Direct injection mechanism for portable sprayer

Description

1 / 9 DIRECT INJECTION MECHANISM FOR PORTABLE SPRAYER

[01] The present invention relates to a direct injection mechanism for coupling to manual (lever) backpack sprayers, allowing the injection of pure chemicals with precise concentration and at low pressure, the chemical concentration being adjustable by the equipment user according to agronomic requirements. In this way, the need for external preparation of the spray mixture is eliminated and, consequently, the user's contact with the concentrated chemical product is reduced, ensuring that there is only clean water in the backpack sprayer tank. FIELD OF APPLICATION

[02] The subject matter of the present invention falls within the field of application of chemical products, in an agricultural environment or urban pest control. CONTEXT

[03] In the state-of-the-art of agriculture, the preparation of spray mixtures is commonly carried out manually, involving the mixing of water and concentrated chemicals in open containers. This process, if not carried out correctly and with the use of personal protective equipment, can expose the farmer to toxic substances, increasing the risk of health problems.

[04] Preparing the spray mixture is typically a manual procedure of a) opening the packaging of the concentrated chemical product, b) pouring the amount specified in the chemical product label into a graduated cup, c) adding the volume separated in the cup to the clean water reservoir, d) homogenizing by stirring the mixture. Therefore, it is subject to several problems such as 1) Petition 870250071320, dated 08 / 13 / 2025, page 5 / 18 2 / 9 The lack of precision in dosage, which can lead to waste of chemicals, underdosing (reducing the effectiveness of the treatment) or overdosing (increasing the environmental impact and production costs), 2) the risk of contamination due to incorrect handling of the chemical and / or the equipment used during the preparation of the mixture. Furthermore, in currently existing sprayers, even state-of-the-art ones, the sprayer tank becomes contaminated because the spray mixture (chemical + water) comes into direct contact with it, requiring thorough cleaning after each application, which is often not carried out.

[05] One possible solution is to carry out what is called direct injection, that is, the injection of a concentrated (pure) chemical product, but in small quantities, as close as possible to the spray tip (or nozzle). In this way, only the final portion of the sprayer is contaminated by the chemical product. In direct injection, it is necessary to be able to vary the concentration of the chemical product that reaches the target to be sprayed. Depending on the target (weeds, insects, fungi, for example), the chemical concentration should be chosen within a typical range of 0.5 to 3%. This concentration, usually expressed as a percentage, is calculated by the ratio of the mass of chemical to the mass of water used in spraying.

[06] Direct injection, found in large, state-of-the-art sprayers, is typically performed immediately before the spray nozzle, which is the last part of the spraying circuit. In this situation, only the nozzle itself, the part where the nozzle is installed, and the hose where the injection occurs are contaminated, which is a great advantage. However, considering that the liquid (usually water) that serves as the vehicle for spraying will be pressurized at high pressures (by Petition 870250071320, dated 08 / 13 / 2025, page 6 / 18 3 / 9 example, 150 to 300 PSI), it becomes necessary for the direct injection system to operate at even higher pressures than these in order to actually inject the chemical into the water stream already pressurized by a powerful pump. Evidently, achieving this high pressure in the injection system is a problem, and it becomes even greater when considering that it is necessary to inject very low flow rates, often on the order of a few milliliters per minute (ml / min). Therefore, designing equipment that has high pressure, low flow rate, and is adjustable is quite challenging.

[07] The present patent proposes low-pressure injection, overcoming the aforementioned problems, and here lies the novelty, as a similar system is not available in the literature.

[08] Even in the state-of-the-art of self-propelled and tractor-mounted sprayers (i.e., not backpack or portable), the topic of direct injection remains challenging. Hence the importance of the present patent, as it brings a simple concept for application in portable equipment. PRIOR ART SEARCH

[09] A search for prior art reveals few approaches to the topic of chemical injection and dosing in manual backpack sprayers. US patent 20130186977 A1 describes a modular backpack sprayer with multiple removable chemical containers. The main objective of this invention is to facilitate the switching between different chemicals, reducing cross-contamination and consequently decreasing user contact with the concentrated chemical. However, a) it does not include a mechanism that guarantees the precise concentration of chemicals during spraying in traditional backpack sprayers and b) it is a highly complex concept, which includes a Petition 870250071320, dated 08 / 13 / 2025, page 7 / 18 4 / 9 multi-valve (manifold) mechanism for mixing and selecting chemicals, always with a large number of parts, resulting in weight and dimensions that are impractical in a real agricultural application.

[010] Patent CN 203087358 U describes a portable sprayer that uses separate containers for different chemicals, connected to the main water tank by means of a valve system. This concept facilitates the storage and controlled mixing of chemicals during spraying, but it is not able to eliminate the problem of contamination of the main tank. Furthermore, it is not a system readily attachable to a manual backpack sprayer (especially to the spray pump), since the concept proposed in that patent only concerns the system for storing chemicals in separate compartments.

