US 3709636 A
A piston pump is provided, adapted to pump measured fluid volumes at selected time intervals, including a timer having a plurality of selectable timing intervals, and a timer switch actuated by the timer to open and close the electric circuit to the pump drive means at a selected time interval, to initiate a stroke of the pumping plunger of the piston pump. Pump drive switch actuating means associated with the pump drive means opens the pump drive switch whenever the plunger is in a starting position and turns off the pump drive means, and closes the pump drive switch whenever the time switch closes and starts operation of the pump drive means, the pump drive switch remaining in the closed position until the plunger starting position, the timer switch overriding the pump drive switch to start the pump drive means only at the starting position for a stroke of the plunger, and the timer and pump drive switches together thereby controlling the plunger operation stroke-by-stroke to control the fluid volume delivered per time interval according to the number of strokes per time interval.
Claims available in
Description (OCR text may contain errors)
United States Patent 1 Rosenberg [4 1 Jan. 9, 1973  TIMER Primary ExaminerRobert M. Walker  Inventor: David Rosenberg, Glen Cove, N.Y. Attorney-Jan & Chapman  Assignee: Pall Corporation, Glen Cove, N.Y.  ABSTRACT  Filed: Sept. 4, 1970 A piston pump is provided, adapted to pump mea-  Appl N OJ 69,981 sured fluid volumes at selected time intervals, includ- Related US. Application Data lja. I40.
ing a timer having a plurality of selectable timing intervals, and a timer switch actuated by the timer to open and close the electric circuit to the pump drive means at a selected time interval, to initiate a stroke of the pumping plunger of the piston pump. Pump drive switch actuating means associated with the pump drive means opens the pump drive switch whenever the plunger is in a starting position and turns off the pump drive means, and closes the pump drive switch whenever the time switch closes and starts operation of the pump drive means, the pump drive switch remaining in the closed position until the plunger starting position, the timer switch overriding the pump drive switch to start the pump drive means only at the starting position for a stroke of the plunger, and the timer and pump driveswitches together thereby controlling the plunger operation stroke-by-stroke to control the fluid volume delivered per time interval according to the number of strokes per time interval.
4 Claims, 4 Drawing Figures PATENIEIJJAM 9 ma SHEET 2 BF. 2
JlllI orr BREAKING SWITCH T U C m C PUMP MOTOR FIG. 4
TIMER This application is a continuation-in-part of U.S. Pat. application Ser. No. 643,083, filed June 2, 1967, now U.S. Pat. No. 3,447,479, dated June 3, 1969, and a division of Ser. No. 830,078, filed June 3, 1969, now U.S. Pat. No. 3,610,848, dated Oct. 5, 1971.
The mechanical clock has long been utilized for actuating mechanical devices. Originally, clocks or other similar timing devices were utilized to either start or stop a particular piece of machinery at a desired time. As needs became more complex, specialized timers were developed to allow the starting and stopping of equipment on a sequential or interval basis. More sophisticated developments in this area include clocks with a choice of timing sequences, in which the sequence desired could be manually selected.
Timers of this type are useful for controlling many different types of industrial, commercial, medical and military equipment that require variable timing cycles for the many different operations that they perform. For example, such a device is useful for selecting and controlling the pumping rate ofa syringe pump.
The syringe pump is a device in which an electric motor in operative connection with a Scotch yoke, pivoted lever arm, or cam reciprocates the plunger of a conventional syringe. By utilizing a check valve in the influent and effluent lines leading to and from the syringe, the pump can be employed to continuously administer doses of medicament to a patient. The rate at which the medicament is administered to the patient is not necessarily, or should not be, constant for all patients and all medicaments. If the motor which reciprocates the plunger of the syringe operates at a constant speed, the motor must be alternately started and stopped at a desired frequency in order to effectively control or change the pumping rate of the syringe. This intermittent operation can be accomplished by utilizing a timer for opening and closing an electrical circuit; the time intervals between actuations of the timer can be constant or variable, and can be manually selected, according to the need.
Unfortunately, the available timers are complex and do not provide sufficient time control to permit long time intervals between actuations. This prevents their use for controlling the pumping rate of a syringe pump, since very low pumping output, wherein there is a long time between each stroke, is often required.
Many timers utilize gear movements which are similar to the gear movements of conventional clocks. Timers have been made to actuate a switch by providing a rotating arm which sequentially makes contact with a plurality of contact points located in the path of its rotary travel, to open and to close an electrical circuit. Other clock-type timing devices utilize rotating cams, which move a cam follower into and out of contact with a contact point. The actuation rate of such timers can be varied by changing the rotational speed of the arm or cam. This is accomplished by relocating the position of several of the gears, an operation which is similar to shifting gears in an automobile transmission.
Due to their complexity, these timers can be difficult to install and use, and can be quite expensive, especially if their size is to be kept at a minimum, if high reliability is to be required, and a large selection of actuation frequencies are to be made available. A timer to variably control the actuation rate of some types of equipment, particularly a syringe pump for administering medicinal fluids to patients, must have high reliability, since human life is often dependent upon it. Such a timer must also be compact, to allow its installation within the pumping unit, to simplify the electrical circuitry and increase its portability, and it must provide a sufficient number of different timing intervals, which can be easily and rapidly selected by an operator.
In accordance with the present invention, a compact, inexpensive, reliable timer is provided, having a plurality of variable timing intervals for the opening and closing of an electrical circuit, and having means to manually or automatically select a desired timing sequence. Due to its versatility, the timer is well suited for use with a wide variety of different equipment, and in particular with a syringe pump.
