Cam device for a needleless injector and needleless injector

Abstract

The utility model provides a kind of cam device and needleless injector for needleless injector, the cam device for needleless injector includes cam, the end surface of the cam is used to promote the movement of the injector's push component, the end surface includes cam push section, the profile line of the cam push section corresponds push curve, the increment of the push of the push curve and the rotation angle of cam presents decreasing relationship.The push curve in the utility model can make driven part, i.e. the push component moves with the rule of constant power during the movement of cam device, which can provide relatively stable power output for motor during movement, avoid the decline of production efficiency caused by power fluctuation, move smoothly, acceleration and impact force are smaller, vibration and noise are low.

Description

Technical Field

[0001] This utility model belongs to the field of medical devices, specifically relating to a cam device for a needleless injector and a needleless injector. Background Technology

[0002] The drive cam mechanism of existing needle-free injector power systems is generally designed independently, typically using stroke control (displacement or stroke control), unrelated to energy-saving control or motor characteristics. The cam's push surface is usually a constant velocity surface, meaning the cam causes the push component to move at a uniform linear speed. As the cam pushes the push component, the push component gradually compresses the spring. As the push increases, the spring's compression force gradually increases, requiring the cam's thrust to increase accordingly. This means the output torque of the motor driving the cam must gradually increase. According to the motor's output characteristics, as torque increases, the motor speed decreases. When the motor is driven at low speed and high torque, vibration and noise are relatively high. The high current causes the motor to generate a lot of heat and has low operating efficiency, resulting in a decrease in the battery's range.

[0003] In addition, when the motor speed decreases, the cam speed also decreases, and the linear motion speed of the push stroke assembly also decreases, resulting in a longer liquid suction time and a lower injection frequency for the metering plunger pump connected to the push stroke assembly. Summary of the Invention

[0004] This invention provides a cam for a needleless injector and a needleless injector to solve problems such as increased motor noise, high motor heat generation, and low motor operating efficiency caused by increased motor torque.

[0005] To solve the above-mentioned technical problems, this utility model provides a cam device for a needleless injector, including a cam. The end face of the cam is used to drive the push stroke component of the injector to move. The end face includes a cam push stroke section. The outline of the cam push stroke section corresponds to a push stroke curve. The increment of the push stroke of the push stroke curve is in a decreasing relationship with the rotation angle of the cam.

[0006] Furthermore, the unfolded projection curve is one of the following: a trigonometric function curve, a polynomial curve, or a cycloid curve.

[0007] Furthermore, the push angle corresponding to the starting point of the cam push segment is zero, and the push angle corresponding to the ending point of the cam push segment is the maximum push angle, the maximum push angle being in the range of 300° to 340°.

[0008] Furthermore, the end face of the cam includes a cam start-stop section, a cam end-stop section, and a cam push-stroke quick-return section. The starting point of the cam push-stroke section is connected to the cam start-stop section, the ending point of the cam push-stroke section is connected to the cam end-stop section, and the cam push-stroke quick-return section connects the cam end-stop section and the cam start-stop section.

[0009] Furthermore, both the initial dwell section and the final dwell section of the cam are planar, and the cam push-stroke quick-return section is a vertical plane perpendicular to the planar.

[0010] This utility model also provides a needleless injector, including a motor, a push-stroke assembly, a spring, and a cam device for a needleless injector according to any embodiment.

[0011] Furthermore, the motor is connected to the cam device, the motor is used to drive the cam device to rotate, and the cam device is used to drive the push stroke assembly to compress the spring. The push stroke y of the cam and the rotation angle θ of the cam satisfy the following relationship:

[0012]

[0013] Where P is the output power of the motor and P is a constant, η is the efficiency of the motor, n is the rotational speed of the cam, k is the stiffness of the spring, and b is the initial compression of the spring.

[0014] Furthermore, the power P of the motor is the power within the target efficiency range, where the target efficiency range is [90%η]. max 100%η max ], where η max This represents the maximum efficiency of the motor.

