An adjustable ECM device

Abstract

The utility model discloses an adjustable ECM device relates to ECM device technical field, including frame, be equipped with electrolytic bin subassembly, lifting adjustment subassembly and be equipped with electrode subassembly on lifting adjustment subassembly on frame, the utility model ECM device drives screw lifting rod rotation through adjusting motor piece, utilizes the sliding fit of lifting adjustment lever in the adjustment hole, will rotary motion convert into linear motion to the control electrode subassembly's up and down position, electrode subassembly adopts even array's multiple electrode piece, under the processing demand of flexible adaptation different workpiece of lifting adjustment, realized the quick accurate regulation of electrode height, solved the problem that the machining operation of current ECM device lacks the lifting function and leads to the low efficiency of restriction, improved the precision and adaptability of deburring significantly.

Description

Technical Field

[0001] This utility model relates to the field of ECM device technology, specifically an adjustable ECM device. Background Technology

[0002] As stated in the published patent CN111843082A, "An ECM Device for Electrochemical Machining of Narrow Grooves," "ECM, or electrochemical machining, has become an important branch of mechanical manufacturing after half a century of development since its inception in the 1950s. Electrochemical machining was first used in the military industry in my country. With the development of high technology and the research and development of new military products, there is an increasing demand for parts made of new, difficult-to-machine materials, requiring high precision, high surface quality, and complex shapes with thin-walled integral structures, opening up broader application prospects for electrochemical machining. A search reveals, for example, a patent CN202943344U, which discloses an ECM device for electrochemical machining of narrow grooves. This invention includes a power supply and a base, on which..." The machine frame is characterized by a fixed seat for holding the parts to be processed on the base, a lifting sliding seat on the frame located above the fixed seat, a vibration mechanism inside the lifting sliding seat, and an electrode clamp and a tool electrode at the bottom of the lifting sliding seat. This invention effectively removes the passivation film to protect the tool electrode and extend its service life. The use of a high-frequency narrow-pulse power supply effectively ensures no residual internal stress inside the parts, resulting in narrower slot pitches and improved product quality. However, currently used ECM devices have a simple structure that is not conducive to assembly; they generally only use two sets of electrodes to pass through narrow slots for electrolytic processing and lack components for quick lifting and combination processing, thus failing to meet current needs.

[0003] In summary, among the related technologies of ECM devices, some ECM devices lack the ability to adjust height, which limits their operational capacity and efficiency. Utility Model Content

[0004] To overcome the shortcomings mentioned above, this utility model aims to provide a technical solution for an adjustable ECM device that can solve the aforementioned problems.

[0005] To achieve the above objectives, this utility model provides the following technical solution: An adjustable ECM device includes a frame on which an electrolysis chamber assembly, a lifting adjustment assembly, and an electrode assembly mounted on the lifting adjustment assembly are installed. The electrolysis chamber assembly includes an electrolysis chamber component, a circulation pump component, and a circulation chamber component fixed on the frame. The circulation pump component drives the electrolyte to circulate between the electrolysis chamber component and the circulation chamber component. The lifting and adjusting assembly includes a lifting mounting plate fixed on the electrolysis chamber component, a threaded lifting rod rotatably mounted on the lifting mounting plate, an adjusting motor component that drives the threaded lifting rod to rotate on the lifting mounting plate, a lifting adjusting plate screwed to the outer wall of the threaded lifting rod, a lifting adjusting rod fixed on the lifting adjusting plate, an adjusting hole opened on the lifting mounting plate, and the lifting adjusting rod sliding up and down in the adjusting hole. The electrode assembly includes an electrode mounting plate fixed to the lower end of the lifting adjustment rod, and a plurality of charged electrode components are evenly arrayed on the electrode mounting plate. As a further embodiment of this utility model: a limiting seat is provided on the lifting mounting plate, and an upper limit switch and a lower limit switch are respectively provided on the upper and lower ends of the limiting seat. The upper and lower limit switches are used to limit the lifting adjustment plate to the upper and lower positions.