The timer of this invention comprises an array of resilient spaced timer contact blades having a portion movable between a first actuating position and a second nonactuating position; a rotatable selector cam disposed in operative juxtaposition to the array of contact blades, to selectively move said portion of at least one contact blade in the array between the actuating and the nonactuating positions; an array of electrical contacts corresponding to the array of contact blades, each disposed to be contacted by said portion of one of the blades when in its actuating position; and a motordriven rotatable timer cam disposed in operative juxtaposition to the movable portions of the array of timer contact blades, and having an array of cam sections corresponding to the array of contact blades, each section having a contoured surface corresponding to a different timing interval, to slidably engage the selected contact blade or blades disposed in the actuating position by the selector cam for timed movement of the blade portions into and out of electrical contact with the corresponding contact, in accordance with the contour of the timer cam surface.
The array of contact blades has at least two blades but can have any number of blades in excess of two. Each contact blade can be formed from an individual strip of a conductive resilient metallic material. Typical metals are copper, silver, tin, alloys of copper such as beryllium-copper and bronze, alloys of silver andtin, and silver-, gold-, rhodium and platinum-plated metals.
Any movable portion of the blade can be arranged to move into and out from engagement with the respective electrical contact. An end portion is easily moved or displaced, and is preferred. A portion intermediate the ends can also be moved or displaced for this pur pose. in the former case, one of the ends of the blade is fixed, so that an intermediate portion can be moved or displaced with respect thereto.
A construction with a movable end can be as follows: One end of each individual blade can be mounted to a support base, to form the array of spaced blades. The array of spaced contact blades can also be formed from a single sheet of a conductive resilientmetal, and thus have a common base. When formed from a single sheet, all of the contact blades are in electrical connection with each other, and the common base can be connected to a single terminal point, thereby simplifying the electrical circuitry of the timer.
A construction with fixed ends takes the form of a single sheet with spaced slits corresponding to the width of the blades, and the sheet is bent in one direction of bow, so that the blades defined by the slits can be moved to change the direction of bow, so as to move into or out from contact with the contact point. The actuating position can be at an unstable intermediate position to the extreme limit of the other stable direction of bow, to which unstable intermediate position it is brought and held by the selector cam, and it is then in contact with the timer cam, on the opposite side, which allows it to move into the contact position at predetermined intervals, and holds it away from contact position at other intervals. Whenever the selector cam is not in the actuating position, and the timer cam moves the blade to the unstable intermediate position, it snaps through to the original direction of bow.
Another form with fixed ends has a plurality of flat strips with a central portion of the strip slotted and cut to form a tongue that is bent in an S-shape and is also fixed at each end. The S-portion of the tongue is adapted to change its direction of bow so as to move into or out of contact with the electrical contact point, as described above.
The array of contact blades is arranged so that the movable portion of each blade can be displaced to or from a normal position by the selector cam and/or the timer cam, and can be resiliently returned to or from its normal position when released by the cams. Therefore, the blades can be in the actuating position when displaced by the cams or when at rest, depending upon the position of the cams and the electrical contacts with respect to the blades.
The blades can also be rigid, and attached at one end to a resilient portion, which bends when it or the rigid portion is moved between actuating and nonactuating positions by the selector cam and/or the timer cam. The blades can also be rigid, and pivotally mounted, as on a hinge or pivot pin, and biased towards the contact position, as by a spring or magnet, with a cooperating magnetic element affixed to the blade, such as a magnet or magnetically susceptible material.
The contact blades are preferably parallel fingers with movable ends extending from the base of the array toward the timer cam. The selector cam can be disposed along the length of the blades between the base of the array and the timer cam to engage the blades for selective movement of each blade into or out from an actuating position. The selector cam can also be disposed at the movable ends of the contact blades and the timer cam disposed along the length of the blades between their base and the selector cam.
The array of contact blades can also be U-shaped wherein two sets of parallel contact blade fingers extend from a common U-base to form the U-arms. This is the preferred shape, since the selector cam can be interdigitally disposed between the contact blade fingers constituting the sides of the U, thus allowing one cam to selectively move two sets of contact blades, simultaneously or separately, without increasing the size of the unit.
The selector cam is mounted rotatable to selectively move each contact blade finger individually in a pivotal direction about its mounting, between actuating and nonactuating positions. In the actuating position, as the term is used herein, the selected contact blade is either in direct electrical contact with a contact point, or positioned upon the surface of the timer cam for movement into and out of electrical contact in accordance with the rotational movement of the timer cam. The contact between a given blade and its contact point can be continuous in every position of the timer cam, or sequential for timed actuation according to the position of the timer cam. A continuous electrical contact with one blade is required to provide current to the timer cam motor, and to the syringe pump or other timed equipment, when their continuous rather than timed operation is desired. During continuous operation, the selector cam and the selected contact blade act merely as a switch to open or close a circuit. During timed operation, the timer cam and the selected blade have this function.
The selector cam is formed with a plurality of cam sections, each having a contoured surface which indirectly corresponds to a different timing interval. Due to the position of the selector cam and the resiliency of the contact blades, at least one contact blade slidably engages the surface of each selector cam section and is displaced by the cam upon its rotation, so that the selected rotational position of the cam determines which blade will engage the timer cam for timed actuation, and which blade will make continuous electrical contact to provide current to the timer cam motor. The selector cam also holds those blades not required for the selected timing sequence in their nonactuating position, or permits them to return to their normal position, if that is the nonactuating position.
The selector cam can be made of metal or plastic and can have any shape suitable for rotational movement about an axis which is approximately perpendicular to the contact blades. Segments along the axis of the cam each have different surface contours, thereby forming a plurality of cam sections. The selector cam can be formed either by permanently fastening a plurality of cam segments to each other, or by forming different contours on the surface of a single cam. A single cam is preferred, since it is more easily and less expensively manufactured, and has higher strength.