[0015] Furthermore, the push stroke assembly includes a cam roller and a push stroke rod. The cam roller abuts against the end face of the cam. When the cam roller is in the initial dwell section of the cam, the pre-compression of the spring is state b.

[0016] Furthermore, a speed reducer is provided between the motor and the cam device.

[0017] Since the increment of the push stroke is positively correlated with the speed of the push stroke assembly, the push stroke assembly moves at its fastest speed when the cam push stroke section just contacts the push stroke assembly due to the largest increment. As the cam's rotation angle gradually increases, the increment of the cam's push stroke gradually decreases, meaning the speed of the push stroke assembly gradually slows down. At this point, although the spring's compression force is relatively large, the power of the push stroke assembly remains essentially constant due to the reduced speed of the push stroke assembly; that is, the output power of the cam remains essentially constant, and the output power of the motor remains constant. Therefore, the push stroke curve in this invention enables the driven component, i.e., the push stroke assembly, to move with a constant power during the movement of the cam device. This allows the motor to provide a relatively stable power output during movement, avoiding a decrease in production efficiency due to power fluctuations, resulting in smooth movement, lower acceleration and impact forces, and lower vibration and noise.

[0018] The above description is merely an overview of the technical solution of this utility model. In order to better understand the technical means of this utility model and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this utility model more apparent and understandable, preferred embodiments are described below in detail with reference to the accompanying drawings. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the overall structure of the needleless injector according to an embodiment of the present invention;

[0020] Figure 2 This is an assembly diagram of the cam device and the push stroke assembly according to an embodiment of the present utility model;

[0021] Figure 3 This is an assembly schematic diagram of the cam device and push stroke assembly from another perspective of an embodiment of the present utility model.

[0022] Figure 4 The characteristic curve of the motor in this embodiment of the utility model is shown.

[0023] Figure 5 This is a schematic diagram of the push curve showing the correspondence between the rotation angle of the cam and the displacement of the push component in an embodiment of the present invention.

[0024] Figure 6 This is a schematic diagram of the push curve showing the correspondence between the circumferential direction of the cam and the movement direction of the push component in an embodiment of the present invention.

[0025] Figure 7 This is a schematic diagram illustrating the kinematic relationship between the cam and the cam roller in an embodiment of the present invention. Attached Figure Description

[0027] 1. Cam; 1.1. Cam initial dwell section; 1.2. Cam push stroke section; 1.3. Cam end dwell section; 1.4. Cam push stroke quick return section; 2. Base; 3. Motor; 4. Metering plunger pump; 5. Connecting sleeve; 6. Spring; 7. Outer guide plate; 8. Push stroke assembly; 8.1. Splined shaft; 8.2. Cam roller; 8.3. Internal spline; 9. Thrust ball bearing shaft system; 9.1. Drive pin; 10. Nozzle. Detailed Implementation

[0028] To further illustrate the technical means and effects adopted by this utility model in order to achieve the intended utility model purpose, the specific implementation methods and effects of this utility model will be described in detail below with reference to the accompanying drawings and preferred embodiments.

[0029] Throughout this specification, references to terms such as "an embodiment," "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. Therefore, the phrases "in one embodiment" or "in one embodiment" appearing in different places throughout this specification do not necessarily refer to the same embodiment. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0030] In the description of the embodiments of this application, the term "multiple" refers to two or more (including two).

[0031] Unless otherwise required by the content, throughout the following description and claims, the word “comprising” and its variations, such as “including”, shall be interpreted in an open-ended, inclusive sense, that is, as “including but not limited to”.

[0032] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "fixation," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0033] This utility model provides a cam device for a needleless injector, such as... Figure 3As shown, the cam device includes a cam 1, the end face of which is used to push the push stroke assembly 8 of the syringe to move. The end face of the cam 1 includes a cam push stroke section 1.2. The contour line of the cam push stroke section 1.2 corresponds to the push stroke curve. The increment of the push stroke of the push stroke curve is in a decreasing relationship with the rotation angle of the cam 1, and the velocity of the push stroke assembly 8 is inversely proportional to the spring force of the push stroke assembly 8.

