Trailer jack having force measuring function

Abstract

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Description

BACKGROUND OF THE PRESENT INVENTION 5 Field of Invention The present disclosure relates to a force measuring jack, and in particular to a trailer jack having a force measuring function. Description of Related Arts 10          The tongue weight of a trailer refers to the total downward vertical pressure exerted by a front drawbar of the trailer. An excessively large or excessively small tongue weight easily causes reduced braking performance of a vehicle, swaying during travel, and loss of control due to fishtailing. Therefore, it is necessary to accurately measure the tongue weight before driving. However, existing tongue weight measurement mostly relies on 15 weighbridges or other external force-measuring equipment, resulting in site limitations, relatively large measurement errors, complex equipment installation, and cumbersome operation, and making it impossible to achieve quick and accurate measurement anytime and anywhere. 20 SUMMARY OF THE PRESENT INVENTION According to first aspect, there is provided a trailer jack having a force measuring function includes a lifting assembly, comprising a lifting assembly, a driving assembly, a sensing assembly, a support assembly, and a fixing assembly, wherein the lifting assembly comprises an outer tube and an inner tube, the outer tube is sleeved on the inner tube, and 25 the outer tube is connected to the fixing assembly; the driving assembly comprises a screw 2026205184   28 Sep 2026 rod and a prime mover, the prime mover drives the screw rod to rotate, and the screw rod is threadedly connected to the inner tube; the sensing assembly comprises a mounting seat and a force measuring unit, the mounting seat is fixed in the outer tube, and the force measuring unit is embedded below the mounting seat; and the support assembly comprises a first 5 support assembly configured to axially support the screw rod, and a second support assembly configured to radially support the screw rod, and the first support assembly is arranged below the force measuring unit, wherein the first support assembly is a thrust bearing, wherein the second support assembly comprises a bearing seat and a radial bearing, the bearing seat is fixedly mounted in the outer tube and is located below the thrust bearing, 10 and the radial bearing is mounted in the bearing seat, and wherein a gap is formed between an upper end surface of an outer ring of the radial bearing and an upper end surface of an inner bore of the bearing seat In one form, the sensing assembly further comprises a display device, the display device is mounted outside the outer tube, and the display device is electrically connected to 15 the force measuring unit. In one form, a baffle plate is arranged below the bearing seat, the baffle plate, the bearing seat, and the outer tube jointly form a lubrication chamber, an injection port is arranged on the outer tube at a position corresponding to the lubrication chamber, the baffle plate is provided with a hole, a size of the hole is greater than that of an outer profile of a 20 lower end of the bearing seat, and a lubrication passage is formed between the hole of the baffle plate and an outer surface of the lower end of the bearing seat. In one form, a nut is arranged at an upper end of the inner tube, the screw rod includes a first plain shaft section, a second plain shaft section, and a threaded section, the nut is connected to the threaded section, a diameter of the first plain shaft section is smaller 25 than that of the second plain shaft section, the first support assembly is arranged at the first 2026205184   28 Sep 2026 plain shaft section, and the second support assembly is arranged at the second plain shaft section. In one form, a first shaft shoulder is formed between the first plain shaft section and the second plain shaft section, a second shaft shoulder is formed at a position of the second 5 plain shaft section close to the threaded section, the first support assembly is a thrust bearing, the thrust bearing is positioned by the first shaft shoulder, and the radial bearing is positioned by the second shaft shoulder. In one form, an upper end of the outer tube is provided with a first through hole, a lower end of the outer tube is provided with a second through hole, a connector is arranged 10 above the outer tube, the first plain shaft section extends out of the first through hole and is then connected to the connector, the connector is connected to the prime mover, and a size of an outer diameter of the connector is greater than that of the first through hole. In one form, the force measuring unit is a force sensor, and the force sensor is a strain-type sensor or a piezoelectric sensor. 