An Improved Excess Load or Strain Detector.
Year: 1888

page_text: Date of Application, 28th July, 1888
Complete Specification Left, 28th May, 1889-Accepted, 29th June, 1889
PROVISIONAL SPECIFICATION.
An Improved Excess Load or Strain Detector.
I WILLIAM SNELGROVE of Bankwood, Church Road, Moseley, in the county of
Worcestershire, Engineer, do hereby declare the nature of this invention to be as
follows:-
My invention relates to the manner in which I construct and arrange an excess
load detector for attachment to chains, ropes, cables, and tension rods used on lifting
and winding machinery, and upon appliances for raising and lowering heavy bodies,
whereby any undue or excess load is automatically signalled by an alarm given from
a gong or bell, or by the detonation of a percussion cap.
In carrying my invention into effect when applying my automatic excess load
detector alarm to an ordinary lift chain, I attach to the end link or hook, a central
eye bolt or hook having a circular stem screwed into a crosshead or nut and secured
to same by a collar or pin in the ordinary manner. This crosshead or nut is
carried by a frame, and is prevented from turning by a guide or guides within the
frame.
One end of this frame I form as an eye or hook to attach to the end of chain,
and the opposite end I form as a boss or projecting shouldered plate, having a
hole in the centre for the eye bolt or hook stem to pass through.
Between the side of the boss or shouldered end of frame, and the underside of
the crosshead or nut, I place around the bolt stem a spiral or other suitably formed
spring, the tension of which is such as to enable it to bear without undue straining or
breaking, the maximum load that can be safely borne by the chain.
To indicate when the maximum load has been passed and to detect and give an
alarm to those using the chain, I place upon the front face of the frame a plate
having a slot or suitably formed groove to receive a projecting pin from the cross-
head or nut sliding within the frame. This pin projecting through the slot or groove
in plate forms a stop against which a hammer or striking lever is forced by a stiff
spring or springs carried upon the plate.
The hammer or striking lever I connect to the plate by jointed adjustable levers or
lever, and upon the lever pressing against the crosshead projecting pin, I arrange a
suitably formed reversing cam to serve as a trigger to carry the hammer back in
opposition to its spring and thereby to allow the full effect of the spring to be spent
upon the hammer when striking.
I connect this reversing cam by a pin or screw to the hammer lever in such a
position that the projecting crosshead pin will not pass by the cam until the excess
load has been placed upon the hook or eye bolt spring.
In another method of construction I pivot the haininer directly on to the plate, and
the reversing cam I pivot on to a frame sliding and adjustable on the hammer, that
is to say instead of making the hammer adjustable as regards its position on the
plate, I make the hammer pivot a fixture and the arm adjustable. The object for thus
providing adjusting devices, either in the form of an adjustable hammer carrying the
cam with it: or of the non-adjustable hammer with the adjustable cam, being, to
adjust or facilitate the adjustment of the cam in such a position relatively to the pin
or stop on the nut that the hammer is released whenever a certain determined weight
or strain is placed upon the spring supporting the crosshead.
This facility for adjustment enables springs varying somewhat in tension to be
used on alarms for indicating at any one fixed weight or strain.
The adjustable cam moreover permits the easy alteration of the indicating point of
the alarm without altering the spring.
ง
The reversing cam or equivalent contrivance acts only to thrust hammer out on

page_text: downward stroke of pin, and allows it to pass freely on its return stroke. Thus when
the excess load has been removed or released the crosshead pin is carried up the
groove past the cam thereby withdrawing the hammer from its gong or detonating
сар.
In using detonating caps to give the alarm I construct by preference a wheel or
segment with circular pins formed from the circumference; upon each pin I place a
detonating cap which when ready for receiving the blow from the hammer stands
slightly away from end of pin and will not pass the cap rest placed upon the plate to
keep the cap in true line with the hammer.
But after the cap has been struck by the hammer it is driven farther upon its pin,
and is then free to pass the rest; being carried past it by means of a spring arranged
to revolve the cap wheel, or a ratchet wheel in direct connection with the cap wheel,
the ratchet wheel being revolved one tooth at a time by means of a pawl driven by
the hammer shaft and thus bringing fresh caps under the hammer.
I construct the hammer shaft with the side which is in contact with the crosshead
pin, sloping away from the vertical line of travel of the said pin, and therefore in such
a form that its head or hammer is only brought into contact with the percussion cap
wheel after the fixed pin on the crosshead has passed and released the cam. When
the crosshead is at its highest point (i.e. when there is no weight attached to the
apparatus) the hammer is retained by the crosshead pin at a short distance apart
from the cap wheel; by this construction of the hammer I ensure that the movement
of the ratchet wheel is only effected as often as the cap wheel is struck.