[0034] Optionally, the cam 1 can be a cylindrical cam, a cylindrical cam, a conical cam, etc., and this utility model is not limited to the specific structure of the cam.

[0035] Specifically, such as Figure 5 As shown, the stroke of cam 1 is y, the rotation angle of cam 1 is θ, and the stroke increment of cam 1 is Δy. Δy and θ have a decreasing relationship; that is, as the rotation angle of cam 1 increases from zero to its maximum value, the stroke increment per unit stroke angle gradually decreases. In other words, the slope of the end face of cam 1 gradually becomes gentler. Initially, the slope of cam 1 is steeper, and the movement speed of the stroke assembly 8 is faster. As the rotation angle of cam 1 gradually increases, the slope of the end face of cam 1 gradually becomes gentler, and the movement speed of the stroke assembly 8 gradually slows down.

[0036] Since the increment of the push stroke is positively correlated with the speed of the push stroke assembly 8, when the cam push stroke segment 1.2 just contacts the push stroke assembly 8, the increment of the push stroke is the largest, so the movement speed of the push stroke assembly 8 is the fastest. As the rotation angle of the cam 1 gradually increases, the increment of the push stroke of the cam 1 gradually decreases, that is, the movement speed of the push stroke assembly 8 gradually slows down. At this time, although the compression force of the spring is large, the power of the push stroke assembly 8 remains basically unchanged because the speed of the push stroke assembly 8 slows down. That is, the output power of the cam 1 remains basically unchanged (i.e., constant power cam), and the output power of the motor remains unchanged.

[0037] In this embodiment, in order to ensure that the output power of cam 1 remains basically constant, that is, cam 1 is a constant power cam, the velocity-like speed of the push stroke component 8 is... It is inversely proportional to the spring force k(y+b) of the push stroke assembly 8 (i.e., the resistance of the push stroke assembly 8 on the cam 1 during rotation).

[0038] Among them, the velocity class of the push component 8 In the formula, ω is the angular velocity of the cam, and v is the displacement velocity of the push rod. In the spring force k(y+b), k is the stiffness of the spring, y is the push stroke of cam 1, that is, the displacement of the push rod assembly 8, and b is the initial compression of the spring.

[0039] The push stroke curve in this invention enables the push stroke component 8 to move with a constant power during the movement of the cam 1, so that the motor can provide a relatively stable power output during the movement, avoid the decrease in production efficiency caused by power fluctuations, and achieve the effects of smooth movement, low acceleration and impact force, and low vibration and noise.

[0040] The decrease in motor speed in this invention is not significant, and the decrease in cam 1 speed is also not significant. Therefore, the liquid aspiration time will not increase, and the number of injections within a fixed time period will not decrease.

[0041] In one embodiment of this utility model, the unfolded push curve is one of a trigonometric function curve, a polynomial curve, or a cycloid curve, so as to conform to the motion law type of the push component 8 when designing the curve of the end face of the cam 1.

[0042] In one embodiment of this utility model, the push angle corresponding to the starting point of the cam push segment 1.2 is zero, and the push angle corresponding to the ending point of the cam push segment 1.2 is the maximum push angle, which ranges from 300° to 340°.

[0043] In one embodiment of this utility model, such as Figure 3 As shown, the end face of cam 1 also includes a cam start dwell section 1.1, a cam end dwell section 1.3, and a cam push stroke quick return section 1.4. The starting point of the cam push stroke section 1.2 is connected to the cam start dwell section 1.1, the ending point of the cam push stroke section 1.2 is connected to the cam end dwell section 1.3, and the cam push stroke quick return section 1.4 connects the cam end dwell section 1.3 and the cam start dwell section 1.1.

[0044] In one embodiment of this utility model, such as Figure 3 As shown, the initial dwell section 1.1 and the final dwell section 1.3 of the cam are both planes, while the rapid return section 1.4 of the cam push stroke is a vertical plane perpendicular to the plane.

