# External Spring Pumps: Liquid Path Isolation and Trace Metal Leaching Prevention
TL;DR — Placing the spring outside the liquid path is a structural design intent, not a materials statement.
The Spring Outside feature is recorded on lotion pump models and on perfume atomizer models VQ-AT-407A/B and VQ-AT-409, while the lotion pump family covers 59 catalog models with output from 0.13 to 4.00 ml per stroke.
The spring is a purchased component and its material identity is not published, and no leaching figures are published either. Leaching prevention is a design intent validated per project — a claim that the liquid is free of metal or leachates needs its own evidence, and this article shows what that evidence would have to look like.
Why: Placement Is Structure, Not an Outcome
The spring is the classic place where metal hides inside an otherwise plastic pump — the small part that carries the return stroke and keeps the check valve seated. One structural response is to move the spring outside the liquid path altogether. That is a real, recorded design direction, and it is not by itself a materials statement:
- The spring is where metal hides — a compression spring is small, load-bearing, and historically metallic, so buyers with regulatory or brand concerns about trace metals ask where it sits;
- Placement is structure, not outcome — where the spring sits describes a mechanism; it says nothing about what the spring is made of;
- Isolation is intent, proof is separate — keeping the spring out of the liquid path is a design intent that still has to be validated for each build;
- Claims need data, not geometry — any guarantee that the product is free of metal or leachates is a claim with its own evidence standard;
- Function is what the program documents — the verification hooks that do exist are life-cycle, dosage/output, and compatibility testing, not claim language.
The packaged question, in short: an external spring reduces the exposure path by design, and the project still owns every confirmation after that.
How: Reading the Feature Record, Then the Design Intent
3.1 The Spring Outside feature record
Spring Outside is a recorded technical feature: it appears on models within the lotion pump family and on perfume atomizer models VQ-AT-407A/B and VQ-AT-409. For contrast, a screw-driven arrangement is recorded on perfume atomizer model VQ-AT-406 — a different mechanism with the drive element inside the assembly rather than displaced outward. The feature distribution is catalog fact; the engineering meaning of each layout is design interpretation.
The lotion pump family these springs serve carries 59 catalog models, with family-level output from 0.13 to 4.00 ml per stroke — the functional envelope within which the feature and its mechanism have to perform.
3.2 What liquid path isolation means mechanically
In an external-spring layout, the spring does its work from outside the liquid path: the fluid travels through the dip tube, the valve, and the dosing chamber, while the spring applies its return force from the other side of the sealing boundaries. The intended consequence is that the liquid never passes over the spring surface during a stroke.
That construction intends to remove one contact surface from the fluid's journey. It is a mechanism-level design intent, and it does not prove anything about the materials involved — the spring still has to be characterized, and the whole assembly still has to hold its seals under use.
3.3 Why isolation is not a leaching figure
Two pieces of the record stay deliberately open. First, the spring is a purchased component and its material identity is not published. Second, no leaching figures are published for these products. Both gaps are information, not problems: they define the shape of the evidence a project must produce.
Leaching prevention in this context is therefore a design intent validated per project — the geometry reduces exposure, and the confirmation that the formulation, the spring, and the seals are compatible is a per-project result. Nothing in the mechanism record authorizes a claim that the liquid is free of metal or leachates.
3.4 The verification hooks the program does document
What the program documents is function: pump life-cycle testing, dosage/output testing, and compatibility testing are all documented capabilities (capability-level, no parameters published). These gates validate that the pump keeps pumping, doses within its family output range, and tolerates the formula it carries. A life-cycle result confirms the stroke survives; the leaching question stays with whoever assembles the material and compatibility evidence per project.
<pre class="language-mermaid"><code>flowchart LR
A[Pump family<br/>lotion 59 catalog models · 0.13–4.00 ml per stroke] –> B[Spring Outside feature<br/>lotion pumps · perfume atomizers VQ-AT-407A/B · VQ-AT-409]
B –> C[External spring<br/>liquid path isolation — design intent]
C –> D{Leaching prevention?}
D –> E[Validated per project<br/>no figures published]
B –> F[Spring component<br/>purchased · material not published]
A –> G[Life-cycle + dosage/output + compatibility<br/>capability-level tests]
E –> H[Release per project]
F –> H
G –> H
</code></pre>
<pre class="language-mermaid"><code>flowchart LR
A[Feature record<br/>Spring Outside · recorded] –> B[Design intent<br/>liquid path isolation]
B –> C{Claim required?}
C –>|Leaching / metal statement| D[Per-project evidence<br/>spring material · compatibility · no published figures]
C –>|Functional statement| E[Documented tests<br/>life-cycle · dosage/output · compatibility]
D –> F[Release per project]
E –> F
</code></pre>
What: Verified Program Data and the Verification Hooks
The list below is the only place in this article where program facts are asserted. Everything else above is design intent and engineering guidance.
- Feature record: Spring Outside is a recorded technical feature on models within the lotion pump family and on perfume atomizer models VQ-AT-407A/B and VQ-AT-409; a screw-driven arrangement is recorded on model VQ-AT-406 by contrast;
- Family scope: the lotion pump family carries 59 catalog models;
- Output class: lotion pump family output spans 0.13 to 4.00 ml per stroke;
- Spring component: the spring is a purchased component and its material identity is not published;
- Leaching boundary: no leaching figures are published; leaching prevention is a design intent validated per project;
- Verification hooks (capability-level): compatibility test, pump life-cycle test, and dosage/output test are documented testing capabilities, with no parameters published.
Gotchas
- Spring Outside is a feature record, not a materials record. It describes where the spring sits, and it is silent on what the spring is made of — the two questions must not be merged.
- Spring material is un-published, and blank is a design signal. Because the spring is a purchased component with no published material identity, any statement that the product is free of metal or leachates requires per-project confirmation you cannot inherit from the catalog.
- Isolation geometry is not a leaching number. Even a perfectly executed liquid-path separation proves arrangement, not outcome; a zero-leaching or leach-free statement needs its own data set.
- The feature appears on specific models, not everywhere. Spring Outside is recorded on the documented lotion pump models and on perfume atomizers VQ-AT-407A/B and VQ-AT-409; before citing the feature, check that the model in question carries the record.
- Life-cycle, dosage/output, and compatibility tests validate function, not claim language. A passed stroke test does not authorize a materials guarantee; the leaching verdict stays with the per-project evidence.
- Family output is a family statement. 0.13–4.00 ml per stroke is the recorded lotion family class, not a promise for every model; the per-model window is confirmed on fill.
Related Resources
- Category: Pumps · Atomizers
- Related insight: All-Plastic Pumps and the Spring Evidence Question · Low-Output Atomizers: Micro-Spring Particle Uniformity · The 12-Test Lab Matrix
- Quality & Testing Capabilities — life-cycle, dosage/output, and compatibility testing