[011] US patent 2021 0394210 A1 describes an accessory for use in agricultural backpack sprayers, where the driving force for dosing comes from the speed of the water flow to be sprayed and the water injection into the cartridge that presses the elastic bag that stores the chemical product. This concept therefore requires a specially made chemical product packaging, which brings a significant competitive disadvantage to the proposal. Furthermore, the direct injection solution is based on a complex Venturi tube system, which can only function correctly under very specific pressure conditions and is therefore limited in agricultural applications, since the pressure is a result of the choice of spray nozzles, agronomic requirements, and the operation of the backpack sprayer. In general, simply varying the spray pressure throughout the agricultural work already results in Petition 870250071320, dated 08 / 13 / 2025, page 8 / 18 5 / 9 variation in the amount of chemical injected, and therefore, precision in controlling the concentration of the chemical product at the sprayer outlet is lost. For practical implementation, the concept contains a high number of parts and mechanisms, which increase the need for maintenance and lower the overall reliability.

[012] In general, there are few prior studies that address the problem of contamination and precision of chemical concentration in the sprayed solution.

[013] The present invention differs from others by offering a mechanism containing a piston pump with adjustable stroke, installable on manual backpack sprayers, which operates in conjunction with the sprayer's traditional pump. This system eliminates direct contact between the operator and chemicals, maintaining only clean water in the main tank and injecting the chemical directly into the spray stream. Furthermore, adjusting the piston stroke allows for precise concentration control, adapting to different agricultural needs. The invention concept is simplified, robust, and cost-effective, dispensing with electronic components or complex systems. DESCRIPTION OF THE INVENTION

[014] To better illustrate the description that follows, reference is made to the following list of figures:

[015] Figure 1 represents a possible way of mounting the direct injection mechanism proposed here, on a traditional manual backpack sprayer.

[016] Figure 2 illustrates a possible constructive form of the object of this patent, containing the hydraulic injection circuit with all its necessary components. Petition 870250071320, dated 08 / 13 / 2025, page 9 / 18 6 / 9

[017] Figure 3 illustrates a suggested way of mounting the concentrated chemical pumping mechanism and its coupling to the main pump of the backpack sprayer.

[018] Figure 4 shows a cross-sectional view illustrating the initial state of the mechanism.

[019] Figure 5 illustrates the state of the mechanism after moving the costal lever.

[020] As described in Figure 1, the direct injection mechanism is mounted on a manual backpack sprayer. This figure is composed of the backpack sprayer tank (101), which stores the water used during spraying; the tank lid (102); the backpack sprayer chamber (103), where the spray mixture is pressurized. The assembly formed by the rod (104) and the lever (105) transmits the movement made by the user to the chamber (103), allowing the gain of hydraulic energy for the liquid. The base of the backpack is represented by (106). Finally, we have the chemical product pumping system, composed of a piston pump (107) and the bottle or container for storing it (108).

[021] It should be noted that the bottle, container or reservoir of concentrated chemical product (108) is a common container in the chemical products market, being the original container of the same and typically having a volume of one liter. Without prejudice to the concept described herein, the present invention allows other volumes to be directly coupled to the proposed mechanism.

[022] Figure 2 illustrates the hydraulic circuit of the injection mechanism and how it is coupled to the chamber of the manual backpack sprayer (103). The piston pump (107), when moving upwards, promotes a negative pressure. Petition 870250071320, dated 08 / 13 / 2025, page 10 / 18 7 / 9 which draws the liquid product contained in the bottle (108), passing through its coupling or bottle / packaging cap (206), through the outlet hose (205), through the (one-way) non-return valve at the pumping system inlet (203) and through its inlet hose (201). As it moves downwards, the piston pump (107) pumps the concentrated chemical product through the outlet hose of the pumping assembly (202), passing through the (one-way) non-return valve at the outlet (204) and continuing through the injection hose (208) to the connection with the chamber cylinder (209). This connection allows the product to enter a low-pressure region comprised of the cylinder (210), which is a traditional functional part of manual backpack sprayers.

[023] This concept described in Figure 2 makes it possible to use low pressures for chemical injection and therefore results in a simple pumping assembly, when compared to injection in regions after the chamber (103), since it would be necessary to exceed the pressure used during spraying to inject in these regions. For example, if the sprayer works with a pressure of 70 PSI, it would be necessary to have a pressure above this number to allow the injection of the chemical. Obviously, this means that it would be necessary to have a more powerful, bulkier direct injection pump, and this would entail costs, weight and complexities. In contrast, the mechanism proposed here performs the injection at low pressure, i.e., before the chamber (103) of the manual backpack sprayer, resulting in a light, small mechanism.

