Information Age & Silicon Revolution (1960–1990)Parallel Robotics & Industrial Automation

Clavel Delta Parallel Robot

US 4,976,582

Fixed-base actuators, spatial parallelograms, and orientation-preserving translation

Inventor(s)Reymond Clavel

Grant DateDecember 11, 1990

Filing DateSeptember 6, 1989

LocationEcublens, Switzerland

US 4,976,582 claims a positioning device in which at least three base-supported actuators drive articulated linking members to a movable member while its inclination and orientation remain fixed. The illustrated form uses three rotary control arms and paired parallel bars, arranged as spatial parallelograms, to translate a platform and a working member. Other claims cover translating inputs, single-bar/cardanic variants, alternative joints, and a separately rotated working member; the grant is not a blanket claim to every later parallel robot.

USPTO PDF

Engineering Analysis & Physical Principles

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

Clavel attacks a familiar factory-robot trade: a serial arm can position a wrist with successive joints, but each downstream axis can put motors or transmission mass on a moving structure. The issued patent instead connects three base-side actuators in parallel to one movable member. Its illustrated paired bars make three deformable spatial parallelograms, so the platform translates while staying parallel with itself. This is a geometric mechanism claim, not a measured performance specification: the grant never supplies link dimensions, motor constants, payload, stiffness, servo gains, trajectory data, or cycle-time measurements.

The Core Breakthrough Mechanism

Each illustrated rotary actuator turns one control arm. At the arm tip, two parallel lower bars run to the movable member through articulated joints. For an idealized display leg i, the two bars preserve their separation vector, $\mathbf{r}_{i,a}-\mathbf{r}_{i,b}=\mathbf{d}_i$ , while their endpoints articulate. Three such constraints make platform translation depend jointly on the three arm positions and preserve its attitude in the pictured paired-bar form. The live exhibit solves only a normalized, deterministic topology that makes those paired links and the attitude invariant inspectable. It refuses metres, newtons, watts, speed, payload, accuracy, or a claim of a FrankenSim/WASM dynamics step because the patent does not publish the necessary parameters.

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

Parallel-Arm and Spatial-Parallelogram Topology

Claim Topology

Source

VISIBLEClaim 1[1]

Paired Bars

Source

2 / LEGClaim 2[1]

Declared bar length

Normalized

1.653normalized exhibit length[1]

Rigid-link closure residual

Normalized

2.22e-16normalized construction[1]

Pair-vector residual

Normalized

0.000normalized construction[1]

Platform center

Normalized

(0.43, -0.72, 0.37)normalized display[1]

Physical performance

Source Refusal

refusedno source dimensions or dynamics[1]

Control arm 1 input+0.12 normalized input

Control arm 2 input-0.18 normalized input

Control arm 3 input+0.06 normalized input

Working-member axis input0 normalized rotation

Claim 1 three-actuator topology1 claim probe

Claim 2 paired parallel bars1 claim probe

Claim 8 base tool-axis motor1 claim probe

Detailed Component Architecture

1Fixed base and three actuator inputs

The first embodiment places three rotary actuator assemblies on one base member, with their fixed portions remaining on that base.

Figure 1 identifies base 1, fixed actuator portions 3, rotary axes 2, and control arms 4. The source says the axes are coplanar and the arm axis is perpendicular to its corresponding rotary axis. A normalized input $q_i$ can move the illustrated arm, but the grant gives neither a physical arm length nor an actuator torque, speed, encoder, or controller law. The model therefore distinguishes topology from performance.

19th-C. Term: fixed portionModern: base-mounted actuator housing or stator-side structure

2Control arms and paired linking bars

Each control arm carries a pair of parallel bars from its outer end to the movable member.

In the illustrated form, 5a and 5b run from arm end 16 through articulated groups 6a/6b and 7a/7b. The pair is structurally important: both bars are drawn and their parallel relation is the source-backed constraint. It is not acceptable to render one decorative rod and call it a Delta mechanism. The visual deliberately draws the two bars for each of three legs and tests their equal normalized separation.

19th-C. Term: linking barsModern: paired lower links forming a parallelogram linkage

3Movable member and attitude constraint

The central movable member is translated by all three legs while the source states that its inclination and orientation remain unchanged.

The claim language requires linking means and two degrees of freedom at each stated end, then fixes platform orientation over actuator motion. A useful normalized closure check is $\mathbf{p}+\mathbf{a}_i=\mathbf{e}_i+\mathbf{u}_{i,a}+\mathbf{l}_{i,a}=\mathbf{e}_i+\mathbf{u}_{i,b}+\mathbf{l}_{i,b}$ for each leg. It checks a display construction; it does not recover the historic workspace or prove stiffness.

19th-C. Term: movable memberModern: moving platform or end-effector carrier

4Working member and supplementary motor

A tool, gripper, sucker, or syringe can sit on the movable member, with a separately rotated longitudinal tool axis.