[0045] In this embodiment, such as Figure 3 and Figure 5 As shown, during the rotation of cam 1, it pushes the pusher assembly 8 upward to its highest position. This stage of the working process is called the push period, and the corresponding end face of cam 1 is called the cam push segment 1.2. The rotation angle of cam 1 corresponding to the push period is called the push angle Ф. The maximum movement distance of the pusher assembly 8 is called the stroke, denoted by h, which is the travel distance of the pusher assembly 8. As cam 1 continues to rotate, the pusher assembly 8 stops at its maximum movement distance, i.e., its farthest position. This process is called the cam far rest period, and the corresponding end face of cam 1 is called the cam end rest segment 1.3. The angle through which cam 1 rotates is Ф. SWhen cam 1 rotates again, the push stroke assembly 8 returns rapidly under the action of the spring. This process is called the cam return period, and the corresponding end face of cam 1 is the cam push stroke quick return section 1.4. Then, the push stroke assembly 8 stops at the starting position of cam 1. This process is called the near-rest period, and the corresponding end face of cam 1 is the cam starting rest section 1.1. The angle through which the cam rotates is Ф. F If the push curve is designed in two segments, Ф1 is the dividing point.

[0046] This utility model also provides a needleless injector, such as Figure 1 As shown, the needleless injector includes a motor 3 and a push-stroke assembly 8 according to the above-described cam device for a needleless injector, wherein the push-stroke assembly 8 includes a spring 6.

[0047] In one embodiment of this utility model, the motor 3 is connected to the cam 1. The motor 3 drives the cam 1 to rotate, and the cam 1 drives the push stroke assembly 8 to compress the spring 6. The push stroke y of the cam 1 and the rotation angle θ of the cam 1 satisfy the following relationship:

[0048]

[0049] Where P is the output power of motor 3 and is a constant, η is the efficiency of motor 3, n is the rotational speed of cam 1, k is the stiffness of spring 6, and b is the initial compression of spring 6. Furthermore, it can be seen from the above formula that, under the condition of constant output power of motor 3, the speed of the push-stroke assembly 8 is... It is inversely proportional to the spring force k(y+b) of spring 1.

[0050] In one embodiment of this utility model, the power P of the motor 3 is the power within the target efficiency range, and the target efficiency range is [90%η]. max 100%η max ], where η max This represents the maximum efficiency of motor 3. In this embodiment, the power value corresponding to a relatively high motor efficiency is selected, which can further reduce the energy consumption of the needle-free injector.

[0051] like Figure 4 As shown, P is the output power-torque curve of motor 3, η is the efficiency-torque curve, N is the speed-torque curve, and I is the motor current-torque curve. Through... Figure 4 It can be seen that the constant power cam profile curve design of cam 1 is based on the performance curve of motor 3 as a constraint condition, that is, motor 3 works at the maximum efficiency point and does not affect the speed. The constant power cam curve refers to the curve profile design that enables the push stroke component 8 to move along the power-torque curve with constant power near the maximum efficiency point of the motor characteristic curve during the movement of cam 1.

[0052] In one embodiment of this utility model, such as Figure 3 As shown, the push stroke assembly 8 includes a cam roller 8.2 and a push stroke rod 8.1. The cam roller 8.2 abuts against the end face of the cam 1. When the cam roller 8.2 is in the cam's initial dwell section 1.1, the pre-compression of the spring 6 is state b.

[0053] Of course, in some embodiments, a follower with a pointed bottom structure can be used instead of the cam roller 8.2, and the pointed bottom structure abuts against the end face of the cam.

[0054] In one embodiment of this utility model, a reducer is provided between the motor 3 and the cam 1. The motor 1 and the reducer constitute a geared motor.

[0055] In this embodiment, motor 3 refers to a micro motor.

[0056] In other embodiments, the motor used in the field of needle-free injection can also be a DC motor, a brushless DC motor, a stepper motor, an AC motor, an AC / DC servo motor, a permanent magnet synchronous motor, etc.