The contoured surface of the cam can be formed by utilizing eccentric cylindrical cam sections or elliptical cam sections having high points with respect to the rotational axis to displace the contact blades. The contours can also be either depressions, protrusions or steps, extending longitudinally across the cam surface to engage or release a corresponding portion of the contact blades. Protrusions on the cam surface can be raised ribs having rounded, flat or sharp peaks. Any other shape of protrusion, such as a rounded bump formed on the surface, can also be employed, provided it can radially move a contact blade in the required direction. When eccentric cylindrical or elliptical cam sections, or protrusions upon a cam surface, are utilized to displace the contact blades, a correspondingly formed section in the blade need not be provided, inasmuch as the raised portion of the cam upon rotation will come in contact with a flat portion of the blade, and thereby move it from its normal position. Depressions formed in the cam surface can be V-shaped or flat bottomed or rounded grooves, or a flat section corresponding to a chord of a circle formed on the periphery of a cylindrical cam.
When the selector cam is disposed along the length of the contact blades between the base of the array and the timer cam, and grooves are utilized, it is preferred that the contact blades be formed with a corresponding protrusion to engage the grooves of the selector cam in their normal position and be displaced by the cam surface when the cam is rotated. If the selector cam is disposed at the movable end of the contact blades, the tips of each blade can engage the grooves, and protrusions on the blades are not required. When flat sections are used on a cylindrical cam, protrusions need not be provided on the contact blade. If the selector cam is rotatably mounted so that the contact blades are released to their normal position when opposite the flat section, simply rotating the selector cam so that the contact blades slidably engage the curved portion will move the blades outwardly to the desired position. The resiliency of the blades returns them to their normal position when this is permitted by the selector cam.
In the preferred embodiment of this invention, in which a U-shaped array of contact blades is utilized, flat sections are provided on the surface of a cylindrical selector cam to release the contact blade fingers on one side of the U. A single flat section isformed on each cam section, and each flat section is disposed at a different angular position upon the cam, thereby releasing a different contact blade at each selected rotary position. The selector cam is interdigitally mounted off center with respect to the sides of the U-shaped contact blades, so that when the flat section on the surface of a cam section is opposite a contact blade, that particular blade will be released from restraint by the selector cam. The tip of the elected blade acts as a cam follower to the rotating timer cam, and moves into and out of electrical contact according to the contour of the timer cam surface. Since the flat surfaces of the other cam sections are disposed at different angles, and will not be opposite the remaining blades, the remaining contact blades will be displaced by the curved portion of the cam, and be held out from engagement with the timer cam.
At least one V-shaped notch or groove is formed in each selector cam section to release the contact blade fingers at the other side of the U. The blades on this side of the U are formed with a corresponding V- shaped protrusion which fits into corresponding notches of the selector cam as it is rotated. Rotational movement of the cam forces the protrusion to move out of the groove, thereby displacing the blades into the actuating or nonactuating position. In the actuating position, the contact blades provide contact for the timer cam motor or the equipment being controlled by the timer, but do not engage the timer cam for timed actuation.
The V-notches in one of the grooved sections of the selector cam also serve to lock the selector cam in a given position. The V-shaped protrusion of one of the contact blades acts as a detent to lock in the grooves, to maintain a given rotary position of the cam. Enough grooves can be provided to lock the cam in each of its rotary positions. The force exerted by the contact blade in resisting displacement by the selector cam from its normal position is sufficient to hold the blade in place,
and prevent undesired rotational movement of the selector cam.
The position of the protrusions, depressions or any other contour upon the surface of the selector cam can be arranged so that any number of blades will be displaced by the rotational movement of the cam. Thus, the selector cam can move one contact blade into continuous electrical contact with a contact point at every position of the timer cam to complete the circuit to the timer cam motor, and at the same time can move another blade into sliding engagement with the timer cam surface to alternately open and close another electric circuit in accordance with a selected time sequence. Furthermore, additional circuits may be opened and closed in accordance with other time sequences by contouring the surface of other selector cam sections in the same or similar manner to permit the corresponding contact blade to simultaneously engage other sections of the timer cam. In this manner the timer of this invention can be used to provide timed control over a number of different devices.
The timer cam is mounted rotatably in operative juxtaposition to the array of contact blades to slidably engage that particular contact blade of the array which has been moved by the selector cam into the actuating position for time operation, and thereby provides for movement of the selected contact blade to open and close an electrical circuit. The timer cam can be disposed to engage the movable end of the selected contact blade or any other portion along its length. The contact blade in the position to which it is displaced by the selector cam is held resiliently against the surface of the timer cam, thus permitting its displacement into and out of electrical contact with a contact point in accordance with the surface contour of the rotating timer cam.
The timer cam is formed with a plurality of cam sections disposed along its length, each having a different contoured surface, to correspond to the number of various timing intervals desired for each blade. As in the case of the selector cam, the timer cam can have any suitable shape, and its surface contours can be depressions, protrusions or steps, extending longitudinally across each cam section. It is preferable that each timer cam section adapted to engage the ends of the contact blades be approximately cylindrical, and contain one or more steps or notches spaced along its circumference. The tip of a selected contact blade sequentially enters each step or notch as it slidably rides along the surface of the rotating cam. Electrical contacts are provided in close juxtaposition to the blade, so that the blade will touch or otherwise engage the contact to complete the circuit, either when it enters the notch, or when it is riding upon the curved surface. Similarly, when disposed to engage a portion along the length of the contact blade, it is preferable that the timer cam surface have protrusions to displace the selected contact blade into or out of electrical contact each time it slidably engages a protrusion. Therefore, the circuit will be opened and closed as many times in one revolution of the timer cam as there are notches or protrusions. The timer cam is designed to rotate at a fixed speed, so that the timer interval between the opening and closing of the circuit to provide timed control for electrical devices is directly dependent upon the number of notches or protrusions in each timer cam section providing the notches or protrusions are evenly spaced.
The selector cam and the timer cam are preferably both formed from a nonconductive material, such as plastic or ceramic, but they can also be of metal if these cams are electrically isolated. Plastic materials, such as Delrin (polyoxymethylene) PPO and Noryl (polyphenylene oxide), nylon, polyvinyl chloride, polyethylene, polypropylene, polycarbonate, and polytetrafluoroethylene, are preferred, since they are inexpensive, readily formed into the desired shapes, and are sufficiently strong to withstand continuous use.