The embodiment names working member 9 and axis 10. Figure 1 places supplementary motor 11 on the base and transmits rotation through a rod system such as telescopic arm 14; Figure 2 permits the motor on the movable member. The mechanism separates tool-axis rotation from the platform-attitude constraint. No gear ratio, motor rating, tool torque, or actual rotation range is printed, so the live control is labeled normalized.

19th-C. Term: working memberModern: end effector or tool interface

5Rotary, translating, and joint alternatives

The claims preserve more than the familiar Figure 1 rotary paired-bar layout.

Claim 4 and Figure 5 describe members translating on straight guides, Claims 5–7 and 22–23 describe single-bar/cardanic alternatives, and Figures 1–2 contrast cardan with ball-and-socket articulations. These variations matter to legal scope. The exhibit's live Claim 2 probe remains intentionally narrow: it illustrates the paired, parallel-bar topology of the canonical first form rather than silently treating every disclosed alternative as the same mechanism.

19th-C. Term: articulation of cardan typeModern: universal-joint-style articulation

Engineering Principles & Equations

Governing Equations & Engineering Principles

Authored explanation paired with its stated mathematical relation

Paired-Bar Displacement and Fixed-Attitude Constraint

Source-Bounded Parallel-Robot TopologyClaim 2

Mathematical Governing Law

\htmlClass{eq-term eq-term-platform_center eq-term-amethyst}{\htmlData{var=platform_center}{\textcolor{#9333ea}{\mathbf{p}^{*}}}}+\textcolor{#0d9488}{\mathbf{a}_i^{*}}=\htmlClass{eq-term eq-term-actuator_input eq-term-cyan}{\htmlData{var=actuator_input}{\textcolor{#0891b2}{\mathbf{e}_i^{*}}}}+\textcolor{#059669}{\mathbf{l}_{i,j}^{*}},\qquad\lVert\textcolor{#059669}{\mathbf{l}_{i,a}^{*}}\rVert=\lVert\textcolor{#059669}{\mathbf{l}_{i,b}^{*}}\rVert=\htmlClass{eq-term eq-term-bar_length eq-term-amethyst}{\htmlData{var=bar_length}{\textcolor{#7c3aed}{L^{*}}}},\qquad\textcolor{#059669}{\mathbf{l}_{i,a}^{*}}-\textcolor{#059669}{\mathbf{l}_{i,b}^{*}}=\htmlClass{eq-term eq-term-pair_residual eq-term-crimson}{\htmlData{var=pair_residual}{\textcolor{#dc2626}{\mathbf{d}_i^{*}}}}

Terms:

Plain English DecoderHover or tap any highlighted phrase

For each leg, the normalized can be reached through either of two lower bars with one declared . The and shared remains zero in the source-bounded construction when Claim 2 keeps both parallel bars present.

\mathbf{p}^{*}

Movable-Member Display Center

Normalized display coordinate of movable member 8

normalized exhibit coordinate[1]

The asterisk marks a teaching coordinate, not metres. US 4,976,582 names a movable member and its orientation constraint but prints no link dimensions or calibrated workspace from which an SI platform position could be reconstructed.

Live Physical Value:

(0.43, -0.72, 0.37) normalized display

Physical Principle & Engineering Insight

This equation is a normalized topology statement. It makes the paired-bar displacement and rigid-link closure construction readable without asserting a historical link length, SI machine solution, stiffness, payload, speed, or FrankenSim/WASM dynamics result.

Historical Context: Claim 2 makes the two parallel bars a concrete structural limit within Clavel's broader orientation-preserving positioning device; the exhibit keeps that legal distinction visible.

Closed-chain position constraintsAuthored Principle 1

Stated relation

$\mathbf{p}+\mathbf{a}_i=\mathbf{e}_i+\mathbf{u}_{i,j}+\mathbf{l}_{i,j}\quad(i=1,2,3;\;j=a,b)$

For each display leg, the platform attachment point equals the arm-tip route through either of the paired lower links. Those simultaneous equalities express closed-chain geometry. The source gives the topology but no numerical lengths, so every vector in the exhibit is a normalized drawing coordinate rather than an SI measurement.

Parallelogram attitude invariantAuthored Principle 2

Stated relation

$\mathbf{l}_{i,a}-\mathbf{l}_{i,b}=\mathbf{d}_i=\text{constant}$

The paired bars retain a fixed separation vector while the joints articulate. In the illustrated construction, three such parallelogram constraints make the movable member remain parallel with itself. This is a kinematic statement about ideal linkage geometry, not a numerical stiffness, compliance, backlash, or accuracy prediction.