[0057] This invention enables the drive cam curve to be a cam curve that satisfies the constant power condition near the maximum efficiency point of the motor. This allows the motor 3 to operate near both its maximum efficiency and rated speed, achieving constant power drive while also saving energy and reducing noise and vibration. The constant power cam curve refers to the curve profile that allows the push stroke assembly 8 to move according to an approximately constant power law during the movement of cam 1. In other words, during the rotation of cam 1, the power obtained by the push stroke assembly 8 remains relatively constant under certain conditions.

[0058] The working principle of the needle-free injector provided by this utility model is as follows:

[0059] Cam 1 and motor 3 are mounted on base 2 and driven by transmission pin 9.1, forming the drive mechanism of cam 1 together with motor 3. Push stroke assembly 8 is bolted to spline shaft 8.1. Outer guide plate 7 is mounted on base 2, and spline shaft 8.1 is guided by outer guide plate 7 and prevented from rotating by its spline hole. Cam 1, driven by motor 3, pushes spline shaft 8.1 along a constant power cam curve. Simultaneously, metering plunger pump 4 completes reagent aspiration, and spline shaft 8.1 compresses spring 6 to store energy. Push stroke assembly 8 rapidly drops from the highest point of cam 1's end face to the lowest point. Push stroke assembly 8 drives the plunger on the coaxial line, causing metering plunger pump 4 to complete one jet injection, and reagent is ejected from nozzle 10, achieving needle-free injection. If push stroke assembly 8 drives spline shaft 8.1 to oscillate back and forth from the highest point to the lowest point of cam 1's end face, the needle-free injector cleaning action is achieved. This invention can achieve efficient, energy-saving, continuous, and stable needle-free injection.

[0060] Specifically, such as Figure 2 and Figure 3 As shown, motor 3 is fixed on base 2 and transmits power to cam 1, which is fixed on thrust ball bearing shaft 9, through transmission pin 9.1. Cam 1 drives thrust assembly 8 through cam roller 8.2, pushing spline shaft 8.1. The inner spline 8.3 of outer guide plate 7 provides guidance and anti-rotation, pulling the plunger of metering plunger pump 4 connected to connecting sleeve 5 to generate vacuum for reagent aspiration. At the same time, spring 6 is compressed to store energy. Its characteristic is that: corresponding to the cam initial dwell section 1.1 of cam 1, spring 6 is in a pre-compressed state. Driven by motor 3, the thrust assembly 8 moves linearly in the cam thrust section 1.2, compressing spring 6 to store energy. Since the spring force increases with the increase of thrust, the transmitted power of cam 1 will increase. Therefore, the pressure angle of cam 1 must be reduced, otherwise... Figure 4 The motor performance curve shown shows that as power increases, speed decreases. However, the cam curve designed based on the constant power principle can provide relatively stable power output from motor 3 during the cam push stroke segment 1.2. This makes the speed change of push stroke component 8 more uniform during the movement, avoids the decrease in production efficiency caused by power fluctuations, and ensures smooth movement with less acceleration and impact, and low vibration and noise.

[0061] Correspondingly, at the end of the cam stop section 1.3, the metering plunger pump 4 completes the reagent aspiration. After triggering the injection switch or sensor, the motor 3 drives the cam 1 to continue rotating until the push stroke assembly 8, under the action of the spring 6, causes the cam roller 8.2 to fall rapidly from the cam push stroke quick return section 1.4. The push stroke assembly 8 drives the plunger on the coaxial axis, enabling the metering plunger pump 4 to complete one jet injection, realizing needle-free injection.

[0062] Motor 3 drives cam 1 to rotate counterclockwise in the cam push stroke section 1.2. Cam 1 drives the metering plunger pump 4 on the push stroke assembly 8 to complete reagent intake. Then it rotates clockwise, and spring 6 drives the metering plunger pump 4 on the push stroke assembly 8 to complete reagent discharge, realizing one cleaning action of needle-free syringe.

[0063] The needle-free injector of this invention can achieve efficient, energy-saving, continuous and stable needle-free injection.

[0064] This utility model also provides a method for calculating the stroke curve, as follows:

[0065] Typically, a cylindrical coordinate system is established with the rotation center of the cylindrical cam 1 as the origin. In this coordinate system, the motion law of the push stroke assembly 8 is transformed into the coordinate expression of points on the profile of the cam 1.