15          In one form, the outer tube has a square tube structure with a rectangular cross-section, the inner tube has a circular tube structure with a circular cross-section, and a guide wheel assembly is mounted below the inner tube. The beneficial effects of the present disclosure are as follows: (1) In the present disclosure, the outer tube is externally connected to a trailer 20 drawbar, the mounting seat having the force measuring unit embedded is fixed in the outer tube, and the first support assembly axially fixed relative to the screw rod is arranged below the force measuring unit. The axial force borne by the screw rod is transmitted to the force measuring unit through the first support assembly, and the force measuring unit transmits the measurement result to the display device, thereby realizing tongue weight measurement 25 of a trailer anytime and anywhere, with accurate results that are convenient to read. 2026205184   28 Sep 2026 (2) By providing the lubrication chamber and the lubrication passage, lubrication can be provided for the screw rod, thereby prolonging the service life of the screw rod. (3) By providing the gap between the upper end surface of the outer ring of the radial bearing and the upper surface of the inner bore of the bearing seat, it is ensured that 5 the axial force is completely transmitted from the thrust bearing to the force measuring unit, thereby improving force measurement accuracy. (4) The size of the outer diameter of the connector is greater than that of the first through hole, the connector is connected to the screw rod, and the screw rod is connected to the inner tube, thereby ensuring that the inner tube does not slide out of the outer tube. 10           (5) The outer tube adopts a square tube structure, facilitating cooperation with the fixing assembly, and the inner tube adopts a circular tube structure, facilitating processing. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic view of an overall structure according to an embodiment of the 15 present disclosure. Fig. 2 is a schematic cross-sectional structural view taken along line A-A in Fig. 1 (without a fixing assembly). Fig. 3 is a partially enlarged schematic structural view of portion B in Fig. 2. Fig. 4 is a schematic structural view of a sensing assembly according to an 20 embodiment of the present disclosure. Fig. 5 is another schematic structural view of a sensing assembly according to an embodiment of the present disclosure. Fig. 6 is a partially enlarged schematic structural view of portion C in Fig. 2. Fig. 7 is a first schematic structural view of an outer tube according to an 25 embodiment of the present disclosure. 2026205184   28 Sep 2026 Fig. 8 is a second schematic structural view of an outer tube according to an embodiment of the present disclosure. Fig. 9 is a schematic structural view of an inner tube and a guide wheel assembly according to an embodiment of the present disclosure. 5           Fig. 10 is a partially schematic structural view of assembly of a screw rod, a first support assembly, and a second bearing according to an embodiment of the present disclosure. Fig. 11 is a schematic structural view of a second support assembly according to an embodiment of the present disclosure. 10           In the figures: 1. lifting assembly; 11. outer tube; 111. first through hole; 112. second through hole; 12. inner tube; 121. nut; 122. groove; 13. baffle plate; 14. injection port; 2. driving assembly; 21. screw rod; 211. first plain shaft section; 212. second plain shaft section; 213. threaded section; 214. first shaft shoulder; 215. second shaft shoulder; 22. prime mover; 23. 15 connector; 3. sensing assembly; 31. mounting seat; 311. first opening; 32. force sensor; 321. second opening; 33. display device; 4. support assembly; 41. first support assembly; 42. second support assembly; 421. bearing seat; 422. second bearing; 423. third opening; 5. fixing assembly; 6. guide wheel assembly. 20 DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT The present disclosure will be further described below with reference to embodiments. Embodiment 1 As shown in Figs. 1 to 5, a trailer jack having a force measuring function includes a 25 lifting assembly 1, a driving assembly 2, a sensing assembly 3, a support assembly 4, a 2026205184   28 Sep 2026 fixing assembly 5, and a guide wheel assembly 6. As shown in Figs. 1 and 7 to 9, the lifting assembly 1 includes an outer tube 11 and an inner tube 12. A first through hole 111 is formed at a top of the outer tube 11, and a second through hole 112 is formed at a bottom of the outer tube 11. The inner tube 12 5 extends into an interior of the outer tube 11 through the second through hole 112 and cooperates with the driving assembly 2 for transmission, so that the driving assembly 2 can drive the inner tube 12 to move axially relative to the outer tube 11. The outer tube 11 is connected to a trailer drawbar through the fixing assembly 5. The fixing assembly 5 adopts a structure having a quick adjustment function, which can greatly improve adjustment 10 efficiency of the frame height. This structure is known in the art, and, for example, the structure disclosed in CN 223879370 U may be adopted. The guide wheel assembly 6 or a support plate (not shown in the drawings) is mounted at a bottom of the inner tube 12. As shown in Figs. 1 to 2, the driving assembly 2 includes a screw rod 21 and a