[0006] As a further embodiment of this utility model: the limiting seat includes a first limiting seat and a second limiting seat mounted side by side on the lifting mounting plate, and a first adjusting motor and a second adjusting motor are respectively mounted on the first limiting seat and the second limiting seat, and a first threaded adjusting rod and a second threaded adjusting rod are respectively fixed to the output shafts of the first adjusting motor and the second adjusting motor. The first limiting seat and the second limiting seat are respectively provided with a vertical first sliding groove and a second sliding groove. The upper limit switch and the lower limit switch are respectively installed in the first sliding groove and the second sliding groove. The upper limit switch and the lower limit switch are respectively screwed onto the first threaded adjusting rod and the second threaded adjusting rod.

[0007] As a further embodiment of this utility model: a lifting bracket is fixedly provided on the lifting mounting plate, and the upper end of the threaded lifting rod is rotatably mounted on the lifting bracket; the upper ends of the first limiting seat and the second limiting seat are fixedly connected to the lifting bracket.

[0008] As a further embodiment of this utility model: the electrode component includes an electrode mounting base fixed on the electrode mounting plate, a probe component is mounted on the electrode mounting base, the probe component extends downward through the electrode mounting plate, and a terminal connector is fixed at the upper end of the probe component.

[0009] As a further embodiment of this utility model: the periphery of the electrode mounting plate is provided with a side plate, and the side plate and the electrode mounting plate together form an electrode mounting chamber.

[0010] As a further embodiment of this utility model: an upper infrared sensor and a lower infrared sensor are respectively installed at the upper end of the first limiting seat and the lower end of the second limiting seat, and the upper infrared sensor and the lower infrared sensor are used to limit the lifting adjustment plate.

[0011] As a further embodiment of this utility model: a base is provided on the inner bottom surface of the electrolysis chamber, a liquid outlet window is provided on the base, and a liquid outlet hole communicating with the liquid outlet window is opened on the inner bottom surface of the electrolysis chamber, and the liquid outlet hole is aligned and matched with the circulation chamber.

[0012] As a further embodiment of this utility model: a V-shaped abutment plate is installed on the side of the lifting adjustment plate, and the V-shaped abutment plate abuts and cooperates with the upper limit switch and the lower limit switch respectively.

[0013] Compared with the prior art, the beneficial effects of this utility model are as follows: This utility model of ECM device drives the threaded lifting rod to rotate by adjusting the motor components. By utilizing the sliding fit of the lifting adjustment rod in the adjustment hole, the rotational motion is converted into linear motion, thereby controlling the up and down position of the electrode assembly. The electrode assembly adopts multiple electrodes in a uniform array, which can flexibly adapt to the processing requirements of different workpieces under the lifting adjustment, realizing the rapid and accurate adjustment of electrode height. It solves the problem of limited processing and low efficiency caused by the lack of lifting function in existing ECM devices, and significantly improves the accuracy and adaptability of deburring. Attached Figure Description

[0014] Figure 1 This is a three-dimensional structural view of the present invention; Figure 2 This is another three-dimensional view of the structure of this utility model; Figure 3 This is a three-dimensional view of the internal structure of this utility model; Figure 4 This is another three-dimensional view of the internal structure of this utility model; Figure 5 This is a three-dimensional structural view of the lifting adjustment component and the electrode component in this utility model; Figure 6 This is another three-dimensional view of the lifting adjustment component and electrode component in this utility model; Figure 7 This is a three-dimensional structural view of the limiting seat component in this utility model; Figure 8 This is a front view of the present invention; Figure 9 yes Figure 8 A cross-sectional view along the AA direction; The reference numerals and names in the figure are as follows: Frame-101, Electrolysis Chamber Assembly-102, Lifting Adjustment Assembly-103, Electrode Assembly-104, Electrolysis Chamber Component-105, Circulation Pump Component-106, Circulation Chamber Component-107, Lifting Mounting Plate-109, Threaded Lifting Rod-110, Adjusting Motor Component-111, Lifting Adjustment Plate-112, Lifting Adjustment Rod-113, Adjustment Hole-114, Electrode Mounting Plate-115, Electrode Component-116, Limit Seat Component-117, Upper Limit Switch-118, Lower Limit Switch-119, First Limit Seat-120, Second Limit Seat-120 Position seat-121, first adjusting motor-122, second adjusting motor-123, first threaded adjusting rod-125, second threaded adjusting rod-126, first slide groove-127, second slide groove-128, lifting bracket-129, electrode mounting seat-130, probe component-131, terminal connector-132, side plate-133, electrode mounting chamber-134, upper infrared sensor-135, lower infrared sensor-136, base-137, liquid outlet window-138, liquid outlet hole-139, V-shaped abutment plate-140. Detailed Implementation