[0066] Based on the known motion laws and the geometric relationship between cam 1 and cam roller 8.2, the coordinates of a series of discrete points on the profile of cam 1 can be calculated mathematically. During the calculation, the rotation angle θ of cam 1 and the corresponding stroke h of the push assembly 8 must be considered, and mathematical tools such as trigonometric functions are used to solve for the coordinate values ​​of the profile points.

[0067] The kinematic requirements of the cam-driven device driven by motor 3 are as follows: the push curve of cam 1 drives the push assembly 8, which stores energy through the linear motion compression spring. This allows the push assembly 8 to quickly return the syringe spline shaft 8.1, completing one aspiration and injection cycle. The stroke h of the push assembly 8 must meet the displacement requirements of the metering plunger pump 4 (i.e., the injection volume per cycle), the speed must meet the injection pressure requirements, and the acceleration must be stable. The required power output is generally below 30 watts, and the operating frequency is below 60 times per minute.

[0068] Based on the constant power requirement, the motion equations of the push-stroke assembly 8 are established. By solving these equations, the displacement, velocity, and acceleration parameters of the push-stroke assembly 8 at different times are obtained. The motion form of the push-stroke assembly 8 is considered, such as constant velocity motion, constant acceleration motion, constant deceleration motion, and cosine acceleration motion. This involves selecting a suitable constant power cam curve type, including polynomial curves (e.g., quadratic, cubic, quintic, and septum), trigonometric function curves (e.g., sine and cosine functions), and some special curves (e.g., cycloidal curves, modified trapezoidal curves), to establish a mathematical model of the constant power cam curve. Generally, based on the motion requirements of the push-stroke assembly 8, the order, coefficients, amplitudes, and frequencies of the mathematical model of the cam curve need to be determined to ensure that the displacement, velocity, and acceleration parameters of the push-stroke assembly 8 meet the design requirements and guarantee constant power. Then, the contour curve coordinates of cam 1 are solved.

[0069] In other words, the kinematic equations are first selected or established, and then the power equations are established. Based on the definition of power and the mechanical analysis of the cam mechanism, a set of equations relating power to the rotation angle θ or time of cam 1 is derived. Since constant power is required, this set of equations should satisfy the constant power condition that the selected motor characteristic curve (power-torque curve) is near the point of maximum efficiency. By solving the set of equations, the parameters of the constant power cam curve are determined. Applying the principle of coordinate transformation, based on the geometric relationship and kinematic principle of the cam mechanism, the displacement equation of the push stroke assembly 8 is converted into the coordinate equation of the profile curve of cam 1.

[0070] When establishing the kinematic equations, based on the selected curve type and the motion law of the push stroke component 8, the equations for the changes in displacement, velocity, and acceleration of the push stroke component 8 with time or the rotation angle of the cam 1 are derived.

[0071] The class velocity and class acceleration of the push-stroke component 8 are obtained by differentiating the displacement function, which is y = y(θ). The class velocity of the push-stroke component 8 is... The equation of acceleration is

[0072] In the above formula, y is the displacement of the push stroke assembly 8, θ is the rotation angle of the cam 1, v is the moving speed of the push stroke assembly 8, and ω is the rotation speed of the cam 1.

[0073] In the cam mechanism of a needle-free injector, when the rotational speed is around 60 rpm and there is a certain friction on cam 1, the displacement formula according to the constant power cam curve with sinusoidal acceleration, i.e., cycloidal motion law, is as follows:

[0074]

[0075] The displacement formula based on the cosine acceleration motion law of the constant power cam curve is:

[0076]

[0077] Where y is the displacement of the stroke component 8, h is the stroke of the stroke component 8, θ is the rotation angle of the cam, and Ф is the push stroke motion angle.

[0078] The displacement formula based on the constant power cam curve and its quadratic polynomial motion law is as follows:

[0079] y(θ)=a0+a1θ+a2θ 2

[0080] Where y is the displacement of component 8, θ is the rotation angle of cam 1, and a0, a1, a2 are the coefficients of the polynomial.

