure 110, so as to realize the transitional connection between the first thrombus capture net 10 and the second thrombus capture net 11. It should be noted that the number of the connecting arms 100 is the same as the number of the arc-shaped bolting structures 110 arranged in parallel in the circumferential direction in the bolting unit, and the number of the arc-shaped bolting structures 110 arranged in parallel in the circumferential direction in the bolting unit is not particularly limited in this embodiment.

In this embodiment, the first thrombus capture net 10 may be disposed at the inner end of the embolectomy device 1, and the outer end of the first thrombus capture net 10 may be folded together, and optionally, as shown in fig. 7, a developing member may be disposed at the folded position of the first thrombus capture net 10, and the developing member may be a first developing member 30 disposed at the folded position of the first thrombus capture net 10, so as to facilitate the intraoperative confirmation of the position of the embolectomy device. Alternatively, as shown in fig. 8, a developing member such as the second developing member 31 provided on the connecting arm 100 of the first thrombus capture net 10 may be provided at the junction of the first thrombus capture net 10 and the second thrombus capture net 11. Alternatively, the first and second developing

members

30 and 31 may be developing springs or developing tubes. This embodiment does not specifically limit this.

In this embodiment, the thrombus removal device 1 can be connected with the distal end of the pushing device through the outer end of the second thrombus capture net 11, so that the thrombus removal device can be pushed and recovered by the pushing device. Alternatively, the outer end of the thrombectomy device may be fixedly attached to the distal end of the pusher device via a visualization attachment.

The thrombus extraction device of the embodiment has better thrombus extraction capability of tortuous vessels than similar instruments on the market, improves the one-time thrombus extraction success rate of complex lesions, and simultaneously, the first thrombus capture net at the far end can prevent thrombus fragments from flowing to farther capillary vessels, thereby reducing the death rate and disability rate of the patients.

The embodiment of the application also provides a intracranial artery blood vessel thrombus removal system which is used for opening intracranial artery blood vessel embolism in the middle cerebral artery, the anterior artery, the basilar artery, the vertebral artery and the like. As shown in fig. 9, the system includes: a pushing device 2 and a thrombus removal device 1 as described in the previous embodiments. The far end of the pushing device 2 is connected with the outer end of the thrombus taking device 1.

Optionally, the pushing device 2 comprises: a reducing push rod 20 with a thin far end and a thick near end and a developing connecting piece 21. The pushing device 2 is connected with the bolt taking device 1 through a developing connecting piece 21. Optionally, the reducing push rod 20 may be a reducing nickel titanium wire. The developing connecting piece 21 can be a developing reinforcing spring or a developing tube, and the reducing push rod 20 can be sleeved with the bolt taking device 2 through the developing tube or bound and connected with the bolt taking device 2 through the developing reinforcing spring. In some examples, the proximal end of the variable diameter pushing rod 20 may further be provided with a safety marker (not shown) for prompting the doctor to turn on the X-ray for confirmation in advance during the operation.

In this embodiment, the thrombectomy device can be loaded in an initial state in an introduction sheath with a size similar to that of the microcatheter. When in use, the thrombus removal device can be guided into the microcatheter by pushing the pushing rod. The distal embolectomy device may be released and retrieved from the microcatheter into the microcatheter by pushing and pulling back the push rod.

The utility model discloses embodiment's intracranial artery blood vessel thrombectomy system because thrombectomy device has the more excellent tortuous blood vessel thrombectomy ability than the apparatus of the same kind on the market, consequently can improve the once thrombectomy success rate of complicacy pathological change, and the first thrombus of distal end catches the net simultaneously and can prevent to garrulous thrombus flow direction farther capillary, reduces patient's mortality and disability rate.

With reference to fig. 9, the application method and steps of the intracranial arterial vessel thrombus removal device and system according to the embodiment of the present application are as follows:

in the intervention treatment of acute cerebral embolism, an instrument intervention channel is established in a femoral artery vessel through a puncture needle, a small-size puncture sheath, a guide wire, a guide catheter, a micro guide wire and a micro catheter. Under the guidance of X-ray, the doctor guides the micro guide wire and the micro catheter to the position where the micro guide wire and the micro catheter pass through the vascular embolism. The microcatheter is reserved and the microcatheter is withdrawn out of the body, then the thrombus taking system of the embodiment is guided in through the microcatheter and sent to the lesion, after the thrombus taking device is confirmed to be positioned at or completely pass through the lesion under the assistance of X rays, one hand fixes the push rod, and the other hand releases the thrombus taking device in a mode of withdrawing the microcatheter, so that the thrombus taking device is attached to the blood vessel wall after being far opened at the lesion or the lesion. After standing for a period of time, the thrombus is pulled out into the guide catheter by pulling back the push rod, and finally the thrombus is completely taken out of the body. Finally, angiography is carried out to confirm that the blood vessels recover normal blood flow.

Although only the cooperating use mode of the thrombus removal device and the pushing device is described, it should be understood that the thrombus removal device disclosed by the embodiment of the application can also be used together with other suitable intracranial arterial vessel embolism thrombus removal devices.

It will be understood by those skilled in the art that the foregoing embodiments are specific examples of the invention, and that various changes in form and details may be made therein without departing from the spirit and scope of the invention in its practical application.

Claims

1. An intracranial arterial vessel embolectomy device, comprising: at least one first thrombus capture net and a second thrombus capture net which can be elastically expanded in the radial direction and are coaxially arranged;

2. The intracranial arterial vessel embolectomy device of claim 1, wherein the arcuate embolectomy structure has two spaced apart first connection ends, the second thrombus capture net further comprising: a plurality of connecting structures each having a connecting rod; the connecting structure has two spaced apart second connecting ends; the two first connecting ends of each arc-shaped bolt taking structure are connected with the two second connecting ends of one connecting structure; the connecting rod is connected with the adjacent arc-shaped bolt taking structure.

3. The intracranial arterial vessel embolectomy device of claim 2, wherein the arc-shaped embolectomy structures in each embolectomy unit are arranged side by side and the arc-shaped embolectomy structures in adjacent embolectomy units are staggered.

4. The intracranial arterial vessel embolectomy device of claim 1, wherein the first thrombus capture mesh extends with a plurality of connecting arms, each connecting arm being connected to the first connecting end of an adjacent arcuate embolectomy structure.

5. The intracranial arterial vessel embolectomy device of claim 1, wherein the number of the first thrombus capture net is one, and the number of the second thrombus capture net is greater than or equal to two; a plurality of the second thrombus capture nets are connected and then connected with the first thrombus capture net; or

6. The intracranial arterial vessel embolectomy device of claim 1, wherein the first and second thrombus capture meshes are each cut from a metal tube.

7. The intracranial arterial vessel embolectomy device of claim 1, wherein the inner end of the embolectomy device and/or the junction of the first and second thrombus capture meshes is provided with a visualization member.

8. The intracranial arterial vessel embolectomy device of any one of claims 1-7, wherein the arcuate embolectomy structure is petal-shaped.

9. An intracranial arterial vessel embolectomy system, comprising a pushing device and an embolectomy device according to any one of claims 1 to 8;

the far end of the pushing device is connected with the thrombus taking device.

10. The intracranial arterial vessel embolectomy system of claim 9, wherein the pusher device comprises: the developing device comprises a reducing push rod with a thin far end and a thick near end and a developing connecting piece;