[0015] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0016] Please see Figure 1-9 An adjustable ECM device includes a frame 101, on which an electrolysis chamber assembly 102, a lifting adjustment assembly 103, and an electrode assembly 104 mounted on the lifting adjustment assembly 103 are installed. The electrolysis chamber assembly 102 includes an electrolysis chamber component 105, a circulation pump component 106, and a circulation chamber component 107 fixed on the frame 101. The circulation pump component 106 drives the electrolyte to circulate between the electrolysis chamber component 105 and the circulation chamber component 107. like Figure 1 and Figure 2 As shown, firstly, in terms of processing accuracy and consistency, the closed-loop electrolyte circulation system driven by the electrolysis chamber component 102 can not only continuously remove electrolysis products and heat, preventing uneven electrolyte concentration and temperature in the processing area, but also fundamentally avoid processing accuracy distortion caused by local boiling or impurity accumulation, thereby ensuring that the dissolution rate is consistent throughout the workpiece surface, guaranteeing contour accuracy and surface quality. It should be noted that the pipelines of the electrolysis chamber 105, the circulation pump 106, and the circulation chamber 107 are omitted in the attached drawings. The circulation of the electrolyte is a common technology in the prior art and will not be described in detail here. The lifting and adjusting assembly 103 includes a lifting mounting plate 109 fixed on the electrolysis chamber component 105. A threaded lifting rod 110 is rotatably mounted on the lifting mounting plate 109. An adjusting motor component 111 that drives the threaded lifting rod 110 to rotate is mounted on the lifting mounting plate 109. A lifting adjusting plate 112 is screwed to the outer wall of the threaded lifting rod 110. A lifting adjusting rod 113 is fixed on the lifting adjusting plate 112. An adjusting hole 114 is opened on the lifting mounting plate 109. The lifting adjusting rod 113 slides up and down in the adjusting hole 114. The electrode assembly 104 includes an electrode mounting plate 115 fixed to the lower end of the lifting adjustment rod 113, and a plurality of charged electrode components 116 are uniformly arrayed on the electrode mounting plate 115. Secondly, the rotational motion is converted into vertical linear motion by driving the precision threaded lifting rod 110 with a servo motor, and the radial runout is eliminated by the sliding cooperation between the lifting adjustment rod 113 and the adjustment hole 114. This makes the lifting and positioning accuracy of the multi-electrode assembly 104 high. This design enables a single device to quickly adapt to workpieces of different heights and structural features. It can even achieve multi-station and different depth stepped processing in a single clamping through program control, thus expanding the range of processes. Finally, in terms of processing efficiency and economy, the multiple independent electrode components 116 evenly arrayed on the electrode assembly 104, combined with its overall height adjustment feature, allow for simultaneous and parallel processing of multiple features or complex contours of the workpiece, thereby expanding the scope of processing operations and shortening the production cycle. This utility model's ECM device drives the threaded lifting rod 110 to rotate via the adjusting motor component 111. By utilizing the sliding engagement of the lifting adjusting rod 113 within the adjusting hole 114, the rotational motion is converted into linear motion, thereby controlling the vertical position of the electrode assembly 104. The electrode assembly 104 employs multiple uniformly arrayed electrode components 116, which can flexibly adapt to the processing requirements of different workpieces under lifting adjustment, achieving rapid and precise adjustment of electrode height. This solves the problem of limited processing operations and low efficiency caused by the lack of lifting function in existing ECM devices, significantly improving the accuracy and adaptability of deburring.