[0081] The displacement formula based on the constant power cam curve using a cubic polynomial motion law is as follows:

[0082] y(θ)=a0+a1θ+a2θ 2 +a3θ 3

[0083] Where y is the displacement of component 8, θ is the rotation angle of cam 1, and a0, a1, a2, a3 are the coefficients of the polynomial.

[0084] A constant power cam curve refers to the curve profile design that enables the push stroke component 8 to move with constant power near the maximum efficiency point of the geared motor characteristic curve during the movement of the cam mechanism. The most significant feature of the constant power cam 1 is that it enables the motor 3 to provide a relatively stable power output during the movement, avoiding the decrease in production efficiency caused by power fluctuations, smooth movement, low acceleration and impact force, and low vibration and noise.

[0085] Based on the known kinematic equations of the push-stroke component 8, and according to the definition of power P = F y v(where P is power, F) y (where v is the velocity and v is the force of the push component 8). Based on the mechanical analysis of the cam mechanism, the relationship equation between power P and cam rotation angle θ or time is established.

[0086] like Figures 5-7 As shown, during the push stroke of cam 1, the resistance F experienced by cam 1 by the push stroke assembly 8 is... y The displacement of the pusher assembly 8 is y, the stroke of the pusher assembly 8 is h, and the circumferential force F on the cam is... x R b Let be the base circle radius of cam 1, b be the pre-compression of spring 6, and k be the stiffness of spring 6. Since the speed during the push stroke of the syringe cam mechanism is relatively low, and the inertial force and friction on the push stroke assembly 8 are ignored, then the resistance F of the push stroke assembly on cam 1 is... y for:

[0087] F y = k(y+b)

[0088] Based on the force relationship of the cam, we can obtain

[0089] F x =F y tanα

[0090] Where α is the pressure angle of cam 1, and the slope at the point of force application is the tangent of the pressure angle, i.e.

[0091]

[0092] Since dx = R b dθ, therefore we can obtain

[0093]

[0094] so

[0095]

[0096] In the cam mechanism of the needleless injector, the rotational speed of cam 1 is around 60 rpm, which is relatively low. The shaft of cam 1 is fixed in a shaft system composed of a planar thrust needle roller bearing and a pair of radial ball bearings. Since the rolling friction of the cam roller 8.2 is very small, neglecting the inertial torque and frictional torque of cam 1, we have:

[0097] T = F x R b

[0098]

[0099] Therefore there is

[0100]

[0101] The formula for calculating motor power is:

[0102]

[0103] Where P is the output power of motor 3 (watts, W), η is the efficiency of motor 1, n is the rotational speed of cam 1 (revolutions per minute, rpm), and T is the torque (Newton-meter, Nm).

[0104]

[0105] Because motor 3 and cam 1 are directly connected, their torque values ​​are equal and are T. Substitution

[0106]

[0107] Where P is the output power of motor 1, and since the power is required to be constant, P in this equation should satisfy... Figure 4 Conditions for the power characteristic curve of a geared motor.

[0108] like Figure 6 As shown, after the base cylindrical surface of cam 1 is unfolded, the unfolded planar movement profile curve of cam roller 8.2 is obtained. The relative trajectory of the center of cam roller 8.2 is the theoretical profile curve, as shown in the attached figure. Figure 6 As shown by reference numeral 20, the developed profile curve of the end face of cam 1 is the actual profile curve, as shown in the attached figure. Figure 6 As shown by label 21. The x-axis represents the circumferential direction of cam 1, and the y-axis represents the direction of movement of the push stroke assembly 8.