The drive for the timer cam is provided by means of a synchronous or other constant speed motor. The timer cam can be either directly connected to the motor shaft or can be indirectly connected by means of is gearing system. The rotational speed of the timer cam determines the type of connection between the motor and the cam. in most cases, it will be necessary to step down the speed of the motor by the utilization of several gears. The utilization of these gears, however, has no detrimental effect upon the reliability of the timer, inasmuch as they are fixed in a permanent axial position, since the speed of the timer cam is maintained at a constant rate.
A synchronous motor is not as suitable as an induction motor for the same power output because it is more expensive, much heavier, and much larger in size. However, an induction motor is not as uniform in rotational speed, with applied load, as a synchronous motor. By using a synchronous motor to operate the timer cam, and the timer to operate an induction motor, it is possible to impose upon the operation of the induction motor the uniformity in operation of the synchronous motor. Moreover, with this arrangement it is possible to get very low effective rpm from an induction motor by permitting it to go only 1 revolution in a predetermined -timer interval, and this is accomplished without special gearing or other expensive expedients.
The electrical contacts can be located at any point along the length of the contact blades, provided that they are sufficiently close to the blades to permit the completion of the electrical circuit upon displacement of the blades by either the selector cam or the timer cam. The contacts can be positioned on either side of the contact blades, so that the circuit will be made by the blades when they are displaced by the cams, or when they are in their normal position. Individual contact points can be provided for each blade, or preferably a single conductive strip can be provided to be contacted by several blades, thus simplifying the required wiring by reducing the number of connections.
The timer operation provided by a given selection of contact blades is obtained by rotating the selector cam to a position at which a blade is moved into contact with a contact point to complete the circuit to the timer cam motor, thus starting rotation of the timer cam for timed actuation, and another contact blade is simultaneously moved into a position to ride upon the surface of a timer cam section. When the contact points are so located that they are contacted by the blades in their normal position, and a notched timer cam is utilized with the surface of the cam holding the blade away from its normal position, each time the selected blade engages a notch in the timer cam, its resiliency will return it to its normal position, thus contacting the point to complete the circuit for timed operation. As
the timer cam continues to rotate, the blade will in due time leave the notch, and will be displaced by the timer cam surface, thereby breaking the circuit, until the blade engages the next notch. If a different timing interval is desired, the selector cam is rotated to another position, in which a different blade will be moved into actuating position, to ride upon the surface of another timer cam section having a different number and/or spacing of notches.
To simplify the selection and actuation of a particular timing interval, one end of the selector cam can be provided with a knob to allow manual rotation of the selector cam. A mark on the knob and a dial having a different designation for each position of the cam is also desirable to indicate the various timing intervals available in the several positions of the selector cam. The timing interval can also be automatically changed by connecting one end of the selector cam to a motor or solenoid which will provide torque to turn the cam to another position. The motor or solenoid can be controlled by the timer of this invention to actuate upon the completion of a particular time cycle.
To turn off the controlled load operated according to the position of the blade riding on the timer cam, such as after one reciprocation of a syringeplunger by a syringe pump, it is desirable to provide an independent switch to break the electrical circuit. if such a switch is used, the contact blades are used only to complete the circuit. The circuit breaking switch can be attached to the equipment being controlled by the timer. A simple inexpensive normally closed switch, such as a snap action switch, can be actuated by, and held open by a lever arm, cam or any other mechanical component connected to and operated by the equipment, each time the equipment completes its operational cycle, to break the circuit and cease operation. The timer cam and the cyclic operation of the equipment must be so set that the time of contact of the contact blade is less than the time required to complete one operation cycle, and the total time required for the timer cam to rotate from one notch to the next must exceed the time for the controlled equipment to complete the cycle. The first can be accomplished simply by forming the notches on the timer cam surface to ensure that the duration of contact by the contact blade is quite short, and the second is obtained by suitably selecting the spacing of the notches or the number of notches on the timer cam, and/or by the rotational speed of the timer cam.
By wiring the timer and the switch in parallel, displacement of the blade from the contact point will not break the circuit, since the switch is normally closed. Only when the lever arm actuates the switch at one end of the cycle will the circuit to the equipment be broken. Having ceased operation upon actuation of the switch, the iever arm of the equipment will hold the switch in the open position. The timer cam, however, continues to rotate at a constant speed, inasmuch as the timer cam motor receives power from another circuit. When the blade falls into another notch upon the cam surface, it will again meet the contact point and complete the circuit to the equipment. When the equipment begins operation, the lever arm will move away from the switch, permittingit to close, and thus repeating the cycle.
It is sometimes desirable for equipment to operate on a single cycle basis, that is, where the equipment will complete one operational cycle and then automatically be stopped. This can be accomplished by utilizing the normally closed circuit breaking switch set to open upon the completion of the operational cycle as discussed above, together with a manually-operated normally open reset switch, which can be a simple push-button switch, or normally open snap acting switch, or the selector cam above can be used as a reset switch, by turning to continuous operation to start the motor, allow enough time for the equipment to clear the circuit-breaking switch, and then turning the selector cam to the off position. The motor will then stop when one cycle has been completed.
Since the timer of this invention is relatively small, it can be put in the same housing as the equipment requiring timed operation. This greatly simplifies the circuitry required, since all wiring will be internal, and many wires can be made common to several circuits. Therefore, when the timer is employed to control the pumping rate of a syringe pump, it is preferable to install both the timer and the drive for the syringe in a single housing.
The syringe pump-timer assembly of the invention comprises, in combination, a syringe having a fluidpumping plunger reciprocably movable therein, drive means including an electric motor operatively associated with the plunger by means of a Scotch yoke, cam, or eccentric drive and a slotted arm, for reciprocably moving the plunger within the syringe to draw fluid into the syringe and pump it out, and a timer in accordance with this invention as described above having a plurality of variable timing intervals which can be manually selected, to open and close an electrical circuit to the pump drive motor at the end of a selected time interval, to control the frequency at which the plunger is reciprocated, and thus the pumping rate of the fluid. The timer can be adapted to actuate the pump drive motor after selected time intervals between each stroke of the syringe, thus providing any desired pump output, from very low to high. The pump is intended to be operated with a check valve assembly in fluid connection with the syringe to allow fluid to be drawn into the syringe from an influent line and to be pumped therefrom via an effluent line by the plunger upon its reciprocating movement.