[0017] In this embodiment of the utility model, a limiting seat 117 is installed on the lifting mounting plate 109. An upper limit switch 118 and a lower limit switch 119 are respectively installed on the upper and lower ends of the limiting seat 117. The upper and lower limit switches 119 are used to limit the lifting adjustment plate 112 to the upper and lower positions respectively. like Figure 6 and7 As shown, the limit seat 117 provided on the lifting mounting plate 109 and the upper limit switch 118 and lower limit switch 119 installed at its upper and lower ends respectively constitute a protection system. When the lifting adjustment plate 112 touches the upper limit switch 118 or the lower limit switch 119 during adjustment, the switch will immediately send a signal to forcibly cut off the power of the adjustment motor 111, thereby forcibly stopping the lifting action. The electrical control sets a clear physical boundary for the movement range of the electrode assembly 104, thereby eliminating the risk of collision between the electrode and the workpiece or the equipment body, or the effective range exceeding the limit caused by over-adjustment. It effectively avoids consequences such as over-processing, scratching of the product, or damage to the electrolysis chamber assembly 102, and significantly improves the automation and reliability of the entire ECM device.

[0018] In this embodiment of the utility model, the limiting seat 117 includes a first limiting seat 120 and a second limiting seat 121 mounted side by side on the lifting mounting plate 109. A first adjusting motor 122 and a second adjusting motor 123 are respectively mounted on the first limiting seat 120 and the second limiting seat 121. A first threaded adjusting rod 125 and a second threaded adjusting rod 126 are respectively fixed to the output shafts of the first adjusting motor 122 and the second adjusting motor 123. The first limiting seat 120 and the second limiting seat 121 are respectively provided with a vertical first sliding groove 127 and a second sliding groove 128. The upper limit switch 118 and the lower limit switch 119 are respectively installed in the first sliding groove 127 and the second sliding groove 128. The upper limit switch 118 and the lower limit switch 119 are respectively screwed onto the first threaded adjusting rod 125 and the second threaded adjusting rod 126. like Figure 7 As shown, the limiting seat 117 adopts a first limiting seat 120 and a second limiting seat 121 arranged in parallel, and is equipped with a first and a second threaded adjusting rod 126 driven independently by the first and second adjusting motors 123 respectively; by controlling the rotation of the corresponding adjusting motor, the upper limit switch 118 or the lower limit switch 119 screwed on the threaded adjusting rod can be driven to move vertically along the corresponding first slide groove 127 or the second slide groove 128, thereby quickly setting the upper and lower travel limits of the lifting adjusting plate 112. This design realizes the electric and precise stepless adjustment of the travel limit point, so that the same ECM device can quickly reconstruct the safe processing range without cumbersome manual disassembly and positioning when dealing with workpieces of different sizes or different processing depth requirements, thus enhancing the adaptability of the equipment; In one embodiment, the upper limit switch 118 and the lower limit switch 119 are respectively screwed onto the first threaded adjusting rod 125 and the second threaded adjusting rod 126 via adapters.

[0019] In this embodiment of the utility model, a lifting bracket 129 is fixedly provided on the lifting mounting plate 109, and the upper end of the threaded lifting rod 110 is rotatably mounted on the lifting bracket 129; the upper ends of the first limiting seat 120 and the second limiting seat 121 are fixedly connected to the lifting bracket 129. like Figure 5 and 6 As shown, by fixing a lifting bracket 129 on the lifting mounting plate 109 and rotatably mounting the upper end of the threaded lifting rod 110 on the bracket, and simultaneously fixing the upper ends of the first limiting seat 120 and the second limiting seat 121 to the same lifting bracket 129, an integrated support structure with the lifting bracket 129 as the core is constructed. This provides a stable and reliable top support for the threaded lifting rod 110, which bears the main load, effectively suppressing the radial sway and bending deformation that may occur in the threaded lifting rod 110 during transmission. At the same time, by integrating and anchoring the two independent limiting seats to the same rigid reference, the structural stability of the entire lifting motion system is ensured.

[0020] In this embodiment of the present invention, the electrode component 116 includes an electrode mounting base 130 fixed on an electrode mounting plate 115, a probe component 131 mounted on the electrode mounting base 130, the probe component 131 extending downward through the electrode mounting plate 115, and a terminal connector 132 fixed at the upper end of the probe component 131. like Figure 5 and 6 As shown, the electrode 116 adopts a modular design, consisting of an electrode mounting base 130 fixed on the electrode mounting plate 115, a probe 131 extending downwards, and a terminal connector 132 at the upper end. The electrode mounting base 130 serves as a stable mechanical foundation, ensuring that the probe 131 is accurately clamped and reliably insulated. The probe 131 serves as the working end that directly performs electrolytic machining, and its lower protruding part forms a stable current path with the workpiece to complete the deburring operation. The terminal connector 132 at the upper end is responsible for quickly and reliably connecting to an external power source. The modular structure allows the installation, replacement, or maintenance of a single probe to be carried out independently.