[0109] like Figure 6 As shown, point B is the point on the theoretical profile curve of cam 1 that corresponds to the rotation angle θ of cam 1. Let the coordinates of point B be (x...). B y B ), is the center point of cam roller 8.2, nn is the normal at point B, α is the pressure angle of cam 1, and point K is the intersection of the normal nn and the actual profile curve. Let the coordinates of point K be (x K y K The theoretical profile curve of cam 1 is expressed by a Cartesian coordinate parametric equation as follows:

[0110]

[0111] When the roller radius is r, the formula for calculating the actual unfolded profile coordinates is:

[0112]

[0113] This invention determines various parameters of the constant power cam curve, such as the coefficients of the polynomial curve, the amplitude and frequency of the trigonometric function, by solving the established kinematic and power equations. The values ​​of these parameters directly affect the shape and performance of the cam curve and need to be rationally selected based on design requirements and optimization objectives. For solving the aforementioned nonlinear equations, an iterative method can be used to solve for the coordinate values ​​of the cam profile curve.

[0114] Polynomial functions (quadratic, cubic, etc.) possess excellent mathematical properties and flexibility, allowing for the adjustment of the polynomial's degree and coefficients to meet various motion requirements. Quadratic polynomial curves can realize simple parabolic motion laws, suitable for applications where high motion precision is not required; while cubic polynomial curves provide smoother motion transitions and can also be used in the design of constant-power cams. The isochronism of cycloidal curves enables more uniform velocity changes in the follower during motion.

[0115] It should be noted that this application may include any feature or combination of features or generalization thereof implied or expressly disclosed herein, and is not limited to any of the foregoing limitations. Any elements, features and / or structural arrangements described herein may be combined in any suitable manner.

[0116] The above are merely preferred embodiments of the present utility model and are not intended to limit the present utility model in any way. Although the present utility model has been disclosed above with reference to preferred embodiments, it is not intended to limit the present utility model. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present utility model. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present utility model without departing from the scope of the present utility model shall still fall within the scope of the present utility model.

Claims

1. A camming device for a needleless injector, characterized by, The device includes a cam, the end face of which is used to drive the push stroke assembly of the syringe. The end face includes a cam push stroke section, the outline of which corresponds to a push stroke curve. The increment of the push stroke curve is in a decreasing relationship with the rotation angle of the cam.

2. The cam device for a needle-free injector according to claim 1, characterized in that The unfolded propagation curve is one of the following: a trigonometric function curve, a polynomial curve, or a cycloid curve.

3. The cam apparatus for a needle-free injector of claim 1, wherein, The starting point of the cam push segment corresponds to a push angle of zero, and the ending point of the cam push segment corresponds to a push angle of the maximum push angle, which ranges from 300° to 340°.

4. The cam apparatus for a needle-free injector of claim 1, wherein, The end face of the cam includes a cam start-stop section, a cam end-stop section, and a cam push-stroke quick-return section. The starting point of the cam push-stroke section is connected to the cam start-stop section, the ending point of the cam push-stroke section is connected to the cam end-stop section, and the cam push-stroke quick-return section connects the cam end-stop section and the cam start-stop section.

5. The cam means for a needle-free injector according to claim 4, wherein, The initial dwell section and the final dwell section of the cam are both planar, and the cam push stroke quick return section is a vertical plane perpendicular to the planar plane.

6. A needleless injector characterized by, It includes a motor, a push-stroke assembly, and a cam device for a needleless injector according to any one of claims 1-5, wherein the push-stroke assembly includes a spring.

7. The needle-free injector of claim 6, wherein, The motor is connected to the cam device, and the motor drives the cam device to rotate. The cam device drives the push stroke assembly to compress the spring. The push stroke y of the cam and the rotation angle θ of the cam satisfy the following relationship: Where P is the output power of the motor and P is a constant, η is the efficiency of the motor, n is the rotational speed of the cam, k is the stiffness of the spring, and b is the initial compression of the spring.

8. The needle-free injector of claim 7, wherein, The power P of the motor is the power within the target efficiency range, and the target efficiency range is [90%η]. max 100%η max ], where η max This represents the maximum efficiency of the motor.

9. The needle-free injector of claim 7, wherein, The push stroke assembly includes a cam roller and a push stroke rod. The cam roller abuts against the end face of the cam. When the cam roller is in the initial dwell section of the cam, the pre-compression of the spring is state b.

10. The needle-free injector of claim 7, wherein, A speed reducer is provided between the motor and the cam device.

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