In the preferred embodiment, an eccentric drive pin and slotted drive arm operatively connect the pump motor and syringe plunger. A normally closed circuitbreaking switch wired in parallel to the timer circuit is utilized to stop the pump motor at the end of each timed interval. The circuit breaking switch is mounted within the housing adjacent the slotted end of the arm. The switch is actuated by the arm to open the circuit when the plunger of the syringe is at a selected position, preferably fully extended. The end of the plunger or any other suitable means can also be utilized to open the switch.
The syringe pump is controlled by manually turning a selector knob to the desired timing interval. This rotates the selector cam of the timer to move a selected contact blade into position to complete the circuit to the timer cam motor and a second selected contact blade released into position to ride upon the surface of a. rotating timer cam section. When the tip of the second contact blade moves in response to the timer cam surface, to complete the circuit to the pump motor, the motor commences operation. As the drive arm begins to reciprocate the plunger of the syringe, the switch closes and completes the parallel circuit. Prior to the completion of l pumping stroke, the contact blade is moved out of electrical contact by the timer cam surface and opens that portion of the circuit. The pump, however, will continue to operate until the plunger returns to its original position, at which time the switch is opened. The cycle will be repeated each time the contact blade is moved into electrical contact by the timer cam surface.
It is preferable that a timer comprising an array of U- shaped contact blades and a notched timer cam be utilized to control the pumping rate of the syringe pump. Since the U-shaped array provides for an increased number of circuits without increasing the size of the timer, such a design allows a great amount of control over the pumping rate of the syringe and yet permits a compact, reliable unit. By utilizing a notched timer cam the pumping rate is controlled by the number of notches in the selected timer cam section, there being a single stroke of the syringe plunger for each notch engaged by the contact blade. If the timer cam rotates at l revolution per minute and has three equally spaced notches, the syringe plunger will begin a stroke every 20 seconds. It is, of course, possible to space the notches on a particular cam section unequally, so that the operation of the syringe pump conforms to a time sequence having unequal intervals. For example, it may be advantageous to cycle the syringe three times in the first 15 seconds of operation and then cease operation for 45 seconds. Assuming that the timer cam is rotating at 1 rpm, this can be accomplished by positioning three notches in the first quadrant of the timer cam section. The 1 rpm rotational speed of the timer cam is by way of illustration only, and in no way limits the scope of its operation. By utilizing the proper gears, the timer cam can be made to rotate at any speed attainable.
The syringe pump timer assembly is lightweight, and compact. The timer cam can be provided with a sufficient number of cam sections and contact blades to provide a wide range of various pump speeds, a reset switch can be provided for single stroke operation, and a selector position can also be provided wherein a contact blade is in continuous electrical contact for continuous rather than sequential pump operation.
The timer of this invention and its utilization with a syringe pump are further explained by reference to the drawings in which:
FIG. 1 is an isometric view of the timer of this invention.
FIG. 2 is an isometric break-away view of the preferred embodiment of the timer.
FIG. 3 is a plan view of the syringe pump-timer assembly, showing a partial internal view of the timer and pump mechanism.
FIG. 4 is a schematic diagram of the electrical circuitry of the syringe pump timer assembly of FIG. 2.
The timer of this invention shown in FIG. 1 comprises an array 1 of four resilient contact blades 2, 3, 4, 5, formed from a sheet of electrically conductive metal. The individually spaced contact blades, 2, 3, 4, 5 extending from the common base 6, are radially movable at their free ends 7, 8, 9, between actuating and nonactuating positions. A manually rotatable selector cam is disposed in operative juxtaposition to the array of contact blades. Protrusions 11a, 12a, 13a, 14a and flat portions 11b, 12b, 13b are positioned in different spaced locations on shaped cam sections 11, 12, 13, 14, opposite the contact blades 2, 3, 4, and 5, to selectively move these contact blades between their ac tuating and nonactuating positions. Conductive strips 16 and 17 act as the electrical contacts, and are disposed to be contacted independently by the conductive blades according to the position of the selector cam, to complete an electrical circuit to the timer cam motor (via blade 5 only) and to the device operated by the timer (blades 2, 3 and 4) at selected time intervals.
A timer cam 18 which is rotatably driven by an electric motor 19 is disposed in operative juxtaposition to the movable ends 7, 8, 9 of the array 1 of contact blades 2, 3, 4, and has cam sections 20, 21, and 22, which are opposite contact blades 2, 3, and 4, respectively. Each timer cam section has a contoured surface with steps 23 which are spaced to correspond to different timing intervals. These surfaces slidably engage the ends 7, 8, 9 of a selected contact blade 2, 3 or 4, disposed in the actuating position by the selector cam 15, for timed movement into and out of electrical contact with the strip 17, in accordance with the spacing of steps 23 in the timer cam section.
The blade 5 has no corresponding timer cam section, but instead it actuates the electric circuit to the timer cam motor 19 when in contact with the contact strip 16, which is when it is in the upper position shown in the drawing. The high area 14a on selector cam section 14 is over a length of cam surface to put blade 5 in the actuating position whenever any of blades 2, 3, 4 is in the actuating position.
The common base 6 of the array 1 of contact blades provides a common electrical connection for all of the contact blades and thus simplifies the wiring of the timer by allowing the use of a single terminal point 25 to connect all of the contact blades to the power source 26.