[0021] In this embodiment of the present invention, a side plate 133 is provided around the periphery of the electrode mounting plate 115, and an electrode mounting chamber 134 is provided around the side plate 133 and the electrode mounting plate 115. like Figure 4 and 9As shown, by surrounding the periphery of the electrode mounting plate 115 with a side plate 133, a relatively closed electrode mounting chamber 134 is constructed together with the electrode mounting plate 115, forming a physical isolation barrier. This barrier covers and protects the key electrical connection parts, such as the terminal connector 132 and the upper end of the electrode component 116 located above the electrode mounting plate 115, effectively isolating them from the working liquid circulating in the electrolysis chamber below. This prevents the conductive and corrosive electrolyte from splashing or spraying into these electrical interfaces, thus improving the long-term working life of the electrode assembly 104 in harsh electrolytic processing environments.

[0022] In this embodiment of the present invention, an upper infrared sensor 135 and a lower infrared sensor 136 are respectively installed at the upper end of the first limiting seat 120 and the lower end of the second limiting seat 121. The upper infrared sensor 135 and the lower infrared sensor 136 are used to limit the lifting adjustment plate 112. like Figure 7 As shown, by installing an upper infrared sensor 135 and a lower infrared sensor 136 at the upper end of the first limit seat 120 and the lower end of the second limit seat 121 respectively, an infrared beam is used to form a second safety barrier. When the lifting adjustment plate 112 enters and blocks its path during operation, the sensor will immediately generate an electrical signal and transmit it to the control system, thereby quickly triggering the stopping or reversing action of the adjustment motor component 111, thus realizing the control of the lifting stroke. Compared with the traditional mechanical limit switch, this non-contact detection method eliminates the problems of component wear, mechanical jamming or positional deviation caused by physical collision, further improving the stability and automation level of the ECM device.

[0023] In this embodiment of the present invention, a base 137 is provided on the inner bottom surface of the electrolysis chamber 105, a liquid outlet window 138 is provided on the base 137, and a liquid outlet hole 139 communicating with the liquid outlet window 138 is opened on the inner bottom surface of the electrolysis chamber 105. The liquid outlet hole 139 is aligned and cooperates with the circulation chamber 107. like Figure 9 As shown, an electrolyte return path is constructed by setting a base 137 with an outlet window 138 on the inner bottom surface of the electrolysis chamber 105, and making the outlet window 138 directly aligned and connected with the circulation chamber 107 below through the outlet hole 139 at the bottom of the electrolysis chamber 105. Under the suction action of the circulating pump 106, the electrolyte after processing the workpiece carries electrochemical products (such as anode mud, hydrogen, etc.) and heat, which can be quickly collected through the liquid outlet window 138 on the base 137 and discharged into the circulating chamber 107 through the opposite liquid outlet hole 139. Then, after filtration and impurity removal in the circulating chamber, the electrolyte achieves a good circulation.

[0024] In this embodiment of the present invention, a V-shaped abutment plate 140 is provided on the side of the lifting adjustment plate 112, and the V-shaped abutment plate 140 abuts and cooperates with the upper limit switch 118 and the lower limit switch 119 respectively. By setting a V-shaped abutment plate 140, the V-shaped abutment plate 140 makes elastic contact with the upper limit switch 118 and the lower limit switch 119 during the contact process, avoiding direct rigid contact that could damage the upper limit switch 118 and the lower limit switch 119.