To indicate the number of caps unexploded I sometimes arrange the segment or
wheel, so that each pin shall display a figure to be visible from the outside of box
cover, and thus to record the number of occasions of overloading.
I protect the whole of the levers, springs and moving parts by strong box covers
which may be locked at will to prevent any tampering being possible.
I arrange the slide for guiding the crosshead so that any undue or sudden shock
shall not cripple or damage the spring; but shall be spent against a shoulder or stop
within the frame.
When applying my excess load detector alarm to cranes and other lifting and
lowering machines or to tension rods carrying very heavy loads I sometimes cause
the load to be supported upon a lever, or system of levers, and the spring to be
attached to some distant portion of the lever or system of levers rather than to sustain
the load direct.
In another system of sustaining the load I employ a cylinder and ram having a
small supplementary cylinder and ram attached or connected therewith in such a
manner that the water under pressure, due to the load, upon the larger ram acts on
the smaller area of the supplementary ram and forces this smaller ram against a
spring acting to resist the proportion of the load due to the difference in areas of the
two rams. To the piston rod of the smaller ram 1 attach or connect the striking
hammer lever and appliances as hereinbefore described when a spring alone is
employed to sustain the load. Instead of a supplementary ram I sometimes employ a
suitable valve and lever worked from same, to work the striking hammer as before
described.
I do not describe in detail the application of a bell or gong, as it would obviously
be placed in a similar position to the cap wheel.
In some forms of my invention I employ both bell and percussion cap with the
same apparatus.
The application of my invention to winding engines, cranes, lifts, pulley blocks,
and other special lifting and lowering machines, using chains, cables, ropes, or tension
rods, differs in no essential respect from the application to an ordinary chain used for
lifting a load as herein before described.
Dated this 26th day of July 1888.

page_text: COMPLETE SPECIFICATION.
An Improved Excess Load or Strain Detector.
I, WILLIAM SNELGROVE, of The Nest, Kings Norton, in the County of Worcester
Engineer, do hereby declare the nature of this invention and in what manner the
same is to be performed, to be particularly described and ascertained in and by the
following statement :-
My invention relates to the manner in which I construct and arrange an excess
load detector for attachment to chains, ropes, cables and tension rods used on lifting
and winding machinery, and upon appliances for raising and lowering heavy bodies,
whereby any undue or excess load is automatically signalled by an alarm given from
a gong or bell, or by the detonation of a percussion cap.
In carrying my invention into effect when applying my automatic excess load
detector alarm to an ordinary lift chain I attach to the end link or hook a central eye
bolt or hook having a circular stem screwed into a crosshead or nut and secured to
same by a collar or pin in the ordinary manner. This crosshead or nut is carried by
a frame, and is prevented from turning by a guide or guides within the frame.
One end of this frame I form as an eye or hook to attach to the end of chain, and
the opposite end I form as a boss or projecting shouldered plate, having a hole in the
centre for the eye bolt or hook stem to pass through.
Between the side of the boss or shouldered end of frame, and the underside of the
crosshead or nut, I place around the bolt stem a spiral or other suitably formed spring
the tension of which is such as to enable it to bear without undue straining or
breaking the maximum load that can be safely borne by the chain.
To indicate when the maximum load has been passed and to detect and give an
alarm to those using the chain. I place upon the front face of the frame a plate
having a slot or suitably formed groove to receive a projecting pin from the crosshead
or nut sliding within the frame. This pin projecting through the slot or groove in
plate forms a stop against which a hammer or striking lever is forced by a stiff spring
or springs carried upon the plate.
The hammer or striking lever I connect to the plate by jointed adjustable levers or
lever, and upon the lever pressing against the crosshead projecting pin, I arrange a
suitably forined reversing cam to serve as a trigger to carry the hammer back in
opposition to its spring and thereby to allow the full effect of the spring to be spont
upon the hammer when striking. connect this reversing cam by a pin or screw to
the hammer lever in such a position that the projecting crosshead pin will not pass
by the cam until the excess load has been placed upon the hook or eye bolt
spring.
In another method of construction I pivot the hammer directly on to the plate, and
the reversing cam I pivot on to a frame sliding and adjustable on the hammer, that is
to say instead of making the hammer adjustable as regards its position on the plate,
I make the hammer pivot a fixture and the arm adjustable. The object for thus
providing adjusting devices, either in the form of an adjustable hammer carrying
the cam with it: or of the non-adjustable hammer with the adjustable cam being,
to adjust or facilitate the adjustment of the cam in such a position relatively
to the pin or stop on the nut that the hammer is released whenever a certain
determined weight or strain is placed upon the spring supporting the crosshead.
This facility for adjustment enables springs varying somewhat in tension to be used
on alarms for indicating at any one fixed weight or strain.
The adjustable cam moreover permits the easy alteration of the indicating point of
the alarm without altering the spring.