The contact blades 2, 3, 4 in their normal position (to which they always strive to return when displaced therefrom) stand free above the flat portions 11b, 12b, 13b, of the selector cam, and have their tips resting against the timer cam sections 20, 21, 22, respectively. The high points 11a, 12a, 13a, on the selector cam sections 11, 12, 13 are each in different radial positions with respect to the contact blades, so that each contact blade will be lifted independently into nonactuating position, and only one at a time will be opposite a flat portion 11b, 12b, 13b, so as to be in actuating position against the timer cam sections 20, 21, 22. The blade 5 is displaced by a high area 140 on the cam surface 14, to make continuous contact with strip 16 to provide continuous electrical current to the timer cam motor 19. In the actuating position the blades 2, 3, 4 are not radially displaced by the selector cam 15 and their movable ends 7, 8, 9 are permitted to slidably engage the surface of the timer cam sections 20, 21, 22 for timed movement into contact with strip 17. The timer cam section steps 23 are so spaced and shaped that the selected contact blade will spring into contact with strip 17 each time the end of the blade is located at the base of a step 23. The spacing between the steps plus the rate of rotation of the timer cam determines the time interval for contact. As the timer cam 18 rotates, the contact blade is engaged by the cam surface and is moved out of contact with the contact strip 17. The blade then rides on the surface of the cam. During the rotation of the cam whenever the blade reaches a step 23, the blade is released, and snaps into contact with strip 17, thus providing for timed actuation of the circuit between points A and B, in accordance with the spacing of the steps 23 in the timer cam surface. Each timer cam section 20, 21, 22 has a different number of steps, so that the time interval between actuations of the circuit will be different for each selected contact blade 2, 3, 4.
In the OFF position the blades 2, 3 and 4 are held out of contact with the timer cams 20, 21, 22 by the selector cam high points 11a, 12a, 13a of the cam sections 11, 12 and 13. The low point of the cam section 14 at this time faces the blade 5 thereby permitting it to move out of contact with the strip 16.
In operation, the selector cam 15 is rotated to the desired position, which corresponds to a particular timing interval. This moves two of the selector blades 2, 3, 4 into a nonactuating position leaving one blade in its normal position, with its end resting on timer cam 18. Blade 5 contacts strip 16 to provide continuous current for the timer cam motor 19, and timed actuation for the circuit between points A and B. For example, in the position of the selector cam 15 shown in FIG. 1, contact blades 3, 4 are displaced by high points 12a, 13a of cam sections 12, 13, and therefore are in their nonactuating position, while blade 2 is opposite flat portion 11b, is not displaced by section 11, and has its tip 7 slidably engaging the surface of timer cam section 20. Blade 5 is displaced by the high area 14a of selector cam section 14 and is in its actuating position in contact with strip 16, thus providing continuous current to the timer cam motor 19.
Timer cam section 20 has two steps 23 formed in its surface. Therefore, as the timer cam rotates, contact blade 2 will make electrical contact with terminal strip 17 twice in each revolution of the cam. Further rotation of the selector cam will displace blade 2 and individually allow any of remaining contact blades to move into its actuating position upon the respective timer cam section, to provide additional timing intervals.
If desired, blade 5 can be eliminated by adding another position to blades 2, 3, 4, and extending strip 16 so as to be contactable by any of blades 2, 3, 4 in the added position. There must then be two raised portions, or three levels, of the corresponding selector cam sections 11, 12, 13, the highest level raising blades 2, 3, 4 one at a time at different positions of the selector cam into contact with contact strip 16, so that one of blades 2, 3, 4, always actuates the timer motor while one of the remaining blades is in normal actuating position against timer cam 18.
The embodiment of the timer shown in FIG. 2 is preferred for timed control of a syringe pump, since it provides additional circuit connections without appreciably increasing the size of the unit, or decreasing its reliability. It comprises an array 30 of U-shaped contact blades to open and close an electrical circuit at the end of the selected timed interval. A rotatable selector cam 31 having cam sections 32, 33 and 34 is interdigitally disposed between the sides of the U-shaped contact blades and in operative juxtaposition thereto, to selective move the contact blades away from their normal and actuating positions, into a nonactuating position. A motor driven rotatable timer cam 35 having cam sections 36, 37 and 38 is positioned at the tips of the array of timer blades. Each cam section has a notched surface with the notches 54 spaced differently to correspond to different timing intervals, to allow a blade to contact the strip 39 when its tip rests in a notch, and to slidably engage the tip of a selected contact blade for movement out of electrical contact with contact strip 39 whenever the tip contacts a nonnotched portion on the timer cam surface. The number and spacing of the notches and the rate of rotation of the cam determine the timing interval between contacts and thus actuation of the load.
The array 30 of contact blades is formed from a single sheet of silverand gold-plated beryllium-copper and has six spaced-apart resilient fingers 40, 41, 42, 43, 44, 45, three on each side of the U. A single electric line 48 leading from the power source 49 to a common terminal point 47 provides electrical current to all six fingers. When in their normal actuating positions, the tips of contact blade fingers 40, 41 and 42 on one side of the U engage the surface of the several segments 36, 37, 38 of the timer cam 35, and provide for timed actuating of an electrical circuit by movement into and out from contact with strip 39. Finger 43 on the near side of the U when in its actuating position makes electrical contact with contact point 55 to provide continuous current via lines 52, 53 to the load, in this case, a syringe pump. Finger 45 when in its actuating position closes the circuit to the timer cam motor 57 by contacting point 46, and thus turns on the motor. Each of fingers 43, 44, 45 is provided with a protrusion 43a, 44a, 45a. The protrusion 44a on finger 44, which is shorter than the fingers 43 and 45, acts as a detent in combination with the notches 33b on the cam section 33 to hold the selector cam in any selected position. Cam section 33 has a notch 33b corresponding to each rotary position of the cam, to lock the cam in place in every rotary position.
A selector knob 50 is provided for manual rotation of the selector cam 31 to each position. The torque exerted manually upon the knob 50 is sufficient to displace the detent and move the cam to the desired position.