Three coordinated positioning inputsAuthored Principle 3

Stated relation

$\mathbf{p}_{\mathrm{display}}=f(q_1,q_2,q_3;\text{paired-bar topology})$

The source describes three actuator moving portions acting in parallel, so the platform pose is a function of all three inputs under loop closure. It does not disclose f as a calibrated machine model, inverse-kinematics controller, trajectory planner, or numerical workspace. The demonstrator exposes the dependency without inventing those omitted quantities.

Separate tool-axis degree of freedomAuthored Principle 4

Stated relation

$q=[q_1,q_2,q_3,\phi_{tool}]^T$

The patent's supplementary motor can rotate working member 9 about longitudinal axis 10 separately from the three platform-positioning inputs. The coordinate list distinguishes this source-described extra rotation from platform tilt; it is not a claim of a source-provided four-axis controller or a specified angular range.

Interactive Schematic Sheet (1)

Source Figure 1: base 1 carries three fixed actuator portions 3 and rotary axes 2; control arms 4 drive paired bars 5a/5b through cardan articulations to movable member 8 and working member 9.

1.00x

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Why It Still Matters

The patent makes the actuator-placement and closed-chain trade visually legible: three input arms can carry a platform without serially stacking all main drive mass on the moving structure. That topology became central to later high-speed pick-and-place Delta robots. EPFL's historical account identifies Clavel's team with the 1985 invention and later packaging commercialization, while the International Federation of Robotics documents an early packaging deployment. Those later applications are historical context, not numbers silently projected back into the 1990 grant or a claim that this patent alone covers all later parallel robots.

Legal Claims Decoder (25 Numbered Claims)

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

Claim #1Independent Master Claim

1/25

Verbatim Historical Legal Text

“A device for the movement and positioning of an element in space, comprising: at least one base member; at least one movable member; at least three actuators, each actuator comprising a fixed portion, substantially immovably fixed on the base member, and a moving portion having a single degree of freedom with respect to said fixed portion; and means fixing in space the inclination and orientation of the movable member with respect to the base member for all motions of the moving portions of the actuators, said fixing means comprising at least three linking means respectively connecting the moving portion of each actuator to the movable member, each of the linking means having a first end mounted by articulation onto the moving portion of its respective actuator and a second end mounted by articulation onto the movable member, the device providing two and only two degrees of freedom between the first end of each linking means and the moving portion of its respective actuator, the device providing two and only two degrees of freedom between the second end of each linking means and the movable member.”

Plain English Engineering Translation

Claim 1 is the broadest issued orientation-preserving positioning combination. It requires a base, a movable member, at least three one-degree-of-freedom actuator moving portions, and at least three articulated linking means. The legal limit is not merely three motors: the mechanism must fix the movable member's inclination and orientation over those input motions while supplying only the stated two degrees of freedom at each link end. It therefore targets a constrained parallel mechanism, not every serial robot or arbitrary parallel linkage.

Key Protected Innovations:

Fixed base memberThree single-degree actuator portionsArticulated linking meansPlatform attitude constraint

Historical Legal Impact:

Principal independent claim for the general base-actuator / orientation-preserving parallel-linkage architecture.

The Historical Bottleneck

The patent describes the need to transfer light pieces rapidly while avoiding the serial arrangement in which downstream drive or transmission mass can be carried by upstream axes.

Why Prior Art Failed

•The specification describes conventional serial industrial-robot axes as referenced in sequence, with motors or complicated transmissions located at successive axes.
•It says a six-axis parallel arrangement similar to a flight simulator can keep motors fixed but reaches only a restricted working volume.
•It distinguishes the cited Pollard paint-gun mechanism and an extensible-member French application from its own fixed-support, orientation-preserving arrangement.

The Breakthrough Insight

“Use three base-supported actuator inputs and linked spatial parallelograms to translate one movable member while preserving its inclination and orientation; then treat tool-axis rotation as a separate transmission problem.”

After the Grant

EPFL identifies Clavel's team with the 1985 Delta invention and says the concept was licensed to Demaurex in 1987 for packaging. The International Federation of Robotics records an early packaging installation sold to Roland in 1992. Those are later adoption facts, kept distinct from the patent's unquantified technical assertions.

Civilizational Impact

This grant gives a particularly clear primary-source account of the geometry that came to define the Delta parallel-robot family. It ties the fixed-base-actuator and orientation-preserving-linkage idea to rapid handling and packing applications, making it a useful museum record for the parallel-kinematics design trade rather than a generic history of all robots.

Further Context

The grant's title is descriptive; “Delta robot” is the later common name for this parallel-robot family, not the title printed on the patent.
The facsimile includes an official 4 August 1992 Certificate of Correction. It corrects specification typographical errors and textual issues in claims 6, 7, and 15; the archival edition preserves both the original printed claims and the correction.
No patent conflict is asserted here: the reviewed source packet supports an honest empty patent-wars record rather than an invented dispute narrative.