Information Age & Silicon Revolution (1960–1990)Medical Devices & Mechatronics

Kamen Pulse-Counted Lead-Screw Injection Mechanism

US 3,858,581

Motor rotation, uniform-pitch lead screw, pulse counting, and timed motor intervals

Inventor(s)Dean Kamen

Grant DateJanuary 7, 1975

Filing DateJuly 2, 1973

LocationRockville Centre, New York

Kamen's 1975 grant claims a mechanically coupled motor, uniform-pitch lead screw, striker-operated pulse switch, and pulse-counting control for a syringe plunger. The claims connect a count of screw rotations to motor operation and add timers, a clutch, a visual signal, and a scale. This historical record does not establish a modern dosage, delivery-rate, pressure, or treatment protocol.

USPTO PDF

Engineering Analysis & Physical Principles

How It Works: Step-by-Step Mechanical & Physical Breakdown

The legal core is an electromechanical counting chain. A motor turns a lead screw; a nonrotating follower advances a plunger; a striker closes a switch once each screw rotation; and a pulse counter keeps the motor running for a selected count. The important engineering move is not a generic motorized syringe but using discrete rotational events to govern a linear actuator. The museum visual keeps this strictly nonclinical because the grant does not supply a safe dose, patient condition, fluid-pressure limit, or therapeutic prescription.

The Core Breakthrough Mechanism

For an ideal uniform-pitch screw, a follower displacement can be described as $x = n p$ , where $n$ is the rotation count and $p$ is the unreported thread pitch. The striker makes an electrical pulse for each rotation, so the source couples the same count to the controller. Claim 1 links that mechanical and electrical chain; Claims 2–5 add scheduling, clutch disengagement, signaling, and a scale. The source supports this causal relation, not numerical calibration for real medication delivery.

Interactive Real-Time Physical Simulation

Drag to rotate · Scroll to zoom · Shared controls update the displayed modelDrag to rotate · Pinch to zoom · Shared controls update the displayed model

INITIALIZING THREE.JS WEBGL SIMULATION...

Host-Model Telemetry/Computed Readout

Pulse-Counted Lead-Screw Mechanism (Nonclinical)

Lead-Screw Position

Normalized

32% normalized[1]

Counter Progress

Normalized

32% normalized[1]

Mechanism State

Source

COUNTING PULSESsource topology[1]

Claim Probe

Source

CLAIM 1source claim[1]

Clinical Delivery Prediction

Source Refusal

REFUSEDnot in source[1]

Lead-Screw Rotation0.32 normalized

Pulse-Counter Target0.68 normalized

Motor Circuit1 open/closed

Clutch Relief Path0 hidden/shown

Detailed Component Architecture

1Motor and uniform-pitch lead screw

A motor drives lead screw 22; the threaded follower advances along the screw rather than rotating with it.

The basic kinematic reading is $x = n p$ . The patent says the pitch is uniform but does not print $p$ , a motor speed, backlash, friction, or a safe operating load. The exhibit therefore uses normalized screw position only.

19th-C. Term: rotatively mounted lead screwModern: motor-driven screw linear actuator

2Follower and plunger interface

Follower 18 and head 16 translate screw motion into linear movement of syringe plunger 14.

The mechanism constrains the follower against co-rotation so a rotation of the screw produces longitudinal advance. The claim is about the relation of these parts, not an asserted flow or therapy metric.

19th-C. Term: pushing meansModern: traveling nut / plunger driver

3Striker, switch, and pulse counter

A rotating striker reaches switch 84 once per rotational traverse and supplies the event count used by the control circuit.

In the ideal source relationship $N_{pulse}=n_{turns}$ . That identifies a countable motion event, but the patent does not turn it into a modern encoder accuracy or safety specification.

19th-C. Term: pulse-emitting switchModern: rotation-event switch

4Timing and clutch additions

Dependent claims add a scheduled interval, a visual signal, and a clutch that can interrupt the motor-to-screw drive.

The source describes timer and clutch functions as circuit and coupling relationships. It gives neither a validated alarm threshold nor a medically safe timing program, so the interactive treatment presents only state topology.

19th-C. Term: additional timing meansModern: interval-control circuit

Engineering Principles & Equations

Governing Equations & Engineering Principles

Authored explanation paired with its stated mathematical relation

Lead-Screw Rotation and Pulse-Count Relation (Nonclinical)

Mechatronics & Historical ControlClaim 1

Mathematical Governing Law

\htmlClass{eq-term eq-term-pulse_count eq-term-cyan}{\htmlData{var=pulse_count}{\textcolor{#0891b2}{N_{pulse}}}}=\htmlClass{eq-term eq-term-turn_count eq-term-sapphire}{\htmlData{var=turn_count}{\textcolor{#2563eb}{n_{turns}}}}; \quad \htmlClass{eq-term eq-term-position eq-term-emerald}{\htmlData{var=position}{\textcolor{#16a34a}{x}}}=\htmlClass{eq-term eq-term-turn_count eq-term-sapphire}{\htmlData{var=turn_count}{\textcolor{#2563eb}{n}}}\htmlClass{eq-term eq-term-pitch eq-term-amethyst}{\htmlData{var=pitch}{\textcolor{#9333ea}{p}}}

Terms:

Plain English DecoderHover or tap any highlighted phrase

The source ties a to lead-screw , while the screw's symbolic relates those turns to a displayed follower .