The protrusions 43a and 45a act as cam followers which, in combination with the selector cam sections 32 and 34 and the notches 32b and 34b, move the fingers into and out of actuating position. The notch 32b is of a sufficient depth and width so that the protrusion 43a fits loosely therein so that the finger 43 freely rests against the contact 55 without interference by the cam section 32. Notch 34b is of the same depth as notch 32b. This depth is also sufficient to permit the finger 45 to move completely clear of the contact 46 so that the protrusion 45a rests against the bottom of the notch 34b.
Flat sections 32a, 33a and 34a are formed on the surface of selector cam sections 32, 33 and 34, respectively, to release the blades so that the contact blade fingers 40, 41,42 assume their normal positions, in which they do not contact the cam sections 32, 33, 34, and their tips slide along timer cam segments 36, 37, 38. Each flat section is disposed at a different angular position upon the selector cam 31, thereby releasing independently into an actuating position a different contact blade finger at each selected rotary position of the cam. When the flat section on the surface of a selector cam section is opposite an adjacent finger of the contact blade, that particular finger (either finger 40, 41 or 42) will be in its normal actuating position with its tip riding upon the timer cam. ln the position of the selector cam 31 shown as illustrative in FIG. 2, the fiat section 32a of cam section 32 is opposite contact blade finger 40, thereby allowing the tip of finger 40 to remain in its normal actuating position and ride upon the surface of timer cam section 36. Since the flat sections 33a and 34a of selector cam sections 33 and 34 are disposed at different angles, they will not be opposite to fingers 41 and 42. Therefore, these fingers will be displaced to their nonactuating positions, away from timer cam sections 37 and 38 by the cylindrical surface of selector cam sections 33 and 34.
When released by the flat portions of the selector cam 31 to their actuating positions, the tips of the contact blades 40, 41, 42, ride upon the surface of the corresponding timer cam section, in response to the contour of which they move into and out of electrical contact with strip 39. In the position shown, blade 40 rides upon the surface of timer cam section 36, and moves into electrical contact with strip 39 each time it engages a notch 54. Since there are ten notches on the surface of timer cam section 36, the circuit will be opened and closed ten times, in one revolution of the timer cam,
The timer cam 35 is rotatably driven by a constant speed electric motor 57, the speed of which is stepped down by gears 58 and 59. Selector cam section 34 determines the position of contact blade finger 45 and whether the circuit via contact 46 and line 49 will be closed to power the timer cam motor 57. In the position shown, protrusion 45a of contact blade finger 45 is resting upon the cylindrical surface of the selector cam section 34, thereby displacing the finger 45 into contact with 46, its actuating position, to complete the electric circuit to the timer cam motor 57. When the protrusion 45a engages the groove 34b, finger 45 is released to its normal position, thus breaking the circuit, and halting the timer cam motor.
The timer cam motor is a low powered motor with a long life, and can be left on continuously if desired. In this event, it can be powered outside the timer circuit, or, alternatively, contact finger 45 can be arranged to close contact 46 in every position of the selector cam 34. The selector cam 31 also determines which of contact blade fingers 40, 41, 42, will engage the timer cam 35 to provide timed operation.
In the OFF position of the selector knob 50, none of the contact blade fingers meets any contact point. Thus, no power either timed or continuous is fed to the equipment via lines 52 and 53.
In position A of the selector knob 50, electric current can be continually fed to a syringe pump via lines 52 and 53. Fingers 40, 41 and 42 are all displaced by the selector cam 31 and do not engage the timer cam 35. The protrusion 45a of finger 45 fits into the notch 34b of selector cam section 34, so that finger 45 is in its nonactuating position, and does not make electrical contact with contact point 46, and thus no electrical power is fed to the timer cam motor. Protrusion 43a of blade 43 fits into notch 32b of selector cam section 32, thus allowing blade 43 to move into its actuating position, and engage contact terminal 55. Since point 55 is electrically connected to line 52, this completes an electrical circuit which provides continuous current to the load, such as a syringe pump.
ln position B, as shown in FlG. 2, blade 40 is released, being opposite the flat 32a on cam portion 32, thus allowing its tip to ride on the surface of timer cam section 36, and be moved away from and into electrical contact with strip 39 for timed completion of the circuit to the load, in accordance with its engagement of the notches 54. In this position, the tip of contact blade 45 is displaced by selector cam section 34 into its actuating position, to meet contact point 46, and provide electrical power from source 26 to the timer cam motor 57, via lines 49 and 56. Blades 41, 42, 43 are held away from their actuating positions by selector cam sections 33, 34, and 32, respectively, and detent 44a locks the selector cam in this position.
ln position C, contact blade 42 is released into its actuating position being opposite the flat section 340 of selector cam section 34. The tip of the blade 42 thereby rides upon the surface of timer cam section 38 and is moved into and out of electrical contact with strip 39 each time it engages a notch 54, which is 3 times per cam revolution. In this position also, contact blade 45 is in its actuating position. Blades 40, 41, 43 are held away from their actuating positions by selector cam sections 32 and 33, and detent 44a locks the selector cam in this position.
In position D, blade 41 is released into its actuating position, being opposite the flat section 33a of selector cam section 33, for timed completion of the load circuit once per revolution, when it engages notch 54 of timer cam section 37. In this position also, contact blade 45 is in its actuating position. Blades 40, 42, 43 are held away from their actuating positions by selector cam sections 32 and 34, and detent 44a locks the selector cam in this position.
