Technical Field

The present invention relates to the technical filed of paint tinting machines, in particular to a tinter dispenser for use in a paint tinting machine.

Background Art

In an attempt to alleviate the disadvantages of prior art paint mixing devices, the applicant of the present invention has proposed paint mixing devices in two Chinese Invention Nos. 200520065534.9 and 200610035665.1. The paint mixing devices described therein adopt high precision image detection techniques for detecting paint flow rate so as to obtain a paint flow rate. The calculating method is described in detail as follows.

As shown in Fig.1 , an image detector adopted in these prior designs comprises a light-emitting part 11 and a light-receiving part 12. A tinter (which essentially contains a colourant to add to a base paint to produce a coloured paint) dispenser 10 has an outlet arranged above an intermediate position between the light-emitting part 11 and the light-receiving part 12. Upon activation of the image detector, a net of light is established between the light-emitting part 11 and the light-receiving part 12. When tinter is dispensed from the outlet, it will inevitably pass through the net of light. When the tinter passes through the net, the cross-section of a paint cylindrical drop or droplet 13 cut by the net of light can be measured very accurately by the image detector. Next, the principle of calculation will be described in detail with reference to the paint droplet 13. Fig.2a shows a paint droplet 13 with a height L and a cross section S at an arbitrary position, with the cross section S being approximated as a circle. When the paint droplet 13 is divided into n segments along its longitudinal direction, each of these segments can be regarded as a circular cylinder with a respective height L1 , L2, L3... Ln as well as a respective sectional area S1 , S2, S3...

Sn. Thus, the approximate volume V of the paint droplet 13 may be calculated by i V=L1 ^* S1 +L2 ^* S2+L3 ^* S3+...+l_n ^* Sn. Turning to Figs. 2b and 2c, the overall height of the paint droplet 13 can be calculated as long as its velocity has been obtained. In this case, the total volume of the paint droplet passing through the net of light can be calculated by determining sectional areas of the droplet at different moment. Specifically, the diameter and thus the area of each section of the paint droplet can be determined from the width of the section detected by the image detector when the paint droplet passes through the net of light. For example, during the course that the paint droplet 13 passes through the net of light, the image detector measures, at a substantially small time interval t (small enough), the cross section of the paint droplet 13, such that a total of four cross sectional areas s1 , s2, s3 and s4 are obtained at moments t1 , t2, t3 and t4, respectively. In case of a flow velocity v of the paint droplet 13, the volume V of the paint droplet 13 may be calculated by V=s1 ^* vt1 +s2 ^* vt2+s3 ^* vt3 +s4 ^* vt4. As long as the time interval t is small enough, the volume of the paint flow may be calculated accurately. However, it has been found out by the applicant that the shape of the paint droplet (or cylindrical drop) is irregular due to such factors as air resistance, surface tension, etc.. As a result, there might be an error in the calculated paint flow rate, thus the colour of paint obtained is likely to deviate from what is desired.

In addition, prior art devices are disadvantageous in that the nozzle tends to be blocked by residual tinter which may cure easily in the nozzle, and can cause a failure of the devices.

The present invention is developed to alleviate the foregoing disadvantages.

Summary The invention aims to overcome the drawbacks of prior art devices and to provide a dispenser for use in a paint tinting machine which may measure a paint flow rate precisely and may eliminate the problem of cure of tinter residue in the dispenser nozzle.

To solve the above mentioned technical problem, the invention proposes that the tinter dispenser comprises a needle body that is communicated with a paint inlet tube and is inserted into a sealed canal, and a paint return tube that is communicated with the canal. The needle body may be driven in such a manner that a needle tubing provided at the lower end of the needle body can be inserted into or penetrates through the canal.

Preferably the needle body and the sealed canal are disposed in a casing.

Preferably the needle body comprises a fastening end, the needle tubing and a thrusting rod provided on the fastening end. A slot is provided on the casing at a position corresponding to that of the thrusting rod, such that the thrusting rod for driving the needle body to move up and down may extend out through the slot.

Preferably the sealed canal comprises a canal body and sealing members that are hermetically fitted at both ends of the canal body and are subjected to insertion of the needle tubing. The paint return tube communicates with the canal body.

Preferably the sealing member comprises a sealing rubber portion and flexible sealing body provided in the sealing rubber portion.

Preferably a taper opening is formed at the lower end of the canal body of the canal, thus to facilitate smooth and precise insertion of the needle tubing.