prime mover 22. The screw rod 21 includes a plain shaft section and a threaded section 213. The 15 plain shaft section extends out of the outer tube 11 through the first through hole 111, and a connector 23 is mounted at the top of the outer tube 11. A size of an outer diameter of the connector 23 is greater than that of the first through hole 111, thereby preventing the screw rod 21 from being detached from the outer tube 11. The prime mover 22 is connected to the connector 23. The prime mover 22 may be a hand crank as shown in Fig. 1, or may be a 20 motor (not shown in the drawings). A nut 121 is arranged at a top of the inner tube 12, and the threaded section 213 is threadedly connected to the nut 121 at the top of the inner tube 12, thereby enabling the prime mover 22 to drive the screw rod 21 to rotate, and enabling the screw rod 21 to drive the inner tube 12 to move axially relative to the outer tube 11 through threads. 25          As shown in Figs. 3 to 4, the sensing assembly 3 is mounted in the outer tube 11, 2026205184   28 Sep 2026 and the support assembly 4 is mounted below the sensing assembly 3. The sensing assembly 3 includes a mounting seat 31, a force sensor 32, and a display device 33. The mounting seat 31 is fixed in the outer tube 11, and the force sensor 32 is embedded in a lower portion of the mounting seat 31. The force sensor 32 may be a strain-type sensor or a piezoelectric 5 sensor, and the force borne by the force sensor 32 is balanced by the mounting seat 31. The display device 33 is fixed on an outer wall of the outer tube 11, and the force sensor 32 is electrically connected to the display device 33. In addition, the measurement values from the force sensor 32 can also be obtained using a mobile phone through a wireless signal connection. 10          The support assembly 4 includes a first support assembly 41 and a second support assembly 42. The first support assembly 41 mainly bears an axial force, and may be a thrust bearing. In this embodiment, a thrust ball bearing is adopted. As shown in Figs. 6 and 11, the second support assembly 42 mainly bears a radial force, and includes a bearing seat 421 and a second bearing 422 mounted in the bearing seat 421. The second bearing 422 may be 15 a radial bearing or a radial-thrust bearing. In this embodiment, the second bearing 422 is a radial ball bearing. The screw rod 21 is reliably supported axially and radially by the thrust ball bearing and the radial ball bearing. The thrust ball bearing is configured to provide axial support for the screw rod 21, and the radial ball bearing is configured to provide radial support for the screw rod 21. 20           As shown in Fig. 10, the plain shaft section includes a first plain shaft section 211 and a second plain shaft section 212. The first plain shaft section 211 is located at an end portion and has a diameter smaller than that of the second plain shaft section 212. The second plain shaft section 212 is located between the first plain shaft section 211 and the threaded section 213 and has a diameter smaller than that of the threaded section 213. A 25 first shaft shoulder 214 is formed between the first plain shaft section 211 and the second 2026205184   28 Sep 2026 plain shaft section 212, and a second shaft shoulder 215 is formed at a position of the second plain shaft section 212 close to the threaded section 213. The thrust bearing is sleeved on the first plain shaft section 211 and is located between the force sensor 32 and the first shaft shoulder 214. The bearing seat 421 is fixed in the outer tube 11 and is located 5 below the thrust bearing. The second bearing 422 is mounted in the bearing seat 421 and is positioned by the second shaft shoulder 215. A first opening 311 and a second opening 321 are formed in middle portions of the mounting seat 31 and the force sensor 32 respectively, and a third opening 423 is formed in the bearing seat 421. The first plain shaft section 211 passes through the second opening 10   321 and the first opening 311 and is then connected to the connector 23, and the second plain shaft section 212 passes through the third opening 423. As shown in Figs. 7 to 9, in this embodiment, the outer tube 11 has a square tube structure with a rectangular cross-section, and the inner tube 12 has a circular tube structure with a circular cross-section. With this configuration, the outer tube 11 can conveniently 15 cooperate with the fixing assembly 5, and the circular inner tube 12 is more convenient to process. Working principles: The trailer drawbar is connected through the fixing assembly 5, the screw rod 21 is driven to rotate through the driving assembly 2, and the inner tube 12 moves downward in the axial direction relative to the outer tube 11 until the guide wheel 20 assembly 6 or the support plate mounted at the bottom of the inner tube 12 completely contacts the ground, thereby supporting the trailer. When the trailer jack is in a support state, a support force applied to the trailer by the guide wheel assembly 6 or the support plate is transmitted sequentially through the inner tube 12 and the