In FIG. 3, the preferred embodiment of the timer is in operative connection with a syringe pump, to control the pumping strokes thereof. Both the pumping drive mechanism and the timer are mounted within a plastic housing 60. The timer is essentially as described with relation to FlG. 2. A selector knob 50 is provided to manually rotate selector cam 31 to individually displace an array 30 of U-shaped contact blades 40, 41, 42, into position to ride upon the surface of timer cam 35, and thereby provide timed operation of the syringe pump. Blade 43 provides continuous operation of the pump. The pump comprises a motor drive wheel 64, and a slotted arm 61 to reciprocate the plunger 62 of syringe 70. The arm 61 is pivotally mounted to the housing 60 by means of a pin 63. A slot 69 is provided in one end of the arm 61 so that it may be slidably connected by means of eccentric pin 68 to the drive wheel 64. A slot 73 is formed at the other end of arm 61 to engage the flange 62a of plunger 62. A normally closed snap acting switch 72 wired in parallel with the timer is mounted within the housing in close juxtaposition to the end of the arm 61 connected to the drive wheel. When the plunger 62 reaches the bottom of the stroke, the arm 61 contacts the switch 72, causing it to actuate and open the parallel circuit to the pump motor. By choosing timed intervals that are always longer than the time necessary for the pump to make one stroke, the switch 72 will always be in the open position when the timer contacts close. A standard electric plug 65 and a wire 66 are used to connect the syringe pump-timer assembly to an electrical outlet.
in operation, the selector knob 50 is rotated to the desired timing sequence, selected from those represented by the letters A, B, C, and D, which correspond to the different cyclic frequencies of the pump. The rotational movement of the knob 50 in turn rotates selector cam 31. The selector cam 31 moves the selected contact blade (Position A, 43, Position B, 40, Position C, 42, Position D, 41) into its actuating position. In position A, blade 43 is in contact with point 55, and gives continuous pump operation; blade 45 is in a nonactuating position. When blades 40, 41, 42 engage the corresponding grooved segment 36, 37, 38 of the timer cam 35, for timed cycling of the syringe pump, the contact blade 45 is moved into its actuating position, to complete the circuit to the timer cam motor. Each time the tip of a selected contact blade engages a groove in the surface of the timer cam 35, it is released into contact with contact strip 39, to complete the electric circuit to the pump motor.
As the pump motor begins its operation, drive wheel 64 rotates, causing arm 61 to pivot about point 63. The movement of the arm reciprocates the plunger 62 of the syringe 70, thus drawing in fluid through the check valve assembly 71 from fluid line 74 during the downstroke, and pumping fluid into fluid line 75 via the check valve assembly during the upstroke. As the timer cam 35 continues to rotate, the contact blade riding thereupon will be forced out of contact with strip 39 when it leaves the groove. This, however, does not stop the operation of the pump, since switch 72 which is in a parallel circuit is normally closed. When the plunger 62 reaches the bottom of its stroke, the end of the arm 61 will actuate switch 72, thus stopping the flow of current to the pump motor, and halting its operation. As the timer cam 35 continues to rotate, the selected contact blade will again engage a notch 54 in the surface of the timer cam 35, and come in contact with contact strip 39, to again feed current to the pump motor, and begin its operation. When the arm 61 moves out of contact with the switch 72, the switch automatically closes.
Since switch 72 is used to break the circuit, and the contact blades and points are used only to complete the circuit, the life of the contact blades and points will be appreciably greater than if they were used to both open and close the circuit. In addition, the use of switch 72 to stop the pump ensures that the plunger 62 will be at the bottom of its stroke at the beginning and end of each cycle. In this manner, the syringe will be filled with fluid at the start of each pumping stroke, and will immediately pump fluid into fluid line 75 upon movement of the plunger.
In FIG. 4, the circuitry of the syringe pump-timer assembly of FIG. 3 is shown. It can be seen in this schematic diagram that both the switch and the timer are in parallel with respect to the pump motor. Therefore, if either is closed, the pump will be in operation. This allows both continuous operation of the pump and timed operation, in accordance with the selected position of the timer.
When continuous pumping is desired, the timer motor is not operating and current is fed directly through the contact blades via a contact point to the pump motor. Although the arm of the pump will open the switch at the end of each stroke, this will not cease the pumping operation, inasmuch as current will still be fed via the cam operated contact blade. When timed operation is desired, the rotating timer cam displaces the contact blade away from the contact point thus breaking the timer circuit to the pump motor. The switch, however, is normally closed so that the pump will continue its operation until the arm actuates the switch, at which point both parallel circuits will be opened and no current will flow to the pump motor. When a contact blade again is moved into position to complete the circuit by the timer cam, the operation cycle of the pump will repeat.
l. A piston pump adapted to pump measured fluid volumes at selected time intervals, comprising, in combination, a pump chamber having a fluid-pumping plunger reciprocably movable therein; pump drive means including an electric motor operatively associated with the plunger for reciprocably moving the plunger within the pump chamber, to draw fluid into the pump chamber and pump it out; a timer having a plurality of selectable timing intervals; a timer switch actuated by the timer to open and close the electric circuit to the pump drive means at a selected time interval to initiate a stroke of the plunger; a pump drive switch in parallel to the timer switch, to open and close the electric circuit to the pump drive means; and pump drive switch actuating means associated with the pump drive means to open the pump drive switch whenever the plunger is in a starting position and turn off the pump drive means, and to close the pump drive switch whenever the timer switch closes and starts operation of the pump drive means; the pump drive switch remaining in the closed position until the plunger returns to the starting position; the timer switch over riding the pump drive switch to start the pump drive means only at the starting position for a stroke of the plunger, and the timer and pump drive switches together thereby controlling the plunger operation stroke by stroke, to control the fluid volume delivered per time interval according to the number of strokes per time interval.
2. A piston pump in accordance with claim 1, which includes a check valve assembly in fluid connection with the pump chamber to allow fluid to be drawn into and pumped from the chamber by the plunger upon its reciprocating movement.
3. A piston pump in accordance with claim 1, which comprises a syringe having a fluid pumping plunger reciprocably moveable therein; and pump drive means operatively associated with the plunger for reciprocably moving the plunger within the syringe, to
draw fluid into the syringe and pump it out.
. A piston pump in accordance with claim 1, in
which the pump drive switch actuating means comprises a pivotable lever arm connected at one end to the plunger, and arranged at the other end to engage and pivot into and away from engagement with the pump drive switch, the switch being normally open, and closed only while engaged by the lever arm.