The paint dispenser according to the invention operates as follows. The paint is extruded under pressure through the paint inlet tube and the needle body. Since the inner diameter of the needle tubing of the needled body is small, the flow rate can be well controlled and the paint droplets from the needle tubing may have a shape of a standard water droplet. The paint flow rate can be precisely calculated by the calculation method described previously and thus may be accurately controlled. When the paint needs to be dispensed, the needle body may move downwardly by means of an external driving force (i.e. via the thrusting rod which is driven by a driving means so as to move upward or downward). The needle tubing of the needle body passes through the sealed canal and the paint starts to flow out via the needle tubing. On the other hand, in case the dispenser is not used, the needle body moves upwardly by means of an external driving force, such that an outlet of the needle tubing is retracted into the sealed canal. The paint continues to be dispensed to fill the entire canal. The excess paint will flow back to the paint container via the paint return tube, thus a circulation is obtained. The paint in the needle tubing is prevented from curing since the needle tubing is immersed in the liquid paint. For next use, the user simply needs to push the needle body downwardly to spray the paint again.

As compared with prior art solutions, the dispenser according to the invention is capable of calculating paint flow rate precisely. Moreover, it obviates the risk of paint curing in the dispenser nozzle and enables the product to be used constantly.

Brief Description of the Drawings

The invention will be described in detail in the following with reference to the accompanying drawings, in which:

Fig. 1 is a schematic view of an image detector in a prior art paint mixing device;

Fig. 2 shows a principle of paint volume determination by a prior art paint mixing device;

Fig. 3 is a schematic view of a structure of the present invention;

Fig. 4 is a perspective view showing the inner structure of the present invention;

Fig. 5 is a schematic view of an inner structure of the present invention;

Fig. 6 illustrates a reference view showing a state of operation of the present invention; and

Fig. 7 illustrates the application of the present invention in a tinting machine.

Detailed Description

Reference is made to Figs. 3-5. The tinter dispenser according to the present invention comprises a casing 1 , a paint inlet tube 2, a needle body 3, a sealed canal 4 and a paint return tube 5.

The casing 1 has a sector configuration, such that a plurality of casings 1 may be assembled together to form a circular cylinder which can be mounted in a paint tinting machine, with each casing containing a tinter of one colour (Figure 7). The paint inlet tube 2 is in communication with the needle body 3 which comprises a fastening end 30, a needle tubing 31 and a thrusting rod 32 provided on the fastening end 30. A slot 11 is provided on the casing 1 at a position corresponding to that of the thrusting rod 32. The thrusting rod 32 extends outward through the slot 11 and drives the needle body 3 to move up and down. In other words, the entire needle body 3 can be driven up and down by the thrusting rod 32 which in turn is driven by a driving means, thereby driving the needle tubing 31 into the canal 4 or penetrating through the canal 4.

The sealed canal 4 comprises a canal body 41 and sealing members 42 that are hermetically fitted at both ends of the canal body 41 and may be inserted by the needle tubing 31. The paint return tube 5 communicates with the canal body 41.

To ensure the sealing effect of the sealing members 42 even after long term operation, the invention proposes that the sealing members 42 comprise a sealing rubber portion 421 and a flexible sealing body 422 provided in the sealing rubber portion. The sealing rubber portion 421 is provided at the outer side and functions as a bracket to keep the seal 2 in place within the canal 4. The flexible sealing body 422 is provided at the inner side and can be made of silica gel that is stretchable and flowable to a certain extent, such that during movement of the needle tubing, the gap induced by the movement of the needle tubing may close instantaneously to ensure a good sealing of the whole canal 4. As a result, a paint leakage is prevented.

Since the needle tubing 31 needs to inserted into and pulled out of the sealing member 42 at the lower end of the canal repeatedly, a taper opening 43 may be provided at the lower end of the canal body of the canal 4 to ensure an accurate insertion of the needle tubing. In this case, the needle tubing 31 may be inserted along the taper opening 43, which improves the accuracy of the insertion and reduces the potential for damage to the sealing member 42.

When it is required to dispense tinter to the outside (for example to a paint container), the needle tubing is driven downward, and the needle thereof penetrates through the sealing members 42 such that the tinter may flow. When not used, the needle is driven upward into the canal 4. Tinter is dispensed continuously to fill the canal 4 and the excess paint will be returned to a paint reservoir through the paint return pipe, thereby forming a circulation path. Since the needle is immersed in the paint within the canal, the paint in the needle will not get cured. Thus, in next use, paint may be dispensed again by simply driving the needle body downwards.

As shown in Fig. 6, when in use, calculation means 6 may be arranged below the tinter dispenser of the invention, by which the paint flow rate can be calculated and controlled precisely.

Referring to Fig. 7, it shows an application of the tinter prayer according to the invention in a tinting machine. The tinting machine consists of a number of tinter dispensers according to the invention, each containing a tinter with one colour. In this case, a required colour may be achieved by driving the corresponding tinter dispenser to dispense out the required tinter according to the colour recipe.

Hereinbefore are merely preferred embodiments of the present invention, but are not used to limit the scope of the present invention. All variations or modifications of the shape, configuration, feature and spirit within the scope of the present invention defined by the appended claims will be included in the present invention.