nut 121 to the screw rod 21. The screw rod 21 then applies the force to the 25 first support assembly 41 through the first shaft shoulder 214, and the force is transmitted to 2026205184   28 Sep 2026 the force sensor 32. The force sensor 32 further transmits the force to the drawbar through the mounting seat 31, the outer tube 11, and the fixing assembly 5, and the force is balanced with the tongue weight of the trailer. Therefore, the force sensed by the force sensor 32 is the tongue weight of the trailer, and the value of the force can be visually shown by the 5 display device 33. It should be noted that, if an upper end surface of an outer ring of the second bearing 422 is brought into close contact with an upper surface of an inner bore of the bearing seat 421 during installation, part of the axial force transmitted through the screw rod 21 is shared by the bearing seat 421 through the second bearing 422, and the force cannot be completely 10 applied to the first support assembly 41, resulting in an error in the measurement value of the tongue weight. Therefore, in order to ensure the measurement accuracy of the force sensor 32, a certain axial gap is maintained between the upper end surface of the outer ring of the second bearing 422 and the upper surface of the inner bore of the bearing seat 421. The axial gap is preferably greater than 3 mm, so that the majority of the axial force borne 15 by the screw rod 21 can be transmitted to the force sensor 32, thereby ensuring measurement accuracy. Embodiment 2 The difference from Embodiment 1 lies in that a groove 122 is arranged at an upper end of the nut 121, and a baffle plate 13 is fixedly mounted in the outer tube 11. The baffle 20 plate 13 is located below the bearing seat 421, and a hole having a diameter greater than a size of an outer profile of a lower end of the bearing seat 421 is formed in the baffle plate 13. The outer tube 11, the bearing seat 421, and the baffle plate 13 jointly form a lubrication chamber. An injection port 14 is arranged on the outer tube 11 at a position corresponding to the lubrication chamber. Grease is injected into the lubrication chamber through the 25 injection port 14. After the grease fills the lubrication chamber, the grease enters the groove 2026205184   28 Sep 2026 122 at the upper portion of the nut 121 through a gap between the baffle plate 13 and the bearing seat 421. When the screw rod 21 rotates, the grease is drawn between the screw rod 21 and the nut 121, providing a continuous lubrication effect, reducing rotational resistance of the screw rod 21, and prolonging the service life of the screw rod 21. 5          The above are merely specific embodiments of the present disclosure and should not be construed as limiting the implementation scope of the present disclosure. Therefore, replacement with equivalent components, or equivalent changes and modifications made according to the patent protection scope of the present disclosure, shall still fall within the scope covered by the claims of the present disclosure. 10           The reference to any prior art in this specification is not, and should not be taken as, an acknowledgement or any form of suggestion that such prior art forms part of the common general knowledge. It will be understood that the terms “comprise” and “include” and any of their derivatives (e.g. comprises, comprising, includes, including) as used in this specification, 15 and the claims that follow, is to be taken to be inclusive of features to which the term refers, and is not meant to exclude the presence of any additional features unless otherwise stated or implied. In some cases, a single embodiment may, for succinctness and / or to assist in understanding the scope of the disclosure, combine multiple features. It is to be understood 20 that in such a case, these multiple features may be provided separately (in separate embodiments), or in any other suitable combination. Alternatively, where separate features are described in separate embodiments, these separate features may be combined into a single embodiment unless otherwise stated or implied. This also applies to the claims which can be recombined in any combination. That is a claim may be amended to include a feature 25 defined in any other claim. Further a phrase referring to “at least one of” a list of items 2026205184   28 Sep 2026 refers to any combination of those items, including single members. As an example, “at least one of: a, b, or c” is intended to cover: a, b, c, a-b, a-c, b-c, and a-b-c. It will be appreciated by those skilled in the art that the disclosure is not restricted in its use to the particular application or applications described. Neither is the present 5 disclosure restricted in its preferred embodiment with regard to the particular elements and / or features described or depicted herein. It will be appreciated that the disclosure is not limited to the embodiment or embodiments disclosed, but is capable of numerous rearrangements, modifications and substitutions without departing from the scope as set forth and defined by the following claims.