[0025] It will be apparent to those skilled in the art that this invention is not limited to the details of the exemplary embodiments described above, and that it can be implemented in other specific forms without departing from the spirit or essential characteristics of this invention. Therefore, the embodiments should be considered illustrative and non-limiting in all respects, and the scope of this invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within this invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

Claims

1. An adjustable ECM device, characterized in that, Includes a frame (101), on which an electrolysis chamber assembly (102), a lifting adjustment assembly (103), and an electrode assembly (104) mounted on the lifting adjustment assembly (103) are installed. The electrolysis chamber assembly (102) includes an electrolysis chamber component (105), a circulation pump component (106), and a circulation chamber component (107) fixed on the frame (101). The circulation pump component (106) drives the electrolyte to circulate between the electrolysis chamber component (105) and the circulation chamber component (107). The lifting adjustment assembly (103) includes a lifting mounting plate (109) fixed on the electrolysis chamber component (105). A threaded lifting rod (110) is rotatably mounted on the lifting mounting plate (109). An adjustment motor component (111) that drives the threaded lifting rod (110) to rotate is mounted on the lifting mounting plate (109). A lifting adjustment plate (112) is screwed to the outer wall of the threaded lifting rod (110). A lifting adjustment rod (113) is fixed on the lifting adjustment plate (112). An adjustment hole (114) is opened on the lifting mounting plate (109). The lifting adjustment rod (113) slides up and down in the adjustment hole (114). The electrode assembly (104) includes an electrode mounting plate (115) fixed to the lower end of the lifting adjustment rod (113), and a plurality of charged electrode components (116) are uniformly arrayed on the electrode mounting plate (115).

2. The adjustable ECM device according to claim 1, characterized in that, The lifting mounting plate (109) is equipped with a limiting seat (117). The upper end and lower end of the limiting seat (117) are respectively equipped with an upper limit switch (118) and a lower limit switch (119). The upper and lower limit switches (119) are used to limit the lifting adjustment plate (112) to the upper and lower positions respectively.

3. An adjustable ECM device according to claim 2, characterized in that, The limiting seat (117) includes a first limiting seat (120) and a second limiting seat (121) mounted side by side on the lifting mounting plate (109). A first adjusting motor (122) and a second adjusting motor (123) are respectively mounted on the first limiting seat (120) and the second limiting seat (121). A first threaded adjusting rod (125) and a second threaded adjusting rod (126) are respectively fixed to the output shafts of the first adjusting motor (122) and the second adjusting motor (123). The first limiting seat (120) and the second limiting seat (121) are respectively provided with a first sliding groove (127) and a second sliding groove (128). The upper limit switch (118) and the lower limit switch (119) are respectively installed in the first sliding groove (127) and the second sliding groove (128). The upper limit switch (118) and the lower limit switch (119) are respectively screwed onto the first threaded adjusting rod (125) and the second threaded adjusting rod (126).

4. An adjustable ECM device according to claim 3, characterized in that, A lifting bracket (129) is fixedly mounted on the lifting mounting plate (109), and the upper end of the threaded lifting rod (110) is rotatably mounted on the lifting bracket (129); the upper ends of the first limiting seat (120) and the second limiting seat (121) are fixedly connected to the lifting bracket (129).

5. An adjustable ECM device according to any one of claims 1-4, characterized in that, The electrode component (116) includes an electrode mounting base (130) fixed on an electrode mounting plate (115), a probe component (131) is mounted on the electrode mounting base (130), the probe component (131) extends downward through the electrode mounting plate (115), and a terminal connector (132) is fixed at the upper end of the probe component (131).

6. An adjustable ECM device according to claim 5, characterized in that, The electrode mounting plate (115) is surrounded by a side plate (133), and the side plate (133) and the electrode mounting plate (115) together form an electrode mounting chamber (134).

7. An adjustable ECM device according to claim 3, characterized in that, The upper end of the first limiting seat (120) and the lower end of the second limiting seat (121) are respectively equipped with an upper infrared sensor (135) and a lower infrared sensor (136), which are used to limit the lifting adjustment plate (112).

8. An adjustable ECM device according to claim 6, characterized in that, The inner bottom surface of the electrolysis chamber (105) is provided with a base (137), the base (137) is provided with a liquid outlet window (138), and the inner bottom surface of the electrolysis chamber (105) is provided with a liquid outlet hole (139) communicating with the liquid outlet window (138). The liquid outlet hole (139) is aligned and matched with the circulation chamber (107).

9. An adjustable ECM device according to claim 8, characterized in that, The side of the lifting adjustment plate (112) is equipped with a V-shaped abutment plate (140), which abuts against the upper limit switch (118) and the lower limit switch (119) respectively.

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