The reversing cam or equivalent contrivance acts only to thrust hammer out on
downward stroke of pin, and allows it to pass freely on its return stroke. Thus when
the excess load has been removed or released the crosshead pin is carried up the
groove past the cam thereby withdrawing the hammer from its gong or detonating
cap.

page_text: In using detonating caps to give the alarm I construct by preference a wheel or
segment with circular pins formed from the circumference; upon each pin I place a
detonating cap which when ready for receiving the blow from the hammer stands
slightly away from end of pin and will not pass the cap rest placed upon the plate to
keep the cap in true line with the hammer.
But after the cap has been struck by the hammer it is driven farther upon its pin,
and is then free to pass the rest, being carried past it by means of a spring arranged
to revolve the cap wheel, or a ratchet wheel in direct connection with the cap wheel
the ratchet wheel being revolved one tooth at a time by means of a pawl driven by
the hammer shaft and thus bringing fresh caps under the hammer. I construct the
hammer shaft with the side which is in contact with the crosshead pin, sloping away
from the vertical line of travel of the said pin, and therefore in such a form that its
head or hammer is only brought into contact with the percussion cap wheel after the
fixed pin on the crosshead has passed and released the cam. When the crosshead
is at its highest point (i.e. when there is no weight attached to the apparatus) the
hammer is retained by the crosshead pin at a short distance apart from the cap
wheel; by this construction of the hammer I insure that the movement of the
ratchet-wheel is only effected as often as the cap wheel is struck.
To indicate the number of caps unexploded I sometimes arrange the segment or
wheel, so that each pin shall display a figure to be visible from the outside of box
cover, and thus to record the number of occasions of overloading,
I protect the whole of the levers, springs and moving parts by strong box covers
which may be locked at will to prevent any tampering being possible.
I arrange the slide for guiding the crosshead so that any undue or sudden shock
shall not cripple or damage the spring; but shall be spent against a shoulder or
stop within the frame.
When applying my excess load detector alarm to cranes and other lifting and
lowering machines or to tension rods carrying very heavy loads I sometimes cause
the load to be supported upon a lever, or system of levers, and the spring to be
attached to some distant portion of the lever or system of levers rather than to
sustain the load direct.
In another system of sustaining the load I employ a cylinder and ram having
a small supplementary cylinder and ram attached or connected therewith in such a
manner that the water under pressure due to the load upon the larger ram acts
on the smaller area of the supplementary ram and forces this smaller ram against
a spring acting to resist the proportion of the load due to the difference in areas
of the two rams. To the piston rod of the smaller ram I attach or connect the
striking hammer lever and appliances as hereinbefore described when a spring alone
is employed to sustain the load.
Instead of a supplementary ram I sometimes employ a suitable valve and lever
worked from same, to work the striking hammer as before described.
In some cases I attach the bolt or link connecting the hook which sustains the
load to the spring which is compressed or extended by the load, to a pointer, or
levers and pointer to register the weight hung upon it as well as to give an alarm
or indication when the intended load has been exceeded. The pointer travels over
a suitably marked dial plate so that the detector weighs as well as provides a safe-
guard.
I also arrange a metal disc so that when the determined load is exceeded the disc
shall appear and shall not disappear again until all or nearly all the load has been
taken off.
In order that the alarm bell may ring continuously until the excess load is removed
I may arrange to actuate it electrically but I do not confine myself to any particular
position of the bell or battery.
I do not describe in detail the application of a bell or gong as it would obviously
be placed in a similar position to the cap wheel.
In some forms of my invention I employ both bell and percussion cap with the
same apparatus.

page_text: The application of my invention to winding engines, cranes, lifts, pulley blocks,
and other special lifting and lowering machines using chains, cables, ropes, or tension
rods differs in no essential respect from the application to an ordinary chain used
for lifting a load as hereinbefore described.
In order that my invention may be fully understood and readily carried into
effect, I append hereunto 4 sheets of explanatory drawings which I will now
describe.
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Figure 1 on' sheet 1 is a front elevation and figure 2 is a side elevation of my excess
load alarm with the firing and striking mechanism removed, in order that it may
the more clearly described and understood.
The load or weight is suspended from the central eye bolt A which is forined with a
crosshead or nut B at its top end, this crosshead rests upon a suitably formed spiral
spring enclosed within the frame D, and the frame is formed with a hook or ring E
to attach to the main lifting hook or chain that is to receive and lift the load.
The crosshead B has a pin or pins F projecting from it to actuate the mechanism
of the gong striking alarm or the hammer for striking the detonating cap or cartridge.
The crosshead B is held within the frame and prevented from turning by guides b¹ b
formed upon or attached to the frame D. The spring is constructed to bear without
undue straining the maximum load that is safely to be carried by the chain or levers
of the machine to which the excess load alarm may be attached.