Claims

1. A trailer jack having a force measuring function, comprising a lifting assembly, a driving assembly, a sensing assembly, a support assembly, and a fixing assembly, wherein the lifting assembly comprises an outer tube and an inner tube, the outer tube is sleeved on the inner tube, and the outer tube is connected to the fixing assembly; the driving assembly comprises a screw rod and a prime mover, the prime mover drives the screw rod to rotate, and the screw rod is threadedly connected to the inner tube; the sensing assembly comprises a mounting seat and a force measuring unit, the mounting seat is fixed in the outer tube, and the force measuring unit is embedded below the mounting seat; and the support assembly comprises a first support assembly configured to axially support the screw rod, and a second support assembly configured to radially support the screw rod, and the first support assembly is arranged below the force measuring unit;wherein the first support assembly is a thrust bearing;wherein the second support assembly comprises a bearing seat and a radial bearing, the bearing seat is fixedly mounted in the outer tube and is located below the thrust bearing, and the radial bearing is mounted in the bearing seat; andwherein a gap is formed between an upper end surface of an outer ring of the radial bearing and an upper end surface of an inner bore of the bearing seat.

2. The trailer jack having a force measuring function according to claim 1, wherein the sensing assembly further comprises a display device, the display device is mounted outside the outer tube, and the display device is electrically connected to the force measuring unit.

3. The trailer jack having a force measuring function according to claim 1, wherein a baffle plate is arranged below the bearing seat, the baffle plate, the bearing seat, and the outer2026205184   28 Sep 2026tube jointly form a lubrication chamber, an injection port is arranged on the outer tube at a position corresponding to the lubrication chamber, the baffle plate is provided with a hole, a size of the hole is greater than that of an outer profile of a lower end of the bearing seat, and a lubrication passage is formed between the hole of the baffle plate and an outer surface of the lower end of the bearing seat.

4. The trailer jack having a force measuring function according to claim 1, wherein a nut is arranged at an upper end of the inner tube, the screw rod comprises a first plain shaft section, a second plain shaft section, and a threaded section, the nut is connected to the threaded section, a diameter of the first plain shaft section is smaller than that of the second plain shaft section, the first support assembly is arranged at the first plain shaft section, and the second support assembly is arranged at the second plain shaft section.

5. The trailer jack having a force measuring function according to claim 4, wherein a first shaft shoulder is formed between the first plain shaft section and the second plain shaft section, a second shaft shoulder is formed at a position of the second plain shaft section close to the threaded section, the thrust bearing is positioned by the first shaft shoulder, and the radial bearing is positioned by the second shaft shoulder.

6. The trailer jack having a force measuring function according to claim 4, wherein an upper end of the outer tube is provided with a first through hole, a lower end of the outer tube is provided with a second through hole, a connector is arranged above the outer tube, the first plain shaft section extends out of the first through hole and is then connected to the connector, the connector is connected to the prime mover, and a size of an outer diameter of the connector is greater than that of the first through hole.2026205184   28 Sep 20267. The trailer jack having a force measuring function according to claim 1, wherein the force measuring unit is a force sensor, and the force sensor is a strain-type sensor or a piezoelectric sensor.

8. The trailer jack having a force measuring function according to claim 1, wherein the outer tube has a square tube structure with a rectangular cross-section, the inner tube has a circular tube structure with a circular cross-section, and a guide wheel assembly is mounted below the inner tube.

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