[024] On the opposite side of the cylinder (210), there is another non-return valve (212) and its connection (211), used for the entry of clean water into the cylinder and to prevent the chemical product (which has already been sucked through) from entering. Petition 870250071320, dated 08 / 13 / 2025, page 11 / 18 8 / 9 (209) into chamber (103) and cylinder (210)) contaminate the backpack tank. The entry of water is promoted by the negative pressure generated by the elevation of chamber (103) during the raising of the drive lever (105).

[025] Figure 3 illustrates the assembly of the direct injection mechanism in the backpack sprayer, with emphasis on the mechanical couplings for motion transmission. When moving the chamber (103), the motion is transmitted to the piston pump (107) by means of the piston coupling (301), the transfer beam (302) and the chamber fixing system (303). This pumping assembly is fixed to a rigid support (305), which in turn is connected to the traditional backpack sprayer by means of the packing gland (304) and the threaded hole of the tank (306).

[026] To illustrate a use case, in Figure 4. With the operating lever (105) lowered, the chamber (103) is in its rest position. When the lever is raised, the movement is transmitted, through the transmission assembly composed of the piston coupling (301), the beam (302) and the chamber fixing system (303), to the external piston pump on the backpack (107) responsible for pumping concentrated chemical product. An adjustment knob (401) allows regulating the stroke of the piston (402) of the concentrated chemical product piston pump, thus controlling the amount of chemical product that is sucked up with the up and down movement of the lever (105) of the backpack sprayer. During the upward movement of the piston (402), the pump sleeve (403) is filled with the correct amount of chemical product.

[027] Figure 5 shows the traditional backpack sprayer with the mechanism proposed here installed in one possible configuration, with the lever (105) shown in its raised position. This figure is used as Petition 870250071320, dated 08 / 13 / 2025, page 12 / 18 9 / 9 complementing Figure 4, the arrangement of the aforementioned components of the concentrated chemical product pump (107) can be observed, these being (402) and (403), in their fully extended state (filled with the concentrated chemical product, which will be injected into the cylinder (210) shown in Figure 2. By lowering the operating lever (105), the chemical product is pumped through the hydraulic circuit, as described in Figure 2. Simultaneously, the high-pressure chamber (103) is filled with the correct mixture of clean water and chemical product, coming from the cylinder (210), and subsequently the spraying is done by the conventional lance of the manual backpack sprayer. Petition 870250071320, dated 08 / 13 / 2025, page 13 / 18

Claims

1 / 2 CLAIMS 1. DIRECT INJECTION MECHANISM FOR PORTABLE SPRAYER characterized by containing a piston pump with adjustable stroke that is mechanically coupled to the main pump of the portable backpack sprayer, such that its adjustable stroke allows varying the amount of chemical product injected directly into the cylinder of the backpack sprayer pump, said cylinder being the low-pressure region of the backpack sprayer, so that the mechanism proposed here performs direct injection at low pressure, that is, before the spray mixture is pressurized.

2. DIRECT INJECTION MECHANISM FOR PORTABLE SPRAYER, according to claim 1, characterized by containing a support for installing the concentrated chemical product packaging, this support allowing for easy installation and removal of the packaging without the need for operator contact with the concentrated chemical product.

3. DIRECT INJECTION MECHANISM FOR PORTABLE SPRAYER, according to claim 1, characterized by allowing direct connection of the reservoir (or packaging) of concentrated chemical product, without the need for a special or additional reservoir.

4. DIRECT INJECTION MECHANISM FOR PORTABLE SPRAYER, according to claim 1, characterized by containing at least two one-way valves to limit the direction of flow of concentrated chemical product, with no clean water entering the concentrated chemical product reservoir and no chemical product entering the clean water reservoir of the backpack sprayer.

5. DIRECT INJECTION MECHANISM FOR PORTABLE SPRAYER, Petition 870250008246, dated 01 / 31 / 2025, page 18 / 29 2 / 2 according to claim 1, characterized by using the lifting and lowering movement of the backpack sprayer pump itself as a driving force to perform the movement of the piston of the adjustable stroke direct injection pump, through mechanical coupling between both.

6. DIRECT INJECTION MECHANISM FOR PORTABLE SPRAYER, according to claim 1, characterized by drawing clean water from the sprayer tank into the cylinder when the lever is moved upwards and injecting concentrated chemical product, in a quantity defined by the stroke of the adjustable piston pump, into the sprayer cylinder when the lever is moved downwards.

7. DIRECT INJECTION MECHANISM FOR PORTABLE SPRAYER, according to claim 1, characterized by mixing water and chemical product inside the cylinder of the backpack sprayer pump, homogenizing such mixture by the pump's own up and down movement and the liquid inlet and outlet flows in this cylinder, without the need for homogenization parts or mechanisms.

8. DIRECT INJECTION MECHANISM FOR PORTABLE SPRAYER, according to claim 1, characterized by allowing the adjustable piston pump to be removable from the backpack sprayer when necessary. Petition 870250008246, dated 01 / 31 / 2025, pp. 19 / 29

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