ELECTRICALLY OPERATED PIPETTE

Abstract: Electrically operated pipette in which the piston is displaced by means of an electric motor (10). The pipette is provided with an adjustable limiter (19), by means of which the stroke length of the piston can be varied.

Description: Electrically operated pipette The present invention is concerned with an electrically operated pipette provided with a piston, which said pipette comprises a body, a cylinder in the body, as well as a piston displaceable by the force of an electric motor so as to suck liquid into the cylinder and to remove the liquid out of the cylinder. In prior art some electrically operated pi- pettes are known, which have, however, not permitted adjustment of the volume. The object of the present invention is above all to provide an electrically operated pipette with adjustable volume. The pipette now invented has an electric motor rotable in either direction, which said motor rotates a cogwheel resting against a toothed rack provided on the piston rod of the pipette. In this way, it is possible to move the piston inwards to suck liquid into the pipette cylinder, and outwards to administer liquid out of the cylinder. The movement of the piston is limited by an upper limiter and a lower limiter, whereat it is possible to adjust the location of one (or both) of the said li iters in the direction of movement of the pisto'i- In this way it is possible to adjust the quantity of liquid for dosage. Preferably only the location of the upper limiter is adjustable. The location of the limiter is best adjustable by means of a screw-nut joint, whereby, for example, the limiter is connected with a screw oriented in the direc¬ tion of movement of the piston, around which said screw a revolving nut is fitted which remains stationary re¬ lative the body in the direction of movement of the piston. The volume adjustment is connected with a volume display. This can be provided, e.g., by means of mechanical display means comprising numeral rings or equivalent. A turnable volume adjustment is best associated with an electronic volume detector, to whose shaft the adjustment movement is transmitted. The movement of the volume detector is converted by means of an electronics card, e.g., to a liquid crystal display. The invention, its objectives, and some pre¬ ferred embodiments will be described in further detail in the following description and in the related drawings. Figure I is a sectional side view of a pipette in accordance with the invention; in the figure the recharging device can also be seen. Figure II is a partly sectional side view of a second embodiment together with a recharging stand. Figure III shows a further embodiment as a sectional side view. The main parts of the pipette in accordance with the invention are the handle 1 , the frame 2, and the cylinder part 3. The voltage source 4 consists of an accumulator or a battery, which can be inserted straight into a housing provided at the end of the handle. If an accu¬ mulator is used, it can be recharged by means of a recharging device 5. For recharging, the accumulator may also be removed out of the handle. The handle is provided with an operating switch 6 and with a speed adjustment switch 7. The speed adjustment may be continuous or, e.g., have two steps. The handle is attached to the body by means of a vertically pivotable articulated joint 8. Thus, the operator may choose the handle position most appropriate for him. ' For example, for the time of transportation and storage, the handle can be pivoted into contact with the body, in which case the pipette requires a minimum of space. Inside the body, there is a DC motor provided with a gearbox 9. By means of the operating switch 6 the voltage can be passed to the motor 10 in any of the two directions , thereby rotating the motor in the de¬ sired direction. A gliding clutch 12 is attached to the output shaft 11 of the gearbox. The clutch 12 comprises a clutch flange 13 attached to the output shaft 11, an end flange 14 at the end of the shaft, as well as a cogwheel 15 and a spiral spring 16 fitted on the shaft between the flanges 13 and 14 so that the spring presses the cogwheel against the clutch flange. In this way a clutch is formed which slips at a certain limit torque, preventing strains from impact loads from acting upon the motor and the gearbox. The cogwheel 15 is fitted so that it displaces a toothed rack 17 in the body. At the bottom end, the movement of the toothed rack 17 is limited by a station¬ ary limiter 18 and at the upper end by an adjustable limiter 19. The adjustable limiter is connected with a screw 20, on which a nut knob 21 is fitted as revolving in a hole in the body. Thus, by turning the knob 21 , it is possible to displace the adjustable limiter 19 in the vertical direction. The piston 22 is attached to the bottom end of the toothed rack 17 by means of a flange 23. Corres¬ pondingly, the cylinder 24 of the piston is attached to the body by means of a flange 25. The pi__.'Lon 22 and the cylinder 24 are attached to the pipette by pushing from the side, and they are removed by pressing the knob 26. In this way it is easy to replace the cylinder part and to provide the pipette with a cylinder part operating within the desired volume range. The fastening flange 25 of the cylinder is provided with elevations 27 or, at corresponding loca¬ tions, with plane portions which, when the cylinder is being inserted into its position, press or do not press the selector switches 28 for volume range, which rest against the elevations. The elevations 27 form a code by means of which the volume display becomes auto- matically placed within the correct range for each cylinder. The adjusting knob 21 is provided with a cog¬ wheel 29, which rotates the shaft of the volume detector 31 by means of a transmission cogwheel 30. The volume detector 31 may be, e.g., a pulse detector or a poten¬ tiometer. The detector 31 is connected to an electronics card 32, wherein the signal is converted in a known way to numerical form in a liquid crystal display 33 while taking the volume range set by the volume selector switches 28 into account. The electronics card 32 is also connected to limit switches 34 and 35, which signal when the piston has moved to its extreme position, whereby the motor stops automatically. The limit switch may be a mechan¬ ical microswitch or, e.g., a reed tube or a Hall element. When reed tubes or Hall elements are used, magnets 36 and 37 are fitted on the toothed rack accordingly. The upper limit switch 35 provided in the adjustable limiter is connected to the electronics card 32 by means of a flexible conductor 38. The card 32 may also be connected with other adjustment or selection members, such as, for example, calibration trimmers 39, by means of which it is possible to calibrate the initial setting of the display. In the pipette shown in Fig. II, the handle 1' is attached to the body 2' stationarily. The volume detector 31 ' is fitted concentrically with the adjust¬ ment knob 21 and the screw 20, whereby the shaft of the knob also acts as the spindle of the detector. ' In the figure, the liquid crystal display 33, the calibra¬ tion trimmers 39 and the tip vessel 40 are also shown. Fig.. II further shows a pipette stand 41, to which the recharging device 5 is connected. Fig. Ill shows an embodiment in which the body 2 T ' also acts as the handle and in whose interior all the necessary parts are fitted. The top portion of the body is provided with a projection 42 so as to permit a good grip. In view of minimizing the space requirement, the motor 10 is connected to the clutch 12 by means of a right-angle bevel gear 9' ' . The batteries 4 ' ' are placed above the motor, and the operating switch 6 11 in the top portion of the body. The volume detector 31 ' is placed in the same way as in the embodiment shown in Fig. II.