N_{pulse}

Rotation-Event Count

Count of striker-triggered electrical events in the Claim 1 mechanism

Events[1]

Claim 1 says the radially oriented striker reaches the pulse-emitting switch during each lead-screw rotation. The grant does not give a pulse frequency or a clinical setting.

Live Physical Value:

32 % normalized

Physical Principle & Engineering Insight

This is a historical kinematic and event-count relation only. The source does not provide any dose, concentration, pressure, patient condition, safe delivery rate, clinical outcome, or medical recommendation.

Historical Context: The claim links a familiar mechanical actuator to countable electrical events and motor-state control; its archival value is the mechatronic architecture, not a present-day clinical protocol.

Lead-screw displacement relationAuthored Principle 1

Stated relation

x = n p

Each ideal full rotation advances a uniform-pitch follower by pitch

p

. Kamen's source supplies the qualitative uniform-pitch relationship but not a numerical pitch, so

x

remains a symbolic mechanical relation here.

Rotation-event countingAuthored Principle 2

Stated relation

N_{pulse}=n_{turns}

Claim 1 says the radially oriented striker engages the pulse-emitting switch during each rotation of the lead screw. The counter therefore receives a discrete event tied to the screw traversal.

State-sequenced actuationAuthored Principle 3

Stated relation

motor\;on \xrightarrow{N\;pulses} motor\;off \xrightarrow{timer} motor\;on

Claims 2 and 4 describe an interval and pulse-operated timing logic. The notation represents the claimed state sequence, not a medical schedule or a promise of a clinical result.

Interactive Schematic Sheet (Fig. 1)

Figure 1 shows the source device as an assembled object; the museum schematic does not treat it as a current clinical product.

1.00x

Click any numbered callout pin or use arrow keys [← / →]Tap any numbered pin1 Curated Callouts

Callout Pin Inspector

Select Any Numbered Pin

Click pins on the schematic or select from the list below to inspect historical specifications.

Why It Still Matters

The grant is a compact early example of a familiar mechatronic pattern: turn a physical actuator state into countable electrical events, then use the count to decide the next machine state. The pattern appears in many nonmedical position-controlled machines. The archive presents the historical device's mechanism while refusing to turn a 1975 document into medical guidance.

Legal Claims Decoder (5 Numbered Claims)

Compare dense legalistic claims directly with decoded plain-English functional specifications.

Claim #1Independent Master Claim

1/5

Verbatim Historical Legal Text

“A medication injection device comprising a syringe for dispensing medication in accordance with linear displacement of a plunger thereof, means secured to said syringe for connection to a patient for dispensing said medication to said patient, a rotatively mounted lead screw with threads of uniform pitch disposed in substantially parallel relation to the linear displacement path of said syringe plunger, pushing means mounted on said lead screw for advancement therealong in pushing engagement with said syringe plunger, a motor operatively arranged to power said lead screw in rotation to cause advancement of said pushing means and corresponding linear displacement of said syringe plunger, a radially oriented striker mounted on said lead screw, a pulse-emitting switch located adjacent said lead screw in the path of the rotational traverse of said striker so as to be engaged thereby to cause an emission of an electrical pulse during each rotation of said lead screw, and a pulse-counting means electrically connected to receive the transmission of each aforesaid pulse and operatively connected to permit the operation of said motor for the duration of the transmission thereto of a selected number of said pulses, whereby medication is dispensed in accordance with the linear displacement of said syringe plunger as a function of the number of rotational traverses of said lead screw as counted by said pulse-counting means.”

Plain English Engineering Translation

Claim 1 protects the complete count-governed actuator chain: syringe and plunger, uniform-pitch screw, advancing pusher, motor, rotating striker, nearby pulse switch, and counter that permits motor operation for a selected count. The legal work is in coupling the repeated screw rotation to a count that governs the actuator interval, not merely in naming any one of those familiar components.

Key Protected Innovations:

Uniform-pitch lead screwRadial strikerPulse-emitting switchPulse-counting motor control

Historical Legal Impact:

The independent claim makes the mechanical-to-electrical counting chain the legal center of the grant.

The Historical Bottleneck

The source describes an attempt to make a motor-driven plunger stroke depend on repeated physical rotation events rather than relying on elapsed motor time alone, which can vary with the driving situation described in the specification.

Why Prior Art Failed

•The specification says a prior motor could deliver different amounts when viscosity differed.
•It identifies wear and changing frictional resistance as factors that could affect a time-based prior device.
•The source describes manual time-based control as inadequate for the repeated on/off behavior it sought.

The Breakthrough Insight

“Use one mechanical rotation of a uniform-pitch lead screw as a countable event, then let a pulse counter and timers control the motor state. This joins a linear actuator, a rotation switch, and old electronic counting logic into one claimed chain.”

After the Grant

Google Patents records a 1983 assignment from Auto Syringe, Inc. to Baxter Travenol Laboratories, Inc. The public record establishes an ownership transaction; it does not make this archival entry a recommendation of any medical product or use.

Civilizational Impact

The historical significance lies in the combined actuator-and-event-count architecture. It shows an early compact mechatronic approach to linking physical motion with discrete control logic, while the document alone cannot establish the safety or suitability of a present-day medical device.

Further Context

The front page prints five claims and six drawing figures.
The reviewed source face retains the historical language; the interactive visual deliberately omits any dose, volume, flow, or therapy setting.