In Figures 3, 4 and 5 the projecting pin F working in a slot f formed in the
cover plate conveys the movement caused by the extension or compression of the
main spring to the indicating and explosion mechanism.
The pin F travels from right to left in each case causing by pressure on the
movable cam
piece Ga lifting or withdrawal of the hammer H against the tension
of flat or coiled springs 1.
When the pin F has travelled a fixed distance proportionate to a given load on
the main spring C, it passes beyond the point of. cain G and this cam being rigidly
secured to or formed upon the hammer lever causes the hammer H to strike the
detonating cap L standing upon the cap wheel K, or to strike a gong which may be
employed instead of the cap wheel.
The hammer H is prevented from reaching the cap in any other position than that
caused by the full movement of the pin F (consequent upon an excess load being
applied) by a projecting plate M formed on the lever h in Figures 3 and 4, and in
Figure 5 by the stop lever M₁. By reason of these projections and the stop lever,
the position of the hammer is lower at striking than at any other time.
In Figure 4a ratchet wheel and pawl is not absolutely necessary, the charge or
cap wheel K being revolved by means of a coiled spring within its central portion ;
the unexplo led caps stand a little higher above the nipple than the spent or exploded
ones, so that a fixed stop N prevents the cap being carried out of the path of the
hammer, and upon the cap being struck the spring carries it round under the stop N
and brings another charged cap against it ready for the next blow that may be
caused.
Figure shows the arrangement of the indicator and signal alarm. The pin F
travels from left to right and upon the maximum load being reached the pointer P₁
worked by a rack and pinion Q Q₁ from a bar actuated by the pin F will denote the
extent of the load on the dial marked in tons and cwts., or any other scale that may
be desired; and at the same time the red signal disc O is caused to fall over the
face of dial by the movement of the pin F, which on reaching the catch lever P
forces it back off the end of the signal lever O, thus allowing the signal disc Oto
fall by its own weight.
The signal disc remains over the dial until the whole of the load being removed
from the hook or chain allows the pin F to be carried back to its zero position
and the lever O₁₁ to be thereby again raised into its normal and covered place,
where it is held by the catch lever P.
The position of the striking cam G is adjusted by means of the screws R attached
to the lever h, which moves the cam plate S carried by the lever backwards and

page_text: forwards at will. While the peculiar shape of the cam G allows the pin to travel
in its return stroke without moving the hammer lever.
On sheet 2 Figure 3 and on sheet 3 Figure 5 the cap wheel K. is moved tooth by
tooth by means of the pawl T carried on the hammer lever, the coiled central
spring ensures that the ratchet wheel teeth shall be kept steadily pressed against
the pawl, and the flat spring U prevents the backward motion of the wheel.
Figure 7 sheet 4 shows the arrangement of my excess load detector with one link
and the front of fork removed, when employed for very heavy loads, too great for the
direct application to the main spring as hereinbefore described. A₁ is the central eye
bolt attached to the crosshead B₁ by means of the nut b₁; D₁ is the main beam to
attach or connect to the lifting chains or main hook; C₁ is the spring receiving a
portion of the dead pull through the levers V V₁; W is the motion bar actuated by
the movement of the levers, and carrying in any convenient position the projecting
pin F; XX₁ are suspending links connected to the main beam at one end and
carrying knife edges for supporting the crosshead B, and the levers V V₁; Y Y₁ are
straps for tieing the links XX, together and thus keeping them rigid. By this
arrangement of knife edges and points the portion of the load transmitted to the
spring C is not an undue one; but is such that can be readily arranged for.
One end of the spring C₁ I attach to the main beam D, while to other end carries
a shackle and knife edge Z to receive the pull of the coupled levers V and V1.
Having now particularly described and ascertained the nature of my said
invention, and in what manner the same is to be performed I declare that what I
claim is :-
•
1. The combination and arrangement of an excess load alarm actuated by the
movement of a spring or springs which carry the load or a part of the same, sub-
stantially as, and for the purposes herein before described and illustrated in the
accompanying drawings.
2. The application of detonating caps or cartridges, to be fired by a hammer
controlled by the load applied to the hook or chain, to give an alarm as and for the
purposes herein before described and illustrated in the accompanying drawings.
3. The combination of a signal and indicator with a weighing dial to register
the excess load, as and for the purposes hereinbefore described and illustrated in
the accompanying drawings.
4. The application and combination of a gong with mechanism actuated by the
load carried by the hook or chain, as and for the purposes hereinbefore described and
illustrated in the accompanying drawings.
5. The application of an automatic excess load alarm or stress indicator to cranes,
chains, hooks, tension rods and levers, of machines for carrying light or heavy bodies,
as and for the purposes herein before described and illustrated in the accompanying
drawings.
Dated this 27th day of Mo 1990
MARKS & CLERK,
13, Temple Street, Birmingham, Agents for Applicant.