Claims: WHAT IS CLAIMED IS: 1. Electrically operated pipette, which comprises a body (2), a cylinder (24) connected to the body and a piston (22) in the cylinder, a toothed rack (17) at the upper end of the piston, a lower limiter (18) and an upper limiter (19) of the movement of the toothed rack, an electric motor (10), which rotates a cogwheel (15) resting against the toothed rack, as well as an operating switch (6) for the electric motor, by means of which the motor can be rotated in either direction, c h a r a c t e r i z e d in that the location of one of the limiters (19) is adjustable. 2. Pipette as claimed in claim 1, c h a r - a c t e r i z e d in that the electric motor (10) rotates the cogwheel (15) by the intermediate of a clutch (12) slipping at a certain limit torque. 3. Pipette as claimed in claim 1 , c h a r ¬ a c t e r i z e d in that the adjustment limiter (19) is connected with a volume detector (31) , whose signal is converted by means of an electronics card (32) so as to indicate the volume to be pipetted in a liquid crystal display (33) . 4. Pipette as claimed in claim 1, c h a r - a c t e r i z e d in that the location of the upper limiter (19) is adjustable. 5. Pipette as claimed in claim 4, c h a r ¬ a c t e r i z e d in that in the upper limiter (19) there is a screw (20) parallel to the direction of move- ment of the piston and that in a hole in the body there is a stationarily revolving nut adjustment knob (21) resting against the said screw. 6. Pipette as claimed in claims 3 and 5, c h a r a c t e r i z e d in that in the volume detec- tor (31) the detector member consists of a revolving shaft and that, when revolving, the adjustment knob (21) also rotates the shaft of the volume detector. 7. Pipette as claimed in claim 1, c h a r ¬ a c t e r i z e d in that the cylinder (24) with its piston (22) is replaceable. 8. Pipette as claimed in claims 3 and 7, c h a r a c t e r i z e d in that the cylinder (24) has code elevations or recesses (27) and that the body has volume-range selection switches (28) which rest against the said projections or recesses, which are con¬ nected to the electronics card (32) , and which set the volume range corresponding to the code. 9. Pipette as claimed in claim 1, c h a r ¬ a c t e r i z e d in that the body is provided with a projecting handle (1). 10. Pipette as claimed in claim 9, c h a r - a c t e r i z e d in that the handle (1) is attached to the body by means of a vertically pivotable articulated joint (8) . 11. Pipette as claimed in claim 1 , c h a r ¬ a c t e r i z e d in that the voltage source of the electric motor (10) is a battery or an accumulator (4). 12. Pipette as claimed in claim 11 , c h a r ¬ a c t e r i z e d in that the battery or the accumulator (4) is located in the pipette in an open housing.

Inventors: TERVAMAEKI JUKKA, TERVAMAEKI, JUKKA
Applicants: LABSYSTEMS OY
Application year: 1986
Main classification: B01L3
IPC codes: B01L3, G01N1